Goodbye to the transformer

Transcription

1 Goodbye to the transformer An even more diverse range of inverters was presented at Intersolar than last year. There were no sensational novelties, but a few trends may be recognised which constitute logical answers as to how PV technology will continue to delevop. In the words of the boss: Managing board member Günther Cramer presents the Sunny Boy 5000TL from SMA, Germany. Photos (6): Wilhelm Breuer 162 Sun & Wind Energy 3/2007

2 The first point was easy to recognise in Freiburg: the trend is still towards overall higher capacities and higher currents on the input side a consequence of more powerful modules with larger cells. For DC circuit breakers the integrated variant is taking hold, which was to be expected, once older devices without a circuit breaker, which therefore had components fitted to the outside, had been sold off. In the race to reach higher efficiency, more and more manufacturers are saying goodbye to an important component: the output transformer. This is also because several countries are giving up their rigid stance on transformerless devices. Industry leader SMA sees a movement on the Spanish market towards transformerless designs, and the same tendency in other European countries and even Korea. Only the USA is standing tough. Inverters without output transformers still have no chance over there, recording to SMA.»It is understandable when you know about the qualifications of the local installers,«says SMA managing board member Günther Cramer. By the way: US inverter supplier Power One confirms:»our transformerless devices with 5 and 6 kw are approved in California.«Whilst market leader SMA has set itself an export target of 50 %, Asian companies continue to force their way onto the German market. They have been doing some homework, making the sometimes weak performance features of their products conform to German expectations. Long-established manufacturers are trying to counter with increased convenience and comprehensive after-sales service and with good performance too, of course. Wandering through the exhibition halls The German company Delta Energy Systems GmbH presented itself with its own inverters for the first time in Freiburg. The company, which belongs to the Taiwanese group Delta, has been producing inverters since 2001, but only as OEM products up to now. Delta lines up with two series of inverters: The Top Line models are to deliver optimum performance in every respect, whilst the new Value Line offers devices for»less demanding environments«, as the company puts it. Several models are transformerless devices, and with its Top Line, Delta shows that respectable levels of efficiency are also reachable with this component. The new SI 5000 with an output power of 5 kw extends the range upwards from the SI 3300, bringing it up to 96 % peak efficiency. The European standard efficiency stands just 1 % under this. Like the other Delta inverters, the Happy families: Riello from Italy is putting a whole sextet of new inverters on the market, four of which can be seen here. Sun & Wind Energy 3/

3 Nice casing: Sunways, Germany, exhibited a design of the PT 30k. The inner workings are still taking shape. SI 5000 also works with IP 65, without a fan, and promises full output between -25 and +57 C that is remarkable. The two MPP trackers move between 150 and 450 V, the device should reach its maximum output between 175 and 450 V. Both models of the new Value Line, the VL 2000 and the VL 3600, make slight compromises on certain features: The optimal MPP range only extends from 210 to 400 V, the derating begins at 45 C, and the efficiency is down 0.6 % from those of the SI Fronius International GmbH from Austria took its time with its new generation of inverters. By the end of last year the devices were already being mentioned under the family name IG Plus, at the Intersolar they made their first appearance. The idea behind the new concept is to combine different power elements with each connection area. They are attached via a simple power plug, and then determine the output power of the IG Plus 50, 100 and 150 at values of 4, 8 and 12 kw. If a fault occurs in the power element, only this is disconnected, the connection element, together with its settings and cabling, can remain in place. Stand-out features of the IG Plus are its high permissible input current of 18.3 A per four kilowatts of output, its high MPP adaptation efficiency of %, and its own consumption at night: This is held to stand at 0 W. With a maximum efficiency of 96.1 %, the devices do not belong to the leading group, but they do have a typical Fronius trick up their sleeve: The inverter adapts, via connecting to the boost chopper, to different subranges of the input voltage between 230 and 500 V, bringing about three peak efficiencies rather than just one. Fronius argues that this should also facilitate system planning for the installer. He just has to make sure he knows exactly where these peaks lie. There is no room for confusion here. Fronius gives the installer free rein for choosing the earthing, which can be connected variously according to the module type in the inverter. Kaco Gerätetechnik GmbH, Germany, is launching the Powador 8000xi, whose 8 kw AC output makes it a device in the medium performance class for solar power systems of up to 9 kw p. In fact, with the 8000xi, the company from Neckarsulm wants to mount an offensive on the central inverter sector. When three of the new Kaco devices are connected together, they advance into this sector s sovereign territory, yet they should undercut it in price terms. However, the»band of three«then also competes with the company s own 25000xi central inverter, as the outputs of the devices are almost matched. Like other manufacturers have done with their concepts for split inverters, Kaco uses the selling point of damage limitation in case of a crisis: If any one of the inverters operating as a triumvirate should stop working, the integrated imbalance recognition turns down the two other devices until the point is reached where they keep to the maximum permissible output difference of 4.6 kw between two phases at least their yield is then saved for the time it takes for the service engineer to arrive. Kaco reports to have increased the efficiency rating of its circuit thanks to new IGBT (insulated-gate bipolar transistor) with»extremely low conduction losses«. The new inverter reaches a maximum of 96.2 % and a European standard efficiency of 95.4 %. Its own consumption during operation stands at 11 W. In its product information, Kaco approaches the subject of the»mpp window«with some aggression: Whilst with many devices one is confronted with input voltage ranges whose lower limit is nowhere near the voltage at which the rated output is reached, and what is more serious whose upper limit is unrealistically near to the destruction voltage, Kaco specifies a sensibly usable range of 350 to 600 V. It also keeps a safe distance from the maximum voltage of 800 V. A triad of 8000xi devices comes around 5 to 6 % cheaper than the 33000xi central inverter including generator connection box. Kaco has carried out further development on the already familiar central inverters 25000xi, 30000xi and 33000xi for use in solar parks Spain sends its regards. The new version fittingly receives an added»park«on the end of its model description, and distinguishes itself 164 Sun & Wind Energy 3/2007

4 Not everything has to be as efficient as a SolarMax! C-Series, the new PV inverter generation by SolarMax Sputnik Engineering AG Höheweg Biel Switzerland Phone + 41 (0) Fax + 41 (0) sputnik@solarmax.com SolarMax innovative, reliable and above all efficient! With a maximum degree of efficiency of 96%.Therefore SolarMax is among the top three on the European market for grid-connected PV inverters. The youngest, innovative generation of SolarMax PV inverters offers you unique advantages with installation, functions and efficiency with its newly thought out design. Thanks to carefully selected materials, SolarMax guarantees optimal longevity and a great deal of operational reliability. We ve been on the market since 1992 and over 3000 of our inverters are in operation - so we can guarantee you a product that s on the technical cutting-edge. Our service contract will, furthermore, guarantee that your SolarMax central inverter will operate trouble-free for 20 years. SolarMax inverters offer you unique advantages in efficiency as well as in savings. Central Inverter SolarMax 100C Highlights of the new SolarMax C-Series: Compact PWM grid tied PV Inverter Maximum degree of efficiency MPP efficiency of over 99% Digital signal process control (DSP) Attractive price/performance ratio Guarantee extension up to 20 years possible Integrated interface for MaxCommBasic Always a sunbeam ahead

5 Provider Series/product Number of devices System of protection Inverter type Transformer type Feed-in system max. AC power [kw] European efficiency [%] DC voltage range [V] Delta SI IP 65 string high frequency single-phase to 450 VL 3600 / VL IP 54 string high frequency single-phase 3.6 / to 400 Fronius Fronius IG Plus 4 IP 43 string high frequency single-phase (4 / 8 kw), two-phase (8 kw), three-phase (12 kw) 4 / 8 / to 600 Kaco Powador 8000xi 1 IP 54 string without single-phase to 600 Motech Instruments Powador 33000xi Park / Powador 30000xi Park / Powador 25000xi Park 3 IP 54 central without three-phase 33.3 / 29.9 / to MS 1 IP 65 string without single-phase to 450 Power One PVI-4200S-OUTD 1 IP 65 string without single-phase to 580 PVI-Central IP 20 central without (LV transformer optional) three-phase (95.7) 460 to 850 Riello UPS Helios Power IP 65 string without three-phase to 800 Sanyo SSI-TL27AE1 1 IP 65 string without single-phase to 600 SMA Sunny Boy 5000TL 1 IP 65 (electronic) Sputnik Solarmax 2000 S / 3000 S / 4200 S / 6000 S Solarmax 20 S / Solarmax 35 S string without single-phase to IP 54 string without single-phase 1.8 / 2.5 / 3.8 / / 95.5 / 95.8 / to IP 54 central without three-phase 20 / to 800 New off-grid inverters at the Intersolar fair Source: manufacturers information from the basic model on three points: Firstly, the new IGBT were also employed here. Secondly, in order to increase the efficiency, Kaco has also lowered the transistor clock frequency to 9 khz. This reduces switching losses, but also pushes the operating noise of these components into the human hearing range. The noise apparently resembles the chirping of crickets, and does not exceed 35 db. Finally, with an eye to the heat at their installation location, the central inverters were given new fans in order to improve the cooling of the sensitive components. It is somewhat contested that the operators have the option of supplying the fans with electricity from the grid, so that they can feed more solar energy back in and they are by no means the only manufacturer to integrate this option into their central inverters. With these three tricks, Kaco has been able to increase the peak efficiency from 95.5 % to 97.1 %, and the European standard efficiency to a remarkable 96.5 %. The Park devices are now available, and cost 3 to 5 % less than their predecessor. The Taiwanese manufacturer Motech Industries Inc. did not present any new models, but there have been changes to the inner workings of the familiar devices PV Mate 3300MS, 3800MS and 4600MS. Last year the efficiency still fluctuated within a range which put a question mark over the product for the interested parties. Motech has done away with this and labelled the predecessors»prototypes«. This year, the PV Mates are presented with peak efficiencies of 96.3 % and European standard efficiencies of between 95.2 and 95.4 %. The input voltage range, at 150 to 450 V, does not turn out to be particularly extravagant, but this does not rule out the devices having a good design. The inverters incorporate two or three (4600 MS) strings, each of which is controlled via its own MPP tracker. Motech also claims that the PV Mate 4600 MS reaches respectable efficiency levels at partial loads, giving values of over 96 % from 1.7 kw output power. According to Motech, the devices show no derating (output limitation with rising temperatures) up to 55 C. This is above average, and makes them an interesting option for hot installation locations, particularly as the surrounding humidity can be as high as 95 %. As a target for 2007, Motech aims to introduce transformerless devices for the US market. It also wants to have more performance classes. With these, one feels well-equipped»to move into the ODM business,«says Marketing Manager YM Yen. An ODM (Original Design Manufacturer) designates a manufacturer who develops devices from scratch according to customer needs, rather than one which modifies standard products (OEM). The manufacturer name Magnetek is a thing of the past. Since the takeover of the company by the US group Power One, the inverters are also sold under this company name. The family name for the devices Aurora has, however, remained. In Freiburg the new owner also exhibited two new inverters from the Power One Aurora series, one string inverter and one central inverter. The first, the PVI-4200S-OUTD, with its 166 Sun & Wind Energy 3/2007

6 Market launch Manufacture Website Germany: autumn 2007, rest of the world: n/a Germany: autumn 2007, rest of the world: n/a Germany / Austria: middle of 2007, worldwide: 2007 own production in Slovakia own production in Austria France / Germany / Italy / Korea / Spain: September 2007 France / Germany / Italy / Korea / Spain: summer 2007 own production in Germany Germany / Italy / Spain / Taiwan and other Asian countries: summer 2007 France / Germany / Greece / Italy / Spain / USA: end of 2007 France / Germany / Greece / Italy / Spain / USA: end of 2007 own production in Taiwan own production in Italy Germany / Italy / Spain: end of 2007 own production in Italy Japan: available, Germany: early 2008 own production in Japan n/a own production in Germany all European countries: August 2007 all European countries: end of 2007 own production in Switzerland own production in Switzerland 4.2 kw AC output, fills the gap between the more powerful models, which start at 5.0 kw, and the lightweight models of up to 3.6 kw. Beneath the thick cowling there is no fan, cooling is purely passive. The transformerless device can claim a very good separation between the maximum and the European standard efficiency: 97.0 % and 96.4 %. In fact, according to the gradients supplied, at its»optimal«input voltage of 345 V, the inverter already reaches an efficiency of 95 % at a load of under 10 %. It is commendable that the Power One supplies a colour diagram with the data sheet for the new PVI-4200, which plots the efficiency against the input voltage and output. This gives a comprehensive picture of where the efficiency ranges are situated and how far they extend, and thus of the behaviour of the inverter in various working states. This makes system planning significantly easier. The picture shows that the peak efficiency as usual only takes up a very small area, but the range of 96.8 % extends so far that a system may comfortably be fitted to it. The newly presented PVI-Central-100 inverter, in its basic version, is made up of two 50 kw units which may be connected in a master/slave network with an MPP tracker, or as a multi-master combination with two separate MPP trackers. The central inverter can be extended modularly in steps of 50 to 300 kw. One advantage of this kind of architecture is that if one 50 kw module stops working, the others continue to operate unperturbed. Depending on whether or not the system is to be connected to the grid, the PVI-Central-100 can be purchased with a low-voltage transformer, or as the transformerless PVI-Central-100TL for direct connection to the medium-voltage grid. This model gains around two percent on its efficiency: instead of 95.7 % (η max ) and 94.9 % (η euro ), the transformerless version reaches 97.5 % (ηmax) and 96.9 % (η euro ). Power One says that both devices should be available in the last quarter of the year, the prices will be around 0.34 /W for the PVI-4200S-OUTD and 0.29 /W for the PVI-Central-100. So far, Italian Riello Elettronica had introduced six inverters in their Helios Power series. Now the company»ramps up«to a whopping 10 kw with the new Helios Power Basically the same design as its six siblings this new inverter comes equipped with a fan due to its higher output power. Also, it feeds into the grid on all three phases whereas its predecessors had been single

7 INTRODUCING... Two Battery Solar Controller with Remote Meter NEW! Ideal for RV s, caravans, boats and cottages. Independently charges both the house and engine battery. Charging priority is user selectable. Remote meter displays digital and pictorial system information. 25 Amps at 12 volts DC Phone: Fax: phase units. Still it operates without a transformer which enables it to deliver 96.3 % European efficiency, which is even more than the maximum efficiency the earlier Helios Power had to offer. The three MPP-inputs operate between 300 and 800 V which leaves the reader somewhat puzzled since the maximum input voltage is said to be 800 V, as well. This is either an inaccuracy or Riello here defines its own terms: For safety reasons you would expect the upper MPP-limit quite a bit lower than the maximum input voltage. Also remarkable, but in a good way, is the s ability to swallow peak currents up to 27 A per input. Riello s latest product is announced for the end of this year. And there is the company s hint that Riello is out for» big«business in 2008 with a 40 and a 100 kw central inverter. At least the model description of the long-awaited inverter from Sanyo Component Europe GmbH has already been decided: SSI-TL27 AE1. It will not come onto the market, however, before Nevertheless, it is operating in field trials in several German systems. The transformerless device will supply 2.7 kw of output power, and with a peak efficiency of 96 % and a European standard efficiency of 95.5 %, it should deliver very respectable performance. The data on the MPP range and the maximum input voltage, on the other hand, does not appear to be coherent. The MPP tracker covers from 100 to 600 V, yet according to the data sheet, the latter value should also be the upper voltage limit. This is confusing for the German customers enter marketing employee Christian Comes explains:»sanyo defines the MPP limit as the maximum input voltage. But of course the inverter can withstand higher voltages.«a better point of reference for planning is offered by the nominal voltage figure of 350 V. This may be the value at which the device reaches its best performance. Well packaged in metal housing, with the protection degree IP 65, the 17 kg device is entirely suitable for outdoor use. However, the data sheet gives no information on the permissible environmental conditions for the fanless inverter. Incidentally, the device is only really new to us Europeans, as in Japan it has already been selling very well for some time. Amongst the changes made for the German market was the reprogramming of the control software which had been carried over from air conditioning technology. Sanyo remains tightlipped on prices for the moment. Germann SMA AG presented with great aplomb their new generation of inverters, represented at the fair by the first of the offspring, the Sunny Boy 5000TL. Managing board member Günther Cramer personally guided visitors through the presentation, saying that the new generation embodies»over 20 years of experience with photovoltaic system technology«. The singlephase device, with an AC output of 4.6 kw, supersedes the 5000TL HC and brings with it, amongst other things, a newly developed power element. This is apparently one of the reasons for the peak efficiency, which stands at a good 97 %, with an input voltage range of 125 to 550 V, which is also greater than that of the predecessor. The European standard efficiency stands at 1 % under the maximum. 168 Sun & Wind Energy 3/2007

8 An old friend from Japan: In its native country, the Sanyo inverter has long been a fast seller; newly programmed, it is set to break onto the German market. SMA is marketing its new inverters under the slogan:»complete. Simple.«The technology is held to be complete, and the installation and operation simple. For example, the inverter can be adapted to country-specific conditions using two rotary switches located under the cowling. The installer just has to choose the identification which corresponds to the code supplied with the product. The device then configures itself and also sets the display to the language of the country. Furthermore, the grid connection and wiring of the two strings is made easy by special spring-coil clamps, tools are no longer necessary. With one fifth less weight on the ribs than its predecessor just 25 kg the device should be comparatively light. The new inverters communicate with the outside world, for instance in order to carry out the wireless system diagnosis, via the somewhat outdated radio standard Bluetooth, which nevertheless carries the advantage of being globally recognised and unlicensed. The Bluetooth signals can only reach up to 100 m, however. With IP 65, the 5000TL is suitable for outdoor use, and for this reason SMA has given it an extra bolt-cutter-proof U-lock as theft prevention. German Mannheimer Versicherung insurance has already given a positive appraisal of this add-on, and recognised it as»premium-reducing«. The Sunny Boy 5000TL and its smaller brother the 4000TL should be on the market from January The list price of the 5000TL will stand at 2,450, making it less expensive than its predecessor. There were a few new things on show from Sputnik Engineering AG: The Swiss firm has brought out a new series (Solarmax S) and taken the opportunity to depart from plain aluminium grey, presenting the new devices in snazzy yellow. The rated output of the four transformerless newcomers, at 1.8 to 4.6 kw, corresponds fairly accurately with that of the C series, and the same goes for the efficiency level. The S series devices have an MPP range of 100 to 550 V, and reach European standard efficiency levels of between 95.4 and 96.2 % comparable with the predecessors of the C series.

9 Sunrise with Power One: The Power One inverters are called Aurora (the red of dawn), and begin to work at 120 V. This is how an inverter looks at Motech, Taiwan. ODM customers may, however, request any other kind of presentation or, above all, construction. Photo: Motech Industries What is new, however, is the reduced weight of 2.3 kg, improved heat dissipation, and the possibility of integrating the inverter into the communications network via Ethernet. Furthermore, the new string inverters no longer work with an MSD for grid monitoring, rather they employ the oscillator method, which is apparently more effective at preventing unnecessary grid disconnections. With this method, the inverter induces a phase jump in the grid and uses this to measure the angle between current and voltage. It recognises a stand-alone set-up in that the current follows the voltage extremely closely. Sputnik raises the quality of the electricity fed into the grid by using a digital sine wave generator, with which it is possible to attain a lower distortion factor. Sputnik has also come up with successors to its large inverters: The two central inverters Solarmax 20 S and Solarmax 35 S the figures represent the AC output mark the swing towards transformerless technology, even at high outputs. The resulting devices weigh just one third as much as their predecessors and reach a maximum efficiency of 96.5 %. The European standard efficiency stands just 0.7 % below this value. A patented switching mechanism apparently minimises leakage currents, which is certainly essential for large inverters, since one often wishes to use them in conjunction with thin-film technology. The MPP window extends from 400 to 800 V, setting it comfortably apart from the upper voltage limit of 900 V. The central inverters practise veritable three-phase grid feeding, and therefore only have to store a small amount of current in the intermediate circuit. Sputnik has taken advantage of this in order to say goodbye to electrolytic capacitors and to put in their place foil capacitors which have, in principle, an unlimited service life. The central inverters will be on the market from summer 2008, the string inverters Solarmax 2000 S, 3000 S, 4200 S and 6000 S should be available in November. Steca GmbH from Memmingen, Germany, announces the arrival of its first large inverter, the Stecagrid ph, for The model description alone reveals that this is a three-phase device with 9 kw of AC output. On the input side, the device can receive up to 10.5 kw whilst still accepting a current of up to 32 A. Together with its MPP range of 300 to 750 V, the Stecagrid allows for diverse system designs. The switching concept with one tracker requires, admittedly, systems»with an identical module orientation and without shadow problems«, as is stressed in the data sheet. The transformerless device reaches a peak efficiency of 96.2 % and a European standard efficiency of 95.3 %. Even without electrical isolation, the device apparently only produces low DC leakage currents, and is therefore kind on thin-film modules. The Stecagrid 9000 s own standby consumption makes a good impression at less than 0.5 W. The derating, which takes effect from 170 Sun & Wind Energy 3/2007

10 50 C, leaves room for improvement. With the protection degree IP 54, the device is suitable for protected outdoor use. Sunways AG gave news of a new product with the Solar Inverter PT 30k an inverter for larger systems, as the name gives away. The transformerless device will operate with input voltages between 420 and 800 V. A multi-chamber system, which channels hot and cold air flows separately through the inner workings of the A connection element for every occasion: In its IG Plus series, Fronius from Austria incorporates a connection element with power elements of three different strengths. In new dimensions: With the Stecagrid ph, Steca, Germany, presents its first inverter for systems with an output of around 10 kw. Photo: Steca device, is supposed to ensure optimal cooling. Not a lot of information was given on the underlying performance technology hence the initials PT but this is likely to be based on the NT models. The 30-kW device is to come onto the market in the first quarter of 2008, and should certainly be more affordable than three 10-kW devices. How long it can actually be before announcements turn into products is shown by the AT models, which are just now going into mass production, exactly a year after their first appearance in Freiburg. There is something new and concrete to report from the models of the NT series. The engineers in Constance were able to raise the efficiency once again, it now reaches 97.5 %. The devices reveal an amazingly small gap between maximum and European standard efficiency: for the NT 6000 this is 0.5 %, whilst the NT 4000 leaves a difference of just 0.3 % between the two values. The efficiency curves at various input voltages also lie very close to one another, and all devices reach their maximum at 350 V. The reason for this increase is optimised components, one of which is an inductor which has a higher efficiency of its own. The control was also redesigned.»the switching still had potential, and was just waiting for better components,«says Martin Buchholz, product manager at Sunways. To get up to 98 % will be a tall order, however. To accomplish this, one would have to restrict the input voltage range, and this would appear to make little sense, says Buchholz. Andreas Schlumberger 22nd European Photovoltaiv Solar Energy Conference and exhibition