JP6541622B2 - Power converter - Google Patents

Description

  The present invention relates to a power converter that drives a motor that is a load.

  The power converter includes, for example, an inverter circuit that converts a DC voltage into an AC voltage. The inverter circuit drives a motor which is a load, for example, by PWM (Pulse Width Modulation). When driving the motor by the PWM method, the inverter circuit applies a rectangular voltage to the motor. Hereinafter, in order to distinguish between the rectangular voltage generated by the inverter circuit and the voltage applied to the motor, the rectangular voltage generated by the inverter circuit is referred to as “inverter output voltage” and the voltage applied to the motor is “motor applied voltage”. It is called.

  The inverter output voltage is transmitted to the motor terminal through a cable which is an output wiring for connecting the output terminal of the inverter circuit and the motor terminal. At this time, since LC resonance is generated by the cable, the waveform of the voltage applied to the motor becomes a vibration waveform having an excessive peak. Such a vibration waveform attenuates after a certain amount of time. However, if a new motor applied voltage is applied before the previous motor applied voltage is completely damped, the original vibration is overlapped with a new vibration and the two are reinforced to cause an excessive voltage to be applied to the motor terminal. The The excessive voltage generated in this manner is referred to as a microsurge voltage.

  Patent Document 1 below describes the estimation of the cable length, which is the length of the cable, for the purpose of reducing the overvoltage applied to the load.

Unexamined-Japanese-Patent No. 2007-252190

  However, in the method of Patent Document 1, it is necessary to determine the optimum delay time which is the time interval for applying two voltage pulses based on the current value obtained by the current sensor. In Patent Document 1, a propagation time and a cable length of a voltage propagating in a cable are estimated using a predetermined optimal delay time. For this reason, in the method of patent document 1, the process which calculates optimal delay time is needed separately, and it was not able to estimate cable length simply and rapidly. Cable lengths vary greatly depending on the specifications of the customer, and it is also necessary to respond quickly to changes in the layout at the customer. Therefore, it has been required to simply and quickly estimate the cable length.

  This invention is made in view of the above, Comprising: It aims at obtaining the power converter device which can estimate cable length simply and rapidly.

  In order to solve the problems described above and achieve the object, a power conversion device according to the present invention includes a power conversion circuit, a measurement unit that measures a surge current flowing in a cable connecting the power conversion circuit and a motor, and a measurement unit A first operation unit is provided to calculate the cable length of the cable from the time difference between the measured rise time of the surge current and the fall time of the surge current.

  According to the present invention, the cable length can be easily and quickly estimated.

Block diagram showing the main configuration of the power conversion device according to the first embodiment Diagram showing example of microsurge voltage waveform when applying step voltage Diagram showing an example of microsurge voltage waveform at single pulse and step voltage application Diagram showing an example of PWM control that causes generation of microsurge voltage Figure showing an example of microsurge voltage reduction Diagram showing the concept of cable length calculation processing Flow chart of the first embodiment according to cable length calculation processing Diagram showing the concept of PWM control considering the cable length Diagram showing the concept of characteristic impedance calculation processing Flow chart of the first embodiment according to the characteristic impedance calculation process Flowchart of Embodiment 2 relating to cable length calculation processing during PWM driving Block diagram showing a main configuration of a power conversion device according to a third embodiment Block diagram showing a main configuration of a power conversion apparatus according to a fourth embodiment Block diagram showing a main configuration of a power conversion apparatus according to a fifth embodiment A block diagram showing an example of a hardware configuration for realizing the functions of a motor control operation unit and a cable characteristic operation unit according to first to fifth embodiments A block diagram showing another example of the hardware configuration for realizing the functions of the motor control calculation unit and the cable characteristic calculation unit in the first to fifth embodiments

  Below, the power converter concerning the embodiment of the present invention is explained in detail based on a drawing. The present invention is not limited by the following embodiments.

Embodiment 1
FIG. 1 is a block diagram showing the main configuration of the power conversion device according to the first embodiment. As shown in FIG. 1, the power conversion device 1 according to the first embodiment is a main circuit of the power conversion device 1 and measures an inverter circuit 2 which converts a DC voltage applied from a DC power supply 40 into an AC voltage, and A surge current waveform measurement unit 4 which is a second unit, a cable characteristic calculation unit 5 which is a first calculation unit, a motor control calculation unit 3 which is a second calculation unit, and a cable characteristic display unit 6 which is a display unit. Prepare. The power conversion device 1 and the motor 50 which is a load are connected via a cable 7. The power conversion device 1 PWM drives the motor 50 which is a load.

  The surge current waveform measurement unit 4 is disposed on the output side of the inverter circuit 2. The motor 50 shown in FIG. 1 is an example of a three-phase motor, and the cable 7 consists of three for the U phase, the V phase and the W phase. The surge current waveform measurement unit 4 detects the current flowing in each phase of the cable 7 connecting the inverter circuit 2 and the motor 50.

  The surge current waveform measurement unit 4 of the present embodiment is required to have an ability to accurately capture the surge current caused by the microsurge voltage. As described later, the surge current fluctuates in a short time of, for example, 1 us or less. For this reason, it is preferable to use a shunt method as the surge current waveform measurement unit 4. In addition, it is preferable to use a high-accuracy low resistance body for the detector of the surge current waveform measurement unit 4.

  The cable characteristic calculation unit 5 calculates the cable length of the cable 7 based on the surge current waveform measured by the surge current waveform measurement unit 4.

  The cable characteristic display unit 6 displays the cable length calculated by the cable characteristic calculation unit 5. In addition, a liquid crystal display unit is provided in a general inverter product. For this reason, the cable length information may be displayed by parameter operation using an existing display function without providing a new display unit.

  When the cable characteristic calculation unit 5 calculates the cable length, the motor control calculation unit 3 applies an output voltage to an arbitrary phase of the motor 50, that is, one of three phases. Further, the motor control calculation unit 3 performs control calculation for PWM driving the motor 50. Specifically, control calculation is performed by reflecting the information of the cable length calculated by the cable characteristic calculation unit 5 in PWM control, and a command signal based on the control calculation is generated and output to the inverter circuit 2.

  In FIG. 1, the surge current waveform measurement unit 4 is shown on the output side of the inverter circuit 2, that is, outside, but may be configured inside the inverter circuit 2. If a specific example is given, the form which mounts the low resistance body used as a detector in the inside of the power module which comprises the inverter circuit 2 can be considered. In addition, it is good also as a form mounted in the printed circuit board to which the power module was connected.

  A high frequency common mode noise current accompanying the switching operation of the inverter circuit 2 flows through the cable 7 between the inverter circuit 2 and the motor 50. Therefore, a filter for common mode noise reduction may be provided on the front stage of the surge current waveform measurement unit 4 so as not to be affected by the common mode noise current.

  Further, a control circuit such as a control power supply circuit of the inverter product and a control board has a circuit which performs switching operation at a higher speed than the inverter circuit 2. Therefore, high frequency noise is easily generated in the control circuit, and the inverter circuit 2 and the surge current waveform measurement unit 4 may be affected by the noise. Therefore, the surge current waveform measurement unit 4 and the circuit unit electrically connected to the surge current waveform measurement unit 4 have a structure to spatially or magnetically isolate from noise generation factors. Good. In addition, the method of covering the circumference | surroundings of the circuit part which wants to prevent the influence of noise as a specific example of a magnetic isolation structure with the metal structure which has a magnetic shielding performance is mentioned.

  Next, the microsurge voltage applied to the motor 50 will be described with reference to FIGS. 2 and 3. FIG. 2 is a diagram showing an example of a microsurge voltage waveform when a step voltage is applied. FIG. 3 is a diagram showing a waveform example of a microsurge voltage when a single pulse and a step voltage are applied. Note that Vdc in the figure is the power supply voltage, that is, the voltage of the DC power supply 40.

  As described in the background art section, the microsurge voltage is generated due to the LC resonance of the cable 7. Since the LC resonance of the cable 7 is the cause, as shown in FIG. 2, the microsurge voltage is also generated by the application of a single pulse. FIG. 2 shows that when the inverter output voltage of 300 V is applied, the peak of the waveform of the first wave in the motor applied voltage jumps to 576 V.

  Further, FIG. 3 shows a waveform in the case where after applying an inverter output voltage of 300 V for a period of about 1 μs, a rest time of about 1 μs is provided and then reapplied. As described in the background art section, when a new motor application voltage is applied before the motor application voltage applied earlier attenuates, both voltages overlap and strengthen each other, and the motor application voltage becomes excessive. The situation is shown. Specifically, FIG. 3 shows a state in which the peak of the motor applied voltage jumps up to 978 V immediately after the waveform of the inverter output voltage applied later.

  The microsurge voltage is generated due to an interval of PWM pulses (hereinafter referred to as "switching interval") and a cable length which control switching elements constituting the inverter circuit when performing PWM control of the inverter circuit.

  One of the measures to reduce the microsurge voltage is to make the switching intervals of each phase sufficiently wide. In FIG. 3, the time between the time when the single pulse voltage falls and the time when the step voltage rises is shown as t. If the time t is increased, the next voltage is applied after the voltage oscillation at the motor terminal is attenuated, and the microsurge voltage is less likely to occur. Therefore, the microsurge voltage can be reduced by widening the section of time t, that is, the section in which the inverter output voltage is zero.

  Next, the influence of the time t on the PWM operation will be described. FIG. 4 is a diagram showing an example of PWM control that causes generation of a microsurge voltage. FIG. 5 is a diagram showing an example of reduction of the microsurge voltage.

  The upper part of FIG. 4 shows a section in which the W phase is all off and the U phase and the V phase perform switching operation, and the V phase voltage command shows a crossing at the peak of the triangular wave which is the carrier wave. It is done. At this time, the line voltage U-V and the line voltage V-W become narrow pulse-like voltages. This narrow pulse-like voltage is a factor which shortens the time of the switching interval shown in FIG. Hereinafter, the narrow pulse-like voltage referred to here is abbreviated as "thin pulse".

  As described above, the generation of the microsurge voltage is caused by the generation of narrow pulses during PWM control. For this reason, it is understood that control may be performed to eliminate the narrow pulse. Specifically, as shown by hatching in FIG. 5, the peak portion of the triangular wave in the PWM control is made to be a prohibited area. The prohibited area is an area where the switching operation of the inverter circuit 2 is not permitted, in other words, an area where the switching operation is prohibited. By setting such a prohibited area, generation of a narrow pulse as shown in FIG. 4 can be avoided.

  However, when performing PWM control of microsurge voltage reduction as shown in FIG. 5, it is necessary to determine the magnitude of the allowable pulse width, that is, the lower limit value of the pulse width. On the other hand, to set the lower limit value of the pulse width, it is necessary to grasp the cable length in the installation environment. However, in general, the cables from the power conversion device to the motor are laid along complicated routes in the factory. For this reason, it was difficult to accurately grasp the cable length.

  Under the circumstances as described above, conventionally, the lower limit of the pulse width which causes no problem even with the maximum value (for example, 500 m long) of the cable length specification has been set. However, this means that the zero voltage level section is made larger than necessary. As a result, there is a problem that the section in which the voltage applied to the motor terminal is also zero becomes large and the motor causes uneven rotation.

  Next, the operation of the main part of the power conversion device according to the first embodiment will be described based on the flowchart of FIG. 7 with reference to the drawings of FIGS. 6 and 8 as appropriate. FIG. 6 is a diagram showing the concept of cable length calculation processing. In FIG. 6, the voltage applied to the motor is indicated by a broken line waveform, and the surge current flowing in the cable is indicated by a solid line waveform. Moreover, FIG. 7 is a flowchart which shows the processing flow which concerns on the calculation process of cable length. FIG. 8 is a diagram showing the concept of PWM control in consideration of the cable length.

  First, in step S101 of FIG. 7, the motor control calculation unit 3 applies a voltage to an arbitrary phase in the motor 50. The voltage applied to the motor 50 may be a step voltage as indicated by an alternate long and short dash line in FIG. At this time, as shown by the solid line in FIG. 6, a surge current waveform that rises in synchronization with the rising of the applied voltage is observed. For this reason, the application time of the voltage may be as short as the rise waveform of the first wave that rises first and the fall waveform of the same first wave are generated.

  In each of the next steps S102 and S103, the surge current waveform measurement unit 4 measures the rise time t1 of the first wave and the fall time t2 of the first wave. Furthermore, in the next step S104, the surge current waveform measurement unit 4 calculates the difference between the falling time t2 of the first wave and the rising time t1 of the first wave, that is, the time difference T1 in the surge current waveform shown in FIG. Do. The information on the time difference T1 calculated here is transmitted to the cable characteristic calculation unit 5.

  Here, since the first wave of the surge current is a trapezoidal wave as shown in FIG. 6, the start and end times at which the surge current reaches the peak value may be set as the rise time t1 and the fall time t2, respectively. However, the rise time t1 may be the rise time of the applied voltage. The falling time t2 may be a time when the applied voltage rises and falls to a current value equivalent to the current value at t1 when the rising time is t1. Further, the falling time t2 may be a time when the surge current becomes zero or a time when the surge current changes from a positive value to a negative value. Further, the rise time t1 and the fall time t2 may be set to times at which the current value is, for example, 90% of the current peak value.

  As described above, the rise time and the fall time may be determined in consideration of the surge current waveform, the sampling period of the current, and the like. The definition of the rise time and the fall time affects the error of the cable length obtained from the equation (1), and therefore, may be determined in the range in which the error of the cable length is acceptable.

  In the next step S105, the cable characteristic calculation unit 5 calculates the cable length from the time difference T1. Here, the equation for calculating the cable length is as follows.

  Cable length = time difference T1 × propagation speed / 2 (1)

The propagation speed in the above equation (1) is the speed at which the surge current is transmitted in the cable. This propagation speed is expressed by the following equation.
Propagation speed = light speed / ((effective relative permittivity of transmission line medium)
= Speed of light / ((relative permeability of transmission line medium × relative permittivity)

  In this embodiment, since the propagation velocity of the surge current is measured to be about half of the light velocity, the following equation (1a) can be used as the equation (1).

  Cable length = time difference T1 × (speed of light / 2) / 2 (1a)

  In the present embodiment, the propagation velocity may be calculated on the basis of about one half of the velocity of light as in the above equation (1a). Also, create a table in which the relative permeability and dielectric constant of the cable insulation material are stored beforehand according to the cable manufacturer and the wire size, select this relative permeability and relative permittivity, and calculate equation (1) Then, the calculation accuracy of the cable length is further improved.

  Furthermore, in the next step S106, the cable characteristic display unit 6 displays the cable length calculated by the cable characteristic calculation unit 5.

  As apparent from the above equation (1), in calculating the cable length in the case of using the present embodiment, it is only necessary to know the time difference T1 of the first wave in the surge current waveform, There is no need to apply a voltage pulse of For this reason, according to the method of the first embodiment, the cable length can be easily and quickly estimated.

  The motor control calculating unit 3 generates a command signal for PWM control using the information of the cable length calculated by the cable characteristic calculating unit 5. As described above, the microsurge voltage is easily generated when the switching command signal generated by the PWM control has a narrow pulse shape on the time axis. For this reason, in the motor control calculation unit 3, the cable length is reflected in the prohibited area so that the narrow pulse is not generated.

  Specifically, as shown in FIG. 8, the width of the prohibited area around the peak of the triangular wave is changed according to the cable length. Here, the “width of the prohibited area” referred to here is the width in the vertical axis direction in the hatched portion shown by hatching in FIG. The “width of the prohibited area” may be replaced with “the range of the voltage command value in which the switching operation is not permitted”.

  Returning to the explanation of FIG. 8, when the calculated cable length is long, as shown on the left side of the drawing, the width of the prohibited area is relatively enlarged. On the other hand, when the calculated cable length is short, as shown on the right side of the drawing, the width of the prohibited area is made relatively small. As shown in FIG. 8, when the cable length is short, the lower limit value of the pulse width can be reduced by narrowing the width of the prohibited area. By adjusting the width of the prohibited area according to the cable length, it is not necessary to set the switching interval larger than necessary even at the maximum value of the conventional wiring length specification such as 500 m, for example, and the voltage range usable in PWM control is expanded can do. Therefore, the voltage control rate in the power converter can be improved. In addition, since the section in which the voltage applied to the motor terminal is zero can be reduced, it is possible to suppress uneven rotation of the motor.

  As is apparent from the calculation formula of (1) above, in the method of the first embodiment, the cable length can be calculated from the information on the time difference T1 and the light velocity without using the information on the cable thickness. Even if the thickness of the cable changes, it is possible to apply uniformly.

  Although the cable length is determined in the flow of FIG. 7, the characteristic impedance may be determined together with the calculation of the cable length. The process of calculating the characteristic impedance will be described below with reference to FIGS. 9 and 10. FIG. 9 is a diagram showing the concept of characteristic impedance calculation processing. FIG. 10 is a flowchart showing a process flow relating to the process of calculating the characteristic impedance.

  First, in step S201 of FIG. 10, the motor control calculation unit 3 applies a voltage to any phase in the motor 50. The voltage applied to the motor 50 may be a step voltage as indicated by an alternate long and short dash line in FIG. At this time, as shown by the solid line in FIG. 9, a surge current waveform that rises in synchronization with the rising of the applied voltage is observed. For this reason, the application time of the voltage may be as short as the rise waveform of the first wave that rises first and the fall waveform of the same first wave are generated.

  In the next step S202, the surge current waveform measurement unit 4 measures the current peak I1 of the first wave. In the next step S203, the amplitude value V1 of the output voltage waveform when the current peak I1 occurs is measured. Since the amplitude value V1 of the output voltage waveform is a voltage value corresponding to the DC bus voltage in the inverter circuit 2, it can be grasped using the voltage measurement function originally provided in the inverter circuit 2. Information on the current peak I1 and the amplitude value V1 measured here is transmitted to the cable characteristic calculation unit 5.

  In the next step S204, the cable characteristic calculation unit 5 calculates the characteristic impedance Z using the following equation.

  Characteristic impedance Z = amplitude value V1 / current peak I1 (2)

  Then, in the next step S205, the cable characteristic display unit 6 displays the value of the characteristic impedance Z calculated by the cable characteristic calculation unit 5.

  In addition, the information of the calculated | required characteristic impedance Z turns into useful information for specification of a cable. If the information on the characteristic impedance Z is managed together with the information on the cable length, maintenance and management of the cable can be facilitated.

  As described above, according to the power conversion device according to the first embodiment, the cable length can be calculated using only the time difference T1 measured by the surge current waveform measurement unit 4 and the light speed. Can be done simply and quickly.

  Further, in the method of the first embodiment, the cable length which has conventionally been unknown or difficult to grasp can be easily calculated by electrical means, and the calculated cable length is applied to PWM control of the inverter. . Thereby, the switching interval at the time of PWM control of the inverter circuit can be made the necessary minimum interval according to the cable length, and the effects of suppression of the microsurge voltage and improvement of the voltage control rate can be enhanced. It becomes possible. That is, the switching interval at the time of performing PWM control can be made smaller than before, and the suppression of the microsurge voltage and the improvement of the voltage control rate can be realized.

  Conventionally, as for the cable length, as described above, a method of setting parameters such as the lower limit value of the pulse width which can correspond to the maximum specification of the cable length, and a long wiring mode which is an inverter operation mode corresponding to a long cable A method was arbitrarily used by the user. According to the first embodiment, it is not necessary for the user to set the long wiring mode, and it becomes possible to set parameters corresponding to the cable length.

  Further, according to the power conversion device according to the first embodiment, since the information of the cable length can be stored, it is possible to display on the display device at an arbitrary timing. This makes it possible to provide the necessary information to the maintenance personnel at the manufacturer or the site manager at an appropriate timing. In addition, if the information of cable length is managed for every installation or every model, maintenance management of a cable becomes easy. As a result, it is possible to stock a necessary length of cable, and it is not necessary to purchase extra wiring, and maintenance costs can be reduced.

  Conventionally, there is also a method of adding passive elements such as an inductor and a capacitor for microsurge voltage suppression. However, there is a concern that the size of the substrate or the case may be increased, which may lead to an increase in cost. Since the microsurge voltage can be suppressed by using this embodiment, it becomes possible to realize miniaturization of the passive element or to dispense with the passive element, which leads to cost reduction.

  Although the inverter circuit is used as the power conversion circuit in the present embodiment, the present invention can also be applied to a converter circuit.

  Further, although the driving method of PWM control according to the cable length has been described in the present embodiment, the filter (EMC filter, sine filter, dV / dt filter for overvoltage and leakage current is calculated by calculating the cable length in the present embodiment. It is also possible to adjust certain load parameters, such as the choice of) and stator resistance.

Second Embodiment
The first embodiment is an embodiment in which a voltage for calculation is applied when calculating the cable length and the characteristic impedance. On the other hand, even while the power conversion device 1 is performing PWM driving of the motor 50, calculation of the cable length and the characteristic impedance is possible. In the second embodiment, a calculation method when the power conversion device 1 PWM-drives the motor 50 will be described. The configuration of the power conversion device according to the second embodiment is the same as or equivalent to the configuration of the first embodiment shown in FIG. 1, and the same reference numerals are given to those components, and redundant description will be given. I omit it.

  FIG. 11 is a flowchart showing a processing flow relating to cable length calculation processing during PWM driving. As a premise of using the processing flow of FIG. 11, it is assumed that the command signal to be output to the inverter circuit 2, that is, the PWM signal has a switching interval to such an extent that it does not become a narrow pulse as shown in FIG.

  First, in step S301 in FIG. 11, the cable characteristic calculation unit 5 calculates an increase rate per unit time with respect to the surge current value received from the surge current waveform measurement unit 4. Then, in the next step S302, the cable characteristic calculation unit 5 determines whether or not the calculated increase rate exceeds a predetermined set value. If the calculated increase rate does not exceed the set value (No at step S302), the process at step S301 is repeated. On the other hand, if the calculated increase rate exceeds the set value (Yes at step S302), it is determined that the waveform portion corresponding to the time before and after the time that exceeds the surge is the rising portion of the surge current. It shifts and memorizes the time t3 concerned.

  Further, in the next step S304, the cable characteristic calculation unit 5 calculates a reduction rate per unit time with respect to the surge current value received from the surge current waveform measurement unit 4. Then, in the next step S305, the cable characteristic calculation unit 5 determines whether or not the calculated decrease rate exceeds a predetermined set value. If the calculated reduction rate does not exceed the set value (No at step S305), the process at step S304 is repeated. On the other hand, if the calculated decrease rate exceeds the set value (Yes at step S305), it is determined that the waveform portion corresponding to the time before and after the time that exceeds the surge current falls and step S306 And store the time t4.

  In the next step S307, the cable characteristic calculation unit 5 calculates the time difference T2 using the following equation based on the stored times t3 and t4.

  Time difference T2 = time t4−time t3 (3)

  The time difference T2 calculated by the above equation (3) corresponds to the time difference T1 measured by the surge current waveform measurement unit 4 in the first embodiment.

  Then, in the next step S308, the cable characteristic calculation unit 5 calculates the cable length from the time difference T2. The cable length may be calculated by the following equation in the same manner as the above equation (1).

  Cable length = time difference T2 × (speed of light / 2) / 2 (4)

  Furthermore, in the next step S309, the cable characteristic display unit 6 displays the cable length calculated by the cable characteristic calculation unit 5.

  After the time difference T2 is obtained in the process of step S307, the obtained value may be reset for the next measurement.

  Further, in the process of step S303 above, the time when the rate of increase of the surge current value per unit time exceeds the set value is stored as t3, but using the PWM signal of each phase, it is constant from the rise time of the PWM signal. The time t3 'of the surge current that has risen within the time range of (1) may be stored.

  Also, in the process of step S306 above, the time when the rate of decrease of the surge current value per unit time exceeded the set value was stored as t4, but using the PWM signal of each phase, from the fall time of the PWM signal The time t4 'of the surge current falling within a certain time range may be stored.

  And in the process of said step S307, said time difference T2 can be calculated using following Formula based on said time t3 ', t4'.

  Time difference T2 = time t4′−time t3 ′ (5)

  Further, in the above processing flow, the processing of step S301 to step S306 has been described as processing of the cable characteristic calculation unit 5, but may be processing of the surge current waveform measurement unit 4. The determination of the rate of increase or decrease per unit time in the surge current value can be performed using processing circuits such as a differential circuit or a differential circuit and a comparison circuit. In addition, generally the short circuit detection circuit is provided in the existing inverter product. Therefore, the existing short circuit detection circuit may be diverted to the detection of the rise time and the fall time of the surge current.

Third Embodiment
FIG. 12 is a block diagram showing the main configuration of a power conversion device according to a third embodiment. As shown in FIG. 12, the power conversion device according to the third embodiment is provided with a storage unit 8 that holds a surge current peak target value in the configuration of FIG. 1. The other configuration is the same as or equivalent to the configuration of the first embodiment shown in FIG. 1, the same reference numerals are given to those components, and the redundant description will be omitted.

  After determining the width of the prohibited area according to the cable length, the motor control operation unit 3 in the third embodiment performs the following operation as necessary. When receiving the peak value of the current measured by surge current waveform measurement unit 4 (hereinafter referred to as “current peak value”), motor control operation unit 3 determines the surge current peak that is separately determined and held in storage unit 8. The width of the prohibited area is adjusted based on the comparison result in comparison with the target value. Specifically, if the current peak value does not reach the surge current peak target value, the motor control calculation unit 3 performs control to reduce the width of the prohibited area. The direction of control is control of a direction that allows generation of a narrow pulse. On the other hand, when the current peak value reaches or exceeds the surge current peak target value, the motor control calculation unit 3 performs control to increase the width of the prohibited area. The direction of control is control of the direction in which the generation of the narrow pulse is suppressed. If a control system that performs such control is configured in the motor control calculation unit 3, the peak of the surge current can be automatically set to a desired value, so that the voltage control rate can be improved. Further, since the section in which the voltage applied to the motor terminal becomes zero can be reduced, it is possible to suppress the uneven rotation of the motor.

Fourth Embodiment
FIG. 13 is a block diagram showing the main configuration of a power conversion apparatus according to a fourth embodiment. As shown in FIG. 13, the power conversion device according to the fourth embodiment has the configuration shown in FIG. 1 with the time difference T1 between the peak value of the surge current measured by the surge current waveform measurement unit 4 and the first wave of the surge current waveform. Alternatively, a surge current peak storage unit 9 for storing the time difference T2 is provided. Further, a surge application history storage unit 10 is provided which stores the history of the surge current peak value held in the surge current peak storage unit 9 and the history of the time difference T1 or the time difference T2. Although FIG. 13 illustrates that the storage areas of the surge current peak storage unit 9 and the surge application history storage unit 10 are separately provided, they may be configured as one storage unit. The other configuration is the same as or equivalent to the configuration of the first embodiment shown in FIG. 1, the same reference numerals are given to those components, and the redundant description will be omitted.

  According to the power conversion device of the fourth embodiment, the surge application history storage unit 10 for storing the history of the surge current peak value and the history of the time difference T1 or the time difference T2 is provided. Or, it becomes possible to provide the manager of the site with necessary information at a desired timing.

Embodiment 5
FIG. 14 is a block diagram showing the main configuration of the power conversion device according to the fifth embodiment. The power conversion apparatus according to the fifth embodiment is configured to be able to transmit data of the surge application history storage unit 10 to the external maintenance server 11 via the network in the configuration of the fourth embodiment shown in FIG. ing. The other configuration is the same as or equivalent to the configuration of the fourth embodiment shown in FIG. 13, the same reference numerals are given to those components, and the redundant description will be omitted.

  According to the power conversion device of the fifth embodiment, the data of the surge application history storage unit 10, that is, the history data of the surge current peak value and the history data of the time difference T1 or the time difference T2 are expanded to the external maintenance server 11. As a result, it is possible to obtain necessary information without going to the site and without operating the on-site equipment.

  In addition, if degradation diagnosis of the motor is performed using information on surge application history and the result of degradation diagnosis is stored in the maintenance server 11, it becomes possible to predict equipment update as needed. It is possible to deploy the device update prediction result to the user.

  Finally, a hardware configuration for realizing the functions of motor control operation unit 3 and cable characteristic operation unit 5 in the present embodiment will be described with reference to FIG. When the functions of the motor control calculation unit 3 and the cable characteristic calculation unit 5 are realized, as shown in FIG. 15, a CPU (Central Processing Unit: central processing unit) 200 that performs calculation and a program read by the CPU 200 are stored. Memory 202 and an interface 204 for inputting and outputting signals. The CPU 200 may be referred to as an arithmetic unit, a microprocessor, a microcomputer, a processor, or a DSP (Digital Signal Processor). Further, the memory 202 is, for example, a nonvolatile or volatile semiconductor memory such as a random access memory (RAM), a read only memory (ROM), a flash memory, an EPROM (erasable programmable ROM) or an EEPROM (electrically EPROM). Is the case.

  Specifically, the memory 202 stores a program for executing the functions of the motor control calculation unit 3 and the cable characteristic calculation unit 5. The CPU 200 performs various kinds of arithmetic processing described in the present embodiment by exchanging necessary information via the interface 204.

  The CPU 200 and the memory 202 shown in FIG. 15 may be replaced with the processing circuit 203 as shown in FIG. The processing circuit 203 may be, for example, a single circuit, a complex circuit, a programmed processor, a parallel programmed processor, an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination thereof. Applicable

  The configuration shown in the above embodiment shows an example of the content of the present invention, and can be combined with another known technique, and a configuration without departing from the scope of the present invention It is also possible to omit or change part of.

  DESCRIPTION OF SYMBOLS 1 power converter, 2 inverter circuit, 3 motor control calculating part, 4 surge current waveform measurement part, 5 cable characteristic calculating part, 6 cable property display part, 7 cable, 8 memory part, 9 surge current peak memory part, 10 surge Application history storage unit, 11 maintenance server, 40 DC power supplies, 50 motors, 200 CPUs, 202 memories, 203 processing circuits, 204 interfaces.

Claims (10)

A power converter for driving a motor,
A power conversion circuit,
A measurement unit that measures a surge current flowing in a cable connecting the power conversion circuit and the motor;
A first operation unit that calculates the cable length of the cable from the time difference between the rise time of the surge current measured by the measurement unit and the fall time of the surge current;
The power converter characterized by being provided.   The first arithmetic unit is characterized in that the cable length is calculated from the time difference between the rise time of the first wave of the surge current and the fall time of the first wave observed after application of the step voltage. The power converter device according to claim 1.   The first computing unit computes the characteristic impedance of the cable using the information on the current peak of the first wave and the information on the voltage applied to the power conversion circuit when the surge current is generated. The power converter according to claim 2, characterized in that.   The first operation unit sets the time when the rate of increase of the surge current exceeds the set value during the switching operation of the power conversion circuit as the rise time, and the time when the rate of decrease of the surge current exceeds the set value The power conversion apparatus according to claim 1, wherein the time difference is calculated as the falling time.   5. A second operation unit for performing PWM control operation for PWM driving the motor according to the cable length calculated by the first operation unit. The power converter according to the item.   The power conversion device according to claim 5, wherein the width of the prohibited area where the switching operation of the power conversion circuit is not permitted is set according to the cable length calculated by the first calculation unit.   The second computing unit is characterized in that the width of the prohibited area is adjusted based on the comparison result between the peak value of the surge current measured by the measurement unit and the preset surge current peak target value. The power conversion device according to claim 6.   The surge application history storage unit storing the history of the peak value of the surge current measured by the measurement unit and the history of the information on the time difference measured by the measurement unit is provided. Power converter according to claim 1. The power conversion device according to claim 8 , wherein the power conversion device is configured to be able to transmit data of the surge application history storage unit to an external server via a network.   The power conversion device according to any one of claims 1 to 9, further comprising a display unit configured to display information on the cable length calculated by the first calculation unit.

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