| As a new type of transmission technology, HVDC Light uses all-controlled power devices and the technology of pulse width modulation, which makes the HVDC light technology have its own technical advantages. HVDC Converter has the advantage of simple structure、small volume and strong function, which can effectively compensate for the defects of conventional HVDC to passive network power supply system. Therefore, HVDC Light technology has gradually become a hot spot of research in power system. The paper focuses on research of dynamic and simulation for HVDC Light system in passive networks.According to the topology of 3-phase and 2-level voltage source converter,the system structure, working principle and power transmission characteristic of the HVDC Light are studied and the SPWM modulation trigger principle、inverter commutation of SVPWM trigger principle for rectifier converter are analyzed. Based on the constraints of the system voltage,current, P and Q, a dynamic mathematical model for the voltage source converter in dq0 coordinates is established and control strategy of HVDC Light system and the selection of the system parameters are studied.Based on the analysis of the basic control principle of the HVDC Light system, DC voltage control mode in rectifier side and AC voltage control mode are designed, the double closed-loop control structure of inner current and outer voltage for transmission system are established, the independent control of d axis and q axis electric current are achieved, and DC-side voltage are corrected in fuzzy PID control method.On the basis of Matlab/Simulink simulation software, simulation model of HVDC Light system power supply to passive network and SVPWM Modulation technology are established,and the results of active power、reactive power, current voltage of DC system are obtained. The simulation results show that SVPWM modulation method effectively improvesthe utilization ratio of DC voltage and realizes the independently control for active and reactive power. |
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