Digital phase locking method suitable for balanced three-phase power grid

Abstract

The invention provides a digital phase locking method suitable for a balanced three-phase power grid. The method comprises the following steps of: initializing the frequency of a first cyclic wave of A-phase power grid voltage ua to be 50Hz; setting the frequency of each of the other cyclic waves of ua to be the that of the last cyclic wave of ua, which is detected through a zero-crossing point detection circuit, and if the frequency is detected to be abnormal, transmitting a frequency failure alarming signal; and if the frequency is detected to be normal, performing multiplication between the frequency of a current cyclic wave of ua and the time Deltat of a corresponding counter and related simple operation to obtain a phase angle ThetaA of the A-phase power grid voltage ua and further obtain a phase angle ThetaABC of the balanced three-phase power grid. The digital phase locking method is quick, accurate, stable and reliable, and the dynamic by-the-cyclic-wave refreshing of the balanced three-phase power grid is realized.

Description

technical field [0001] The invention relates to the application field of three-phase power grid control technology, in particular to a digital phase-locking method suitable for a three-phase balanced power grid. Background technique [0002] At present, the phase-locking method applied to the three-phase power grid is generally a phase closed-loop control method composed of a phase detector, a loop filter and a voltage-controlled oscillator. When the closed-loop is adjusted to a steady state, the phase of the output signal and the input signal , The frequency is synchronized. This phase-locked method mainly has the following disadvantages: (1) The phase-locked loop tracking method is essentially a kind of differential tracking. The error is more obvious; (2) The synchronous response speed is slow. There is a tracking delay in the phase-locked loop, and it cannot track the phase change in real time. When the frequency or phase changes greatly, it will take a certain time to...

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Problems solved by technology

This phase-locked method mainly has the following disadvantages: (1) The phase-locked loop tracking method is essentially a kind of differential tracking. The error is more obvious; (2) The synchronous response speed is slow

There is a tracking delay in the phase-locked loop, and it cannot track the phase change in real time. When the frequency or phase changes greatly, it will take a certain time to track the phase change; (3) If the phase-locking method is implemented in hardware, it will be necessary to design a more complex hardware circuit At the same time, it is necessary to solve some difficult problems on the hardware, such as DC zero point drift, device saturation, initial calibration, etc.; if this phase-locking method is implemented by software, the calculation will be more complicated, the real-time performance is poor, and the system is reliable. sex is also poor

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