JP2010063294A - Power conversion apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power conversion apparatus which is configured to discharge electric charges of a capacitor when the level of a charge voltage in the capacitor exceeds an excess voltage level, and is smaller in size, weight, and cost than a conventional power conversion apparatus. <P>SOLUTION: When an excess voltage detecting means 20 detects an excess voltage at the capacitor 5, an excess voltage detection signal Sov stops the operation of a power converter 3 and turns off a line breaker 4 and a power route interrupting switching element 9. Meanwhile, an excess voltage suppressing means 30 calculates an inductive voltage Vm at a synchronizer 2, and then turns on an excessive voltage suppressing switching element 7 to discharge accumulated electric charges from the capacitor 5 only when a charge voltage Vc at the capacitor 5 detected by a voltage detecting means 10 is larger than the inductive voltage Vm and the excess voltage detection signal Sov is output. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power converter for driving a synchronous machine used in an electric vehicle such as an electric vehicle or an electric vehicle, and more particularly to a power converter capable of dealing with an induced voltage of the synchronous machine during high-speed operation. About.

  Conventionally, in this type of power conversion device used for an electric vehicle or the like, AC power collected from an overhead line via a pantograph is converted into DC power by a converter. Alternatively, direct current power is collected directly from the pantograph. The DC power is input to the power converter through an energy storage capacitor for suppressing fluctuations in the power supply voltage. The DC power input to the power converter is converted to AC power having a variable voltage and a variable frequency by the power converter and supplied to the permanent magnet type synchronous machine.

  Here, since the synchronous machine has a built-in permanent magnet, it always induces an electromotive force even during rotation. This induced voltage increases in proportion to the speed, and when the electric vehicle is traveling at a high speed, an induced voltage exceeding the power supply voltage is generated. For this reason, the driving torque of the synchronous machine is controlled by performing so-called weakening magnetic field control that controls the current of the synchronous machine together with this induced voltage with a power converter during power running, and the brake torque of the synchronous machine is controlled during regeneration. I have control.

  On the other hand, the voltage of the energy storage capacitor may exceed the overvoltage level due to fluctuations in the power supply voltage when AC power is converted into DC power by the converter. In this way, when the voltage of the capacitor exceeds the overvoltage level, the switching element constituting the discharging DC circuit connected in parallel with the capacitor is turned on so that the current flows, and the accumulated charge of the capacitor is discharged to discharge the capacitor. Suppression of voltage rise is performed.

  However, if the induced voltage of the synchronous machine becomes larger than the voltage of the capacitor along with the discharge of the capacitor to suppress this overvoltage, there is no impedance between the synchronous machine and the capacitor. Large currents may flow and damage the switching elements constituting the power converter.

  Therefore, in the prior art, a load contactor is provided between the power converter and the synchronous machine, and when the voltage of the capacitor exceeds the overvoltage level, the conversion operation of the power converter is stopped and the power converter and the synchronous machine are stopped. The load contactor between is opened (off) and the power line is cut off, so that regenerative energy does not flow into the capacitor even if the induced voltage exceeds the voltage of the capacitor (for example, Patent Document 1).

Japanese Patent Laid-Open No. 2000-50410 (page 6, FIG. 1)

  As described above, conventionally, when the voltage of the capacitor reaches an overvoltage level, the switching element of the discharge DC circuit is turned on to discharge the capacitor charge, thereby suppressing the voltage rise. Along with this, if the induced voltage of the synchronous machine becomes larger than the voltage of the capacitor, a large current may flow from the synchronous machine toward the power converter and damage the switching element. The power converter is disconnected.

  However, when a load contactor is provided between the power converter and the synchronous machine as in the prior art, this load contactor needs a large one to cut off a large current. There was a problem of being hindered and costly.

  The present invention has been made to solve the above-described problems, and has a configuration in which when a capacitor charging voltage exceeds an overvoltage level, a switching element of a discharging DC circuit is turned on to discharge a capacitor charge. Even in this case, it is not necessary to provide a load contactor between the synchronous machine and the power converter as in the prior art, and it is possible to provide a power converter that can be reduced in size, weight, and cost. Objective.

  In order to solve the above-described problems, the present invention includes a power converter that converts DC power into AC power and outputs the AC power to a synchronous machine, and an energy storage capacitor is connected to the DC side of the power converter. In addition, in the power converter in which a discharge series circuit including an overvoltage suppression resistor and an overvoltage suppression switching element is connected in parallel with the capacitor, and a circuit breaker is connected to the power supply side of the discharge series circuit, The following configuration is adopted.

  That is, in the present invention, a power path intermittent switching element for turning on / off a DC power supply path between the capacitor and the power converter, a voltage detection means for detecting a charging voltage of the capacitor, and the voltage detection means An overvoltage detection signal that stops the operation of the power converter and turns off both the circuit breaker and the power path intermittent switching element when the voltage detected in step S is equal to or higher than a preset overvoltage set value. Overvoltage detection means for outputting the induced voltage of the synchronous machine, the detected voltage of the voltage detection means is larger than the calculated induced voltage, and the overvoltage detection signal is output from the overvoltage detection means. The overvoltage suppression switching element is turned on to output an overvoltage suppression signal for discharging the charge of the capacitor. It is characterized in that it comprises a control means.

  According to the present invention, when an overvoltage of the capacitor is detected by the overvoltage detection means, the operation of the power converter is stopped by outputting an overvoltage detection signal, and the circuit breaker and the switching element for interrupting the power path are provided. When the induced voltage of the synchronous machine is calculated by the overvoltage suppressing means, the voltage detected by the voltage detecting means is larger than the calculated induced voltage, and the overvoltage detection signal is output. The overvoltage suppressing switching element is turned on to discharge the capacitor charge.

  In other words, conventionally, when an overvoltage of a capacitor is detected, the load contactor provided between the synchronous machine and the power converter is unconditionally opened to cut off the power line between the synchronous machine and the power converter. In the present invention, when the capacitor overvoltage is detected, the capacitor charge is discharged. In this case, the induced voltage of the synchronous machine is monitored. However, since the charge of the capacitor is discharged so that the voltage of the capacitor does not fall below the induced voltage, there is no possibility that a large current flows from the synchronous machine to the power converter and damages the switching element. For this reason, the load contactor conventionally provided between a synchronous machine and a power converter can be made unnecessary, and there exists a remarkable effect that size reduction, weight reduction, and cost reduction of a power converter device are realizable. .

Embodiment 1 FIG.
FIG. 1 is a configuration diagram illustrating a power conversion device according to Embodiment 1 of the present invention.
The power conversion device according to the first embodiment converts three-phase switching elements Gu, Gv, Gw, Gx, Gy, Gz that convert DC power supplied from the DC power source 1 into AC power and output the same to the synchronous machine 2. A power converter (inverter) 3 having An energy storage capacitor 5 is connected to the DC side of the power converter 3, and an overvoltage suppressing resistor 6 and a thyristor 7 serving as an overvoltage suppressing switching element are connected in parallel with the capacitor 5. A series circuit 8 is connected. A current breaker 4 is provided between the positive electrode side of the DC power supply 1 and the high voltage side of the capacitor 5. In this example, the synchronous machine 2 is composed of a permanent magnet type synchronous machine that creates a field with a permanent magnet attached to a rotor. Further, if the thyristor 7 is used as an overvoltage suppressing switching element, there is an advantage that the overvoltage can be suppressed at a low cost.

  Further, between the capacitor 5 and the power converter 3, there is a power path intermittent switching element 9 composed of a self-extinguishing element such as an IGBT for turning on / off the DC power supply path. The voltage detection means 10 for detecting the charging voltage Vc of the capacitor 5 is further provided for the synchronous machine 2, and the rotation speed detection means 11 for detecting the rotation speed is provided.

  Furthermore, in the first embodiment, an overvoltage detection means 20 and an overvoltage suppression means 30 are provided.

  Here, the overvoltage detection means 20 stops the operation of the power converter 3 when the charging voltage Vc of the capacitor 5 detected by the voltage detection means 10 is equal to or higher than a preset overvoltage set value Vsh (Vc ≧ Vsh). And an overvoltage detection signal Sov for turning off both the circuit breaker 4 and the power path intermittent switching element 9 is output, and includes an overvoltage set value setting means 21 and a comparator 22.

  In this case, the overvoltage set value setting means 21 is preset with an overvoltage set value Vsh that serves as a reference value from which it can be determined that the capacitor 5 is overvoltage. Further, the comparator 22 compares the overvoltage set value Vsh given from the overvoltage set value setting means 21 with the charging voltage Vc of the capacitor 5 detected by the voltage detecting means 10, and the charging voltage Vc is equal to or higher than the overvoltage set value Vsh ( When Vc ≧ Vsh), the overvoltage detection signal Sov is output to the power converter 3, the circuit breaker 4, and the power path intermittent switching element 9, respectively. The comparator 22 has a latch function and maintains the output of the overvoltage detection signal Sov until a restart signal for the power converter 3 is given from a controller (not shown).

  On the other hand, the overvoltage suppression means 30 calculates the induced voltage Vm of the synchronous machine 2 based on the information on the rotational speed ω of the synchronous machine 2 detected by the rotational speed detecting means 11, and detects the voltage from the calculated induced voltage Vm. When the charging voltage Vc detected by the means 10 is large (Vc> Vm) and the overvoltage detection signal Sov is output from the overvoltage detection means 20, the overvoltage suppression switching element 7 is turned on to charge the capacitor 5 The overvoltage suppression signal Scc for discharging the signal is output, and includes an induced voltage calculation means 31, a comparator 32, and an AND gate 33.

  In this case, the induced voltage calculating means 31 calculates and outputs the induced voltage Vm of the synchronous machine 2 based on the information on the rotational speed ω of the synchronous machine 2 detected by the rotational speed detecting means 11. That is, the induced voltage calculation means 31 uses the value of the maximum value φf of the armature linkage flux by the permanent magnet, which is a predetermined constant determined from the rotational speed ω of the synchronous machine 2 and the characteristics of the synchronous machine 2, for example, The induced voltage Vm of the synchronous machine 2 is calculated from the equation (1). Instead of using equation (1), it is also possible to use a table memory in which data indicating the relationship between the rotational speed ω and the induced voltage Vm is registered in advance. In addition, the induced voltage Vm of the synchronous machine 2 may exceed the voltage Vdc of the DC power supply 1 but does not become larger than the overvoltage set value Vsh that is a criterion for determining the overvoltage of the capacitor 5.

  The comparator 32 compares the induced voltage Vm calculated by the induced voltage calculating means 31 with the charging voltage Vc of the capacitor 5 detected by the voltage detecting means 10, and the charging voltage Vc is the induced voltage Vm. Higher than (Vc> Vm), a high level gate open signal is output. The AND gate 33 outputs the overvoltage suppression signal Scc to the thyristor 7 of the discharging series circuit 8 when the gate open signal is output from the comparator 32 and the overvoltage detection signal Sov is output from the comparator 22 of the overvoltage detection means 20. Output to.

  Next, in the power conversion device having the above configuration, an operation when an overvoltage occurs in the capacitor 5 will be described with reference to a timing chart shown in FIG.

  In FIG. 2, since the voltage Vc of the capacitor 5 detected by the voltage detection means 10 is smaller than the overvoltage set value Vsh (Vc <Vsh) until the time t1 is reached, the comparator 22 of the overvoltage detection means 20 Does not output the overvoltage detection signal Sov. Accordingly, both the breaker 4 and the power path switching element 9 are turned on, and the power converter 3 performs a switching operation. Further, since the overvoltage detection signal Sov is not output from the comparator 22 of the overvoltage detection means 20, the overvoltage suppression signal Scc is not output from the AND gate 33 of the overvoltage suppression means 30, and therefore the thyristor 7 is in an off state. It has become.

  Next, when the charging voltage Vc of the capacitor 5 exceeds the overvoltage level, that is, the overvoltage set value Vsh (Vc ≧ Vsh) at time t1 due to fluctuations in the power supply voltage, the comparator 22 of the overvoltage detection means 20 An overvoltage detection signal Sov is output. With this overvoltage detection signal Sov, both the circuit breaker 4 and the power path intermittent switching element 9 are turned off, and the operation of the power converter 3 is also stopped. Thereby, even when the induced voltage Vm of the synchronous machine 2 becomes larger than the charging voltage Vc of the capacitor 5 due to the discharge accompanying the overvoltage detection of the capacitor 5, the regenerative energy from the synchronous machine 2 passes through the power converter 3. It is reliably prevented from flowing into the capacitor 5.

  At the time t1, the charging voltage Vc of the capacitor 5 is larger than the induced voltage Vm of the synchronous machine 2 (Vc> Vm), so that the comparator 32 of the overvoltage suppression means 30 outputs a high level gate open signal. Is output. Therefore, since the gate open signal is input from the comparator 32 to the AND gate 33 and the overvoltage detection signal Sov is input from the comparator 22 of the overvoltage detection means 20, the voltage suppression signal Scc is output from the AND gate 33. Is output and the signal Scc is applied to the thyristor 7 of the discharging series circuit 8. As a result, the thyristor 7 is turned on, so that the accumulated charge in the capacitor 5 is discharged through the overvoltage suppressing resistor 6 and the thyristor 7, and the charging voltage Vc of the capacitor 5 gradually decreases.

  When the charging voltage Vc of the capacitor 5 coincides with the induced voltage Vm of the synchronous machine 2 at time t2, the high level gate opening signal is not output from the comparator 32 of the overvoltage suppressing means 30. As a result, the output of the voltage suppression signal Scc from the AND gate 33 is stopped, whereby the thyristor 7 is turned off and the discharge of the capacitor 5 is stopped. At this time, the charging voltage Vc of the capacitor 5 is lowered to a voltage level at which the power converter 3 can be activated.

  Thereafter, when a restart signal is given to the comparator 22 of the overvoltage detection means 20 from a controller (not shown) in order to restart the power converter 3 at time t3, the comparator 22 is unlatched to detect the overvoltage. The output of the signal Sov is stopped. In response to this, both the current breaker 4 and the power path intermittent switching element 9 are turned on, and the operation of the power converter 3 is resumed. As a result, the supply of DC power from the DC power source 1 to the power converter 3 is resumed via the circuit breaker 4 and the power path intermittent switching element 9, and the DC power of the power converter 3 has a predetermined frequency. Converted to voltage.

  As described above, in the first embodiment, when an overvoltage of the capacitor 5 is detected, the thyristor 7 is turned on to discharge the charge of the capacitor 5. At this time, the rotational speed detecting means 11 and the overvoltage are discharged. The induced voltage Vm of the synchronous machine 2 is monitored with the suppression means 30 so that the charging voltage Vc of the capacitor 5 does not fall below the induced voltage Vm. When the charging voltage Vc matches the induced voltage Vm, the capacitor 5 Since the discharge is stopped, there is no fear that a large current flows from the synchronous machine 2 toward the power converter 3 to damage the switching element. For this reason, the load contactor conventionally provided between the synchronous machine 2 and the power converter 3 can be made unnecessary, and the power converter can be reduced in size, weight, and cost. Further, since it is possible to prevent the electric power from flowing backward, an effect of preventing generation of unnecessary brake torque can be obtained.

  In the first embodiment, DC power is supplied from the DC power source 1 to the power converter 3. However, as shown in FIG. 3, PWM that converts AC power supplied from the AC power source 12 into DC power. Of course, the same effect can be obtained even in the case of a configuration including the rectifier circuit 13 such as a converter for performing control (pulse width modulation control).

Embodiment 2. FIG.
FIG. 4 is a configuration diagram showing a power conversion device according to the second embodiment of the present invention, and components corresponding to those in the first embodiment shown in FIG.

  The feature of the second embodiment is that, in the overvoltage suppressing means 30, a predetermined value is added to the value of the induced voltage Vm calculated by the motor calculating means 31 between the induced voltage calculating means 31 and the comparator 32. The adder 34 is provided. In this case, the predetermined value added to the induced voltage Vm by the adder 34 is an appropriate value in the range of 1% to 5% of the voltage Vdc of the DC power supply 1. Therefore, the adder 34 outputs Vm1 = Vm + Vdc × k (where 0.01 ≦ k ≦ 0.05).

  The grounds are as follows. The inventors of the present invention are the sum of the on-voltage due to the on-resistance of the switching elements Gu, Gv, Gw, Gx, Gy, and Gz constituting the power converter 3 and the on-voltage due to the on-resistance of the switching element 9 for power path interruption. Is found to be 1% or more and 5% or less of the voltage Vdc of the DC power supply 1.

Therefore, as shown in the timing chart of FIG. 5, the charging voltage Vc is higher than the induced voltage Vm by Vdc × k at the time of discharging accompanying the overvoltage detection of the capacitor 5 (time t1 to t2 in FIG. 5). As long as discharging is allowed, the charging voltage Vc of the capacitor 5 can be reliably kept at a level always higher than the induced voltage Vm of the synchronous machine 2, and current flows from the synchronous machine 2 toward the power converter 3. Can be reliably prevented.
Since other configurations and operational effects are the same as those of the first embodiment, detailed description thereof is omitted here.

  As described above, in the second embodiment, as in the first embodiment, the regenerative energy from the synchronous machine 2 flows into the capacitor 5 via the power converter 3 when discharging due to the overvoltage detection of the capacitor 5. Therefore, there is no need to provide a load contactor between the synchronous machine 2 and the power converter 3 as in the prior art, and the power converter can be reduced in size, weight and cost. Moreover, since it is possible to prevent the electric power from flowing backward, unnecessary brake torque can be prevented from being generated at the same time.

  In particular, in the second embodiment, the on-voltage due to the on-resistance of the switching elements Gu, Gv, Gw, Gx, Gy, Gz constituting the power converter 3 and the on-voltage due to the on-resistance of the switching element 9 for power path interruption Therefore, when comparing the charging voltage Vc of the capacitor 5 with the voltage Vm1 when the capacitor 5 is discharged, the margin is always larger than the induced voltage Vm by Vdc × k. Vc> Vm is compensated for and the regenerative energy of the synchronous machine 2 can be more reliably prevented from flowing into the capacitor 5 via the power converter 3 as compared with the first embodiment.

Embodiment 3 FIG.
FIG. 6 is a block diagram showing a power conversion device according to Embodiment 3 of the present invention, and the same reference numerals are given to the components corresponding to those of Embodiment 2 shown in FIG.

  In the third embodiment, the rotation speed detecting means 11 for detecting the rotation speed of the synchronous machine 2 as shown in the first and second embodiments is not provided, and instead, the synchronous machine 2 and the power converter 3 are provided. Between the two, line voltage detecting means 14a and 14b are provided. The overvoltage suppressing means 30 is a three-phase / αβ converting means 35 for converting the line voltages Vuv and Vvw (three-phase AC voltage) detected by the line voltage detecting means 14a and 14b into two-phase AC voltages Vα and Vβ. The induced voltage calculation means 31 calculates the voltage effective value Vm of the synchronous machine 2 based on the two-phase AC voltages Vα and Vβ, and outputs this as the induced voltage of the synchronous machine 2. Yes.

  That is, one of the line voltage detecting means 14 a detects the line voltage Vuv between the UVs of the synchronous machine 2. The other line voltage detecting means 14b detects the line voltage Vuv between the VWs of the synchronous machine 2.

  The line voltages Vuv and Vuv detected by the line voltage detection means 14 a and 14 b are input to the three-phase / αβ conversion means 35. The line voltages Vuv and Vvw input to the three-phase / αβ conversion means 35 are converted into two-phase AC voltages Vα and Vβ by the following equation (2).

  Note that the three-phase AC voltages Vuv and Vvw (or Vu, Vv, and Vw) are converted into the two-phase AC voltages Vα and Vβ by the equation (2). At this time, the three-phase AC coordinates (uv) shown in FIG. -W) Conversion is performed from the system using the relationship of the two-phase AC coordinates (α-β).

  Next, the induced voltage calculation means 31 calculates the effective value Vm of the line voltage of the synchronous machine 2 from the α-axis voltage Vα and the β-axis voltage Vβ calculated by the three-phase / αβ conversion means 35 according to the following equation (3): Calculated by

The effective value Vm of the line voltage calculated by the induced voltage calculating means 31 is input to the comparator 32 as an induced voltage in the synchronous machine 2. Subsequent operations are the same as those in the second embodiment.
In addition, since other configurations and operational effects in the third embodiment are the same as those in the second embodiment, detailed description thereof is omitted here.

  As described above, in the third embodiment, similar to the second embodiment, the regenerative energy from the synchronous machine 2 passes through the power converter 3 through the power converter 3 when discharging due to the overvoltage detection of the capacitor 5. Therefore, there is no need to provide a load contactor between the synchronous machine 2 and the power converter 3 as in the prior art, and the power converter can be reduced in size, weight and cost. it can. Moreover, since it is possible to prevent the electric power from flowing backward, unnecessary brake torque can be prevented from being generated at the same time.

  In particular, in the third embodiment, by providing the line voltage detecting means 14a and 14b, the rotational speed detecting means 11 as in the first and second embodiments is not required. In general, the rotational speed detecting means 11 is more expensive than the line voltage detecting means 14a, 14b. Therefore, the cost of the apparatus can be further reduced by using the line voltage detecting means 14a, 14b.

Embodiment 4 FIG.
FIG. 8 is a block diagram showing a power conversion device according to Embodiment 4 of the present invention, and the same reference numerals are given to the components corresponding to those of Embodiment 1 shown in FIG.

  The feature of the fourth embodiment is that the power path intermittent switching element 9 is not provided between the power converter 3 and the capacitor 5 as in the first embodiment, but instead, in the discharge series circuit 8. A self-extinguishing element such as an IGBT is used as the overvoltage suppressing switching element 7 constituting the circuit 8.

  The reason is as follows. When the power path intermittent switching element 9 provided between the power converter 3 and the capacitor 5 as shown in the first embodiment is omitted, regenerative energy flows transiently from the power converter 3 into the capacitor 5. At this time, even when a current exceeding the capacity flows through the overvoltage suppressing resistor 6 of the discharging series circuit 8, it is necessary to reliably turn off the path. Therefore, in the fourth embodiment, an IGBT, GTO, or the like that can reliably perform the on / off operation without being influenced by the magnitude of the flowing current, instead of providing a thyristor as the overvoltage suppressing switching element 7. A self-extinguishing element such as a MOSFET is used.

Furthermore, in the fourth embodiment, current detection means 16 is provided between the synchronous machine 2 and the power converter 3 to monitor the current flowing from the synchronous machine 2 through the power converter 3 into the capacitor 5. Further, the overvoltage suppressing means 30 is provided with a comparator 36 and an AND gate 37 in addition to the configuration of the first embodiment, and the current Iu detected by the current detecting means 16 becomes the capacitance of the overvoltage suppressing resistor 6. When the reference value is larger than a reference value Imax set in advance (Iu ≧ Imax), the overvoltage suppression signal Scc applied to the overvoltage suppression switching element 7 is forcibly cut off to turn off the switching element 7. ing. The comparator 36 and the AND gate 37 correspond to the gate means in the claims.
Since other configurations are the same as those in the first embodiment, detailed description thereof is omitted here.

  In the above configuration, the current Iu detected by the current detection unit 16 is input to the overvoltage suppression unit 30. The comparator 36 compares the current Iu detected by the current detection means 16 with a reference value Imax set in advance based on the capacity of the overvoltage suppressing resistor 6.

  At this time, when the current Iu detected by the current detection means 16 is smaller than the reference value Imax (Iu <Imax), it indicates that no current flows from the synchronous machine 2 to the capacitor 5, so the comparator 37 is Outputs a high level gate open signal. Thereby, the gate of the AND gate 37 is opened. At this time, when the overvoltage suppression signal Scc is output from the preceding AND gate 33 (between times t1 and t2 in FIG. 9), the overvoltage suppression signal Scc is The signal passes through the gate 37 and is given to the overvoltage suppressing switching element 7. As a result, the overvoltage suppressing switching element 7 is turned on, and the charge of the capacitor 5 is discharged.

  On the other hand, when the current Iu detected by the current detection means 16 is larger than the reference value Imax (Iu ≧ Imax), the current may flow from the synchronous machine 2 to the capacitor 5 via the power converter 3. There is. Therefore, the comparator 36 outputs a low level gate closing signal. As a result, the gate of the AND gate 37 is closed, so that the overvoltage suppression signal Vcc is not output, whereby the overvoltage suppression switching element 7 is turned off.

  As described above, in the fourth embodiment, as in the first embodiment, the regenerative energy from the synchronous machine 2 is transferred to the capacitor 5 via the power converter 3 when discharging due to the overvoltage detection of the capacitor 5. Therefore, there is no need to provide a load contactor between the synchronous machine 2 and the power converter 3 as in the prior art, and the power converter can be reduced in size, weight and cost. it can. Moreover, since it is possible to prevent the electric power from flowing backward, unnecessary brake torque can be prevented from being generated at the same time.

  In particular, in the fourth embodiment, the current detection unit 16 is provided, the overvoltage suppression unit 30 is provided with the comparator 36 and the AND gate 37, and the current Iu detected by the current detection unit 16 is the overvoltage suppression resistor 6. When the reference value Imax is larger than a preset reference value Imax based on the capacity of the current (Iu ≧ Imax), the overvoltage suppression signal Scc applied to the overvoltage suppression switching element 7 is forcibly cut off to turn off the switching element 7 Therefore, it is possible to reliably prevent the power from flowing backward, and it is not necessary to provide a power path intermittent switching element between the power converter 3 and the capacitor 5. Since the switching element is generally more expensive than the current detection means 16, the use of the current detection means 16 can further reduce the cost of the device.

  In the fourth embodiment, the configuration in which the current detection unit 16, the comparator 36, and the AND gate 37 are added to the configuration described in the first embodiment has been described. Assuming the configuration of the second and third embodiments shown in FIGS. 4 and 6 (that is, the configuration in which the adder 34 is provided in the overvoltage suppression unit 30), the current detection unit 16, the comparator 36, and the AND gate A configuration to which 37 is added is also possible.

It is a block diagram which shows the power converter device in Embodiment 1 of this invention. It is a timing chart with which it uses for operation | movement description of the power converter device. It is a block diagram which shows the modification of the power converter device in Embodiment 1 of this invention. It is a block diagram which shows the power converter device in Embodiment 2 of this invention. It is a timing chart with which it uses for operation | movement description of the power converter device. It is a block diagram which shows the power converter device in Embodiment 3 of this invention. It is explanatory drawing which shows the relationship at the time of converting from a three-phase alternating current coordinate system to a two-phase alternating current coordinate. It is a block diagram which shows the power converter device in Embodiment 4 of this invention. It is a timing chart with which it uses for operation | movement description of the power converter device.

Explanation of symbols

1 DC power supply, 2 synchronous machine, 3 power converter (inverter), 4 circuit breaker,
5 capacitor, 6 overvoltage suppression resistor,
7 Overvoltage suppression switching element (thyristor, self-extinguishing element),
8 series circuit for discharge, 9 switching element for intermittent power path, 10 voltage detection means,
11 rotational speed detection means, 14a, 14b line voltage detection means, 16 current detection means,
20 overvoltage detection means, 30 overvoltage suppression means, Sov overvoltage detection signal,
Scc Overvoltage suppression signal.

Claims (6)

It has a power converter that converts DC power to AC power and outputs it to the synchronous machine. An energy storage capacitor is connected to the DC side of this power converter, and an overvoltage suppression resistor is connected in parallel with this capacitor. In the power conversion device in which a series circuit for discharge composed of switching elements for overvoltage suppression is connected, and a circuit breaker is connected to the power supply side of the series circuit for discharge,
A power path intermittent switching element for turning on / off a DC power supply path between the capacitor and the power converter, a voltage detection means for detecting a charging voltage of the capacitor, and a voltage detected by the voltage detection means An overvoltage detection means for outputting an overvoltage detection signal for stopping the operation of the power converter and turning off both the circuit breaker and the power path intermittent switching element when the overvoltage set value is higher than a preset value. When the induced voltage of the synchronous machine is calculated, the detected voltage of the voltage detecting means is larger than the calculated induced voltage, and the overvoltage detection signal is output from the overvoltage detecting means Overvoltage suppression means for turning on the overvoltage suppression switching element and outputting an overvoltage suppression signal for discharging the charge of the capacitor. Power converter according to claim. The power converter according to claim 1, wherein the overvoltage suppressing switching element is a thyristor. The power converter according to claim 1, wherein the overvoltage suppression unit calculates the induced voltage based on a rotation speed of the synchronous machine detected by a rotation speed detection unit. . 3. The electric power according to claim 1, wherein the overvoltage suppressing means calculates the induced voltage based on the line voltage of the synchronous machine detected by the line voltage detecting means. Conversion device. While omitting the switching element for interrupting the power path, the current detection means for detecting the current flowing through the synchronous machine is provided, and the current detected by the current detection means is preset in the overvoltage suppression means. 2. The power conversion according to claim 1, further comprising gate means for forcibly blocking an overvoltage suppression signal applied to the overvoltage suppression switching element when the value is larger than a value to turn off the switching element. apparatus. The power converter according to claim 5, wherein the overvoltage suppressing switching element is a self-extinguishing element.

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