Voltage Margin Method Research Articles

Voltage margin control for offshore multi-use platform integration

This paper discusses a multiterminal direct current (MTDC) connection proposed for integration of offshore multi-use platforms into continental grids. Voltage source converters (VSC) were selected for their suitability for multiterminal dc systems and for their flexibility in control. A five terminal VSC-MTDC which includes offshore generation, storage, loads and ac connection, was modeled and simulated in DigSILENT Power Factory software. Voltage margin method has been used for reliable operation of the MTDC system without the need of fast communication. Simulation results show that the proposed system was able to maintain constant dc voltage operation during fluctuations in the generation and changes in the demand. Moreover, it was able to secure power supply to passive loads during loss of a dc voltage regulating terminal and to perform a dispatch scheme where it is possible to buy, sell or store energy attending to the price in the electricity market

Dynamic Behaviour of Multi-Terminal VSC-Based HVDC after a Converter Outage: DC Control Strategy

aim of this paper is to evaluate the effect of DC-voltage control strategy on the dynamic behaviour of multi-terminal Voltage-Source Converter (VSC)-Based HVDC after a converter outage. In this paper, two dc voltage control strategies are considered: (i) standard voltage margin method (SVMM) and (ii) standard voltage-droop method (SVDM). The impact is evaluated in this paper using time-domain simulations on a simple test system using DIgSILENT ® PowerFactory TM considering a sudden disconnection of a converter-station. Simulation results demonstrate how important is the dc-voltage control strategy and the location/number of dc-buses involved in the dc-voltage on the dynamic response of the MTDC systems. The voltage margin control is capable of surviving a converter outage just if this converter is operating in constant power mode.

Design and Implementation of Multi-Terminal VSC-HVDC Transmission Systems for Offshore Wind Power Plants

This paper discusses a multi-terminal VSC HVDC system proposed for integration of deep sea wind farms and offshore thermal and nuclear platforms in to the 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 MATLAB/SIMULINK 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 switching, step changes in power demand and was able to secure power to passive loads during loss of a DC voltage regulating VSC-HVDC terminal without the use of communication between terminals.

Description and Comparison of DC Voltage Control Strategies for Offshore MTDC Networks: Steady-State and Fault Analysis

Estimates are that circa 40 GW of offshore wind power capacity is going to be installed throughout Europe by the end of this decade. In this scenario, a pan-European offshore grid network is needed in order to efficiently integrate large amounts of offshore wind into the different European countries’ transmission networks. In this paper, the dynamic model of a multi-terminal HVDC (MTDC) transmission system composed of voltage-source converters is presented. Afterwards, the dynamic models are used to compare four different methods for controlling the DC voltage inside MTDC networks, viz.: droop control, ratio control, priority control and voltage margin method. Lastly, a case study is performed in a four-node MTDC network and the different control strategies are compared during steady-state and an onshore three-phase fnult.

Development of a control system for a high-performance self-commutated AC/DC converter

A self-commutated AC/DC converter composed of controlled turn-off devices to be applied to future system interconnection is described. The advantages of a control system for this type of converter are: (1) commutation does not fail when the system voltage is decreased or distorted by a power system fault; (2) it needs no equipment for reactive power supply, such as static capacitors or synchronous rotating condensers, when used in a low short-circuit capacity power system; and (3) it can independently control active power through DC lines and reactive power from each terminal. The proposed back-to-back (BTB) control system using the voltage margin method was verified with a simulator, and the results demonstrated the excellent features of the high-performance self-commutated converter.

Novel control strategies for HVDC system with self‐contained converter

AbstractThis paper discusses newly developed control strategies of a self‐commutated converter applied to the HVDC system. An upper and lower power‐limited dc voltage control establishes high performance in a two‐terminal HVDC system. A voltage margin method to reverse dc transmission power also is introduced. Even when the communication system is shut down, if required, dc transmission power can be changed with the authors' proposed controls applied to the terminal control. Furthermore, the dc voltage control scheme with two‐stage voltage control characteristic is presented for multiterminal HVDC system use. When one terminal is collapsed, the multiterminal HVDC system can be operated because of the proposed control characteristics.Simulator studies were carried out to verify the proposed control performance in the two‐terminal HVDC system and successful test results such as power reversal and a terminal start‐up during other terminal operations are shown.