High-frequency oscillation suppression method with two band-stop filters for new energy multiple machines connected to weak power grid
A band-stop filter, high-frequency oscillation technology, applied in the field of new energy distributed generation, can solve the problems of increasing the equivalent impedance of the power grid, the impedance of the power grid cannot be ignored, and the threat of stable and reliable operation of the system, so as to avoid the phenomenon of harmonic resonance, Improve the anti-interference ability and inhibit the effect of harmonic current flowing into the power grid
Active Publication Date: 2021-09-21
HUNAN UNIV
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[0003] However, in large-scale new energy power plants, on the one hand, the grid impedance cannot be ignored due to long-distance transmission lines; on the other hand, when multiple inverters are connected to the same grid common coupling point, any grid-connected inverter The grid equivalent impedance corresponding to the point will increase as the number of inverters increases
At this time, due to the existence of harmonics on the inverter side and the grid side, the distributed impedance network formed by multiple inverters and the grid at the common coupling point will inevitably be excited by the harmonic source and interact with each other, which has a great impact on the system. Stable and reliable operation is a potential threat
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[0032] figure 1 It is the structural diagram of the three-phase inverter grid-connected system, the left side is the inverter subsystem, and the right side is the grid subsystem, where: when the photovoltaic array and DC / DC converter or the fan unit and AC / DC converter pass When the LCL grid-connected inverter is connected to the distribution network, the input of the LCL grid-connected inverter can be equivalent to a DC source. m=1,2,...,n; inverter side inductance L 1m , filter capacitor C 1m and grid side inductance L 2m form the LCL filter, R L1m and R L2m L respectively 1m and L 2m The parasitic resistance, Z g is the grid impedance, U dc is the DC side voltage, u invm is the output voltage of the inverter, u C1m is the filter capacitor voltage, u PCC is the common coupling point voltage, u g is the grid voltage, i L1m i C1m i om and i g They are inverter side inductor current, filter capacitor current, grid side inductor current and grid-connected current...
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The invention discloses a method for suppressing high-frequency oscillation with two band-stop filters for new energy multiple machines connected to a weak power grid. And current inner loop PR controls three parts. This method is equivalent to connecting the virtual impedance in series with the output impedance of the grid-connected inverter. At the fundamental frequency, the parallel virtual impedance presents a high impedance, and the series virtual impedance presents a low impedance, making the fundamental current flow into the power grid; at high frequencies, the parallel virtual impedance presents a low impedance, and the series virtual impedance presents a high impedance, making the high-frequency harmonics Current flows into the parallel virtual impedance branch. The method effectively restrains the harmonic current of the inverter from flowing into the power grid, improves the anti-interference ability of the grid-connected inverter, and avoids the occurrence of harmonic resonance.
Description
technical field [0001] The invention relates to the field of new energy distributed power generation, in particular to a method for suppressing high-frequency oscillations of two band-stop filters for multiple new energy machines connected to a weak power grid. Background technique [0002] Large-scale new energy power plants have become an important trend in the new energy power generation industry with their unique advantages of high efficiency and centralized management. It adopts a system structure with multiple inverters connected in parallel to the grid, which can not only improve the output power of new energy power generation and fault redundant operation, but also realize the optimal configuration of grid-connected inverter capacity. [0003] However, in large-scale new energy power plants, on the one hand, the grid impedance cannot be ignored due to long-distance transmission lines; on the other hand, when multiple inverters are connected to the same grid common co...
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IPC IPC(8): H02J3/38H02J3/01
CPCH02J3/382H02J3/01Y02E40/40
Inventor 罗安杨苓陈燕东陈智勇周乐明周小平伍文华谢志为
Owner HUNAN UNIV