Research on Key Technology and Equipment for Zhangbei 500kV DC Grid

Pang, Hui; Wei, Xiaoguang

doi:10.23919/ipec.2018.8507575

Cited by 115 publications

(99 citation statements)

References 3 publications

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“…The SM string current waveforms of the four phases were almost identical but interleaved with 90° electrical angle, which generated continuous HV and LV DC currents iH and iL. In addition, the peak-to-peak value of the SM capacitor voltages is about 5V, which agrees with the theoretical result in (8). On the other hand, Fig.…”

Section: Operation Cycle Th=10mssupporting

confidence: 84%

“…iPa appears trapezoidal waveform with positive amplitude of IH to charge the SMs in the string and with negative amplitude of IL-IH to discharge them. The SM capacitors are designed according to (8), in which SM capacitor voltage ripple ε is equal to 10%. Besides, the SM capacitor voltages are well balanced, but it can be observed that in each cycle there are slight differences among them, this is due to the low switching frequency of each SM.…”

Section: Simulation Studymentioning

confidence: 99%

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A Monopolar Symmetrical Hybrid Cascaded DC/DC Converter for HVDC Interconnections

Zhang

Cheng

et al. 2021

IEEE Trans. Power Electron.

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With the rapid development of voltage source converter (VSC) based high voltage direct current (HVDC) transmission, it is an irresistible trend that HVDC grid will come into being. High-voltage and high-power DC/DC converters will serve as DC transformers in HVDC grid to interconnect DC lines with different voltage ratings. This paper proposes a monopolar symmetrical DC/DC converter which is composed of cascaded half-bridge sub-modules (SMs) and series-connected IGBTs. This hybrid topology features low capital costs, high efficiency, small footprint, and bidirectional power transfer capability. Operation principle, parameter design, and the control strategies of this topology are introduced. A 480MW, ±500kV/±160kV monopolar symmetrical DC/DC converter is simulated to verify its performance and evaluate the efficiency. In addition, a downscaled prototype rated at 2.4kW, ±300V/±100V has been built and tested. Experimental results further validate the effectiveness of the proposed DC/DC converter.

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Section: Operation Cycle Th=10mssupporting

confidence: 84%

Section: Simulation Studymentioning

confidence: 99%

A Monopolar Symmetrical Hybrid Cascaded DC/DC Converter for HVDC Interconnections

Zhang

Cheng

et al. 2021

IEEE Trans. Power Electron.

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“…HANKS to the extensive research and field applications in the past years, modular multilevel converter based highvoltage direct-current (MMC-HVDC) technology is getting mature and has been deployed in many projects including multiterminal HVDC networks [1]- [2]. Currently, most of the commissioned MMC HVDC projects are symmetrical monopoles [3].…”

Section: Introductionmentioning

confidence: 99%

Double-Thyristor-Based Protection for Valve-Side Single-Phase-to-Ground Faults in HB-MMC-Based Bipolar HVDC Systems

Liu

Joseph

et al. 2020

IEEE Trans. Ind. Electron.

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The valve-side single-phase-to-ground (SPG) faults in half-bridge modular multilevel converter (HB-MMC) based bipolar high-voltage direct-current (HVDC) systems induce some special fault consequences: overvoltage on the submodule (SM) capacitors in converter upper arms and non-zero-crossing currents in the grid-side ac circuit breaker (ACCB). In this letter, a protection strategy based on converter embedded double-thyristors is proposed to address these issues. The double-thyristors are installed in parallel with each SM in the lower arms of the converter. By triggering the double-thyristors, the SPG fault is converted into a three-phase short-circuit which ensures current zerocrossings in the grid-side ACCB. Moreover, as the voltages of converter AC buses are clamped by the ground through the triggered double-thyristors, the upper arm overvoltage is mitigated. The effectiveness of the proposed protection strategy has been verified in a bipolar HB-MMC HVDC link built in PSCAD/EMTDC.

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“…As voltage source converters (VSCs)based (or modular multilevel converters) high-voltage DC (MTDC) transmission is economical and flexible, they are used for large-scale wind farm integration and energy transmission. Furthermore, multi-terminal high-voltage DC (MTDC) transmission is a suitable method for interconnecting multi-asynchronous power grids and wind farms [2], [3], and a four-terminal ±500 kV high-voltage DC (HVDC) system is under development to interconnect largescale onshore wind farms in the Zhangbei area [4].…”

Section: Introductionmentioning

confidence: 99%

Adaptive Virtual Capacitor Control for MTDC System With Deloaded Wind Power Plants

2020

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Coordinated droop control strategies can provide frequency support for AC area grids from wind farms integrated through multi-terminal high-voltage DC (MTDC) transmission. However, such a strategy inevitably causes DC voltage deviation for transmitting AC area frequency information, thereby deteriorating the stability and security of the MTDC system operation. This paper reports an improved adaptive virtual capacitor control strategy that can provide inertial support for the system. Instead of increasing the capacitance of the physical capacitor, a virtual capacitor is generated by utilizing the rest energy of the deloaded wind farm. Furthermore, an S-shape function is designed to adaptively adjust the capacitance of the virtual capacitor based on the operating points of the system, in order to provide a better inertial support than with the fixed virtual capacitor control strategy. The proposed strategy not only enhances the DC voltage nadir but also improves the frequency nadir of the AC area by releasing additional power from the deloaded wind farm., a MTDC system of a four-terminal voltage source converter with two wind farms is simulated using PSCAD/EMTDC. Case studies are conducted to compare and demonstrate the effectiveness of the proposed strategy under sudden load variations. INDEX TERMS droop control, frequency regulation, wind farm, inertia response, virtual capacitor, VSC-MTDC.

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Research on Key Technology and Equipment for Zhangbei 500kV DC Grid

Cited by 115 publications

References 3 publications

A Monopolar Symmetrical Hybrid Cascaded DC/DC Converter for HVDC Interconnections

A Monopolar Symmetrical Hybrid Cascaded DC/DC Converter for HVDC Interconnections

Double-Thyristor-Based Protection for Valve-Side Single-Phase-to-Ground Faults in HB-MMC-Based Bipolar HVDC Systems

Adaptive Virtual Capacitor Control for MTDC System With Deloaded Wind Power Plants

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