Variable Speed Generator Market Size, Share and Global Trend By Generator Type (Permanent Magnet Synchronous Generator, Variable Speed Self exited Induction Generator, Wound Rotor Induction Generator, Doubly Fed Induction Generator), By Technology (Mechanical, Power Electronics), By Application (Renewable Power Generation, Hydroelectric Power Generation, Oil & Gas, Mining, Commercial and Residential, Others) and Regional Forecast, 2026-2034