Design and Performance Evaluation of an Active Power Filter for Harmonic Compensation in Hospital Electrical Systems in Ibadan

This study designs and experimentally evaluates an active power filter for harmonic compensation in hospital electrical distribution systems in Ibadan, Oyo State, South West Nigeria. Hospitals concentrate numerous non-linear loads including medical imaging equipment, variable speed drives for ventilation, UPS systems, and LED drivers that collectively generate harmonic currents causing voltage distortion, neutral conductor overloading, transformer heating, and interference with sensitive biomedical equipment. The active power filter is designed around a three-phase voltage source inverter controlled by a DSP-based control platform. The control strategy employs the instantaneous reactive power theory to detect harmonic current components in real time by computing the distorting power components from sampled current and voltage waveforms. The computed harmonic reference current is tracked by the VSI using a hysteresis current control scheme, injecting compensating currents into the distribution bus to cancel the harmonic content drawn by the non-linear loads. The APF hardware prototype is rated at 30kVAr reactive power compensation capacity and designed for connection to the secondary bus of the hospital's main 11kV/0.415kV distribution transformer. Performance evaluation was conducted at a 200-bed private hospital in Ibadan. Measurements before and after APF commissioning confirm reduction of bus voltage THD from 9.4 percent to 2.3 percent, and supply current THD reduction from 28.7 percent to 3.8 percent, both achieving compliance with IEEE 519 limits. Neutral conductor current was reduced by 64 percent, significantly reducing fire risk from overloaded neutral conductors. Keywords: active power filter, harmonic compensation, hospital electrical system, THD, Ibadan.