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

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...

AI Technical Summary

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 regulator, and its output reaches saturation; When the network is running, the PI regulator output has a long dynamic adjustment time and a large overshoot, so the standard value of the inner loop current fluctuates, which affects the stability of the AC and DC bus voltage

Images