The Research On The Waveform Control Of Delta Compensated UPS Under Unbalanced And Nonlinear Load

Delta compensated UPS is a power supply with the comprehensive compensation ability. This device can suppress grid harmonic current and compensate for grid voltage fluctuation and reactive current. This device can isolate the grid from the load. It can realize compensation function very well, whether the grid or the load appears power quality problems. At the same time, the device has the characteristics of large capacity, low loss, high efficiency and strong ability of overload. With social progress and the development of science, it will be important of studying the Delta compensated UPS under the conditions of the higher power performance and the more complex loads.Firstly, compared with the high-frequency-IGBT-rectifier UPS which is the most popular product in the market, it is well-known that the Delta compensated UPS has more advantages. After analyzing the direct and indirect control strategy, it is known that the direct control strategy is more suitable for the Delta compensated UPS. This paper has analyzed the power flow under different conditions on the basis of the operating principle of the Delta compensated UPS. It is helpful for understanding the operating characteristics of the Delta compensated UPS.This paper has analyzed the characteristics of the unbalanced and nonlinear loads. And it has pointed out the reason of the voltage distortion. This paper has presented a control strategy of the unbalanced and nonlinear loads based on constructing mathematics model of the parallel converter. With the unbalanced and nonlinear loads the output voltage negative sequence component, zero sequence component and harmonic components have communication features in dq0 coordinate, combines voltage and current double closed-loop PI control and PR control to make the output voltage symmetry and has small distortion under unbalanced and nonlinear loads. This paper mainly focuns voltage and current double closed-loop PI control, quasi PR control and repetitive control for theoretical analysis and parameter design. Then the mathematical models of the series converter are established, give the control strategy of series converter. This paper calculates the given input current, analyzes the average three-phase input current under the unbalanced load. By the mathematical model of DC bus this paper get the control strategy of the positive and negative DC bus voltage balance.Analyzing simulation results by using MATLAB/Simulink simulation software. Finally the experiment platform was set up, which using TMS320F28335 chip for digital control. Simulation and experimental results verified the system theoretical analysis and the feasibility of the proposed waveform control strategy.