This project integrates a 500kW PV system and a 2MWh ESS. The hybrid microgrid project can operate both grid-connected and off-grid. It uses solar power to supply loads, with the grid for shortfalls and excess storage. The ESS optimizes energy use. It charges during off-peak times and discharges during peak times. It leverages peak-valley pricing for revenue.
Table of Contents
Hybrid Microgrid Project Introduction
The system has a 500kW PV system and a 2MWh ESS. It forms a microgrid that is both grid-connected and off-grid. PV power generation supplies the load, the grid supplements any shortfall, and the ESS batteries store excess PV power. The ESS charges and discharges during peak and off-peak periods to earn revenue from the peak-valley price difference. The same grid-connected cabinet connects both the PV system and ESS. The entire system is connected to the low-voltage side of the user-side transformer.
PV System
- The area available for installing PV modules can accommodate a PV system with a capacity of about 500kW.
- The modules use 450Wp monocrystalline silicon cell components. They connect 17 modules in series as one string. There are 70 strings, for a total of 1,190 PV modules. The total capacity is 535.5kWp.
- The PV arrays connect to two 150kW PV-storage machines. They then connect to the low-voltage side of the user-side transformer via the grid-connected cabinet.
ESS
- Each battery cluster in this project includes 9 battery modules, each module being 51.2V/280Ah with a capacity of 14.336kWh.
- Each cluster has a capacity of 129kWh. The high-voltage box is integrated within the battery cluster for real-time protection.
- The entire ESS consists of a battery system, a confluence cabinet, a PV-storage machine, an automatic fire extinguisher, and a temperature control system. The battery system includes multi-level master-slave control, a high-voltage box, a rack, and a battery pack.
- The entire battery system has a total of 16 battery clusters. Every 8 battery clusters are connected to an 8-in-1-out confluence cabinet through a high-voltage box. Each confluence cabinet is connected to the DC side of a 150kW PV-storage integrated machine after confluence. The total capacity of the entire ESS is 2.064MWh.
- The battery compartment and electrical compartment have separate designs. The battery compartment has a smoke sensor, a temperature sensor, a heptafluoropropane fire extinguishing system, and an air conditioning heat management system. The cable penetrations are sealed with fire-resistant mud. The battery compartment is in an independent space to further enhance fire safety protection measures.
PV-Storage Integrated ESS
The project uses two 150kW PV-storage integrated containers with the following features:
- Grid-connected charging/discharging and independent inverter functions, suitable for various application scenarios
- Grid-connected and off-grid functions, can operate in parallel, with good scalability
- Can interface with various batteries, with multiple charging/discharging working modes
- Can receive real-time system and BMS dispatch instructions via RS485, CAN, and Ethernet.
- Supports IEC104 and MODBUS communication protocols
- Adjustable reactive power, power factor range exceeding 0.9 leading to 0.9 lagging
- Wide DC voltage working range
- Low voltage and zero voltage ride-through capabilities to cope with complex grid conditions
- Autonomous and controlled frequency and voltage regulation functions
- Strong off-grid three-phase unbalanced load capability
- Strong system overload capability
- Dry contact output, supporting remote control of diesel generators
Electrical Schematic
FAQ
What is the difference between a grid-connected and off-grid microgrid?
A grid-connected microgrid is connected to the main utility grid and can exchange power with it. An off-grid microgrid operates independently without a connection to the main grid. A microgrid that can operate in both modes, like the one in this project, is sometimes called a hybrid microgrid.
How does the PV system supply power to the load?
The PV system generates electricity from solar energy and directly supplies power to the load. When the PV generation is insufficient to meet the load demand, the shortfall is supplemented by the main grid. When the PV generation exceeds the load demand, the excess power is stored in the ESS batteries for later use.
How is fire safety addressed in the ESS design?
Fire safety is a critical consideration in ESS design due to the high energy density of batteries. In this project, several measures are taken to enhance fire safety:
1. The battery compartment and electrical compartment are physically separated
2. The battery compartment is equipped with smoke sensing, temperature sensing, and a heptafluoropropane fire extinguishing system
3. Cable penetrations are sealed with fire-resistant mud
4. The battery compartment is located in an independent space to isolate potential fire hazards
How does the hybrid microgrid project connect to the main grid?
The PV system and ESS are connected to a grid-connected cabinet, which then connects to the low-voltage side of the user-side transformer. This transformer serves as the interface between the microgrid and the main grid, allowing power to flow in both directions as needed.
What are some of the challenges in implementing a hybrid microgrid project?
While hybrid microgrids offer many benefits, there are also several challenges in their implementation:
1. Higher upfront capital costs compared to traditional grid-connected systems due to the need for additional equipment such as ESS and control systems
Increased complexity in system design, control, and operation to ensure seamless transition between grid-connected and off-grid modes
2. Need for advanced energy management systems to optimize the operation of various microgrid components based on factors such as load demand, PV generation, electricity prices, and grid conditions
3. Regulatory and interconnection challenges, as the rules and procedures for connecting microgrids to the main grid may vary by jurisdiction and utility
4. Ensuring the safety and reliability of the microgrid, particularly the ESS, through proper design, maintenance, and operational practices
