Small-signal state-space modeling of an HVDC link with modular multilevel converters

Freytes, Julian; Akkari, Samy; Dai, Jing; Gruson, François; Rault, Pierre; Guillaud, Xavier

doi:10.1109/compel.2016.7556693

Cited by 35 publications

(24 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In this case, for the selected values the system remains stable. It is known that the converters dynamics depend on the operating point [19]. The same parametric sweep as the previous example is performed with the opposite power transfer direction (i.e.…”

Section: B Stability Analysismentioning

confidence: 99%

Improving Small-Signal Stability of an MMC With CCSC by Control of the Internally Stored Energy

Freytes

Bergna-Diaz

Suul

et al. 2018

IEEE Trans. Power Delivery

Self Cite

View full text Add to dashboard Cite

Abstract-The DC-side dynamics of Modular Multilevel Converters (MMCs) can be prone to poorly damped oscillations or stability problems when the second harmonic components of the arm currents are mitigated by a Circulating Current Suppression Controller (CCSC). This paper demonstrates that the source of these oscillations is the uncontrolled interaction of the DC-side current and the internally stored energy of the MMC, as resulting from the CCSC. Stable operation and improved performance of the MMC control system can be ensured by introducing closed loop control of the energy and the DC-side current. The presented analysis relies on a detailed state-space model of the MMC which is formulated to obtain constant variables in steady state. The resulting state-space equations can be linearized to achieve a Linear Time Invariant (LTI) model, allowing for eigenvalue analysis of the small-signal dynamics of the MMC. Participation factor analysis is utilized to identify the source of the poorly damped DC-side oscillations, and indicates the suitability of introducing control of the internal capacitor voltage or the corresponding stored energy. An MMC connected to a DC power source with an equivalent capacitance, and operated with DC voltage droop in the active power flow control, is used as an example for the presented analysis. The developed small-signal models and the improvement in small-signal dynamics achieved by introducing control of the internally stored energy are verified by time-domain simulations in comparison to an EMT simulation model of an MMC with 400 sub-modules per arm.

show abstract

Section: B Stability Analysismentioning

confidence: 99%

Improving Small-Signal Stability of an MMC With CCSC by Control of the Internally Stored Energy

Freytes

Bergna-Diaz

Suul

et al. 2018

IEEE Trans. Power Delivery

Self Cite

View full text Add to dashboard Cite

show abstract

“…• Classic control [9], [11], [15] without off-diagonal (cross) coupling, K 2 = K 3 = 0: this control structure is based on extrapolating the 2L-VSC structure to the MMC. The AC current reference (i q * s ) is controlled by the DC voltage (V dc t ) controller, whereas the DC circulating current reference (i 0dc * sum ) is controlled by the total energy (W t ) controller.…”

Section: A MMC Energy-based Control Structuresmentioning

confidence: 99%

“…This will affect the energy, which will be compensated through the DC current. A feed-forward of the AC power is usually added after the output of the total energy PI controller [9], [11], [18], otherwise the gains of that PI controller have to be increased notably to obtain a stable system. • Cross control [17], [18] without diagonal coupling, K 1 = K 4 = 0: the outputs of the outer controllers are connected to the opposite current reference inputs as in the classic control structure.…”

Section: A MMC Energy-based Control Structuresmentioning

confidence: 99%

Optimal Multivariable MMC Energy-Based Control for DC Voltage Regulation in HVDC Applications

Sánchez‐Sánchez

Groß

Prieto‐Araujo

et al. 2020

IEEE Trans. Power Delivery

View full text Add to dashboard Cite

The penetration of renewable energy resources is changing the way the power system is understood and operated. With an increasing number of power electronics devices integrated into the power system, the MMC is arising as one of the key technologies for HVDC applications. While several control strategies for MMCs have been proposed in the last years, designing controls for MMCs remains a challenging and non-trivial problem due to its large number of degrees of freedom. In this paper, a general multivariable control structure is proposed that generalizes and improves upon previously reported approaches. Moreover, to fully exploit the degrees of freedom offered by this control, a model-based tuning methodology is presented that extends results from optimal H2 structured control design to MMC applications. A case study using an HVDC link is used to illustrate and analyze the performance of the MMC using the proposed approach in different scenarios.

show abstract

“…Moreover, it imposes parasitic circulating current components that require additional current control loops to attenuate them [3]. An alternative approach is to implement an energy-based method, also known as compensated modulation or closed-loop modulation [8][9][10][11]. This control method does not generate parasitic voltage components, but energy controllers are required to ensure an asymptotically stable system [12].…”

Section: Introductionmentioning

confidence: 99%

Interaction Assessment and Stability Analysis of the MMC-Based VSC-HVDC Link

et al. 2020

View full text Add to dashboard Cite

This paper investigates the dynamic behavior of a modular multi-level converter (MMC)-based HVDC link. An overall state-space model is developed to identify the system critical modes, considering the dynamics of the master MMC and slave MMC, their control systems, and the HVDC cable. Complementary to the state-space model, an impedance-based model is also derived to obtain the minimum phase margin (PM) of the system. In addition, a relative gain array (RGA) analysis is conducted to quantify the level of interactions among the control systems of master and slave MMCs and their impacts on stability. Finally, with the help of the results obtained from the system analysis (eigenvalue, phase margin, sensitivity, and RGA), the system dynamic performance is improved.3 of 19 an eigenvalue and participation factors analysis in Section 6. Moreover, the system minimum PM is calculated through an impedance-based analysis using the Nyquist plot, and the level of interactions among control loops is studied using a frequency-dependent relative gain array (RGA) analysis. Finally, in Section 7, based on the results achieved from the system analyses, the stability of the system is improved by tuning the DC voltage control loop. System DescriptionA typical HVDC link between two AC networks is shown in Figure 1. In such configuration, the master MMC regulates DC voltage while the slave MMC controls active power exchange [27]. Either AC voltage or reactive power can be regulated at both ends. AC network 1 HVDC cable AC network 2 Master Slave V dc control P control

show abstract

Small-signal state-space modeling of an HVDC link with modular multilevel converters

Cited by 35 publications

References 18 publications

Improving Small-Signal Stability of an MMC With CCSC by Control of the Internally Stored Energy

Improving Small-Signal Stability of an MMC With CCSC by Control of the Internally Stored Energy

Optimal Multivariable MMC Energy-Based Control for DC Voltage Regulation in HVDC Applications

Interaction Assessment and Stability Analysis of the MMC-Based VSC-HVDC Link

Contact Info

Product

Resources

About