JP4166680B2 - Ground fault detector - Google Patents

Description

  The present invention relates to a ground fault detection device mounted on a vehicle or the like, for example.

Conventionally, for example, by selectively switching and connecting a ground fault detection current detector or voltage detector to the anode side and the cathode side of a DC circuit equipped with a high-voltage DC power supply, the DC circuit can be connected at an appropriate position. A ground fault detection method for detecting the presence or absence of occurrence of a ground fault is known (see, for example, Patent Document 1).
Further, in such a ground fault detection method, the power source voltage of the high-voltage DC power source is detected, and the detection result of the current detector or the voltage detector for ground fault detection accompanying the fluctuation of the power source voltage is detected according to the detected value of the power source voltage. A detection method for correcting the fluctuation is known (see, for example, Patent Document 2).
JP-A-4-12616 Japanese Patent No. 2838462

However, in the ground fault detection method according to the above-described prior art, it is necessary to include a voltage detection unit for detecting the power supply voltage of the high-voltage DC power supply. Further, based on the detection result by the voltage detection unit, ground fault detection This requires a configuration for correcting fluctuations in the detection result of the current detector or voltage detector, resulting in a problem that the device configuration becomes complicated.
In addition, if there is a stray capacitance component in a DC circuit equipped with a high-voltage DC power supply, for example, a current dependency or a voltage change due to the switching connection of a current detector for detecting a ground fault or a voltage detector will be time-dependent. Therefore, there is a possibility that the presence / absence of the ground fault cannot be accurately detected only by performing detection with the current detector or the voltage detector at the time of executing the switching connection.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a ground fault detection device capable of accurately detecting the presence or absence of a ground fault while preventing the device configuration from becoming complicated. To do.

In order to solve the above problems and achieve the object, the ground fault detection device according to the present invention is a ground fault detection resistor (for example, positive side detection resistor 33a, negative side detection in the embodiment). Resistor 33b) and a protective circuit (for example, positive electrode side protective resistor 31a, negative electrode side protective resistor 31b in the embodiment) and a constant current source (for example, positive electrode side constant current source 34a, negative electrode in the embodiment) Each of the positive side ground fault detection circuits (for example, the positive side circuit 21 in the embodiment) and the negative side ground fault detection circuit (for example, the negative electrode in the embodiment). The side circuit 22) is connected to each positive side terminal (for example, the positive side terminal 11p in the embodiment) of the ungrounded DC power source (for example, the ungrounded DC power source 11 in the embodiment) and ground (for example, the embodiment). And the negative terminal (example) For example, a ground fault detection device connected between the negative electrode side terminal 11n) in the embodiment and the ground (for example, the ground portion 20 in the embodiment), each positive side ground fault detection circuit. And an abnormality detection means (for example, step S11, step S12, step S13 in the embodiment) for detecting whether or not an abnormal condition has occurred for each negative ground fault detection circuit, and the abnormality detection means at the positive ground When the occurrence of an abnormal state in the fault detection circuit is detected, it is determined that a ground fault has occurred in the negative line connected to the negative terminal of the non-grounded DC power source, and the fault detection unit detects the ground fault. When the occurrence of an abnormal state is detected in the negative ground fault detection circuit, it is determined that a ground fault has occurred in the positive line connected to the positive terminal of the non-grounded DC power supply, and the abnormality detection means The positive side ground fault detection circuit and the negative side ground fault at When an occurrence of an abnormal state in the output circuit is detected, a ground fault determination unit that determines that a ground fault has occurred inside the ungrounded DC power supply (for example, step S13, step S14, step in the embodiment) S16), and a protection means for cutting off the connection between the ground fault detection resistor and the protection resistor when the voltage generated at both ends of the ground fault detection resistor exceeds a predetermined protection voltage. Yes.

According to the ground fault detection device having the above-described configuration, it is possible to detect a ground fault generated on the positive side or the negative side of the non-grounded DC power source or inside the non-grounded DC power source, and by acquiring the ground fault occurrence position, for example, The work for eliminating the generated ground fault can be easily performed, and an appropriate response to the generated ground fault is possible.
Further, in the ground fault detection device according to claim 1, when the current value is changed by the current value changing means for changing the current value of the current output from the constant current source, and the current value changing means. A ground fault for detecting a ground fault resistance value related to a ground fault generated in the negative line, the positive line, or the non-grounded DC power source based on a change in voltage between terminals at both ends of the ground fault detection resistor. Each of the positive ground fault detection circuit and the negative ground fault detection circuit based on the ground fault resistance value detected by the ground fault resistance value detection means. By detecting whether or not an abnormal state occurs every time, it is possible to obtain a detection result that does not depend on the output voltage of the non-grounded DC power supply, and it is possible to detect a ground fault with high accuracy.

Further, the ground fault detection device according to the second aspect of the present invention includes a ground fault detection resistor (for example, the positive electrode side detection resistor 33a and the negative electrode side detection resistor 33b in the embodiment) and a protective resistor (for example, the embodiment). And a constant current source (for example, the positive side constant current source 34a and the negative side constant current source 34b in the embodiment) are connected in parallel. Each positive side ground fault detection circuit (for example, the positive side circuit 21 in the embodiment) and the negative side ground fault detection circuit (for example, the negative side circuit 22 in the embodiment) are connected to a non-grounded DC power source (for example, Between the positive terminals (for example, the positive terminal 11p in the embodiment) and the ground (for example, the grounding unit 20 in the embodiment) and the negative side of the non-grounded DC power supply 11) in the embodiment. Terminal (for example, negative electrode side terminal 11n in the embodiment) A ground fault detection device connected to ground (for example, the grounding unit 20 in the embodiment), and a current value of current output from the constant current source (for example, current in the embodiment) Current value changing means (for example, step S03, step S08 in the embodiment) for changing the values I1, I2), and both ends of the ground fault detection resistor when the current value is changed by the current value changing means On the negative terminal of the non-grounded DC power source based on the change in the voltage between the terminals (for example, the voltages V2 (I1), V2 (I2), the voltages V4 (I1), V4 (I2) in the embodiment). A ground fault resistance value related to a ground fault generated in the negative line connected to the positive side line connected to the positive terminal of the non-grounded DC power source or the non-grounded DC power source (for example, in the embodiment) Ground fault resistance RLn, ground fault resistance RLp Ground fault resistance value detecting means for detecting a ground fault resistance RLnp) (e.g., control unit 23 in the embodiment, step S05, and step S10), and the ground fault detection voltage is predetermined protection voltage generated across the resistor And a protection means for cutting off the connection between the ground fault detection resistor and the protection resistor .

  According to the ground fault detection apparatus having the above-described configuration, it is possible to obtain a detection result that does not depend on the output voltage of the non-grounded DC power supply, and it is possible to detect a ground fault with high accuracy.

According to the ground fault detection device of the first aspect of the present invention, by acquiring the ground fault occurrence position in addition to the presence or absence of the occurrence of the ground fault, for example, an operation for eliminating the generated ground fault can be easily performed. It can be executed, and an appropriate response can be made to the generated ground fault.
Further, according to the ground fault detection device of the present invention described in claim 2, it is possible to improve the detection accuracy of ground fault detection without depending on the output voltage of the ungrounded DC power supply.

Hereinafter, a ground fault detection apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.
The ground fault detection device 10 according to the present embodiment is mounted on a vehicle such as a fuel cell vehicle or a hybrid vehicle, for example, and is, for example, an ungrounded DC power source (hereinafter simply referred to as a DC power source) that is electrically insulated from a grounded vehicle body. 11) detecting a ground fault occurring on the positive electrode side or the negative electrode side of 11 or the DC power source 11, that is, the presence or absence of dielectric breakdown.
Here, the DC power supply (voltage value Vbatt) 11 is a capacitor in which a plurality of capacitor cells, such as electric double layer capacitors or electrolytic capacitors, are connected in series, or a plurality of cells (for example, two batteries such as a lithium ion battery). A secondary battery is connected in series.

The ground fault generated on the positive electrode side of the DC power source 11 is a dielectric breakdown that occurs at an appropriate position on the positive electrode side line connected to the positive terminal 11p of the DC power source 11. When this ground fault occurs A ground fault resistance RL (for example, the ground fault resistance RLp shown in FIG. 1) having an appropriate magnitude related to the ground fault is set between an appropriate position of the positive electrode side line and the grounded vehicle body or the like.
Moreover, the ground fault generated on the negative electrode side of the DC power source 11 is a dielectric breakdown that occurs at an appropriate position on the negative electrode side line connected to the negative electrode side terminal 11n of the DC power source 11. When this ground fault occurs A ground fault resistance RL (for example, ground fault resistance RLn shown in FIG. 1) having an appropriate magnitude related to the ground fault is set between an appropriate position of the negative electrode side line and the grounded vehicle body or the like.
Moreover, the ground fault generated in the DC power supply 11 is, for example, a dielectric breakdown that occurs between capacitor cells connected to each other, contact points between the cells, and the like. A ground fault resistance RL having a magnitude (for example, a ground fault resistance RLnp shown in FIG. 1) is set between an appropriate position inside the DC power supply 11 and a grounding portion such as a grounded vehicle body.
The DC power supply 11 is connected in parallel to a motor drive circuit 13 that controls the drive and regenerative operation of a motor 12 as a vehicle drive source, for example, as shown in FIG.

The motor drive circuit 13 includes a PWM inverter based on pulse width modulation (PWM), which is configured by a bridge circuit using a plurality of switching elements such as transistors, for example. The energization is sequentially commutated.
That is, for example, when the motor 12 is driven, the motor drive circuit 13 converts the DC power supplied from the DC power supply 11 into AC power to the motor 12 based on a torque command output from a motor control device (not shown). Supply. On the other hand, when a driving force is transmitted from the driving wheel W side to the motor 12 side via the transmission (T / M) during regenerative operation such as when the vehicle is decelerated, the motor driving circuit 13 causes the motor 12 to generate power. To generate a so-called regenerative braking force and recover the kinetic energy of the vehicle body as electric energy.

For example, as shown in FIG. 1, the ground fault detection device 10 according to the present embodiment includes a grounding unit 20 that is grounded by being connected to, for example, a vehicle body, a positive circuit 21, a negative circuit 22, and a control. The ground part 20 is arranged between the positive circuit 21 and the negative circuit 22 connected in series, and the positive circuit 21 and the negative circuit 22 are connected to the DC power supply 11 and the motor drive circuit 13. Connected in parallel.
For example, as shown in FIG. 2, the positive side circuit 21 includes a positive side protective resistor 31a (resistance value R1) and a positive side switching element connected in series sequentially from the positive side terminal 11p of the DC power source 11 to the ground unit 20. (S1) 32a and positive-side detection resistor 33a (resistance value R2), a positive-side constant current source 34a connected in parallel to a series of these elements, and further connected in parallel to the positive-side detection resistor 33a And is used to detect a ground fault occurring on the negative electrode side of the DC power supply 11 and a ground fault occurring inside the DC power supply 11.
For example, as shown in FIG. 3, the negative electrode side circuit 22 includes a negative electrode side protective resistor 31b (resistance value R3) and a negative electrode side switching element that are connected in series from the negative electrode side terminal 11n of the DC power supply 11 to the ground unit 20. (S3) 32b and the negative electrode side detection resistor 33b (resistance value R4), a negative electrode side constant current source 34b connected in parallel to a series of these elements, and further connected in parallel to the negative electrode side detection resistor 33b. And is used to detect a ground fault occurring on the positive side of the DC power source 11 and a ground fault occurring inside the DC power source 11.

Here, the positive side switching element 32a is an FET such as an n-channel MOSFET (Metal Oxide Semi-conductor Field Effect Transistor), the drain is connected to the positive side protection resistor 31a, and the source is connected to the positive side detection resistor 33a. The gate is connected to the control unit 23.
The negative-side switching element 32b is an FET such as a p-channel MOSFET, the drain is connected to the negative-side protection resistor 31b, the source is connected to the negative-side detection resistor 33b, and the gate is connected to the control unit 23. Yes.

For example, as shown in FIG. 4, the positive-side constant current source 34a includes an operational amplifier 41a, a switching element (S2) 42a made of an FET such as an n-channel MOSFET, a resistor 43a (resistance value Ra), a power source 44a, The first to third resistors 45a, 46a, 47a (respective resistance values Ra1, Ra2, Ra3), a switch 48a, and a current limiting resistor 49a are provided.
One terminal of the resistor 43a is grounded by being connected to the ground unit 20, and the other terminal is connected to the inverting input terminal of the operational amplifier 41a and the source of the switching element 42a. The drain of the switching element 42a is connected to the positive terminal 11p of the DC power supply 11, and the gate of the switching element 42a is connected to the output terminal of the operational amplifier 41a via the current limiting resistor 49a.
The power supply 44a is sequentially connected to the ground unit 20 through first to third resistors 45a, 46a, 47a connected in series, and a connection portion between the first resistor 45a and the second resistor 46a is an operational amplifier 41a. The switch 48a is connected in parallel to the third resistor 47a.

  Here, the output voltage (voltage value V0) of the power supply 44a and an appropriate reference voltage Vri corresponding to the on / off state of the switch 48a are input to the non-inverting input terminal of the operational amplifier 41a, and the inverting input terminal of the operational amplifier 41a. Is input with a voltage (I × Ra) corresponding to the current I flowing through the resistor 43a (resistance value Ra), and a difference ΔV = (Vri−I × Rb) between the voltage (I × Ra) and the reference voltage Vri. ), The voltage Am × ΔV obtained by amplifying the difference ΔV with an appropriate gain Am is input from the operational amplifier 41a to the gate of the switching element 42a. Here, the potential of the source of the switching element 42a, that is, the voltage input to the inverting input terminal of the operational amplifier 41a is the order of the PN junction between the gate and the source terminal of the switching element 42a from the voltage Am × ΔV input to the gate. A value (Am × ΔV−Vf) obtained by subtracting the direction voltage Vf is obtained. This value, for example, is substantially equal to the reference voltage Vri and the resistance 43a when the gain Am is set to a sufficiently large value. The current I flowing through the capacitor has a constant current value (for example, Vri / Ra).

As a result, the current value of the current I flowing through the resistor 43a is regulated to be a value equal to or less than an appropriate current value according to the reference voltage Vri.
The reference voltage Vri changes according to the on / off state of the switch 48a controlled by the control unit 23. When the switch 48a is in the off state, the output voltage of the power source 44a is equal to the resistance value Ra1 of the first resistor 45a. 2 and the combined resistance value (Ra2 + Ra3) of the third resistors 46a and 47a (V0 × (Ra2 + Ra3) / (Ra1 + Ra2 + Ra3)). On the other hand, when the switch 48a is on, the output voltage of the power supply 44a is divided by the resistance value Ra1 of the first resistor 45a and the resistance value Ra2 of the second resistor 46a (V0 × Ra2 / (Ra1 + Ra2)). It becomes.
That is, the current value of the current I output from the positive-side constant current source 34a changes according to the on / off state of the switch 48a. In the following, the current value I1 is set when the switch 48a is off, and the switch 48a is turned on. In this state, the current value is I2.
The gate of the switching element 42a is connected to the control unit 23. When the gate of the switching element 42a is grounded in the control unit 23, the switching element 42a is turned off and output from the positive-side constant current source 34a. The current value of the current I is zero.
Further, the reference voltage Vri input to the non-inverting input terminal of the operational amplifier 41a and the voltage (I × Ra) input to the inverting input terminal are positive voltages.

Further, for example, as shown in FIG. 5, the negative-side constant current source 34b includes an operational amplifier 41b, a switching element 42b made of an FET such as a p-channel MOSFET, a switching element (S4) 42b, and a resistor 43b (resistance value Rb). ), A power supply 44b, fourth to sixth resistors 45b, 46b, 47b (respective resistance values Rb1, Rb2, Rb3), a switch 48b, and a current limiting resistor 49b.
One terminal of the resistor 43b is grounded by being connected to the ground unit 20, and the other terminal is connected to the non-inverting input terminal of the operational amplifier 41b and the source of the switching element 42b. The drain of the switching element 42b is connected to the negative terminal 11n of the DC power supply 11, and the gate of the switching element 42b is connected to the output terminal of the operational amplifier 41b via the current limiting resistor 49b.
The power supply 44b is sequentially connected to the ground unit 20 through fourth to sixth resistors 45b, 46b, 47b connected in series, and a connection portion between the fourth resistor 45b and the fifth resistor 46b is an operational amplifier 41b. The switch 48b is connected in parallel to the sixth resistor 47b.

  Here, the output voltage (voltage value V0) of the power supply 44b and an appropriate reference voltage Vri according to the on / off state of the switch 48b are input to the inverting input terminal of the operational amplifier 41b, and the non-inverting input terminal of the operational amplifier 41b. Is input with a voltage (I × Rb) corresponding to the current I flowing through the resistor 43b, and there is a difference ΔV = (I × Rb−Vri) between the voltage (I × Rb) and the reference voltage Vri. A voltage Am × ΔV obtained by amplifying the difference ΔV with an appropriate gain Am is input from the operational amplifier 41b to the gate of the switching element 42b. Here, the potential of the source of the switching element 42b, that is, the voltage input to the non-inverting input terminal of the operational amplifier 41b is the voltage Am × ΔV input to the gate of the PN junction between the gate and source terminals of the switching element 42b. The value obtained by adding the forward voltage Vf (Am × ΔV + Vf) is obtained. For example, when the gain Am is set to a sufficiently large value, the value is substantially equal to the reference voltage Vri, and the resistance 43b The flowing current I has a constant current value (for example, Vri / Rb).

As a result, the current value of the current I flowing through the resistor 43b is regulated to be a value equal to or less than an appropriate current value according to the reference voltage Vri.
The reference voltage Vri changes according to the on / off state of the switch 48b controlled by the control unit 23. When the switch 48b is in the off state, the output voltage of the power source 44b is equal to the resistance value Rb1 of the fourth resistor 45b. And a voltage value (V0 × (Rb2 + Rb3) / (Rb1 + Rb2 + Rb3)) divided by the combined resistance value (Rb2 + Rb3) of the fifth and sixth resistors 46b and 47b. On the other hand, when the switch 48b is in the ON state, the output voltage of the power source 44b is divided by the resistance value Rb1 of the fourth resistor 45b and the resistance value Rb2 of the fifth resistor 46b (V0 × Rb2 / (Rb1 + Rb2)). It becomes.
That is, the current value of the current I output from the negative-side constant current source 34b changes according to the on / off state of the switch 48b. In the following description, the current value I1 is set when the switch 48b is off, and the switch 48b is turned on. In this state, the current value is I2.
The gate of the switching element 42b is connected to the control unit 23. When the gate of the switching element 42b is grounded in the control unit 23, the switching element 42b is turned off and output from the negative-side constant current source 34b. The current value of the current I is zero.
The reference voltage Vri input to the inverting input terminal of the operational amplifier 41b and the voltage (I × Rb) input to the non-inverting input terminal are negative voltages.

The control unit 23 is configured by an electronic circuit including a CPU and the like, and controls on / off switching of the positive side switching element 32a of the positive side circuit 21 and the negative side switching element 32b of the negative side circuit 22, and the positive side constant current source 34a. The on / off switching control of the switching elements 42a and 42b and the switches 48a and 48b of the negative constant current source 34b and the voltages output from the positive voltage detector 35a and the negative voltage detector 35b are performed. Whether or not a ground fault has occurred is determined based on the values V2 and V4.
For example, the control unit 23 grounds the respective gates of the switching elements 32a and 42a of the positive circuit 21 and the switching elements 32b and 42b of the negative circuit 22 except when the ground fault detection process is performed. Each switching element 32a, 42a, 32b, 42b is set to an OFF state.
For example, the control unit 23 performs the positive-side switching element (S1) of the positive-side circuit 21 at the time of executing the ground fault detection process for the ground fault occurring on the negative side of the DC power source 11 and the ground fault occurring inside the DC power source 11. ) 32a and the switching element (S2) 42a of the positive-side constant current source 34a are released from grounding, and each switching element 32a is set so that an ON signal of an appropriate voltage level is input to each gate. , 42a are set to the on state.
At this time, the control unit 23 outputs an off signal for setting the switch (S5) 48a to the off state or an on signal for setting the switch to the on state, whereby the current value of the current I output from the positive-side constant current source 34a. Is changed to the current value I1 or the current value I2.
Further, for example, the control unit 23 performs the negative-side switching element (S3) of the negative-side circuit 22 at the time of executing the ground-fault detection process for the ground fault occurring on the positive side of the DC power source 11 and the ground fault occurring inside the DC power source 11. ) 32b and the switching element (S4) 42b of the negative-side constant current source 34b are released from grounding and set so that an ON signal of an appropriate voltage level is input to each gate. , 42b are set to the on state.
At this time, the control unit 23 outputs an off signal for setting the switch (S6) 48b to an off state or an on signal for setting the switch to an on state, whereby the current value of the current I output from the negative constant current source 34b. Is changed to the current value I1 or the current value I2.

For example, as shown in FIG. 6, when the ground fault of the ground fault resistance RLn is generated on the negative electrode side of the DC power supply 11, the positive side circuit 21 is turned on (that is, each switching element 32 a of the positive side circuit 21, 42a is turned on) and the negative side circuit 22 is turned off (that is, the switching elements 32b and 42b of the negative side circuit 22 are turned off). The first closed circuit L1 through which a suitable current flows back to the DC power supply 11 through the positive-side switching element (S1) 32a, the positive-side detection resistor 33a, and the ground fault resistance RLn, and the DC power supply 11 in order, A current value I1 or a current value I that flows through the side constant current source 34a and the ground fault resistance RLn and changes to the DC power source 11 according to the on / off state of the switch 48a. A second closed circuit L2 is formed of the current I is refluxed.
Here, when the current I output from the positive-side constant current source 34a is the current value I1, the voltage V2 (I1) detected by the positive-side voltage detector 35a connected in parallel to the positive-side detection resistor 33a. Is described as, for example, the following formula (1), and the voltage V2 (I2) detected by the positive voltage detector 35a when the current I output from the positive constant current source 34a is the current value I2. Is described, for example, as shown in Equation (2) below.

  When the ground fault resistance RLn is described based on the difference (V2 (I1) −V2 (I2)) between the above formulas (1) and (2), for example, as shown in the following formula (3), the voltage value Vbatt of the DC power supply 11 The value does not depend on.

For example, as shown in FIG. 7, when the ground fault of the ground fault resistance RLp is generated on the positive electrode side of the DC power supply 11, the negative circuit 22 is turned on (that is, each switching element of the negative circuit 22 32b and 42b are turned on) and the positive side circuit 21 is turned off (that is, the switching elements 32a and 42a of the positive side circuit 21 are turned off). And a third closed circuit L3 through which an appropriate current flows back to the DC power source 11 through the negative electrode side detection resistor 33b, the negative electrode side switching element (S3) 32b, and the negative electrode side protection resistor 31b, and the DC power source 11 sequentially. , The current value I1 or the electric current that changes according to the on / off state of the switch 48b to the DC power source 11 through the ground fault resistance RLp and the negative-side constant current source 34b. Current I value I2 and a fourth closed circuit L4 refluxing is formed.
Here, when the current I output from the negative-side constant current source 34b is the current value I1, the voltage V4 (I1) detected by the negative-side voltage detector 35b connected in parallel to the negative-side detection resistor 33b. Is described as, for example, the following mathematical formula (4), and the voltage V4 (I2) detected by the negative voltage detector 35b when the current I output from the negative constant current source 34b is the current value I2. Is described, for example, as shown in Equation (5) below.

  When the ground fault resistance RLp is described based on the difference (V4 (I1) −V4 (I2)) between the above formulas (4) and (5), for example, as shown in the following formula (6), the voltage value Vbatt of the DC power supply 11 The value does not depend on.

Further, when the ground fault of the ground fault resistance RLnp occurs at an appropriate position inside the DC power supply 11, the positive circuit 21 is turned on (that is, the switching elements 32a and 42a of the positive circuit 21 are turned on). ) And the negative circuit 22 is turned off (that is, the switching elements 32b and 42b of the negative circuit 22 are turned off), for example, sequentially from the positive terminal 11p of the DC power supply 11, as shown in FIG. The appropriate current flows back to the ground fault occurrence position 11np in the DC power supply 11 through the positive protection resistor 31a, the positive switching element (S1) 32a, the positive detection resistor 33a, and the ground fault resistance RLnp. From the closed circuit L5 and the positive terminal 11p of the DC power supply 11, the positive constant current source 34a and the ground fault resistor RLnp are sequentially distributed to the DC power supply 11 inside. To earth 絡発 raw position 11Np, and the sixth closed circuit L6 current I of the current value I1 or the current value I2 that varies according to the on / off state of the switch 48a is reflux was formed.
Further, in this case, when the ground fault of the ground fault resistance RLp is generated on the positive electrode side of the DC power supply 11, the negative electrode side circuit 22 is turned on (that is, the switching elements 32b and 42b of the negative electrode side circuit 22). Is turned on) and the positive circuit 21 is turned off (that is, the switching elements 32a and 42a of the positive circuit 21 are turned off). For example, as shown in FIG. From the position 11np, an appropriate current is passed through the ground fault resistor RLnp, the negative electrode side detection resistor 33b, the negative electrode side switching element (S3) 32b, and the negative electrode side protective resistor 31b sequentially to the negative electrode side terminal 11n of the DC power supply 11. From the seventh closed circuit L7 that circulates and the ground fault occurrence position 11np in the DC power source 11, the ground fault resistance RLnp and the negative-side constant current source 34b are sequentially distributed to To the negative terminal 11n of the power source 11, and the eighth closed circuit L8 current I of the current value I1 or the current value I2 that varies according to the on / off state of the switch 48b is reflux was formed.

That is, when a ground fault occurs in the DC power supply 11, the voltage V2 (I1) and the voltage V2 (I2) detected by the positive voltage detector 35a connected in parallel to the positive detection resistor 33a. For example, as shown in the following formula (7), the ground fault resistance RLpn can be described as a value independent of the voltage Va between the positive terminal 11p and the ground fault occurrence position 11np, and further, the negative side Based on the voltage V4 (I1) and the voltage V4 (I2) detected by the negative voltage detector 35b connected in parallel to the detection resistor 33b, for example, as shown in the following formula (8), the ground fault occurrence position 11np Ru can be described grounding resistor RL np as a value that does not depend on the voltage Vb between the negative terminal 11n.
The right side of the following formula (7) is equivalent to the right side of the formula (3), and the right side of the following formula (8) is equivalent to the right side of the formula (6).

When the control unit 23 sets the positive side switching element 32a of the positive side circuit 21 or the negative side switching element 32b of the negative side circuit 22 to the on state during the execution of the ground fault detection process, the DC power source 11 It is grounded by being connected to, for example, a vehicle body via the side protection resistor 31a and the positive electrode side detection resistor 33a, or via the negative electrode side protection resistor 31b and the negative electrode side detection resistor 33b.
For this reason, the control part 23 sets the positive electrode side switching element 32a to an OFF state, when the electric current which flows into the positive electrode side protection resistance 31a and the positive electrode side detection resistance 33a exceeds a predetermined electric current value, and becomes large excessively. An off signal that outputs an off signal and sets the negative side switching element 32b to an off state when the current flowing through the negative side protection resistor 31b and the negative side detection resistor 33b exceeds a predetermined current value and becomes excessively large. Is output.
That is, a predetermined protection voltage Vgate is set for the voltage value V2 of the output voltage generated at both ends of the positive electrode detection resistor 33a detected by the positive electrode voltage detector 35a, for example, no ground fault has occurred. As in the case, when the ground fault resistances RLn and RLnp are relatively large, the voltage value V2 of the output voltage is set so as not to exceed the protection voltage Vgate. Similarly, the voltage value V4 of the output voltage generated at both ends of the negative electrode side detection resistor 33b detected by the negative electrode side voltage detector 35b is set so as not to exceed a predetermined protection voltage Vgate.

The control unit 23 determines whether or not a ground fault has occurred on the positive or negative side of the DC power supply 11 or inside the DC power supply 11 based on the above formulas (3), (6), (7), and (8). Determine.
If it is determined that a ground fault has occurred, the determination result is output to, for example, an alarm device (not shown).

  The ground fault detection apparatus 10 according to the present embodiment has the above-described configuration. Next, the operation of the ground fault detection apparatus 10 will be described with reference to the accompanying drawings.

First, for example, in step S01 shown in FIG. 10, the positive side circuit 21 is set to an on state and the negative side circuit 22 is set to an off state. Thus, for example, at time t1 shown in FIG. 11, the positive side switching element (S1) 32a and the switching element (S2) 42a are turned on, and the negative side switching element (S3) 32b and the switching element (S4) 42b are turned on. Is turned off.
In step S02, for example, at time t1 shown in FIG. 11, the switch (S5) 48a of the positive-side constant current source 34a is turned off to output the current I having the current value I1 from the positive-side constant current source 34a. The voltage V2 (I1) is detected by the positive voltage detector 35a connected in parallel to the positive detection resistor 33a. The detection result of the positive voltage detector 35a is AD-converted by an AD converter (not shown) at time t2 to time t3 shown in FIG. 11, for example.
Next, in step S03, for example, at time t3 shown in FIG. 11, the switch (S5) 48a of the positive-side constant current source 34a is switched from the off state to the on state, and output from the positive-side constant current source 34a. The current I is switched from the current value I1 to the current value I2.
In step S04, the voltage V2 (I2) is output by the positive voltage detector 35a connected in parallel to the positive detection resistor 33a in a state where the current I having the current value I2 is output from the positive constant current source 34a. Is detected. The detection result of the positive voltage detector 35a is AD converted by an AD converter (not shown), for example, from time t4 to time t5 shown in FIG.
In step S05, the ground fault resistance RLn of the ground fault generated on the negative electrode side of the DC power source 11 is calculated based on the formula (3).

Next, in step S06, the negative side circuit 22 is set to an on state and the positive side circuit 21 is set to an off state. Accordingly, for example, at time t5 shown in FIG. 11, the positive side switching element (S1) 32a and the switching element (S2) 42a are turned off, and further, for example, at time t6 shown in FIG. 11, the negative side Switching element (S3) 32b and switching element (S4) 42b are turned on.
Next, in step S07, for example, at time t6 shown in FIG. 11, the switch 48b of the negative-side constant current source 34b is turned off to output the current I having the current value I1 from the negative-side constant current source 34b. The voltage V4 (I1) is detected by the negative voltage detector 35b connected in parallel to the side detection resistor 33b. The detection result of the negative voltage detector 35b is AD converted by an AD converter (not shown) at time t7 to time t8 shown in FIG. 11, for example.
Next, in step S08, for example, at time t8 shown in FIG. 11, the switch 48b of the negative side constant current source 34b is switched from the off state to the on state, and the current I output from the negative side constant current source 34b is changed. The current value I1 is switched to the current value I2.
In step S09, the voltage V4 (I2) is output by the negative voltage detector 35b connected in parallel to the negative detection resistor 33b while the current I having the current value I2 is output from the negative constant current source 34b. Is detected. The detection result of the negative voltage detector 35b is AD-converted by an AD converter (not shown), for example, from time t9 to time t10 shown in FIG.
In step S10, the ground fault resistance RLp of the ground fault generated on the positive electrode side of the DC power supply 11 is calculated based on the above formula (6).

In step S11, it is determined whether or not the negative side ground fault resistance RLn is equal to or less than a predetermined determination threshold #R.
If this determination is “NO”, the flow proceeds to step S 15 described later.
On the other hand, if this determination is “YES”, the flow proceeds to step S12.
In step S12, it is determined whether the positive side ground fault resistance RLp is equal to or less than a predetermined determination threshold value #R.
If the determination result in step S12 is “NO”, the process proceeds to step S13, where it is determined that a ground fault has occurred on the negative electrode side of the DC power supply 11, and the series of processing ends.
On the other hand, if the determination result in step S12 is “YES”, the process proceeds to step S14, where it is determined that a ground fault has occurred in the DC power supply 11, and the series of processes is terminated.
In step S15, it is determined whether or not the positive side ground fault resistance RLp is equal to or less than a predetermined determination threshold #R.
If the determination result in step S12 is “YES”, the process proceeds to step S16, where it is determined that a ground fault has occurred on the positive electrode side of the DC power supply 11, and the series of processes is terminated.
On the other hand, if the determination result in step S12 is “NO”, the process proceeds to step S17, where it is determined that no ground fault has occurred, and the series of processes is terminated.

The switching elements 32a, 42a, 32b, 42b and the switches 48a, 48b described above are executed in durations of ON / OFF states, time required for AD conversion, for example, from time t10 to time t11 shown in FIG. The time required for the determination processing in steps S11 to S17 described above can be set to an appropriate length.
Further, in the above-described series of processing from step S01 to step S17, first, the positive side circuit 21 is turned on and then the negative side circuit 22 is turned on. However, the present invention is not limited to this. The circuit 22 may be turned on, and then the positive side circuit 21 may be turned on.

As described above, according to the ground fault detection device 10 according to the present embodiment, it is possible to detect a ground fault occurring on the positive electrode side or the negative electrode side of the DC power source 11 or inside the DC power source 11, and the position of the ground fault occurrence is determined. By acquiring, for example, work for eliminating the generated ground fault can be easily performed, and an appropriate response to the generated ground fault can be performed.
In addition, a detection result that does not depend on the output voltage of the DC power source 11 can be obtained, and a ground fault can be detected with high accuracy.

It is a lineblock diagram of vehicles carrying a ground fault detection device concerning one embodiment of the present invention. It is a block diagram of the positive electrode side circuit of the ground fault detection apparatus shown in FIG. It is a block diagram of the negative electrode side circuit of the ground fault detection apparatus shown in FIG. It is a block diagram of the positive electrode side constant current source shown in FIG. It is a block diagram of the negative electrode side constant current source shown in FIG. It is a figure which shows an example in case the ground fault of the ground fault resistance RLn has generate | occur | produced in the negative electrode side of DC power supply. It is a figure which shows an example in case the ground fault of the ground fault resistance RLp has generate | occur | produced in the positive electrode side of DC power supply. It is a figure which shows an example in case the ground fault of the ground fault resistance RLnp has generate | occur | produced in DC power supply. It is a figure which shows an example in case the ground fault of the ground fault resistance RLnp has generate | occur | produced in DC power supply. It is a flowchart which shows operation | movement of the ground fault detection apparatus shown in FIG. It is a timing chart which shows operation | movement of the ground fault detection apparatus shown in FIG.

Explanation of symbols

10 Ground fault detection device 11 Ungrounded DC power supply 11p Positive terminal (positive terminal)
11n Negative terminal (negative terminal)
12 Motor 20 Grounding part 21 Positive side circuit (Positive side ground fault detection circuit)
22 Negative circuit (negative ground fault detection circuit)
23 Control unit (ground fault resistance detection means)
32a Positive side switching element (switching element)
32b Negative side switching element (switching element)
33a Positive side detection resistor (ground fault detection resistor)
33b Negative electrode side detection resistor (ground fault detection resistor)
34a Positive current source (constant current source)
34b Negative current source (constant current source)
35a Positive side voltage detector 35b Negative side voltage detector Step S03, Step S08 Current value changing means Step S05, Step S10 Ground fault resistance value detecting means Step S11, Step S12, Step S15 Abnormality detecting means Step S13, Step S14, Step S16 Ground fault determination means

Claims (2)

Connect each positive-side ground fault detection circuit and negative-side ground fault detection circuit, which consists of a series circuit consisting of a ground fault detection resistor and protective resistance, and a constant current source in parallel to each positive terminal of the ungrounded DC power supply and ground. And a ground fault detection device connected between the negative terminal and the ground,
An abnormality detection means for detecting the presence or absence of an abnormal state for each of the positive ground fault detection circuit and the negative ground fault detection circuit;
When the abnormality detection means detects the occurrence of an abnormal state in the positive ground fault detection circuit, a ground fault has occurred in the negative line connected to the negative terminal of the non-grounded DC power supply. Judgment,
When the abnormality detection means detects the occurrence of an abnormal state in the negative ground fault detection circuit, a ground fault has occurred in the positive line connected to the positive terminal of the non-grounded DC power supply. Judgment,
When the abnormality detection means detects the occurrence of an abnormal state in the positive ground fault detection circuit and the negative ground fault detection circuit, it is determined that a ground fault has occurred in the non-grounded DC power source. A ground fault determination means; and a protection means for cutting off a connection between the ground fault detection resistor and the protection resistor when a voltage generated at both ends of the ground fault detection resistor exceeds a predetermined protection voltage. A ground fault detection device. Connect each positive-side ground fault detection circuit and negative-side ground fault detection circuit, which consists of a series circuit consisting of a ground fault detection resistor and protective resistance, and a constant current source in parallel to each positive terminal of the ungrounded DC power supply and ground. And a ground fault detection device connected between the negative terminal and the ground,
Current value changing means for changing the current value of the current output from the constant current source;
Based on the change in the voltage across the terminals of the ground fault detection resistor when the current value is changed by the current value changing means, the negative line connected to the negative terminal of the non-grounded DC power source or the A ground fault resistance value detecting means for detecting a ground fault resistance value related to a ground fault generated in the positive line connected to the positive terminal of the non-grounded DC power source or in the non-grounded DC power source, and the ground fault detection A ground fault detection device comprising: protection means for cutting off a connection between the ground fault detection resistor and the protection resistor when a voltage generated at both ends of the resistor exceeds a predetermined protection voltage .

Images