Towards truly modular power electronics

Hard real-time controllers are ubiquitous !

Power converters are becoming part of everyone’s life. From the smallest battery chargers to large wind farms, going through electrical mobility, the range of applications is very broad. Nevertheless, these systems have in common that they must operated - at any point in time and in a reliable manner - using appropriate current, voltage and power control algorithms. Such algorithms guarantee that the converters operate as expected, provide the desired power with a suitable quality, and respond to security measures when necessary.

 

Different needs for different applications

In low-power applications, these tasks are usually performed by low cost integrated circuits. Respectively, medium-power applications often require the use of one or several digital signal processors, while most multi-megawatt systems require a distributed control architecture, typically relying on several coordinated networked controllers.

 

Modularization for a better standardization

In recent years, power conversion systems have evolved towards an increased modularity, mostly due to the related benefits in terms of scalability, product standardisation, ease of maintenance, etc. This is not only true at the plant level, but also inside each sub-element, down to the power semiconductors. In fact, most mid- to high-power converters are now made of standard blocks that are assembled together to form a single large system. In some cases, the number of building blocks can even be in the range of thousands!

 

Challenging control applications

This increased modularity also leads to an increased complexity regarding the control of these systems, especially for the hardware that executes the necessary algorithms. In fact, due to performance concerns, the existing control hardware is not much modular nor standardized, but remains highly application-specific and tailored for a given project or product.

 


Large-scale systems are complex


Standardizing control makes power conversion systems more flexible


Simplifying the control implementation

Key benefits

Imperix currently develops a communication technology that helps the manufacturers of power converters to simplify their systems by standardizing a part of its control. This involves two main actions. On the one hand, all the communication media (wires, optical fibers, etc.) that connect the power converter systems to the controller(s) are replaced by one single optical fiber. On the second hand, the communication system guarantees an extreme flexibility and scalability, hence leading to reduced engineering efforts, time and costs.

 

The RealSync technology

In order to achieve these results, imperix relies on an innovative way to organize the control systems, which become highly modularized and distributed, similarly to how the power stages are now commonly implemented. The key to enabling this distribution of the control in standardized sub-elements is first to guarantee an excellent synchronization of all elements and second to provide a very low-latency communication mechanism between them. These two aspects constitute the key innovation in imperix’s so-called RealSync technology.

 

modules-and-control
Unhierarchized and centralized control


modules-and-control2
Hierarchized and distributed control


In fast closed-loop control applications, such as needed for the control of power converters, the natural dynamics are generally fast, which sets several demanding requirements, such as follows:

RS_icons_time Synchronization

In multi-modular systems, or when power semiconductor switches are assembled in series or in parallel, their operation must be precisely coordinated in time, as precisely as down to a few tens of nanoseconds.

RealSync guarantees a time accuracy better than 50ns throughout the control network.

RS_icons_scalability Scalability

To be truly highly reusable, a control system must be flexible enough to a broad product range, independently from the number of modules or the final application.

With RealSync, additional power modules or controllers can be added to the system at any point in time to extent its capabilities.

RS_icons_bw Bandwidth

With up to a few thousands modules in a single converter, bidirectional communication between each elements or to/from the central intelligence must be fast enough to allow all modules to be exchange data within a few microseconds.

RealSync used multi-gigabit Ethernet-based communication for maximum data bandwidth.

RS_icons_redundancy Redundancy

Utility-scale power conversters are often part of vital infrastructures that must guarantee high degrees of reliability. Therefore, as for the power stage, the control system must possess some redundancy.

RealSync has been designed from the start with such contraints and guarantees at least N+1 redundancy.

Complexity handled through a control network


Where power electronics and communication technologies meet to enable distributed control and modulation


Introducing a real-time distributed control technology

Augmenting Ethernet with high-precision time dissemination and low-latency communication mechanisms, imperix creates a real-time communication technology that supports the operation of large-scale power conversion systems.

In practice, this enables the implementation of fast local or global control loops (<100us) at any level across a pyramid-shaped network tree. Besides, thanks to the high-precision synchronization mechanism (<20ns), parallel- or series-connected switches can be operated from anywhere in the network, the same way as for interleaved subsystems.

The early technology development started in 2014 with the support of the TheArk Energy fund. In 2015, imperix has validated, patented and demonstrated the core of this technology. Today, imperix is working towards the full development of this technology as well as its integrations in future products.

RStopology-tree
Pyramidal control network