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Three Day Digital Control Course August 22-24 California

Friday, July 22nd, 2016

The ELMG Digital Power Electronics Control Course

Three days of focused unique training in digital control of power electronics!

Our Digital Power Electronics Control Course overs the essential knowledge and know-how for engineers to implement digital power electronic control!

Come to the Three Day Digital Control Course in Camarillo, California August 22-24, 2016.  Register here.

How did the course came about?

Essentially the course came about because we were asked by one of our customer’s to provide one. The story is we were in the middle of a “fix up” job where the power supply had shown some control instability at its final release testing. The testing that showed the problem was passing a short circuit test of parallel connected power supplies. When the short circuit was removed the supplies came out of current limit, however they did not come out of the limit at exactly the same time. This created an oscillation where individual power supplies came out of current limit and then returned to current limit.  It was possible for the oscillation to continue indefinitely.  This was an unacceptable and embarrassing problem.

Six months of expertise in a three day course

During the six month project to rework the control code we spent lots of time teaching the team about the underlying issues that had been missed when the controller had been designed, coded and tested.  And part way through the “fix-up” the R and D manager suggested we could put a course together covering all that the team needed to know.

And so the digital control course was born

The first course covered exactly what we had discovered during the fix up job.  This included lots of digital expertise targeted for power electronics.  The areas we covered were diverse from;

  • Numeric precision loss in filters
  • Improvement of modulation spectral performance
  • Stability
  • The effect of numeric precision on stability
  • Best filter forms
  • Direct digital control design
  • Linearising control loops

What is covered in our course?

The course was created at the request of a Power Electronics Research  and Development manager.  He asked that we make it specific his team’s needs.  And this is why the course has the unique structure that it has.  We have been through the pain and heartbreak of having digital control development go wrong and have seen clearly where the repeated problems lie; our course addresses those areas.

Digital PWM and VPO modulators

One of the big differences between digital power electronics control and conventional analog control is the timer precision in digital modulators. This difference can be corrected or made negligible and in some cases can be made an advantage.  Spectral control in digital modulators is a focus area in the course as it is so effective.

Digital Precision in control blocks

It is possible to use a digital system and adjust the coefficients of the filters so that small inputs result in no output from the filter. Such scaling issues often lead to a loss of precision in the digital control system. The resulting slip-strike behavior can create limit cycle oscillations in the power converter output.

Direct Digital design of controllers

The “design then translation” approach of taking analog controllers to digital form can be avoided by using the direct digital design approach. This simple but powerful method of digital control loop design is covered in the course.

Converter non-linearity correction

Certain converter topologies are non-linear either in the control input to the output or the conversion ration.  Dealing with the converter non-linearity to achieve high bandwidth is key to stable parallel connected converters.

Stability

The course covers the fundamentals of stability from a physical basis with a focus on measurements of power converter transfers.  This along with a simple framework for managing margins and robustness is an integral part of the course.

Why we offer the course?

Understanding and implementing digital control of power electronics offers great advantages for configuration and flexibility. However, this is not without road blocks and issues that need to be designed around. This course provides the know how to get digital control working robustly and reliably.

How do I get on the course?

The course is next being run in Camarillo, California USA August 22-24.  To register for the course, click and visit the information page here. Press the ‘Register’ button on the page and this will take you to the shopping cart for the course. Complete the purchase to register for the course.

Next course

The next course is being held August 22-24 in Camarillo, California, USA.

Hotels

HOTELS

There are several hotels a short distance from the Ridley Engineering Design Center. The prices below reflect their current prices for August 2016. The last hotel listed is a nice beachfront resort if you do not mind the 25-minute commute to the office. Regardless of your selection, we recommend arriving on Sunday evening and departing Wednesday evening or Thursday.

 

Best Western Inn

295 E Daily Drive, Camarillo

 0.3 mi.

805-987-4991

 $100/night

Book.western.com
Residence Inn by Marriott

2912 Petit Street, Camarillo

 2.8 mi.

805-388-7997

 $185/night

Marriott.com
Courtyard by Marriott

4994 Verdugo Way, Camarillo

 4.3 mi.

805-388-1020

 $180/night

Marriott.com
Hampton Inn & Suites

50 W Daily Drive, Camarillo

 1.1   mi.

805-389-9898

 $175/night

Hilton.com
Hilton Garden Inn

200 Solar Dr., Oxnard

 5.6 mi.

805-983-8600

 $155/night

Hilton.com
Embassy Suites Mandalay Beach Resort

2101 Mandalay Beach Rd., Oxnard

 15.4 mi.

805-984-2500

 $200/night

Hilton.com

Travelling to the course

Transportation

Airports: There are three options for airports. Bob Hope Airport in Burbank will be the least congested and is serviced by American, United, Delta, Southwest and JetBlue:

Bob Hope Airport (BUR)

Los Angeles International Airport (LAX)

Santa Barbara Airport (SBA)

Shuttle: The Roadrunner Shuttle is a Camarillo-based service that provides door-to-door service from the airport. www.rrshuttle.com

Driving:

Bob Hope Burbank Airport (BUR) via US 101

https://goo.gl/maps/caMGB9QSEqP2

Los Angeles International Airport (LAX) via US 101

https://goo.gl/maps/kRBDQifyVfM2

Los Angeles International Airport (LAX) via Pacific Coast Highway (PCH)

https://goo.gl/maps/XPbBhNQYTzj

Santa Barbara Airport (SBA) via US 101

https://goo.gl/maps/2fGP3K7FMZx

About the presenter

3 Day Digital Control Course

Dr. Hamish Laird

Dr. Hamish Laird is a well regarded digital power electronics control engineer, researcher, lecturer and teacher.  Hamish is Chief Technology Officer at ELMG Digital Pwoer and holds a visiting academic position at the University of Canterbury in Christchurch, New Zealand.

During his career Dr Laird has worked on the control for;

  • High Voltage Direct Current Transmission
  • Reactive Power Compensators
  • AC and DC Motor Drives
  • DC to DC converters including LLC and phase shifted bridges
  • Medium and low voltage AC motor starters

Dr. Laird has worked for;

  • Alstom Grid (GEC Alsthom)
  • Eurotherm Drives
  • University of Canterbury
  • Aucom

Through ELMG Digital Power Dr. Laird  has provided advice, services and products to;

  • ABB
  • Enphase
  • Comsys
  • Evashred
  • TNEI
  • Eaton

Dr Laird says

“In designing and presenting the course we aim to have engineers able to use digital control in power electronics to achieve robust and reliable results.  See you in Camarillo”.

 

How to Register

Click here to register.  

P.S. Please note that the ELMG Digital Power course is being hosted at the Ridley Engineering Centre in Camarillo, California.  Ridley Engineering are processing all course registrations viatheir webstore.  Click here to register.  

JTAG Boundary Scan Testing with AutoBuzz

Tuesday, November 17th, 2015

FPGAs have very large numbers of pins.  Ensuring that these are connected and are not shorted to each other requires electrical test vectors and sensing of shorts.

Boundary Scan

To run up FPGA PCBAs a great solution is boundary scan using a JTAG connection.  This lets you drive or sense, in turn, each and every pin on an FPGA or processor without having code loaded into the chip.

Continuity, possible shorted connections or pins stuck high or low can be detected very quickly.

Good low cost solution JTAG Live

We use a simple JTAG pod  to do JTAG Live FPGA Boundary Scan Testing.  It is really useful for PCBA run up and for short run production testing.

AutoBuzz

The video shows the use of the JTAG Live Autobuzz test function.  In this the AutoBuzz learns the connections on the board allowing rapid testing of connections.  It is a great first step in board run up.  Watch the video in full screen to see the detail.  Click the right bottom corner of the video to see it full screen.

 

 

Migration from MCU/DSP to FPGA for Power Electronics: Part 1 Software

Tuesday, November 17th, 2015

In a recent discussion we were asked about the migration path from MCU/DSP to FPGA.

“I am probably not alone when I use MCU/DSP devices to implement control algorithms, protection, logic etc to control the power hardware, using code such as ASM, C or C++, but want the advantages of FPGA. What suggestions do you have to start this migration, both in terms of a cheap evaluation board, and software tools, that can be targeted at driving various topologies and speeds.”

Thanks to Anthony W. for the question.  We get asked similar migration from MCU/DSP to FPGA for power electronics questions where the emphasis is more about retaining the value of an existing code base and coding team expertise while leveraging the flexibility of the FPGA.

As the first question states MCU/DSP devices are a common tool to implement control algorithms, protection, logic and sequencing for  control power hardware, using code such as ASM, C or C++.  However they do not have the power and flexibility of FPGAs. What is the best way to approach a migration from MCU/DSP to FPGA, both in terms of evaluation boards, and software tools, for a wide range of power electronic applications?

Best migration path MCU/DSP to FPGA for Power Electronics

There are a number of pathways to do this. The first one is High Level Synthesis. This is basically writing FPGA code in C. It is a very powerful tool but it does take some know how to make sure that you can get the most benefit out of the transition to FPGA. The downside of this is that it is quite expensive. There are however a couple of FPGA kits out there that do come with a kit-locked license (node-locked and locked to the FPGA model on the board).

Processor Inside

Another way is to use an FPGA with a processor, or processors, inside it. These processor can be soft-cores like Xilinx’s Microblaze or hard-cores like the twin ARM A9s in Xilinx’s Zynq series. (Reports on FPGA development projects show that almost 50% have some sort of processor.)  This processor allows you to directly port your code from your MCU/DSP to the Zynq/Microblaze and be ready to go. This may seem counter-productive as going from one processor to another without really gaining FPGA power is work for no reward.  The advantages come when you move parts of your code (the high intensity tasks such as the control algorithms) from C to the FPGA hardware. This provides a power boost for the important parts of your code whilst still having the simplicity of C for the easy flow of your code. A good analogy would be that the FPGA parts are the equivalent of the ASM parts on the MCU/DSP but with the superman type speed advantage of doing things in parallel in the FPGA fabric.

Best of both

Xilinx has also combined the HLS and the C coding options with their SDSoC product. It is designed for the Zynq SoC .  The coding is done in C. However you can use HLS to accelerate certain parts of the code for you to gain the most benefit.

Getting the most out of the Zynq solution does require either the expensive HLS toolchain and training in that or writing your own HDL. Another option is to purchase IP that other companies have written.  This allows you to create a fast and efficient system without needing to know coding of an FPGA in HDL or C.  ELMG Digital Power has a large suite of power electronics IP to get your application off the ground fast.

Prototyping and Development Platforms

In part 2 of this blog post, which is coming later, the answers to the questions

“How can I prototype this when the chip is BGA only?”

and

“What is an appropriate development platform or dev board?”

are covered.

Download the report ‘Your Digital Power Future – Roadblocks to Avoid’ to learn about the three key issues to watch out for in the Digital Control of Power electronics.


Download report now

Touchscreen Driver TMG120

Monday, August 31st, 2015

Touch Screen Dash

We acquired a shiny Avnet Display Kit for use with our Microzed board.  Our first project on this kit was a basic dash display demo, which ran Xilinx Linux on a Zynq 7Z010 SoC with the aid of some Xylon graphics IP.  However we hit a speed bump in our progress.  Our touchscreen wouldn’t work under Linux!

Problems with the touchscreen driver TMG210

After a few days of discussions with various forums and our local Xilinx FAE we found the problem.  The touchscreen chipset was the same but as the chipset (the TMG120 from Cypress) is basically a touch screen microcontroller – it can come with various firmware.  It turns out Avnet had changed the firmware supplier with a new version of the kit.   Not worrying about this we looked into the Linux driver for the old firmware.  We identified the key code and with the aid of some standalone code drivers which worked, changed a couple of lines and it worked.  It still needs some work but it was good enough for our demo!

If you are having driver issues with your kit, feel free to download the changed C file Touchscreen Driver TMG120 below and enjoy:

Driver File C Code

Let us know how it goes.

Fixed Point Numerical Systems for Digital Control

Saturday, August 29th, 2015

One question which is commonly asked is “how do I represent fractional numbers on my fixed-point MCU, DSP or FPGA?” One of the best solutions to this is use of the Q number system.

The Q number system is a fixed point system where the available bits are divided amongst the integer bits (those to the left of the decimal point), fractional bits (those to the right of the decimal point) and a sign bit. You may ask “I know how integers are represented in binary but not fractions?” The answer is that just like integers, fractional bits are just multiplied by powers of two, except the powers are negative. For example:

  • 0.011B = 0*2-1+1*2-2+1*2-3 = 0.375

Q numbers can take on multiple forms with different numbers of fractional and integer bits. They are commonly written mQn or Qm.n where m is the number of integer bits and n is the number of fractional bits. Note m+n+1 = total number of bits available.

Arithmetic

Addition/Subtraction:

Q numbers of the same form can be added together with no issue. The only thing to consider here is overflow.

If you have different forms they need to be converted before the arithmetic. This can be done by shifting. For example:

  • 2Q13 << 1 is now 1Q14 (lose an integer bit and gain a fractional bit) and
  • 3Q12 >> 1 is now 4Q11 (lose an fractional bit and gain an integer bit)

Multiplication:

  • The rule when multiplying two Q numbers together is:
  • m1Qn1 * m2Qn2 = (m1+m2)Q(n1+n2)

Once the multiplication is complete, then a shift is needed to get it into the Q format the system needs.

The big issue with multiplication is overflow and precision loss. When there exists m > 0, then scaling back to your original system is difficult. For example:

  • 2Q13 * 2Q13 = 4Q26

In order to scale this back to the original 16 bits you either have to sacrifice integer bits (you have to be very careful that the top integer bits don’t contain information – limit the overflow) or lose precision by discarding fractional bits. The solution to this is to try and use systems where m=0.

Digital Control

Choosing the Q number system for digital control is important. The general rule of thumb is you want as much precision as possible and you want to avoid overflows in multiplication. Therefore the best solution is to make all your bits fractional (i.e. m=0). This gives as much precision as your system allows and makes sure there are no overflows (<1 x <1 = <1). In a 16-bit system this is 0Q15 (referred to as Q15).

Once you have your system then you need to make sure that all inputs and outputs fit this system and falls within the range -1 <= x < 1. This is as simple as setting your inputs and outputs to be +1 = full scale positive and -1 = full scale negative.

The key for this to work in a digital control system is to remember the gains on the inputs and outputs. This means remembering what +1 and -1 stand for. For example a voltage input may be -230V to +230V and an output maybe -400V to 400V. The input gain is therefore 1/230 and the output gain 400. Once you have these gains you need to include them in your design of the control system, whether it be through calculation or simulation. Failing to include them leads to incorrect margins and possibly instability.

One potential pitfall of the m=0 approach is how to deal with numbers greater than one. In digital control these can come up quite often generally in biquad filters. The trick is to this is to scale the coefficients by ½, perform the multiplies and then scale back by 2 (shift left 1). This does lose one bit of precision in this particular calculation however it is better than losing one fractional bit in all calculations.

Conclusion

Q number systems allow the designer to use a reliable fixed point system to represent fractional numbers. This allows the use of less expensive fixed point processors instead of the more complex and generally more expensive floating point alternatives.

Download the report ‘Your Digital Power Future – Roadblocks to Avoid’ to learn about the three key issues to watch out for in the Digital Control of Power electronics.


Download report now