Energy Storage Inverter (Power Conversion System, PCS) is a key power electronic device. Its primary function is to achieve bidirectional conversion of electric energy, i.e., converting DC power to AC power for grid or load use, and converting AC power to DC power for storage in batteries. This bidirectional conversion capability makes PCS a bridge between the battery system and the grid (or load).
PCS involves three main processes: DC input, inversion process, and AC output. First, PCS receives energy input from renewable energy devices or other DC batteries, filters, and voltage regulation to ensure stable input voltage and current. Then, through the inversion process, DC power is converted to AC power. Finally, the AC output can either be fed into the grid or directly supply AC loads. PCS technical parameters include rated power, conversion efficiency, input/output voltage, and frequency range, ensuring stable and efficient system operation. Additionally, current detection technology is crucial in PCS, with common technologies including resistance sampling and Hall sensor sampling, which improve the system's control precision and stability.
Evaluating PCS performance and efficiency requires considering multiple aspects such as charge/discharge efficiency, grid-connected inversion efficiency, response capability, and stability. For example, a study shows that in residential scenarios, PCS's charge/discharge efficiency can reach 90%, while in large battery energy storage systems, PCS's overall efficiency can generally reach 96%. These data indicate that PCS efficiency directly impacts the operating efficiency and economy of the entire energy storage system. Moreover, inverter testing should not be limited to basic performance and safety evaluations but should also deeply analyze its response and efficiency under different conditions. This necessitates precise testing of PCS to ensure optimal operation under various environments and to predict and prevent potential issues. PCS performance testing items include charge/discharge conversion time detection, active grid-connected and off-grid switching tests, and more, comprehensively evaluating its stability and reliability in actual applications.
In terms of current detection technology, the latest developments include:
- The application of high-precision current sensors, which enhances the performance and safety of energy storage systems.
- Anti-reverse flow detection solutions, which, by installing meters or current sensors, monitor the current flow to the grid in real-time, improving system efficiency and safety.
- Development of energy storage inverter testing, such as the inclusion of over-frequency active power feed-in control function tests, to meet the requirements of international automatic frequency control services for energy storage systems.
- Improvements in Hall current sensor applications, designing zero magnetic flux Hall current sensors to address the shortcomings of traditional Hall current sensors, improving accuracy and efficiency in current detection.
These advances improve the precision and reliability of current detection, driving the development and application of energy storage technology.
