Standardized evaluation of multi-level grid control strategies for future converter-dominated electric energy systems

Sarstedt, Marcel; Dokus, Marc; Gerster, Johannes; Himker, Niklas; Hofmann, Lutz; Lehnhoff, Sebastian; Mertens, Axel

doi:10.1515/auto-2019-0061

Cited by 12 publications

(7 citation statements)

References 30 publications

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“…Consequently, a model of a single loop voltage-controlled converter is derived based on Fig. 2 which yields the equivalent TFs in (22). Again, all resistances are neglected.…”

Section: B: Single Loop Voltage Control (Slvc)mentioning

confidence: 99%

“…The converter system is completely modelled by the developed Thévenin equivalent {G cl,SLVC (s), Z C,SLVC (s)} in (22). In addition, the closed loop control characteristics G cl,SLVC (s) are illustrated in Fig.…”

Section: B: Single Loop Voltage Control (Slvc)mentioning

confidence: 99%

“…In particular, the impedance-based framework is also suitable to analyse large power networks based on the equivalent models due to its modular nature. An exemplary analysis based on sequence impedance models is illustrated in [22] and [23]. However, all these small-signal methods require model linearisation either in time domain or in frequency domain around the steady-state operation point.…”

Section: Introductionmentioning

confidence: 99%

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On the Coupling of Power-Related and Inner Inverter Control Loops of Grid-Forming Converter Systems

Dokus

Mertens

2021

IEEE Access

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In the last decade, different control concepts for the synchronisation of voltage-controlled power converters have been proposed in order to form converter-based power systems. The interoperability of these grid-forming power controls is often analysed based on reduced-order models covering only the slow controls or modes. In this article, the coupling of the outer, power-related and inner, inverter outputrelated control of multiple grid-forming power converter systems is analysed, based on a minimal working example. The elementary study cases each consist of a different grid-forming converter coupled with an external (and passive) grid. Here, the investigated stability problems are already manifested in the simplest possible setup. The analysis of these coupling effects is performed by modelling the system in impedancebased, state-space and phase portrait-based frameworks. In particular, small coupling impedances, like short transmission lines or small short circuit impedances, can be challenging for the controller stability of gridforming converters while the inner controls can even enhance this issue. The impact of this phenomenon and the participating subsystems are identified in this work. Thus, recommendations concerning modelling techniques and their legitimate assumptions are given. Laboratory experiments validate the performed analysis by indicating a close correlation between analytical models and experimental results. INDEX TERMSCoupling effects, grid-forming power converter, power-related control, stability analysis, voltage control.

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“…Consequently, a model of a single loop voltage-controlled converter is derived based on Fig. 2 which yields the equivalent TFs in (22). Again, all resistances are neglected.…”

Section: B: Single Loop Voltage Control (Slvc)mentioning

confidence: 99%

Section: B: Single Loop Voltage Control (Slvc)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

On the Coupling of Power-Related and Inner Inverter Control Loops of Grid-Forming Converter Systems

Dokus

Mertens

2021

IEEE Access

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“…For the period of one-time interval, costs are considered constant. Examples are monetary costs for electricity given by time-varying prices, or set points given by some external smart grid control strategy (Sarstedt et al 2019). In the latter case, costs are defined by the deviation from the desired energy feed-in.…”

Section: Problem Statementmentioning

confidence: 99%

Ant colony optimization for feasible scheduling of step-controlled smart grid generation

Bremer

Lehnhoff

2021

Swarm Intell

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The electrical energy grid is currently experiencing a paradigm shift in control. In the future, small and decentralized energy resources will have to responsibly perform control tasks like frequency or voltage control. For many use cases, scheduling of energy resources is necessary. In the multi-dimensional discrete case–e.g., for step-controlled devices–this is an NP-hard problem if some sort of intermediate energy buffer is involved. Systematically constructing feasible solutions during optimization, hence, becomes a difficult task. We prove the NP-hardness for the example of co-generation plants and demonstrate the multi-modality of systematically designing feasible solutions. For the example of day-ahead scheduling, a model-integrated solution based on ant colony optimization has already been proposed. By using a simulation model for deciding on feasible branches, artificial ants construct the feasible search graphs on demand. Thus, the exponential growth of the graph in this combinatorial problem is avoided. We present in this extended work additional insight into the complexity and structure of the underlying the feasibility landscape and additional simulation results.

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“…TSO-DSO coordination is an important topic which has been pushed by ENTSO-E during the last years [1][2][3][4]. Coordination between grid operators has to be strengthened to prevent conflicting or counteracting use of flexibility options [5]. To reduce complexity for TSOs at the TSO/DSO interface and to enable TSOs to consider the flexibility potential of DGs in its operational management and optimization processes, methods are needed which allow for the determination and standardized representation of the aggregated flexibility potential of DGs.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Random Sampling and Heuristic Optimization-Based Methods for Determining the Flexibility Potential at Vertical System Interconnections

Gerster

Sarstedt

Veith³

et al. 2021

2021 IEEE PES Innovative Smart Grid Technologies Europe (ISGT Europe)

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In order to prevent conflicting or counteracting use of flexibility options, the coordination between distribution system operator and transmission system operator has to be strengthened. For this purpose, methods for the standardized description and identification of the aggregated flexibility potential of distribution grids are developed. Approaches for identifying the feasible operation region (FOR) of distribution grids can be categorized into two main classes: Random sampling/stochastic approaches and optimization-based approaches. While the former have the advantage of working in real-world scenarios where no full grid models exist, when relying on naive sampling strategies, they suffer from poor coverage of the edges of the FOR due to convoluted distributions. In this paper, we tackle the problem from two different sides. First, we present a random sampling approach which mitigates the convolution problem by drawing sample values from a multivariate Dirichlet distribution. Second, we come up with a hybrid approach which solves the underlying optimal power flow problems of the optimization-based approach by means of a stochastic evolutionary optimization algorithm codenamed REvol. By means of synthetic feeders, we compare the two proposed FOR identification methods with regard to how well the FOR is covered and number of power flow calculations required.

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Standardized evaluation of multi-level grid control strategies for future converter-dominated electric energy systems

Cited by 12 publications

References 30 publications

On the Coupling of Power-Related and Inner Inverter Control Loops of Grid-Forming Converter Systems

On the Coupling of Power-Related and Inner Inverter Control Loops of Grid-Forming Converter Systems

Ant colony optimization for feasible scheduling of step-controlled smart grid generation

Comparison of Random Sampling and Heuristic Optimization-Based Methods for Determining the Flexibility Potential at Vertical System Interconnections

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