Basic Knowledge of Energy Storage | Three Core Systems – Energy Storage Converter (PCS)

In the process of accelerating the achievement of dual-carbon goals and building a new type of power system, energy storage technology is gradually becoming one of the key technologies to support the stable operation and optimize resource allocation of the new power system. Among them, the PCS (Power Conversion System) energy storage converter, as a core device of the energy storage system, its performance and application directly affect the overall efficiency and stability of the energy storage system. This article will conduct an in-depth analysis and interpretation of the definition, working principle, main features, operating modes, application scenarios, and future development trends of the PCS energy storage converter.

The PCS energy storage converter, full name Power Conversion System, is a key device in the energy storage system, used to achieve energy conversion and bidirectional flow between the energy storage battery and the power grid. It can convert direct current to alternating current or convert alternating current to direct current to meet the power grid’s charging and discharging needs of the energy storage system. The PCS energy storage converter plays the role of a “bridge” in the energy storage system, connecting the energy storage battery and the power grid, ensuring the efficient and stable operation of the energy storage system.

The working principle of the PCS energy storage converter is mainly based on electronic technology, achieving energy conversion and bidirectional flow by controlling the opening and closing of switching devices. When the power grid needs the energy storage system to discharge, the PCS energy storage converter converts the direct current from the energy storage battery to alternating current and outputs it to the power grid; when the power grid needs the energy storage system to charge, the PCS energy storage converter converts the alternating current from the power grid to direct current and stores it in the energy storage battery. During the discharging process, the PCS energy storage converter also needs to carry out precise power control and energy management according to the needs of the power grid and the status of the energy storage battery to ensure the stable operation and efficient use of the energy storage system.

1. Efficient Energy Conversion: The PCS energy storage converter uses advanced power electronic technology and control strategies to achieve efficient and stable energy conversion and bidirectional flow. Its conversion efficiency is as high as over 95%, which can significantly reduce the operating costs of the energy storage system.
2. Precise Power Control: The PCS energy storage converter has precise power control capabilities and can adjust in real-time according to the needs of the power grid and the status of the energy storage battery. Through precise power control, the PCS energy storage converter can achieve rapid response and precise regulation of the energy storage system, improving the stability and reliability of the power system.
3. Intelligent Energy Management: The PCS energy storage converter also has intelligent energy management functions, which can intelligently schedule and optimize according to the load conditions of the power grid and the status of the energy storage battery. Through intelligent energy management, the PCS energy storage converter can achieve maximum utilization and minimum loss of the energy storage system, improving the economic and environmental protection of the entire power system.
4. Flexible Configuration and Expansion: The PCS energy storage converter uses a modular design and can be flexibly configured and expanded according to actual needs. By increasing or reducing the number of modules, precise adjustment of the energy storage system capacity can be achieved to meet the needs of different application scenarios.

1. Grid-connected mode: Achieve bidirectional energy conversion between the battery pack and the power grid according to the power instructions issued by the upper-level dispatch; such as charging the battery pack during the low load period of the power grid, and feeding back to the power grid during the peak load period;
2. Off-grid/Island mode: Under certain conditions, disconnect from the main power grid and provide local partial load with alternating current energy that meets the power grid quality requirements.
3. Hybrid mode: The energy storage system can switch between grid-connected mode and off-grid mode. The energy storage system is in a microgrid, and the microgrid 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 off-grid mode to provide the main power source for the microgrid. Common applications include filtering, stabilizing the power grid, regulating power quality, and creating self-healing networks.

1. Energy Time-shifting: In user-side energy storage systems, PCS energy storage converters can be used for energy time-shifting, storing excess photovoltaic power generated during the day and releasing it through the PCS during the evening or cloudy weather periods when there is no photovoltaic power generation, to achieve maximum utilization of photovoltaic power for self-consumption.
2. Peak Valley Arbitrage: In user-side energy storage systems, especially in commercial parks with time-of-use electricity pricing, PCS energy storage converters can be used for peak valley arbitrage. By charging during low electricity price periods and discharging during high electricity price periods, low charge and high discharge arbitrage can be achieved to save the overall electricity cost of the park.
3. Dynamic Capacity Expansion: In scenarios with limited power capacity, such as electric vehicle charging stations, dynamic capacity expansion can be achieved through PCS energy storage converters and energy storage batteries. During charging peaks, the PCS energy storage converter discharges to provide additional power support; during charging troughs, the PCS energy storage converter charges and stores low-cost electrical energy for standby, which can achieve peak valley arbitrage and dynamic capacity expansion of the charging station.
4. Microgrid Systems: In microgrid systems, PCS energy storage converters can achieve coordinated control of distributed power sources and energy storage systems, improving the stability and power supply quality of microgrids. Through precise power control and intelligent energy management of the PCS energy storage converter, balance and optimize the scheduling of power sources and loads in the microgrid system.
5. Power System Frequency Regulation and Peak Shaving: In the power system, PCS energy storage converters can be used for frequency regulation and peak shaving, improving the stability and reliability of the power grid. When the power grid load is high, the PCS energy storage converter can release energy from the energy storage battery to provide additional power support to the power grid; when the power grid load is low, the PCS energy storage converter can absorb excess energy from the power grid to charge the energy storage battery for later use.

At present, centralized PCS is widely used in large-scale energy storage stations, where one high-power PCS controls multiple clusters of batteries in parallel, and the imbalance issue between battery clusters cannot be effectively addressed; while string-type PCS, one medium-small power PCS only controls one cluster of batteries, achieving one cluster one management, effectively avoiding the wooden barrel effect between battery clusters, enhancing system life, and improving the full life cycle discharge capacity. The trend of large-scale application of string-type PCS has taken shape, and in industrial and commercial integrated energy storage cabinets, string-type PCS has become the industry’s mainstream solution, and will also achieve large-scale application in large-scale energy storage stations in the future.

With the rapid development of new energy and smart grids, as well as the continuous progress of energy storage technology, PCS energy storage converters will face greater development opportunities and challenges. In the future, PCS energy storage converters will develop towards higher efficiency, greater intelligence, and more flexibility.

On the one hand, with the continuous advancement of power electronics technology and the continuous application of new materials, the conversion efficiency of PCS energy storage converters will be further improved. On the other hand, with the continuous development and application of big data, cloud computing, artificial intelligence and other technologies, the intelligent energy management capabilities of PCS energy storage converters will be further enhanced to better meet the needs and optimize the scheduling of the power system. In addition, with the continuous expansion and deepening of energy storage system application scenarios, PCS energy storage converters will also face more customized needs and innovative challenges.