CN2807593Y - Transducer capable of filtering common mode and differential mode voltage change rate - Google Patents

Abstract

The utility model relates to a pulse width modulation frequency converter. The frequency converter capable of filtering out common-mode and differential-mode voltage change rates includes a rectifier 1, an inverter 2, a smoothing capacitor C4, a first inductor LI, a second inductor LII, a third inductor LIII, a fourth inductor LIV, and a fifth inductor Inductor LV, sixth inductance LVI, seventh inductance LVII, first capacitor C1, second capacitor C2, third capacitor C3 and resistor R, one end of LI, one end of LII and one end of LIII are respectively connected to 2, and the The other end is connected to LIV and one end of C1, the other end of LII is connected to one end of LV and C2, LIII is connected to one end of LVI and C3, the other end of C1 is connected to the other end of C2, C3 and one end of R, and the other end of R is connected to LVII One end of LVII, the other end of LVII is connected to the negative or positive input of 2, LIV, LV, LVI and LVII are the same and wound on the same ring core T in the same phase. By eliminating dv/dt, it eliminates the harm of dv/dt to the electrical energy quality of the motor and the grid.

Description

Frequency converters that filter common-mode and differential-mode voltage rates of change

Technical field:

The utility model relates to a pulse width modulation (PWM) frequency converter with a passive filter used in systems such as electric drive and electric drive.

Background technique:

Frequency conversion speed regulation is an AC drive control technology with high benefit, good performance and wide application. As a control device for frequency conversion and speed regulation, the frequency converter has been widely used in various fields such as industry, agriculture and national defense, and will play an increasingly important role in the future world. However, frequency converters have made great contributions in terms of energy saving, improvement of human living environment, reduction of production costs, improvement of product quality, and improvement of industrial automation, while also producing some significant negative effects. With the rapid development of modern power electronic devices, the switching frequency of power switching devices, such as insulated gate bipolar transistors IGBT, can reach tens of kHz, and its fast turn-on and turn-off characteristics make the output of the inverter produce high dv/dt( voltage change rate). Excessively high dv/dt will cause a series of hazards to the drive system of the inverter, which can be summarized as follows: (1) During the high-speed on-off period of the power switching device, the high-frequency dv/dt will excite eddy currents in the motor core laminations and cause Heat loss will also cause the copper wire winding of the motor to consume more energy through the skin effect, aggravate the heat loss of the motor, increase the power loss of the motor, and reduce the efficiency, thereby affecting the performance of the motor. When the frequency of the high-frequency electromagnetic oscillation generated by the frequency converter is close to the natural oscillation frequency of the components of the motor, it will induce mechanical resonance and noise. (2) Due to the distributed capacitance of the power line and the parasitic capacitance inside the motor at high frequency, a charging and discharging current I _1g (I _1g is called leakage current, which is proportional to dv/dt) will be generated, which will flow into the ground wire and the leakage current will exceed It will cause malfunction of the motor protection circuit. (3) When the high-carrier frequency voltage-type PWM inverter drives the motor, when the high-frequency dv/dt acts on the parasitic capacitance inside the motor, not only will a charging and discharging current be generated, but also the rotor shaft will be damaged due to the cumulative effect of the capacitance. The voltage rises. Both of these will cause the breakdown of the lubricating oil film and produce EDM, which will cause premature damage to the motor bearing, increase the maintenance cost of the motor, and affect the normal operation of the system; (4) Leakage current with frequency ranging from 100kHz to several megabytes It flows back to the three-phase power supply of the system through the ground wire, generating high-frequency electromagnetic interference (EMI). It will lead to a decrease in power supply efficiency; it will also cause the relay protection device to malfunction due to interference, affect the normal operation of other electronic equipment on the grid, and even cause damage to the equipment; (5) When the motor and the frequency converter are inevitably When long-line transmission cables are used, such as in oil exploration, papermaking, mining and other fields, the distributed inductance and distributed capacitance due to long-line cables will produce reflected waves, which will double the dv/dt at the motor end. The doubling of the dv/dt of the common-mode voltage can further aggravate the above hazards.

Utility model content:

The utility model provides a frequency converter capable of filtering out common-mode and differential-mode voltage change rates, which can simultaneously eliminate the dv/dt of differential-mode voltage and the dv/dt of common-mode voltage, thereby eliminating the impact of dv/dt on the electric energy of the motor and the grid. quality hazards. It includes a rectifier 1, an inverter 2 and a smoothing capacitor C4, one end of the smoothing capacitor C4 is connected to the positive output terminal of the rectifier 1 and the positive input terminal of the inverter 2, and the other end of the smoothing capacitor C4 is connected to the negative output of the rectifier 1 terminal and the negative input terminal of the inverter 2, it also includes the first inductance LI, the second inductance LII, the third inductance LIII, the fourth inductance LIV, the fifth inductance LV, the sixth inductance LVI, the seventh inductance LVII, the A capacitor C1, a second capacitor C2, a third capacitor C3 and a resistor R, one end of the first inductance LI, one end of the second inductance LII and one end of the third inductance LIII are respectively connected to the three-phase output terminals of the inverter 2 , the other end of the first inductance LI is connected to one end of the fourth inductance LIV and one end of the first capacitor C1, the other end of the second inductance LII is connected to one end of the fifth inductance LV and one end of the second capacitor C2, and the third inductance LIII is connected to One end of the sixth inductance LVI and one end of the third capacitor C3, the other end of the first capacitor C1 is connected to the other end of the second capacitor C2, the other end of the third capacitor C3 and one end of the resistor R, and the other end of the resistor R is connected to the second end One end of the seven inductance LVII, the other end of the seventh inductance LVII is connected to the negative or positive input end of the inverter, the fourth inductance LIV, the fifth inductance LV, the sixth inductance LVI and the seventh inductance LVII are the same and wound in the same phase On the same toroidal core T, the capacitance values of the first capacitor C1, the second capacitor C2 and the third capacitor C3 are equal, and the first inductance L I, the second inductance LII and the third inductance LIII are the same. When the utility model works, the other ends of LIV, LV and LVI are respectively connected to the three-phase power input terminals of the motor, and LI, LII, LIII, C1, C2 and C3 form a differential mode filter to filter out the dv/ of the differential mode voltage. dt, C1, C2, C3, R, LI, LII, LIII, LIV, LV, LVI and LVII form a common-mode filter to filter out the dv/dt of the common-mode voltage, and the filter in the frequency converter of the present invention can filter In addition to dv/dt, the harm of dv/dt to the power quality of the motor and the grid is avoided, and because the fourth inductance LIV, the fifth inductance LV, the sixth inductance LVI and the seventh inductance LVII have the same number of turns and are wound in the same phase On a toroidal core T, the suppression of the common mode voltage dv/dt is basically not affected by the frequency change of the frequency converter. The utility model has the advantages of reasonable design, reliable operation and great popularization value.

Description of drawings:

Fig. 1 is a circuit structure schematic diagram of the present utility model, and Fig. 2 is the fourth inductance LIV, the fifth inductance LV, the sixth inductance LVI, the seventh inductance LVII and the ring iron core T winding connection schematic diagram, Fig. 3 is without filter Motor terminal common mode voltage schematic diagram, Fig. 4 is the motor terminal common mode voltage schematic diagram after applying the filter of the utility model, Fig. 5 is the motor terminal differential mode voltage schematic diagram without the filter, Fig. 6 has applied the utility model Schematic diagram of the differential mode voltage at the motor end after the filter.

Detailed ways:

Specific Embodiment 1: The present embodiment will be specifically described below with reference to FIG. 1 to FIG. 6 . In this embodiment, the rectifier 1, the inverter 2 and the smoothing capacitor C4 are connected. One end of the smoothing capacitor C4 is connected to the positive output terminal of the rectifier 1 and the positive input terminal of the inverter 2, and the other end of the smoothing capacitor C4 is connected to the terminal of the rectifier 1. The negative output terminal and the negative input terminal of the inverter 2, which also includes a first inductor LI, a second inductor LII, a third inductor LIII, a fourth inductor LIV, a fifth inductor LV, a sixth inductor LVI, and a seventh inductor LVII , the first capacitor C1, the second capacitor C2, the third capacitor C3 and the resistor R, one end of the first inductance L I, one end of the second inductance LII and one end of the third inductance LIII are respectively connected to the three-phase inverter 2 On the output terminal, the other end of the first inductance LI is connected to one end of the fourth inductance LIV and one end of the first capacitor C1, the other end of the second inductance LII is connected to one end of the fifth inductance LV and one end of the second capacitor C2, and the third The inductance LIII is connected with one end of the sixth inductance LVI and one end of the third capacitor C3, the other end of the first capacitor C1 is connected with the other end of the second capacitor C2, the other end of the third capacitor C3 and one end of the resistor R, and the other end of the resistor R One end is connected to one end of the seventh inductance LVII, the other end of the seventh inductance LVII is connected to the negative or positive input end of the inverter, the fourth inductance LIV, the fifth inductance LV, the sixth inductance LVI and the seventh inductance LVII are the same and Wound on the same annular iron core T in the same phase, the capacitance values of the first capacitor C1, the second capacitor C2 and the third capacitor C3 are equal, and the first inductance LI, the second inductance LII and the third inductance LIII are the same. The output voltage of the three-phase voltage-type PWM inverter includes positive and negative sequence components (ie, differential mode voltage) and zero sequence components (ie, common mode voltage), which are commonly referred to as line voltage and phase voltage.

Claims (1)

1, but the frequency converter of filtering common mode and differential mode voltage rate of change, it comprises rectifier (1), inverter (2) and flat wave capacitor (C4,) end of flat wave capacitor (C4) connects the cathode output end of rectifier (1) and the electrode input end of inverter (2), the other end of flat wave capacitor (C4) connects the cathode output end of rectifier (1) and the negative input of inverter (2), it is characterized in that it also comprises first inductance (LI), second inductance (LII), the 3rd inductance (LIII), the 4th inductance (LIV), the 5th inductance (LV), the 6th inductance (LVI), the 7th inductance (LVII), first electric capacity (C1), second electric capacity (C2), the 3rd electric capacity (C3) and resistance (R), one end of first inductance (LI), one end of one end of second inductance (LII) and the 3rd inductance (LIII) is connected on the three-phase output end of inverter (2), the other end of first inductance (LI) connects an end of the 4th inductance (LIV) and an end of first electric capacity (C1), the other end of second inductance (LII) connects an end of the 5th inductance (LV) and an end of second electric capacity (C2), the 3rd inductance (LIII) connects an end of the 6th inductance (LVI) and an end of the 3rd electric capacity (C3), the other end of first electric capacity (C1) connects the other end of second electric capacity (C2), one end of the other end of the 3rd electric capacity (C3) and resistance (R), the other end of resistance (R) connects an end of the 7th inductance (LVII), the other end of the 7th inductance (LVII) connects the negative input or the electrode input end of inverter, the 4th inductance (LIV), the 5th inductance (LV), the 6th inductance (LVI) and homophase identical with the 7th inductance (LVII) is wound on the same annular core (T), first electric capacity (C1), the capacitance of second electric capacity (C2) and the 3rd electric capacity (C3) equates, first inductance (LI), second inductance (LII) is identical with the 3rd inductance (LIII).

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