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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Energy Science and Technology".

Deadline for manuscript submissions: closed (25 September 2019) | Viewed by 38064

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Special Issue Editor

Prof. Dr. Gilsoo Jang

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Guest Editor

School of Electrical Engineering, Korea University, Seoul 136-713, Korea
Interests: HVDC control; transient stability; HVDC system planning
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

We are inviting submissions of original research to a Special Issue of Applied Sciences on the subject of “HVDC for Grid Services in Electric Power Systems”.

The modern electric power system has evolved into a huge nonlinear complex system, due to the interconnection of thousands of generation and transmission systems. The unparalleled growth of renewable energy resources (RES) has caused significant concern regarding grid stability and power quality, and it is essential to find ways to control such a massive system for effective operation. The controllability of HVDC and FACTs devices allows for improvement of the dynamic behavior of grids and their flexibility. Research is being carried out at both the system and component levels of modelling, control, and stability. This Special Issue aims to present novel topologies or operation strategies to prevent abnormal grid conditions.

Prof. Dr. Gilsoo Jang
Guest Editor

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Keywords

Control, operation and planning of HVDC Systems
Active control of HVDC systems
HVDC control for special protection systems
HVDC operation scheme for stability improvement
Intelligent strategies for HVDC voltage support
New control techniques in HVDC
New HVDC applications
HVDC protection schemes

Published Papers (11 papers)

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Editorial

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3 pages, 155 KiB

Open AccessEditorial

Special Issue on HVDC for Grid Services in Electric Power Systems

by Gilsoo Jang

Appl. Sci. 2019, 9(20), 4292; https://doi.org/10.3390/app9204292 - 12 Oct 2019

Viewed by 1298

Abstract

The modern electric power system has evolved into a huge nonlinear complex system, due to the interconnection of a lot of generation and transmission systems [...] Full article

(This article belongs to the Special Issue HVDC for Grid Services in Electric Power Systems)

Research

Jump to: Editorial

21 pages, 7307 KiB

Open AccessArticle

A Virtual Impedance Control Strategy for Improving the Stability and Dynamic Performance of VSC–HVDC Operation in Bidirectional Power Flow Mode

by Yuye Li, Kaipei Liu, Xiaobing Liao, Shu Zhu and Qing Huai

Appl. Sci. 2019, 9(15), 3184; https://doi.org/10.3390/app9153184 - 05 Aug 2019

Cited by 11 | Viewed by 3448

Abstract

It is a common practice that one converter controls DC voltage and the other controls power in two-terminal voltage source converter (VSC)–based high voltage DC (HVDC) systems for AC gird interconnection. The maximum transmission power from a DC-voltage-controlled converter to a power-controlled converter is less than that of the opposite transmission direction. In order to increase the transmission power from a DC-voltage-controlled converter to a power-controlled converter, an improved virtual impedance control strategy is proposed in this paper. Based on the proposed control strategy, the DC impedance model of the VSC–HVDC system is built, including the output impedance of two converters and DC cable impedance. The stability of the system with an improved virtual impedance control is analyzed in Nyquist stability criterion. The proposed control strategy can improve the transmission capacity of the system by changing the DC output impedance of the DC voltage-controlled converter. The effectiveness of the proposed control strategy is verified by simulation. The simulation results show that the proposed control strategy has better dynamic performance than traditional control strategies. Full article

(This article belongs to the Special Issue HVDC for Grid Services in Electric Power Systems)

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19 pages, 5197 KiB

Open AccessArticle

Development of A Loss Minimization Based Operation Strategy for Embedded BTB VSC HVDC

by Jaehyeong Lee, Minhan Yoon, Sungchul Hwang, Soseul Jeong, Seungmin Jung and Gilsoo Jang

Appl. Sci. 2019, 9(11), 2234; https://doi.org/10.3390/app9112234 - 30 May 2019

Cited by 4 | Viewed by 2551

Abstract

Recently, there have been many cases in which direct current (DC) facilities have been placed in alternating current (AC) systems for various reasons. In particular, in Korea, studies are being conducted to install a back-to-back (BTB) voltage-sourced converter (VSC) high-voltage direct current (HVDC) to solve the fault current problem of the meshed system, and discussions on how to operate it have been made accordingly. It is possible to provide grid services such as minimizing grid loss by changing the HVDC operating point, but it also may violate reliability standards without proper HVDC operation according to the system condition. Especially, unlike the AC system, DC may adversely affect the AC system because the operating point does not change even after a disturbance has occurred, so strategies to change the operating point after the contingency are required. In this paper, a method for finding the operating point of embedded HVDC that minimizes losses within the range of compliance with the reliability criterion is proposed. We use the Power Transfer Distribution Factor (PTDF) to reduce the number of buses to be monitored during HVDC control, reduce unnecessary checks, and determine the setpoints for the active/reactive power of the HVDC through system total loss minimization (STLM) control to search for the minimum loss point using Powell’s direct set. We also propose an algorithm to search for the operating point that minimizes the loss automatically and solves the overload occurring in an emergency through security-constrained loss minimization (SCLM) control. To verify the feasibility of the algorithm, we conducted a case study using an actual Korean power system and verified the effect of systematic loss reduction and overload relief in a contingency. The simulations are conducted by a commercial power system analysis tool, Power System Simulator for Engineering (PSS/E). Full article

(This article belongs to the Special Issue HVDC for Grid Services in Electric Power Systems)

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11 pages, 7257 KiB

Open AccessArticle

A Novel Overcurrent Suppression Strategy during Reclosing Process of MMC-HVDC

by Bin Jiang and Yanfeng Gong

Appl. Sci. 2019, 9(9), 1737; https://doi.org/10.3390/app9091737 - 26 Apr 2019

Cited by 2 | Viewed by 2360

Abstract

A modular multilevel converter based high-voltage DC (MMC-HVDC) system has been the most promising topology for HVDC. A reclosing scheme is usually configured because temporary faults often occur on transmission lines especially when overhead lines are used, which often brings about an overcurrent problem. In this paper, a new fault current limiter (FCL) based on reclosing current limiting resistance (RCLR) is proposed to solve the overcurrent problem during the reclosing process. Firstly, a mesh current method (MCM) based short-circuit current calculation method is newly proposed to solve the fault current calculation of a loop MMC-HVDC grid. Then the method to calculate the RCLR is proposed based on the arm current to limit the arm currents to a specified value during the reclosing process. Finally, a three-terminal loop MMC-HVDC test grid is constructed in the widely used electromagnetic transient simulation software PSCAD/EMTDC and the simulations prove the effectiveness of the proposed strategy. Full article

(This article belongs to the Special Issue HVDC for Grid Services in Electric Power Systems)

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13 pages, 6113 KiB

Open AccessArticle

Application of a DC Distribution System in Korea: A Case Study of the LVDC Project

by Juyong Kim, Hyunmin Kim, Youngpyo Cho, Hongjoo Kim and Jintae Cho

Appl. Sci. 2019, 9(6), 1074; https://doi.org/10.3390/app9061074 - 14 Mar 2019

Cited by 4 | Viewed by 2977

Abstract

With the rapid expansion of renewable energy and digital devices, there is a need for direct current (DC) distribution technology that can increase energy efficiency. As a result, DC distribution research is actively underway to cope with the sudden digitization and decentralization of load environment and power supply. To verify the possibility of DC distribution, Korea Electric Power Corporation (KEPCO) Research Institute made a DC distribution system connected with a real power system in Gwangju. The construction of the demonstration area mainly includes design of protection and grounding systems, operating procedures of insulation monitoring device (IMD), and construction of power converters. Furthermore, this paper goes beyond the simulation and the lab testing to apply DC distribution to a real system operation in advance. It is designed as a long-distance low-loaded customer for rural areas and operated by the DC distribution. In addition, safety and reliability are confirmed through field tests of DC distribution elements such as power conversion devices, protection and grounding systems. In particular, to improve the reliability of non-grounding system, the insulation monitoring device was installed and the algorithms of its operational procedures are proposed. Finally, this paper analyzes the problems caused by operating the actual DC distribution and suggests solutions accordingly. Full article

(This article belongs to the Special Issue HVDC for Grid Services in Electric Power Systems)

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12 pages, 2114 KiB

Open AccessArticle

A Quantitative Index to Evaluate the Commutation Failure Probability of LCC-HVDC with a Synchronous Condenser

by Jiangbo Sha, Chunyi Guo, Atiq Ur Rehman and Chengyong Zhao

Appl. Sci. 2019, 9(5), 925; https://doi.org/10.3390/app9050925 - 05 Mar 2019

Cited by 13 | Viewed by 3199

Abstract

Since thyristor cannot turn off automatically, line commutated converter based high voltage direct current (LCC-HVDC) will inevitably fail to commutate and therefore auxiliary controls or voltage control devices are needed to improve the commutation failure immunity of the LCC-HVDC system. The voltage control device, a synchronous condenser (SC), can effectively suppress the commutation failure of the LCC-HVDC system. However, there is a need for a proper evaluation index that can quantitatively assess the ability of the LCC-HVDC system to resist the occurrence of commutation failures. At present, the main quantitative evaluation indicators include the commutation failure immunity index and the commutation failure probability index. Although they can reflect the resistance of the LCC-HVDC system to commutation failures to a certain extent, they are all based on specific working conditions and cannot comprehensively evaluate the impact of SCs on suppressing the commutation failure of the LCC-HVDC system under certain fault ranges. In order to more comprehensively and quantitatively evaluate the influence of SCs on the commutation failure susceptibility of the LCC-HVDC system under certain fault ranges, this paper proposes the area ratio of commutation failure probability. The accuracy of this new index was verified through the PSCAD/EMTDC. Based on the CIGRE benchmark model, the effects of different synchronous condensers on LCC-HVDC commutation failure were analyzed. The results showed that the new index could effectively and more precisely evaluate the effect of SCs on commutation failures. Moreover, the proposed index could provide a theoretical basis for the capacity allocation of SCs in practical projects and it could also be utilized for evaluating the impact of other dynamic reactive power compensators on the commutation failure probability of the LCC-HVDC system under certain fault ranges. Full article

(This article belongs to the Special Issue HVDC for Grid Services in Electric Power Systems)

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14 pages, 2535 KiB

Open AccessArticle

A Frequency–Power Droop Coefficient Determination Method of Mixed Line-Commutated and Voltage-Sourced Converter Multi-Infeed, High-Voltage, Direct Current Systems: An Actual Case Study in Korea

by Gyusub Lee, Seungil Moon and Pyeongik Hwang

Appl. Sci. 2019, 9(3), 606; https://doi.org/10.3390/app9030606 - 12 Feb 2019

Cited by 6 | Viewed by 3221

Abstract

Among the grid service applications of high-voltage direct current (HVDC) systems, frequency–power droop control for islanded networks is one of the most widely used schemes. In this paper, a new frequency-power droop coefficient determination method for a mixed line-commutated converter (LCC) and voltage-sourced converter (VSC)-based multi-infeed HVDC (MIDC) system is proposed. The proposed method is designed for the minimization of power loss. An interior-point method is used as an optimization algorithm to implement the proposed scheduling method, and the droop coefficients of the HVDCs are determined graphically using the Monte Carlo sampling method. Two test systems—the modified Institute of Electrical and Electronics Engineers (IEEE) 14-bus system and an actual Jeju Island network in Korea—were utilized for MATLAB simulation case studies, to demonstrate that the proposed method is effective for reducing power system loss during frequency control. Full article

(This article belongs to the Special Issue HVDC for Grid Services in Electric Power Systems)

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17 pages, 4492 KiB

Open AccessArticle

Analysis of Six Active Power Control Strategies of Interconnected Grids with VSC-HVDC

by Sungyoon Song, Minhan Yoon and Gilsoo Jang

Appl. Sci. 2019, 9(1), 183; https://doi.org/10.3390/app9010183 - 06 Jan 2019

Cited by 8 | Viewed by 4534

Abstract

In this paper, the generator angle stability of several active power control schemes of a voltage-source converter (VSC)-based high-voltage DC (HVDC) is evaluated for two interconnected AC systems. Excluding frequency control, there has been no detailed analysis of interconnected grids depending upon the converter power control, so six different types of active power control of the VSC-HVDC are defined and analyzed in this paper. For each TSO (transmission system operator), the applicable schemes of two kinds of step control and four kinds of ramp-rate control with a droop characteristic are included in this research. Furthermore, in order to effectively evaluate the angle stability, the Generators-VSC Interaction Factor (GVIF) index is newly implemented to distinguish the participating generators (PGs) group which reacts to the converter power change. As a result, the transient stabilities of the two power systems are evaluated and the suitable active power control strategies are determined for two TSOs. Simulation studies are performed using the PSS^®E program to analyze the power system transient stability and various active power control schemes of the VSC-HVDC. The results provide useful information indicating that the ramp-rate control shows a more stable characteristic than the step-control for interconnected grids; thus, a converter having a certain ramp-rate slope similar to that of the other generator shows more stable results in several cases. Full article

(This article belongs to the Special Issue HVDC for Grid Services in Electric Power Systems)

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15 pages, 7188 KiB

Open AccessArticle

Assessment of Appropriate MMC Topology Considering DC Fault Handling Performance of Fault Protection Devices

by Ho-Yun Lee, Mansoor Asif, Kyu-Hoon Park and Bang-Wook Lee

Appl. Sci. 2018, 8(10), 1834; https://doi.org/10.3390/app8101834 - 06 Oct 2018

Cited by 5 | Viewed by 3696

Abstract

The eventual goal of high-voltage direct-voltage (HVDC) systems is to implement HVDC grids. The modular multilevel converter (MMC) has been identified as the best candidate for the realization of an HVDC grid by eliminating the shortcomings of conventional voltage source converter (VSC) technology. The related research has focused on efficient control schemes, new MMC topologies, and operational characteristics of an MMC in a DC grid, but there is little understanding about the fault handling capability of two mainstream MMC topologies, i.e., half bridge (HB) and full bridge (FB) MMCs in combination with an adequate protection device. Contrary to the existing research where the fault location is usually fixed (center of the line), this paper considered a variable fault location on the DC line, so as to compare the fault interruption time and maximum fault current magnitude. From the point of view of fault interruption, AC and DC side transient analyses were performed for both MMC topologies to suggest the appropriate topology. The simulation result confirmed that the fault handling performance of an HB-MMC with a DC circuit breaker is superior due to the smaller fault current magnitude, faster interruption time, lower overvoltage magnitude, and lesser stresses on the insulation of the DC grid. Full article

(This article belongs to the Special Issue HVDC for Grid Services in Electric Power Systems)

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25 pages, 15837 KiB

Open AccessArticle

A Study on Stability Control of Grid Connected DC Distribution System Based on Second Order Generalized Integrator-Frequency Locked Loop (SOGI-FLL)

by Jin-Wook Kang, Ki-Woong Shin, Hoon Lee, Kyung-Min Kang, Jintae Kim and Chung-Yuen Won

Appl. Sci. 2018, 8(8), 1387; https://doi.org/10.3390/app8081387 - 16 Aug 2018

Cited by 7 | Viewed by 6038

Abstract

This paper studies a second order generalized integrator-frequency locked loop (SOGI-FLL) control scheme applicable for 3-phase alternating current/direct current (AC/DC) pulse width modulation (PWM) converters used in DC distribution systems. The 3-phase AC/DC PWM converter is the most important power conversion system of DC distribution, since it can boost 380 V_rms 3-phase line-to-line AC voltage to 700 V_dc DC output with various DC load devices and grid voltages. The direct-quadrature (d-q) transformation, positive sequence voltage extraction, proportional integral (PI) voltage/current control, and phase locked loop (PLL) are necessary to control the 3-phase AC/DC PWM converter. Besides, a digital filter, such as low pass filter and all pass filter, are essential in the conventional synchronous reference frame-phase locked loop (SRF-PLL) method to eliminate the low order harmonics of input. However, they limit the bandwidth of the controller, which directly affects the output voltage and load of 3-phase AC/DC PWM converter when sever voltage fluctuation, such as sag, swell, etc. occurred in the grid. On the other hand, the proposed control method using SOGI-FLL is able to do phase angle detection, positive sequence voltage extraction, and harmonic filtering without additional digital filters, so that more stable and fast transient control is achieved in the DC distribution system. To verify the improvement of the characteristics in the unbalanced voltage and frequency fluctuation of the grid, a simulation and experiment are implemented with 50 kW 3-phase AC/DC PWM converter used in DC distribution. Full article

(This article belongs to the Special Issue HVDC for Grid Services in Electric Power Systems)

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14 pages, 6588 KiB

Open AccessFeature PaperArticle

Novel Transient Power Control Schemes for BTB VSCs to Improve Angle Stability

by Sungyoon Song, Sungchul Hwang, Baekkyeong Ko, Seungtae Cha and Gilsoo Jang

Appl. Sci. 2018, 8(8), 1350; https://doi.org/10.3390/app8081350 - 11 Aug 2018

Cited by 7 | Viewed by 3403

Abstract

This paper proposes two novel power control strategies to improve the angle stability of generators using a Back-to-Back (BTB) system-based voltage source converter (VSC). The proposed power control strategies have two communication systems: a bus angle monitoring system and a special protection system (SPS), respectively. The first power control strategy can emulate the behaviour of the ac transmission to improve the angle stability while supporting the ac voltage at the primary level of the control structure. The second power control scheme uses an SPS signal to contribute stability to the power system under severe contingencies involving the other generators. The results for the proposed control scheme were validated using the PSS/E software package with a sub-module written in the Python language, and the simple assistant power control with two communication systems is shown to improve the angle stability. In conclusion, BTB VSCs can contribute their power control strategies to ac grid in addition to offering several existing advantages, which makes them applicable for use in the commensurate protection of large ac grid. Full article

(This article belongs to the Special Issue HVDC for Grid Services in Electric Power Systems)

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