INVERTER

Inverter:

Inverter is an electrical device which converts/inverts DC (Direct current) power to AC (Alternating) power at a desired frequency. It is the arrangement, control of power semiconductor devices making the DC power to flip back and forth, creating AC power. The rate of flipping can be controlled using electronics. The inverter does not produce any power; the power is provided by the DC source. This plays a predominant role in distributed power generation due to renewable sources in particular, as most of the renewable sources like Wind, Solar etc., used for power generation outputs DC power and to utilize the generated power it has to be converted to AC because most of the loads work on AC power. Also in generation side the reason to have AC power is that it can be stepped to very high voltage levels and can be transmitted comfortably over long distances compared to DC transmission which is very complex process & with higher voltages the power losses are very less.

A simple 1-phase inverter circuit

Applications:

• Inverter can be used to run the loads during the outages of utility grid provided a battery is connected to the input of the inverter, here the battery can be stored by any means of power i.e., with the regular supply or from renewable sources (solar, wind etc)

• In Grid tied solar applications “inverter” acts as interface between two energy sources, one is PV generation and other side utility grid.

• Inverters can also be used for wave generators (stepped, square), Voltage controller and frequency controller.

Types of inverters: The following classification is based on the output power (1-pahse/3-phase)

Single phase inverter: It is used to convert the input DC power to single phase AC power which is used to power single phase loads (voltage level of 1-phase is 230V AC).

Three phase inverter: Same as single phase inverter but the output voltage level is like 440V AC. It is used to power 3-Phase loads.

Inverters in Solar Applications:

As solar generation is proven effective over other renewable technologies, it is widely     practicing and energy generation is increasing from MW’s range to GW’s range. In this context the demand for power conversion technologies/devices got increased like anything, however the challenges, complexities are also high in the design of Inverters.

Central inverter: Central inverters are usually of very high capacity, remains as a single unit in power conversion process. Complexity arises to employ single inverter as the generation capacity increases

If the power generations are too high then the process of power conversion (DC to AC) with a single Inverter becomes too complex. Thereby, the concept of string inverters is evolved.

String Inverters: Breaking the generation capacity into convenient levels & employing several small inverters and connected them accordingly to reduce the complexity of inverter design. The entire PV system is divided into several sections (PV strings), each string contains a fixed no. of PV modules. For each string an inverter is connected which in turn called as String inverter.

Advantages of string inverters:

1. Reduces the inverter design complexity.

2.Improvements in overall efficiencies, fault detection is made easy.

Types of different inverters and their connections with PV modules

     Micro inverters:  These are similar to grid tie inverters working wise, but these inverters are of small capacity (Module capacity) inbuilt with an MPP tracker used for each PV module. The output from several micro inverters is combined and often connected to the Utility grid. 

     Micro inverters have several advantages over conventional inverters. The main advantage is that small amounts of shading, debris or snow lines on any one solar module, or even a complete module failure, do not disproportionately reduce the output of the entire array. Each micro inverter harvests optimum power by performing maximum power point tracking for its connected module. Simplicity in system design, added safety are some other factors introduced with the micro inverter solution.

Disadvantages include Installation complexities, higher cost per Watt-peak compared to string/central inverters.

figure showing the connection differences between string and micro inverter.

Inverters mainly used in these categories:

Off grid inverter

 On grid (grid tied) inverter: Two types of on grid inverters

1.      With transformer grid tie inverter

2.      Transformer less (TL) grid tie inverter

Off grid inverter (Stand alone inverter): These inverters are used to drive the loads which are not in touch with the grid (Isolated systems).The loads draws the required AC power from the inverter which extracts DC power from the batteries which are charged by the PV system.

On grid (Grid tied) inverter: The generated DC power from the PV arrays are converted and connected directly to the respective utility grid. These systems do require a UPS just to power the Switchgear in case of any grid outages and not for energy storing. Inverters in this category contain grid synchronizing mechanism which synchronizes input parameters (voltage, frequency) with output parameters. Voltage and frequency are termed as grid stability parameters.

1. With transformer grid tie inverter: Conventional inverters are built with an internal transformer that synchronizes the DC voltage with the AC output. The use of transformer in Grid tie inverters is to normalize the harmonic content at inverter output, also to provide galvanic isolation feature. Used for large power conversions and mostly used for grid tied configuration.

2.Transformer less (TL) inverters:  It uses a computerized multi-step process and electronic components to convert DC to high frequency AC, back to DC, and ultimately to standard-frequency AC. TL inverters are directly connected to grid and no grounding should be done at PV side. Mostly used for small power conversions.

Peak efficiency of 98.8% can be achieved with TL inverters which is 2% more than Conventional inverters. For lower power applications TL inverters are more effective in terms of performance and cost as transformer is avoided.

Characteristics of Inverters:

Generally most of the data sheets by manufacturers will contain the following data irrespective of type inverter. However some additional information needs to be added for respective type of inverter.

Output parameters:

Rated output power (KVA): This is the output power (AC) of an inverter, based on which the inverter is rated.

Maximum Output Voltage (V): It is the maximum output voltage (AC) of an inverter.

Nominal output Voltage (V): It is the average output voltage (AC) of an inverter. (230V for 1-Phase, 440V for 3-Phase).

Maximum output current (A): It is the maximum current (AC) that an inverter can supply.

Peak efficiency (%): The maximum efficiency of the inverter generally ranges from 90% to 95%.

Loss of power (in the form of heat) is due to the power conversion process (DC to AC).

Weighed efficiency (%): It is the average efficiency of the inverter, always less than peak efficiency.

Frequency range (HZ): Output power will have the following frequency (variations).

Harmonics (%): The amount of harmonics that an inverter output contains. It should be less than 3% (lower harmonic inverter is always superior).

Input parameters:

Rated Input power (W): It is the maximum power (DC) that an inverter can take. It depends on the PV system output, also defines the rating of the inverter.

Maximum input current (A): The maximum input current (DC) that the inverter can take (the peak current of MOSFETS/IGBTS used in the inverter).

MPP (maximum power point) Tracking voltage (V): This is the DC voltage range for which the maximum power can be extracted from the Photo voltaic module/string/array.

Start voltage (V): Minimum input voltage (DC) required to start the inverter & its operation.

Protection: As this category is very important to have a safe/optimum operation of the inverter system. The following protections need to be addressed to have a good & safe inverter.

• DC disconnection (Islanding  protection)
• Ground fault protection
• Galvanic Isolation feature( for GTI- with transformer)
• Arc fault circuit interrupter
• DC reverse polarity/Residual current protection.
• AC short circuit protection

Data sheet of an inverter:

The following link gives the typical datasheet of an inverter (SMA manufacturer).

http://files.sma.de/dl/18726/SB5000TL-US-DUS143847.PDF

Manufacturers:

The following is the leading manufacturers of inverters (International).

NAME OF THE COMPANY	MANUFACTURING CAPACITY (MW)
ABB	NA
SMA	1730
SCHNEIDER	693
SUNGROW	638
SANTERNO	462
POWER ONE	433
BONFIGLIOLI	401
EMERSON	317
SIEMENS	239
SATCON	197
INGETEAM	166
ASEA BROWN BOVERI	149
AE ADVANCED ENGERGY	148
GUANYA	148
TBEA SUN OASIS	131
TMEIC	52
XANTREX	51

 The following is the leading Indian Inverter manufacturers.

NAME OF THE COMPANY	ADDRESS
GENUS POWER INFRASTRUCTURES LTD.	Genus Power Infrastructures Ltd. SPL-3, RIICO Industrial Area, Sitapura, Tonk Road, Jaipur -302 022, India Phone: +91 141 7102400 / 500 Fax: +91 141 7102503 / 2770319
DELTA POWER SOLUTIONS INDIA LTD.	Hyderabad Plot No:68, Nagarjuna Hills, Road No:1, Banjara Hills, Hyderabad - 500082, India +91 40 – 67274510
SUKAM POWER SYSTEMS	plot no: 54, udyog vihar, Phase VI, sector 37, Gurgoan, haryana
MICROTEK INTERNATIONAL	B-10, Hemkunt Tower, 98, Nehru Place, Nehru Place, New Delhi, Delhi 110019
HITACHI HIGH REAL POWER ELECTRONICS	B-14/1 & 171, B-117 & 118, GIDC Electronics Zone, Sector 25, Gandhinagar, Gujarat 382044
AMARA RAJA ELECTRONICS LTD.	Astra Tower, 5, Floor, Cii Building, Kondapur, Kondapur, Hyderabad, Telangana 500082 Phone:040 2339 4597
APLAB LTD.	Address: 54 sri lakshmi towers 1st floor malani colony chinna thokota new, Bowenpally, Telangana Phone:040 2775 5101
UNILINE ENGERGY SYSTEMS LTD.	198/23,Ramesh Market, East of Kailash, New Delhi, Delhi 110065 Phone:011 2646 9108
CONSUL CONSOLIDATED PVT LTD.	Block No 508, 5th Floor, Eros Apartment, Nehru Place, New Delhi - 110019
TRUE POWER INTERNATIONAL	29-A, Teacher Colony, Samaypur, Delhi - 110042 E-mail: info@truepower.in Trade Enquiry: 1800 11 2020
CONSUL NEO WATT	119,120,120A, Electrical and Electronics Industrial Estate, Perungudi, Chennai - 600 096, Tamil Nadu (India).
ELENT ELECTRONICS PVT LTD.	39, D.S.I.D.C. Sheds, Okhla Industrial Area Phase - I, New Delhi, Delhi 110020 Phone:011 4070 4444
EPOCH ELECTRONICA	66, Salkia School Road, Howrah-711106, Kolkata Howrah Kolkata, 711106 Phone:033 2665 9123
UPS INVERTER (UTL)	53A/6 , Rama Road Industrial Area, Near Satguru Ram Singh Marg Metro, Station,, Near NDPL Grid Office, Delhi-110015, New Delhi, Delhi 110015 Phone:099532 29883
LUMINOUS	Across India
POWER ONE MICRO SYSTEM PVT LTD	Bangalore
STUDER INNOTEC INDIA PVT LTD.	376, 43rd Cross Rd, 5th Block, Jayanagar, Bengaluru, Karnataka 560070 Phone:080 2665 5771
NOVERGY ENGERGY SOLUTIONS PVT. LTD	208, Second Floor, Daulat Chambers,, Near Lal Bagh Restaurant, Udaipur, Rajasthan 313001 Phone:0294 241 5487
OPTIMAL POWER SYNERGY INDIA LTD.	Phase 3, Peenya, Bengaluru, Karnataka 560058 Phone:080 4214 6833
AEI POWER INDIA PVT. LTD.	Gat.No.433, Near Weikfield Village Lonikand, Taluka Haveli, Pune - 412216 Maharashtra, India
TECHSER POWER SOULTIONS PVT. LTD	1st Floor, Laxminagar, Wellington Road, Picket, Secunderabad, Telangana 500026 Phone:040 2780 4431

* Note: The above information may subject to vary without any notice and we will be not responsible for such happenings.

Here, the source for the manufacturers list is Wikipedia, Electronicb2b.com