The reduction of Total Harmonic Distortion and electromagnetic interference in high pressure sodium street lighting using single stage electronic ballast

This paper presents the design of single stage electronic ballast for a conventional 250W High Pressure Sodium (HPS) street lighting. Historically the HPS street lighting operating hours is from sunset to dawn which is 12 hours in full brightness. The existing conventional street lighting HPS are powered by magnetic ballasts. The magnetic ballast is a device which consists of coil and core. It is an uncontrolled device, not energy efficient and generate flicker before it can give steady light. The use of electronic ballast provides a rapid start and energy efficient but will create electromagnetic interference and harmonic. This will reduce the circuit performance. To overcome the problems, the single stage design electronic ballast is used for the HPS lamp. The effect of the electromagnetic interference (EMI) and harmonic to the designed system is assessed. This is performed in three different stages; (i) with and without EMI filter, (ii) the half-bridge and (iii) the full-bridge inverter. For stage (ii) and (iii), the comparison of harmonic produced in electronic ballast was evaluated. The operating frequency for electronic ballast is 68 kHz. The findings show that the Total Harmonic Distortion current (THDi) of 5.55% for full bridge inverter compared to the half bridge inverter with THDi of 8.73%. A reduction of 36% of THD is obtained when full bridge inverter is applied. The current waveform result indicates a reduction of 25% without EMI filter from the original waveform. The reduction of both EMI and THDi can give benefit to street lighting system and energy efficiency.