Simulation And Performance Study Of Two Kinds Soft Open Point Based On Static Synchronous Series Compensator And Back-to-back Converter

With its own environmental friendliness,economy and flexibility,distributed generation has gradually become an important part of the current power system.On the one hand,it optimizes the power supply structure of the traditional power system,but on the other hand,it also introduces some new problems to the power system,such as the rise of the bus voltage of the power grid which even exceeding the critical value after the distributed power supply is connected.Therefore,it is necessary to introduce a more efficient and reliable power flow control method to manage the distributed generation connected to the power grid.The soft open point technology at the distribution system level has been extensively studied.This technology can improve the ability of the distribution network to absorb distributed generation without restructuring the existing network.The common structure of soft open point is a back-to-back converter.In order to reduce the construction cost and operating cost of soft open point devices,this paper proposes to use a static synchronous series compensator(SSSC)with fewer switching devices and lower operating power consumption as a soft open point to control the line voltage and power flow,meanwhile carries on simulation research and performance analysis of these two soft open point devices,SSSC and back-to-back converter.The SSSC device is mainly composed of a three-phase voltage inverter,a filter,and a coupling transformer,besides the back-to-back converter is composed of two threephase voltage converters and an energy storage capacitor.This paper first determines the model structure of the distribution network used in the research,the structure and parameters of the two soft open point devices,and the control scheme.Then,the working principles of SSSC and back-to-back converter are introduced.On this basis,mathematical models of two soft open point devices in dq0 coordinate system are established,and the corresponding control strategy is designed according to the mathematical model.Next,the power flow control of two soft open point devices is studied,including the design of two soft open point controllers.The rectifier side of the back-to-back converter adopts double-loop control,that is,DC bus voltage outer loop control and line current inner loop control,and the inverter side adopts current control;SSSC is similar to the back-to-back rectifier side,adopts double loop control plus DC bus voltage control.In the Simulink simulation,the load balancing between adjacent feeders in the 10 k V distribution system was achieved through the given control strategy,and the distributed power generation was reasonably absorbed.Finally,based on the number of switching devices used in the two soft open point devices and the power loss of the two devices under different load conditions,the construction cost and operating cost of the two devices can be calculated to verify the low-cost advantages of the SSSC device.