Modeling and stability analysis of MTDC grids for offshore wind farms: A case study on the North Sea benchmark system

2013

Self Cite

257

122

Abstract-Following a converter outage in an MTDC grid, it is critical that the healthy converter stations share the power mismatch/burden in a desirable way. A fixed value of powervoltage droop in the DC link voltage control loops can ensure proper distribution according to the converter ratings. Here a scheme for adapting the droop coefficients to share the burden according to the available headroom of each converter station is proposed. Advantage of this adaptive (variable) droop scheme for autonomous power sharing is established through transient simulations on an MTDC grid with four bipolar converters and DC cable network with metallic return. Results for both rectifier and inverter outages under two different scenarios are presented. Post contingency steady-state operating points obtained from transient simulation are shown to be consistent with those derived analytically. Impact of varying droop coefficients on the stability of the MTDC grid is established. An averaged model in Matlab/SIMULINK which has been validated against detailed switched model in EMTDC/PSCAD is used for the stability and modal analysis.

Section: B DC Cable Network Modelingmentioning

confidence: 99%

Adaptive Droop Control for Effective Power Sharing in Multi-Terminal DC (MTDC) Grids

2013

Self Cite

257

122

“…The readers are referred to [14], [15] for further details. It should be noted that the converter outage was simulated by opening both the DC side and the AC side breakers at the respective converter pole.…”

Section: Positive Pole Networkmentioning

confidence: 99%

“…2(b)). The converter AC side current was transformed into the AC system common d − q reference to solve the current balance equations [14], [15].…”

Section: Combined Ac-mtdc Grid Modelingmentioning

confidence: 99%

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System Frequency Support Through Multi-Terminal DC (MTDC) Grids

Majumder²,

2013

Self Cite

175

Abstract-Control of the converter stations in a multi-terminal DC (MTDC) grid to provide frequency support for the surrounding AC systems is the subject matter of this paper. The standard autonomous power sharing control loop for each converter is modified with a frequency droop control loop. The objective is to minimize the deviation from nominal AC system frequency and share the burden of frequency support among the converter stations of the MTDC grid. The effectiveness of the frequency support is demonstrated through nonlinear simulation of a test system consisting of three isolated AC systems interconnected through an MTDC grid with four converter stations. An averaged model of the MTDC grids is developed to carry out modal analysis of combined multi-machine AC-MTDC systems. Modal analysis is used to characterize and substantiate the time domain behavior in presence of frequency droop control. It is established that appropriate droop control loop for the MTDC grid converters could be effective in reducing the deviation from nominal AC system frequency provided the sensitivity of the system eigen-values to changes in control parameters (e.g. droop coefficients) is accounted for apriori through modal analysis.

“…Compared with the mature point-to-point HVDC (PTPDC) connection for offshore wind power, multiterminal HVDC (MTDC) technology is more capable in sharing and transmitting bulk wind power from multiple areas [13] [14]. Master-slave control (MSC) and DC voltage droop control (VDC) schemes are two major control patterns for VSC-HVDC.…”

Section: Introductionmentioning

confidence: 99%

Investigation on Economic and Reliable Operation of Meshed MTDC/AC Grid as Impacted by Offshore Wind Farms

Wei

Wang

et al. 2017

 Abstract-The influence of complementarity, balancing, connected grid and control of offshore wind power generation on the economic and reliable operation of hybrid multi-terminal HVDC (MTDC) and AC power system is investigated in the paper. The variances of distribution curve of both transmission loss of AC/DC system and voltage of critical nodes assessed by cumulantbased method are used to demonstrate how the different complementarity conditions, generation balancing strategies, MTDC grid topologies and control schemes affects power system operation. In this paper, a study case of 16-generator 68-bus power system connected with three offshore wind farms is presented. The variance indices of transmission loss and voltage magnitude are calculated and then compared under different complementarity levels, active power balancing strategies, HVDC transmission systems and controls respectively. The analysis reveals that higher complementarity and multi-machine balancing strategy can effectively reduce system operational cost and enhance operational reliability. Compared to the point-to-point topology, the control pattern and parameter setting of multi-terminal topology are two key factors to determine its impact on system operation.