Research On High Voltage Ride Through Control Of Three-phase Grid-connected Inverter

With a large-scale distributed generation system of photovoltaic(PV) and wind energy connected to the grid, the grid codes appearing to standard grid system, and to ensure the quality of power supply. Grid codes require that grid-connected inverter should have fault ride through(FRT) capability when grid is in fault. Energy will flow from grid to inverter side when grid swells, at the same time output voltage of inverter increases, overmodulation and off-grid accidents occurred. Therefore, this paper studies the control of grid-connected inverter when grid swells, high voltage ride through(HVRT) control strategies are proposed.Control strategies and standards of HVRT at home and aboard are introduced firstly in this paper. The impact of grid swelling on inverter has been analyzed, and the objective of this paper is summed up. Then the mathematical model of grid-connected inverter is established. Based on the mathematical model of the system high voltage ride through control schemes are proposed to suppress the overmodulation and the control schemes are analyzed. Then, reference currents of active and reactive are designed based on the relationship between the power and current in the instantaneous power theory, and the structure of the control scheme is shown. And the proposed strategies are simulated and compared with the traditional fault ride through strategy. After that, the influences of voltage unbalance factor and the injected power to modulation wave are analyzed by using the control variable method, the corresponding conclusion is drawn.Finally, experiments are carried out on the experimental platform of hardware-in-the-loop(HIL) and the experimental platform of three-phase inverter with TMS320F2812 as the main control chip. The effectiveness of proposed strategies is verified by comparing with the traditional fault ride through strategy.