Method for separating positive and negative sequence components on basis of OVPR under non-ideal micro-grid condition

Abstract

The invention provides a method for separating positive and negative sequence components on basis of OVPR under a non-ideal micro-grid condition. The method comprises the following steps of: transforming micro-grid voltage from a three-phase a/b/c coordinate system to a two-phase static <alpha>/<beta> coordinate system through Clark transform; and obtaining a positive sequence component and a negative sequence component of the voltage through a signal separation subsystem: carrying out subtraction on the micro-grid voltage transformed to the two-phase static <alpha>/<beta> coordinate system and sum of components obtained through separation, forming negative feedback through a fundamental wave positive sequence detection unit and a negative sequence detection uniform formed by a first-order vector resonant controller, and taking output of each unit as the positive sequence component and negative sequence component of the voltage. The method has the characteristics of being relatively rapid in response, free of instant symmetric component separation and simple to realize, and is capable of rapidly, correctly and directly realizing positive sequence, negative sequence and harmonic wave separation. Simulation results and analysis prove the correctness and effectiveness of the method.

Description

technical field [0001] The invention relates to a method for separating positive and negative sequence components based on OVPR under non-ideal microgrid conditions. Background technique [0002] Due to its ability to overcome the adverse effects of distributed generation and give full play to its advantages, microgrid has attracted widespread attention. However, due to the characteristics of the micro-grid itself, it is easily affected by the nonlinear and high-power loads in the grid, which makes the grid voltage unbalanced and harmonically distorted. Therefore, higher requirements are put forward for the control of the power electronic converter as a micro-power interface, so that it can achieve multiple control objectives such as no fluctuation in active power, no fluctuation in reactive power, and no harmonics in the output current. To achieve multiple control objectives, it is necessary to effectively and quickly separate the voltage positive and negative sequences an...

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Problems solved by technology

[0005] Li Coral, Du Xiong, Wang Liping, et al. Decoupling multi-synchronous reference frame grid voltage synchronization signal detection method [J]. Journal of Electrotechnical Society, 2011, 26(12): 183-189, proposed the use of multi-synchronous dq rotating coordinates In the system method, in multiple positive and negative sequence rotating coordinate systems, the decoupling method is used to realize the voltage conversion and harmonic elimination, but its structure is relatively complicated, and an external LPF filter is required to filter the harmonics, which affects the The dynamic response performance of the system

[0006] The positive and negative sequence component detection system based on the second order generalized integrator SOGI (second order generalized integrator) and the complex integrator can effectively detect the voltage signal in the non-ideal grid environment, but this method cannot directly distinguish the positive and negative sequence components. It is also necessary to separate the positive and negative sequence components through the calculation of instantaneous symmetrical components, and the detection results are easily affected in the case of high harmonic content

In order to eliminate the influence of harmonics, Yazdani D, Mojiri M, BakhshaiA, et al.A fast and accurate synchronization technique for extraction of symmetrical components[J].IEEE Transactions on Power Electronics,2009,24(3):674-684 and Tu Juan, Tang Ningping. Power Grid Voltage Synchronization Signal Detection Based on Improved DSOGI-PLL[J]. Chinese Journal of Electrical Engineering, 2016, 36(9): 2350-2356 respectively uses SOGI to form a harmonic elimination module, and then multiple modules Sequential cascading eliminates each harmonic in turn, realizing the separation and detection of the positive and negative sequence components of the grid voltage fundamental wave and each harmonic signal, but the order of the system increases due to the cascading of multiple modules, and the system becomes more complex. The complexity increases the difficulty of system analysis and parameter design, and may also reduce the phase margin and reduce system stability, and this method still needs to use instantaneous symmetric components to calculate

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