Study On Dstatcom Controller For Three-Phase Four-Wire System

With wide application of power electronics devices and non-linear load, reactive power and harmonics pollution is a growing problem, which brings a series of hazards to power system and consumer. DSTATCOM, as an important device for dynamic reactive and harmonics compensation, has gradually become a hot spot in dynamic reactive power compensation of power system. In recent years, the problem of harmonics and unbalanced of load is increasingly prominent in three phase four wire system. For this reason, in this paper, integrate compensation of reactive and harmonics is researched, and DSTATCOM has designed using DSP.First of all, current detection method for three-phase four-wire system is researched. Reactive current detection algorithm is critical factor to dynamic performance of DSTATCOM. Based on conventional ip-iq detecting method which is only available for three-phase three-wire system, a new detecting method is used in three-phase four-wire system by eliminating the zero-order current. The experimental results indicate that this method can be used to detect the reactive power and harmonic current exactly in three-phase four-wire system.DSTATCOM control algorithm is studied. Three-bridge arm tow-level inverter is selected as main circuit. Dynamic current hysteresis PWM method is designed to control DC voltage and keep DC neutral-point voltage balance. Through MATLAB simulation, effectiveness of control method is verified, which is capable of compensating reactive power, eliminating harmonic wave and balancing three-phase current of unbalanced system to eliminate neutral current.Finally, DSTATCOM experimental system has been built. This system, which adopts DSP 'as the control core, consists of sample circuit, protect circuit, drive circuit etc. The control algorithm is realized by programming; furthermore, the joint debugging of experimental system has been completed. The experiment results correspond to simulation, which suggests that DSTATCOM based on direct current control can not only give a real-time compensation to reactive power, but also have fast response and high compensate precision.