Abstract

This diploma thesis presents a technique for simulating and testing of power devices in real time with real laboratory equipment. This technique is called Power- Hardware-In-the-Loop (PHIL) and is a novel tool for testing as it features the interconnection of a piece of hardware in the real world, called the Hardware Under Test (HUT) with a Simulated System running in a Real-Time Simulator. A Power Amplifier (interface) is necessary to perform the coupling of the hardware and simulated system.

The first section, of the thesis, contains general information about Renewable Energy Sources and microgrids since this is a useful environment for conducting PHIL experiments.

Moreover the Real Time Digital Simulator (RTDS), that emulates the simulated system, is briefly described followed by a summary of the PHIL technique as well as issues related to PHIL simulation stability and accuracy. Reference is made to the criteria Nyquist, Routh and Root Locus, which are used for determining the PHIL stability.

The second section of this thesis begins with the characterization of the laboratory power amplifier in two different ways. Theoretically considering its output filter, and practically through experiments in steady state and dynamic conditions, assuming that is a “black box”, using Matlab Identification toolbox in order to process the data. Then we present and compare five different methods in order to examine PHIL stability, namely: Nyquist, Routh and Root Locus stability criteria, SimPower-System simulation circuit (simulink implementation with SimPowerSystems library) and Signal flow simulation (simulink implementation with Simulink library.). The comparison shows gaps and errors of existing methods and new methods for determining the PHIL stability are proposed. Then followed the presentation and comparison of two methods from literature for determining the PHIL accuracy and the accuracy of the voltage divider circuit is examined with and without the addition of the power amplifier.

Finally, the Low Voltage Ride Through capability of Distributed Generation is presented and taking into account all the above the stability of a PHIL experiment with the laboratory photovoltaic inverter as HUT is examined. PHIL tests are executed using a LVRT simulated network according to standards and the behavior of the physical inverter during voltage dips is examined.

Key words : Power-Hardware-In-the-Loop (PHIL), microgrid, Power Amplifier (Interface), Real Time Digital Simulator (RTDS), Hardware Under Test (HUT), Simulated System, Nyquist, Routh, Root Locus, Low Voltage Ride Through (LVRT), photovoltaic inverter

Author: Dimitris Barakos

Responsible PhD: Panos Kotsampopoulos / kotsa@power.ece.ntua.gr

Supervising Professor: Nikos Hatziargyriou / nh@power.ece.ntua.gr

PDF: Full version (Greek) and Short version (English)