Research On Control For SPWM Inverters

Presently, with the rapid development of information technology,more and more attention is paid to the digital control and parallel control for inverter systems. This dissertation mainly deals with the control techniques for single phase full bridge SPWM inverter with PID control law. In the analog/digital hybrid control mode, based on the analog voltage regulator, some aspects such as sinusoidal reference generator, SPWM control signal generator are implemented by digital controller to maintain the advantages of both analog control manner and digital control manner. The design and realization of two types of hybrid control modes are analyzed and discussed respectively, and some comparison research on their performance is also carried out. In the inverter system with full digital control mode, the digital voltage regulator is the core component, which may be designed by means of the traditional continuous control theory and the digitalization methods. The sampling delay effect of control variables may be decreased or eliminated by choosing the reasonable analog-to-digital sampling and conversion operation modes. From the side of the generation principle of switching signals for power switches, the output delay of digital voltage regulator is studied and compensated by certain correction strategy. A hybrid distributed load sharing control method for inverters in parallel operation is presented, where the current sharing control and output synchronization control are accomplished in analog manner and digital manner respectively. All the inverter modules are electrically isolated through optocouplers to realize a really redundant parallel system. The parallel operation control of the inverter modules with root-mean-square voltage regulators is also studied, and some measures are taken to improve the current sharing performance. The validity and feasibility of the analysis are verified by the simulation and experiment results.