Research On Intelligent Control Strategy Of D-STATCOM

As the human society has entered the highly electrified era, electricity is closely related with the industry, agriculture, national defense, and people's daily life. With the increasing of the electrical loads, a large amount of impulse and fluctuant loads in the power system may cause the voltage fluctuation, flicker, and three-phase unbalance. In severe cases, may cause the event of a power system collapse may happen, and a huge financial loss could be brought to the power customer. Therefore, improving power quality and compensating the reactive power become very significant for the stable operation of power system. Distribution Static Synchronous Compensator (D-STATCOM), which is designed for the distribution network, has developed rapidly in recent years.Firstly, this paper introduces the system composition, the main circuit and the basic principle of D-STATCOM. And then, the direct voltage control strategy of D-STATCOM based on the instantaneous active and reactive power balance principle is analyzed in detail. Taking into account the characteristics of complex working conditions and fast response, the fuzzy PI control is used in D-STATCOM. Secendly, the influence of power system voltage imbalance on D-STATCOM's output voltage and current is analyzed, and the negative sequence voltage feedforward control is utilized to improve the performance of D-STATCOM. Lastly , the implementation scheme of SHEPWM is discussed after the principle of the two-level and three-level SPWM, SVPWM, and SHEPWM are introduced.The steady and dynamic performance of D-STATCOM is simulated by use of MATLAB/SIMULINK .The simulation results show that the direct voltage control D-STATCOM can compensate the reactive power and maintain the PCC (point of common coupling) voltage when the grid voltage is balanced, and the fuzzy PI controller can shorten the response time. Meanwhile, positive and negative sequence voltage superimposed control D-STATCOM can compensate the reactive power effectively and make the three-phase voltage balanceing. The utilization of SHEPWM in D-STATCOM can greatly reduce the harmonic components and improve the performance of D-STATCOM.