With the rapid development of China's industry and power systems, long HVAC transmission lines generate substantial capacitive charging power. This results in significant fluctuations in reactive power demand between capacitive and inductive, especially with new energy base power flow variations. The frequent no-load operation of the power system brings excess capacitive reactive power and severe voltage over-limits, restricting HV line operation. Although SVC and SVG can achieve continuous reactive power regulation, they are limited by device ratings, need transformers for HV connection, and have harmonic problems. In contrast, MCR can be directly connected to the HV grid, adjusting impedance to release line-charging reactive power and control voltage. This paper proposes a coordinated control strategy for new energy collection systems. By connecting MCR to the HV busbar, it enables continuous reactive power compensation. The study of MCR's electromagnetic models reveals factors affecting response speed, leading to a new IGBT-controlled excitation structure. Simulation and experimental results verify that this structure can limit MCR's magnetization and demagnetization time within 100 ms, effectively enhancing its response performance for better power grid voltage stability.