As an important power source for the DC systems of power plants, substations and converter stations, battery packs provide uninterrupted power for relay protection, communication control, emergency lighting and other equipment. Their power supply capacity is the final guarantee for the stable operation of plant and station equipment, and their performance is directly related to the safety and reliability of power and communication systems. Therefore, the stability and actual discharge capacity of battery packs are of great significance to ensure the normal operation of power equipment.

Clause 5.3.3.4 of The 18 Major Anti-Accident Measures for Power Grids of State Grid Corporation of China (2018) requires a capacity verification discharge test for newly installed batteries once every 2 years, and an annual capacity verification discharge test after 4 years, so as to track and check the voltage, internal resistance, temperature, capacity and other parameters of battery packs. Traditional on-site capacity verification operations are cumbersome and consume a lot of manpower and material resources, yet battery faults still cannot be detected in a timely manner. Due to the lack of online monitoring and online safety maintenance devices, the operation and maintenance mode has certain limitations. There is an urgent need for a more effective online monitoring and operation and maintenance system to grasp the real-time status, detect faulty batteries in a timely manner and eliminate potential safety hazards.

△ MDC-2000 Substation Battery Comprehensive Monitoring and Remote Automatic Maintenance System

The MDC-2000 Substation Battery Comprehensive Monitoring and Remote Automatic Maintenance System is a multifunctional modular comprehensive monitoring and management system with multi-state monitoring and remote online automatic charging and discharging, developed by Wuhan Haomai Electric Power based on years of DC operation and maintenance experience. It overcomes the shortcomings of the current static, offline and intermittent battery maintenance methods, can completely replace the manual maintenance mode and realize remote online capacity verification discharge maintenance. The system monitors the operating and performance parameters of DC systems and battery packs online, fully understands the performance status of batteries, detects lagging single cells in a timely manner, realizes medium and long-term big data analysis, eliminates potential safety hazards, and provides technical guidance and good guarantee for the reliable operation of battery packs and DC systems.

The system consists of two parts: a remote management background system (management layer) and a station-side online monitoring and automatic capacity verification maintenance system (execution layer). The remote host manages the station-side capacity verification systems of multiple substations through the integrated data network, realizing online status monitoring and data analysis of the DC systems of each substation, as well as remote control of the automatic discharge and charge capacity verification of each battery pack in each station.

△ MDC-2000A Remote Automatic Maintenance System for Single Battery Pack

The remote discharge test of batteries is divided into a battery discharge supervision module and an inverter module, which monitor the battery pack terminal voltage, pack terminal current and other parameters. When the battery charging and discharging requirements are met, the battery is automatically disconnected from the bus, then connected to the inverter discharge device, and the discharge device is controlled to start the discharge process. After the discharge is completed, the switch connecting the battery to the inverter is automatically turned off, so that the charger performs the equalizing charge process for the battery pack. When the charger status changes from equalizing charge to floating charge, the battery is put into the normal operation of the bus.

Remote offline capacity verification discharge is to automatically perform battery capacity verification discharge regularly or under control, and detect various parameters under the dynamic charging condition of the battery. The big data throughout the whole life cycle is used for all-round and multi-variable analysis of the battery health status, so as to detect lagging batteries in a timely manner and realize online automatic maintenance of batteries. The safe remote capacity verification discharge technology reduces on-site workload and solves the problem of long-term charging without discharging of batteries. At the same time, the online discharge electric quantity is fed back to the power grid through inversion, the discharge heat is greatly reduced, the tripping current of protection and control equipment is guaranteed, the discharge safety is improved, and it meets the requirements of green environmental protection.

Internet of Things & Cloud Platform: It can form an independent network and connect to the remote operation and maintenance platform for data management and analysis.

Comprehensive and Long-term Online Monitoring: Battery pack operation status, pack terminal voltage, AC/DC voltage and current, charging and discharging current, various switch statuses, ambient temperature, voltage, internal resistance and temperature of each single battery, etc.

One-click Inversion Capacity Verification Discharge: Realize remote one-click automatic capacity verification test of batteries in dual-charger dual-battery and single-charger single-battery systems.

Fully Electric-controlled Automatic Operation: Remotely control the switchover of various switches to discharge status, realize bus parallel connection, with one battery pack discharging for the bus and the other battery pack isolated for offline discharge.

Local Data Viewing and Analysis: Real-time viewing of operating data charts, historical record data charts, real-time and previous charging and discharging curve data, etc., as well as data analysis and alarm.

Background Data Recording, Archiving and Analysis: Real-time operating data, charging and discharging data and historical data are all transmitted to the background remotely to realize long-term big data management and analysis. The background monitors the charging and discharging process in real time.

Alarm and Early Warning: Real-time analysis, timely detection and alarm of battery and AC/DC faults, and intelligent analysis for early warning.

Intelligent Multiple Protection: Safety prevention for battery thermal runaway monitoring, anti-islanding protection function, termination of discharge in case of AC/DC system abnormalities and device faults, etc., to ensure safe discharge and system safety.

△ Application Site

The MDC-2000 Substation Battery Comprehensive Monitoring and Remote Automatic Maintenance System has been widely promoted and applied in substations, power plants, large power consumers, railways, telecommunications and other fields across the country. Replacing traditional manual work with battery pack online comprehensive monitoring and remote charging and discharging technology features simple operation and safe automatic protection, which greatly reduces the intensity of operation and maintenance work and has been unanimously recognized by user units. Through real-time online monitoring of battery packs, the real-time status is grasped, faulty batteries are detected in a timely manner, potential safety hazards are eliminated, the service life of batteries is effectively prolonged, the uninterrupted operation of the power supply system is guaranteed, and a strong guarantee is provided for the safe and stable operation of the power grid.