The Research And Experiment Of Static Var Generator Control System Based On DSP

The transformers and machines of power system and a large numbers ofinductive load in distribution network make the system issue the reactive power,while generating active power, which could increase the apparent power.Theloss of transmission will also be increased. The power factor of system will bedecreased, and make the power quality decline.In terms of electrical equipment,the calorific and equipment maintenance costs will increase. The unbalancedthree-phase current are directly reflected by unbalanced load, which will makethe PCC voltage unbalanced indirectly. The unbalanced three-phase currentcould endanger the normal operation of the power system’s relay andtransformer. Traditional reactive power compensation device is difficult to meetthe compensation requirements of power system’s multi-objective. The controlresult of steady-state accuracy and dynamic response is unsatisfactory. CurrentlyStatic Var Generator (SVG) is the most widely studied and applied reactivepower compensation device, which is self-commutated phase bridge invertercircuit compensating devices using full-controlled electronic device. Thecompensating performance is excellent. In this paper, the principle of various reactive power compensation deviceis introduced briefly, the operational principle of SVG is highlighted.Three-phase three-wire SVG is regarded as the research object, themathematical model of the two-phase rotating (d, q) coordinate system is builtunder balanced load and unbalanced load conditions, the reactive currentinstruction is detected based on instantaneous reactive power theoryid iqmethod. The advantage and disadvantage of the direct current control andindirect current control is analyzed, nonlinear controller is designed based onthe theory of passivity,which is used to trace the instrction current, theparameters of controller is easy to regulate, the steady-state precision is high.The voltage space vector modulation (SVPWM) is used to generate PWMcontrol signal. The improved method is proposed to extract and separate theinstrction current of positive and negative sequence control. The positive andnegative dual sequence synchronous is designed to achieve the compensation ofreactive current and negative sequence current at the same time.The software of MATLAB is used to model and simulate the SVG controlsystem：under balanced load, the current controller based on passivity controlcan effectively track the reactive current command value. Under unbalancedload, the positive sequence controller is used to compensate the reactive current,improving system’s power factor, the negative sequence controller is used tocompensate negative sequence current, decreasing three-phase currentimbalance. The simulation results demonstrate the effectiveness of the control strategy.The SVG hardware experiment platform is built, including: hardwarezero-crossing detection circuit, detection and conditioning circuits, theovervoltage of dc capacitor alarm protection circuit, IPM periphery protectioncircuit, fault signal processing circuit. The principle and function of each circuitis described in detail. DSP F2812is regarded as the control unit.According tothe modular principle, the C language is used to program each functionsubroutine program of the above mentioned control strategy. Finally, thehardware platform and programming is debugged and tested together. Theexperimental result is proven that the theory of passivity control strategy and thepositive and negative sequence synchronous dual-control strategy is feasible andeffective again.