In the calculation, the following design requirements need to be met. First, the control circuit needs to realize energy storage, and secondly, the interlocking/closing action must be interlocked. That is, the closing and opening should not occur at the same time. In addition, in the power failure state, the sub-gate can still be completed. A closing a trip three times, and requires the opening of the closing action time interval Q3s, and then from the closing to the opening of the action time interval is 0. 1s In addition, but also to take into account the rapidity of charging, Comprehensive selection of circuit parameters ensures that the power MOSFETs and thyristors work safely and reliably. Taking into account the above factors, this paper proposes the main circuit structure of the sub-switching and closing control circuit of the permanent magnet operating mechanism. As shown in the ABB company developed in 1997, a vacuum circuit breaker with a permanent magnet mechanism of the VMI type is adopted. Bistable dual-coil structure This article uses a self-developed bistable single-coil structure (see), which has a simpler structure and higher reliability. Whether it is closing operation or opening operation, the excitation current passes through the same coil. And the indicators such as the quickness of operation are not lower than the operating structure of the bi-stable dual coil. This makes the commutation circuit commutation and other control methods are different from the bistable two-coil structure and its control circuit design is more complex. The control circuit designed in this paper solves these practical problems and achieves bistable Single coil permanent magnet mechanism control. It has passed technical appraisal and parameter selection in the type circuit. First, the value of the capacitor C3 should be determined according to the energy required for the closing action of the actuator, and then the charging time constant f=RiCb should be determined according to the requirements of rapidity of charging. After the AC voltage of the current resistance Ri is filtered by the D2C2 rectifier, the C4 is charged. At this time, the trigger signal 2 is at a high level, the power MOSFET Q2 is turned on to form the charging circuit 2, and at the same time, the trigger signal 4 is at a low level, the power MOSFET Q4 is turned off, and the opening circuit 4 is opened. The open-closing charging circuit formed at this time is shown in (b). According to the requirement of the energy required for the opening operation of the operating mechanism, the value of the capacitor C4 is selected. 2.2 The closing period When the closing signal arrives, the trigger signal 1 is low level. The power FET Qi is in an off state, and then the charging capacitor C3 of the charging circuit 1 is discharged, and the current flowing in the coil LG causes a change in the magnetic field in the permanent magnet mechanism to complete the closing operation. In order to prevent overvoltage across Q3, breakdown thyristor, composed of RbDb and C5 buffer circuit as shown in (c) As thyristor Qb does not have self-interruption ability, the closing loop current will always exist until the capacitor discharge ends according to the design. Requirements, closing process should be completed within 100ms. After a reasonable selection of the parameters of each component, closing circuit 3 can turn off the thyristor at 100ms. The design principle of the closing circuit is as follows: When the thyristor turns on, capacitor C3 starts to discharge, and coil LG has inductance L and internal resistance R. The circuit can be seen as a RLC series circuit. If the initial voltage of the (e) capacitor is Uc(0) and the initial current of the inductor is iL(0) at zero, the response in the circuit is the discharge of the capacitor C3 through the resistor R and the inductor L. As a result, there is the following equation: The maximum load can reach 160MW, which can meet the needs of the district's electricity 3.2.3 Residential area analysis The maximum expected load of the area in 2005 is up to 350MW, and the maximum output of full power generation is 300MW. In the case of a power grid with a power shortage of 70 MW and a power shutdown of 100 MW units, the power shortage is 170 MW. The power shortage in the district can only be fully loaded by the yuanzhuang 220kV station from the Yuanzhuang 220kV station and the Yuanzhuang 220kV station in the normal mode. It is no longer possible to supply power to the Suidian Community. The active current in the normal mode of the West Shuanghui return line is still 210MW (full of Fengning Hydropower), which is close to the thermal stability limit and has reached the allowable protection current value. Fengning Hydropower does not generate electricity in winter, and the new Shangying and Xiaoying 110kV stations are powered by the double-circuit lines. The double-circuit lines have no power supply capacity, so the problem of the card neck is more serious. Before the Zhouyingzi and Xingzhou 220kV stations are put into operation, Only the way of RBL 3.2.4 Yuanzhuang plot analysis The current capacity of 220kV station is 240MW. Under the normal mode, Yuanzhuang transformers only have Yuanzhuang cell load fully loaded, and Yuanzhuang 220kV station as a hub station is no longer able to The power supply in the residential area of ​​Suidian provides more unresolved problems in the N-1 overload of the main transformer. Only by perfecting the network structure, the Xingzhou 220kV station can be built as soon as possible to solve the equipment overload problem. 3.2.5 The Shushugou Community in Shushugou Community is expected to be in 2005 Maximum load 190 At the end of 2005, the maximum load of the residential construction project was 250MW), and the 220kV transformer capacity of the 220kV station at Yushugou was 240MVA. At the end of 2005, the main transformer was overloaded in the normal mode. Currently, only the main transformer at Yushugou station can accommodate the main transformer overload. , By the end of 2005, Baohe 220kV station will finally meet the power supply needs of the district and improve the 110kV network. 4 Conclusions and recommendations Substation and capacity of Chengde 220kV station before it goes into operation will not be satisfied The power demand, normal and overhaul methods all have power shortages, equipment overload, and low grid voltage. The grid will continue to face power shortages. Given current problems in the power grid, it is imperative to urge the construction of 220kV power transmission projects and Yushugou. The Rongchang 3 project will be put into operation as soon as possible, and the main network structure will be improved at the same time. The Zhouyingzi, Baohe and Xingzhou 220kV stations will be built and constructed to solve the problem of overloading the Yushugou main transformer in Yuanzhuang and to strengthen the double-necked card neck problem in western Fujian. The Chengde Power Grid is in contact with the external power grid. With the ability to add electricity to the power grid, only the construction of a 500 kV power station at Chengde Power Grid can completely solve the weak network structure of Chengde Power Grid, and at the same time meet the power supply requirements and directly engage in power grid operation.
(Continued from page 16) ((1)) is a computer simulation result; U) is a digital oscilloscope output result. This figure shows the waveform of the voltage across the capacitor G during charging, that is, the rectified waveform of the AC voltage.
It can be seen that the two experimental results are the same.
(b) In order to charge the voltage across the charging capacitor C3 during the charging process, it is required to complete the charging of the capacitor G for 8 seconds so that the voltage can reach 300V. It can be seen that the simulation results are in line with the design requirements. The output waveform of the digital oscilloscope also fully complies with the design requirements. (C is computer simulation waveform; (C2) is the result of physical experiment. This figure is the waveform of the voltage across capacitor C3 during the closing process. It can be seen from the figure that the voltage of capacitor C3 is first reduced to zero and then reversed, ie, the energy is released first. The process of reverse charging, and the entire process is completed within 100ms and is consistent with the circuit analysis results. Conclusion This paper proposes a new type of control circuit for a vacuum circuit breaker with a permanent magnet mechanism, giving a detailed analysis of its structure and working mechanism. Computer simulation experiments and physical experiments have shown that the experimental results are in line with the design requirements. This new type of control circuit has passed reliability testing and is applied to practical equipment. It solves the problem of sub-closing control of single-coil permanent magnet mechanisms. A new type of permanent magnet mechanism vacuum circuit breaker with electronic operation has broad application prospect and practical value
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