Efficiency Mapping and Weighted Average Efficiency for Large Hydrogenerators

Abstract

This paper presents the concept of efficiency mapping for large synchronous hydrogenerators, which are useful for evaluating hydropower generation performance vis-àvis interconnected intermittent generation to machine efficiencyoriented design. Tests for loss segregation at rated conditions are needed, and models for loss variation along all operational areas are presented. The weighted average efficiency is obtained as the summation of all operating load point efficiencies times related weights, defined according to criteria or from a 2D-histogram of machine operation. The proposed methodology is applied and compared for two machine designs and to an existent machine under operation.

The Energy Transition's Impact on the Accumulated Average Efficiency of Large Hydrogenerators

“…O VER the last decade, the load cycling intervals of large hydropower plants have changed fundamentally from rated conditions to a diverse set of operating points. As a result of a significant integration of intermittent renewable energy sources (RES) to the grid, the classical generators have responded more often to dispatch the fluctuations in both voltage and power [1]- [3]. These operating regimes bring new economic costs into consideration, as the efficiency now becomes a significant differentiator.…”

The Energy Transition’s Impact on the Accumulated Average Efficiency of Large Hydrogenerators

“…( 1) and the power factor angle given by φ = tan −1 (Q/P ). E g is the fictive induced voltage behind X d and X q , while E p lies behind X p , as explained in [20], [21], and further applied in [1]. However, before obtaining E g and E p , their respective voltage angles, δ and θ, are often estimated, if not an all-in-one complex formulation is utilized.…”

The Energy Transition’s Impact on the Accumulated Average Efficiency of Large Hydrogenerators

“…The increasing prevalence of these kinds of operational regimes requests the need for calculation models that can accurately quantify the overall impact for hydrogenerators [7], in addition to the operational burden at the turbine-side as well [12], [13]. The calculation model weighted average efficiency (WAE) offers a viable solution to quantify the RES' impact on hydro generators [1]- [3]. The computational scheme is a sampling average approximation approach to obtain the overall operating efficiency of generators varying over different loading conditions during a finite time period.…”

“…( 10) occurs 1 3 of the time during its yearly operation, it would mean that one has not accurately quantified the actual machine losses during 1 3 of the generators' operating time. Let us consider a simple example where the generator operates in two distinct operating points over a full period, where the generator operates at rated conditions 2 3 of its time, ∆t (i.e., ∆t T = 2 3 ), with efficiency η n , and as a synchronous condenser during 1 3 of its operating time, T − ∆t (i.e., 1 − ∆t T = 1 3 ). Insertion of these conditions into eq.…”

“…al. [1] that uses a fourth-order polynomial regression of the non-linear saturation characteristic to provide five polynomial coefficients. This method has a high accuracy for expressing the saturation curve but needs more arbitrary valued coefficients and a separate equation for the air gap line below a certain threshold.…”