Table 3 MMC-HVDC of OWFs researches
References | Year | Goals | Objectives | Performance | Complexity | Superiority | ||
|---|---|---|---|---|---|---|---|---|
Modulation strategy | Submodule equalization | AC/DC fault protection | ||||||
Gi et al. [75] | 2018 | √ |  |  | •  DC series-connected wind farm •  Tap changing transformer | •  Stable power transmission | *** | *** |
Fan et al. [76] | 2018 | √ |  |  | •  Voltage droop control •  Improve PI control | •  Active power balance achieved •  DC-side volatile stability enhanced •  Conventional PI control improved | *** | *** |
Yao et al. [77] | 2019 |  | √ | √ | •  AC/DC converter •  Six-phase PMSG | •  Minimum torque ripple and harmonics ensured •  Voltage fluctuation suppressed | **** | **** |
Zun et al. [78] | 2019 | √ |  |  | •  Capacitor energy of MMC-HVDC submodule •  Over-speed reserve capacity | •  Fast frequency support provided •  System inertia improved | **** | *** |
Meng et al. [79] | 2020 | √ | √ |  | •  Parallel multiple submodule (PM-SM) •  Carrier phase-shift modulation | •  Power quality of the system improved •  High frequency filtered | **** | *** |
Zhang et al. [80] | 2021 | √ |  |  | •  Hybrid MMC •  Unloading resistor | •  Reactive power support enhanced •  Voltage drops alleviated | **** | **** |