Enhanced Equivalent Model of the Modular Multilevel Converter

Ajaei, Firouz Badrkhani; Iravani, Reza

doi:10.1109/tpwrd.2013.2294651

Cited by 91 publications

(33 citation statements)

References 11 publications

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“…1 shows the three-terminal HVDC system considered. All converter stations are modeled as HBMMCs using modified average models [7][8][9]23]. The system parameters are listed in Table I.…”

Section: Consideration Of DC Fault-tolerant Operationmentioning

confidence: 99%

“…The losses introduced by short-circuit currents expose the diodes to thermal stresses and are usually measured by the integral of the surge current I 2 t. ABB, Infineon and Dynex provide IGBT and the anti-parallel diode with 3.3kV voltage rating and their diode I 2 t are 911kA 2 s, 730kA 2 s and 720kA 2 s respectively [4]. Bypass elements, typically thyristors, are used to protect the freewheeling diodes of the HB sub-modules (SMs) in MMC [5][6][7][8][9]. However, prolonged system outage still occurs.…”

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confidence: 99%

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Continuous Operation of Radial Multiterminal HVDC Systems Under DC Fault

Holliday

et al. 2016

IEEE Trans. Power Delivery

143

112

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Abstract -For a large multi-terminal HVDC system, it is important that a DC fault on a single branch does not cause significant disturbance to the operation of the healthy parts of the DC network. Some DC circuit breakers (DCCBs), e.g. mechanical type, have low cost and power loss, but have been considered unsuitable for DC fault protection and isolation in a multi-terminal HVDC system due to their long opening time. This paper proposes the use of additional DC passive components and novel converter control combined with mechanical DCCBs to ensure that the healthy DC network can continue to operate without disruption during a DC fault on one DC branch. Two circuit structures, using an additional DC reactor, and a reactor and capacitor combination, connected to the DC-link node in a radial HVDC system are proposed to ensure over-current risk at the converters connected to the healthy network is minimized before the isolation of the faulty branch by mechanical DCCBs. Active control of DC fault current by dynamically regulating the DC components of the converter arm voltages is proposed to further reduce the fault arm current. Simulation of a radial three-terminal HVDC system demonstrates the effectiveness of the proposed method.

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“…1 shows the three-terminal HVDC system considered. All converter stations are modeled as HBMMCs using modified average models [7][8][9]23]. The system parameters are listed in Table I.…”

Section: Consideration Of DC Fault-tolerant Operationmentioning

confidence: 99%

mentioning

confidence: 99%

Continuous Operation of Radial Multiterminal HVDC Systems Under DC Fault

Holliday

et al. 2016

IEEE Trans. Power Delivery

143

112

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“…Compared to the average model with only one equivalent capacitance, the modified average model in Fig. 3 reproduces MMC behavior during dc fault ride-through operation.model derivation and switching logic is represented in [18], [19] and [20]. …”

Section: Revised Generic MMC Average Modelmentioning

confidence: 99%

Mechanism to Regulate DC Fault Currents in DC Solid State Transformers under Continuous Working Performance of Multi-Terminal HVDC Systems

Chiranth¹

2017

IJRASET

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Once the pole-to-pole dc fault occurs in a multi-terminal HVDC system, it is desirable that the stations and dc solidstate transformers on healthy cables continue to operate, rather than blocking. To reduce the fault current of a modular multilevel converter based dc solid-state transformer, active fault current control is proposed, where the dc and ac components of fault arm currents are controlled independently. By dynamically regulating the dc offset of the arm voltage rather than being set at half the rated dc voltage, the dc component in the fault current is reduced significantly. Additionally, reduced ac voltage operation of the dc solid-state transformer during the fault is proposed, where the ac voltage of transformer is actively restricted in the controllable range of both converters in the transformer to effectively suppress the ac component of the fault current. The fault arm current peak and the energy absorbed by the surge arrester in the dc circuit breakers are reduced by 31.8% and 4.9% respectively, thereby lowering the capacities of switching devices and circuit breakers. The novel active fault current control mechanism and the essential control strategy are presented and simulation results confirm its feasibility. I. INTRODUCTIONThe deregulation of international energy markets and the trend to decentralized power generation are increasing the demand for advanced power electronic systems. For this application field multilevel converters with a high number of voltage levels seem to be the most suitable types, MMC was first proposed for HVDC applications at 2003from a Marquardt and it is first employed commercially in Trans Bay Cable project in a San Francisco. In the present scenario the Modular Multi-Level Converter (MMC) is becoming the most common type of a voltage source converter for HVDC applications. DC fault protection is an issue to be resolved for the development of modular multilevel converter (MMC) based HVDC transmission systems. [1][2][3][4]. The dc circuit breakers (DCCBs) have the potential to isolate a dc fault and protect stations from damage and limiting reactors are series connected with the fast acting DCCBs (e.g. solid-state DCCBs, hybrid DCCBs) to limit the fault current di/dt and decrease the fault current peak. Recently, the concept of the dc solid-state transformer (DCT) has been proposed which uses active controlled power electronic components to optimize converter performance. [6][7][8][9]. Similar to the ac transformer, the dc solid-state transformer can adapt the dc voltage to any higher or lower voltage level. By blocking all the converters of the dc solid-state transformer, dc faults can be isolated without significantly affecting the healthy system parts. Thus, the dc solid-state transformer appears the only approach to connect and interconnect existing HVDC links with different dc voltages. These transformers are available in different configurations which include the thyristor based solid-state transformer[10],the dual-active bridge (DAB) transformer [1...

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“…To reduce model complexity, the SM number per arm N is reduced and chosen as 24 with half-bridge (HB) SMs operating at 50 kV. In typical applications, hundreds of submodules with voltage rating of several kilovolts are required, however from a simulation perspective, assuming the adopted model with reduced SMs accelerates simulation time but does not significantly affect the quality of the outcome [6,16,19].…”

Section: A Power Lossesmentioning

confidence: 99%

“…Each SM in the tested model represents several tens of series-connected SMs of a practical implementation [19]. The parameters of the IGBTs and diodes are thus required to be set according to the equivalent series-connected circuit.…”

Section: A Power Lossesmentioning

confidence: 99%

Influence of third harmonic injection on modular multilevel converter ‐based high‐voltage direct current transmission systems

Fletcher

Williams

2016

IET Generation, Transmission & Distribution

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Abstract-Whilst third harmonic injection is extensively used in modular multilevelconverter (MMC) control, its significant advantages over sinusoidal modulation have not been fully explored. This paper evaluates the influence of third harmonic injection on system power losses, submodule capacitance, circulating current, and fault current and mathematical models are derived. Station conduction losses are reduced by 11%, yielding higher efficiency and lowering cooling system capacity. The submodule capacitance is reduced by 24%, which significantly lowers the capital cost, weight, and volume of the station converter. Additionally, the phase energy variation is reduced by around 18%, which benefits circulating current control. Due to the lower AC currents, the semiconductor current stresses are correspondingly reduced. In addition to the performance improvement in normal operation, the third harmonic injection reduces the DC fault currents by 13.4% and thus the fault current stresses on semiconductors and DC circuit breakers are lowered. Simulation of a point-to-point HVDC system demonstrates the effectiveness of the above analysis.Index Terms-DC fault current, HVDC transmission, modular multilevel converter (MMC), power loss, submodule capacitance, third harmonic injection.

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Enhanced Equivalent Model of the Modular Multilevel Converter

Cited by 91 publications

References 11 publications

Continuous Operation of Radial Multiterminal HVDC Systems Under DC Fault

Continuous Operation of Radial Multiterminal HVDC Systems Under DC Fault

Mechanism to Regulate DC Fault Currents in DC Solid State Transformers under Continuous Working Performance of Multi-Terminal HVDC Systems

Influence of third harmonic injection on modular multilevel converter ‐based high‐voltage direct current transmission systems

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