Current control method of single-phase photovoltaic grid-connected inverter with quasi-pci and pi joint control

Abstract

The invention discloses a current control method of a single-phase photovoltaic grid-connected inverter under combined control of quasi-PCI and PI in the field of new energy photovoltaic power generation technology, including adding a cut-off frequency to a proportional complex integral (PCI) controller , constituting a quasi-PCI controller; realize the complex domain in single-phase quasi-PCI through the hysteresis output of the second-order generalized integrator (Second-Order Generalized Integrator, SOGI); the given grid-connected current i ref and actual grid current i L The difference is used as the input of the quasi-PCI controller; the grid-connected current DC reference value I L‑dc The difference with the grid-connected current DC is used as the input of the PI controller; the output of the quasi-PCI controller is added to the output of the PI controller, and then the switching tube of the inverter is controlled to be turned on and off through PWM modulation. The invention not only suppresses the influence of grid voltage fluctuation and frequency offset on the grid-connected current, but also eliminates the DC component of the grid-connected current, and realizes high-quality control while simplifying the design of the current controller of the non-isolated photovoltaic grid-connected inverter.

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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