The Research Of Three-Phase Four-Wire Distribution Static Synchronous Compensator Control Method

DSTATCOM is in great need in research on modern static reactive power compensation as important reactive power compensation device, especially with bidirectional compensate timely. For compensating reactive power unbalanced loads and harmonic, negative-sequence and zero-sequence current in distribution power system, control method of Three-phase four-wire DSTATCOM is studied.The main works are as follows:Firstly, for compensating reactive power of balanced power system, this paper studies control method of Three-phase three-wire DSTATCOM.Three-leg two-level inveter is selected as main circuit. According to its equivalent circuit, the math model is established.The control strategy of DSTATCOM adopts double loop control.Outer loop control adopts PI control of DC Voltage and reactive current detection. Inner loop control adopts feedforward decoupling current control. Space Vector Modulation is adopted.The simulations of the compensation effects are studied by Electromagnetic Transient Program for DC/Power System Computer Aided Design(PSCAD/EMTDC) under different loads.The results suggest that DSTATCOM has good compensation effects with different loads.And it has good transient stability when break load.The Secondly, for DSTATCOM is applied in three-phase four-wire power system.DSTATCOM should be capable of compensating harmonic, negative-sequence and zero-sequencecurrent, besides reactive power compensation. DSTATCOM using three dimensions voltage space vector modulation is developed. Four-leg two-level inveter is selected as main circuit.According to its equivalent circuit, the math model based on aβ0 coordinate system is established.On the basis of math model, Three Dimensions voltage Space VectorModulation theory is analyzed in detail, the selection of Tetrahedrons and detailed control is developed.The instantaneous i_p -i_q theory is selected after introducing several kinds of reference current detection. DC voltage control adopts energy PI controller.At last, DSTATCOM is simulated based on PSCAD/EMTDC.The results of simulation show that the DSTATCOM adopts 3DSVPWM not only can compensate reactive power, but also can eliminate the harmonic, zero-sequence and negative-sequence current effectively.