Power grid alternating current flexible loop closing control device and control method thereof

Abstract

The invention discloses a power grid alternating current flexible loop closing device and a control method thereof. The device is a series-parallel connection device and comprises a series connection coupling unit, a parallel connection coupling unit, other bypass switch circuits and a loop closing main controller. After a loop closing instruction is received, the loop closing control device is set to work in a voltage control mode, and when the amplitude and the phase of the output voltage of the device side coincide with the other section, the system enters a loop closing state. And after entering a loop closing state, the device works in a PQ control mode. Before loop closing is quitted, P and Q of the device are gradually reduced to zero, then the access switches are sequentially disconnected, and the loop closing process is finished. The device has the advantages that the device is simple in structure, low in cost and high in efficiency, the voltage amplitude and phase of a loop closing point can be adjusted online, active and reactive power flow between loop closing areas can be adjusted online in a bidirectional mode, and the power factor of the loop closing areas is kept at the optimal value. Flexible power supply transfer between the distribution networks and rapid exit during a fault can be realized, and the load rate and the load balance of a distribution network power supply area are improved.

Description

technical field [0001] The invention belongs to the technical field of distribution network optimization operation control, and in particular relates to an AC flexible loop closing control device for power grid and a control method thereof. Background technique [0002] my country's distribution network usually adopts the method of "closed-loop design, open-loop operation", that is, when the power grid is closed, the network structure can be optimized by adjusting the state of the contact switch and the segment switch, so as to maintain the efficient and reliable operation of the distribution network and realize the fault area. Quick power restoration. However, this method of realizing closed-loop operation through tie switches cannot achieve flexible power control because the power flow is naturally distributed with impedance. When closing the loop, if there is a voltage difference and a phase difference between the two sides of the loop closing point, not only will a circu...

AI Technical Summary

Problems solved by technology

However, there are also the following problems: the short-circuit fault current level of the system is relatively high during closed-loop operation, and the requirements for circuit breakers or load switches are relatively high; when a fault occurs, the load on the entire ring is transferred to a feeder, and the feeder cable should consider redundant design; The power grid must be equipped with differential protection, which requires a large investment, and the configuration of secondary protection is relatively complicated, and the workload of operation and maintenance is large.

The typical defects of the equipment are large capacity, large volume, and high equipment cost; the other is the DC loop closure method, which realizes the power distribution power supply mode as an AC-DC hybrid power supply mode, and the DC loop closure adopts the DC bus loop closure scheme in different regions

Another typical defect of these two kinds of flexible ring closing devices is low efficiency. The flexible interconnection device is composed of back-to-back / multi-port power electronic converters. If the average operating efficiency of a single power electronic converter is calculated as 98%, then the The transfer loss is about 4%, which is much greater than the line loss of the system after the power flow optimization of the flexible loop closure device

It can be seen that in order to ensure the energy efficiency of the power grid system, the flexible loop closing device is only applicable to application scenarios such as fault recovery and emergency dispatch of active power under the circumstances of excess power generation of new energy. The equipment utilization rate of this type of flexible loop closing device is low. The overall cost is high, which will greatly limit its application and promotion

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