A Phase Locking Method Based on Instantaneous Virtual Reactive Power Detection

Abstract

The invention relates to an instantaneous virtual reactive power detection-based phase lock method. The method includes the following steps that: phase-locked loop output voltages are adopted as three-phase alternating-current power source voltages which are connected with three-phase grid voltages through virtual resistors, and the difference values of the alternating-current power source voltages and the three-phase grid voltages are calculated, so that voltage drops on the virtual resistors can be obtained; the voltage drops on the virtual resistors are divided by a virtual resistance value, so that virtual current passing through the virtual resistors can be obtained through calculation; an instantaneous virtual reactive power value outputted by an alternating current power source can be obtained through calculation; the three-phase instantaneous virtual reactive power which is obtained through calculation is inputted into a loop filter; the output of the loop filter and the rated frequency of a power grid are added together, and the addition result is adopted as phase-locked loop output voltage frequency; after the phase-locked loop output voltage frequency passes through a voltage-controlled oscillator, the phase of the phase-locked loop output voltage can be obtained; and the phase-locked loop output voltage of which the phase is changed is fed back to an input end; and the above steps are repeated, so that a closed-loop feedback loop can be formed.

Description

Technical field: [0001] The invention belongs to the technical field of phase-locked loops, and in particular relates to a phase-locking method based on instantaneous virtual reactive power detection. Background technique: [0002] In distributed grid-connected inverters, active power filters, static var compensation devices and other systems, it is necessary to monitor the phase and frequency of the grid voltage in real time, so as to control the normal and stable operation of the system. This requires a stable and reliable phase-locking method to accurately obtain information on grid voltage phase and frequency changes in real time. Compared with the traditional hardware phase-locked loop, the software phase-locked loop can overcome the temperature drift phenomenon existing in the analog circuit, and has higher phase-locked precision and stability. Therefore, software phase-locked loops have received more and more attention in the field of power electronic control. [00...

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Problems solved by technology

[0004] Although the phase-locked loop method based on the synchronous reference coordinate system can meet the requirements of tracking the voltage phase of the power grid, it needs a series of coordinate transformations, the control structure is relatively complicated, and it is impossible to completely eliminate the third harmonic interference in the three-phase power grid.

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