SAI phase-locked loop method applicable to non-ideal power grid

Abstract

The invention discloses an SAI phase-locked loop method applicable to a non-ideal power grid. The method comprises steps of: extracting three-phase power grid voltage, transforming the power grid voltage to a [alpha][beta] coordinate system through Clarke transform, extracting the positive sequence fundamental wave of the voltage transformed to the [alpha][beta] coordinate system by using an SAI regulator, subjecting the extracted positive sequence fundamental wave to Park transform in order to transform the same to a dq coordinate system, passing the output of a q axis through a PI regulatorto obtain the synchronous angular frequency of the power grid, and obtaining the phase angle of the power grid after integration. The method not only can accurately track the phase under the balance state of the power grid, but also can accurately obtain a power grid synchronization signal under non-ideal power grid environments such as three-phase imbalance, voltage sag or swell, harmonic pollution and frequency jump, greatly expands the application of the phase-locked loop, and improves tracking accuracy of the power grid synchronization signal.

Description

technical field [0001] The invention relates to the field of modulation and control of power electronic power converters, in particular to a SAI phase-locked loop technology suitable for non-ideal power grids in conditions such as three-phase unbalance, voltage drop or sudden rise, harmonic pollution and frequency jump. Background technique [0002] It is the main function of the phase-locked loop to track and lock the phase of the AC signal and, if necessary, provide information about the frequency and amplitude of the signal. In the PWM rectifier control, in order to realize the active and reactive power control on the grid side, it is necessary to dynamically obtain the phase information of the grid voltage, so that the phase-locked loop is used to lock the grid voltage. In practical applications, especially in large-scale new energy grid-connected power generation occasions, PWM rectifiers are often required to adapt to the operation of non-ideal grid environments (three...

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Problems solved by technology

[0004] When the grid voltage is balanced, the grid voltage only has positive sequence components. At this time, the traditional SRF-PLL can accurately track the synchronization signal of the grid voltage. When the grid voltage is unbalanced, due to the introduction of negative sequence components, the traditional SRF-PLL It is difficult to achieve satisfactory results

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