DuPont-SECI

New Delhi

25th June 2015

Inverter and AC System in Solar PV Grid Tied Power Plants

By

Rajneesh Shrotriya

CTO-Solar

COMBINER BOX

INVERTERSOLAR MODULES

SYSTEM CONCEPT

Magic of Static Power Generation

• No Moving parts

• Almost completely solid state

• More scalable & modular

• Only most complex component is the inverter

• DC to AC Inversion

• Maximum Power Point Tracking

• Grid Interconnection & Disconnection ( protection against islanding operation)

Basic PV Block

MPPT

IGBT – The Main component inside inverter

IGBT –Main Component Thermal image @ Operation

Voltage Regulation , PF control and LVRT

As there is no moving parts therefore instability and reactive power drawingfrom GRID is almost nil. The internal algorithm of inverter maintains the power factor within the range of 0.95 lag to 0.95 lead.

Voltage Regulation;-The inverter has +/- 10 % regulation with IT GRID connection

Typical Solar Inverter Station

Presenting Common issues being faced by Developers and EPC

Concern Expectation

Location Radiation Data Source

DC: AC Ratio of Plant Capacity

Loading of Inverters at DC side

No. of Inputs at Inverter

GIS / 3 Tier/ Meteonorm / NASA / correlation with Local nearby Weather station /others

Plant Capacity on AC equipment rating – Inverter / Inverter Transformer cumulative .

Temperature rating of Inverter required to be fixed like modules i.e. 40 deg C/50 Deg C: 980 KW -1150 KW

Continue …..

Awarded AC Capacity 10 MW

Tolerance Should be provided

Standardization of parameters and Norms for Solar Modules, Inverters , execution and other components

Inverter cumulative Capacity – 9.75 MW / 10.35 MW

Capacity certification basis for Nodal agency / MNRE and CEIG .

IS is required to be created , contractors are confused with certain IS codes which is for conventional power plant and not applicable for PV

Continue……

Harmonics % at rated load and different other less loads

Reactive power absorption Grid code -No clarity

Parameters are varying at different loads in % .

As PV plant operates at unity PF, Absorption at 0.8 /0.85 leads to reduction in yield and commercial loss to Developer. Compensation policy is required to be set.

Continue….

Forecasting- No clarity

Radiation History and Generation DATA of installed plant should be available at a single website

Guidelines in line with SLDC norms is required to be set and communicated

For planning of plant capacity and expansion

Continue….

Power Transmission Infrastructure information based on CEA as well state wise network.

Standard Procedure for accessing Plant Performance

Load flow study is required for all potential PV area and nearby MV-HV transmission network , space availability at SS

Availability, PR, CUF acceptability , Uncertainties.

Bankers and Financial institutions should be aware of this procedures

Continue

Air Quality for PV Plant

Isolation Devices and Protection Philosophy

Inverter Layout 2- For Discussion

Hot Air Duct and Inverter Transformer for Discussion

Internal Heat Duct, Aux. System –Inverter Room

Typical String Combiner Box

Connection Space for Cables-A critical factor

Switch yard

Keeping the switchyard block in middle of the plot for low losses and less cable cost

66/11 KV Double Bay Switchyard-Metering bays

Thank You