To solve the difficulty of medium voltage variable frequency drive of fan or pump, a technique, rotor-side variable frequency drive (RVFD), is introduced that a less power (0.2-0.3P/sub N/) low voltage (<400 V) IGBT converter is used to adjust speed of a full power medium voltage (6-10 kV) motor. The features of the technique are: simple circuit, less large devices, better power factor and smaller harmonics. An improved RVFD based on PFC technique is proposed, it can remove the influence caused by diode rectifier.

Use a less power low voltage IGBT converter to adjust speed of a full power medium voltage induction motor of fan or pump

A general constant-frequency power-factor-correction (PFC) controller is proposed for three-phase rectifiers with parallel-connected dual-boost topologies. This paper shows that unity power factor and low current distortion in all three phases can be realized by one-cycle control using one integrator with reset along with a few near and logic components. This new extension of one-cycle control provides the core PFC function to the dual-boost topologies. It does not require multipliers, as used in most other control approaches to scale the current reference according to the output power level. In each 60/spl deg/ of AC line cycle, only two switches are switched at high frequency; therefore the switching losses are significantly reduced. All switches are switched at low current, which results in reduced current ratings. This control method is simple and general. It is applicable to three-phase rectifiers that can be decoupled into parallel-connected dual-boost topologies by slight modification of the logic circuit. This control method is verified by experimental results. The proposed controller is suitable to be integrated into a three-phase PFC control chip.

A general three-phase PFC controller for rectifiers with a parallel-connected dual boost topology

A different circuit configuration for the slip-power recovery system is presented in this paper. A boost chopper is used to connect the diode rectifier to the DC-link voltage, which is composed of a capacitor and a voltage-source inverter (VSI). The diode rectifier gives rise to mains current harmonies of variable frequency, which can present subharmonics, harmonics, and interharmonics that can lead to flicker in the mains. Two simple solutions to this drawback are studied. In the first solution, additional inductances were connected on the AC side of the rotor circuits to increase the overlap angle. In the second solution, the stator current harmonics are compensated by a VSI that can work simultaneously as an inverter and as an active power filter. This system represents a very interesting and useful application for active power filters. The merits of the configuration presented are cost, control simplicity, the possibility of reactive power control over a wide range, and quasi-optimum exploitation of the electrical machine. The characteristics of the proposed system and its control are presented in this paper. It is concluded that, although the system proposed is much simpler than others, it has interesting performance.

Use a less power low voltage IGBT converter to adjust speed of a full power medium voltage induction motor of fan or pump

References

A general three-phase PFC controller for rectifiers with a parallel-connected dual boost topology

A simple slip-power recovery system with a DC voltage intermediate circuit and reduced harmonics on the mains