Circulating current suppression control dynamics and impact on MMC converter dynamics

Far, Ali; Jovcic, Dragan

doi:10.1109/ptc.2015.7232762

Cited by 10 publications

(21 citation statements)

References 10 publications

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“…• is the magnitude (norm) operator. A similar equation for the first harmonic component, i c1 , is derived by following the same reasoning and approach, as shown in (18). The relevant energy harmonics, for the first harmonic current, are the first harmonic component of the sum energies and the second harmonic components of the difference energies.…”

Section: Parameter Error Correctionmentioning

confidence: 99%

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Online Parameter Adjustment Method for Arm Voltage Estimation of the Modular Multilevel Converter

Taffese

Jong

D’Arco

et al. 2019

IEEE Trans. Power Electron.

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The method used to calculate insertion indexes plays an important role in determining the overall performance of the Modular Multilevel Converter (MMC). Direct voltage control, which is the simplest option, results in a large circulating current ripple because this modulation technique does not account for the arm voltage ripples. This led to the development of compensated modulation techniques that compensate for the arm voltage ripples thereby eliminating the circulating current ripple. There are two variants of compensated modulation: closed-loop and openloop. The closed-loop version requires measurement of the arm voltages without distortion and delay, which is difficult to achieve in practice. The open-loop method overcomes this challenge by using estimated arm voltages. However, accurate knowledge of the system parameters is needed for effective removal of the circulating current ripples. This is a limitation because the parameters change with time and operating conditions. This paper presents a modified version of the open-loop method, which includes a scheme for correcting parameter errors online. The method estimates the parameters, the arm capacitances and time delay, by using feedback controllers acting on the circulating current ripples. Mathematical derivation of the method, together with its validation using simulation and experimental tests, is presented in detail.

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Section: Parameter Error Correctionmentioning

confidence: 99%

“…Circulating current suppression controllers [7], [14]- [17] have been proposed to suppress the ripple, but the oscillation problem [13] is not solved by such controllers. Furthermore, it was found that these controllers can negatively interact with other higher level controllers [18].…”

mentioning

confidence: 99%

Online Parameter Adjustment Method for Arm Voltage Estimation of the Modular Multilevel Converter

Taffese

Jong

D’Arco

et al. 2019

IEEE Trans. Power Electron.

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show abstract

“…2) The approaches proposed in [17]- [19], [21] consider all the internal variables of the MMC, under the assumption of a control system with a Circulating Current Suppression Controller (CCSC) implemented in a negative sequence double frequency SRRF [22]. Indeed, the methods proposed in [17], [18], [21] model the MMC by representing the internal second harmonic circulating currents and the corresponding second harmonic arm voltage components in a SRRF rotating at twice the fundamental frequency. However, the harmonic superposition principles assumed in the modelling, corresponding to phasor-based representation, 4 could affect the information about the non-linear characteristics of the MMC, and correspondingly limit the applicability of the models in non-linear techniques for analysis and control system design.…”

Section: Introductionmentioning

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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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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“…Additionally, the model neglects the effect of circulating current ripple and the associated suppression controllers. It has been shown that the effect of Circulating Current Suppression Controllers (CCSCs) cannot be neglected because they can interact with external systems [16]. Therefore, the main goal of this paper is to develop a simplified model that can include the circulating current dynamics while keeping the state count to a minimum.…”

Section: Introductionmentioning

confidence: 99%

Simplified Modelling of the F2F MMC-Based High Power DC-DC Converter Including the Effect of Circulating Current Dynamics

Taffese

Tedeschi

2018

2018 IEEE 19th Workshop on Control and Modeling for Power Electronics (COMPEL)

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The Front-to-Front Modular Multilevel Converter (MMC) is one of the topologies being considered for highvoltage, high-power, dc-dc conversion. Hence, there is a need for the development of simplified models for such a converter in order to study how it behaves in a large power system. Direct interconnection of two MMC models is one option but it leads to high number of states. Moreover, symmetry of the converter offers further simplification opportunities. The use of this fact to develop a simplified models was reported in literature. However, the resulting models are only applicable when compensated modulation is used. Furthermore, these models neglect the effect of Circulating Current Suppression Controllers (CCSCs), which makes the models inaccurate in the presence of such controllers. This paper proposes a more general simplification approach that captures the effect of CCSC while minimizing the number of states. The proposed model is validated by using time domain simulations and modal (eigenvalue) analyses.

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Circulating current suppression control dynamics and impact on MMC converter dynamics

Cited by 10 publications

References 10 publications

Online Parameter Adjustment Method for Arm Voltage Estimation of the Modular Multilevel Converter

Online Parameter Adjustment Method for Arm Voltage Estimation of the Modular Multilevel Converter

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

Simplified Modelling of the F2F MMC-Based High Power DC-DC Converter Including the Effect of Circulating Current Dynamics

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