JP2021151065A - Short circuit failure detection device of power conversion apparatus - Google Patents

Abstract

To provide a short circuit failure detection device capable of detecting both an arm short circuit and a load short circuit in a power conversion apparatus by using a Rogowskii coil.SOLUTION: A short circuit failure detection device 100 comprises: a first Rogowskii coil 101 which outputs a first detection signal S1 corresponding to a current flowing through an arm due to the short circuit of an arm 10; a second Rogowskii coil 102 which outputs a second detection signal S2 corresponding to a current flowing through the arm 10 due to the short circuit of a load; an arm short circuit discrimination circuit 111 for discriminating an arm short circuit based on the first detection signal S1; a load short circuit discrimination circuit 112 for discriminating a load short circuit based on the second detection signal S2; and a short circuit detection circuit 120 which detects a short circuit failure based on an output signal from the arm short circuit discrimination circuit 111 and an output signal from the load short circuit discrimination circuit 112.SELECTED DRAWING: Figure 2

Description

The present invention relates to a short-circuit failure detection device that detects a short-circuit failure of a power conversion device such as an inverter.

In a power conversion device that drives a load such as a motor, an excessive current may flow in a semiconductor switching element constituting the power conversion device. If such an excessive current flows over a long period of time, the semiconductor switching element may be destroyed. Therefore, the power conversion device is provided with a short-circuit failure detection device that detects an excessive current flowing through the semiconductor switching element and stops the power conversion device.

In this type of short circuit failure detection device, a shunt resistor, a CT (Current Transformer), a Rogowski coil, or the like is used to detect a current flowing through a semiconductor switching element. Among them, the Rogoski coil has an advantage that the short circuit failure detection device can be miniaturized and a large current can be measured because it does not have a core.

Patent Document 1 discloses a technique for detecting a short-circuit failure of an arm by a Rogowski coil in a power conversion device that drives a load via an arm including a semiconductor switching element. FIG. 9 is a circuit diagram showing the configuration of the device disclosed in Patent Document 1. In FIG. 9, the gate drive circuit 6 supplies a gate voltage to the semiconductor switching element 1 via the gate resistor 5 to drive the semiconductor switching element 1. The Rogoski coil 7 outputs an inter-terminal voltage proportional to the time gradient di / dt of the current flowing through the semiconductor switching element 1. The short-circuit detector 8 determines that an arm short-circuit has occurred by detecting that the voltage between the terminals of the Rogoski coil 7 has continued to be a large value for a certain period of time or longer, and determines that an arm short-circuit has occurred, and the semiconductor switching element 1 by the gate drive circuit 6 Stop driving.

However, short-circuit failures that can occur in the power conversion device include, in addition to the arm short-circuit described above, a load short-circuit in which the load connected to the output side of the power conversion device is in a short-circuit state. Therefore, Patent Document 2 discloses a technique of detecting an arm short-circuit current by an air-core coil and detecting a load short-circuit current by a CT (Current Transformer).

Japanese Unexamined Patent Publication No. 2001-169533

International Publication No. 2018/073909

The technique disclosed in Patent Document 1 described above is effective for detecting an arm short circuit, but has a problem that it is difficult to detect a load short circuit. This problem will be described below.

FIG. 10 is a circuit diagram illustrating a current path RT1 of a short-circuit current when an arm short-circuit occurs in a power conversion device. Further, FIG. 11 is a circuit diagram illustrating a current path RT2 of a short-circuit current when a load short-circuit occurs in the power conversion device.

In the power conversion device illustrated in FIGS. 10 and 11, an arm including a semiconductor switching element SW1 and a flywheel diode D1 connected in antiparallel between the terminals of a capacitor storing a DC voltage E and a semiconductor connected in antiparallel. An arm including a switching element SW2 and a flywheel diode D2 is connected in series. Further, an arm composed of the semiconductor switching element SW3 and the flywheel diode D3 connected in antiparallel and an arm composed of the semiconductor switching element SW4 and the flywheel diode D4 connected in antiparallel are connected in series between the terminals of the capacitor. Has been done. Then, a load Z such as a motor winding is connected between the common connection node of the semiconductor switching elements SW1 and SW2 and the common connection node of the semiconductor switching elements SW3 and SW4. Further, in FIGS. 10 and 11, L1 is a self-inductance intervening in the current path of the short-circuit current when the arm is short-circuited. Further, L2 is a self-inductance intervening in the current path from the common connection node of the semiconductor switching elements SW1 and SW2 to the common connection node of the semiconductor switching elements SW3 and SW4 via the load Z.

In the example shown in FIG. 10, when the semiconductor switching element SW1 is OFF and the semiconductor switching element SW2 is ON, a short-circuit failure of the semiconductor switching element SW1 occurs, and a capacitor that outputs a DC voltage E → a semiconductor switching element SW1 → a semiconductor. The arm short-circuit current ia flows through the current path RT1 of the switching element SW2 → the capacitor. In this case, the following equation holds for the arm short-circuit current ia.
E = L1 × dia / dt …… (1)

In the example shown in FIG. 11, when the semiconductor switching elements SW1 and SW4 are ON and the semiconductor switching elements SW2 and SW3 are OFF, a short-circuit failure of the load Z occurs, and a capacitor that outputs a DC voltage E → a semiconductor switching element SW1 → Load Z → Semiconductor switching element SW4 → Load short-circuit current ir flows through the current path RT2 of the capacitor. In this case, the following equation holds for the load short-circuit current ir.
E = (L1 + L2) × dir / dt …… (2)

Here, the relationship L1 << L2 is established between the self-inductances L1 and L2. Therefore, it can be seen from the above equations (1) and (2) that the following equation holds.
dir / dt << dia / dt …… (3)

FIG. 12 is a diagram illustrating current waveforms of the arm short-circuit current ia and the load short-circuit current ir. In FIG. 12, the horizontal axis is the time t and the vertical axis is the current value i. The self-inductance L1 intervening in the current path RT1 of the arm short-circuit current ia is small. Therefore, if the semiconductor switching element SW2 is turned on at t = 0, the arm short-circuit current ia rises to a large current value in a short time, and the electric charge accumulated in the capacitor that outputs the DC voltage E is discharged in a short time. Discharge to. Therefore, the arm short-circuit current ia is generated within a short time after the semiconductor switching element SW2 is turned on. On the other hand, the self-inductance L2 intervening in the current path RT2 of the load short-circuit current ir is much larger than the self-inductance L1. Therefore, the load short-circuit current ir increases with a very gentle time gradient after the semiconductor switching elements SW1 and SW4 are turned on. Focusing on the frequency domain, the upper limit frequency of the frequency band of the arm short-circuit current is orders of magnitude higher than the upper limit frequency of the frequency band of the load short-circuit current.

In order to detect the load short-circuit current ir with a small time gradient, for example, it is necessary to increase the number of turns of the Rogoski coil and increase the sensitivity of the Rogoski coil. However, when the number of turns of the Rogoski coil is increased, the self-inductance of the Rogoski coil becomes high. However, in order to accurately detect the voltage between the terminals of the Rogowski coil both when the arm is short-circuited and when the load is short-circuited, the self-inductance of the Rogowski coil is lowered to reduce the self-inductance and parasitic capacitance of the Rogowski coil. It is necessary to sufficiently raise the resonance frequency of the LC resonance circuit composed of the above. Specifically, it is necessary to make the resonance frequency higher than the upper limit frequency of the frequency band of the voltage between the terminals of the Rogoski coil when the arm is short-circuited. This is because if this resonance frequency is within the frequency band, the voltage waveform between the terminals of the Rogowski coil is distorted due to the influence of resonance, and it becomes difficult to detect an arm short circuit. Therefore, in order not to be affected by resonance, it is necessary to reduce the self-inductance of the Rogoski coil and increase the resonance frequency. However, in order to reduce the self-inductance of the Rogoski coil, the sensitivity of the Rogoski coil must be lowered. In this case, since the time gradient dia / dt of the load short-circuit current ia is extremely small, the voltage between the terminals of the Rogoski coil is buried in noise, and it is extremely difficult to detect the load short-circuit.

In the technique disclosed in Patent Document 2, the arm short-circuit current is detected by the air-core coil, and the load short-circuit current is detected by CT. However, when CT is used, there is a problem that the cost increases and the number of discrete parts increases, which complicates the configuration of the power conversion device.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a short-circuit failure detection device capable of detecting both an arm short-circuit and a load short-circuit of a power conversion device by using a Rogowski coil. do.

The short-circuit failure detection device according to the present invention is a short-circuit failure detection device of a power conversion device that has a plurality of arms including semiconductor switching elements and supplies power from a DC power supply to a load via the plurality of arms. A first Rogowski coil that outputs a first detection signal corresponding to an arm short-circuit current flowing through the arm due to a short circuit of the arm or another arm, which is a current flowing through one arm of the arm. A second Rogowski coil that outputs a second detection signal corresponding to a load short-circuit current flowing through the arm due to a short-circuit of the load, which is a current flowing through one arm of the arm, and the first detection signal. An arm short-circuit discrimination circuit that discriminates a short-circuit of the arm based on the above, a load short-circuit discrimination circuit that discriminates a short-circuit of the load based on the second detection signal, an output signal of the arm short-circuit discrimination circuit, and the load short-circuit. It is characterized by having a short-circuit detection circuit that detects a short-circuit failure based on an output signal of the discrimination circuit.

According to the present invention, the arm short-circuit current is detected by the first Rogoski coil, and the load short-circuit current is detected by the second Rogoski coil different from the first Rogoski coil. Therefore, the sensitivity of the second Rogoski coil is set to a value suitable for detecting the load short-circuit current, and even if the self-inductance of the second Rogoski coil becomes large due to this, the arm short-circuit current due to the first Rogoski coil is increased. Does not interfere with the detection of. Therefore, both an arm short circuit and a load short circuit can be detected.

It is a circuit diagram which shows the structure of the power conversion apparatus which includes the short circuit failure detection apparatus which is one Embodiment of this invention. It is a circuit diagram which shows the structure of the short circuit failure detection apparatus. It is a waveform figure which shows the operation of the same embodiment. It is a waveform figure which shows the operation of the same embodiment. It is a waveform figure which shows the operation of the same embodiment. It is a figure which shows the 1st specific example of the same embodiment. It is a figure which shows the 2nd specific example of the same embodiment. It is a figure which shows the 3rd specific example of the same embodiment. It is a figure which shows the 4th specific example of the same embodiment. It is a figure which shows the 4th specific example. It is a figure which shows the 5th specific example of the same embodiment. It is a circuit diagram which shows the structure of the conventional short circuit failure detection apparatus. It is a circuit diagram which shows the current path of the arm short circuit current in a power conversion apparatus. It is a circuit diagram which shows the current path of the load short-circuit current in the power conversion apparatus. It is a figure which shows the current waveform of the arm short-circuit current and the load short-circuit current.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit diagram showing a configuration of a power conversion device including a short circuit failure detection device according to an embodiment of the present invention. In this power conversion device, the capacitor 30 is charged by the DC power supply 40 and outputs a DC voltage. Arms 10_1 and 10_2 are connected in series between both terminals of the capacitor 30, and arms 10_3 and 10_4 are connected in series between the terminals. Then, a load Z such as a motor winding is connected between the common connection node between the arms 10_1 and 10_2 and the common connection node between the arms 10_3 and 10_4. Each arm 10_1 to 10_4 includes a semiconductor switching element. The gate drive circuits 20_1 to 20_4 drive each semiconductor switching element by generating a gate signal given to each semiconductor switching element of the arms 10_1 to 10_4. As described above, the power conversion device has arms 10_1 to 10_4 including a semiconductor switching element, and power is supplied from the DC power supply 40 to the load Z via the arms.

Focusing on one arm (for example, arm 10_1) in the power conversion device, when a short-circuit failure occurs in the arm 10_1 or a short-circuit failure occurs in the other arm 10_1, the arm 10_1 has a short-circuit failure. Arm short circuit current flows. Further, in the power conversion device, when a short-circuit failure of the load Z occurs, a load short-circuit current flows through the arm 10_1. If such an arm short-circuit current or a load short-circuit current flows through the arm 10_1 for a long period of time, the semiconductor switching element of the arm 10_1 may be destroyed. Therefore, a short-circuit failure detection device 100_1 that detects the occurrence of an arm short-circuit or a load short-circuit based on the current flowing through the arm 10_1 and stops the drive of the semiconductor switching element by the gate drive circuit 10_1 is provided for the arm 10_1. Similar arm short-circuit currents and load short-circuit currents may flow in the other arms 10_2 to 10_4. Therefore, the short-circuit failure detection device 100_1 to 100_3 similar to the short-circuit failure detection device 100_1 is provided for the arms 10_2 to 10_4.

In the following, when it is not necessary to distinguish between them, the arms 10_1 to 10_4 are collectively referred to as an arm 10, the gate drive circuits 20_1 to 20___ are collectively referred to as a gate drive circuit 20, and the short circuit failure detection devices 100_1 to 100_4 are short-circuited. Collectively referred to as a failure detection device 100.

FIG. 2 is a circuit diagram showing a configuration example of the short circuit failure detection device 100 according to the present embodiment. In FIG. 2, the arm 10 and the gate drive circuit 20 are shown together with the short-circuit failure detection device 100 in order to facilitate understanding of the short-circuit failure detection device 100.

In FIG. 2, the arm 10 includes a semiconductor switching element 11 and a flywheel diode 12 connected in antiparallel to the semiconductor switching element 11. In this example, the semiconductor switching element 11 is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor; an electrolytic effect transistor having a metal-oxide film-semiconductor structure). The drain of the semiconductor switching element 11 is connected to the capacitor 30 or another arm via the conductor 51, and the source of the semiconductor switching element 11 is connected to the capacitor 30 or another arm via the conductor 52. The gate drive circuit 20 drives the semiconductor switching element 11 ON / OFF by supplying a gate signal to the semiconductor switching element 11.

In the example shown in FIG. 2, the conducting wire 52 is inserted into the first Rogoski coil 101 and the second Rogoski coil 102. Here, the first Rogoski coil 101 is provided for the purpose of detecting the arm short-circuit current, and the second Rogoski coil 102 is provided for the purpose of detecting the load short-circuit current. When a current flows through the conducting wire 52, a magnetic field that rotates in a circle is generated around this current, and the voltage corresponding to the time change of the intensity of this magnetic field is the first Rogoski coil 101 and the second Rogoski coil 102. Is induced in. As a result, the first detection signal S1 and the second detection signal S2 of the voltage waveform proportional to the time gradient di / dt of the current flowing through the conducting wire 52 are transmitted from the first Rogoski coil 101 and the second Rogoski coil 102. Each is output.

In the present embodiment, the first Rogowski coil 101 is a coil optimized for detecting an arm short-circuit current, and the second Rogowski coil 102 is a coil optimized for detecting a load short-circuit current. Focusing on the sensitivity of the current to be detected to the time gradient di / dt, that is, the ratio of the output voltage of the Rogoski coil to the time gradient di / dt of the current, the sensitivity of the first Rogoski coil 101 is the second. It is lower than the sensitivity of the Rogoski coil 102. Specifically, for example, the number of turns of the first Rogoski coil 101 is smaller than the number of turns of the second Rogoski coil 102. The sensitivity of the first Rogowski coil 101 is made lower than the sensitivity of the second Rogowski coil 102 by lowering the self-resonance of the first Rogowski coil 101. This is to increase the resonance frequency of the LC resonance circuit composed of the self-inductivity and the parasitic capacitance of the above, and to make this resonance frequency out of the frequency band of the arm short-circuit current. Further, the sensitivity of the second Rogoski coil 102 is made higher than the sensitivity of the first Rogoski coil 101 in order to accurately detect the load short-circuit current having a small time gradient.

The arm short-circuit determination circuit 111 is a circuit that determines that an arm short-circuit has occurred in the power conversion device based on the first detection signal S1. Specifically, in the arm short-circuit determination circuit 111, when the first detection signal S1 maintains a higher level than the first reference level Vref1 beyond the first reference time Tref1, an arm short-circuit occurs. To determine. When the arm short-circuit determination circuit 111 determines the arm short-circuit, the short-circuit determination signal E1 is changed from the inactive level "0" to the active level "1".

The load short-circuit determination circuit 112 is a circuit that determines that a load short-circuit has occurred in the power conversion device based on the second detection signal S2. Specifically, in the load short-circuit determination circuit 112, a load short-circuit occurs when the second detection signal S2 maintains a higher level than the second reference level Vref2 beyond the second reference time Tref2. To determine. When the load short-circuit discrimination circuit 112 determines that a load short-circuit has occurred, the short-circuit discrimination signal E2 is changed from the inactive level “0” to the active level “1”.

The short-circuit detection circuit 120 indicates that some short-circuit failure has occurred in the power conversion device based on the short-circuit discrimination signal E1 output by the arm short-circuit discrimination circuit 111 and the short-circuit discrimination signal E2 output by the load short-circuit discrimination circuit 112. This is a circuit that generates a short circuit detection signal E. In this example, the short-circuit detection circuit 120 is an OR circuit that outputs the logical sum of the short-circuit discrimination signal E1 and the short-circuit discrimination signal E2 as the short-circuit detection signal E. The gate drive circuit 20 stops the operation of driving the semiconductor switching element 11 when the short-circuit detection signal E reaches the active level “1”.

3A, 3B and 3C are waveform diagrams showing an operation example of this embodiment. FIG. 3A shows the waveform of the current i flowing through the lead wire 52, the waveform of the first detection signal S1, and the level determination signal D1 generated in the arm short-circuit determination circuit 111 for each of the normal time, the arm short-circuit, and the load short-circuit. The waveform of the short circuit determination signal E1 and the waveform of the short circuit determination signal E1 output by the arm short circuit determination circuit 111 are shown. Further, in FIG. 3B, the waveform of the current i flowing through the lead wire 52, the waveform of the second detection signal S2, and the level determination generated in the load short-circuit determination circuit 112 are shown in each of the normal time, the arm short-circuit, and the load short-circuit. The waveform of the signal D2 and the waveform of the short-circuit discrimination signal E2 output by the load short-circuit discrimination circuit 112 are shown. Further, FIG. 3C shows the waveform of the current i flowing through the lead wire 52, the waveform of the short-circuit discrimination signal E1 output by the arm short-circuit discrimination circuit 111, and the load short-circuit discrimination circuit 112 for each of the normal, arm short-circuit, and load short-circuit. The waveform of the short-circuit discrimination signal E2 output by the short-circuit detection circuit 120 and the waveform of the short-circuit detection signal E output by the short-circuit detection circuit 120 are shown. In these figures, the horizontal axis is time t and the vertical axis is voltage value, current value or truth value.

First, the operation of the arm short-circuit determination circuit 111 will be described with reference to FIG. 3A. In the arm short-circuit determination circuit 111, the first detection signal S1 output from the first Rogoski coil 101 is compared with the first reference level Vref1, and the first detection signal S1 exceeds the first reference level Vref1. When this is done, the level determination signal D1 is set to the active level “1”. When the arm is short-circuited, a current i having a large time gradient di / dt flows through the conductor 52. Therefore, the arm short-circuit determination circuit 111 is required to detect such a large time gradient di / dt. Therefore, the first reference level Vref1 is set to a sufficiently large voltage value suitable for comparison with the first detection signal S1 when an arm short circuit occurs. Further, in the arm short-circuit determination circuit 111, when the level determination signal D1 exceeds the first reference time Tref1 and maintains the active level “1”, the arm short-circuit determination signal E1 is set to the active level “1”. When the arm is short-circuited, the time for the current i having a large time gradient di / dt to flow through the conductor 52 is short. Therefore, the first reference time Tref1 is set to a sufficiently short time during which an arm short circuit can be detected, for example, several tens to several hundreds ns.

Normally, the current i flowing through the conducting wire 52 rises from the turn-on of the semiconductor switching element 11, and the first detection signal S1 indicating the rising period of the current i and the time gradient di / dt of the current i sets the first reference level Vref1. When the level is exceeded, the level determination signal D1 becomes the active level “1”. However, the rising period of the current i is short, and the period during which the level determination signal D1 becomes the active level “1” is shorter than the first reference time Tref1. Therefore, the short-circuit determination signal E1 does not become the active level “1”.

At the time of load short circuit, the current i flowing through the conducting wire 52 rises from the turn-on of the semiconductor switching element 11, and then the current i increases with a time gradient determined by the self-inductance intervening in the current path of the load short circuit current. In this case, the first detection signal S1 indicating the rising period of the current i and the time gradient di / dt of the current i exceeds the first reference level Vref1. However, as in the normal case, the rising period of the current i is short, and the period during which the level determination signal D1 becomes the active level “1” is shorter than the first reference time Tref1. Therefore, the short-circuit determination signal E1 does not become the active level “1”.

The operation when the arm is short-circuited is as follows. If a short-circuit failure occurs in another arm 10 connected in series with the semiconductor switching element 11 when the semiconductor switching element 11 of the arm 10 is turned on, the current i flowing through the conducting wire 52 intervenes in the current path of the current i. It rises with a time gradient determined by self-inductance. As a result, the first detection signal S1 indicating the time gradient di / dt of the current i exceeds the first reference level Vref1, and the level determination signal D1 becomes the active level “1”. The rising period of the current i in this case is longer than the rising period of the current i in the normal operation, and the level determination signal D1 maintains the active level “1” beyond the first reference time Tref1. Therefore, the short-circuit determination signal E1 becomes the active level “1”.

In this example, the first Rogoski coil 101 detects the time gradient di / dt of the current when the first detection signal S1 is in the region A1p or the region A1n with high accuracy. Then, the first reference level Vref1 is in the region A1p. Therefore, the arm short-circuit determination circuit 111 can accurately detect the arm short-circuit.

Next, the operation of the load short-circuit determination circuit 112 will be described with reference to FIG. 3B. In the load short-circuit determination circuit 112, the second detection signal S2 output from the second Rogoski coil 102 is compared with the second reference level Vref2, and the second detection signal S2 exceeds the second reference level Vref2. When this is done, the level determination signal D2 is set to the active level “1”. When the load is short-circuited, a current i having a small time gradient di / dt flows through the conductor 52. Therefore, the load short-circuit determination circuit 112 is required to detect such a small time gradient di / dt. Therefore, the second reference level Vref2 is set to a sufficiently small voltage value suitable for comparison with the second detection signal S2 when a load short circuit occurs. Further, in the load short-circuit determination circuit 112, when the level determination signal D2 exceeds the second reference time Tref2 and maintains the active level “1”, the short-circuit determination signal E2 is set to the active level “1”. When the load is short-circuited, the time at which the time gradient di / dt of the current i flowing through the conductor 52 increases is longer than that during the normal time and when the arm is short-circuited. Therefore, the second reference time Tref2 is set to a value of several tens to several hundred times with respect to a sufficiently long time, for example, the reference time Tref1, so that the normal operation or the arm short circuit is not mistaken for a load short circuit. ..

Normally, the current i flowing through the conducting wire 52 rises due to the turn-on of the semiconductor switching element 11, and the second detection signal S2 indicating the rise period of the current i and the time gradient di / dt of the current i sets the second reference level Vref2. When the level is exceeded, the level determination signal D2 becomes the active level “1”. However, the period during which the level determination signal D2 becomes the active level “1” is shorter than the second reference time Tref2. Therefore, the short-circuit determination signal E2 does not become the active level “1”.

If the semiconductor switching element 11 connected in series with the semiconductor switching element 11 is short-circuited and the semiconductor switching element 11 is turned on, an arm short circuit occurs. At this time, the current i flowing through the conducting wire 52 rises with a time gradient determined by the self-inductance intervening in the current path of the arm short-circuit current. As a result, the second detection signal S2 indicating the time gradient di / dt of the current i exceeds the second reference level Vref2, and the level determination signal D2 becomes the active level “1”. However, when the arm is short-circuited, the first detection signal S1 also exceeds the first reference level Vref1, and the level determination signal D1 becomes the active level “1”. Since each short-circuit detection time is Tref1 << Tref2, when an arm short-circuit occurs, the short-circuit discrimination signal E1 becomes the active level “1” before the short-circuit discrimination signal E2. Therefore, even if an arm short circuit occurs, the short circuit determination is not detected.

At the time of load short circuit, the current i flowing through the conducting wire 52 rises from the turn-on of the semiconductor switching element 11, and then the current i increases with a time gradient determined by the self-inductance intervening in the current path of the load short circuit current. While the current i rises in this way and then increases with a constant time gradient, the second detection signal S2 indicating the time gradient di / dt of the current i exceeds the second reference level Vref2, and the level determination signal D2 is active. It becomes level "1". When the load is short-circuited, the level determination signal D2 maintains the active level “1” beyond the second reference time Tref2. Therefore, the short-circuit determination signal E2 becomes the active level “1”.

In this example, the second Rogoski coil 102 detects the time gradient di / dt of the current in which the second detection signal S2 becomes a signal in the region A2 with high accuracy. Then, the second reference level Vref2 is in the region A2. Therefore, the second detection signal S2 generated by the load short circuit can be detected with high accuracy.

Next, the operation of the short circuit detection circuit 120 will be described with reference to FIG. 3C. As shown in FIG. 3C, the short-circuit detection circuit 120 outputs the logical sum of the short-circuit discrimination signal E1 and the short-circuit discrimination signal E2 as the short-circuit detection signal E. Therefore, when an arm short circuit or a load short circuit occurs, the short circuit detection signal E is output to the gate drive circuit 20, and the drive of the semiconductor switching element 11 by the gate drive circuit 20 is stopped.

As described above, according to the present embodiment, both the arm short circuit and the load short circuit that occur in the power conversion device can be accurately detected by using the Rogoski coil. Further, according to the present embodiment, since a discrete component such as a CT is not used to detect the short-circuit current, the cost can be reduced and the size of the short-circuit failure detection device can be avoided.

Hereinafter, various specific examples of this embodiment will be described.

<First specific example>
The first specific example and the second to third specific examples described later are the first Rogoski coil 101 capable of generating the first detection signal S1 having an appropriate size when the arm is short-circuited, and the first Rogoski coil 101 which is suitable when the load is short-circuited. This is a specific example of a second Rogoski coil 102 capable of generating a second detection signal S2 having a large size.

FIG. 4 is a diagram showing a first specific example of the present embodiment. In this first specific example, the first Rogoski coil 101A for detecting an arm short circuit includes an outward path 41 wound in a toroidal coil shape and a return path 42 connecting the winding start and winding end of the toroidal coil and rewinding. Consists of. The second Rogoski coil 102A also includes an outward path 43 and a return path 44 similar to the outward path 41 and the return path 42. In the first specific example, the number of turns n1 of the first Rogoski coil 101A for detecting an arm short circuit and the number of turns n2 of the second Rogoski coil 102A for detecting a load short circuit are different. Specifically, there is a relationship of n2> n1 between the number of turns n1 of the outward path 41 of the first Rogoski coil 101A and the number of turns n2 of the outward path 43 of the second Rogoski coil 102A. The reason will be described below.

The voltage v induced in the Rogoski coil is given by the following equation.
v = -μ ・ (SQ ・ n / LG) ・ (di / dt) …… (4)
Here, μ is the magnetic permeability of air (same as the magnetic permeability of vacuum), SQ is the magnetic path cross-sectional area of the Rogowski coil, n is the number of turns of the Rogowski coil, LG is the magnetic path length of the Rogowski coil, di / dt is the time gradient of the current i that is the detection target of the Rogowski coil. The magnetic path cross-sectional area SQ is the cross-sectional area of the space surrounded by the toroidal coils forming the outward path in the outward paths 41 and 43 of the Rogoski coil. The magnetic path length is the length of the space surrounded by the toroidal coil in the Rogoski coil, and is substantially equal to the length of the return paths 42 and 44.

The following equation is obtained by solving the above equation (5) for the number of turns n.
n =-(LG · v) / (μ · SQ · (di / dt)) …… (5)
This equation (5) shows that when the time gradient di / dt of the current is small, it is necessary to increase the number of turns n in order to obtain a sufficiently large voltage v from the Rogoski coil.

Therefore, in the first specific example, since the time gradient di / dt of the current to be detected is small for the second Rogoski coil 102A, the number of turns n2 is larger than the number of turns n1 of the first Rogoski coil 101A. I'm increasing. Specifically, in the equation (5), the required number of turns n1 and n2 is set by setting the time gradient di / dt of the current when the arm is short-circuited to, for example, about 10 times the time gradient di / dt of the current when the load is short-circuited. The logoski coils 101A and 102A having the obtained turns n1 and n2 are provided. By doing so, both the arm short circuit and the load short circuit can be detected with high accuracy.

<Second specific example>
FIG. 5 is a diagram showing a second specific example of the present embodiment. In this second specific example, the magnetic path cross-sectional area SQ1 of the first Rogowski coil 101B for detecting an arm short circuit and the magnetic path cross-sectional area SQ2 of the second Rogowski coil 102B for detecting a load short circuit are different. .. Specifically, there is a relationship of SQ2> SQ1 between the magnetic path cross-sectional areas SQ1 and SQ2.

The following equation is obtained by solving the above equation (5) with respect to the magnetic path cross-sectional area SQ.
SQ =-(LG · v) / (μ · n · (di / dt)) …… (7)
This equation (7) shows that it is necessary to increase the magnetic path cross-section seat SQ in order to obtain a sufficiently large voltage v from the Rogoski coil when the time gradient di / dt of the current is small. There is.

Therefore, in the second specific example, since the time gradient di / dt of the current to be detected is small for the second Rogoski coil 102B, the magnetic path cross-sectional area SQ2 thereof is changed to the magnetic path breakage of the first Rogoski coil 101B. The area is larger than SQ1. Specifically, in the equation (7), the required magnetic path cross-sectional area SQ1 is set by setting the time gradient di / dt of the current when the arm is short-circuited to, for example, about 10 times the time gradient di / dt of the current when the load is short-circuited. And SQ2 are calculated, and the Rogoski coils 101B and 102B having the obtained magnetic path cross-sectional areas SQ1 and SQ2 are provided. By doing so, both the arm short circuit and the load short circuit can be detected with high accuracy.

<Third specific example>
FIG. 6 is a diagram showing a third specific example of the present embodiment. In this third specific example, the magnetic path length LG1 of the first Rogoski coil 101C for detecting an arm short circuit and the magnetic path length LG2 of the second Rogoski coil 102C for detecting a load short circuit are different. Specifically, there is a relationship of LG1> LG2 between the magnetic path lengths LG1 and LG2.

The following equation is obtained by solving the above equation (5) for the magnetic path length LG.
LG =-(μ ・ SQ ・ n ・ (di / dt)) / v …… (8)
Therefore, in the third specific example, in the equation (8), the time gradient di / dt of the current when the arm is short-circuited is set to, for example, about 10 times the time gradient di / dt of the current when the load is short-circuited, and the required magnetic path is obtained. The Rogoski coils 101C and 102C having magnetic path lengths LG1 and LG2 obtained by calculating the lengths LG1 and LG2 are provided. By doing so, both the arm short circuit and the load short circuit can be detected with high accuracy.

<Fourth specific example>
The fourth specific example is a specific example relating to the mounting of the first Rogoski coil 101 and the second Rogoski coil 102. 7A and 7B are diagrams showing a fourth specific example. Here, FIG. 7A is a diagram showing a first Rogoski coil 101D and a second Rogoski coil 102D seen from the semiconductor switching element 11D side of FIG. 7B. 7B is a cross-sectional view taken along the line AA'of FIG. 7A.

In FIG. 7B, a multilayer wiring board composed of a first layer wiring board 61, a second layer wiring board 62, and a third layer wiring board 63 is sandwiched between the semiconductor switching element 11D and the main wiring board 70. ing. Here, the first layer wiring board 61 is separated from the main wiring board 70, the second layer wiring board 62 is separated from the first layer wiring board 61, and the third layer wiring board 63 is separated from the second layer wiring board 62. However, the semiconductor switching element 11D is separated from the third layer wiring board 63.

The conductors 51 and 52 correspond to the conductors 51 and 52 in FIG. 1 above, and are connected to the source and drain of the semiconductor switching element 11D, respectively. These conductors 51 and 52 extend from the semiconductor switching element 11D, pass through the third layer wiring board 63, the second layer wiring board 62, and the first layer wiring board 61, and are connected to the main wiring board 70. ing. The semiconductor switching element 11D is connected to another semiconductor switching element or power supply line in the power conversion device via the lead wire 51 or 52 and the main wiring board 70.

The first Rogoski coil 101D for detecting an arm short circuit is arranged on the first layer wiring board 61, the second layer wiring board 62, and the third layer wiring board 63 so as to surround the conducting wire 51. .. Further, the second ROGOVSKI coil 102D for detecting a load short circuit is arranged on the first layer wiring board 61, the second layer wiring board 62, and the third layer wiring board 63 so as to surround the conducting wire 52. ..

More specifically, the first Rogoski coil 101D is composed of an outward path 41 wound in a toroidal coil shape and a return path 42 connecting the winding start and winding end of the toroidal coil and rewinding. The return path 42 is formed on the second layer wiring board 62. Further, the outbound route 41 includes wiring on the first layer wiring board 61 and wiring from the first layer wiring board 61 to the third layer wiring board 63 via a through hole formed in the second layer wiring board 62. It is composed of wiring on the third layer wiring board 63. The second Rogoski coil 102D is also composed of an outward path 43 and a return path 44 similar to the outward path 41 and the return path 42 of the first Rogoski coil 101D.

Also in this fourth specific example, both the arm short circuit and the load short circuit can be detected with high accuracy. Further, according to the fourth specific example, unlike the configuration shown in FIG. 1 above, the first Rogoski coil 101D and the second Rogoski coil 102D are divided into a source side and a drain side of the semiconductor switching element 11D. It is arranged. That is, in the fourth specific example, the first Rogoski coil 101D and the second Rogoski coil at each position on one side (for example, the conducting wire 51) and the other side (for example, the conducting wire 52) of the arm in the current path passing through the arm. 102D is arranged. Therefore, the fourth specific example has an advantage that the wiring length between the semiconductor switching element 11D and the capacitor 30 (see FIG. 1) can be shortened.

<Fifth specific example>
FIG. 8 is a diagram showing a fifth specific example of the present embodiment. In the fifth specific example, the first Rogoski coil 101E for detecting an arm short circuit and the second Rogoski coil 102E for detecting a load short circuit are arranged so as to cover the current path 104 to be measured such as a bus bar. Then, in the fifth specific example, the shield plate 103 made of metal or the like is arranged between the first Rogoski coil 101E and the second Rogoski coil 102. According to this fifth specific example, it is possible to prevent the current flowing through the first Rogoski coil 101E and the current flowing through the second Rogoski coil 102 from interfering with each other.

<Other embodiments>
Although one embodiment of the present invention has been described above, other embodiments of the present invention can be considered. For example:

(1) In the above embodiment, the short circuit failure detection device according to the present invention is applied to a two-phase inverter having four arms. However, the scope of application of the short circuit failure detection device according to the present invention is not limited to this. The short circuit failure detection device according to the present invention may be applied to an inverter having a number of phases other than two phases, such as a three-phase inverter. Further, the short circuit failure detection device according to the present invention may be applied to a power conversion device other than an inverter, such as a DC / DC converter.

(2) In the above embodiment, MOSFET is mentioned as an example of the semiconductor twinching element, but the semiconductor switching element is not limited to this, and other examples such as IGBT (Insulated Gate Bipolar Transistor) and the like. It may be a semiconductor switching element of.

(3) Any two, three, four, or all of the first to fifth specific examples may be combined. For example, the number of turns of the second Rogowski coil 102 is larger than the number of turns of the first Rogowski coil 101, and the number of turns of the second Rogowski coil 102 is larger than the cross-sectional area of the coil in the first Rogowski coil 101. The cross-sectional area of the coil in the above may be increased, and the magnetic path length of the second Rogowski coil 102 may be shorter than the magnetic path length of the first Rogowski coil 101.

(4) In the fourth specific example, both the first Rogowski coil 101D and the second Rogowski coil 102D are arranged on the first layer wiring board 61, the second layer wiring board 62, and the third layer wiring board 63. However, only one of them may be arranged on the first layer wiring board 61, the second layer wiring board 62, and the third layer wiring board 63.

(5) In the above embodiment, the arm short-circuit determination circuit 111, the load short-circuit determination circuit 112, and the short-circuit detection circuit 120 are provided individually, but these circuits may be mounted as one circuit.

(6) In the above embodiment, the short circuit detection signal E is input to the gate drive circuit 20, but the short circuit determination signals E1 and E2 may be directly input to the gate drive circuit 20. Further, since the arm is short-circuited when the short-circuit determination signal E1 is output, the restart of the gate drive circuit 20 is prohibited after the gate drive circuit 20 is stopped, and the load is short-circuited when the short-circuit determination signal E2 is output. If it can be confirmed that the short circuit of the load is released after the gate drive circuit 20 is stopped, the protection operation may be changed by an output short circuit determination signal such as restarting the gate drive circuit 20.

100 ... Power converter, 30 ... Condenser, 40 ... DC power supply, 10_1 to 10_4, 10 ... Arm, 20_1 to 20_4, 20 ... Gate drive circuit, 100_1 to 100_4, 100 ... Short circuit failure detector, 11, 11D ... Semiconductor switching element, 12 ... Flywheel diode, 51, 52 ... Conduction wire, 101, 101A, 101B, 101C, 101D, 101E ... First Rogowski coil, 102, 102A, 102B, 102C , 102D, 101E ... 2nd Rogowski coil, 41, 43 ... Outward route, 42, 44 ... Return route, 70 ... Main wiring board, 61 ... 1st layer wiring board, 62 ... 2nd layer wiring Board, 63 ... Third layer wiring board, 111 ... Arm short circuit discrimination circuit, 112 ... Load short circuit discrimination circuit, 120 ... Short circuit detection circuit, 103 ... Shield plate, Z ... Load.

Claims (8)

In a short-circuit failure detection device of a power conversion device having a plurality of arms including each semiconductor switching element and supplying power from a DC power supply to a load via the plurality of arms.
A first Rogoski coil which is a current flowing through one arm in the plurality of arms and outputs a first detection signal corresponding to an arm short-circuit current flowing through the arm due to a short circuit of the arm or another arm.
A second Rogoski coil which is a current flowing through one arm in the plurality of arms and outputs a second detection signal corresponding to the load short-circuit current flowing through the arm due to the short-circuiting of the load.
An arm short-circuit determination circuit that determines a short-circuit of the arm based on the first detection signal, and an arm short-circuit determination circuit.
A load short-circuit determination circuit that determines a short-circuit of the load based on the second detection signal, and a load short-circuit determination circuit.
A short-circuit failure detection device including a short-circuit detection circuit that detects a short-circuit failure based on an output signal of the arm short-circuit discrimination circuit and an output signal of the load short-circuit discrimination circuit. The short-circuit failure detection device according to claim 1 or 2, wherein the number of turns of the second Rogoski coil is larger than the number of turns of the first Rogoski coil. The short-circuit failure detection device according to claim 1 or 2, wherein the cross-sectional area of the coil in the second Rogowski coil is larger than the cross-sectional area of the coil in the first Rogowski coil. The short circuit failure according to any one of claims 1 to 3, wherein the magnetic path length of the coil in the second Rogoski coil is shorter than the magnetic path length of the coil in the first Rogoski coil. Detection device. The short-circuit failure detection device according to any one of claims 1 to 4, wherein at least one of the first Rogoski coil and the second Rogoski coil is incorporated in a wiring board. Claims 1 to 5, wherein the first Rogoski coil and the second Rogoski coil are arranged at each position on one side and the other side of the arm in the current path passing through the arm. The short circuit failure detection device according to any one of the items. The short-circuit failure detection device according to any one of claims 1 to 6, wherein a shield is provided between the first Rogoski coil and the second Rogoski coil. A gate drive circuit according to claim 1, wherein the drive of the semiconductor switching element is stopped based on the short circuit determination signal output by the short circuit failure detection device.

Images