Research And Application Of DC-side Small-signal Model Of A PWM Converter With A DC Voltage Controller

Along with the shortage of global energy and the increasing demand of electricity,the grid scale expands rapidly.The existing city power grid are also beginning to expose various problems,such as space truss structure is weak,the short circuit current is larger and the shortage of dynamic reactive power.Therefore,it is an urgent need to adopt a more flexible,economical and environmentally friendly way of transmission.At the same time,because of the rapid development of new energy technology,the future of distributed power supply and micro network widely access will lead to the height of the grid power supply diversification.Therefore,DC power distribution network based on VSC in future urban power grid has considerable potential applications.DC power distribution lines usually contact AC power grid with PWM inverter,therefore,inverter DC side model is directly related to analysis and design of DC network.The right to establish the mathematical model of PWM rectifier is the basis to research and analysis the mathematical of rectifier.Scholars from various countries have proposed a number of mathematical models on PWM Rectifier,including continuous and discrete mathematical model based on coordinate transformation,the mathematical model of the low frequency transformer,small-signal model,etc,and the mathematical model of a thorough theoretical study.However,the model is not only a very large amount of calculation,it is difficult to apply to complex network analysis and calculation,and did not take into account the influence of the DC voltage control.This paper established the DC micro contact network and communication in the grid inverter control model,combined with the inverter AC voltage balance equation,through the exchange of inverter AC/DC side active balance equation of linearization,inverter DC side of the small signal model,and further transformation to get composed of resistance and inductance in parallel inverter DC input impedance.Then the circuit model was applied to the stability of the DC micro network analysis,analysis of the inverter control parameters effect on the stability of the DC micro network.PSCAD simulation results verify the effectiveness of the proposed equivalent circuit model.