Will HVDC replace UHV AC transmission in the future?

Under the existing technical conditions, high-voltage DC transmission cannot replace (ultra-) high-voltage AC transmission. Here, from the point of view of HVDC transmission, UHV AC is not well understood. So let's talk about why HVDC cannot completely replace UHV AC transmission (not for UHV AC transmission). First of all, let's look at the characteristics of HVDC transmission: the converter control is complex and the cost is high; The cost of DC transmission line is low, and the farther the transmission distance, the more economical it is. There is no power angle stability problem of AC transmission system, which is suitable for long-distance transmission; Suitable for submarine cable (island power supply, offshore wind power) and urban underground cable transmission; It can connect two AC power grids asynchronously (with the same frequency, out of phase or different frequencies) without increasing the short-circuit capacity; The transmission power is controllable and the control speed is fast, which can effectively support the AC system; The converter consumes a lot of reactive power (note that for LCC-HVDC and VSC-HCDC, reactive power can be controlled independently and flexibly, and the differences between the two systems will be explained below. ), and produce harmonics; There are DC bias and electrochemical corrosion problems (grounding current hazard) in the operation of bipolar asymmetric grounding loop; Passive system is difficult to supply power (still LCC-HVDC system), and it is difficult to form a multi-terminal DC system (because DC has no zero crossing point, it is difficult to extinguish the arc, so there is no large-capacity DC circuit breaker now, and it is impossible to cut off the short circuit fault of transmission lines, which limits the development of multi-terminal DC transmission. ABB seems to have produced this thing recently, but I don't know. Economic problems: HVDC transmission is mainly due to expensive converter stations at both ends and cheap lines. Therefore, compared with AC transmission, the farther the distance, the more economical it is.