Research Of SVC Based On Instantaneous Reactive Power Theory

The rapid development of power electronic technology make more and more power electronic devices applied to various fields of life and production. These equipments have lower power factor, and asymmetry and impact, which is result to some power quality problems such as power grid three-phase voltage and current imbalance, voltage fluctuation and flicker. Voltage and frequency is the most indicators of power quality, to ensure the normal operation of the power system, voltage and frequency must be stable in a certain range. By controlling the power system reactive power balance can make the the power supply voltage Keep in a centain range.Static Var Compensator(SVC) can compensate reactive power in power system dynamicly, and SVC has the characteristics of rapid response and continuous adjustment, and maintain the system voltage closed to a constant value, in order to ensure the normal operation of power system. Among them, the Thyristor Controlled Reactor+Fixed Capacitor and Thyristor Switching Capacitor (TSC) are widely used. By changing the thyristor trigger Angle continuous, TCR can control the reactor’s cuting capacity to adjust reactive power continuous which has a high compensation accuracy. TSC is unable to adjust reactive power continuous, so it only can cut in groups for split phase compensation, generally applied in the place that has low compensation accuracy.The topic about the TCR is analyzed and studied. First, the circuit structure and compensation principle of TCR is analyzed, secondly analyzed passive filter and the reactor’s structure and working principle, in the single tuned filter as an example to make the derivative process of filter element parameters of the capacitance and the reactance value. Based on finite element electromagnetic simulation software Ansoft Maxwell established the reactor model, after setting the required parameters to analyze the electromagnetic field simulation, by looking at the distribution of magnetic fiux to improve the reactor.The control scheme for TCR is analyzed and studied comprehensive. The voltage and current coordinate transformation was carried out with the improving instantaneous reactive power theory, digital filtering for the current to get the fundamental wave reactive component of positive sequence and negative sequence, finally to obtain calculation formula of compensated admittance, formulated the control strategy for three-phase unbalanced load. By theoretical analysis, simulation under Matlab and experimental validation, paper proves the validity of the above control strategy.