Power Conversion System (PCS)

As one of the core components of the energy storage system, the PCS controls the charging and discharging process of the battery pack and realizes AC to DC conversion, but also directly supplies power to AC loads when there is no power grid. After receiving the background command, the control unit in the PCS controls the converter to charge or discharge the battery and adjust the active and reactive power of the grid through the sign and size of the power command. In addition, the PCS control unit communicates with the BMS through the CAN interface to obtain battery pack status to perform protective charging and discharging to ensure safe battery operation.

The PCS’s working modes include grid-connected and off-grid. Its main function is to control the charging and discharging process of the energy storage battery, i.e., to convert the DC power from the battery into AC and connect it to the grid, or to convert the AC power from the grid into DC power and store it in the battery, and to precisely control the voltage, frequency, and transmission power of the grid during the conversion process.

As shown in the figure below, a single-phase grid-connected PCS generally consists of two stages: front DC/DC and rear DC/AC. The front DC/DC is used as the power control stage of the battery and consists of a bi-directional BUCK-BOOST circuit, which responds to charging and discharging commands by controlling the current flowing through the battery; the rear DC/AC is used as a bridge connecting the grid and the battery, to capture the voltage and frequency of the grid to control and connect the PCS to the grid and adjust the bus voltage to a voltage platform suitable for energy storage work. The APM32F107 series industrial-grade interconnected MCUs with high-efficiency computing capability, rich peripherals, and enhanced storage can realize the application requirements of single-phase grid-connected PCS front and rear stage control with a single chip.

APM32F107 Single-phase Grid-connected PCS Solution Advantages

•  32-bit Arm® Cortex®-M3 core, operating at 96MHz and supporting DC to DC and DC to AC conversion

•  Built-in two 12-bit high-precision ADCs with up to 16 external channels, support DMA, meeting the 3-channel voltage and 3-channel current acquisition requirements of DC to DC and DC to AC units

•  A 16-bit advanced timer with 7-channel PWM output supports functions such as dead-zone generation and brake input to meet DC to DC, and DC to AC control requirements and the brake input can quickly stop in an emergency to protect the device from damage

•  Four 16-bit universal timers with capture function to capture power grid frequency in real time

•  Three USART communication interfaces to support battery and upper system interaction requirements

•  Flash up to 256KB, SRAM up to 64KB to meet program storage and computing requirements, and has redundancy to support program expansion

•  84 Bytes backup registers can flexibly save control parameters without external EEPROM

The APM32F107 series MCU is an industrial-grade interconnected MCU released in November 2022, which is the preferred product for embedded applications with high performance, low power consumption, transmission connectivity, and real-time functions. At present, this series has been developed and applied by customers in the fields of industrial gateways, PLCs, building controllers, PV inverters, and switches.

To provide all-around product services to the market, Geehy provides a variety of PCS solutions to help customers achieve more different functional needs. At the same time, it will also continuously upgrade APM32 series MCUs’ product performance and application expansion.