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Grid-connected and off-grid operation switching system and switching method for micro-grid

A technology for operation switching and microgrid, which is applied in the parallel feeding arrangement of single network, photovoltaic power generation, load balancing of AC network, etc. It can solve the disturbance of microgrid system, large overvoltage or overcurrent of equipment, and increased investment in circuit breaker equipment, etc. problems, to achieve the effect of improving stability and reliability and saving costs

Active Publication Date: 2020-06-05
CHINA ENERGY ENG GRP GUANGDONG ELECTRIC POWER DESIGN INST CO LTD
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  • Claims
  • Application Information

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Problems solved by technology

However, the strategy of Scheme 2 will lead to an increase in investment in circuit breaker equipment. Due to the discreteness of the closing and opening time of the circuit breaker, there will be a large overvoltage or overcurrent impact on the equipment, and there will be large disturbances in the microgrid system.

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  • Grid-connected and off-grid operation switching system and switching method for micro-grid

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specific Embodiment approach

[0056] Specifically, for the DC microgrid operating in the off-grid operation mode, due to the elimination of the ±10kV distribution grid side fault or the planned grid connection, the DC microgrid operation control system issues the grid connection command to realize the non-stop switching mode. The specific implementation is as follows:

[0057] 1) After receiving the off-grid to grid-connected switching command, the DC microgrid operation control system adjusts the droop curve of the energy storage system to keep the low-voltage DC bus voltage of the DC microgrid close to the low-voltage DC bus voltage on the low-voltage side of the DC transformer.

[0058] 2) When the voltage difference on both sides of the grid-connected switch reaches the allowable switching range, the DC grid-connected device controls the DC circuit breaker CB1 on the low-voltage side of the DC transformer to close to complete the off-grid to grid-connected mode switching.

[0059] At this time, the DC ...

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Abstract

The invention discloses a grid-connected and off-grid operation switching system for a micro-grid. The system comprises a medium-voltage direct-current power distribution network, a direct-current transformer, a low-voltage direct-current micro-grid, a switch module and a first circuit breaker. The low-voltage direct-current micro-grid comprises an energy storage system, a photovoltaic system anda direct-current load system. The medium-voltage direct-current power distribution network is connected with the direct-current transformer through the switch module. The direct-current transformer isconnected with the energy storage system, the photovoltaic system and the direct-current load system through the first circuit breaker. The invention further discloses a grid-connected and off-grid operation switching method for the micro-grid. According to the technical scheme, grid-connected and off-grid switching between the medium-voltage direct-current power distribution network and the low-voltage direct-current micro-grid can be realized, and the stability and reliability of grid-connected and off-grid switching operation are improved.

Description

technical field [0001] The invention relates to the technical field of power grid control, in particular to a microgrid parallel-off operation switching system and switching method. Background technique [0002] As a new type of distribution network, DC microgrid has the unparalleled advantages of AC microgrid in terms of operational reliability, energy utilization efficiency and operational flexibility. As the technology of medium-voltage DC distribution network becomes more and more mature, it is possible to reduce the voltage from medium-voltage DC distribution network to low-voltage DC distribution network. The DC distribution network can be directly stepped down through power electronic transformers, which can improve the efficiency of energy transmission. Microgrids can also improve the reliability of power supply. In order to realize the step-down from the medium-voltage DC distribution network to the low-voltage DC distribution network, there are two common solution...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J3/38H02J3/28
CPCH02J3/28Y02E10/56
Inventor 周钰张浩鲁丽娟施世鸿伦振坚
Owner CHINA ENERGY ENG GRP GUANGDONG ELECTRIC POWER DESIGN INST CO LTD