Multi-interface Power Hardware in the Loop for MVDC Power Systems

  Copyright: RWTH Aachen Physical PHIL testing platform

The objective of this project is to design and build a Pow- er Hardware in the Loop (PHIL) testing platform to validate innovative control strategies for stability in MVDC systems with multiple generators and multiple constant power loads (CPLs).

Research work is ongoing to compare various power dis- tribution solutions for the all-electric ship (AC and DC, i.e. MVDC versus HFAC). From here it emerges that one chal- lenge of the MVDC option is the lack of multi-interface PHIL testing platform to validate controls in detailed multi-gene- rators multi-CPLs systems. The single-interface PHIL setup for power converters enforces emulated electrical variables at one port of the converter, while the other port is connec- ted to the physical system (generator or load). In particular, for testing stabilizing controls in interface converters for MVDC systems, we should connect at one port the physi- cal generator or the CPL, and emulate the electrical varia- bles at the other port, based on the real time simulation of the detailed and complex model of the rest of the system. However, the complexity and cost of implementing the full physical system to one port of the converter make this im- plementation unfeasible. This challenge is addressed by our PHIL solution, which feeds emulated variables to both ports of the converters under test.

In this multi-interface PHIL platform, the multi-generators and CPLs systems connected to the interface converters under test may be both simulated in real time simulation software. The only physical hardware is the power converter and its controller, which is the focal point of our research in MVDC systems. In this platform we can represent the de- tails and complexity of the modeled portion of the power system and components, such as gas turbines, synchronous machines, CPLs at a broad extent although within the limits of the power interfaces of the PHIL platform. The main chal- lenges of the platform are stability and accuracy, because of the interaction of dynamics, time delays, and measurement noise of multiple interfaces.

In order to solve the challenges above, high performance power amplifiers with sufficient bandwidth and high quality sensors are extremely important. A sample platform has been built in our lab to test the feasibility of this PHIL se- tup. The device under test is DC/DC converter that feeds a single CPL from a single generator DC power sys- tem. Detailed generator and CPL models are simulated in RTDS. The power signal at the two ports of the DC/DC con- verter are voltage of the generator and the current of the CPLs respectively, and they are physically fed by the Flexible Power Simulator (FlePS). The FlePS works as power ampli- fier, tracking voltage and current reference signals calcula- ted in real time in RTDS. The measurements from the sen- sors of the DC/DC converter are fed back to RTDS and drive the simulation.

This multi-interface PHIL platform is suitable for testing, in repeatable conditions, converters connected to generators, which may be unavailable or difficult or expensive to build, such as wind farm, PV, and loads with complex structures.