Centre for Development of Advanced Computing(CDAC)

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1C-DAC Thiruvananthapuram C-DAC All Rights Reserved

Grid tied / Stand alone Solar inverters–

Technology perspective

Centre for Development of Advanced

Computing(CDAC)Thiruvananthapuram

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2C-DAC Thiruvananthapuram

Organisation of the Presentation

• Activities of Power Electronics Group - CDAC-Thiruvananthapuram

• National Mission on Power Electronics Technology

• Some of the development projects showcasing the capability of

CDAC

• Development activities related to Solar Photo Voltaic Systems and

other renewable sources

• Concluding Remarks

C-DAC All Rights Reserved

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CDAC is a Scientific Society of the Department of Information

Technology, Ministry of Communication & Information

Technology, Government of India.

CDAC Thiruvananthapuram has the following Development

Groups.

Power Electronics Group

Broadcast & Communications Group

Hardware Design Group

Control and Instrumentation Group

Strategic Electronics Group

www.cdactvm.in


Centre for Development of Advanced Computing(CDAC)

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• Power Quality Improvement

• Electric traction and Automotive electronics

• Integrated power modules and packaging techniques

• Distributed power generation/ Renewable energy and Micro

generator control

• Modelling/Simulation packages

• New topologies for Converter/inverter applications


CDAC- Power Electronics Group-Focus Area-

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A national mission programme launched in November 2004 by

the Department of Information Technology (DIT) under Ministry

of Communications & Information Technology, Government of

India.

Vision:

To provide the country with capability to become a dominant

player in Power Electronics Technology at the international level.

Nodal Agency: C-DAC, Thiruvananthapuram

Participating agencies

• Academic Institutes( IISc, IITs, NITs and premier technical

institutes like BESU)

• Manufacturing Industries- both private and public sector

• User Industries like railways


NaMPETNational Mission on Power Electronics Technology

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• Indian Railways

• Indian Air force

• NMRL

• Electrohms

• CatterPillar Pvt. Ltd.

• Emerson Network Power (India)

Ltd.

• Numeric Power Systems

• Hykon Power Electronics (P) Ltd

• Amara Raja Power Systems

• HBL Power Systems


NaMPET

Industry Partners

•Industrial Controls and Drives Ltd

•Keltron

•Kerala Automobiles Ltd

•Megatech Power Equipments (P) Ltd.

•Power-one MicroSystems (P) Ltd

•Veeral Controls

•Techser Power Solutions Ltd.

•Integrated Electric Co. Bangalore

•Power Line Kolkata

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Development Projects involving Grid

Connected Inverters

Power Quality Solutions

• STATCOM (Up to 500kVA single unit)

• Active Filter (Up to 500kVA single unit)

• UPQC (250 kW)

Power Electronics for Renewable Energy Conversion

• 250kW Intelligent Power Controller for Wind Electric

Generator

• 25 kW grid interactive Solar PV System

• Technology for Micro grids


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Shunt compensator synthesized with power electronic devices is

called STATCOM or Static VAR Compensator


STATCOM- STATic COMpensator

Iia

Iib

Iic

L

IGBT Voltage Source Inverter

Capacitor

Bank

Vag

Vbg

Vcg

Vbi

Vci

Vai

Grid

Load

IlaIlbIlc

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9C-DAC Thiruvananthapuram C-DAC All Rights Reserved

300 kVAR STATCOM- For Highly Fluctuating Industrial Load -

Grid voltage and Grid Current

before compensation

Grid voltage and Grid Current

after compensation

STATCOM developed by CDAC

Digital Controller developed by CDAC

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Deployment of 750 kVA Active Filter for

Compensation of Current Harmonics


Auxiliary

Load

4 MW Induction Furnace

Fluctuating loads like lifts,

magnetic separators, drives etc.

11kV Incomer

250 KVA, 2 Level STATCOM 500 KVA, 3 Level STATCOM

* Through this project CDAC has

developed and validated operation of

3-Level Inverters

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Deployment of 750 kVA Active Filter


1) Grid current: 2 A 5 ms

2) Load current: 2 A 5 ms

Compensated Grid Current

Load CurrentHigh power inverter stack developed by CDAC

(Interconnections are with sandwich busplates)

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Unified Power Quality Controller


GRID LOAD

Vdc

Series Active

FilterShunt Active

Filter

Ls

• UPQC mitigates voltage

swells and sags

• UPQC compensates reactive

power or harmonic currents drawn

by the load

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4-Wire STATCOMs


Capacitor

Bank

IGBT Voltage

Source Inverter-4 leg

Iia

Iib

Iic

L

Vbi

Vci

VaiVag

Vbg

Vcg

Grid

Load

IlaIlbIlc Iin

Compensates

Reactive currents

Harmonic Currents

Unbalance Currents

&

Neutral Currents

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4-Wire STATCOMs for IT Parks


500 kVA, 4-Wire STATCOM

CONVERTER STACK

• This system is installed at TECHNOPARK Trivandrum

• It can be used in IT parks where the computer loads are single phase

and non linear with large triplen harmonic currents in the neutral

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Intelligent Power Controller for Wind

Electric Generators (WEG)

WEG GRID

Digital

Controller

Machine side

Inverter

Grid side

Inverter

• WEG Operates at Maximum Power Point (Induction generator is driven in

variable speed)

• Power generation with lower wind speed

• Power export at UPF(without PF compensating capacitors) and minimum

THD in grid current

• Each Inverter is rated for 250 kW and are IGBT based

• The system was deployed and the technology was validated with a 250 kW

VESTAS WEG which uses an induction generator for power conversion.

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Intelligent Power Controller for WEG


250 kW proto unit

Digital Controller

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Solar Energy Conversion

• Solar Thermal – Technology for harnessing solar

energy for thermal energy

• Solar Photo Voltaic(SPV) - Photovoltaic devices use

semiconductor materials that directly generate electric

power when exposed to light


Cell ModuleArray

Made of crystalline silicon (mono crystalline/ multi crystalline/ Amorphous)

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Schemes for Solar PV Energy

Conversion


Inverter Filter

Storage

Solar PV Array

To load

Stand alone scheme

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Schemes for Solar PV Energy

Conversion


Inverter Filter

Storage

Grid

Solar PV Array

Grid Connected scheme

Both the above designs should consider Overall conversion efficiency

Maximum Power Point Tracking(MPPT)

Cost and size of converters

System reliability

Protections

Modularity, Servicability and repeatability

Optional

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Technology for Micro-grid


Solar PV systems can be used in conjunction with other energy

technologies to provide an integrated, flexible system for power

generation – typically for remote locations without grid availability.

These systems are referred to as hybrid systems, which can form

micro grids.

Common configurations of hybrid systems could include solar PV

array, wind generator, bio-mass/diesel generator set which would

allow generation in all weather conditions.

CDAC, through NaMPET, with technical collaboration with IIT Kanpur

has undertaken R&D project for developing technology for Micro-

grid.

System developed for Moushuni Island with support of WBREDA.

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Technology for Micro grids


BIM

BIM

BIM

BIM

BIO-MASS

WIND

GENERATOR

BIM – Basic Power Electronics

Interface Module

SOLAR PHOTOVOLTAIC

ARRAY

BATTERY

BANK

YMICRO-

GRID

CO

NS

UM

ER

L

OA

DS

Y

Y

Y

* All sources interfaced to common AC bus

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Power Converter ModuleThe power converter module – Basic Interface Module (BIM)

can work with both AC and DC sources.(Modular,

serviceable)

Individual Modules are rated for 10 kW. 3 modules are

connected in parallel makes a 30kW unit.


Basic Interface Module (BIM)

GATE DRIVER INTERFACE CIRCUITS

SO

UR

CE

LO

AD

CONVERTER INVERTER

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Salient Features


• Modular Power Electronic Hardware

• DSP & FPGA Based Control Hardware

• Optimum Power Extraction from Solar with

MPPT(Maximum Power Point Tracking)

• Optimum Power Extraction from WEG

Parallel Operation of Inverters

• Synchronized Voltage reference from a Central

controller

• Current sharing between parallel inverters

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Digital Controller


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Digital Controller

Controls 6 independent

inverters(36 PWMs)

DSP-FPGA architecture

CAN communication link

Fast ADCs

I/O ports, LED ports

HMI interface


Digital Controller

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Grid Interactive Solar Photo Voltaic System

Technology developed

• Inverter for SPV system

• Control algorithm for Maximum

Power Point Tracking from SPV

• Control Algorithm for Power export

at UPF and minimum THD

• Protection Schemes

Salient Features of the system

• Modular Power Electronic Hardware

• DSP & FPGA Based Control

Hardware

• MPPT controller

• Grid connected front-end inverter for

power exchange

• Display and user Interface

• Power export at UPF

• Anti-islanding protection


• All the sub modules associated with the inverter (power and control) are

indigenously developed

• The above system is commissioned at roof top of WBREDA office building,

Salt Lake, Kolkata

• System is operational for last 5 months. Exporting around 40 units per day

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Control Block Schematic


3Ф Voltage Source Inverter

SPV

Idc

Vdc

A

B

C

Ia

Ib

Ic

Va

Vb Vc

MPPT

Algorithm

Vdc

Idc

Va

Vb

Vc

Iactive*

Iactive3-2 Phase

Transformation

Unit Vector

Generation

+-

Ireactive*

+

Ireactive

Current

Controller

&

Reference

Voltage

Calculator

Va

Vc

-

Vb

Vdc

Cosθ

Sinθ

Space

Vector

Modulator

Va *

Vb *

Vc *

PWM1

PWM6

Idc

Va

Vb

Vc

Vdc

Ib

Ic

Ia

PWM1

PWM6

Gate

Driver

PWM1

PWM6

VaVbVc

IbIc

Ia

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Voltage and Current

waveforms at various

power levels

Y

Solar Photovoltaic Array

Power Electronic Interface Module

Transformer

Utility Grid

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Digital Controller

30kW Panel

Inverter Module

• The digital controller is built with DSP and FPGA

• This controller can control six numbers of 3 phase inverters

• 32 Analog channels for sensing various signals

• Inverter modules are easily replaceable

• Sandwich bus plate architecture

• Integrated gate driver circuit and cooling arrangements

• Each inverter module is rated for 10kVA with DC bus

rating of 400V

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Specification of the Grid Interactive System


Rated Power 30kW

Grid Voltage 415(+10%/-15%), 3 Phase

Solar PV Array Voltage 400V max, 320 Nominal

Grid Frequency 50Hz5%

Operating Power factor Unity above 50% Load

Grid Current THD <5% when source THD is

<2%

Power Converter IGBT based

Cooling Forced Air Cooling

Panel Suitable for Indoor

deployment

Efficiency Better than 90% above 50%

of the load

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Standards for Grid Interactive Solar PV

Systems• IEEE-928 - IEEE Recommended Criteria for Terrestrial Photovoltaic

Power Systems

• IEEE 929-2000 - IEEE Recommended Practice for Utility Interface of

Photovoltaic (PV) Systems

• IEEE 1547-2003 - IEEE Standard for Interconnecting Distributed

Resources with Electric Power Systems

• IEEE 519 - IEEE Recommended Practices and Requirements for

Harmonic Control in Electrical Power Systems

• IS 9000 – Basic Environmental testing Procedures for Electronic and

Electrical Systems

The above standards are mostly related to construction, test procedures, testing

methodology, protection guidelines and grid connection procedures of solar PV

inverter

There are different standards in relation to the SPV array


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Solar Power Plants with MW Rating

The system is realised by connecting inverters in parallel

Individual inverter rating is 100kW

The co-ordination of the inverters is achieved with data exchange

between controllers of individual inverters through CAN

communication link

System features

• Operation sequence and protection schemes as per the relevant

standards

• Auto turn off and auto start

• Active inverters selected optimally according to solar power

availability

• Remote data access

• Minimum power consumption by auxiliary circuits


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Conclusions

CDAC has expertise in

• Design of single phase inverters, 3 phase inverters and multi level inverters up

to 500kVA ratings, using IGBTs, IPMs etc.

• Design and realisation of digital hardware for control of inverters for various

applications

CDAC has developed

• Grid Interactive Solar PV System with Indigenous technology

• Technology for Micro grids using various renewable energy sources (AC and

DC) and storage systems

CDAC can associate with prospective industries for commercialisation of the

technology for renewable energy sources-solar in particular


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Thank You


Centre for Development of Advanced Computing(CDAC)

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