Research On Waveform Correction For UPS Inverter And Monitor Control Technique For UPS

In this paper, the output waveform correction technology of inverters in UPS and intelligent monitor control system of UPS are discussed.In our ups, a Diode-clamped three-level inverter with three phase and four wires are adopted. Then, the Space vector PWM method doesn't work in solving the Neutral-point balance problem in this situation. So, a method that controlling the time of the switching state is presented to solve the Neutral- point problem. And this method are efficient in the simulation with MATLAB software .Without the Neutral-point balance problem, a SPWM inverter is equal to the three-level inverter. The mathematic model of a single phase SPWM inverter is presented in this paper.Then, the reasons that causing the waveform distortion are presented and we analyses system stability, error convergence and steady-state error of a repetitive control system. We use a low-pass FIR filter instead of the trap filter with a second order filter to be the main part of the repetitive controller. We also show the advantages of this FIR filter in the repetitive control system. How to design the FIR filter in a repetitive control system is presented and experiments prove it can get nice static characteristics.We use state feedback pole-assignment control in series with the repetitive control to get well dynamic response. We use the same FIR filter to be main part of the repetitive controller. Experiments are carried out and the dynamic response is faster then before. Experiments also prove that once the FIR filter designed, if the situation did not changed largely, it also can be used and work well.In the end, we design a intelligent monitor control system of a UPS with ten modules and a bypass center. The SPI communication technology and CAN IC are used in communication and well designed agreement between master DSP and salve DSP made the system to be intelligent.