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Application of hybrid on/off grid energy storage inverter in photovoltaic energy storage system
- Sep 10, 2018 -

In recent years, with the decline of PV subsidies in various countries, the investment income of PV projects has declined, and PV energy storage systems have become the choice of more and more people.

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According to different applications, photovoltaic energy storage power generation systems can be divided into four types.

· On/off-grid energy storage system

· Off-grid power generation system

· On-grid energy storage system

· Multi-energy hybrid microgrid system

Among them, the off-grid energy storage system is widely used in photovoltaic applications for self-use of photovoltaics, the self-use electricity price is much more expensive than the on-grid electricity price, and the peak electricity price is much more expensive than the trough electricity price.

The photovoltaic on/off-grid energy storage system consists of a photovoltaic array, a hybrid on/off-grid energy storage inverter, a battery pack, a load, and a power grid. The photovoltaic array converts the solar energy into electrical energy in the presence of light, and supplies power to the load through the on/off-grid energy storage inverter to charge the battery pack; when there is no light, the battery and the power grid supply the AC load.

Compared with the grid-connected power generation system, the cost of the off-grid integrated system has increased, but the application range is wider and the function is more powerful.

The core part of the system is the hybrid on/off-grid energy storage inverter. Through the setting of the inverter, a variety of working modes can be realized.

On/off-grid energy storage inverter working mode:

1. Self utilization mode: Applicable to areas with low subsidies and high electricity prices.

1) In the daytime when the sun is shining, the energy from the solar panels is supplied to the load first, and the excess energy is first supplied to the battery for charging and then sold to the grid.

a. Solar panel power generation

b. Load consumption

c. Excess energy is stored in the battery

d. The remaining energy is sold to the grid

2) When the solar panel does not generate electricity at night, the battery is first discharged to the load. When the battery stores the power, the grid supplies power to the load.

a. battery discharge

b. The grid supplies power to the load

c. Load consumption

2. Economic model: Applicable to areas with large gaps between peak and valley electricity prices. By manually setting the charge and discharge period of the battery, the peaks and valleys are filled, and the electricity price difference between the peaks and valleys is earned. .

1) During the period when the electricity price is cheap, the load uses the electricity of the grid, and at the same time, the electricity generated by the panel is stored.

2) During the period when the electricity price is high, the load is preferentially used for the battery.

a. Solar panel power generation

b. Store energy in the battery

c. Load consumption

d. The grid supplies power to the load

3. Backup power mode: Applicable to areas with frequent power outages, used as backup power when the grid is out of power.

In this mode, when there is a grid access, the battery will always be in a state of charging and will not discharge. When the grid is out of power, the battery is discharged for use. When the grid resumes power supply, it will automatically connect to the grid.

a. Solar panel power generation

b. Load consumption, first use the electricity in the battery

c. Battery discharge

d. When the battery is not energetic enough, the grid supplies power to the load.

4. Off-grid mode: Applicable to areas without grid access.

In areas where there is no grid access, the daytime battery pack supplies power to the load, excess power is stored in the battery, and the battery discharges power to the load at night.

1). Solar panel power generation

2). The battery supplies power to the load

3). Load consumption

On/off-grid energy storage inverter has many working modes and functions, so it is widely used in energy storage system.