Reactive Power And Voltage Optimization Control In Distribution System Based On Electronic Power Transformer

Voltage quality is one of the important indexes of evaluating the power quality of the power system, which depends on mainly whether reactive power flow is rational. The system operation voltage will be difficult to guarantee if the reactive power is insufficient, and operating On-Load Tap Changer (OLTC) will probably induce voltage collapse under this condition. Reactive power is extremely insufficient in the distribution system for a long time in our country, the network power loss is increasingly serious, so, solving reactive power compensation problem of the distribution network well can maintain the system voltage level effectively, improve system voltage stability and avoid the long distance transmission of a large amount of reactive power so that reduce power loss and generating electricity expenses arising from it. As a result, optimal control of voltage and reactive power has important meanings for network security and energy-saving.Reactive power and voltage optimization control in the distribution network is to find the optimal dispatch strategy for shunt capacitor banks and OLTC so as to minimize the power loss and improve voltage quality. As the relatively frequent operations of the tap switch of the OLTC increase the probability of fault, and influences seriously the secure operation of the system and electric equipments. In particularly, voltage collapse fault for several times around international has direct correlations with the insufficient reactive power and the operation of the OLTC. In view of this, Electronic Power Transformer (EPT) is proposed to apply in the reactive power optimization for the distribution power system. Because EPT has the following remarkable advantages: EPT can not only absorb reactive power as reactive load so that prevent distribution network from pollution by the reactive power flow reversely but generate the reactive power so as to reduce power loss owing to the long distance transmission of a large amount of reactive power flow; can maintain basically the network voltage constant regardless of load varying, moreover, can realize the continuous regulation of voltage to overcome the disadvantage of the OLTC. Smaller size and weigh is also an important advantage which make it be worth applying in the power system. Moreover, the discrete characteristics of the control variables make it proper to find global optimum solution by genetic algorithm. Due to the slower convergence speed, the algorithm has improved such respects as coding and hereditary operators of the simple GA, put forward roulette gamble selection combined to superior individual save strategy and the self-adaptation regulation of the penalty factor etc.Simulation results show that EPT has the excellent characteristic in the reactive power and voltage control in the distribution network and voltage stability.