Research On D-STATCOM Parallel Operation Technology

A good power quality of power distribution network, the power terminal, in which contains various types of electrical equipment, is the basis of the normal work. However, due to the nonlinear load increases and the use of a large number of asynchronous motor, low power factor, serious harmonic pollution in power distribution network and asymmetrical three-phase power quality problem and economical efficiency increase. D-STATCOM can comprehensive control the power quality problems, reduce the power loss, thus, improve the power quality significantly. However, restricted by the capacity of the power electronic switching devices, the capacity of the single D-STATCOM can not satisfy the requirements of the compensation capacity, D-STATCOM parallel operation is an optimal mathod to solve it.This paper introduces topology, compensation current detection, mean low-pass filter and detection strategy of D-STATCOM. In view of the traditional dc voltage PI control has the disadvantage of overshoot and slow speed adjustment, subsection PI control method is put forward. Then the key technology of D-STATCOM parallel operation is analyzed. To realize parallel operation, we should consider the problems such as topology, compensation capacity allocation and control strategy. Based on the analysis of these problems, dc side independent bus structure and improvement distributed control method is put forward. The method combined the system current measurement with load current measurement to ensure the compensation stable and reasonable capacity allocation. The simulation analysis shows that the system can achieve the expected results with reasonable capacity allocation.In order to set up D-STATCOM to do the experiments, main electrical components parameters, control circuit, main program and subroutine is designed. Then two 50 kVA experimental prototype of D-STATCOM is implemented. Experiment resuilts shows that D-STATCOM can effectively compensate the reactive power, harmonic and unblanced current, proposed method can relize compensation current averaged for each parallel operation D-STATCOM.