Droop control-based smooth switching method

Abstract

A droop control-based smooth switching method is provided. Output voltage amplitude and frequency are adjusted through adopting droop control, namely the balance of reactive power and active power, such that an inverter can either be in autonomous operation or be in grid-connected operation. When the state of a power grid is normal, a control unit adjusts the output voltage amplitude and frequency of the inverter; after the output voltage amplitude and frequency satisfy a requirement for grid connection, a grid-connection switch is switched off; the inverter will output proper voltage and frequency according to a droop equation based on frequency and voltage changes before and after the switching of two operation modes of a system, such that the stability of the voltage and frequency of the system can be maintained; and when an abnormal state of the power grid is detected, or an autonomous operation mode is required to be switched to, the grid-connection switch is switched off, and at the same time, because of the frequency and the voltage changes of the system, the inverter will automatically output proper reactive power and active power according to the droop equation, such that the balance of the reactive power and active power of the system can be maintained. The droop control-based smooth switching method can realize smooth switching of the autonomous operation or the grid-connected operation of the inverter through adopting the droop control.

Description

technical field [0001] The invention relates to an inverter switching control method. Background technique [0002] While countries around the world are vigorously developing new energy power generation and improving distributed power generation technology, inverters are an indispensable link. In photovoltaic grid-connected power generation, AC-DC-AC variable speed wind power grid-connected power generation in wind power generation, biomass energy grid-connected power generation and other grid-connected power generation systems, the inverter converts DC power or irregular AC power into standard AC power, connected to the grid or directly supplying power to loads, plays the role of a bridge to convert energy, and is also one of the key technologies of distributed power generation systems. [0003] To a certain extent, the performance of the inverter directly affects the reliability and safety of the distributed generation system. Moreover, as the requirements for the large ...

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Problems solved by technology

[0004] Traditional inverters generally work in the grid-connected state or autonomous state, and rarely can satisfy the two working modes. Even if they are satisfied, there are two modes of switching. During the mode switching process, due to the difference in control mode and operating state, it is easy to Cause system instability, so that the inverter or load can self-protect, seriously burn out the inverter and load or even cause irreparable damage to the power grid

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