Load Sharing Controller vs PMS

PMS has all the bells and whistles and Load Sharing Controller is a bare bones system....

..."A Load Sharing Controller (LSC) and a Power Management System (PMS) are related but distinct concepts in power generation and distribution. LSCs focus on distributing the load among parallel generators, while PMS encompasses a broader range of functions, including load sharing, load shedding, and overall power system stability.

Here's a more detailed breakdown: Load Sharing Controller (LSC):

• Primary Function: To ensure that multiple generators operating in parallel share the total load evenly, preventing any one generator from being overloaded.
• Mechanism: LSCs typically use algorithms to adjust the output of each generator based on the overall load demand and individual generator capabilities.
• Focus: Load sharing specifically within a power generation system, often used with multiple generators connected to a common bus.
• Example: A LSC might be used to distribute load between two or more diesel generators, according to an example provided by a source.

Power Management System (PMS):

• Primary Function: To manage and optimize the entire power system, encompassing aspects like load sharing, load shedding, synchronization, voltage regulation, and power quality.
• Scope: Broader than LSC, managing the entire power system, including multiple generators, loads, and even interconnection with the grid.
• Features: PMS often includes features like:
• Load Sharing: Distributing load among generators, as handled by LSC.
• Load Shedding: Reducing load during emergencies to prevent system instability.
• Generator Control: Starting, stopping, and synchronizing generators.
• Data Logging and Monitoring: Tracking system performance and identifying potential problems.
• Example: A PMS on a ship might manage the power system for the entire vessel, including generator control, load sharing, and monitoring various loads like thrusters and cargo pumps, according to Wikipedia.

Key Differences:

You don’t need a load sharing computer to parallel generators, but you do need to adjust each generator speed governor response so that no one machine will assume the load. When running islanded, the largest machine is run isochronously, that is, at fixed speed, and parallel machines have droop dialed into their speed regulators. As each of the smaller machines approach full load, the droop in the speed regulator stops adding more power to the prime mover, so that the generator can not assume the entire power system load, which it eventually would do without droop.

It would seem to be unproductive to centralize generator load sharing into a single control system, as the delays and sensing errors would detract from the response speed necessary to get your best performance. Simplicity breeds reliability.

The same concept applies to each machine’s voltage regulators. Fixed voltage for one, droop for the smaller machines.

If the load is too much for the generation, that’s when you need a load control computer, or perhaps power management controller. If the generation is overloaded, then the frequency will drop. The computer has a prioritized group of loads it can drop, calculated to provide the smallest upset possible for the situation. A sudden large drop in frequency will cause a large block of load to be dropped quickly. The computer can be programmed for rate of rise or fall detection, to anticipate corrective action. Once the frequency has stabilized, then the computer can allow the dropped loads to be restored, in a timely and efficient manner.