Solar Power String Inverter with Harmonic Filter
Kanai Banerjee
Electrical Harmonics, Power Quality, Green Building Design & HVAC&R Professional, owner at Encon Engineers
Solar String Inverter
An automobile industry was facing high incident of harmonic failure in SCADA, motor drive & electrical equipment after installing 1MW solar power inverter. The rated capacity of 1.0MW DC solar power is evacuated through 16Nos, 50kW, 3Phase, 415Volts, 50Hz solar string inverter which itself got affected with the harmonic problem. While designing the solar string inverter a 20% power loss is considered by the solar panel manufacturer for conversion from DC solar panel power to AC power delivered in the 3Ph, 415V, 50Hz electrical power grid. Every day during the peak solar power generation when the sun is at the top of the sky, randomly one inverter trips and remains switched off for several hours. It causes a loss of 3 to 5% in the solar power generation by considering that the inverter trips at the most productive time. The solar power inverters diagnose it as over voltage tripping. But during the root cause analysis carried out before installing harmonic filter, we did not find any over voltage problem in the factory's electrical power system. We designed the harmonic filter for troubleshooting the factory's electrical and electronic equipment failure as well as providing a photo voltaic solar string inverter solution by mitigating its over voltage tripping condition.
A 1407A Encon Harmonic Filter is installed during Nov. 2017 at the 415V main incomer PCC of 2500KVA transformer. It's designed for the full transformer load including the 1.0 MW solar power harmonic at the downstream of transformer. Passive harmonic filter being a harmonic absorption type, engulfs harmonics from both downstream as well as upstream within its range.
