PIN 4K6313 - Caterpillar

Background
Load sharing is the process of sharing the real power (kW) and reactive power (KVAR) between gensets while still maintaining proper frequency and voltage.General Considerations
The controlling factors for kW and frequency is the same. Both are based upon the torque or power being provided by the engine. Increasing the power from the engine will either increase the kW being provided, which must be consumed, or the frequency will increase. The KVAR and voltage are based on the excitation of the generator. Increasing the excitation will provide additional KVARs which must be consumed, or the voltage will increase. For these reasons, the tuning of Load Sharing is more difficult since multiple factors are driving a single control point.Strategy
Since each of these factors have multiple controlling factors, a means of approaching the tuning of load sharing is required. One item to keep in mind is that full concentration on any portion of the load sharing is not possible since these different factors interact with each other. For example, any instability in the voltage/KVAR sharing affects the frequency/kW since the power consumed by the load is usually affected by the voltage. For this reason, multiple items must be considered simultaneously.Guidelines
Be sure to be familiar with navigation of the screens and setpoints before attempting to develop a set of gains. Read through and become familiar with how to view the information about the load status along with information on the electrical output of the generator set. Since load sharing affects multiple units in the system, it is easy for the system to become unstable.All protective relay settings such as reverse power and reverse KVAR should be reviewed and possibly tightened for commissioning in order to protect the generator set. It is recommended to use a resistive and reactive load bank to tune generator load sharing. While it is possible to tune the real power sharing with just a resistive load bank, tuning of both parameters require kW and KVAR control. If customer load is going to be used for tuning, care must be taken to ensure that the voltage and frequency variations will not cause damage to the load.The process of load sharing tuning is an iterative procedure. It is NOT possible to arrive at optimum settings for 1 setting before tuning the other settings. In addition, it is NOT possible to tune 1 genset without tuning the other generator sets with which it is load sharing. If the generator sets are equivalent power ratings, tuning is easier since the setpoints can be copied from one unit to the next. The use of multiple people or use of ET on 1 unit with the laptop near the second unit will help in modifying the setpoints of multiple units.In order to keep the frequency (voltage) gains from overpowering kW (KVAR) gains, the frequency and voltage gains are turned off when the generators are close to nominal frequency and voltage. This may cause a slight ripple in frequency and voltage while it oscillates around