Archive for the ‘Grid Connection’ Category

Inverter grid synchronisation – Six AC system frequency facts

Thursday, December 9th, 2021

With inverter grid synchronisation the key problem is that the grid frequency can vary.  In fact the frequency of AC systems around the world is different and is constantly changing.

  1. Aircraft AC systems run at 400Hz three phase.  They do this to make the motors lighter with less iron due to the volt second integral being lower.
  2. Some railway locomotive AC systems are 16.7Hz single phase.  These frequencies are chosen to minimise the current needed to charge the capacitance of the overhead line and so minimises the number of substations needed.  The 16.7Hz  is chosen to so as to not be a multiple of 50Hz.  The was made by rotary frequency changers (this is truly what they were called as power engineers often lack imagination) but is now also made by static power electronic frequency changers.  With modern static frequency changers with inverter grid synchronisation 16.7Hz is achieved.
  3. In Switzerland the railway has their own separate distribution grid.
  4. There have been railway frequencies as low as 8Hz and some train locomotives even operate from very low frequency AC with a frequency of zero.  DC is the AC you have when you are not having AC.
  5. Early on GE decided that 40Hz would be good for AC distribution but it did not catch on.
  6. There are aluminium smelters in Australia where they have or had 60Hz, 50Hz, 25Hz and 16 2/3 Hz AC systems and reportedly all at the same time.

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Other useful information for synchronisation.

  • NATO ships are 60 Hz,
  • The Swiss, German, and Austrian rail network reportedly changed to 16.7 Hz from 16 2/3 Hz  in 1995.  This to prevent over heating in rotary converters.
  • Japan has both 50 Hz and 60 Hz with the 50Hz built by the British and the 60Hz by the US after the second world war.  The two systems are linked by HVDC links.
  • 60 Hz is probably a better choice than 50Hz but it is too late now for the 50Hz countries.
  • Reportedly Tesla (not the car company) chose 50Hz first and then 60Hz.
  • There is a power station on the Argentina/Brazil border where half the generators make 60Hz for Brazil and half make 50 Hz for Argentina.
  • Sometimes, in some countries, on some days, 50Hz AC systems will run at 38Hz.  This presents an interesting inverter grid synchronisation problem.

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Grid frequency varies constantly as the mismatch between generator and load power changes.  In most countries the variation is not as large as the change to 38Hz.

Grid connected power converters must track or lock to the grid the grid.  The best way to do this is with a phase locked loop or a frequency locked loop.

Inverter Grid Synchronisation

Phase locked loops to track grid frequency are an essential part of grid connected converters. Click here to ask us about using an ELMG phase locked loop for inverter grid synchronisation.

May 18 Webinar – Basics of Digital Control of Power Electronics

Friday, May 14th, 2021

Our webinar series is back! Grab your lunch or a coffee and join us for this free webinar on the basics of digital control of power electronics.

From the comfort of your own desk you can join ELMG Digital Power for a free webinar to expand your knowledge and expertise about the advantages that digital electronics provides including:

* Flexibility
* Configurability
* Re-tuning the loop for component variation such as Electrolytic capacitor freeze out at low temperatures
* Management of the non-linearity of the converter
* Self-measurement of the loop response in closed and open-loop

and learn about the three key basics of digital control of power electronics these being

1. Limited number of bits.

2. Power converter characteristics including non-linearity

3. Limited PWM timer precision

This webinar will be hosted and presented by Dr. Hamish Laird, ELMG Digital Power’s CTO and a Principal FPGA and Power Electronics Engineer. Hamish has considerable experience in the design and implementation of varied digital control systems and IP for power electronics on FPGA platforms.

The webinar on Basics of Digital Control of Power Electronics: Where to start and what is important will be held May 18, 2021, at 12 Noon PDT on Zoom.

Spaces are limited.  

See you at the webinar.

Click here to register

Free Webinar – Digital Control of Power Electronics using Zynq

Friday, January 31st, 2020

If you have just sat down at your desk with a coffee, then put that aside for a minute and grab your diary. Review your schedule for Tuesday 4th February and consider this stellar opportunity: on that day ELMG Digital Power will be hosting a FREE webinar on Digital Control of Power Electronics using Zynq.

That’s right, from the comfort of your own desk you can join ELMG Digital Power (Members of the Xilinx Alliance Program) for their Zynq Digital Power Webinar and expand your knowledge and expertise by discovering:

* What is important in digital power, including numeric precision and latency
* Why you would use a FPGA for digital power and why the Zynq SoC in particular
* Key issues in digital controllers in programmable logic, such as the serial-parallel trade-off, fixed or floating point,      choosing sample rates and what precision to use
* Building blocks for digital control with ELMG’s licensable IP cores
* Using the ARM cores in the Zynq to your full advantage.

This webinar will be hosted and presented by Dr. Hamish Laird, ELMG Digital Power’s CTO and a Principal FPGA and Power Electronics Engineer. Hamish has considerable experience the design and implementation of varied digital control systems and IP for power electronics on FPGA platforms.

The webinar on Digital Control of Power Electronics using Zynq, which includes a short Q&A session, will be held on Tuesday 4th Pacific Standard Time at 10am and is available globally.

Spaces are limited.  

See you at the webinar.

Click here to register

Inductor Go Round – Redux

Wednesday, May 9th, 2018

ELMG Redux from 2010

This post was originally published in 2010.  It is republished here because it looks like people are still doing the inductor-go-round.

So what is the inductor-go-round?  It is like a merry-go-round (carousel) except with inductors.  It can cost companies (or their startup backers) lots of time and money.  And usually when you are on the inductor-go-round it feels much like a carousel at a fair.  Round and round and sadly, not much progress.

Power Converters

Often the optimization of a power converter’s performance comes down to the optimization of the converter inductor. (It can also be optimization of the transformer but lets for the moment assume a non-isolated converter). For people with big and small inductors there is, it seems, an inductor go round.

What is a big inductor? At ELMG Digital Power we generally say that any inductor with mass more than 1 kg – and yes it says kilograms (1kg = 2.2 pounds) – is a big inductor. Some of you will say that until you have a 40kg inductor you don’t really have an inductor. Other inductors will be smaller.  I guess it is all a matter of what you are familiar with.

For the inductors for grid connected inverters people start with laminated iron or some other laminated material.  This is typically the  inexpensive choice.  Some others choose ferrite cores. Some start with another core material.

Air cored next

Then running first into core material problems they then move to air cored as the core is the cause of all the problems. They then either come up against either;

  • the magnetic field interference problem (the enclosure is now the core),
  • the fault rupture problems that occur with designing air cored mechanical restraints,
  • or the size constraint.

Powdered?

From here most people head to a modern core material such a powder core. These materials are not necessarily homogeneous and so they then realize that to get long life times requires careful consideration of the wear out mechanisms and to meet this requirement means using a quality core material vendor (See Thermal aging explanation for a good first discussion on thermal aging). The lesson here is that not all core materials are the same.

Back again

At this point some people go back to iron or ferrite and others go to an alternative core material like an amorphous alloy. If they then cannot meet the price point then they may well go back to laminated iron.

At this stage the realization is that there is no magic answer. The optimization of power inductors becomes the requirement and there is usually a realization that the inductor vendors are not as able as they seem. In the defense of the inductor manufacturers it must be said that most power electronics companies struggle to correctly specify inductors.

Getting off the inductor go round means designing the inductor completely.

Advanced Digital Control Power Electronics Course

Wednesday, October 19th, 2016

Digital Control Power Electronics course – January 30 to February 2

The next Advanced Digital Control of Power Electronics training course is running in

Camarillo, California

January 30 to February 2

Registrations open now – click here or on the button below


Register now


Course outline is here.

Four days

The course has been expanded to four days and includes lab sessions each day to reinforce the learning on

  • Precision extension of Digital Modulators
  • Digital Loop closing
  • The effects of delay
  • Loop measurement using the control processor.

What people who have attended say about the course?

“Had very high expectations of this course. Hamish delivered. Excellent for power engineers who are starting digital power. Thanks for putting this on…I only regret it is a 3 day course. I could sit here for 3 more days”

“This course was full of critical material not found in the app notes.  Very enjoyable and well taught.”

“Good course. Hamish knows his material. I’ll be able to apply this coursework to my work.”

 

“I would highly recommend the ELMG digital control course to all power electronics engineers.  What makes this course particularly valuable is in the practical approach and relevance to the control of power electronics.  The topic of digital control is a very broad subject and hence the specific challenges and applicable tools are very different depending on the application details. Many digital control / DSP courses try to approach the topic from a very generic broad approach, treating all applications in the same way.  The classic approach involves starting from a conventional analog control model and then adding ADC and DAC blocks to change between the analog and digital domains with a digital controller replacing the traditional analog controller. The problem with this classic approach is that it is not a practical or applicable method for designing high bandwidth controllers for use for the control of power converters. The ELMG digital control course specifically focuses on the control of power electronics and hence the course only considers concepts and techniques that are applicable to the control of power electronics.  The course covers a wide range of digital control theory and introduces the power electronics engineer to all of the state of the art digital control concepts.  This course is a must for any power electronics engineer who is involved in the digital control of power converters.”

Michael Harrison – Director of Power Conversion, Enphase.

Register by clicking below





Register now





 

Free Webinar High Performance Digital Control on Zynq

Sunday, July 10th, 2016

If you have just sat down at your desk with a coffee, then put that aside for a minute and grab your diary.

Review your schedule for Tuesday 12th July 2016 and consider this stellar opportunity: on that day ELMG Digital Power will be hosting a FREE webinar on Digital Power using Xilinx Zynq SoC.

That’s right, from the comfort of your own desk you can join ELMG Digital Power (Members of the Xilinx Alliance Program) for their Zynq Digital Power Webinar and expand your knowledge and expertise by discovering:

* What is important in digital power, including numeric precision and latency
* How to design a compensator in the digital domain
* Why you would use a FPGA for digital power and why the Zynq SoC in particular
* Key issues in digital controllers in programmable logic, such as the serial-parallel trade-off, fixed or floating point,      choosing sample rates and what precision to use
* The building blocks for digital control and ELMG’s licensable IP cores
* IIR digital filter design (a case study) along with understanding the delta operator
* Using the ARM cores in the Zynq to your full advantage.

This webinar will be hosted and presented by Dr. Tim King, ELMG Digital Power’s Principal FPGA Engineer. Tim has considerable experience the design and implementation of varied digital control systems and IP for power electronics on FPGA platforms.

The webinar, which includes a short Q&A session, will be held on Tuesday 12th July and is available globally. Just choose a time that best suits you from these three options:

1. July 12th 2016 – commencing at 4pm in Christchurch NZ. (This will be 2pm Sydney, 1pm Tokyo, and 9:30am Delhi)





Register for Asia-Pacific




 

2. July 12th 2016 – commencing at 9am London (10am Berlin)





Register for Europe




 

3. July 12th 2016 – commencing at 1pm San Francisco (3pm Houston, 4pm New York)





Register for USA



Spaces are limited.  

See you at the webinar

 

 

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