Rotational coordinate transformation based current decoupling control method for three-phase grid-connected inverter

Abstract

The invention discloses a rotational coordinate transformation based current decoupling control method for a three-phase grid-connected inverter. With regard to a grid-connected inverter with an LCL (Inductor Capacitor Inductor) filter, an inversion three-phase output current signal and a grid-side three-phase current signal are transformed into two groups of orthogonal current signals in a synchronous rotation coordinate system through adopting coordinate transformation, the two groups of orthogonal current signals are subjected to the calculation of weighted average to be used as an inverter current controlled feedback signal and an inverter current controlled decoupling signal under a rotational coordinate system, the feedback signal is compared with a control given signal to obtain an error signal, and the obtained error signal is subjected to proportional-integral regulation and then is subjected to a combined operation with the decoupling signal to obtain a pulse duty-ratio signal for controlling a three-phase inverter switch to operate under the rotational coordinate system, so that output current waveform and amplitude control of the grid-connected inverter can be realized. Through adopting the method disclosed by the invention, the signal coupling problem existing in three-phase current control of the LCL filter three-phase grid-connected inverter can be effectively solved, the capacity of independently controlling each phase of output current is enhanced, and the favorable output current waveform of a grid-connected system can be achieved.

Description

technical field [0001] The invention relates to a control method for a three-phase grid-connected inverter, in particular to a current decoupling control method for a three-phase grid-connected inverter based on rotational coordinate transformation. Background technique [0002] Three-phase grid-connected inverter power supply with LCL filtering, its main circuit and control block diagram refer to figure 1 As shown, it usually includes a three-phase three-phase inverter circuit based on high-frequency switches, a three-phase LCL low-pass filter (three-phase symmetry) for inverter grid-connected connection, a three-phase current transmitter and a current detection circuit And the inverter controller, wherein the inverter controller includes a current control loop and a PWM pulse generator, and controls the output current during grid-connected operation to ensure the power quality of grid-connected power generation. Since the three-phase currents are interrelated, the three-p...

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Problems solved by technology

Traditional decoupling operations often select state variables from the system and use them directly for decoupling items. There are various problems such as large sampling amount of state variables, large calculation amount, and large interference of differential operations, which have great impact on the cost and control performance of the control system. had an adverse effect on

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