Study On Damping Power System Oscillation And Limiting Short Circuit Current With DCIPC Based On VSC

Flexible alternating current transmission System (FACTS) is a new one of theregulation and control equipments in power systems. It’s combined withautomatically control, communication technology and power electronic technologytogether and they are the perfect combination. The interphase power controller is adeveloping technology in recent years, and still in the theory research stage in Chinaand have been put into use in some countries. Because of the many excellentcharacteristics of its performance in electric power system, experts and powerdepartments put more and more attention in the IPC.The working principle of IPC is actually to change the phase angles andreactance parameters of the line by phase and inductor, capacitor branch control.Because the regulating process of the IPC contained of conventional components isinflexible and slow, it’s improved in IPC control speed and operation performance bythe electronic modifications to the conventional IPC. According to the basicprinciples and working characteristic of the IPC and voltage source converter (VSC),they’re combined into the continuous adjustable dynamic controlled interphase powercontroller (DCIPC).The reference voltage value is made as the control quantity to the modulation ofVSC to change the voltage which is injected into the inductance and capacitancebranches with the purpose of changing phase-shifting angles in branches quickly andcontinuously and realizing phase shifting. The mathematical relational expressionbetween the transmission power of lines and DCIPC phase shift angles isestablished, and the regulatory role of the phase angle to the transmission power inlines is analyzed, and the phase voltage made by VSC is designed by the generatorangular velocity changes as the feedback control signal to achieve control of dampingpower oscillation. The DCIPC inductance branch is replaced by TCR, and the DCIPC capacitancebranch is replaced by TCSC capacitive vernier mode, and the short-circuit currentlimitation effect of the TCR and TCSC branch reactances is analyzed, and the DCIPCequivalent parameters is changed by the thyristor trigger angle as the control signal,so as to realize the control of limiting short circuit current. As an example of thesystem of Dual power supply connected by tie line with DCIPC, the oscillation of thepower system damping and the restrict of short-circuit current is simulated andverified by controlling the phase-shifting link and the equivalent parameter in DCIPC.On the basis of the above study and from two perspectives of mathematicalmodel and control mechanism, the IPC of voltage injection is analyzed in theregulation types on line transmission powers and the bus voltages. Firstly, amathematical model of DCIPC is established in the dq0coordinates; then the controlof voltage source converter is realized by using the indirect current control strategy:through the control of PWM modulation ratio M and phase-shifting angle and theinjected voltage of VSC, the transmission power and the bus voltage are regulated;finally the system of Dual power supply connected by tie line with DCIPC is made asan example, the functions of power and voltage continuous regulation in the IPC ofthe voltage injection type is verified.