A frequency converter DC bus overvoltage regulating circuit

Abstract

The utility model discloses a kind of frequency converter DC bus overvoltage regulating circuit, including voltage detection circuit, overvoltage point drive circuit and overvoltage regulating circuit, the overvoltage regulating circuit includes energy consumption unit and control switch, the energy consumption unit is accessed DC bus by control switch, the input end of voltage detection circuit is connected with DC bus, the output end of voltage detection circuit is connected with the input end of overvoltage point drive circuit, the output end of overvoltage point drive circuit is connected with control switch. The utility model aims at monitoring DC bus voltage in real time and automatically adjusting overvoltage range when overvoltage, to guarantee the safety and stable operation of frequency converter.

Description

Technical Field

[0001] This utility model relates to the field of frequency converter technology, specifically to a DC bus overvoltage regulation circuit for frequency converters. Background Technology

[0002] Frequency converters play an irreplaceable role in many key industries due to their speed regulation, energy saving, and automatic control functions. They are used in fields such as industrial transmission, metallurgical uncoilers, fans and pumps, building equipment and elevators, air conditioning and refrigeration, energy, traffic signals, and photovoltaic power generation.

[0003] In actual drive and mechanical transmission, there are not only electric operation modes but also generator operation modes. For example, the rapid shutdown and generator generation of a crane, the energy feedback of an external mechanical drive motor, and the increase in the input voltage of the frequency converter will all lead to an increase in the DC bus voltage of the frequency converter. When the DC bus voltage exceeds the rated voltage of the DC bus capacitor or exceeds the withstand voltage of the device, it will lead to serious accidents such as overvoltage damage or explosion of the frequency converter. Utility Model Content

[0004] The purpose of this utility model is to overcome at least one defect in the prior art and provide a DC bus overvoltage regulation circuit for a frequency converter, which aims to monitor the DC bus voltage in real time and automatically adjust the overvoltage range when overvoltage occurs, so as to ensure the safe and stable operation of the frequency converter.

[0005] The technical solution of this utility model is implemented as follows: This utility model discloses an overvoltage regulation circuit for a DC bus of a frequency converter, including a voltage detection circuit, an overvoltage point drive circuit, and an overvoltage regulation circuit. The overvoltage regulation circuit includes an energy consumption unit and a control switch. The energy consumption unit is connected to the DC bus through the control switch. The input terminal of the voltage detection circuit is connected to the DC bus, the output terminal of the voltage detection circuit is connected to the input terminal of the overvoltage point drive circuit, and the output terminal of the overvoltage point drive circuit is connected to the control switch.

[0006] Furthermore, the voltage detection circuit includes a voltage sampling circuit, an isolation amplifier circuit, and an operational amplifier circuit. The input terminal of the voltage sampling circuit is connected to the DC bus, the output terminal of the voltage sampling circuit is connected to the input terminal of the isolation amplifier circuit, the output terminal of the isolation amplifier circuit is connected to the input terminal of the operational amplifier circuit, and the output terminal of the operational amplifier circuit is connected to the overvoltage point driving circuit.

[0007] Furthermore, the voltage sampling circuit employs a voltage divider resistor network.

[0008] Furthermore, the isolation amplifier circuit employs an isolation amplifier.

[0009] Furthermore, the operational amplifier circuit includes an operational amplifier U1. The non-inverting input terminal of the operational amplifier U1 is connected to one end of resistor R7 and one end of resistor R9, respectively. The other end of resistor R7 is connected to the positive output terminal of the isolation amplifier circuit, and the other end of resistor R9 is grounded. The inverting input terminal of the operational amplifier U1 is connected to one end of resistor R8 and one end of resistor R10, respectively. The other end of resistor R8 is connected to the negative output terminal of the isolation amplifier circuit, and the other end of resistor R10 is connected to the output terminal of the operational amplifier U1. The output terminal of the operational amplifier U1 is connected to one end of resistor R11, and the other end of resistor R11 is connected to one end of capacitor C1 and the output terminal of the voltage detection circuit, respectively. The other end of capacitor C1 is grounded.

[0010] Furthermore, there are two overvoltage point driving circuits, namely a first overvoltage point driving circuit and a second overvoltage point driving circuit. The overvoltage regulation circuit also includes a first switch and a second switch. The input terminal of the first overvoltage point driving circuit is connected to the output terminal of the voltage detection circuit, and the output terminal of the first overvoltage point driving circuit is connected to the first switch. The input terminal of the second overvoltage point driving circuit is connected to the output terminal of the voltage detection circuit, and the output terminal of the second overvoltage point driving circuit is connected to the first switch. The second overvoltage point of the second overvoltage point driving circuit is greater than the first overvoltage point of the first overvoltage point driving circuit. The first switch, the second switch, and the control switch are electromagnetic switches. The auxiliary contacts of the first switch and the second switch are connected in series in the power supply circuit of the control switch. The first normally open contact of the control switch is connected in parallel with the auxiliary contact of the second switch. The second normally open contact of the control switch is connected in series with the energy consumption unit, with one end connected to the positive terminal of the DC bus and the other end connected to the negative terminal of the DC bus.

[0011] Furthermore, the first overvoltage point driving circuit includes a first comparison circuit and a first driving circuit. The first input terminal of the first comparison circuit is connected to the output terminal of the voltage detection circuit, the second input terminal of the first comparison circuit is connected to the first overvoltage point, the output terminal of the first comparison circuit is connected to the input terminal of the first driving circuit, and the output terminal of the first driving circuit is connected to the first switch.

[0012] The second overvoltage point driving circuit includes a second comparison circuit and a second driving circuit. The second input terminal of the second comparison circuit is connected to the output terminal of the voltage detection circuit. The second input terminal of the second comparison circuit is connected to the second overvoltage point. The output terminal of the second comparison circuit is connected to the input terminal of the second driving circuit. The output terminal of the second driving circuit is connected to the second switch.

[0013] Furthermore, the first switch is a relay K1, the second switch is a relay K2, and the control switch is a contactor KM.

[0014] The energy-saving braking and self-locking control process of this utility model is as follows: Relays K1 / K2 close → the coil of control contactor KM is energized → contactor KM operates → the second auxiliary contact KM_ON2 of contactor KM connects the energy-saving resistor (BR). Self-locking function: The first auxiliary contact KM_ON1 of contactor KM short-circuits the normally open contact of relay K2, ensuring that KM remains energized until the voltage drops below OU_REF1.

[0015] The dynamic adjustment process of this utility model is as follows: During the voltage boosting process, when the voltage exceeds the first threshold voltage OU_REF1 (e.g., OU_REF1=7.03V, corresponding to a high voltage input of 703V), relay K1 is energized, and the auxiliary contact of relay K1 closes, preparing for DC bus voltage adjustment; when the voltage exceeds the second threshold voltage OU_REF2 (e.g., OU_REF2=7.61V, corresponding to a high voltage input of 761V), relay K2 is energized, and the auxiliary contact of relay K2 closes. At this time, the control function coil C is energized and engaged, and contactor KM operates.

[0016] The auxiliary contacts KM_ON1 and KM_ON2 of contactor KM change from normally open to normally closed. Then, auxiliary contact KM_ON1 of contactor KM short-circuits the auxiliary contact of relay K2, realizing the self-locking function and keeping contactor KM continuously energized. Auxiliary contact KM_ON2 of contactor KM connects the energy-consuming resistor BR, consuming the energy of DC bus "INVP+" and "INVN-".

[0017] The dynamic adjustment process involves an overvoltage trigger sequence during voltage reduction. As the energy-consumption braking occurs, the DC bus voltage gradually decreases. When it falls below the second threshold voltage OU_REF2 (e.g., OU_REF2 = 7.61V, corresponding to a high-voltage input of 761V), relay K2 is de-energized. Because the auxiliary contact KM_ON1 of the contactor short-circuits the auxiliary contact of relay K2, it self-locks, so the control function coil C remains energized and engaged, causing contactor KM to operate and continuously consume energy. When the DC bus voltage continues to decrease, falling below the first threshold voltage OU_REF1 (e.g., OU_REF1 = 7.03V, corresponding to a high-voltage input of 703V), the output relay K1 disconnects, the control function coil C is de-energized and disconnects, contactor KM is de-energized and disconnects, its auxiliary contact KM_ON2 also disconnects, the energy-consumption circuit resistor BR disconnects, and energy-consumption braking stops. When the DC bus voltage falls below the overvoltage point OU_REF1 (e.g., OU_REF1 = 7.03V, corresponding to a high-voltage input of 703V), the voltage returns to normal.

[0018] Furthermore, the first driving circuit is the same as the second driving circuit. The first driving circuit includes a driving output circuit, an isolation optocoupler unit, and a switch control circuit. The input terminal of the driving output circuit is connected to the output terminal of the first comparator circuit. The output terminal of the driving output circuit is connected to the input terminal of the isolation optocoupler unit. The output terminal of the isolation optocoupler unit is connected to the input terminal of the switch control circuit. The output terminal of the switch control circuit is connected to the first switch.

[0019] Furthermore, the drive output circuit includes a transistor Q1. The base of transistor Q1 is connected to one end of resistor R18. The other end of resistor R18 is connected to one end of resistor R17, one end of capacitor C2, and the output terminal of the first comparator circuit. The other end of resistor R17 is connected to the positive terminal of the first power supply. The other end of capacitor C2 is grounded. The base of transistor Q1 is connected to one end of resistor R19 and one end of capacitor C3. The other ends of resistor R19 and capacitor C3 are connected to the emitter of transistor Q1. The emitter of transistor Q1 is grounded. The collector of transistor Q1 is connected to the input terminal of the isolation optocoupler unit.

[0020] The switch control circuit includes a transistor Q2, the collector and emitter of which are connected in series in the power supply circuit of the first switch, and the base of the transistor Q2 is connected to the output terminal of the isolation optocoupler unit.

[0021] Furthermore, the isolation optocoupler unit includes an optocoupler U6. The first input terminal of the optocoupler U6 is connected to the positive terminal of the first power supply. The second input terminal of the optocoupler U6 is connected to one end of resistor R21 and one end of resistor R20, respectively. The other end of resistor R21 is connected to the positive terminal of the first power supply. The other end of resistor R20 is connected to the collector of transistor Q1. The first output terminal of the optocoupler U6 is connected to the positive terminal of the second power supply. The second output terminal of the optocoupler U6 is connected to one end of resistor R22. The other end of resistor R22 is connected to the base of transistor Q2.

[0022] Furthermore, the base of transistor Q2 is connected to one end of resistor R23 and one end of capacitor C4, the other end of resistor R23 and the other end of capacitor C4 are connected to the emitter of transistor Q2, the emitter of transistor Q2 is connected to the negative terminal of the second power supply, and the collector of transistor Q2 is connected to the first switch.

[0023] Furthermore, the first overvoltage point is provided by the first reference circuit, and the second overvoltage point is provided by the second reference circuit.

[0024] Furthermore, the reference circuit includes a reference voltage regulator. The cathode of the reference voltage regulator is connected to one end of resistor R13 and one end of resistor R14, respectively. The other end of resistor R13 is connected to the positive terminal of a third power supply. The other end of resistor R14 is connected to one end of resistor R15 and the reference terminal of the reference voltage regulator, respectively. The other end of resistor R15 and the anode of the reference voltage regulator are grounded.

[0025] Furthermore, the energy-consuming unit uses an energy-consuming resistor.

[0026] This invention has at least the following beneficial effects: The DC bus overvoltage regulation circuit of this inverter achieves automatic overvoltage range protection through dual threshold relay control. When the DC bus voltage rises due to energy feedback (such as crane braking, excessive incoming line voltage, or generator switching), when the voltage exceeds the first overvoltage point OU_REF1 (e.g., 703V), relay K1 is triggered; when the voltage continues to exceed the second overvoltage point OU_REF2 (e.g., 761V), relay K2 is triggered, causing contactor KM to engage; the auxiliary contact KM_ON1 of KM achieves self-locking, and the auxiliary contact KM_ON2 of KM connects the energy consumption resistor BR (760V / 50A operating condition) for energy consumption. When the voltage drops, when the voltage is lower than the second overvoltage point OU_REF2, K2 opens but self-locking is maintained, and the energy consumption resistor BR (760V / 50A operating condition) continues to be connected for energy consumption; when the voltage is lower than the first overvoltage point OU_REF1, K1 opens, KM releases, and energy consumption braking stops. The fully automatic overvoltage range adjustment is achieved through the continuous cyclic operation of K1, K2, KM, and BR.

[0027] This invention provides real-time detection of the DC bus voltage input of the frequency converter and, based on the set overvoltage range, precisely implements automatic overvoltage adjustment to achieve overvoltage protection. It regulates the DC bus voltage range to keep it within the rated voltage range, ensuring stable and reliable system operation. Moreover, it does not require PWM digital control, DSP software, IGBTs, or other resources, but uses a simple and reliable hardware circuit to detect the DC bus voltage in real time and automatically adjust the overvoltage with high accuracy and fast response. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic block diagram of the DC bus overvoltage regulation circuit of a frequency converter disclosed in one embodiment of the present invention;

[0030] Figure 2 This is a circuit diagram of a voltage detection circuit disclosed in one embodiment of the present invention;

[0031] Figure 3 This is a circuit diagram of an overvoltage point driving circuit disclosed in one embodiment of the present invention;

[0032] Figure 4 This is a circuit diagram of an overvoltage regulation circuit disclosed in one embodiment of the present invention. Detailed Implementation

[0033] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model.

[0034] In the description of this utility model, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0035] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this utility model, unless otherwise stated, "a plurality of" or "several" means two or more.

[0036] The input line of a typical frequency converter is generally AC380V. After rectification by the rectifier bridge, the rated DC bus voltage is about DC540V. Considering that the peak overvoltage is generally about 700V, this solution samples 0-1000V to cover various voltage points. At the same time, the protection range is adjustable from 540V to the upper limit of 1000V.

[0037] See Figures 1 to 4This utility model provides an overvoltage regulation circuit for a DC bus of a frequency converter, including a voltage detection circuit, an overvoltage point drive circuit, and an overvoltage regulation circuit. The overvoltage regulation circuit includes an energy consumption unit and a control switch. The energy consumption unit is connected to the DC bus through the control switch. The input terminal of the voltage detection circuit is connected to the DC bus, the output terminal of the voltage detection circuit is connected to the input terminal of the overvoltage point drive circuit, and the output terminal of the overvoltage point drive circuit is connected to the control switch.

[0038] In some embodiments, the energy-consuming unit is an energy-consuming resistor. In one embodiment, the energy-consuming resistor is 10Ω. Of course, the energy-consuming unit of this invention is not limited to an energy-consuming resistor; it can also be one or more components with energy-consuming functions.

[0039] In some embodiments, the voltage detection circuit includes a voltage sampling circuit, an isolation amplifier circuit, and an operational amplifier circuit. The input terminal of the voltage sampling circuit is connected to the DC bus, the output terminal of the voltage sampling circuit is connected to the input terminal of the isolation amplifier circuit, the output terminal of the isolation amplifier circuit is connected to the input terminal of the operational amplifier circuit, and the output terminal of the operational amplifier circuit is connected to the overvoltage point driving circuit.

[0040] In some embodiments, the voltage sampling circuit employs a voltage divider resistor network. For example... Figure 2 As shown, the voltage divider network includes several resistors. Resistors R1, R2, R3, and R4 are connected in series, with one end connected to the positive terminal of the DC bus. The other ends are connected to one end of resistor R6 and one end of resistor R5, respectively. The other end of resistor R6 is connected to the negative terminal of the DC bus, and the other end of resistor R5 is connected to the positive input terminal of the isolation amplifier circuit. The negative input terminal of the isolation amplifier circuit is connected to the negative terminal of the DC bus. The voltage sampling circuit uses resistors R1-R4 and R6 to divide the voltage, with resistor R5 connected to the input terminal of the isolation amplifier circuit. The voltage sampling circuit samples the divided voltage through resistors R1-R6, converting the 0-1000V DC bus voltage V0 into a 0-0.25V small signal (V1). The voltage signal V1 = V0 / (R1+R2+R3+R4+R6)*R6, where V0 is the input voltage. When the maximum input voltage V0 is 1000V, the corresponding V1 is 0.25V.

[0041] In some embodiments, the isolation amplifier circuit employs isolation amplifier U7. In this embodiment, isolation amplifier U7 is an AMC1301 digital isolation amplifier, featuring an isolation voltage up to 4000V, low power consumption, and a wide temperature range. It effectively isolates high voltage and protects measurements. The input V1 range of U7 is 0-0.25V, with a maximum input of 0.25V. The output V2 range of U7 is 0-2V, with a maximum output of 2V.

[0042] In some embodiments, the operational amplifier circuit includes an operational amplifier U1. The non-inverting input terminal of the operational amplifier U1 is connected to one end of resistor R7 and one end of resistor R9, respectively. The other end of resistor R7 is connected to the positive output terminal of the isolation amplifier circuit, and the other end of resistor R9 is grounded. The inverting input terminal of the operational amplifier U1 is connected to one end of resistor R8 and one end of resistor R10, respectively. The other end of resistor R8 is connected to the negative output terminal of the isolation amplifier circuit, and the other end of resistor R10 is connected to the output terminal of the operational amplifier U1. The output terminal of the operational amplifier U1 is connected to one end of resistor R11, and the other end of resistor R11 is connected to one end of capacitor C1 and the output terminal of the voltage detection circuit, respectively. The other end of capacitor C1 is grounded.

[0043] Operational amplifier U1 is an OPAMP integrated operational amplifier that amplifies the signal voltage V2 by 5 times, and outputs DBVD of 10V. In this way, through sampling, isolation and operational amplifier, the DC bus voltage of 0-1000V is converted into a DBVD signal of 0-10V, which is equivalent to reducing the voltage signal by 100 times and completing the high voltage signal isolation and conversion to a low voltage signal in real time.

[0044] In some embodiments, there are two overvoltage point driving circuits, namely a first overvoltage point driving circuit and a second overvoltage point driving circuit. The overvoltage regulation circuit also includes a first switch and a second switch. The input terminal of the first overvoltage point driving circuit is connected to the output terminal of the voltage detection circuit, and the output terminal of the first overvoltage point driving circuit is connected to the first switch. The input terminal of the second overvoltage point driving circuit is connected to the output terminal of the voltage detection circuit, and the output terminal of the second overvoltage point driving circuit is connected to the first switch. The second overvoltage point of the second overvoltage point driving circuit is greater than the first overvoltage point of the first overvoltage point driving circuit. The first switch, the second switch, and the control switch are electromagnetic switches. The auxiliary contacts of the first switch and the second switch are connected in series in the power supply circuit of the control switch. The first normally open contact of the control switch is connected in parallel with the auxiliary contact of the second switch. The second normally open contact of the control switch is connected in series with the energy consumption unit, with one end connected to the positive terminal of the DC bus and the other end connected to the negative terminal of the DC bus.

[0045] In some embodiments, the first overvoltage point is 703V and the second overvoltage point is 761V. Of course, the first overvoltage point is not limited to 703V and the second overvoltage point is not limited to 761V. The values ​​of the first and second overvoltage points can be set according to actual needs or operating conditions.

[0046] This embodiment employs two overvoltage point drive circuits to achieve automatic overvoltage range protection. (When the inverter's DC bus voltage exceeds the second overvoltage point (e.g., 761V), adjustment begins, continuously reducing the voltage from the second overvoltage point to the first overvoltage point (e.g., 703V), thus achieving automatic overvoltage range adjustment protection and avoiding frequent adjustments that could damage the device. Of course, this invention can also use a single overvoltage point drive circuit to drive the control switch (e.g., when the voltage exceeds the overvoltage point, e.g., 761V, adjustment begins to bring the voltage below the overvoltage point, e.g., 761V; however, this would cause frequent adjustments in the circuit, potentially damaging the device). Furthermore, the overvoltage point drive circuit of this invention can also utilize an MCU for overvoltage detection and control. Overvoltage range adjustment can also be achieved through software adjustment within the MCU. Because signal transmission, superposition, and software algorithms require time, the hardware implementation of this solution is faster, more economical, and lower cost than software-based solutions.

[0047] The first overvoltage point driving circuit includes a first comparison circuit and a first driving circuit. The first input terminal of the first comparison circuit is connected to the output terminal of the voltage detection circuit. The second input terminal of the first comparison circuit is connected to the first overvoltage point OU_REF1, i.e., the first threshold voltage. The output terminal of the first comparison circuit is connected to the input terminal of the first driving circuit. The output terminal of the first driving circuit is connected to the first switch.

[0048] The second overvoltage point driving circuit includes a second comparison circuit and a second driving circuit. The second input terminal of the second comparison circuit is connected to the output terminal of the voltage detection circuit. The second input terminal of the second comparison circuit is connected to the second overvoltage point OU_REF2, i.e., the second threshold voltage. The output terminal of the second comparison circuit is connected to the input terminal of the second driving circuit. The output terminal of the second driving circuit is connected to the second switch.

[0049] Furthermore, the first switch, the second switch, and the control switch are electromagnetic switches. The auxiliary contacts of the first switch and the second switch are connected in series in the power supply circuit of the control switch. That is, after the auxiliary contacts of the first switch and the second switch are connected in series with the coil of the control switch, one end is connected to the positive terminal of the second power supply, and the other end is connected to the negative terminal of the second power supply. The first normally open contact of the control switch is connected in parallel with the auxiliary contact of the second switch. After the second normally open contact of the control switch is connected in series with the energy consumption unit, one end is connected to the positive terminal INVP+ of the DC bus, and the other end is connected to the negative terminal INVN- of the DC bus.

[0050] In some embodiments, the auxiliary contact of the first switch is a normally open contact, and the auxiliary contact of the second switch is a normally open contact.

[0051] In some embodiments, the first switch is a relay K1, the second switch is a relay K2, and the control switch is a contactor KM.

[0052] The first overvoltage point OU_REF1, i.e., the first threshold voltage, is provided by the first reference circuit, and the second overvoltage point OU_REF1, i.e., the second threshold voltage, is provided by the second reference circuit. The first reference circuit includes a reference voltage regulator U4. The cathode of the reference voltage regulator U4 is connected to one end of resistor R13, one end of resistor R14, and the second input terminal of the first comparator circuit, respectively. The other end of resistor R13 is connected to the positive terminal of a third power supply (e.g., 15V). The other end of resistor R14 is connected to one end of resistor R15 and the reference terminal of the reference voltage regulator U4, respectively. The other end of resistor R15 and the anode of the reference voltage regulator U4 are grounded.

[0053] The second reference circuit includes a reference voltage regulator U3. The cathode of the reference voltage regulator U3 is connected to one end of resistor R2, one end of resistor R3, and the second input terminal of the second comparator circuit. The other end of resistor R2 is connected to the positive terminal of a third power supply (e.g., 15V). The other end of resistor R3 is connected to one end of resistor R4 and the reference terminal of the reference voltage regulator U3. The other end of resistor R4 and the anode of the reference voltage regulator U3 are grounded.

[0054] This invention employs a dual-zone overvoltage protection mechanism with adjustable threshold values ​​for both zones. Figure 3 As shown, OU_REF1 = 2.5 / R15*(R14+R15), and this first overvoltage point OU_REF1 is adjustable based on resistors R14 and R15. Specifically, OU_REF1 = 2.5 / 3.01*(5.49+3.01) = 7.05V. Simulation results show an actual voltage of approximately 7.035V, which is a 100-fold reduction based on the voltage signal. This corresponds to an actual DC bus voltage of 703V, meeting both theoretical and error requirements. OU_REF1 uses a precision voltage regulator U4, resistors R13, R14, and R15 to form a sampling point.

[0055] like Figure 3 As shown, OU_REF2 = 2.5 / R4*(R3+R4), and the second overvoltage point OU_REF1 is adjustable based on resistors R3 and R4. Specifically, OU_REF2 = 2.5 / 2*(4.12+2) = 7.65V, which, according to simulation, is approximately 7.61V. The voltage signal has been scaled down by a factor of 100, corresponding to an actual DC bus voltage of 761V. The theoretical and error requirements are met. OU_REF2 is sampled using a precision voltage regulator U3, resistors R2, R3, and R4.

[0056] The first comparison circuit uses comparator U2A, and the second comparison circuit uses comparator U1A. The comparators (U2A / U1A) compare DBVD with the threshold and output a high level (OU1 / OU2) to trigger the optocoupler (TL521) and the relay (K1 / K2).

[0057] In some embodiments, the comparator U2A uses a comparator chip LM293AD. Its positive input pin "+" is connected to the DC bus voltage signal DBVD through resistor R12, and its negative input pin "-" is connected to the first overvoltage point OU_REF1. Through internal differential comparison and biasing of the U2A comparator chip LM293AD, the output is connected to resistor R16. When the DC bus voltage DBVD is greater than the first overvoltage point OU_REF1, the U2A comparator chip outputs a high level. When the DC bus voltage DBVD is less than the first overvoltage point OU_REF1, the U2A comparator chip outputs a high level OU1.

[0058] The comparator U1A uses a comparator chip LM293AD. Its positive input pin "+" is connected to the DC bus voltage signal DBVD through resistor R1, and its negative input pin "-" is connected to the first overvoltage point OU_REF1. Through the internal differential comparison and bias of the U1A comparator chip LM293AD, the output is connected to resistor R5. When the DC bus voltage DBVD is greater than the second overvoltage point OU_REF2, the U1A comparator chip outputs a high level. When the DC bus voltage DBVD is less than the second overvoltage point OU_REF2, the U1A comparator chip outputs a high level OU2.

[0059] In some embodiments, the first driving circuit is the same as the second driving circuit.

[0060] The first driving circuit includes a first driving output circuit, a first isolation optocoupler unit, and a first switch control circuit. The input terminal of the first driving output circuit is connected to the output terminal of the first comparator circuit. The output terminal of the first driving output circuit is connected to the input terminal of the first isolation optocoupler unit. The output terminal of the first isolation optocoupler unit is connected to the input terminal of the first switch control circuit. The output terminal of the first switch control circuit is connected to the first switch.

[0061] In some embodiments, see Figure 3 The first drive output circuit includes a transistor Q1. The base of transistor Q1 is connected to one end of resistor R18. The other end of resistor R18 is connected to one end of resistor R17, one end of capacitor C2, and the output terminal of the first comparator circuit. The other end of resistor R17 is connected to the positive terminal of the first power supply. The other end of capacitor C2 is grounded. The base of transistor Q1 is connected to one end of resistor R19 and one end of capacitor C3. The other ends of resistor R19 and capacitor C3 are connected to the emitter of transistor Q1. The emitter of transistor Q1 is grounded. The collector of transistor Q1 is connected to the input terminal of the first isolation optocoupler unit.

[0062] The first switch control circuit includes a transistor Q2, the collector and emitter of which are connected in series in the power supply circuit of the first switch, and the base of the transistor Q2 is connected to the output terminal of the first isolation optocoupler unit.

[0063] The first isolation optocoupler unit includes an optocoupler U6. The first input terminal of the optocoupler U6 is connected to the positive terminal of the first power supply. The second input terminal of the optocoupler U6 is connected to one end of resistor R21 and one end of resistor R20, respectively. The other end of resistor R21 is connected to the positive terminal of the first power supply. The other end of resistor R20 is connected to the collector of transistor Q1. The first output terminal of the optocoupler U6 is connected to the positive terminal of the second power supply. The second output terminal of the optocoupler U6 is connected to one end of resistor R22. The other end of resistor R22 is connected to the base of transistor Q2.

[0064] The base of transistor Q2 is connected to one end of resistor R23 and one end of capacitor C4. The other end of resistor R23 and the other end of capacitor C4 are connected to the emitter of transistor Q2. The emitter of transistor Q2 is connected to the negative terminal of the second power supply. The collector of transistor Q2 is connected to one end of the coil of relay K1. The other end of the coil of relay K1 is connected to the positive terminal of the second power supply VSS (e.g., 24V).

[0065] The output OU1 of comparator U2A is filtered by capacitor C2, pulled up to the 5V power supply of VCC by resistor R17, and input to the base of transistor Q1 by resistor R18. The base and emitter of transistor Q1 are connected to resistor R19 and capacitor C3. The emitter of transistor Q1 is connected to GND, and the collector of Q1 is connected to the cathode of optocoupler U6. When an overvoltage signal makes the output OU1 high, transistor Q1 is turned on, thus making the input of optocoupler U6 valid. If OU1 is low, transistor Q1 is turned off, thus turning off the input of optocoupler U6. The isolation optocoupler U6 is model TL521. Its input stage consists of a 5V power supply, resistors R20 and R21, and transistor Q1, forming the input control unit. Its output stage consists of a 24V power supply, relay K1, transistor Q2, resistor R23, and capacitor C4, forming the output unit. When there is an overvoltage, current flows through pins 1 and 2 of the input stage of the isolation optocoupler U6, driving the optocoupler U6 to work. Pins 3 and 4 of the output stage drive transistor Q2 to conduct through the 24V power supply. One end of the coil of relay K1 (the first terminal) is connected to 24V, and the other end (the second terminal) is connected to the collector of transistor Q2. With the output of optocoupler U6, transistor Q2 conducts. At this time, the first terminal of the coil of relay K1 is connected to COM through the collector and emitter of transistor Q2, and relay K1 is activated. The auxiliary contact K1 of relay K1 changes from normally open to closed. Through actual simulation application, when there is no overvoltage of DC bus voltage signal DBVD, the auxiliary contact of relay K1 is normally open. When there is an overvoltage, the auxiliary contact of relay K1 changes from normally open to closed.

[0066] The second driving circuit includes a second driving output circuit, a second isolation optocoupler unit, and a second switch control circuit. The input terminal of the second driving output circuit is connected to the output terminal of the second comparator circuit. The output terminal of the second driving output circuit is connected to the input terminal of the second isolation optocoupler unit. The output terminal of the second isolation optocoupler unit is connected to the input terminal of the second switch control circuit. The output terminal of the second switch control circuit is connected to the second switch.

[0067] In some embodiments, see Figure 3 The second drive output circuit includes a transistor Q3. The base of transistor Q3 is connected to one end of resistor R7. The other end of resistor R7 is connected to one end of resistor R6, one end of capacitor C1, and the output terminal of the second comparator circuit. The other end of resistor R6 is connected to the positive terminal of the first power supply (e.g., 5V). The other end of capacitor C1 is grounded. The base of transistor Q3 is connected to one end of resistor R8 and one end of capacitor C5. The other ends of resistor R8 and capacitor C5 are connected to the emitter of transistor Q3. The emitter of transistor Q3 is grounded. The collector of transistor Q3 is connected to the input terminal of the second isolation optocoupler unit.

[0068] The second switch control circuit includes a transistor Q4, the collector and emitter of which are connected in series in the power supply circuit of the second switch, and the base of which is connected to the output terminal of the second isolation optocoupler unit.

[0069] The second isolation optocoupler unit includes an optocoupler U5. The first input terminal of the optocoupler U5 is connected to the positive terminal of the first power supply VCC (e.g., 5V). The second input terminal of the optocoupler U5 is connected to one end of resistor R10 and one end of resistor R9, respectively. The other end of resistor R10 is connected to the positive terminal of the first power supply, and the other end of resistor R9 is connected to the collector of transistor Q3. The first output terminal of the optocoupler U5 is connected to the positive terminal of the second power supply VSS (e.g., 24V). The second output terminal of the optocoupler U5 is connected to one end of resistor R11, and the other end of resistor R11 is connected to the base of transistor Q4.

[0070] The base of transistor Q4 is connected to one end of resistor R25 and one end of capacitor C6. The other end of resistor R25 and the other end of capacitor C6 are connected to the emitter of transistor Q4. The emitter of transistor Q4 is connected to the negative terminal of the second power supply. The collector of transistor Q4 is connected to one end of the coil of relay K2. The other end of the coil of relay K2 is connected to the positive terminal of the second power supply VSS (e.g., 24V).

[0071] The output OU2 of comparator U1A is filtered by capacitor C1, pulled up to the 5V power supply of VCC by resistor R6, and input to the base of transistor Q3 by resistor R7. The base and emitter of Q3 are connected to resistor R8 and capacitor C5. The emitter of transistor Q3 is connected to GND, and the collector of transistor Q3 is connected to the cathode of optocoupler U5. When overvoltage causes the output OU2 after comparison to be high, transistor Q3 is turned on, thus making the input of optocoupler U5 valid. If OU2 is low, transistor Q3 is turned off, thus turning off the input of optocoupler U5. The isolation optocoupler U5 is model TL521. Its input stage consists of a 5V power supply, resistors R10 and R9, and transistor Q3, forming the input control unit. Its output stage consists of a 24V power supply, relay K2, transistor Q4, resistor R25, and capacitor C6, forming the output unit. When there is an overvoltage, current flows through pins 1 and 2 of the input stage of the isolation optocoupler U5, driving the optocoupler U5 to work. Pins 3 and 4 of the output stage drive transistor Q3 to conduct through the 24V power supply. One end of relay K2, or first terminal, is connected to 24V, and the other end, or second terminal, is connected to the collector of transistor Q4. With the output of the U5 isolation optocoupler, transistor Q4 conducts. At this time, the first terminal of relay K2 is connected to COM through the collector and emitter of transistor Q4, and relay K2 operates. The auxiliary contact of relay K2 changes from normally open to closed. Through actual simulation application, when there is no overvoltage of DC bus voltage signal DBVD, the auxiliary contact of relay K2 is normally open. When there is an overvoltage, the auxiliary contact of relay K2 changes from normally open to closed.

[0072] The working principle of the inverter DC bus overvoltage regulation circuit of this utility model is as follows:

[0073] The DC bus voltage of a frequency converter is generally within the rated voltage operating range. However, in actual driving and mechanical transmission, such as in generator mode, rapid shutdown of a crane, energy feedback from an external mechanical drive motor, or an increase in the input voltage of the frequency converter, the DC bus voltage of the frequency converter will increase.

[0074] When the DC bus voltage increases, the synchronous DC bus voltage detection signal DBVD also increases. When it rises to the first overvoltage point OU_REF1, the auxiliary contact of relay K1 closes, ready for DC bus voltage regulation.

[0075] As the DC bus voltage continues to rise, the synchronous DC bus voltage detection signal DBVD also rises. When it rises to the second overvoltage point OU_REF2, the auxiliary contact of relay K2 closes.

[0076] After the auxiliary contacts of relays K1 and K2 are closed, the coil C of the control contactor KM is energized and attracted, the contactor KM operates, and the auxiliary contacts KM_ON1 and KM_ON2 of the contactor KM change from normally open to normally closed.

[0077] Next, the auxiliary contact KM_ON1 of the contactor KM shorts K2 to achieve the self-locking function, so that KM is always energized and working. Its auxiliary contact KM_ON2 connects the energy-consuming resistor BR, which consumes the energy of the DC bus "INVP+" and "INVN-". The speed of energy consumption is determined by the DC voltage of the DC bus "INVP+" and "INVN-" and the resistance of BR. For this application, a 10Ω resistor is selected, which is about 50A and the voltage is about 760V.

[0078] As the energy-consuming braking occurs, the DC voltage of the DC bus “INVP+” and “INVN-” gradually decreases, falling below the second overvoltage point OU_REF2. Relay K2 disconnects, and its auxiliary contact K2 disconnects. Since the contactor auxiliary contact KM_ON1 shorts the relay K2 auxiliary contact, it achieves a self-locking function. Therefore, the control function coil C is always energized and engaged, and the contactor KM operates, continuously consuming energy.

[0079] When the voltage of the DC bus “INVP+” and “INVN-” continues to decrease and falls below the first overvoltage point OU_REF1, relay K1 disconnects, its auxiliary contact disconnects, the coil C of control contactor KM is de-energized and disconnects, contactor KM is de-energized and disconnects, its auxiliary contact KM_ON2 also disconnects, the energy consumption circuit resistor BR disconnects, energy consumption braking stops, the voltage of the DC bus “INVP+” and “INVN-” falls below the first overvoltage point OU_REF1, and the voltage returns to normal.

[0080] During the change of DC bus voltage, the operating sequence of relays K1 and K2, the coil C of control contactor KM, the auxiliary contact KM_ON1 of contactor KM, and the auxiliary contact KM_ON2 of contactor KM will be repeated continuously to connect and disconnect the energy-consuming resistor, consume the DC bus voltage energy, and then restore the normal DC bus voltage. This cycle continues to automatically adjust, thereby achieving the purpose of automatically detecting and adjusting overvoltage.

[0081] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A DC bus overvoltage regulation circuit for a frequency converter, characterized in that: It includes a voltage detection circuit, an overvoltage point driving circuit, and an overvoltage regulation circuit. The overvoltage regulation circuit includes an energy consumption unit and a control switch. The energy consumption unit is connected to the DC bus through the control switch. The input terminal of the voltage detection circuit is connected to the DC bus, the output terminal of the voltage detection circuit is connected to the input terminal of the overvoltage point driving circuit, and the output terminal of the overvoltage point driving circuit is connected to the control switch.

2. The inverter DC bus overvoltage regulation circuit as described in claim 1, characterized in that: The voltage detection circuit includes a voltage sampling circuit, an isolation amplifier circuit, and an operational amplifier circuit. The input terminal of the voltage sampling circuit is connected to the DC bus, the output terminal of the voltage sampling circuit is connected to the input terminal of the isolation amplifier circuit, the output terminal of the isolation amplifier circuit is connected to the input terminal of the operational amplifier circuit, and the output terminal of the operational amplifier circuit is connected to the overvoltage point drive circuit.

3. The inverter DC bus overvoltage regulation circuit as described in claim 2, characterized in that: The voltage sampling circuit uses a voltage divider resistor network.

4. The inverter DC bus overvoltage regulation circuit as described in claim 2, characterized in that: The isolation amplifier circuit uses an isolation amplifier.

5. The inverter DC bus overvoltage regulation circuit as described in claim 2, characterized in that: The operational amplifier circuit includes operational amplifier U1. The non-inverting input terminal of operational amplifier U1 is connected to one end of resistor R7 and one end of resistor R9, respectively. The other end of resistor R7 is connected to the positive output terminal of the isolation amplifier circuit, and the other end of resistor R9 is grounded. The inverting input terminal of operational amplifier U1 is connected to one end of resistor R8 and one end of resistor R10, respectively. The other end of resistor R8 is connected to the negative output terminal of the isolation amplifier circuit, and the other end of resistor R10 is connected to the output terminal of operational amplifier U1. The output terminal of operational amplifier U1 is connected to one end of resistor R11, and the other end of resistor R11 is connected to one end of capacitor C1 and the output terminal of the voltage detection circuit, respectively. The other end of capacitor C1 is grounded.

6. The inverter DC bus overvoltage regulation circuit as described in claim 1, characterized in that: There are two overvoltage point driving circuits, namely a first overvoltage point driving circuit and a second overvoltage point driving circuit. The overvoltage regulation circuit also includes a first switch and a second switch. The input terminal of the first overvoltage point driving circuit is connected to the output terminal of the voltage detection circuit, and the output terminal of the first overvoltage point driving circuit is connected to the first switch. The input terminal of the second overvoltage point driving circuit is connected to the output terminal of the voltage detection circuit, and the output terminal of the second overvoltage point driving circuit is connected to the first switch. The second overvoltage point of the second overvoltage point driving circuit is greater than the first overvoltage point of the first overvoltage point driving circuit. The first switch, the second switch, and the control switch are electromagnetic switches. The auxiliary contacts of the first switch and the second switch are connected in series in the power supply circuit of the control switch. The first normally open contact of the control switch is connected in parallel with the auxiliary contact of the second switch. The second normally open contact of the control switch is connected in series with the energy consumption unit, with one end connected to the positive terminal of the DC bus and the other end connected to the negative terminal of the DC bus.

7. The inverter DC bus overvoltage regulation circuit as described in claim 6, characterized in that: The first overvoltage point driving circuit includes a first comparison circuit and a first driving circuit. The first input terminal of the first comparison circuit is connected to the output terminal of the voltage detection circuit. The second input terminal of the first comparison circuit is connected to the first overvoltage point. The output terminal of the first comparison circuit is connected to the input terminal of the first driving circuit. The output terminal of the first driving circuit is connected to the first switch. The second overvoltage point driving circuit includes a second comparison circuit and a second driving circuit. The second input terminal of the second comparison circuit is connected to the output terminal of the voltage detection circuit. The second input terminal of the second comparison circuit is connected to the second overvoltage point. The output terminal of the second comparison circuit is connected to the input terminal of the second driving circuit. The output terminal of the second driving circuit is connected to the second switch.

8. The inverter DC bus overvoltage regulation circuit as described in claim 7, characterized in that: The first driving circuit is the same as the second driving circuit. The first driving circuit includes a driving output circuit, an isolation optocoupler unit, and a switch control circuit. The input terminal of the driving output circuit is connected to the output terminal of the first comparator circuit. The output terminal of the driving output circuit is connected to the input terminal of the isolation optocoupler unit. The output terminal of the isolation optocoupler unit is connected to the input terminal of the switch control circuit. The output terminal of the switch control circuit is connected to the first switch.

9. The inverter DC bus overvoltage regulation circuit as described in claim 8, characterized in that: The drive output circuit includes a transistor Q1. The base of transistor Q1 is connected to one end of resistor R18. The other end of resistor R18 is connected to one end of resistor R17, one end of capacitor C2, and the output terminal of the first comparator circuit. The other end of resistor R17 is connected to the positive terminal of the first power supply. The other end of capacitor C2 is grounded. The base of transistor Q1 is connected to one end of resistor R19 and one end of capacitor C3. The other ends of resistor R19 and capacitor C3 are connected to the emitter of transistor Q1. The emitter of transistor Q1 is grounded. The collector of transistor Q1 is connected to the input terminal of the isolation optocoupler unit. The switch control circuit includes a transistor Q2, the collector and emitter of which are connected in series in the power supply circuit of the first switch, and the base of the transistor Q2 is connected to the output terminal of the isolation optocoupler unit.

10. The inverter DC bus overvoltage regulation circuit as described in claim 1 or 6, characterized in that: The energy-consuming unit uses an energy-consuming resistor.

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