String versus central versus modular: what’s next for inverter technology? – PV-Tech


A Solis inverter assembly line. Image: Ginlong Solis.

Essentially the brains of a PV plant, inverters’ key function remains the particular conversion associated with DC power to AC. However , their design and configuration is continually evolving, and so are the strategies of the companies making this important piece of kit, writes Jonathan Touriño Jacobo.


For many years, the utility-scale solar PV market has been dominated by central and string inverters, with each claimed to have their own benefits for utility-scale photo voltaic applications. Lately, modular inverters have also entered the particular scene, claiming to combine the benefits of both string and main inverters. This feature will explore different uses associated with each of these technologies, the current technology trends for inverters and how they have adapted to different types of environments ranging from desert areas to floating PV.

There is furthermore the fact that more and more utility-scale projects are developed with energy storage in mind, either to be co-located at the same time or with the particular possibility in order to add it at a later point. This is something that inverter suppliers have been working around as demand increases. Finally, we look at how inverter suppliers are preparing themselves for the introduction of 600/700W+ modules in the sun market.

String and central inverters are usually still favoured

With do it yourself inverters claimed to combine the strengths of string and main inverters with a modular design, manufacturers have started to embrace that new technology. Modularity allows Spanish manufacturer Power Electronics to improve efficiency and availability, says Maribel Trenzano, the particular company’s solar power & storage product & applications manager. “The effectiveness improves because depending on the available power, only the necessary modules will need to operate. The availability increases because the system can keep working even if some modules are failing, and the power associated with the faulty module could be redistributed with the working segments. ”

Ginlong’s inverter brand Solis meanwhile continues to specialise in chain inverters which are flexible and suitable for various scenarios, says Lucy Lu, the particular manufacturer’s global marketing director. “With solar PV projects increasing in size and sorts, application scenario is more plus more complex, it [design] needs in order to consider inverter devices with regard to higher environmental adaptability and security. ” For agricultural or mountain terrain PV projects, higher maximum power point tracking (MPPT) is needed plus better algorithms for inverters to increase power generation. Meanwhile regarding desert places, Solis takes into consideration both wind and sand resistance with better heat dissipation, adds Lu.

If some suppliers are advancing on modular inverters, for German developer BayWa r. e., this is still not an option it is envisioning to use as they are even now too expensive, says Tino Weiss, head of purchasing plus product development. If possible, the developer would rather opt intended for string inverters. “Because we are one of the drivers of string technologies. So, whatever we built, if we have the chance to change from central to string, we will go to get string, ” adds Weiss.

The company sees a big advantage for thread inverters within terms associated with operations and maintenance (O& M), as they always go along with 10-year warranties. “We have a longer period of time without the risk of having additional costs on inverter exchange or even replacement expenses. ” For the US, it is a whole various story because central inverters are preferred due to utilities and financing banks not accepting line inverters. “There we still go with central inverters, ” says Weiss. BayWa r. e. did use modular inverters pertaining to one project due in order to issues related to energy differences, to rectify mismatch losses, but its price is still not attractive enough meant for widespread adoption, according in order to Weiss.

Although the nascent floating PHOTOVOLTAIC market includes various new technologies plus project configurations, inverters are still of course a key component. Located on water, there has thus already been a need to adapt to the different new environment the inverters are being installed in. Chinese inverter maker Sungrow is one associated with the marketplace leaders within the floating PV market, supplying to more than 1. 7GW of suspended systems around the world, according to the company.

Jia Zhang, product marketing director designed for utility-scale PHOTOVOLTAIC plants in Sungrow, says that planned location of projects in complex conditions “has put forward higher requirements on each hardware and software style of the particular inverter. ” With their lifespans being possibly shortened amid increased humidity levels, this requires an ingress protection degree of IP65 and a safe high-level anti-corrosion design.

And given that level of the water where the floating PV, or ‘floatovoltaic’ system is located will differ during the day, Sungrow has designed inverters that will “adopt a lightweight plus modular design for easy lifting, ” adds Zhang. Its newer products, the SG350HX and the 1+X model inverter, have been favoured just for floating projects.

Soli’s Lucy Lu adds that for the purpose of floating PHOTOVOLTAIC, inverters require more stable and reliable leakage current protection plus potential induced degradation (PID) repair functionality.

Another trend in the inverter market will be connected to the growing energy tariffs across Europe and other regions which ask for higher power era efficiency associated with PV systems. “Inverters that have a higher wattage and higher strength density have become a good irresistible pattern, ” says Zhang.

From a developer point of view, BayWa l. e. is not in favour of string inverters getting bigger plus bigger, power wise, with some inverters reaching 350kW. “From our standardisation approach, the bigger the inverter, the a lot more complicated is usually our standard approach block design due to the fact the blocks get too big, ” states Tino Weiss. Inverters of 500kW are not something Weiss envisages procuring. Instead, improvements need in order to be delivered from other angles instead.

Some of the issues that BayWa r. electronic. is currently facing are usually related to pack controlling, given that if two or more PV plants are connected to the same grid connection, you would need to know which one in order to shut down first and thus would need a complicated regulation, says Weiss. “If inverters could do this rather of the power controller, this would be I think among the next step developments for inverter suppliers. ”

Lowering failure rates and yield reliability associated with just 0. 2% might have a bigger impact than price difference on inverters, adds Weiss. “Yield reliability and failure rate will be the decision factors in the particular future. ”

As with regard to the future of inverters, Zheng states that in three or even five years, the use of AI technology inside inverters could help developers increase their plants’ power production more efficiently.

But probably the most important technology trend regarding inverters nowadays is the growth of co-located tasks. Across the industry, optimising intended for co-located energy storage seems to be an even more essential aspect to figure out than the particular impact the introduction associated with modular inverters might have.

Adapting to new environments, technologies and PHOTOVOLTAIC plant configurations is essential to get inverters to keep pace with the particular industry. Floating solar is definitely a perfect example. Picture: Sungrow Floating.

Different ways in order to adjust to the chip shortage

As more and more systems rely on the particular use of semiconductors, or chips, within diverse industries from automotives to video game entertainment and associated with course photovoltaic, demand offers outpaced supplies. This provides been severely affected by the pandemic in 2020 plus even inside 2021. Inverter manufacturers have got not already been spared simply by this ongoing challenge and have replied differently to this. Power Electronics has pertaining to example modified to the particular changing conditions. “The inverters’ design has had to adapt at the same time as the availability of materials, ” states Maribel Trenzano. While Solis has managed the issue by actively exploring new chip suppliers, “we sincerely hope that outstanding chip enterprises can increase the nick capacity of PV inverters to meet the rapid development of the particular PV industry”, says worldwide marketing movie director Lucy Lu. And with no end nevertheless in sight, inverter manufacturers may still have in order to cope with the present constraints of the chip shortage affecting many sectors.


Inverter suppliers adapting to power storage

As more and more tasks are built with battery energy storage space system (BESS) technology, possibly at the time of first commissioning or even using the option to add it as a retrofit at a later time, inverter providers have followed the tendency. “Energy storage is the biggest trend, ” says Lucy Lu, global marketing director at Solis. The company is working on coupling its inverters along with energy storage, not just in utility-scale projects, but also in commercial plus industrial (C& I) and residential, which usually takes another dimension if we add chargers for electric vehicles.

Solar PV inverters need to be designed to allow for DC-coupling with batteries to be since easy as it can be, says Power Electronics’ Maribel Trenzano. Power Electronics’ Bus Plus option enables the connection associated with various DC/DC converters inside parallel with all the connection of batteries meant for solar PV and with a direct channel between the inverter plus the converter that allows for simultaneous control of the particular system. The demand designed for inverters with batteries in utility-scale projects has increased a lot in 2021, states Trenzano. With some associated with Power Electronics’ Freemaq brand models, the ability to connect up to four independent BESS can be working particularly well this year in the US, the UK and Australia. “The long term of renewable plants goes through the co-location of energy storage, the particular demand of hybrid systems is growing, and the regulation is already adapted in order to it or in the process to [do so] in many countries, ” Trenzano says.

The make use of power storage co-located with utility-scale solar PHOTOVOLTAIC or because a standalone will keep increasing within the many years ahead in order to integrate variable renewable generation, and thus it really is simply no surprise that for many suppliers it is one of the most important subject nowadays. Sungrow is no exception. “Energy storage is usually a very popular topic in the last few years, ” says Zhang. Sungrow’s R& D department has invested a lot of resources and time into optimising the link between inverters and energy storage. This is the particular case along with their latest modular inverter that has a built-in energy storage space interface.

“For inverter businesses, the deployment of integrated optical storage and charging products plus solutions will be a new business growth stage. Solis is also actively laying out this area and expects to launch related products and solutions in 2023, ” adds Lu. Some Solis inverters already possess in mind the use associated with energy storage space at a later stage, without the need to change existing plant designs, with an “expandable storage interface to accommodate peak saving and provide electricity to support loads and in order to reduce the overall power supply cost, ” claims Lu.

BayWa r. e. ’s strategy for solar PV plants co-located with electric battery storage so far has not really changed the choice of inverter, although “if you have a DC-coupled system, the central inverter could be a good solution, ” says Weiss. The developer is still looking into aspects of co-located tasks but is certainly not sure if it wants to “accept the disadvantages we get through the particular central inverter compared to the chain inverter advantages we have right now, ” adds Weiss. From a development perspective, what they are usually already doing is reserving space just for battery storage space in every task.

Even inverters with small batteries currently integrated into them do not seem of interest for the purpose of BayWa ur. e. inside terms of utility-scale projects, but they may be ideal for the commercial and industrial (C& I) segment. “If you have got rooftops with one or two megawatts, adding hybrid inverters can be doable, ” states Weiss.

Increased module power output

As modules are increasing their own power output to 600/700W or more, and since inverters are usually the bridge between the modules and the load, manufacturers have had to boost the power associated with the conversion components. Manufacturers are actively looking from the enhance in energy output plus optimising their particular inverters accordingly. In reaction to that modify, Solis offers optimised the system voltage level of resistance, component compatibility and system safety, among other features. Solis worldwide marketing movie director Lucy Lu adds: “At present, impacted by the progress of 600W/700W+ modules, inverters with a string present of 15A-20A has become the mainstream. ”

In the case of Power Electronics, the ability of its third era of 1500V inverters provides increased 15. 5% in comparison with the previous generation. “This allows in order to get the particular highest performance and reduce LCOE from the solar energy PV plant, ” says solar & storage product & applications manager with Power Electronics, Maribel Trenzano.

Meanwhile Sungrow has improved the MPPT current of its thread inverters through 30 to 40 amperes in response to the module strength output raise. “Our do it yourself product performance is not affected by the particular PV module current alter, ” states Jia Zhang.

Importance of communication between suppliers and developers

One of the “key strengths” associated with BayWa 3rd there’s r. e. is its relationship with inverter manufacturers this works along with, to optimise the inverters to best suit every project’s needs. Before settling with Huawei and Sungrow, BayWa r. e. had a strong partnership with Italian inverter provider Power One.

“We were deeply involved in the product roadmap and designing their brand new inverters and of course, we had been driving all of them to style the line inverters to our system design needs, and they followed us quite intensively until a certain period of time when pricing dropped because a lot of new players, Chinese gamers, came into the market and developed very big chain inverters. So, they were not really competitive anymore plus they adopted that route. ”

When Power 1 and BayWa r. electronic. went their separate ways in close to 2013-2014, BayWa r. e. decided to work with Huawei, despite the company being a newcomer in the particular inverter business; with the caveat that instead of keeping a single source for their inverters, the developer also added a second supplier in Sungrow. “A single source in our market dimension will be a really big risk, ” provides Weiss. Such was the situation when Huawei was upon the US sanction list during the presidency associated with Donald Trump, which blocked the supply of the inverters for US solar PV projects.

“We have really strong relationships and with very few providers. It’s similar on everything all of us do. On modules you have five or six because a person need them. For transformer or with regard to switchgear supply, we usually have only one or two suppliers we all mainly work with. That’s one of our strategies, having the close connection. Being involved in the particular development plus of program, being a big customer in order to influence development. ”