Solar inverters help farm generate 900MWh

High output ABB PRO-33s cut number of inverters needed and deliver short build time

The first solar power plant in the UK to use the new ABB PRO-33 string inverters is set to produce 900MWh a year at a farm in Shropshire.

The Priest Weston project uses nearly 4,000, 250 Wp solar modules, arranged into 166 individual strings. A total of 28 ABB PRO-33 string inverters are mounted in four groups on the backs of the rows.

The plant was built by solar power company Westflight Energy, which specialises in designing, building and commissioning renewable energy solutions for farmers and landowners.

“I wanted to use string inverters rather than central inverters because this is a low voltage site and central inverters are more suitable for 11 kV sites with powers of around 4 to 5 MW,” said Chris Brooks, owner of Westflight Energy. “I usually use another vendor’s inverter but I was persuaded to try the ABB PRO-33 and have found it to be an excellent product. The Aurora Vision® monitoring system is the best I have used and the offer is very competitive. Another major attraction for me was the fact that ABB is a global brand.”

ABB’s three-phase PRO-33 string inverter is designed for medium and large de-centralised photovoltaic (PV) systems, either on large scale commercial and industrial rooftops or ground-mounted PV plants such as Priest Weston. The single maximum power point tracker is suitable for this type of uniform-shaped PV plant, with long strings connected to the inverter.

As commercial PV plants get larger, installing the 33 kW, 11 kV PRO-33 allows more PV modules to be connected in series to each inverter. This means that fewer inverter units are needed, cutting cabling costs and installation time.

This contributed to the short build time of the project, with the entire plant installed in eight weeks.

The PRO-33 incorporates a built-in string combiner box. This includes a DC switch, string current monitoring with alarm, PV fuses and monitored surge protection devices, reducing the need for costly external devices. The inverter is also protected to IP65, making it suitable for continuous service at outdoor sites.

A major attraction for Westflight Energy is the complete electrical connection package provided by ABB’s system integration partner Barrett Energy, which installed the high-voltage connection to the supply grid, a transformer, packaged substation and low voltage sub-distribution connection to the inverters. It also provided its expertise on issues such as electrical balance of plant and earthing.

ABB’s Aurora Vision® Plant Management Platform is another benefit cited by Brooks. Provided as a free service, it is flexible,scalable and expandable – suitable for any size of installation, from domestic systems to commercial scale power plants. It offers a traditional solar monitoring system and a comprehensive asset management system.

“Aurora Vision’s impressive in-depth analysis offers the functionality to drill down to string level, which is very important. All our installed systems are client owned by farmers, so they have a great interest in how their system is performing.” Brooks continued, “They need to be confident the system is producing as it should - Aurora Vision® gives them that. For my part, I see all plant performance figures from the system. It also offers me to fault monitor, allowing me to see any issues before the client. Personal trust is paramount in this business so it is vital I use quality products.”

Westflight is contracted to provide continued monitoring, support and maintenance. ABB can also access data for the inverters on the end-user’s site, contributing its expertise to resolving any performance or fault finding issues.

Another benefit of ground mounted installations such as Priest Weston is that the land occupied by the power plant can continue to be used for some agricultural purposes such as sheep grazing.

The project is accredited to receive the feed-in tariff and the generation output is forecast to exceed 900MWh per year. The generation is sold within a Power Purchase Agreement on an annual contract. Levy Exemption Certificates (LECs) and Renewable Energy Guarantees of Origin (REGOs) are claimed and passed to the PPA provider as part of the contract.

About ABB
ABB ( is a leader in power and automation technologies that enable utility, industry, and transport and infrastructure customers to improve their performance while lowering environmental impact. The ABB Group of companies operates in roughly 100 countries and employs about 140,000 people.

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