Multi-terminal VSC-HVDC system for integration of offshore wind farms and green electrification of platforms in the North Sea

This paper discusses a multi-terminal VSC-HVDC system proposed for integration of deep sea wind farms and offshore oil and gas platforms in to the Norwegian national grid onshore. An equivalent circuit of the VSC in synchronous d-q reference frame has been established and decoupled control of active and reactive power was developed. A three terminal VSC-HVDC was modeled and simulated in EMTDC/PSCAD software. Voltage margin method has been used for reliable operation of the HVDC system without the need of communication. Simulation results show that the proposed multi-terminal VSC-HVDC was able to maintain constant DC voltage operation during load switchings, step changes in power demand and was able to secure power to passive loads during loss of a DC voltage regulating VSC-HVDC terminal with out the use of communication between terminals.reviewe

Understanding of tuning techniques of converter controllers for VSC-HVDC

A mathematical model of a voltage source converter is presented in the synchronous reference frame for investigating VSC-HVDC for transferring wind power through a long distance. This model is used to analyze voltage and current control loops for the VSC and study their dynamics. Vector control is used for decoupled control of active and reactive power and the transfer functions are derived for the control loops. In investigating the operating conditions for HVDC systems, the tuning of controllers is one of the critical stages of the design of control loops. Three tuning techniques are discussed in the paper and analytical expressions are derived for calculating the parameters of the current and voltage controllers. The tuning criteria are discussed and simulations are used to test the performance of such tuning techniques.reviewe

Digital Variable Frequency Control for Zero Voltage Switching and Interleaving of Synchronous Buck Converters

Abstract-When a synchronous buck converter is operated with zero voltage switching (ZVS) and fixed frequency, the direction of the current in the output inductor is alternated each switching period. Thus the output current ripple of the converter is high to ensure zero voltage switching operation at maximum load. With interleaved outputs this leads to high circulating currents at low loads. In this paper, to minimize circulating currents at low loads, solutions for digital control of ZVS with variable switching frequency and interleaving control for bidirectional power flow are presented. The methods have been implemented in a DSP and verified by measurements

Power electronic : Converter, application, and design

Xvii,802 : 26 c

Power electronics : converters, applications, and design / Ned Mohan, Tore M. Undeland, William P. Robbins.

Includes bibliographical references and index.System requirements for accompanying CD-ROM: Windows 98 and Windows 2000.xvii, 802 p. :Gives a cohesive presentation of power electronics fundamentals for applications and design in the power range of 500 kW or less. Describes a variety of practical and emerging power electronic converters made feasible by the new generation of power semiconductor devices