Research On Three-level Grid-connected Inverter And Control Technology

In order to guarantee energy security and ensure the healthy and stable economic development of the national economy,most countries and regions around the world are currently making energy transformations urgently to achieve sustainable energy development.Compared with fossil energy,nuclear energy and other energy,renewable energy has a series of unique advantages.Take the example of solar photovoltaic power generation,first of all,sunlight is everywhere,and sunlight can cover most countries and regions in the earth,and it is free from transportation,unlimited reserves,and easy to obtain.But solar energy needs to be processed before it can be used by humans.First,it is supposed to be transformed into direct current power through solar photovoltaic equipment,and then supplied to users after being connected to the grid through inverters.This paper mainly studied the three-level grid-connected inverter and control technology.The main research contents and methods are as follows:(1)This paper analyzed the working principle of the diode-clamped three-level gridconnected inverter,and a mathematical model is established,and then it introduced modulation methods and proposed control strategies.To eliminate some odd-numbered harmonics in the low frequency band of the control system,multi-resonance compensation control(MRCC)method suitable for control of three-level grid-connected inverters is proposed.Grid-connected control adopts a multi-resonance compensation control method to perform current closed loop and adjust PR parameters and performe phase compensation.For the neutral point balance of the DC side of the three-level gridconnected inverter,space vector pulse width modulation(SVPWM)method with time factor is adopted.Via MATLAB SIMULINK simulation analysis,it can be seen that the output current of the diode-clamped three-level grid-connected inverter system meets the grid-connected demands,and the current harmonic wave content is low.(2)A DSP-based diode-clamped three-level grid-connected multi-resonance compensation control(MRCC)inverter system was set up for experimental research,and the theoretical and practical design scheme about the system is introduced in detail,and the off-grid and on-grid experimental waveforms and experimental data were obtained,and finally the agility of the control method and the usability about the system were verified.