MICRO-INVERTER

Micro-inverter

Micro-inverter is same as an inverter, used for power conversion process i.e., DC power to AC power, but micro-inverter is rated for low power, typically the power rating is 330W (Maximum) which is the power capacity of the PV module. It is designed for module power level in order to overcome some disadvantages over string/central inverter on system performance. It is expected that the power output of the overall system gets increased by a good margin with the use of micro-inverter.

Micro-inverter connection with PV module

Advantages using micro-inverter:

• Higher energy yield.
• Design flexibility.
• Redundancy.
• Modularity.
• Longer warranty.
• Easy monitoring/trouble shooting.
• Efficient for small systems.

Disadvantages:

•  Higher costs.
• Complex installation process/maintenance.

Problems with conventional string/central inverter:

As the string inverter is one big inverter which is normally rated for higher power (KW range), it is associated with a MPP Tracking (Maximum power point) mechanism & operates certain number of PV modules. If one MPP tracker is employed for a string of modules then power output of that string depends on the I-V characteristics taken across the string & not for the individual module, MPP tracker by its natures will extract the maximum power from that I-V characteristic. Whenever some modules underperforms due to some reason then it will drag down the I-V curve of the total string resulting in low output power which is not appreciable (performance of better performing modules decreases). The same case with central inverter as it employed for no. of strings and power performance is even poorer than string type.

To overcome these issues every module is equipped with an inverter called micro-inverter, which looks after the performance of the module to which it is associated, separate MPP tracking is allowed with micro-inverter (inbuilt with MPPT) setup. The performance of every module is independent as it is managed independently of its neighbouring module, which makes the entire string perform better.

Also in case of any malfunction, failure of inverter happens then the power production has to be interrupted until the issue is rectified, but with micro-inverter the faulted devices are replaced (with spare devices it’s like plug & play) or left out easily without any interruption in PV plant. With electronic & communication it is easy to locate & fix the issues.

Figure showing the connections of different inverters with PV system.

a) Central inverter b) String inverter c) Micro-inverter type system

The following diagram(below) shows the advantage of employing Micro-inverter over string/centralized inverter.

The below left conventional string/central inverter, where due to a partial shading the entire power output is reduced to 50% of its maximum capacity this is because of having a single inverter(MPPT inbuilt) for the total shown system, MPPT changes the I-V curve as explained in “ problems with “. On the other side micro-inverter will exclude exactly the shaded part of the module, there by the performance of other modules are not affected. A panel can under-perform because of many reasons such as: It is ageing differently, shaded by a smell pipe, chimney/tree, it is dirtier than the other panels

Figure showing grid connected micro-inverter PV system

Technical parameters of micro-inverter:

Input side:

• Power input DC (Watts): It is the recommended input power from the PV module.
• Maximum input voltage (DC): It is the maximum voltage that can be given for the micro-inverter.
• Maximum input current (DC): Short circuit current from the PV modules that a micro-inverter can withstand.
• Maximum power tracking voltage (DC): Range of input voltage for which the max. power can be extracted from the respective PV module.
• Minimum/start voltage (DC): Amount of voltage required for a micro-inverter to start its operation is start voltage. Minimum voltage is the min. input voltage that a PV module can generate for the micro-inverter.

Output Side:

• Peak output power AC (Watts): The maximum power that a micro-inverter outputs.
• Maximum output Current (A): Maximum current can be drawn from a micro-inverter.
• Nominal output voltage range (V): It is the range of voltage that the micro-inverter will able to supply.
• Frequency range (Hz): Micro inverter can sustain the following variations in the frequency.

• Power factor: the phase displacement b/w the voltage and current output of the device.

• Harmonics (%): Amount of harmonics that the micro-inverter’s output consists.

• Peak Efficiency: Maximum efficiency achieved by the device (around 95%).

• Weighted (CEC) efficiency (%): It is the average efficiency of micro inverter which is always less than peak efficiency.

• MPPT efficiency (weighted): It is the average efficiency of the maximum power point tracker.

• Power consumption (mW): Self consumption of micro-inverter for its functioning (DC to AC conversion).

• Operating/ with-sand temperature range: working temperature range/extreme temperatures (+ or – ⁰C) of micro-inverter.

• Enclosure environmental rating: A typical NEMA (National electrical manufacturers association) enclosure might be rated to provide protection against environmental hazards such as water, dust, oil or coolant or atmospheres containing corrosive agents such as acetylene or gasoline.

• Protection: The following protection features needs to be addressed while choosing micro inverter.
• DC disconnection
• Short circuit protection (DC/AC side)

• Monitoring/surveillance:  Options available for online monitoring (wireless)/accessing data which is important to trace the fault location/module/inverter.

Datasheet:

The following link directs to a technical data sheet of a micro-inverter (open in new tab)

http://www.enphase.com/sites/default/files/M215_DS_EN_60Hz.pdf

Pricing:

By the end of 2012, panels were widely available in wholesale at 65 to 70 cents, and string inverters around 30 to 35 cents/W. In comparison, micro-inverters have proven relatively immune to these same sorts of price declines, moving from about 65 cents/W to 50 to 55 cents/W. Further improvements in semiconductor devices may reduce the price. (Source: Wikipedia)

Eg: In India Micro inverter of 300W is priced around 8000 INR.

On grid PV systems Grid Code Requirements: A grid code is a specification which defines the parameters a facility connected to an electric network has to meet to ensure safe, secure and proper economic functioning of the electric system. These include voltage regulation, reactive power supply and power factor limits, response to a system fault (short-circuit), response to changes in the frequency on the grid, and requirement to "ride through" short interruptions of the connection.

Voltage regulation: This means that by the connecting the DG, the voltage at the PCC shall not be outside a specified range.

Frequency Deviation: In the same way the frequency deviations shall also not go outside a specified range.

Synchronization: While synchronizing a DG with a utility grid it shall not cause a voltage fluctuation of more than ± 5% of the existing voltage level at the Point of Common Coupling (PCC).

Isolation system: Whenever required by utility grid operating practice for making or breaking the connection, an isolation device shall be located between the DG unit and the utility grid.

Harmonics: The allowable voltage harmonic distortion is specified at the PCC. It is normally required that the maximum voltage total harmonic distortion is 5% and maximum individual frequency voltage harmonic is 3% of the fundamental component.

DC current injection: A DG and its interconnection system shall not inject dc current greater than 0.5% of its rated output current into the utility grid at the PCC .

The above mentioned specifications are intended for safe power transactions b/w grid and generation site, also not to impose any instability issues to the grid which is a serious concern (not allowed) due to the addition of DG's (Distributed Generation). The instability issues actually raises worst conditions like outages in the power system which proves DG's integration ineffective.

Manufacturers list:

Name of the company Address  Latronics Latronic Sunpower PTY LTD PO Box 73 Moffat Beach QLD 4551 Australia Selectronic Suite 5,20 Fletcher Road,Chirnside Park,Victoria, 3116,Australia. Fronius Address:Fronius International GmbH,Froniusplatz 1,A-4600 Wels, China Analytic systems 8128 River Way Delta BC V4G 1K5 Canada Xantrex (acquired by schneider) Phocos Phocos AG Magirus-Deutz-Straße 12 89077 Ulm Germany Siemens Siemens AG Energy Sector Freyeslebenstrasse 1 91058 Erlangen Germany SMA SMA Solar Technology AG Sonnenallee 1 34266 Niestetal Germany Convertitori Statici - based in Italy Convertitori Statici Via Pietro Giardini, 1271/C 41126 Modena Italy Master volt Mastervolt International BV Snijdersbergweg 93 1105 AN AMSTERDAM ZO The Netherlands Atersa - spain c/ Embajadores, 187 28045 Madrid, Spain Mitsubishi - japan http://global.mitsubishielectric.com solener Soluciones Energéticas S.A. (Solener) Avenida Real de Pinto, 146 28021 Villaverde Alto Madrid Studer STUDER INNOTEC SA Rue des Casernes 57 1950 Sion Switzerland Cobra Cobra Electronics Corporation 6500 West Cortland Street Chicago, IL 60707 United States Rich electric 31Keji 5th Road Annan Distict Tainan Technology Industrial Park 70955 Taiwan Exel tech EXELTECH 7317 Jack Newell Blvd N Fort Worth, TX 76118 USA Morning star Morningstar Corporation 8 Pheasant Run Newtown, PA 18940 USA Sinergex http://www.sinergex.com/ Sensata Sensata Technologies, Inc. 529 Pleasant Street P.O. Box 2964 Attleboro, MA 02703-0964 USA Vanner Vanner, Inc. 4282 Reynolds Drive Hilliard, OH 43026 USA Delta energy systems germany GmbH Business type: manufacturer, wholesale supplier, exporter Product types: DC to AC power inverters, microinverters. Address: Tscheulinstr. 21, 79331 Teningen, Germany Telephone: +49 180 10 Solar (76527) FAX: +49 180 16 Solar (76527) Web Site: http://www.solar-inverter.com Enphase energy Business type: manufacturer Product types: DC to AC power inverters, micro-inverters. Address: 201 1st Street Suite 111, Petaluma, California USA 94952 Telephone: +1-707-763-4784 or Toll Free 877-797-4743 FAX: 707-763-0784 Web Site: http://www.enphaseenergy.com Power one Inc Business type: manufacturer Product types: DC to AC power inverters, microinverters. Address: 740 Calle Plano, Camarillo, California USA 93012 Telephone: 805-987-8741 Web Site: http://www.power-one.com Solar bridge technologies Business type: manufacturer Product types: DC to AC power inverters, microinverters. Address: 8310-1 N Capital of Texas Highway, Suite 295, Austin, Texas USA 78731 Telephone: 512-637-6860 FAX: 512-637-6878 Web Site: http://www.solarbridgetech.com Rene sola ltd. Business type: manufacturer, wholesale supplier, exporter Product types: photovoltaic cell materials, monocrystalline and multicrystalline silicon wafers. Address: F16, Tower D, Beijing Global Trade Center, No. 36 North Third Ring East Road, Dongcheng District, Beijing, P. R. China 100013 Telephone: +86 1058256599 FAX: +86 1058256390 Web Site: http://www.renesola.com Neat power co. ltd. Business type: manufacturer, exporter Product types: backup power systems, DC to AC power inverters sine wave, DC to DC power converters, battery chargers, microinverters, solar charge controllers, Monitoring Webcard. Service types: design Address: 7F., No. 32, Gongyuan Road, Guishan Dist., Taoyuan City, Taiwan 333 Telephone: +886-3-3286028 Web Site: http://neatechpower.com P&P energy co ltd. Business type: manufacturer, retail sales, wholesale supplier, exporter, importer Product types: microinverters, photovoltaic systems residential, photovoltaic systems commercial. Service types: consulting, design, project development services, research services Address: No. 100 Waihuan Xi Road, Guangzhou Higher Education Mega Center, Panyu District, Guangzhou, Guangdong China 510600 Telephone: +86-20-39323011 Web Site: http://www.ppnewenergy.com A SSGHK solar system Business type: manufacturer, wholesale supplier, exporter Product types: hybrid power systems, photovoltaic systems, photovoltaic systems commercial, microinverters, DC to AC power inverters, solar roofing systems, solar energy storage. Service types: design, installation, construction, engineering, contractor services Address: 33/F., Shui On Centre, , 6-8 Harbour Road, , Wanchai, China Telephone: +852 2159 5001 Web Site: http://www.assghk.com B&B power co ltd. Business type: manufacturer Product types: DC to AC power inverters, DC to AC power inverters sine wave, DC to DC power converters, microinverters, photovoltaic systems, solar roofing systems. Service types: design, engineering, project development services Address: No 9, Zhongshan Garden Road, Nanshan District, Shenzhen, Guangdong China 518000 Telephone: 86-755-86567100 Web Site: www.bbpower.cn Carisol Business type: manufacturer, retail sales, wholesale supplier, exporter, importer, distributor Product types: air cooling systems, air cooling system components, wind energy systems (large), batteries deep cycle, photovoltaic systems, solar water heating systems, solar air conditioner system. Service types: consulting, design, installation, construction, engineering, project development services, education and training services, research services, site survey and assessment service, financial services, a... Address: 38 Cassia Park Road, Kingston, Jamaica Jamaica 33000 Telephone: 8769252783 Web Site: http://www.carisol.org Conergy  renewable energys singapore ltd. Business type: manufacturer Product types: photovoltaic modules, photovoltaic systems, photovoltaic module mounting systems, solar charge controllers, microinverters. Service types: consulting, design, installation, construction, engineering, project development services Address: 120 Robinson Road, #12-01 Parakou Building, Singapore 068913 Telephone: +65 68495540 FAX: + 65 68495559 Web Site: http://www.conergy.com Decen techonology co ltd. Business type: manufacturer, exporter Product types: DC to AC power inverters sine wave, DC to AC power inverters, microinverters, photovoltaic module mounting systems, photovoltaic systems residential, photovoltaic systems residential, solar grid tie inverters. Service types: design Address: Yongchun science and technology park, songming road, songgang town, Shenzhen City, Guangdong Province China 518105 Telephone: +86 0755 32998961-604 Web Site: http://www.decengroup.com/ Dongguan Kaideng Energy Technology Co., Ltd Business type: manufacturer, exporter Product types: micro inverter, solar modules system, photovoltaic systems, sun solar, solar for homes, DC to AC power inverters sine wave, DC to AC power inverters, grid tie inverter, grid connected inverters, power inverters. Service types: consulting, design, engineering, project development services, research services, maintenance and repair services Address: Chang'an Town, Dongguan, Guangdong China 523850 Telephone: 8615989614971 FAX: +0086-0769-81888841 Web Site: http://www.alibaba.com/product-gs/874329809/Solar_power_system_micro_Inverter_WVC.html ELE advance ceramics Business type: manufacturer, exporter Product types: microinverters. Service types: design, engineering Address: Rm2302 Dihao building, No. 820 Xiahe Road, Xiamen, Fujian China 361004 Telephone: 00865922960185 FAX: 00865922960178 Web Site: http://www.eleceramic.com Enecsys limited Business type: manufacturer Product types: microinverters. Address: Harston Mill, Royston Rd, Cambridge, United Kingdom CB22 7GG Telephone: +44 (0) 1223 792 101 Web Site: www.enecsys.com Frequency inverters Business type: manufacturer, wholesale supplier, exporter, distributor, electric utility Product types: microinverters, energy efficient appliances, backup power systems, DC to AC power inverters, DC to AC power inverters sine wave, DC to DC power converters. Service types: installation, engineering Address: Building 2 Xuwu Gongle Xixiang, Bao'an District, Shenzhen, Guangdong China 518000 Telephone: 8675526037586 Web Site: http://www.frequencyinverters.org Involar Business type: manufacturer Product types: microinverters. Address: 887 Zuchongzhi Road, #84-407, Shanghai, China 201203 Telephone: (86) 21-5109 8006 Ext. 821 Web Site: http://www.involar.com Midnite solar Business type: manufacturer Product types: solar charge controllers, solar electric power systems, battery enclosures, power conditioning equipment, microinverters, meters and measuring equipment, battery charge controllers. Address: 17722 67th Ave NE, Arlington, Washington USA 98223 Telephone: 360-403-7207 FAX: 360-691-6862 Web Site: http://www.midnitesolar.com Power cell energies pvt ltd Business type: manufacturer, exporter,Web Site: http://www.powercellenergies.com Product types: solar charge controllers, DC to AC power inverters sine wave, hybrid power systems, power conditioning equipment, battery chargers, microinverters, INVERTER WITH BIG CHARGERS 20AMPS, 30AMPS. Address: B-219, a, Vasant Kunj Enclave, New Delhi India 110070 Telephone: 011-32313133 FAX: 011-2689630 Sensol solar technology Business type: manufacturer Product types: micro inverters, DC to AC power inverters, photovoltaic systems residential, photovoltaic systems commercial, PV modules. Service types: installation, construction, engineering, project development services, contractor services Address: Technology Innovation Park, Sunshine Industrial Area, Anji County, Zhejiang China 313300 Telephone: +86 572 5858001 Web Site: http://www.sensolgroup.com Solar IC ltd. Business type: manufacturer Product types: backup power systems, DC to AC power inverters, microinverters, solar charge controllers, solar electric power systems, LED lighting, Energy Saving Appliances LED light /FAN. Service types: design, installation, engineering, project development services, research services Address: Road # 8, House # 2/A, Baridhara Diplomatic Area, Dhaka, Dhaka Bangladesh 1212 Telephone: +880 (2) 9884551, +880 (2) 8811154, +88-01750-150250 FAX: +880 (2) 8835244 Web Site: http://www.solar-ic.com Unipar Business type: manufacturer, retail sales Product types: uninterruptible power supplies UPS, microinverters, backup power systems. Service types: installation Address: #1337, Muniagappa Layout, Kavalbyra Sandra, R. T. Nagar, Bangalore, Karnataka India 560032 Telephone: 080 23332078 Web Site: http://www.unipar.in VFD system Business type: manufacturer, wholesale supplier, exporter Product types: power conversion equipment, microinverters. Address: 1st Floor, Pulachiwadi Behind Deccan Jymkhana, Shivajinagar, Pune India 411029 Telephone: 919970176466 Web Site: http://www.vfds.in Wuxi think power new energy technology co. ltd. Business type: manufacturer, exporter Product types: DC to AC power inverters, DC to DC power converters, photovoltaic systems residential, solar electric power systems, photovoltaic module mounting systems roof mount, microinverters, PV grid tied inverter. Service types: design Address: Building No. 22, No. 100 Jinxi Road, Binhu district, Wuxi, Jiangsu China 214125 Telephone: +86 510 85192198 Web Site: http://www.thinkpower.com.cn HI-Q engineering pvt ltd. Business type: manufacturer, retail sales, wholesale supplier Product types: backup power systems, DC to AC power inverters, microinverters, batteries lead acid, solar charge controllers, appliances. Service types: consulting, design, installation, engineering, research services Address: 109 Chinhoyi Street, Harare, ZW Zimbabwe Telephone: +263 912 381 417

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

Here, the information source for manufacturers list is energy.sourceguides.com & solar-facts.com