Filter out the high frequency part of the pulsating voltage to get the envelope of the pulsating voltage, and after rectification, get the lower half of the envelope of the pulsating voltage, which is a voltage containing synchronization information, called the whole step voltage.

The characteristics of the step voltage are: (1) The step voltage changes periodically with the phase angle difference δ; (2) The step voltage changes periodically with time t, and when δ changes for a period from 0 to 360, the pulsating voltage also changes for a period, which is also the period of the step voltage; (3) The lowest point of the whole step voltage reflects the size of the voltage difference.

The main function of linear step voltage is to provide voltage signal with corresponding waveform for load.

The linear step voltage is divided into three parts. 1, shaping circuit 2, phase sensitive circuit 3, filtering circuit.

1 shaping circuit converts the voltage sine wave of generator and system into square wave with the same frequency and phase;

2. The phase-sensitive circuit passes the square wave through the XOR gate at the same time, and outputs a high level when the two levels are the same, otherwise it is a low level;

The filter circuit consists of a low-pass filter and an emitter follower, and the linear waveform of linear step voltage and phase angle difference is obtained.

Automatic quasi-synchronization is based on the principle of frequency difference check, pressure difference check and constant lead time, and is synthesized by time program and logic circuit according to certain control strategy, which can successfully complete the basic requirements of quasi-synchronization juxtaposition. ASA for short.

Automatic quasi-synchronous device is a special automatic device. Automatically monitor the voltage difference and frequency difference, analyze and calculate the appropriate synchronization time, and issue a closing command ahead of time to ensure that the circuit breaker is connected to the grid at an ideal angle, so that the circuit breaker can be closed when the phase angle difference is 0. The microcomputer automatic quasi-synchronization device has been able to complete the in-phase point grid connection for the first time after starting the synchronization.

The device is equipped with automatic voltage regulation and frequency modulation unit, which sends out control pulse when the pressure difference and frequency difference do not meet the conditions. If the frequency difference does not meet the requirements, automatically adjust the speed of the prime Mover, increase or decrease the frequency, and promote the arrival of the same period; If the voltage difference does not meet the requirements, automatically adjust the generator voltage to make it close to the system voltage.