Research On Improved UPQC Topology And Control Strategy For Distribution Network Users

With the rapid development of smart grid and intelligent substation, the structure of the distribution network and the power load user will be increasingly complicated, and the probability of various power quality problem have seriously affected the smart grid user security stability and reliability of power supply, so research on power quality control technology has become an important link of the development of smart grid. Unified Power Quality Conditioner (UPQC) as an integrated power quality compensator, it fully meet the real-time control and comprehensive regulation of smart grid development requirements, and has extensive prospects for development.By introducing the associated content of active power filter, the system configuration and the function of UPQC are explained in the thesis at first. Based on this theory, designing an practical topology of the UPQC, which has power voltage dynamic adjustment and dynamic reactive power compensation and harmonic filtering comprehensive adjustment function and Electric vehicle charging function, making it more consistent with the actual requirement of Engineering application. This paper sets the practical UPQC as the study object, to analyze the system structures, functions and working principles Meanwhile, mathematical model of series and parallel converter and the DC energy storage unit is established, and the power flow characteristics are also analyses deeply.Due to the current detection process must always require the phase tracking the fundamental positive sequence voltage, This paper uses a combinational harmonic voltage-current detection method based on the Park transformation, it could make the results of voltage detection are used in the current detection, as a result, the phase of the reference currents can follow the phase of positive fundamental frequency voltage, the current detection without phase-locked loop of three-phase voltage. The advantage of the method is that neither the phase-locked loop, the corresponding detection errors can be avoided. And according to the engineering background built the simulation model, the result proves that the method can achieve good detection effect.The control strategy of practical UPQC used in the thesis includes two parts, a series control and a parallel control. In order to overcome the deficiencies of the existing control method, parallel side uses timer control method, while the serial side uses Space Vector Pulse Width Modulation method, and detailed analysis of these control algorithm was conducted. Finally, based on the combinational harmonic voltage-current detection method, Simulation results given in the thesis verify the correctness of the detection method of voltage and current and the control strategy proposed in the thesis.In summary, this paper design the main circuit topology of practical UPQC, researching and improving the detection and control method, from the aspect of compensation function and the charge and discharge function and efficient detection and control method to make it more suitable for the State Grid of He Bei Lin Zhang Jia Kou 110kV Smart Substation power quality regulation.