Micro-Grids, also known as Micro-Networks, are small-scale power distribution systems composed of distributed power sources, energy storage devices, energy conversion devices, loads, monitoring and protection devices, and more. They provide power to loads and primarily address the reliability of power supply.
What is a Micro-Grid?
A Micro-Grid is an autonomous system capable of self-control, protection, and management. It functions as a complete power system, relying on its own control and management to achieve power balance control, system operation optimization, fault detection and protection, and power quality management.
Purpose and Benefits
The concept of Micro-Grids aims to achieve flexible and efficient application of distributed power sources, addressing the challenges of integrating a vast number of diverse distributed power sources into the grid. Developing and extending Micro-Grids can fully promote the large-scale integration of distributed and renewable energy sources, ensuring reliable supply to various forms of loads. This serves as an effective way to transition traditional power grids to smart grids.
Key Components of a Micro-Grid
Micro-Grids typically consist of small-capacity distributed power sources with power electronic interfaces. These include micro gas turbines, fuel cells, photovoltaic cells, small wind turbines, and energy storage devices such as supercapacitors, flywheels, and batteries. These components are connected on the user side, characterized by low cost, low voltage, and minimal pollution.
Example System Setup
- **Energy Storage Converter**: A 50kW grid-connected/off-grid bi-directional energy storage converter, connected to the 0.4KV AC bus, enabling bi-directional energy flow.
- **Lithium Iron Phosphate Battery**: 110KWh
- **EMS & BMS**: Systems that control the charging and discharging of the energy storage system and monitor battery SOC information based on higher-level dispatch instructions.
System Features
1. **Peak Shaving and Backup Power**: The system is primarily used for peak shaving and as a backup power source, avoiding power capacity increases and improving power quality.
2. **Comprehensive Functionality**: The energy storage system boasts complete communication, monitoring, management, control, early warning, and protection functions, ensuring long-term safe operation.
3. **Advanced Communication and Monitoring**: The BMS system communicates with the EMS system and directly with the PCS via RS485 bus, achieving comprehensive battery monitoring and protection.
Operational Strategy
- **Grid Interaction**: The energy storage system can operate in grid-connected mode, regulating active and reactive power through PQ mode or droop mode to meet charging and discharging needs.
- **Peak Management**: During peak electricity prices or high load periods, the energy storage system discharges to the load, achieving peak shaving and energy supplementation.
- **Seamless Transition**: The energy storage converter can switch from grid-connected mode to island (off-grid) mode upon detecting a grid anomaly.
- **Independent Operation**: In off-grid mode, the energy storage converter acts as the primary voltage source, providing stable voltage and frequency to local loads.
Energy Storage Converter (PCS)
- **Advanced Parallel Technology**: Supports unrestricted parallel operation of multiple machines.
- **Multi-Source Integration**: Can directly network with diesel generators.
- **High Power Sharing Accuracy**: Achieves a power sharing degree of up to 99% in voltage source parallel mode.
- **Seamless Mode Switching**: Supports online seamless switching between grid-connected and off-grid modes.
- **High Efficiency**: Optimized hardware and software design, with a conversion efficiency of up to 98.7%.
- **Long Lifespan**: Designed for a lifespan of 20 years.
Communication Methods
1. **Ethernet Communication**: Direct connection between the energy storage converter's RJ45 port and the upper computer's RJ45 port for monitoring.
2. **RS485 Communication**: Optional RS485 communication scheme based on standard Ethernet MODBUS TCP communication.
3. **BMS Communication**: The energy storage converter communicates with the battery management unit BMS for state monitoring and protection.
BMS System
The Battery Management System (BMS) monitors battery voltage, current, insulation status, SOC, and more. It ensures the safety and reliability of battery operation, providing alerts and emergency protection for potential faults.
EMS System
The Energy Management System (EMS) is the top-level management system for the energy storage system, focusing on monitoring, data analysis, and real-time scheduling. It ensures reliable power supply and enhances system economy.
Key Functions:
- **Device Monitoring**: Real-time data monitoring and control of system equipment.
- **Energy Management**: Optimization control strategy for energy storage and load coordination.
- **Event Alerts**: Multi-level alert system with adjustable thresholds and response measures.
- **Report Management**: Comprehensive data statistics, analysis, and reporting functionalities.
- **Safety Management**: System operation authority configuration to ensure secure operation.
Safety and Monitoring
- **Comprehensive Monitoring**: Multi-channel video security monitoring covering key equipment and operation spaces, supporting long-term video data storage.
- **Fire and HVAC Systems**: Separate cooling and fire protection measures for equipment and battery compartments, utilizing advanced fire suppression systems like heptafluoropropane for efficient and safe fire management.
In summary, Micro-Grids represent a significant advancement in achieving flexible, efficient, and reliable energy supply solutions, particularly with the integration of distributed and renewable energy sources. By leveraging advanced technologies and comprehensive management systems, Micro-Grids pave the way for the future of smart grids.
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Post time: Jul-31-2024
