In this article we will talk about PERUN’s approach to accelerated development: WHAT it is? WHY it matters? We will discuss differences between rapid prototyping and accelerated development, and discover the way PERUN’s products – LARA-100 and PowerDesk – help you build, test, and deploy power electronic solutions in a small fraction of time you would spend building them from scratch.

Accelerated Development: What? and Why?

Driven by the fast pace of progress in the field of power electronics and the growing diversity of applications, rapid prototyping has become the standard development method in many industries and also in academia, where limited time and financial resources demand quick development of sub-optimal solutions and proof-of-concept prototypes. The typical development cycle is the following one: In the first step, we gather the initial requirements, asses the development and production costs, make the initial trade-offs, etc. As a result, the initial specification of the device is obtained, which is used to build a prototype in the second step. The prototype should be a fully functional device, satisfying a majority of the initial requirements. During prototype development, however, much of the initial specification often needs to be adjusted, polished, and sometimes even completely re-written. This is the experimentation step, when different architectures are compared and benchmarked. A good prototype should not only validate the requirements, and produce final blueprints for the serial production, it should also be a window into the future, providing guidelines for development of consequent products. In the third step, the blueprint is produced at large and pushed into the market. More and more often, however, the mass-production step is omitted. Modern economy requires small series of highly customized products, and many companies are targeting small and ever-shifting niches of customers. In these cases, a prototype becomes a product in its own right, and ability to quickly adopt and modify existing offer outweighs optimality of the final design.

Each power electronic device has several distinct layers (or stages). The core of every power-electronic unit is the power stage, which handles the energy flow by means of fast switching devices, such as IGBTs. These switching devices are typically managed by digital signal processors (DSPs) or other digital control devices. Digital processor, together with accompanying interface circuits and drivers, as well as communication circuits, is typically referred to as the control stage. An intrinsic part of this stage is the firmware which the processor is executing. The firmware comprises of control codes, communication protocols, software-level safety procedures, etc. On top of everything is the supervision stage, typically a PC software which enables a holistic view of the functionality and state of the lower stages. Obviously, the development process  spans a very broad skill-set and requires a significant amount of time. In fact it is very unlikely that a single engineer possess the required expertise and experience necessary to build a reliable power electronic product on his own. We never met such an engineer. Have you?

The reality is that usually the development team will not bee broad enough, and that the time constraints will be too strict. Even if the constraints are somewhat loose, spending too much time in developing a new product without being able to actively offer it on the market may cause a significant losses in terms of missed opportunities. At the end, you may find yourself holding a perfect device which no one is interested in.

The basic idea of the accelerated development process, as we see it in PERUN Technologies, is to use pre-built components whenever possible. Assembling a power electronic device should be like playing a game of puzzle. We should be able to combine different components with one another, so that the development time for new devices with innovative functionality is reduced, and the frequency of time-to-market cycle is increased. If you are only interested in building a custom power stage, using advanced topology and/or untested technology, do it! But why would you need to bother yourself with interfacing with the controller as well, or with writing low-level communication codes, or with developing a supervisory-control software! On the other hand, if you are playing with advanced control algorithms applicable to some non-standard micro-grid scenario, then do it! But do not bother yourself with the switching circuitry of the power stage! Build only what you would like to customize, using the expertise you poses, and use available off-the-shelf solutions for the other parts of the system.

LARA platform is PERUN Technologies answer to the challenge of accelerated development.

What is LARA-100?

LARA-100 is an open R&D platform in the area of power electronics and electrical power engineering in general. It bundles several hardware and software components and provide tools for automating reconfiguration, control code development, validation and testing. Importantly, it performs all of this while not compromising on reliability and safety measures! In fact, LARA-100 is a highly capable replacement for the standard, much more rigid and less flexible, laboratory test bench.

LARA-100 Power Stage

LARA platform ships with two distinct power stage components.

The first one, LARA-100 PS, has been built around a conventional three-phase converter bridge. Being one of the most universal topologies, it can be reduced to one of several DC-DC (four-quadrant chopper, buck or boost converter, or an interleaved versions of either) and DC-AC (single-phase inverter, three-phase inverter) converter topologies. It therefore covers a variety of DC applications (DC motor drive applications, photo-voltaics, battery or fuel-cell conversion systems, and switched voltage regulators) and AC applications (synchronous or induction motor drive, UPS applications, grid-connected controller applications, including: static VAr compensator, active filter, etc.). Additionally, connection of two LARA-100 units in a back-to-back topology further expands reconfiguration capacities of the installation.

The second one, LARA-100k PS, has the same topological and functional features, but is custom made and built using advanced SiC technology and is capable of operating in the 100 kHz range. If you are interested in learning more about this product, please contact us.

LARA-100 Motherboard

LARA-100 Motherboard is the central component of the LARA platform, binding all other components together. The Motherboard connects the controller (TMS C200 series DSP, such as TMS320F28335, for example) to the LARA system. It enables reconfiguration, and also ensures proper functionality of the protection circuits. Combined with LARA-100 expansion boards it dramatically expands the applicability of the overall solution. The expansion include LARA-100 Application Boards, LARA-100 Communication Boards and LARA-100 GPIO board.

PowerDesk

PERUN PowerDesk (PPD) is a Windows PC application, which govern the process of LARA-100 utilization, incorporating supervisory control functionality together with a set of data acquisition and signal processing tools. PowerDesk provides a structured, project-based environment supported by a number of built-in tools which greatly simplify hardware development, validation and testing. The Scope tool, in combination with Real-Time Data Acquisition (RT-DAQ) Module, enables software oscilloscope-like functionality, supporting triggering and decimation, while offering an effective visualization system. Essentially, Scope enables waveform visualization for an arbitrary variable defined in the controller. Tag Explorer enables online access (reading and writing) of all variables defined in control and communication code. It can be used for handling the control execution (run/stop, etc.), online modifications of different control parameters, debugging and testing. The obtained results, measured and/or calculated, can be analyzed using the Signal Processing and Analysis Toolkit. All the mentioned functions and tools combine and complement each other to create a powerful and safe environment for development, debugging and testing.

Accelerated Development of the Control Code

If you are a MATLAB/Simulink user, the control code for the LARA platform may be automatically generated from appropriate Simulink models (the so called autocoding functionality). The support includes a library of hardware-specific blocks and functions, including setup and execution routines for establishing a real-time communication with PowerDesk. PERUN provides several beginner-friendly templates in order to bootstrap the development for novice users. In addition, several examples are also provided, enabling you to build your knowledge gradually and gain experience in a variety of specific application fields. If you are interested to know more about these examples, please contact us.

MATLAB autocoding environment implements generation of the C code from the model file. The C code can then be compiled by an appropriate compiler, producing a binary file which is downloaded into the controller (.out file). From the .out file, PowerDesk is able to extract the list of all code variables, their data type and memory addresses. This feature provides direct access for reading out and writing in the values of all variables Tag Explorer and also for accessing their waveforms through Scope.

All LARA 100 hardware and software components meet yet another mandatory requirement—reliability of the tool chain. It is crucial, especially during the development and testing stage, that control unit and accompanying software maintain full control over the execution of control code and state of all the peripherals in all operating conditions, regular ones, such as downloading of the new code, as well as fault conditions, e.g. task overrun situations.

LARA-100 testing capabilities extend to even the most demanding user’s needs. In the order of complexity Tag Explorer comes first as a basic tool with the most direct feel for the data, namely its content, location and format (data type). It provides access to every code variable, every parameter or configuration register content. The main visualization tool is Scope. It provides comprehensive eight-channel oscilloscope functionality over the underlying sampling period (synchronized with the PWM period). There are three types of scope functions currently supported in PowerDesk,

1. Signal Scope specifically designed for transient response visualization, it depicts signals as functions of time;
2. Spectrum Scope tailored for spectrograms and other frequency-dependent quantities, such as filter amplitude characteristics;
3. XY Scope used to visualize relative dynamic response of two or more selected signals; it plots one signal as a function of another;

The Signal Processing and Analysis Toolkit considerably boosts Scope applicability and the power of LARA-100 system in testing application. As an illustration, here are some of the functions supported by the toolkit: defining custom signals from mathematical expressions, point-wise transformations of signals, point-wise operations on a pair of signals, filtering signals, spectral analysis, etc.

Finally, Scripting functionality of PowerDesk software enables the user to access the LARA-100 platform easily using many higher-order languages, including MATLAB, Python, Java, etc. Each active PowerDesk instance acts as a server, listening for client requests on a dedicate IP port of the host machine. The client program sends requests to the PowerDesk instance as if accessing a remote procedure. Additionally, the protocol allows the client to operate on a different machine so long as it is on the same network as PowerDesk host. The scripting functionality facilitates many additional opportunities to the user, development of advanced diagnosis procedures, automation of common and repetitive tasks, building graphical user interfaces, etc. Importantly, through PowerDesk, each client application maintains direct access to the LARA-100 hardware.The figure above shows fast aperiodic response of the reactive power-carrying current component (iqm – red trace) in the first test. The active power component idm (blue trace) stays unaffected, as required.

Conclusions

This blog has introduced LARA-100 platform, our answer to the problem of accelerated development for University Labs and Industrial R&D Facilities. The following blogs will introduce each and every component of the platform in more detail. If you are interested in our products, or if you see other opportunities for collaboration, we are always happy and eager to hear from you. Contact us!