Research On AC Electronic Load Based On Voltage Type PWM Converter

All kinds of power sources are applied in every respect of industrial production and our daily life. Their qualities are so important that they must be tested before being put into the market. Real loads such as resistances, inductances and capacitors are used in conventional tests, which wastes a lot of test energy. So conventional tests can’t meet the requirements of the various testing occasions. To solve the problem, this paper proposes a novel equipment named AC electronic load based on power electronic switches to test power sources, thus the current values, power factor and other parameters can be flexibly set to fulfill various tests, and the test energy can be fed back to the power grid with little loss, high power factor and low current THD. The in-depth work of this thesis is organized as follows:The thesis presents the main circuits of single-phase and three-phase AC electronic load, and analyzes how AC electronic load simulate all kinds of linear or nonlinear loads.The control strategy of input current is discussed and hysteresis current-tracking control method is used to control the input current of load-simulating rectifier to change with its instruction. Besides, effective ways for calculating the parameters of main circuit components such as input AC inductance and DC bus capacitor are discussed. The simulation model of the load-simulating rectifier is built on MATLAB/Simulink platform and all kinds of load types are simulated, which proves the methods to be practical and effective.At the side of AC power grid, two strategies are proposed. The first one is to adopt voltage source PWM rectifier as the main circuit of the grid-connected invert and it uses conventional double closed-loop control. The inside current loop assures actual current follows the change of its instruction, and the outside voltage loop keeps DC bus voltage to be a special constant. The other strategy is to adopt a novel circuit and use one-cycle control to control the output current of the grid-connected invert to be sinusoidal by controlling the output voltage. In the end, the simulation models based on the two strategies are both built on MATLAB/Simulink platform and the results are analyzed and compared.