| The most common power quality problems in power system can be effective solved by double three-phase bridge AC/DC PWM converters with appropriate control, which is an ideal power quality controller. This paper focuses on the series-parallel compensated UPS, in order to research on the double three-phase bridge AC/DC PWM converters, especially in the design and control strategies of series converter. The main contents of this thesis are as follows:Firstly, the system functions and the main operation principle of the series-parallel compensated UPS are analyzed. The mathematical models of series-parallel compensated UPS are established in both ABC frame and dq0 frame. The control strategy for series converter with ideal input voltage is introduced.Secondly, control schemes in series-parallel compensated UPS are discussed. Then the control strategy of dq axis voltage and current dual-loop based on direct current control scheme is used in this thesis, and the design method of PI regulator parameters is given. In this thesis control strategies for series converter are discussed with ideal and non-ideal input voltage, especially analyzed the influences of non-ideal input voltage. Based on MATLAB SIMULINK environment, a circuit modeling simulating method is introduced. For suppressing the influences of input voltage imbalances and harmonic voltage, a control method with an input harmonic voltage feed-forward in dq0 frame was taken. Simulation results verified the effectiveness of this control method.Finally, a hardware experimental system of the series-parallel compensated UPS is designed and established, including hardware design and DSP software design of series converter. A Large number of experiments have been done in various conditions. Experimental results show that the total harmonic distortions (THD) of input current is less than 5%and the input power factor is almost unity. These results prove that the series converter can effectively improve the current quality of power system. |
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