Research On High-power PV Grid-connected Inverter Control Strategy

As an important alternative energy of21st century, Photovoltaic power generation is getting more and more extensive application as it has advantages such as rich resources, free pollution and building integration. But as it is a kind of intermittent energy sources, there are still many technical problems in the grid application need to be addressed, especially high-power photovoltaic(PV) grid system, the impact on power grid power system should not be neglected. Therefore, based on the single-stage high power photovoltaic grid-connected inverter, the control system was analyzed, and is verified by simulation and experiment.First, this article made mathematical modeled about photovoltaic cell, and set up simulation model with single-peak and multiple-peak output characteristic. Analyzed about commonly used MPPT algorithm, proposed a variable step disturbance observation method, and connecting with the power prediction algorithm can solve the misjudgment problem which happened using commonly algorithm. In addition, based on global scanning method for simulation model under multiple peak feature. The above algorithm is verified by simulation.This article set up mathematical modeled about two level parallel three-phase photovoltaic inverter, deduced the coordinate transformation based on general vector transformation, constructed double closed-loop control based on current feed forward decoupling, using LCL-filter derived and used the active damping control strategy based on capacitive current feed forward, and verified by simulation.Studied on the influence of the grid photovoltaic about Unbalanced three-phase power grid condition, based on trap processing of positive and negative sequence separation technology, with double current loop closed loop control strategy, and improved the commonly used dq-axis software phase-lock-loop can make the control system stability with locking the fundamental component of positive sequence voltage to achieve the goal of stable phase lock. Through simulation to validate the control algorithm.Islanding effect mechanism was studied, in view of the LCR load in parallel, analyses the commonly used active island prevention strategies. On the basis of disturbance prevention island detection method using reactive power, the reactive power scopes of perturbation and disturbance cycle are analyzed. Through the simulation verify the effectiveness of the reactive power perturbation algorithm.On grid inverter main circuit parameters is designed, and the hardware configuration and software interrupt program of the control system has carried on the narration. Finally, in order to verify the system performance, in view of the CGC/GF001:2009standard requirements specified in the test.