Research On Reactive Power Compensation Applied To The Three-phase Unbalanced Loads In Distribution Network

In the 220V low-voltage distribution network, a large number of unbalanced loads are applied increasingly, which result in unbalanced distribution network and voltage drop at the end of transmission line. The power quality has been not able to meet the requirement of users. Reactive power compensation techniques not only compensate the inductive reactive power generated in the gird to improve power factor and reduce the power consumption, but make the distribution network loads balanced. So research on reactive power compensation applied to the three-phase unbalanced loads in distribution network is becoming more and more significant.This paper is divided into two parts.The first part analyzes the basic principles of imbalance compensation and the way of reactive power compensation. In addition that, the final mathematics model of full capactive reactive power compensation applied to distribution network is given. Then according to nonlinear constraints and combinatorial optimization, a non-linear constraints equation which symbolizes the power loss to strike the optimal capacity of compensation is established.Secondly, a model of three-phase unbalanced loads in distribution network is built in Matlab/Simulink.With capacitors zero-crossing switching, the simulation experiment datas vertify the correction of full capactive reactive power compensation.At the same time, the power loss is calculated before and after full capactive reactive power compensation which vertifies that it can save energy. Finally, the thesis also analyzes the hardware and software of full capactive reactive power compensation device in detail. The control system centers on STM32F207, which is high-speed and real-time.ADC adopts 16 bites and high-precision ADS8556 chip.The hardware mainly includes a sampling circuit, test circuits, control circuits and protection circuits, etc. The software adopts C programming language which mainly includes main programming and interrupt subroutine. Through field trails, it is proved that the device basically reslove the problem of three-phase unbanlced loads in distribution network.The other part analyzes the rationales and control strategies of APF firstly, then research on SVPWM rationale is studied. Secondly, the model of APF controlled by SVPWM is built in Matlab/Simulink and current detection module is improved, which is applied to three-phase unbalanced loads in distribution network. Through the simulation, it vertifies that besides harmonic filtering, APF can resolve three-phase unbanlced loads in distribution network. At last, the software and hardware design of APF are summarized and compared with full capactive reactive power compensation.