Phase-locked loop compensation control circuit based on first-order complex vector filter under weak power grid

Abstract

The invention relates to a phase-locked loop compensation control circuit based on a first-order complex vector filter under a weak power grid, and belongs to the field of electronic circuits. The novel first-order complex vector filter is connected in series in front of a phase-locked loop and a common coupling point voltage feed-forward channel, and stability analysis is performed by using an equivalent impedance model of a grid-connected system. Theoretical analysis shows that the method reduces the influence of disturbance quantities such as power grid impedance and phase-locked loop bandwidth on the equivalent output impedance of the inverter, a control system can still have enough stability margin when the power grid impedance changes in a wide range, and the robustness of the grid-connected inverter is improved. Finally, the effectiveness of the method is verified through a simulation result.

Description

technical field [0001] The invention belongs to the field of electronic circuits, and relates to a phase-locked loop compensation control circuit based on a first-order complex vector filter under weak power grids. Background technique [0002] Generally speaking, the introduction of a large number of nonlinear loads in the power grid leads to the existence of background harmonics in the PCC voltage at the common coupling point. As the disturbance of the grid-connected control system, the grid-connected current of the inverter will contain harmonic components of the same frequency, which will seriously affect the On-grid power quality. In order to reduce the influence of grid voltage background harmonics on grid-connected current distortion, the method of suppressing background harmonics through PCC voltage proportional feedforward has been widely used. However, in the weak grid, the grid-connected control system will couple with the positive feedback channel of the traditi...

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Problems solved by technology

For example, some literatures have derived the frequency-domain expression of the phase-locked loop output phase angle, and proposed an adaptive PLL control strategy to enhance the robustness of the PLL system, but this method needs to calculate the d-axis component of the PCC voltage in real time; There are literatures to improve system stability by establishing a PLL small-signal model considering grid impedance and PLL output phase angle compensation correction, but the design of this method is relatively complicated

[0007] In summary, the influence of PLL and grid voltage feed-forward on the stability of grid-connected inverters under weak grid conditions has not been fully resolved

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