Research On Photovoltaic Inverter Control With Harmonic Control Function

With the rapid development of new energy power generation,the number of PV inverters increased significantly,but the current PV inverter only has the basic power conversion function,and still causes the power grid harmonic pollution,voltage fluctuations and other power quality problems,so,photovoltaic inverter with no power quality perturbation,and even to help the grid to improve the power quality,will be the future trend.Traditional multi-function inverter with active filter function mainly uses the conventional active filter method,need to detect the harmonic current of other circuits for harmonic control,which makes these photovoltaic inverter useless in reality.The main purpose of this paper is to study a harmonic voltage that only needs to detect the grid access point.And by using the harmonic damping control strategy proposed in this paper,the photovoltaic inverter can improve the power quality.In this paper,the three-level photovoltaic inverter is firstly studied,and the mathematical model of the three-level photovoltaic inverter with midpoint clamp is established.The PI parameters of the inner and outer loop are designed,and bulid simulation model with PSCAD / EMTDC.In this paper,focusing on the limitation of the harmonic compensation method of the traditional active filter,a harmonic damping active filter control based on the detection of the harmonic voltage of the access point is proposed.And the power maximization control strategy is proposed.Because of the existence of positive,negative and zero sequence components in the harmonic of the power grid,the vast majority of PV inverters can not compensate the zero sequence components.It is proposed to compare the positive and negative sequence components of harmonic voltage and current respectively.Based on the comparision of multi-rotation coordinate system,DFT and FFT algorithm,an algorithm based on FFT for detecting positive and negative sequence components is proposed.The algorithm is fast,accurate and consumes less resources,and is very suitable to use in photovoltaic inverters.Based on the study of photovoltaic inverter and harmonic damping control algorithm,this paper simulates the harmonic damping strategy based on positive and negative sequence detection.On this basis,the algorithm of maximizing the absorption harmonic power is simulated,and the spectrum leakage and zero sequence component problem encountered in equipment development were also simulated.A multi-function inverter with harmonic damping active filter based on TMS320F28335 is designed.The detailed design process is given from the aspects of overall system design,main circuit topology,secondary circuit and software algorithm.The experimental results show that the theory of harmonic damping control and the correctness of the simulation,laid an important foundation for the future of photovoltaic power generation to become a green power generation.