Networked layered compensation method for voltage unbalance of PCC (Point of Common Coupling) of islanded microgrid

Abstract

The invention relates to a networked layered compensation method for voltage unbalance of a PCC (Point of Common Coupling) of an islanded microgrid. The method comprises the following steps: (1), establishing a networked layered control system structure; (2), performing real-time detection, and converting all the electrical quantities into an alpha-beta coordinate system; (3), obtaining positive and negative sequence components of voltage or current; (4), computing the positive sequence active power and positive sequence reactive power at the PCC; (5), obtaining an output reference voltage and a reference angular frequency; (6), obtaining the input of a reference occurrence module; (7), obtaining the reference voltage at an alpha-beta stationary coordinate system; (8) sending the voltage v<abc> at the PCC to a secondary controller; (9), obtaining positive and negative sequence components; (10), obtaining UCR<alpha beta>; (11), feeding back the UCR<alpha beta> to a primary controller of each DG (Distributed Generator); (12), figuring out v<V alpha beta>; (13), calculating the reference value of a current control loop; (14), obtaining the switching drive pulse of an inverter; (15) driving switching tubes of a three-phase full bridge inversion circuit to switch on or off by the switching drive pulse, and controlling the inverter to output rated sine-wave voltage. According to the invention, the voltage at the PCC can be subjected to global compensation, and the reactive power distribution precision is improved.

Description

technical field [0001] The invention relates to the fields of new energy power generation, microgrid operation and control, and in particular to a networked layered compensation method for voltage unbalance at common coupling points of island microgrids. Background technique [0002] In recent years, in order to solve the problem of distributed power access, coordinate the contradiction between large power grids and distributed power generation, and improve the comprehensive utilization of energy, microgrids have been proposed and received extensive attention. [0003] Microgrid ("microgrid" for short) refers to a small power generation system composed of distributed power supply, energy storage system, energy conversion device, load and monitoring system and protection device. An autonomous system that can operate in parallel with an external grid or in isolation. [0004] However, in the low-voltage microgrid composed of three-phase inverters, there is a common phenomenon...

AI Technical Summary

Problems solved by technology

Therefore, scholars have proposed a voltage unbalance compensation method using distributed generation, but most of them are aimed at the unbalance compensation of DGs terminal voltage. The compensation methods are all based on peer-to-peer control of local droop characteristics, which cannot be well adapted to the operation of low-voltage microgrids. surroundings

For example, the Chinese patent CN103368191B "A Method for Compensating Voltage Unbalance of Multiple Inverters in Parallel Microgrid" points out that the voltage unbalance compensation method using distributed generation adopts the traditional droop control strategy, and the reactive power distribution accuracy of this method is poor. , and cannot well adapt to the operating environment of the low-voltage microgrid

Chinese patent CN103715704A "A Microgrid Public Bus Voltage Unbalance Suppression Method" points out that each distributed power source in the microgrid is used to adjust the PCC point bus voltage unbalance compensation method, adopting the traditional droop control strategy, and the reactive power distribution accuracy Poor, when the system is seriously unbalanced, it is easy to cause the inverter to over-current, which cannot well adapt to the operating environment of the low-voltage microgrid

[0006] According to the hierarchical control theory in traditional power systems, Secondary Control Scheme for Voltage Unbalance Compensation in an Islanded Droop-Controlled Microgrid【Mehdi Savaghebi, Alireza Jalilian, Juan C. Vasquez, and Josep M. Guerrero, IEEE Transactions on Smart Grid, vol.3, no.2, pp. 797-807, 2012.] put forward hierarchical microgrid control, using centralized control to realize secondary control of microgrid, which can complete PCC point voltage unbalance compensation, but centralized control The method requires the MicroGrid Central Controller (MGCC) to communicate with all DGs, resulting in high communication bandwidth, low reliability, and poor scalability of the system, which is not suitable for large-scale microgrid integration into power distribution. network

[0007] As mentioned above, the technical problems of three-phase unbalanced compensation and power sharing at the PCC point of the low-voltage microgrid have not been completely solved in the prior art

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