JP7189005B2 - Dead band period adjusting device for adjusting dead band period of switching element, inverter, power conversion system, and motor driving device - Google Patents

Description

The present invention relates to a dead band period adjusting device, an inverter, a power conversion system, and a motor driving device for adjusting the dead band period of a switching element.

In machine tools, forging machines, injection molding machines, industrial machines, and motor drive devices that control the drive of motors in various robots, AC power supplied from an AC power supply is converted into DC power by a converter (rectifier). In addition, the DC power in the DC link is converted into AC power by an inverter, and this AC power is supplied as drive voltage to a motor provided for each drive shaft. "DC link" refers to the circuit part that electrically connects the DC output side of the converter and the DC input side of the inverter. It is also called a "DC bus" or "DC intermediate circuit".

In a motor drive device, an inverter that supplies driving power to a motor has a main circuit section composed of a bridge circuit in which a switching element is provided in each of an upper arm and a lower arm, and the switching element is turned on and off based on a drive command. As a result, the DC power supplied from the DC side is converted into AC power and output.

During the on/off operation of the switching elements in the inverter, if the switching elements of the upper and lower arms in the same phase are turned on at the same time, a short circuit occurs in the same phase and the circuit is destroyed due to overcurrent. Therefore, a switching dead zone period (hereinafter simply referred to as a "dead zone period") is a period during which the switching elements of the upper and lower arms in the same phase are not turned on (conducted) at the same time during the ON/OFF driving of the switching elements in the inverter. is inserted. The dead band period is sometimes referred to as "dead time" or the like.

During the dead band period, the switching elements of the upper and lower arms do not conduct, so no current flows through the arms. The switching element of the upper arm and the switching element of the lower arm are alternately turned on and off within the same phase. turns on.

For example, Patent Literature 1 states, "If the switching elements of the upper and lower arms are turned on at the same time, the switching elements of the upper arm and the switching elements of the lower arm are short-circuited, and the switching elements may be destroyed. , generally, a dead time is set as a short-circuit prevention period in which the switching elements of the upper and lower arms are turned off at the same time."

For example, a motor driving device for a motor that drives a feed shaft or spindle of a machine tool, or an arm of an industrial machine or an industrial robot, which includes a plurality of power elements, and switches the power elements to generate a DC voltage. an inverter that generates an AC voltage for driving the motor, a current detection unit that detects the current input from the inverter to the motor, and a voltage command based on the current command and the current detection value detected by the current detection unit. a dead band width of the output stage, which is a period during which both the power elements of the upper arm and the lower arm constituting the output stage of the inverter are turned off in response to the voltage command from the current control unit to be generated and the voltage command from the current control unit; a gate drive command generator for generating a drive command for the plurality of power elements so as to have a dead band width of , and a signal for driving the gates of the plurality of power devices upon receiving the drive command from the gate drive command generator. and a dead band width estimating unit for estimating the dead band width of the output stage caused by the signal driving the gates of the plurality of power elements from the difference between the current command and the detected current value. There is known a motor drive device characterized by having the following (see, for example, Patent Document 2).

Further, for example, at least a pair of upper and lower switching elements are provided, and the on/off state of the upper and lower switching elements is switched to convert direct current to alternating current. generating an upper pulse signal for on/off controlling the switching element on the upper side based on the voltage, and a lower pulse signal for controlling on/off the switching element on the lower side based on the DC voltage or its boosted voltage; An inverter device comprising: a pulse generation circuit for generating a signal; and a command value output means for outputting a command value for controlling the alternating current generated by the inverter circuit to the pulse generation circuit, wherein the command value is supplied to the inverter circuit. storage means for storing a correction relationship that is determined based on the relationship between the DC voltage applied and the dead band of the inverter circuit, and the correction amount is determined from the DC voltage; the correction relationship stored in the storage means; and command value correction means for determining a correction amount based on the DC voltage supplied to the inverter circuit and correcting the command value based on the determined correction amount. (See Patent Document 3, for example).

JP 2010-057242 A JP 2016-021793 A JP 2007-074766 A

If the switching elements of the upper and lower arms in the same phase of the inverter are turned on at the same time, a short circuit will occur in the same phase. Therefore, it is necessary to insert a certain amount of dead band period during the ON/OFF driving of the switching elements. Since there are individual differences and aging in the characteristics of switching elements, it is not easy to determine the length of the dead band period. During this dead band period, the switching elements of the upper and lower arms do not conduct, so no current flows through the arms. For example, in a motor driving device provided with an inverter, since drive power cannot be supplied to the motor during the dead band period, the controllability of the motor deteriorates as the dead band period becomes longer. Also, for example, in a machine provided with an inverter other than a motor drive device, energy efficiency is poor because power cannot be supplied to the machine during the dead band period. Therefore, in an inverter composed of a bridge circuit in which switching elements are provided in each of the upper arm and the lower arm, the technology can easily set the optimal length of the dead zone period inserted during the ON/OFF driving of the switching elements. is desired.

According to one aspect of the present disclosure, the bridge circuit includes a switching element provided in each of the upper arm and the lower arm, and the switching element is turned on and off to convert DC power supplied from the DC side into AC power. a main circuit section for converting and outputting; a driving section for driving the switching elements on and off; and a dead band period adjusting device that adjusts the length of a dead band period in which they are not turned on at the same time, wherein the dead band period adjusting device adjusts the upper arm and the lower arm in the same phase in an adjustment mode different from the normal operation mode of the inverter. A dead zone period changing unit that sequentially sets the provisional length of the dead zone period according to the a short circuit determining unit for determining whether or not a short circuit has occurred between the upper arm and the lower arm when a dead band period having a provisional length set by the dead band period changing unit is inserted during ON/OFF driving; The adjusted length of the dead zone period is obtained by adding the length having at least the step size to the provisional length set by the dead zone period changing section when the judging section first determines that a short circuit has occurred. and the drive unit has the provisional length set by the dead band period changing unit for each switching element of the upper arm and the lower arm in the same phase in the adjustment mode. On-off driving is performed by inserting a dead band period, and the DC voltage applied to the DC side of the main circuit section in the adjustment mode is lower than the DC voltage applied to the DC side of the main circuit section in the normal operation mode .

Further, according to one aspect of the present disclosure, the inverter includes a bridge circuit in which a switching element is provided in each of the upper arm and the lower arm. A main circuit unit that converts electric power into AC power and outputs it, a driving unit that turns on and off the switching element, and the dead zone period adjusting device. Each switching element of the lower arm is turned on and off by inserting a dead zone period having a provisional length set by the dead zone period changing unit.

Further, according to one aspect of the present disclosure, a power conversion system includes a converter that converts AC power supplied from an AC power supply into DC power and outputs the DC power to a DC link, a capacitor provided in the DC link, and the DC link. the inverter connected to the converter via the DC link to convert the DC power supplied from the DC link into AC power and output; , in the adjustment mode, when the current detector detects a current flowing from the DC link to the inverter, it is determined that a short circuit has occurred between the upper arm and the lower arm in the same phase.

Further, according to one aspect of the present disclosure, a motor drive device includes the above power conversion system, and a main circuit unit of an inverter converts DC power supplied from a DC link into AC power for driving the motor. Output.

According to one aspect of the present disclosure, in an inverter composed of a bridge circuit in which a switching element is provided in each of an upper arm and a lower arm, the optimal length of the dead zone period inserted during on/off driving of the switching element can be easily determined. can be set.

1 illustrates a dead band period adjuster, an inverter, a power conversion system, and a motor driver according to an embodiment of the present disclosure; FIG. FIG. 10 is a diagram illustrating a dead band period adjuster, an inverter, a power conversion system, and a motor drive in which the DC link voltage in the adjust mode is set according to a fourth aspect, in an embodiment of the present disclosure; FIG. 10 is a diagram illustrating a dead band period adjusting device, an inverter, a power conversion system, and a motor driving device in which the DC link voltage in the adjusting mode is set according to the fifth form, in an embodiment of the present disclosure; 4 is a flow chart showing an operation flow of a dead zone period adjusting device according to an embodiment of the present disclosure;

A dead band period adjusting device for adjusting the dead band period of a switching element, an inverter, a power conversion system, and a motor driving device will be described below with reference to the drawings. In order to facilitate understanding, the scales of these drawings are appropriately changed. The form shown in the drawing is an example of implementation and is not limited to the illustrated embodiment.

Here, as an example, an inverter provided in a motor drive device will be described, but the present embodiment can also be applied when an inverter is provided in a machine other than the motor drive device.

FIG. 1 is a diagram illustrating a dead band period adjustment device, an inverter, a power conversion system, and a motor drive device according to one embodiment of the present disclosure.

As an example, a case where a motor drive device 1000 connected to an AC power supply 2 controls an AC motor (hereinafter simply referred to as "motor") 3 will be shown. In this embodiment, the type of motor 3 is not particularly limited, and may be, for example, an induction motor or a synchronous motor. Also, the number of phases of the AC power supply 2 and the motor 3 is not particularly limited in this embodiment, and may be three-phase or single-phase, for example. In the illustrated example, the AC power supply 2 and the motor 3 each have three phases. Examples of the AC power supply 2 include a three-phase AC 400V power supply, a three-phase AC 200V power supply, a three-phase AC 600V power supply, a single-phase AC 100V power supply, and the like. Machines provided with the motor 3 include, for example, machine tools, robots, forging machines, injection molding machines, industrial machines, various electrical appliances, trains, automobiles, and aircraft.

A power conversion system 200 provided in a motor drive device 1000 includes a converter 101 , a capacitor 102 , an inverter 103 , a current detection section 104 , a voltage detection section 105 and a control device 300 .

Converter 101 converts AC power input from AC power supply 2 into DC power, and outputs the DC power to a DC link on the DC side. Examples of the converter 101 include a diode rectifier circuit, a 120-degree conduction rectifier circuit, and a PWM switching control type rectifier circuit having a switching element inside. Converter 101 is configured as a three-phase bridge circuit when AC power supply 2 is three-phase, and is configured as a single-phase bridge circuit when AC power supply 2 is single-phase. When the converter 101 is a diode rectifier circuit, it rectifies the AC current supplied from the AC power supply 2 and outputs the DC current to the DC link. If the converter 101 is a 120-degree conduction type rectifier circuit or a PWM switching control type rectifier circuit, the converter 101 converts the AC power supplied from the AC power supply 2 into DC power and outputs it to the DC link, and also performs power regeneration. Sometimes, it is realized as a power conversion device capable of bi-directional conversion of DC power in a DC link to AC power and returning it to the AC power supply 2 side. When the converter 101 is a PWM switching control type rectifier circuit, it is composed of a switching element and a diode bridge circuit connected in anti-parallel to the switching element. In this case, examples of switching elements include FETs, IGBTs, thyristors, GTOs, SiCs, and transistors. good. Although an AC reactor, an AC line filter, and the like are provided on the AC input side of the converter 101, they are omitted from the drawing.

A DC link connecting the DC output side of converter 101 and the DC input side of inverter 103 is provided with a capacitor (DC link capacitor) 102 . Capacitor 102 has a function of accumulating DC power used by inverter 103 to generate AC power and a function of suppressing pulsation of the DC output of converter 101 . Examples of the capacitor 102 provided in the DC link include, for example, electrolytic capacitors and film capacitors.

Inverter 103 converts DC power supplied from the DC link (that is, DC power in the DC link) into AC power for driving motor 3 and outputs the AC power to motor 3 . In this embodiment, the inverter 103 includes a main circuit section 21 , a driving section 22 , and the dead zone period adjusting device 1 .

The main circuit section 21 of the inverter 103 is composed of a bridge circuit in which a switching element is provided in each of the upper arm and the lower arm. Inverter 103 is configured as a three-phase bridge circuit when motor 3 is a three-phase AC motor, and is configured as a single-phase bridge circuit when motor 3 is a single-phase AC motor. In the illustrated example, the motor 3 is a three-phase AC motor, so the main circuit section 21 is configured as a three-phase bridge circuit. Here, the upper arm of the _U phase of the main circuit section 21 is represented by UU, and the lower arm of the U _phase is represented by UL. The V-phase upper arm of the main circuit section 21 is denoted by _VU , and the V-phase lower arm is denoted by _VL . The W-phase upper arm of the main circuit unit 21 is denoted by _WU , and the W-phase lower arm is denoted by _VL . In each arm, a switching element and a diode are connected in antiparallel. Examples of switching elements include FETs, IGBTs, thyristors, GTOs, SiCs, and transistors, but the types of switching elements themselves do not limit the present embodiment, and other switching elements may be used.

The inverter 103 has two operation modes: a normal operation mode in which the DC power in the DC link is converted into AC power for driving the motor 3 and output; and an adjustment mode. In both the normal operation mode and the adjustment mode, the inverter 103 converts the DC power supplied from the DC side into AC power by turning on and off the switching elements in the main circuit unit 21 and outputs the AC power.

Control device 300 controls inverter 103 that performs power conversion between DC power in a DC link and AC power that is driving power or regenerative power for motor 3, as in a general motor driving device. That is, the control device 300 controls the speed of the motor 3 (speed feedback), the current flowing through the windings of the motor 3 (current feedback), a predetermined torque command, the operation program of the motor 3, and the like. A switching command for controlling the torque or the position of the rotor is generated according to, for example, a PWM control method. Note that the control device 300 generates a switching command and controls the power conversion of the inverter 103 in both the normal operation mode and the adjustment mode. In the switching command generated by the control device 300, a dead zone period is set during which the switching elements of the upper arm and the lower arm in the same phase are not turned on simultaneously. However, the length of the dead band period differs between the adjustment mode and the normal operation mode in inverter 103 . That is, a dead band period having a provisional length is set in the adjustment mode, and a dead band period having an adjusted length is set in the normal operation mode.

The drive unit 22 turns on and off the switching elements in the main circuit unit 21 according to the switching command received from the control device 300 . More specifically, when the switching elements in the main circuit section 21 are composed of FETs, IGBTs, thyristors, GTOs, or SiC, the driving section 22 switches the switching elements according to switching instructions received from the control device 300. A gate driving voltage is applied to the gate of the switching element to turn on/off the switching element. When the switching elements in the main circuit section 21 are composed of bipolar transistors, the drive section 22 applies a base driving voltage to the base of the switching element according to the switching command received from the control device 300, and to drive on and off. As described above, during ON/OFF driving of the switching elements, a dead zone period is inserted in which the switching elements of the upper arm and the lower arm in the same phase are not simultaneously turned on. Under drive control by the drive unit 22, the switching element is driven on and off under a dead zone period having an adjusted length in the normal operation mode, and is driven on and off under a dead zone period having a provisional length in the adjustment mode.

The current detection unit 104 detects current flowing into the main circuit unit 21 of the inverter 103 . When the inverter 103 is in the adjustment mode, the value of the current flowing from the DC link into the main circuit section 21 of the inverter 103 detected by the current detection section 104 is sent to the dead band period adjustment device 1 described later, and used in the short circuit determination process. be done. In the normal operation mode of the inverter 103, the value of the current flowing into the main circuit unit 21 of the inverter 103 detected by the current detection unit 104 is sent to the control device 300 and used to control the power conversion operation of the inverter 103. may be used.

A voltage detection unit 105 detects a capacitor voltage value, which is a potential difference between both ends of the capacitor 102 . This capacitor voltage value corresponds to the voltage (DC link voltage) applied to the DC side of inverter 103 . When the inverter 103 is in the adjustment mode, the value of the DC link voltage (capacitor voltage) detected by the voltage detection unit 105 is sent to the dead band period adjustment device 1, which will be described later. In the normal operation mode of inverter 103 , the value of the DC link voltage detected by voltage detection unit 105 may be sent to control device 300 and used to control the power conversion operation of inverter 103 .

In the adjustment mode, the dead zone period adjusting device 1 adjusts the length of the dead zone period inserted during the ON/OFF driving of the switching elements in the bridge circuit forming the inverter 103 . The dead band period having the adjusted length generated by the dead band period adjusting device 1 is inserted during the ON/OFF driving of each switching element in the normal operation mode of the inverter 103 . In the present embodiment, the dead band period adjusting device 1 includes a dead band period changing section 11 , a short circuit determining section 12 , a dead band period determining section 13 and a storage section 14 .

In the adjustment mode, the dead zone period changing unit 11 successively sets the temporary length of the dead zone period for the upper arm and the lower arm in the same phase while changing the temporary length so as to be gradually shortened by a predetermined step size. The step width may be set, for example, from several tens of nanoseconds to several microseconds. The provisional length of the dead band period is set by the dead band period changer 11 for each of the U-phase, V-phase, and W-phase. Each time the dead band period changer 11 sets the temporary length, data relating to the dead band period having the temporary length is sent to the short-circuit determining unit 12 and the control device 300 .

In the adjustment mode, the control device 300 generates a switching command to include the dead zone period having the provisional length set by the dead zone period changing section 11 and sends it to the drive section 22 . Upon receiving a switching command from the control device 300 in the adjustment mode, the drive unit 22 sets the dead band having the provisional length set by the dead band period changing unit 11 to each switching element of the upper arm and the lower arm in the same phase. Execute on-off drive with a period inserted.

Since the temporary length of the dead band period sent from the dead band period changing unit 11 to the control device 300 gradually becomes shorter, the upper arm and the lower arm in the same phase that are turned on and off by the driving unit 22 controlled by the control device 300 The dead band time of each switching element is gradually shortened, and finally, between the upper arm and the lower arm in the same phase (that is, between the positive terminal of the upper arm and the negative terminal of the lower arm in the same phase). short circuit will occur.

When the dead zone period having the provisional length set by the dead zone period changing part 11 is inserted during the ON/OFF driving of the switching elements of the upper arm and the lower arm in the same phase, the short circuit judging part 12 It is determined whether or not a short circuit has occurred between the upper arm and the lower arm. The short-circuit determination by the short-circuit determination unit 12 is performed for each of the U-phase, V-phase, and W-phase. In the adjustment mode, the short-circuit determination unit 12 determines that a short-circuit has occurred between the upper arm and the lower arm in the same phase when the current detection unit 104 detects a current flowing from the DC link to the main circuit unit 21 of the inverter 103. I judge. In order to prevent malfunction, the threshold value used by the short-circuit determination unit 12 to determine whether a short circuit has occurred is a current value (eg, several [A]) that is sufficiently higher than the noise level (eg, several [mA]). should be set to For example, in the adjustment mode, when the current flowing from the DC link detected by the current detection unit 104 to the main circuit unit 21 of the inverter 103 exceeds the threshold value, the short-circuit determination unit 12 detects the upper arm and the lower arm in the same phase. It is determined that a short circuit has occurred between Each time the dead band period changing unit 11 sets the temporary length, the driving unit 22 controlled by the control device 300 controls the operation of each of the upper arm and the lower arm in the same phase during the dead band period having the temporary length. The switching element is turned on and off, and the short-circuit determination unit 12 determines whether or not a short circuit has occurred between the upper arm and the lower arm during the dead zone period having the temporary length during the on-off drive.

In the adjustment mode, the temporary length of the dead zone period is gradually shortened, and eventually a short circuit occurs between the upper arm and the lower arm. Therefore, in order to avoid the breakdown of various components in the circuit, including the switching elements, due to a short circuit, the DC link voltage (that is, the DC voltage applied to the DC side of the main circuit section 21 of the inverter 103) in the regulation mode is , is set to be lower than the DC link voltage in the normal operation mode. For example, when the DC link voltage in the normal operation mode is 200 [V], the DC link voltage in the adjustment mode is set to about 20 [V]. Also, for example, the DC link voltage in the adjustment mode may be set based on the on-resistance and allowable current that are predefined for the switching element. The on-resistance and permissible current of the switching element are defined, for example, in a standard table. For example, when the on-resistance of the switching element is 1 [Ω] and the allowable current is 100 [A], a DC voltage (DC link voltage) of 20 [V] is applied to the DC side of the main circuit section 21 of the inverter 103 in the adjustment mode. is applied, even if a short circuit occurs between the upper arm and the lower arm, a current of 20 A, which is smaller than the allowable current of 100 A, flows through the switching element, so the switching element is not destroyed. Note that the specific numerical values given here are merely examples, and other numerical values may be used. An example of setting the DC link voltage in the adjustment mode to be lower than the DC link voltage in the normal operation mode will be described later.

The dead band period determination unit 13 adds a length (i.e., the above-mentioned length equal to or greater than the step width) is determined as the adjusted length of the dead zone period. The reason why the adjusted length of the dead band period is decided by the dead band period deciding section 13 as described above is as follows.

In the adjustment mode, each time the dead zone period changing unit 11 sets the provisional length, the driving unit 22 performs ON/OFF driving of the switching element and the short-circuit determination processing is performed by the short-circuit determination unit 12 based on the control of the control device 300. be. Through a series of processing by the dead band period changing unit 11, the control device 300, and the driving unit 22, the dead band time of each switching element of the upper arm and the lower arm in the same phase is gradually shortened by a predetermined step width, and finally , a short circuit will occur between the upper arm and the lower arm in the same phase. This means that the short-circuit determination unit 12 first determines that a short-circuit has occurred, and the dead-band period is longer than the "provisional length of the dead-band period set by the dead-band period changing unit 11". This means that if the switching elements of the arm and the lower arm are turned on and off, no short circuit will occur between the upper arm and the lower arm in the same phase. That is, the length obtained by adding at least the length having the step width (that is, the length equal to or greater than the step width) to the provisional length of the dead zone period when the short-circuit determination unit 12 first determines that a short circuit has occurred. If there is a dead band period, even if the switching elements of the upper arm and the lower arm in the same phase are turned on and off during the dead band period, a short circuit will not occur between the upper arm and the lower arm in the same phase. does not occur. Therefore, in the present embodiment, the dead zone determining unit 13 changes at least the above step width to the provisional length set by the dead zone changing unit 11 when the short circuit determining unit 12 first determines that a short circuit has occurred. is determined as the adjusted length of the deadband period. It should be noted that the length obtained by adding the above step width to the "temporary length of the dead zone period" used during ON/OFF driving of the switching element when it was first determined that the short circuit occurred is the provisional length set by the dead zone period changing unit 11 immediately before it is first determined (that is, it is not determined that a short circuit has occurred at this time), so this length is called the "adjusted length ” may be used. A value obtained by adding at least the length having the above step width to the "provisional length of the dead zone period" used during ON/OFF driving of the switching element when it was first determined that a short circuit occurred, is defined as "adjusted , the switching element can be safely turned on and off. The larger the value added to the "provisional length of the dead zone period" used during the ON/OFF driving of the switching element when it was first determined, the safer the ON/OFF driving of the switching element. It should be noted that the controllability of the motor 3 deteriorates if the value added to the "provisional length of the dead zone period" is too large.

The adjusted length of the dead band period determined by the dead band period determination unit 13 in the adjustment mode is stored in the storage unit 14 . The storage unit 14 is composed of an electrically erasable/storable non-volatile memory such as EEPROM (registered trademark), or a random access memory such as DRAM or SRAM that can be read and written at high speed. . The dead band period having the adjusted length stored in the storage unit 14 is sent to the control device 300 and used for on/off driving of the switching element in the normal operation mode.

As described above, in the present embodiment, the dead zone period adjustment device 1 gradually shortens the temporary length of the dead zone period in predetermined increments so that a short circuit does not occur between the upper arm and the lower arm in the same phase. It is possible to find the last dead band period that does not occur. The predetermined step width can be set to, for example, several nanoseconds to several tens of nanoseconds. Conventionally, a large dead band period of, for example, several microseconds has been set by securing a certain amount of margin in consideration of individual differences and secular changes in the characteristics of switching elements. In contrast, according to the present embodiment, the dead zone period sufficiently shorter than several microseconds can be easily adjusted on the order of “nanoseconds”. The dead zone period change processing by the dead zone period changing unit 11, the short circuit judgment by the short circuit judging unit 12, the dead zone period determination processing by the dead zone period housing unit, and the storage processing by the storage unit 14 are performed for each phase. That is, when the inverter 103 is composed of a three-phase bridge circuit, the short-circuit determination unit 12 determines each of the U-phase, V-phase, and W-phase, and when the inverter 103 is composed of a single-phase bridge circuit, for one phase, Each process is executed.

The dead band period adjustment device 1 and the control device 300 may be constructed in the form of software programs, for example, or may be constructed by combining various electronic circuits and software programs, or may be constructed only by various electronic circuits. good too. For example, if they are constructed in a software program format, the function of each part described above can be realized by operating an arithmetic processing unit such as a DSP or FPGA in the motor drive device 1000 according to this software program. Alternatively, the dead band period adjustment device 1 and the control device 300 may be implemented as a semiconductor integrated circuit into which a software program for implementing the functions of each section is written. Alternatively, the dead band period adjustment device 1 and the control device 300 may be realized as a recording medium in which a software program for realizing the function of each part is written. Further, the dead band period adjustment device 1, the current detection section 104, the voltage detection section 105, and the control device 300 may be provided in, for example, a numerical control device of a machine tool. Also, the dead zone period adjustment device 1 may be provided in the control device 300 . Further, the current detection section 104, the voltage detection section 105, and the driving section 22 may be configured by a combination of digital circuits and analog circuits, or may be configured by analog circuits alone.

Next, several forms of setting the DC link voltage in the adjustment mode to be lower than the DC link voltage in the normal operation mode will be listed. In any form, in order to avoid destruction of various parts in the circuit including switching elements due to a short circuit, the dead band period adjustment device 1 detects that the DC link voltage is set to DC in the normal operation mode by the voltage detection unit 105 . After confirming that it is lower than the link voltage, dead zone period adjustment processing in the adjustment mode is executed.

First, the setting of the DC link voltage in the adjustment mode according to the first embodiment will be explained.

In the first mode, the adjustment mode in which the length of the dead band period is adjusted by the dead band period adjusting device 1 is such that during the discharge period of the capacitor 102 after the end of the normal operation mode, the DC link voltage is Provided when lower than the DC link voltage. In the motor driving device 1000, when the driving of the motor 3 in the normal operation mode ends, the supply of AC power from the AC power supply 2 to the motor driving device 1000 is cut off, the charge accumulated in the capacitor 102 is discharged, and the DC The link voltage drops gradually. During the discharge period of the capacitor 102 after the end of the normal operation mode, when the DC link voltage becomes sufficiently lower than the DC link voltage in the normal operation mode, the normal operation mode is shifted to the adjustment mode to adjust the dead band period. The apparatus 1 executes processing for adjusting the length of the dead band period. For example, when the DC link voltage (the DC voltage applied to the DC side of the main circuit section 21 of the inverter 103) in the normal operation mode is 200 [V], during the discharge period of the capacitor 102 after the normal operation mode ends, When the DC link voltage drops to about 20 [V], the normal operation mode is shifted to the adjustment mode, and the dead zone period adjusting device 1 executes processing for adjusting the length of the dead zone period. Note that the specific numerical values given here are merely examples, and other numerical values may be used. In the adjustment mode, the dead band period having the adjusted length determined by the dead band period determining unit 13 of the dead band period adjusting device 1 and stored in the storage unit 14 is set during the normal operation mode of the motor driving device 1000 after the next power-on. used for on/off driving of switching elements in Therefore, according to the first mode, in the adjustment mode provided during the discharge period of the capacitor 102 after the end of the normal operation mode, the dead zone period adjustment device 1 determines the optimum length for the next normal operation mode. can be easily obtained. Further, in the next normal operation mode, the switching element of the main circuit unit 21 in the inverter 103 is turned on and off during the dead band period having an optimum length, so that the AC drive power can be supplied to the motor 3. , the controllability of the motor 3 is improved as compared with the conventional one. Note that the first mode can be applied to any of a diode rectifier circuit, a 120-degree current-carrying rectifier circuit, and a PWM switching control type rectifier circuit.

Next, setting of the DC link voltage in the adjustment mode according to the second embodiment will be described.

In the second mode, the adjustment mode in which the length of the dead band period is adjusted by the dead band period adjusting device 1 is during the initial charging period of the capacitor 102 before the start of the normal operation mode, and the DC link voltage is is lower than the DC link voltage of . In the motor drive device 1000, the capacitor 102 has a predetermined value from immediately after AC power supply 2 starts supplying AC power to the motor drive device 1000 and before the start of the normal operation mode of the motor 3 (that is, before the start of the power conversion operation by the inverter 103). must be charged to a voltage of the magnitude of This charging is commonly referred to as initial charging (or pre-charging). During the initial charging period, the converter 101 converts the AC power supplied from the AC power supply 2 into DC power, the DC power charges the capacitor 102, and the DC link voltage gradually increases. During the initial charging period of the capacitor 102 before starting the normal operation mode, when the DC link voltage is lower than the DC link voltage in the normal operation mode, the adjustment mode is started and the dead band period adjustment device 1 extends the dead band period. Execute processing to adjust the depth. For example, when the DC voltage applied to the DC side of the main circuit unit 21 of the inverter 103 in the normal operation mode is 200 [V], the DC link voltage is 20 V during the initial period of the capacitor 102 before starting the normal operation mode. Before the voltage rises to about [V], the dead zone period adjusting device 1 executes processing for adjusting the length of the dead zone period. Note that the specific numerical values given here are merely examples, and other numerical values may be used. The dead band period having the adjusted length determined by the dead band period determination unit 13 of the dead band period adjusting device 1 and stored in the storage unit 14 in the adjustment mode is the same as that in the normal operation mode of the motor driving device 1000 after the adjustment mode ends. used for on/off driving of switching elements in Therefore, according to the second aspect, it is possible to easily obtain a dead zone period having an optimum length before starting the normal operation mode. Further, in the normal operation mode, the switching elements of the main circuit unit 21 in the inverter 103 are turned on and off during the dead band period having an optimum length, and AC driving power can be supplied to the motor 3. 3 controllability is improved compared to the conventional one. Note that the second mode can be applied to any of a diode rectifier circuit, a 120-degree current-carrying rectifier circuit, and a PWM switching control type rectifier circuit.

Next, the setting of the DC link voltage in the adjustment mode according to the third embodiment will be explained.

In the third embodiment, the converter 101 is configured by a PWM converter (a rectifier circuit of PWM switching control system) that converts the AC voltage applied from the AC power supply 2 into a DC voltage of a desired magnitude and outputs the DC voltage to the DC link. . The converter 101, which is a PWM converter, receives an adjustment mode start command from the dead band period adjustment device 1, and outputs a voltage lower than the voltage output to the DC link in the normal operation mode in the adjustment mode. In this adjustment mode, the dead zone period adjusting device 1 executes processing for adjusting the length of the dead zone period. For example, when the DC link voltage (the DC voltage applied to the DC side of the main circuit section 21 of the inverter 103) is 200 [V] in the normal operation mode, the converter 101, which is a PWM converter, has a DC link voltage of 20 [V]. ], and the dead zone period adjusting device 1 executes processing for adjusting the length of the dead zone period. Note that the specific numerical values given here are merely examples, and other numerical values may be used. As described above, according to the third embodiment, the converter 101 is configured by a PWM converter that can easily generate a DC link voltage lower than the DC link voltage in the normal operation mode. It is possible to set the adjustment mode with .

Next, the setting of the DC link voltage in the adjustment mode according to the fourth embodiment will be explained. FIG. 2 is a diagram illustrating a dead band period adjuster, an inverter, a power conversion system, and a motor driver in which the DC link voltage in the regulation mode is set according to a fourth aspect, in one embodiment of the present disclosure.

In the fourth form, the power conversion system 200 further includes a variable-ratio transformer 111 provided between the AC power supply 2 and the converter 101 . Transformer 111 receives an adjustment mode start command from dead band period adjusting device 1 and changes the transformation ratio in the adjustment mode, thereby changing the AC voltage applied to converter 101 to the AC voltage applied to converter 101 in the normal operation mode. step down to a voltage lower than When the AC voltage applied to converter 101 by transformer 111 is stepped down, the DC voltage output from converter 101, that is, the DC link voltage is lower than the DC link voltage in the normal operation mode. In this adjustment mode, the dead zone period adjusting device 1 executes processing for adjusting the length of the dead zone period. For example, when the DC link voltage (the DC voltage applied to the DC side of the main circuit section 21 of the inverter 103) is 200 [V] in the normal operation mode, the transformer 111 outputs from the converter 101 in the adjustment mode In order to step down the AC voltage applied to the converter 101 so that the DC voltage (DC link voltage) is about 20 [V], the transformation ratio is changed. Note that the specific numerical values given here are merely examples, and other numerical values may be used. Thus, according to the fourth aspect, it is possible to easily create a DC link voltage that is lower than the DC link voltage in the normal operation mode, and to set the adjustment mode at a timing desired by the operator. be. Note that the fourth mode can be applied to any of a diode rectifier circuit, a 120-degree conducting rectifier circuit, and a PWM switching control type rectifier circuit.

Next, setting of the DC link voltage in the adjustment mode according to the fifth embodiment will be described. FIG. 3 is a diagram illustrating a dead band period adjuster, an inverter, a power conversion system, and a motor drive in which the DC link voltage in the regulation mode is set according to the fifth aspect, in an embodiment of the present disclosure.

In the fifth form, power conversion system 200 further includes DCDC converter 112 provided between converter 101 and inverter 103 . The DCDC converter 112 receives an adjustment mode start command from the dead band period adjusting device 1, and steps down the DC voltage output from the converter 101 in the adjustment mode, thereby applying the DC voltage to the main circuit unit 21 of the inverter 103. is stepped down to a voltage lower than the DC voltage applied to the main circuit section 21 of the inverter 103 in the normal operation mode. In this adjustment mode, the dead zone period adjusting device 1 executes processing for adjusting the length of the dead zone period. For example, when the DC voltage applied to the DC side of the main circuit unit 21 of the inverter 103 in the normal operation mode is 200 [V], the DCDC converter 112 outputs the DC voltage (DC link voltage) in the adjustment mode. It should be about 20[V]. Note that the specific numerical values given here are merely examples, and other numerical values may be used. Thus, according to the fifth embodiment, it is possible to easily create a DC link voltage lower than the DC link voltage in the normal operation mode, and to set the adjustment mode at a timing desired by the operator. be. Note that the fifth mode can be applied to any of a diode rectifier circuit, a 120-degree current-carrying rectifier circuit, and a PWM switching control type rectifier circuit.

Next, an operation flow of the dead zone period adjusting device according to an embodiment of the present disclosure will be described. FIG. 4 is a flow chart showing the operation flow of the dead band period adjustment device according to one embodiment of the present disclosure. The following flow chart can be applied to any of the first to fifth modes of setting the DC link voltage in the adjustment mode.

In step S101, the dead zone period adjustment device 1 determines whether or not it is in adjustment mode. As described above, in the case of the first form, the adjustment mode causes the DC link voltage to be sufficiently lower than the DC link voltage in the normal operation mode during the discharging period of the capacitor 102 after the end of the normal operation mode. It is set when it becomes. In the second case, regulation mode is provided when the DC link voltage is lower than the DC link voltage in normal operation mode during the initial charging period of capacitor 102 prior to initiation of normal operation mode. In the case of the first form and the second form, the adjustment mode should be defined in the operation program of the motor driving device 1000. FIG. In the case of the third to fifth forms, the adjustment mode can be provided at the timing desired by the operator. The adjustment mode may be started by instructing the dead zone period adjusting device 1 to start the adjustment mode.

If the adjustment mode is determined in step S101, the dead zone period changing unit 11 sets the temporary length of the dead zone period in step S102.

In step S<b>103 , control device 300 generates a switching command to include the dead zone period having the provisional length set in step S<b>102 , and sends it to driving section 22 . Upon receiving a switching command from the control device 300 in the adjustment mode, the drive unit 22 sets the dead band having the provisional length set by the dead band period changing unit 11 to each switching element of the upper arm and the lower arm in the same phase. Execute on-off drive with a period inserted.

In step S104, the short-circuit determination unit 12 detects that a short-circuit has occurred between the upper arm and the lower arm in the same phase during ON/OFF driving of the switching elements of the upper arm and the lower arm in the same phase (step S103). Determine whether or not it has occurred.

If it is not determined in step S104 that a short circuit has occurred between the upper arm and the lower arm in the same phase, the process returns to step S102, and in step S102, the temporary length set last time is increased by a predetermined increment width. Set a deadband period with a short interim length. By repeatedly executing the processes of steps S102 to S104, the short-circuit determination is performed while gradually shortening the temporary length of the dead zone period.

If it is determined in step S104 that a short circuit has occurred between the upper arm and the lower arm within the same phase, the process proceeds to step S105. In step S105, the dead band period determining unit 13 changes the temporary length set by the dead band period changing unit 11 in step S102 when the short circuit determining unit 12 determines in step S104 that a short circuit has occurred. The value plus the length with width (that is, the length equal to or greater than the step size) is determined as the adjusted length of the dead band period.

In step S106, the storage unit 14 stores the adjusted length of the dead band period determined by the dead band period determination unit 13 in step S105, and the dead band period adjusting device 1 ends the dead band period adjusting process. The dead band period having the adjusted length stored in the storage unit 14 is sent to the control device 300 and used for on/off driving of the switching element in the normal operation mode.

As described above, in this embodiment, by repeatedly executing the processing of steps S102 to S104, the provisional length of the dead zone period is gradually shortened by a predetermined step size, and in step S105, the upper arm and the upper arm in the same phase are shortened. A last dead zone period that does not cause a short circuit with the lower arm is determined, and this is stored as the adjusted length in step S106.

In the above embodiments, the inverter provided in the motor driving device has been described as an example. According to this embodiment, the dead zone period is adjusted to have an optimum length, so that the controllability of the motor driven by the motor driving device is improved. In addition, this embodiment can be applied even when an inverter is provided in a machine other than a motor drive device. Improves energy efficiency.

1 dead zone period adjusting device 2 AC power supply 3 motor 11 dead zone period changing section 12 short circuit determination section 13 dead zone period determination section 14 storage section 21 main circuit section 22 drive section 101 converter 102 capacitor 103 inverter 104 current detection section 105 voltage detection section 111 transformer Device 112 DCDC converter 200 Power conversion system 300 Control device 1000 Motor drive device

Claims (10)

The main circuit section consists of a bridge circuit in which a switching element is provided in each of the upper arm and the lower arm, and the switching element is turned on and off to convert DC power supplied from the DC side into AC power and output it. When,
a driving unit that turns on and off the switching element;
a dead zone period adjusting device that is inserted during on/off driving of the switching elements in the bridge circuit and adjusts the length of the dead zone period during which the switching elements of the upper arm and the lower arm in the same phase are not simultaneously turned on ;
An inverter comprising
The dead zone period adjustment device
In an adjustment mode different from the normal operation mode of the inverter, the provisional length of the dead zone period relating to the upper arm and the lower arm in the same phase is sequentially set while being changed so as to be gradually shortened by a predetermined step size. A dead zone period changing part that
When the dead zone period having the provisional length set by the dead zone period changing unit is inserted during the ON/OFF driving of the switching elements of the upper arm and the lower arm in the same phase, the upper arm and the a short circuit determination unit that determines whether or not a short circuit has occurred with the lower arm;
A value obtained by adding at least the length having the step width to the provisional length set by the dead zone period changing unit when the short circuit determination unit first determines that the short circuit has occurred is defined as the dead zone. a dead zone period determination unit that determines the adjusted length of the period;
with
In the adjustment mode, the driving section inserts the dead zone period having the provisional length set by the dead zone period changing section to the switching elements of the upper arm and the lower arm in the same phase. to drive on and off,
The DC voltage applied to the DC side of the main circuit unit in the adjustment mode is lower than the DC voltage applied to the DC side of the main circuit unit in the normal operation mode.
inverter. 2. The inverter according to claim 1, wherein said dead band period adjustment device further comprises a storage unit that stores the adjusted length of said dead band period determined by said dead band period determination unit. 2. The inverter according to claim 1 , wherein the DC voltage applied to the DC side of said main circuit section in said adjustment mode is set based on an on-resistance and allowable current predetermined for said switching element. a converter that converts AC power supplied from an AC power supply into DC power and outputs the DC power to a DC link;
a capacitor provided in the DC link;
The inverter according to any one of claims 1 to 3 , which is connected to the converter via the DC link, converts DC power supplied from the DC link into AC power, and outputs the AC power;
a current detection unit that detects a current flowing from the DC link to the inverter;
with
The power conversion system, wherein, in the adjustment mode, the short-circuit determination unit determines that a short-circuit has occurred between the upper and lower arms in the same phase when the current detection unit detects a current flowing from the DC link to the inverter. . 5. The adjustment mode is provided when the voltage of the DC link is lower than the voltage of the DC link during the normal operation mode during the discharging period of the capacitor after the normal operation mode is terminated. The power conversion system according to . 3. The regulation mode is provided when, during an initial charging period of the capacitor prior to initiation of the normal operation mode, the voltage of the DC link is lower than the voltage of the DC link during the normal operation mode. 5. The power conversion system according to 4 . The converter is a PWM converter that converts an AC voltage applied from the AC power supply into a DC voltage of a desired magnitude and outputs the DC voltage to the DC link,
5. The power conversion system according to claim 4 , wherein said PWM converter outputs, in said adjustment mode, a voltage lower than the voltage output to said DC link during said normal operation mode. Further comprising a transformer with a variable transformation ratio provided between the AC power supply and the converter,
3. The transformer changes the transformation ratio in the adjustment mode to step down the AC voltage applied to the converter to a voltage lower than the AC voltage applied to the converter in the normal operation mode. 5. The power conversion system according to 4 . further comprising a DCDC converter provided between the converter and the inverter;
In the adjustment mode, the DCDC converter steps down the DC voltage output from the converter to reduce the DC voltage applied to the main circuit section of the inverter to the main circuit of the inverter in the normal operation mode. 5. The power conversion system according to claim 4 , wherein the voltage is stepped down to a voltage lower than the DC voltage applied to the part. A power conversion system according to any one of claims 4 to 9 ,
The motor drive device, wherein the main circuit unit of the inverter converts DC power supplied from the DC link into AC power for driving the motor and outputs the AC power.

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