Increasing Micro Generation Output: On-Board Micro Inverters

Micro inverters are a very innovative apporach to deploying truly modular solar PV systems.

A number of different micro inverter models have been developed lately, largely based on an innovation originating at Cambridge University and commercially developed by Enecsys. The Involar M-250 micro inverter is another implementation based on this concept, and while there is a certain smell to it, we are reporting on that latter product here. All micro inverters convert DC collected from a single solar panel or two into AC, tie PV modules together using AC connections rather than expensive and highly resistant DC connections, later transport the generated power to the grid, and usually also include components for monitoring power generation data. On top of the Involar M-250, we also offer the European-made Enecsys quality micro inverter models ranging from 200 Watts to 480 Watts and will add U. S. quality inverters in the near future. Enecsys inverters are fully UL-approved for the U. S. and Canada with the European models CE, UK G-83, German VDE 0126-1-1 certified.

The micro inverter concept has been developed in the U. K. by Cambridge University and launched to the market by Enecsys, Cambridge-based engineering firm

 

The following is quoted (and slightly polished) from the Chinese producer’s description:


A schmeatic overview of a micro inverter setup

The following steps elucidate the basic working princilples behind the INVOLAR micro inverter:

Step One

Solar photovoltaic modules convert light energy to direct current through the photoelectric effect.

Step Two

Micro inverters attached to photovoltaic modules finish the DC-AC conversion process.

Step Three

Synchronize and transport energy to the grid through phase-lock technologies with speed and precision.

Remark 1:Independent modules supported by micro inverters (250W) could form a parallel connection for a larger power requirement
Remark 2:MIS =Micro Inverter System

Features of the M250 Microinverter

      * Maximizes energy harvest – Different from conventional centralized inverters, M250 micro inverters conduct per-module MPPT, maximizing the efficiency of each single module with a consequent 25% increase in energy harvest.

 

      * Applicable to various conditions – M250 micro inverters allow for mismatch of photovoltaic modules, and each module can make flexible reactions to obstruction shading, inter-row shading, and obstacles such as dust or debris to avoid a sharp decrease in system efficiency.

 

      * Improved safety – With the built-in DC-AC conversion function, M250 micro inverters avoid dangerous HV DC circuits necessary to photovoltaic systems supported by conventional centralized inverters.

 

      * Fast problem diagnosis & solution – With PLC (Power Line Communications, i e electricity network) or WiFi technology, it is convenient to maintain real-time monitoring of every single module in the photovoltaic system.

 

      * Low failure rate – M250 micro inverter’s distributed framework ensures no single point of failure that would result in bringing the whole system down.

 

      * Plug-and-play installation – Free from the HV DC circuit, photovoltaic systems supported by M250 micro inverters could have fast, easy, and safe installation by allowing for PV module mismatch, a 15-25% decrease of installation time and cost, and flexibility in the changing of systems.

 

      * excellent INVOLAR M250 micro inverter is the result of the technical design with a high efficiency in its standard of air power supply, high power density, and high reliability.

 

      * By making use of the resonance soft-switching technology in MAC250 micro inverter’s main circuit, the switch frequency reaches near thousands of kHz, reducing wear and tear of the switch.

 

      * small, lightweight, high frequency transformer that achieves electrical isolation, power conversion, and high power density.

 

    * intrinsically safe current source hardware topology and high reliability.

Micro inverter technology by INVOLAR has resulted in a revolutionary device that is fully integrated into each individual module, converting DC to AC at the module level, with an independent MPPT function. INVOLAR’s micro-inverters outperform centralized inverters in:

1. Module-level Maximum Power Point Tracking (MPPT)

Different from the conventional centralized PV inverter, the microinverter enables each individual module to achieve MPPT, which allows for module mismatches and can harvest more solar power.

2. Increased Efficiency during the System’s Life Cycle

With the microinverter technology, the photovoltaic system receives a dramatically higher power output, more than 25% additional energy harvest in a less-than-ideal environment with possible obstruction shading, inter-row shading, and obstacles such as dust or debris.

3.Intelligence and Reliability

With the distributed microinverter framework, there is no single point of failure, which means that failure of any module will only affect its own performance and will NOT affect the other modules’ performances.

Involar’s unique Power Line Communication (PLC) and internet technologies enable real-time monitoring of every single module in the photovoltaic system for fast diagnosis and solution to a problem, thus improve reliability and system uptime.

We recommend switching off the integrated WiFi transmitters and use powerline communications instead in order to avoid potentially harmful EMF exposure; shield powerlines if necessary in order to insulate against powerline-transmitted high frequency signals. The full set of monitoring features is still available when using the less hazardous PLC and cable-Ethernet data transmission.

The INVOLAR remote monitoring system is based on a so-called ETU which is in effect a piggy-back box containing a data transmission unit. This unit is locked to transmit data to the manufacturer’s central data base on a proprietary protocol using internet protocol (high port 7001). If micro inverter user employs any sort of meaningful firewalling policy (blocking transmissions from the inside over non-standard ports) or if you just feel uneasy (actually, we do somehow…) to send your private solar energy data to some black box located in China and Chinese-controlled, you may want to use the “naked” micro inverter or multiple micro inverter units only.

Internet usage directives and Netiquette require every internet user to save bandwith and not flood the network or cause any jams by unnecessary usage. Transmitting a continuous data stream all the way to China is not exactly in line with proper internet use or common sense.

INVOLAR micro inverters can as well be run, and their other technical advantages such as increased output per panel can be used, without remote monitoring and without the “ETU” add-on. In order to lower installation cost — and in light of the above security considerations — you might be well-advised or simply want to go for such a bare-bones solution.

We do provide both solutions as an option, but feel it is our duty to be fair and raise the issue above for everyone to decide for themselves. In a simple consumer or Home Power setting the above issue may be less significant.

With or without the ETU the Involar M250 micro inverter enhances both modularity and configurability of solar PV arrays and, by eliminating DC line resistance, increase performance per solar panel up to 25%. Using a micro inverter, both accessory unit cost and maintenance cost can be decreased significantly in solar PV systems.

Micro inverters may also be used with micro wind turbines and is suitable for models from 50 W up to approx 1000 W rated power (depending on actual local wind conditions) when connected to a suitable regulator (or diversion or dump load). The Involar M250 along with the high-quality U. K.-manufactured Enecsys micro inverters are currently undergoing tests with LE-v50, LE-300 and the Airdolphin DC turbines.

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