Theoretical Research On Power Exchange Basestation And Its Prototype Design

The distribution network plays an important role in power system which is a connecting link between the higher voltage level transmission network and user load.However,lOkV and lower voltage level distribution network,which covers a large propotion of middle voltage distribution network,has disadvantages such as great line loss,a relatively lower reliability,unbanlance of power flow,deficiencies in close loop operation.In addition,with the expansion of the scale of distributed energy,traditional distribution network has a limited capability of receiving these energy.In order to overcome the deficiencies mentioned above,a brand new device called power exchange basestation(PE basestation)is proposed in this paper.It takes the active distribution network into advantage and the power electronic converter is its core device.Power exchange basestation is suitable in the middle voltage distribution networks and makes their power flow which is restrained by their structure and parameters be actively cotrolled to reach the objective of optimal power flow in the regional distribution network.The compositon and applicable cite of power exchange basestation is introduced.It has a two-layer control structure and two operational modes:distribution network level control and station level control;loss-reducing mode and emergency mode.The implement details of the two operation modes have been introduced.The topology structure of power exchange basestation is analyzed as well as its mathematical model in the fundamental frequency is established.The hardware of the basestation is preliminarily designed including its main operation parameters like inductance and capacitor.The circuit board of driving intelligent power module is designed as well as current and voltage sampling.The control strategy of power exchange basestation is analyzed also.The control of PE basestation is divided into 3 level.Using Park transformation and other theories,the control strategy of AC/DC converter,the core device in the PE basestation,is established.The converter is divided into 2 parts called(Q,Udc)converter and(P,Q)converter according to the control target of the converter.SVPWM modulation is used as well as zero-sequence current suppression which is used to suppress the potential zero-sequence current is added to complete the whole control.Through simulation,the ability of quick and accurate power flow adjustment of the PE basestation is verified.With the widespread of electric vehicles,a change-discharge module is proposed to conncet the battery with the DC side of the PE basestation.During the charging process,there can be no flow-back power by using dual-phase-shift control.The feedforward compensation control is also proposed to increase the dynamic stability of the DC bus voltage.The simulation result shows that the validity of the control strategy mentioned above.At last,a prototype of the PE basestation is designed in this paper.Basic parameters of the prototype are determined and relative devices are selected according to these parameters.Also,the start and stop control strategy is determined and verified by simulation and experiment.A example network containing the basestation has been established to verify the loss-reducing ability of power exchange basestation.