Power Conversion System (PCS) in Energy Storage Systems

Definition and Role

The Power Conversion System (PCS) is the core energy conversion device in an energy storage system that connects the storage battery with the external power grid or loads. It serves as the energy hub of the entire system. Its fundamental function is to realize bidirectional conversion between direct current (DC) and alternating current (AC), while also taking on key responsibilities such as energy scheduling and safety control within the system.
Energy Conversion Capability

At the level of energy conversion, the core value of the PCS lies in bridging the energy form gap between the storage battery and the grid or loads. Since the storage battery stores direct current and the grid and most loads use alternating current, the PCS enables flexible charging and discharging through its bidirectional conversion capability. During charging, it converts alternating current from the grid into direct current and efficiently stores it in the battery, for example by using off-peak electricity at night or surplus electricity generated from photovoltaics or wind power. During discharging, it converts direct current from the battery into alternating current to supply power during peak demand or feed electricity back to the grid for peak shaving or energy trading. This bidirectional capability forms the foundation for completing the energy storage and release cycle.

Energy Scheduling and System Coordination

The PCS does not simply perform passive energy conversion but actively carries out energy scheduling based on system strategies. It operates in real-time coordination with the Battery Management System (BMS), dynamically acquiring key parameters such as the state of charge, temperature, and state of health of the battery, and adjusts charging and discharging current and voltage accordingly to prevent overcharging or over-discharging. This effectively protects battery lifespan. At the same time, it works closely with the Energy Management System (EMS) to automatically switch charging and discharging modes according to electricity pricing policies, grid dispatch instructions, and load demands. This maximizes the economic and functional performance of the energy storage system.

Grid Compatibility and Safety Protection

In terms of grid compatibility and safety protection, the PCS plays a vital role. During discharging, it must ensure that the output alternating current fully matches the grid or load in voltage, frequency, and phase, for example by meeting the 380V and 50Hz standard. This avoids harmonic pollution or current surges and ensures stable grid operation. The PCS is also equipped with multiple built-in safety protections including overcurrent, overvoltage, overtemperature, and short-circuit protection, as well as anti-islanding protection to prevent backfeeding when the grid is offline. These functions effectively prevent equipment damage and safety incidents.

Performance Indicators and Application Scenarios

In addition, performance indicators of the PCS such as conversion efficiency, response speed, and power rating directly determine the applicable scope of the energy storage system. In residential and commercial energy storage scenarios, it supports time-of-use arbitrage and emergency backup to reduce electricity costs. In renewable energy supported storage systems, it helps absorb the fluctuation of photovoltaic and wind power and improves renewable energy utilization. On the grid side, it can participate in frequency regulation and peak shaving to support grid stability. In microgrid systems, it serves as the core device for switching between grid-connected and off-grid modes, ensuring power supply for remote areas or critical facilities.

Conclusion

In summary, the Power Conversion System is both the bridge that enables bidirectional DC and AC energy flow within the storage system and the central unit that ensures safe and efficient system operation. Its performance directly determines the economic viability, reliability, and application scope of the energy storage system. It is a key pillar for the practical implementation of energy storage technologies.

● Top 10 High Power PCS Suppliers Worldwide (2024)

According to the report released by the China Energy Storage Industry Alliance (CNESA) in July 2025, the top 10 Chinese enterprises in global PCS shipments in 2024 are as follows: