This paper proposes a coordinated optimization of a geothermal-solar-wind multi-energy microgrid (MEM) considering energy quality. In this MEM, geothermal, solar, and wind energy are converted and conditioned for electricity, thermal energy, and gas productions, in which multi-energy complementarities are fully exploited based on electrolytic thermos-electrochemical effects. Exergy is introduced to understand and quantify the quality of energy carriers, which is formulated as an objective function to reduce the exergy loss rate. The aforementioned issue is thus addressed through the implementation of coordinated optimization to achieve a trade-off between two conflicting objectives. Simulation results on a high-renewable MEM reveal the effectiveness and superiority on flexibility and overall economic enhancements.

This paper presents a harmonic state space (HSS) model analysis for thyristor-controlled LC (TCLC) voltage source converters (VSCs). The analysis primarily addresses the time-variant characteristics of thyristor switching in TCLC systems. Traditionally, the state space model (SSM) has been unable to effectively analyze linear time-periodic (LTP) models. However, by leveraging the periodic nature of these systems, the HSS model—an adaptation of the SSM—can effectively analyze the operational characteristics of TCLC-VSCs. Building on the findings from the HSS model, the harmonic representation of the modulation voltage was introduced, which is instrumental for DC voltage design in this paper. Ultimately, simulation results validating the proposed model and control strategies were presented, compared with previous studies.

Aiming at the renewable energy access problems and the three-phase power imbalance of high-speed railway traction power supply system, the most promising multi-port railway power conditioner (MRPC) is studied and a hybrid optimal power flow control method is proposed to comprehensively consider the maximum renewable energy access and the tolerance for negative sequence currents. Firstly, as the number of locomotives and renewable energy generation are volatile and uncertain, the possibility of power flow should be analyzed and the capacity design of MRPC is accomplished. Secondly, to take full advantage of power converters’ capacity of MRPC, a hybrid optimal power-flow control method is proposed by ac power-flow optimization to minimize negative sequence currents and DC power-flow optimization to maximum renewable energy access. Finally, Simulations are accomplished to verify the effectiveness of the hybrid optimal power flow compensation control to renewable energy access and power quality improvements.

The advent of third-generation semiconductors brings the switching frequency into a much higher level, which enables high-frequency transformer with a smaller footprint in power electronics. Due to its inherent ability of voltage amplification, the transformer-based voltage-multiplier becomes prevalent in step-up converters which are the inevitable parts in the usage of low-voltage renewable resources. Though its feasibility has been verified in many researches, an uncertain error in voltage conversion ratio exists between the reality and ideal, which leaves a theoretical gap. Accordingly, the key affecting characteristics, the reverse recovery process of the leakage inductance, is considered and analyzed in this paper. The power transmission mechanism is clarified, and the root-mean-square error of the gain can be reduced from 24.31% to 3.13%, and the maximum output power together with power effect on the gain are obtained. With the conclusion of this paper, parameters of power supply can be optimized at the beginning of design to satisfy the demand of maximum output power and gain over a wide power range, which can save the unnecessary trial-and-error during the case-by-case design.

This article proposes a cascaded multilevel battery energy storage based parallel dynamic voltage compensator (DVC) for medium voltage industrial distribution systems. In this parallel DVC, fast switch is series-connected for voltage sag detection, and cascaded multilevel battery energy storage is parallel-connected for voltage support during the voltage sag period. According to the grid-side voltage sags or not, corresponding circuits and three-layer control strategies are developed. While the feedforward proportional–integral control method is adopted in the outer layer to track the ideal compensation voltage when the grid-side voltage sags, the ideal compensation current when the grid-side voltage does not sag is obtained through battery charging current as well as reactive power, harmonics, and negative sequence load current components. In order to cope with parameter differences in cascaded multilevel battery energy storage, the middle layer interphase and the inner layer intermodular state of charge equalization control are adopted in two scenarios. Furthermore, the parallel DVC is quantitatively compared with series DVC in the aspect of required battery capacity, and their advantages and disadvantages are systematically analyzed. Case studies are performed to verify the effectiveness and superiority of the proposed methodology on voltage support.

Smart meter monitors electricity consumption through modern metering devices connected to the Internet via Internet of Things (IoT) technology, which can provide intelligent and fast applications on-site such as arc fault protection based on nonintrusive monitoring load classification with fast safety responses for varying electric loads. Traditional three, four, and five layers of the IoT architecture cannot support such fast responses under loading variation. This article aims to propose six layers of IoT Cloud-Edge Infrastructure equipped with a reconfigurable mixed-signal controller as a smart meter platform for adaptation to different environments and, for example, deal with fast arc fault detection corresponding to different load characteristics. Such an architecture can reduce the processing time for safety, reduce bandwidth for communication, improve arc detection accuracy under different loading environments, and lower the overall computation cost.

In this paper, the comparisons of different hybrid inverters are provided for power quality compensation and/or active inverter injection. In detail, the characteristics are compared for inductive coupling grid connected inverter (IGCI), capacitive coupling grid connected inverter (CGCI), static var compensator (SVC) in parallel with a CGCI (SVC//CGCI), and hybrid grid connected inverter (HGCI). The comparisons are separately provided for two applications: 1) power quality compensation 2) both power quality compensation and active power injection. In this paper, the circuit configurations of different inverters are proposed firstly. Then, the design of each hybrid inverters is provided. After that, the comparisons are provided for above mentioned applications. Finally, the simulation results are provided to verify the characteristics of different hybrid inverters.

In this paper, a voltage mode controller called Quasi proportional-resonant (Quasi-PR) controller has adopted in a three-phase capacitive-coupling grid-connected inverter (CGCI) PV system. Under CGCI structure, the function of the inverter is to compensate the reactive power as well as generate the active power to the grid with low operating dc-link voltage. The Quasi-PR controller could be effectively applied in a sinusoidal current tracking problem with low steady-state error and suppressing the system voltage disturbance at the fundamental frequency. Experimental results are given to verify the effectiveness of the suggested controller in CGCI.

This paper presents an adaptive hybrid off-grid inverter with low DC-link voltage and active part rating under inductive load. The inverter's DC-link voltage and active part rating with adaptive LCC (A-LCC) filter is much lower than that with traditional LC filter which is normally used in islanding mode. The A-LCC filter in inverter can maintain stable power supply in standalone mode when the load is dynamic. In this paper, the design of A-LCC filter's inverter-side inductor and parallel capacitor parameters are investigated with the consideration of low inverter's DC-link voltage and active part rating. Then, a new algorithm is proposed to calculate the load-side capacitor value of A-LCC filter for reactive power compensation according to the dynamic load. The capacitors control part of A-LCC filter can regulate the suitable capacitors connect into the circuit. In this structure, the reactive power is compensated completely, and the active part of inverter supplies active power only. Simulation and experimental results are provided to verify its effectiveness in comparison with the inverter conventional with LC filter.

Previously, the required dc-link voltage of the three-phase four-wire (3 P 4W) LC- coupling hybrid active power filter (LC-HAPF) was developed based on balanced loading condition. To extend its operation into unbalanced loading cases, this paper presents a general mathematical deduction of the LC-HAPF required dc-link voltage through the circuit models in zero-, positive- and negative-sequence (0-1-2 coordinate). However, a significant high dc-link voltage will be required to compensate both reactive and unbalanced currents when the coupling LC part is designed based on the original method. Thus, the LC-HAPF will lose its key benefit with low dc-link operating voltage, and increasing the system initial cost, switching loss and switching noise. In this paper, a novel coupling LC design method is proposed to effectively reduce the LC-HAPF dc-link voltage, which is based on the considerations in both reactive and unbalanced currents. Finally, representative simulation results of the 3P4W LC-HAPF for reactive and unbalanced currents compensation are given to verify the correctness and effectiveness of the proposed deduced and designed methods.

Nowadays, with global development in Internet of Things (IoTs), electricity, water, and gas information readings should be done in a convenient way. However, existing smart electric meters (SM) mainly focus on the information of financial transactions (the energy bill), whereas little effort has been done to promote the instrumentation dimension of the metering infrastructure. In this paper, we propose and develop a power quality indexes (PQIs) measurement system platform with remote alarm notification for electrical systems. Compared with the existing state-of-the-art, the proposed platform requires less development and maintenance cost, exhibiting higher flexibility. In this system we include the main power quality indexes, including root-mean-square (RMS) value, active power P, reactive power Q, apparent power S, power factor (PF), fundamental power factor (PF1) and total harmonic distortion (THD). To acquire those power quality indexes, we use a anticonjugate decomposition cascaded delayed signal cancellation (ACD-CDSC) technique. At last, we provide the experimental results of PQIs in a single-phase system to verify the effectiveness of the measurement platform with remote alarm notification in comparison with the Fluke power quality analyzer.

Compared with traditional active power filter (APF), the hybrid active power filter (HAPF) can be considered as a good tradeoff between compensation range and active inverter rating. However, the load harmonic and reactive power is easily beyond the compensation range of HAPF, the HAPF with the conventional control methods cannot provide satisfactory compensation performance. Therefore, this paper proposes a selective power management control to keep the satisfactory harmonic power compensation performance and partial reactive power compensation for above situation. In this paper, the capacity of the HAPF in terms of reactive power, harmonic power and dc-link voltage is deduced firstly. Then, a selective control method is proposed to selectively manage reactive and harmonic power based on pre-designed HAPF capacity. After that, the reference compensating current can be obtained through pulse width modulation (PWM) to control the HAPF. Finally, simulation results are provided to verify the effectiveness of the proposed selective power management control for the HAPF.

In this paper, a new structure of a single-phase hybrid active power filter (HAPF) with adaptive passive part and active part is proposed. The HAPF as a state-of-the-art power quality compensator is combining the advantage of passive filter and active filter. However, it may still suffer the high initial and operational costs situation under the capacitive load case. With the proposed topology, the reactive power and harmonics of the loading can be compensated dynamically. The structure can be applied to general household appliances including inductive and capacitive loading. Compared with the traditional APF for inductive loading compensation and HAPF for capacitive loading compensation, the proposed HAPF requires a low dc-linked voltage under both inductive and capacitive loading compensation, which can reduce the initial and operational costs. Especially, the transient condition has been analyzed when the passive part is switched to verify the feasibility of this topology. Finally, representative simulation and experimental results are presented to prove the compensation effect of this single-phase HAPF with adaptive passive part.

A 3-level boost (3LB) converter has the characteristics of higher voltage conversion efficiency, lower inductor current ripples, output voltage ripples and voltage stresses on switches when compared with the conventional boost converters in continuous conduction mode (CCM). When the 3LB is integrated on a chip, we cannot avoid its discontinuous conduction mode (DCM) operation due to a small inductance and load variation. In this paper we'll present and discuss the design and control of a 3LB converter in DCM operation, implemented in a 65-nm CMOS process. Transistor level simulation results show that it operates at 100 MHz with a 5nH inductor, a 4nF output capacitor and a 2.5nF fly capacitor achieving an output conversion range of 1.5 V to 2.1V from a 1.2 V input supply, with a peak efficiency of 83.2%@90mW, a load transient response of 141mV and 1.64ns/mA for undershoot, 136mV and 1.93ns/mA for overshoot, and a voltage ripple less than 60/85mV when ILoad =40/80mA with a typical and the maximum output voltage ripple of less than 90mV in the worst corner.

This paper presents the DC analysis of the Negative Output Elementary Luo Converter (NOELC), which includes the continuous-conduction mode (CCM) voltage gain and the boundary condition between the CCM and the discontinuous-conduction mode (DCM). The main features of the NOELC are the high gain with small ripple and the reverse output. Additionally, we address the parameters design of the NOELC and propose an output voltage ripple estimation method. Through MATLAB Simulink simulation, we further demonstrate that the parameters design and the output voltage estimation method can achieve more accurate results when compared with those from the conventional one.

In this paper, a new structure and the coordinated control method of a delta connected static var compensator (SVC) based hybrid active power filter (SVC-HAPF) for reactive current, harmonic current and unbalanced current compensation are proposed. The proposed delta-connected SVC-HAPF has the desirable characteristics of wide compensation range with low voltage/current rating requirement in the active inverter part. Simulation results are provided to verify the effectiveness of the proposed structure and control method.