| With the increase in the demand for electrical energy in the whole society,traditional energy based on fossil energy is no longer suitable for environmental protection and sustainable development requirements.Therefore,clean energy such as photovoltaic power generation and wind power generation have been widely developed.Due to its own development advantages,distributed photovoltaic power generation has become the main form of photovoltaic utilization in the future,but there are still many problems at this stage.The stable operation of traditional power grids is inseparable from the inherent rotational inertia and damping characteristics of synchronous generators.After large-scale grid-connected distributed photovoltaics based on power electronic components,their own inertia-free damping and randomness have led to grid regulation.Ability and anti-interference ability are severely reduced.Virtual synchronous generator technology is a scheme that enables the inverter power supply to have the characteristics of a synchronous generator.This paper aims at a distributed photovoltaic grid-connected system consisting of photovoltaic cells,small-capacity super capacitors,DC-DC converters,DC-AC converters,etc.,and adapted a virtual synchronous generator scheme.The specific work is as follows:1)The mathematical model and engineering model of photovoltaic cells are summarized,and the photovoltaic cell engineering model is used to analyze its output characteristics on the MATLAB platform;the principle of photovoltaic cell maximum power tracking and the boost circuit model are introduced in detail,and established on the MATLAB / Simulink platform The maximum power tracking control model of disturbance observation method was verified by simulation.2)A small-signal model of bidirectional DC-DC circuit based on complementary PWM control is researched,and a super capacitor charge-discharge control system is designed on the basis of this;a limited port condition is proposed to quickly determine the ripple inductance and capacitance parameters.The method was established and simulated on the MATLAB / Simulink platform to analyze the ability of the super capacitor tosuppress the voltage fluctuation of the equivalent load terminal through the bidirectional DC-DC converter.3)The working mechanism of single-phase inverter and three-phase inverter is introduced.The mathematical model of three-phase inverter in static coordinate system and rotating coordinate system is analyzed,and the decoupling of inverter is deduced.Inner loop control model;A virtual synchronous generator control strategy for distributed photovoltaic-small capacity super capacitor grid-connected systems is proposed,and the effectiveness of the grid-connected system is verified by simulation on the MATLAB /Simulink platform. |
