Monitoring: Driving reliability and O&M efficiency


Inverter monitoring and control systems are using increasingly sophisticated analysis of sensor data to remotely optimize the integrated levelized cost of energy (LCOE) across different manufacturers’ inverters within a single plant. This data is used to holistically control plant and portfolio generation, while planning O&M in the most cost-effective manner.

These more advanced inverter monitoring systems are in greater demand today than ever to assure the resilience of PV plants due to both the new surge of power outages, along with the historic problem of random surges in power demand. These problems can cost asset owners millions of dollars per day in lost revenue without advanced monitoring, opines Pritil Gunjan, a senior research analyst at Navigant Research.

The demand for such inverter monitoring technology is increasing rapidly. The global market for renewable energy monitoring and control solutions is expected to reach an estimated $82.9 billion in cumulative revenue between 2019 and 2028, reflecting a compound annual growth rate of 12.5%, according to a February report from Navigant.

Driving features of the inverter monitoring systems are one-click smart I-V curve diagnosis across entire plants, grid-side failure function recording, and online inverter support service with 24/7 fast response. At the same time, these monitoring systems are equipped to analyze both 600 V and 1,500 V operations, as the industry migrates to higher voltages.

Advanced algorithmic data analytics, robotics, and machine learning have made inverter monitoring solutions both more intelligent and more economically attractive, Gunjan writes.

Measuring more variables

I-V curve diagnostics are said by Growatt to be the most useful function in inverter monitoring systems, using algorithms with a one-click diagnosis to helps to check performance of the entire system, and locate faults. “With string monitoring and I-V curve scanning, it’s easier to recognize a fault in a string or a low performance string,” says Lucas Wu, European product manager for Growatt.

The most advanced inverter monitoring systems also enable total harmonic distortion voltage (THDv), ISO and grid line impedance analysis, and the wave record of the inverter. “The THDv and grid voltage waveform can also help us to know the grid’s condition. The DC isolation and AC line impedance show the system condition on the DC/AC side to let us know when, where, and why there may be a fault,” says Wu. “Further, the fault wave form record function is a special tool for remote diagnostics when complex problems occur.” Growatt engineers are testing and analyzing systems remotely, without on-site visits, he adds.

As more electronics move into inverters and away from external controller modules, the data provided by the inverters become more granular in shorter periods of time, allowing specific functional analysis within seconds, rather than minutes or hourly tracking that earlier systems relied upon. With such granularity, the need for advanced communications capabilities arises, so that data is transmitted wirelessly to the web, which also permits remote decision-making.

Analysis is also moving toward individual inverters, rather than aggregate plant performance and failure monitoring, with the use of variable set point triggers that capture records used in monitoring and decision-making. “Customers want to divide their plants into subarrays, so that they can manage their generation by plant, by subarray, or by device view,” says Wu.

Global support platforms

Inverter monitoring systems have evolved to the point that they are plant-location agnostic, with Internet-based access by customers or O&M operators anywhere in the world. These analysis and reporting systems also have become responsive 24/7, so that an asset portfolio manager can have a single, seamless view of plant performance across the globe.

“Our customers ask questions directly through our operating system which then becomes a fast-response work order dispatched to our service engineering teams in Europe and in China, no matter what the time,” confirms Wu. “This enables a faster response mechanism with a powerful dispatch function.” The company has more than a dozen offices and warehouses worldwide.

The size of an inverter monitoring system is also crucial to providing 24/7 response. Some inverter monitoring system providers are merely regional or national, which limits aggregate intelligence across geographies. Growatt has the reach to provide a global solution, having shipped more than 5 GW of inverters in 2019 to make it the world’s eighth-largest global inverter supplier, Wu points out.

Re-tooling inverter monitoring

Among the market drivers that affect the adoption of new, more advanced monitoring and control solutions are renewable assets that are nearing the end of their warranty agreements, according to Navigant’s Gunjan. “Achieving cost reductions while improving efficiency is one of the key strategic priorities for all asset operators.”

Longer-term O&M service contracts that carry performance guarantees help asset owners calculate their return on investment, and to plan for future O&M repairs. These guarantees also help define grey areas of O&M projections in bankability studies required for new developments.

However, new global disruption in the PV supply chain caused by Covid-19 now also poses a threat to the response time for PV repair equipment, which can increase downtime, particularly for off-grid or remote on-grid locations. Thus O&M service agreements that provide strategic stockpiles of equipment that can be used for rapid retrofitting deployment should become more attractive.

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