Loss Modeling of Large Hydrogenerators for Cost Estimation of Reactive
Power Services and Identification of Optimal Operation
Abstract
As a result of the worldwide energy transition, reactive power
generation has started to become a more scarce resource in the power
grid. Until recently, reactive power has been an auxiliary grid service
that classical power generation facilities have provided without
necessarily allocating any cost for this valuable service. In this
paper, a new approach for predicting the additional costs of reactive
power services delivered by large hydrogenerators is proposed. We derive
the optimal reactive power with minimal losses as a function of the
active power level within the generator’s capability diagram. This
pathway can then be used to calculate additional losses from operational
regimes deviating from the optimal reactive power for each active power
level. To back up the analysis, a dedicated population study was
handpicked consisting of four real-world generators scaled in terms of
power rating, i.e., 15 MVA, 47 MVA, 103 MVA, and 160 MVA. The objective
was to identify how the optimal reactive power scale from smaller to
larger MVA-sized generators. Moreover, a sensitivity analysis explores
the link between the standard parameters, the stator losses, the rotor
losses, the optimal reactive power, and the optimal efficiency. We find
the ratio between the rotor and stator losses as the determining factor.
Finally, the operational pathway introduces a new way to allocate the
power producer’s cost associated with their reactive power services and
can be used to justify potential profit for this service, especially
considering that the intermittent reactive power needs are projected to
increase in the future.