New method for optimized control of parallel, speed controlled centrifugal pumps for district heating saves electrical energy

摘要

Centrifugal pumps are used to convey fluids, such as water, oil or chemicals, and are for example installed as water pumps in piping networks of a drinking water transmission or distribution system, a distinct heating distribution system or a cooling water system in a power plant. In the most cases a group of two to five or even more identical speed controlled parallel pumps are used for such a task. In a system with parallel pumps it is common to choose the number of active pumps with fixed preprogramed acting points or by operator decision. This approach is easy to implement but does not take the efficiency into account. With the large pumps being a big part of the auxiliary power of a power plant it is important to take the efficiency of the pump groups into account. A new method for an efficiency based optimization of such pump groups is presented within this presentation. This optimization adds to existing control logic and decides on turning on an additional pump or switching of a running pump in order to pump the demanded flow with minimum use of electrical energy. This is done without the need of taking any characteristic curve into account. This is a big advantage cause the characteristic curve is often hard to grasp or ever variable due to controlled valves in the hydraulic system.