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...

AI Technical Summary

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 of calculation, and PR The control always has the problem of poor dynamic performance

Proportional Complex Integral (PCI) control introduces a complex domain on the basis of PI control, making its gain at the fundamental frequency infinite, which can not only achieve zero-difference adjustment at the specified frequency, but also eliminate grid-connected The DC component of the current, but the ability of PCI control to suppress the higher harmonic component of the grid voltage and the ability to resist grid frequency disturbance is not strong

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