The Compound Control Technique Of Three-phase Inverter

With the rapid development of the distributed power generation, like wind, photovoltaic and tidal power generation, the grid-connected inverter has made great development.as we know, the non-grid-connected inverter is widely applied in the fields of military, medical, bank and telecommunications etc. Meanwhile, the research on it is relatively not enough. Therefore, in this paper, we focus on the control technique of inverter's output voltage and the load disturbance rejection.Firstly, through the compare of different aspects, this paper established the main circuit topology, and then designed the filter. After that, follow the state space method and sampling theory, the mathematical models of inverter in Stationary and rotating reference frame were established. Meanwhile the transfer functions and block diagram was derived. Through the open loop frequency test, achieved the accurate control object. base on the model established before, this paper designed the voltage controller. First of all, introducing the working principle, evaluation rules of Steady-state and dynamic performance, the method of design, of the Repetitive controller. Then, on the parallel structure and series structure hybrid controller of PI controller and Repetitive controller, make the theoretical derivation. Through the comparison of formula and bode, this paper choose the parallel structure hybrid controller which can suppress low-frequency harmonics better as the controller. To protect the inverter, design the hardware and software current-limiting protection. Finally, through the experiment and simulation verified the effectiveness of hybrid controller.In the last, load current feedforward control is proposed to eliminate the steady-state error and improve the dynamic performance. Through deriving the transformation equations, the full feedforward function and block diagram is obtained. Under the control in rotating reference frame, although the full feedforward strategy is effective, but its function is complicated, and it would amplify high frequency noise, so the simplification of full feedforward functions is proposed. Through the simulation proves the simplified feedforward control is effective and practical.