Research On Digital Control Technique For Inverters

With the demands that important departments and electric equipments need high quality power supply ascending,high performance PWM inverter are taken more and more attention. Digital control is gradually taking place of analog control with its incomparable merits. In this dissertation digital control technique of two typical inverter: staircase wave inverter and SPWM inverter are studied.As the staircase wave inverter's output voltage is out of control,phase-shifted controll is used, by adjusting the phase shift between the two Series 12 staircase wave inverters to regulate the output voltage.Firstly,the principle of staircase wave superposition is analyzed, then digital signal processor and complex programmable logic device controller are used to realize the digital control of the phase-shifted 12 staircase wave inverter,the method of program and the results of simulation are gived. Finally,this cheme is verified in a 5kVA inverter,and the advantage of digital control technique in the phase_shifted 12 staircase wave inverter is gived.As the application of staircase wave inverter is limit, and it is difficult to control the output voltage waveform. Therefore,in the behind of this dissertation a single-phase full-bridge SPWM inverter is studied, the continuous and discrete mathematical models of the inverter are established, The influence of dead-time, PWM over modulation and nonlinear load on inverter output waveform is analyzed. A variety of high-performance waveform control technique are studied and the corresponding controller are designed.At last ,the control strategies are implemented on a phototype 1 kVA inverter and validated by means of experimental tests.Finally,some questions of digital control technique for inverters are discussed and analyzed,some suggestions for farther research are presented.