Control Strategy Research Of Wide Input Inverter

As a useful complement to traditional power generation, distributed generation has advantages of low environment pollution and high transmission efficiency. The solar and fuel cell is important energy source of distributed generation. But the output voltage of them has a wide range. The inverter should have the ability to boost the input voltage.Based on a wide input inverter with dual mode modulation, the unity sine pulse width modulation(SPWM) strategy which means a modulation wave can achieve sliding switching between the two modes was proposed. Considering the nonlinear load and dual mode modulation, the parameters of conventional PI controller is hard to get. Based on the unity SPWM and the input voltage decoupling, the repetitive controller was adopted, of which the compensation function was designed in detail in this paper. The analysis indicates that if the compensation function is properly designed, the periodic disturbance above mentioned can be repressed by repetitive controller.The repetitive + PI controller gird connected control strategy and the design of the compensation function of repetitive controller was introduced. The compensated equivalent controlled object which is constructed by “inner loop” with compensation function complies with the requirements of the repetitive controller.Due to the constrained boost capacity of traditional boost circuit, a wide input inverter with coupled inductors is proposed, and the operating mode of the circuit is analyzed. In constant boost ratio modulation, modifying the duty ratio of the boost AC/AC circuit with the coupled inductors in time can make the gain of the circuit constant.Then dual mode modulation of the proposed inverter is analyzed and a comparison with constant boost ratio modulation is made. The analysis indicates when in boost mode, in dual mode modulation, the inverter has longer direct energy transimisson time and less time when the switches work in high frequecncy, which helps to raise the efficiency of the circuit.A wide input inverter prototype was designed in the lab. Simulation and experiment results verify the feasibility of the dual mode close-loop control strategy in independent load or gird connected condition and the two modulation stragies of the proposed inverter.