Self-adaptive grid-tied converter single phase soft phase-locked loop

Abstract

The invention discloses a self-adaptive grid-tied converter single phase soft phase-locked loop. The self-adaptive grid-tied converter single phase soft phase-locked loop comprises a phase discriminator, a low pass filter, a loop filter and an integrator module, wherein the loop filter is composed of a self-adaptive moving average filter and a proportion integration differentiation (PID) regulator, the phase discriminator is a multiplication phase discriminator, an input signal is a trigonometric function of an output angle of power grid voltage and a phase-locked loop, and an output signal is transmitted into the moving average filter; an input signal of the moving average filter is output of the phase discriminator and output of the low pass filter, and the output signal is transmitted to the PID regulator; and an input signal of the PID regulator is an output signal of the moving average filter, and the output signal is transmitted into the low pass filter and the integrator module. The self-adaptive grid-tied converter single phase soft phase-locked loop has the advantages that the loop filter is improved, effects of secondary ripple and harmonic voltage on phase lock result in the steady state are eliminated, and simultaneously the rapidity of the phase lock is guaranteed.

Description

Technical field: [0001] The invention belongs to the field of electrical engineering, and relates to a single-phase soft phase-locked loop for an adaptive grid-connected converter, in particular to a grid voltage software phase-locked loop based on an adaptive sliding window filter. Background technique: [0002] Grid-connected converters (PWM rectifiers, photovoltaics, wind power, APF, SVG, etc.) need to obtain accurate grid phase information for normal operation, which is particularly important in low-voltage ride-through and other occasions that need to quickly and accurately obtain the positive and negative sequences of the grid. The current phase-locked loops include: voltage zero-crossing point phase-locking, which mainly obtains grid phase information by detecting the grid voltage zero-crossing point. This method is generally implemented by hardware circuits. When the voltage distortion is large, there are multiple zero-crossings, which will lead to Phase-locked failu...

AI Technical Summary

Problems solved by technology

The current phase-locked loops include: voltage zero-crossing point phase-locking, which mainly obtains grid phase information by detecting the grid voltage zero-crossing point. This method is generally implemented by hardware circuits. When the voltage distortion is large, there are multiple zero-crossings, which will lead to Phase-locked failure; the loop filter adopts PI control phase-locked loop, this method is to apply the analog hardware phase-locked loop method in software, there is a contradiction between phase-locked speed and elimination of secondary ripple, which cannot be solved well, this The structure of a phase-locked loop is as figure 1 As shown; based on the synchronous coordinate system phase-locked loop, it mainly constructs a three-phase voltage through the fundamental wave voltage, and then transforms it into the synchronous coordinate system through coordinate transformation, and controls the d-axis or q-axis voltage to zero to realize the grid phase locked, a typical structure such as figure 2 As shown, this method will have a relatively large phase-locking error when the harmonic is relatively large; the dual-DQ coordinate system phase-locked loop, this method also constructs a three-phase voltage, and then uses two coordinate transformations to improve the efficiency of the negative sequence voltage of the power grid. The influence of the phase-locked loop of the synchronous coordinate system is an improved phase-locked loop of the synchronous coordinate system, but this method is more complicated to calculate, and has poor adaptability to frequency changes and poor dynamic tracking performance of the phase; based on the digital notch filter The soft phase-locked loop, this method essentially eliminates the influence of the negative sequence voltage of the power grid on the phase-locked loop of the synchronous coordinate system. Similarly, this method is relatively complicated, takes up more computing resources, and has a good effect on the elimination of harmonics. poor

[0003] And due to the special structure of the single-phase phase-locked loop, the output phase detector of the phase-locked loop will have relatively large secondary fluctuations, which will cause secondary fluctuations in the locked phase of the phase-locked loop. Large harmonics will also cause the phase-locked loop to produce fluctuations that are integer multiples of the fundamental wave

If the traditional phase-locking method is used, the loop filter uses a PI regulator. If a large adjustment coefficient is selected, the phase-locking speed will be fast, but the phase-lock output fluctuates greatly, and the result is inaccurate; if a small adjustment coefficient is selected, although the fluctuation will be reduced. Small, but the phase-locking speed will be greatly reduced, and it is difficult to meet the requirements of low-voltage ride-through

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