ALLPCB
Overview
An energy storage converter, or power conversion system (PCS), also called a bidirectional storage inverter, is the core component that enables two-way energy flow between an energy storage system and the grid. It controls battery charging and discharging and performs AC-DC and DC-AC conversion. In recent years, global energy storage demand has increased, and manufacturers in China are expanding overseas, making PCS a focus of technical attention.
Principle of Operation
The PCS operates as a converter capable of controlled four-quadrant operation on both AC and DC sides, enabling bidirectional conversion between AC and DC energy. It follows microgrid control commands to enforce constant-power or constant-current control for charging or discharging the battery, while smoothing output from variable sources such as wind and solar.
PCS Components
A PCS is built from hardware such as IGBTs (insulated-gate bipolar transistors), printed circuit board, cabling, and other components. Its main functions include power smoothing, data exchange, and protection. PCS design determines output power quality and dynamic performance, and it significantly affects battery lifetime.
Operating Modes
PCS operates mainly in three modes: grid-connected, islanded (off-grid), and hybrid. In grid-connected mode, the PCS enables bidirectional energy exchange between the battery and the grid. It follows microgrid control commands to implement constant-power or constant-current control for charging or discharging the battery, and smooths variable outputs from wind and photovoltaic generation. In islanded mode, the PCS supplies local loads with AC power that meets grid-quality requirements according to demand. In hybrid mode, the PCS can switch between grid-connected and islanded operation.
Main Functional Features
Key PCS features include protections against over- and under-voltage, overload, overcurrent, short circuit, and overtemperature; islanding detection for mode switching; communication interfaces for higher-level control systems and energy managers; and smooth control for transitions between grid-connected and islanded operation.
Application Scenarios
By application, PCS equipment falls into four main categories: utility-scale energy storage plants, centralized or string-level systems, commercial and industrial systems, and residential systems. The primary difference among them is power scale. Utility-scale PCS typically exceed 10 MW, use cascaded multilevel topologies and IGBT module designs, often install multiple AC converters in containers, support parallel operation of multiple units, and connect to the grid via step-up transformers. Centralized PCS usually start from around 250 kW, commonly use two-level topologies and modular IGBT designs, and can reach MW-class single-unit power with high reliability requirements. Commercial and industrial PCS are typically below 250 kW, often use three-level topologies, integrate with distributed PV for self-consumption and time-of-use optimization. Residential PCS are below 10 kW, pair with rooftop PV as backup power and for electricity cost management, and have higher requirements for safety and acoustic performance.
Development Trends
Technology routes divide into centralized inverters, string inverters, distributed inverters, and microinverters. Currently, many battery energy storage systems use centralized PCS, where paralleling many battery strings can cause imbalance among battery clusters. String-level PCS enable cluster-level management, improving system lifetime and usable discharge capacity over the life cycle. String-level PCS are beginning to scale. As the energy storage market grows, PCS is evolving from a simple conversion device to a more integrated unit. Future PCS will trend toward higher integration, using software development, upgrades, and optimization to enable intelligent control and enhanced safety, improving energy storage integration into the grid.
Industry Landscape and Providers
The PCS market includes many players from fields such as PV inverters, uninterruptible power supplies (UPS), EV chargers, and grid-side power transmission and distribution equipment. According to CNESA data, in 2022 in the Chinese market, the top ten China-based energy storage PCS providers by shipments were: Shangneng Dianqi, Kehua Shuneng, Suoying Dianqi, Yangguang Dianyuan, Huichuan Jishu, Nanrui Jibao, Shenghong Gufen, Hewang Dianqi, Zhiguang Chuneng, and Pinggao. In the 2022 global market, the top ten China-based providers by shipments were: Yangguang Dianyuan, Kehua Shuneng, Shangneng Dianqi, Guriwate, Shenghong Gufen, Nanrui Jibao, GoodWe, Suoying Dianqi, Huichuan Jishu, and Shouhang New Energy.
