Short-Term Peak-Shaving Dispatch for Cascade Hydropower Based on Load Curve Reconstruction
Abstract
The increasing integration of variable renewable energy (VRE) into power grids has significantly widened the peak-to-valley difference in net load and intensified its volatility. To follow these rapid load changes, cascade hydropower plants must frequently adjust their output, operate within unstable oscillation zones, or undergo repeated start-stop cycles. This creates a growing conflict between the system’s demand for peak shaving and the actual operational capabilities of hydropower plants. To address this challenge, this paper proposes a method for reconstructing the load curve based on fuzzy recognition of peak-valley characteristics. By adaptively adjusting the number of identified features, the method transforms the highly fluctuating net load into a multi-segment linear form. This preserves essential peak and valley information while promoting output stability. Building on this reconstructed load curve, a short-term peak-shaving model for cascade hydropower is developed, aiming to minimize the standard deviation of the residual load. The model is solved using an improved progressive optimality algorithm (POA) that integrates feasible region reduction with a multi-segment, variable-step-size search strategy. The peak-shaving performance is evaluated under three VRE penetration scenarios: low (10%), medium (20%), and high (40%). A case study conducted on China’s Wujiang River demonstrates the effectiveness of the proposed method. The load curve reconstruction transforms hydropower output from hourly sawtooth-like fluctuations into a stepwise pattern, albeit with a slight reduction in the peak-to-valley difference optimization rate (PVOR). For example, in the 10% penetration scenario, the frequency of output adjustments decreases by 73.2%. As the VRE penetration rate increases, the net peak-to-valley load difference grows sharply, and the PVOR of the reconstruction scheme declines from 26.70% to 9.12%. Nevertheless, the frequency of output adjustments does not exceed 15 times, thereby maintaining stable operation. The proposed approach achieves a reasonable trade-off between peak-shaving effectiveness and operational stability, offering a practical solution for hydropower dispatch in grids with high VRE penetration rates.