FPGA Technology and Software IP in Power Electronics Applications

Electric motor power savings: The true impact of the device selection

It’s been a while that I want to write a post to discuss about the real impact of the electronic/semiconductor device selection on the energy consumption of electric motor-driven systems.  It seems that every chip on the market has capabilities for “more energy-efficient” motor control but I never saw a single article actually showing that. The real question: is this possible?

As a first step, for those interested in the subject of power savings or energy-efficient motor drive systems, I highly recommend to read the latest report of the Internation Energy Agency called “Energy-Efficiency Policies for Electric Motor-driven Systems” published last year (2011). Like any similar report published in the last 20 years on this subject (like this one , this one or this one) the recommandations are :

1- Make sure your motor sizing (nominal power) is correct for your application. In large industrial motor applications this can have a very significant impact on the power consumption. The rationale is easy to understand, why would you drive a Hummer when the only thing you need is a Toyota (keeping in mind that the best way to save energy is to keep them in the garage) ? Correct motor sizing has nothing to do with the device or even motor control driver selection.

2- Use Variable-Frequency Drives (VFD). That’s the famous 20-50% power savings we see everywhere. Knowing that power output is the product of the torque and the speed, instead of fixing motor speed at nominal speed and varying the power output by varying the torque only, the idea of VFD is to regulate power using both speed and torque (hence the name variable-frequency).

It may be seducing to think that since the VFD motor control software is running on an electronic device, then it MUST certainly have an impact on the performance but it is not true. It’s all in the software and any energy-saving motor control software feature can be implemented on any kind of electronics device, wheter it is a MCU, a DSP or a FPGA:

- VFD via scalar or vector control

- flux optimization of induction motor and permanent magnet synchronous motors

- power switching and time-harmonic losses via advanced PWM algorithm (like this excellent recent article from Xilinx)

Why ? Because you need to think that electric motor are electro-mechanical devices and even though you think those system have “fast dynamics” they are still very slow (kHz range) compared to the computing bandwidth of most electronic devices on the market (MHz range). And even though you crunch number infinitely fast, you will always be limited by your power converter PWM frequency to keep switching losses in the power converter at a low level.

OK. But what about spindle drives running at 30,000 RPM ? Yes, those application needs high control bandwidth but they are not “power applications” since the motor that are typically used are low-power motors but mostly because the motor is not used as an electro-mechanical power converter (focus is on transfering energy) but rather as an eletro-mechanical actuator (focus is on the precise dynamics).

Bottom line:  Device selection has no impact on electric motor power savings. It’s all about the correct motor sizing for the load profile, the correct power converter sizing and the motor control software (optmized for the application itself). Are there devices where this software is easier to develop and integrate ? That’s another question that relies more on the design tools and business model of the device manufacturer than the device itself.

 

FPGA-based motor control – A Review of 2010

This time of the year is a great moment to take a few steps back and observe what the last year has been made of and to speculate on what we can expect in 2011. We already know that 2010 has been a very important year for FPGAs with 47% growth in sales (check Kevin Morris’ recap article ‘Banner Year: 2010 in FPGAs in Review’). With no surprise, 2010 has also been a great year for FPGA-based motor control / power electronics apps, here are the highlights:

FPGA vendors and motor control kits

After Altera released 2 motor control kits in 2008 (Arrow’s MotionFire and EBV’s Falcon Eye), Xilinx and Microsemi have both announced the release of a new FPGA-based motor control kit. Actel/Microsemi did initially demo theirs at ESC in April 2010 while Xilinx have announced their new Targeted Design Platform at SPS/IPC/DRIVES 2010 conference.

At the same conference, Altera has announced new EBV’s three-level inverter demo for motor control and solar power conversion applications. It is interesting to see such demo featuring advanced inverter topologies (i.e. something different than usual two-level inverter) in which FPGA can uniquely differentiate and provide application’s improvement (three-level inverter reduce time-harmonics losses in the converter and the load but require more computation than conventional two-level inverter, more in this article showing 44% power loss reduction in wind power conversion apps).

It is worth mentionning that National Instruments – with their FPGA-based CompactRIO platform – has made noticeable appearance at the EETimes Virtual Conference on Motor Control (having Altera & Texas Instrument as Gold sponsors) with NI’s VP of Industrial and Embedded Product Lines as keynote speaker.

Alizem COTS Motor Control IP

In May 2010, Alizem has released its COTS Motor Control IP for Pump and Fan applications for Altera FPGAs. It is the first application-specific COTS Motor Control IP to be designed and sold as a plug-and-play virtual chip and meant to take advantage of FPGA technical capabilities to increase application performance and to be used by non-motor control and non-FPGA experts (see this blog articles article Motor Control IC vs Motor Control IP and also Why FPGAs are better than DSP for Motor Control ?). This IP has been demoed at ECCE2010 conference and has been the object of an article published by EETimes Programmable Logic Designline.

Some important articles

In August, Motion Control Association published an article of FPGA Motor Control (“Playing the field“) featuring Alizem, Xilinx and National Instruments. A great article on FPGA-based motor control has also been published by Xilinx (“Creating a Greener Future for Industrial Motor Control“) in october.

FPGA-as-a-platform

I think one of the biggest event in 2010 has been one that’s impacting not only Motor Control but any high-level embedded system applications which is the paradigm shift toward “FPGA-as-a-platform”, that is considering the FPGA not as a chip (like a DSP or MCU) both rather as a component (IP) integration platform (like a “software” PCB). Of course, this idea is not new (i.e. that’s not the first year that we are speaking about the concept of system-on-chip), but many important event have happened in 2010 that’s making it a reality.

One of them is Cadence’s EDA 360 manifesto (that’s directed to the whole electronic industry not only FPGA SoC design) which is about “apps-driven” design, i.e. making the application’s requirements at the center of system design instead of the current hardware-first paradigm. Apple’s iPhone has been used by many people in the industry as a concrete example of this new approach to system-level design (Steve Leibson, Daniel Nenni, Kevin Morris, Jim Turley, Brian Bailey and many others).

This shift in design approach is opening a system-level IP/apps era providing new levels of productivity to the system designer (Altera has already upgraded its own tools in that direction with Qsys). That’s exactly what’s needed in complex applications such as motor control where designers are still loosing so much time learning tools and demystiyfing motor control while they could spend this time working on their true product’s differentiation (if you have doubts about this, attend a motor control webinar given by any motor control IC vendor).

Is anything important missing ?

Please let me know. Meanwhile, I wish you success in 2011 in your FPGA-based power electronics applications design ! Thanks for your interest in reading this blog !

Smart Grid : An opportunity for FPGAs in Home Appliance space?

According to this EEtimes article, the Association of Home Appliance Manufacturers (AHAM) took the opportunity of being at the United Nations Climate Change Conference in Copenhagen to release a very well written 25 pages document titled “The Home Appliance Industry’s Principles & Requirements for Achieving a Widely Accepted Smart Grid“. In this document, the AHAM – based on its unique perspective to the Smart Grid Vision – is intended to provide three essential requirements for the Smart Grid’s interaction with consumers in order for the Smart Grid to be successful. Among those three requirements, the second one is the most interesting from a technological (embedded systems) perspective :

Communication Standards must be open, flexible, secure, and limited in number

This requirements then splits in four requirements : open, flexible, secure and limited in number.

From a FPGA perspective, flexible sounds very familiar because its embedded in the name of the technology itself : Field-Programmable. But is this flexibility may solve problems and help the development of Smart Grid enabled homes ? According to the authors,

Smart Grid enabled homes will have varying levels of sophistication, depending on the type of appliances, devices, and networks that are installed. There are many configurations, combinations, and options for energy management inside the home. Some possibilities could include a simple email notice for a manual demand response by the consumer, a smart meter directly communicating with a specific appliance to ask it to turn on and off, or a meter communicating with a Programmable Communicating Thermostat allowing for temperature adjustment.”

From now to the moment that every appliance is going to talk the same language – even with such standardization, that is limited to the US only – one can think that this is going to be long and costly. This process has been started since a long time on industrial side (with many types of protocols) and there is still no single communication standard. Altera and Xilinx are actually taking advantage of this massive willingness to connect but protocol-segmented environment. Their programmable chip solutions enables them to sell a platform on which industrial equipment manufacturers can then use to build their own platform which is going to be finally customized with a regional/market-specific set of IP blocks. This approach enables flexibility while also reducing costs and time to market.

Is the same idea is going to happen in Home Appliance space ? As we all know, this high-volume market is very focused on costs. Not considering smart grid, a chip to chip price analysis would probably give only small chances to FPGAs. But considering that :

- according to a recent Whirlpool survey, 84% of consumers choose energy – not water or time – as most important when it comes to home appliance efficiency, and that

- according to Electric Power Research Institute, the implementation of Smart Grid technologies could reduce electricity use by more than 4 percent by 2030 providing a mean savings of $20.4 billion for businesses and consumers,

… there may have an opportunity there for FPGA chip manufacturers. Among the most important ones, Altera is already there.

Motor Energy Efficiency, Power Factor and Actel mixed-signal FPGAs

Here’s a very extensive article written in two parts (part 1 here, part 2 here) by John Smitty of Actel Corporation.

According to Smitty, “the potential energy savings are staggering. Over 40 million electric motors are used in manufacturing operations in the United States alone. Electric motors account for 65 to 70 percent of industrial electrical energy consumption and approximately 57 percent of all electrical consumption worldwide. Saving even a few percent of the world’s estimated 16,000-plus terawatt-hours (TWh) annual consumption of electricity amounts to several hundreds of trillions of watt-hours per year.”

High-performance motor control design is one way to achieve those energy savings and this may be done using DSP chips but those rapidly limited because “they are sequential state machines that can only do a very limited amount of computation in a single clock cycle“. Here’s how the author explains why mixed-signal FPGAs can overcome this situation:

Unlike DSPs, the mixed-signal FPGA can do many computations in parallel, and can do certain specialized computations such as computing sines and cosines (which are generally required by these algorithms) much faster than most any DSP microcontroller, at a lower cost per computation. As a bonus, FPGAs invariably consume less power than any type of microcontroller doing the same function“.

Also, “FPGAs offer much flexibility. For instance, if your algorithm requires an extra PWM, it can easily be added to an FPGA solution. PWMs pre-built into a DSP or ASSP integrated circuit may or may not perform the PWM algorithm you want, or take into consideration the needs of your power circuitry. With an FPGA, the PWM can be customized exactly to your specifications. An FPGA can be adapted to accept most any type of feedback sensor (encoder, Hall effect, or tachometer, for example) or a sensorless algorithm based upon motor back-EMF measurements can be implemented“.

Using NI CompactRIO for FPGA-based motor control in Factory Automation

Here’s a recent article written by Greg Crouch, Embedded Systems Business Director at National Instrument., on the topic of FPGA-based motor control for Factory Automation.

Embedded-machine builder EUROelectronics reduced power use with FPGA-based field-oriented control (Source : National Instruments)

FPGA-based algorithm control delivers better efficiency than microprocessors can achieve. A wide range of control-system algorithms are available, including trapezoidal, sinusoidal and field-oriented.

Trapezoidal, or six-step, control is the simplest but lowest-performance method. For each of the six commutation steps, the motor drive provides a current path between two windings while leaving the third motor phase disconnected. However, torque ripple causes vibration, noise, mechanical wear and greatly reduced servo performance.

Sinusoidal control, also known as voltage-over-frequency commutation, addresses many of these issues. A sinusoidal controller drives the three motor windings with currents that vary smoothly. This eliminates torque ripple issues and offers smooth rotation.

More information on NI CompactRIO can be found directly on their website.

Altera FPGA in Motor control solutions for industrial applications

Here’s a recent brochure from Altera on Motor control solution in industrial space.

While microcontrollers and DSP devices may be well suited to certain aspects of motor control systems, they lack flexibility to support motor control IP and interfaces in hard logic. With our Cyclone® III FPGA, you can integrate processors, digital logic interfaces, DSP functions, motor control IP and multiple Industrial Ethernet protocols into one device, reducing board size and complexity. Operating across industrial communication networks, motion control solutions with drive-controlled motors can be very energy efficient. Aside from saving power, this can also lead to net cost savings in the long run.”

Source: Altera

It may be important to mention that this type of system architecture in industrial space – with industrial ethernet connection – is “smart-grid” ready, i.e. information is going in two direction : to the motor drive system for motor control and from the motor drive system for condition-monitoring purposes.

In that latter case, the motor drive system may become a “broadcaster” of useful information to the main control system if the Motor Control IP contains fault-detection and diagnosis algorithms that are running simulataneously with torque and speed control algorithms.

Altera FPGA and Energy-Efficient Motor Control IP

Here’s a recent article published in Industrial Embedded Systems magazine on the topic of using FPGA to increase flexibility of design, power savings are costs reduction. The article has been written by Jason Chiang, Sr. Technical Marketing Manager Industrial Business Unit, Altera Corporation.

This article has a couple of interesting points regarding the use of Motor Control IP to reduce overall system costs (which is certainly a disadvantage of FPGA chips being more expensive than traditionnal MCU/DSP chips) :

Motor control IP is designed to provide a very high-performance interchangeable platform. The practical motor control IP for an application is achieved by selecting and integrating the right combination of IP. FPGAs are flexible and can support many types of communications protocols, motor control IP, and industrial I/O interfaces on one device or platform.

Another advantage of implementing the motor control IP (and network connectivity) on the FPGA is that it mitigates the risk of product obsolescence. With long product life cycles, FPGAs are built with industrial longevity, system flexibility, and reliability in mind. Designers can modify their systems or migrate to new generations of FPGAs with ease. Contrast this methodology to MCUs or DSPs, which require intensive software resources and involve long development cycles when moving to a new processor architecture to update any hardware features.”

Altera’s CEO speaks on FPGA-based Motor Control for power savings

In a recent article, Altera’s CEO, John Daane, has clearly expressed the idea that FPGA are well positionned to enable “technology which allows people to save energy“.

According to Daane, “66 per cent of the world’s industrial electricity runs motors, but only five per cent use variable speed drivers. FPGAs can be used in most motor controllers because they are programmable”. Those figures are comparable with other well-known published numbers on world’s energy consumption, such as those of IEEE-Fellow Dr. Bimal Bose’s article on the environmental impact of power electronic applications.

This article also reveals the existence of two new Altera FPGA-based Motor Control development platforms : Arrow’s Motion Fire and EBV’s Falcon Eye. Those platforms are meant to design motor controller for industrial applications using PMSM, BLDC or induction motors. Both kits are currently bundled with BLDC motors. You can even get a feeling of the Motion Fire on YouTube.

Those are the first Altera platforms for Motor Control but not the first FPGA-based. There has been Xilinx-IRF Accelerator Platform but we don’t hear about it anymore. The second one has been the Fusion-based Actel-Ishnatek platform who is still available for purchase.

With the recent rise of energy prices and the need for power savings, is this the first sign of a new battle in the motor control field ?