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Control method and system for parallel connection of alternating current sides of photovoltaic inverters

A technology for photovoltaic inverters and control methods, applied in the fields of converting irreversible DC power input into AC power output, photovoltaic modules, photovoltaic power generation, etc.

Active Publication Date: 2015-04-22
SUNGROW POWER SUPPLY CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] Although the inverters connected in parallel on the AC side have advantages, there are parasitic capacitances between the positive and negative poles of the PV array to the ground, which causes coupling on the DC side of each inverter in the parallel system, thereby forming a common-mode loop and causing common-mode circulation problems.

Method used

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  • Control method and system for parallel connection of alternating current sides of photovoltaic inverters
  • Control method and system for parallel connection of alternating current sides of photovoltaic inverters
  • Control method and system for parallel connection of alternating current sides of photovoltaic inverters

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Embodiment 1

[0049] see image 3 , which is a flow chart of Embodiment 1 of the control method for the parallel connection of photovoltaic inverters on the AC side provided by the present invention.

[0050]The control method for the parallel connection of the AC side of the photovoltaic inverter provided in this embodiment is applied to an inverter system in which the AC side is connected in parallel and the DC side is independent, and at least includes the following two inverters: the first inverter and the second inverter. Two inverters; the input end of the first inverter is connected to the first PV array, the input end of the second inverter is connected to the second PV array, and both the first PV array and the second PV array exist a parasitic capacitance to ground, the first inverter and the second inverter are coupled through the parasitic capacitance to form a common-mode loop;

[0051] Include the following steps:

[0052] S301: Detect the first DC voltage of the first inver...

Embodiment 2

[0072] see Figure 4 , which is a flow chart of Embodiment 2 of the control method for the parallel connection of photovoltaic inverters on the AC side provided by the present invention.

[0073] In this embodiment, the inverters connected in parallel are divided into master and slave as an example for illustration. Still taking two inverters as an example, the first inverter acts as a master, and the second inverter acts as a slave.

[0074] S401: Detect the first DC voltage of the first inverter and the second DC voltage of the second inverter;

[0075] Specifically, the host sends its own first DC voltage to the slave, and the slave compares the first DC voltage with its own second DC voltage;

[0076] It can be understood that the inverters connected in parallel can communicate with each other.

[0077] S402: Obtain the absolute value of the difference between the first DC voltage and the second DC voltage;

[0078] It can be understood that since the difference may be...

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Abstract

The invention provides a control method and system for parallel connection of the alternating current sides of photovoltaic inverters. The control method and system are applied to an inverter system with alternating sides connected in parallel and direct current sides independent. The input end of the first inverter is connected with a first PV array, the input end of the second inverter is connected with a second PV array, ground stray capacitance exists in the first PV array and the second PV array, and the first inverter and the second inverter are coupled to form a common mode loop through the ground stray capacitance. The control method comprises the steps of detecting the first direct current voltage of the first inverter and the second direct current voltage of the second inverter, acquiring the difference value of the first direct current voltage and the second direct current voltage, and adjusting the direct current voltages of the inverters to control the difference value within a preset range and control the common mode voltage in the common mode loop within a preset range. The smaller the difference value of the inverters is, the smaller the common mode voltage difference between the inverters will be, and the smaller the common mode current will be, so that common mode loop current between the inverters is restrained.

Description

technical field [0001] The invention relates to the technical field of photovoltaic power generation, in particular to a control method and system for parallel connection of alternating current side of photovoltaic inverters. Background technique [0002] With the continuous expansion of the capacity of new energy power stations, in order to realize the optimal allocation of grid-connected inverter capacity and realize the single-machine WM-level solution, the parallel connection of inverters has become a trend of technological development. Parallel connection of the AC side of the inverter has the following advantages: [0003] The double-split transformer can be replaced by a double-winding transformer on the AC side, saving system investment costs; the original maximum power point tracking MPPT is not lost, and there are few changes in system layout and structure. [0004] see figure 1 , which is a schematic diagram of inverters connected in parallel on the AC side in t...

Claims

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Application Information

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IPC IPC(8): H02J3/38
CPCH02J3/381H02J2300/26H02J3/46H02M7/493H02J2300/24Y02E10/56H02M1/123H02S40/32H02M7/44
Inventor 潘年安程林陶磊
Owner SUNGROW POWER SUPPLY CO LTD