Dual-mode smooth switching control method for cascaded h-bridge photovoltaic grid-connected inverters
A control method and smooth switching technology, applied in photovoltaic power generation, single-grid parallel feeding arrangement, AC network circuit, etc., can solve the problem of smooth switching between two modes of inverter current source and voltage source, without considering the maximum power of photovoltaic power generation. Tracking, failure to involve cascading photovoltaic inverters, etc.
Active Publication Date: 2020-11-24
HEFEI UNIV OF TECH
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[0008] (1) The inverter current source voltage source dual-mode switching control method studied in the prior art is mostly aimed at the difference between the inverter current source and voltage source modes caused by the inverter in both grid-connected and off-grid conditions. The problem of mutual switching, less involving how to realize the smooth switching of the current source voltage source dual mode when the inverter is connected to the grid
[0009] (2) Current-source-voltage-source dual-mode switching control methods for inverters studied in the prior art are mostly aimed at three-phase centralized energy storage inverters, but fail to involve cascaded photovoltaic inverters
[0010] (3) The inverter current source voltage source dual-mode switching control method studied in the prior art is mostly aimed at the stable power supply on the DC side of the inverter, and does not consider the maximum power tracking of photovoltaic power generation
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[0075] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention will be further clearly and completely described below in conjunction with the accompanying drawings and embodiments.
[0076] figure 1 It is the topological structure of the cascaded H-bridge photovoltaic grid-connected inverter according to the embodiment of the present invention. As shown in the figure, the cascaded H-bridge photovoltaic grid-connected inverter consists of N H-bridge units with photovoltaic modules, filtering Inductance L S and filter capacitor C f composition. Specifically, the DC sides of N H-bridge units are sequentially connected to N photovoltaic panels PV1, PV2...PVN, and the working conditions of the photovoltaic panels are at a rated temperature of 25°C and a rated light intensity of 1000W / m 2 The maximum power point voltage is 30.40V, each photovoltaic panel is connected to each H-bridge unit through a 14.1mF capacito...
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The invention discloses a dual-mode smooth switching control method for cascaded H-bridge photovoltaic grid-connected inverters, which comprises a current source mode and voltage source mode switchingcontrol method. When the control is switched from a current source mode to a voltage source mode, the reference value of the active component of the current of a filter inductor and the power distribution coefficients of N H-bridge units in a current source mode in the period before switching are latched, and the feed-forward control quantity of a DC voltage regulator in each voltage source modeis calculated, so as to smoothly switch an inverter from a current source mode to a voltage source mode. When the control is switched from a voltage source mode to a current source mode, the referencevalue of the active component of the current of the filter inductor and the power distribution coefficients of the N H-bridge units in a voltage source mode in the period before switching are latched, and the feed-forward control quantity of the DC voltage regulator in each current source mode is calculated, so as to smoothly switch the inverter from a voltage source mode to a current source mode. By adopting the method, smooth switching between the two control modes can be realized, and maximum tracking of photovoltaic generation power can be realized.
Description
technical field [0001] The invention relates to a dual-mode smooth switching control method for cascaded H-bridge photovoltaic grid-connected inverters, and belongs to the technical field of cascaded photovoltaic inverter control. Background technique [0002] Photovoltaic grid-connected power generation has attracted much attention because it provides clean energy and is environmentally friendly. In the face of how to improve the efficiency of photovoltaic systems and reduce power generation costs, cascaded H-bridge multilevel inverters have become a research hotspot due to their advantages such as modularization, easy expansion, high system efficiency, and low total harmonic distortion of grid-connected current. . [0003] Since the output of the cascaded H-bridge photovoltaic inverter is directly connected to the grid, the step-up transformer at the grid-connected end is omitted, which improves the overall efficiency of the photovoltaic power generation system. However,...
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IPC IPC(8): H02J3/38
CPCH02J3/383Y02E10/56
Inventor 张兴毛旺胡玉华赵涛王付胜李飞
Owner HEFEI UNIV OF TECH