Microgrid control method having functions of voltage unbalance compensation and harmonic suppression

Abstract

The invention discloses a microgrid control method having functions of voltage unbalance compensation and harmonic suppression. An integrated controller acquires a common bus voltage and calculates an unbalance factor vector, a characteristic order harmonic component positive-sequence compensation reference vector and a characteristic order harmonic component negative-sequence compensation reference vector of the common bus voltage, and transmits the vectors to a local controller of every parallel inverter through low-bandwidth communication. In the local controller, a characteristic order harmonic positive- and negative-sequence compensation voltage vector is calculated and is superposed with a reference voltage vector, a virtual impedance voltage vector and the common bus voltage unbalance factor vector to synthesize and correct a voltage regulating reference vector, and unbalance compensation and harmonic suppression of the common bus voltage is carried out through inverter voltage and current control. By applying the method provided by the invention to a multi-inverter parallel system in which a common bus is connected with a three-phase unbalanced load and a nonlinear load, three-phase voltage balance of the microgrid can be maintained, output voltage distortion of three-phase inverters can be reduced, and output power of the parallel inverters can be accurately allocated.

Description

technical field [0001] The invention relates to a microgrid multi-inverter control method with voltage unbalance compensation and harmonic suppression, and belongs to the technical field of distributed power generation and smart grid. Background technique [0002] The widespread use of new energy power generation systems has made microgrid systems based on a variety of distributed power sources, loads, and energy storage devices the basic unit of smart grids. The microgrid is composed of distributed micro-sources, energy conversion devices and local loads interconnected through the network. It is a local power generation system capable of self-control, protection and management, and can operate in two states of islanding and grid-connected. In the microgrid, many distributed micro-sources are connected to the AC bus through the inverter interface, thus forming a multi-inverter parallel operation environment. [0003] In the microgrid composed of three-phase inverters, when ...

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Problems solved by technology

However, this patent needs to perform fast Fourier transform on the instantaneous active power and instantaneous reactive power, and detect the power of each characteristic sub-harmonic by frequency division, and then calculate and synthesize the harmonic reference voltage for each characteristic sub-harmonic respectively, specifically The implementation process is too complicated, and the calculation amount of the program is relatively large, which may affect the rapid response speed of the system

In addition, this method is used for single-phase inverter control, mainly used in the occasions where the common bus is connected with non-linear loads, and cannot be applied to occasions with three-phase unbalanced loads

[0012] Chinese patent document CN102437589B discloses a single-phase solar power multi-inverter parallel power sharing control method, which overcomes the shortcomings of PID control for both voltage and current double loops

However, when the microgrid system is connected with nonlinear loads, a large number of harmonics will be generated. This method cannot suppress harmonics, so this method cannot be applied to three-phase unbalanced loads and nonlinear loads connected at the same time. microgrid system

[0014] In summary, the existing technology does not provide a good solution for the complex operating conditions of the island microgrid system connected with three-phase unbalanced loads and nonlinear loads at the same time

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