Apparatus for detecting inverter output short-circuit current and method therefor

Abstract

The present invention relates to an apparatus and method for detecting an output short circuit of an inverter, the apparatus according to the present invention comprising: a shunt resistor that measures the magnitude of current between a positive terminal of a DC link capacitor and an inverter unit; a comparator that receives a voltage applied to the shunt resistor through a first input terminal and receives a reference voltage through a second input terminal to output a comparison result; a feedback resistor that connects the output terminal of the comparator and the second input terminal of the comparator; and an inverter control unit that controls the operation of the inverter unit on the basis of the output voltage from the output terminal of the comparator. The present invention, by extending the inverter short-circuit detection time, can detect a pulse-type short-circuit current, thereby protecting inverter elements and the inverter from failure or burnout.

Description

Inverter output short-circuit current detection device and method thereof

[0001] The present invention relates to a technique for detecting an output short circuit of an inverter.

[0002]

[0003] An inverter is a power conversion device that converts direct current (DC) power into alternating current (AC) power.

[0004] A typical universal inverter that drives an electric motor receives three-phase AC power, converts it to DC in the rectifier, stores it in the DC-Link capacitor, and then converts it back to AC in the inverter to drive the electric motor.

[0005] The inverter is a VVVF (Variable Voltage Variable Frequency) system that controls the speed of the motor by adjusting the voltage and frequency input to the motor according to the PWM output.

[0006] An inverter output short circuit is one of the major failure modes of the inverter, and is a failure mode that occurs when the external output of the inverter is short-circuited, an internal short circuit of the inverter is generated, or the inverter output is grounded.

[0007] When an inverter output short-circuit occurs, a large short-circuit current can instantaneously occur, causing current exceeding the inverter's tolerance to flow through the inverter. This can lead to damage, fire, or explosion. Therefore, general-purpose inverters incorporate a circuit that detects and blocks output short-circuits, protecting the inverter.

[0008] However, when an output short circuit occurs during low-speed operation with a low inverter output voltage reference, the powering mode time is formed very briefly, so the inverter protection circuit may not detect the output short circuit. Although such short-term output short circuits that are not detected by the inverter protection circuit occur in less than a few microseconds (us), if they occur repeatedly, the stress caused by the short circuit accumulates, which can ultimately lead to inverter damage.

[0009] The inventors of the present invention have devoted extensive research efforts to addressing the problems inherent in conventional inverter protection circuits. After extensive research and development, they have developed an inverter output short-circuit current detection device and method capable of detecting extremely short-term output short-circuits that conventional inverter protection circuits fail to detect. The inventors have now completed the present invention.

[0010]

[0011] An object of the present invention is to provide an inverter output short-circuit detection device and method capable of detecting an output short-circuit for a very short time that may cause inverter damage if accumulated.

[0012] Meanwhile, other unspecified purposes of the present invention will be additionally considered within the scope that can be easily inferred from the detailed description and effects thereof below.

[0013]

[0014] In order to solve the above technical problem, an inverter output short-circuit detection device according to one embodiment of the present invention comprises: a shunt resistor installed in a path for detecting an output short-circuit; a comparator which receives a first voltage identical to a voltage applied to the shunt resistor as a first input unit and a reference voltage as a second input unit, respectively, and outputs a second voltage or 0 V according to a comparison result; a feedback resistor connected to change the reference voltage in response to an output voltage of the comparator; As a result of changing the reference voltage, the output time of the second voltage can be extended compared to a case where there is no change.

[0015] In one embodiment of the present invention, the comparator can output the second voltage when the first voltage is less than the reference voltage, and can output 0 V when the first voltage is equal to or greater than the reference voltage.

[0016] In one embodiment of the present invention, the change in the reference voltage is a change between a first reference voltage and a second reference voltage, the second reference voltage is formed higher than the first reference voltage, and the first reference voltage can be changed to the second reference voltage when the first voltage becomes lower than the first reference voltage.

[0017] In one embodiment of the present invention, the second reference voltage may be changed to the first reference voltage when the first voltage becomes greater than the second reference voltage.

[0018] In one embodiment of the present invention, a first resistor; and a second resistor; are further included, and the reference voltage can be distributed as a preset third voltage according to the connection relationship of the first resistor, the second resistor, and the feedback resistor.

[0019] In one embodiment of the present invention, when the comparator outputs the second voltage, the first resistor and the feedback resistor may be connected in parallel to form a first composite resistor, and the reference voltage may be a second reference voltage obtained by dividing the third voltage by the composite resistor and the second resistor.

[0020] In one embodiment of the present invention, when the comparator outputs the 0 V, the second resistor and the feedback resistor are connected in parallel to form a second composite resistor, the reference voltage is a first reference voltage obtained by dividing the third voltage by the first resistor and the second composite resistor, and the second reference voltage can be formed higher than the first reference voltage.

[0021] In one embodiment of the present invention, an inverter control unit may further be included that determines whether an output short circuit occurs in response to the second voltage.

[0022] In one embodiment of the present invention, the inverter control unit can block a path in which an output short circuit is detected in response to the judgment result.

[0023] In one embodiment of the present invention, a photo coupler for transmitting the second output voltage signal to the inverter control unit is further included, and the photo coupler can transmit the signal while the output unit of the comparator and the inverter control unit are insulated.

[0024] In addition, in order to solve the above technical problem, an inverter output short-circuit detection method according to an embodiment of the present invention can be performed by a control device including at least one processor and memory, and can include the steps of: measuring a first voltage applied to a shunt resistor installed in a path for detecting an output short-circuit; comparing the first voltage with a first reference voltage; changing the first reference voltage to a second reference voltage greater than the first reference voltage when the first voltage is lower than the first reference voltage; and detecting a short-circuit until the first voltage becomes greater than the second reference voltage.

[0025] According to the present invention, by varying the operating level for detecting an output short circuit of an inverter with hysteresis, it is possible to detect an inverter output short circuit in the form of a short pulse that could not be detected in the prior art.

[0026] In addition, there is an advantage in that the inverter can be prevented from being broken down or damaged by an accumulated pulse-shaped output short circuit by detecting a short pulse-shaped inverter output short circuit.

[0027] Meanwhile, even if the effect is not explicitly mentioned herein, it is added that the effect and its provisional effect described in the following specification expected by the technical features of the present invention are treated as described in the specification of the present invention.

[0028]

[0029] FIG. 1 is a structural diagram of an inverter including an inverter output short-circuit detection device according to a preferred embodiment of the present invention.

[0030] FIG. 2 is a schematic structural diagram of an inverter output short-circuit detection device according to a preferred embodiment of the present invention.

[0031] FIG. 3 is a graph showing the relationship between a reference voltage and a shunt resistor voltage for inverter output short-circuit detection in a preferred embodiment of the present invention.

[0032] FIG. 4 is a schematic flowchart of an inverter output short-circuit detection method according to another preferred embodiment of the present invention.

[0033] Fig. 5 is a schematic structural diagram of an inverter output short-circuit detection circuit according to the prior art.

[0034] Fig. 6 is a graph showing the relationship between the reference voltage and the shunt resistor voltage for inverter output short-circuit detection according to the prior art.

[0035] Fig. 7 shows voltage and current waveforms of an inverter output short-circuit detection circuit according to the prior art.

[0036] ※ It is to be noted that the attached drawings are provided for reference only to help understand the technical concept of the present invention, and the scope of the rights of the present invention is not limited thereby.

[0037] Hereinafter, with reference to the drawings, the configuration of the present invention, guided by various embodiments thereof, and the effects resulting from such configurations will be examined. In describing the present invention, detailed descriptions of related, well-known functions that are obvious to those skilled in the art and that may unnecessarily obscure the gist of the present invention will be omitted.

[0038] Terms such as "first" and "second" may be used to describe various components, but the components should not be limited by these terms. These terms may only be used to distinguish one component from another. For example, without departing from the scope of the present invention, a "first component" may be referred to as a "second component," and similarly, a "second component" may also be referred to as a "first component." Furthermore, singular expressions include plural expressions unless the context clearly dictates otherwise. Terms used in the embodiments of the present invention may be interpreted as having meanings commonly known to those of ordinary skill in the art, unless otherwise defined.

[0039] Hereinafter, with reference to the drawings, the configuration of the present invention guided by various embodiments of the present invention and the effects resulting from the configuration will be examined.

[0040]

[0041] FIG. 1 is a structural diagram of an inverter including an inverter output short-circuit detection device according to a preferred embodiment of the present invention.

[0042] An inverter (1) is used to control a motor (2).

[0043] The inverter (1) converts AC power into DC power through a rectifier (11), stores it in a DC link capacitor (12), and then converts it back into AC power through an inverter (13) and transmits it to the motor (2), thereby controlling the rotational speed of the motor (2).

[0044] The inverter section (13) is generally composed of semiconductor switching elements, and converts direct current into alternating current by having two switches connected in series alternately turn on and off.

[0045] However, if a situation occurs where two switches are turned on at the same time, a large current will suddenly flow to the inverter unit (13), which may cause a breakdown or damage to the inverter (1), and the entire system may become unusable due to a fire or other reasons due to an explosion of the inverter (1).

[0046] To prevent such a situation, there are various methods for detecting an output short circuit of the inverter unit (13). One of them is to install a shunt resistor between the DC link capacitor (12) and the inverter unit (13) and measure the current flowing through the shunt resistor (110) to detect an output short circuit.

[0047]

[0048] Fig. 5 is a schematic structural diagram of an inverter output short-circuit detection circuit according to a conventional technique for detecting an inverter output short-circuit using a shunt resistor.

[0049] The inverter output short circuit detection circuit (200) detects an inverter output short circuit by comparing the size of the current flowing through the shunt resistor with the reference voltage by a comparator (220).

[0050] Fig. 6 is a graph showing the relationship between the reference voltage and the shunt resistor voltage for inverter output short-circuit detection according to the prior art.

[0051] A reference voltage (Vref) and a voltage (Vin) passing through a shunt resistor are input to the comparator (220). The comparator (220) outputs the power voltage (Vcc) when the reference voltage Vref is greater than Vin, and outputs 0V (Gnd) in the opposite case.

[0052] Therefore, if a large current flows due to a short circuit in the shunt resistor, the voltage drop of Vin will be large, and if Vin becomes smaller than Vref for a time corresponding to t, it can be determined that there is a short circuit in the inverter's output.

[0053] Fig. 7 shows voltage and current waveforms of an inverter output short-circuit detection circuit according to the prior art.

[0054] However, if the time t during which Vin becomes less than Vref is less than a few microseconds (μs), a short circuit in the inverter output may not be detected using conventional techniques. However, if such pulse-type short circuits are repeated and accumulated, they can cause fatal damage to the inverter.

[0055] Therefore, the inverter output short circuit detection device according to the present invention is designed to solve the problems of the prior art.

[0056]

[0057] FIG. 2 is a schematic structural diagram of an inverter output short-circuit detection device according to a preferred embodiment of the present invention.

[0058] The inverter output short circuit detection device (100) according to the present invention may include a shunt resistor (110), a comparator (120), a feedback resistor (130), an inverter control unit (140), and a photo coupler (150).

[0059] The shunt resistor (110) is used to measure the current flowing between the DC link capacitor (12) of the inverter (1) and the inverter section (13).

[0060] When the current flowing through the shunt resistor (110) increases, a large voltage drop occurs as the positive voltage (DCP) of the DC link capacitor (12) passes through the shunt resistor (110), so this is used to detect whether the output of the inverter unit (13) is short-circuited.

[0061] A comparator (120) is used to measure the magnitude of the voltage drop occurring across the shunt resistor (110).

[0062] A voltage that has experienced a voltage drop across a shunt resistor (110) is input to the first input of the comparator (120), a reference voltage is input to the second input, and the comparison result is output to the output.

[0063] Specifically, when the voltage input to the second input of the comparator (120) is greater than the voltage input to the first input, the power supply voltage (DCP_VCC) is output, and in the opposite case, 0V (Ground) is output.

[0064] The reference voltage input to the second input section is determined as a value obtained by dividing the power supply voltage (DCP_VCC) by the ratio of the first resistor (161, R1) and the second resistor (162, R2).

[0065] However, since the inverter output short circuit detection device (100) according to the present invention has a feedback resistor (130, R3) connecting the output portion of the comparator (120) and the second input portion, the reference voltage changes in response to the output result of the output portion of the comparator (120).

[0066] When the output of the comparator (120) is High (DCP_VCC), the feedback resistor (130) and the first resistor (161) are connected in parallel, so the reference voltage is the second reference voltage (V ref_up ) becomes. The specific formula is as follows [Mathematical Formula 1].

[0067]

[0068]

[0069]

[0070] Conversely, when the output of the comparator (120) is Low (0 V), the feedback resistor (130) and the second resistor (162) are connected in parallel, so the reference voltage is the first reference voltage (V ref_down ) becomes. The specific formula is as follows [Mathematical Formula 2].

[0071]

[0072]

[0073]

[0074] In this way, the inverter output short circuit detection device (100) according to the present invention can set the reference voltage differently as the first reference voltage and the second reference voltage by including a feedback resistor (130) in the path fed back from the output of the comparator (120), thereby increasing the time for detecting the inverter output short circuit.

[0075] FIG. 3 is a graph showing the relationship between a reference voltage and a shunt resistor voltage for inverter output short-circuit detection in a preferred embodiment of the present invention.

[0076] In the t0 section, since the voltage drop due to the shunt resistor (110) is not large, the input voltage (Vin) of the first input of the comparator (120) remains greater than the reference voltage of the second input. At this time, the output of the comparator (120) becomes 0 V, so the reference voltage becomes the first reference voltage as discussed above.

[0077] When Vin becomes less than the first reference voltage at the start of the t section, the inverter output short circuit detection device (100) starts short circuit detection.

[0078] When a short circuit is detected, that is, when Vin of the first input of the comparator (120) becomes smaller than the first reference voltage of the second input, the output of the comparator (120) rises to the power supply voltage, so the reference voltage input to the second input of the comparator (120) becomes the second reference voltage as discussed above.

[0079] When the reference voltage is changed to a second reference voltage that is greater than the first reference voltage, the time that Vin remains less than the second reference voltage increases by t1.

[0080] Accordingly, the time for which the inverter output short circuit detection device (100) can detect an output short circuit of the inverter unit (130) increases to t+t1, and thus, even if a pulse-shaped short circuit current flows, it can be detected and the inverter unit (13) can be shut off.

[0081] To this end, the inverter output short circuit detection device (100) of the present invention includes an inverter control unit (140) for controlling the inverter unit (13).

[0082] The inverter control unit (140) can protect the inverter (1) by controlling the switch of the inverter unit (13) to be turned off when an output short circuit is detected based on the output result of the comparator (120).

[0083] The comparator (120) and the inverter control unit (140) can be connected via a photo coupler (150) for insulation. The inverter control unit (140) can receive the output result of the comparator (120) while being insulated from the remaining circuits of the inverter output short-circuit detection device (100) by the photo coupler (150).

[0084]

[0085] FIG. 4 is a schematic flowchart of an inverter output short-circuit detection method according to another preferred embodiment of the present invention.

[0086] The inverter output short circuit detection method according to the present invention can be performed by a control device (not shown) including one or more processors and memories.

[0087] First, the voltage (V) applied to the shunt resistor (110) connected between the positive pole of the DC link capacitor of the inverter and the inverter part in ) is measured (S110).

[0088] The comparator (120) measures the voltage (V) applied to the shunt resistor (110). in ) is the first reference voltage (V ref_low ) becomes smaller than (S120), the power supply voltage (V cc ) is printed (S130).

[0089] Power voltage (V) from comparator (120) cc ) is output, and the first reference voltage (V ref_low ) is the second reference voltage (V ref_high) is changed (S130). In addition, the corresponding signal is transmitted to the inverter control unit (140) by the photo coupler (150), and the inverter control unit (140) can recognize this and detect a short circuit (S131).

[0090] The comparator (120) measures the voltage (V) applied to the shunt resistor (110). in ) is the second reference voltage (V ref_high ) is greater than (S140), 0 V is output (S140). At this time, short circuit detection is terminated (S141). In summary, short circuit detection is V in This V ref_low After it becomes smaller (T=0), V again in This V ref_low After it becomes equal to (T=t), V in This V ref_high It can be performed until it becomes larger (T=t+t1) (S141). Compared to the prior art, it can detect a short circuit for a longer time period of t1, thereby improving the short circuit detection capability.

[0091] Additionally, the second reference voltage (V ref_high ) is again the first reference voltage (V ref_low ) is changed to (S150).

[0092]

[0093]

[0094] According to the inverter output short-circuit detection device and method according to the present invention as described above, pulse-type short-circuit current can also be detected by changing the comparison standard according to the magnitude of the voltage applied to the shunt resistor, and accordingly, there is an effect of protecting the inverter from breakdown or damage due to the accumulated pulse-type short-circuit current.

[0095]

[0096] The scope of protection of the present invention is not limited to the description and expression of the embodiments explicitly described above. Furthermore, it should be noted that the scope of protection of the present invention may not be limited by obvious modifications or substitutions within the technical field to which the present invention pertains.

Claims

1. Shunt resistor installed in the path to detect output short circuit; A comparator that receives a first voltage identical to the voltage applied to the shunt resistor as a first input and a reference voltage as a second input, and outputs a second voltage or 0 V according to the comparison result; and A feedback resistor connected to change the reference voltage in response to the output voltage of the comparator; An inverter output short-circuit detection device in which, as a result of a change in the reference voltage, the output time of the second voltage is extended compared to when there is no change.

2. In paragraph 1, The above comparator is, An inverter output short circuit detection device that outputs the second voltage when the first voltage is less than the reference voltage and outputs 0 V when the first voltage is equal to or greater than the reference voltage.

3. In paragraph 2, The change in the above reference voltage is a change between the first reference voltage and the second reference voltage, The second reference voltage is formed higher than the first reference voltage, An inverter output short circuit detection device in which the first reference voltage is changed to the second reference voltage when the first voltage becomes lower than the first reference voltage.

4. In paragraph 3, An inverter output short circuit detection device in which the second reference voltage is changed to the first reference voltage when the first voltage becomes greater than the second reference voltage.

5. In paragraph 2, 1st resistance; and Including a second resistor; An inverter output short circuit detection device in which the reference voltage is a third voltage that is preset and distributed according to the connection relationship between the first resistor, the second resistor, and the feedback resistor.

6. In paragraph 5, When the above comparator outputs the second voltage, An inverter output short-circuit detection device in which the first resistor and the feedback resistor are connected in parallel to form a first composite resistor, and the reference voltage is a second reference voltage obtained by dividing the third voltage by the composite resistor and the second resistor.

7. In paragraph 6, If the above comparator outputs 0 V, The second resistor and the feedback resistor are connected in parallel to form a second composite resistor, and the reference voltage is a first reference voltage in which the third voltage is divided by the first resistor and the second composite resistor. An inverter output short circuit detection device in which the second reference voltage is formed higher than the first reference voltage.

8. In paragraph 1, An inverter output short circuit detection device further comprising an inverter control unit that determines whether an output short circuit occurs in response to the second voltage.

9. In paragraph 8, The above inverter control unit is an inverter output short circuit detection device that blocks a path in which an output short circuit is detected in response to the above judgment result.

10. In paragraph 1, Further comprising a photocoupler for transmitting the second output voltage signal to the inverter control unit, The above photocoupler is an inverter output short-circuit detection device that transmits a signal while the output section of the comparator and the inverter control section are insulated.

11. A method for detecting an inverter output short circuit performed by a control device including at least one processor and memory, A step of measuring a first voltage applied to a shunt resistor installed in a path for detecting an output short circuit; A step of comparing the first voltage and the first reference voltage; A step of changing the first reference voltage to a second reference voltage greater than the first reference voltage when the first voltage is lower than the first reference voltage; and A method for detecting a short circuit in an inverter output, comprising: a step of detecting a short circuit until the first voltage becomes greater than the second reference voltage.

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