Research Of The Reactive Power Compensation Technology Based On The SVG

With the development of science and technology,a large number of applications of nonlinear devices in the power grid lead to the increase of phase difference generated between grid-side voltage and grid-side current,resulting in relatively insufficient capacity of original reactive power compensation in power grid.The traditional technology of reactive power compensation is mainly achieved by adopting the synchronous compensator or capacitor switching,but there exist problems such as poor dynamic characteristics and large active power loss.Directed against these deficiencies,the(SVG)Static Var Generator will be utilized in this paper to compensate the reactive power in power grid in order to achieve the purpose of reducing the phase difference between voltage and current,at the same time,it can ensure better dynamic performance and lower active power loss in the process of the system running.At first,the vector method is utilized in this paper to explain the basic working principle of SVG based on the single-phase equivalent circuit;and the advantages and disadvantages of topological structures of voltage mode and current mode are systematically analyzed.And then,directed at the three-phase circuit structure,the method of combining reconstruction technique for phase current and space-vector modulator approach is proposed to detect the three-phase current instantaneous output value of SVG.The simulation results demonstrate that this idea can effectively lessen the use number of current sensors and reduce the system cost on the premise of ensuring the detection precision.In consideration of reactive power compensation only,the feedforward decoupling method is put forward in order to eliminate the cross-coupling terms existing in the system;the method of combining the direct compensation control and quasi(PR)Proportional Resonant control is applied in terms of the situation of reactive-power harmonic wave superposition compensation.The voltage,current phase and(THD)Total Harmonic Distortion value after the operation of two control methods are compared;the results manifest that the system with the design of quasi PR current inner-ring can utilize its characteristics of resonance oscillation to achieve the effect of reactive power compensation at the same time of playing the role of harmonic suppression;and it can also solve the problem of too large current overshoot in systemtransient process caused by using direct compensation control method.Finally,the experiment platform is established for verification.The experimental results indicate that the SVG-based technology scheme of reactive power compensation can ensure that the grid-side current is approximate to the same phase with voltage taking two bits of effective value;and the effective adjustment of power factor in power grid side can be achieved.The THD value in measured system that less than 5% exactly fully demonstrates the effectiveness of the SVG-based technology scheme of reactive power compensation in this paper.