Frequency converter circuit and frequency converter

Abstract

The utility model provides a frequency converter circuit and a frequency converter. The frequency converter circuit comprises an input rectification filter circuit used for receiving alternating current output by a distribution box and converting the alternating current into direct current; the buck-boost circuit is connected with the input rectification filter circuit and is used for receiving the direct current output by the input rectification filter circuit and carrying out boost or buck processing on the direct current; the input end of the inverter circuit is connected with the buck-boost circuit, the output end of the inverter circuit is connected with the motor, and the inverter circuit is used for converting the direct current subjected to boost or buck processing into alternating current with adjustable frequency and voltage and outputting the alternating current to the motor. Compared with the prior art, the frequency converter circuit can provide appropriate voltage for the motor, noise caused by voltage mismatching is reduced, the problem of insulation damage caused by overvoltage of the motor is avoided, and the service life of the motor is prolonged.

Description

TECHNICAL FIELD

[0001] The utility model relates to frequency converter technical field especially, it is a kind of frequency converter circuit with boost-buck circuit. BACKGROUND

[0002] In the field of industrial control and electrical transmission, frequency converter is widely used in the speed control of motor. The traditional frequency converter often has the problem of insufficient adaptability when facing different rated voltage motors. Because the types of motor rated voltage are various, and the output voltage of conventional frequency converter is relatively fixed, when the output voltage of frequency converter does not match the rated voltage of motor, a series of adverse effects will be produced. For example, if the output voltage of frequency converter is higher than the withstand voltage of motor, it may cause motor insulation damage, greatly shorten the service life of motor; if the output voltage is lower than the rated voltage of motor, the motor cannot normally operate in the best state, and may have problems such as insufficient torque and serious heating.

[0003] In addition, the motor is easy to produce large noise in the running process due to unstable or unmatched voltage, which affects the equipment running environment and overall performance. SUMMARY

[0004] The utility model aims at providing a kind of frequency converter circuit, the frequency converter circuit has boost-buck circuit, can solve the insufficient of existing frequency converter when adapting different voltage motor, and reduce motor noise and prevent the impact on motor life due to withstand voltage problem.

[0005] To achieve the above-mentioned purpose, the utility model provides a kind of frequency converter circuit, comprising:

[0006] Input rectifier filter circuit is used to receive the alternating current output by distribution box, and convert the alternating current into direct current;

[0007] Boost-buck circuit is connected with the input rectifier filter circuit, used to receive the direct current output by the input rectifier filter circuit, and boost or buck the direct current; and

[0008] Inverter circuit is connected with the boost-buck circuit at input end, and connected with motor at output end, used to convert the direct current after boost or buck into alternating current with adjustable frequency and voltage, and output to the motor.

[0009] As a further improvement of the utility model, it further comprises a control circuit connected with the boost-buck circuit, and a first feedback circuit connected between the output end of the input rectifier filter circuit and the control circuit, the first feedback circuit is used to feed back the voltage and current output by the input rectifier filter circuit to the control circuit.

[0010] As a further improvement of the utility model, still include the second feedback circuit that connects between the output of the boost and buck circuit and the control circuit, and the third feedback circuit that connects between the output of the inverter circuit and the control circuit, the second feedback circuit is used for the voltage and current feedback of boost and buck circuit output to the control circuit, the third feedback circuit is used for the voltage and current feedback of inverse circuit output to the control circuit.

[0011] As a further improvement of the utility model, still include output filter circuit, the input of output filter circuit is connected with the inverter circuit, and the output is connected with the motor, is used to filter processing after the alternating current of inverter circuit output is given to the motor.

[0012] As a further improvement of the utility model, the alternating current of distribution box output is three-phase alternating current, the input rectification filter circuit includes rectifier bridge circuit and filter circuit, the rectifier bridge circuit is composed of six diodes that are connected with three-phase alternating current respectively, and the filter circuit includes filter capacitor C1 that is connected with the rectifier bridge circuit in parallel.

[0013] As a further improvement of the utility model, the boost and buck circuit includes first switch tube T1 and second switch tube T2 that are connected in series, third switch tube T3 and fourth switch tube T4 that are connected in series, energy storage inductance L1 and capacitor C2, one end of energy storage inductance L1 is connected between first switch tube T1 and second switch tube T2, the other end is connected between third switch tube T3 and fourth switch tube T4, and the two ends of capacitor C2 are connected with third switch tube T3 and fourth switch tube T4 respectively.

[0014] As a further improvement of the utility model, in boost mode, when first switch tube T1 and fourth switch tube T4 are turned on, energy storage inductance L1 is charged, when first switch tube T1 and third switch tube T3 are turned on, energy storage inductance L1 is discharged, capacitor C2 is charged and boosted.

[0015] As a further improvement of the utility model, in buck mode, when first switch tube T1 and third switch tube T3 are turned on, energy storage inductance L1 is charged, when second switch tube T2 and third switch tube T3 are turned on, energy storage inductance L1 is discharged, capacitor C2 is charged.

[0016] As a further improvement of the utility model, the inverter circuit is bridge structure, including fifth switch tube T5 and sixth switch tube T6 that are connected in series, seventh switch tube T7 and eighth switch tube T8 that are connected in series and ninth switch tube T9 and tenth switch tube T10 that are connected in series, for the PWM chopper control of direct current after boost or buck processing.

[0017] The utility model also aims at providing a frequency converter, which can flexibly adjust output voltage to adapt to motors of various rated voltages, and greatly improves the versatility of the frequency converter.

[0018] To achieve the above object, the utility model provides a frequency converter, which comprises the frequency converter circuit.

[0019] The utility model discloses the frequency converter circuit utilizes input rectification filter circuit to convert alternating current into direct current and exports to the step -up and step -down circuit, is handled by the step -up and step -down circuit to step -up or step -down, exports to inverter circuit again, and direct current after step -up or step -down is converted to adjustable frequency and voltage alternating current by inverter circuit, exports to motor again, provides suitable voltage for motor, effectively reduces the motor noise caused by voltage mismatch, and avoids the insulation damage problem of motor due to overvoltage, prolongs the service life of motor significantly, improves the stability and reliability of entire electrical transmission system. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is the structural schematic diagram of the utility model frequency converter circuit.

[0021] Figure 2 It is the circuit architecture drawing of the utility model frequency converter circuit.

[0022] Figure 3 It is Figure 2 the circuit architecture drawing of the step -up and step -down circuit.

[0023] Figure 4 It is Figure 2 the circuit architecture drawing of the inverter circuit.

[0024] Figure 5 It is the voltage and current trend chart when the first switch tube T1 and the fourth switch tube T4 are conducted under the step -up mode.

[0025] Figure 6 It is the voltage and current trend chart when the first switch tube T1 and the third switch tube T3 are conducted under the step -up mode.

[0026] Figure 7 It is the voltage and current trend chart when the first switch tube T1 and the third switch tube T3 are conducted under the step -down mode.

[0027] Figure 8 It is the voltage and current trend chart when the second switch tube T2 and the third switch tube T3 are conducted under the step -down mode. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] like Figure 1 As shown, this utility model discloses a frequency converter circuit and a frequency converter having the frequency converter circuit. The frequency converter circuit includes an input rectifier and filter circuit, a step-up / step-down circuit, an inverter circuit, and an output filter circuit. The input rectifier and filter circuit receives AC power from the distribution box and converts it into DC power. The step-up / step-down circuit is connected to the input rectifier and filter circuit and receives the DC power output from the input rectifier and filter circuit, and steps up or steps down the DC power. The inverter circuit is connected to the step-up / step-down circuit and converts the DC power after step-up or step-down conversion into AC power with adjustable frequency and voltage. The input terminal of the output filter circuit is connected to the inverter circuit, and the output terminal is connected to a motor M, used to filter the AC power output from the inverter circuit before outputting it to the motor M. Of course, the output filter circuit can be omitted according to actual needs, and this is not a limitation.

[0030] In this embodiment, the AC power output from the distribution box is three-phase AC power, generally used in factories with three-phase 380V; of course, the AC power output from the distribution box can also be single-phase AC power, generally used in homes with 220V. That is to say, the frequency converter circuit of this utility model can be applied to both three-phase AC power and single-phase AC power.

[0031] like Figure 2 As shown, the input rectifier and filter circuit includes a rectifier bridge circuit and a filter circuit. The rectifier bridge circuit consists of six diodes connected to the three-phase AC power supply, and the filter circuit includes a filter capacitor C1 connected in parallel with the rectifier bridge circuit. After the input three-phase AC power or single-phase AC power enters the input rectifier and filter circuit, it is rectified by the rectifier bridge circuit and filtered by the filter capacitor C1 to obtain a relatively smooth DC power.

[0032] like Figure 2 and Figure 3 , Figures 5 to 8As shown, the voltage boosting and reducing circuit comprises first and second switch tubes T1 and T2 connected in series, third and fourth switch tubes T3 and T4 connected in series, an energy storage inductor L1, and a capacitor C2. One end of the energy storage inductor L1 is connected between the first and second switch tubes T1 and T2, the other end is connected between the third and fourth switch tubes T3 and T4, and the capacitor C2 is connected between the third and fourth switch tubes T3 and T4. Optionally, the first, second, third and fourth switch tubes T1, T2, T3 and T4 are all power switch tubes, so that the input DC voltage can be boosted or reduced by controlling the on and off of the power switch tubes, to obtain a DC output voltage suitable for different motor M rated voltages.

[0033] Specifically, in the voltage boosting mode, when the first and fourth switch tubes T1 and T4 are turned on, the energy storage inductor L1 is charged, and the capacitor C2 is charged and boosted by the energy storage inductor L1 discharging. Figure 5 When the first and third switch tubes T1 and T3 are turned on, the energy storage inductor L1 discharges, and the capacitor C2 is charged and boosted. Figure 6 These two steps are alternately operated, constituting a voltage boosting circuit. In the voltage reducing mode, when the first and third switch tubes T1 and T3 are turned on, the energy storage inductor L1 is charged. Figure 7 When the second and third switch tubes T2 and T3 are turned on, the energy storage inductor L1 discharges, and the capacitor C2 is charged with a reduced voltage. Figure 8 These two steps constitute a voltage reducing circuit.

[0034] That is, by reasonably controlling the pulse width modulation (PWM) signals of the power switch tubes, precise voltage boosting and reducing functions are realized. For example, when boosting is needed, the switch tubes are controlled to turn on and off according to a pre-set timing sequence, so that the energy storage inductor L1 is charged and releases energy at a corresponding time to superimpose with the input voltage, thereby increasing the output voltage; when reducing is needed, the on and off time ratio of the switch tubes is adjusted to control the energy storage and energy release ratio of the energy storage inductor L1, thereby reducing the output voltage. The "pre-set timing sequence", "corresponding time" and "adjusting the on and off time ratio of the switch tubes" can be set according to actual needs, which are not limited here.

[0035] As shown in FIG. 2, the voltage boosting and reducing circuit comprises a first switch tube T1, a second switch tube T2, a third switch tube T3, a fourth switch tube T4, an energy storage inductor L1, and a capacitor C2. Figure 4As shown, the inverter circuit is of a bridge structure, comprising the fifth switch tube T5 and the sixth switch tube T6 connected in series with each other, the seventh switch tube T7 and the eighth switch tube T8 connected in series with each other, and the ninth switch tube T9 and the tenth switch tube T10 connected in series with each other, for PWM chopping control of the direct current after the voltage boosting or voltage reducing processing, i.e. converting the direct current into three-phase alternating current by PWM chopping mode to drive the motor M.

[0036] In the embodiment, the fifth switch tube T5, the sixth switch tube T6, the seventh switch tube T7, the eighth switch tube T8, the ninth switch tube T9 and the tenth switch tube T10 are all IGBT power tubes, and by controlling the conduction and turn-off sequence and conduction time of these switch tubes, the direct current can be chopped and controlled to cut out the required alternating voltage.

[0037] The motor M does not need to run at full load and full voltage in most time, so the inverter voltage is appropriately reduced in real-time running process, which can prolong the voltage endurance life of the motor M. In particular, the motor M does not need to start at full voltage, but only needs to have appropriate voltage. This is because: the torque required to be provided mainly comes from the current, and when the speed increases, the voltage needs to be increased to increase the speed due to the back electromotive force, so the starting voltage can be appropriately lowered to prolong the life of the motor M, and at the same time, the power tube duty ratio becomes larger after the voltage is lowered, which can improve the electromagnetic noise.

[0038] For example, when the boost and buck circuit charges the capacitor C2, the voltage of the capacitor C2 slowly increases from 0V, and in the process of increasing, according to the back electromotive force characteristics of the motor M, the output duty ratio of the inverter circuit reaches about 50% when driving the motor M, which can prevent the electromagnetic noise caused by the instability of the switch tube due to high voltage and low duty ratio starting, and low voltage starting is also beneficial to the insulation protection of the motor M. In summary, in the running process, the output voltage of the capacitor C2 can be adjusted in real time according to the running speed and load of the motor M, and the duty ratio of the switch tubes T5-T10 in the inverter circuit is adjusted at the same time, so that the motor M runs in an ideal state. The boost function is mainly applied in the case that the supply voltage is not enough, and the required inverter voltage is supplemented by boosting and real-time adjustment.

[0039] When the output filter circuit is adopted, the output filter circuit can adopt a filter capacitor for filtering processing, or other structures for filtering processing, which is not limited here.

[0040] For example, Figure 1The utility model discloses an inverter circuit, which comprises an input rectification filter circuit, a boost-buck circuit connected to the input rectification filter circuit, an inverter circuit connected to the boost-buck circuit, and an output filter circuit connected to the inverter circuit.

[0041] The working principle of the frequency converter circuit of the utility model will be described as follows: first, three-phase alternating current or single-phase alternating current enters the input rectification filter circuit, and after rectification by a rectification bridge and filtering by a filter capacitor C1, relatively smooth direct current is obtained. Then, the direct current enters the boost-buck circuit, and the control circuit generates corresponding PWM control signals to drive the power switch tubes in the boost-buck circuit to turn on and turn off according to pre-set motor rated voltage parameters or real-time detected motor operating state information. For example, in the boost mode, when the corresponding power switch tube is turned on, the input current flows through the energy storage inductor L1, and the energy storage inductor L1 stores energy; at this time, the capacitor C2 supplies power to the load; when the corresponding power switch tube is turned off, the energy storage inductor L1 generates an induced electromotive force superimposed with the input voltage, and charges the capacitor C2 and the load, thereby realizing voltage boosting. Then, the direct current with appropriate voltage obtained through the boost-buck circuit enters the inverter circuit, and the inverter circuit converts the direct current into alternating current with adjustable frequency and voltage. Finally, the output filter circuit can be used to filter the alternating current output by the inverter circuit according to actual needs, remove high-frequency harmonic components, and obtain relatively pure alternating current output to the motor M, thereby realizing efficient and stable speed control of the motor M, effectively reducing the noise of the motor M in the whole process, and protecting the motor M from voltage problems.

[0042] In summary, the frequency converter circuit of the utility model utilizes input rectification filter circuit to convert AC into DC and output to the boost-buck circuit, and the boost-buck circuit carries out boost or buck processing, and then outputs to the inverter circuit, and the inverter circuit converts the DC after boost or buck processing into AC with adjustable frequency and voltage, and then selectively carries out filtering processing through the output filter circuit and outputs to the motor, so that the motor is provided with appropriate voltage, the motor noise caused by voltage mismatch is effectively reduced, the insulation damage problem of the motor caused by overvoltage is avoided, the service life of the motor is significantly prolonged, and the stability and reliability of the entire electrical transmission system are improved.

[0043] The above embodiments are only used to illustrate the technical scheme of the utility model and not limit it, and although the utility model has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical scheme of the utility model can be modified or replaced equivalently without departing from the spirit and scope of the technical scheme of the utility model.

Claims

1. A frequency converter circuit, characterized in that The application relates to a power supply device for a motor, which comprises: an input rectification filter circuit for receiving alternating current output by a distribution box and converting the alternating current into direct current; a boost-buck circuit connected to the input rectification filter circuit, for receiving the direct current output by the input rectification filter circuit and performing boost or buck processing on the direct current; and an inverter circuit, the input end of which is connected to the boost-buck circuit and the output end of which is connected to a motor, for converting the direct current after boost or buck processing into alternating current with adjustable frequency and voltage and outputting the alternating current to the motor.

2. The frequency converter circuit of claim 1, wherein: The application further comprises a control circuit connected to the boost-buck circuit, and a first feedback circuit connected between the output end of the input rectification filter circuit and the control circuit, for feeding back the voltage and current output by the input rectification filter circuit to the control circuit.

3. The frequency converter circuit of claim 2, wherein: The application further comprises a second feedback circuit connected between the output end of the boost-buck circuit and the control circuit, and a third feedback circuit connected between the output end of the inverter circuit and the control circuit, the second feedback circuit being used for feeding back the voltage and current output by the boost-buck circuit to the control circuit, and the third feedback circuit being used for feeding back the voltage and current output by the inverter circuit to the control circuit.

4. The frequency converter circuit of claim 1, wherein: The application further comprises an output filter circuit, the input end of which is connected to the inverter circuit and the output end of which is connected to the motor, for performing filter processing on the alternating current output by the inverter circuit and outputting the alternating current to the motor.

5. The frequency converter circuit of claim 1, wherein: The alternating current output by the distribution box is three-phase alternating current, the input rectification filter circuit comprises a rectification bridge circuit and a filter circuit, the rectification bridge circuit is composed of six diodes connected to the three-phase alternating current respectively, and the filter circuit comprises a filter capacitor C1 connected in parallel to the rectification bridge circuit.

6. The frequency converter circuit of claim 1, wherein: The boost-buck circuit comprises a first switch tube T1 and a second switch tube T2 connected in series, a third switch tube T3 and a fourth switch tube T4 connected in series, an energy storage inductor L1, and a capacitor C2, one end of the energy storage inductor L1 is connected between the first switch tube T1 and the second switch tube T2, the other end of the energy storage inductor L1 is connected between the third switch tube T3 and the fourth switch tube T4, and the two ends of the capacitor C2 are connected to the third switch tube T3 and the fourth switch tube T4 respectively.

7. The frequency converter circuit of claim 6, wherein: In the boost mode, when the first switch tube T1 and the fourth switch tube T4 are turned on, the energy storage inductor L1 is charged; when the first switch tube T1 and the third switch tube T3 are turned on, the energy storage inductor L1 is discharged, the capacitor C2 is charged and boosted.

8. The frequency converter circuit of claim 6, wherein: In the buck mode, when the first switch tube T1 and the third switch tube T3 are turned on, the energy storage inductor L1 is charged; when the second switch tube T2 and the third switch tube T3 are turned on, the energy storage inductor L1 is discharged, the capacitor C2 is charged.

9. The frequency converter circuit of claim 1, wherein: The inverter circuit is of a bridge structure, comprising a fifth switch tube T5 and a sixth switch tube T6 connected in series with each other, a seventh switch tube T7 and an eighth switch tube T8 connected in series with each other, and a ninth switch tube T9 and a tenth switch tube T10 connected in series with each other, for PWM chopping control of the direct current after the voltage boosting or voltage dropping treatment.

10. A frequency converter characterized by: A frequency converter circuit comprising the inverter circuit of any one of claims 1-9.

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