Research On Dynamic Phasor Modelling And Control Strategy Of High Voltage Direct Current System

In order to serve the rapid development of economical society of our courtry,and make use of the coal,hydropower,wind,light and other primary energy in the Central and Western China,the power grid of our courtry has been developed fast in the last decades and become a grid with the structure that most of energy center is located in the Central and Western China and load center is located in the Central and Eastern China,electricity is transmitted from the western areas to Eastern China,the northern power grid is connected with the southern power grid together,the AC and DC system operate parallellly.Mainly for the development of the AC and DC system and the wind power in the power grid of our country,in order to supply a new modelling and simulation method for the AC and DC system dynamic perfomance analysis and reasonable High Voltage Dirrect Current(HVDC)system emergency power support control strategy and the transmitted power of the HVDC system follow the fluctuation of wind power control strategy,the paper focuses on the dynamic phasor modelling of HVDC system which can reflect the harmonic characteristic of converter,the three-phasor dynamic phasor modelling of HVDC system which can reflect the dynamic characteristic of HVDC system under asymmetrical faults of AC system,electromagnatic-dymanic phasor hybrid simulaiton of the power system with power electronic device and AC-DC system and the HVDC system emergency power support control strategy based on adaptive dynamic surface control and the transmitted power of the HVDC system follow the fluctuation of wind power control strategy based on constant power control strategy,the contents as follows:(1)An HVDC system dynamic phasors model including the model of converter,DC line and controller based on dynamic phasors theory which can reflect the harmonic characteristic of the converter of HVDC system is proposed,and the simulaiton process of HVDC system dynamic phasors model is analyzed.The simulaiton results show that the proposed HVDC system dynamic phasors model can reflect the dynamic performances of the HVDC system,especially the harmonic characteristics of the converter in AC system side,when the dynamic phasor model of converter which is a algebraic model and a large simulation step are used.This proposed model improve the modelling of HVDC system based on dynamic phasor.(2)In order to improve the appliability of the HVDC system dynamic phasors model,a HVDC system three-phasor dynamic phasor model including the model of converter,DC line and controller used under AC system asymmetrical condition is proposed,and the simulaiton process of HVDC system three-phasor dynamic phasors model is analyzed.The simulaiton results show that the proposed HVDC system three-phasor dynamic phasor model can reflect the dynamic performance s of the HVDC system under AC system asymmetrical condition when the dynamic phasor model of converter which is a algebraic model and a large simulation step are used.This proposed HVDC system three-phasor dynamic phasors model improve the applicability of HVDC system under asymmetrial condition of AC system.(3)In order to take advantege of the electromagnetic transient modelling method in building the model of AC system and the dynamic phasors modelling method in building the model of power eletronic device,a electromagnetic transient-dynamic phasor hybrid simulation method of power system with power electronic device where the electromagnetic transient model and dynamic phasor model are used to build the model of AC system and power eletronic device respectively is proposed,model partition and mutual equvalent method are analysed,and the AC-DC system is used as a example to analyse the simulation process of electromagnetic transient-dynamic phasors hybrid simulation.The electromagnetic transient-dynamic phasor hybrid simulaiton of AC-DC system is achieved by using the proposed dynamic phasor model of HVDC system which can reflect the harmonic characteristics of the converter of HVDC system.The simulation resluts show tha t the proposed hybrid simulation can reflect the dynamic charecteristic s of AC-DC system by using the dynamic phasors model which is simpler than electromagnetic model and a large simulation step.A new hybrid simulation method of the power system with power electronic device is proposed.(4)An HVDC wide area emergency power support control strategy based on adaptive dynamic surface control is proposed.This strategy which can deal with the unkown modelling error and extenal disturbance is desigened by using the center of inertia(COI)equavilent model of AC-DC system based on the global information of AC-DC system measured by the wide area measurement system(WAMS)and the dynamic surface control strategy and adaptive control theory.The stability of the AC-DC system controlled by the control strategy is proved based on Lyapunoe function method.The simulation analysis of this proposed control strategy is made and the simulation results show that this control strategy is adaptive and robustness for different operation modes and faults and robustness for time delay of signal.What's more,the performance of this control strategy is better than the HVDC emergency control strategy based on the pole placement method and ba ck stepping method.(5)A control strategy of HVDC system for wind-thermal-bundled power system transmitted by HVDC system based on the constant power control strategy to make the transmitted power of the HVDC system follows the wind power fluctuation and to transmit the power fluctuation of the sending area with weak ability of peak regulation and frequency modulation cased by the wind power to the receiving area with strong ability of peak regulation and frequency modulation is researched.Meanswhile,a scheme that SVC replaces the conventional reactive compensation device to reduce the action times of the conventional reactive compensation device when the transmitted power of HVDC system follows the wind power fluctution is researched and the coordinate control strategy between the SVC and conventional reactive compensation device is researched.The simulation analysis of the control strategy is made and the simulation results show that the proposed control strategy is feasibility and effectiveness.