The Value of Reactive Power for Voltage Control in Lossy Networks

Abstract

Reactive power has been proposed as a method of voltage control for distribution networks, providing a means of increasing the amount of energy transferred from distributed generators to the bulk transmission network. The value of reactive power can therefore be measured according to an increase in transferred energy, where the transferred energy is defined as the total generated energy, less the total network losses. If network losses are ignored, an error in the valuation of a given amount of reactive power will be observed (leading to reactive power provision being under-or over-valued). The non-linear analytic solution of a two-bus network is studied, and non-trivial upper and lower bounds are determined for this 'valuation error'. The properties predicted by this two-bus network are demonstrated to hold on a three-phase unbalanced distribution test feeder with good accuracy. This allows for an analytic assessment of the importance of losses in the valuation of reactive power in arbitrary networks.

Voltage control loss factors for quantifying DG reactive power control impacts on losses and curtailment

“…The combination of the analytic (Two‐Bus) approach with detailed simulations shows similarities with [10–12]. The authors of [12] highlight reasons as to why certain DG generation profiles lead to a greater curvature in the total losses with DG penetration (i.e., a narrower ‘U‐shaped curve'), whilst the authors of [10] present analytic arguments to propose improved settings for inverter controls.…”

“…For example, we have shown that network voltage drop has a huge effect on relative losses when using voltage control, and we have also clearly demonstrated the existence of non‐trivial bounds on the VCLF. To our knowledge, these points have not been explored in prior works, with the exception of related analytic results we first presented in [11] for the related (but distinct) valuation error metric. Here we present a wider range of analysis (e.g., considering $$ PQ$$ and $$ PV$$ control), and provide detailed simulations that were missing in that earlier paper—the simulations in this work have enabled the validation of the approach comprehensively.…”

“…In [10], the authors compare the relative performance of volt‐var control schemes for a range of LV network configurations, demonstrating the key role that control settings play in the interaction between curtailment and losses. The previous work by the authors briefly considers the error in an estimation of the valuation of reactive power control, should losses be ignored, as a function of $$ R/X$$ ratio [11]. In [12], it is noted that losses due to DGs follow a ‘U‐shape’ curve with respect to DG penetration: losses first decline as the penetration of DG increases, before starting to increase.…”

“…Simulation-based (OpenDSS) and Analytic-based (Two-Bus) VCLF bounds for each of the six case studies. Simulation bounds are determined as in(11), whilst analytic (Two-Bus) bounds are determined using (23) and (25)…”