JP2019083676A - Motor drive control device - Google Patents

Abstract

To perform dead time compensation with ease without performing detection of a phase current of a motor nor complicated coordinate conversion processing.SOLUTION: A motor drive control device 4 that performs drive control of a motor 2 by using a PWM inverter 3 comprises a dead time compensation unit 44. The dead time compensation unit 44 calculates a compensation amount for compensating an error of an output voltage of the PWM inverter 3 that is generated by providing a dead time for avoiding simultaneous turning-on of respective switching elements series-connected in the PWM inverter 3, and outputs a voltage command added with the compensation amount to the PWM inverter 3. The dead time compensation unit 44 calculates the compensation amount on the basis of a magnitude of a current command vector indicating a vector of a current that should be followed by a current flowing in the motor 2. The current command vector is defined by a coordinate system synchronized with a rotor of the motor 2, or a coordinate system corresponding to the above coordinate system.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a motor drive control device.

  In an inverter circuit that outputs a drive voltage to a motor, usually, when switching on and off of the series-connected upper and lower switching elements, the switching elements are not simultaneously turned on to prevent a short circuit. A period is provided in which both of the elements are off. The above period is generally called dead time. At the dead time timing, current continues to flow due to the motor inductance and the free wheeling diode of the inverter circuit. Then, depending on the direction in which the current flows, a difference occurs between the voltage to be output from the inverter circuit to the motor and the voltage actually output to the motor. The above difference is hereinafter referred to as "the error of the output voltage". Conventionally, dead time compensation is generally performed to compensate for an error in the output voltage caused by providing a dead time.

  For example, in Patent Documents 1 and 2, the dead time compensation amount of each phase is added or subtracted from each voltage command value of three phases, and each voltage command value after addition or subtraction is PWM (Pulse Width Modulation; pulse width A technique is disclosed that performs dead time compensation by inputting to a modulation) circuit and turning on / off each switching element (for example, a transistor) of the inverter circuit by PWM control.

In particular, in patent document 1, when performing dead time compensation, the three-phase current command values iu ^* , iv ^* , iw ^* are calculated from the two-phase current command values id ^* and iq ^*, and the three-phase current command values are calculated. A configuration is disclosed that uses iu ^* , iv ^* , iw ^* to calculate dead time compensation amounts ed (iu ^* ), ed (iv ^* ), ed (iw ^* ). Furthermore, in Patent Document 1, the actual output current values (three phases) of the inverter circuit are detected, and the current command values id ^* and iq ^{* of} two phases and the actual output current values (coordinate conversion from three phases to two phases) Calculating the current error with the current value), and outputting voltage command values ed ^* and eq ^* corresponding to the current error, and the voltage command values ed ^* and eq ^* are three-phase voltage command values eu ^* and ev ^*, into a ew ^*, the voltage command values ^{eu *,} ev *, ew ^* to the dead time compensation amount ^{ed (iu *), ed (} iv *), ed (iw *) to be also disclosed configured to add each There is.

  Further, in Patent Document 2, a voltage command is issued based on a result of determination as to whether the PWM pulse changes from on to off or from off to on. A configuration for adding or subtracting the dead time compensation voltage to generate a compensated voltage command is disclosed.

JP-A 9-261974 (see claim 1, paragraphs [0005], [0010], FIG. 5, and FIG. 9) JP 2011-55608 A (see claim 1, paragraphs [0021], [0022], [0025] to [0027], FIG. 1, etc.)

Conventionally, when performing dead time compensation, it is necessary to obtain an output current value (a current detection value of a motor) of an inverter circuit, in other words, to detect a phase current of the motor as in Patent Documents 1 and 2. Furthermore, in patent document 1, in order to perform dead time compensation, complex coordinate conversion processing is necessary to convert two phase current command values id ^* and iq ^* into three phase current command values iu ^* , iv ^* and iw ^*. Met. Therefore, conventionally, dead time compensation could not be easily performed.

  An object of the present invention is to provide a motor drive control device capable of easily performing dead time compensation without performing detection of a phase current of a motor and complicated coordinate conversion processing.

  An exemplary motor drive control device according to the present invention uses a PWM inverter that outputs a voltage to a motor by converting a voltage command into a PWM pulse and switching on and off each switching element connected in series by the PWM pulse. A motor drive control device for driving and controlling the motor, wherein an error in the output voltage of the PWM inverter is caused by providing a dead time for avoiding simultaneous on of the switching elements connected in series in the PWM inverter. A dead time compensation unit for obtaining a compensation amount for compensating the voltage, and outputting the voltage command including the compensation amount to the PWM inverter, and the dead time compensation unit is a current to be followed by the current flowing through the motor Based on the magnitude of the current command vector indicating a vector of Determine the amount, the current command vector coordinate system synchronized with the rotor of the motor, or has been a vector defined in a coordinate system based thereon.

  According to the above configuration, it is possible to easily perform dead time compensation without performing detection of phase current and complicated coordinate conversion processing regarding current command.

FIG. 1 is a block diagram showing the overall configuration of a motor drive system according to an embodiment of the present invention. FIG. 2 is a circuit diagram showing the configuration of a part of the motor drive system. FIG. 3 is an explanatory view showing an example of waveforms of three-phase AC voltages applied to the motor of the motor drive system. FIG. 4 is an explanatory view showing a relationship between a voltage level of each phase voltage and a carrier signal in PWM control, and a waveform of a PWM pulse applied to each switching element. FIG. 5A is an equivalent circuit around the armature winding at timings T0 to T1 in FIG. 4. FIG. 5B is an equivalent circuit around the armature winding at timings T1 to T2 in FIG. 4. FIG. 5C is an equivalent circuit around the armature winding at timings T2 to T3 in FIG. 4. FIG. 5D is an equivalent circuit around the armature winding at timings T3 to T4 in FIG. 4. FIG. 6A is an explanatory view showing an analysis model of the motor in a case where θ is the phase of the d axis with respect to the reference axis A. FIG. 6B is an explanatory view showing an analysis model of the motor in a case where θ is a phase of q axis with respect to the reference axis A. FIG. 7 is an explanatory drawing showing an example of how to obtain the conventional general dead time compensation amount. FIG. 8 is an explanatory view showing how to obtain the compensation amount in the embodiment of the present invention. FIG. 9 is an explanatory view schematically showing a current command vector. FIG. 10 is an explanatory view showing a current command vector when the d-axis current command is set to 0 [A]. FIG. 11 is an explanatory drawing showing the amount of compensation when the magnitude of the current command vector is equal to or greater than the current threshold. FIG. 12 is an explanatory view showing a waveform of each phase current and a change with time of an electrical angle phase of a rotor of the motor. FIG. 13 is an explanatory view schematically showing a method of determining the polarity of the compensation amount for the U phase using the value of the electrical angle phase of the rotor. FIG. 14 is an explanatory view schematically showing a method of determining the polarity of the compensation amount for the V phase using the value of the electrical angle phase of the rotor. FIG. 15 is an explanatory view schematically showing a method of determining the polarity of the compensation amount for the W phase using the value of the electrical angle phase of the rotor. FIG. 16 is an explanatory view showing the waveform of the U-phase current and the change with time of the electrical angle phase of the rotor when the rotational speed of the rotor is negative.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, the value of the voltage command (voltage command value) is simply referred to as a voltage command, and the value of the current command (current command value) is simply referred to as a current command.

<Schematic Configuration of Motor Drive System>
FIG. 1 is a block diagram showing an overall configuration of a motor drive system 1 according to an exemplary embodiment of the present invention, and FIG. 2 is a circuit diagram showing a partial configuration of the motor drive system 1. The motor drive system 1 includes a motor 2, a PWM inverter 3, a motor drive controller 4, a DC power supply 5, and a position sensor 6. The details of the motor drive control device 4 will be described later. As shown in FIG. 2, the DC power supply 5 outputs a DC voltage between the positive output terminal 5a and the negative output terminal 5b, with the negative output terminal 5b as the low voltage side.

  The motor 2 is configured of, for example, a three-phase brushless DC motor (BLDC motor). More specifically, as shown in FIG. 2, the motor 2 is provided with a rotor 21 provided with permanent magnets, and U-phase, V-phase and W-phase armature windings 22u, 22v and 22w. And a stator 22. The armature windings 22 u, 22 v and 22 w are Y-connected around the neutral point 23. In armature windings 22 u, 22 v and 22 w, non-connected ends opposite to neutral point 23 are connected to terminals 24 u, 24 v and 24 w respectively.

  The PWM inverter 3 includes a power unit 31 and a PWM circuit 32. The PWM circuit 32 performs PWM control of the power unit 31 based on the voltage commands Vu_ref ′, Vv_ref ′ and Vw_ref ′ output from the motor drive control device 4. The voltage commands Vu_ref ', Vv_ref' and Vw_ref 'are voltage commands in consideration of the dead time compensation amount acquired by the method described later.

  The power unit 31 includes a U-phase half bridge circuit, a V-phase half bridge circuit, and a W-phase half bridge circuit. Each half bridge circuit has a pair of switching elements. In each half bridge circuit, a pair of switching elements are connected in series between positive output terminal 5a and negative output terminal 5b of DC power supply 5, and a DC voltage from DC power supply 5 is applied to each half bridge circuit. Each switching element is formed of, for example, a field effect transistor, but may be formed of another transistor such as an IGBT (insulated gate bipolar transistor).

  The U-phase half bridge circuit includes a high voltage side switching element 33 u and a low voltage side switching element 34 u connected in series with each other. The V-phase half bridge circuit includes a high voltage side switching element 33 v and a low voltage side switching element 34 v connected in series with each other. The W-phase half bridge circuit includes a high voltage side switching element 33 w and a low voltage side switching element 34 w connected in series with each other.

  Diodes 35u, 35v and 35w are respectively connected in parallel to the high voltage side switching elements 33u, 33v and 33w, with the direction from the low voltage side to the high voltage side of the DC power supply 5 as a forward direction. Similarly, diodes 36u, 36v and 36w are connected in parallel to the low voltage side switching elements 34u, 34v and 34w, respectively, with the direction from the low voltage side to the high voltage side of the DC power supply 5 as a forward direction. Each of the diodes 35 u, 35 v, 35 w, 36 u, 36 v and 36 w functions as a free wheeling diode.

  The connection point between the switching element 33 u and the switching element 34 u connected in series is connected to the terminal 24 u. Similarly, a connection point between the switching element 33v and the switching element 34v connected in series is connected to the terminal 24v, and a connection point between the switching element 33w and the switching element 34w connected in series is connected to the terminal 24w.

  The PWM circuit 32 generates a PWM pulse (pulse width modulation signal) for each phase based on the voltage commands Vu_ref ′, Vv_ref ′ and Vw_ref ′ of three phases (U phase, V phase and W phase), and the PWM pulse To the control terminal (gate or base) of each switching element of the power unit 31. Thereby, it is possible to switch on (conductive) and off (nonconductive) of each of the switching elements.

  Therefore, in the PWM inverter 3, the DC voltage from the DC power supply 5 is applied to the motor 2 by the switching operation of each switching element according to the PWM pulse, whereby each armature winding 22 u of the motor 2 is , 22v and 22w, currents according to the voltages of the three phases flow, and the motor 2 is driven. The relationship between the switching operation of each switching element and the current (phase current) flowing to the motor 2 will be described later.

  From the above, the PWM inverter 3 of this embodiment converts the voltage commands Vu_ref ′, Vv_ref ′ and Vw_ref ′ into PWM pulses, and switches the on / off of the respective switching elements connected in series by the PWM pulse, Can be said to output a voltage to

  The position sensor 6 shown in FIG. 1 is a sensor that outputs a signal according to the rotational position of the rotor 21 of the motor 2 and uses, for example, a rotary encoder or a Hall element. A signal output from the position sensor 6 is input to a motor drive control device 4 described later.

<Relationship between switching operation of each switching element and phase current>
Next, the relationship between the switching operation of each switching element in the power unit 31 of the PWM inverter 3 and the phase current of the motor 2 will be described. In the following, for convenience of explanation, a line connecting the low voltage side switching elements 34 u, 34 v and 34 w in the power unit 31 and the negative output terminal 5 b of the DC power supply 5 is called a bus G. The current flowing through the bus G is called bus current. In addition, currents flowing in armature windings 22 u, 22 v and 22 w of motor 2 are respectively referred to as U-phase current, V-phase current and W-phase current, and each of them (or collectively Call. Regarding the polarity of the phase current, the polarity of the phase current in the direction of flowing into the neutral point 23 from the terminal 24 u, 24 v or 24 w is positive, and the polarity of the phase current in the direction of flowing out of the neutral point 23 is negative.

  FIG. 3 is an explanatory view showing an example of the waveforms of three-phase AC voltages applied to the motor 2. In FIG. 3, 25 u, 25 v and 25 w respectively represent waveforms of U-phase voltage, V-phase voltage and W-phase voltage to be applied to the motor 2. Each of the U-phase voltage, the V-phase voltage, and the W-phase voltage (or generically, they are collectively referred to as a phase voltage). When a sinusoidal current is supplied to the motor 2, the output voltage of the PWM inverter 3 is sinusoidal.

  As shown in FIG. 3, the high / low relationship between the voltage levels of the U-phase voltage, the V-phase voltage and the W-phase voltage changes with the passage of time. The high-low relationship is determined by the three phase voltage commands Vu_ref ', Vv_ref' and Vw_ref ', and the PWM inverter 3 determines the conduction pattern for each phase based on the three phase voltage commands Vu_ref', Vv_ref 'and Vw_ref'. Do.

  Here, the following eight patterns exist in the above-mentioned energization pattern. The first energization pattern is an energization pattern in which the switching elements 34u, 34v and 34w on the low voltage side of the U, V and W phases are all turned on. The second conduction pattern is a conduction pattern in which the W phase high voltage side switching element 33w is turned on and the U phase and V phase low voltage side switching elements 34u and 34v are turned on. The third energization pattern is an energization pattern in which the switching element 33v on the high voltage side of the V phase is turned on, and the switching elements 34w and 34u on the low voltage side of the W phase and the U phase are turned on. The fourth energization pattern is an energization pattern in which the switching elements 33v and 33w on the high voltage side of the V phase and the W phase are turned on, and the switching element 34u on the low voltage side of the U phase is turned on. The fifth energization pattern is an energization pattern in which the U-phase high voltage side switching element 33u is turned on and the V-phase and W-phase low voltage side switching elements 34v and 34w are turned on. The sixth energization pattern is an energization pattern in which the switching elements 33w and 33u on the high voltage side of the W phase and the U phase are turned on and the switching element 34v on the low voltage side of the V phase is turned on. The seventh conduction pattern is a conduction pattern in which the switching elements 33u and 33v on the high voltage side of the U phase and the V phase are turned on and the switching element 34w on the low voltage side of the W phase is turned on. The eighth conduction pattern is a conduction pattern in which the switching elements 33u, 33v and 33w on the high voltage side of the U, V and W phases are all turned on.

  In addition, in two switching elements of the same phase (connected in series), the high voltage can be avoided if the dead time for avoiding a short circuit due to simultaneous turning on of the switching element on the high voltage side and the switching element on the low voltage side is ignored. While the switching element on the side is on, the switching element on the low voltage side is off, and the switching element on the low voltage side is on while the switching element on the high voltage side is off.

  Actually, the dead time is provided when switching each switching element on and off, but in the dead time period, the switching element on the high voltage side and the switching element on the low voltage side of the same phase are simultaneously turned off It becomes. Further, as described above, by providing the dead time, an error (error in output voltage) occurs between the voltage output from the PWM inverter 3 to the motor 2 and the voltage (voltage command) desired to be output. . In the present embodiment, an error of the output voltage is compensated by the dead time compensation unit 44 described later.

  FIG. 4 is an explanatory view showing the relationship between the voltage level of each phase voltage and the carrier signal and the waveform of the PWM pulse applied to each switching element when performing PWM control for three phases. Here, the above dead time is ignored for the purpose of simplifying the explanation. Further, “high voltage side SW” and “low voltage side SW” in FIG. 4 indicate a high voltage side switching element and a low voltage side switching element, respectively. Although the level relationship of the voltage level of each phase voltage changes variously, in FIG. 4, attention is paid to an arbitrary timing 26 in FIG. 3 for the purpose of the description. That is, FIG. 4 shows the case where the voltage level of the U-phase voltage is the maximum and the voltage level of the W-phase voltage is the minimum.

  In FIG. 4, a symbol CS represents a carrier signal to be compared with the voltage level of each phase voltage. The carrier signal is a periodic triangular wave signal, and the period of the signal is referred to as a carrier period. Since the carrier cycle is much shorter than the cycle of the three-phase AC voltage shown in FIG. 3, if the triangular wave of the carrier signal shown in FIG. 4 is represented on FIG. 3, the triangular wave becomes one line. Looks like.

  5A to 5D are equivalent circuits around the armature winding at each timing of FIG. 4. The start timing of each carrier cycle, that is, the timing at which the carrier signal is at the lowest level is denoted by T0. At timing T0, the switching elements 33u, 33v and 33w on the high voltage side of each phase are turned on.

  The period excluding the period between the timing T1 and the timing T6 from the carrier period represents the pulse width of the PWM pulse for the switching element on the high voltage side of the W phase, and the period between the carrier period and the timing T2 and T5. The period excluding T represents the pulse width of the PWM pulse for the switching element on the high voltage side of V phase, and the period excluding the period between timings T3 and T4 from the carrier period is the switching on the high voltage side of U phase Represents the pulse width of the PWM pulse for the element.

  In the above, the case where the magnitude relation of voltage levels is in the order of U phase voltage> V phase voltage> W phase voltage has been described as an example, but even when the magnitude relation of voltage levels is in other order, the same PWM The control can control the phase current of the motor 2.

<About counter control of voltage command>
Specifically, voltage commands Vu_ref ′, Vv_ref ′ and Vw_ref ′ of U phase, V phase and W phase are represented as count setting values CntU, CntV and CntW of a counter (timer) (not shown) in PWM circuit 32. Ru. Then, as the phase voltage is higher, a larger count set value is given. For example, in the case of FIG. 4, CntU>CntV> CntW is established.

  The above counter counts up the count value from 0 every carrier period with reference to the timing T0. Then, when the count value reaches CntW, the switching element 33w on the high voltage side of the W phase is switched from the on state to the switching element 34w on the low voltage side to the on state. Subsequently, when the count value reaches CntV, the switching element 33v on the high voltage side of the V phase is switched from the on state to the switching element 34v on the low voltage side to the on state. Thereafter, when the count value reaches CntU, the switching element 33u on the high voltage side of the U phase is switched from the on state to the switching element 34u on the low voltage side to the on state. After the carrier signal reaches the maximum level, the count value is down-counted and the reverse switching operation is performed.

  When a triangular carrier signal shown in FIG. 4 is used, up-counting is turned back to down-counting at half the carrier period. The up-counting and down-counting described above are performed in synchronization with a predetermined clock.

  The pulse width (and the duty) of the PWM pulse for each phase is generated by count set values CntU, CntV and CntW corresponding to U-phase, V-phase and W-phase voltage commands Vu_ref ', Vv_ref' and Vw_ref '.

<About various definitions>
Next, before describing the details of the motor drive control device 4 described above, various definitions are shown below. 6A and 6B are explanatory diagrams showing an analysis model of the motor 2. The U-phase axis, the V-phase axis and the W-phase axis are fixed axes, and they are mutually offset by 120 ° in electrical angle. Reference numeral 21 a is a permanent magnet provided on the rotor 21 of the motor 2. In a rotating coordinate system that rotates at the same speed as the magnetic flux produced by the permanent magnet 21a, the direction of the magnetic flux produced by the permanent magnet 21a is taken as the d axis, and the q axis is taken a phase advanced 90 ° in electrical angle from the d axis. A coordinate system having a d-axis and a q-axis is called a dq coordinate system, and coordinates obtained by selecting the d-axis and the q-axis as coordinate axes are called dq coordinates. The dq coordinate system is a coordinate system synchronized with the rotor 21 of the motor 2.

  The phase of the d-axis or q-axis with respect to a certain reference axis A (fixed axis) is represented by θ (electrical angle phase) at dq coordinates at any instants of the rotating d-axis and q-axis. In the present embodiment, a certain reference axis A is a U phase axis, and the phase of the q axis with respect to the U phase axis is represented by θ (electrical angle phase). That is, when the electrical angle phase of the rotor 21 is represented in the range of -180 ° to + 180 °, for example, the reference axis A corresponds to the electrical angle phase 0 °. Assuming that the deviation between the U-phase axis and the reference axis A at the electrical angle is θa, the deviation θa is determined by the motor drive system 1, and in the present embodiment, the electrical angle is 0 °, for example. The information on the deviation θa may be stored, for example, in a memory (not shown) of the motor drive control device 4.

  Further, the entire motor voltage applied from the PWM inverter 3 to the motor 2 is represented by Va, and the entire motor current supplied from the PWM inverter 3 to the motor 2 is represented by Ia. The d-axis component and the q-axis component of motor voltage Va are represented by d-axis voltage vd and q-axis voltage vq, respectively, and the d-axis component and q-axis component of motor current Ia are respectively d-axis current id and q-axis current Represented by iq.

  Further, command values (voltage command values) for the d-axis voltage vd and the q-axis voltage vq are represented by a d-axis voltage command vd_ref and a q-axis voltage command vq_ref, respectively. The d-axis voltage command vd_ref and the q-axis voltage command vq_ref represent voltages (voltage values) to be followed by the d-axis voltage vd and the q-axis voltage vq, respectively, and are calculated in the motor drive system 1.

  Further, command values (current command values) for the d-axis current id and the q-axis current iq are represented by a d-axis current command id_ref and a q-axis current command iq_ref, respectively. The d-axis current command id_ref and the q-axis current command iq_ref represent currents (current values) to be followed by the d-axis current id and the q-axis current iq, respectively, and are calculated in the motor drive system 1.

<Details of Motor Drive Controller>
Based on the above definition, the motor drive control device 4 will be described. The motor drive control device 4 shown in FIG. 1 is a control unit that drives and controls the motor 2 using the PWM inverter 3 and includes a position detection unit 41, a current controller 42, a coordinate converter 43, and dead time compensation. And a unit 44. The motor drive control device 4 is composed of, for example, a microcomputer having a central processing unit (CPU).

  The position detection unit 41 detects the electrical angle phase θ of the rotor 21 based on the output signal from the position sensor 6 described above. Information of the detected electrical angle phase θ is output from the position detection unit 41 to the coordinate converter 43 and the dead time compensation unit 44 as position information of the rotor 21.

  The current controller 42 converts the d-axis current command id_ref and the q-axis current command iq_ref that are input into the d-axis voltage command vd_ref and the q-axis voltage command vq_ref, and outputs the d-axis current command id_ref and the q-axis voltage command vq_ref to the coordinate converter 43.

  The coordinate converter 43 converts the d-axis voltage command vd_ref and the q-axis voltage command vq_ref input from the current controller 42 into U-phase, V-phase and W-phase voltage commands Vu_ref, Vv_ref and Vw_ref, respectively. The signal is output to the compensation unit 44. Information on the electrical angle phase θ of the rotor 21 is input from the position detection unit 41 to the coordinate converter 43, and the deviation θa at the electrical angle between the U phase axis and the reference axis A is also known in advance, From the relationship shown in FIG. 6A and FIG. 6B, the coordinate converter 43 uses the electrical angle phase θ and the deviation θa of the rotor 21 to command each voltage in the d-axis direction and q-axis direction (two-phase voltage command) Can be coordinate-converted in each direction of the U-phase axis, the V-phase axis, and the W-phase axis to obtain voltage commands (three-phase voltage commands) for the U-phase, the V-phase, and the W-phase.

  Dead time compensation unit 44 compensates for an error in the output voltage of PWM inverter 3 caused by providing a dead time for avoiding simultaneous turning on of the respective switching elements connected in series in PWM inverter 3. And outputs a voltage command to the PWM inverter 3 in consideration of the compensation amount ΔVd. That is, dead time compensation unit 44 adds or subtracts compensation amount ΔVd for each phase to voltage commands Vu_ref, Vv_ref and Vw_ref of the U phase, V phase and W phase input from coordinate converter 43. Voltage commands Vu_ref ′, Vv_ref ′ and Vw_ref ′ taking into account the compensation amount ΔVd of each phase are respectively generated and output to the PWM inverter 3. It should be noted that compensating the error of the output voltage caused by providing the dead time, that is, generating the voltage commands Vu_ref ′, Vv_ref ′ and Vw_ref ′ taking into account the compensation amount ΔVd of each phase is also referred to as dead time compensation. Call.

  Here, FIG. 7 is an explanatory view showing how to determine the conventional general compensation amount ΔVd. For example, when considering the compensation amount ΔVd for the U phase, conventionally, the instantaneous value (instantaneous value) of the U phase current is detected, and if the detected current is less than the threshold value, the compensation amount ΔVd is proportional to the detected current value Was determined. Then, the obtained compensation amount ΔVd is added to or subtracted from the U-phase voltage command to generate a voltage command in which the compensation amount ΔVd is added. On the other hand, when the detected current exceeds the threshold value, the compensation amount ΔVd is uniformly set to the fixed value ΔVd ′. In such dead time compensation, since detection of a phase current (U-phase current in the above example) is required, dead time compensation can not be easily performed. Note that how to set such a compensation amount ΔVd is also disclosed in the above-mentioned Patent Document 2 (see FIG. 8 of Patent Document 2).

  On the other hand, FIG. 8 is an explanatory view showing how to obtain the compensation amount ΔVd in the present embodiment. In the present embodiment, the dead time compensation unit 44 obtains the compensation amount ΔVd based on the magnitude of the current command vector I_ref indicating the vector of the current to be followed by the current flowing through the motor 2. Thereby, dead time compensation can be easily performed without detecting the phase current described above. Hereinafter, the dead time compensation of the present embodiment will be described in more detail. In the following, the case of obtaining the compensation amount ΔVd for any one of the U phase, V phase, and W phase (for example, U phase) will be described as an example, but the compensation amount can be obtained using the same method for other phases. ΔVd can be determined.

FIG. 9 schematically shows the current command vector I_ref. The current command vector I_ref is a composite vector of each vector component of the d-axis current command id_ref and the q-axis current command iq_ref described above. Assuming that the magnitude of the current command vector I_ref is | I_ref |, | I_ref | is expressed by the following equation (1).
| I_ref | = √ {(id_ref) ² + (iq_ref) ² } (1)

Here, in order to simplify the calculation further, as shown in FIG. 10, the d-axis current command id_ref is considered as 0 [A]. That is, the dead time compensation unit 44 obtains the compensation amount ΔVd based on the magnitude of the current command vector I_ref when the d-axis current command id_ref is 0 [A]. In this case, the magnitude (| I_ref |) of the current command vector I_ref is expressed by the following equation (2), and becomes the magnitude itself of the q-axis current command iq_ref.
| I_ref | = | iq_ref | (2)

Specifically, in the present embodiment, the compensation amount ΔVd is obtained as follows using | I_ref | (= | iq_ref |). In FIG. 8, a current waveform corresponding to a phase current (for example, a U-phase current) is shown by a sine wave of a broken line. The current waveform is indicated by a broken line in the present embodiment, unlike the case of FIG. 7, because the phase current is not detected. The above-mentioned | I_ref | (= | iq_ref |) corresponds to the amplitude of the current waveform of the phase current in FIG. Therefore, in the present embodiment, a predetermined fixed value of the compensation amount is ΔVd ′, the q-axis current command is iq_ref (t) [A] with time t as a variable, and the current threshold is ith [A]. At this time, the dead time compensation unit 44 determines ΔVd obtained by the calculation of the following equation (3) as a compensation amount. However, it is assumed that | I_ref | (= | iq_ref |) is less than the current threshold ith.
ΔVd = ΔVd ′ × | iq_ref (t) | / ith (3)

  As shown in FIG. 8, the polarity of the compensation amount ΔVd is positive in a period in which the polarity of the phase current is positive (for example, a period of t0 to t1, a period of t2 to t3), and the polarity of the phase current is negative. It becomes negative in the following period (for example, the period of t1 to t2, the period of t3 to t4). The polarity of the compensation amount ΔVd is determined by a method described later, and here, the magnitude (absolute value) of the compensation amount ΔVd is determined first by the equation (3).

  In a period in which the value of | I_ref | corresponding to the amplitude of the phase current is constant (period of t0 to t2 and period of t2 to t4 in FIG. 8), the compensation amount ΔVd (absolute value) is Take a constant value according to. Then, when | I_ref | is less than the current threshold ith, for example, in the period from t2 to t4 in which | I_ref | becomes smaller than the value in the period from t0 to t2, the compensation amount ΔVd is t0 to t2. It becomes smaller than the value in the period. Conversely, in a period in which | I_ref | is larger than the value in the period from t0 to t2, the compensation amount ΔVd is larger than the value in the period from t0 to t2.

  On the other hand, FIG. 11 is an explanatory view showing a compensation amount ΔVd when | I_ref | (= | iq_ref |) is equal to or larger than the current threshold ith. If the absolute value | iq_ref (t) | of the q-axis current command is equal to or greater than the current threshold ith, the dead time compensator 44 determines the fixed value ΔVd ′ as the compensation amount ΔVd. That is, in the equation (3), the current threshold ith is used instead of the absolute value | iq_ref (t) | of the q-axis current command. As a result, from the equation (3), ΔVd = ΔVd ′. Therefore, the compensation amount ΔVd does not exceed the fixed value ΔVd ′ even if | I_ref | (= | iq_ref |) increases beyond the current threshold ith.

  As described above, in the present embodiment, the dead time compensation unit 44 obtains the compensation amount ΔVd based on the current command vector I_ref that is a composite vector of the d-axis current command id_ref and the q-axis current command iq_ref. It becomes unnecessary to detect the phase current, which was necessary for time compensation. Moreover, in the above-mentioned Patent Document 1, when performing dead time compensation, two-phase current commands (for example, respective d-axis and q-axis current commands) can be converted to three-phase current commands (for example, U-phase, V-phase, and W-phase). Although complicated coordinate conversion processing for converting each current command) is necessary, in the configuration of the present embodiment, coordinate conversion processing of such two-phase / three-phase current commands is also unnecessary. Therefore, according to the configuration of the present embodiment, it is possible to easily obtain the compensation amount ΔVd and perform the dead time compensation easily without performing the detection of the phase current or the complicated coordinate conversion processing of the current command.

  Further, the dead time compensation unit 44 obtains the compensation amount ΔVd based on the magnitude of the current command vector I_ref when the d-axis current command id_ref is 0 [A]. In this case, since the magnitude of the current command vector I_ref is equal to the magnitude of the q-axis current command iq_ref according to equation (2), the dead time compensation unit 44 compensates ΔVd based on only the q-axis current command iq_ref. Can be calculated. Therefore, compared with the case where the compensation amount ΔVd is calculated using both the d-axis current command id_ref and the q-axis current command iq_ref, the calculation of the compensation amount ΔVd becomes easier, and the compensation amount ΔVd can be easily obtained.

  Further, when the d-axis current command id_ref is set to 0 [A], the dead time compensation unit 44 determines ΔVd obtained by the calculation of the equation (3) described above as the compensation amount. The fixed value ΔVd ′ and the current threshold ith are predetermined and can be handled as a constant at the time of calculation. The q-axis current command iq_ref (t) also exists as control information. Therefore, the dead time compensation unit 44 can perform the dead time compensation by obtaining the compensation amount ΔVd in proportion to the absolute value | iq_ref (t) | of the q-axis current command without performing complicated processing.

  Further, since the dead time compensation unit 44 calculates the compensation amount ΔVd using the absolute value | iq_ref (t) | of the q-axis current command, the compensation amount ΔVd (absolute value) can be obtained without considering the polarity. it can. Although the polarity of the compensation amount ΔVd differs for each phase (for example, for each of the U phase, V phase, and W phase), the polarity determined by separately obtaining the above polarity by the method described later and the above compensation amount ΔVd (absolute value) Dead time compensation can be performed on the basis of.

  When the absolute value | iq_ref (t) | of the q-axis current command is equal to or greater than the current threshold ith, the dead time compensation unit 44 determines the fixed value ΔVd ′ as the compensation amount ΔVd. When the absolute value | iq_ref (t) | of the q-axis current command is smaller than the current threshold ith, ΔVd <ΔVd ′ is obtained according to equation (3). On the other hand, when the absolute value | iq_ref (t) | of the q-axis current command is equal to or larger than the current threshold ith, the dead time compensator 44 sets ΔVd = ΔVd ′ in order to set the fixed value ΔVd ′ as the compensation amount ΔVd. Therefore, the relationship of ΔVd ≦ ΔVd ′ is always maintained. That is, the compensation amount ΔVd can be set in a range not exceeding the upper limit (ΔVd ′).

  In the above, a composite vector of vector components of the d-axis current command id_ref and the q-axis current command iq_ref defined in the dq coordinate system is considered as the current command vector, but the current command vector is a coordinate system synchronized with the rotor 21 It may be a vector defined in a coordinate system according to it, and is not limited to a vector defined in a dq coordinate system having a d axis and a q axis.

<Dead time compensation in consideration of polarity (addition or subtraction) of compensation amount ΔVd>
Next, the dead time compensation of the present embodiment will be described including a method of deciding whether to add or subtract the compensation amount ΔVd obtained by the above-described method to the voltage command before compensation. Here, as described above, the electric angle phase θ of the rotor 21 is in the range of −180 ° to + 180 °, and the reference of the electric angle phase θ is 0 °. In addition, the rotation direction of the rotor 21 which makes the value of the electrical angle phase θ increase (going from 0 ° to + 180 °) is positive, and the rotation of the value of the electric angle phase θ decreases (going from 0 ° to -180 °) The rotational direction of the child 21 is negative. Further, the rotational speed 0 0 indicates that the rotor 21 rotates in the positive direction or is in the stopped state, and the rotational speed <0 indicates that the rotor 21 rotates in the negative direction (the opposite direction to the positive direction) Point to

  First, the case where the q-axis current command iq_ref ≧ 0 and the rotational speed (0 (positive torque) (condition 1) will be described as an example. Under the condition 1, the respective waveforms of the U-phase current, the V-phase current and the W-phase current, and the change over time of the electrical angle phase of the rotor 21 are as shown in FIG. Since the U-phase current, the V-phase current and the W-phase current are not actually detected, the current waveforms of the respective phases are indicated by broken lines in FIG. Incidentally, the phases of the U-phase current, the V-phase current and the W-phase current are shifted by 120 ° in electrical angle.

  Here, the first phase of the motor 2 is a U phase, the second phase is a V phase, and the third phase is a W phase. Then, the phase difference at the electrical angle between the timing Ta when the U phase current (but not determined in this embodiment) becomes 0 [A] and the timing Tb when the electrical angle phase of the rotor 21 becomes 0 ° is The initial phase difference is θA. In the present embodiment, the initial phase difference θA is 90 °. The 90 ° initial phase difference θA is predetermined by the system.

  In FIG. 12, the electrical angle phase θ of the rotor 21 changes linearly with time, and this change is periodically repeated. A line indicating a change in the electrical angle phase θ shown in FIG. 12 is L0. Then, as shown in FIG. 13, a line obtained by shifting the line L0 in the direction of increasing the electrical angle phase θ by an amount (90 °) corresponding to the initial phase difference θA is L1. From FIG. 13, in the line L1, a period in which the value of the electrical angle phase θ is larger than 0 ° (a period in which the value of the electrical angle phase θ is positive) coincides with a period in which the polarity of the U-phase current is positive, It can be seen that a period in which the value of the electrical angle phase θ is smaller than 0 ° (a period in which the value of the electrical angle phase θ is negative) coincides with a period in which the polarity of the U-phase current is negative. Therefore, by using the line L1, it is possible to estimate the polarity of the U-phase current from the value (polarity) of the electrical angle phase θ indicated by the line L1, without actually detecting the phase current. So, in this embodiment, dead time compensation is performed as follows based on line L1.

(Dead time compensation for U phase)
The dead time compensation unit 44 obtains the polarity of the compensation amount ΔVd based on the q-axis current command iq_ref and the electrical angle phase θ of the rotor 21 detected by the position detection unit 41, thereby dead for the U phase. Perform time compensation. More specifically, the dead time compensation unit 44 adds or subtracts the initial phase difference θA to or from the value of the electrical angle phase θ of the rotor 21 acquired by the position detection unit 41 (here, 90 ° The value of the electrical angle phase θ is added and the voltage of the first phase (U phase) input to the dead time compensation unit 44 when the value of the shifted electrical angle phase θ is positive. While the value obtained by multiplying the compensation amount ΔVd by the polarity of the q-axis current command iq_ref with respect to the command Vu_ref is added and output, the first value is obtained if the value of the shifted electrical angle phase θ is negative. A value obtained by multiplying the compensation amount ΔVd by the polarity of the q-axis current command iq_ref with respect to the voltage command Vu_ref of the phase (U phase) is subtracted and output.

As a result of the above calculation in the dead time compensation unit 44, the voltage command Vu_ref 'after compensation for the U phase is
If the value of the electrical angle phase θ after shifting is positive,
Vu_ref '= Vu_ref + ΔVd × (polarity of q-axis current command iq_ref)
... (8a)
Represented by
If the value of the electrical angle phase θ after shifting is negative,
Vu_ref ′ = Vu_ref−ΔVd × (polarity of q-axis current command iq_ref)
... (8b)
Is represented by

Under condition 1, since the polarity of the q-axis current command iq_ref is positive, the voltage command Vu_ref ′ after compensation is expressed as follows from the equations (8a) and (8b). That is, the voltage command Vu_ref 'after compensation is
If the value of the electrical angle phase θ after shifting is positive,
Vu_ref '= Vu_ref + ΔVd (9a)
Represented by
If the value of the electrical angle phase θ after shifting is negative,
Vu_ref '= Vu_ref-ΔVd (9b)
Is represented by The equation (9a) means that the compensation amount ΔVd is added to the voltage command Vu_ref before compensation because the polarity of the compensation amount ΔVd is positive. On the other hand, since the polarity of the compensation amount ΔVd is negative, the equation (9b) means that the compensation amount ΔVd is subtracted from the voltage command Vu_ref before compensation.

  On the other hand, Condition 2 is a case where the q-axis current command iq_ref <0 and the rotational speed) 0 (positive torque). Under the condition 2, the relationship between the addition processing and the subtraction processing of the compensation amount ΔVd becomes opposite to that of the condition 1 due to the negative polarity of the q-axis current command iq_ref.

That is, under condition 2, since the polarity of the q-axis current command iq_ref is negative, the voltage command Vu_ref ′ after compensation is expressed as follows from the equations (8a) and (8b). That is, when the value of the electrical angle phase θ after the shift is positive, the voltage command Vu_ref ′ after compensation is:
Vu_ref '= Vu_ref-ΔVd (10a)
Is represented by That is, in the second term of the right side of the equation (8a), the polarity of the compensation amount ΔVd becomes negative by multiplying + ΔVd and the negative polarity of the q-axis current, and the compensation amount ΔVd is subtracted as a total become. On the other hand, when the value of the electrical angle phase θ after the shift is negative, the compensated voltage command Vu_ref ′ is
Vu_ref '= Vu_ref + ΔVd (10b)
Is represented by That is, in the second term of the right side of the equation (8b), the polarity of the compensation amount ΔVd becomes positive by combining −ΔVd and the negative polarity of the q-axis current, and the compensation amount ΔVd is added as a total It will be.

  As described above, under Condition 1 and Condition 2, the relationship between the addition processing and the subtraction processing in the total of the compensation amount ΔVd is reversed. However, when the value of the shifted electric angle phase θ is positive, a value obtained by multiplying the compensation amount ΔVd by the polarity of the q-axis current command iq_ref is added to the voltage command Vu_ref, and the shifted electric If the value of angular phase θ is negative, conditions 1 and 2 are common in that a value obtained by multiplying compensation amount ΔVd by the polarity of q-axis current command iq_ref is subtracted from voltage command Vu_ref. It can be said that

  As described above, in the present embodiment, the dead time compensation unit 44 is based on the q-axis current command iq_ref (especially the polarity) and the electric angle phase θ of the rotor 21 detected by the position detection unit 41. The polarity of the compensation amount ΔVd (whether ΔVd is added or subtracted) is determined. By this, detection of the phase current, which was conventionally required at the time of dead time compensation, and the previously determined dead without performing complicated coordinate conversion processing for converting the two-phase current command into the three-phase current command Dead time compensation can be performed by correcting the voltage command by adding the above polarity to the time compensation amount ΔVd (absolute value) (adding / subtracting the compensation amount to the voltage command).

  In addition, when performing dead time compensation, basically, for each of the U, V, and W phases, the compensation amount ΔVd is added to the voltage command before compensation in the case of phase current 0 0. If the phase current is less than 0, processing for subtracting the compensation amount ΔVd is performed. In the present embodiment, since the phase current is not detected, the polarity of the phase current can not be determined directly. However, according to the relationship between the line L1 (electrical angle phase θ after shift) shown in FIG. 13 and the waveform of the U-phase current, even if the U-phase current is not actually detected, The polarity of the U-phase current can be estimated from the polarity and the polarity of the q-axis current command iq_ref. Thus, it can be simply determined whether the compensation amount ΔVd should be added or subtracted from the voltage command before compensation.

  Therefore, as described above, the dead time compensation unit 44 determines the value of the electrical angle phase θ indicated by the line L1 (the value of the electrical angle phase θ after 90 ° shift) and the q-axis current command iq_ref (especially the polarity) Based on the compensation amount ΔVd to determine the polarity (addition or subtraction), adding or subtracting the compensation amount ΔVd to calculate the voltage command Vu_ref 'after compensation, as in the prior art U-phase current detection, The voltage command Vu_ref ′ after compensation taking into account the compensation amount ΔVd can be easily obtained for the U phase without performing complicated coordinate conversion processing from the two-phase current command to the three-phase current command. Thereby, dead time compensation can be easily performed for the U phase.

  In the example of FIG. 12, since the timing Tb is later in time than the timing Ta, the value of the electrical angle phase θ of the rotor 21 acquired by the position detection unit 41 is initial as shown in FIG. The phase difference θA is added (here, 90 ° is added) to shift the value of the electrical angle phase θ. For example, when the timing Tb is earlier in time than the timing Ta, the initial phase difference θA is subtracted from the value of the electric angle phase θ of the rotor 21 acquired by the position detection unit 41 to obtain the electric angle phase θ The line L1 similar to FIG. 13 can be obtained by shifting the value of. Therefore, also in this case, dead time compensation unit 44 multiplies voltage command Vu_ref before compensation by compensation amount ΔVd by the polarity of q-axis current command iq_ref based on the value of electrical angle phase θ after shifting. Dead time compensation can be performed by adding or subtracting these values.

(Dead time compensation for V phase)
FIG. 14 is an explanatory view showing the waveform of the V-phase current under the condition 1 and the change with time of the electric angle phase θ of the rotor 21 together. However, the q-axis current command iq_ref ≧ 0, and the rotational speed of the rotor 21 回 転 子 0 (positive torque). Since the phase of the V-phase current is delayed by 120 ° in electrical angle with respect to the phase of the U-phase current, as shown in FIG. 14, the electrical angle of the line L1 corresponds to 120 ° in electrical angle. The phase θ is shifted in the decreasing direction. Let L2 be the line after shift.

  From FIG. 14, in the line L2, a period in which the value of the electrical angle phase θ is larger than 0 ° (a period in which the value of the electrical angle phase θ is positive) coincides with a period in which the polarity of the V phase current is positive, It can be seen that a period in which the value of the electrical angle phase θ is smaller than 0 ° (a period in which the value of the electrical angle phase θ is negative) coincides with a period in which the polarity of the V-phase current is negative. Therefore, by utilizing the line L2, it is possible to deduce the polarity of the V-phase current from the value (polarity) of the electrical angle phase θ indicated by the line L2 without actually detecting the phase current. Therefore, for the V phase, dead time compensation is performed as follows based on the line L2.

  That is, dead time compensation unit 44 compensates for compensation amount ΔVd for voltage command Vv_ref of the second phase (V phase) delayed by 120 ° in electrical angle with respect to the first phase (U phase) of motor 2 When adding or subtracting, the value of the electrical angle phase θ after the 120 ° subtraction after subtracting 120 ° from the value of the electrical angle phase θ shifted above (corresponding to the line L1) is positive Is the value obtained by multiplying the compensation amount ΔVd by the polarity of the q-axis current command iq_ref with respect to the voltage command Vv_ref of the second phase (V phase) input to the dead time compensation unit 44. On the other hand, when the value of the electrical angle phase θ after subtraction of 120 ° is negative, the compensation amount ΔVd is the polarity of the q-axis current command iq_ref with respect to the voltage command Vv_ref of the second phase (V phase). Subtract and output the multiplied value.

As a result of the above calculation in dead time compensation unit 44, voltage command Vv_ref ′ after compensation for the V phase is
If the value of the electrical angle phase θ after subtraction of 120 ° is positive,
Vv_ref '= Vv_ref + ΔVd × (polarity of q axis current command iq_ref)
Represented by
If the value of the electrical angle phase θ after subtraction of 120 ° is negative,
Vv_ref ′ = Vv_ref−ΔVd × (polarity of q-axis current command iq_ref)
Is represented by

  When condition 2 (q-axis current command iq_ref <0, rotational speed 0 0 (positive torque)), the relationship between the addition processing and the subtraction processing of the compensation amount ΔVd is opposite to that in the case 1; It is quite similar to the case of dead time compensation for U phase.

  As described above, in the dead time compensation for the V phase, the dead time compensation unit 44 calculates the value of the electrical angle phase θ indicated by the line L2 (the value of the electrical angle phase θ after subtraction of 120 °) and the q axis current command Based on iq_ref (particularly, polarity), the polarity (whether to add or subtract) of the compensation amount ΔVd is determined, and the voltage command Vv_ref ′ after compensation is calculated. As a result, without performing detection of the V-phase current and complicated coordinate conversion processing from the two-phase current command to the three-phase current command as in the prior art, after compensation taking into account the compensation amount ΔVd for the V-phase. Voltage command Vv_ref 'can be easily obtained. Thereby, dead time compensation can be easily performed for the V phase.

  In the above, the line L1 is shifted in the direction of decreasing the electric angle phase θ (subtracted by 120 °) to obtain the line L2, but the line L0 is reduced in the direction of the electric angle phase θ The line L2 can be obtained even if it is shifted to (30.degree. Subtracted). Therefore, the dead time compensation unit 44 adds or subtracts the initial phase difference θA from the value of the electrical angle phase θ of the rotor 21 acquired by the position detection unit 41 (here, 90 ° is added) After further subtracting 30 °, when the value of the electrical angle phase θ after the 30 ° subtraction is positive, the compensation amount ΔVd is set to the voltage command Vv_ref of the V phase input to the dead time compensation unit 44. The value obtained by multiplying the polarity of the q-axis current command iq_ref is added and output, while when the value of the electrical angle phase θ after subtraction of 30 ° is negative, compensation is performed for the voltage command Vv_ref of the V phase. It can also be said that a value obtained by multiplying the amount ΔVd by the polarity of the q-axis current command iq_ref may be subtracted and output.

(Dead time compensation for W phase)
FIG. 15 is an explanatory view showing the waveform of the W-phase current under the condition 1 and the change with time of the electric angle phase θ of the rotor 21 together. However, the q-axis current command iq_ref ≧ 0, and the rotational speed of the rotor 21 回 転 子 0 (positive torque). Since the phase of the W-phase current leads the phase of the U-phase current by 120 ° in electrical angle, as shown in FIG. 15, the electrical angle of the line L1 corresponds to 120 ° in electrical angle. The phase θ is shifted in the increasing direction. Let the line after shift be L3.

  From FIG. 15, in the line L3, a period in which the value of the electrical angle phase θ is larger than 0 ° (a period in which the value of the electrical angle phase θ is positive) coincides with a period in which the polarity of the W phase current is positive, It can be seen that a period in which the value of the electrical angle phase θ is smaller than 0 ° (a period in which the value of the electrical angle phase θ is negative) coincides with a period in which the polarity of the W-phase current is negative. Therefore, by utilizing the line L3, it is possible to estimate the polarity of the W-phase current from the value (polarity) of the electrical angle phase θ indicated by the line L3 without actually detecting the phase current. Therefore, for the W phase, dead time compensation is performed based on the line L3 as follows.

  That is, the dead time compensation unit 44 compensates the compensation amount ΔVd for the voltage command Vw_ref of the third phase (W phase) advancing by 120 ° in electrical angle with respect to the first phase (U phase) of the motor 2 When performing addition or subtraction, add 120 ° to the value of the electrical angle phase θ shifted above (corresponding to line L1), and the value of the electrical angle phase θ after 120 ° addition is positive Is the value obtained by multiplying the compensation amount ΔVd by the polarity of the q-axis current command iq_ref with the voltage command Vw_ref of the third phase (W phase) input to the dead time compensation unit 44 On the other hand, when the value of the electrical angle phase θ after 120 ° addition is negative, the compensation amount ΔVd is the polarity of the q-axis current command iq_ref with respect to the voltage command Vw_ref of the third phase (W phase). Subtract and output the multiplied value.

As a result of the above calculation in the dead time compensation unit 44, the voltage command Vw_ref 'after compensation for the W phase is
If the value of the electrical angle phase θ after the 120 ° addition is positive:
Vw_ref '= Vw_ref + ΔVd × (polarity of q-axis current command iq_ref)
Represented by
If the value of the electrical angle phase θ after the 120 ° addition is negative:
Vw_ref ′ = Vw_ref−ΔVd × (polarity of q-axis current command iq_ref)
Is represented by

  When condition 2 (q-axis current command iq_ref <0, rotational speed 0 0 (positive torque)), the relationship between the addition processing and the subtraction processing of the compensation amount ΔVd is opposite to that in the case 1; It is quite similar to the case of dead time compensation for U phase.

  As described above, in the dead time compensation of the W phase, the dead time compensation unit 44 calculates the value of the electrical angle phase θ indicated by the line L3 (the value of the electrical angle phase θ after 120 ° addition) and the q axis current command Based on iq_ref (especially, polarity), the polarity (whether to add or subtract) of the compensation amount ΔVd is determined, and the voltage command Vw_ref ′ after compensation is calculated. As a result, without performing W-phase current detection and complicated coordinate conversion processing from the two-phase current command to the three-phase current command as in the prior art, after compensation taking into account the compensation amount ΔVd for the W phase Voltage command Vw_ref 'can be easily obtained. Thereby, dead time compensation can be easily performed for the W phase.

  In the above description, the line L1 is shifted in the direction in which the electrical angle phase θ increases (by adding 120 °) to obtain the line L3, but the direction in which the electrical angle phase θ decreases the line L0 described above The line L3 can be obtained even if it is shifted (even by subtracting 150.degree.). Therefore, the dead time compensation unit 44 adds or subtracts the initial phase difference θA from the value of the electrical angle phase θ of the rotor 21 acquired by the position detection unit 41 (here, 90 ° is added) After further subtracting 150 °, if the value of the electrical angle phase θ after subtraction of 150 ° is positive, the compensation amount ΔVd for the W-phase voltage command Vw_ref input to the dead time compensation unit 44 The value obtained by multiplying the polarity of the q-axis current command iq_ref is added and output, while if the value of the electrical angle phase θ after subtraction of 150 ° is negative, compensation is performed for the voltage command Vw_ref of the W phase. It can also be said that a value obtained by multiplying the amount ΔVd by the polarity of the q-axis current command iq_ref may be subtracted and output.

(In case of rotation angle <0)
FIG. 16 is an explanatory view showing the waveform of the U-phase current and the change with time of the electrical angle phase θ of the rotor 21 in the case of rotational speed <0 (positive torque). However, q-axis current command iq_ref ≧ 0. When the rotational speed is less than 0, the change over time of the electrical angle phase θ is opposite to that when the rotational speed is greater than or equal to 0, and indicates a transition in which the electrical angle phase θ decreases with time. However, even in this case, the processing relating to dead time compensation is the same as in the case of rotational speed 速度 0.

(Supplement)
In the above, the first phase, the second phase and the third phase have been described as the U phase, the V phase and the W phase, respectively, but for example, the first phase, the second phase and the third phase In order, it may be V phase, W phase, U phase, and may be W phase, U phase, V phase.

  Although the electric angle phase θ of the rotor 21 has been described above as the range of −180 ° to + 180 °, it may be in the range of 0 ° to + 360 °. In this case, the dead time compensation similar to that of the present embodiment is performed by positively correlating the range of + 180 ° or more and less than 360 ° with the reference of + 180 ° and negatively corresponding the range of 0 ° or more and less than 180 °. be able to.

  Although the calculation of the compensation amount ΔVd and the dead time compensation in the case of driving the motor 2 in the three phases of U phase, V phase and W phase have been described above, the method of the present embodiment is limited to three phase motors The present invention can also be applied to the case of driving a motor with four or more phases, and also in this case, the same effect as that of the present embodiment can be obtained.

  The calculation of the compensation amount ΔVd and the dead time compensation described in the present embodiment can be applied to a system in which an error occurs in the output voltage to the motor by providing the dead time and this error needs to be compensated. Therefore, the motor to be subjected to drive control may be a motor other than the BLDC motor. For example, the calculation of the compensation amount ΔVd and the dead time compensation described in the present embodiment can be applied to drive control of an induction machine (induction motor).

  The motor drive system 1 described in the present embodiment can also be expressed as follows. That is, the motor drive system 1 converts a voltage command into a PWM pulse with the motor 2 and switches on / off of each switching element (33u, 34u etc.) connected in series by the PWM pulse to thereby apply a voltage to the motor 2 The motor drive control device 4 includes the PWM inverter 3 that outputs and the motor drive control device 4 that drives and controls the motor 2 using the PWM inverter 3. The motor drive control device 4 includes the dead time compensation unit 44 of this embodiment.

  The embodiment of the present invention has been described above, but the scope of the present invention is not limited to this, and various modifications can be made without departing from the scope of the invention. In addition, the above-described embodiment and the modifications thereof can be arbitrarily combined arbitrarily.

  The present invention is applicable to a motor drive control device that compensates for an error in an output voltage generated by providing a dead time in drive control of a motor.

Reference Signs List 2 motor 3 PWM inverter 4 motor drive control device 6 position sensor 21 rotor 33 u, 33 v, 33 w switching element 34 u, 34 v, 34 w switching element 41 position detection unit 44 dead time compensation unit

Claims (9)

A motor drive control device that drives and controls a motor using a PWM inverter that outputs a voltage to a motor by converting a voltage command into a PWM pulse and switching on / off of each switching element connected in series by the PWM pulse. ,
A compensation amount for compensating for an error of the output voltage of the PWM inverter, which is caused by providing a dead time for avoiding simultaneous turning on of the series-connected switching elements in the PWM inverter, is determined, and the compensation amount is calculated. A dead time compensation unit for outputting the voltage command added to the PWM inverter,
The dead time compensation unit determines the compensation amount based on a magnitude of a current command vector indicating a vector of a current to be followed by the current flowing through the motor.
The motor drive control device, wherein the current command vector is a coordinate system synchronized with a rotor of the motor or a vector defined by a coordinate system according to the coordinate system.   The motor drive control device according to claim 1, wherein the current command vector is a composite vector of vector components of a d-axis current command and a q-axis current command in a dq coordinate system having a d-axis and a q-axis.   The motor drive control device according to claim 2, wherein the dead time compensation unit obtains the compensation amount based on a magnitude of the current command vector when the d-axis current command is set to 0 [A]. Assuming that a predetermined fixed value of the compensation amount is ΔVd ′, the q-axis current command is iq_ref (t) [A] with time t as a variable, and a current threshold is ith [A].
The dead time compensation unit
ΔVd = ΔVd ′ × | iq_ref (t) | / ith
The motor drive control device according to claim 3, wherein ΔVd obtained by the calculation of is determined as the compensation amount.   The dead time compensation unit determines the fixed value ΔVd ′ as the compensation amount ΔVd when the absolute value | iq_ref (t) | of the q-axis current command is equal to or more than the current threshold ith. Motor drive control device. It further comprises a position detection unit that detects the electrical angle phase of the rotor based on an output signal from a position sensor that outputs a signal according to the rotational position of the rotor of the motor.
The motor drive control device according to any one of claims 3 to 5, wherein the dead time compensation unit obtains the polarity of the compensation amount based on the q-axis current command and the electrical angle phase of the rotor. . The position detection unit detects the electrical angle phase in a range of −180 ° to + 180 °,
When the phase difference at the electrical angle between the timing when the current command for the first phase of the motor becomes 0 [A] and the timing when the electrical angle phase of the rotor becomes 0 ° is taken as the initial phase difference ,
The dead time compensation unit shifts or shifts the value of the electrical angle phase by adding or subtracting the initial phase difference from the value of the electrical angle phase of the rotor acquired by the position detection unit. When the value of the electrical angle phase is positive, the compensation amount is multiplied by the polarity of the q-axis current command with respect to the voltage command of the first phase input to the dead time compensation unit. When the value of the shifted electrical angle phase is negative, the polarity of the q-axis current command is added to the compensation amount with respect to the voltage command of the first phase. The motor drive control device according to claim 6, wherein a value obtained by multiplying the two is subtracted and output.   The dead time compensation unit is shifted when adding or subtracting the compensation amount to a voltage command of a second phase delayed by 120 ° in electrical angle with respect to the first phase of the motor When the value of the electrical angle phase after subtracting 120 ° from the value of the electrical angle phase is further positive and the value of the electrical angle phase after the 120 ° subtraction is positive, the second phase input to the dead time compensation unit While adding a value obtained by multiplying the compensation amount by the polarity of the q-axis current command with respect to the voltage command and outputting the result, when the value of the electrical angle phase after 120 ° subtraction is negative, The motor drive control device according to claim 7, wherein a value obtained by multiplying the compensation amount by the polarity of the q-axis current command is subtracted from the voltage command of the second phase and the result is output.   The dead time compensation unit is shifted when adding or subtracting the compensation amount to or from the voltage command of the third phase advancing by 120 ° in electrical angle with respect to the first phase of the motor. If the value of the electrical angle phase after adding 120 ° to the value of the electrical angle phase is further positive and the value of the electrical angle phase after 120 ° addition is positive, the third phase of the dead phase compensator is added While adding a value obtained by multiplying the compensation amount by the polarity of the q-axis current command with respect to the voltage command and outputting the result, when the value of the electrical angle phase after 120 ° addition is negative, 9. The motor drive control device according to claim 7, wherein a value obtained by multiplying the compensation amount by the polarity of the q-axis current command is subtracted from the voltage command of the third phase and output.