We explain the benefits of smart grid-ready UPS at the first ever Powered On Live digital event.
Last month saw influential industry magazine Electrical Review stage its inaugural virtual event Powered On Live. The online conference built on the popular ‘Powered On’ podcast and brought the electrical sector together for two days of debate and discussion.
The event featured keynote presentations and expert panels tackling some of the hot topics facing the industry, including net zero, energy storage, cybersecurity, and power distribution.
Our Technical Services Manager Jason Yates appeared on day 2 of Powered On Live, leading a session on smart grid-ready UPS and the role they can play in the ongoing energy transition.
Jason’s informative talk explained how a smart grid UPS actually works, before going on to outline several practical examples of its application.
These include an overview of our grid frequency response project in partnership with RWE. This initiative enables data centres to participate in the energy market without taking on any of the risk.
Jason’s Powered On Live presentation also looked at some of the other functions of a smart grid UPS, including peak shaving, voltage stabilisation, and waveform correction.
He then goes on to outline alternatives to the typical lead-acid battery, such as lithium-ion batteries and supercapacitors, before concluding with a look to the future and the potential of silicon carbide components.
Watch the full Powered On Live video below, which is followed by the transcript.
Powered On Live Video Transcript
Good morning everyone. As introduced, I am Jason Yates and I am the Technical Services Manager for Riello UPS Ltd.
Today we’re going to be looking at smart grid-ready uninterruptible power supplies basically becoming partners of the energy transition.
Now, just to give you a little bit of background about Riello UPS Ltd, we are the UK subsidiary of the Italy-based Riello Elettronica Group. Riello Elettronica is a leading manufacturer in the uninterruptible power supply market with the well-known brand Riello UPS.
Energy represents the group’s core business, in particular with the manufacture of UPS that are able to guarantee the quality of the electrical supply to critical loads and maintain power continuity in case of blackouts or any other anomalies within the electrical system.
Riello UPS designs and produces UPS solutions for every kind of requirement: from banks to hospitals, transport to infrastructure, from small domestic applications up to large-scale data centres.
We have two R&D facilities, one in Legnago near Verona and one in Cormano in Milan, these are both dedicated to the development and testing of UPS. Now, Riello UPS is always looking to improve performance by continuously innovating, so much so that today, we have more than 32 lines of UPS products specifically for energy management based across a broad range of technological architectures.
So what are we going to talk about today? Well first of all, I’m going to explain just what smart grid-ready uninterruptible power supplies are.
We’ll also take a look at some of the applications, firstly with the UPS operating as a grid frequency stabiliser. We’ll also look at using a UPS for peak shaving, voltage stabilisation, or waveform correction.
In conjunction with those, we’ll also take a look at UPS with lithium batteries, supercapacitors, and for power storage.
And finally we’ll finish off by briefly looking at the future of UPS and how things are changing in terms of UPS efficiency and silicon carbide.
What Is A Smart Grid-Ready UPS?
So first of all, what is a smart grid-ready UPS system? Basically it is a UPS that firstly and most importantly has the potential to communicate with local power systems.
This helps them to potentially stabilise the grid, store energy using either lead or lithium batteries, they can peak shave or force the load to go off-grid, they can be used to voltage stabilise or optimise, and they can be used to waveform correct or power factor correct.
In addition they can integrate with solar systems and they obviously need to operate at high efficiencies.
Basically, UPS have the potential to play a big part in the ever-evolving energy network and thanks to advanced interconnectivity and communication, this effectively turns the UPS into a ‘virtual power plant’.
Just to show you one of the projects that we did, this is a project for a grid frequency stabiliser. This project was done in conjunction with RWE. The brief was to enable data centres and large power users to become partners in the energy transition.
Now the ongoing transition to a decentralised, zero-carbon electricity system requires increased flexibility from demand and generation, along with frequency regulation to compensate for lower synchronous generation.
Now, data centres and large installations can obviously contribute to the energy transition as prosumers.
The Master+ system we developed was specifically designed to profit from the energy market without taking on any of the energy market risks, and to provide increased reliability through an advanced UPS, 24/7 monitoring and extended battery backup time.
The system comprised of four key parts: firstly a highly efficient UPS system; secondly cycle-proof premium batteries; then we needed an integrated control system; and finally a route-to-market contract.
Now the key part was the UPS system, as you can see from the photo on the right, these are the two 200 kW test machines that we put into the pilot project over in Germany.
These two machines are obviously smart grid-ready. They offer smart grid communication protocols and are true online UPS systems. They are highly efficient and offer unity power, so the kW and the kVA are the same. They are full IGBT and DSP-based technology with high fault and short-circuit capacity.
They also offer multiple power options for flexibility, offer parallel mode for resilience and capacity, are built using existing resilient and proven technology, and offer full galvanic isolation.
Now a UPS system is obviously nothing without its batteries. This particular installation used cycle-proof premium lead-acid batteries from an established producer, although for this type of application we could also use lithium as that would be a viable option.
The main benefit of this system was that it offered significant space saving because it was a very compact battery arrangement. That meant there was sufficient battery capacity for both the critical equipment support and the commercialisation purposes.
The system had real-time battery monitoring to aid with predictive maintenance, along with intelligent battery charge/discharge control.
Making The Most Of The Batteries
Now the battery system itself was split virtually into two separate parts, the first part the backup segment, the second part the commercial segment.
The backup segment of the battery represented about 30% of the total useable capacity. Now this part of the battery is configured and controlled by the UPS system and cannot be accessed by RWE. Basically it is preserved for the critical load only.
The commercial segment represents the remaining 70% of the total capacity. While this capacity is again configured and controlled by the UPS, RWE was able to access it for grid stabilisation and, if required, the critical load.
Typically, when the system is operating the state of charge oscillates between 60-70%. If there was a mains supply failure on the site where this system is installed, the site would have access to an extended backup autonomy because they have use of the guaranteed backup segment, plus any remaining in the commercial segment.
Now you require a fully-integrated control system for the UPS and the batteries. Here, the integrated control system’s priority was to monetise the solution within the energy markets. It obviously had to have a high IT security design.
The priority of the UPS is always to protect the critical infrastructure onsite. So during a supply disruption, the system only supports the critical load and you cannot apply any commands to the system.
Basically, the Master+ is a standard UPS and therefore can be integrated into an existing infrastructure.
The Route To Market
The final part of the project was the route to market. Now, the way the system works is that RWE and Riello UPS provided a system to participate in the energy markets, with all the energy market risks taken by RWE in respect to frequency response and grid cost avoidance.
Now the benefit to the site owner was that they received a significantly discounted battery system, along with extended warranty on all main components, remote control and 24/7 monitoring, preventive maintenance, extended backup time, and potential to reduce grid charges.
In return, RWE gets the usage rights for the commercial segment of the battery.
So how does it work? Well this is the data, which is taken from one of the live systems.
As you can see, the blue line represents the grid frequency. The red line represents the power demanded from the system. And the yellow line represents the power that’s being provided by the system.
As the frequency increases above 50 Hz, what we effectively do is take power from the grid and push it into the battery system. Then when the grid frequency falls down below 50 Hz, we take the power from the batteries and push it back into the grid again.
Therefore we are trying to stabilise the grid by either taking power out when the frequency is too high or pushing power back into the grid if the frequency is too low.
Other Smart Grid Uses
That was just one of the projects we did with a smart grid-ready UPS. Another project involved using a UPS for peak shaving, voltage stabilisation, and waveform correction.
For those of you who are not familiar, peak shaving is where we utilise the UPS to effectively limit the amount of power that’s being taken from the mains supply.
The way we do that is, if the load on the output of the UPS system increases beyond the set or predefined level, then what the UPS does is take a proportion of the load from the mains supply and the remainder from the batteries. Therefore the UPS can effectively peak shave the load that’s coming onto the incomer versus the load that’s being put onto the actual output of the UPS.
There are typically four peak shaving modes of operation: the first is static, where the UPS has a fixed or defined level and the system just sits there and peak shaves to that point. You can take that one step further by letting the user actually decide when to limit the power, this command can be pushed through to the UPS by volt-free contacts, Modbus/TCP etc.
You also have impact load buffering, which is similar to peak shaving, but if you’ve got a system with a weak power source or weak generator or anything like this. If you have a site where you have a large impact of load, then the UPS can in affect buffer or slow down the incoming mains supply.
Finally, and probably the most commonly used, is dynamic peak shaving, whereby the system works automatically in line with onsite conditions.
Just to explain and expand on this a little further, this would be a typical dynamic peak shaving application whereby you have the incoming grid coming onto a site with power metering. This power metering is interconnected through the communications cards on the UPS system. You’ve got your critical load connected to the output of the UPS system and its backup batteries, and then you’ve got the general site load.
So what happens is as the load increases, then the UPS can put a share of that load onto its batteries instead of overloading the main incomer.
Now this such system was used on a site recently where the contractual limit for the site was limited to 1 MW. Their typical load moved around between 500-900 kW and they had a critical load of around 300 kW.
In real-terms, that’s a maximum load of 1.2 MW, which would go beyond their contract. Therefore during these short durations, the UPS was there to push that power onto the batteries and when the power coming onto the site was low, we could use that power to recharge the batteries, that’s a good example of where we’ve used dynamic peak shaving.
UPS As A Voltage Stabiliser
Another function is using the UPS as a voltage stabiliser, something people sometimes refer to as voltage optimisation.
If you’re not familiar with an online UPS system, this diagram is a typical dual conversion online UPS. We call it dual conversion because the mains supply comes in, we convert the AC to DC – that’s conversion one – then we reinvert the DC back to AC again – and that’s our second conversion. The term online basically means the load is always being powered by the inverter.
One of the benefits of an online UPS is that it has a very high input tolerance in terms of voltage and frequency. As you can see there, a typical UPS will have an input tolerance from +20% down to -10%, and at lower loads or if the UPS is oversized, that tolerance can increase from +20% to -40%.
One of the key benefits of that is that no matter the incoming supply, the UPS will always deliver a stable voltage, in this case 400Vac + or – 1%. An online UPS provides this voltage stabilisation with or without a battery backup, it doesn’t need to have batteries connected to do this.
The load is always powered from the inverter – VFI, which stands for voltage and frequency independent – which means whatever comes into the UPS isn’t passed onto the connected load, and this operates with a very precise tolerance.
A UPS is perfect for power conditioning and/or voltage stabilisation applications.
Waveform Correction
Another smart grid-ready UPS function is waveform correction. Again, this is the typical diagram of an online dual conversion UPS. In this case, however, we have two power flows. We have the power flowing into the UPS from the rectifier, and we also have the mains power currently passing through the bypass line.
Now in this mode of operation, the UPS operates on bypass but the inverter is still running, so what’s happening is that the inverter operates in parallel with the bypass in order to correct the waveform that is being applied to the incomer.
For example, and these are only representative figures, if we applied a load to the output of the system, in this case a high total harmonic distortion (THDi) of the current greater than 30% with a low power factor, because of the way the waveform corrector is working, what happens is the system corrects that waveform, reducing the THDi to 6% and improve the overall power factor.
In reality, the performance of the system will rely on what we’re supplying in and exactly what tolerance it needs to be.
One of the key benefits is that it’s still a UPS, so it still provides battery backup, so if there’s an interruption to supplies it switches to batteries, and then returns to waveform correction.
The mode significantly reduces the harmonic content applied to the mains supply. It provides active input power factor correction, so you don’t need any power factor correction systems. And in this mode, because it’s operating in bypass, it can run at a highly efficient 98.5%.
So they are just a few of the smart grid-ready applications we can use a UPS for.
Lithium Batteries, Supercaps And Other Alternatives
Now typically UPS systems are commonly supplied by lead-acid battery systems. But we are now seeing a move to alternative technologies such as lithium batteries, supercapacitors, and being utilised for power storage.
This is a typical lithium battery system we supply. Obviously, lithium batteries are improving all the time, but there are still pros and cons.
They’re lighter and more compact. They have a high power density and greater flexibility. They can have high discharge/recharge rates and a higher temperature tolerance. They have a longer life span and also an increased number of cycles.
On the other hand, management of lithium batteries is critical. There are vendor specific battery management systems, which I’ll touch on in more detail in a moment. They are still more expensive, although the prices are coming down. And obviously the inherent safety concerns.
Now a lot of people are saying are they the real substitute for lead? Well I’ll leave you guys to decide that, especially when you’ve got pure lead batteries, which may also be an alternative, but we’ll see how the markets pan out.
Touching on the communication between a UPS and a lithium battery system, as I was saying, there are BMS specific communications protocols for each manufacturer.
You can buy a lithium battery system that you can connect directly onto a UPS, but the problem with that is that it isn’t a fully integrated package.
Therefore, we developed a solution where the UPS system can communicate correctly with the lithium system, as there are certain circumstances where you want the UPS to stop charging or charge or do certain things.
It’s imperative that the lithium system is fully integrated with the UPS system, not only for the control but for the monitoring and the information the UPS is putting out to the outside world in terms of autonomy times, recharge times and so on.
Supercapacitors are another form of power storage. Supercapacitors offer an eco-friendly alternative to traditional battery-based UPS. They are high power density energy storage devices that deliver autonomy in the range of seconds, anywhere from five seconds up to a couple of minutes, which makes them ideal for sites prone to very short power interruptions or where they have rapid online generation.
They offer a high number of cycles, a supercapacitor can have a million or more cycles compared to around 300 for a typical lead-acid battery set. This means they can offer long-term TCO savings on battery monitoring, replacement, recycling and disposal.
They also have a wide operating temperature range from -30oC to +45oC without any need for energy-intensive air conditioning or heating.
Again, supercapacitors are improving all the time and becoming a viable option for energy storage.
Now in terms of energy storage systems, again this is becoming more and more a hot topic. This is a typical energy storage UPS system that’s being used in conjunction with PV arrays on the input and the output. It’s still a UPS, so will offer protection against blackouts on the electrical system, overvoltages, power surges, frequency imbalances etc. so it can be used to backup critical infrastructure.
The way UPS are going these days is that the UPS is playing a bigger role in the energy storage market, and as more and more demand comes along for this, more and more developments are being made in the UPS sector.
Looking To The Future
So, where are we going with UPS systems?
Well the main thing about UPS is efficiency, we want to have UPS systems that are as efficient as possible. Efficiency plays a key role in UPS and the biggest change the market is seeing at the moment is silicon carbide components.
These make it possible for a UPS to achieve more than 98% efficiency whilst operating in online mode. As silicon carbide components become more readily available, their use throughout many industries is becoming more common.
The high efficiency of these components significantly reduces the energy and cost used in running the UPS and increases the overall performance of the UPS.
These reduced losses mean that the UPS produces less heat, which in turn means less cooling on site.
In effect, the UPSs of the future, you will see more and more coming through with silicon carbide options, and eventually it will all be silicon carbide as the price comes down and the availability increases.
So that’s an overview of smart grid-ready UPS systems and battery storage systems and where we might be going in the future, so I will open the floor up to any questions…
Q&A Session
A short question and answer session followed Jason’s presentation, with Electrical Review editor Jordan O’Brien posing the questions.
Jordan: Perfect, thanks Jason. There are currently no questions from the audience, but the one question that I do have, and it’s based on the fact that we have a panel straight after this on microgrids, is where do UPS potentially sit in a microgrid situation?
Jason: There are a few areas where they could be used, they are actually real at the moment, they exist, I suppose it depends on the application to be honest with you, there are so many things there could actually be and if somebody does have a specific application it’s something we can certainly look at it because we obviously have full design and control of the UPS system.
The UPS can do a lot of things that people don’t actually realise they can do, there’s lots of parts it could play in terms of microgrids.
Jordan: Also, how much revenue could you potentially earn from a virtual power station?
Jason: Oh I knew you were going to ask me this! This is an RWE question… I can find out and if you want I can present some kind of information and data. I knew somebody would ask this, I should have got an answer to the question, but I’m not entirely sure to be honest with you I’d have to ask RWE on that front because we don’t actually deal with that side of it.
Jordan: Fair enough, we do have a question from the audience. Mark Perez says what are the features of silicon carbide that help with efficiency and why are these just emerging now? Is it advanced manufacturing or 3D printing?
Jason: Yes, I think it’s a bit of everything. Obviously, silicon carbide back in the day was extremely expensive, the technology didn’t exist. It’s like going back to the way UPS systems changed over to RGBT technology as component manufacturer and the demand becomes greater, the components become available.
And obviously, it’s in terms of development cost. Before it was too expensive to build a UPS from silicon carbide, whereas now we can. Obviously, silicon carbide UPS will carry an increase in cost, but primarily the driving factor as far as now it is possible to build UPS, as technology changes, things get cheaper or more cost-effective, you start to get pre-build packages for bi-level and tri-level inversion and rectification, and so as the manufacturers produce these components it becomes more readily available to all. It’s just the natural migration of components.
Jordan: Perfect! Is there anything else you would like to add?
Jason: I would say with UPS systems, it’s changing all the time, storage systems, lithium systems and so on. It’s continually being developed, the UPS systems are getting smaller and more efficient. The main thing for us, we can only take a UPS system down as small as possible with connection sizes, things like that, but that’s our main driving factor.
The market is ever-expanding. UPSs are being used in so many different sectors these days. You know a UPS system in terms of a smart grid can be utilised for so many different things now and what we try to do is encourage people to actually say if they have an application, we’ll always look at these in terms of whether it’s impossible.
You know, everybody’s next idea could be the next greatest idea and that’s the way it goes! Because a UPS can do so many different things, providing single-phase from three-phase supplies, providing three-phase supplies from single-phase, from balancing single-phase power or three-phase supplies. There are so many different things the UPS can do, it’s just an every-changing world.
Jordan: They’re pretty versatile technology and it’s getting even more versatile?
Jason: Yes, it is absolutely, because the requirement from more vendors is that we need to offer more communication protocols, more control, and develop new systems utilising power. You know we’ve done many projects I haven’t covered here, things like car chargers whereby we store energy in containerisation to enable dealers to provide high power car charging in the daytime, so we charge overnight or use PV in the day and therefore we can utilise the UPS in terms of energy storage for high power car chargers.
There are lots of things that we do. Again, more and more people are demanding more and more because the infrastructure isn’t quite there yet in places so therefore there are options available to people and it’s not just a case of a closed book.
Jordan: I guess most people just assume UPSs are there for emergency power but they do so much more…
Jason: Precisely! I think two of the biggest things are yes, people don’t understand the potential for UPS, and in terms of the UPS systems themselves, especially with the likes of the RWE project, the technology is very far more advanced and I think it’s people’s reluctance at the moment to trust the technology. But I think over time that will come, especially with the ever-increasing cost of energy at the moment.
Jordan: Perfect, thank you so much Jason for your time.
