Active power load sharing

 Active power (kW) load sharing is the proportional distribution of real power demand among multiple paralleled generators, managed by regulating engine speed governors to increase or decrease fuel input. It prevents individual unit overloading, ensures system stability, and maintains constant frequency, typically using droop or isochronous control methods.

Principles of Active Power Load Sharing

• Definition: The proportional division of total system kW load among parallel generators to ensure no unit exceeds its capacity.
• Engine Governor Control: Active power is controlled by the engine's speed governor. Increasing fuel to one engine increases its proportion of the total kW load, not its speed, provided it's in parallel.
• Droop Control (P - f): A method where a generator’s speed decreases slightly as its load increases (typically 4-5% from no-load to full-load), allowing units to share load.
• Isochronous Control: A method where load-sharing controllers manage kW sharing without frequency dropping, keeping speed constant.

Key Concepts in Active Power Control

• Load Sharing vs. Balancing: Load sharing splits load based on capacity, while load balancing may look at total system efficiency.
• Reverse Power: If one generator loses power (fault), other units can drive it, causing reverse power. Proper load sharing prevents this.
• Active vs. Reactive Power: Active power (kW) is handled by the fuel system (governor), while reactive power (kVAr) is managed by the alternator's excitation system (AVR).
• Communication methods such as CANbus are often used to exchange data between controllers for precise, rapid load sharing.

Common Control Strategies

• Droop Speed Control: Ensures stability and simple load sharing, though frequency may drop with increased load.
• Isochronous Load Sharing: Uses electronic controllers to maintain constant frequency while sharing load equally.
• Master-Slave/Peer-to-Peer: Different control modes, with peer-to-peer (e.g., droop) offering better reliability and no need for communication in some cases

Active power load sharing is the proportional division of the real power (measured in kilowatts, kW) between multiple power sources, such as generators or inverters, operating in parallel to supply a common electrical load. This process ensures that no single unit is overloaded and that the entire system remains stable and efficient.

Core Mechanism

In traditional generator systems, active power sharing is directly controlled by the engine speed governor.

• Fuel Regulation: To increase the active power output of a specific generator, the governor increases fuel flow to its engine.
• Constant Speed: Because the generators are synchronized to a common bus, increasing fuel does not increase the engine's speed; instead, it increases the torque applied to the rotor, allowing that generator to take a larger share of the total system kW.
• Balancing: If one generator increases its output, the others will automatically reduce theirs to maintain the constant system frequency.

Common Control Methods

Key Benefits

• Reliability: Prevents total system failure if one unit trips; the remaining units automatically absorb the shed load.
• Efficiency: Allows units to run at their optimal load range (typically 75–80%), reducing fuel consumption and engine wear.
• Scalability: New power sources can be added to the system to meet growing demand without replacing existing infrastructure.

For industrial applications, modern digital controllers like the Deep Sea Electronics (DSE) 8610 or Woodward Controllers are standard for managing these complex real-time adjustments.