According to recent improvements in microgrid and Renewable Energy Sources (RESs), it is vital to use an alternative system for conventional transformers due to its lack of controllability and having high volume and weight. So, the senses gathered to the Solid-State Transformer (SST) because of its relevant advantages. A power electronic converter converts a low-frequency ac voltage waveform to a medium frequency voltage with variable amplitude in most SST structures. First, there is a need to convert the DC voltage to a pure sinusoidal one for using the High Voltage DC (HVDC) in Distributed Generator (DG) sources such as Photovoltaic (PV) farms and microgrids. Then an ac-ac converter is used to produce a medium frequency waveform. These structures need two stages of energy conversions. This paper proposes a new configuration with a specific modulation method to convert the DC voltage waveform directly to a medium frequency voltage waveform with variable maximum amplitude. The simplicity of the control system, reduced volume, and weight, as well as the reduced number of energy conversion stages are the advantages of the proposed system.

In this paper, a novel boost-based quasi resonant DC-DC converter is proposed, featuring low component count. The proposed topology also achieves a high voltage gain with a wide output power range while profiting from a simple structure. An inductor is introduced in the termination of the circuit that takes part in the resonant process instead of creating a voltage spike across the switch during the switching time. Moreover, the circuit achieves soft switching (ZVS-ZCS in turn on/off transitions of the switch), leading to reduced losses and improved efficiency. Working with a suitable switching frequency is a contributory factor in reducing the size of passive components. The operational principles and a comprehensive steady state analysis in the continuous conduction mode (CCM) as well as design considerations for the proposed converter are discussed in details.

Grid connected voltage source converters have become inevitable means for expanding and supporting power systems. In this paper, a combined method is adapted to the converter control of grid connected micro grids against multiple risks. A single control system is proposed to cope with high power fluctuations, short circuit faults, and unbalanced operations at the same time. It is realized by using the advantages of a current control scheme in connection with a smart converter switching logic. As a result, no extra means are needed for tackling each of the undesirable conditions. The control system provides stable operation and fault-rid through capability even under unbalanced conditions. It is presented with and without virtual flux calculations. The system operation under the proposed control system is compared with the one under a conventional control system to confirm its performance superiority.

This paper proposes a model-free predictive current phasor control for three-phase grid-connected voltage source converters. The control method regulates the grid current vector magnitude and phase with respect to the grid voltage vector in a stationary reference frame. The method inherently enjoys a fast transient response and high-power quality with a low sampling frequency. It avoids any system model information in the control algorithm for current vector prediction. A direct and effective current limitation routine is embedded into the control algorithm. The method features a simple control structure and low computation burden. It lacks any pulse-width modulation sub-system, additional sensor, lookup table, state observer, and grid voltage and current transformation. The proposed method is evaluated through simulation studies, where the results illustrate the effectiveness of the method and its superiority over conventional methods under the parameter mismatch conditions.

Wireless power transmission (WPT) systems can be a safe, efficient, and economical option in the long run for motor supplying in electric vehicles. The precise design of magnetic structures has a significant impact on the performance of such systems. In dynamic WPT (DWPT) systems, especially for wireless drive applications, due to the vehicle moving in four directions, the misalignment between the primary and secondary sides is considered as a limitation of this technology. In this paper, for a DWPT system with Double D magnetic pads for both sides, adding auxiliary windings in the secondary side, and introducing a suitable compensator in the primary side, a structure is proposed that tolerates the misalignment in all four directions.

Three phase grid connected power electronic converters (GCCs) are unavoidable means for developing and supporting power systems todays. However, their harmonic injection and high frequency switching may lead to reduction of power quality. Thus, GCCs injected harmonics should respect to the corresponding standards. In this paper, a novel control method is proposed for the GCCs to improve the power quality and current THD under both balanced and unbalanced grid operation. The method employs a virtual flux in connection with a combined control for the first time. Compared to the conventional virtual flux direct power control, the method provides much better power quality, reduced THD, plus less grid parameters sensitivity. In comparison with the conventional combined control method, it does not have grid voltage sensors and cumbersome controller tuning. In addition, the proposed method well respect the standards using the appropriate current references without positive and negative sequence extraction under unbalanced grid conditions.

Grid connected voltage source converters (VSCs) are unavoidable means for developing and supporting power systems. Nevertheless, their harmonic injection may cause deterioration of power quality and current THD. Therefore, injected harmonics through VSCs must observe the corresponding standards, while lower switching frequencies and rapid transient responses are required. This paper, presents a sensorless virtual flux direct power control of VSCs based on a novel modified switching table for fast dynamic response, high power quality and low current THD. An analysis is carried out to determine the best voltage vector for virtual flux direct power control of VSCs at transient and steady states. It mathematically proves that the vector is oriented along the grid voltage vector, which is perpendicular to the grid virtual flux vector, at transient state. Moreover, the modified switching table uses a new logic for selecting the voltage vectors under steady to provide smooth performance. In comparison with the conventional direct power control, the proposed method enjoys faster transient response and lower power ripples and current THD due to utilization of the modified switching table, without requiring grid voltage sensors.

This paper presents a model-free finite control set predictive direct power control for grid-connected converters. As the proposed method does not use the model parameters, their uncertainties do not cause prediction error and inappropriate voltage vector selection, unlike the conventional predictive direct power control method. A new form of cost function is adopted in the method that directly uses the time-derivatives (slopes) of the active and the reactive powers. The slopes are predicted free of model parameters with low computational burden and without additional sensors. The method is evaluated through simulation and its performance is compared with the one of the conventional model predictive direct power control method. The results show the effectiveness of the proposed method and its superiority over the conventional method.

Wireless Power Transfer has been proposed for electric vehicle charging applications to obviate problems associated with battery size, weight and cost. This paper proposes a control method to achieve maximum efficiency and load voltage regulation in such applications. The resonance frequency of the system is used as the optimum operating frequency and a DC-DC Buck converter is employed for tuning equivalent load resistance. Because the system optimum operating point depends on the mutual inductance of the transmitter and receiver coils, an estimation method is introduced to determine the inductance and the optimum operating point online. The control scheme adjusts the duty ratio of transmitter side inverter to fix the load voltage upon changes in the mutual inductance. This would be a cost saving solution since it does not use an extra converter.

Using a shunt resistor sensor in the DC-Link of inverters, instead of three Hall-Effect sensors for measuring stator currents, results in cost saving and volume reduction in AC motor drives. This approach is followed in the current paper in permanent magnet synchronous (PMS) motor drives, without the common practice of stator current reconstruction. It is shown that motor line currents can be controlled indirectly by regulating the DC-Link current. To obtain sufficient information for motor control from the DC-Link, new voltage vectors are defined. Each new vector is synthesized by two original active vectors. Then a command is calculated for DC-Link current based on the motor set-points and maximum torque per Ampere (MTPA) strategy. Finally, a simple control law for voltage vector selection based on the DC-Link current error is presented. The proposed method shows similar performance to Direct Torque Control (DTC) method, while its implementation is easier due to the employment of a few simple equations. Therefore, the method is fitting for low cost but high performance applications that do not use powerful processors. The validity of the proposed method is verified by simulation of a 370-W PMS motor.