Automatic Voltage Regulating Research Based On New On-load Tap-changer

On-load tap-changing transformer has very important significance in the security and economic of power system by voltage regulating without cutting off the power load. On-load tap-changing transformer can stable the voltage of load center, it can also improve power quality and the efficiency of production; by controlling and adjusting the power flow between the networks, reduce the power loss in transmission. On-load tap-changer (OLTC) as the important components of the transformer, if we can improve its performance, it will be conducive to the using of the transformer in power system.Mechanical OLTC is widely used in the power system, but it has some disadvantages including low operating speed, large arcs, shorter lifetime and heavy size. The arcs can be basically solved by the Electronically Assisted OLTC, but operating speed and voltage control accuracy is not improved, so its application in the power system is restricted. Solid-state OLTC can improve the operating speed and reduce the failure rate, but this kind of switch needs many electronic devices, and the cost is very high. There is a lot of work to do in solving the heating and protecting during the operation.This paper presents a new OLTC, which can effectively solve the arcs and can also improve the operating speed. By using magnetic latching relay instead of the switch, eliminating the complicated mechanical driving mechanism to shorten the voltage regulating time, reduce the failure rate and the cost; it also enhance the controllability of regulating process, make it easy to realize automatic control. Through the reasonable design of the assisted circuit, using the parallel thyristor as assisted switch to reduce the arcs produced in the tap-changing process, the overvoltage circuit makes the trigger control is more effective and reliable; assisted circuit is paralleled with the main switch, just operating in the tap-changing process, which avoids the problem of heating and protecting.Based on the new OLTC the paper studies the automatic regulating, with the Single-Chip Microcomputer as the control chip, through designing the load voltage acquisition circuit, the switch control and power circuit, making reasonable regulating measures, writing the corresponding program to control magnetic latching relay and make the tap-changing automatically.Finally through the Proteus simulation software, build a model of the system. The correctness of the circuit design and programming in the scheme is verified, analysis the tap-changing transient process, observe voltage and current in different tap-changing time, research the effect of different nature of the load during the transient process and improve the scheme in view of the problems in the process of simulation.