Voltage sampling circuit and controller applicable to dual-power automatic transfer switch

Abstract

A voltage sampling circuit applicable to a dual-power automatic transfer switch comprises a surge suppression and voltage detection circuit, an isolation amplification circuit and a level conversion and signal amplification circuit. An input end of the detection circuit is connected with a phase line and a neutral line for sampling voltage, and an output end of the detection circuit is connected with the isolation amplification circuit and used for suppressing interference signals coupled to a sampling voltage port and converting alternating current power frequency signals into first current signals I1 for output. An output end of the isolation amplifier circuit is connected with the level conversion and signal amplification circuit and is used for isolating and amplifying the first current signals I1 into second current signals I2 for output and improving interference resistance of the sampling circuit. The level conversion and signal amplification circuit 16 is used for converting the second current signals I2 into sampling voltage signals U2 which can be received by a microprocessing unit. The controller for the dual-power automatic transfer switch employs the voltage sampling circuit to achieve precision detection low in temperature influence for common and standby power supplies high in interference resistance, and comprehensive detection of voltage loss, undervoltage, overvoltage and three-phase unbalance.

Description

technical field [0001] The invention relates to a dual-power automatic transfer switch commonly used in a power supply system, in particular to a transfer switch with a voltage sampling circuit, which can be automatically controlled to realize comprehensive voltage detection and reliable and accurate conversion. Background technique [0002] The dual-power automatic transfer switch is an important electrical appliance in the power distribution system. Generally, the automatic transfer switch is connected to the common power supply and the backup power supply of the power supply system, and can automatically switch between the two power supplies to ensure the continuity of power supply to the load. and reliability. According to the different positions where the electrical appliances are installed in the circuit, the automatic transfer switch is divided into a power supply position, a power distribution position, and a load position changeover switch. [0003] The controller ...

AI Technical Summary

Problems solved by technology

This kind of high-end controller, such as the power supply phase failure detection device disclosed in the Chinese utility model patent CN2482094Y, its voltage vector sum detection method can only detect phase failure and three-phase serious unbalance detection, and cannot perform overvoltage and undervoltage Detection, single detection function

For example, the Chinese utility model patent CN200944134Y discloses the switching power supply failure monitoring circuit, which judges the three-phase unbalance, phase failure and power loss through the three-phase voltage vector and the optocoupler, and uses the transformer to step down the voltage. The dual measures of voltage measurement by single-chip A / D ensure the reliability of the above-mentioned voltage detection. However, it is extremely rare in the world that the capacitance accuracy is better than 5%. The capacitance is greatly affected by temperature, and the capacitor rectification method has large ripples. The final waveform distortion is considerable, so the accuracy of the voltage measured by the bridge capacitor rectification method is very low, and it is easy to cause overvoltage and undervoltage to advance or lag the conversion

Moreover, the voltage measurement in this prior art only measures single-phase and the accuracy is too low, and it is impossible to perform accurate over-voltage and under-voltage detection on all three-phase power supply voltages.

Another example is the controller disclosed in the Chinese utility model patent CN200976513Y. The common three-phase and standby A-phase voltages are stepped down through a transformer. After being rectified and divided by a rectifier bridge and a capacitor, the voltage is measured by a single-chip A / D, and its measurement accuracy is low. , and the detection of the standby voltage quality is not comprehensive

[0005] It can be seen that the currently used automatic transfer switch controllers using single-chip microcomputers and integrated circuits have a single voltage detection function, low detection accuracy of power supply voltage, no comprehensive detection of each phase of the common power supply and backup power supply voltage, and are greatly affected by temperature. The dual power switch is often mistakenly switched, which is easy to cause the defect of overvoltage, undervoltage, early or late switching

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