A design method for multi-parallel photovoltaic grid-connected inverters
A design method and inverter technology, applied in the circuit field, can solve problems affecting system stability, affecting the current loop control of multi-parallel photovoltaic grid-connected inverters, reducing the system phase margin, etc., and achieving a good grid-connected current waveform , stable grid connection and strong adaptability
Active Publication Date: 2019-06-07
CHONGQING UNIV
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The existence of grid impedance will affect the current loop control of multi-parallel photovoltaic grid-connected inverters, reduce the phase margin of the system, and affect the stability of the system
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[0028] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings; it should be understood that the preferred embodiments are only for illustrating the present invention, rather than limiting the protection scope of the present invention.
[0029] Such as figure 1 Shown is the structure diagram of multi-parallel photovoltaic grid-connected inverters. In the figure, there are n single-phase photovoltaic grid-connected inverters running in parallel, and the output of the inverters is connected to the grid through the LCL filter. Among them, u ri i 1i and i 2i are the output voltage, output current and grid-connected current of the i-th grid-connected inverter, L 1i 、C 1i and L 2i are the inverter-side inductance, filter capacitor and grid-side inductance of the i-th inverter, Z g =R g +sL g is the grid impedance, u pcc is the grid-connected point voltage, u g and i g are grid voltage and grid curr...
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The invention discloses a multi-parallel photovoltaic grid-connected inverter design method, which comprises the following steps of (1) determining a side inductor L1 of an inverter of an LCL filter; (2) if the inverter adopts the single inductor L1 for filtering, designing a controller Gc (s), and determining system open-loop cut-off frequency omega c at the moment; (3) determining a corresponding filter capacitor C1; (4) determining an optimal grid side inductor L2, meanwhile, verifying if fres0 is larger than 10 times of grid frequency and smaller than half of switching frequency or not, and if not, returning to the step (3) for adjusting a value of C1; (5) designing an active damping coefficient kd, drawing a system open-loop transfer function Bode diagram, checking if a system control performance meets the requirement or not, and if not, adjusting parameters of the controller Gc (s). The multi-parallel photovoltaic grid-connected inverter design method provided by the invention can realize stabilized grid connection under different power grid impedances, has a favorable grid-connection current waveform, and has higher applicability on power grid impedance.
Description
technical field [0001] The invention relates to the field of circuits, and more specifically, to a design method for multi-parallel photovoltaic grid-connected inverters. Background technique [0002] With the continuous reduction of the cost of photovoltaic cells and the maturity of photovoltaic power generation technology, the proportion of photovoltaic power generation in the total power generation is getting higher and higher. As an important trend of photovoltaic development in the future, large-scale photovoltaic power plants and large-capacity distributed power generation mostly use multiple photovoltaic grid-connected inverters to connect to the grid in parallel. Grid impedance inevitably exists in the grid, and changes in grid operation mode will also cause changes in grid impedance. When the grid impedance changes, it may cause problems such as the stability of the multi-parallel photovoltaic grid-connected inverter and the harmonic content of the grid-connected c...
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IPC IPC(8): H02J3/38H02M7/537
CPCH02J3/383H02M7/537Y02E10/56
Inventor 解宝周林
Owner CHONGQING UNIV