PID-Based Electronic Load Control Card Design for Self-Excited Induction Generators Driven by Pump-as-Turbine Systems

This paper presents the design, simulation, and experimental validation of a low-cost PID based electronic load control (ELC) card for a self-excited induction generator (SEIG) driven by a pump-as-turbine (PAT) system operating in off-grid conditions. The primary challenge addressed is the regulation of terminal voltage and output frequency under varying single-phase resistive loads connected to a three-phase SEIG via the C-2C (Steinmetz) capacitor configuration. A ballast load driver circuit employing an IGBT switched at 500 Hz by PWM is governed by a PID algorithm implemented on an Arduino UNO microcontroller. The system is first modelled in MATLAB/Simulink, where the PID gains are manually tuned by iterating over Kp, Ki, and Kd and evaluating the closed-loop rise time, overshoot, settling time, and steady-state error as the tuning criteria, then validated on a physical test bench comprising two centrifugal pumps — one operating as the pressurised hydraulic supply and the other as the PAT driving the SEIG. The experimental setup is documented in full, including schematic and photographic evidence. Results show that the proposed ELC constrains the terminal voltage deviation to within ±3% of the 230 V reference under load-switching transients up to 600 W, with settling times of 100 ms (load shedding) and 180 ms (load acceptance). Without ELC, the uncontrolled system exhibited a peak voltage deviation of 25.9% and a frequency excursion of 16.3% across the full load range. Total harmonic distortion (THD) increased by only 0.037 percentage points when the ballast driver was active, from 0.880% to 0.917%. Both values remained below the 8.0% voltage THD reference limit specified by IEEE Std 519-2022 for systems with a PCC voltage of (V\leq1) kV. The total component cost of the control card was low, confirming the economic viability of the solution for remote micro-hydropower electrification.