State-space modeling of modular multilevel converters including line frequency transformer

Abstract

This paper presents a detailed state-space modeling of a Modular Multilevel Converter (MMC) in combination with line frequency transformer (LFT). The classical MMC topology is compared with the recently proposed Open-End Winding MMC (OEWMMC) topology, which integrates the LFT in the converter arm. The line frequency transformer parameters are added in the model, some of which are often neglected in the available literature. Both models are verified and compared by means of numerical simulations in open-loop. Despite integration attractiveness offered by the OEWMMC topology, there are also some inherent drawbacks affecting the overall system sizing that are discussed in the paper.

PI Passivity-Based Control and Performance Analysis of MMC Multiterminal HVDC Systems

“…The AAM of a single MMC as obtained in Section IIbefore the multi-frequency coordinates transformationand its multiterminal counterpart. This model can be also found in [16], [18], [19] and is implemented using the Simulation results with this model are identified in the legend of the figures by "EMT". For the simulations, we assume that in the multi-terminal configuration all MMCs are characterized by the same parameters and that transmission lines can be represented by the frequency-dependent model detailed in [28], where the line inductance effect is neglected to simplify our tractation 4 .…”

PI passivity-based control of modular multilevel converters for multi-terminal HVDC systems

“…Due to the complexity of the system, suitable, simplified models are usually employed in literature, based on the following assumptions-see [10], [16], [17] for more details.…”

Port-Hamiltonian modelling of Modular Multilevel Converters with fixed equilibrium point

“…(1). This modelling approach, here referred to as the Arm Averaged Model (AAM), is represented by a controlled voltage source (instead of the series connected SMs) and by an equivalent arm capacitance C σ = C/N , representing the internal arm voltage dynamics [9], [10], [11]. This simplification does not consider the switching dynamics of the IGBTs nor the dynamics of the sub-module capacitor voltage balancing algorithm, but instead is based on the averaged continuous behaviour of the arm, and still preserves relevant non-linearities of the MMC.…”

“…It is possible to easily extract from (10) the dissipation matrix R as in (11), from where it can be seen that the dissipation elements are only associated to the currents of the system, and that as expected R = R .…”