Robust Conservation Voltage Reduction Evaluation using Soft Constrained Gradient Analysis

Evaluation of conservation voltage reduction (CVR) effect is critical to peak load reduction, energy conservation, and many CVR-related power system control/optimization strategies. This paper proposes a novel robust CVR evaluation method using soft constrained gradient analysis based on time-varying load modeling and real utility field measurements. Firstly, the ZIP parameter identification is formulated as an over-determinant problem composed of first-order gradient with respect to each coefficient and soft constraints representing temporal correlation of loads in each time step, in order to improve the robustness and smoothness of CVR evaluation. Then, problems in time series are coordinated with a sliding window approach. A necessary condition for selecting the smallest window size is proposed and strictly proved to guarantee the existence and uniqueness of the solution of time-varying load modeling problem. Finally, time-varying CVR factors are accurately and robustly calculated with real measurements and the identified load model. Case studies are performed using sufficient field measurements obtained from a real utility. The robustness of the proposed approach is validated under measurement outliers and large disturbances of loads.