Stability analysis of VSC MTDC grids connected to multimachine ac systems

Chaudhuri, Nilanjan Ray; Chaudhuri, Balarko

doi:10.1109/pesgm.2012.6344647

Cited by 44 publications

(71 citation statements)

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“…The first step consists in expressing the abc vectors in the stationary frame as functions of their respective dqz equivalents. This 9 can be seen in the second line of (11)…”

Section: Voltage-based Formulationmentioning

confidence: 84%

“…Voltage sum SSTI dynamics derivation 1) Initial formulation: The SSTI dynamics for the voltage sum can be derived in a similar way as for the voltage difference. The starting point is indeed the SSTP dynamics of the variable given in (9) and recalled in (34a) for convenience. The first step consist in expressing the stationary frame abc vectors present in (34a) as functions of their respective dqz equivalents.…”

Section: ) Final Formulationmentioning

confidence: 99%

See 1 more Smart Citation

Generalized Voltage-Based State-Space Modeling of Modular Multilevel Converters With Constant Equilibrium in Steady State

Bergna-Diaz

Freytes

Guillaud

et al. 2018

IEEE J. Emerg. Sel. Topics Power Electron.

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This paper demonstrates that the sum and difference of the upper and lower arm voltages are suitable variables for deriving a generalized state-space model of an MMC which settles at a constant equilibrium in steady-state operation, while including the internal voltage and current dynamics. The presented modelling approach allows for separating the multiple frequency components appearing within the MMC as a first step of the model derivation, to avoid variables containing multiple frequency components in steady-state. On this basis, it is shown that Park transformations at three different frequencies (+ω, −2ω and +3ω) can be applied for deriving a model formulation where all state-variables will settle at constant values in steady-state, corresponding to an equilibrium point of the model. The resulting model is accurately capturing the internal current and voltage dynamics of a three-phase MMC, independently from how the control system is implemented. The main advantage of this model formulation is that it can be linearised, allowing for eigenvalue-based analysis of the MMC dynamics. Furthermore, the model can be utilized for control system design by multi-variable methods requiring any stable equilibrium to be defined by a fixed operating point. Time-domain simulations in comparison to an established average model of the MMC, as well as results from a detailed simulation model of an MMC with 400 sub-modules per arm, are presented as verification of the validity and accuracy of the developed model.

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“…The first step consists in expressing the abc vectors in the stationary frame as functions of their respective dqz equivalents. This 9 can be seen in the second line of (11)…”

Section: Voltage-based Formulationmentioning

confidence: 84%

Section: ) Final Formulationmentioning

confidence: 99%

Generalized Voltage-Based State-Space Modeling of Modular Multilevel Converters With Constant Equilibrium in Steady State

Bergna-Diaz

Freytes

Guillaud

et al. 2018

IEEE J. Emerg. Sel. Topics Power Electron.

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“…3 was modeled in DIgSILENT PowerFactory. This network is based upon the one described in [9] employing the same parameters for the DC lines and converter stations. It consists of four asynchronous AC systems interconnected through a DC grid.…”

Section: Simulation Resultsmentioning

confidence: 99%

Frequency changes in AC systems connected to DC grids: Impact of AC vs. DC side events

Sanz

Chaudhuri

Štrbac

2014

2014 IEEE PES General Meeting | Conference &Amp; Exposition

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Each converter station within a DC grid can be equipped with a power frequency droop control loop in addition to the power voltage droop control normally used for autonomous power sharing. Presence of the power frequency droop control allows exchange of frequency support among the AC systems connected to the DC grid. Following an event (or disturbance), there are two distinctly different patterns of dynamic variation of the frequencies of the AC systems connected to the DC grid. In this paper, an analytical basis is provided to support the different trends. Simulation results using a 4-terminal DC grid model set up in DIgSILENT PowerFactory are used to validate the analysis. The different patterns of dynamic variation of the frequencies for AC and DC side disturbances could have significant implications for extraction of inertial/frequency support from offshore wind farms connected through MTDC grids. Index Terms--Multi-Terminal DC (MTDC), VSC-HVDC, frequency droop control, AC/DC interaction.I.

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“…The ac side voltages of the DCT are set to produce an approximate modulation index of 0.7, when sinusoidal modulation is used [24][25][26]. Each cable is modeled with 10 pi sections to simulate high frequency behavior during a fault and obtain satisfactory simulation accuracy [27,28]. As the active fault current control to be proposed does not depend on the fundamental operating frequency of the dc transformer, the DCT MMCs are operated at 50Hz for simulation simplicity.…”

Section: A System Configurationmentioning

confidence: 99%

Active Control of DC Fault Currents in DC Solid-State Transformers During Ride-Through Operation of Multi-Terminal HVDC Systems

Yao

et al. 2016

IEEE Trans. Energy Convers.

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When a pole-to-pole dc fault occurs in a multiterminal HVDC system, it is desirable that the stations and dc solid-state transformers on healthy cables continue contributing to power transfer, rather than blocking. To reduce the fault current of a modular multilevel converter based dc solid-state transformer, active fault current control is proposed, where the dc and ac components of fault arm currents are regulated independently. By dynamically regulating the dc offset of the arm voltage rather than being set at half the rated dc voltage, the dc component in the fault current is reduced significantly. Additionally, reduced ac voltage operation of the dc solid-state transformer during the fault is proposed, where the ac voltage of transformer is actively limited in the controllable range of both converters in the transformer to effectively suppress the ac component of the fault current. The fault arm current peak and the energy absorbed by the surge arrester in the dc circuit breakers are reduced by 31.8% and 4.9% respectively, thereby lowering the capacities of switching devices and circuit breakers. Alternatively, with the same fault current level, the dc-link node inductance can be halved by using the proposed control, yielding lowered cost and volume. The novel active fault current control mechanism and the necessary control strategy are presented and simulation results confirm its feasibility. Index Terms-Active fault current control, average model, dc fault protection, dc solid-state transformer, modular multilevel converter (MMC), multi-terminal HVDC system, ride-through operation. Rui Li received the M.S. and Ph.D degrees in electrical engineering from Harbin Institute of Technology, Harbin, China, in 2008 and 2013, respectively. Since 2013, he has been working as a research associate with University of Strathclyde in Glasgow, UK.His research interests include HVDC transmiision system, grid integration of renewable power, power electronic converters, and energy conversion.Lie Xu (M'03-SM'06) received the B.Sc. degree in

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Stability analysis of VSC MTDC grids connected to multimachine ac systems

Cited by 44 publications

References 0 publications

Generalized Voltage-Based State-Space Modeling of Modular Multilevel Converters With Constant Equilibrium in Steady State

Generalized Voltage-Based State-Space Modeling of Modular Multilevel Converters With Constant Equilibrium in Steady State

Frequency changes in AC systems connected to DC grids: Impact of AC vs. DC side events

Active Control of DC Fault Currents in DC Solid-State Transformers During Ride-Through Operation of Multi-Terminal HVDC Systems

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