TY - JOUR
T1 - Improved control strategy of mmc–hvdc to improve frequency support of ac system
AU - Zhang, Zicong
AU - Lee, Junghun
AU - Jang, Gilsoo
N1 - Funding Information:
Figure 11. Relationship between inertia constant, ESCR of AC system, and number of offshore wind turbine deviations. turbine deviations. 6. Conclusions 6. Conclusions In this paper, an improved inertia constant control that uses the ESCR value of the AC system In this paper, an improved inertia constant control that uses the ESCR value of the AC system is presented. This method aids the system in maintaining its frequency stability by using the energy stored in the capacitor of the MMC submodules and via effective damping of the frequency oscillations owing to load loss. The simulation results show that improved inertia control can better support the frequency stability of the AC system under various conditions. Whether it is under 10% load reduction or 20% load reduction, the improved inertia control strategy provides good support for system stability. In addition, the control accuracy of this method is higher even if the system is in a relatively weaker state (and even in the case of a system with an extremely low inertia constant). The improved inertia control can also help the generators connected to it, which can effectively contain the fault effect and provide better stability support and primary frequency control for the imprsystem.oves significantly. The stability of the system itself was strengthened to ensure the stability of the As the type-4 wind-turbine penetration level decreases, the inertia constant of the MMC-HVDC improves significantly. The stability of the system itself was strengthened to ensure the stability of the system frequency when the regenerative-energy penetration level increases in the future, and a Authorfault croContributions:ssing capabiConceptualization,lity was realized. Z.Z.andJ.L.;validation,G.J.;Datacuration. Z.Z.andJ.L.;Investigation, Z.Z. and J.L.; Methodology, G.J.; Writing-original draft, Z.Z.; Writing-review & editing, J.L. and G.J. All authors Author Contributions: Conceptualization, Z.I. and J.L.; validation, G.J.; Data curation. Z.I. and J.L.; FuInnvdeisntgig:aTtihoins,w Zo.Ir.k awnda sJs.Lu.p; pMorettehdodboyloKgoyr,e aGI.nJ.s;tiWturtietionfgE-onreigrginyaTledcrhanfto, lZog.Iy.; EWvariltuiantgio-rnevainedwP &la nedniitnigng(,K JE.LT.E aPn)d grantG.J.fundedbytheKoreagovernment(MOTIE)(No. 20191210301890). Thisworkwassupportedby“Human Resources Program in Energy Technology” of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea. (No.20194030202420). Funding: This work was supported by Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government (MOTIE) (No. 20191210301890). This work was supported by “Human
Publisher Copyright:
© 2020 by the authors. Licensee MDPI, Basel, Switzerland.
PY - 2020/10/2
Y1 - 2020/10/2
N2 - With the continuous development of power electronics technology, variable-speed offshore wind turbines that penetrated the grid system caused the problem of inertia reduction. This study investigates the frequency stability of synchronous, offshore wind-farm integration through a modular-multilevel-converter high-voltage direct-current (MMC–HVDC) transmission system. When full-scale converter wind turbines (type 4) penetrate the AC grid, the AC system debilitates, and it becomes difficult to maintain the AC system frequency stability. In this paper, we present an improved inertial-response-control method to solve this problem. The mathematical model of the synchronous generator is based on the swing equation and is theoretically derived by establishing a MMC–HVDC. Based on the above model, the inertia constant is analyzed using a model that integrates the MMC–HVDC and offshore synchronous generator. With the new improved control method, a more sensitive and accurate inertia index can be obtained using the formula related to the effective short-circuit ratio of the AC system. Moreover, it is advantageous to provide a more accurate inertial control evaluation for AC systems under various conditions. Furthermore, the impact of the MMC–HVDC on system safety is assessed based on the capacitor time constant. This simulation was implemented using the PSCAD/EMTDC platform.
AB - With the continuous development of power electronics technology, variable-speed offshore wind turbines that penetrated the grid system caused the problem of inertia reduction. This study investigates the frequency stability of synchronous, offshore wind-farm integration through a modular-multilevel-converter high-voltage direct-current (MMC–HVDC) transmission system. When full-scale converter wind turbines (type 4) penetrate the AC grid, the AC system debilitates, and it becomes difficult to maintain the AC system frequency stability. In this paper, we present an improved inertial-response-control method to solve this problem. The mathematical model of the synchronous generator is based on the swing equation and is theoretically derived by establishing a MMC–HVDC. Based on the above model, the inertia constant is analyzed using a model that integrates the MMC–HVDC and offshore synchronous generator. With the new improved control method, a more sensitive and accurate inertia index can be obtained using the formula related to the effective short-circuit ratio of the AC system. Moreover, it is advantageous to provide a more accurate inertial control evaluation for AC systems under various conditions. Furthermore, the impact of the MMC–HVDC on system safety is assessed based on the capacitor time constant. This simulation was implemented using the PSCAD/EMTDC platform.
KW - Effective short circuit ratio (ESCR)
KW - Full-scale converter wind turbines (type 4), improved inertia-response control
KW - Modular multilevel-converter high-voltage direct-current (MMC-HVDC) transmission system
UR - http://www.scopus.com/inward/record.url?scp=85092777399&partnerID=8YFLogxK
U2 - 10.3390/app10207282
DO - 10.3390/app10207282
M3 - Article
AN - SCOPUS:85092777399
SN - 2076-3417
VL - 10
SP - 1
EP - 19
JO - Applied Sciences (Switzerland)
JF - Applied Sciences (Switzerland)
IS - 20
M1 - 7282
ER -