Design And Realization Of Single-phase Inverter Power Based On Digital Control

To overcome the inherent defects of the analog control, and take the adventages of the digital control and adjust to the development requirements of the inverter power with digital control, a design of single-phase inverter power based on the FPGA processor with digital control is proposed and implemented in this thesis.In order to acquire a more accurate sine waves output, the thesis fully takes the advantages of the diode freewheeling effect and proposes a newl no dead-zone SPWM (NODZ SPWM) by analyzing the basic structure and working principle of the inverter power. Compares with the traditional SPWM+Deadzone modulation, the new modulation can improve the output accuracy of the inverter power and the bus voltage utilization.and then the new SPWM modulation technique is used in the FPGA.For the design of inverter power's control system, firstly, the single-phase mverter mathematical model is established and a set of improved PID control algorithm is used. And then the single-closed-loop control strategy and double-closed-loop control strategy are analyzed detailedly, the double-closed-loop control strategy is slected.At the same time,a number of Matlab simulations about the double-closed-loop control system are used, including the traditional SPWM+Deadzone modulation, the ideal SPWM modulation and the no-dead-zone SPWM modulation. According to the FFT analysis of simulation results, the waveform with the no-dead-zone SPWM modulation is better than the waveform with the traditional SPWM+Deadzone modulation and the problem of the ideal solution SPWM modulation is difficult to implement in practice has been solved.Finally, the correctness of this system with no-dead-zone modulation and double-closed-loop control strategy has been conclused through both the theoretical analysis and simulation.According to the technical requirements of inverter power, the hardware circuit uses the FPGA as the core is designed, which includes the main control circuit, the detection circuit and the drive circuit. It can realize the instantaneous value control of the inverter and improve the dynamic response of the inverter based on the digital control by the parallel processing features of FPGA. The detection circuit uses the 12 bit serial AD chip, which can detect the real-time bus voltage and inverter output voltage. According to the experiment platform of the inverter, a safe and reliable drive circuit is designed to improve inverter output stability.