Protection device and method of frequency converter, frequency converter and air conditioner

Abstract

The invention discloses a protection device and method for a frequency converter, the frequency converter and an air conditioner, and the device comprises a current sampling unit which samples one-phase current of the frequency converter, and obtains a second sampling value of the one-phase current after carrying out the first-stage scaling, biasing, second-stage scaling and filtering processing; wherein a first sampling value of one-phase current is obtained after first-stage scaling and bias processing; the overcurrent protection unit is used for setting an overcurrent protection threshold range of the frequency converter, and performing comparison and clamping processing based on the first sampling value and the overcurrent protection threshold range to obtain an overcurrent protection signal of the frequency converter; and the control unit performs overcurrent protection processing based on the second sampling value and the overcurrent protection signal to realize overcurrent protection. According to the scheme, two-stage scaling is adopted in the current sampling circuit, the bias voltage is obtained through the reference voltage stabilizing circuit, the protection value is obtained through the reference voltage stabilizing circuit in the overcurrent protection circuit, protection can be conducted in time when the frequency converter is abnormal, and safety and reliability are improved.

Description

Technical Field

[0001] This invention belongs to the field of frequency converter technology, specifically relating to a protection device, method, frequency converter, and air conditioner for a frequency converter, and particularly to a current sampling circuit and protection circuit and method for a high-power frequency converter, as well as a frequency converter and air conditioner. Background Technology

[0002] Currently, high-power frequency converters are widely used in refrigeration and other industrial fields. For the control of frequency converters, overcurrent protection is necessary. Current solutions use differential amplifier circuits composed of operational amplifier chips for signal sampling and employ a resistor divider to construct the protection value based on the power supply voltage. However, this approach has weak anti-interference capabilities and is prone to false protection, affecting the safety and reliability of the frequency converter.

[0003] The above content is only used to help understand the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0004] The purpose of this invention is to provide a protection device, method, inverter, and air conditioner for a frequency converter. This addresses the problem in frequency converter overcurrent protection where a differential amplifier circuit composed of operational amplifier chips is used for signal sampling, and a protection value is constructed using a resistor divider based on the power supply voltage. Protection is achieved by comparing the real-time operating value and the protection value. However, this method suffers from weak anti-interference capability and false protection, affecting the safety and reliability of the frequency converter. The invention achieves this by using a two-stage scaling circuit in the current sampling circuit and obtaining a bias voltage through a reference voltage regulator circuit. The overcurrent protection circuit uses a reference voltage regulator circuit to obtain the protection value, enabling timely protection when the frequency converter malfunctions, thus improving the safety and reliability of the frequency converter.

[0005] This invention provides a protection device for a frequency converter, comprising: a control unit, and a current sampling unit and an overcurrent protection unit configured for each phase current of the frequency converter; wherein, the current sampling unit is used to sample the phase current of the frequency converter, and after performing first-level scaling, biasing, second-level scaling and filtering processing, obtain a second sampled value of the phase current of the frequency converter; wherein, after first-level scaling and biasing processing, a first sampled value of the phase current of the frequency converter is obtained; the overcurrent protection unit is used to set the overcurrent protection threshold range of the frequency converter, and after comparing and clamping the first sampled value of the phase current of the frequency converter with the overcurrent protection threshold range of the frequency converter, obtain an overcurrent protection signal of the frequency converter; the control unit is used to perform overcurrent protection processing based on the second sampled value of the phase current of the frequency converter and the overcurrent protection signal of the frequency converter, thereby realizing overcurrent protection for the frequency converter.

[0006] In some embodiments, the inverter is further provided with a bias voltage regulator unit for each phase current of the inverter; wherein the bias voltage regulator unit is used to perform voltage division and voltage regulation based on a preset first power supply voltage to obtain a preset bias voltage.

[0007] In some embodiments, the bias voltage regulator unit includes: a first resistor module, a second resistor module, a third resistor module, and a TL431 chip; wherein, a preset first power supply voltage is grounded after passing through the third resistor module, the second resistor module, and the first resistor module; the common terminal of the second resistor module and the first resistor module is connected to the reference terminal of the TL431 chip; the cathode of the TL431 chip is connected to the common terminal of the third resistor module and the second resistor module, and is used to output a preset bias voltage; the anode of the TL431 chip is grounded.

[0008] In some embodiments, the current sampling unit includes: a sampling module, a first scaling module, a bias module, a second scaling module, and a filtering module; wherein, the current sampling unit samples one phase current of the frequency converter, performs first-level scaling, biasing, second-level scaling, and filtering processing to obtain a second sampled value of the one phase current of the frequency converter; including: the sampling module, used to sample one phase current of the frequency converter; the first scaling module, used to perform first-level scaling processing on the sampled one phase current of the frequency converter to obtain a first-level scaled value of the one phase current of the frequency converter; The bias module is used to perform a first-level scaling process on the one-phase current of the inverter based on a preset bias voltage to obtain a first sampled value of the one-phase current of the inverter; the preset bias voltage is obtained by voltage division and regulation based on a preset first power supply voltage; the second scaling module is used to perform a second-level scaling process on the first sampled value of the one-phase current of the inverter to obtain a second-level scaling value of the one-phase current of the inverter; the filtering module is used to perform a filtering process on the second-level scaling value of the one-phase current of the inverter to obtain a second sampled value of the one-phase current of the inverter.

[0009] In some embodiments, the first scaling module includes: a first differential operational amplifier circuit; a sampled phase current of the inverter can be input to the non-inverting input terminal of the first differential operational amplifier circuit; the output terminal of the first differential operational amplifier circuit can output a first-level scaling value of the phase current of the inverter; and / or, if a bias regulating unit is further provided for each phase current of the inverter, the bias regulating unit includes a first bias regulating circuit, and the bias module includes: a second differential operational amplifier circuit and a first bias regulating circuit; the first-level scaling value of the phase current of the inverter and a preset bias voltage provided by the first bias regulating circuit can... The superimposed values ​​are input to the non-inverting input of the second differential operational amplifier circuit; the output of the second differential operational amplifier circuit can output the first sampled value of one phase current of the frequency converter; and / or, the second scaling module includes: a third differential operational amplifier circuit; the first sampled value of one phase current of the frequency converter can be input to the non-inverting input of the third differential operational amplifier circuit; the output of the third differential operational amplifier circuit can output the second-order scaled value of one phase current of the frequency converter; and / or, the filtering module includes: an RC filter circuit; the second-order scaled value of one phase current of the frequency converter, after passing through the RC filter circuit, can obtain the second sampled value of one phase current of the frequency converter.

[0010] In some embodiments, the single-channel overcurrent protection unit includes: a first reference module, a second reference module, a comparison module, and a clamping module; the single-channel overcurrent protection unit sets the overcurrent protection threshold range of the inverter, and obtains the overcurrent protection signal of the inverter by comparing and clamping a first sampled value of the current of one phase of the inverter with the overcurrent protection threshold range of the inverter, including: the first reference module is used to obtain the lower limit of the overcurrent protection threshold range of the inverter based on a preset first bias voltage and after a first voltage following process; the preset first bias voltage is obtained by performing a first voltage division and a first voltage regulation process based on a preset first power supply voltage; the second reference module is used to obtain the lower limit of the overcurrent protection threshold range of the inverter based on a preset first bias voltage and after a first voltage following process; the preset first bias voltage is obtained by performing a first voltage division and a first voltage regulation process based on a preset first power supply voltage; The second bias voltage, after being processed by the second voltage follower, yields the upper limit of the overcurrent protection threshold range of the frequency converter. The preset second bias voltage is obtained by performing a second voltage division and a second voltage regulation process based on a preset first power supply voltage. The comparison module is used to compare the first sampled value of the one-phase current of the frequency converter with the overcurrent protection threshold range of the frequency converter to obtain a comparison signal of the one-phase current of the frequency converter. The overcurrent protection threshold range of the frequency converter includes the lower limit of the overcurrent protection threshold range and the upper limit of the overcurrent protection threshold range of the frequency converter. The clamping module is used to clamp based on the comparison signal of the one-phase current of the frequency converter to obtain the overcurrent protection signal of the frequency converter.

[0011] In some embodiments, where a bias voltage regulator unit is further provided for each phase current of the inverter, the bias voltage regulator unit includes a second bias voltage regulator circuit. The first reference module includes a second reference voltage regulator circuit and a first voltage follower. A preset first bias voltage provided by the second reference voltage regulator circuit is input to the non-inverting input terminal of the first voltage follower. The output terminal of the first voltage follower can output the lower limit of the overcurrent protection threshold range of the inverter. And / or, where a bias voltage regulator unit is further provided for each phase current of the inverter, the bias voltage regulator unit includes a third bias voltage regulator circuit. The second reference module includes a third reference voltage regulator circuit and a second voltage follower. A preset second bias voltage provided by the second reference voltage regulator circuit is input to the non-inverting input terminal of the second voltage follower. The output terminal of the second voltage follower can output the upper limit of the overcurrent protection threshold range of the inverter. And / or, the comparison module includes a first comparator and a second comparator. The lower limit of the overcurrent protection threshold range of the inverter can be input to... The first comparator has an inverting input terminal; a first sampled value of the inverter's one-phase current can be input to the non-inverting input terminal of the first comparator; the first comparator's output terminal can output a comparison signal of the inverter's one-phase current; the upper limit of the inverter's overcurrent protection threshold range can be input to the non-inverting input terminal of the second comparator; the first sampled value of the inverter's one-phase current can be input to the inverting input terminal of the second comparator; the second comparator's output terminal can output a comparison signal of the inverter's one-phase current; and / or, the clamping module includes: a fourth resistor module, a fifth resistor module, an output capacitor module, and a diode clamping circuit; a preset second power supply voltage is grounded after passing through the fourth resistor module, the fifth resistor module, and the output capacitor module; the output terminal of the inverter's one-phase current comparison signal is connected to the common terminal of the fourth resistor module and the fifth resistor module; the common terminal of the fifth resistor module and the output capacitor module is connected to the clamping terminal of the diode clamping circuit and can output the inverter's overcurrent protection signal.

[0012] In conjunction with the above-described device, the present invention further provides a frequency converter, comprising: the protection device for the frequency converter described above.

[0013] In conjunction with the above-described device, the present invention further provides an air conditioner, comprising: a protection device for the inverter described above, or the inverter described above.

[0014] In conjunction with the aforementioned frequency converter, this invention further provides a protection method for the frequency converter, comprising: sampling one phase current of the frequency converter through the aforementioned current sampling unit, performing first-level scaling, biasing, second-level scaling, and filtering processing to obtain a second sampled value of the one phase current of the frequency converter; wherein, after the first-level scaling and biasing processing, a first sampled value of the one phase current of the frequency converter is obtained; setting an overcurrent protection threshold range for the frequency converter through the aforementioned overcurrent protection unit, and comparing and clamping the first sampled value of the one phase current of the frequency converter with the overcurrent protection threshold range of the frequency converter to obtain an overcurrent protection signal for the frequency converter; performing overcurrent protection processing based on the second sampled value of the one phase current of the frequency converter and the overcurrent protection signal of the frequency converter to achieve overcurrent protection for the frequency converter.

[0015] Therefore, the solution of the present invention, for overcurrent protection of the input current and / or output current of the frequency converter, sets up a current sampling circuit and an overcurrent protection circuit for each phase current; wherein, the current sampling circuit includes: a first-stage scaling circuit, a bias circuit, a second-stage scaling circuit, and a filter circuit arranged in sequence, the bias circuit operates based on the bias voltage provided by the bias regulating circuit, the bias circuit outputs the sampled value of the current for one phase (such as the real-time current sampled value U_OUT), and the filter circuit outputs a further processed value of the sampled value of the current for one phase (such as the signal U_OUT.DSP); the overcurrent protection circuit includes: a reference circuit arranged in sequence. The system includes a comparator circuit and a clamping circuit. The comparator circuit compares the positive and negative reference values ​​provided by the reference circuit with the sampled value of one current channel (such as the real-time current sample value U_OUT). The clamping circuit outputs an overcurrent protection signal (such as the signal U_TZ.DSP). The controller performs overcurrent protection processing based on the output value of the filter circuit and the overcurrent protection signal output by the clamping circuit. Thus, by using a two-stage scaling circuit in the current sampling circuit and obtaining the bias voltage through the reference voltage regulator circuit, and using the reference voltage regulator circuit in the overcurrent protection circuit to obtain the protection value, timely protection can be provided when the frequency converter malfunctions, improving the safety and reliability of the frequency converter.

[0016] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a structure of an embodiment of the protection device for the frequency converter of the present invention;

[0019] Figure 2 A block diagram of the current sampling and overcurrent protection circuit for a frequency converter;

[0020] Figure 3 This is a schematic diagram of the internal hardware circuitry of the TL431.

[0021] Figure 4 This is a schematic diagram of a reference voltage regulator circuit composed of TL431.

[0022] Figure 5 This is a schematic diagram of the current sampling circuit of a frequency converter;

[0023] Figure 6 This is a schematic diagram of the overcurrent protection circuit of a frequency converter.

[0024] Figure 7 This is a flowchart illustrating an embodiment of the inverter protection method of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0026] Considering that the overcurrent protection of the frequency converter uses a differential amplifier circuit composed of operational amplifier chips for signal sampling and uses the power supply voltage to form the protection value through resistor division, its anti-interference capability is weak, and false protection may occur, affecting the safety and reliability of the frequency converter. For frequency converter control, it is necessary to sample real-time data such as input and output current and bus voltage to implement algorithm control. Therefore, a stable sampling circuit with small error is crucial. Furthermore, from the perspective of safe operation, designing a highly reliable protection circuit is also essential to ensure timely shutdown in case of abnormal operation of the frequency converter, protecting the frequency converter and the unit from damage.

[0027] In the relevant solutions, for the current sampling circuit and protection circuit applied to high-power frequency converters, the current sampling circuit uses a differential amplifier circuit composed of operational amplifier chips for signal sampling; the protection circuit uses the power supply voltage to form a protection value through resistor division, and achieves the protection function by comparing the real-time operating value and the protection value. However, the relevant solutions still have some drawbacks. For example, using a reference voltage chip to obtain the bias voltage in the sampling circuit, because the output value of the reference voltage chip is not adjustable, different models of reference chips may need to be replaced for different frequency converter models, resulting in poor circuit applicability. The protection circuit uses the power supply voltage to form a protection value through resistor division. If the power supply voltage becomes unstable during operation due to environmental interference or load fluctuations, the protection value will have a large error, which can easily lead to false protection shutdown of the frequency converter.

[0028] Therefore, the present invention proposes a protection device for a frequency converter, specifically a current sampling circuit and protection circuit for a high-power frequency converter. It employs a two-stage differential amplifier circuit composed of operational amplifier chips as the current sampling circuit, and obtains a stable bias voltage using a reference voltage regulator circuit, which is then input into the current sampling circuit. Furthermore, the protection circuit uses a reference voltage regulator circuit to obtain a reference protection value, ensuring timely protection of the frequency converter in case of abnormal conditions, reducing the possibility of false protection, and improving the safety and reliability of the frequency converter.

[0029] According to an embodiment of the present invention, a protection device for a frequency converter is provided. See also Figure 1 The diagram shows a structural schematic of an embodiment of the device of the present invention. The frequency converter has a rectifier section and an inverter section, the input terminal of the frequency converter is the input terminal of the rectifier section, and the output terminal of the frequency converter is the output terminal of the inverter section. In the solution of the present invention, as... Figure 1 As shown, the protection device of the frequency converter includes: a control unit, and a current sampling unit and an overcurrent protection unit for each phase current of the frequency converter. The control unit is as follows: Figure 2 The controller DSP shown has one current sampling unit as follows: Figure 2 The current sampling circuit shown includes one overcurrent protection unit. Figure 2 The overcurrent protection circuit shown; the current per phase of the inverter includes: the current per phase at the input terminal of the inverter, and / or the current per phase at the output terminal of the inverter.

[0030] The current sampling unit is used to sample one phase current of the inverter, and after performing first-level scaling, biasing, second-level scaling and filtering, obtains the second sample value of one phase current of the inverter; wherein, after first-level scaling and biasing, the first sample value of one phase current of the inverter is obtained.

[0031] The overcurrent protection unit is used to set the overcurrent protection threshold range of the frequency converter, and after comparing and clamping the first sampled value of the phase current of the frequency converter with the overcurrent protection threshold range of the frequency converter, the overcurrent protection signal of the frequency converter is obtained.

[0032] The control unit is used to perform overcurrent protection processing based on the second sampled value of one phase current of the frequency converter and the overcurrent protection signal of the frequency converter, so as to realize overcurrent protection of the frequency converter.

[0033] Figure 2 The block diagram of the current sampling and overcurrent protection circuit for a frequency converter, as shown in the present invention, illustrates the proposed solution for this frequency converter. The present invention proposes a current sampling circuit and protection circuit for a high-power frequency converter, as illustrated in the circuit block diagram below. Figure 2 As shown. Figure 2 As shown, the inverter's current sampling and overcurrent protection circuit mainly consists of three parts: a current sampling circuit, an overcurrent protection circuit, and a bias voltage regulator circuit. Compared with related solutions, Figure 2 The example shown improves the bias circuit and overcurrent protection circuit. For example... Figure 2 As shown, the inverter's current sampling and overcurrent protection circuit includes: a current sampling circuit, an overcurrent protection circuit, a controller digital signal processing (DSP) system, and a bias voltage regulator circuit. During inverter operation, the current sensor collects the current before rectification and after inversion and transmits it to the inverter controller's current sampling port in voltage form. Protection is provided for both the inverter's input and output: the input protects the rectifier diodes to prevent overcurrent damage; the output protects the IGBT module to prevent overcurrent damage. Because commonly used current sensors do not have internal bias and their output voltage range includes negative voltage, a bias voltage processing is required after the first-stage scaling processing in the current sampling circuit. After bias processing, one path is input to the main control DSP after the second-stage scaling and filtering processing in the current sampling circuit. The software needs to read the DSP's current sampling value for algorithm modulation control of the motor; the other path enters the protection circuit and is compared with the set overcurrent protection value. If it is within the overcurrent protection range, the TZ overcurrent protection is triggered, and the signal is transmitted to the main control DSP after clamping through the clamping circuit.

[0034] This invention proposes a current sampling circuit and protection circuit for high-power frequency converters. It employs a two-stage differential amplifier circuit composed of operational amplifier chips as the current sampling circuit, and obtains a stable bias voltage using a reference voltage regulator circuit, which is then input into the current sampling circuit. Furthermore, the protection circuit uses a reference voltage regulator circuit to obtain a reference protection value, ensuring timely protection of the frequency converter in case of abnormal conditions, reducing the possibility of false protection, and improving the safety and reliability of the frequency converter. This invention overcomes the shortcomings of related solutions and features stability and strong applicability.

[0035] In some embodiments, the protection device for the frequency converter described in the present invention further includes: a bias voltage regulating unit for each phase current of the frequency converter, such as a bias voltage regulating circuit in the current sampling unit for providing a preset bias voltage to the bias circuit, and two bias voltage regulating circuits in the overcurrent protection unit for providing a preset bias voltage to the reference circuit, specifically as follows: Figure 2 The bias regulator circuit shown is shown.

[0036] The bias voltage regulator unit is used to perform voltage division and regulation based on a preset first power supply voltage to obtain a preset bias voltage as the required bias voltage.

[0037] In the present invention, a two-stage differential amplifier circuit composed of operational amplifier chips is used as the current sampling circuit. A stable bias voltage is obtained by using a reference voltage regulator circuit and input into the sampling circuit. This can boost the negative voltage at the sampling front end to meet the input range of the DSP's analog-to-digital converter (i.e., A / D converter, or ADC for short, which usually refers to an electronic component that converts analog signals into digital signals). Furthermore, the combination of the two-stage differential amplifier circuit and the reference voltage regulator circuit can reduce the impact of noise on the sampling results and improve the sampling accuracy and anti-interference capability.

[0038] In some embodiments, the bias regulating unit includes: a first resistor module, a second resistor module, a third resistor module, and a TL431 chip, wherein the first resistor module is as follows: Figure 4 The resistor R1 and the second resistor module shown are as follows: Figure 4 The resistor R2 and the third resistor module shown are as follows: Figure 4 The resistors R3, R1, R2, and R3 shown are used in the voltage divider module, and the TL431 chip is used for voltage regulation.

[0039] The preset first power supply voltage is grounded after passing through the third resistor module, the second resistor module, and the first resistor module; the common terminal of the second resistor module and the first resistor module is connected to the reference terminal of the TL431 chip; the cathode of the TL431 chip is connected to the common terminal of the third resistor module and the second resistor module, and is used to output a preset bias voltage; the anode of the TL431 chip is grounded.

[0040] Figure 3 This is a schematic diagram of the internal hardware circuitry of the TL431. Figure 3 As shown, the TL431 mainly consists of a reference voltage source, an error amplifier, a transistor, and a diode. The TL431 operates as follows: when the input voltage from terminal REF is greater than the internal reference voltage VREF, the output of the error amplifier turns on the internal transistor; the larger the error value, the larger the collector current Ic of the transistor. When the input voltage from terminal REF is less than the internal reference voltage VREF, the output of the error amplifier turns off the internal transistor.

[0041] Figure 4 This is a schematic diagram of a reference voltage regulator circuit constructed using a TL431. Figure 4 As shown, the reference voltage regulator circuit composed of TL431 utilizes the characteristics of TL431 to maintain the output voltage Uo at a stable value. Figure 4 As shown, the reference voltage regulator circuit proposed in this invention includes: resistors R1, R2, and R3, and a TL431 chip U7. The power supply VDD is grounded after passing through resistors R3, R2, and R1. The common terminal of resistors R3 and R2 is connected to the cathode of the TL431 chip U7, and also connected to the output terminal Uo of the reference voltage regulator circuit. The common terminal Ur of resistors R2 and R1 is connected to the reference terminal (REF) of the TL431 chip U7; the anode of the TL431 chip U7 is grounded.

[0042] exist Figure 4 In the example shown, resistors R1, R2, and R3 form a resistor voltage divider circuit. When the frequency converter is running under load, the power supply voltage VDD will fluctuate, which will cause the output voltage to fluctuate, resulting in the frequency converter malfunctioning and shutting down. The reference voltage regulator circuit composed of TL431 can dynamically adjust to make the output voltage more stable and avoid the frequency converter malfunctioning and shutting down.

[0043] Reference voltage regulator circuit, such as Figure 4As shown, the reference voltage regulator circuit consists of a power supply voltage VDD, resistors R1, R2, and R3, and a TL431 (i.e., chip U7). The internal reference voltage of the TL431 is Uref, and the Uref of the TL431 used in this invention is 2.5V. The voltage Ua of resistor R1 relative to ground, obtained by dividing the power supply voltage VDD through resistors R1, R2, and R3, is:

[0044]

[0045] When selecting resistors R1, R2, and R3, Ua should be greater than 2.5V. If Ur > 2.5V, TL431 will conduct, increasing the current flowing through resistor R3, thus decreasing the voltage Ur. If Ur < 2.5V, TL431 will be cut off, and Ur = Ua, causing Ur to increase. Through continuous negative feedback adjustment, Ur can be stabilized at 2.5V, at which point the output voltage Uo will stabilize at:

[0046]

[0047] In this invention, a reference voltage regulator circuit composed of the power supply voltage and TL431 is used to obtain the protection value, which is then input into a comparator and compared with the real-time operating value. If the real-time operating value is within the protection value range, the TZ protection shutdown is triggered. In the current sampling circuit, the combination of a two-stage differential amplifier circuit and a reference voltage regulator circuit reduces the impact of noise on the sampling results, improving sampling accuracy and anti-interference capability. In the protection circuit, the use of a reference voltage regulator circuit to obtain the protection value ensures timely protection of the inverter in case of abnormal conditions, reduces the possibility of false protection, and improves the safety and reliability of the inverter.

[0048] In some embodiments, the current sampling unit includes: a sampling module, a first scaling module, a bias module, a second scaling module, and a filtering module, wherein the sampling module is as follows: Figure 2 The current sensor shown has a first scaling module as follows: Figure 2 The first scaling circuit shown has a bias module as follows: Figure 2 The bias circuit shown, the second scaling module is as follows Figure 2 The second scaling circuit shown has a filtering module as follows: Figure 2 The filter circuit shown.

[0049] The current sampling unit samples one phase current of the frequency converter, performs first-level scaling, biasing, second-level scaling, and filtering processing to obtain a second sampled value of the one phase current of the frequency converter; including:

[0050] The sampling module is used to sample one phase current of the frequency converter.

[0051] The first scaling module is used to perform a first-level scaling process on the sampled phase current of the inverter to obtain a first-level scaled value of the phase current of the inverter.

[0052] The bias module is used to bias the first-level scaling value of one phase current of the frequency converter based on a preset bias voltage to obtain the first sample value of one phase current of the frequency converter; the preset bias voltage is obtained by voltage division and voltage regulation based on a preset first power supply voltage.

[0053] The second scaling module is used to perform secondary scaling processing on the first sampled value of the one-phase current of the frequency converter to obtain the secondary scaled value of the one-phase current of the frequency converter.

[0054] The filtering module is used to filter the secondary scaling value of one phase current of the frequency converter to obtain the second sampled value of one phase current of the frequency converter.

[0055] like Figure 2 As shown, the current sampling circuit includes: a current sensor, a controller sampling port, a first scaling circuit, a bias circuit, a second scaling circuit, and a filter circuit. Taking the sampling of the U-phase current from the three-phase currents (U, V, W) output by the frequency converter as an example, the current sensor samples the U-phase current, which is then transmitted through the controller sampling port to obtain the signal U_IN. The signal U_IN is processed by the first scaling circuit, the bias circuit, the second scaling circuit, and the filter circuit to obtain the signal U_OUT.DSP. The signal U_OUT.DSP is then processed by the controller DSP. A bias voltage regulator circuit provides a bias voltage U_BIAS to the bias circuit, and the bias circuit outputs the signal U_OUT.

[0056] exist Figure 2 In the example shown, the combination of a two-stage differential amplifier circuit and a reference voltage regulator circuit can reduce the impact of noise on the sampling results and improve the sampling accuracy and anti-interference ability.

[0057] In some embodiments, the first scaling module includes: a first differential operational amplifier circuit, the first differential operational amplifier circuit being as follows: Figure 5 The resistors R12, R13, R14, and R15, capacitors C7 and C8, and operational amplifier U4 are shown. The sampled one-phase current of the frequency converter can be input to the non-inverting input of the first differential operational amplifier circuit. The output of the first differential operational amplifier circuit can output a first-level scaled value of the one-phase current of the frequency converter. In the solution of this invention, the sampling accuracy of the first-level scaling processing can be guaranteed by performing a first-level scaling on the sampled one-phase current of the frequency converter through the first differential operational amplifier circuit.

[0058] And / or, if a bias voltage regulator unit is further provided for each phase current of the inverter, the bias voltage regulator unit includes a first bias voltage regulator circuit, and the bias module includes: a second differential operational amplifier circuit and the first bias voltage regulator circuit; the second differential operational amplifier circuit and the bias voltage regulator unit, wherein the second differential operational amplifier circuit is as follows: Figure 5 The resistors R16, R17, R18, and R19, capacitors C9 and C10, operational amplifier U5, and the bias regulator circuit shown are as follows: Figure 5 Resistors R31, R32, and R33, along with the TL431 chip U7, are shown. The first-level scaled value of one phase current of the inverter, and the preset bias voltage provided by the first bias regulator circuit, can be superimposed and input to the non-inverting input of the second differential operational amplifier circuit. The output of the second differential operational amplifier circuit can output the first sampled value of one phase current of the inverter. In this invention, the second differential operational amplifier circuit and the bias regulator unit are used to output the first-level scaled value of one phase current of the inverter to the output of the first differential operational amplifier circuit. The differential operational amplifier circuit has high sampling accuracy, and the bias voltage output by the reference regulator circuit is stable, ensuring that the value finally sampled by the main control chip has a small error compared to the actual value.

[0059] And / or, the second scaling module includes: a third differential operational amplifier circuit, such as resistors R20, R21, R22, and R23, capacitors C11 and C12, and operational amplifier U6; the preceding bias circuit increases the voltage amplitude, and direct input to the DSP may exceed the range (DSP: 0-3.3V), so a second-level scaling circuit is added, which also improves the sampling accuracy. The first sampled value of one phase current of the frequency converter can be input to the non-inverting input terminal of the third differential operational amplifier circuit; the output terminal of the third differential operational amplifier circuit can output the second-level scaled value of one phase current of the frequency converter. In the solution of the present invention, the second-level scaling of the first sampled value of one phase current of the frequency converter by the second differential operational amplifier circuit can ensure the sampling accuracy of the second-level scaling processing.

[0060] And / or, the filtering module includes: an RC filter circuit, such as resistor R24 ​​and capacitor C13; the second-order scaled value of one phase current of the frequency converter, after passing through the RC filter circuit, can obtain the second sampled value of one phase current of the frequency converter. In the solution of the present invention, filtering out the second-order scaled value of one phase current of the frequency converter through the RC filter circuit can improve the accuracy of the obtained second sampled value of one phase current of the frequency converter, which is beneficial to improving the accuracy of overcurrent protection.

[0061] Figure 5 This is a schematic diagram of the current sampling circuit of a frequency converter. Figure 5As shown, the current sampling circuit of the frequency converter includes: resistors R12, R13, R14, R15, R16, R17, R18, R19, R20, R21, R22, R23, R24, R31, R32, and R33; capacitors C7, C8, C9, C10, C11, C12, and C13; operational amplifiers U4, U5, and U6; and a TL431 chip U7. Figure 5 As shown, the current sampling circuit of the frequency converter proposed in this invention is a differential operational amplifier circuit composed of operational amplifiers. It can perform a series of voltage scaling on the input sampling voltage and adds a bias circuit to perform negative voltage boosting, so as to meet the input range requirement of 0V to 3.3V of the main control DSP sampling port.

[0062] exist Figure 5 In the example shown, resistors R12, R13, R14, and R15, capacitors C7 and C8, and operational amplifier U4 constitute the first scaling circuit. Taking the sampling of the U-phase current of the frequency converter as an example, the signal U_IN is connected to the non-inverting input of operational amplifier U4 after resistor R12; resistor R14 and capacitor C7 are connected in parallel between the non-inverting input of operational amplifier U4 and ground. The inverting input of operational amplifier U4 is grounded, and resistor R15 and capacitor C8 are connected in parallel between the inverting input and the output of operational amplifier U4.

[0063] exist Figure 5 In the example shown, resistors R16, R17, R18, and R19, capacitors C9 and C10, and operational amplifier U5 constitute a bias circuit. The function of the bias circuit is to superimpose a bias voltage onto the input voltage and use it as the output signal. The two-stage scaling circuit only scales the input voltage. Figure 5 U4, U5, U6, Figure 6 U8 and U9 are both operational amplifiers. Figure 6U10 and U11 are comparators. In the bias circuit, the output of operational amplifier U4 is connected to the non-inverting input of operational amplifier U5 via resistor R17. The inverting input of operational amplifier U5 is grounded via resistor R16. Resistor R18 and capacitor C9 are connected in parallel between the inverting input and output of operational amplifier U5, and the output of operational amplifier U5 outputs the signal U_OUT. Resistor R19 and capacitor C10 are connected in parallel between the output of the bias regulator circuit and the non-inverting input of operational amplifier U5. The output of the bias regulator circuit outputs the signal U_BIAS. In the bias regulator circuit, the power supply VDD is grounded via resistors R33, R32, and R31. The common terminal of resistors R33 and R32 is connected to the cathode of TL431 chip U7, and the common terminal of resistors R33 and R32 is also connected to the output Uo of the reference regulator circuit. The common terminal Ur of resistors R32 and R31 is connected to the reference terminal (REF) of TL431 chip U7; the anode of TL431 chip U7 is grounded.

[0064] The bias voltage U_BIAS in the relevant solutions is obtained through resistor voltage divider or bias chip. The voltage value obtained by resistor voltage divider will have a large error during operation due to power supply voltage instability caused by environmental interference or load fluctuations. Furthermore, the bias chip has a single output value, and the same chip cannot be adapted to multiple inverter models. Figure 5 In the example shown, the bias voltage U_BIAS of the current sampling circuit is obtained from the reference voltage regulator circuit composed of TL431. The output voltage amplitude can be changed by resistor matching, and the output voltage is stable.

[0065] exist Figure 5 In the example shown, resistors R20, R21, R22, and R23, capacitors C11 and C12, and operational amplifier U6 constitute the second scaling circuit. In the second scaling circuit, the signal U_OUT is input to the non-inverting input of operational amplifier U6 after passing through resistor R21; resistor R23 and capacitor C12 are connected in parallel between the non-inverting input of operational amplifier U6 and ground; the inverting input of operational amplifier U6 is grounded after passing through resistor R20, and resistor R22 and capacitor C11 are connected in parallel between the inverting input of operational amplifier U6 and the output of operational amplifier U6.

[0066] exist Figure 5In the example shown, resistor R24 ​​and capacitor C13 constitute a filter circuit. Resistors R31, R32, and R33, along with the TL431 chip U7, constitute a bias voltage regulator circuit. In the filter circuit, the output of operational amplifier U6 is grounded via resistor R24 ​​and capacitor C13. The common terminal of resistor R24 ​​and capacitor C13 serves as the output of the filter circuit, enabling the output signal U_OUT.DSP.

[0067] Inverter current sampling circuit, such as Figure 5 As shown, the first-stage scaling circuit is a differential operational amplifier circuit composed of operational amplifier chip U4, resistors R12, R13, R14, and R15, and capacitors C7 and C8. The resistance values ​​R12 = R13, R14 = R15, and capacitors C7 and C8 are filter capacitors. The scaling ratio is R14 / R12.

[0068] The bias circuit consists of a reference voltage regulator circuit and a proportional operational amplifier circuit, which can boost the sampled negative voltage. The analysis of the reference voltage regulator circuit is as described above. The output voltage U_BIAS can be made to meet the bias voltage U_BIAS requirement by adjusting the selection of resistors R31, R32, and R33.

[0069]

[0070] The output voltage U_OUT of the bias circuit is:

[0071]

[0072] Because the sampling port input range of the main control DSP is relatively small, a second scaling circuit is designed to further scale U_OUT. The second-stage scaling circuit is a differential operational amplifier circuit composed of operational amplifier chip U6, resistors R20, R21, R22, and R23, and capacitors C11 and C12. Among them, the resistance values ​​R20 = R21, the resistance value R22 = R23, and capacitors C11 and C12 are filter capacitors. The scaling ratio is R22 / R20.

[0073] Therefore, the relationship between the sampled value U_OUT.DSP input to the main control DSP and the input voltage U_IN is as follows:

[0074]

[0075] The voltage output by the current sensor does not meet the sampling range of the main control chip and cannot be directly input into it. It needs to be scaled and biased by the inverter's current sampling circuit. Therefore, the technical effect of the inverter's current sampling circuit is to process the voltage output by the current sensor. The differential operational amplifier circuit has high sampling accuracy, and the bias voltage output by the reference voltage regulator circuit is stable, ensuring that the value finally sampled by the main control chip has a small error compared with the actual value.

[0076] In the present invention, a two-stage differential amplifier circuit composed of operational amplifier chips is used as the current sampling circuit. A stable bias voltage is obtained by using a reference voltage regulator circuit and input into the sampling circuit. This can boost the negative voltage at the sampling front end to meet the input range of the DSP's ADC sampling port. Furthermore, the combination of the two-stage differential amplifier circuit and the reference voltage regulator circuit can reduce the impact of noise on the sampling results and improve the sampling accuracy and anti-interference capability.

[0077] In some embodiments, the overcurrent protection unit includes: a first reference module, a second reference module, a comparison module, and a clamping module, wherein the first reference module and the second reference module are as follows: Figure 2 The reference circuit shown has a comparison module as follows: Figure 2 The comparator circuit shown, the clamping module is as follows Figure 2 The clamping circuit shown.

[0078] The overcurrent protection unit sets the overcurrent protection threshold range of the frequency converter, and after comparing and clamping the first sampled value of the current of one phase of the frequency converter with the overcurrent protection threshold range, obtains the overcurrent protection signal of the frequency converter, including:

[0079] The first reference module, such as Figure 6 The first reference value circuit shown is used to obtain the lower limit of the overcurrent protection threshold range of the frequency converter based on a preset first bias voltage and after a first voltage following process; the preset first bias voltage is obtained by performing a first voltage division and a first voltage regulation process based on a preset first power supply voltage.

[0080] The second reference module, such as Figure 6 The second reference value circuit shown is used to obtain the upper limit of the overcurrent protection threshold range of the frequency converter based on a preset second bias voltage and after second voltage following processing; the preset second bias voltage is obtained by performing a second voltage division and a second voltage regulation process based on a preset first power supply voltage; the preset first power supply voltage is such as VDD.

[0081] The comparison module is used to compare the first sampled value of the one-phase current of the frequency converter with the overcurrent protection threshold range of the frequency converter to obtain a comparison signal of the one-phase current of the frequency converter; the overcurrent protection threshold range of the frequency converter includes: the lower limit of the overcurrent protection threshold range of the frequency converter and the upper limit of the overcurrent protection threshold range of the frequency converter.

[0082] The clamping module is used to clamp based on a comparison signal of one phase current of the inverter to obtain the overcurrent protection signal of the inverter.

[0083] like Figure 2 As shown, the overcurrent protection circuit includes: a reference circuit, a comparator circuit, and a clamping circuit. The bias circuit outputs a signal U_OUT to the comparator circuit. The reference circuit provides a reference signal to the comparator circuit, the comparator circuit outputs the comparison result to the clamping circuit, and the clamping circuit outputs a signal U_TZ.DSP to the controller DSP.

[0084] exist Figure 2 In the example shown, using a reference voltage regulator circuit to obtain the protection value ensures that the frequency converter can protect itself in a timely manner when abnormal conditions occur, reduces the possibility of false protection, and improves the safety and reliability of the frequency converter.

[0085] In some embodiments, where a bias voltage regulator unit is further provided for each phase current of the frequency converter, the bias voltage regulator unit includes a second bias voltage regulator circuit, and the first reference module includes: a second reference voltage regulator circuit and a first voltage follower, the first reference voltage regulator circuit being as follows: Figure 6 The resistors R41, R42, and R43 shown, along with the TL431 chip U14, form the first voltage follower. Figure 6 The comparator U8 shown; the preset first bias voltage provided by the second reference voltage regulator circuit is input to the non-inverting input of the first voltage follower; the output of the first voltage follower can output the lower limit of the overcurrent protection threshold range of the frequency converter. In the solution of the present invention, using the first reference voltage regulator circuit and the first voltage follower to obtain the lower limit of the overcurrent protection threshold range of the frequency converter can ensure that the frequency converter can protect in a timely manner when abnormal conditions occur, reduce the possibility of false protection, and improve the safety and reliability of the frequency converter.

[0086] And / or, if a bias voltage regulator unit is further provided for each phase current of the inverter, the bias voltage regulator unit includes a third bias voltage regulator circuit, and the second reference module includes: a third reference voltage regulator circuit and a second voltage follower, the second reference voltage regulator circuit being as follows: Figure 6 The resistors R51, R52, and R53 shown, along with the TL431 chip U15, form the first voltage follower. Figure 6 The comparator U9 shown; the preset second bias voltage provided by the second reference voltage regulator circuit is input to the non-inverting input of the second voltage follower; the output of the second voltage follower can output the upper limit of the overcurrent protection threshold range of the frequency converter. In the solution of the present invention, using the second reference voltage regulator circuit and the second voltage follower to obtain the upper limit of the overcurrent protection threshold range of the frequency converter can ensure that the frequency converter can protect in a timely manner when abnormal conditions occur, reduce the possibility of false protection, and improve the safety and reliability of the frequency converter.

[0087] And / or, the comparison module includes: a first comparator and a second comparator, the first comparator being as follows: Figure 6 The comparator U10 shown, the second comparator is as follows Figure 6 The comparator U11 shown includes: the lower limit of the overcurrent protection threshold range of the frequency converter, which can be input to the inverting input of the first comparator; the first sampled value of one phase current of the frequency converter, which can be input to the non-inverting input of the first comparator; the output of the first comparator, which can output a comparison signal of one phase current of the frequency converter; the upper limit of the overcurrent protection threshold range of the frequency converter, which can be input to the non-inverting input of the second comparator; the first sampled value of one phase current of the frequency converter, which can be input to the inverting input of the second comparator; and the output of the second comparator, which can output a comparison signal of one phase current of the frequency converter. In the solution of the present invention, by using the first comparator and the second comparator to compare with the upper limit and the lower limit of the overcurrent protection threshold range of the frequency converter, respectively, it is possible to ensure that the frequency converter provides timely protection when abnormal conditions occur, reduce the possibility of false protection, and improve the safety and reliability of the frequency converter.

[0088] And / or, the clamping module includes: a fourth resistor module, a fifth resistor module, an output capacitor module, and a diode clamping circuit, wherein the fourth resistor module is as follows: Figure 6 The resistor R29 shown is the fifth resistor module. Figure 6 The resistor R30 shown, the output capacitor module such as capacitor C17, and the diode clamping circuit are shown below. Figure 6 The clamping circuit formed by diodes D1 and D2 is shown. A preset second power supply voltage is grounded after passing through the fourth resistor module, the fifth resistor module, and the output capacitor module. The output terminal of the comparison signal for one phase current of the inverter is connected to the common terminal of the fourth and fifth resistor modules. The common terminal of the fifth resistor module and the output capacitor module is connected to the clamping terminal of the diode clamping circuit and can output the overcurrent protection signal of the inverter. The preset second power supply voltage is as follows... Figure 6 The +3.3V shown indicates that the clamping terminal of the diode clamping circuit is as follows: Figure 6 The common terminal of diodes D1 and D2 is shown. In the solution of this invention, voltage division is achieved through the fourth and fifth resistor modules, clamping is achieved through the diode clamping circuit, and voltage stabilization and filtering are achieved through the output capacitor module, making the output overcurrent protection signal of the frequency converter accurate and stable, which helps to improve the reliability of overcurrent protection.

[0089] Figure 6 This is a schematic diagram of the overcurrent protection circuit for a frequency converter. The overcurrent protection circuit for the frequency converter proposed in this invention is as follows: Figure 6 As shown. Figure 6 As shown, the overcurrent protection circuit of the frequency converter includes: resistors R29, R30, R41, R42, R43, R51, R52, and R53; capacitor C17; diodes D1 and D2; comparators U8, U9, U10, and U11; and TL431 chips U14 and U15. Figure 6 In the example shown, the inverter's overcurrent protection circuit determines the protection voltage range using a reference voltage regulator circuit composed of the power supply voltage and a TL431 to obtain the protection value range. The real-time current sample value U_OUT is then compared with the protection value range using a comparator. If the real-time current sample value U_OUT is within the protection value range, the comparator outputs a low-level TZ signal, which, after passing through a clamping circuit, is input to the main control DSP to trigger the TZ overcurrent protection.

[0090] exist Figure 6 In the example shown, resistors R41, R42, R43, TL431 chip U14, and comparator U8 constitute the circuit for determining the negative overcurrent protection reference value, denoted as the first reference value circuit; resistors R51, R52, R53, TL431 chip U15, and comparator U9 constitute the circuit for determining the positive overcurrent protection reference value, denoted as the second reference value circuit; the first and second reference value circuits constitute the reference circuit. The power supply voltage VDD is grounded after passing through resistors R43, R42, and R41; the common terminal of resistors R43 and R42 is connected to the non-inverting input of comparator U8; the common terminal of resistors R43 and R42 is connected to the cathode of TL431 chip U14, and the common terminal of resistors R42 and R41 is connected to the reference terminal (REF) of TL431 chip U14; the anode of TL431 chip U14 is grounded. The inverting input of comparator U8 is connected to its output. The output of comparator U8 provides a voltage Umin, which serves as the lower limit of the protection range. The power supply voltage VDD is grounded via resistors R53, R52, and R51. The common terminal of resistors R53 and R52 is connected to the non-inverting input of comparator U9. The common terminal of resistors R53 and R52 is connected to the cathode of TL431 chip U15, and the common terminal of resistors R52 and R51 is connected to the reference terminal (REF) of TL431 chip U15. The anode of TL431 chip U15 is grounded. The inverting input of comparator U9 is connected to its output. The output of comparator U9 provides a voltage Umax, which serves as the upper limit of the protection range.

[0091] exist Figure 6In the example shown, comparators U10 and U11 constitute a comparator circuit. The output voltage Umin of comparator U8 is fed to the inverting input of comparator U10. The output voltage Umax of comparator U9 is fed to the non-inverting input of comparator U11. The real-time current sample value U_OUT is input to the non-inverting input of comparator U10 and the inverting input of comparator U11, respectively. The outputs of comparators U10 and U11 output signal TZ.

[0092] exist Figure 6 In the example shown, resistors R29 and R30, capacitor C17, and diodes D1 and D2 form a clamping circuit. Signal TZ is grounded after passing through the first and second terminals of resistor R30 and capacitor C17. The +3.3V power supply is connected to the first terminal of resistor R30 after passing through resistor R19. The second terminal of resistor R30 is connected to the cathode of diode D1 and the anode of diode D2, respectively. The anode of diode D1 is grounded, and the cathode of diode D2 is connected to the +3.3V power supply. The common terminal of resistor R30, capacitor C17, and diodes D1 and D2 outputs the signal U_TZ.DSP.

[0093] In the relevant scheme, the overcurrent protection reference value of the protection circuit is obtained through resistor voltage division. However, the protection value obtained by resistor voltage division will have a large error during operation due to environmental interference or load fluctuations causing power supply voltage instability. Figure 6 In the protection circuit shown, the positive overcurrent protection reference value and the negative overcurrent protection reference value are both obtained from the reference voltage regulator circuit composed of TL431. The output voltage amplitude can be changed by resistor matching, and the output voltage is stable.

[0094] In this invention, a reference voltage regulator circuit composed of the power supply voltage and TL431 provides stable positive and negative overcurrent protection reference values, which are then input to a comparator for comparison with the real-time operating value. If the operating value is within the protection range, the TZ protection shutdown is triggered. This protection circuit provides stable protection values, preventing the inverter from erroneously shutting down.

[0095] The overcurrent protection circuit of the frequency converter, such as Figure 6 As shown, the overcurrent protection circuit has two reference protection values: the maximum protection value Umax and the minimum protection value Umin. The maximum protection value Umax is determined by a circuit consisting of operational amplifier chip U9, TL431 chip U15, and resistors R51, R52, and R53. The minimum protection value Umin is determined by a circuit consisting of operational amplifier chip U8, TL431 chip U14, and resistors R41, R42, and R43. Therefore, the inverter's protection value range is:

[0096]

[0097] The real-time operating current sample value U_OUT is compared with the set protection values ​​Umin and Umax by comparators U10 and U11. When Umin < U_OUT < Umax, the comparator outputs a high-level TZ overcurrent protection signal, and the inverter operates normally. When U_OUT < Umin or U_OUT > Umax, the comparator outputs a low-level TZ overcurrent protection signal. After passing through the clamping circuit and the filtering circuit, the TZ overcurrent protection signal is transmitted to the DSP chip to trigger the TZ overcurrent protection.

[0098] The inverter overcurrent protection circuit ensures the safe operation of the inverter. When an abnormal phenomenon occurs during operation that causes an increase in current, the overcurrent protection circuit can ensure that the inverter stops in time to prevent damage to components due to overcurrent. The overcurrent protection circuit of this invention provides stable positive and negative overcurrent protection reference values ​​to prevent the inverter from falsely shutting down.

[0099] In this invention, a two-stage differential amplifier circuit composed of operational amplifier chips is used as the current sampling circuit, and a reference voltage regulator circuit is used to provide a stable bias voltage for the current sampling circuit. This allows for applicability to different inverter models simply by adjusting the resistor, solving the problems of poor applicability and anti-interference capability of the current sampling circuit in related solutions. Furthermore, the protection circuit uses a reference voltage regulator circuit to obtain a reference protection value, solving the problem of inverter false protection shutdown caused by unstable power supply voltage in related solutions.

[0100] It should be noted that the relevant parameters in the solution of the present invention are not limited to the parameters designed in the example, and the parameters can be adjusted and designed according to the actual application.

[0101] This invention proposes a current sampling and protection circuit suitable for frequency converters, which improves current sampling accuracy and anti-interference capability, resulting in stronger circuit stability. In current sampling, a differential amplifier circuit composed of operational amplifier chips is used as the current sampling circuit. A bias voltage is obtained through a reference voltage regulator circuit and input to the sampling circuit, which can boost the negative voltage at the sampling front end to meet the input range of the DSP's ADC sampling port. In overcurrent protection, a reference voltage regulator circuit composed of the power supply voltage and TL431 is used to obtain the protection value, which is input to a comparator and compared with the real-time operating value. If the operating value is within the protection value range, protection shutdown is triggered. Two stages of differential amplifier circuits composed of operational amplifier chips are used as the current sampling circuit. A stable bias voltage is obtained through a reference voltage regulator circuit composed of the power supply voltage and TL431 and input to the sampling circuit, which can boost the negative voltage at the sampling front end to meet the input range of the DSP's ADC sampling port. Furthermore, by combining a two-stage differential amplifier circuit and a reference voltage regulator circuit, the impact of noise on the sampling results can be reduced, thereby improving the sampling accuracy and anti-interference capability.

[0102] The current sampling circuit in related solutions uses a bias chip for its bias circuit. The drawback is that the output voltage of the bias chip is not adjustable, resulting in low circuit flexibility and difficulty in adapting to different models. The solution of this invention optimizes this by using a reference voltage regulator circuit for the bias circuit. This not only ensures a stable output bias voltage but also allows the bias voltage to be adjusted via a resistor. For current sampling of different models, the circuit structure remains unchanged; only the resistor value needs to be changed for matching.

[0103] Furthermore, the overcurrent protection circuit in related solutions uses a resistor voltage divider method. The power supply voltage is divided to obtain positive and negative protection reference values. However, during operation, especially under heavy load, the power supply voltage fluctuates significantly, leading to inaccurate positive and negative protection reference values. This can cause the inverter to shut down abnormally due to overcurrent (even when no overcurrent actually occurs). In contrast, the solution of this invention uses a reference voltage regulator circuit to obtain the positive and negative protection reference values. Even if power supply voltage fluctuations occur during operation, the voltage regulator circuit can dynamically adjust and maintain the output voltage, i.e., the positive and negative overcurrent reference values, constant, thus preventing abnormal overcurrent shutdown.

[0104] The technical solution of this invention provides overcurrent protection for the input and / or output current of the frequency converter. For each phase current, a current sampling circuit and an overcurrent protection circuit are configured. The current sampling circuit includes, in sequence, a first-stage scaling circuit, a bias circuit, a second-stage scaling circuit, and a filter circuit. The bias circuit operates based on the bias voltage provided by the bias regulator circuit and outputs a sampled value for one current phase (e.g., real-time current sampled value U_OUT). The filter circuit outputs a further processed value of the sampled current phase (e.g., signal U_OUT.DSP). The overcurrent protection circuit includes, in sequence, a reference circuit... The system includes a current sampling circuit, a comparator circuit, and a clamping circuit. The comparator circuit compares the positive and negative reference values ​​provided by the reference circuit with the sampled value of one current channel (such as the real-time current sample value U_OUT). The clamping circuit outputs an overcurrent protection signal (such as the signal U_TZ.DSP). The controller performs overcurrent protection processing based on the output value of the filter circuit and the overcurrent protection signal output by the clamping circuit. Thus, by using a two-stage scaling circuit in the current sampling circuit and obtaining the bias voltage through the reference voltage regulator circuit, and using the reference voltage regulator circuit in the overcurrent protection circuit to obtain the protection value, timely protection can be provided when the frequency converter malfunctions, improving the safety and reliability of the frequency converter.

[0105] According to an embodiment of the present invention, a frequency converter corresponding to a protection device for a frequency converter is also provided. This frequency converter may include the protection device for the frequency converter described above.

[0106] Since the processing and functions implemented by the frequency converter in this embodiment are basically the same as those in the embodiments, principles and examples of the device, any details not covered in this embodiment can be found in the relevant descriptions in the foregoing embodiments, and will not be repeated here.

[0107] According to an embodiment of the present invention, an air conditioner corresponding to a protection device for a frequency converter is also provided. The frequency converter may include: the protection device for the frequency converter described above, or the frequency converter described above.

[0108] Since the processing and functions implemented by the air conditioner in this embodiment are basically corresponding to the embodiments, principles and examples of the device, any details not covered in the description of this embodiment can be found in the relevant descriptions in the foregoing embodiments, and will not be repeated here.

[0109] According to embodiments of the present invention, a protection method for a frequency converter is also provided, such as... Figure 7 The diagram shows a flowchart of an embodiment of the method of the present invention. The protection method for the frequency converter may include steps S110 to S130.

[0110] In step S110, the current of one phase of the inverter is sampled by the current sampling unit, and after first-level scaling, biasing, second-level scaling and filtering, the second sampled value of the current of one phase of the inverter is obtained; wherein, after first-level scaling and biasing, the first sampled value of the current of one phase of the inverter is obtained.

[0111] In step S120, the overcurrent protection threshold range of the frequency converter is set through the one-channel overcurrent protection unit, and the overcurrent protection signal of the frequency converter is obtained after comparing and clamping the first sampled value of the one-phase current of the frequency converter with the overcurrent protection threshold range of the frequency converter.

[0112] In step S130, overcurrent protection processing is performed based on the second sampled value of one phase current of the frequency converter and the overcurrent protection signal of the frequency converter to realize overcurrent protection of the frequency converter.

[0113] The present invention employs a two-stage differential amplifier circuit composed of operational amplifier chips as a current sampling circuit, and obtains a stable bias voltage by using a reference voltage regulator circuit and inputs it into the current sampling circuit; in addition, a reference voltage regulator circuit is used in the protection circuit to obtain a reference protection value, which can ensure that the frequency converter can be protected in time when abnormal conditions occur, reduce the possibility of false protection, and improve the safety and reliability of the frequency converter.

[0114] Since the processing and functions implemented by the method in this embodiment are basically the same as the embodiments, principles and examples of the aforementioned frequency converters, any details not covered in this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0115] In summary, it is readily understood by those skilled in the art that, without conflict, the aforementioned advantageous methods can be freely combined and superimposed.

[0116] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A protection device for a frequency converter, characterized in that, include: The control unit, and the inverter are equipped with a current sampling unit and an overcurrent protection unit for each phase current; wherein, The current sampling unit is used to sample one phase current of the inverter, and after performing first-level scaling, biasing, second-level scaling and filtering, obtains the second sample value of one phase current of the inverter; wherein, after first-level scaling and biasing, the first sample value of one phase current of the inverter is obtained. The overcurrent protection unit is used to set the overcurrent protection threshold range of the frequency converter, and after comparing and clamping the first sampled value of the phase current of the frequency converter with the overcurrent protection threshold range of the frequency converter, the overcurrent protection signal of the frequency converter is obtained. The control unit is used to perform overcurrent protection processing based on the second sampled value of one phase current of the frequency converter and the overcurrent protection signal of the frequency converter, so as to realize overcurrent protection of the frequency converter.

2. The protection device for the frequency converter according to claim 1, characterized in that, Also includes: A bias voltage regulator unit is also provided for each phase current of the frequency converter; wherein, The bias voltage regulator unit is used to perform voltage division and regulation based on a preset first power supply voltage to obtain a preset bias voltage.

3. The protection device for the frequency converter according to claim 2, characterized in that, The bias voltage regulator unit includes: a first resistor module, a second resistor module, a third resistor module, and a TL431 chip; wherein, A preset first power supply voltage is grounded after passing through the third resistor module, the second resistor module, and the first resistor module; the common terminal of the second resistor module and the first resistor module is connected to the reference terminal of the TL431 chip; the cathode of the TL431 chip is connected to the common terminal of the third resistor module and the second resistor module, and is used to output a preset bias voltage; the anode of the TL431 chip is grounded.

4. The protection device for the frequency converter according to any one of claims 1 to 3, characterized in that, The current sampling unit includes: a sampling module, a first scaling module, a bias module, a second scaling module, and a filtering module; wherein, The current sampling unit samples one phase current of the frequency converter, performs first-level scaling, biasing, second-level scaling, and filtering processing to obtain a second sampled value of the one phase current of the frequency converter; including: The sampling module is used to sample one phase current of the frequency converter; The first scaling module is used to perform a first-level scaling process on the sampled one-phase current of the inverter to obtain a first-level scaled value of the one-phase current of the inverter. The bias module is used to bias the first-level scaling value of one phase current of the frequency converter based on a preset bias voltage to obtain the first sample value of one phase current of the frequency converter; the preset bias voltage is obtained by voltage division and voltage regulation based on a preset first power supply voltage. The second scaling module is used to perform a second-level scaling process on the first sampled value of the one-phase current of the frequency converter to obtain the second-level scaled value of the one-phase current of the frequency converter. The filtering module is used to filter the secondary scaling value of one phase current of the frequency converter to obtain the second sampled value of one phase current of the frequency converter.

5. The protection device for the frequency converter according to claim 4, characterized in that, in, The first scaling module includes: a first differential operational amplifier circuit; a sampled phase current of the inverter can be input to the non-inverting input terminal of the first differential operational amplifier circuit; and the output terminal of the first differential operational amplifier circuit can output a first-level scaling value of the phase current of the inverter. And / or, In the case where a bias voltage regulator unit is also provided for each phase current of the inverter, the bias voltage regulator unit includes a first bias voltage regulator circuit. The bias module includes: a second differential operational amplifier circuit and the first bias voltage regulator circuit; a first-level scaling value of one phase current of the inverter and a preset bias voltage provided by the first bias voltage regulator circuit can be superimposed and input to the non-inverting input terminal of the second differential operational amplifier circuit; the output terminal of the second differential operational amplifier circuit can output the first sampled value of one phase current of the inverter. And / or, The second scaling module includes: a third differential operational amplifier circuit; a first sampled value of the phase current of the inverter, which can be input to the non-inverting input terminal of the third differential operational amplifier circuit; and an output terminal of the third differential operational amplifier circuit, which can output a second-level scaling value of the phase current of the inverter. And / or, The filtering module includes: an RC filter circuit; the second-level scaling value of one phase current of the frequency converter, after passing through the RC filter circuit, can obtain the second sample value of one phase current of the frequency converter.

6. The protection device for the frequency converter according to any one of claims 1 to 5, characterized in that, The overcurrent protection unit includes: a first reference module, a second reference module, a comparison module, and a clamping module; The overcurrent protection unit sets the overcurrent protection threshold range of the frequency converter, and after comparing and clamping the first sampled value of the current of one phase of the frequency converter with the overcurrent protection threshold range, obtains the overcurrent protection signal of the frequency converter, including: The first reference module is used to obtain the lower limit of the overcurrent protection threshold range of the frequency converter based on a preset first bias voltage and after a first voltage following process; the preset first bias voltage is obtained by performing a first voltage division and a first voltage regulation process based on a preset first power supply voltage; The second reference module is used to obtain the upper limit of the overcurrent protection threshold range of the frequency converter based on a preset second bias voltage and after second voltage following processing; the preset second bias voltage is obtained by performing a second voltage division and a second voltage regulation process based on a preset first power supply voltage; The comparison module is used to compare the first sampled value of the current of one phase of the inverter with the overcurrent protection threshold range of the inverter to obtain a comparison signal of the current of one phase of the inverter; the overcurrent protection threshold range of the inverter includes: the lower limit of the overcurrent protection threshold range of the inverter and the upper limit of the overcurrent protection threshold range of the inverter. The clamping module is used to clamp based on a comparison signal of one phase current of the inverter to obtain the overcurrent protection signal of the inverter.

7. The protection device for the frequency converter according to claim 6, characterized in that, in, In the case where a bias voltage regulator unit is also provided for each phase current of the inverter, the bias voltage regulator unit includes a second bias voltage regulator circuit, and the first reference module includes: a second reference voltage regulator circuit and a first voltage follower; a preset first bias voltage provided by the second reference voltage regulator circuit is input to the non-inverting input terminal of the first voltage follower; the output terminal of the first voltage follower can output the lower limit of the overcurrent protection threshold range of the inverter; And / or, In the case where a bias voltage regulator unit is also provided for each phase current of the inverter, the bias voltage regulator unit includes a third bias voltage regulator circuit and a second reference module, including: a third reference voltage regulator circuit and a second voltage follower; a preset second bias voltage provided by the second reference voltage regulator circuit is input to the non-inverting input terminal of the second voltage follower; the output terminal of the second voltage follower can output the upper limit of the overcurrent protection threshold range of the inverter; And / or, The comparison module includes: a first comparator and a second comparator; the lower limit of the overcurrent protection threshold range of the frequency converter can be input to the inverting input terminal of the first comparator; a first sampled value of the one-phase current of the frequency converter can be input to the non-inverting input terminal of the first comparator; the output terminal of the first comparator can output a comparison signal of the one-phase current of the frequency converter; the upper limit of the overcurrent protection threshold range of the frequency converter can be input to the non-inverting input terminal of the second comparator; the first sampled value of the one-phase current of the frequency converter can be input to the inverting input terminal of the second comparator; the output terminal of the second comparator can output a comparison signal of the one-phase current of the frequency converter. And / or, The clamping module includes: a fourth resistor module, a fifth resistor module, an output capacitor module, and a diode clamping circuit; a preset second power supply voltage is grounded after passing through the fourth resistor module, the fifth resistor module, and the output capacitor module; the output terminal of the comparison signal of one phase current of the frequency converter is connected to the common terminal of the fourth resistor module and the fifth resistor module; the common terminal of the fifth resistor module and the output capacitor module is connected to the clamping terminal of the diode clamping circuit and can output the overcurrent protection signal of the frequency converter.

8. A frequency converter, characterized in that, include: The protection device for the frequency converter as described in any one of claims 1 to 7.

9. An air conditioner, characterized in that, include: The protection device for the frequency converter as described in any one of claims 1 to 7, or the frequency converter as described in claim 8.

10. A protection method for a frequency converter as described in claim 8, characterized in that, include: The current sampling unit samples one phase current of the inverter, performs first-level scaling, biasing, second-level scaling and filtering to obtain the second sample value of one phase current of the inverter; wherein, after first-level scaling and biasing, the first sample value of one phase current of the inverter is obtained. The overcurrent protection unit sets the overcurrent protection threshold range of the frequency converter, and after comparing and clamping the first sampled value of the current of one phase of the frequency converter with the overcurrent protection threshold range of the frequency converter, the overcurrent protection signal of the frequency converter is obtained. Overcurrent protection is achieved by performing overcurrent protection processing based on the second sampled value of one phase current of the frequency converter and the overcurrent protection signal of the frequency converter.

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