EPE Association: EPE 2020 - LS2c: HVDC & FACTS

EPE 2020 - LS2c: HVDC & FACTS
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2020 ECCE Europe - Conference > EPE 2020 - Topic 06: Grids, Smart Grids, AC & DC > EPE 2020 - LS2c: HVDC & FACTS

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   Analysis Of DC-side Fault Response of MMCs with Controlled Fault Blocking Capability for Different Transmission Line Types
By Willem LETERME [View]
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Abstract: MMCs with controlled fault blocking capability retain control of their currents during a dc-side fault, thereby reducing the required interruption capabilities for switchgear. To design the dc-side control to achieve this capability, it is important to take into account the interaction between the converter control and the transmission line during a short-circuit on the transmission line. This paper uses a dc-side equivalent model to assess the interactions of the converter control for two types of converters, i.e., full-bridge and hybrid, with two main types of transmission lines, i.e., cable and overhead line, during dc-side faults. In general, the dc-side voltages and currents for a full-bridge MMC connected to an overhead line show more oscillatory behavior compared to an MMC connected to a cable. Furthermore, a hybrid MMC connected to an overhead line may provide a more damped dc-side fault response due to its limited negative voltage capability.

   Assessment of Aging and Performance Degradation of Supercapacitors Integrated into a Modular Multilevel Converter
By Florian ERRIGO [View]
[Download]

Abstract: The interest for modular multilevel converter (MMC) with energy storage systems (ESSs) has increasedquickly over the last decades. Since an MMC has several hundreds of sub-modules (SMs) and ESSperformances usually deteriorate quickly, the ability of the converter to provide the expected serviceduring its lifetime must be investigated. In this work, supercapacitors are used as ESS and the reduction of their capacity is first calculated through lifetime simulation of the ESS using aging models. Then, simulations are used to analyze the available energy of the proposed converter considering dispersions for the initial parameters of ESSs and for the aging rate. Finally, the results are compared with different levels of redundancy and maintenance intervals to discuss the viability of the solution. For the depicted case study, results show that oversizing the ESSs without carrying any maintenance operations during the lifetime of the converter minimizes the total number of cells required.

   Modelling and experimental validation of a laboratory-scaled HVDC cable emulator tested in an MMC-based platform
By Enric SÁNCHEZ-SÁNCHEZ [View]
[Download]

Abstract: Typical Modular Multilevel Converter (MMC)-based HVDC systems don't include capacitors directly connected to the DC-side in parallel with the HVDC lines. The dynamics of the HVDC line voltage depend on the equivalent capacitance of the HVDC system, which in turn depends on the length of the lines. Recent work in the literature has shown that this can become problematic for HVDC line voltage control in the case of short links. This paper describes the operation of a laboratory-scaled MMC-based HVDC short link platform devised to study this phenomenon. Special emphasis is put on the design and the scaling of a frequency-dependent cable emulator. Experimental results are compared with a benchmark high-voltage simulated model.

   Small-Signal Stability of HVDC System Comprising DC Reactors
By Kosei SHINODA [View]
[Download]

Abstract: This paper attempts to shed light on potential stability issues in MMC-based HVDC systems. In particular, the focus is given to the influence of converter control parameters on the small-signal stability of an HVDC system equipped with large fault current limiting DC reactors. Those DC reactors are often required to reduce the rate-of-rise in fault currents and thus to limit the currents below the maximum interruption capability of DC Circuit Breakers (DCCBs). However, the introduction of large DC reactors can degrade the system stability. The small-signal stability analysis of an MMC-based HVDC system model, including control loops, DC reactors, and frequency-dependent HVDC cables, corroborates the unstable behavior of the system in the presence of large DC reactors. Furthermore, the influences of the bandwidth of the closed-loop power controller and the DC voltage droop parameter on the stability margin of the system are investigated. The obtained results suggest that special attention should be paid to the design and parameter of the controller in each control mode when MMC-based HVDC systems are equipped with large DC reactors.

EPE 2020 - LS2c: HVDC & FACTS
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2020 ECCE Europe - Conference > EPE 2020 - Topic 06: Grids, Smart Grids, AC & DC > EPE 2020 - LS2c: HVDC & FACTS
	[return to parent folder]

	Analysis Of DC-side Fault Response of MMCs with Controlled Fault Blocking Capability for Different Transmission Line Types By Willem LETERME	[View] [Download]
Abstract: MMCs with controlled fault blocking capability retain control of their currents during a dc-side fault, thereby reducing the required interruption capabilities for switchgear. To design the dc-side control to achieve this capability, it is important to take into account the interaction between the converter control and the transmission line during a short-circuit on the transmission line. This paper uses a dc-side equivalent model to assess the interactions of the converter control for two types of converters, i.e., full-bridge and hybrid, with two main types of transmission lines, i.e., cable and overhead line, during dc-side faults. In general, the dc-side voltages and currents for a full-bridge MMC connected to an overhead line show more oscillatory behavior compared to an MMC connected to a cable. Furthermore, a hybrid MMC connected to an overhead line may provide a more damped dc-side fault response due to its limited negative voltage capability.

	Assessment of Aging and Performance Degradation of Supercapacitors Integrated into a Modular Multilevel Converter By Florian ERRIGO	[View] [Download]
Abstract: The interest for modular multilevel converter (MMC) with energy storage systems (ESSs) has increasedquickly over the last decades. Since an MMC has several hundreds of sub-modules (SMs) and ESSperformances usually deteriorate quickly, the ability of the converter to provide the expected serviceduring its lifetime must be investigated. In this work, supercapacitors are used as ESS and the reduction of their capacity is first calculated through lifetime simulation of the ESS using aging models. Then, simulations are used to analyze the available energy of the proposed converter considering dispersions for the initial parameters of ESSs and for the aging rate. Finally, the results are compared with different levels of redundancy and maintenance intervals to discuss the viability of the solution. For the depicted case study, results show that oversizing the ESSs without carrying any maintenance operations during the lifetime of the converter minimizes the total number of cells required.

	Modelling and experimental validation of a laboratory-scaled HVDC cable emulator tested in an MMC-based platform By Enric SÁNCHEZ-SÁNCHEZ	[View] [Download]
Abstract: Typical Modular Multilevel Converter (MMC)-based HVDC systems don't include capacitors directly connected to the DC-side in parallel with the HVDC lines. The dynamics of the HVDC line voltage depend on the equivalent capacitance of the HVDC system, which in turn depends on the length of the lines. Recent work in the literature has shown that this can become problematic for HVDC line voltage control in the case of short links. This paper describes the operation of a laboratory-scaled MMC-based HVDC short link platform devised to study this phenomenon. Special emphasis is put on the design and the scaling of a frequency-dependent cable emulator. Experimental results are compared with a benchmark high-voltage simulated model.

	Small-Signal Stability of HVDC System Comprising DC Reactors By Kosei SHINODA	[View] [Download]
Abstract: This paper attempts to shed light on potential stability issues in MMC-based HVDC systems. In particular, the focus is given to the influence of converter control parameters on the small-signal stability of an HVDC system equipped with large fault current limiting DC reactors. Those DC reactors are often required to reduce the rate-of-rise in fault currents and thus to limit the currents below the maximum interruption capability of DC Circuit Breakers (DCCBs). However, the introduction of large DC reactors can degrade the system stability. The small-signal stability analysis of an MMC-based HVDC system model, including control loops, DC reactors, and frequency-dependent HVDC cables, corroborates the unstable behavior of the system in the presence of large DC reactors. Furthermore, the influences of the bandwidth of the closed-loop power controller and the DC voltage droop parameter on the stability margin of the system are investigated. The obtained results suggest that special attention should be paid to the design and parameter of the controller in each control mode when MMC-based HVDC systems are equipped with large DC reactors.