Steady-State Analysis and Performance of Low Frequency AC Transmission Lines

Ngo, Tuan; Lwin, Min; Santoso, Surya

doi:10.1109/tpwrs.2015.2502139

Cited by 32 publications

(15 citation statements)

References 8 publications

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“…In this subsection, it is important to discuss about the low frequency transmission line X/R issue. Due to the low frequency used, the obtained X/R ratio will be 6 times smaller than that of the 60 Hz for a given rated voltage level, in which it is 1.5 in our case [38,39]. Therefore, the system will become less inductive.…”

Section: Stator Impedance Adjustermentioning

confidence: 85%

A Novel Control Scheme for Multi-Terminal Low-Frequency AC Electrical Energy Transmission Systems Using Modular Multilevel Matrix Converters and Virtual Synchronous Generator Concept

et al. 2020

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This paper proposes a new control scheme for the low frequency AC transmission (LFAC) system aiming at extending the point-to-point configuration to form a multi-terminal electrical energy network. The multi-terminal low frequency ac (MT-LFAC) system configuration is based on the use of modular multilevel matrix converters (M3Cs) and virtual synchronous generator (VSG) control. The M3C is the next ac/ac converter generation, which is used as an interface with the conventional AC network and the LFAC electrical energy system. Application of VSG control is proposed to enable proper power sharing, to provide synchronization of each terminal, and frequency stabilization, thus, to offer multiterminal forming capability. Two different operation modes are applied in the system to damp the frequency deviation after a dynamic perturbation, which provides additional stabilization feature to the VSG. Frequency restoration mode and commanded mode of power sharing are applied as dynamic states to validate the robustness of the VSG control system. Besides, to solve the negative impact of low X/R ratio in the LFAC electrical energy system, we enhance the VSG control by proposing a virtual-impedance-based solution, which increases the output total impedance on the low frequency side and prevents the coupling between P and Q. The operation of the proposed system is examined by simulation results with a precise model of M3Cs in the PSCAD/ EMTDC software environment (version 4.2.1, Winnipeg, MB, Canada).Energies 2020, 13, 747 2 of 19 delivery. However, neither technology is flawless. For example, the existence of the power electronic switches in the dc circuit breakers make them more vulnerable than the HVAC transmission system, especially when a fault takes place in the converter, due to the low dc-side impedances and sensitive semiconductor power converters [1,2]. On the other hand, the HVAC system offers advantages, such as more reliability of the well-known protection schemes and the change capability of voltage levels using transformers [3]. However, the HVAC transmission system's main disadvantage is the existence of the reactive power in comparison to no reactive power in the HVDC electrical energy system. Due to that, the existence of the reactive power can be translated as losses in the grid [4].The aforementioned points have led to an alternative solution which combines both sets of HVACs and HVDC advantages, known as a low frequency ac (LFAC) transmission system, or a fractional frequency transmission system (FFTS) [5][6][7]. This system transmits the power at a lower frequency range of about 1-60/3 Hz. The LFAC has already been proposed for the offshore wind energy and has offered attractive advantages compared to both transmission solutions. For example, in the HVDC electrical energy system, the implementation of a high capacity dc circuit breaker is difficult due to the absence of the zero crossing points of the DC current [8]. On the other hand, the LFAC system has zero-crossing, thus, the protection is more advantag...

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Section: Stator Impedance Adjustermentioning

confidence: 85%

A Novel Control Scheme for Multi-Terminal Low-Frequency AC Electrical Energy Transmission Systems Using Modular Multilevel Matrix Converters and Virtual Synchronous Generator Concept

et al. 2020

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“…where the real power P l,k and the reactive power Q l,k injected into LF-HVac grid l from bus k in (11) are obtained with an expression similar to (4). Similar to HVac grid s, voltage constraints (5) at voltagecontrolled buses, wind generation limits (6), capacitor dispatch constraint (7), line current limits (9), and line power limits (10) apply for LF-HVac grid l.…”

Section: Constraints Of Lf-hvac Grid Lmentioning

confidence: 99%

Loss Minimization With Optimal Power Dispatch in Multi-Frequency HVac Power Systems

Nguyen

Lao

et al. 2020

IEEE Trans. Power Syst.

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Low-frequency high voltage ac transmission scheme has recently been proposed as an alternative approach for bulk power transmission. This paper proposes a multi-period optimal power flow (OPF) for a multi-frequency HVac transmission system that interconnects both conventional 50/60-Hz and lowfrequency grids using back-to-back converters with a centralized control scheme. The OPF objective is to minimize system losses by determining the optimal dispatch for generators, shunt capacitors, and converters. The OPF constraints include the operational constraints of all HVac grid and converter stations. The resulting mixed-integer nonlinear programing problem is solved using a proposed framework based on the predictor-corrector primaldual interior-point method. The proposed OPF formulation and solution approach are verified using a multi-frequency HVac transmission system that is modified from the IEEE 57-bus system. The results with the optimal dispatch from the proposed method during a simulated day show a significant loss reduction and an improved voltage regulation compared to those when an arbitrary dispatch is chosen.Index Terms-Back-to-back converter, Low-frequency AC transmission, Multi-frequency power systems, Optimal power flow, Interior point method. * , Q conv * power from/to BTB converters; Q sh * injected reactive power into grid from shunt capacitors at 1 pu;

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“…In (10), the active power P [19]- [22], in practice, it may become ineffective following a failure of the converter connected to the slack bus in HV de grid d. To improve the robustness of the formulation, this paper also considers and implements distributed linear and nonlinear droop controls [26]- [28]. The most generalized droop control is the V-P droop, in which the set point of converter power p:onv varies according to the local de voltage in a nonlinear curve with dead-bands and voltage limits, as shown in Fig.…”

Section: E Vsc Converters Between Hvac and Hvdc Gridsmentioning

confidence: 99%

“…The purpose of this section is to propose an algorithm for solving power flow in general multi-frequency power systems. Power balance equations (1), (3), (7), (8), (10), and (11) are solved using the Newton-Raphson method. These equations can be combined as follows: g(X) = g( [Os , Vs , 0t , Vi , vd, p ; onv , Pi conv , P:J, onv ]) = [ g; ,g<j ,g[' ,g'fJ ,gf ,g� ,g� ,gt oo p ] = 0 .…”

Section: Algorithm For Solving Power Flow In Multi-frequency Hvacmentioning

confidence: 99%

“…LF-HVac systems combine the ad vantages of the two existing configurations, such as high power-carrying capability over long distance, the use of mesh connected (multi-terminal) networks, and straightforward ac protection system [6]- [9]. In addition, a significant reduction in reactance at low frequency benefits LF-HVac transmission systems in terms of superior voltage profile due to lower voltage drop, and improved system stability [10]- [12]. In [13] and [14], the possibility of implementing 16.7 Hz LF-HVac transmission for practical offshore wind farm applications in Europe is investigated.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Power Flow in a Multi-Frequency HVac and HVdc System: Formulation, Solution, and Validation

Nguyen

Todeschini

Santoso

2019

IEEE Trans. Power Syst.

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This paper proposes a novel power flow formulation and solution algorithm for a generalized large-scale intercon nected transmission system encompassing multi-frequency HVac and HV dc grids having arbitrary numbers of buses, topologies, and operating frequencies. Back-to-back and ac/dc voltage-source converters are employed to interconnect and control the voltage and power interchange between two power grids operating at different frequencies. The power flow formulation is based on a steady-state model of back-to-back and ac/dc converters operated in centralized and distributed droop control strategies. Each power grid is represented by a set of nonlinear power balance equations. These equations are solved simultaneously using a unified power flow algorithm, taking into account generator and converter limits. It is shown that the solution convergence is achieved rapidly despite the system size, topology, and converter control strategies. The efficacy and accuracy of the proposed steady-state solution algorithm are demonstrated by comparing the numerical solution to the one obtained by time-domain electromagnetic models of multi-frequency HVac and HV de transmission systems with fully controllable back to-back and ac/dc converters. The results obtained by using the proposed algorithm and the time-domain simulation are practically identical.

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Steady-State Analysis and Performance of Low Frequency AC Transmission Lines

Cited by 32 publications

References 8 publications

A Novel Control Scheme for Multi-Terminal Low-Frequency AC Electrical Energy Transmission Systems Using Modular Multilevel Matrix Converters and Virtual Synchronous Generator Concept

A Novel Control Scheme for Multi-Terminal Low-Frequency AC Electrical Energy Transmission Systems Using Modular Multilevel Matrix Converters and Virtual Synchronous Generator Concept

Loss Minimization With Optimal Power Dispatch in Multi-Frequency HVac Power Systems

Power Flow in a Multi-Frequency HVac and HVdc System: Formulation, Solution, and Validation

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