Research On Control Strategy Of D-STATCOM Based On Dynamic Phasor Sequence Components

As an important composition of the customer power technologies,the distribution static synchronous compensator(D-STATCOM)can realize the continuous reactive power compensation including both inductive and capacitive reactive power in distribution network.D-STATCOM is of many advantages,which are fast response,high precision and flexible control.It is a good approach to improve the load power factor and power quality.The performance of D-STATCOM is decided by the parameters in the mail circuit and the control strategies in the controller.Therefore,it is very necessary to study the designation of the main circuit and the controller based on the mathematic model of D-STATCOM.The analytical model of D-STATCOM based on the dynamic phasor sequence components(DPSCs)is presented in this thesis.A novel deterministic design method for LCL filters and a control strategy based on DPSCs is provided.The main studies are summarized as follows.Firstly,the time domain mathematical model of D-STATCOM is transformed into time-frequency domain model based on DPSCs.This model can be used to analyze the frequency dynamic response of D-STATCOM.It is also the foundation of the following research.Secondly,the deterministic design method of LCL filter is presented.The DPSC model can be applied to calculate the high order harmonic components of D-STATCOM quantitively.Thus,the inverter side inductor,the filter capacitor and the grid side inductor can be designed with different constraints definitely.This method can reduce the trials for the designation of LCL filter and improve the designation efficiency.Thirdly,a control strategy of D-STATCOM based on DPSCs is proposed.The nonlinear equations describing the interaction between the fundamental positive component of current of ac side and the dc voltage on dc side has been extracted from the DPSC model of D-STATCOM.The equations are solved with Newton-Raphson method after the detection of reactive power.The amplitude and phase of sinuous modulation signal is the solution result.Pulse width modulation(PWM)signals can drive the switch of power electronic devices.The reactive power output by the D-STATCOM can follow the desired value.Finally,the experiment platform of D-STATCOM is established.The controller is based on the digital signal processer(DSP)which type is TMS320F28335.The designation of hardware and software in the controller are presented.The designation method and control strategy proposed here are tested by the experiment platform.The experimental results show that the designed parameter of LCL filter is suitable and the control strategy is valid.The control strategy of D-STATCOM based on DPSCs is with clear physical meaning,which can be realized easily.The approach provided here can reduce the complexity of controller and improve the economy of the device.