In solar power systems, transformers play a crucial role in managing voltage levels and ensuring efficient power distribution. The inverter output AC voltage at 50 Hz or 60 Hz is connected to a distributed PV system inverter transformer, which is designed to step up the voltage to medium voltage (MV) if needed while accommodating polarity reversals and pulsations inherent to the inverting process.
Here’s a closer look at the types of transformers used in solar power plants and their specific roles:
1- Inverter Transformer – to step up PV inverter AC output voltage to MV voltage
2- Auxiliary Transformer – to meet station load and power supply to inverter
3- Earthing Transformer – to provide a virtual neutral to the MV grid
4- Collector Transformer- to collect the output of several inverter transformers and step it up to feed to the distribution lines or HV power grid.
– Inverter Transformer
Inverter transformers are used in solar parks for stepping up the AC voltage output from solar inverters MV voltages to feed the collector transformer. LV side of transformer will see voltage polarity reversals, pulsation and heavy harmonic voltage/current content from the solar inverters.
Usually, a grounded electrostatic shield is provided between LV and HV windings to filter out these harmonics reaching HV side. Mineral oil or ester is used as insulating liquid in these transformers.
– Collector Transformer
Power from individual inverter transformers is collected by the Collector Transformer and stepped up to HV voltage level. Maximum MVA of collector transformer is limited by the rating of MV breaker used on LV side.
collector transformers are used up to a specific rating of MVA with LV side split into two circuits to limit fault level within the MV breaker capacity.
– Auxiliary Transformer
Auxiliary Transformer is a low kVA transformer to supply power to inverter and provide station load. It can be a standalone unit or integrated with the inverter enclosure. Primary may be connected to power grid or to the pulsed output voltage of the inverter.
– Earthing Transformer
Earthing (grounding) transformer (zig- zag connected) will be required at the ungrounded MV circuit to get a grounding neutral. This is a single winding zig-zag connected, short time (10 second) rated transformer, with the neutral solidly grounded or grounded through a resistor.
Transformers are integral to the efficient operation of solar power plants, ensuring voltage regulation, harmonic filtering, and reliable power distribution. Each type, from inverter to earthing transformers, fulfills a specialized role to optimize the performance and safety of solar energy systems.
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