Seamless grid-connected inverter with grid-connected point dynamic voltage compensation function and method thereof

Abstract

The invention discloses a seamless grid-connected inverter with a grid-connected point dynamic voltage compensation function and a method thereof, and belongs to the technical field of grid security. The seamless grid-connected inverter comprises an input module, a direct current power supply, a transformer, a voltage and current detection module, a voltage deviation calculation and voltage compensation control unit, an inverting control unit and an inverting module. Before grid connection, the inverting control unit controls the inverting module through an excitation instruction operation module to output an idle component for pre-excitation of the transformer; after grid connection, voltage compensation currents are output through the voltage deviation calculation and voltage compensation control unit, the voltage compensation currents and idle reference currents are superposed to obtain new idle reference currents, the grid-connected inverter is controlled to absorb or sent out idle currents, grid-connected point voltage is recovered within the voltage deviation range, and safe seamless grid connection of the grid-connected inverter is achieved accordingly. Seamless grid connection of the inverter can be achieved, over-current impact is prevented, system loss is reduced, and system reliability and stability are improved.

Description

technical field [0001] The invention relates to a grid-connected inverter and a grid-connected control method thereof, belonging to the technical field of power grid safety. Background technique [0002] Domestic inverters have two working modes: off-grid and grid-connected. The grid-connected type puts forward higher requirements for the inverter. On the one hand, it is the need for grid-connected safety. On the other hand, the power fed back to the grid must meet the grid regulations. indicators, and cannot cause harmonic pollution to the power grid. Therefore, it will bring the following two problems: On the one hand, the direct connection of the output side of the grid-connected inverter transformer to the grid will cause problems such as overcurrent and shock oscillation. The traditional control method for this problem is: first connect to the power grid through a closed switch with charging resistors in series, and pre-excite the transformer; then switch to connect to...

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Problems solved by technology

Therefore, it will bring the following two problems: On the one hand, the direct connection of the output side of the grid-connected inverter transformer to the grid will cause problems such as overcurrent, shock oscillation, etc.

This control method can prevent the shock during the process of connecting to the grid to a certain extent, but there will be a certain current shock in the process of switching to the power grid and increase the system cost, and the output side of the inverter cannot be ideal. Connect to the grid

On the other hand, traditional inverter voltage control equipment is based on fixed reactive power control methods, fixed power factor control methods, active power-power factor control methods, steady-state voltage amplitude-reactive power droop control methods, etc. , these voltage control strategies are steady-state voltage control strategies rather than dynamic voltage adjustment strategies, so they cannot effectively compensate for dynamic voltage changes when the inverter is connected to the grid

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