JP6494809B2 - Inverter control device - Google Patents

Description

  The present invention relates to an inverter control device for controlling an inverter that converts DC power used in a rotating machine, in particular, electric motor into AC power.

  Conventionally, in a power converter that drives a motor by feedback control using phase current by converting DC power to AC power, a means for detecting the phase current is required. Instead of providing a current sensor between them, a method has been proposed in which the motor current (phase current) is restored by the current value detected from the DC bus of the power converter (inverter).

  For example, in the inverter control device disclosed in Patent Document 1, a voltage command vector that creates a voltage command vector that is a vector of voltages that should be followed by the three-phase voltage of the inverter and that is a composite voltage vector of the three-phase voltages. A voltage command vector correction unit that corrects the generated voltage command vector, and controls the inverter according to the corrected voltage command vector, and the voltage command vector correction unit includes the voltage command vector correction unit. The voltage command vector after being corrected by the correcting means is corrected so as to be a vector outside the region where the three-phase current cannot be detected in the current detection interval, and in the current non-detection interval within the carrier period, It is disclosed that reverse correction is performed to cancel the correction in the current detection section. As a result, in the current non-detection period where current detection is not required within the carrier cycle, reverse correction is performed to cancel the correction of the voltage command vector performed for current detection in the current detection period, and the distortion of the phase current accompanying the correction Can be reduced.

  Further, in the three-phase voltage type PWM inverter device disclosed in Patent Document 2, two basic voltage vector components V4 and V5 having different phases of 60 degrees capable of generating a command voltage vector are output within a first period of 1 PWM cycle. At the same time, two basic voltage vector components V1 and V2 that are 180 degrees out of phase with respect to the basic voltage vector component are output within a second period that forms one PWM cycle continuous with the first period. Therefore, even when the degree of modulation is small or when the phase of the output voltage vector is close to a single basic voltage vector, the pulse width is sufficiently long, and current detection can be performed with high accuracy. This makes it possible to detect current with high accuracy even when the degree of modulation is small or when the phase of a single basic voltage vector is close.

JP 2012-178927 A JP 2005-12934 A

However, in the inverter control methods of Patent Literature 1 and Patent Literature 2, while the modulation rate region in which current detection is possible increases, the command voltage vector component always decreases in a region where the modulation rate of the command voltage is small, such as during low-speed driving. Since it becomes impossible to secure a section for performing current detection, it is necessary to apply a voltage vector for performing current detection.
Also, a compensation voltage vector is required to make the applied voltage in each switching period the same as the command voltage. As a result, current ripple increases, causing noise. Furthermore, in these two patent documents, since the voltage to be applied is determined depending on the command voltage, the phase detected in each control cycle is determined by the voltage command and cannot be selected. There is a problem in that the detection accuracy is lowered at the place where the magnitude relationship is switched. In addition, the current ripple of the maximum voltage phase and the minimum voltage phase of the three-phase command voltage is large, and the current ripple of the voltage intermediate phase is small. That is, there has been a problem that a periodic change in current ripple occurs depending on the three-phase voltage command, and a roaring sound having a period 6 times the frequency of driving the electric motor is generated as noise.

  Furthermore, in the inverter device of Patent Document 2, the three-phase alternating current can be restored only once every two switching cycles, and the current detection accuracy is lowered when the carrier frequency is small and the switching cycle is long. there were.

  The present invention has been made to solve the above-described problem, and restores a three-phase AC current value based on a current value for two phases detected from a DC bus without depending on a three-phase voltage command. By making it possible, it is possible to set the phase to be detected in each control cycle. By performing processing such as always detecting the same phase, it is possible to improve the detection accuracy, and noise. An object of the present invention is to provide an inverter control device capable of reducing the beat sound.

  In order to solve the above-described problems, an inverter control device according to the present invention includes an inverter control unit that controls a switching element of an inverter that converts DC power into AC power according to a predetermined switching time, and a DC that supplies DC power to the inverter. A current detection unit that detects a current value of a power supply; a detection current storage unit that sets a current value detection time based on the switching time; and acquires, stores, and holds the current value from the current detection unit; and the detection Based on the phase current calculation unit that calculates and restores the AC current value generated by the inverter from the current values for the number of phases required for restoration from the current storage unit, and based on the restored AC current value and the rotational speed command value A command voltage vector generator that generates a command voltage vector and a command voltage vector corrected based on the command voltage vector. A correction command voltage vector generation unit, and a switching time setting unit that sets the switching time based on the corrected command voltage vector and outputs the switching time to the inverter control unit and the detected current storage unit, and The correction command voltage vector generation unit is configured such that when n is 3 or more in n periods (n is a natural number of 2 or more) of the unit period, where ½ of the switching period of the inverter is a unit period, Applying a plurality of voltage vectors whose sum is a zero vector, and when n is 2, apply the plurality of voltage vectors whose sum is a zero vector in the four periods of the unit period to correct the correction. A command voltage vector is generated.

  According to the inverter control apparatus of the present invention, in the n period where ½ of the switching period is a unit period and n is a natural number of 3 or more, the total of the voltage vectors for detection becomes a zero vector in at least two periods. In other periods, the current value detection section for applying the voltage vector based on the command voltage vector is set, so detection is performed in each control cycle without depending on the command voltage vector. It is possible to set the phase, whereby the magnitude of the current pulsation changes periodically by setting k to a natural number of n or less and the voltage vector to be applied to the kth in the n period always being the same. In particular, there is an effect that it is possible to reduce the roaring sound that is derived from the noise.

1 is a schematic configuration diagram of a motor control system including an inverter control device according to Embodiment 1. FIG. FIG. 10 is a diagram for describing a procedure for setting a current detection time for acquiring a current value from a DC bus by the current detection unit in the first embodiment. 6 is a diagram illustrating an example of a voltage vector applied in a correction command voltage vector generation unit in the first embodiment. FIG. 6 is a diagram illustrating an example of a voltage vector applied in each cycle in the first embodiment. FIG. 6 is a diagram illustrating an example of switching of a voltage vector to be applied in Embodiment 1. FIG. It is a figure explaining the relationship between the command voltage vector in Embodiment 1, the applied voltage vector, and switching time. FIG. 4 is a diagram showing an output current waveform of an inverter in the first embodiment. It is a figure which shows the output current waveform of the inverter of a prior art. FIG. 3 is a diagram illustrating a hardware configuration of the inverter control device according to the first embodiment. It is a schematic block diagram of the motor control system containing the inverter control apparatus which concerns on Embodiment 2. It is a figure explaining the relationship between the command voltage vector in Embodiment 2, the voltage vector to apply, and switching time.

Embodiment 1 FIG.
FIG. 1 is a schematic configuration diagram of a motor control system including an inverter control device according to the first embodiment. FIG. 2 is a diagram for explaining a procedure for setting a current value detection time for acquiring a current value from a DC bus by the current detection unit. FIG. 3 is a diagram illustrating an example of a voltage vector applied in the correction command voltage vector generation unit. FIG. 4 is a diagram for explaining an example of a voltage vector applied in each cycle. FIG. 5 is a diagram illustrating an example of switching of a voltage vector to be applied. FIG. 6 is a diagram for explaining the relationship between the command voltage vector, the applied voltage vector, and the switching time. FIG. 7 is a diagram illustrating an output current waveform of the inverter.

  As shown in FIG. 1, the motor control system 1 according to the first embodiment includes a motor 2 that is a rotating machine, an inverter 3 that supplies a three-phase AC current value to the motor 2, and DC power that is supplied to the inverter 3. A DC power supply 4, a DC bus 5 that energizes and connects the DC power supply 4 and the inverter 3, and an inverter control device 10 that controls the inverter 3 are configured.

  Here, the inverter 3 includes three pairs (for three phases) of a pair of switching elements 31s on the upper arm 31 (positive side) and switching elements 32s on the lower arm 32 (negative side), and switching elements 31s for these phases. , 32s and diodes 31d, 32d connected in antiparallel to each other, and the inverter control device 10 controls conduction / shutoff (on / off) of the switching elements 31s, 32s of each phase. The DC power supplied from the DC power supply 4 is converted into three-phase AC power. The electric motor 2 as a load is driven by the three-phase AC power. As the switching element, a semiconductor switching element such as a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is generally used.

  As shown in FIG. 1, the inverter control device 10 acquires a current value Idc from the current detection unit 11 at a set current value detection time, and a current detection unit 11 that detects a current value flowing through the DC bus 5. The detection current storage unit 12 for storing and holding, and the three-phase AC current values Iu, Iv, Iw flowing in the motor 2 from the two-phase current values IdcA, IdcB stored in the detection current storage unit 12 are restored. Phase current calculation unit 13, and three-phase command voltage vectors Vu, Vv, Vw targeted based on the restored three-phase AC current values Iu, Iv, Iw and the rotational speed command value Wref instructed from the outside. The command voltage vector generation unit 14 that generates the command voltage and the three-phase command voltage vectors Vu, Vv, and Vw generated by the command voltage vector generation unit 14 are compared with the current three-phase command voltage vectors Vu, Vv, and Vw. A corrected command voltage vector generation unit 15 that generates the corrected three-phase command voltage vectors Vu ′, Vv ′, and Vw ′, and a three-phase command voltage vector Vu ′ that is corrected by the correction command voltage vector generation unit 15. A switching time setting unit 16 that sets a switching time for driving the switching elements 31 s and 32 s based on Vv ′ and Vw ′, and a switching time Sup, Svp, Swp, Swn, Svn, Sun set by the switching time setting unit 16. Outputs on / off control signals Guu, Gvu, Gwu to the gates of the three-phase switching elements 31 s, 32 s, and on / off control signals Gul, Gvl, Gwl to the gates of the three-phase switching elements 32 s, respectively. And a control unit 17.

Next, each function of each part which comprises the inverter control apparatus 10 shown in FIG. 1 is demonstrated.
The current detection unit 11 includes a current detection element for detecting a current value installed in the path of the DC bus 5. As the current detection element, for example, a Hall sensor, a resistor, a current transformer, or the like is used to detect the voltage across the current detection element or the output voltage via an amplifier and a buffer as necessary. In addition, in FIG. 1, although the example in which the current detection element is provided on the low voltage (negative electrode) side of the DC power supply 4 is shown, the case where the current detection element is provided on the high voltage (positive electrode) side may be used. It does not affect the operation of the present embodiment.

  The detection current storage unit 12 acquires and stores the current value Idc from the current detection unit 11 at current value detection times Ta and Tb set by the switching time setting unit 16 described later. The detected current values IdcA and IdcB for two phases are held.

  The phase current calculation unit 13 uses the current values IdcA and IdcB for two phases detected from the DC bus 5 stored in the detection current storage unit 12, and the three-phase AC current value flowing in the motor 2. Iu, Iv, Iw are calculated and restored. Here, the three-phase AC current values Iu, Iv are corrected using the corrected three-phase command voltage vectors Vu ′, Vv ′, Vw ′ output from the correction command voltage vector generation unit 15 described later. , Iw is calculated.

  The command voltage vector generation unit 14 is set for each set switching cycle based on the rotation speed command value Wref according to an instruction from the outside and the three-phase AC current values Iu, Iv, Iw restored by the phase current calculation unit 13. Then, new three-phase command voltage vectors Vu, Vv, and Vw, which are driving targets of the inverter 3, are generated and updated.

  The corrected command voltage vector generation unit 15 has a current for two phases having a magnitude that enables current value detection with respect to the three-phase command voltage vectors Vu, Vv, and Vw generated by the command voltage vector generation unit 14. A voltage vector Va for value detection and a voltage vector Vb for canceling the voltage vector Va are applied to generate corrected three-phase command voltage vectors Vu ′, Vv ′, Vw ′, and a switching time setting unit 16 Output to. The newly corrected three-phase command voltage vectors Vu ′, Vv ′, and Vw ′ are also output to the phase current calculation unit 13 and used.

  Based on the corrected three-phase command voltage vectors Vu ′, Vv ′, Vw ′ generated by the correction command voltage vector generation unit 15, the switching time setting unit 16 switches the switching elements 31 s, 32 s constituting the inverter 3. The switching times Sup, Svp, Swp, Swn, Svn, Sun to be driven are set, and the switching elements 31s, 32s are turned on / off at the set switching times Sup, Svp, Swp, Swn, Svn, Sun. The inverter 3 is driven by outputting a control signal.

  The detection current storage unit 12 sets the current value detection times Ta and Tb using the switching times Sup, Svp, Swp, Swn, Svn, Sun set by the switching time setting unit 16, and the set current value detection At times Ta and Tb, the current values IdcA and IdcB of the DC bus 5 detected by the current detector 11 are acquired, stored and held.

  Further, the inverter control unit 17 uses the switching times Sup, Svp, Swp, Swn, Svn, Sun set by the switching time setting unit 16 and supplies an on / off control signal to the gate of the switching element 31s of the upper arm. Guu, Gvu, Gwu are output. At the same time, on / off control signals Gul, Gvl, Gwl opposite to those of the upper arm switching element 31s are output to the gate of the lower arm switching element 32s.

Next, the operation of the inverter control device 10 will be described with reference to FIGS.
FIG. 2 is a diagram for explaining a procedure for setting the current value detection times Ta and Tb from the switching times Sup, Svp, and Swp of the switching element 31 s constituting the upper arm. Here, FIG. 2 (a), FIG. 2 (b), and FIG. 2 (c) show the switch states of the switching element 31s constituting the upper arm of each phase, and each of the voltage maximum phase (U phase). The switch state, the voltage intermediate phase (V phase) switch state, and the voltage minimum phase (W phase) switch state are shown. 2 (d) shows the current value of the DC bus 5, FIG. 2 (e) shows the current value detection times Ta and Tb, and FIG. 2 (f) shows the switching times Sup, Svp, Swp, Swn, Svn, Sun are shown.

  The switching time setting unit 16 sets the current value detection times Ta and Tb using the switching times Sup, Svp, and Swp of the switching element 31s. In order to detect the current values IdcA and IdcB for two phases from the DC bus 5, the switch states of the three-phase upper arm switching elements 31 s are all on or not all off, that is, non-zero vector switches It is necessary to select two types from the current value detection section, which is a state section, and perform detection in that section. Therefore, the current value detection times Ta and Tb for detecting the current values IdcA and IdcB are set depending on the switching time of the voltage intermediate phase (V phase) switching element 31s. Of the corrected three-phase command voltage vectors Vu ′, Vv ′, and Vw ′ generated by the correction command voltage vector generation unit 15, the largest voltage phase, the middle voltage phase, and the smallest voltage phase are defined in order from the largest. For example, FIG. 2 shows a case where Vu ′ is the maximum voltage phase (U phase), Vv ′ is the voltage intermediate phase (V phase), and Vw ′ is the minimum voltage phase (W phase).

  2A, 2B, and 2C show the switch state of the switching element 31s that constitutes the upper arm of each phase, the switching element that constitutes the lower arm. The 32s switch state is the opposite of the upper switch state. That is, when the switching element 31s of the upper arm of the maximum voltage phase (U phase) is on (conducting), the switching element 32s of the lower arm of the maximum voltage phase (U phase) is turned off (cut off).

  Of the detected current values IdcA and IdcB for two phases, the current value of the DC bus 5 detected during the first non-zero voltage vector period is detected as IdcA, and the second non-zero voltage vector period is detected. The current value of the DC bus 5 is IdcB. 2 which is the current value detection time of the current value IdcA is set a predetermined time T1 before the switching time Svp of the voltage intermediate phase (V phase) switching element 31s. Here, T1 is set to a time longer than the time required for current value detection. Subsequently, Tb in FIG. 2 which is the current value detection time of the current value IdcB is set after a predetermined time T2 from Ta. Here, T2 considers a dead time interval provided in order to prevent the switching elements 31s and 32s pair connected in series in the inverter 3 from being conducted simultaneously, and the current value Idc of the DC bus 5 is In some cases, the current vibrates due to a sudden change in voltage associated with the on / off operation of the switching elements 31s and 32s, and it is necessary to set the current in consideration of the vibration of the current.

  FIG. 2 shows an example of this, and the current oscillates due to a sudden change in voltage accompanying the on / off operation of the switching element 31s in the non-zero voltage vector section of the switching times Sup, Svp, Swp of the switching element 31s. A section in which value detection is impossible (hereinafter referred to as a current value non-detectable section Ti) and a current value detectable section Tp are described. Therefore, T2 is set so that Tb does not enter the current value non-detectable section Ti. At this time, IdcA indicates the current value of the maximum voltage phase (U phase), and IdcB indicates the current value of the minimum voltage phase (W phase). The phase current calculation unit 13 calculates the current value of the voltage intermediate phase (V phase) from the current values of the two phases, and the difference between the current value detection times of IdcA and IdcB is set as short as possible. This is because current flows through the electric motor 2 due to the non-zero voltage vector and the current value of the DC bus 5 also changes. Therefore, if Ta and Tb are separated, the current value detection accuracy of the voltage intermediate phase (V phase) decreases. It is to do.

  FIG. 2 shows an example in which current value detection is performed in the first two non-zero voltage vector periods of four non-zero voltage vector periods in the switching period T. The current value may be detected in the vector period, and the same processing is performed. In this case, IdcA indicates the current value of the DC bus 5 detected during the third non-zero voltage vector period, and IdcB indicates the current value of the DC bus 5 detected during the fourth non-zero voltage vector period. Will be shown. At this time, IdcA indicates the current value of the minimum voltage phase (W phase), and IdcB indicates the current value of the maximum voltage phase (U phase).

  The phase current calculation unit 13 has a role of restoring the three-phase AC current values Iu, Iv, and Iw from the detected current values IdcA and IdcB for two phases stored in the detection current storage unit 12. Based on the three-phase command voltage vectors Vu, Vv, and Vw generated by the command voltage vector generation unit 14, the signs of the two-phase current values are determined. The remaining one-phase current value can be easily obtained from the two-phase current values IdcA and IdcB whose signs have already been determined by utilizing the fact that the sum of the three-phase current values is zero. By the above calculation, it is possible to restore the three-phase AC current values Iu, Iv, and Iw that flow through the electric motor 2 that is required. The calculated three-phase AC current values Iu, Iv, and Iw are used for, for example, update (generation) processing of the three-phase command voltage vector in the command voltage vector generation unit 14 or used for output monitoring of the electric motor 2. It is used for control processing of each part.

  The command voltage vector generation unit 14 has a role of generating target three-phase command voltage vectors Vu, Vv, and Vw output from the inverter 3. Various command voltage vector generation methods are known depending on the control method of the electric motor 2, but are not the essence of the present invention.

  The corrected command voltage vector generation unit 15 has a role of applying a voltage vector to the command voltage vector V (Vu, Vv, Vw) generated by the command voltage vector generation unit 14. Here, the applied voltage vector is a voltage vector that makes it possible to secure a current value detection section for two phases. For example, the voltage vectors are different voltage vectors Va and Vb, respectively. It is necessary to satisfy the condition that the sum of the voltage vectors Va and Vb applied at a unit cycle of n is a zero vector, with 1/2 being a unit cycle. Furthermore, the voltage vectors Va and Vb applied in each cycle of the switching cycle are preferably combined vectors of continuous basic voltage vectors V1 (100) to V6 (101) in order to reduce switching loss.

  Here, the three numbers in parentheses of the basic voltage vector represent the switch states of the U-phase, V-phase, and W-phase switching elements 31s from the left in the case of the upper-arm switching element 31s, and “1 "" Represents on and "0" represents off. For example, V1 (100) indicates that the U-phase switching element 31s is on and the other-phase switching elements 31s are off. The same applies to the lower arm switching element 32s.

  Here, an example of a voltage vector to be applied will be described with reference to FIG. In FIG. 3, the unit period n is assumed to be 3 for the sake of simplicity. In the first cycle of the unit cycle shown in FIG. 3A, nonzero voltage vectors V1 (100) and V2 (110) are output based on the command voltage vector V, and the unit cycle shown in FIG. In the second period, V2 (110) and V3 (010) are output as the voltage vector Va for securing the current value detection section. In addition, in the third period of the unit period shown in FIG. 3C, V5 (001) so that the voltage vector Va in the second period of the unit period is canceled as the voltage vector Vb for securing the current value detection section. , V6 (101) is output. Accordingly, since the sum of the voltage vectors Va and Vb applied in addition to the command voltage vector V in the three unit cycles is a zero vector, after the voltage vectors Va and Vb for securing the current detection interval are applied. The command voltage vector V is equal to the command voltage vector V before application of the voltage vectors Va and Vb when viewed as a total of three unit cycles.

  FIG. 4 shows an example of the relationship between the command voltage vector V and the output voltage vector Vo in each unit cycle. 4A shows the relationship between the command voltage vector V and the output voltage vector Vo from the first cycle to the nth cycle when the unit cycle is n, and FIG. 4B shows the n + n cycle from the (n + 1) th cycle. The relationship between the command voltage vector V up to the eye and the output voltage vector Vo is shown. In a unit cycle from the first cycle to the nth cycle, a voltage vector obtained by combining V6 and V1 is applied to the k cycle, a voltage vector obtained by combining V4 and V5 is applied to the m cycle, and V2 is applied to the n cycle. And a voltage vector obtained by combining V3. As described above, the sum of the voltage vectors applied during the unit period from the first period to the n-th period is a zero vector, so the output voltage vector Vo in the first period is the same as the command voltage vector V. It becomes. Similarly, in the unit cycle from the (n + 1) th cycle to the (n + n) th cycle, a voltage vector obtained by combining V6 and V1 is applied to the kth cycle, and a voltage vector obtained by combining V4 and V5 is applied to the mth cycle, A voltage vector obtained by combining V2 and V3 is applied in the nth period. Since the sum of the voltage vectors applied during the unit cycle from the (n + 1) -th cycle to the n-th cycle is a zero vector, the (n + 1) -th cycle output voltage vector Vo is the same as the command voltage vector V. However, the values of the output voltage vector Vo in the first period and the output voltage vector Vo in the n + 1 period are different. That is, the sum of the voltage vectors applied during the unit period is a zero vector, and the same voltage vector is always applied in the kth period and the n + kth period every n periods. That is, a voltage vector that does not depend on the command voltage vector V is applied.

  FIG. 5 shows an example of switching of the applied voltage vector. As shown in FIG. 4, the voltage vector applied to the k period of the n period (the voltage vector obtained by combining V6 and V1) always applies the same voltage vector, but a period larger than the drive period, for example, an inverter A voltage vector (a voltage vector obtained by synthesizing V4 and V5) different from that before the operation stop is applied at such a timing that 3 stops the operation and then restarts. As shown in FIG. 4, the switched voltage vector always applies the same voltage vector every n cycles.

  As described above, the correction command voltage vector generation unit 15 has a current for two phases having a magnitude that allows current value detection with respect to the three-phase command voltage vector V generated by the command voltage vector generation unit 14. A voltage vector Va for value detection and a voltage vector Vb for canceling the voltage vector Va are applied to generate corrected three-phase command voltage vectors Vu ′, Vv ′, Vw ′.

  The switching time setting unit 16 switches the switching times Sup, Svp, Swp, Sun, Svn based on the corrected three-phase command voltage vectors Vu ′, Vv ′, Vw ′ generated by the correction command voltage vector generation unit 15. , Swn is set. FIG. 6 is a diagram for explaining the relationship between the command voltage vector, the applied voltage vector, and the switching time. FIG. 6 shows an example in which the switching times Sup to Swn are set based on the first cycle command voltage vector V generated in FIG. 6A shows the output voltage vector Vo, FIG. 6B shows the voltage vector Va to be applied, FIG. 6C shows the command voltage vector V, and FIG. , The output voltage vector Vo is shown. Similarly to FIG. 2, FIG. 6 (e), FIG. 6 (f), and FIG. 6 (g) show the switch state of the gate of the switching element 31s of the upper arm of each phase, The switch state of the phase (U phase), the switch state of the voltage intermediate phase (V phase), and the switch state of the minimum voltage phase (W phase) are shown. The switch state of the gate of the switching element 32s of the lower arm is opposite to the switch state of the gate of the switching element 31s of the upper arm. FIG. 6H shows the switching times Sup, Svp, Swp, Swn, Svn, Sun of the switching elements 31s, 32s.

  Here, as shown in FIG. 6 (d), the command voltage vector V (FIG. 6 (c)) and the applied voltage vector Va (FIG. 6 (b)) are output separately within n periods of the unit period. Is done. In FIG. 6D, the numbers in parentheses in the output voltage vector Vo column indicate basic voltage vectors. “0” represents V0 (000), all three-phase switching elements 31s are in an off state, “7” represents V7 (111), and all three-phase switching elements 31s are in an on state. It shows that each. In the example of FIG. 6, first, from the state where all the three-phase switching elements 31 s are turned off, the V-phase switching element 31 s is turned on based on the applied voltage vector Va, and the U-phase switching element 31 s is turned on. Subsequently to the state, all of the three-phase switching elements 31s are turned on. Further, based on the command voltage vector V, the W-phase switching elements 31s are turned off, and the V-phase and W-phase switching elements 31s. Is finally turned off, and finally all the three-phase switching elements 31s are turned off.

  Therefore, as shown in FIG. 6 (d), the section of the output pulse voltage for switching based on the voltage vector Va applied to the three phases becomes the current value detection section of the DC bus 5. In addition, since the command voltage vector V and the applied voltage vector Va are output separately within the switching period, the current value can be detected in the output section of the applied voltage vector Va in each switching period. The three-phase AC current values Iu, Iv, and Iw can be restored.

  The inverter control unit 17 performs on / off control on the gate of the three-phase switching element 31s of the upper arm based on the switching times Sup, Svp, Swp, Sun, Svn, Swn set by the switching time setting unit 16. The signals Guu, Gvu, and Gwu are supplied to the gate of the three-phase switching element 32s of the lower arm, and the on / off control signal Gul, inverted from the three-phase switching element 31s of the upper arm. Gvl and Gwl are output, and the phase current output by the inverter 3 is controlled.

  An example of the output waveform of the phase current by the inverter control apparatus of the present embodiment is shown in FIG. Moreover, the output waveform of the phase current by the conventional inverter control method shown by patent document 1 is shown in FIG. Here, in order to compare the effect of the technique disclosed in Patent Document 1 and the technique according to the present embodiment, the waveform of the phase current in the case of driving at a switching frequency of 2 kHz and a frequency command of 0.5 Hz is shown. As is clear from FIG. 7, it can be seen that the periodic current ripple change (portion surrounded by a circle in FIG. 8) generated in the prior art is reduced in the present embodiment.

  Therefore, by applying only the minimum voltage vector necessary for securing the current value detection section of the DC bus, no compensation voltage depending on the magnitude relation of the command voltage vector is required, and the applied voltage Since the vector is also set without depending on the command voltage vector, it is possible to set the phase to be detected in each control cycle. Thereby, for example, it is possible to always detect the current value of the same phase and improve the detection accuracy. Also, by making the k-th applied voltage vector constant every n cycles, the shape of the current ripple is constant regardless of the magnitude relationship of the command voltage vector, and no periodic change occurs. By eliminating the periodic change of the current ripple, it is possible to eliminate a beat sound having a frequency six times the frequency at which the electric motor 2 is driven. In addition, by switching the k-th applied voltage vector in a cycle longer than the drive cycle, it is possible to prevent the switching elements from being consumed by repeatedly performing the same switching.

  As described above, in the inverter control device according to the first embodiment, the voltage applied for detecting the current value in at least two cycles in the n cycle in which ½ of the switching cycle is a unit cycle and n is a natural number of 3 or more. Depends on the command voltage vector because the total of the vectors is set to be the zero vector, and in other periods, the current value detection interval is set by applying a voltage vector based on the command voltage vector. Therefore, it is possible to set the phase to be detected in each control cycle, and thereby k is a natural number equal to or less than n, and the voltage vector applied to the kth in the n cycle is always the same, There is an effect that it is possible to reduce the roaring sound, which is a noise derived from the fact that the magnitude of the current pulsation changes periodically.

  FIG. 9 shows the hardware configuration of the inverter control device according to the first embodiment. The inverter control device 10 is composed of a processor 50, a storage device 51, and a current sensor 52. These are realized. For example, in addition to the control program, the storage device 51 stores various data such as data obtained by calculation, a detected current value, and a three-phase command voltage vector. The processor 50 performs an operation using each program and data necessary for executing the operation of the present embodiment stored in the storage device 51. The current sensor 52 that is a current detection element acquires a current value from the DC bus 5. The storage device 51 includes a volatile storage device such as a random access memory and a nonvolatile auxiliary storage device such as a flash memory. Further, as the nonvolatile auxiliary storage device, an auxiliary storage device such as a hard disk may be provided instead of the flash memory.

Embodiment 2. FIG.
FIG. 10 is a schematic configuration diagram of a motor control system including the inverter control device according to the second embodiment. FIG. 11 is a diagram for explaining the relationship between the command voltage vector, the applied voltage vector, and the switching time. The difference between the inverter control device according to the second embodiment and the inverter control device according to the first embodiment is that the inverter control device 20 in the motor control system 9 according to the second embodiment stores the detected current as shown in FIG. The part 12 is changed to a detected current storage part 22, and the phase current calculation part 13 is changed to a phase current calculation part 23. The other components are the same as those in FIG.

  In the first embodiment, as shown in FIG. 6, the case where n is 3 or more and current value detection is performed in the output section of the voltage vector applied at the unit cycle n period which is ½ of the switching period has been described. In the second embodiment, a case where current value detection is performed when n is 2 will be described. When n is 2, since there is only one output section of the voltage vector to be applied, the switching cycle is divided into the first half and the second half as shown in FIG. A voltage vector for current value detection is applied.

Next, the operation of the inverter control device 20 according to the second embodiment will be described with reference to FIGS. 10 and 11.
In the first embodiment, as shown in FIG. 6, the command voltage vector V and the voltage vector Va to be applied for securing a current value detection section are separately set for each cycle of a unit cycle that is ½ of the switching cycle. Although output, the output voltage vector Vo needs to be the same as the command voltage vector V in unit period n. Therefore, at least two unit cycles are required to apply the applied voltage vectors Va and Vb, and when combined with at least one unit cycle for outputting the command voltage vector V, three unit cycles are required. In the second embodiment, as shown in FIG. 11, the switching time setting unit 16 sets the command voltage vector V to one of the two periods of the unit cycle and the voltage vector Va applied to secure the current value detection section to the other. Output. Further, the order in which the separate output of the command voltage vector V and the applied voltage vectors Va and Vb is output every switching cycle is changed. Along with this, the position of the current value detection is also switched every cycle. In this way, it is possible to cancel the voltage vector Va applied for current value detection applied in the first cycle with the voltage vector Vb applied for current value detection applied in the second cycle. The voltage vector Vb to be applied for cancellation as in 1 becomes unnecessary within n cycles, and the output of the command voltage vector V and the voltage vectors Va and Vb to be applied in order to secure a current value detection section in two cycles of the unit cycle is obtained. It becomes possible.

  The detected current storage unit 22 has a function of acquiring and storing the detected current values IdcA, IdcB, IdcC, and IdcD for the two most recent switching cycles. The phase current calculation unit 23 detects the four detected values. A function of calculating three-phase AC current values Iu1, Iv1, Iw1, Iu2, Iv2, Iw2 for two switching cycles from the current value and outputting the averaged three-phase AC current values Iu, Iv, Iw have. Thus, by changing the current value detection position in the two most recent switching cycles and outputting the average value, highly accurate current detection with little influence of current ripple is possible.

  As described above, in the inverter control device according to the second embodiment, one of the two unit cycles is output as a command voltage vector, and the other is output as a voltage vector applied to secure a current value detection section. Since the value detection section is set, it is possible to set the phase to be detected in each control cycle without depending on the command voltage vector, and thereby the voltage vector to be applied first in the two cycles. Is always the same, there is an effect that it is possible to further reduce the roaring sound that is a noise derived from the periodic change in the magnitude of the current pulsation.

  The inverter control device according to the present invention is useful for motor control systems that are widely compatible with systems that drive rotating machines such as various electric motors, and is particularly driven in a region where a low triangular carrier frequency and a command voltage modulation rate are low. Suitable for motor control system that performs

  Also, within the scope of the present invention, the embodiments can be freely combined, or the embodiments can be appropriately modified or omitted.

  Moreover, in the figure, the same code | symbol shows the same or an equivalent part.

  DESCRIPTION OF SYMBOLS 1,9 Motor control system, 2 Electric motor, 3 Inverter, 4 DC power supply, 5 DC bus, 10 Inverter control apparatus, 11 Current detection part, 31s, 32s Switching element, 31d, 32d Diode, 12, 22 Detection current storage part, 13, 23 Phase current calculation unit, 14 command voltage vector generation unit, 15 correction command voltage vector generation unit, 16 switching time setting unit, 17 inverter control unit, 50 processor, 51 storage device, 52 current sensor

Claims (8)

An inverter control unit that controls a switching element of the inverter that converts DC power into AC power according to a predetermined switching time;
A current detection unit that detects a current value of a DC power supply that supplies DC power to the inverter;
Based on the switching time, a current value detection time is set, a detection current storage unit that acquires, stores and holds the current value from the current detection unit;
A phase current calculation unit that calculates and restores the alternating current value generated by the inverter from the current values for the number of phases required for restoration from the detection current storage unit;
A command voltage vector generation unit that generates a command voltage vector based on the restored AC current value and rotation speed command value;
A corrected command voltage vector generation unit that generates a command voltage vector corrected based on the command voltage vector;
A switching time setting unit that sets the switching time based on the corrected command voltage vector and outputs the setting to the inverter control unit and the detected current storage unit, and
The correction command voltage vector generator generates a vector when n is 3 or more in n periods (n is a natural number of 2 or more) of the unit period, where ½ of the switching period of the inverter is a unit period. Apply a plurality of voltage vectors whose total is a zero vector, and when n is 2, apply a plurality of voltage vectors whose total is a zero vector in the four periods of the unit period to correct the correction An inverter control device that generates a command voltage vector that has been generated.   The n cycles are 3 cycles or more, and at least in the two cycles, the plurality of voltage vectors having such a magnitude that each of the current value detection sections corresponding to the number of phases required for the restoration can be secured is applied. The inverter control device according to claim 1.   3. The inverter control device according to claim 2, wherein k is a natural number equal to or less than n, and the voltage vector applied in the k-th cycle of the n cycles is the same voltage vector in units of n cycles.   4. The inverter control device according to claim 3, wherein the voltage vector applied in the k-th cycle is switched to a different voltage vector when the voltage vector is larger than the n cycle.   The n period is two periods, and the plurality of voltage vectors having a size that can secure the detection period of the current value for the number of phases necessary for the restoration is applied in one of the first half period and the second half period. The inverter control device according to claim 1, wherein the plurality of voltage vectors are alternately applied in the first half cycle and the second half cycle every different n cycles.   The voltage vector applied in the first half cycle is the same voltage vector in 2n cycles, and the voltage vector applied in the second half cycle is the same voltage vector in 2n cycles. 5. The inverter control device according to 5.   The inverter control device according to claim 6, wherein, in one of the first half cycle and the second half cycle, the plurality of voltage vectors to be applied are switched to voltage vectors having different values when larger than the n cycles. .   8. The average value of each of the current values for the number of phases necessary for the restoration detected in the different n periods is set as the current value. 9. Inverter control device.

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