Study On Control Strategy For Photovoltaic Grid-connected Power System

The advantages of pollution-free, safe and reliable, short construction period and inexhaustible make the photovoltaic industry popular in the word.Research status in the word, power generation principle and system components of PV power generation are illustrated in this paper. The maximum power point tracking (MPPT) technology and grid-connected inverter control strategy are discussed. The above-mentioned two control strategies are improved based on the discussion of the traditional solutions. The followings are discussed in the paper:(1) The maximum power of the photovoltaic power generation system is easily affected by the external environment, and when the external environment mutations, the traditional MPPT algorithm (such as disturbance observer method and incremental conductance method) have the shortcomings of slow tracking speed, poor anti-disturbance ability and low tracking accuracy etc. To solve this problem, the traditional sliding mode variable structure control algorithm is adopted. Terminal sliding mode control algorithm is proposed based on the inadequacies of the traditional sliding mode control algorithm, and it can achieve finite time convergence of the state variables. So, the maximum power tracking precision is improved.(2) A high-performance control strategy is adopted to ensure that the grid-connected inverter output current waveform is sinusoidal and meet the requirements of unity power factor. The PI parameters of current loop of the traditional double-loop control strategy are not sensitive to the tracking current frequency, and this method makes tracking deviation is too large. So, a control strategy based on the PR controller is presented in this paper. This control strategy is a good solution to the problem of fast and accurate tracking the inverter output sinusoidal current. It does not require coordinate transformation, and has the advantages of harmonic compensation easy and simple calculation.