Coordinated secondary frequency regulation of thermal power units and feeder loads under high renewable penetration: Joint economy-performance optimization and distribution network PCC power tracking

Large-scale integration of high-penetration renewables aggravates net-load fluctuations and brings uncertainties to secondary frequency-regulation demands. Limited by adjustable capacity, ramping capability and operational costs, conventional thermal generating units cannot independently provide frequency-regulation support balancing economic and dynamic performance. Different from existing user-side frequency-regulation schemes relying on end-user authorization, massive communication terminals, aggregator coordination and dedicated compensation-settlement mechanisms, this work exploits voltage-power coupling of feeder loads and grid-controllable voltage-regulation devices to incorporate feeder clusters into the active-power frequency-regulation resource pool. Three core challenges are addressed: quantification of feeder safe adjustable capacity, coordinated command allocation among heterogeneous resources, and sustained Point of Common Coupling (PCC) power tracking over regulation cycles. First, the Conservation Voltage Reduction (CVR) coefficient of feeder loads is identified via grid-side voltage-driven exogenous excitation. Combined with a Z -bus-based linearized power-flow model, feeder safe adjustable capacity is evaluated subject to full-node voltage constraints. Second, considering discrepancies in cost, tracking accuracy and response speed between continuously-regulated thermal units and feeder clusters, a joint economy-performance command-decomposition model is built. The trade-off solution is obtained using the ε-constraint method, Pareto filtering, TOPSIS evaluation and knee-point identification. Finally, a real-time tracking strategy with disturbance observation and sensitivity-weighted allocation is proposed to mitigate PCC deviations induced by second-scale source-load fluctuations. Simulations verify that the proposed method reduces frequency-regulation costs, improves response accuracy and speed, and enhances PCC tracking and system frequency-support capability while guaranteeing feeder node-voltage security.