The use of virtual synchronous generator (VSG) strategy for a photovoltaic (PV) inverter can achieve inertia and damping support. The traditional VSG cannot provide transient reactive voltage support for the system and cannot meet the demand for voltage regulation during the low-voltage ride-through (LVRT) periods. After the occurrence of a grounding fault, the VSG control of the PV inverter is switched to model predictive control (MPC). After the grounding fault is removed, the MPC is switched back to the VSG control strategy. To improve the target current tracking capability during the LVRT periods, an adaptive objective function is set in the MPC. MATLAB/ Simulink simulation and experimental results show that the PV VSG under the novel MPC has an LVRT capability. During the LVRT periods, the MPC current control is precise, and there is no transient current surge during the switching from the MPC to VSG control.

In view of the problems of dual-stator winding induction machines (DSWIMs) under traditional direct torque and flux control such as large torque, large flux and large current ripple, and considering that it is difficult to control the flux at low speed and the corresponding noise level is high, a novel direct control method for speed and flux based on super twisting sliding mode controller (STSMC) is proposed for DSWIMs. A nonlinear controller with zero convergence error in finite time is designed, which meets the Lyapunov stability condition. On this basis, a novel torque allocation algorithm for DSWIMS is put forward, which can make the DSWIMs run in a wider speed range, including zero speed. The electromagnetic torque is provided by two sets of winding according to its rated power. In addition, a full-order observer based on sliding mode control is designed for DSWIMs, which can accurately estimate the winding flux, flux angle and rotor speed to achieve the optimal flux state. Finally, an experimental test was carried out on a 3.3 kW DSWIM drive system to evaluate the performance of the proposed DSWIM control scheme. Experimental results show that the proposed control method, torque allocation algorithm and full-order observer were effective in different speed regions.

The wide applications of insulated gate bipolar transistors (IGBTs) pose high requirements for their switching performance. However, the conventional gate drive(CGD) has limited regulation effect on voltage and current overshoots in the switching process of IGBTs, because it always sacrifices the switching time and switching loss while reducing overshoots. A novel active gate drive(AGD) control method is proposed to suppress the current and voltage overshoots generated in the switching process of IGBTs, i.e., the driving voltage at the high di/dt and dv/dt stages of IGBTs is adjusted to reduce the changing rates of current and voltage, so as to suppress the current and voltage overshoots. Experimental results show that compared with the conventional driving methods, the proposed method can significantly reduce the current and voltage overshoots in the switching processes of IGBTs without reducing the switching speed or increasing the switching loss.

Aimed at uncertainties in the output from grid-connected wind turbine, the scenario analysis method based on probability occurrence is adopted to transform the uncertainty model into a multi-scenario problem with different occurrence probabilities, and a reactive power optimization model with the goal of minimizing the active power loss and voltage deviation is established. In view of the poor diversity of Pareto frontiers obtained using the traditional methods, an adaptive grid multi-objective particle swarm optimization (AG-MOPSO) algorithm is proposed, which uses adaptive grids to obtain the density of particles in external archives, selects the global optimal particles and maintains the scale of the external storage library according to the density information as well as the betting mechanism, thus effectively ensuring the uniformity and diversity of the Pareto frontier distribution. This algorithm is used to perform reactive power optimization calculations on an IEEE 33-bus system with wind power, and it is also compared with the existing NSGA-II algorithm. Results show that the Pareto frontier obtained using this algorithm is better, which verifies the feasibility of the proposed model and algorithm.

Aimed at the high harmonic content of a model predictive controller (MPC) without modulation modules, a novel model-based variable sampling period MPC strategy is proposed and applied to a five-phase induction motor drive system. The problem caused by the fixed-discretization of time in the MPC is analyzed, but the introduction of modulation or modulation substitution to solve this problem will increase the complexity of the control system. Therefore, a simpler and more natural idea is adopted. Specifically, the sampling interval is changed based on the pursuit algorithm, and the optimal control action and implementation time are determined by combining with the MPC, thus realizing the variable sampling period MPC strategy. Experiments were carried out using the five-phase induction motor drive system, and experimental results verified the excellent reference tracking and current harmonic performance of the novel variable sampling period MPC.

Aimed at the problems in the existing nine-level inverter such as many devices and a complex modulation strategy, a novel switched capacitor nine-level inverter is proposed. The topology of this inverter is composed of only one single DC power supply, nine switches, two capacitors and two diodes, and it can output nine levels and double the boost at the same time. The voltages of capacitors are self-balancing, and the complex control algorithm and external voltage sharing circuit are not required. The phase disposition PWM strategy is adopted to modulate the inverter. The working states of four pairs of switches in the inverter are complementary, and the NOT gate logic circuit can be used to reduce the complexity of the modulation strategy. First, the topology and working principle of the inverter are analysed theoretically. Second, the modulation strategy is introduced in detail, and the advantages of this topology are introduced by comparing it with other nine-level inverters. Finally, the feasibility and effectiveness of the proposed topology and modulation strategy were verified based on the established simulation circuit and experimental platform.

To improve the metal object detection performance for an electric vehicle wireless charging system, a sensitivity optimization method for the detection coil was proposed. The equivalent electromagnetic model of a rectangular detection coil with a metal object approaching was established. The changing mechanism of the physical parameters of the coil was studied, and a theoretical formula for changes in the parameters of the detection coil which were caused by metal objects of different sizes was obtained. The influence of several configuration parameters on the sensitivity of the detection coil was analyzed, and the configuration of the detection coil was optimized by combining the actual operating conditions of wireless charging. Through the electromagnetic field simulation and experimental verification, the accuracy of the theoretical model was proved. Finally, a metal object detection experiment was carried out in a 3 kW wireless charging system, which verified that the metal object detection system built on the basis of the optimized detection coil can detect metal objects with a size of 25 mm and above. In addition, it had anti-interference capability.

At present, the transmitting coil in a dynamic wireless charging system for electric vehicles usually adopts a segmented guide rail structure to realize the relay dynamic wireless charging. However, the problem of mutual inductance drop will occur at the switching of the guide rail and result in the reduction of the system transmission efficiency, and this is more prominent at the corner. A corner dynamic wireless charging model was established, and the relationship between the mutual inductance of primary and secondary coils and the deflection angle was deduced through theoretical analysis. An improved structure of the guide rail transmitting coil at the corner was proposed and simulated, and a corner dynamic wireless charging platform based on resonance magnetic coupling was built. Simulation and experimental results show that by using the improved guide rail transmitting coil structure, the mutual inductance drop of the wireless charging system was significantly reduced, and the system transmission efficiency was improved by 8.66% at the maximum deflection angle, thereby verifying the effectiveness of the improved coil structure.

Although the LCL filter has a good performance of suppressing high-frequency harmonics, it may cause problems such as resonance oscillation and instability. For an LCL grid-connected inverter, the conventional capacitor-current-feedback type active damping method can suppress the resonant peak effectively, at the cost of additional current sensors. Under this background, a novel active damping control strategy based on an H∞ filter is proposed. The state space model and process noise model of the LCL filter are derived to solve the H∞ filter. The filter capacitor current can be estimated according to the information about grid current and the voltage at a point of common coupling, and feedback is further completed. The system damping is improved, and the estimation accuracy can be guaranteed even if parameter perturbations exist in the LCL filter. Simulation and experimental results show that the proposed method was insensitive to changes in the parameters of the LCL filter and the grid impedance, thereby verifying its feasibility and superiority.

The accurate and reliable switching current information is important for power electronic converters to realize closed-loop control, harmonic suppression and short-circuit protection, which is conducive to further improving the reliability of power devices. The PCB Rogowski coil current sensor has an important research value and application prospect owing to its advantages of high bandwidth, small size, low cost and low intrusion. However, its measurement accuracy is seriously limited by the drift error and droop error in the traditional integral processing circuit. A resettable integrator is used to avoid the continuous accumulation of drift error while eliminating the influence of droop error. At the same time, a digital compensation strategy for the drift error and offset error in the resettable integrator is proposed, which uses a digital signal processor to control the digital-to-analog conversion module to generate an analog compensation signal and eliminates errors by means of a high-speed subtractor. As a result, this method has advantages of a high compensation accuracy and simple adjustment, and it can greatly reduce the influence due to integral errors. Finally, double-pulse, multiple-pulse and short-circuit protection experiments were carried out based on a double-pulse test platform, and the performance of the proposed PCB Rogowski coil current sensor was verified.