The medium voltage (MV) DC collection and transmission technology for photovoltaics (PVs) offers numerous advantages, such as low transmission line losses, fewer power conversion stages, high efficiency, and good stability. The DC/DC boost converter is the core equipment of the collection system. Employing a resonant converter with a wide adjustable input voltage range can eliminate a maximum power point tracking (MPPT) stage, enabling single-stage PV collection. This paper proposes a clamped resonant DC/DC boost converter for PV collection, which ensures quasi-zero current switching (QZCS) and zero voltage switching (ZVS) over the entire input voltage range. A wide adjustable input voltage control strategy with low current stress and corresponding parameter design methods are provided. Finally, the effectiveness of the proposed scheme is verified through a 250kW simulation.

In this article, an underwater simultaneous wireless power and data transfer (SWPDT) system with 1-Mbps full-duplex communication link is proposed. The communication channel shares the coupler with the power channel without using additional communication coils. The transducers inject and extract high-frequency data carriers through the taps of the coupling coils to send and receive data. The proposed method for constructing a full-duplex communication channel no longer pursues the resonant relationship between inductance and capacitance. It takes advantage of the inherent characteristics of the higher-order circuit to simplify the circuit structure and maintain a high degree of design freedom. In addition, the center frequencies of the two communication channels do not shift with the change in the transmission distance, realizing the capability of misalignment tolerance. To improve the utilization efficiency of the communication frequency bands and achieve a high data rate, the system uses the minimum shift keying (MSK) modulation and coherent demodulation implemented by Xilinx Zynq-7000 FPGA. A 1-kW underwater SWPDT prototype with 1-Mbps full-duplex communication is presented to demonstrate the proposed system.

This article proposes a simultaneous wireless power and data transfer system with full-duplex multiple-input multiple-output (MIMO) communication channels for underwater applications. The system uses power coils to transfer information without additional antennas. Two independent communication channels are constructed, which form$2\times 2$MIMO communication channels. The data rate is doubled compared with the system with only a single communication channel. So a dedicated channel can be assigned from the two channels to transfer high-priority information, such as control signals and feedback signals, thereby improving communication reliability. Moreover, using two channels can also enhance communication speed. Data can be transferred in parallel on these two channels. To create two communication channels, transceivers load high-frequency carriers onto the coils using two taps for each power coil, resulting in a communication channel with a significantly high-order circuit. In addressing the challenge of designing high-order circuits, this article proposes the reduced-order model for the communication channel. Finally, a 1.1-kW prototype was built with two 1 Mbps full-duplex channels and a total transmission rate of 2 Mbps to verify the feasibility.

To address the high-dimensional and complex scheduling issues in the low-carbon economic dispatch (LCED) with carbon capture plants, in this article, we propose a novel safe reinforcement learning (SRL) based on heterogeneous action space representation, which can make fast decisions for both optimal power flow and carbon capture operation. First, SRL is designed based on the feasible set to ensure that the dispatch results continuously remain within the preset range. Then, to tackle the problem of having a large number of discrete and continuous variables in the LCED, this article employs a parameterized Markov process to represent these discrete–continuous actions and uses a conditional variational autoencoder to depict heterogeneous space. To learn the correlation between discrete and continuous action spaces, a mechanism for approximating action space based on small-sample behavior cloning is proposed, and a method based on dynamic time warping for calculating environment similarity is designed for determining the value of the regularization term. Finally, numerical simulations validate the superiority and scalability of the proposed method in enhancing decision-making efficiency and promoting the low-carbon economic operation of the power system.

Accurate rotor position information is important for the high-performance operation of position sensorless permanent magnet synchronous motor drives. However, during steady-state operation and variable speed conditions, traditional sliding mode observer with phase-locked loop (PLL) causes position estimation error. In this paper, an observer designed in rotary reference frame is proposed to reduce position estimation error during steady-state operation. Besides, a PLL with speed compensation is proposed to suppress the position estimation error caused in variable speed conditions. Experiments and simulation results verify the effectiveness of these two methods for position estimation error suppression.

Dual active bridge (DAB) converters are applied widely due to the advantages of high efficiency, easy realization of soft switching and bidirectional isolation. For power converters, dead time effect is more and more difficult to be neglected because of the increasing switching frequency promoted by higher power density. However, most of the researches based on DAB converters focuses on optimal control strategies without considering dead time. Therefore, this paper gives a detailed analysis of DAB converters under EPS control with dead time consideration, and the intervals of inductor current zero point is used to distinguish conditions of each sub mode. Recessive-dead-time mode which is not affected by dead time is selected in this paper. Finally, the simulation results verify the correctness of the theoretical analysis.

Compared to the traditional magnetic integration technique, the emerging electromagnetic integration technique (EMIT) has a greater potential for compact design of power converters since it has the capacity to integrate both inductive and capacitive components. As the most representative method, the flexible multilayer foil (FMLF) technique still needs to be further studied for extending and promoting its applications. In this paper, the FMLF technique is utilized to improve harmonic filter design for single-phase voltage-source power converters, a unified integrated LC and LCL filtering module is proposed. In this design, two symmetrical regular FMLF windings and EIE-shape magnetic cores are employed. By sharing the gapped EIE cores and properly arranging the windings with three-terminal configuration, the integrated module can flexibly serve as an LC or LCL filter and realize magnetic decoupling between the two inductors. Taking a 1-kW single-phase SiC-MOSFET converter as the application scenario, simulations and experiments have been conducted to reflect feasibility of the proposed approach.

A novel position estimation strategy for high-frequency (HF) pulsating injection based position sensorless permanent magnet synchronous machine (PMSM) drives is proposed in this paper. The method performs the inverse tangent of HF response currents to realize the decoupling of current information and the extraction of position tracking error can be obtained simply, which reduces the use of low-pass filters. In addition, there is no need to introduce additional demodulation signals, which simplifies the adjustment process. Finally, the feasibility and effectiveness of the proposed scheme are verified on a 2.2-kW sensorless PMSM drive.

Electrolytic capacitors are usually most seriously affected by aging in power electronic systems and it is necessary to timely indicate the degradation status of the electrolytic capacitor for ensuring the safe operation of the system. An online estimation method of the DC-link capacitance based on impedance analysis for permanent magnet synchro-nous motor (PMSM) drives with the boost power factor correction (PFC) converter is proposed, which does not need any additional signal injection or DC-link capacitor current sensor. Based on the principle of area equivalence, the capacitor current can be reconstructed by the inductor current and the duty ratio in the boost PFC converter. The bandpass filter (BPF) is applied to extract the 100Hz ripples from DC-link voltage and capacitor current. Through analyzing the capacitor impedance characteristics, the DC-link capacitance can be estimated by the 100Hz ripple voltage and the 100Hz ripple current. The experimental results verified the effectiveness of the estimation method.

In order to expand the modulation index of the single DC-link shunt permanent magnet synchronous motor drive and improve the motor's operating frequency and load capacity, an improved overmodulation strategy is proposed in this paper. A phase current reconstruction strategy based on vector phase shifting is applied to both modulation linear and nonlinear region. To improve the stability of the motor at high speed, an improved flux weakening strategy based on the voltage angle control method is applied, which can effectively reduce the current harmonics. In addition, this paper proposes a dual-mode overmodulation strategy considering the influence of vector phase shift, and the analysis shows that this strategy can effectively improve the modulation index. Finally, the experimental results show the effectiveness of the proposed method in different operation conditions.

The control accuracy of PMSM depends largely on the inductance. In the traditional inductance identification methods, the ideal PMSM mathematical model is applied, where d-axis and q-axis are assumed completely decoupled. In this case, only the d-axis and q-axis inductances are considered. However, the cross-coupling effect exists in the actual model of PMSM, which leads to the mutual inductance between d-axis and q-axis. In this paper, a high-frequency (HF) equivalent impedance model of PMSM under virtual axis is proposed. According to the HF signal injection, the inductance matrix of PMSM considering the cross-coupling effect can be accurately identified. The experimental results show the effectiveness of the proposed method under different PMSM operation conditions.

The space vector modulation-based direct torque control (SVM-DTC) based permanent magnet synchronous motor (PMSM) suffers from large speed ripples due to the periodic fluctuation of load torque. An adaptive load torque feedforward compensation method is proposed based on the observation of the periodic pulsation component in the load torque. The reference torque in the torque loop is compensated according to the torque feedforward. This method can effectively reduce the speed ripples and improve the steady-state performance meanwhile maintaining the advantages of the conventional SVM-DTC. The effectiveness of the proposed method is verified by conducting experiments on the 1.5kW air conditioning compressor.

As a power supply method with high spatial freedom, megahertz (MHz) wireless power transfer (WPT) has great potential in particular application fields. The role and importance of WPT are described from the perspective of interdisciplinary. This article starts with WPT systems’ performance at different frequencies, emphasizes the basic composition and working principle of MHz systems, and focuses on a comprehensive review of recent years on inverters, rectification, impedance compression, dynamic impedance matching, coupling structure design, and multiload model establishment. Meanwhile, different technologies are summarized, compared, and classified. Current challenges and future development trends are discussed.

Efficient and simple modulation of output power is demanding for radio frequency plasma and wireless power transmission,magnetic resonance imaging systems. In this article, a power modulation strategy that can improve the linearity, power capability and efficiency simultaneously is proposed. The control modes ofon/offand Outphasing are combined to ensure shallow phase depth in a wide power range. Hybrid modules composed of load independent class Φ2structure and symmetrical class Φ2structures are adopted ason/offmodules and PS module to match the proposed control scheme, which are able to provide constant output voltage while remaining zero voltage switching (ZVS) state under resistive-inductive and resistive-capacitive load separately. Theon/offmodule is uniquely designed to behave as a static load when turned off. With the cooperation of control strategy and circuit architecture, the proposed system is able to regulate power linearly with optimal efficiency and minimal voltage and current stress. An implementation with four modules, 13.56 MHz, 25–200 W inverter system is demonstrated, the output power can be seamlessly and linearly controlled with efficiency always within 82%–93.5%. The heat dissipation in prototype is uniform, and is feasible to expand to a higher power compared with other control and circuit structures.

In the high frequency boost power factor correction (PFC) converter, it is necessary to obtain the phase of the grid side voltage. However, in some cost-sensitive applications, there is only a sensor to detect the rectified voltage. This paper proposes a digital phase locked loop (PLL) scheme with a frequency predistortion digital bandpass filter to obtain the rectified voltage phase. Based on analyzing the frequency domain response characteristics of the digital bandpass filter, the continuous bandpass filter is digitized by bilinear transformation with frequency predistortion. On this basis, the rectified voltage is filtered to obtain its fundamental component as the PLL input. Then the grid side voltage phase is obtained at the output side, so the in-phase PFC reference current signal can be generated. Experiments have been carried out on the platform of the 70kHz PFC converter to verify the effectiveness of the strategy.

To solve the power supply problem of the high-voltage side detection module in HVDC applications, a multi-relay wireless power transfer (WPT) system with an operating frequency of 800 kHz is designed. This paper establishes the model of multi-relay WPT system and derives the expressions of the efficiency and output power. By analyzing the influence of the insulator metal flanges and optimizing the coil spacing, the energy transfer efficiency of the system can be improved. A 1.1m prototype with 8 resonant coils and 2 metal flanges is built and the experimental results verify the influence of metal flanges on the multi-relay WPT system and the feasibility of optimized arrangement of coils.

An accurate inertia identification is particularly important for the controller self-tuning to achieve high-performance permanent magnet synchronous motor (PMSM) drives. In this paper, a variable-period inertia identification strategy based on Landau adaptive method is proposed to improve the identification accuracy under low-acceleration conditions. According to the speed measurement rule of low-resolution encoder, the speed updating period of the Landau adaptive inertia identification method is redesigned and auto-adjusted under low-acceleration conditions. Finally, the proposed method is verified on a 2.2-kW PMSM drive platform.

This paper presents a regulated 24V-to-1V series-capacitor buck converter to achieve single-stage high step-down dc-dc power conversions with high efficiency and high power density. Many of the challenges faced by conventional buck converters are overcome by this converter topology. The switching losses and noise of all switching elements in this topology are sufficiently reduced because the voltage stress of switches is reduced to one-fourth of the input source voltage at switching periods. By taking advantage of the benefits from the series-capacitor buck converter topologies, all switching elements of the converter allow for low withstand voltage MOSFETs with low drain-source on-state resistance and low gate charge total characteristics. Further, the use of coupled inductors can achieve a small steady-state current ripple and enhance transient response to the load steps. The effectiveness of the topology is verified by a 24V-1V/20A prototype with a peak efficiency of 91.6%.

The slim film capacitor driving mode can prolong the operating life of the PMSM system and reduce the system volume. However, the small DC-link capacitor and the grid-side filter inductor are prone to LC resonance. Many stability control methods have been investigated, but they cannot work well under the situation of the grid impedance change. An adaptive stability control strategy is proposed to improve the power quality of the grid side for the electrolytic capacitor-less motor drive in this paper. Through the analysis of the phenomenon of the LC resonance on the grid side, the active damping control strategy based on DC-link voltage feedback is designed with the detection of the THD of the grid current. and the control parameters are adaptively changed. Then, the harmonics of the gird currents can be suppressed effectively. Finally, the simulation results verify the feasibility of the strategy.

Permanent magnet linear synchronous motor (PMLSM) has many superior advantages, but the unique structure leads to the large end force. And PMLSM is also affected by other disturbance forces such as the cogging force and friction force. These forces result in the large thrust ripples, which seriously reduce the performance of PMLSM drives. Firstly, the dynamic model and thrust ripple characteristics of PMLSM are analyzed. On this basis, a thrust ripple suppression method based on the Fourier transform compensator cascaded an improved extended state observer (ESO) is proposed. The Fourier transform compensator extracts the amplitude of the 2nd harmonic of the speed ripple, and outputs the feedforward compensation to suppress the detent force in the thrust ripples. The improved ESO observes and compensates other harmonic components. These two parts adopt cascade structure to comprehensively suppress the thrust ripples of PMLSM. Finally, experiments are carried out on a 750W PMLSM drive platform to verify the effectiveness of the proposed suppression method.

High frequency (HF) signal injection is commonly used in sensorless permanent magnet synchronous motor (PMSM) drives at low speeds and standstill. However, the extra acoustic noises caused by additional signal injection impose restrictions on its further applications. To address this issue, a pseudo-random frequency pulse voltage injection scheme is proposed for sensorless PMSM drives at low speeds. Compared with the pseudo-random signal injection, the proposed pseudo-random frequency pulse voltage injection scheme with pulse width adjustment can make all the discrete harmonics in the noise spectrum disappear, thus achieving effective noise attenuation. The signal injection design is performed via current power spectral density (PSD) analysis. According to the form of the injected signals, the signal demodulation procedure is designed to obtain estimated rotor position. The validity of the proposed scheme is verified on 2.2-kW IPMSM platform.

The current loop is the key to realizing high-precision permanent magnet synchronous motor (PMSM) drives. However, the performance of the current loop is deteriorated by the dc and ac disturbances. To deal with the problem, this article proposes a discrete-time repetitive control-based active disturbance rejection control (ADRC) for the current loop. The discrete-time repetitive controller is embedded in the control law of the ADRC and operates in parallel with the discrete-time extended state observer (DESO), which is the core of the ADRC. The repetitive controller is designed to compensate for the ac disturbance, while the DESO is designed to suppress the dc disturbance. The stability and antidisturbance capability of the studied scheme are analyzed theoretically in the discrete-time domain, which can guide the tuning of control parameters. Compared with the existing ADRC-based PMSM control schemes, the studied scheme can suppress the dc and ac disturbances simultaneously, thereby improving dynamic- and steady-state performance of the current loop. Finally, the effectiveness of the studied scheme is validated on a 4.4-kW PMSM drive platform.

In order to further improve the boost ratio of the traditional impedance source inverter, and to improve the DC bus voltage spikes during switching transient caused by the leakage inductance of the coupled inductor. A new high-step up and low-spikes impendence inverter based two coupled inductors is proposed. By using two T-type coupled inductors to replace the inductance in the classic Z-source inverter, the proposed inverter can flexibly control the turns ratio of the two coupled inductors to obtain a much higher boost ratio. The DC bus voltage spike absorption circuit composed of several passive components effectively recovers the leakage inductance energy and suppresses the DC bus voltage spikes. In order to show the characteristics of the proposed topologies, the operating principles, analysis are shown in this paper. Experimental results verify the feasibility of the proposed inverters.

To achieve high-performance sensorless control of interior permanent magnet synchronous motor (IPMSM) drives, this paper proposes an extended flux observer by using the current model to modify the voltage model. The current model is set to correct the voltage model through the PI regulator to form closed-loop control. The proposed closed-loop control method effectively suppresses the DC offsets and integral saturation in the voltage model, which greatly improves the stability and accuracy of sensorless control. On this basis, for the 5th and 7th harmonics caused by the inverter nonlinearity, this paper proposes a filter network composed of multiple second-order generalized integrators (Multiple SOGIs), and uses the integral characteristic of the second-order generalized integrator to replace the pure integral of the voltage model. Multiple SOGIs greatly filter out the high-order harmonics in the back electromotive force (EMF) and improve the accuracy of sensorless control. The effectiveness of the proposed scheme is verified on a 2.2kW IPMSM drive platform.

Motor drives with reduced DC-link capacitance may face grid current distortion or even instability under weak grid condition. In this paper, the small signal model of reduced DC-link capacitance drive system under weak grid condition is derived and analyzed. On this basis, an impedance reshaping method is proposed to suppress the harmonics of the grid-side current. By extracting DC-link harmonics near the LC resonant frequency and reconstructing the virtual admittance of the drive, the active damping voltage control signal is generated to suppress the harmonic of the grid-side current at the specific frequency. The THD of the grid-side current was reduced from 53% to 39%. The experiment was carried out on a 5.5kW permanent magnet motor drive platform with reduced DC-link capacitance, and the effectiveness of the control strategy was verified by experiments.

This paper proposed a quadrature phase-locked loop (PLL) with a second-order complex-coefficient filter (SCCF) to improve the position estimation accuracy of sensorless interior permanent magnet synchronous motor (IPMSM) drives. Due to the inverter nonlinearity and flux spatial harmonics, it exists 5th and 7th harmonics, and dc offsets in the back-electromotive force, reducing the accuracy of estimated position. For this problem, the studied SCCF-PLL can suppress the harmonics and dc offsets with the operation-frequency-adaptive character. The stability of the studied PLL are analyzed by establishing a small-signal model. Compared with the conventional PLL, the studied PLL can reduce the estimation error of the position observer effectively. The availability of the studied method is verified by the contrastive simulation results.

In the traditional overmodulation, the reference of voltage loop is selected as a constant. However, it keeps the motor working in the six-step mode regardless of torque demand, resulting in current and speed harmonics. To address this problem, an operation-area-selected (OAS) overmodulation strategy is proposed for flux-weakening control of surface-mounted permanent magnet synchronous motor. The compensation of the inscribed circle reference voltage is obtained by logical judgments of two designed reference voltages in an auxiliary closed-loop. The proposed scheme can adjust the reference of voltage loop dynamically according to different working conditions, leading to reduced current and speed ripples. The simulation results verify the effectiveness of the studied scheme.

Under low PWM-to-output frequencies ratio conditions, the performance of the discrete adaptive full-order observer (DAFO) deteriorates sharply with the forward Euler (FE) method. This seriously affect the stability of speed sensorless induction motor (IM) drives. To address the problem, this paper proposes an improved DAFO with the "prediction-correction" method. The studied method can improve the discretization accuracy of the observer. Compared with the conventional DAFO, the proposed DAFO ensure stable operation at low PWM-to-output frequencies ratio. The experimental results from a 3.7kW IM drive system verify the effectiveness of the studied observer.

In order to avoid the failure of electrolytic capacitor due to the influence of ambient temperature, film capacitors are applied in the DC-link of permanent magnet synchronous motor (PMSM) drive systems. In this paper, an online estimation method of DC-link capacitance is proposed for the electrolytic capacitorless motor drive system. The power signals of the drive system are analyzed, and the characteristic frequency of the DC-link capacitance power is determined. The instantaneous capacitor power is obtained by the sampled grid input power and the reconstructed inverter power, which is determined by the DC-link voltage and inverter input current. The components of capacitor power and the result of multiplication of DC-link voltage and its derivative at the expected frequency are obtained to calculate the DC-link capacitance by a band-pass filter. The estimation process can be carried out when the system operates normally, and no additional sensors are required. The experimental results verify the effectiveness of the proposed method.

A variable gate resistance SiC MOSFET drive circuit is proposed. The switching speed of SiC MOSFET is improved by switching different drive resistors at different stages of the SiC MOSFET switching process. In the early stage of the device switch, two driving resistors are used to charge and discharge the gate electrode together to reduce the delay of the device switch and increase the rising rate of voltage and current. Then the small drive resistance is cut out and the large drive resistance is used to suppress the voltage and current spikes and oscillations in the switching process of SiC MOSFET. The SiC MOSFET driving circuit test platform was built to verify the effectiveness of the proposed driving circuit. The experimental results show that the rising rate of drain current Idin the switching process of SiC MOSFET driven by variable grid resistance SiC MOSFET is increased by 118%, the rising rate of drain-source voltage Vdsin the switching process is increased by 117%, and the total loss in the switching process is reduced by 15.34%.

The capability of misalignment tolerance is vital for an inductive power transfer (IPT) system. A new method that designs the parameters of series/series-parallel (S/SP) compensation topology with undiscovered strong misalignment-tolerant capability is proposed in this article. This article shows the possibility of keeping the output voltage basically constant even with high misalignment if the load is not too heavy and the parameters of the compensation circuit are properly designed. The relationship between primary input impedance angle and secondary input impedance angle with coupling coefficient and load resistance was also analyzed to achieve high efficiency over a wide load range. Then, a 60-W prototype with the performance of strong misalignment-tolerant capability was designed to verify the system performance, and it can be used for wireless charging of laptops or other desktop devices.

This article proposed a novel scheme integrating full-duplex communication into high-power wireless power transfer systems. The power and data are transferred through the same inductive link. A pair of coupling coils with taps are employed to omit the trap inductors that are widely employed in former simultaneous wireless power and data transfer (SWPDT) systems. The proposed scheme can reduce the system cost and size and improve the power transfer efficiency. The power and bidirectional data are transmitted using carriers of different frequencies. Frequency division multiplexing technique is utilized for full-duplex communication. The duplexer is carefully designed to separate the transmitted and received data signals. The circuit model of the system is built to analyze the power and data transfer performance. The crosstalk between the power and data transfer is also discussed. To improve the performance of data transfer, the method to determine the optimal coil tap position is proposed. A 300-W SWPDT prototype with a full-duplex data rate of 500 kb/s was built to demonstrate the feasibility of the proposed system.

Loosely coupled transformers (LCTs) play an important role in wireless power transfer (WPT) systems. The flat solenoid coupler and planar square coupler are two most commonly utilized LCTs. To compare the performance of these two structures, simulation using ANSYS Maxwell is conducted. For the sake of fairness, the length, width and height of the ferrite core, the length of the air gap, and the specification of the Litz wire are consistent. The coil turns is optimized to make the self-inductance of these two LCTs equal. Finally, the two optimized LCTs are comprehensively compared in terms of self-inductance variation, coupling coefficient, misalignment tolerance, leakage magnetic flux intensity, and cost.

This paper presents a fully distributed finite-time dual-layer control system to guarantee an economic global load power sharing for DC multi-microgrids (MGs). Local and global coordination controllers are developed to handle respectively the optimal operation within a finite settling time for individual MGs and the entire cluster of interconnected MGs by using a dual-layer sparse communication network. In the local control layer, not only the incremental costs (ICs) of all DGs within each MG are equalized to realize optimal load sharing between DGs, but also the local generations and demands are balanced by MG's average voltage restoration using the finite time consensus protocol. Furthermore, the economic power flow among MGs is regulated by the distributed global controllers through fine-tuning of MGs local reference voltages to attain the minimal global total generation cost (TGC). The feasibility of the proposed controller is verified by simulation under various testing scenarios.

In this paper, an isolated synchronous rectification DC-DC converter based on GaN HEMT is proposed, which can achieve soft-switching characteristics and reduce the conduction loss of the rectifier. In conventional rectifier converter, fast-recovery schottky diodes are used for resonant rectification, and the diode forward voltage drop results in larger diode conduction losses, which causes the power converter to be less efficient. To solve this problem, the proposed topology, whose rectifier diode is replaced by a synchronous switch, adopts synchronous rectification, which helps to improve the efficiency of power converters. Meanwhile, the transformers with magnetic core are also replaced by coreless planar transformers to reduce the volume. Thus, the system efficiency and power density can be improved. To achieve soft switching and reduce switching losses, the driving circuit of the rectifier circuit is optimized and the detailed design method of the proposed converter is analyzed. In tens of megahertz, the GaN HEMTs are adopted to reduce the driving loss, switching loss and conduction loss. A 20MHz prototype based on the proposed topology is designed in this paper. The experimental results verify the feasibility of the proposed converter and corresponding design method.

High-stiffness servo system is easy to cause mechanical resonance in elastic coupling servo system. Although on-line adaptive notch filter is effective in most cases, it will lead to a severer resonance when resonance frequency deviated from the natural torsional frequency. To explain this phenomenon, an improved discrete system model is proposed. This paper quantitatively analyzes the influence of damping, discretization and current loop time constant on mechanical oscillation frequency. A conclusion is drawn that the most effective notch frequency is the natural torsional frequency when resonant frequency is deviate. Simulation and experimental results verify the accuracy and effectiveness of the theoretical analysis.

For motor control applications, the speed loop performance is largely depended on the accuracy of speed feedback signal. M/T method, due to its high theoretical accuracy, is the most widely used in incremental encoder adopted speed measurement. However, the inherent encoder optical grating error and A/D conversion error make it hard to achieve theoretical speed measurement accuracy. In this paper, hardware caused speed measurement errors are analyzed and modeled in detail; a Single-Phase Self-adaptive M/T method is proposed to ideally suppress speed measurement error. In the end, simulation and experiment show the advantages and verify the validity of the proposed method.

UV-lamp driver especially for radiation at 253.7nm plays an important role in sewage treatment. In this paper, characteristics of the excitation of mercury atoms in the lamp are investigated deeply based on both theoretical knowledge on collision and experimental results on relationship between the irradiance at 253.7nm with the lamp power. An optimization design scheme is proposed to prolong the life span of the UV-lamp and enhance the irradiation of 253.7nm. The irradiance in each waveband emitted by the lamp is measured by illuminometers to validate the accuracy of the proposed optimization scheme. Experimental results verify the soundness of the theoretical analyses.

The parameters of the resistance model are obtained through various experiments under different lamp power in this study. Polynomial fitting curves are obtained for these parameters to get the values under some certain lamp power. Then simulations in PSIM are conducted by using the calculated values to verify the reliability and accuracy of the method adopted. Good agreement is obtained between the experimental results and simulation results. Finally, In order to improve the lifetime of the lamp and increase the UV irradiance at 253.7nm, the double capacitor topology is proposed and studied.

Recently, modular multilevel converters (MMC) have attracted extensive research interest in the field of HVDC and motor drives. However in motor drives, it appears that the inherent problem of the fluctuation of capacitor voltage particularly at low frequencies limits its further application. This paper proposes a new back-to-back hybrid MMCs topology, of which one MMC is directly connected to the grid and another MMC that controlled to drive an AC motor is connected to the previous one with a DC bus. This paper proposes the corresponding control strategies to drive the motor in wide speed range with basically constant fluctuation of capacitor voltage under constant-load operation at the same time. The grid-side MMC is controlled to generate constant DC current to the DC bus while the motor-side MMC is regulated to generate a constant AC output current to maintain the load torque. The effectiveness of the topology and its control strategies are verified by Matlab/Simulink.

Voltage phase control is a novel field-weakening scheme for PMSM which was reported as more stable in high speed region. This paper provides a current ripple reduce method and a frequency-compensation method. The current ripple reduce method deals with the problem that the voltage phase control has bigger current ripple compared to the tradition method. The frequency-compensation method decreases the frequency reference before entering the unstable region. Experimental results show that the proposed methods are effective in current noise reduce and stable running region limit.

Grid-connected converters have been widely used in distributed generations. However, the resonance brought by converters in weak grid has been a great threat to system stability. Impedance-based method provides a powerful tool for stability analysis. Active damping is also widely applied to improve system stability. This paper derives the impedance model of grid-connected converter system and analyzes the harmonic resonance mechanism. The effects of passive damping and active damping are also compared, especially their influence on non-passive region. Impact of capacitor current feedback gain on the output admittance is also analyzed. High-pass filter is used to compensate the digital control delay and reduce the non-passive region of output admittance. An improved active damping is proposed to eliminate second harmonic introduced by active damping. The performance of proposed method is verified in Matlab/Simulink simulations. The simulation result shows the effectiveness of proposed method.

This paper proposes a novel on-line algorithm to obtain knowledge of moment of inertia by iteratively computing. Since load torque and moment of inertia are variables which cannot be decoupled, so it is hard to achieve good performance when load torque varies. This paper eliminates this problem and realizes ideal online inertia identification regardless of load condition. The algorithm in this paper introduces adaptive controllers to Recursive Least Squares to enhance its robustness. A Kalman Filter is employed to obtain a more accurate value of inertia. It has better performance during iteratively load torque computation and moment of inertia. Compared with traditional method, the validity of the proposed algorithm is proved by simulation and experiment results.

A deadbeat predictive control based current sensorless control method is proposed as a backup method in this paper, by replacing the current feedback with the predicted current at one sampling period ahead, the feedback current information is not needed, thus current sensors can be omitted. Noticing that parameter mismatch will largely influence the control performance of predictive control, q axis inductance is identified online by recursive least square (RLS) method when the motor is functioning with healthy current sensors. Effectiveness of the proposed methods is verified through experiment on a 750W PMSM servo system and it shows that favorable speed response can be achieved.

The series HVDC tap based on modular multilevel converter (MMC) has been proposed to provide power supply for rural places. However, most of current capacitor voltage balancing control strategies are not suitable for series MMC tap. In this paper, the principle of power transfer between phases, arms and sub-modules (SMs) in a series MMC are analyzed. A hierarchical capacitor voltage balancing control strategy is then proposed which can automatically balance the voltage of each SM capacitor. Particularly, the control layers are decoupled from each other to improve the stability of the system. Finally, correctness of the proposed control strategy is proved by simulation results.

A novel sensorless rotor position detection method based on field current pulsation for high power synchronous motors is proposed in this paper. Because of the reduced component count, this method can reduce hardware cost and improve system reliability. Position information is extracted from three-phase back electromotive force. An appropriate pulsation frequency is selected and a suitable control method is proposed. Finally, a series of experiment results are provided proving that proposed rotor position detecting method in this paper is correct and feasible.

This paper presents a PWM predictive speed and current (PPSC) controller for PMSM drive. The main contribution of this controller is that speed and current controllers are combined together to substitute conventional cascade PI structure, and such non-cascade controller largely improves system dynamic performance. The number of state variables and length of prediction horizon are largely reduced compared with other non-cascade predictive controllers, so that the computation complexity is small which leads to PPSC more feasible in practical application. Moreover, to solve the problem that q-axis current reference cannot be obtained directly, this paper adopts estimated load torque to resolve it. Furthermore, a novel approach to constrain currents and voltages is proposed. Effectiveness of the PPSC controller is verified through experiments on a 750W PMSM.

Compensation is a vital part in Inductively Coupled Power Transfer (ICPT) to achieve higher efficiency, power density and reliability. This article proposes two unilateral LC compensation topologies for ICPT system after thorough theoretical analysis, which achieve both zero-voltage switching and constant voltage output characteristics over a wide range of load. A 300W phase-shifted full bridge DC-DC Wireless Power Transfer device is designed and built which achieves an efficiency of 87.8% using proposed structure.

A novel online inductance and flux identification method for AC servo motor based on PWM predictive current control is proposed in this paper. The influences of inductance and flux inconsistency on d,q current responses are theoretically deduced, by achieving the d axis feedback current as zero after the successful identification of real motor inductance according to d axis current error during the steady state. The complexity of q axis current formula can be decreased and makes the flux identification possible according to q axis current error. The proposed method is quite convenient to be realized in servo systems and the dynamic performance of predictive current control is greatly enhanced. Effectiveness of the proposed methods is verified through simulation and experiment on a 750W PMSM servo system.

High Frequency (HF) voltage injection methods have been widely used in the low speed drive applications of Permanent Magnet Synchronous Machines (PMSMs). This paper compares two of the HF voltage injection methods, which are HF sinusoidal voltage injection method in the d-q reference frame and INdirect Flux detection by On-line Reactance Measurement (INFORM) method in the α-β reference frame. Implementation methods are deliberated in detail and the position estimation error caused by magnetic field distortion is also discussed. Experiments using a commercial PMSM are carried out for verifications.

The main objective of this paper is to focus on the study of limit cycle characteristics due to backlash nonlinearity in drive system. For a two-mass system, the existence of gear reduction mechanism or ball screw will introduce transmission backlash inevitably, which can aggravate mechanical resonance. Therefore, it is essential to study the limit cycle characteristics, so as to provide a good theoretical basis for limit cycle suppression. Firstly, based on describing function analysis, the system is separated into linear part and nonlinear part in order to facilitate the analysis. Then the stability and oscillation frequency of limit cycle are predicted. Through the study, it is found that the increasing of backlash amplitude does not affect the limit cycle frequency, yet it will aggravate the oscillation amplitude. Moreover, the limit cycle frequency and amplitude will increase with the increasing of system control stiffness. Finally, the theoretical analyses are confirmed by the experimental results.

This paper proposed one novel control method for modular multilevel converter(MMC) to tackle its low frequency operation problems as the module capacitor voltage ripples. Comparing with conventional control, this paper proposed one asymmetric control by alternating work sates of upper and lower arms, to achieve excellent capacitor voltage ripples suppression effect. To avoid the limited modulation range and enhance performance, hybrid or full bridge MMC structure is employed. The detailed control is analytical discussed, with full simulation results to verify the proposed methods.

In this paper, a grid connected shunt converter for mitigation of voltage sags in weak grids is described. The VSC keeps the grid voltage magnitude at the point of connection constant by injecting reactive power to compensate for the voltage dip. A novel flatness-based control (FBC) is proposed for this purpose that gives higher performance and robustness with an inductor/capacitor/inductor (LCL)-filter in between the VSC and the grid. Simulation model includes the practical limitation of voltage source converter output voltage. Then, the simulation results for the FBC under balanced voltage dips are presented and compared with traditional proportional integral controller. Finally, the sensitivity analysis of the FBC for grid impedance and to system parameter variations is presented.

Compared with wye-connected winding machine, the delta-connected shows merits in wider constant power speed range (CPSR) and higher efficiency because of the full utilization of terminal voltage, which is promising for electric vehicles (EVs), industries and domestic appliances, etc. However, circulating loss caused by triple-order harmonics impedes the application of delta-connected winding in permanent magnet synchronous machines (PMSMs). This paper discusses the advantages of delta-connected winding, and proposes an optimal design methodology on interior permanent magnet (IPM) rotors to minimize the triple-order harmonics, aiming to arouse the awareness of adopting delta connection in PMSMs for higher performance. A 22kW IPMSM prototype with delta-connected winding is manufactured, and the minimized triple order harmonics and super premium efficiency (IE4) are verified by experiments.

This paper presents a novel algorithm to eliminate d-q axis static current error of PMSM predictive current control when the model in predictive controller has parameter mismatch with real system. The relationship between current error and parameter mismatch is analyzed numerically, and the static current error is eliminated by introducing current error integration in d-axis current control while dynamically adjusting the parameter of controller flux according to the q-axis current error. The algorithm is quite suitable for industrial application and is verified through simulation and experiment on a 3.3kW PMSM servo platform.

The flexibility of transmission mechanisms in two-mass servo system can lead to its mechanical resonance. If the oscillation amplitude is beyond the shaft tolerance, it will lead to system insecurity problems. In this paper, the model of transmission mechanisms is firstly established, and based on that, four strategies: engineering design, pole placement method, shaft torque state feedback method and model predictive control are studied to suppress mechanical vibration and protect the safety of transmission. Simulation results show the advantages and disadvantages of the four strategies, meanwhile confirm MPC as the optimal method. MPC can suppress mechanical resonance, limit the amplitude of the shaft torque and allow the system to complete the transient process with maximum acceleration, taking dynamic performance and security into account at the same time.

High impedance characteristics of weak grid can easily lead to some problems such as poor stability of photovoltaic (PV) power generation system, high grid-connected current harmonics and so on. For solving these problems, this paper establishes a system stability criteria based on impedance matching for current-source PV power generation system, deduces the output impedance model of single-phase grid-connected PV inverter, and studies the impact of weak grid on inverter stability and grid-connected current harmonics. Then proposes a control method based on virtual inductance for increasing the output impedance of inverter to improve the system stability, and adopts a grid synchronization method based on second-order generalized integrator phase locked loop (SOGI-PLL) to improve the quality of the grid-connected current. Finally, simulation and experimental results verify that the proposed method can effectively improve the stability of PV grid power system and reduce the grid-connected current harmonics under weak grid.

This paper presents an autonomous control scheme for DC micro-grid system both in grid-connected and islanding conditions. The proposed DC micro-grid architecture consists of a wind turbine generation unit, a photovoltaic generation unit, two battery stack units, a grid-connected inverter/rectifier and loads. Corresponding control strategy of each unit is presented. DC droop control method is adopted into voltage control loop to suppress the circulating current when two or more voltage sources are connected to DC bus. The energy that flows through each unit and different operating modes of the system both in grid-connected and islanding conditions are analyzed. Power management method to balance the energy of the system and stable the DC bus voltage is presented. Simulation results verify the effectiveness of the proposed control scheme in various operating conditions.

Multi-Terminal HVDC based on three-level neutral-clamped voltage source converters (VSC) is an ideal approach for the integration of DFIG wind farms to the power grid. However, dc-link faults and ac faults are major concerns for the safety and consistency of VSC-HVDC system. This paper demonstrates methods employing both full bridge and half bridge DC-DC converters for the fast clearance and protection of dc and ac ground faults respectively. In addition, control strategies incorporating decoupling control and feed-forward compensation on both grid side and wind farm side VSCs are also presented. Normal operations are observed to examine the performance of the MT-HVDC system, and also dc-link fault and three-phase ground fault at inverter side are simulated to verify the effectiveness of the approach employing DC-DC converters to suppress dc current overshoot in case of dc-link fault and mitigate dc voltage overshoot during three-phase ac ground fault. This proposed MT-HVDC transmission system and the fault-ride through capabilities provided by the dc choppers is validated by the simulation studies using detailed Matlab/Simulink model for normal operation, dc and ac ground faults.

Parallel three-phase inverters structure has become a popular way to increase capacity. However, circulating current will be produced. In practical application, inverters are controlled by digital system. Consequently, it is inevitable to consume time due to sampling and computing. As a result, the performance of zero-axis current loop would be directly affected. This paper presents a dual updating SVPWM-based method to control the circulating current exhibited in parallel three phase PWM inverters. With the employment of PI controller, better circulating current suppression performance can be achieved by means of the proposed method because of the realized dual sampling and dual PWM duty ratios updating (DSDU) in a carrier period, which results in dual updating of the circulating current control variable in a PWM period with switching frequency unchanged nor extra hardware added. By comparing the performance with the traditional SSSU method, the effectiveness of the proposed method is validated with implementation using TMS3202812 digital signal processor.

For double-fed induction generator (DFIG) wind power system, when grid voltage fault happens, transient DC flux component will emerge in the stator. The transient DC flux will affect the performance of output power and electromagnetic torque of DFIG. In serious conditions over voltage and current will be induced in rotor side. To mitigate this problem, a novel flux damping control strategy of DFIG is proposed based on grid voltage oriented vector control and imaginary damping winding in this paper. Firstly the transient process of stator flux under grid faults is analyzed based on the electromagnetic relationship of DFIG. The stability of DFIG grid voltage vector oriented control strategy is also analyzed. Then based on the function of damping winding in synchronous generator the novel flux control is proposed and principles of it are introduced in details. The effects of the rotor-side converter's rate and the generator operation state are considered. The validity of the proposed method is verified using a typical 1.5MW DFIG in the Matlab/Simulink simulation environment. The proposed control strategy is proven to be able to increase damping rate of the transient DC flux component in stator effectively and improve the stability of control system.

Servo driver can greatly reduce the harm of backlash if it owns the function of identifying backlash automatically. Aiming at the problem of backlash identification in servo drive system, the automatic identification schemes on servo driver are reviewed. Based on the dead-zone model of backlash, five different identification methods are summed up. Each implementation process is analyzed specifically, mainly interpreting assumptions, hardware requirements and the problems that will be encountered in practice. The accuracy of theoretical analysis of various solutions is verified by simulation experiment. With the comparison of those simulation results, the speed difference integral method that needs few additional conditions and simple operations can obtain the accurate identification result just by a position sensor in servo motor side. So it is feasible strongly and is the best identification scheme, and the experimental result also proves it.

Incremental encoders are popular for detecting angular position and speed. However, the conventional incremental encoder-based methods for estimating speed are prone to poor performance at low speed where the encoder output rate is correspondingly low, leading to a number of research efforts in improved low-speed detection algorithms. To improve speed control performance, a speed detection method based on reduced-order observer is presented in this paper. The observer can interpolate speed and position which is the integration of speed and compared with real data from the encoder when the encoder pulse is detected between encoder pulses. Furthermore, inertia identification based on recursive extended least square algorithm is presented to reduce sensitivity of the speed estimation. Experimental results show that low speed control performance using the reduced-order order is superior to that of conventional one

The rapid growth of digital multimedia and Internet technologies has made copyright protection, copy protection, and integrity verification three important issues in the digital world. To solve these problems, the digital watermarking technique has been presented and widely researched. Traditional watermarking algorithms are mostly based on discrete transform domains, such as the discrete cosine transform, discrete Fourier transform (DFT), and discrete wavelet transform (DWT). Most of these algorithms are good for only one purpose. Recently, some multipurpose digital watermarking methods have been presented, which can achieve the goal of content authentication and copyright protection simultaneously. However, they are based on DWT or DFT. Lately, several robust watermarking schemes based on vector quantization (VQ) have been presented, but they can only be used for copyright protection. In this paper, we present a novel multipurpose digital image watermarking method based on the multistage vector quantizer structure, which can be applied to image authentication and copyright protection. In the proposed method, the semi-fragile watermark and the robust watermark are embedded in different VQ stages using different techniques, and both of them can be extracted without the original image. Simulation results demonstrate the effectiveness of our algorithm in terms of robustness and fragility.

Dual Stator Variable Reluctance Motors (VRM) are electrically commutated ac machines and can be used as direct drive actuators, but inherent nonlinearity of VRM results in difficulties, when smooth and quiet operation are required. In this paper, a high performance control system for VRM is presented. The whole control algorithms consist of four closed-loop controllers: position, velocity, torque and current controller. In the torque controller, the torque ripple is reduced via the torque-sharing function and current PWM control, and the command current is easily obtained from the shared torque command via the proposed nonlinear model of the motor. The velocity controller is a combination of fuzzy and proportional-integral algorithm. The lead angle algorithm is also introduced to improve the performance of system in high speed. The position controller is intended for velocity trajectory tracking. The experimental results illustrate the effectiveness of the control system.

In this paper we introduce wall-climbing robots of two different absorption schemes: one with single suction cup and the other with permanent magnetic crawlers. The former adopts an omnidirectional vehicle and can perform remote-control inspection of nuclear storage tanks. Moreover, it is further developed for cleaning both the ceramic tile and glass surfaces of high-rise buildings. The latter consists of two types of robots: one is for maintenance automation of storage tanks in petrochemical enterprises, which can perform operations of sand-blasting, spray-painting and inspection; and the other is for monitoring the boiler wall water tubing.