Laboratory Testing of Multi-terminal VSC-HVDC

Abstract

This report documents laboratory testing of multi-terminal HVDC system in down-scaled model. First, analytical method for solving DC power flow is introduced and explained. Power flow equations are set up and implemented by means of admittance matrix and Newtons method. Second, laboratory test set-up is presented. Necessary components for steady state tests are described and control and monitoring system is developed. Third, steady state test results are presented and compared with analytical solution of DC power flow. Finally, conclusions on the results and further work are discussed.Analytical method consists of simple DC power flow equations. Newtons method is explained and Matlab code for finding the solution using iterations is presented. Some simplifications for lower number of power flow equations are made and justification for them is given.Laboratory test set-up consists of existing and new equipment. Existing equipment will be described briefly and references to relevant documents are given in the following chapters. Missing components in the system were ordered, custom-made or created in conjunction with the two. New equipment is introduced and any further improvements in making the model more realistic are suggested.Control system for the laboratory test set-up is presented. Existing components in the control system are described together with the description of the signal processing methodology. The structure of controlling the system, as used in the laboratory, is presented and user interface for controlling and monitoring the system is shown. A user interface program is described and code is given.Testing was conducted in organized manner adding the complexity to the test set-up gradually. Tests are presented so that every next test scenario would have something in common with the one before making the change in outcome easier to observe. Comments on the expected and laboratory values are given, whereas possible reasons for inconsistencies in the results are discussed.Work on building up a laboratory test system for studying dynamic changes in MTDC systems was started. Results are presented in the second part of the report. Further work for setting up mode true-to-real model of MTDC system is discussed. Any improvements on the existing hardware and software are brought out.