Advances in Solar Energy and Battery Technology – onsemi, Würth Elektronik and Mouser
[Music] solar energy is the most abundant energy resource on Earth and solar panels are the most popular method of collecting solar energy and did you know that in 2022 the United States alone generated 1456 tatt hours of solar power and for the last eight years solar energy has been the fastest growing source of electricity so what do we do with all of this electricity to keep Pace with advancements and solar energy we need to further innovate in our energy storage systems as well hi I'm Amelia Dalton host of chalk talk passive components will play an important role in the next generation of solar and energy storage systems in this episode of chalk talk Prasad parui from on semi and Walter fusto from worth electronic and I explore Trends challenges and Solutions in solar and energy storage systems we also examine Emi considerations for energy storage systems the benefits that battery Management Systems brings to these kinds of dis designs and how passive components can make all the difference in solar and energy storage systems and before we get started don't forget to click that link there you can find even more information about this topic hi Walter thank you so much for joining me hi milia how are you I'm great and hi Prasad thank you for joining me thank you so prad we are talking about next generation and energy storage systems today but before we dig into the Solutions in this Arena can you give us an upper level view of these kind of designs Yes Energy story is becoming predominantly important in various segments of the end applications starting from residential storage at homes and then commercial buildings also adding the storage nowadays and also the utilities for high power level they're also adding the storage the storage can be segmented into two ways based on power level and also the whether it is a AC coupled or DC coupled coming to the power level singlephase Solutions are starting with from 4 Kow to 7 kilowatt and going to the higher level from 12 to 15 kilowatt for residential applications in the US it may have a split phase and in Europe maybe a single phase residential applications while for commercial applications the power level is in the range of 100 Kow to 2 megawatt but they may have a power blocks in the range of 15 Kow to 150 Kow and they parall multiple of those higher power modules to get into the 2 megaw power range then there's a third is related to the utility scale and those are mostly the three-phase and can go to the power level 5 megawatts and above with a power building blocks of 150 kW to 300 Kow and one of the major reasons for the storage systems and customers are adding for load shifting in case of utility application and as a backup power either residential or commercial applications and also the peak power support for example in EV charging applications where you have multiple cars are coming at the same time for charging stations there's a lot of burden on the utility the energy storage at the charging stations help you to take the peak power support So pad what kind of Trends are you seeing in the solar and storage Arenas there are two different segments based on the power level and also the isolation required whether it is a AC coupled or DC coupled and then when coming to the power level we have different power level for different application segments like resal applications commercial application and utility scale for residential application the power levels are in the range of 4 to 7 Kow for the low end applications and then from 12 to 15 Kow for little bit high-end systems then for the commercial applications we will have like a 100 Kow to 2 megawatt and with a power building blocks of 15 Kow to 150 Kow then similarly Utility Systems there is a three-phase systems can be as high as 5 megawatt systems but with building blocks of 2 1225 Kow to 350 Kow the DC bus used to be 1100 Volts for the Utility Systems and now they are moving to the 1500 volts and that necessites the 2 KS power modules customers normally use discrete components like t247 package are in some cases d square pack toll package like a medium voltage pets in general they are using the toll packages and for micro inverter applications also the customers using the toll package then there's a new package for the higher power inverters like a 7 to 15 Kow we talked about there may be a possibility of mix of discrete or power modules in case of the discrete there's a new package called the bpack which is a top pool package they are customers preferring and in case of commercial and utilities mostly they are using our modules like q1 and Q2 modules for the inverter and storage applications then also there's a new module called easy F5 module with a base plate and this is more popular nowadays for the high voltage applications like 1500 volts bus application with 2kb die so Walter what passive components are used in solar applications so the use of silicon carbide modules allows to work with higher switching frequencies so when it comes to the Boost converter the magnetic component that shows the best tradeoff between cost and performance is a flat wire inductor also we want our solar inverters to be as reliable as possible to avoid frequent maintenance and this is why it is advis to use film capacitors instead of electrolytic ones finally from the block diagram shown in this slide we can see that the use of storage system comes with a higher operating voltage it is critical to isolate the control circuits for the gate drivers and for battery management with dedicated Transformers so overall these are the trends for Passive components that we can mention that makes sense so Walter let's talk about the market size of solar and storage systems right so the residential and solar photovolatic inverter Market was valued at 5.2 billion US doar in 2022 and it is projected to grow at 11.3% cagr from 2023 to 2032 driving this growth include several factors among these we can name for example the increasing Global energy demand significant investments in rooftop solar deployment and also favorable business environment if you want to look more on the product level we can see a difference between string inverters and microinverter Technologies and string inverters are gaining popularity due to their cost Effectiveness compared to micro inverters what is more string inverters allow individual connections with a single solar module where then thus resulting in lower failure rates and obviously cost benefits what we can add is that regulatory concerns about effective interconnection of grid type solar installation can also so further enhance the deployment of potential for string inverters and one last thing that we can add is that efforts towards Energy Efficiency and conservation will also boost the adoption of energy storage system in residential premises so prad can you give me some details on an inverter for these kind of bidirectional systems yes so we normally have in the residential inverter applications there are different topologies customers normally use and one of the topology normally they use is a hit bridge that means they have a one hob Bridge doing the high frequency switching and then there's an Emi filter and go to as a line and then the second hridge is basically create a neutral and this is very popular topology the main advantages of it have fewer Parts but it have a little bit bigger inductor and maybe a lower efficiency and THD is okay but the design is very simple and straightforward forward in us they may use a split phase solution then you may have additional hridge in addition to the single line then to improve the performance of efficiency and better THD heric topology is one of the popular technology and that slightly more complex control but it added two more additional switches and that maybe having a higher cost but the output inductor is a smaller and then efficiency is higher and it have a better THD then the third one we also have a lot of customers are nowadays using which is a h 6.5 inverter topology
and this have two additional fats plus one diode clamping diode is also needed but it have a lower switch stress it is a higher cost because of the more switches but it also have a smaller inductor a efficiency and better THD that is one of the reason on semi developed a a custom module to add all these power switches into a single module that simplify the design on semi also have Elite S power simulator and both H bridge and H 6.5 can be simulated in Elite power simulator so Walter can you talk to me about EMC for energy storage systems as bit as well of course so from an EMC perspective the photov volti system includes various subsystems components and also auxiliary devices we can focus on some key elements from an EMC point of view which would be the photovoltaic cells of course inverters battery controllers and cables so I will start with saying that evaluating Emi in photov voltech generation system is a complex topic because it requires analyzing an equivalent circuit with elements from both the AC and DC sides to identify the sources of interference EMC regarding the DC side largely depends on two factors first of all the capacitance of the photovolt generator system and and secondly the inductance of the DC lines so grounding the PV panel frames is crucial because impacts both EMC and safety furthermore shielding the DC lines can significantly reduce electromagnetic fields but this is effective only if the shield is grounded on both ends with a high quality connection to Earth then we can add the shielded and well grounded DC lines of also offer optimal lightning protection which is always good and the length of the DC cables affects not only the distributed transversal capacitance but also the longitudinal inductance so this inductance forms what is called a resonance circuit potentially causing the PV system to act as an unintended antenna so we don't want that the values of the equivalent circuit resistor and capacitor depend on the cell parameters while the inductance is primarily depending by the cell connection geometry so there is this difference between the two equivalent circuit parameters if we want to talk about the impedance of these components this varies with factors such as cell volage solar radiation temperature and also frequency so this re reconnects to the fact that it's a complex topic that takes into consideration several aspects of the system itself if we move on to a more schematic level depending on the power level and amount of attenuation needed for differential and common mode noise there are different filter configurations so in most cases a two-stage Line Filter is used for the single phase inputs so this single phase is good for up to around 7.4 Kilt anything about this power level is usually designed for a three-phase system so the two stage filter that is shown refers to the use of two common mode chokes together with the respective X and Y caps the X capap across the L lines provide differential mode noise reduction by forming an LC filter with the leakage inductors of the Comm mode chock itself so we don't need another component to create this LC filter it's done directly with the Comm mode choke V electronic provides with our selection tool red expert the possibility to select a Comm mode choke not only based on the common mode inductance but also on the leakage inductance so that customers can really select a common mode choke that complies to both differential and common mode noise reduction for lower power levels moving to a three-phase system as the current is in three live lines the noise is also equally distributed among these three lines therefore a single stage filter usually enough as we can see in the bottom figure on the left especially for passing limits in industrial environments but the higher we go in power and the use of this charging stations in all installations more stringed limits of the Class B need to be attained so in this case when we move up above 25 kilowatt we cannot avoid of having a two- stage filters so we need a two- stage filter for common mode noise Automation and additional LC filter for differential noise filtering on the bottom right finally we can see a graph that illustrates the conducted Emi noise behavior from a battery power supply under condition of 24 DC voltage input and 127 ac voltage output the noise level exceeded standard limits in frequency bands from 150 khz to 5 MHz with some Peaks staying below limits in the 5 MHz to 16 MHz and 20 24 MHz to 76 MHz ranges but it is absolutely obvious that an EMC filter is needed and what we can also provided some guidelines to consider to minimize interference it's good to place the PV inverter far from interference sensitive appliances it's good to install appropriate EMC filter on the AC side of the PB inverter which should be positioned close to the inverter to minimize the connected cable length which can radiate disturbances basically the cable behave as an antenna we should keep cables between the PV inverter filter and PV generator system well separated from AC main Supply cables and cables between PV panel and PV inverter should be twisted pairs grounding the shield to avoid contamination finally we should also use an electrically sheeted metal wiring cabinet for both the inverter and the filter and we should provide low impedance CMC ground which is distinct from the safety ground to protect against electrocution while reducing a Emi okay so prad what about the converter what does that look like yes ped on the power level of the storage systems we may Implement different power converters and also it depends upon what is the voltage of the battery whether it is the battery voltage is lower than the panel voltage or it is higher than the panel voltage if the output battery voltage is lower than the panel voltage normally we use synchronous Buck converters so that means you are able to use MPP function and then take the maximum PowerPoint tracking of the solar panel and then charge the batteries using a synchronous buug converter while in a similar way if the panel voltage is lower and for example if the panel voltage is 24 volts and the battery voltage is 48 volts then we need to use use synchronous boost converter that means you are boosting the power level from the panel lower panel voltage to the higher battery voltage the battery voltages are depending on different customers it can be 48 volts or maybe 96 volts and in the residential systems some customers want to have the panel voltage low or higher but the having the battery voltage 48 Volts for example the panel voltage can be 24 Vols to 96 volts in this condition the customers try to combine the both synchronous buck and boost into you what we call as a for switch buck boost converter and these three topologies are popular in the market for residential market then when you go for a commercial storage or the utility storage you require the higher power level applications for that we do recommend symmetrical buck boost topology based on the three level topology and the one of the reason why we prefer to use the three-level topology is the power devices can use half the rated voltage of the system level for example in the Solar industry the storage of the 1100 volts DC bus is common till last couple of years but now the industry is moving to 1500 Vol DC bus for the utility solar and commercial solar and 1500 Vol DC bus required more than 1700 volts or 2 K device but by using the three level symmetrical buck boost topology you can able to use industry stand 1200 Vol silon carbide fets this topology also reduce the losses on Emi but it have a more complex control because it is a high power applications this also may be a little bit more expensive so this type of storage used in your different market segments for UPS applications in the data center are commercial storage and the utility storage applications on semi have dedicated hridge modules to configure this type of topology and there's a plan to do a single module with adding the all the four switches into the application but then there are some applications required an isolation from the high voltage DC to the low voltage DC in those conditions we required a isolated dcdc converters and the two popular topologies for isolated dcdc converters are dual active Bridge topology and in this case you have a primary side devices have a medium voltage fets which are normally maybe 80 volts 100 volts or 1 15 volts based on the input voltage then the output voltage based on the inverter output voltage either 120 volts or the 240 volts you will have the DC bus voltage of like 200 volts or 400 volts so you require a 650 volts either silicon carbide fats needed and most of these isolated topologies are operating at higher frequency in the range of 100 to 140 khge applications in some cases for like micro inverters they may can go as high as maybe couple of 100 khoh to we are seeing the trend in the micro inverters to implement even Gan devices or silicon carbide devices then other topology is a resonant CLC topology this topology also have both primary side Bridge circuit and the secondary side Bridge circuit but we have additional LC resonant components both on the primary side and secondary side and both topologies will provide you soft switching and wide voltage range operation both topologies can be used as a bidirectional converters the main advantage of the Dual active Bridge compared to the resurant CLC is you don't need the resonant capacitors in series with it which are normally sometimes high peak currents need to be required and so reliability sometimes case compromises so the Dual active Bridge benefit on that part because it doesn't use any capacitors so Walter can you explain to me why it's better to have flatwire inductors in these kinds of applications yes so it is well known that flatwire inductors are used because they offer a better DCR due to a more efficient use of the wire geometrical section basically you have a better usage of the section compared to a round wire however there is another critical difference when it comes to high frequency applications and to prove this we took an example of conducting a test using two samples of a similar inductor one is a standard flatwire part like the standard toroidal flat wire family from V electronic that was recently released and the other one one is a hand wound round wire part so both samples use the same core same number of turns and equivalent sides wires to achieve a similar DCR so we're comparing this time two components that have a similar flat wire we want to check what's the advantage so let's start from the values the results show that there is a minimal difference in DCR only 0.6 milliohms however there is a bigger difference in inter winding capacitance which is significantly different so 100 54 P ofar for a round wire compared to just three P ofar for the flat wire so basically when using round wire for winding typically there are multiple layers involved leading to potential issues so the image illustrates the multiple layers create a parasitic capacitance between wires both within and between layers and this results in complex parasitic capacitance increasing the overall capacitance of the component in contrast using flat wires eliminates capacitance coupling between vertical layers leaving only horizontal parasitic capacitance as a consequence the total capacitance is lower since it's seen just in series for example if we take an inductor with round wire and 200 micro hand inductance this has a self-resonant frequency at about 1 megahertz due to 154 P ofar parasitic capacitance meanwhile an inductor with flat wire and three pigat parasitic capacitance will resonates at 6.5 mahz is important because a higher resonance means a broader frequency spectrum where the component functions as an inductor we all not that beyond the resonance point it will act as a capacitive element therefore a higher resonant frequency enables the inductor to operate efficiently at a higher switching frequencies there is a common Trend in solar inverter applications so Walter earlier you mentioned it is better to use film capacitors and instead of electrolytic can you talk about the comparison between these two capacitor Technologies absolutely so the main difference lies in the construction of a dieseling capacitor compared to an electrolytic capacitor a diesel link film capacitor is based on different amount of layers of metallized polypropylen film only one side of metallization is added to the polypropylen film thus isolating each layer due to the nature of the material itself these film caps have what we call self-healing properties due to the size of the Metalized film surface and the isolation between each layer basically the film cap is able to withstand High Ripple current and it has a longer expected load life and another important thing is that the resin inside the cap will provide self-extinguishing properties so as we can imagine in solar inverter applications where the DC link is probably located in a remote location and we don't want to do maintenance very often it is better to have fil capacitors because of the fact that there is less probability that they need to be replaced so if you want to achieve the same capacitance using fi capacitors and electrolytic capacitors with electrolytic capacitors we would need higher capacitance per volume so we will need bigger volume which will increase the size of our product what is more they will also have a higher ECR because they need to be connected in serus so our overall system will turn to be less efficient using Electro capacitor this is why BR electronic recommends to use dcing capacitors for this application and we have now a dedicated series of capacitors specifically designed for these applications so pad what kind of Trends concerning integration are you seeing in the residential solar Market yes uh what we are seeing is a consolidation of all-in-one bidirectional inverter that means the customers are looking for an integration of MPP dcdc converter and then the solar inverter and the battery charger all into one big system in the power level of 8 Kow to 15 Kow in addition to the integration we are also seeing a lot of intelligence into the system like a system monitoring like a over current protection over voltage protection under voltage protection or short circuit protection these are becoming more and more important and the grid monitoring like a blockouts or anti landing and those things are also becoming important like outside of your house you have a breaker system and the utility people came there and then shut off the breakers but if your solar inverter is connected to that then they can get a shock so it need to monitor the grid and make sure there is no issues often it is less expensive to add the fewer components for example as we told that uh if you want to add an additional battery storage you can add extra battery storage in this application then it is also easier to install because there's not more wiring and because all the system is integrated one sometimes it may require a different applications what we have AC coupling and DC coupling capability fantastic now pad how can Engineers deal with galvanic I installation of the several modules used in an energy storage system yes and when we driving these power switches we required a gate drivers and these gate drivers are normally required a galvanic isolation from 3.3 Kow to 5.2 kts and there are various methods to implement for the galvanic isolated gate drivers some of them are Gate Drive Transformers and also you can use galvanic IC based gate drivers in the IC gate driver based system systems you have a two different isolations one is a capacitor isolation and then other one is a Transformer based isolation and on semi have isolated gate drivers based on Transformer isolated based gate driver IC so Walter can you talk to me about the parasitic elements in the gate drivers yes so what I can explain now is that if you have an isolated gug driver with a Transformer it is very important to consider the interwinding capacity of the Transformer itself I will start with defining the common mode transan immunity that is typically called cmti and it is measured as the kilovolts by microc it is an indication basically of the maximum rate of change of voltage DB over DT which can be tolerated across the isolation barrier of the gug driver system before malfunction occurs so if this happens there will be a loss of control of the silicon carbide device and we don't want that to happen so the cmti rating directly depends on the parasitic capacitance value across the isolation barrier this is why it is important to have a transformer for the isolation of the gug driver which features a very low interwinding Capac and this is why BR electronic released a specific family of auxiliary Gay Drive Transformers which have very low interwinding capacitance down to 6.8 POF
farat therefore helping the guge driver system to achieve cmti rating above 100 Kilt by micros besides the functional and relability aspect we can also improve the Emi performance with a lower interwinding capacitance because the higher the impedance seen by any common mode noise currents that try to couble between the low voltage and high voltage side so keeping these noisy currents in the high voltage side we can get away with a smaller EMC filter so prad can we also talk a bit about battery battery storage integration what does that look like for on semi yeah so the battery storage integration normally consists of AC couple versus DC couple there are advantage and disadvantages of the both the systems and I will start with the AC coupled solar energy system in case of this what we have is a MPP boost dcdc converter and the inverter DCT AC inverter are combined into a hybrid solar inverter and then it also required additional battery storage system module where you have a charging and discharging the dcdc converter for the battery but also it need to have additional ac2dc inverter that means you have a two different ac2dc inverters are needed so the overall system cost maybe a little bit higher but the flexibility of adding the storage battery in a separate box and if you need add the more storage you can easily add to the whole system that is the major advantage of it but then it requires additional conversance steps two inverters and then you require a b directional charger plus inverter in the battery pack system but with appropriate size and Battery we can add easily the additional DC to DC storage while coming to the DC coupled solar energy storage you have integrated system one like a MPP boost dcdc converter and an inverter where you have a b directional inverter is implemented and then you have also dc2dc converter which have the capability for charging and discharging so that means the Power Electronics is integrated into the one box but that power box level is a multiple power levels you can have like a 7.4 Kow or maybe a double the power level of up to 15 kows but then you can add extra storage easily without any problem too and it enables the bidirectional dcdc converters so Walter how are the battery packs monitored so I can answer that by defining what are the main goals of a battery management system so a battery management system of BMS is an electronic system that manages a rechargeable battery with the goal to make it safe and reliable so basically we want to protect the battery from operating outside of their operating area we want to monitor the state of charge and state of health of the battery we want also to calculate some other secondary data and reported data so that we can control the environment and if necessary we can authenticate and balance the data itself typically BMS system and the battery packs are monitored with every battery cell is monitored by a separate charging or monitoring unit and the communication between these battery units and the BMS controller is done on a specific communication protocol so between the components or the PCB connected in series there will be a voltage difference between the control circuit and the charging circuits of the battery themselves so there will be voltage differences and electromagnetic interference that can happen because of the difference of in voltage so a Transformer is needed in a BMS when there is a high voltage difference a Transformer that can be used to isolate the components from each other and also suppress Emi interference so basically we need a Transformer that also typically has common chokes integrated in the same component if we look at a typical block diagram for a residential energy storage system you will normally have an inverter and then you will have an isolated power supply which generates some battery protection and then you will have a number of cell monitors depending on the type of Stack that you're doing or on the individual application there will be a simple isolation into the microcontroller and then normally there will be some kind of isolated Communications so in this slide we can see that the magnetic Associated to the isolated communication therefore the Transformer is placed between the cell Monitor and the microcontroller creating the isolation there is required to make sure that there is no electromagnetic interference and that the voltage difference can create problems in the system itself so prad talk to me about the popular topology used in residential storage and solar inverters yeah so in the residential applications there are two different concepts one is a micro inverter and the other one is the string inverters so in case of the micro inverters they have the whole inverter is in a low power range like 800 wats type of applications while for the string inverters you have a power level can be 7.4 Kow to 15 KW and then you have a front end is the Boost module which is what we call dcdc converter or in some cases customers call DC Optimizer then you have power inverter module where you use H 6.5 inverter is one of the example then it also have a dc2dc converter to charge and discharge the battery so what type of passive components are used well this is a good example to recap all the components that we have mentioned so far to today in regards of the DC link or DC bus connection a DC film capacitor is strongly recommended because of the reliability at the output of the inverter a very important section would be the Emi filter so filter inductors and capacitors together with over voltage protections are recommended if we go to consider the several isolated gauge driver systems in this solar converter topology if a Transformer is required we can recommend the auxiliary gaug Drive Transformers and last but not least to monitor the battery packs with an isolated communication we will need also the BMS Transformers to isolate between the different voltages in the application yeah Oni have silicon carbide mosfets igbts and super Junction fats also the Silicon fats for the dcdc optimizers then I will start with Oni have a silicon carbide MOS fets mainly targeting ration shell inverter applications they are focused on 650 volts devices Oni have M2 product line which are in production from last 2 to three years then developing the Next Generation M3s 650 Vols technology targeting for residential inverters like a 12 mohms 650 volts is very popular part in that market then similarly for DC todc optimizers Oni have medium voltage FS from 80 volts to 100 volts and 150 volts so these are all good on semi products for the dcdc applications specifically the power trench T10 silicon mosfets are good for dc2dc optimizers while for inverter stage Elite six silicon carbide fets are very popular but if customers are looking for a lower cost option and especially we do see in Asia Market lot of customers are using 650 volts igbts and on may have fs4 igbts to Target these applications in micro inverter applications some customers use also super Junction fets in the microinverter applications Oni do have silicon carbide diodes or silicon diodes with the different Technologies covering the 650 volts and 1200 volts then the last one Oni also have a silicon carbide modules targeting for the higher power level like a commercial utility inverters commercial storage or utility storage applications with the voltage ranges from 650 volts to 1200 volts releasing the new 2kv devices to Target the 1500 R DC bus utility storage applications so Walter can you give me some more indepth details about this portfolio right so I can highlight that virtual electronic offers a specific portfolio of high current inductors distinguished between uh wecf ft and WF so both through Edge all or SMD components we have a very wide portfolio of common mode choke feri beats estd and search protection devices in regards to the power factor correction we can offer the toroidal PFC chalk but we also have non- toroidal PFC inductors to complete with your application we can also offer several types of capacitors not only the FI capacitors but also electrolytic and ml CC I would also highlight the fact that we can offer current sense Transformer which is another important component that can be used in solar inverter application and of course it is always good to remind that V electronic also offer quartz crystals and oscillators and electromechanic components such as high current connectors that come with the commercial name of Red Cube connectors okay well I think that's all I have time for today thank you so so much for joining me Walter thank you so much Amia for having me and thank you for joining me prad thank you and before we go you didn't forget to click that link did you there you can find even more information about this topic for chalk talks I'm Amilia Dalton from E journal.com for more chalk talks head on over to the chalk talk section of e Journal you can't miss it it's right across the top or head on on over to YouTube youtube.com/ ejournal
2024-08-19 09:46
