Quasi-PCI and PI combined control single-phase photovoltaic grid-connected inverter current control method

Abstract

The invention discloses a quasi-PCI and PI combined control single-phase photovoltaic grid-connected inverter current control method in the technical field of new energy photovoltaic power generation.The method comprises the following steps of: adding a cut-off frequency into a proportional complex integral (PCI) controller to form a quasi-PCI controller; realizing a complex number field in a single-phase quasi PCI through a lag output item of a second-order generalized interactor (SOGI); taking a difference value between a given grid-connected current iref and an actual grid-connected current iL as the input of the quasi-PCI controller; taking a difference value between a grid-connected current direct current quantity reference value IL-dc and a grid-connected current direct current quantity as an input of a PI controller; and after the output of the quasi PCI controller and the output of the PI controller are added, controlling the switching-on and switching-off of an inverter switching tube through PWM modulation. According to the invention, the influence of power grid voltage fluctuation and frequency offset on the grid-connected current is suppressed, the direct-current component of the grid-connected current is eliminated, and high-quality control is realized while the design of a non-isolated photovoltaic grid-connected inverter current controller is simplified.

Description

technical field [0001] The invention belongs to the technical field of new energy photovoltaic power generation, and in particular relates to a current control method of a single-phase photovoltaic grid-connected inverter controlled by quasi-PCI and PI joint control. Background technique [0002] With the increasingly serious problem of fossil energy crisis and environmental pollution, solar energy, which is clean, environmentally friendly and renewable, has entered the stage of large-scale development and utilization. The main way to utilize solar energy is to generate DC power through photovoltaic panels, and then transmit AC power to the grid through grid-connected inverters. In order to obtain AC power that meets grid-connected requirements, it is necessary to select an appropriate grid-connected current control technology for the inverter. At present, the current control technologies of single-phase photovoltaic grid-connected inverters are widely used: proportional int...

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Problems solved by technology

PI control is simple and easy to implement, and can eliminate DC steady-state error, but it cannot realize no-difference adjustment to AC volume; repetitive control can correct voltage cycle by cycle, has good steady-state output, and can realize AC volume theoretically. No-difference adjustment, but it has a one-cycle output delay, so the dynamic response is not good; PR control can achieve no-difference adjustment to the fundamental frequency, but in practical applications, PR control is at least a second-order system, with a large amount o

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