CN113098331B - AC-DC-AC variable frequency pump-up voltage suppression circuit and working method thereof - Google Patents
AC-DC-AC variable frequency pump-up voltage suppression circuit and working method thereof Download PDFInfo
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- CN113098331B CN113098331B CN202110556255.6A CN202110556255A CN113098331B CN 113098331 B CN113098331 B CN 113098331B CN 202110556255 A CN202110556255 A CN 202110556255A CN 113098331 B CN113098331 B CN 113098331B
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- 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
- H02P3/00—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters
- H02P3/06—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters for stopping or slowing an individual dynamo-electric motor or dynamo-electric converter
- H02P3/18—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters for stopping or slowing an individual dynamo-electric motor or dynamo-electric converter for stopping or slowing an ac motor
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- 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
- H02P3/00—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters
- H02P3/06—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters for stopping or slowing an individual dynamo-electric motor or dynamo-electric converter
- H02P3/18—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters for stopping or slowing an individual dynamo-electric motor or dynamo-electric converter for stopping or slowing an ac motor
- H02P3/22—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters for stopping or slowing an individual dynamo-electric motor or dynamo-electric converter for stopping or slowing an ac motor by short-circuit or resistive braking
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
The invention provides an alternating current-direct current alternating frequency pump-up voltage suppression circuit and a working method thereof, and provides a hysteresis suppression technology aiming at the problem that a bus side brake unit is repeatedly started and stopped in a smaller working period in the alternating current-direct current alternating frequency speed modulation process of a motor. The technology takes the application of a hysteresis comparator as a core, and the brake unit is stopped when the voltage of a bus decreases to a certain value smaller than the maximum allowable value after the brake unit is started to work. The bus voltage is not too large, meanwhile, the brake unit can work in a hysteretic mode in the interval of the upper limit value and the lower limit value of the bus voltage, and frequent starting and stopping of the brake unit are avoided.
Description
Technical Field
The invention belongs to the technical field of electric transmission, and particularly relates to an alternating current-direct current (AC-DC-AC) frequency pumping voltage suppression circuit and a working method thereof.
Background
In the ac-dc-ac speed regulation main circuit of an asynchronous motor, a brake unit is generally composed of a brake resistor and an IGBT tube connected in series. The function of the motor is to prevent the damage of devices caused by the continuous rise of the bus voltage at the direct current side in the deceleration process of the motor. If the common variable frequency power supply is designed, the braking unit can be omitted; however, if the frequency converter for open-loop speed regulation of the motor is designed, the braking unit is necessary. This is because, in the process of the motor decreasing with the given frequency, the synchronous speed also immediately decreases, but the rotor speed of the motor cannot immediately follow the decrease of the synchronous speed due to the mechanical inertia, so that the phenomenon that the rotor speed exceeds the synchronous speed occurs, that is, at this time, the motor is actually in a feedback braking state, the feedback current is absorbed by the filter circuit after passing through the inverter, the dc-side filter capacitor is charged, the voltage of the dc-side filter capacitor is continuously increased, and the increased voltage is called a pumping voltage. When the pumped voltage rises to a certain extent, the rectifying device and the inverter device are damaged. Therefore, a braking unit needs to be designed, when the voltage of the direct current side rises to the maximum allowable value in the motor deceleration process, the IGBT tube of the braking unit is started, and feedback electric energy is consumed on the braking resistor, so that the bus voltage is not overlarge.
However, when the bus voltage exceeds the maximum allowable value, the brake unit starts to work immediately, and when the bus voltage drops and is lower than the maximum allowable value, the brake unit stops working immediately. The operating time of the brake unit is thus only brief, after which the electric motor is still in the decelerated state, and the bus voltage continues to rise above the maximum permissible value again after the brake unit has stopped operating. Therefore, during the deceleration process of the motor, the brake unit can be repeatedly started and stopped with a smaller work period.
Disclosure of Invention
In view of the above, in order to make up for the blank and the deficiency of the prior art, the present invention provides an ac-dc alternating-frequency pumping voltage suppression circuit and an operating method thereof, which provides a hysteresis suppression technology for solving the problem that a bus-side braking unit is repeatedly turned on and off in a short duty cycle during the ac-dc alternating-frequency speed regulation process of a motor. The technology takes the application of a hysteresis comparator as a core, and the brake unit is stopped when the bus voltage is reduced to a certain value smaller than the maximum allowable value after the brake unit is started to work. The bus voltage is not too large, meanwhile, the brake unit can work in a hysteretic mode in the interval of the upper limit value and the lower limit value of the bus voltage, and frequent starting and stopping of the brake unit are avoided.
The invention specifically adopts the following technical scheme:
an AC-DC-AC frequency-conversion pump-up voltage suppression circuit is characterized in that: the method comprises the following steps: the circuit comprises a sampling circuit, a voltage following circuit, a hysteresis comparison circuit and a drive isolation circuit;
the sampling circuit is used for sampling a half value of the bus voltage;
the voltage follower circuit is used for outputting a voltage as a reference voltage V ref Supplying to a hysteresis comparator and making V ref 5V is kept unchanged and is not influenced by the load of the later stage;
the hysteresis comparison circuit comprises a hysteresis comparator;
the drive isolation circuit is used for enabling the output signal V of the hysteresis comparator O And the control signal is supplied to the control signal input end of the brake unit after passing through the optocoupler circuit.
Furthermore, the sampling circuit is composed of resistors R1 and R2 which are connected; the other end of the resistor R1 is connected with a direct-current side bus voltage neutral point of the three-phase asynchronous motor, the other end of the resistor R2 is grounded, and a common connection point of the resistor R1 and the resistor R2 is connected with a resistor R7 of the hysteresis comparison circuit.
Further, the voltage follower circuit comprises resistors R3-R6 and a second amplifier of LM 358P; one end of the resistor R3 is connected with a 15V voltage source, and the other end of the resistor R3 is connected with the resistor R4; the other end of the resistor R4 is connected with resistors R5 and R6 respectively; the other end of the resistor R5 is grounded, and the other end of the resistor R6 is connected with a pin 5 of the LM 358P; the pins 6 and 7 of the LM358P are connected and output a reference voltage V ref 。
Further, the hysteresis comparison circuit comprises resistors R7-R10 and a first set of LM 358P; the resistor R7 is connected with a pin 2 of the LM 358P; one end of the resistor R8 is connected with a reference voltage V ref The other end of the resistor is connected with a pin 3 of LM358P and a resistor R9 respectively; the other end of the resistor R9 is respectively connected with the 1 pin of the LM358P and the resistor R10 and used for outputting a signal V O (ii) a The other end of the resistor R10 is connected with a 15V voltage source.
Furthermore, the driving isolation circuit consists of two PC817 optical coupler chips and resistors R11-R13; the 1 pin of the first optocoupler chip is connected with an output signal V of the hysteresis comparator O Pin 2 is grounded through a resistor R11, pin 3 is connected with pin 2 of the second optocoupler chip and grounded, and pin 4 is connected with pin 1 of the second optocoupler chip and a resistor R12; the other end of the resistor R12 is connected with a 3.3V voltage source; pins 3 and 4 of the second optocoupler chip are grounded, and connected with a resistor R13 and used as a control signal input end of the brake unit; the other end of the resistor R13 is connected with a 15V voltage source.
Further, the resistance R1 takes the value of 200k, and the resistance R2 takes the value of 3.1k.
Further, the values of the resistors R8, R9, and R10 are 2k, 47k, and 51k, respectively.
Further, when the bus voltage does not reach the action upper limit value, the hysteresis comparator outputs a high level, the control signal input end of the braking unit is enabled to be the high level after the isolation of the optical coupling circuit, and the braking unit does not work; when the bus voltage exceeds 680V, the hysteresis comparator outputs low level, so that the control signal input end of the brake unit becomes low level, and the brake unit is started to work; when the bus voltage drops to 630V, the hysteresis comparator outputs high level, so that the control signal input end of the brake unit becomes high level, and the brake unit stops working.
Compared with the prior art, the application of the hysteresis comparator is taken as a core in the invention and the optimal scheme thereof, so that the brake unit is stopped when the bus voltage is reduced to a certain value smaller than the maximum allowable value after the brake unit is started to work. The bus voltage is not too large, meanwhile, the brake unit can work in a hysteretic mode in the interval of the upper limit value and the lower limit value of the bus voltage, and frequent starting and stopping of the brake unit are avoided.
Drawings
The invention is described in further detail below with reference to the following figures and detailed description:
FIG. 1 is a schematic diagram of a main circuit of an AC/DC AC speed regulation system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a hysteresis comparator circuit according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of the transmission characteristics of a hysteretic comparator according to an embodiment of the invention;
FIG. 4 is a schematic diagram of a voltage follower circuit according to an embodiment of the present invention;
fig. 5 is a schematic diagram of a pumped voltage hysteresis suppression circuit according to an embodiment of the present invention.
Detailed Description
In order to make the features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail as follows:
1. AC-DC-AC variable frequency speed regulation main circuit and brake unit thereof
An ac-dc-ac speed regulation main circuit of a typical three-phase asynchronous motor is shown in fig. 1, and comprises rectification circuits (D1-D6), a current limiting unit (R1), dc filter circuits (R2, R3, C1-C4), braking units (R4, T7), inverter circuits (T1-T6), an absorption capacitor (C5), and the like.
The brake unit is formed by connecting a brake resistor R4 and an IGBT tube T7 in series, and has the function of inhibiting the pumping voltage, so that the IGBT tube of the brake unit is opened when the voltage of a direct-current side bus rises to a maximum allowable value in the motor deceleration process, feedback electric energy is consumed on the brake resistor, and the condition that the voltage of the bus is not too large is ensured.
The inverter circuit can adopt a single six-IGBT switch tube design or an integrated intelligent power module IPM, and the design adopts an IPM (model number PM25RLA 120) of Mitsubishi corporation. The PM25RLA120 comprises six switching tubes of an inverter bridge and a driving and protecting circuit thereof, and also comprises a T7 tube of a brake unit, so that the brake unit is designed only by being externally connected with a brake resistor R4. The accurate calculation of the brake resistance is troublesome, and involves many factors such as the torque, the moment of inertia and the load characteristic of the motor, and the calculation methods given by different manufacturers of frequency converters are different and not strict, so the necessity of accurately calculating the brake resistance is not great, and a simple and general calculation method is adopted.
In the formula: u shape DH Is the operating voltage of the brake unit; i is N Is the rated current of the motor; r is the resistance of the brake resistor; p R Is the power of the brake resistor; v is a correction factor, is related to the load property, is generally in the range of 0.15-0.4, and can be 0.2.
In the peripheral interface circuit design of PM25RLA120, the control signal input of the brake unit is Br, and Br is active low. When Br is input to low level, the T7 tube of the driving brake unit is switched on, so that the feedback electric energy of the motor is consumed on the R4 of the brake resistor; when Br is input to high level, T7 tube is cut off, and the brake unit stops working.
2. Pumped voltage hysteresis suppression circuit design
If only the maximum allowable value of the bus voltage is designed, the brake unit can be frequently started and stopped at the maximum allowable value, feedback electric energy cannot be continuously consumed in time, and the pumped voltage still can damage the rectifying device and the inverter device. In order to solve the problem, in this embodiment, a hysteresis suppression technology is designed, so that after the braking unit is started, the braking unit is stopped when the bus voltage continuously decreases to a value smaller than the maximum allowable value by a certain value, and at this time, even if the bus voltage slightly increases due to feedback electric energy, the braking unit cannot be restarted under the condition that the maximum allowable value is not reached, because the bus voltage has decreased to a value smaller than the maximum allowable value by a certain value, the braking unit is stopped, and thus frequent start and stop of the braking unit are avoided.
The core of the hysteresis suppression technology is the application design of a hysteresis comparator, the hysteresis comparator has a difference between a non-inverting input and an inverting input, and the design adopts an inverting input hysteresis comparator. In addition, the hysteresis comparator can only receive positive feedback, otherwise, if receive negative feedback, the amplification factor of the amplifier is no longer infinite, and the comparator can not be formed. The circuit schematic of the inverting input hysteretic comparator is shown in fig. 2, and its transfer characteristics are shown in fig. 3. And has the following components:
in the formula: v th1 Is the lower limit value of the action of the hysteresis comparator; v th2 Is an action upper limit value; v ref Inputting a reference voltage for the positive terminal; v cc To output a pull-up voltage; v low The output voltage of the comparator is 0.047V when the comparator outputs low level, if the comparator LM393N is adopted, V is obtained in the approximate calculation low ＝0V。
To ensure V ref The reference voltage is not influenced by the load and is kept unchanged, so that the reference voltage can be supplied to the hysteresis comparator after passing through the voltage follower. The circuit diagram of the voltage follower is shown in fig. 4.
If the input voltage of the rectifier bridge is 380V, the direct current voltage at the bus side is U DC =1.35 × 380v =513v. System for makingThe maximum allowable value of the motion unit, i.e. the motion upper limit value, can be approximated by:
U upper part of ＝130％U DC ＝130％×513V＝667V (5)
The lower limit of actuation of the brake unit may be approximated by:
U lower part ＝110％U DC ＝130％×513V＝564V (6)
Taking into account the fluctuation rate of the grid of 15%, i.e. the maximum value on the bus side
In order to ensure that the frequency converter can still normally operate under normal power grid fluctuation, the U is adopted Lower part ≥U DCmax . Finally, taking U from the design Upper part of ＝680V，U Lower part ＝630V。
The pump-up voltage hysteresis suppression circuit finally designed in the present embodiment is shown in fig. 5. The circuit consists of a sampling circuit, a voltage following circuit, a hysteresis comparison circuit and a drive isolation circuit.
The sampling circuit is composed of R1 and R2, the R1 value is 200k, the R2 value is 3.1k, the P2 point is a DC side bus voltage neutral point, namely a connection point of C2 and C4 in figure 1, namely, a half value of the bus voltage is sampled, and thus, the action upper limit value 680V and the action lower limit value 630V of the brake voltage respectively correspond to the sampling voltage V i 5.2V and 4.8V.
The voltage following circuit consists of R3-R6 and (5-7 pins), and the output voltage is used as reference voltage V ref The purpose of the voltage follower circuit provided for the hysteresis comparator is to let V ref Keep 5V unchanged and is not influenced by the load of the later stage. It should be noted that, experiments show that the voltage follower can adopt a common operational amplifier LM358 (the output may not be pulled up), but cannot adopt a comparator LM393N (the output must be pulled up), and if the operational amplifier is replaced by the comparator, the output must be connected with a pull-up resistor, and the magnitude of the pull-up resistor affects the magnitude of the output voltage, that is, the following effect cannot be achieved. However, a common operational amplifier can be used as a comparator after being pulled up through output and connected with a positive feedback line. Therefore, for design convenience, LM358 is uniformly used for both the hysteresis comparator and the voltage follower in this design.
The hysteresis comparison circuit comprises R7-R10 and the first amplifier (1-3 pins) of LM358P, wherein R7-R10 correspond to R in FIG. 2 Z1 -R Z4 . R8-R10 take the values of 2k, 47k and 51k respectively, so that the action voltages of the hysteresis comparator can be calculated to be 4.8V and 5.2V according to the formulas (3) - (4), and the design is met.
The drive isolation circuit consists of two PC817 opto-coupler chips and R11-R13, and is designed to output a signal V by the hysteresis comparator circuit O After passing through the PC817 optocoupler circuit, the signals are supplied to a Br pin (a control signal input end of a brake unit) of the IPM, so that the drive isolation effect is achieved.
The pump-up voltage hysteresis suppression circuit shown in fig. 5 achieves the following effects: when the bus voltage is normal (namely the bus voltage does not reach the action upper limit value), the hysteresis comparator outputs a high level, the Br end is enabled to be the high level after the isolation of the optical coupler circuit, and the brake unit does not work; when the bus voltage exceeds 680V, the hysteresis comparator outputs low level, so that the Br end becomes low level, and the brake unit is started to work; when the bus voltage drops to 630V, the hysteresis comparator outputs high level, so that the Br end becomes high level, and the brake unit stops working.
Therefore, the circuit realizes the hysteretic operation of the brake unit between 630V and 680V, and avoids the frequent start and stop of the brake unit.
The present invention is not limited to the above preferred embodiments, and various other types of ac/dc/ac pump-up voltage suppression circuits and their operation methods can be obtained by anyone who has taught the present invention.
Claims (4)
1. An AC-DC-AC frequency-conversion pump-up voltage suppression circuit is characterized in that: the method comprises the following steps: the circuit comprises a sampling circuit, a voltage follower circuit, a hysteresis comparison circuit and a drive isolation circuit;
the sampling circuit is used for sampling a half value of the bus voltage;
the voltage follower circuit is used for outputting a voltage as a reference voltage V ref Supply hysteresisComparator, and let V ref 5V is kept unchanged and is not influenced by a rear-stage load;
the hysteresis comparison circuit comprises a hysteresis comparator;
the drive isolation circuit is used for enabling the output signal V of the hysteresis comparator O After passing through the optocoupler circuit, the signal is supplied to a control signal input end of the brake unit;
the sampling circuit consists of resistors R1 and R2 which are connected; the other end of the resistor R1 is connected with a neutral point of a direct-current side bus voltage of the three-phase asynchronous motor, the other end of the resistor R2 is grounded, and a common connection point of the resistors R1 and R2 is connected with a resistor R7 of the hysteresis comparison circuit;
the voltage follower circuit comprises resistors R3-R6 and a second amplifier of LM 358P; one end of the resistor R3 is connected with a 15V voltage source, and the other end of the resistor R3 is connected with the resistor R4; the other end of the resistor R4 is connected with resistors R5 and R6 respectively; the other end of the resistor R5 is grounded, and the other end of the resistor R6 is connected with a pin 5 of the LM 358P; the pins 6 and 7 of the LM358P are connected and output a reference voltage V ref ；
The hysteresis comparison circuit comprises resistors R7-R10 and a first amplifier of LM 358P; the resistor R7 is connected with a pin 2 of the LM 358P; one end of the resistor R8 is connected with a reference voltage V ref The other end of the resistor is connected with a pin 3 of the LM358P and a resistor R9 respectively; the other end of the resistor R9 is respectively connected with the 1 pin of the LM358P and the resistor R10 and used for outputting a signal V O (ii) a The other end of the resistor R10 is connected with a 15V voltage source;
the driving isolation circuit consists of two PC817 opto-coupler chips and resistors R11-R13; the 1 pin of the first optocoupler chip is connected with an output signal V of the hysteresis comparator O Pin 2 is grounded through a resistor R11, pin 3 is connected with pin 2 of the second optocoupler chip and grounded, and pin 4 is connected with pin 1 of the second optocoupler chip and a resistor R12; the other end of the resistor R12 is connected with a 3.3V voltage source; pins 3 and 4 of the second optical coupler chip are grounded, and connected with a resistor R13 and used as a control signal input end of the braking unit; the other end of the resistor R13 is connected with a 15V voltage source.
2. The ac-dc alternating frequency pumped voltage suppression circuit of claim 1, wherein: the resistance R1 is 200k, and the R2 is 3.1k.
3. The ac-dc alternating frequency pumped voltage suppression circuit of claim 1, wherein: the values of the resistors R8, R9 and R10 are respectively 2k, 47k and 51k.
4. The method of operating an ac-dc-ac pumped voltage suppression circuit of claim 1, further comprising: when the bus voltage does not reach the action upper limit value, the hysteresis comparator outputs a high level, the control signal input end of the braking unit is enabled to be the high level after the isolation of the optical coupling circuit, and the braking unit does not work; when the bus voltage exceeds 680V, the hysteresis comparator outputs low level, so that the control signal input end of the brake unit is changed into low level, and the brake unit is started to work; when the bus voltage drops to 630V, the hysteresis comparator outputs high level, so that the control signal input end of the brake unit becomes high level, and the brake unit stops working.
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| CN202110556255.6A CN113098331B (en) | 2021-05-21 | 2021-05-21 | AC-DC-AC variable frequency pump-up voltage suppression circuit and working method thereof |
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2021
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| CN101561456A (en) * | 2008-04-15 | 2009-10-21 | 上海电气集团股份有限公司 | Direct current side high-voltage detecting method of compressor driver |
| CN202373972U (en) * | 2011-10-27 | 2012-08-08 | 北京精密机电控制设备研究所 | Control circuit for reliable management of regenerated energy |
| CN205544261U (en) * | 2016-02-01 | 2016-08-31 | 凯迈(洛阳)电子有限公司 | Powered storage battery joins conversely monitoring devices |
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