WO2023006973A1 - Electric machine overvoltage suppression circuit - Google Patents

Electric machine overvoltage suppression circuit Download PDF

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Publication number
WO2023006973A1
WO2023006973A1 PCT/EP2022/071405 EP2022071405W WO2023006973A1 WO 2023006973 A1 WO2023006973 A1 WO 2023006973A1 EP 2022071405 W EP2022071405 W EP 2022071405W WO 2023006973 A1 WO2023006973 A1 WO 2023006973A1
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WO
WIPO (PCT)
Prior art keywords
voltage
terminal
electric machine
inductor
module
Prior art date
Application number
PCT/EP2022/071405
Other languages
French (fr)
Inventor
Er Ke FAN
Bin Chen
He Song LIU
Cheng Hai GAO
Original Assignee
Siemens Aktiengesellschaft
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens Aktiengesellschaft filed Critical Siemens Aktiengesellschaft
Publication of WO2023006973A1 publication Critical patent/WO2023006973A1/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H02M1/34—Snubber circuits
    • H02M1/346—Passive non-dissipative snubbers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/08—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors
    • H02H7/09—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors against over-voltage; against reduction of voltage; against phase interruption
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H02M1/126—Arrangements for reducing harmonics from ac input or output using passive filters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
    • H02P29/02—Providing protection against overload without automatic interruption of supply
    • H02P29/024—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load
    • H02P29/0241—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load the fault being an overvoltage

Definitions

  • the present utility model relates to the field of electric machine protection, in particular to an electric machine overvoltage suppression circuit.
  • frequency converters are often used to adjust the speed of electric machines, and play an important role in allowing people to make use of electric power.
  • electric cables are often needed to connect the frequency converter to the electric machine which it drives.
  • the output voltage of a frequency converter is generally a PWM pulse voltage
  • the transmission time of a voltage pulse in the long cable is more than half of the pulse rise time.
  • a high reflected voltage will arise at the electric machine side.
  • the peak value of voltage at the electric machine side therefore rises, and overvoltage thus arises at the electric machine side. This overvoltage will accelerate ageing of the electric machine winding insulation, and is liable to cause a reduction in electric machine life or even damage thereto.
  • the present utility model provides an electric machine overvoltage suppression circuit, which can simultaneously suppress overvoltage at the electric machine side, in order to reduce the risk that the electric machine will suffer a reduction in lifespan or even damage due to overvoltage.
  • Embodiments of the present application provide an electric machine overvoltage suppression circuit, comprising: a voltage fluctuation suppression module and a voltage clamping module, the voltage fluctuation suppression module being connected to a frequency converter, and the voltage clamping module being connected separately to the voltage fluctuation suppression module and the electric machine; when the frequency converter outputs a first control voltage in AC form for controlling speed adjustment of the electric machine to the voltage fluctuation suppression module, the voltage fluctuation suppression module processes the first control voltage to reduce the rate of change of voltage of the first control voltage, and the voltage clamping module clamps the first control voltage processed by the voltage fluctuation suppression module and a reflected voltage formed from the first control voltage processed by the voltage fluctuation suppression module, to obtain a second control voltage outputted to the electric machine, such that the value of the second control voltage is less than the sum of the first control
  • the voltage fluctuation suppression module comprises three inductors, wherein the three inductors are respectively a first inductor, a second inductor and a third inductor, and the voltage clamping module comprises a first input terminal, a second input terminal and a third input terminal; a first terminal of the first inductor is connected to a first-phase output terminal of three-phase output terminals of the frequency converter, a second terminal of the first inductor is connected to the first input terminal of the voltage clamping module, and the second terminal of the first inductor is further connected to a first-phase input terminal of three- phase input terminals of the electric machine; a first terminal of the second inductor is connected to a second-phase output terminal of the three-phase output terminals of the frequency converter, a second terminal of the second inductor is connected to the second input terminal of the voltage clamping module, and the second terminal of the second inductor is further connected to a second-phase input terminal of the three-phase input terminals of the electric machine; a first terminal of the second
  • the voltage clamping module comprises a three-phase full-bridge rectifier circuit.
  • the diode is a fast recovery diode.
  • the electric machine overvoltage suppression circuit further comprises a voltage filtering module, the voltage filtering module being connected between the voltage fluctuation suppression module and the voltage clamping module, and the voltage filtering module being configured to filter the first control voltage processed by the voltage fluctuation suppression module; the voltage clamping module clamps the first control voltage processed by the voltage filtering module and a reflected voltage formed from the first control voltage processed by the voltage filtering module.
  • the voltage filtering module comprises: at least three filter capacitors, wherein at least one of the filter capacitors is connected between the second terminals of each pair of the inductors.
  • the at least three filter capacitors comprise a first filter capacitor, a second filter capacitor and a third filter capacitor, a first terminal of the first filter capacitor is connected to the second terminal of the first inductor, a second terminal of the first filter capacitor is connected to the second terminal of the second inductor, a first terminal of the second filter capacitor is connected to the second terminal of the second inductor, a second terminal of the second filter capacitor is connected to the second terminal of the third inductor, a first terminal of the third filter capacitor is connected to the second terminal of the third inductor, and a second terminal of the third filter capacitor is connected to the second terminal of the first inductor.
  • the electric machine overvoltage suppression circuit further comprises three voltage absorption modules, each of the three voltage absorption modules being connected in parallel at two ends of one of the three inductors, with different said voltage absorption modules being connected in parallel at two ends of different said inductors; the voltage absorption module absorbs at least some of a spike voltage arising across the inductor due to a jump in the first control voltage.
  • the voltage absorption module comprises an absorption resistor and an absorption capacitor, the absorption resistor being connected in series with the absorption capacitor, wherein a first terminal of the absorption resistor is connected to the first terminal of the inductor, a second terminal of the absorption resistor is connected to a first terminal of the absorption capacitor, and a second terminal of the absorption capacitor is connected to the second terminal of the inductor.
  • the voltage fluctuation suppression module of the electric machine overvoltage suppression circuit in this embodiment is connected to the frequency converter, the voltage clamping module thereof is connected separately to the voltage fluctuation suppression module and the electric machine, and when the frequency converter outputs a first control voltage in AC form for controlling speed adjustment of the electric machine to the voltage fluctuation suppression module, the voltage fluctuation suppression module can process the first control voltage to reduce the rate of change of voltage of the first control voltage, and furthermore, the voltage clamping module can clamp the first control voltage processed by the voltage fluctuation suppression module and a reflected voltage formed from the first control voltage processed by the voltage fluctuation suppression module to obtain a second control voltage outputted to the electric machine, such that the value of the second control voltage is less than the sum of the first control voltage and the reflected voltage, overvoltage caused by reflected voltage at the electric machine side is suppressed.
  • the problem of accelerated ageing of electric machine winding insulation caused by overvoltage can be mitigated effectively, and the risk that the electric machine will suffer a reduction in lifespan and damage due to overvoltage
  • Fig. 1 shows a structural schematic diagram of an optional electric machine overvoltage suppression circuit according to an embodiment of the present application.
  • Fig. 2 shows a structural schematic circuit diagram of an optional electric machine overvoltage suppression circuit according to an embodiment of the present application.
  • Fig. 3 shows a structural schematic diagram of another optional electric machine overvoltage suppression circuit according to an embodiment of the present application.
  • Fig. 4 shows a structural schematic circuit diagram of another optional electric machine overvoltage suppression circuit according to an embodiment of the present application.
  • 10 - voltage fluctuation suppression module 10 - voltage clamping module; 30 - frequency converter; 40 - electric machine; 50 - voltage filtering module;
  • Frequency converters are often used to adjust the speed of electric machines.
  • electric cables are often needed to connect the frequency converter to the electric machine which it drives.
  • the output voltage of a frequency converter is generally a PWM pulse voltage
  • the transmission time of a voltage pulse in the long cable is more than half of the pulse rise time.
  • a high reflected voltage will arise at the electric machine side.
  • the peak value of voltage at the electric machine side therefore rises, and overvoltage thus arises at the electric machine side. This overvoltage will accelerate ageing of the electric machine winding insulation, and is liable to cause a reduction in electric machine life or even damage thereto.
  • the electric machine 40 in this embodiment is a three-phase electric machine
  • the frequency converter 30 also comprises three phases.
  • Three-phase output terminals of the frequency converter 30 each output a first control voltage for controlling speed adjustment of the electric machine 40 to three-phase input terminals of the electric machine 40.
  • the electric machine overvoltage suppression circuit in this embodiment can separately process the first control voltages outputted by the three-phase output terminals of the frequency converter, to generate a corresponding second control voltage, such that ultimately, the second control voltage with a value less than the sum of the first control voltage and a reflected voltage is outputted to the electric machine 40.
  • the frequency converter 30 may be connected to the electric machine 40 by electric cables; once the electric machine overvoltage suppression circuit in this embodiment has been connected between the frequency converter 30 and the electric machine 40, at least the voltage clamping module 20 may be connected to the electric machine 30 by electric cables.
  • the length of the electric cables may be of any length, e.g. may be 50 m, 100 m, 200 m, 300 m, 1000 m, etc. It should be understood that for any length of electric cables, as long as overvoltage arises at the electric machine side thereof, a good effect can be achieved in this embodiment in terms of suppression electric machine overvoltage.
  • the electric machine overvoltage suppression circuit in this embodiment may preferably be used in situations where the length of electric cables between the frequency converter 30 and the electric machine 40 reaches 100 m or more, in which case it can suppress overvoltage at the electric machine side effectively and fully.
  • the voltage fluctuation suppression module 10 can reduce the rate of change of voltage of the first control voltage outputted by the frequency converter.
  • the rate of change of voltage is dv/dt, i.e. the derivative of voltage with respect to time, and can be used to describe the gradient of pulse voltage at positions where it jumps (rising edges or falling edges). Because the first control voltage outputted by the frequency converter 30 is a PWM pulse signal, and the jump duration is almost instantaneous, the rate of change of voltage of the first control voltage is very high at the jumps.
  • the voltage fluctuation suppression module 10 reduces the rate of change of voltage of the first control voltage, and furthermore can effectively reduce the size of the reflected voltage arising at the electric machine side.
  • the voltage clamping module 20 can clamp the first control voltage processed by the voltage fluctuation suppression module 10 and the reflected voltage formed from the first control voltage processed by the voltage fluctuation suppression module 10, to obtain the second control voltage outputted to the electric machine.
  • the voltage clamping module 20 can in fact clamp the line voltage of the three-phase input terminals of the electric machine, so that the value of the second control voltage actually outputted to the electric machine is less than the sum of the first control voltage and the reflected voltage; that is to say, it reduces the effect of the reflected voltage on the electric machine side, thereby reducing overvoltage at the electric machine side, and reducing the risk that the electric machine will suffer a reduction in lifespan and damage due to overvoltage.
  • the voltage clamping module 20 in this embodiment clamps the first control voltage processed by the voltage fluctuation suppression module 10 and the reflected voltage formed from the first control voltage processed by the voltage fluctuation suppression module 10, the outputted second control voltage is equal to the first control voltage, i.e.: the voltage clamping module 20 can eliminate the reflected voltage, so that overvoltage at the electric machine side is fully suppressed.
  • the voltage clamping module 20 can eliminate the reflected voltage, so that overvoltage at the electric machine side is fully suppressed.
  • this ideal situation is generally unattainable, and the second control voltage resulting from actual clamping will be slightly greater than the first control voltage. In this embodiment, no specific restrictions are imposed in this regard.
  • the electric machine overvoltage suppression circuit voltage fluctuation suppression module 10 in this embodiment comprises three inductors, wherein the three inductors are respectively a first inductor LI, a second inductor L2 and a third inductor L3, and the voltage clamping module 20 comprises a first input terminal, a second input terminal and a third input terminal.
  • a first terminal of the first inductor LI is connected to a first-phase output terminal U1 of the three-phase output terminals of the frequency converter
  • a second terminal of the first inductor LI is connected to the first input terminal of the voltage clamping module 20
  • the second terminal of the first inductor LI is further connected to a first-phase input terminal U2 of the three-phase input terminals of the electric machine.
  • a first terminal of the second inductor L2 is connected to a second- phase output terminal VI of the three-phase output terminals of the frequency converter, a second terminal of the second inductor L2 is connected to the second input terminal of the voltage clamping module 20, and the second terminal of the second inductor L2 is further connected to a second-phase input terminal V2 of the three-phase input terminals of the electric machine.
  • a first terminal of the third inductor L3 is connected to a third-phase output terminal W1 of the three-phase output terminals of the frequency converter, a second terminal of the third inductor L3 is connected to the third input terminal of the voltage clamping module 20, and the second terminal of the third inductor L3 is further connected to a third-phase input terminal W2 of the three-phase input terminals of the electric machine.
  • an LC filter loop Due to the electrical characteristics of the inductor, an LC filter loop easily forms between the inductor and the parasitic capacitance of an electric cable, and when the first control voltage jumps, the voltage across the inductor will not rise to a peak value instantaneously, but instead will rise relatively slowly.
  • the rate of change of voltage i.e. dv/dt
  • the value of dt is increased while dv remains unchanged, thereby effectively reducing the rate of change of voltage.
  • the rates of change of voltage of the three first control voltages for controlling electric machine speed adjustment outputted by the frequency converter 30 to the electric machine 40 are processed separately.
  • the rates of change of voltage of the first control voltages can be effectively reduced, and the size of the reflected voltage arising at the electric machine side can thereby be effectively reduced.
  • the three inductors are three inductors in the same three-phase reactor; this improves the stability of the voltage fluctuation suppression module 10 in this embodiment.
  • Harmonic currents easily arise in the inductor when the first control voltage outputted to the voltage fluctuation suppression module 10 by the frequency converter jumps, the harmonic currents and impedance easily giving rise to a spike voltage across the inductor.
  • the electric machine overvoltage suppression circuit further comprises: three voltage absorption modules, each of the three voltage absorption modules being connected in parallel at two ends of one of the three inductors, with different said voltage absorption modules being connected in parallel at two ends of different said inductors.
  • the voltage absorption module absorbs at least some of the spike voltage arising across the inductor due to a jump in the first control voltage.
  • the voltage absorption module comprises: an absorption resistor and an absorption capacitor, the absorption resistor being connected in series with the absorption capacitor, wherein a first terminal of the absorption resistor is connected to the first terminal of the inductor, a second terminal of the absorption resistor is connected to a first terminal of the absorption capacitor, and a second terminal of the absorption capacitor is connected to the second terminal of the inductor.
  • the three voltage absorption modules comprise three absorption resistors and three absorption capacitors.
  • the three voltage absorption modules are respectively a first voltage absorption module, a second voltage absorption module and a third voltage absorption module.
  • the three absorption resistors are respectively a first absorption resistor Rl, a second absorption resistor R2 and a third absorption resistor R3.
  • the three absorption capacitors are respectively a first absorption capacitor C7, a second absorption capacitor C8 and a third absorption capacitor C9.
  • the first voltage absorption module comprises the first absorption resistor R1 and the first absorption capacitor C7, the first absorption resistor R1 being connected in series with the first absorption capacitor C7, the first terminal of the first absorption resistor R1 being connected to the first terminal of the first inductor LI, the second terminal of the first absorption resistor R1 being connected to the first terminal of the first absorption capacitor C7, and the second terminal of the first absorption capacitor C7 being connected to the second terminal of the first inductor LI.
  • the second voltage absorption module comprises the second absorption resistor R2 and the second absorption capacitor C8, the second absorption resistor R2 being connected in series with the second absorption capacitor C8, the first terminal of the second absorption resistor R2 being connected to the first terminal of the second inductor L2, the second terminal of the second absorption resistor R2 being connected to the first terminal of the second absorption capacitor C8, and the second terminal of the second absorption capacitor C8 being connected to the second terminal of the second inductor L2.
  • the voltage absorption module described above it is possible to effectively absorb at least some of the spike voltage arising across the inductor due to a jump in the first control voltage, thereby eliminating the effect of the spike voltage on the inductor during operation, and enhancing the effectiveness of the inductor in terms of reducing the rate of change of voltage of the first control voltage, and it is thus also possible to reduce the size of the reflected voltage arising at the electric machine side more effectively.
  • the voltage absorption module in this optional embodiment includes the absorption resistor, this can improve the current distortion rate in the circuit despite increasing the power consumption of the electric machine overvoltage suppression circuit in this embodiment, and due to the presence thereof, the cost of the three-phase reactor can also be reduced.
  • the anode of the fourth diode D4, the anode of the fifth diode D5 and the anode of the sixth diode D6 are all connected to a negative output terminal DCN of the DC bus of the frequency converter.
  • the anode of the first diode Dl is connected to the cathode of the fourth diode D4, the anode of the second diode D2 is connected to the cathode of the fifth diode D5, and the anode of the third diode D3 is connected to the cathode of the sixth diode D6.
  • the overvoltage When the first control voltage processed by the voltage fluctuation suppression module 10 and the reflected voltage formed from the first control voltage processed by the voltage fluctuation suppression module 10 (to facilitate explanation of this operating process, the sum of these two voltages is called the overvoltage hereinbelow) experiences a jump, it is inputted to the first coupling capacitor from two sides, namely from the first inductor LI and the electric machine respectively.
  • the overvoltage of the rising edge is inputted from the anode of the first diode Dl, and is outputted from the cathode of the first diode Dl to the positive output terminal DCP of the DC bus of the frequency converter, such that the positive overvoltage can be absorbed by the DC bus of the frequency converter.
  • the voltage clamping module 20 in this embodiment it is possible to effectively reduce the effect of the reflected voltage on the electric machine side, thereby reducing the overvoltage at the electric machine side, and reducing the risk that the electric machine 40 will suffer a reduction in lifespan and damage due to overvoltage.
  • the electric machine overvoltage suppression circuit in this embodiment has better filtering performance.
  • the first control voltage first has its rate of change of voltage reduced by the voltage fluctuation suppression module 10, and is then filtered in the voltage filtering module 50; at this time, the voltage clamping module 20 then clamps the first control voltage and the reflected voltage formed from the first control voltage, to obtain the second control voltage outputted to the electric machine, such that the value of the second control voltage is less than the sum of the first control voltage and the reflected voltage, thus enabling the electric machine overvoltage suppression circuit to achieve a better effect in use when suppressing overvoltage at the electric machine side.
  • the voltage filtering module 50 may specifically be configured to reduce a high-frequency differential-mode voltage of the first control voltage processed by the voltage fluctuation suppression module 10.
  • the voltage filtering module 50 comprises: at least three filter capacitors, wherein at least one of the filter capacitors is connected between the second terminals of each pair of the inductors.
  • the at least three filter capacitors are connected to each other in a triangle formation, with three terminals connected to the second terminals of the three inductors respectively.
  • the at least three filter capacitors comprise a first filter capacitor C4, a second filter capacitor C5 and a third filter capacitor C6.
  • a first terminal of the first filter capacitor C4 is connected to the second terminal of the first inductor LI, a second terminal of the first filter capacitor C4 is connected to the second terminal of the second inductor L2, a first terminal of the second filter capacitor C5 is connected to the second terminal of the second inductor L2, a second terminal of the second filter capacitor C5 is connected to the second terminal of the third inductor L3, a first terminal of the third filter capacitor C6 is connected to the second terminal of the third inductor L3, and a second terminal of the third filter capacitor C6 is connected to the second terminal of the first inductor LI.
  • This particular circuit structure enables the electric machine overvoltage suppression circuit in this embodiment to have better filtering performance, minimizing the high-frequency differential-mode voltage of the firs control voltage processed by the voltage fluctuation suppression module 10, and thus enabling the electric machine overvoltage suppression circuit to achieve a better effect in use when suppressing overvoltage at the electric machine side.
  • the electric machine overvoltage suppression circuit in this embodiment has a marked effect in terms of suppressing electric machine overvoltage. Additionally, it has been found in the course of actual simulations and actual use that it also has a good suppressing effect on common-mode voltages.
  • a corresponding method is further provided for selecting parameter values of each inductor, capacitor and resistor, to enable the electric machine overvoltage suppression circuit in this embodiment to have better usability and fully achieve its remedial effects.
  • the parameter values of C7 - C9 are chosen according to the parameter values of LI - L3.
  • C7 and LI, C8 and L2, and C9 and L3 are respectively such that the resonant frequency fr ⁇ 30 kHz, so based on the formula capacitances of C7, C8 and C9 can be worked out.
  • capacitors C4, C5 and C6 can suppress high-frequency differential-mode voltages, and generally have small values; for example, a preferred parameter value range may be 2.2 nF - 10 nF.
  • the parameter values of Cl - C3 are chosen according to the parameter values of Li - L3.
  • Cl and Li, C2 and L2, and C3 and L3 are respectively such that the resonant frequency fr ⁇ 4 kHz, so based on the formula , the capacitances of Cl, C2 and C3 can be worked out.
  • the voltage fluctuation suppression module 10 of the electric machine overvoltage suppression circuit in this embodiment is connected to the frequency converter, the voltage clamping module 20 thereof is connected separately to the voltage fluctuation suppression module 10 and the electric machine, and when the frequency converter outputs a first control voltage in AC form for controlling speed adjustment of the electric machine to the voltage fluctuation suppression module 10, the voltage fluctuation suppression module 10 can process the first control voltage to reduce the rate of change of voltage of the first control voltage, and furthermore, the voltage clamping module 20 can clamp the first control voltage processed by the voltage fluctuation suppression module 10 and the reflected voltage formed from the first control voltage processed by the voltage fluctuation suppression module 10 to obtain the second control voltage outputted to the electric machine 40, such that the value of the second control voltage is less than the sum of the first control voltage and the reflected voltage, overvoltage caused by reflected voltage at the electric machine side is suppressed.
  • the problem of accelerated ageing of electric machine winding insulation caused by overvoltage can be mitigated effectively, and the risk that the
  • the electric machine overvoltage suppression circuit in this embodiment may be used in an electric machine control system, which may be a system in which a frequency converter controls electric machine speed adjustment.
  • the electric machine control system may comprise: a frequency converter 30, an electric machine 40 and the electric machine overvoltage suppression circuit described above, the electric machine overvoltage suppression circuit being connected between the frequency converter 30 and the electric machine 40; the frequency converter 30 outputs a first control voltage in AC form for controlling speed adjustment of the electric machine to the electric machine overvoltage suppression circuit, the electric machine overvoltage suppression circuit processes the first control voltage to generate a second control voltage outputted to the electric machine 40, and the electric machine 40 undergoes speed adjustment in response to the second control voltage.
  • the electric machine overvoltage suppression circuit is connected between the frequency converter 30 and the electric machine 40 in the electric machine control system, overvoltage caused by reflected voltage at the electric machine side can be suppressed, so that the electric machine will not suffer a reduction in lifespan or damage due to overvoltage, and the stability of the electric machine control system is thereby also increased.
  • the electric machine overvoltage suppression circuit in this embodiment may also be used in electric machine protection systems.
  • damage to the electric machine due to overvoltage at the electric machine side can be effectively prevented, so that the electric machine will not suffer a reduction in lifespan or damage due to overvoltage.

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  • Power Engineering (AREA)
  • Inverter Devices (AREA)
  • Control Of Ac Motors In General (AREA)

Abstract

Electric machine overvoltage suppression circuit (filter), comprising: a voltage fluctuation suppression module and a voltage clamping module, the voltage fluctuation suppression module being connected to a frequency converter, and the voltage clamping module being connected separately to the voltage fluctuation suppression module and the electric machine; when the frequency converter outputs a first control voltage in AC form for controlling speed adjustment of the electric machine to the voltage fluctuation suppression module, the voltage fluctuation suppression module processes the first control voltage to reduce the rate of change of voltage of the first control voltage, and the voltage clamping module clamps the first control voltage processed by the voltage fluctuation suppression module and a reflected voltage formed from the first control voltage processed by the voltage fluctuation suppression module. The voltage clamping module is a full-bridge rectifier circuit.

Description

Electric machine overvoltage suppression circuit
Technical field
The present utility model relates to the field of electric machine protection, in particular to an electric machine overvoltage suppression circuit.
Background art
Nowadays, frequency converters are often used to adjust the speed of electric machines, and play an important role in allowing people to make use of electric power. In real work situations, electric cables are often needed to connect the frequency converter to the electric machine which it drives. Because the output voltage of a frequency converter is generally a PWM pulse voltage, there is a very high rate of change of voltage at the pulse edges thereof. When the cable length exceeds a certain value, the transmission time of a voltage pulse in the long cable is more than half of the pulse rise time. Furthermore, due to mismatch between the cable impedance and the electric machine impedance, a high reflected voltage will arise at the electric machine side. The peak value of voltage at the electric machine side therefore rises, and overvoltage thus arises at the electric machine side. This overvoltage will accelerate ageing of the electric machine winding insulation, and is liable to cause a reduction in electric machine life or even damage thereto.
Summary of the utility model
The present utility model provides an electric machine overvoltage suppression circuit, which can simultaneously suppress overvoltage at the electric machine side, in order to reduce the risk that the electric machine will suffer a reduction in lifespan or even damage due to overvoltage. Embodiments of the present application provide an electric machine overvoltage suppression circuit, comprising: a voltage fluctuation suppression module and a voltage clamping module, the voltage fluctuation suppression module being connected to a frequency converter, and the voltage clamping module being connected separately to the voltage fluctuation suppression module and the electric machine; when the frequency converter outputs a first control voltage in AC form for controlling speed adjustment of the electric machine to the voltage fluctuation suppression module, the voltage fluctuation suppression module processes the first control voltage to reduce the rate of change of voltage of the first control voltage, and the voltage clamping module clamps the first control voltage processed by the voltage fluctuation suppression module and a reflected voltage formed from the first control voltage processed by the voltage fluctuation suppression module, to obtain a second control voltage outputted to the electric machine, such that the value of the second control voltage is less than the sum of the first control voltage and the reflected voltage.
In an optional embodiment, the voltage fluctuation suppression module comprises three inductors, wherein the three inductors are respectively a first inductor, a second inductor and a third inductor, and the voltage clamping module comprises a first input terminal, a second input terminal and a third input terminal; a first terminal of the first inductor is connected to a first-phase output terminal of three-phase output terminals of the frequency converter, a second terminal of the first inductor is connected to the first input terminal of the voltage clamping module, and the second terminal of the first inductor is further connected to a first-phase input terminal of three- phase input terminals of the electric machine; a first terminal of the second inductor is connected to a second-phase output terminal of the three-phase output terminals of the frequency converter, a second terminal of the second inductor is connected to the second input terminal of the voltage clamping module, and the second terminal of the second inductor is further connected to a second-phase input terminal of the three-phase input terminals of the electric machine; a first terminal of the third inductor is connected to a third-phase output terminal of the three-phase output terminals of the frequency converter, a second terminal of the third inductor is connected to the third input terminal of the voltage clamping module, and the second terminal of the third inductor is further connected to a third- phase input terminal of the three-phase input terminals of the electric machine.
In an optional embodiment, the voltage clamping module comprises a three-phase full-bridge rectifier circuit.
In an optional embodiment, the three-phase full-bridge rectifier circuit comprises: six diodes and three coupling capacitors, wherein the six diodes are respectively a first diode, a second diode, a third diode, a fourth diode, a fifth diode and a sixth diode, and the three coupling capacitors are respectively a first coupling capacitor, a second coupling capacitor and a third coupling capacitor; the cathode of the first diode, the cathode of the second diode and the cathode of the third diode are all connected to a positive output terminal of a DC bus of the frequency converter; the anode of the fourth diode, the anode of the fifth diode and the anode of the sixth diode are all connected to a negative output terminal of the DC bus of the frequency converter; the anode of the first diode is connected to the cathode of the fourth diode, the anode of the second diode is connected to the cathode of the fifth diode, and the anode of the third diode is connected to the cathode of the sixth diode; a first terminal of the first coupling capacitor is connected to the second terminal of the first inductor, and a second terminal of the first coupling capacitor is connected to the anode of the first diode; a first terminal of the second coupling capacitor is connected to the second terminal of the second inductor, and a second terminal of the second coupling capacitor is connected to the anode of the second diode; a first terminal of the third coupling capacitor is connected to the second terminal of the third inductor, and a second terminal of the third coupling capacitor is connected to the anode of the third diode; wherein the first terminal of the first coupling capacitor serves as the first input terminal of the voltage clamping module, the first terminal of the second coupling capacitor serves as the second input terminal of the voltage clamping module, and the first terminal of the third coupling capacitor serves as the third input terminal of the voltage clamping module.
In an optional embodiment, the diode is a fast recovery diode.
In an optional embodiment, the electric machine overvoltage suppression circuit further comprises a voltage filtering module, the voltage filtering module being connected between the voltage fluctuation suppression module and the voltage clamping module, and the voltage filtering module being configured to filter the first control voltage processed by the voltage fluctuation suppression module; the voltage clamping module clamps the first control voltage processed by the voltage filtering module and a reflected voltage formed from the first control voltage processed by the voltage filtering module.
In an optional embodiment, the voltage filtering module comprises: at least three filter capacitors, wherein at least one of the filter capacitors is connected between the second terminals of each pair of the inductors.
In an optional embodiment, the at least three filter capacitors comprise a first filter capacitor, a second filter capacitor and a third filter capacitor, a first terminal of the first filter capacitor is connected to the second terminal of the first inductor, a second terminal of the first filter capacitor is connected to the second terminal of the second inductor, a first terminal of the second filter capacitor is connected to the second terminal of the second inductor, a second terminal of the second filter capacitor is connected to the second terminal of the third inductor, a first terminal of the third filter capacitor is connected to the second terminal of the third inductor, and a second terminal of the third filter capacitor is connected to the second terminal of the first inductor.
In an optional embodiment, the electric machine overvoltage suppression circuit further comprises three voltage absorption modules, each of the three voltage absorption modules being connected in parallel at two ends of one of the three inductors, with different said voltage absorption modules being connected in parallel at two ends of different said inductors; the voltage absorption module absorbs at least some of a spike voltage arising across the inductor due to a jump in the first control voltage.
In an optional embodiment, the voltage absorption module comprises an absorption resistor and an absorption capacitor, the absorption resistor being connected in series with the absorption capacitor, wherein a first terminal of the absorption resistor is connected to the first terminal of the inductor, a second terminal of the absorption resistor is connected to a first terminal of the absorption capacitor, and a second terminal of the absorption capacitor is connected to the second terminal of the inductor.
Due to the fact that the voltage fluctuation suppression module of the electric machine overvoltage suppression circuit in this embodiment is connected to the frequency converter, the voltage clamping module thereof is connected separately to the voltage fluctuation suppression module and the electric machine, and when the frequency converter outputs a first control voltage in AC form for controlling speed adjustment of the electric machine to the voltage fluctuation suppression module, the voltage fluctuation suppression module can process the first control voltage to reduce the rate of change of voltage of the first control voltage, and furthermore, the voltage clamping module can clamp the first control voltage processed by the voltage fluctuation suppression module and a reflected voltage formed from the first control voltage processed by the voltage fluctuation suppression module to obtain a second control voltage outputted to the electric machine, such that the value of the second control voltage is less than the sum of the first control voltage and the reflected voltage, overvoltage caused by reflected voltage at the electric machine side is suppressed. Thus, the problem of accelerated ageing of electric machine winding insulation caused by overvoltage can be mitigated effectively, and the risk that the electric machine will suffer a reduction in lifespan and damage due to overvoltage is reduced.
Brief description of the drawings
The accompanying drawings below are merely intended to illustrate and explain the present application schematically, without limiting the scope thereof.
Fig. 1 shows a structural schematic diagram of an optional electric machine overvoltage suppression circuit according to an embodiment of the present application.
Fig. 2 shows a structural schematic circuit diagram of an optional electric machine overvoltage suppression circuit according to an embodiment of the present application.
Fig. 3 shows a structural schematic diagram of another optional electric machine overvoltage suppression circuit according to an embodiment of the present application. Fig. 4 shows a structural schematic circuit diagram of another optional electric machine overvoltage suppression circuit according to an embodiment of the present application.
Labels used in the accompanying drawings:
10 - voltage fluctuation suppression module; 20 - voltage clamping module; 30 - frequency converter; 40 - electric machine; 50 - voltage filtering module;
LI - first inductor; L2 - second inductor; L3 - third inductor; Cl - first coupling capacitor; C2 - first coupling capacitor; C3 - first coupling capacitor;
C4 - first filter capacitor; C5 - first filter capacitor; C6 - first filter capacitor;
C7 - first absorption capacitor; C8 - first absorption capacitor; C9 - first absorption capacitor;
R1 - first absorption resistor; R2 - first absorption resistor; R3 - first absorption resistor;
D1 - first diode; D2 - second diode; D3 - third diode; D4 - fourth diode; D5 - fifth diode; D6 - sixth diode;
U1 - first-phase output terminal of three-phase output terminals of frequency converter;
VI - second-phase output terminal of three-phase output terminals of frequency converter;
W1 - third-phase output terminal of three-phase output terminals of frequency converter;
U2 - first-phase input terminal of three-phase input terminals of electric machine;
V2 - second-phase input terminal of three-phase input terminals of electric machine;
W2 - third-phase input terminal of three-phase input terminals of electric machine;
DCP - positive output terminal of DC bus of frequency converter; negative output terminal of DC bus of frequency converter.
Detailed description of embodiments To enable those skilled in the art to better understand the technical solution in the embodiments of the present application, the technical solution in the embodiments of the present application is described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the embodiments described are only some, not all, of the embodiments of the present application. All other embodiments obtained by those skilled in the art on the basis of embodiments in the embodiments of the present application should fall within the scope of protection of the embodiments of the present application.
Frequency converters are often used to adjust the speed of electric machines. In real work situations, electric cables are often needed to connect the frequency converter to the electric machine which it drives. Because the output voltage of a frequency converter is generally a PWM pulse voltage, there is a very high rate of change of voltage at the pulse edges thereof. When the cable length exceeds a certain value, the transmission time of a voltage pulse in the long cable is more than half of the pulse rise time. Furthermore, due to mismatch between the cable impedance and the electric machine impedance, a high reflected voltage will arise at the electric machine side. The peak value of voltage at the electric machine side therefore rises, and overvoltage thus arises at the electric machine side. This overvoltage will accelerate ageing of the electric machine winding insulation, and is liable to cause a reduction in electric machine life or even damage thereto.
Referring to Figs. 1 - 4, an electric machine overvoltage suppression circuit is provided in this embodiment, the electric machine overvoltage suppression circuit comprising: a voltage fluctuation suppression module 10 and a voltage clamping module 20, the voltage fluctuation suppression module 10 being connected to a frequency converter 30, and the voltage clamping module 20 being connected separately to the voltage fluctuation suppression module 10 and the electric machine 40; when the frequency converter 30 outputs a first control voltage in AC form for controlling speed adjustment of the electric machine 40 to the voltage fluctuation suppression module 10, the voltage fluctuation suppression module 10 processes the first control voltage to reduce the rate of change of voltage of the first control voltage, and the voltage clamping module 20 clamps the first control voltage processed by the voltage fluctuation suppression module 10 and a reflected voltage formed from the first control voltage processed by the voltage fluctuation suppression module 10, to obtain a second control voltage outputted to the electric machine 40, such that the value of the second control voltage is less than the sum of the first control voltage and the reflected voltage.
Due to the fact that, in the electric machine overvoltage suppression circuit in this embodiment, the voltage fluctuation suppression module 10 thereof is connected to the frequency converter 30, the voltage clamping module 20 thereof is connected separately to the voltage fluctuation suppression module 10 and the electric machine, and when the frequency converter outputs a first control voltage in AC form for controlling speed adjustment of the electric machine to the voltage fluctuation suppression module 10, the voltage fluctuation suppression module 10 can process the first control voltage to reduce the rate of change of voltage of the first control voltage, and furthermore, the voltage clamping module 20 can clamp the first control voltage processed by the voltage fluctuation suppression module 10 and a reflected voltage formed from the first control voltage processed by the voltage fluctuation suppression module 10 to obtain a second control voltage outputted to the electric machine 40, such that the value of the second control voltage is less than the sum of the first control voltage and the reflected voltage, overvoltage caused by reflected voltage at the electric machine side is suppressed. Thus, the problem of accelerated ageing of electric machine winding insulation caused by overvoltage can be mitigated effectively, and the risk that the electric machine 40 will suffer a reduction in lifespan and damage due to overvoltage is reduced.
Specifically, the electric machine 40 in this embodiment is a three-phase electric machine, and the frequency converter 30 also comprises three phases. Three-phase output terminals of the frequency converter 30 each output a first control voltage for controlling speed adjustment of the electric machine 40 to three-phase input terminals of the electric machine 40. The electric machine overvoltage suppression circuit in this embodiment can separately process the first control voltages outputted by the three-phase output terminals of the frequency converter, to generate a corresponding second control voltage, such that ultimately, the second control voltage with a value less than the sum of the first control voltage and a reflected voltage is outputted to the electric machine 40.
Optionally, the frequency converter 30 may be connected to the electric machine 40 by electric cables; once the electric machine overvoltage suppression circuit in this embodiment has been connected between the frequency converter 30 and the electric machine 40, at least the voltage clamping module 20 may be connected to the electric machine 30 by electric cables. In this embodiment, there is no restriction on the length of the electric cables, which may be of any length, e.g. may be 50 m, 100 m, 200 m, 300 m, 1000 m, etc. It should be understood that for any length of electric cables, as long as overvoltage arises at the electric machine side thereof, a good effect can be achieved in this embodiment in terms of suppression electric machine overvoltage. Preferably, the electric machine overvoltage suppression circuit in this embodiment may preferably be used in situations where the length of electric cables between the frequency converter 30 and the electric machine 40 reaches 100 m or more, in which case it can suppress overvoltage at the electric machine side effectively and fully.
In this embodiment, the voltage fluctuation suppression module 10 can reduce the rate of change of voltage of the first control voltage outputted by the frequency converter. The rate of change of voltage is dv/dt, i.e. the derivative of voltage with respect to time, and can be used to describe the gradient of pulse voltage at positions where it jumps (rising edges or falling edges). Because the first control voltage outputted by the frequency converter 30 is a PWM pulse signal, and the jump duration is almost instantaneous, the rate of change of voltage of the first control voltage is very high at the jumps. In this embodiment, there is no particular restriction on the specific structure of the voltage fluctuation suppression module 10, which only needs to be able to effectively suppress and reduce the rate of change of voltage of the first control voltage outputted by the frequency converter.
The voltage fluctuation suppression module 10 reduces the rate of change of voltage of the first control voltage, and furthermore can effectively reduce the size of the reflected voltage arising at the electric machine side.
In this embodiment, the voltage clamping module 20 can clamp the first control voltage processed by the voltage fluctuation suppression module 10 and the reflected voltage formed from the first control voltage processed by the voltage fluctuation suppression module 10, to obtain the second control voltage outputted to the electric machine. In other words, the voltage clamping module 20 can in fact clamp the line voltage of the three-phase input terminals of the electric machine, so that the value of the second control voltage actually outputted to the electric machine is less than the sum of the first control voltage and the reflected voltage; that is to say, it reduces the effect of the reflected voltage on the electric machine side, thereby reducing overvoltage at the electric machine side, and reducing the risk that the electric machine will suffer a reduction in lifespan and damage due to overvoltage.
It must be explained here that ideally, when the voltage clamping module 20 in this embodiment clamps the first control voltage processed by the voltage fluctuation suppression module 10 and the reflected voltage formed from the first control voltage processed by the voltage fluctuation suppression module 10, the outputted second control voltage is equal to the first control voltage, i.e.: the voltage clamping module 20 can eliminate the reflected voltage, so that overvoltage at the electric machine side is fully suppressed. However, in actual working conditions, this ideal situation is generally unattainable, and the second control voltage resulting from actual clamping will be slightly greater than the first control voltage. In this embodiment, no specific restrictions are imposed in this regard.
In one embodiment, referring to Fig. 2, the electric machine overvoltage suppression circuit voltage fluctuation suppression module 10 in this embodiment comprises three inductors, wherein the three inductors are respectively a first inductor LI, a second inductor L2 and a third inductor L3, and the voltage clamping module 20 comprises a first input terminal, a second input terminal and a third input terminal. A first terminal of the first inductor LI is connected to a first-phase output terminal U1 of the three-phase output terminals of the frequency converter, a second terminal of the first inductor LI is connected to the first input terminal of the voltage clamping module 20, and the second terminal of the first inductor LI is further connected to a first-phase input terminal U2 of the three-phase input terminals of the electric machine. A first terminal of the second inductor L2 is connected to a second- phase output terminal VI of the three-phase output terminals of the frequency converter, a second terminal of the second inductor L2 is connected to the second input terminal of the voltage clamping module 20, and the second terminal of the second inductor L2 is further connected to a second-phase input terminal V2 of the three-phase input terminals of the electric machine. A first terminal of the third inductor L3 is connected to a third-phase output terminal W1 of the three-phase output terminals of the frequency converter, a second terminal of the third inductor L3 is connected to the third input terminal of the voltage clamping module 20, and the second terminal of the third inductor L3 is further connected to a third-phase input terminal W2 of the three-phase input terminals of the electric machine.
Due to the electrical characteristics of the inductor, an LC filter loop easily forms between the inductor and the parasitic capacitance of an electric cable, and when the first control voltage jumps, the voltage across the inductor will not rise to a peak value instantaneously, but instead will rise relatively slowly. Thus, in the rate of change of voltage (i.e. dv/dt), the value of dt is increased while dv remains unchanged, thereby effectively reducing the rate of change of voltage.
Thus, through the connection of the first inductor Li, the second inductor L2 and the third inductor L3 to the three-phase output terminals of the frequency converter 30, the rates of change of voltage of the three first control voltages for controlling electric machine speed adjustment outputted by the frequency converter 30 to the electric machine 40 are processed separately. Thus the rates of change of voltage of the first control voltages can be effectively reduced, and the size of the reflected voltage arising at the electric machine side can thereby be effectively reduced.
Optionally, the three inductors are three inductors in the same three-phase reactor; this improves the stability of the voltage fluctuation suppression module 10 in this embodiment. Harmonic currents easily arise in the inductor when the first control voltage outputted to the voltage fluctuation suppression module 10 by the frequency converter jumps, the harmonic currents and impedance easily giving rise to a spike voltage across the inductor. Thus, to prevent the three inductors from being affected by spike voltages, in one embodiment, referring to Fig. 4, the electric machine overvoltage suppression circuit further comprises: three voltage absorption modules, each of the three voltage absorption modules being connected in parallel at two ends of one of the three inductors, with different said voltage absorption modules being connected in parallel at two ends of different said inductors. The voltage absorption module absorbs at least some of the spike voltage arising across the inductor due to a jump in the first control voltage.
In this embodiment, no restrictions are imposed on the structure of the voltage absorption module, which may be any type of circuit structure capable of being used to absorb a spike voltage. For example, in a preferred embodiment, the voltage absorption module comprises: an absorption resistor and an absorption capacitor, the absorption resistor being connected in series with the absorption capacitor, wherein a first terminal of the absorption resistor is connected to the first terminal of the inductor, a second terminal of the absorption resistor is connected to a first terminal of the absorption capacitor, and a second terminal of the absorption capacitor is connected to the second terminal of the inductor.
Specifically, for three inductors, the three voltage absorption modules comprise three absorption resistors and three absorption capacitors. The three voltage absorption modules are respectively a first voltage absorption module, a second voltage absorption module and a third voltage absorption module. The three absorption resistors are respectively a first absorption resistor Rl, a second absorption resistor R2 and a third absorption resistor R3. The three absorption capacitors are respectively a first absorption capacitor C7, a second absorption capacitor C8 and a third absorption capacitor C9. The first voltage absorption module comprises the first absorption resistor R1 and the first absorption capacitor C7, the first absorption resistor R1 being connected in series with the first absorption capacitor C7, the first terminal of the first absorption resistor R1 being connected to the first terminal of the first inductor LI, the second terminal of the first absorption resistor R1 being connected to the first terminal of the first absorption capacitor C7, and the second terminal of the first absorption capacitor C7 being connected to the second terminal of the first inductor LI. The second voltage absorption module comprises the second absorption resistor R2 and the second absorption capacitor C8, the second absorption resistor R2 being connected in series with the second absorption capacitor C8, the first terminal of the second absorption resistor R2 being connected to the first terminal of the second inductor L2, the second terminal of the second absorption resistor R2 being connected to the first terminal of the second absorption capacitor C8, and the second terminal of the second absorption capacitor C8 being connected to the second terminal of the second inductor L2. The third voltage absorption module comprises the third absorption resistor R3 and the third absorption capacitor C9, the third absorption resistor R3 being connected in series with the third absorption capacitor C9, the first terminal of the third absorption resistor R3 being connected to the first terminal of the third inductor L3, the second terminal of the third absorption resistor R3 being connected to the first terminal of the third absorption capacitor C9, and the second terminal of the third absorption capacitor C9 being connected to the second terminal of the third inductor L3.
Thus, by means of the voltage absorption module described above, it is possible to effectively absorb at least some of the spike voltage arising across the inductor due to a jump in the first control voltage, thereby eliminating the effect of the spike voltage on the inductor during operation, and enhancing the effectiveness of the inductor in terms of reducing the rate of change of voltage of the first control voltage, and it is thus also possible to reduce the size of the reflected voltage arising at the electric machine side more effectively.
In addition, because the voltage absorption module in this optional embodiment includes the absorption resistor, this can improve the current distortion rate in the circuit despite increasing the power consumption of the electric machine overvoltage suppression circuit in this embodiment, and due to the presence thereof, the cost of the three-phase reactor can also be reduced.
In this embodiment, no restrictions are imposed on the particular circuit structure of the voltage clamping module 20; in one embodiment, the voltage clamping module 20 comprises a three-phase full-bridge rectifier circuit. Preferably, the three-phase full-bridge rectifier circuit is a diode three-phase full-bridge rectifier circuit.
Specifically, the three-phase full-bridge rectifier circuit comprises: six diodes and three coupling capacitors, wherein the six diodes are respectively a first diode Dl, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5 and a sixth diode D6. The three coupling capacitors are respectively a first coupling capacitor Cl, a second coupling capacitor C2 and a third coupling capacitor C3. The cathode of the first diode Dl, the cathode of the second diode D2 and the cathode of the third diode D3 are all connected to a positive output terminal DCP of a DC bus of the frequency converter. The anode of the fourth diode D4, the anode of the fifth diode D5 and the anode of the sixth diode D6 are all connected to a negative output terminal DCN of the DC bus of the frequency converter. The anode of the first diode Dl is connected to the cathode of the fourth diode D4, the anode of the second diode D2 is connected to the cathode of the fifth diode D5, and the anode of the third diode D3 is connected to the cathode of the sixth diode D6. A first terminal of the first coupling capacitor Cl is connected to the second terminal of the first inductor LI, and a second terminal of the first coupling capacitor Cl is connected to the anode of the first diode D1. A first terminal of the second coupling capacitor C2 is connected to the second terminal of the second inductor L2, and a second terminal of the second coupling capacitor C2 is connected to the anode of the second diode D2. A first terminal of the third coupling capacitor C3 is connected to the second terminal of the third inductor L3, and a second terminal of the third coupling capacitor C3 is connected to the anode of the third diode D3. The first terminal of the first coupling capacitor Cl serves as the first input terminal of the voltage clamping module 20, the first terminal of the second coupling capacitor C2 serves as the second input terminal of the voltage clamping module 20, and the first terminal of the third coupling capacitor C3 serves as the third input terminal of the voltage clamping module 20.
Preferably, the six diodes are all fast recovery diodes, with good switching performance and a short recovery time, so are able to meet the demands of use very well.
In this circuit, the three coupling capacitors have the effect of blocking DC and passing AC. Specifically, the operating process of the voltage clamping circuit 20 in this embodiment is explained below with reference to Fig. 2. As the operating processes of the three phases in the circuit are similar, to facilitate explanation, only the operating process of a sub circuit consisting of the first diode Dl, the fourth diode D4 and the first coupling capacitor Cl is explained.
When the first control voltage processed by the voltage fluctuation suppression module 10 and the reflected voltage formed from the first control voltage processed by the voltage fluctuation suppression module 10 (to facilitate explanation of this operating process, the sum of these two voltages is called the overvoltage hereinbelow) experiences a jump, it is inputted to the first coupling capacitor from two sides, namely from the first inductor LI and the electric machine respectively. If the jump is a rising edge and the PWM peak voltage is a positive voltage, then the overvoltage of the rising edge is inputted from the anode of the first diode Dl, and is outputted from the cathode of the first diode Dl to the positive output terminal DCP of the DC bus of the frequency converter, such that the positive overvoltage can be absorbed by the DC bus of the frequency converter. If the jump is a falling edge and the PWM peak voltage is a negative voltage, then the overvoltage of the falling edge is inputted from the cathode of the fourth diode D4, and is outputted from the anode of the fourth diode D4 to the negative output terminal DCN of the DC bus of the frequency converter, such that the negative overvoltage can be absorbed by the DC bus of the frequency converter.
The operating processes of a sub-circuit consisting of the second diode D2, the fifth diode D5 and the second coupling capacitor C2, and a sub-circuit consisting of the third diode D3, the sixth diode D6 and the third coupling capacitor C3, are similar, so are not described needlessly here.
Thus, by means of the voltage clamping module 20 in this embodiment, it is possible to effectively reduce the effect of the reflected voltage on the electric machine side, thereby reducing the overvoltage at the electric machine side, and reducing the risk that the electric machine 40 will suffer a reduction in lifespan and damage due to overvoltage.
In an embodiment, referring to Figs. 3 and 4, the electric machine overvoltage suppression circuit further comprises: a voltage filtering module 50, the voltage filtering module 50 being connected between the voltage fluctuation suppression module 10 and the voltage clamping module 20, and the voltage filtering module 50 being configured to filter the first control voltage processed by the voltage fluctuation suppression module 10; the voltage clamping module 20 clamps the first control voltage processed by the voltage filtering module 50 and a reflected voltage formed from the first control voltage processed by the voltage filtering module 50.
In this embodiment, as a result of having the voltage filtering module 50 configured to filter the first control voltage processed by the voltage fluctuation suppression module 10, the electric machine overvoltage suppression circuit in this embodiment has better filtering performance.
On this basis, the first control voltage first has its rate of change of voltage reduced by the voltage fluctuation suppression module 10, and is then filtered in the voltage filtering module 50; at this time, the voltage clamping module 20 then clamps the first control voltage and the reflected voltage formed from the first control voltage, to obtain the second control voltage outputted to the electric machine, such that the value of the second control voltage is less than the sum of the first control voltage and the reflected voltage, thus enabling the electric machine overvoltage suppression circuit to achieve a better effect in use when suppressing overvoltage at the electric machine side.
In this embodiment, there is no restriction on the particular structure of the voltage filtering module 50; in a preferred embodiment, the voltage filtering module 50 may specifically be configured to reduce a high-frequency differential-mode voltage of the first control voltage processed by the voltage fluctuation suppression module 10. As an optional example, the voltage filtering module 50 comprises: at least three filter capacitors, wherein at least one of the filter capacitors is connected between the second terminals of each pair of the inductors.
Preferably, the at least three filter capacitors are connected to each other in a triangle formation, with three terminals connected to the second terminals of the three inductors respectively. Referring to Fig. 4, specifically, the at least three filter capacitors comprise a first filter capacitor C4, a second filter capacitor C5 and a third filter capacitor C6. A first terminal of the first filter capacitor C4 is connected to the second terminal of the first inductor LI, a second terminal of the first filter capacitor C4 is connected to the second terminal of the second inductor L2, a first terminal of the second filter capacitor C5 is connected to the second terminal of the second inductor L2, a second terminal of the second filter capacitor C5 is connected to the second terminal of the third inductor L3, a first terminal of the third filter capacitor C6 is connected to the second terminal of the third inductor L3, and a second terminal of the third filter capacitor C6 is connected to the second terminal of the first inductor LI. This particular circuit structure enables the electric machine overvoltage suppression circuit in this embodiment to have better filtering performance, minimizing the high-frequency differential-mode voltage of the firs control voltage processed by the voltage fluctuation suppression module 10, and thus enabling the electric machine overvoltage suppression circuit to achieve a better effect in use when suppressing overvoltage at the electric machine side.
Of course, the circuit structure of the three filter capacitors described above is merely a preferred example; the three filter capacitors could also be connected in a Y shape, or, based on the circuit structure described above, a resistor could be connected to each filter capacitor, and so on. In this embodiment, no restrictions are imposed on these possible derived embodiments.
The electric machine overvoltage suppression circuit in this embodiment has a marked effect in terms of suppressing electric machine overvoltage. Additionally, it has been found in the course of actual simulations and actual use that it also has a good suppressing effect on common-mode voltages.
In the embodiments of the present application, in addition to the preferred particular circuit structures of the electric machine overvoltage suppression circuit set out above, a corresponding method is further provided for selecting parameter values of each inductor, capacitor and resistor, to enable the electric machine overvoltage suppression circuit in this embodiment to have better usability and fully achieve its benefical effects.
Referring to the circuit structure diagram of the electric machine overvoltage suppression circuit in Fig. 4, in this embodiment :
(D Selection of parameter values of the first inductor LI, the second inductor L2 and the third inductor L3: these are selected chiefly according to the electric cable length between the frequency converter and the electric machine, and the electric machine power. As an example, for a 100 m long shielded cable, the values of inductance may be chosen according to Uk = 1.5%; for a 300 m shielded cable, the values of inductance may be chosen according to Uk = 3%, wherein Uk is the short-circuit voltage of the electric machine (or impedance voltage, expressed as a percentage of the rated voltage of the electric machine). @ Selection of parameter values of the first absorption capacitor C7, the second absorption capacitor C8 and the third absorption capacitor C9: the parameter values of C7 - C9 are chosen according to the parameter values of LI - L3. Preferably, C7 and LI, C8 and L2, and C9 and L3 are respectively such that the resonant frequency fr < 30 kHz, so based on the formula
Figure imgf000024_0001
capacitances of C7, C8 and C9 can be worked out. @ Selection of parameter values of the first absorption resistor R, the second absorption resistor R2 and the third absorption resistor R3: once Li - L3 and C7 - C9 have been determined, parameter scanning is performed by means of a simulation tool, and optimal resistances are chosen; for example, a preferred resistance range may be 16 - 22 W.
(?) Selection of parameter values of the first filter capacitor C4, the second filter capacitor C5 and the third filter capacitor C6: capacitors C4, C5 and C6 can suppress high-frequency differential-mode voltages, and generally have small values; for example, a preferred parameter value range may be 2.2 nF - 10 nF.
(?) Selection of parameter values of the first coupling capacitor Cl, the second coupling capacitor C2 and the third coupling capacitor C3: the parameter values of Cl - C3 are chosen according to the parameter values of Li - L3. Preferably, Cl and Li, C2 and L2, and C3 and L3 are respectively such that the resonant frequency fr < 4 kHz, so based on the formula
Figure imgf000024_0002
, the capacitances of Cl, C2 and C3 can be worked out.
(6) Selection of the six diodes D1 - D6: suitable fast recovery diodes D1 - D6 can be chosen according to actual needs.
Thus, summarizing the above content, it can be seen that because the voltage fluctuation suppression module 10 of the electric machine overvoltage suppression circuit in this embodiment is connected to the frequency converter, the voltage clamping module 20 thereof is connected separately to the voltage fluctuation suppression module 10 and the electric machine, and when the frequency converter outputs a first control voltage in AC form for controlling speed adjustment of the electric machine to the voltage fluctuation suppression module 10, the voltage fluctuation suppression module 10 can process the first control voltage to reduce the rate of change of voltage of the first control voltage, and furthermore, the voltage clamping module 20 can clamp the first control voltage processed by the voltage fluctuation suppression module 10 and the reflected voltage formed from the first control voltage processed by the voltage fluctuation suppression module 10 to obtain the second control voltage outputted to the electric machine 40, such that the value of the second control voltage is less than the sum of the first control voltage and the reflected voltage, overvoltage caused by reflected voltage at the electric machine side is suppressed. Thus, the problem of accelerated ageing of electric machine winding insulation caused by overvoltage can be mitigated effectively, and the risk that the electric machine 40 will suffer a reduction in lifespan and damage due to overvoltage is reduced.
As an optional application, the electric machine overvoltage suppression circuit in this embodiment may be used in an electric machine control system, which may be a system in which a frequency converter controls electric machine speed adjustment. For example, the electric machine control system may comprise: a frequency converter 30, an electric machine 40 and the electric machine overvoltage suppression circuit described above, the electric machine overvoltage suppression circuit being connected between the frequency converter 30 and the electric machine 40; the frequency converter 30 outputs a first control voltage in AC form for controlling speed adjustment of the electric machine to the electric machine overvoltage suppression circuit, the electric machine overvoltage suppression circuit processes the first control voltage to generate a second control voltage outputted to the electric machine 40, and the electric machine 40 undergoes speed adjustment in response to the second control voltage. Because the electric machine overvoltage suppression circuit is connected between the frequency converter 30 and the electric machine 40 in the electric machine control system, overvoltage caused by reflected voltage at the electric machine side can be suppressed, so that the electric machine will not suffer a reduction in lifespan or damage due to overvoltage, and the stability of the electric machine control system is thereby also increased.
In addition, the electric machine overvoltage suppression circuit in this embodiment may also be used in electric machine protection systems. When the electric machine overvoltage suppression circuit is used in an electric machine protection system, damage to the electric machine due to overvoltage at the electric machine side can be effectively prevented, so that the electric machine will not suffer a reduction in lifespan or damage due to overvoltage.
It should be understood that expressions such as "first", "second", "first" or "second" used in the embodiments of the present application can modify various components, and have nothing to do with order and/or importance, but these expressions do not restrict the corresponding components. The above expressions are merely intended to distinguish one component from another component.
Finally, it should be explained that the embodiments above are merely intended to explain the technical solution of the embodiments of the present application, without limiting it. Although the present application has been explained in detail with reference to the embodiments above, those skilled in the art should understand that they can still amend the technical solution recorded in each embodiment above or perform equivalent replacement of some of the technical features therein, and such amendments or replacements will not cause the essential nature of the corresponding technical solution to depart from the spirit and scope of the technical solution of each embodiment of the present application.

Claims

Claims
1. An electric machine overvoltage suppression circuit, wherein the electric machine overvoltage suppression circuit comprises: a voltage fluctuation suppression module (10) and a voltage clamping module (20), the voltage fluctuation suppression module (10) being connected to a frequency converter (30), and the voltage clamping module (20) being connected separately to the voltage fluctuation suppression module (10) and the electric machine (40); when the frequency converter (30) outputs a first control voltage in AC form for controlling speed adjustment of the electric machine (40) to the voltage fluctuation suppression module (10), the voltage fluctuation suppression module (10) processes the first control voltage to reduce the rate of change of voltage of the first control voltage, and the voltage clamping module (20) clamps the first control voltage processed by the voltage fluctuation suppression module (10) and a reflected voltage formed from the first control voltage processed by the voltage fluctuation suppression module (10), to obtain a second control voltage outputted to the electric machine (40), such that the value of the second control voltage is less than the sum of the first control voltage and the reflected voltage.
2. The electric machine overvoltage suppression circuit as claimed in claim 1, wherein the voltage fluctuation suppression module (10) comprises three inductors, wherein the three inductors are respectively a first inductor (LI), a second inductor (L2) and a third inductor (L3), and the voltage clamping module (20) comprises a first input terminal, a second input terminal and a third input terminal; a first terminal of the first inductor (LI) is connected to a first-phase output terminal (Ul) of three-phase output terminals of the frequency converter, a second terminal of the first inductor (LI) is connected to the first input terminal of the voltage clamping module (20), and the second terminal of the first inductor (LI) is further connected to a first-phase input terminal (U2) of three-phase input terminals of the electric machine; a first terminal of the second inductor (L2) is connected to a second-phase output terminal (VI) of the three-phase output terminals of the frequency converter, a second terminal of the second inductor (L2) is connected to the second input terminal of the voltage clamping module (20), and the second terminal of the second inductor (L2) is further connected to a second-phase input terminal (V2) of the three-phase input terminals of the electric machine; a first terminal of the third inductor (L3) is connected to a third-phase output terminal (Wl) of the three-phase output terminals of the frequency converter, a second terminal of the third inductor (L3) is connected to the third input terminal of the voltage clamping module (20), and the second terminal of the third inductor (L3) is further connected to a third-phase input terminal (W2) of the three-phase input terminals of the electric machine.
3. The electric machine overvoltage suppression circuit as claimed in claim 2, wherein the voltage clamping module (20) comprises a three-phase full-bridge rectifier circuit.
4. The electric machine overvoltage suppression circuit as claimed in claim 3, wherein the three-phase full-bridge rectifier circuit comprises: six diodes and three coupling capacitors, wherein the six diodes are respectively a first diode (Dl), a second diode (D2), a third diode (D3), a fourth diode (D4), a fifth diode (D5) and a sixth diode (D6), and the three coupling capacitors are respectively a first coupling capacitor (Cl), a second coupling capacitor (C2) and a third coupling capacitor (C3); the cathode of the first diode (Dl), the cathode of the second diode (D2) and the cathode of the third diode (D3) are all connected to a positive output terminal (DCP) of a DC bus of the frequency converter; the anode of the fourth diode (D4), the anode of the fifth diode (D5) and the anode of the sixth diode
(D6) are all connected to a negative output terminal (DCN) of the DC bus of the frequency converter; the anode of the first diode (Dl) is connected to the cathode of the fourth diode (D4), the anode of the second diode (D2) is connected to the cathode of the fifth diode (D5), and the anode of the third diode (D3) is connected to the cathode of the sixth diode (D6); a first terminal of the first coupling capacitor (Cl) is connected to the second terminal of the first inductor (LI), and a second terminal of the first coupling capacitor (Cl) is connected to the anode of the first diode (Dl); a first terminal of the second coupling capacitor (C2) is connected to the second terminal of the second inductor (L2), and a second terminal of the second coupling capacitor (C2) is connected to the anode of the second diode (D2); a first terminal of the third coupling capacitor (C3) is connected to the second terminal of the third inductor (L3), and a second terminal of the third coupling capacitor (C3) is connected to the anode of the third diode (D3); wherein the first terminal of the first coupling capacitor (Cl) serves as the first input terminal of the voltage clamping module (20), the first terminal of the second coupling capacitor (C2) serves as the second input terminal of the voltage clamping module (20), and the first terminal of the third coupling capacitor (C3) serves as the third input terminal of the voltage clamping module (20).
5. The electric machine overvoltage suppression circuit as claimed in claim 4, wherein the diode is a fast recovery diode.
6. The electric machine overvoltage suppression circuit as claimed in claim 2, wherein the electric machine overvoltage suppression circuit further comprises a voltage filtering module (50), the voltage filtering module (50) being connected between the voltage fluctuation suppression module (10) and the voltage clamping module (20), and the voltage filtering module (50) being configured to filter the first control voltage processed by the voltage fluctuation suppression module (10); the voltage clamping module (20) clamps the first control voltage processed by the voltage filtering module (50) and a reflected voltage formed from the first control voltage processed by the voltage filtering module (50).
7. The electric machine overvoltage suppression circuit as claimed in claim 6, wherein the voltage filtering module (50) comprises: at least three filter capacitors, wherein at least one of the filter capacitors is connected between the second terminals of each pair of the inductors.
8. The electric machine overvoltage suppression circuit as claimed in claim 7, wherein the at least three filter capacitors comprise a first filter capacitor (C4), a second filter capacitor (C5) and a third filter capacitor (C6), a first terminal of the first filter capacitor (C4) is connected to the second terminal of the first inductor (Li), a second terminal of the first filter capacitor (C4) is connected to the second terminal of the second inductor (L2), a first terminal of the second filter capacitor (C5) is connected to the second terminal of the second inductor (L2), a second terminal of the second filter capacitor (C5) is connected to the second terminal of the third inductor (L3), a first terminal of the third filter capacitor (C6) is connected to the second terminal of the third inductor (L3), and a second terminal of the third filter capacitor (C6) is connected to the second terminal of the first inductor (Li).
9. The electric machine overvoltage suppression circuit as claimed in any one of claims 2 - 8, wherein the electric machine overvoltage suppression circuit further comprises three voltage absorption modules, each of the three voltage absorption modules being connected in parallel at two ends of one of the three inductors, with different said voltage absorption modules being connected in parallel at two ends of different said inductors; the voltage absorption module absorbs at least some of a spike voltage arising across the inductor due to a jump in the first control voltage.
10. The electric machine overvoltage suppression circuit as claimed in claim 9, wherein the voltage absorption module comprises an absorption resistor and an absorption capacitor, the absorption resistor being connected in series with the absorption capacitor, wherein a first terminal of the absorption resistor is connected to the first terminal of the inductor, a second terminal of the absorption resistor is connected to a first terminal of the absorption capacitor, and a second terminal of the absorption capacitor is connected to the second terminal of the inductor.
PCT/EP2022/071405 2021-07-30 2022-07-29 Electric machine overvoltage suppression circuit WO2023006973A1 (en)

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CN202121773849.4U CN215956302U (en) 2021-07-30 2021-07-30 Motor overvoltage suppression circuit

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5784236A (en) * 1997-05-22 1998-07-21 Tycor International Corp. Variable frequency drive reflected wave suppressors
KR101448920B1 (en) * 2013-11-20 2014-10-14 (주)인텍에프에이 Motor protection apparatus and motor controlling system having the same

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5784236A (en) * 1997-05-22 1998-07-21 Tycor International Corp. Variable frequency drive reflected wave suppressors
KR101448920B1 (en) * 2013-11-20 2014-10-14 (주)인텍에프에이 Motor protection apparatus and motor controlling system having the same

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
ANONYMOUS: "Schwingkreis - Wikipedia", 6 July 2021 (2021-07-06), XP055981321, Retrieved from the Internet <URL:https://de.wikipedia.org/w/index.php?title=Schwingkreis&oldid=213619560> [retrieved on 20221115] *

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