Four-quadrant frequency converter

Abstract

The invention belongs to the technical field of frequency converters and provides a four-quadrant frequency converter. According to the four-quadrant frequency converter, a frequency converter is arranged between a power grid and an induction motor; an energy feedback unit is arranged at a direct current (DC) busbar side of the frequency converter; a negative pole end DC- of a direct current busbar on the frequency converter is electrically connected with the DC- of the energy feedback unit; the DC+ on the frequency converter is electrically connected with DC+ of the energy feedback unit; three-phase alternating current output of the energy feedback unit is connected to input sides R, S and T of the frequency converter in parallel; a PE (Protecting Earthing) terminal of the energy feedback unit is reliably connected to the ground; when the busbar voltage of the frequency converter is detected by the energy feedback unit to be up to a set valve, feedback electric energy is converted to power frequency and transferred to the power grid to carry out energy saving regulation. The four-quadrant frequency converter provided by the invention has the advantages that through an external energy feedback device, the electric energy produced by the motor is added to the input end to the frequency converter after feedback and an electric reactor is additionally arranged to avoid the harmonic pollution, so that the power factor is greatly improved and the efficient utilization ratio of the electric energy is realized.

Description

technical field [0001] The invention belongs to the technical field of frequency converter control, and relates to a four-quadrant frequency converter used in some occasions of fast braking, such as elevators, hoists, mine hoists, centrifuges, oil field pumping units, and wind power grid-connected power generation. . Background technique [0002] Frequency conversion speed regulation technology involves many disciplines such as electronics, electrical engineering, information and control. The use of frequency conversion speed regulation technology is an important way to save energy, reduce consumption, improve control performance, and increase product output and quality. It has achieved good application in applications. Most of the general-purpose inverters are voltage-type AC-DC-AC inverters, that is, the three-phase AC first passes through the diode uncontrolled rectifier bridge to obtain pulsating DC power, then filters and stabilizes the voltage through electrolytic capa...

AI Technical Summary

Problems solved by technology

However, full-control devices represented by GTR and IGBT have low withstand voltage, and excessive pumping voltage may damage switching devices, electrolytic capacitors, and even damage the insulation of the motor, thereby threatening the safe operation of the system, which limits the general-purpose The range of application of the frequency converter; in order to solve the regenerative energy generated by the motor in the state of regenerative power generation, Germany's Siemens has launched a voltage-type AC-DC-AC frequency converter for four-quadrant operation of the motor, and Japan's Fuji company has also successfully developed a power regeneration device. Such as RHR series and FRENIC series power regeneration units, which separate the active inverter unit from the inverter and directly serve as a peripheral device of the inverter, which can be connected in parallel to the DC side of the inverter to feed back the regenerative energy to the grid

The common problem is that these devices are expensive, and some products have high requirements on the power grid, which is not suitable for my country's national conditions

Most domestic small and medium-capacity systems adopt energy-consuming braking, that is, the electric energy is consumed in high-power resistors through built-in or external braking resistors to realize the four-quadrant operation of the motor. Although this method is simple, it has the following serious problems: Disadvantages: (1) waste energy and reduce the efficiency of the system; (2) serious heating of the resistor affects the normal operation of other parts of the system; (3) simple energy-consuming braking sometimes cannot suppress the pumping voltage generated by rapid braking in time , which limits the improvement of braking performance (large braking torque, wide speed range, good dynamic performance)

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