WO2017130447A1

WO2017130447A1 - Power conversion device and rotating electric machine driving device

Info

Publication number: WO2017130447A1
Application number: PCT/JP2016/074082
Authority: WO
Inventors: 壮太佐野; 覚寺島; 弘淳福岡; 佐竹　彰; 古谷　真一
Original assignee: 三菱電機株式会社
Priority date: 2016-01-28
Filing date: 2016-08-18
Publication date: 2017-08-03
Also published as: JPWO2017130447A1; CN108633323A; CN108633323B; JP6419361B2

Abstract

When a triangular carrier wave is divided into two intervals, that is, a monotonically increasing interval and a monotonically decreasing interval, a DC bus line current detection unit (2) detects, in a first cycle of two continuous triangular carrier wave cycles, a DC bus line current value in one of the monotonically increasing interval and the monotonically decreasing interval, and detects, in the second cycle thereof, a DC bus line current value in the other interval in which the DC bus line current value has not been detected in the first cycle. A phase current calculation unit (4) calculates three-phase AC current values on the basis of two-phase DC bus-line current values that are each detected by the DC bus line current detection unit (2) in the monotonically increasing interval and the monotonically decreasing interval in the most recent two continuous triangular carrier wave cycles.

Description

Power conversion device and rotating electrical machine drive device

The present invention relates to a power conversion device for a rotating electrical machine and a rotating electrical machine driving device using the power conversion device.

In the power converter that drives the motor by feedback control using the phase current, a means for detecting the phase current is required. In order to reduce the cost, there has been a method of calculating the motor current from the DC bus current of the inverter instead of providing a current sensor between the power converter and the motor. For example, in Patent Document 1, a pulse current corresponding to a phase current flowing in a DC bus of a power converter main circuit in accordance with switching of a switching element of each phase is detected by a current detection unit, and the obtained current detection value is obtained. It is disclosed that the phase currents for three phases are detected and reproduced by one current detection means by distributing to each phase from the switching state at the time of detection.

However, since it is difficult to detect the center of the current ripple of the phase current in the above method, there is a problem that the current detection accuracy is lowered. Therefore, in

Patent Documents

2 and 3, for example, current detection in the first half cycle of the triangular carrier wave and current detection in the second half cycle are alternately performed, and the current detection error is compensated from the current detection value obtained from each, It is disclosed that appropriate current detection can be realized even with an electric motor having a small impedance and a large current ripple.

JP-A-11-004594 JP 2010-11639 A JP2013-55772A

In order to realize the above-described conventional method, in Patent Document 2, only an interval that is an integral multiple of the triangular carrier period is detected between the current detection in the first half period of the triangular carrier wave and the current detection in the second half period of the triangular carrier wave. A current detection hold section for holding current detection is provided. In Patent Document 3, detection is performed in the second half of the first period and the first half of the second period among the two carrier signal periods. As a result, the current detection period and the accompanying voltage command update period are 1.5 times or more of the carrier period in Patent Document 2 and twice in Patent Document 3. For this reason, the time resolution of the voltage update is lowered, for example, when a high frequency voltage is output at the time of low carrier driving, and the output voltage accuracy is lowered. Further, in Patent Document 2, the detection accuracy is improved by performing current detection in the first half of the triangular carrier wave and current detection in the second half of the triangular carrier wave at a position symmetrical to the control cycle start point. In such a method, current ripples are periodically generated at the same place, and noise of the same frequency is generated intensively.

The present invention is for solving the above-described problems. Even when the electric motor has a small impedance, the current is detected with high accuracy, and the current is detected and the voltage is updated every one period of the triangular carrier. Also, it is an object of the present invention to provide a power converter capable of minimizing a decrease in output voltage accuracy.

The power converter according to the present invention includes a PWM converter that compares a three-phase voltage command with a triangular carrier wave and converts it into a PWM pulse, and a power that drives a switching element based on the PWM pulse and converts a DC voltage into a three-phase AC voltage. The converter main circuit, the DC bus current detector for detecting the current flowing in the DC bus of the power converter main circuit, and the current for two phases are detected by the DC bus current detector at least once in one period of the triangular carrier wave. A timing determination unit that sets two detection timings based on the switching timing of the switching element, and a period of a triangular carrier wave based on a DC bus current value for two phases detected at a timing determined by the timing determination unit A phase current calculation unit that calculates a three-phase AC current value once, and updates a three-phase voltage command based on the three-phase AC current value once in one period of a triangular carrier wave Equipped with a pressure command generating unit,
When the triangular carrier wave is divided into two sections, a monotone increasing section and a monotonic decreasing section, the DC bus current detection unit has one of the monotonically increasing section or the monotonic decreasing section in the first period of two consecutive triangular carrier periods. The DC bus current value is detected in a section of the period that is not detected in the first period of the monotonically increasing section or the monotonically decreasing section in the second period of two consecutive triangular carrier wave periods. Detect
The phase current calculation unit calculates a three-phase AC current value based on the two-phase DC bus current value detected by the DC bus current detection unit in the monotonically increasing section and the monotonically decreasing section in the immediately preceding two triangular carrier periods. It is to calculate.

According to the power conversion device configured as described above, the voltage update is performed for each period of the triangular carrier wave period, and the current detection is alternately switched between the monotonically increasing section and the monotonically decreasing section. Thus, the voltage update cycle can be shortened. Furthermore, current detection from the DC bus can be performed with high accuracy even during low carrier driving, and a decrease in output voltage accuracy can be minimized. In addition, the current detection position in the monotonically increasing section and the monotonically decreasing section is set asymmetrically with respect to the control cycle start point located between them, so that the position of the current ripple is dispersed within the control period, causing noise. Can also be dispersed.

FIG. 3 is a block configuration diagram illustrating a hardware configuration of the power conversion device according to the first embodiment. It is a block block diagram which shows the specific structure of the power converter device by Embodiment 1. FIG. It is a flowchart which shows the operation | movement by a timing determination part. It is a diagram for demonstrating the operation | movement which determines the timing of the electric current detection implemented in a timing determination part. It is a circuit diagram which shows the state through which the electric current at the time of detecting an electric current flows. It is a circuit diagram which shows the state through which the electric current at the time of detecting an electric current flows. FIG. 5 is a partially enlarged view of the DC bus current waveform diagram shown in FIG. 4. It is a diagram (A) and (B) explaining an example for securing an electric current detectable section. It is a figure which shows the timing chart of the electric current detection process with respect to a triangular carrier wave period, an electric current calculation process, and a voltage generation process. It is a figure which shows the timing chart of the electric current detection process with respect to a triangular carrier wave period, and an electric current calculation process. FIG. 10 is a diagram for explaining the operation of the power conversion device according to the second embodiment.

Embodiment 1 FIG.
Hereinafter, the power converter according to Embodiment 1 will be described in detail with reference to the drawings. FIG. 1 is a block configuration diagram illustrating a hardware configuration of the power conversion device according to the first embodiment. In the figure, a power converter 10 includes a processor 100, a storage device 101, a power converter main circuit 1, and a DC bus current detector 2 that detects a current flowing through the DC bus 102 as hardware. Although not shown, the storage device 101 includes a volatile storage device such as a random access memory and a nonvolatile auxiliary storage device such as a flash memory. Although not shown, the storage device 101 may include an auxiliary storage device such as a hard disk instead of the nonvolatile auxiliary storage device.

The processor 100 executes the program input from the storage device 101. Since the storage device 101 includes an auxiliary storage device and a volatile storage device, a program is input to the processor 100 from the auxiliary storage device via the volatile storage device. The processor 100 may output data such as a calculation result to the volatile storage device of the storage device 101, or may store the data in the auxiliary storage device via the volatile storage device.

FIG. 2 is a block configuration diagram showing a specific configuration of the power conversion apparatus 10. As shown in FIG. 2, the power conversion device 10 of the present embodiment has a control unit 6, and the control unit 6 compares a three-phase voltage command with a triangular carrier wave TW and converts it into a PWM pulse. The three-phase voltage command is compared with the triangular carrier wave TW and converted into gate switching timings Sup to Swn, and the current detection point determination for outputting the DC bus current detection timings T _A to T _D from these gate switching timings Sup to Swn It has a gate switching timing and current detection timing determination unit (hereinafter abbreviated as a timing determination unit) that also serves as means. In addition, the PWM converter adds a correction amount to the voltage command on the current detection side of the monotonically increasing section and the monotonically decreasing section so that it can be detected when it is determined that the DC bus current detection is difficult. A current detection section generation unit that subtracts the correction amount from the voltage command. Furthermore, the power converter 10 includes a power converter main circuit 1, a DC bus current detector 2, a detected current storage 3, a phase current calculator 4, and a voltage command generator 5. Here, the power converter main circuit 1 drives the switching elements SW1 to SW6 based on the gate switching timings Sup to Swn to convert the DC voltage into a three-phase AC voltage. The DC bus current detection unit 2 detects a current flowing through the DC bus 102. The detected current storage unit 3 acquires and holds the current value detected by the DC bus current detection unit 2 using the DC bus current detection timings T _A to T _D. The phase current calculation unit 4 calculates the DC bus current stored in the detection current storage unit 3 as a three-phase AC current value. The voltage command generator 5 updates the three-phase voltage commands Vu to Vw once in one cycle of the triangular carrier wave TW.

Rotating machine M is connected to power converter main circuit 1, and the object of this embodiment is to detect a three-phase alternating current flowing between them with DC bus 102. As the rotating machine M connected here, for example, any rotating machine such as a synchronous motor, an induction motor, or a generator may be used. In addition, in the rotating machine M of FIG. 1, FIG. 2, although the case where the connection of a stator winding is a Y connection is shown, you may use (DELTA) connection. 2 is a processor 100 that executes a program stored in the storage device 101, or a processing circuit such as a system LSI (not shown). The phase current calculator 4, the voltage command generator 5, and the controller 6 in FIG. It is realized by. The detected current storage unit 3 is realized by a volatile storage device of the storage device 101. A plurality of processors 100 and a plurality of storage devices 101 may execute the function in cooperation, or a plurality of processing circuits may execute the function in cooperation. Further, the above functions may be executed in cooperation with a combination of a plurality of processors 100 and a plurality of storage devices 101 and a plurality of processing circuits.

FIG. 3 is a flowchart showing the operation of the timing determination unit. As shown in FIG. 3, a current detection interval is derived from the difference in the magnitudes of the three-phase voltage commands Vu to Vw generated by the voltage command generation unit 5 (step S301), and in the DC bus 102 in the current detection interval. It is determined whether or not current detection is possible (step S302). When the DC bus current cannot be detected, a correction amount is added to the voltage commands Vu to Vw so that the total value within the voltage update period does not change as described later (step S303). The gate switching timings Sup to Swn of the switching elements SW1 to SW6 of the power converter main circuit 1 are determined from the voltage commands Vu to Vw to which correction amounts are added as necessary (step S304), and the gate switching timings Sup to Swn are used. Then, the DC bus current detection timings T _A to T _D are determined (step S305), and the DC bus current detection unit 2 detects the current.

As shown in FIGS. 1 and 2, the power converter main circuit 1 is composed of six switching elements SW1 to SW6 and diodes, and has a role of converting DC power into three-phase AC power. That is, the power converter main circuit 1 constitutes an inverter circuit, and includes a U-phase upper arm switching element SW1, a U-phase lower arm switching element SW2, a V-phase upper arm switching element SW3, a V-phase lower arm switching element SW4, and a W-phase. It is composed of an upper arm switching element SW5 and a W-phase lower arm switching element SW6. Each of the switching elements SW1 to SW6 is driven by receiving signals according to gate switching timings Sup to Swn input from the timing determination unit. In the DC bus current detection unit 2, a detection element (for example, a hall sensor, a resistor, a current transformer, etc.) for current detection is inserted in the path of the DC bus 102, and an amplifier, a buffer, etc. The detected current value Idc is sent to the detected current storage unit 3. 1 and 2, the detection element is provided on the low voltage side of the DC power supply, but may be provided on the high voltage side.

The detection current storage unit 3 has a role of acquiring and holding the detection current detected by the DC bus current detection unit 2 at the DC bus current detection timings T _A to T _D determined by the timing determination unit. FIG. 4 is a diagram for explaining the operation of determining the current detection timings T _A to T _D performed by the timing determination unit. In order to detect the current of two phases from the DC bus 102, the switching states of the three-phase switching elements need to be all on or not all off, that is, the so-called non-zero voltage vector switching state interval, that is, It is necessary to select two types from such current detection intervals and perform detection in those intervals. The DC bus current detection timings T _A to T _D are determined depending on the gate switching timing of the voltage intermediate phase (V phase in the case of FIG. 4) determined in the timing determination unit. Of the three-phase voltage commands Vu, Vv, and Vw generated by the voltage command generator 5, the maximum phase voltage command, the intermediate phase voltage command, and the minimum phase voltage command are defined in order from the largest, but in FIG. The case where the phase voltage command is Vu, the intermediate phase voltage command is Vv, and the minimum phase voltage command is Vw is shown. In FIG. 4, Bu indicates the maximum phase (U phase) upper arm switch state, Bv indicates the intermediate phase (V phase) upper arm switch state, and Bw indicates the minimum phase (W phase) upper arm switch state.

In FIG. 4, the DC bus current value detected during the first non-zero voltage vector period of the two-phase detection current is IdcA, and the DC bus current detected during the second non-zero voltage vector period. Let the value be IdcB. _{T A} is the detection timing of the current value IdcA is determined from the gate switching timing Svp of the gate of the intermediate phase (V phase) (TS) before the predetermined time T1. Here, the time T1 is set to a time longer than the time required for current detection. Then _{T B} is the detection timing of the current value IdcB is determined from the timing _{T A} after a predetermined time T2. Here, the determination of the time T2 takes into account a dead time interval provided in order to prevent the switching element pairs connected in series in the power converter main circuit 1 from conducting at the same time, and the DC bus current is determined as On On of the switching element. , The current may vibrate due to a sudden change in voltage associated with the Off operation, and it is necessary to consider the current vibration. That is, if one of the upper arm switching element and the lower arm switching element (for example, SW1 and SW2) is On, the other is in an Off relationship. Is set to On, and the time T2 is determined in consideration of the dead time interval. Furthermore, high-frequency vibration of DC current is generated due to the influence of surge voltage generated when the switching element is switched (refer to current detection impossible section T10). However, such high-frequency vibration of DC current is attenuated and amplitude vibration is below a predetermined value. It is also necessary to consider the interval until. FIG. 4 shows an example of this, and shows a current undetectable section T10 and a current detectable section T11 in the non-zero voltage vector section of the gate switching timings Sup to Swn. That timing _{T A} is determined in the current detectable period T11. Hereinafter, a section in which current detection cannot be performed is described as a section in which current detection is not possible.

Thus, time T2 is the timing T _B is set so as not to the current undetectable period. That is, T2> T1 + (current detection impossible section). At this time, the current value IdcA indicates the current value of the maximum voltage phase (U phase), and the current value IdcB indicates the current value of the minimum voltage phase (W phase).
FIG. 5 is a circuit diagram showing a state in which currents Iu, Iv, Iw flow when detecting the current value IdcA, and FIG. 6 is a circuit showing a state in which currents Iu, Iv, Iw flow when detecting the current value IdcB. FIG. In FIG. 5, since the switching elements SW1, SW4, and SW6 are On and SW2, SW3, and SW5 are Off, the detected current is Iu, that is, the voltage maximum phase (U phase) current. In FIG. 6, since the switching elements SW1, SW3, SW6 are On and the switching elements SW2, SW4, SW5 are Off, the detected current is Iw, that is, the current of the minimum voltage phase (W phase). . In FIGS. 5 and 6, arrows indicated by dotted lines indicate the directions of currents flowing in the respective phases. Further, between the gate switching timings Swp and Swn, since the switching elements SW1, SW3, SW5 of the upper arm are all On and the switching elements SW2, SW4, SW6 of the lower arm are all Off, the current is The reflux flows through the diode, and no current is detected by the DC bus current detector 2. Similarly, when all the switching elements of the upper arm are OFF, the reflux flows through the diode, and the DC bus current detection unit 2 does not detect the current. The phase current calculation unit 4 calculates the current value of the voltage intermediate phase (V phase) from these two current values IdcA and IdcB. The difference in detection timing between the current value IdcA and the current value IdcB is set as short as possible. This is because the current flows through the rotating machine M due to a non-zero voltage vector, and the DC bus current also changes if time passes too much. Therefore, if the timing T _A and the timing T _B are separated, the current detection accuracy of the intermediate phase decreases. It is. That is, as described above, in order to detect the current for two phases from the DC bus 102, the switching states of the three-phase switching elements are not all on or all off, so-called non-zero voltage vector switching state intervals. It is necessary to select two types from such current detection intervals, and it is necessary to perform detection in those intervals.

Further, timings T _C and T _{D in} FIG. 4 indicate detection timings of current values IdcC and IdcD when current detection is performed in the latter half of the triangular carrier wave period, respectively. Timing _T C, _{T D} is determined voltage intermediate phase gate switching timing Svn of (V-phase) (TS) to the reference timing _T A, _{T B} likewise timing _{T C} is the voltage intermediate phase of gate-off of the (V-phase) together is determined from the gate switching timing Svn predetermined time before T1, the timing T _D is determined after a predetermined time timing T _C T2. At this time, the current value IdcC indicates the current value of the minimum voltage phase (W phase), and the current value IdcD indicates the current value of the maximum voltage phase (U phase). This determines the current detection timing of the two-phase current detection possible section side to be detected for each triangular carrier wave period, detects the DC bus current at that timing, and detects the current values IdcA to IdcD detected by the detection current storage unit 3. It can be stored.

Here, in order to detect current with high accuracy, it is necessary to reduce the influence of current ripple. That is, the DC bus current value does not become horizontal, but rises to the right between the gate switching timings Sup and Swp as shown in FIG. 4, and falls to the right between the gate switching timings Swn and Sun. Need to reduce the impact of FIG. 7 is a partially enlarged view of the DC bus current waveform diagram shown in FIG. In FIG. 7, a section T70 and a section T71 each indicate a non-zero voltage vector section, and a current value X indicates an average current value in the non-zero voltage vector section. As shown in FIG. 7, there is a difference between the current values IdcB and IdcC and the average current value X in the non-zero voltage vector section, and the differences appear positively and negatively, respectively. The same can be said for the current values IdcA and IdcD. Therefore, in order to reduce the error due to current ripple, it is necessary to detect the current values IdcA and IdcB and the current values IdcC and IdcD alternately. That is, a method is suitable in which the monotonous decrease interval and the monotone increase interval of the triangular carrier wave TW are detected alternately and the average value of the detection values is obtained. Therefore, it is necessary for the detected current storage unit 3 to store current values IdcA, IdcB, IdcC, and IdcD for two points (two intervals of a monotonically decreasing interval and a monotonically increasing interval) and a total of four points for two phases. The stored current value data is called to the phase current calculation unit 4 at the time of calculation to start the calculation, and the phase current calculation unit 4 obtains the average value of the current of each phase in the current for two phases.

The phase current calculation unit 4 calculates a three-phase alternating current from the two-phase detection current stored in the detection current storage unit 3. Based on the three-phase voltage commands Vu, Vv, and Vw generated by the voltage command generator 5, the signs of the two-phase current values are determined. The remaining one-phase current value can be easily obtained from the already obtained two-phase current value by utilizing the fact that the sum of the three-phase current values is zero. From the above calculation, it is possible to detect the three-phase alternating current value flowing through the rotating machine M. The voltage commands Vu, Vv, Vw are determined based on the phase current value, and the phase current is used for monitoring the output of the rotating machine M. It is also used for each part control process.

The voltage command generator 5 has a role of generating voltage commands Vu, Vv, and Vw that are three-phase voltage commands to be output to the power converter main circuit 1. Various voltage command generation methods are known depending on the control method of the rotating machine M, but the description is omitted because it is not the essence of the present embodiment. The voltage command generation unit 5 generates voltage commands Vu, Vv, and Vw that are three-phase voltage commands to be output to the timing determination unit (control unit). Next, each operation content of the timing determination unit shown in the flowchart of FIG. 3 will be described. First, the current detection section shown in FIG. 4 is obtained from the difference in magnitude between the voltage commands Vu, Vv, and Vw generated by the voltage command generator 5. The current detection interval is determined depending on the difference between the magnitudes of the voltage commands Vu, Vv, and Vw. The smaller the difference is, the shorter the current detection interval is.

Subsequently, it is determined whether or not the DC bus current detection timings T _A to T _D can be determined in the current detection section. Whether or not the DC bus current detection timings T _A to T _D can be determined is determined by comparing the current detection section T12 and the current detection non-cancellation section T10, and when the current detection section T12 is smaller than the current non-detection section T10 It is determined that detection is impossible. Details will be described below with reference to FIG. When it is determined that the detection is impossible, it is necessary to add a correction amount to the voltage commands Vu, Vv, and Vw so that a current detection section can be secured.

FIGS. 8A and 8B are diagrams illustrating an example for securing a current detectable section when it is determined that detection is impossible in the current detection section obtained from the voltage commands Vu, Vv, and Vw. Here, an example is shown in which the DC bus current detection is performed in the monotonically decreasing section of the triangular carrier wave TW, but the same processing can be performed also in the monotonically increasing section. The voltage commands Vu, Vv, and Vw input from the voltage command generator 5 are set to a maximum phase voltage command Vu, an intermediate phase voltage command Vv, and a minimum phase voltage command Vw in descending order. The voltage commands Vu, Vv, Vw and the triangular carrier wave TW are compared to determine the gate switching timings Sup to Swn. However, detection becomes difficult when the current detection interval is equal to or less than the current detection disabled interval shown in FIG. In the section T80 in FIG. 8 (A), the the current detection section is smaller than the current undetectable period, it is determined that it is not possible to determine the DC bus current detection timing T _B.

Therefore, as shown in FIG. 8 (B), when it is determined that detection is not possible in the current detection section, the triangular carrier wave period is divided into two on the detection section securing side and the voltage compensation side, and detected on the voltage command on the detection section securing side. The voltage amount ΔV is added so that the section can be secured, and the same amount of voltage amount ΔV is subtracted from the voltage command on the voltage compensation side. To become larger than the interval T81 the interval T80 in FIG. 8 (B), the current detection section becomes larger than the current undetectable period, it is possible to ensure the DC bus current detection timing T _B. Here, the voltage amount ΔV for securing the detection section is determined depending on the section where current detection is impossible. Then, the gate switching timings Sup to Swn are corrected according to the corrected voltage command. As a result, the DC bus current can be detected without changing the length of the On time of the switching elements of each phase, that is, without changing the output voltage of the inverter. Although FIG. 8 shows an example in which the correction amount is added to the intermediate phase voltage command Vv, the correction amount is similarly added to the maximum phase voltage command Vu or the minimum phase voltage command Vw as necessary. Furthermore in FIG. 8 (A) have dealt with the case can not be secured to the timing T _B the difference between Vv and Vw is small, even when the difference between the Vu and Vv can not determine the reduced timing T _A. At this time, the voltage amount ΔV is subtracted from the voltage command on the detection section ensuring side, and the same amount of voltage ΔV is added to the voltage command on the voltage compensation side.

By performing the above operation, current detection can be performed even when the difference in magnitude between the phases of the voltage command becomes small. Further, when the magnitude of the voltage command of each phase is switched, for example, even when the voltage command Vv is larger than the voltage command Vu due to driving conditions and the rotating machine M is driven, current detection can be performed. . Also, current detection can be performed under all driving conditions such as low-speed driving where the currents Iu, Iv, and Iw are small. In addition, since the current cannot be detected on the voltage compensation side when the detection section is secured, detection is performed only in one of the pair of the current value IdcA and the current value IdcB or the pair of the current value IdcC and the current value IdcD in one period of the triangular carrier wave. Absent. As described above, the update period of the voltage command Vv to which the correction amount ΔV is added in order to secure the current detection section needs to be the same as or longer than the triangular carrier wave period. In addition, since it is basically necessary to determine whether or not the current can be detected every period, the period of the voltage commands Vu, Vv, and Vw input to the timing determination unit needs to be equal to or longer than the triangular carrier period. .

Finally, the voltage command Vv to which the correction amount ΔV is added as necessary is compared with the triangular carrier wave TW to determine the gate switching timings Sup to Swn for the three phases, and the DC bus current using the gate switching timings Sup to Swn. The detection timings T _A to T _D are determined, and the detection current detected by the DC bus current detection unit 2 is acquired and held. Further, the gate switching timings Sup to Swn are output to the power conversion unit main circuit 1, the DC bus current detection timings T _A to T _D are output to the detection current storage unit 3, and the operation of the timing determination unit is terminated.

As described above, in order to perform highly accurate current detection from the DC bus current without being affected by the current ripple, the current detection is performed alternately between the monotonically decreasing section and the monotonically increasing section of the triangular carrier wave TW, and the voltage command Vu , Vv, Vw need to be equal to or longer than the triangular carrier period. In order to minimize the decrease in output voltage accuracy under these conditions, the update period of the voltage commands Vu, Vv, Vw needs to be the same as the triangular carrier wave period. Processing for realizing this will be described below. FIG. 9 is a timing chart of current detection processing (E), current calculation processing (F), and voltage command generation processing (G) for a triangular carrier wave period. Here, the current detection process (E) is a process of storing the current value detected by the DC bus current detection unit 2 in the detection current storage unit 3, and the current calculation process (F) is a phase current calculation unit 4. The voltage command generation process (G) is a process of generating the voltage commands Vu, Vv, and Vw by the voltage command generation unit 5.

As described above, highly accurate current detection can be performed from the DC bus current by performing current detection alternately in the monotonically decreasing section and the monotonically increasing section of the triangular carrier wave TW. For this purpose, the triangular carrier period is first divided into two sections, a monotonically decreasing section and a monotonically increasing section. One of them is set as a current detection section. The current detection timing is determined within the section, the current is detected, and the detected value is stored. In the next cycle, the current detection interval is the opposite of the current detection interval in the previous cycle, the current is detected in the same manner, and the detected value is stored. That is, in FIG. 9, current detection is performed in the monotonically decreasing section in the first cycle, and current detection is performed in the monotonically increasing section in the second cycle. Here, as described above, the current detection value in the monotonic decrease section of the triangular carrier wave TW and the current detection value in the monotonous increase section have errors due to current ripple appearing in positive and negative directions, so the current detection values for the previous two cycles are used. Thus, it is possible to obtain the detected current values in the monotonically decreasing section and the monotonically increasing section, and by performing the averaging process in the next phase current calculation unit 4, it is possible to reduce the influence of the detection error caused by the current ripple. I can do it.

Subsequently, a three-phase alternating current calculation process (F) is executed once per period of the triangular carrier wave TW by the phase current calculation unit 4. Although FIG. 9 shows an example in the case of performing in a monotonically decreasing section, it may be performed anywhere such as a monotonically increasing section in one cycle. However, in the next voltage command generation unit 5, when the current calculated by the phase current calculation unit 4 is used, it is necessary to perform it before the voltage command generation process (G). The three-phase alternating current calculation process (F) is performed using the current stored in the detected current storage unit 3, but as shown in FIG. 9, the current ripple is obtained by using the average value of the current values before and after the first cycle. It is possible to reduce the influence of errors caused by. As an example of a specific current calculation method, the average value of the current values IdcA and IdcD stored in the detected current storage unit 3 is the current value of the voltage command maximum phase (U phase), and the average value of the current values IdcB and IdcC is the voltage. The current value of the command minimum phase (W phase) is set, and the current value of the voltage command intermediate phase (V phase) which is the remaining one phase is calculated from the relationship that the total of the current values of the three phases is zero.

Finally, in order to minimize the degradation of the output voltage accuracy, the voltage command generation process (G) is also executed once every period of the triangular carrier wave. FIG. 9 shows an example in the case of performing in a monotonically decreasing section. As shown in FIG. 9, current detection is performed in the monotonic increase interval and monotone decrease interval of the triangular carrier wave, and averaging is performed using the current detection values of the last two times at the start of each triangular carrier cycle, and the current value is calculated. calculate. The voltage command generation process (G) may or may not use the current value. However, FIG. 9 shows the voltage command generation process (G) when the calculated current is used. At this time, the voltage command generation process (G) needs to be executed after the three-phase alternating current calculation process (F). . It should be noted that the period of the voltage command generation process (G) may be equal to or longer than the triangular carrier period within a range in which a decrease in output voltage accuracy is allowed.

Here, there is a time lag difference between the timing of the current calculation process (F) and the two current detection timings. For example, in FIG. 9, in the time lag from the current detection timing in the monotonically increasing section, there are cases where the triangular carrier has 0.5 and 1.5 periods depending on the timing of the current calculation process (F), and further, the monotonically decreasing section In the time lag from the current detection timing at, there are cases where the triangular carrier wave period is 1 period and 2 periods depending on the current calculation timing. In order to eliminate the influence of the difference in time lag from the detection timing, the phase current calculation unit 4 performs coordinate conversion on the current detected at each timing at the time of current calculation using the rotation angle of the timing, and averages the results. Corrections are made. As a result, the detection error of the current detection value can be reduced, so that current calculation and voltage command generation processing can be performed every triangular carrier wave period.

In this way, the current detected at the above timing is transformed into a rotating coordinate system for use in the control. When the current is averaged and then the coordinate transformation is performed, the rotation angle used for the coordinate transformation is influenced by the time lag. As a result, an error occurs in the current value on the rotating coordinate. Therefore, in order to eliminate the influence of the difference in the time lag from the detection timing, the current detected at each timing at the time of current calculation is coordinate-transformed using the rotation angle at that timing, and correction is performed to average the results. Yes. An example is shown in FIG. In FIG. 10, the output when the time lag from the current detection timing in the monotonic increase section described in FIG. 9 is 0.5 period of the triangular carrier wave and the time lag from the current detection timing in the monotone decrease section is 2.0 periods. A procedure for obtaining a three-phase current value and a current value on a rotation coordinate is shown. Here, three-phase current values at the respective timings are calculated from the current values for the two phases detected at the respective timings.

Next, calculate the three-phase current value to be output by averaging the three-phase current at each timing. Subsequently, in many cases where the detected current is fed back to the voltage command generation unit 5, the current value on the rotating coordinate is used instead of the three-phase current value. When the current value on the coordinates is calculated, a difference occurs between the rotation angle used for coordinate conversion and the rotation angle when actual current detection is performed. Therefore, the first rotation angles θ1 and θ2 of each monotonically decreasing section or the monotonically increasing section where the current is detected are detected or estimated, and the three-phase current value detected at each timing is used for each rotation angle of the section. Coordinate conversion. The average value of the current values Id1, Iq1, Id2, and Iq2 on the rotational coordinates at each timing thus obtained is used as the current value on the rotational coordinates. FIG. 10 shows a case where a time lag of 0.5 period and 2.0 period of the triangular carrier wave is shown, but the same processing is performed in the case of 1.0 period and 1.5 period. This can reduce the detection error of the current value on the rotating coordinate, so the current is calculated every triangular carrier wave period, and the voltage command is generated with high accuracy when the voltage command generating process is performed using the current value on the rotating coordinate. Is possible.

In FIG. 10, DC bus current values IdcA and IdcB are detected in a monotonically decreasing section (block 150). Then, the three-phase current values Iu1 to Iw1 are calculated by calculation (block 151). Further, coordinate transformation is performed at the rotation angle θ1 to obtain rotation coordinate system current values Id1 and Iq1 (block 152). On the other hand, in the monotonically increasing section, the DC bus current values IdcC and IdcD are detected (block 200). Then, the three-phase current values Iu2 to Iw2 are calculated by calculation (block 201). Further, coordinate transformation is performed at the rotation angle θ2 to obtain rotation coordinate system current values Id2 and Iq2 (block 202). Finally, the rotating coordinate system current values Id and Iq are obtained by averaging based on Id1, Iq1, Id2, and Iq2 (block 300).

Through the procedure as described above, the voltage commands Vu, Vv, and Vw are updated at every triangular carrier cycle necessary for determining whether or not current detection is possible, and current detection that is less affected by current ripple can be performed. It becomes possible. As a result, even when driving at a small triangular carrier frequency with a long triangular carrier cycle, high-accuracy current detection can be performed and a decrease in output voltage accuracy can be minimized. That is, even if the wavelength of the triangular carrier wave TW is increased and the period is increased, the accuracy is improved because detection is performed every period. By operating as described above, the triangular carrier wave period, the current detection period, and the voltage update period are the same, and the current detection is alternately detected in the monotonically decreasing section and the monotonically increasing section of the triangular carrier wave TW. Because the time difference between the detection timings can be fixed as small and constant as possible, the output voltage accuracy is reduced while accurately detecting the current in all three phases even when the so-called low carrier driving is performed, where the wavelength of the triangular carrier wave TW is large and the period is large. It is possible to drive a rotating machine that minimizes this.

Embodiment 2. FIG.
FIG. 11 is a diagram for explaining the operation of the power conversion device according to the second embodiment. FIG. 11 shows the positional relationship between current detection timings T _A to T _D determined by the timing determination unit according to the second embodiment. In FIG. 11, the triangular carrier wave TW is shown in the upper part, and the state of the output voltage vector is shown in the middle part. Here, as described above, the output voltage vectors are non-zero voltage vector sections H1 to H16 in which currents for two phases can be detected from the DC bus 102, and zero voltage vector sections J1 to J1 in which current cannot be detected. It consists of J7. Further, in FIG. 11, a schematic Z of a one-phase current waveform is shown at the bottom.

Determined from the detection timing T _A that is determined in the timing decision unit in the control unit 6 and the time T20 to the next triangular carrier wave period beginning S1, so that the time T21 from the triangular carrier wave period beginning S1 to timing T _D are different (T20 ≠ T21). And detection timing T _B and time T22 until the next triangular carrier wave period beginning S1, is determined after a predetermined time T2 of the detection timing T _A with the predetermined time of the detection timing T _D from the triangular carrier wave period beginning S1 T2 time T23 to the detection timing _{T C} which is determined before or different (T22 ≠ T23). Similarly, the detection timings T _C and T _D and the time until the next triangular carrier cycle start time S2 and the time from the triangular carrier cycle start time S2 to the detection timings T _B and T _A are also determined to be different (T24). ≠ T25).

Through the procedure as described above, in addition to the effect obtained in the first embodiment, the detection position is different for each triangular carrier wave period, and the position of the current detection section is also different. For example, with reference to the triangular carrier cycle start time S1, the position of the non-zero voltage vector section H1 and the position of the non-zero voltage vector section H8 are different, that is, the relative positions of the current detection sections are different. As a result, the detected current value is different, the current value calculated by the phase current calculation unit 4 is also different, the voltage command generated from the voltage command generation unit 5 is different, and the gate switching timings Sup to Swn are also different. In addition, the shape of the current ripple is deformed every triangular carrier wave period. One example is shown as a one-phase current waveform Z in FIG. As shown in FIG. 11, current waveforms are different in the first two cycles and the second half of the triangular carrier cycle, and the frequency components of the current ripple derived from the triangular carrier cycle are dispersed. As a result, frequencies that cause noise are dispersed, and annoying noise is suppressed.

As described above, the power conversion device according to the present invention is useful for a power conversion system that is widely applicable to various electric motors and systems, and is particularly suitable for a power conversion system that is driven at a small triangular carrier frequency. And a rotary electric machine can be driven with the rotary electric machine drive device using the power converter device concerning this invention.
It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

Claims

A PWM converter that converts the three-phase voltage command to a triangular carrier wave and converts it into a PWM pulse;
A power converter main circuit for driving a switching element based on the PWM pulse and converting a DC voltage into a three-phase AC voltage;
A DC bus current detection unit for detecting a current flowing in a DC bus of the power converter main circuit;
A timing determination unit that sets two detection timings for detecting a current for two phases from the DC bus current detection unit at least once in one period of the triangular carrier wave based on the switching timing of the switching element;
A phase current calculation unit that calculates a three-phase AC current value once in one period of the triangular carrier wave based on the current value of the DC bus for the two phases detected at the timing determined by the timing determination unit;
A voltage command generator that updates the three-phase voltage command once in one period of the triangular carrier wave based on the three-phase AC current value;
In the case where the triangular carrier wave is divided into two sections, a monotone increasing section and a monotonic decreasing section, the DC bus current detection unit has the monotonically increasing section or the monotonically decreasing section in the first period of two consecutive triangular carrier periods. The current value of the DC bus is detected in one of the sections, and in the second period of the two continuous triangular carrier periods, the first period of the monotonically increasing section or the monotonically decreasing section is detected in the first period. Detect the current value of the DC bus in the section that was not,
The phase current calculation unit is based on the current values of the two-phase DC buses detected by the DC bus current detection unit in the monotonically increasing section and the monotonically decreasing section in the immediately preceding two triangular carrier periods. The power converter which calculates the said three-phase alternating current value.
The DC bus current detection unit detects the current of the two phases in each of the monotonically increasing section and the monotonically decreasing section of the triangular carrier wave period, and the phase current calculation unit is configured to detect each phase in the current of the two phases. The power converter of Claim 1 which calculates | requires the average of the electric current of.
A correction amount is added to the three-phase voltage command for the current detection side of the monotonic increase interval and the monotone decrease interval of the triangular carrier wave period, the detection timing is ensured, and the current detection is not performed. Subtract the correction amount from the three-phase voltage command of the section,
Or a current detection section generating unit that subtracts a correction amount from the three-phase voltage command in a section on which current detection is performed and adds the correction amount to the three-phase voltage command in a section on which current detection is not performed. Or the power converter device of Claim 2.
The timing determination unit determines a detection timing of the first phase from the switching timing TS based on the switching timing TS of the switching element related to the voltage intermediate phase whose magnitude of the three-phase voltage command is second. And setting before the time T1, and determining the detection timing of the second phase after a predetermined time T2 from the detection timing of the first phase,
The time T1 is set longer than the time required for current detection,
The time T2 includes a dead time interval provided in order to avoid simultaneous conduction of the switching element pairs connected in series in the power converter main circuit, and high-frequency oscillation of a direct current generated when the switching element is switched. The power conversion device according to any one of claims 1 to 3, wherein the power conversion device has a value that is greater than a sum of a period until the vibration is attenuated and the amplitude vibration is equal to or less than a predetermined value.
The time from the current detection timing of the two phases in the monotonically increasing section to the start time of the next triangular carrier cycle is different from the time from the start of the triangular carrier period to the current detection timing of the two phases in the monotonically decreasing section. ,
Furthermore, the time from the current detection timing for the two phases in the monotonically decreasing section to the start time of the next triangular carrier cycle and the time from the start of the triangular carrier cycle to the current detection timing for the two phases in the monotonically increasing section The power converter device according to any one of claims 2 to 4, which are different from each other.
If there is a difference in the time lag between the current calculation timing by the phase current calculation unit and the current detection timing by the DC bus current detection unit in the monotonically increasing section and the monotonically decreasing section, the current by the phase current calculating section The current detected at each timing at the time of calculation is subjected to coordinate conversion using the rotation angle at that timing, and an average value of current values on the rotation coordinates at each timing is obtained. Power converter.
The time lag is 0.5 period and 1.5 period of the triangular carrier wave when current detection is performed in the monotonically increasing section, and one period of the triangular carrier wave is performed when current detection is performed in the monotonically decreasing section. The power conversion device according to claim 6, wherein there are two cycles.
A rotating electrical machine drive device that drives the rotating electrical machine using the power conversion device according to any one of claims 1 to 7.