Solar Inverters Move to The Front

When it comes to the Solar market, a disproportionate share of attention is always paid to the modules, or more recently, the module supply chain. The global solar PV module market was valued at $127.9 billion in 2020, and is projected to reach $260.2 billion by 2030, growing at a CAGR of 7.4% from 2021 to 2030 according to research firm Allied Market research.

In India, we have seen how the PLI scheme for Manufacture of High Efficiency Solar Modules has galvanised talk around building capacity. Combined with the high solar capacity additions the country is committed to it has also ensured massive interest for upto 40 GW of fresh capacity. It makes sense too as modules can account for between 55 to 60% of the cost of a solar project. Solar Inverters, at between 5% to 10% of projects costs were easily ignored, mixed with the rest of the electrical costs of a typical project.

A well established ecosystem of metal working in the country has meant that structures, the other large cost component, is relatively well supplied domestically.

Solar Inverters as a category are not only vital to the solar expansion underway, but how these inverter firms adapt and deliver relevant products will also decide the pace of expansion in some ways, as we will discover here. And the market is certainly worthwhile. According to research by The Business Research Company (TBRC), The global solar inverter market size is expected to grow from $12.04 billion in 2021 to $13.38 billion in 2022 at a compound annual growth rate (CAGR) of 11.14%.

In fact, in recent years, even as modules have continued their relentless march towards higher efficiency, output and even size, it is changes in the inverter and energy storage market that is shaping the next growth spurt in solar capacity. Especially as solar moves from being an auxiliary energy source to a mainstream option.

Solar inverters in fact, are hardly called that anymore, as the focus shifts to ‘smart’ inverters. And with good reason. Today’s ‘Smart’ inverters go well beyond the basic facility of converting Direct current generated by modules to alternating current. They will increasingly be looked at to provide grid support functions, such as voltage regulation, frequency support, and ride-through capabilities. Also known as Grid-forming Inverters, they have the potential to provide many, if not all, of the grid services currently the province of spinning fossil fuel generators, which they seek to replace so urgently worldwide.

So we decided to speak to a selection of solar inverter manufacturing firms, to better understand the inverter evolution, and what to expect thanks to it.

So Just How have Solar Inverters Evolved?

“Over the previous decade, Sungrow inverters have evolved in two major aspects: technical improvement and the application improvement. First, our inverters have become more efficient in power conversion; most boast max. 99.9% efficiency now, and they have higher power density due to smaller form factors. Besides, all our inverters adopt multi-MPPTs to better handle large currents, synchronised with the Module wafer size upgradation,” says Nataraja MS, Technical Lead, Sungrow India, which recently celebrated the expansion of their inverter manufacturing plant in India to a capacity of 10 GW, by far the largest such setup in the country.

For Sandeep Goyal, on the other hand, Founder and CEO at Pyramid Electronics, a firm that recently moved into grid-tied inverters, the focus is on a key technology change. “From the viewpoint of power electronics technology, the next step in evolution is the replacement of Si IGBTs (Insulated-Gate Bipolar Transistors) with SiC MOSFETs (Metal Oxide Semiconductor Field-Effect Transistor). Our inverters have already evolved in this regard as we are using this technology in our grid tie inverters and EV chargers as well. He adds that “this change in power devices leads to a significant reduction in component count as the power electronics circuitry can be simplified without any sacrifice in efficiency. The efficiency of SiC MOSFET based inverters with simple power converter topologies is at-least 1.5 % higher than the Si IGBT based inverters with more complex power converter topologies. Also higher power densities can be achieved with SiC MOSFET based inverters. Also, IOT capabilities have been added on to the inverters which were not existent a decade back”, he finishes.

Nataraja reminds us about how versatile inverters have had to become too. “Sungrow inverters prove to be highly applicable in various application scenarios including floating environment, high-altitude contexts, chemically-sensitive sites. They are robust and reliable even in deserted, freezing environment. More importantly, Sungrow inverters also support flexible hardware configuration so as to facilitate our customers’ site design” he stresses.

Honey Raza, Sales Head at Solis India, which has been a singular success story in the past few years in India reminds us that with a larger market, service standards have seen a major upgrade to do well. “In the past 10 years, Solis has always insisted that safety and reliability is the core point of the development of series inverters, and has always adhered to the development model of research and development, design, production, sales and service. And to bring customers better and better cluster inverter photovoltaic project solutions, improve customer experience. In terms of product positioning, we always believe that cluster technology is the optimal solution for photovoltaic inverters. Solis initially targeted at the market of small photovoltaic grid-connected inverters and developed a variety of series inverters for customers, with power range ranging from 700W to 5kW. A key differentiator is our insistence on building a local service team to provide timely and effective products and services for all regions of the world”.

Deepak Pandey, industry veteran and now Founder and CEO of his own UK-based firm, Invergy India, points to a seminal shift that he believes will only get stronger. “The inverter segment has evolved from grid to hybrid solutions. In on Grid, systems have evolved from a max size of 50 kW to now 295k W (from Sungrow), so inverter development has been immense. I won’t be surprised to see inverters of 500kW launched with highest level of efficiency soon.

Hybrid systems have been taking advantage of tech development from low voltage to high voltage, high frequency solutions. Now inverters can handle far higher ranges as compared to earlier, efficiency rates have moved from 60-65% to over 90% in hybrid systems too”, he points out.

Interestingly, all the experts we spoke to highlighted the gains made by string inverters over central inverters, even as microinverters, where a key player, Enphase has just started getting active in India, will remain a narrower category within inverters due to its higher cost. While estimates varied, with ever higher capacities, most expected string inverters to continue to gain share for the foreseeable future.

The EV Charging Extension One of the more obvious ‘diversifications’ for most solar inverter firms has been the move into manufacturing EV chargers. Seeing it as a natural extension of their understanding of power electronics and the green transition, leading firms across the world, from Huawei, to Fimer to ABB have already moved into the EV charging business. Firms we spoke to for this story are all in, or have plans to enter the business too. “EV charging is a natural extension of new energy + outdoor + power electronics…Combined with these three keywords, you will find that EV charging products are completely compatible with inverters,” says Raza. “We foresee that larger EV adoption will be a trend since it is now able to stabilise the grid via V2G feature. However, the cornerstone of these opportunities is a good utilisation of solar power, which is based on reliable inverter equipment that Sungrow is offering,” offers Nata-raja MS. When asked if there are viable products to manage charging stations with solar power yet, he says, “Sungrow is also developing its own EV chargers. We now become a core member of CharIN. Worth mentioning, recently, one of our EV chargers supplies the First Road DC Fast EV charging station in Shanghai, China.” Goyal adds that “ From viewpoint of power electronics, grid-tie inverter technology is not very different from EV Charger. However, from viewpoint of a complete solution for EV charging, EV charger is a far more sophisticated/ complicated product compared to grid-tie solar inverter. EV Chargers need to implement OCPP 2.0.1 for communicating with the Central server and also need to implement certain complicated communication protocols for handshaking with BMS of the EV battery. Fast DC charging for EVs with solar power is not feasible with current solar panel technology because of the low power density of solar panel technology. However, slow AC charging is viable.” But Raza is optimistic. “While solar energy is purely green, using PV power generation to charge electric cars can truly achieve zero-carbon travel,” explains Raza, adding, “At the same time, the cost of photovoltaic power generation in most regions is already lower than the price of end-user electricity, so using photovoltaic power genera-tion to charge electric vehicles is also a more economical choice.” “The combination of EV charging and solar energy will be the future trend,” he declares, claiming, “Once we decide to enter the EV charg-ing industry, we will not only make high-quality and costeffective charging equipment, but also cooperate with the PV energy storage to provide overall charging solutions.” A Sungrow DC Fast Charger in Shanghai

The Inverter Of The Future

Raza predicts that “By 2030, the inverter will have added sound protection technology to make the whole PV system safer and more reliable, such as the new anti-PID technology to prevent power station attenuation, such as arc-pulling and cutting technology with AI self-identification, etc.,” anticipates Raza with regards to advancement in inverter technology development, adding, “Reducing the difficulty, time and cost of power station operation and maintenance is also an important direction.” The improvement of inverter performance is of great significance to the whole PV system”

Balasubramanian T, Technical Lead Engineer at GoodWe India, a leading player in the rooftop and commercial segment that has expanded to utilities now, explains. “Smart/String inverter technologies will lead the future solar business in Commercial & Industrial segments as well as utility scale solar power plants. This smart Inverter will have more DC overloading options, flexible MPPT channels, fuseless or in-line fuse options, etc. With the mentioned features, systems will have reduced clipping losses and provide extra generation (kWh) than the conventional inverters. Also string inverters will offer the lower LCOE when compare to central inverters. The reason behind lower LCOE is inverter solar plant down time will reduce significantly and harvest more yield during the system lifetime”. Sungrow’s Nataraja adds to what Pyramid’s Goyal said, by adding that “ Firstly, there will be increased use of wide band gap devices like Silicon Carbide and Gallium Nitride, Multi-level topologies promoting use of Higher Max PV voltage. Inverters will see increased power density by using more high switching frequency and reduced output filter stage. Besides, relying on switching devices interlocking protection, it is also anticipated that PWM (Pulse Width Modulation) algorithms will be optimized and its number will be reduced.

Another possible trend is that inverter operation mode can be shifted to PCS mode in the same hardware condition. Such transition now achieves 90% efficiency and, in the future, its efficiency will be improved.

Apart from the mode transition to PCS, in the future, we also expect inverters to work in synergy with multi modes such as powering the hydrogen-based or EV-Fuel cell-based station, supporting grid, storing surplus electricity etc”.

IoT comes in for special mention too. “In the future, inverter development will benefit a lot from the IOT and the Blockchain technologies, which will further improve its forecasting and diagnostic functions. Besides, inverters can also work closely with other core devices like trackers, cleaning robots. As a result, the overall plant performance will improve during its lifespan,” believes Natraja MS.

By 2030, Goyal says, the smart grid inverters could become smart enough to provide grid support along with feeding power to the grid, which would typically require a reliable communication interface between the inverters and power system operators.

Upcoming Launches

So, when do manufacturers expect to roll out the next big upgrade in their line of offerings? In the third quarter of 2022, Solis is expected to introduce “major upgrades” in its product range: Next-generation inverters; higher voltage inverters to reduce LCOE for PV systems; higher DC/AC ratios; compatible with larger modules. Pyramid Electronics plans to rollout their 20-50 KW grid-tied inverter series by June end. Further, they are also developing VFD controllers for 3-10 HP solar water pumping applications. Finally, Sungrow has launched a new range of inverters: the SG320HX. The new 1+X modular inverter is said to allow flexibility to customers during the design stage, thanks to its ability to work with both 182 mm and 210 mm module sizes. As per the developer’s claims, compared to conventional central inverters, 1+X’s modular design reduces the service time and leads to further decreased downtimes.

“In 2022 Q4, Goodwe India is planning to launch 300kW+ inverter in utility scale solar markets and 100kW+ commercial and industrial energy storage products. At present GoodWe inverters Residential solutions ranging from 0.7 to 15 kW, Commercial and Industrial (C&I) segment ranging from 17 to 136 kW. GoodWe HT 1500V Series (GW250K HT) is GoodWe’s top inverter for utilization in solar utilities with an exten-sive list of features designed to reduce Balance of system (BOS) and O&M costs. GoodWe offers PV+storage (Hybrid) solutions inverters ranging from 3kW to 50kW for residential, commercial and industrial markets,” informs Balasubramanian from GoodWe.

Inverters And Storage. The Next Big Opportunity

In all these changes, perhaps the biggest shift has been the emergence of energy storage, and specialised inverters for both on-grid and off-grid energy storage systems.

This has been made possible by both better quality lithium ion batteries, as well as a drop in price for lithium batteries as well as solar systems per se. So much so that every expert highlighted it as a key focus area, and likely to have an impact on the future market evolution. While already underway in developed markets, the impact will be felt in India soon, is the common refrain.

“The mainstream energy storage inverters all adopt bidirectional DC-DC topology and have a back-up topology, which is different from the traditional grid-connected inverter boot circuit + inverter topology,” ex-plains Raza, adding, “For example, Solis energy storage inverters have at least six control modes to maximise the use of solar energy and improve system benefits.” Goyal states that as the installation of grid-tied inverters is increasing, soon a time will come when generation during day times may start to exceed the load which would lead to grid overvolt-age issues. In such scenarios, it would become a necessity to have energy storage in the power system, he adds.

Goodwe’s Balasubramanian has absolutely no doubt about what needs to be done. “If storage inverter price becomes more competitive when compare to on grid inverters, Indian policy makers should focus on Solar rooftop system with storage options (i.e Solar Hybrid systems), rather than rooftop solar grid connected system. If all state governments will give more importance to solar roof top battery backup system means solar storage solutions price also will reduce drastically similar to grid connected solar roof top systems. Also for encouraging solar hybrid sys-tem, we have to introduce tariff based solar storage system in all DISCOMs”, he stresses.

Sungrow’s Nataraja also looks forward to a storage boom in time.

“Storage plus inverter solution opens the door to future utilization of renewable power. Previously, people used inverters to convert power so that we can use solar energy. Now with the storage plus inverter solution, we can embrace more possibilities such as off-grid appli[1]cation, energy shifting, grid-support, black start capability etc. With storage, renewable energy consumption is more resilient. Storage plus inverter solution makes it possible that renewable energy will become the main body of the energy mix”, he opines.

Invergy’s Deepak Pandey adds that “Besides a market shift from the central inverter to string inverters, as more and more manufacturers focus on string inverters and capacity of string inverters rises, the residential and C&I segment will shift towards storage solutions. More modular plants thanks to string inverters means lower O&M costs. Hybrid inverter technologies thanks to storage makes energy available at a low cost all the time. In On grid systems it is more about the concept of energy savings, and economising on the price of energy usage. Prices of system are coming down, and storage solutions could be as low as on grid system in time”, he predicts.

The expansion of storage has been riding the loading of more AI, IoT and other high end technologies on inverters. “This is an inevitable change. As intelligent inverters integrate more high end technologies, such as AI algorithms, to diagnose the operation of the system more actively and intelligently and reduce the need for maintenance, there will be more changes and improvements in the power station maintenance industry. The addition of SVG features and virtual inertia technology, reactive power compensation will also be implemented through inverters. In terms of household use, the integration of energy storage inverters into AI and energy management systems can bring influence to the smart home industry, but it will be positive. It can be integrated with other equipment in the industry into a system, so as to bring customers more digital, intelligent and visual home energy management services,” states Raza.

Adding to the refrain, Nataraja adds that “In the future, inverter development will benefit a lot from the IOT and the Blockchain technologies, which will further improve its forecasting and diagnostic functions. Besides, inverters can also work closely with other core devices like trackers, cleaning robots. As a result, the overall plant performance will improve during its lifespan,”.

Conclusion

It was back in March 2020 that key inverter industry leader Huawei, in a prediction of PV market trends till 2025, made predictions for 2025, most of which are well within reach today. Be it predicting digitalisation of 90% of PV plants, to use of AI in 70% of plants, to PV plants that transition from adapting to the grid to supporting the grid, as 30% are solar plus storage systems. All of this is more than likely today when we consider the fact that 70% of the solar capacity the world expects by 2030 has not been created yet. With over 200 GW of ever ‘smarter’ installations this year, and a future where solar will need to integrate with everything from the grid to Hydrogen manufacturing and EV charging, the demand is falling into place. Solar’s ability to step up will be visible in the vast array of modules you will see, but making it all happen, quietly and smartly, Ever More Important will be the inverter behind the modules