Effect of Frequency Coupling on Stability Analysis of a Grid-Connected Modular Multilevel Converter System

Wang, Yixing; Xu, Qianming; Guerrero, Josep M.

doi:10.3390/en14206580

Cited by 7 publications

(5 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the control modeling and validation process for (1) and ( 2), it is assumed that the voltage phase angle in the PCC is known and directly applied during the coordinate transformation. The AC/DC systems of MMC are all considered as ideal voltage sources in (1) to (3). Simultaneously, the MMC operates in inverter mode, transmitting rated active power, with a steady-state operating point identical to the open-loop mode.…”

Section: Impedance Responses With Closed-loop Controlmentioning

confidence: 99%

“…The modular multilevel converter, with its high-power quality, decoupled control of active and reactive power, capability of supplying power to passive systems, and modular manufacturing [1][2][3], is widely adopted in many fields, including renewable energy integration, high-voltage direct current transmission (HVDC), and medium-to low-voltage DC distribution [4,5]. Such a trend results in a significant number of MMC system resonance instabilities extending over a wide range of frequencies [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Sequence Impedance Modeling and Analysis of Modular Multilevel Converter Considering DC Port Characteristics

Yan,

2023

Energies

View full text Add to dashboard Cite

The extensive deployment of Modular Multilevel Converters (MMCs) in AC/DC systems can lead to complex resonance issues. Impedance modeling forms the foundation for analyzing the stability of interconnected system. Existing investigations primarily address resonance concerns on the AC side of MMC. In the process of impedance modeling, the DC system is generally approximated as an ideal voltage source, thereby neglecting its dynamic impact on the impedance characteristic of MMC. Such simplification may result in inaccuracies within stability analysis findings. Based on the multi-harmonic linearization method, this paper introduces an impedance modeling approach that takes into account the characteristics of the DC port. Taking DC voltage control as a case study, the impedance model for the AC side of the MMC is established. The results of programming calculation and simulation measurement of sequence impedance are mutually verified. Finally, the MMC impedance responses determined by different DC port characteristics are analyzed. Significant alterations in MMC impedance characteristics are introduced by DC side resistance and capacitance, which may result in negative damping effects and a decrease in system stability margins. The DC side inductance has a relatively minor impact on MMC impedance responses. The analysis results show that the sequence impedance model of MMC considering DC port characteristics can improve the accuracy of stability analysis results.

show abstract

Section: Impedance Responses With Closed-loop Controlmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Sequence Impedance Modeling and Analysis of Modular Multilevel Converter Considering DC Port Characteristics

Yan,

2023

Energies

View full text Add to dashboard Cite

show abstract

“…In [17], the authors investigate the relationship of stability with frequency coupling for a modular multilevel converter-based grid-connected system. The range of frequencies and the grid conditions that lead to the instability due to frequency coupling is identified and a PR controller with a circulating current suppression controller is proposed.…”

Section: Introductionmentioning

confidence: 99%

Decoupler-Based Feedback Control Strategy for Interlinking Converter in a Hybrid Microgrid

Nair

Kanakasabapathy

2023

Designs

View full text Add to dashboard Cite

In a hybrid microgrid with AC and DC subgrids, the interlinking converter (IC) is the key element connecting the two subgrids. The performance of the interlinking converter is adversely affected by the d- and q-axis impedance interaction between the inner control loops. This interaction is highly undesirable since it adversely affects both the dynamic and the steady-state performance of the IC. Based on this, a novel feedback-based decoupling strategy is developed to overcome the cross-coupling effect in the mathematical model of the interlinking converter. This is a novel concept since the feed-forward compensation techniques are utilized to address the cross-coupling effect in prior related works, which has an inherent disadvantage of additional disturbance due to the addition of the compensating terms. In this study, a complete decoupling of the d and q axes was achieved, and the first-order transfer functions were obtained for the control loops using systematic block-reduction algebra and direct synthesis approaches. With this model, computational complexities are reduced and the inner control loops are free from impedance interaction effects, thereby achieving enhanced transient stability. Perfect decoupling of the voltage vectors is achieved by the matrix diagonalization method. Furthermore, the novelty of the proposed control is that the decoupled model is integrated with a normalization-based coordinate control strategy for effective bidirectional power transfer via the interlinking converter. Additionally, the proposed controller’s validity was tested for its performance under different transients in the MATLAB Simulink platform. The simulation results validated the proposed control strategy by showing that a faster response is ensured. A high-quality reference signal is generated due to the effective decoupling achieved. This observation was also validated by comparing the T.H.D. levels of a decoupled model’s reference power signal to one without a decoupling strategy.

show abstract

“…These dynamics must be considered when designing the MMC control for example. Moreover, the MMC internal dynamics and control could eventually lead to undesired interactions with the electrical grid and with other nearby converters [4]- [15]. These possible interactions must be assessed and avoided in order to guarantee a safe and reliable operation of a power-electronic-based power system with an MMC-HVDC connection, which is the case of an OWPP grid that can be seen as a small power-electronic-based electrical system.…”

Section: Introductionmentioning

confidence: 99%

“…However, the MMC behavior can be quite different from the TLC behavior for lower frequencies. Thus, despite the challenges in obtaining an LTI model for the MMC, many different approaches have been recently reported in the literature to achieve this goal [5]- [15], [41]- [47]. The most adopted modeling strategies are based on the harmonic state space (HSS) [5], [6], [8]- [10], dynamic phasors [7], [12], [13], [42]- [44] or multiple dq frames [14], [45]- [47].…”

Section: Introductionmentioning

confidence: 99%

State Space Modeling of an Offshore Wind Power Plant With an MMC-HVDC Connection for an Eigenvalue-Based Stability Analysis

et al. 2022

View full text Add to dashboard Cite

Large offshore wind power plants (OWPPs) installed far from the coastline are emerging to benefit from the strong and steady wind resources available at these locations. The high-voltage direct-current (HVDC) transmission system based on the modular multilevel converter (MMC) is the most appropriate solution to transmit the produced energy to the onshore grid, in a way that a complex power-electronic-based electrical system is formed at the OWPP. Undesired interactions can occur between the MMC-based HVDC station, the several wind-turbine (WT) converters, and the passive elements of the offshore grid. To guarantee a safe and reliable operation of the OWPP, a small-signal analysis must be performed in advance to predict possible unstable situations and their root causes, in a way as to take corrective measures to avoid them. In this paper, a state space model of an OWPP is developed in which a recently proposed model in multiple dq frames is adopted for the MMC. With the developed model, an eigenvalue-based stability assessment is carried out, where participation factors are calculated to identify the main contributors to the unstable modes that appear as a consequence of undesired low-frequency interactions at the offshore grid. As far as the authors know, an eigenvalue-based stability assessment of an OWPP with an MMC-HVDC connection is a topic rarely or never explored in the literature before and, thus, this is the main contribution of this paper. An adaptation to the MMC state space model is proposed so that the converter's dynamics in grid-forming mode can be represented, and this is another contribution of this paper. Finally, various studies are presented to prove that the adopted approximated MMC model is accurate enough for small-signal stability analyses.INDEX TERMS Power-electronic-based power system, small-signal stability analysis, HVDC transmission system, modular multilevel converter, offshore wind power plant.

show abstract

Effect of Frequency Coupling on Stability Analysis of a Grid-Connected Modular Multilevel Converter System

Cited by 7 publications

References 37 publications

Sequence Impedance Modeling and Analysis of Modular Multilevel Converter Considering DC Port Characteristics

Sequence Impedance Modeling and Analysis of Modular Multilevel Converter Considering DC Port Characteristics

Decoupler-Based Feedback Control Strategy for Interlinking Converter in a Hybrid Microgrid

State Space Modeling of an Offshore Wind Power Plant With an MMC-HVDC Connection for an Eigenvalue-Based Stability Analysis

Contact Info

Product

Resources

About