Research On Digital Pid/pid Dual-loop Control Technique For Inverter Based On State-space

As main stream inverter, PWM inverter has been used widely in UPS, variable frequency power source, power system, new energy power supply system. With the increasing demands in these application areas, developing a high-performance inverter, which is of high stability, fast dynamic response and high static accuracy, has become a tendency.This paper is mainly concern waveform quality of output voltage and researches dual loop digital control technology of PWM inverter based on mathematical model. Load current forward feed compensation is adopted and PID controller is used both in outer loop of output voltage and inner loop of inductive current. There are many advantages of this kind of control method which is proven by simulation results, such as small steady state error, excellent dynamic characteristic, low output voltage THD with non-linear load. To solve the issue of limited Dmax and how to reduce observation error, we try to use state and disturbance observers as well as a repetitive compensation, which have been turned out to be very successful by simulation result.In addition, based on the dual loop digital control framework of load current forward feed compensation mention above, we have compared three kinds of dual loop control method without observer between PID /PID, PID/PI and PI/PI. By analyzing a large mount of detail data, we have learned the variation tendency of stability character, THD of dual loop control method when we add a differentiation element D in voltage outer loop or current inner loop.Based on theoretical analysis and simulation results, the conclusion of experiment on a 50HZ SPWM single-phase inverter is that PID/PID dual loop digital control with the application of repetitive compensation and observer is simple, feasible and can meet all the performance requirements of the inverter power source perfectly.