The accuracy of load modeling directly influences power system operation and control. Previous modeling studies have mainly concentrated on the loads connected to a single boundary bus, without thoroughly considering the static load characteristics of the voltage. To remedy this oversight, this paper proposes an accurate modeling approach for area loads with multiple boundary buses and ZIP loads (a combination of constant-impedance, constant-current and constant-power loads) based on Ward equivalence. Furthermore, to satisfy the requirements for real-time monitoring, the model parameters are identified in an online manner using an enhanced reinforcement learning (ERL) algorithm. Parallel tables of value functions are implemented in the ERL algorithm to improve its tracking performance. Three simulation cases are addressed, the first involving a single ZIP load and the second and third involving area loads in the IEEE 57-bus system and in a real 1209-bus power system in China, respectively. The results demonstrate that the ERL algorithm outperforms an existing reinforcement learning algorithm and the improved least-squares method in terms of convergence and the ability to track both step-changing and time-varying loads. Additionally, the results obtained on test cases confirm that the proposed area load model is more accurate than a previously introduced model.
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