A global high-frequency oscillation suppression method for multi-inverter grid-connected systems under weak grid
A multi-inverter, high-frequency oscillation technology, applied in the direction of AC network flicker reduction, AC network circuit, single-network parallel feeding arrangement, etc., can solve the resonance frequency shift, global resonance, and aggravate the risk of system harmonic resonance and other problems to achieve the effect of suppressing parallel resonance, increasing system damping, and enhancing system stability
Active Publication Date: 2021-04-16
HUNAN UNIV
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[0004] For the multi-machine grid-connected system in the weak grid, due to the introduction of the LCL filter and the parallel connection of multiple inverters, a large number of inverters operate in parallel, which will lead to internal, inter-inverter, and inverter Harmonic resonance is formed between the inverter and the grid, and as the number of parallel units increases, the resonant frequency shifts to the low frequency band, which greatly aggravates the risk of harmonic resonance in the system, which may lead to global resonance of the system
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[0031] like figure 1As shown, the structure diagram of the global high-frequency oscillation suppression control system of the multi-inverter grid-connected system under a weak grid according to an embodiment of the present invention includes two parts: a module structure and a control system. The module structure is that n (n=1, 2, 3...) LCL type grid-connected inverter structure sub-modules are connected in parallel to the large power grid. The sub-module includes a photovoltaic array, a front-stage booster circuit, a back-stage DC energy storage capacitor, a back-stage three-phase inverter circuit, and a back-stage LCL grid-connected filter circuit. The post-stage LCL grid-connected filter circuit is connected to the large power grid. Among them, C pv Storage capacitor for boost circuit, VD 0 diode for the boost circuit, L 0 is the boost circuit inductance, S 1 is the switch tube of the boost circuit; C dc is the post-stage DC energy storage capacitor, Q 1 , Q 2 , Q...
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The invention discloses a global high-frequency oscillation suppression method for a multi-inverter grid-connected system under a weak grid. The method introduces the global variable of the voltage of the common node PCC point and the high-frequency component of the grid-connected current to the inverter control link, which can Realize high-frequency oscillation suppression for multi-inverter systems. Firstly, the feed-forward of the PCC point voltage is introduced to construct the virtual resistance of the parallel inverter at the PCC, and the harmonic resonance of the impedance network caused by the harmonic voltage of the inverter and the background harmonic voltage of the grid is suppressed; secondly, the high frequency of the grid-connected current is introduced Component feedback constructs a virtual impedance connected in parallel at both ends of the inverter output filter capacitor, increases the damping of the inverter itself, and suppresses the parallel resonance of multiple inverters. The invention can effectively suppress the harmonic resonance phenomenon of a multi-inverter parallel system, and fundamentally solve the system stability problem caused by the increase in the number of inverters under a weak network.
Description
technical field [0001] The invention relates to PWM inverter control and the field of new energy distributed generation, in particular to a global high-frequency oscillation suppression method for a multi-inverter grid-connected system under a weak grid. Background technique [0002] In order to solve the problems faced by the power industry, new energy power generation has gradually emerged as a new force, and the main force of this new force is grid-connected power generation, independent power generation and multi-energy complementary power generation. As one of the above-mentioned forms, the grid-connected power generation system can be further divided into distributed generation grid-connected and centralized power generation grid-connected. However, although these two grid-connected forms have different structures, they also have something in common, such as: random fluctuation of power quality, high harmonic content, and the need to set up anti-islanding detection and...
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IPC IPC(8): H02J3/01H02J3/38
CPCH02J3/383H02J3/01H02J3/002Y02E10/56Y02E40/40
Inventor 陈燕东谢志为伍文华徐元璨王海宁郭健谢露王翔宇罗安
Owner HUNAN UNIV