Grid-connection/disconnection seamless switching strategy in optical storage alternating current and direct current micro grid

A seamless switching, AC-DC technology, applied in the flicker reduction of AC network, AC network circuit, photovoltaic power generation and other directions, can solve the problems of large overshoot, long dynamic adjustment time, affecting the voltage stability of AC and DC bus, etc The effect of reducing voltage oscillation and ensuring smoothness

Active Publication Date: 2017-06-13
SOUTHEAST UNIV +3
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Problems solved by technology

[0003] When the grid-connected switch command is 1 during grid-connected operation, the voltage outer loop is in an open-loop state at this time, because the bidirectional DC converter and the bidirectional inverter voltage outer loop adopt the traditional PI regulat

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  • Grid-connection/disconnection seamless switching strategy in optical storage alternating current and direct current micro grid
  • Grid-connection/disconnection seamless switching strategy in optical storage alternating current and direct current micro grid
  • Grid-connection/disconnection seamless switching strategy in optical storage alternating current and direct current micro grid

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Embodiment Construction

[0044] The present invention will be further described below in conjunction with the accompanying drawings.

[0045] The present invention takes the optical-storage AC-DC hybrid micro-grid as the object, and its system structure is as follows image 3shown. The AC-DC microgrid system consists of photovoltaic arrays, DC-DC converters, bidirectional DC-DC converters, energy storage batteries, bidirectional AC-DC converters and distribution networks. The photovoltaic array and the energy storage device are respectively connected to the DC bus through a DC-DC converter and a bidirectional DC-DC converter, and the DC bus and the AC bus are connected through a bidirectional DC-AC converter. Both the large AC power grid and the AC load are connected to the AC busbar. The system operates in the grid-connected mode, and the distribution network serves as the microgrid DC bus voltage support. The system operates in off-grid mode, and the energy storage is used as the voltage support ...

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Abstract

The invention discloses a new grid-connection/disconnection seamless switching strategy in an optical storage alternating current and direct current micro grid. The strategy comprises the following steps: at first, designing a new micro grid pre-synchronization algorithm, thus guaranteeing an alternating current bus voltage phase to be smooth and continuous, and laying a foundation for grid-connected/disconnected seamless switching; and then putting forward an improved outer ring which is used as an energy storage control outer ring and an inverter control outer ring according to a system structure of the micro grid and in combination with an outer ring output characteristic during switching micro grid system grid-connection/disconnection operating modes. The improved outer ring realizes a resetting function required by instant output of grid-connection/disconnection mode switching, so as to make up for overshoot caused by line power flow changes when a traditional PI adjuster switches; the problem of alternating current and direct current bus voltage fluctuation in the switching process can be better solved; and seamless switching is realized. By adopting an improved voltage outer ring adjusting strategy, serious overshooting in a transient process can be inhibited; the voltage fluctuation of an alternating current and direct current bus is reduced; and smoothness during switching is guaranteed.

Description

technical field [0001] The invention relates to a micro-grid on / off grid switching strategy, and belongs to the field of micro-grid new energy energy management. Background technique [0002] The country vigorously develops new energy, so the research and application of distributed new energy has broad prospects. Converting new energy into electricity is a typical way for human beings to use new energy, so the research on photovoltaic power generation has always been concerned. With the improvement of the penetration rate of distributed energy and the application of high-power energy storage, AC and DC micro-grid technology has been developed. Compared with the traditional distribution network, the AC-DC micro-grid is based on the AC bus, and the DC bus is specially designed through the power electronic device, so that new sources and loads such as photovoltaics, energy storage, and electric vehicles can be more conveniently connected to the power grid. Reliability of powe...

Claims

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Application Information

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IPC IPC(8): H02J3/38H02J3/24H02J3/40H02J7/35
CPCH02J3/002H02J3/24H02J3/38H02J3/385H02J3/388H02J3/40H02J7/35Y02E10/56
Inventor 薄鑫吴倩赵菲菲郑建勇杨杰缪惠宇杨赟顾盼盼
Owner SOUTHEAST UNIV
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