CN104079227B - A kind of have the electric system reducing common mode disturbances ability - Google Patents

Abstract

The invention discloses a motor system capable of reducing common-mode interference, which includes a motor, a DC power supply, a bridge inverter, a controller and 1 to 2 chopper switches; the invention controls two chopper switches at the same time, and can Reduce the maximum and minimum values of the common-mode voltage of the motor, minimize the change of the common-mode voltage, and improve the electromagnetic compatibility of the system; when only choosing to control any chopper switch tube, it can also reduce the variation of the common-mode voltage of the motor The maximum or minimum value, so that the cost can be reduced under the premise of reducing the common mode interference of the motor. The control strategy of the present invention can be realized only by simple modification on the commonly used motor drive system, which is conducive to the rapid application of the motor system, quickly solves the existing common mode interference problem, and improves the electromagnetic compatibility of the system. Therefore, the realization method Simple and practical.

Description

A motor system with the ability to reduce common-mode interference

technical field

The invention belongs to the technical field of motors, and in particular relates to a motor system capable of reducing common-mode interference.

Background technique

At present, the known motor controller is used to flexibly control the running state of the motor. It is generally composed of two parts: rectification and inverter. Stable operation within the speed range. The pulse width modulation technology acts on the inverter part, and realizes the flexible control of the motor by switching on and off the DC voltage. Due to the superiority of pulse width modulation technology in motor control, it has gradually replaced the application of speed regulation methods such as voltage regulation and pole changing in the field of motor control in recent years.

Although the existing pulse width modulation technology has excellent control performance, its high-frequency switching characteristics will cause high-frequency common-mode interference in the motor drive system, which in turn will cause negative effects such as overvoltage at the motor end, shaft voltage, and bearing current, which will cause Motor damage and environmental electromagnetic pollution.

Taking three-phase as an example, Figure 1 shows the voltage vector diagram of the space voltage vector control algorithm, that is, the motor is controlled by six space voltage vectors and two zero-voltage space vectors, and the eight states correspond to the six inverters. The switching tube is turned on and off, and the motor operation process is divided into six different sectors (① to ⑥ in the figure). In the motor drive system based on the space voltage vector control algorithm, the six switching tubes of the inverter circuit will select different switching states according to the sector where the motor is located, so as to apply an effective voltage space vector to the motor.

However, it is precisely because the operation of the motor needs to switch back and forth among these eight states, which leads to the jump of the common-mode voltage of the motor, which in turn causes the common-mode interference of the motor drive system. Assuming that the DC bus supply voltage is , according to the different switching states of the inverter, the common-mode voltage value of the motor will vary between . This alternating common-mode voltage causes common-mode disturbances in the motor system.

Contents of the invention

Aiming at the above-mentioned technical problems in the prior art, the invention discloses a motor system capable of reducing common-mode interference, which can reduce the common-mode interference of the motor and has a simple structural design.

A motor system with the ability to reduce common-mode interference, including a motor, a DC power supply, a bridge inverter, a controller, and 1 to 2 chopper switches; the AC side of the bridge inverter and the stator winding of the motor Corresponding to the connection, the controller is used to provide drive signals for the bridge inverter and the chopper switch;

If there is only one chopper switch, the positive pole of the DC power supply is connected to the positive terminal of the bridge inverter through the chopper switch, and the negative pole of the DC power supply is directly connected to the negative terminal of the bridge inverter; or the positive pole of the DC power supply is directly connected to the negative terminal of the bridge inverter. The positive terminal of the bridge inverter is connected, and the negative terminal of the DC power supply is connected to the negative terminal of the bridge inverter through a chopper switch;

If there are two chopping switches, the positive and negative poles of the DC power supply are respectively connected to the positive and negative poles of the inverter through one chopping switch.

The DC power supply is an independent DC voltage source or the rectified DC output of the preceding AC power supply.

The chopper switch adopts a switch tube with an antiparallel diode.

The switch tube is MOSFET (metal-oxide layer semiconductor field effect transistor), IGBT (insulated gate bipolar transistor), IGCT (integrated gate commutated thyristor), IEGT (electron injection enhanced gate transistor), GTO (can turn off thyristor), triode or thyristor, etc.

The diodes are Schottky diodes, fast recovery diodes, silicon tubes or silicon carbide diodes.

Under the control of the controller, the chopper switch connected to the positive pole of the DC power supply is turned off only when all the switching tubes of the upper bridge arm in the bridge inverter (that is, the upper tubes of the switching tubes) are closed. The wave switches are all closed; only when the switching tubes of all the lower bridge arms in the bridge inverter (that is, the lower tubes of the switching tubes) are closed, the chopper switch connected to the negative pole of the DC power supply is turned off, and in other cases the chopper switch Both are closed.

The motor and the bridge inverter can be single-phase, two-phase, three-phase or multi-phase.

The present invention reduces common-mode interference problems commonly seen during motor operation by adding a chopper switch on the DC side of the inverter, and its beneficial technical effects are as follows:

(1) The present invention simultaneously controls two chopper switches, which can reduce the maximum and minimum values of the common-mode voltage of the motor, minimize the variation of the common-mode voltage, and improve the electromagnetic compatibility of the system.

(2) The present invention can reduce the maximum or minimum value of the common-mode voltage of the motor when only selecting and controlling any one of the chopper switching tubes, so that the cost can be reduced while reducing the common-mode interference of the motor.

(3) The control strategy of the present invention can be realized only by simple modification on the commonly used motor drive system, which is conducive to the rapid application of the motor system, quickly solves the existing common mode interference problem, and improves the electromagnetic compatibility of the system, so , the implementation method is simple and practical.

Description of drawings

Figure 1 is the space voltage vector diagram of motor control (taking three-phase as an example).

Fig. 2 is a structural schematic diagram of the motor system of the present invention (taking three phases as an example).

FIG. 3 is a schematic diagram of a common-mode voltage waveform of a conventional motor system.

Fig. 4(a) is a schematic diagram of on-off of the chopper switch when the lower switch of the switch tube is fully on under the first control strategy.

Fig. 4(b) is a schematic diagram of on-off of the chopper switch when the upper switch of the switch tube is fully on under the first control strategy.

Fig. 4(c) is a schematic diagram of the common-mode voltage waveform of the motor under the first control strategy.

Fig. 5(a) is a schematic diagram of on-off of the chopper switch when the upper switch of the switch tube is fully on under the second control strategy.

Fig. 5(b) is a schematic diagram of the common-mode voltage waveform of the motor under the second control strategy.

Fig. 6(a) is a schematic diagram of on-off of the chopper switch when the lower switch of the switch tube is fully on under the third control strategy.

Fig. 6(b) is a schematic diagram of the common-mode voltage waveform of the motor under the third control strategy.

detailed description

In order to describe the present invention more specifically, the technical solutions of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 2, the motor drive system includes a DC power supply, a first chopper switch, a second chopper switch, an inverter, a motor and its controller. Wherein, the chopper switch and the inverter high-frequency switch tube can be MOSFET, IGBT, IGCT, IEGT, triode, GTO, thyristor, etc. If the switch tube itself does not have anti-parallel diodes, add anti-parallel diodes. The diodes can be Schottky diodes, fast recovery diodes, silicon tubes, silicon carbide diodes, and the like.

This embodiment takes a three-phase motor system as an example, but is not limited to a three-phase motor system. DC power can be converted from AC power by rectification and filtering circuits, or from DC powered equipment. The positive and negative terminals of the DC power supply are connected in series with a chopper switch S7 and S8, which are used for connecting and shutting off the subsequent stage circuit (inverter) and the preceding stage DC power supply. After the chopping switch, an inverter composed of 6 switching tubes (S1-S6) is connected, which is used to invert the DC power supply into AC power supply and control the operation of the AC motor. Here, each switch tube is an IGBT with an anti-parallel diode as an example, but is not limited to an IGBT. The control strategy of the entire motor drive system is completed by the controller, which outputs 8 drive signals for driving the switch tubes S1 to S8 through the collection of the motor operating characteristics.

As shown in Figure 1, the common space voltage vector control algorithm in the motor control strategy has 8 kinds of space voltage vectors V0~V7, among which V0 and V7 are zero voltage space vectors, and V7 is a high potential zero voltage vector (that is, all switching tubes The tube is turned on), and V0 is the low potential zero voltage vector (that is, all the switch tubes are turned on). Although the zero-voltage space vector is not an effective voltage vector for the motor, it will not produce effective torque, but it can optimize the motor control.

As shown in Figure 3, the conventional motor drive system will cause the motor to generate a large-value alternating common-mode voltage. Figure 3 is a schematic diagram of the waveform of the common-mode voltage of the conventional motor. The common-mode voltage can be calculated by the following formula:

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; CN</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; UM</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; VM</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; W\; M</span>}}<span\; class="notranslate">\; )</span>$

Where: u _CM is the voltage from the motor winding neutral point C to the DC bus clamp midpoint M, u _UM is the voltage from the motor U terminal to the DC bus clamp midpoint M, and u _VM is the motor V terminal to the DC bus clamp The voltage at the midpoint M, u _WM is the voltage from the motor W terminal to the midpoint M of the DC bus clamp.

It can be seen from Figure 3 that without any improvement measures, the peak-to-peak value of the common-mode voltage of the motor will reach the value of the DC bus voltage. When high DC bus voltage is used, strong common mode interference will be generated, causing serious negative effects.

In order to make the AC motor run smoothly, the voltage vector of the motor should be controlled to run smoothly in the voltage space vector diagram shown in Figure 1. For example, when the position of the motor voltage vector to be applied is in sector ①, the space voltage vectors V1, V2 and zero voltage vectors V0, V7 can be used to form a seven-segment control algorithm to achieve the desired voltage vector. During the operation of sector ①, due to different switching states, the common mode voltage of the motor will go from to to, to, and finally to the maximum value. In the same way, when the motor is running in other sectors, the common-mode voltage will also vary from to. Therefore, when the motor is running normally, the switching state is constantly switching among these 8 states (taking three phases as an example), forming a common-mode voltage waveform as shown in Figure 3.

When the zero-voltage space vector acts, the three input terminals of the motor are short-circuited, and the current on the DC bus is zero, which means that the DC power supply and the inverter part are not connected. If the DC power supply and the inverter are disconnected at this time, it will have no effect on the normal operation of the motor. Utilizing this feature, the present invention disconnects the DC power supply and the inverter when the zero-voltage space vector acts, and weakens the common-mode voltage of the motor to follow the change of the switch state, so as to reduce the common-mode interference of the motor.

Embodiment one

The circuit topology of this embodiment is shown in Figure 2. Taking three phases as an example, a switch tube is connected in series with the positive and negative terminals of the DC voltage (the chopper switch connected to the positive pole is S7, and the chopper switch connected to the negative pole is S8. ); chopper switches S7 and S8 are connected to a full-bridge inverter circuit composed of 6 switching tubes, wherein S1 and S4 form the upper and lower arms of the first bridge arm, and S3 and S6 form the upper and lower arms of the second bridge arm. S5 and S2 form the upper and lower arms of the third bridge arm.

When the zero-voltage space vector acts, the common-mode voltage of the motor is . If the DC power supply and the inverter are disconnected at the same time under the action of the zero-voltage space vector, the motor power supply will be in a high-impedance state at this time, and the potential of the motor is completely determined by its own factors, so it will not reach the common mode voltage amplitude.

The control strategy adopted in this embodiment is as follows:

When the lower switches of the inverter are fully turned on, that is, when the zero-voltage space vector V0 acts, the chopper switch S7 is turned on, and the chopper switch S8 is turned off. As shown in Figure 4(a), when the switches S1, S3, and S5 are all turned off, and the switches S4, S6, and S2 are all turned on, the chopper switch S7 is turned on, and the chopper switch S8 is turned off.

When the upper tubes of the inverter are fully turned on, that is, when the zero-voltage space vector V7 acts, the chopper switch S8 is turned on, and the chopper switch S7 is turned off. As shown in Figure 4(b), when the switches S1, S3, and S5 are all turned on, and the switches S4, S6, and S2 are all turned off, the chopping switch S8 is turned on, and the chopping switch S7 is turned off.

In other switch states, that is, when the non-zero voltage space vector acts, both the chopping switches S7 and S8 are turned on.

The above logic control utilizes the influence of the chopper switch on the common-mode voltage to achieve the purpose of reducing the common-mode voltage. As shown in Figure 4(a), when the zero-voltage space vector V0 acts, the chopper switch S8 is turned off to make the motor in a high-impedance state, which can prevent the common-mode voltage of the motor from reaching; similarly, as shown in Figure 4(b) It shows that when the zero voltage space vector V7 acts, disconnecting the chopper switch S7 can prevent the common mode voltage of the motor from reaching.

When the motor drive system is driven according to this control strategy, the motor common-mode voltage shown in Figure 4(c) will be generated. It can be seen from FIG. 4( c ) that this embodiment reduces both the maximum value and the minimum value of the common-mode voltage of the motor. Compared with the common-mode voltage shown in FIG. 3 , under the premise that the DC bus voltage remains unchanged, the peak-to-peak value of the common-mode voltage in this embodiment is reduced to 1/3 of the original. Therefore, by using the control strategy of this embodiment, the range of variation of the common-mode voltage of the motor can be reduced to the greatest extent, and further the common-mode interference of the motor can be reduced to the greatest extent.

Embodiment two

In this embodiment, only the chopper switch S7 at the high voltage is selected for control, and the other chopper switch is always on. In addition, in order to reduce costs and simplify control, this chopper switch can be omitted, and the negative pole of the DC power supply and the inverter The negative terminal is directly connected.

Taking the three-phase as an example, a switch tube is connected in series with the positive terminal of the DC voltage (the chopper switch is S7); behind the chopper switch S7, a full-bridge inverter circuit composed of six switch tubes is connected, among which, S1 and S4 are composed of The upper and lower arms of the first bridge arm, S3 and S6 form the upper and lower arms of the second bridge arm, and S5 and S2 form the upper and lower arms of the third bridge arm.

When the zero-voltage space vector V7 acts, the common-mode voltage of the motor is . If the connection with the DC power supply is disconnected at the same time under the action of the zero-voltage space vector V7, the motor will be in a high-impedance state at this time, and the potential of the motor is completely determined by its own factors, and the common-mode voltage amplitude will not be reached .

The control strategy adopted in this embodiment is as follows:

When the upper tube of the inverter is fully turned on, that is, when the zero-voltage space vector V7 acts, the chopper switch S7 is turned off. As shown in FIG. 5( a ), when the switches S1 , S3 , and S5 are all turned on, and the switches S4 , S6 , and S2 are all turned off, the chopper switch S7 is turned off.

In other switch states, that is, when the zero-voltage space vector V0 or the non-zero-voltage space vector acts, the chopping switch S7 is always on.

The above logic control utilizes the influence of the chopper switch on the common-mode voltage to achieve the purpose of reducing the common-mode voltage. As shown in Figure 5(a), when the zero-voltage space vector V7 acts, disconnecting the chopper switch S7 can prevent the common-mode voltage of the motor from reaching.

When the motor drive system is driven according to this control strategy, the motor common-mode voltage shown in Figure 5(b) will be generated. It can be seen from Fig. 5(b) that the present embodiment reduces the maximum value of the common-mode voltage of the motor. Compared with the common-mode voltage shown in FIG. 3 , under the premise that the DC bus voltage remains unchanged, the peak-to-peak value of the common-mode voltage in this embodiment is reduced to 2/3 of the original. Using the control strategy of this embodiment, the maximum value of the common-mode voltage of the motor can be reduced, thereby reducing the common-mode interference of the motor; at the same time, only one chopper switch is added, which can reduce the cost compared with the first embodiment.

Embodiment Three

In this embodiment, only the chopper switch S8 at the low voltage is selected for control, and the other chopper switch is always on. In addition, in order to reduce costs and simplify control, this chopper switch can be omitted, and the positive pole of the DC power supply and the inverter The positive ends are directly connected.

Also taking the three-phase as an example, a switch tube is connected in series on the negative terminal of the DC voltage (the chopper switch is S8); the chopper switch S8 is connected to a full-bridge inverter circuit composed of 6 switch tubes, among which, S1 and S4 are composed of The upper and lower arms of the first bridge arm, S3 and S6 form the upper and lower arms of the second bridge arm, and S5 and S2 form the upper and lower arms of the third bridge arm.

When the zero-voltage space vector V0 acts, the common-mode voltage of the motor is . If the connection with the DC power supply is disconnected at the same time under the action of the zero-voltage space vector V0, the motor will be in a high-impedance state at this time, and the potential of the motor is completely determined by its own factors, and the common-mode voltage amplitude will not be reached. .

The control strategy adopted in this embodiment is as follows:

When the lower switch of the inverter is fully turned on, that is, when the zero-voltage space vector V0 acts, the chopper switch S8 is turned off. As shown in Figure 6(a), when the switches S1, S3, and S5 are all turned on, and the switches S4, S6, and S2 are all turned off, the chopper switch S8 is turned off.

In other switch states, that is, when the zero-voltage space vector V7 or the non-zero-voltage space vector acts, the chopping switch S8 is always on.

The above logic control utilizes the influence of the chopper switch on the common-mode voltage to achieve the purpose of reducing the common-mode voltage. As shown in Figure 6(a), when the zero-voltage space vector V0 acts, disconnecting the chopper switch S8 can prevent the common-mode voltage of the motor from reaching.

When the motor drive system is driven according to this control strategy, the motor common-mode voltage shown in Figure 6(b) will be generated. It can be seen from FIG. 6( b ) that this embodiment reduces the minimum value of the common-mode voltage of the motor. Compared with the common-mode voltage shown in FIG. 3 , under the premise that the DC bus voltage remains unchanged, the peak-to-peak value of the common-mode voltage in this embodiment is reduced to 2/3 of the original. Using the control strategy of this embodiment, the minimum value of the common mode voltage of the motor can be reduced, thereby reducing the common mode interference of the motor; at the same time, only one chopper switch is added, which can reduce the cost compared with the first embodiment.

Claims (5)

1. A motor system with the ability to reduce common-mode interference is characterized in that: it comprises a motor, a DC power supply, a bridge inverter, a controller and 1 to 2 chopper switches; the bridge inverter AC The side is correspondingly connected with the stator winding of the motor, and the controller is used to provide drive signals for the bridge inverter and the chopper switch; If there is only one chopper switch, the positive pole of the DC power supply is connected to the positive terminal of the bridge inverter through the chopper switch, and the negative pole of the DC power supply is directly connected to the negative terminal of the bridge inverter; or the positive pole of the DC power supply is directly connected to the negative terminal of the bridge inverter. The positive terminal of the bridge inverter is connected, and the negative terminal of the DC power supply is connected to the negative terminal of the bridge inverter through a chopper switch; If there are two chopper switches, the positive and negative poles of the DC power supply are respectively connected to the positive and negative ends of the inverter through a chopper switch; Under the control of the controller, the chopper switch connected to the positive pole of the DC power supply is turned off only when the switch tubes of all the upper bridge arms in the bridge inverter are closed, and the chopper switch is closed in other cases; only when When the switch tubes of all the lower bridge arms in the bridge inverter are closed, the chopper switch connected to the negative pole of the DC power supply is turned off, and in other cases, the chopper switch is closed. 2 . The motor system according to claim 1 , wherein the DC power supply is an independent DC voltage source or a rectified DC output of the previous AC power supply. 3 . 3. The motor system according to claim 1, wherein the chopper switch adopts a switch tube with an anti-parallel diode. 4. The motor system according to claim 3, wherein the switching tube is a MOSFET, IGBT, IGCT, IEGT, GTO, triode or thyristor. 5. The motor system according to claim 3, wherein the diodes are Schottky diodes, fast recovery diodes, silicon tubes or silicon carbide diodes.