Load Sharing System

Overview

A Load Sharing System plays a critical role in managing power distribution efficiently. The monitoring system is a vital component, responsible for collecting data, analyzing it, and providing information to the user or control system for optimal decision-making regarding load distribution or disconnection.

 

Main Functions of the Monitoring System

1. Parameter Measurement

• Voltage and Current: Measurement of voltage and current for each inverter and the grid.
• Active and Reactive Power: Measurement grid and each inverter’s active and reactive power.
• Frequency and Power Factor (PF): Monitoring frequency and PF to maintain grid and inverters stability.

 

2. Status Display

• Real-time status of inverters (ON, OFF, Standby, Fault).
• Status of loads.
• Overall grid status (Voltage, Frequency, Power and Energy).

 

3. Alarm Management

• Detecting faults such as overload, overcurrent, under voltage, over voltage and reverse power.
• Logging and archiving events for later review.

 

4. Data Analysis

• Analyzing load consumption to prioritize loads.
• Identifying weaknesses in the system and providing recommendations for improvement.
• Displaying reports and historical trends.

 

Components of a Load Sharing System

1. Power Sources

• Inverters: Provide power from DC sources.
• Electrical Grid: Acts as the main power supply, operating at 600 volts in your system.

 

2. Electrical Loads

• Equipment and devices consuming power (e.g., electric motors, lighting, heating, and cooling systems).

 

3. Central Controller (PLC)

• Core component for system monitoring and control.
• According to each inverter’s consuming load and producing power, amount grid’s receiving power will be controlled.
• Communicates grid and inverters’ control system with control and monitoring systems.

For example: The load of each inverter is set equally so that:

• 90% of the power is supplied by the hydrogen fuel cell.
• 10% of the power is supplied by the electrical grid.

If the total load demand increases or one of the inverters encounters an issue, the load is redistributed proportionally among the remaining inverters.

 

4. Input/Output (I/O) Modules

• Inputs: Receive signals from circuit breakers and inverters.
• Outputs: Send signals to circuit breakers and inverters.

 

5. Protective Relays

• Control Relays: They protect inner electricity network from overload, over current, under voltage and reverse power.

 

6. Monitoring System and HMI

• HMI (Human-Machine Interface): Displays information and allows operators to input commands.

 

7. Sensors and Instrumentation

• Current and Voltage Measurement: Current Transformers (CT) and Voltage Transformers (VT).
• Power Measurement: Measurement grid and each inverters’ voltage, current, frequency and power.

 

8. Communication and Protocols

• Modbus TCP.

 

9. Load Sharing Logic

• Compare each inverters’ power with incoming power grid and then send the command to the inverters to adjust load sharing between inverters and grid, as a result it prevents overload, over current, under/ over voltage and reverse power.

 

Benefits and Advantages of this Design

• Load Balancing: Uniform power distribution among the inverters prevents overload or underutilization of any inverter.
• Flexibility: Operators can switch between operating modes as needed.
• High Efficiency: Maintaining the 90%/10% ratio reduces costs and extends the life of the hydrogen fuel cell. Optimized load distribution minimizes power losses and improves inverter lifespan.
• System Stability: The grid acts as a backup to ensure continuous power supply to the loads.
• Scalability: The modular design supports future capacity expansion.
• Reliability: Fault-tolerant architecture reduces downtime risks.
• Compliance: Meets IEEE 1547 and IEC 62116 standards for inverter-based power systems.

 

Implement and Execute the Project

How does the system work? a dedicated controller is installed for each inverter and the incoming network power. This controller is responsible for measuring the momentary power of the inverters and the network. To enable accurate measurements, current and voltage transformers (CTs and VTs) are installed on the input from grid and inverters feeders. These devices calculate real-time power values, which are then displayed on the monitoring system to provide continuous updates on load distribution.

When commissioning a new inverter, the maintenance team must assess the operational status of the existing inverters and evaluate their power output, as well as the network capacity, by referring to the HMI, which displays the conditions of the inverters. The setpoint for the new inverter is determined to ensure that the sum of all inverter outputs does not exceed the network’s current capacity, preventing overloading and backfield (power to grid). For instance, if the network input is 500 kW, the total allowable output from the inverters would be limited to 450 kW, leaving a 10% buffer to accommodate network stability.

In automatic mode, the system divides the allowable power equally among the active inverters. If two inverters are operational, each would output 225 kW from the total 450 kW. If three inverters are used, the power is evenly distributed at 150 kW per inverter. This ensures uniform load sharing without manual intervention. In manual mode, operators can adjust the power output of each inverter through the monitoring system, allowing flexibility to match specific operational needs. However, it is critical that the total power output remains within the network’s 500 kW limit to maintain system stability and efficiency. Whether in automatic or manual mode, the load-sharing system harmonizes the inverter outputs with the network capacity, ensuring safe, efficient, and balanced power distribution while adhering to operational constraints.

 

Explanation of Monitoring System

For each inverter, grid and a central control HMI (Human-Machine Interface) monitors will be installed to provide a comprehensive view of the network and inverter parameters, including power and both current and voltage readings. This system will allow operators to monitor not only the specific parameters of each individual inverter but also the overall performance of all inverters and the network simultaneously. By displaying real-time data such as momentary power, current power, total energy in kilowatts (kW), and hourly energy consumption, the monitoring system acts as a centralized hub for tracking system performance.

Furthermore, the system will continuously collect and process data, ensuring that any discrepancies or inefficiencies in power distribution are immediately identified. It will provide valuable insights into the energy flow, helping to optimize the performance of both the inverters and the network. The HMI interface will also allow for remote monitoring and adjustments, offering greater flexibility and control for the operators. In addition, the ability to visualize and analyze trends in energy production and consumption over time ensures that the system operates within optimal parameters, improving both efficiency and longevity of the components involved.