Polyphase power representation by means of symmetrical coordinates

Fortescue, C.L.

doi:10.1109/joaiee.1920.6592720

Cited by 4 publications

(4 citation statements)

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“…The 120 electrical degree phase shift in the "chain-link" voltages results in attendant 6n harmonic voltage in the summed total "chain-link" voltage as shown in Figure 3. Though the techniques of [30,32] were developed for symmetrical network operations, they can still be used under unbalanced conditions for ripple reduction, but because of asymmetry, the cancellation will not be as effective as it will be in a symmetrical system. Further quantitative analysis of the ripple reduction under unbalanced conditions is outside the scope of this paper.…”

Section: Converter Topology and Basic Operationmentioning

confidence: 99%

“…We consider a system where the grid voltage is composed of positive and negative sequence voltages during unbalance. The unbalance factor (β) represents the ratio of the amplitude of the negative to the positive sequence voltages in the circuit [32] [33]. It is considered that the converter is controlled to inject negative sequence voltage proportionate to that in the grid to avoid the circulation of negative sequence current.…”

Section: Converter Operation During Grid Voltage Unbalancementioning

confidence: 99%

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Operation of a hybrid modular multilevel converter during grid voltage unbalance

Amankwah

Watson

Clare

2016

IET Generation, Transmission & Distribution

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The recently proposed parallel hybrid modular multilevel converter is considered to be a low loss, low component count converter with soft switching capability of the 'main' H-bridge. The converter has similar advantages to other emerging modular multilevel converter circuits being considered for HVDC power transmission and can be made compact which is desirable for offshore application. However, during ac network unbalance the individual 'chain-links' exchange unequal amounts of power with the grid which requires appropriate remedial action. This paper presents research into the performance of the converter and proposes a suitable control method that enables the converter to operate during grid voltage unbalance. The proposed control concept involves the use of asymmetric third harmonic voltage generation in the 'chain-links' of the converter to redistribute the power exchanged between the individual 'chain-links' and the grid. Mathematical analysis and simulation modelling with results are presented to support the work described.

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Section: Converter Topology and Basic Operationmentioning

confidence: 99%

Section: Converter Operation During Grid Voltage Unbalancementioning

confidence: 99%

Operation of a hybrid modular multilevel converter during grid voltage unbalance

Amankwah

Watson

Clare

2016

IET Generation, Transmission & Distribution

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“…The unbalance factor (β) represents the amplitude of the negative sequence voltage in the circuit [14] [15]. We consider a system where the grid voltage is composed of positive and negative sequence voltages during unbalance.…”

Section: Converter Operation During Grid Voltage Unbalancementioning

confidence: 99%

Control of a hybrid modular multilevel converter during grid voltage unbalance

Amankwah

Watson

Wheeler

et al. 2015

11th IET International Conference on AC and DC Power Transmission

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The recently proposed parallel hybrid modular multilevel converter is considered to be a low loss, low component count converter with soft switching capability of the 'main' bridge. The converter has similar advantages to other emerging modular multilevel converter circuits being considered for HVDC power transmission. However, during ac network unbalance the individual 'chain-links' exchange unequal amounts of power with the grid which requires appropriate remedial action. This paper presents research into the performance of the converter and proposes a suitable control method that enables the converter to operate during grid voltage unbalance. The proposed control concept involves the use of asymmetric third harmonic voltage generation in the 'chain-links' of the converter to redistribute the power exchanged between the individual 'chain-links' and the grid. Mathematical analysis and simulation modelling with results are presented to support the work described.

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“…One electrical power quality phenomenon that occurs most frequently in electrical installations is voltage unbalance. Even a small voltage unbalance at the transformer level can significantly disturb the current waveform on the connected loads, so it is necessary to quantify the voltage unbalance using unbalance factors [ 1 , 6 , 7 , 8 ]. Under normal operating conditions, excluding the periods with interruptions, the voltage variations should not exceed ±10% of the rated voltage, and during each one-week period, 95% of the 10-min averaged RMS values of the fundamental negative phase-sequence component of the supply voltage should be between 0% and 2% of the fundamental positive phase-sequence component [ 1 ].…”

Section: Introductionmentioning

confidence: 99%

New Smart Sensor for Voltage Unbalance Measurements in Electrical Power Systems

Bogarra

Saura

Rolán

2022

Sensors

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This paper deals with voltage unbalances and how they can be quantified according to the standards. Firstly, a comparison between the different unbalance voltage factors is conducted in order to remark on their divergences. Secondly, according to the standard that better represents the phenomenon, i.e., EN 50160, a new methodology is proposed to quantify the voltage unbalance factor (VUF). In order to do so, it is recommended to measure the voltage unbalance in three-phase installations by means of a new smart sensor based on a single voltage sensor, which measures the direct-current (DC) voltage at the output of a three-phase diode bridge rectifier, while current methods make use of three voltage sensors (which can measure either phase-to-neutral voltages or phase-to-phase voltages). Furthermore, both simulation and experimental results have been carried out to validate the proposed methodology. Finally, a new voltage unbalance factor (and the corresponding methodology to obtain it from the measured DC voltage) is proposed.

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Polyphase power representation by means of symmetrical coordinates

Cited by 4 publications

References 0 publications

Operation of a hybrid modular multilevel converter during grid voltage unbalance

Operation of a hybrid modular multilevel converter during grid voltage unbalance

Control of a hybrid modular multilevel converter during grid voltage unbalance

New Smart Sensor for Voltage Unbalance Measurements in Electrical Power Systems

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