Photovoltaic grid-connected inverter and control method
An inverter, photovoltaic technology, applied in photovoltaic power generation, irreversible DC power input conversion to AC power output, single-grid parallel feeding arrangement, etc., can solve the problem of unstable operation, low output voltage level of photovoltaic system, increased System cost and other issues, to achieve the effect of improving system power level, improving grid-connected power quality, and improving system stability
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Embodiment 1
[0050] see figure 1 , is a structural diagram of a photovoltaic grid-connected inverter according to an embodiment of the present invention. As shown in the figure, the inverter includes a plurality of photovoltaic arrays 11, a plurality of unit cells 12, three AC reactors 13, and three grid-connected switch 14 and a master controller 15.
[0051] Each phase of the inverter is composed of multiple units 12 cascaded through the unit phase-shifting stacking wave technology. The unit units A1, A2...An-1, An in the figure form phase a of the inverter, B1, B2...Bn-1, Bn, etc. constitute phase b of the inverter, and C1, C2...Cn-1, Cn, etc. constitute phase c of the inverter. Unit cascading means that each unit is connected end-to-end to achieve high-voltage output. Using unit cascading or series technology, higher-level voltages can be output, such as direct output voltages of 3kV, 6kV, 10kV, or even higher-level voltages. Wherein, the input end of each unit cell 12 in the branch ...
Embodiment 2
[0056] figure 2 It is the circuit principle diagram of the unit body of the embodiment of the present invention. As shown in the figure, the unit body includes:
[0057] The BOOST circuit 21 is used for performing maximum power tracking on the photovoltaic array, and raising the low voltage output by the photovoltaic array to a high voltage;
[0058] The energy storage battery 22 is used to store the electric energy provided by the BOOST circuit 21, and to provide stable DC power to the rear-stage H-bridge inverter circuit 23; due to the effect of the energy storage battery 22, when the light suddenly disappears, the inverter system does not It will suddenly go offline and stand by, which improves the stability of the system;
[0059] The H-bridge inverter circuit 23 is used to invert the direct current provided by the energy storage battery 22 into alternating current by using carrier phase-shifting SPWM technology;
[0060] The bypass switch 24 is used to perform bypass ...
Embodiment 3
[0064] The unit controller 25 and the main controller 15 will be introduced in detail below, and the control method of the grid-connected inverter will be described in detail.
[0065] Unit controller 25, with digital signal processor (DSP) and programmable logic device (CPLD) as the core, monitors each unit, and feeds back unit failure, temperature, photovoltaic array terminal voltage and output current and other parameter information, and perform maximum power tracking control on the photovoltaic array; the above-mentioned maximum power tracking control on the photovoltaic array is specifically based on the terminal voltage U of each photovoltaic array sampled in real time PVk and output current I PVk , to calculate the output power P PVk (k=a 1 ,...,a n ;b 1 ,...,b n ; c 1 ,...,c n ), using the perturbation and observation method to perform maximum power tracking control on the photovoltaic array, so that the photovoltaic array works at the maximum power point, and s...
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