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The Working Principle And Three Modes Of Energy Storage Converters

2023-04-21

 

What is an energy storage system?

The energy storage system is an important component of the power production process. The energy storage system can effectively perform peak shaving and valley leveling, smooth load, and promote the application of renewable energy; It can adjust peak frequency and improve the stability of power system operation; It can effectively utilize power equipment and reduce power supply costs. The energy storage system has significant strategic significance for the construction of smart grids.

 

 

What is a bidirectional energy storage converter?

Bidirectional energy storage converters (PCs) are interfaces between the power grid and energy storage devices, suitable for applications that require dynamic energy storage (grid connected systems, off grid systems, and hybrid systems). They store energy when there is excess energy, convert the stored energy when there is insufficient energy, and output it to the power grid, or serve as the main power source in the microgrid to support the operation of the microgrid.

The bidirectional energy storage converter PCS product is used in energy storage systems. By connecting with the energy storage components and the public power grid, during the low load period of the power grid, the AC energy in the power grid is converted into DC energy to charge the energy storage components. During the peak load period of the power grid, the DC energy in the energy storage components is converted into AC energy that meets the requirements of the power grid, and fed back to the public power grid, playing the function of peak shaving and valley filling.

Ensure the normal operation of the power grid. A converter with a basic feature of bidirectional converter, which can be applied in grid connected and off grid situations, and has a series of special performance and functions. Implementing a flexible interface between energy storage and the power grid is suitable for the construction of smart grids.

 

What is the working principle of a bidirectional energy storage converter?

The working principle of energy storage converters is a controllable four quadrant operation converter device on the AC and DC sides, which achieves bidirectional conversion of electrical energy between AC and DC. The principle is to use microgrid monitoring commands for constant power or current control, to charge or discharge batteries, while smoothing the output of fluctuating power sources such as wind and solar power.

PCS adopts dual closed-loop control and SPWM pulse modulation method, which can accurately and quickly adjust the output voltage, frequency, active and reactive power.

The bidirectional energy storage converter PCS can respond to load fluctuations through rapid energy storage, absorb excess energy or supplement missing energy, achieve high-power dynamic regulation, and adapt well to frequency regulation and voltage power factor correction, thereby improving the stability of system operation.

 

What are the working modes of bidirectional energy storage converters?

The operation modes of bidirectional energy storage converter pcs are divided into grid connected mode, off grid mode and hybrid mode.

1. Grid connection mode

The grid connection mode includes charging and discharging functions, and users can choose between automatic mode and manual mode. In automatic mode, if the user selects grid connected charging or discharging status, the energy storage inverter will charge or discharge the battery at the previously set value.

In manual mode, users can manually modify the charging or discharging current, voltage, and time values to make the energy storage inverter work in the set charging or discharging state.

In grid connection mode, the energy storage inverter is connected to a large capacity public power grid, which refers to the total capacity of the grid being at least 10 times greater than the capacity of the energy storage inverter. The main feature of grid connection mode is that the energy storage inverter must be synchronized with the existing grid frequency.

To achieve synchronization with the power grid, the energy storage inverter serves as a current source relative to the power grid. In some cases, energy storage inverters must be able to provide voltage support to the power grid through reactive power control. This mode is commonly used for peak shaving and valley filling, power load balancing, and regulating power quality.

2. Off grid mode

An island system is a local "microgrid" formed by one or more power generation systems in parallel. The main feature of an isolated island system is that the local power grid is disconnected from all major power grids, and the rated power of the energy storage system is roughly equal to the total power generated by the local power grid. In this system, the energy storage system must be able to act as a network power source, providing voltage and frequency control to the local power grid.

On the other hand, if a power generation device cannot be synchronized with other power generation devices, such as a diesel generator connected to the local power grid, then the energy storage system must be synchronized as a power source. In some cases, the energy storage system also needs to switch between serving as a power source and synchronizing with the power generation device.

The characteristic of an isolated island system is that the energy storage system is connected to a local power grid, which may exist in remote mountainous areas or small islands. Common applications include smoothing power fluctuations caused by variable power sources and loads, stabilizing the power grid, optimizing fuel usage, and regulating power quality.

3. Mixed mode

The energy storage system can switch between grid connected mode and off grid mode. The energy storage system is in a microgrid, which is connected to the public power grid. Under normal working conditions, it operates as a grid connected system. If the microgrid is disconnected from the public power grid, the energy storage system will operate in an off grid mode to provide the main power supply for the microgrid. Common applications include filtering, stabilizing power grids, regulating power quality, and creating self-healing networks.

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