Getting a 99 MW solar farm operational and safe again

Soon after the commissioning of a newly designed 99 MW solar park in Belgium, electrical equipment connected to one part of the solar park begun to fail – even leading to fire in a transformer. The entire installation was immediately disconnected from the grid. The solar park is divided into two independent parts of approximately 50MW each. With one section out of service, identifying the root cause was vital. Each day without production meant up to tens of thousands of euros in revenue loss. This does not include replacement of damaged parts, possible costs related to contractual obligations, and potential reputation loss due to commissioning and production delays.

Challenge

HyTEPS performed power quality measurements, provided valuable analysis to diagnose the problem, and recommended solutions as soon as possible. Analysis revealed high harmonic voltage distortion at higher frequencies (e.g. 37th, 39th harmonic) caused by resonance. Providing a solution was especially challenging: when working with higher frequencies in MV and HV networks, introducing a solution in one part of the installation may lead to new problems elsewhere.

Objectives

• Find a solution for preventing / reducing the possibility of high harmonic voltage distortion caused by resonance in multiple network confgurations and topologies. 
• Study the solution’s effects on the solar park’s electrical network and avoid problems.
• Choose and recommend appropriate solution based on electrical analysis, expected cost, and other constraints (dimensioning, logistics).

Solution

To understand the electrical network’s characteristics in different configurations, the solar park was modeled in power system analysis software. Power quality measurements were used to verify the accuracy of the designed model by comparing measured values with those from simulations. Several solutions were brainstormed and tested to check for viability. “An excellent challenge for HyTEPS as we’re fully committed to supporting installation managers as well as to facilitating the electrical transition,” explains Lead Engineer Seymour Pijpers. “HyTEPS was requested to perform power quality measurements, provide valuable analysis on diagnosing the crux of the problem, and recommend solutions as soon as possible. Analysis revealed high harmonic voltage distortion at higher frequencies (e.g. 37th, 39th harmonic), caused by resonance. Providing a solution was especially challenging: when working with higher frequencies in MV and HV networks, introducing a solution in one part of the installation may lead to new problems elsewhere.” Network impact of filter designs were tested using simulation tools such as harmonic load flow analysis.

Results

Following customer agreement, the design was finalized. A filter that modifies electrical impedance of the network and distances the resonance frequency from
the harmonic excitation frequency was delivered through one of its manufacturers. Identifcation of the cause of failure, as well as modeling, analysis and solution design on software led to fast, reliable completion. HyTEPS also leveraged its technical capability with industrial connections to rapidly move the solution from idea to reality. The entire project, from electrical failure to solution manufacturing, delivery and installation, took less than six months. The solar park is currently fully operational and customer feedback on the installed filter solution is highly positive.