Research The Effect For Relay Protection Of Distribution System Based On DSTATCOM

The Distribution Static Synchronous compensator (DSTATCOM) is reactive power compensation with the best performance in the power system, which is a critical technique for flexible alternative current transmission system (FACTS). It can improve the stability performance of voltage and compensate the reactive current. The system with the DSTATCOM has the characteristics of flexibility; it has the full utilization of transmission system.The current is basic type protection in power system. It is wide used in the low and medium voltage distribution network; the three-step current protection is combined with each other in transmission line. For the distribution system, the relay protection is impacted with the DSTATCOM compensation, so the model of the system with the DSTATCOM is built and the effect is proposed.Firstly, the principle of DSTATCOM is summarized. The main circuit and the control strategies of DSTATCOM are presented. Then SPWM and SVPWM modulation mode of DSTATCOM are all used in this paper. The EMTDC/PSCAD package and defined modules are used to analyze the dynamic characteristics and protection of distributed power system during system faults. A typical of actual line model in IEEE is built, the effect of the relay protection in distribution system with DSTATCOM is analyzed and a solution is puts forward. Theoretical analysis results show that a DSTATCOM voltage controller can improve by the synthetic compensation of reactive power, the unbalanced reactive current on the fault line is compensated .To ensure the protective selectivity of distribution lines, a new protection scheme of five-step protection scheme is presented. The insensitive zone I is used to improve the operating speed of zone I of transmission line protection. The sensitive zone I is used to improve the sensitivity of zone I. The insensitive zone II is used to improve the operating speed of zone II of transmission line protection. The sensitive zone II is used to improve the protection sensitivity of zone II and is used to improve the operating speed of backup protection of the next circuit. Zone HI is used as the backup protection of the transmission line and also used as the backup protection of the next circuit. By the new scheme of the five-step protection, the sensitivity is improved and the selectivity is ensured. Simulation results verify the validity of the presented scheme.