Calculating electrical load sharing in parallel generators involves determining how the total electrical load is distributed among the generators operating in parallel. The goal is to ensure that each generator carries its fair share of the load to maintain stability and prevent overloading of any individual generator. Here's a step-by-step process to calculate load sharing:
Generator Synchronization: Before load sharing can occur, ensure that all generators are synchronized in terms of frequency, voltage, and phase. This is typically done by using synchronizing relays and adjusting the generator speed or excitation to match the grid's parameters.
Determine the Total Load: Measure or calculate the total electrical load that needs to be supplied by the parallel generators. This could be the total power demand of a facility or a part of the power grid.
Set the Droop Characteristics: Each generator in the parallel configuration should have a droop characteristic, which determines how it responds to changes in load. Droop is represented as a percentage and is usually set in the generator's governor control. The droop characteristic establishes the proportional relationship between the generator's load and its frequency. The most common type is the "frequency droop," which adjusts the generator speed and hence its frequency in response to load changes.
Determine the Droop Settings: For a specific parallel generator setup, each generator's droop setting should be predetermined and configured. This setting is specific to the generator and is determined based on the load sharing requirements and the system's characteristics.
Load Sharing Algorithm: Depending on the type of system and controllers used, various load sharing algorithms can be employed. The most common ones include:
a. Droop Sharing: In this method, each generator's output is adjusted based on its droop setting. As the load increases, the frequency of the generators will drop. The generator with the lowest frequency will increase its output to take up the additional load.
b. Impedance Sharing: This method is based on the impedance of the generator. The generator with the lowest impedance will take up more load as the impedance is inversely proportional to the current flow.
c. Power Factor Sharing: In this approach, generators share load based on their power factor. The generator with the lowest power factor will take up more load.
d. Active Power Sharing with Communication: Some advanced systems use communication between generators to actively coordinate the load sharing, ensuring a more accurate and stable distribution of load.
Monitoring and Control: Continuous monitoring and control of the generators are necessary to maintain proper load sharing. Feedback systems and controllers adjust the generators' output to ensure they share the load according to the predetermined settings.
Avoid Overloading: The load sharing control system should also have safeguards to prevent any generator from getting overloaded. If a generator reaches its capacity, the control system should distribute the excess load among the remaining generators or start another generator if available.
It's essential to set up load sharing carefully and test the system under different load conditions to ensure its stability and reliability. The configuration and control methods can vary based on the specific application and the complexity of the power system. Professional electrical engineers or experts in power systems are usually involved in designing and implementing load sharing schemes for parallel generators.