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Inverter project targets grid PV systems

Posted: 09 Dec 2011 ?? ?Print Version ?Bookmark and Share

Keywords:PV inverter topology? grid-connected? solar electric system?

A photovoltaic (PV) project in Malaysia looked into single-phase multistring five-level inverter topology for grid-connected PV systems. The University of Malaya (UM), through its UM Power Energy Dedicated Advanced Center (UMPEDAC), was awarded about $767 million (RM2.4 million) for five years (2005-2010) to develop local inverter products for market commercialization.

From this initiative, 12 prototypes of single-phase grid-connected PV inverters with powers ranging from 300W to 3.4kW were produced. Among these, four were tested to AS4777.2-2005, AS4777.3-2005 and IEC 61683:1999 standards. "The prototypes passed all the tests, their performance in some surpassing expectations," noted Nasrudin Abd Rahim, professor at UM.

He said a 2kW single-phase grid-connected inverter has been installed in a demo-house in a cluster of houses in Section 24, Shah Alam. A direct-feed system installed comprises 18 Suntech polycrystalline (STP120-24/AC) panels and a 2kW single-phase grid-connected PV inverter with transformer. System monitoring and control are also installed, monitoring reliable functioning of the inverter system and maximum yield of the solar electric system.

Nasrudin indicated that the MBIPV research groups are developing a monitoring station that will remote-monitor and read parameters such as AC power, DC power, solar irradiation, PV array power and temperature. "String inverter concept was used in which PV string arrays are connected to inverter in the power range 1-3kW, to feed energy into the AC grid in a parallel configuration. All developed products are designed for residential application and suitable for local conditions," he stated.

He continued by saying that in this project, inverter technologies that will be applied are single-phase grid-connected inverter topology with digital PI current control, single-phase grid-connected transformer-less PV inverter with digital PI current control, and single-phase multilevel inverter topology. He considered the developed research products present a novel PWM control scheme where two reference signals and a carrier signal are used to generate the PWM switching signals.

The UM research groups are also capable of producing related products such as solar-panel simulator and photovoltaic maximum power point tracking monitoring system, Nasrudin said. "The photovoltaic maximum power point tracking monitoring system product won bronze at the International Invention, Innovation and Technology Exhibition."

He revealed that the developed prototype is now in the process of commercialization with industrial partnerEXT Technologies Sdn Bhd. Nasrudin believed the product has vast market potential as the world market for PV inverters shows huge demand for inverters. "In the long-term, positive growth is predicted to continue, despite on-going price reductions and architecture changes, and the market will double in size again in the next five years."

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