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The regulator section is equipped with four regulators: an intermediate-frequency voltage regulator, a current regulator, an impedance regulator, and an inverter angle regulator.

Among these, the voltage regulator and current regulator together form a conventional current-voltage dual-loop control system. Throughout the entire startup and operation phases, the current loop remains continuously active, whereas the voltage loop operates only during the operation phase. The other component—a impedance regulator—appears, from the input perspective, to be connected in parallel with the input of the current regulator. The only difference lies in the fact that the impedance regulator has a slightly larger negative feedback coefficient than the current regulator. Furthermore, the output of the current regulator controls the DC output voltage of the rectifier bridge, while the output of the impedance regulator controls the ratio between the intermediate-frequency voltage and the DC voltage—that is, the inversion power-factor angle.

Regulator circuit The operating process can be divided into two scenarios: In the first scenario, when the DC voltage has not yet reached its maximum value, the feedback coefficient of the impedance regulator is slightly larger than the setpoint. As a result, the impedance regulator’s setpoint falls below the feedback signal, causing the regulator to enter a limiting state—corresponding to the minimum inverter e-angle. At this point, the impedance regulator can be considered inactive, and the system functions entirely as a standard voltage-current dual-loop control system. In the second scenario, once the DC voltage has reached its maximum value, the current regulator begins to limit its output and effectively ceases to function. Meanwhile, the output of the voltage regulator increases, while the feedback current remains unchanged. For the impedance regulator, when the feedback current signal becomes slightly smaller than the setpoint current, the regulator exits the limiting state and resumes operation, adjusting the e-angle setpoint of the inverter angle regulator to increase the output intermediate-frequency voltage. Consequently, the DC current also rises, eventually reaching a new equilibrium. At this stage, only the voltage regulator and the impedance regulator remain active, and R continues to increase until it reaches the maximum inverter e-angle. The inverter angle regulator ensures that the inverter bridge operates stably at a specific e-angle.