Power conversion device and rotating machine drive system

Abstract

The power conversion device (80) includes a power converter (10) for converting DC power into three-phase AC power for a load, and a control device (30). The control device (30) includes a switching signal generating unit (50). The switching signal generating unit (50) generates a switching signal that synchronizes the timings of at least one of a first group based on the timing of increasing the terminal voltage of a first connection point of a first phase branch and the timing of decreasing the terminal voltage of a second connection point of a second phase branch, or a second group based on the timing of decreasing the terminal voltage of the first connection point and the timing of increasing the terminal voltage of the second connection point. The switching signal generating unit (50) determines the timing of turning on or off the upper branch switching element and the timing of turning on or off the lower branch switching element based on the phase current at the rising and falling timings of the terminal voltage.

Description

Technical Field

[0001] The present disclosure relates to a power conversion device that controls an output voltage by turning on and off a switching element, and a rotating machine drive system that includes the power conversion device and drives a rotating machine. Background Art

[0002] In a power converter, the switching operation of a switching element causes fluctuations in the terminal voltage of each phase, which in turn causes leakage current to flow through floating capacitance between the power converter and the ground, generating electromagnetic noise.

[0003] Rotating machine drive systems equipped with power converters have electromagnetic noise standards defined for each product category. Therefore, electromagnetic noise countermeasures are necessary to prevent electromagnetic noise generated by the power converters from exceeding these limits. Commonly implemented are noise filters composed of passive components. However, this requires space within the power converters for the filters, which increases manufacturing costs.

[0004] Against this background, Patent Document 1 below proposes a technique for reducing electromagnetic noise by adjusting the phase of a carrier wave that determines whether a switching element is turned on or off.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2014 / 073247 Summary of the Invention

[0008] However, the method disclosed in Patent Document 1 does not describe in detail the estimation of the terminal voltage during the dead time period, which is provided to prevent short circuits caused by simultaneous on-state switching of the upper and lower arms. Consequently, the method disclosed in Patent Document 1 suffers from an issue in that it is insufficiently effective in reducing electromagnetic noise caused by synchronization shifts corresponding to the dead time period.

[0009] The present disclosure has been made in view of the above-mentioned circumstances, and an object thereof is to provide a power conversion device capable of reducing electromagnetic noise caused by synchronization deviation corresponding to the dead time.

[0010] In order to solve the above-mentioned problems and achieve the purpose, the power conversion device involved in the present disclosure is a power conversion device that converts DC power into three-phase AC power for a load, and includes a power converter and a control device. In the power converter, multiple single-phase branches formed by connecting upper branch switching elements and lower branch switching elements in series are connected in parallel, and the connection point of the upper branch switching elements and the lower branch switching elements is connected to the load. The control device controls the switching operation of the upper branch switching elements and the lower branch switching elements. The control device includes a switching signal generating unit. The switching signal generating unit generates a switching signal that synchronizes the timing within a first group based on the rising moment of the terminal voltage at the first connection point connected to the load of the first single-phase branch and the falling moment of the terminal voltage at the second connection point connected to the load. Alternatively, the switching signal generating unit generates a switching signal that synchronizes the timing within a second group based on the falling moment of the terminal voltage at the first connection point and the rising moment of the terminal voltage at the second connection point. The switching signal generating unit determines a timing to turn on or off the upper arm switching element and a timing to turn on or off the lower arm switching element based on the phase current at the rising timing and the falling timing of the terminal voltage.

[0011] According to the power conversion device according to the present disclosure, it is possible to reduce electromagnetic noise caused by synchronization deviation corresponding to the dead time. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 1 is a diagram showing a configuration of a rotating machine drive system including a power conversion device according to an embodiment.

[0013] Figure 2 It is a block diagram showing the functional configuration of the control device in the embodiment.

[0014] Figure 3 This is a diagram showing an example of a hardware configuration for realizing the functions of the control device in the embodiment.

[0015] Figure 4 This is a voltage vector diagram for explaining the operation of the switching signal generating unit in the embodiment.

[0016] Figure 5 This is a first timing chart for explaining the operation of the switching signal generating unit in the embodiment.

[0017] Figure 6 This is a second timing chart for explaining the operation of the switching signal generating unit in the embodiment.

[0018] Figure 7 This is a third timing chart for explaining the operation of the switching signal generating unit in the embodiment.

[0019] Figure 8 1 is a block diagram showing a functional configuration of a switching signal generating unit in the embodiment.

[0020] Figure 9 This is a flowchart showing the flow of operations in the control device according to the embodiment.

[0021] Figure 10 This is a comparison diagram of operation waveforms before and after application of the control method according to the embodiment.

[0022] Figure 11 It is a diagram showing the configuration of a rotary machine drive system according to a first modified example of the embodiment.

[0023] Figure 12 It is a diagram showing the configuration of a rotary machine drive system according to a second modified example of the embodiment.

[0024] Figure 13 It is a diagram showing the configuration of a rotary machine drive system according to a third modified example of the embodiment.

[0025] (Explanation of Reference Numerals)

[0026] 1: Processor; 2: Storage device; 10, 110, 210, 310a, 310b: Power converter; 11: DC power supply; 12, 12a, 12b: Capacitor; 12c, 13e, 14e, 15e: Connection point; 13a, 13b, 13c, 13d, 14a, 14b, 14c, 14d, 15a, 15b, 15c, 15d: Switching element; 16: Current detector; 17: DC bus; 18: DC bus; 20, 220, 320a, 320b: Rotary Rotating machine; 21: Angle detector; 22: Three-phase winding; 24U: U-phase terminal; 24V: V-phase terminal; 24W: W-phase terminal; 30, 130, 230, 330: Control device; 40: Voltage command generating unit; 50: Switching signal generating unit; 51: Change time determining unit; 52: Current estimation unit; 53: Switching time calculation unit; 54: Switching signal output unit; 80, 80A, 80B, 80C: Power conversion device; 100, 100A, 100B, 100C: Rotating machine drive system. DETAILED DESCRIPTION

[0027] Hereinafter, a power conversion device and a rotary machine drive system according to an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. In the following, electrical connection and physical connection are not distinguished and are simply referred to as "connection" for explanation.

[0028] Implementation method.

[0029] Figure 11 is a diagram showing a configuration of a rotating machine drive system 100 including a power conversion device 80 according to an embodiment. Figure 1 A rotating machine drive system 100 according to the illustrated embodiment includes a DC power supply 11 and a power conversion device 80. The power conversion device 80 includes a power converter 10, a control device 30, and a current detector 16. A rotating machine 20 serving as a load is connected to the rotating machine drive system 100. The rotating machine 20 is driven by the electric power supplied from the rotating machine drive system 100.

[0030] The power converter 80 converts the DC power supplied from the DC power supply 11 into three-phase AC power for the rotating machine 20, and supplies the power to the rotating machine 20. Hereinafter, each of the three phases will be referred to as a U phase, a V phase, and a W phase.

[0031] exist Figure 1 , a rotating machine 20 having a three-phase winding 22 is illustrated. The rotating machine 20 has a U-phase terminal 24U, a V-phase terminal 24V, and a W-phase terminal 24W. The rotating machine 20 is provided with an angle detector 21 for detecting the rotation angle of a rotor (not shown) in the rotating machine 20. An example of the angle detector 21 is a Hall sensor.

[0032] The power converter 10 includes switching elements 13a, 13b, 13c, and 13d (hereinafter referred to as "13a to 13d" as appropriate, and the same applies to others), switching elements 14a to 14d, switching elements 15a to 15d, and capacitors 12a and 12b.

[0033] Each switching element of power converter 10 includes an insulated gate bipolar transistor (IGBT) and a diode connected in antiparallel to the IGBT. Antiparallel means that the anode of the diode is connected to the terminal corresponding to the emitter of the IGBT, and the cathode of the diode is connected to the terminal corresponding to the collector of the IGBT.

[0034] exist Figure 1 In the example, the transistors of each switching element are IGBTs, but the present invention is not limited to this. Metal oxide semiconductor field effect transistors (MOSFETs) can also be used instead of IGBTs. In addition, when MOSFETs are used as each switching element, parasitic diodes exist within the element. Therefore, when using MOSFETs, the use of parasitic diodes can omit the diode connected in antiparallel.

[0035] Switching elements 13a to 13d operate as U-phase switching elements, switching elements 14a to 14d operate as V-phase switching elements, and switching elements 15a to 15d operate as W-phase switching elements. The power converter 10 operates as a three-level inverter through these switching elements 13a to 13d, 14a to 14d, and 15a to 15d. Figure 1 The illustrated power converter 10 has a structure in which switching elements of each phase are connected in a T-shape, and therefore is sometimes referred to as a “T-type three-level inverter”.

[0036] Switching elements 13a, 14a, and 15a are connected to a DC bus 17 on the high-potential side. Switching elements 13d, 14d, and 15d are connected to a DC bus 18 on the low-potential side. The DC bus 17 is an electrical wiring connected to the positive side of the DC power supply 11. The DC bus 18 is an electrical wiring connected to the negative side of the DC power supply 11. In this document, the switching elements 13a, 14a, and 15a on the high-potential side are referred to as "upper-branch switching elements," and the switching elements 13d, 14d, and 15d on the low-potential side are referred to as "lower-branch switching elements."

[0037] The group of switching elements 13a and 13d, the group of switching elements 14a and 14d, and the group of switching elements 15a and 15d each constitute a phase leg and are connected in parallel to each other.

[0038] Capacitors 12a and 12b are connected in series in this order between DC bus 17 and DC bus 18. The voltage between DC bus 17 and DC bus 18 is referred to as "bus voltage." The bus voltage is equal to the DC voltage output by DC power supply 11. The value of the bus voltage is denoted by "Vdc" as appropriate.

[0039] The pair of switching elements 13b and 13c, the pair of switching elements 14b and 14c, and the pair of switching elements 15b and 15c are connected in series and operate as bidirectional switching elements.

[0040] The pair of switching elements 13b and 13c is connected between connection point 13e and connection point 12c. Connection point 13e is the connection point between switching element 13a and switching element 13d. Connection point 12c is the connection point between capacitor 12a and capacitor 12b. Connection point 12c is sometimes referred to as a "neutral point."

[0041] Similarly, the pair of switching elements 14b and 14c is connected between connection point 14e and connection point 12c. Connection point 14e is the connection point between switching element 14a and switching element 14d. The pair of switching elements 15b and 15c is connected between connection point 15e and connection point 12c. Connection point 15e is the connection point between switching element 15a and switching element 15d.

[0042] Connection point 13e is connected to U-phase terminal 24U of rotating machine 20. Connection point 14e is connected to V-phase terminal 24V of rotating machine 20. Connection point 15e is connected to W-phase terminal 24W of rotating machine 20. Current detectors 16 are arranged in each electrical wiring.

[0043] In the U phase, when switching element 13a is on and the other switching elements are off, the positive electrode potential of DC power supply 11 appears at connection point 13e and is applied to U-phase terminal 24U. Furthermore, when switching element 13d is on and the other switching elements are off, the negative electrode potential of DC power supply 11, or zero potential, appears at connection point 13e and is applied to U-phase terminal 24U. Furthermore, when either switching element 13b or switching element 13c is on and both switching elements 13a and 13d are off, a neutral point potential, equivalent to the potential of connection point 12c, appears at connection point 13e and is applied to U-phase terminal 24U. Furthermore, the capacitances of capacitors 12a and 12b are essentially equal. Therefore, the neutral point potential is 1 / 2 the bus voltage, or "Vdc / 2."

[0044] While the above description describes the operation of the U phase, the switching elements of the V and W phases also operate similarly. Therefore, voltages at three potential levels—positive electrode potential, neutral point potential, and zero potential—are applied to the U-phase terminal 24U, the V-phase terminal 24V, and the W-phase terminal 24W through the switching operation of the corresponding switching elements. Thus, the power converter 10 operates as a three-level inverter. Hereinafter, the voltages applied to the U-phase terminal 24U, the V-phase terminal 24V, and the W-phase terminal 24W of the rotating machine 20 will be referred to as "terminal voltages," and the terminal voltages of each phase will be denoted as "vun," "vvn," and "vwn," respectively, as appropriate.

[0045] Current detector 16 detects the phase current flowing through each phase of rotating machine 20. The detection value of current detector 16 is input to control device 30. Control device 30 controls each switching element of power converter 10 based on the detection values ​​of angle detector 21 and current detector 16. The details of this control will be described later.

[0046] Next, the configuration of the control device 30 will be described. Figure 2 1 is a block diagram showing the functional configuration of the control device 30 in the embodiment. The control device 30 includes a voltage command generating unit 40 and a switching signal generating unit 50 .

[0047] like Figure 2As shown, the voltage command generating unit 40 receives inputs of a torque command, bus voltage, rotor position detected by angle detector 21, and phase current detected by current detector 16. Alternatively, a current command may be used instead of a torque command. The voltage command generating unit 40 calculates a phase voltage command based on the torque command, bus voltage, rotor position, and phase current.

[0048] In addition, if Figure 2 As shown, the phase current detected by the current detector 16 and the phase voltage command calculated by the voltage command generating unit 40 are input to the switching signal generating unit 50. The switching signal generating unit 50 generates and outputs a switching signal based on the phase current and the phase voltage command.

[0049] Figure 3 1 is a diagram showing an example of a hardware configuration for realizing the functions of the control device 30 in the embodiment. The above functions and the following functions in the control device 30 can be realized by Figure 3 The processor 1 and storage device 2 shown are implemented. Although not shown in the figure, the storage device 2 includes a volatile storage device represented by a random access memory and a non-volatile auxiliary storage device represented by a flash memory. Alternatively, an auxiliary storage device such as a hard disk may be included instead of the flash memory.

[0050] Processor 1 executes a program read from storage device 2 to perform some or all of the functions of control device 30. In this case, the program is read from the auxiliary storage device to processor 1 via the volatile storage device. Processor 1 may also output data such as calculation results to the volatile storage device of storage device 2. Alternatively, data may be stored in the auxiliary storage device via the volatile storage device. Furthermore, in addition to processor 1 and storage device 2, logic circuits or analog circuits may also be used for processing.

[0051] Next, refer to Figures 4 to 7 The operation of the switching signal generating unit 50 in the embodiment is described with reference to the accompanying drawings. Figure 4 This is a voltage vector diagram for explaining the operation of the switching signal generating unit 50 in the embodiment. Figure 5 This is a first timing chart for explaining the operation of the switching signal generating unit 50 in the embodiment. Figure 6 This is a second timing chart for explaining the operation of the switching signal generating unit 50 in the embodiment. Figure 7 This is a third timing chart for explaining the operation of the switching signal generating unit 50 in the embodiment.

[0052] exist Figure 4The output voltage vector of the three-level inverter (hereinafter referred to as "voltage vector") is shown in FIG. The voltage vector is represented by (u, v, w). "u" represents the voltage output state of the U phase, "v" represents the voltage output state of the V phase, and "w" represents the voltage output state of the W phase.

[0053] In this embodiment, as a method for reducing electromagnetic noise caused by synchronization deviation of the dead time, control is performed to synchronize the rising timing of the terminal voltage of each phase and the falling timing of the terminal voltage of each phase. To perform this control, in this embodiment, only the time when the change of the common mode voltage of the three phases becomes zero is used. Figure 4 The six voltage vectors shown are V0 (0, 0, 0), V1 (1, 0, -1), V2 (0, 1, -1), V3 (-1, 1, 0), V4 (-1, 0, 1), V5 (0, -1, 1), and V6 (1, -1, 0).

[0054] In addition, in the numerical values ​​in parentheses in each voltage vector, "1" indicates that the terminal voltage is Vdc, "0" indicates that the terminal voltage is Vdc / 2, and "-1" indicates that the terminal voltage is 0.

[0055] Common-mode voltage is a voltage that causes common-mode noise. In this document, the common-mode voltage is defined as (vun + vvn + vwn) / 3, which is the sum of the U-phase terminal voltage vun, the V-phase terminal voltage vvn, and the W-phase terminal voltage vwn divided by 3.

[0056] The switching signal generating unit 50 calculates the output voltage vector and the output order and output time of each voltage vector based on the voltage command of each phase and the current switching state of each switching element. Figure 5 In FIG. 1 , as a specific example, an output voltage vector and an output time when a voltage having a phase angle of −30 to 30 degrees on the αβ axis is output are shown using a time chart.

[0057] exist Figure 4 In the αβ axis, the voltage vectors with phase angles in the range of -30 to 30 degrees are V0 (0, 0, 0), V1 (1, 0, -1), and V6 (1, -1, 0). These V0, V1, and V6 are used. Figure 5In this example, V0 is output in the order of time T1, V6 is output at time T2, V1 is output at time T3, and V0 is output at time T4. The times T1 to T4 for outputting each voltage vector follow the conventional space vector modulation method, so detailed description is omitted. Furthermore, the relationship between times T1 to T4 and the control period Ts is: Ts = T1 + T2 + T3 + T4. Of course, the direction of the voltage vector on the α and β axes is determined by the ratio of time T1 to time T2, and the magnitude of the voltage vector on the α and β axes is determined by the ratio of the sum of time T1 and time T2 to the control period Ts.

[0058] Next, the switching signal generating unit 50 determines the output order of the voltage vectors and the phase thereof, thereby determining the rising timing and falling timing of the terminal voltage of each phase.

[0059] according to Figure 5 In the example shown, the U-phase terminal voltage is determined to be "Vdc / 2" from time 0 to t1, "Vdc" from time t1 to t3, and "Vdc / 2" from t3 to Ts. The V-phase terminal voltage is determined to be "Vdc / 2" from time 0 to t1, "0" from time t1 to t2, and "Vdc / 2" from t2 to Ts. The W-phase terminal voltage is determined to be "Vdc / 2" from time 0 to t2, "0" from time t2 to t3, and "Vdc / 2" from time t3 to Ts.

[0060] As explained above, times t1, t2, and t3 can also be referred to as the times at which the terminal voltage changes. Furthermore, in this document, times t1, t2, and t3 are defined as the elapsed time relative to time 0. With this definition, the following relationship holds true between times t1, t2, and t3 and the times T1, T2, and T3 at which each voltage vector is output.

[0061] t1=T1

[0062] t2=T1+T2

[0063] t3=T1+T2+T3

[0064] according to Figure 5In the example shown, during the control cycle Ts starting at time 0, the sum of the time periods in the low state (low state) of the V-phase and the W-phase, where the terminal voltage changes in the order of decreasing and increasing, is equal to the sum of the time periods in the high state (high state) of the U-phase, where the terminal voltage switches in the order of increasing and decreasing. Therefore, the switching signal generating unit 50 can determine the switching signal so that, within one control cycle, the sum of the time periods in the low state (low state) of all phases, where the terminal voltage changes in the order of decreasing and increasing, is equal to the sum of the time periods in the high state (high state) of all phases, where the terminal voltage switches in the order of increasing and decreasing.

[0065] In addition, Figure 5 The bottom part shows the waveform of the common mode voltage vcm. If the above-defined common mode voltage vcm formula is applied to calculate, then Figure 5 As shown in the bottom part of , it becomes a constant value "Vdc / 2". Therefore, it can be seen that Figure 5 The illustrated examples of the groups, output sequences, and output timings of voltage vectors can contribute to reducing electromagnetic noise caused by common mode voltage.

[0066] Next, the current estimation calculation in the switching signal generating unit 50 of the embodiment will be described. Figure 6 In the figure, the flow of the processing based on the current estimation operation is shown in a time chart. Figure 6 In FIG. 1 , the waveform indicated by the dotted line is the actual current, and the waveform indicated by the solid line is the sampled current. The sampled current is obtained by plotting the current value estimated from the detection value of the current detector 16 .

[0067] exist Figure 6 In the present embodiment, switching signal generation unit 50 estimates current values ​​iph_est1 and iph_est2 based on the respective phase currents iph detected at time 0 of the current control cycle and the respective phase currents iph_old detected at time 0 of the immediately preceding control cycle. Time 0 indicates the beginning of each control cycle. Current value iph_est1 is an estimated current value one control cycle later, as viewed from time 0 of the current control cycle. Current value iph_est2 is an estimated current value two control cycles later, as viewed from time 0 of the current control cycle.

[0068] Furthermore, the current value iph_est1 after one control cycle and the current value iph_est2 after two control cycles are current values ​​reflected in the switching signal. Specifically, the current value iph_est1 after one control cycle and the current value iph_est2 after two control cycles reflected in the switching signal are estimated based on the respective phase currents iph detected in the current control cycle and the respective phase currents iph_old detected in the immediately preceding control cycle.

[0069] also, Figure 6 It is also shown that time 0 of the current control cycle is the time when the phase voltage command calculation begins. The calculation of the phase voltage command is completed within the current control cycle. Furthermore, the actual time when each switching element is turned on, i.e., the on-time, and the time when each switching element is turned off, i.e., the off-time, are also determined within the current control cycle. Furthermore, the generation of the switching signal based on the determined on-time and off-time is started at time 0, one control cycle after time 0 of the current control cycle.

[0070] Assuming that each phase current changes linearly within the control cycle, the current value iph_est1 at time 0 after one control cycle and the current value iph_est2 at time 0 after two control cycles can be estimated using the following equations.

[0071] iph_est1=iph+(iph-iph_old)…(1)

[0072] iph_est2=iph+2(iph-iph_old)…(2)

[0073] like Figure 5 As shown, at time 0 when estimating each current value, a zero voltage vector V0 is output. When zero voltage vector V0 is output, if the rotating machine 20 is rotating at a low speed, the induced voltage generated in the rotating machine 20 is low, so the phase current value is considered to be almost unchanged. In this case, the current values ​​iph_t1, iph_t2, and iph_t3 at times t1, t2, and t3 can be estimated using the following equations.

[0074] iph_t1=iph_est1…(3)

[0075] iph_t2=iph_est1+(iph_est2-iph_est1)×(T2 / (T2+T3))…(4)

[0076] iph_t3=iph_est2…(5)

[0077] On the other hand, when the current ripple associated with the switching operation is large, it is also effective to estimate the amount of current change by performing multiple current detections near time 0. Figure 7 , an example of a case where the secondary phase current is detected around time 0 is shown.

[0078] like Figure 7As shown, the first current value detected near time 0 of the current control cycle is set as iph1, and the second current value is set as iph2. Furthermore, the first current value detected near time 0 one control cycle ago is set as iph1_old. At this time, the estimated current value iph1_est at time 0 one control cycle later is calculated using the following formula.

[0079] iph_dlt1=iph1_old-iph1…(6)

[0080] iph1_est=iph1-iph_dlt1…(7)

[0081] Assuming that the slope of the current ripple is the same within the control period, the current values ​​iph_t1, iph_t2, and iph_t3 at times t1, t2, and t3 are estimated using the following equations.

[0082] iph_dlt2=(iph2-iph1) / dltT…(8)

[0083] iph_t1=iph1_est+T1×iph_dlt2…(9)

[0084] iph_t3=iph1_est-iph_dlt1-T4×iph_dlt2…(10)

[0085] iph_t2=iph_t1+T2×(iph_t3-iph_t1) / (t3-t2)…(11)

[0086] Furthermore, dltT shown on the right side of the above formula (8) is the difference in time between the first detection of the current value iph1 and the second detection of the current value iph2.

[0087] Alternatively, the current values ​​iph_t1, iph_t2, and iph_t3 at times t1, t2, and t3 may be estimated using the following equations (12) to (14) instead of the above equations (8) to (11).

[0088] iph_t1=iph_est1+E / R(1-e (-T1 / τ) )…(12)

[0089] iph_t2=iph_t1+E / R(1-e (-T2 / τ) )…(13)

[0090] iph_t3=iph_t2+E / R(1-e (-T3 / τ) )…(14)

[0091] In the above equations (12) to (14), "R" is the resistance value of the rotating machine 20 when viewed from the power converter 10. "τ" is the time constant, which is given by τ = L / R. "L" is the inductance value of the rotating machine 20 when viewed from the power converter 10. "E" is the voltage generated at each phase terminal of the rotating machine 20, which is given by E = vph - vind - Vdc / 2. "vph" is the voltage applied to the rotating machine 20, "vind" is the induced voltage generated in the rotating machine 20, and "Vdc" is the bus voltage.

[0092] Furthermore, the "ph" in each current value iph_t1, iph_t2, and iph_t3 collectively refers to the three phases, namely, the U phase, the V phase, and the W phase. Therefore, for example, to represent the U phase, "ph" is replaced with "u" or "U." Therefore, the U-phase current values ​​at times t1, t2, and t3 are recorded as "iu_t1," "iu_t2," and "iu_t3," respectively. The same description applies to the V-phase and W-phase. Furthermore, the same description applies to other parameters such as phase voltage commands, switching signals, on-time, and off-time.

[0093] The switching signal generator 50 determines the current polarity based on the current values ​​iph_t1, iph_t2, and iph_t3 calculated above at times t1, t2, and t3. Furthermore, the switching signal generator 50 estimates the terminal voltage during the dead time based on the current polarity. In this document, the direction of current flowing into the rotating machine 20 is defined as positive, and the reverse direction is defined as negative. This definition is for ease of explanation; the reverse direction, i.e., the direction of current flowing out of the rotating machine 20, may also be defined as positive.

[0094] Next, the switching timing calculation process in the switching signal generating unit 50 of the embodiment will be described. First, the switching signal generating unit 50 calculates the on-time and off-time based on the current values ​​iph_t1, iph_t2, and iph_t3 at times t1, t2, and t3.

[0095] Here, in Figure 1 In the circuit configuration of power converter 10 shown, the conduction state of each switching element can result in the following states (A) or (B). In the following description, "SW_ph1" through "SW_ph4" represent the conduction states of switching elements 13a-13d, 14a-14d, and 15a-15d, i.e., the switching signals that control their on / off states. Furthermore, "td" represents the aforementioned "dead time."

[0096] (State A): SW_ph2 is on, SW_ph4 is off, and SW_ph1 and SW_ph3 are switched complementarily.

[0097] (A-1): SW_ph1 is on, SW_ph3 is off

[0098] (A-2): SW_ph1 is cut off, SW_ph3 is cut off

[0099] (A-3): SW_ph1 is off, SW_ph3 is on

[0100] Hereinafter, the above-mentioned (A-1) to (A-3) will be supplemented.

[0101] (A-1): Terminal voltage is "Vdc"

[0102] The switching elements 13a, 14a, and 15a are turned on, and the diodes of the switching elements 13c, 14c, and 15c are reverse biased, so that the positive electrode potential of the DC power supply 11 appears.

[0103] (A-2):

[0104] If iph_t<0: the terminal voltage is "Vdc"

[0105] Since iph_t flows through the diodes of the switching elements 13a, 14a, and 15a, the positive electrode potential of the DC power supply 11 appears.

[0106] If iph_t>0: the terminal voltage is "Vdc / 2"

[0107] Since iph_t flows through the diodes of the switching elements 13c, 14c, and 15c, a neutral point potential appears.

[0108] (A-3): Terminal voltage is "Vdc / 2"

[0109] Since the switching elements 13b, 13c, 14b, 14c, 15b, and 15c are turned on at the same time, a neutral point potential appears.

[0110] (State B): SW_ph1 is off, SW_ph3 is on, and SW_ph2 and SW_ph4 are switched complementarily.

[0111] (B-1): SW_ph2 is on, SW_ph4 is off

[0112] (B-2): SW_ph2 is cut off, SW_ph4 is cut off

[0113] (B-3): SW_ph2 is off, SW_ph4 is on

[0114] Hereinafter, the above-mentioned (B-1) to (B-3) will be supplemented.

[0115] (B-1): Terminal voltage is "Vdc / 2"

[0116] Since the switching elements 13b, 13c, 14b, 14c, 15b, and 15c are turned on at the same time, a neutral point potential appears.

[0117] (B-2):

[0118] When iph_t<0: the terminal voltage is "Vdc / 2"

[0119] Since iph_t flows through the diodes of the switching elements 13b, 14b, and 15b, a neutral point potential appears.

[0120] If iph_t>0: the terminal voltage is "0"

[0121] Since iph_t flows through the diodes of the switching elements 13d, 14d, and 15d, the negative electrode potential of the DC power supply 11 appears.

[0122] (B-3): Terminal voltage is "0"

[0123] The switching elements 13d, 14d, and 15d are turned on, and the diodes of the switching elements 13b, 14b, and 15b are reverse biased, so that the negative electrode potential of the DC power supply 11 appears.

[0124] Based on the conduction state of the switching element, the switching signal generating unit 50 advances the turn-off timing of the switching element that switches the terminal voltage to the low potential side and the turn-on timing of the switching element that switches the terminal voltage to the high potential side by the amount of the dead time when the current polarity during switching is positive. Furthermore, when the current polarity during switching is negative, the turn-off timing of the switching element that switches the terminal voltage to the high potential side and the turn-on timing of the switching element that switches the terminal voltage to the low potential side are advanced by the amount of the dead time.

[0125] Therefore, the U-phase terminal voltage becomes Figure 5 The state shown is "Vdc / 2" from time 0 to t1, "Vdc" from time t1 to t3, and "Vdc / 2" from time t3 to Ts. Therefore, the conduction state of the U-phase switching element is controlled as follows.

[0126] Time 0 to t1':

[0127] (SW_U1, SW_U2, SW_U3, SW_U4)=(0110)…(15)

[0128] Time t1'~t1'+td:

[0129] (SW_U1, SW_U2, SW_U3, SW_U4)=(0100)…(16)

[0130] Time t1'+td~t3':

[0131] (SW_U1, SW_U2, SW_U3, SW_U4)=(1100)…(17)

[0132] Time t3'~t3'+td:

[0133] (SW_U1, SW_U2, SW_U3, SW_U4)=(0100)…(18)

[0134] Time t3'+td~Ts:

[0135] (SW_U1, SW_U2, SW_U3, SW_U4)=(0110)…(19)

[0136] In the above description, the numerical values ​​in parentheses represent the conduction state of the switching element, "0" means that the switching element is off, and "1" means that the switching element is on.

[0137] The times t1 ′ and t3 ′ are set as follows in consideration of the current polarity during switching and the potential of the terminal voltage during the dead time.

[0138] In the case of iu_t1>0, t1'=t1-td...(20)

[0139] In the case of iu_t1<0, t1′=t1…(21)

[0140] In the case of iu_t3>0, t3'=t3...(22)

[0141] In the case of iu_t3<0, t3′=t3-td…(23)

[0142] Supplementary information is provided regarding the above equations (20) to (23). When focusing on the above (A-1) and (A-2), when iph_t<0, even if the state changes from (A-1) to (A-2), the terminal voltage remains "Vdc" and does not change. On the other hand, when iph_t>0, when the state changes from (A-1) to (A-2), the terminal voltage changes from "Vdc" to "Vdc / 2". Therefore, in the case of iph_t<0 where the terminal voltage does not change, the calculated time t1 is used as it is. In addition, in the case of iph_t>0 where the terminal voltage changes, the dead time td is set before time t1. The same description can be given for time t3 where the voltage vector changes. In addition, since the description is repeated, the description here is omitted.

[0143] Therefore, tU1on, tU1off, tU2on, tU2off, tU3on, tU3off, tU4on, and tU4off, which are the on-time or off-time of the U-phase switching element, are set as follows.

[0144] SW_U1: tU1on=t1'+td, tU1off=t3'...(24)

[0145] SW_U2: Always on (tU2on, tU2off not set)…(25)

[0146] SW_U3: tU3off=t1', tU3on=t3'+td...(26)

[0147] SW_U4: Always off (tU4on, tU4off not set)…(27)

[0148] Supplementary information is provided regarding the above equations (24) to (27). When looking at the numerical values ​​in the brackets on the right side of the above equations (15) to (19), SW_U2 is all "1" and SW_U4 is all "0". That is, the switch element 13b is always on and the switch element 13d is always off. Therefore, there is no need to set tU2on, tU2off, tU4on, and tU4off. In addition, SW_U1 changes from "0" to "1" at time t1'+td and changes from "1" to "0" at time t3'. Therefore, it is set as in the above equation (24). In addition, SW_U3 changes from "1" to "0" at time t1' and changes from "0" to "1" at time t3'+td. Therefore, it is set as in the above equation (26).

[0149] The V-phase terminal voltage and the W-phase terminal voltage are described similarly below.

[0150] Make the V-phase terminal voltage Figure 5 The state shown is "Vdc / 2" from time 0 to t1, "0" from time t1 to t2, and "Vdc / 2" from time t2 to Ts. Therefore, the conduction state of the V-phase switching element is controlled as follows.

[0151] Time 0 to t1':

[0152] (SW_V1, SW_V2, SW_V3, SW_V4)=(0110)…(28)

[0153] Time t1'~t1'+td:

[0154] (SW_V1, SW_V2, SW_V3, SW_V4)=(0010)…(29)

[0155] Time t1'+td~t2':

[0156] (SW_V1, SW_V2, SW_V3, SW_V4)=(0011)…(30)

[0157] Time t2'~t2'+td:

[0158] (SW_V1, SW_V2, SW_V3, SW_V4)=(0010)…(31)

[0159] Time t2'+td~Ts:

[0160] (SW_V1, SW_V2, SW_V3, SW_V4)=(0110)…(32)

[0161] The times t1 ′ and t2 ′ are set as follows in consideration of the current polarity during switching and the potential of the terminal voltage during the dead time.

[0162] In the case of iv_t1>0, t1'=t1...(33)

[0163] In the case of iv_t1<0, t1′=t1-td…(34)

[0164] In the case of iv_t2>0, t2'=t2-td...(35)

[0165] In the case of iv_t2<0, t2′=t2…(36)

[0166] Supplementary information is provided regarding the above equations (33) to (36). When focusing on the above (B-2) and (B-3), in the case of iph_t>0, even if the state changes from (B-2) to (B-3), the terminal voltage is "0" and does not change. On the other hand, in the case of iph_t<0, when the state changes from (B-2) to (B-3), the terminal voltage changes from "Vdc / 2" to "0". Therefore, in the case of iph_t>0 where the terminal voltage does not change, the calculated time t1 is used as it is. In addition, in the case of iph_t<0 where the terminal voltage changes, the dead time td is set before time t1. The same description can be given for the time t2 where the voltage vector changes. In addition, since the description is repeated, the description here is omitted.

[0167] Therefore, tV1on, tV1off, tV2on, tV2off, tV3on, tV3off, tV4on, and tV4off, which are the on-time or off-time of the V-phase switching element, are set as follows.

[0168] SW_V1: Always off (tV1on, tV1off not set)…(37)

[0169] SW_V2: tV2off=t1', tV2on=t2'+td...(38)

[0170] SW_V3: Always on (tV3on, tV3off not set)…(39)

[0171] SW_V4: tV4on=t1'+td, tV4off=t2'...(40)

[0172] Supplementary information is provided regarding the above equations (37) to (40). When looking at the numerical values ​​in the brackets on the right side of the above equations (28) to (32), all SW_V1 values ​​are "0", and all SW_V3 values ​​are "1". That is, the switch element 14a is always off, and the switch element 14c is always on. Therefore, there is no need to set tV1on, tV1off, tV3on, and tV3off. In addition, SW_V2 changes from "1" to "0" at time t1', and changes from "0" to "1" at time t2'+td. Therefore, it is set as in the above equation (38). In addition, SW_V4 changes from "0" to "1" at time t1'+td, and changes from "1" to "0" at time t2'. Therefore, it is set as in the above equation (40).

[0173] In addition, the W-phase terminal voltage is set to Figure 5 Since the state shown is "Vdc / 2" from time 0 to t2, "0" from time t2 to t3, and "Vdc / 2" from time t3 to Ts, the conduction state of the W-phase switching element is controlled as follows.

[0174] Time 0 to t2':

[0175] (SW_W1, SW_W2, SW_W3, SW_W4)=(0110)…(41)

[0176] Time t2'~t2'+td:

[0177] (SW_W1, SW_W2, SW_W3, SW_W4)=(0010)…(42)

[0178] Time t2'+td~t3':

[0179] (SW_W1, SW_W2, SW_W3, SW_W4)=(0011)…(43)

[0180] Time t3'~t3'+td:

[0181] (SW_W1, SW_W2, SW_W3, SW_W4)=(0010)…(44)

[0182] Time t3'+td~Ts:

[0183] (SW_W1, SW_W2, SW_W3, SW_W4)=(0110)…(45)

[0184] The times t3 ′ and t4 ′ are set as follows in consideration of the current polarity during switching and the potential of the terminal voltage during the dead time.

[0185] In the case of iw_t2>0, t2'=t2...(46)

[0186] In the case of iw_t2<0, t2′=t2-td…(47)

[0187] In the case of iw_t3>0, t3'=t3-td...(48)

[0188] In the case of iw_t3<0, t3′=t3…(49)

[0189] Supplementary information is provided regarding the above equations (46) to (49). When focusing on the above (B-2) and (B-3), when iph_t>0, even if the state changes from (B-2) to (B-3), the terminal voltage remains "0" and does not change. On the other hand, when iph_t<0, when the state changes from (B-2) to (B-3), the terminal voltage changes from "Vdc / 2" to "0". Therefore, in the case of iph_t>0 where the terminal voltage does not change, the calculated time t2 is used as it is. In addition, in the case of iph_t<0 where the terminal voltage changes, the dead time td is set before time t2. The same description can be given for the time t3 where the voltage vector changes. In addition, since the description is repeated, the description here is omitted.

[0190] Therefore, tW1on, tW1off, tW2on, tW2off, tW3on, tW3off, tW4on, and tW4off, which are the on-time or off-time of the W-phase switching element, are set as follows.

[0191] SW_W1: Always off (tW1on, tW1off not set)…(50)

[0192] SW_W2: tW2off=t2', tW2on=t3'+td...(51)

[0193] SW_W3: Always on (tW3on, tW3off not set)…(52)

[0194] SW_W4: tW4on=t2'+td, tW4off=t3'...(53)

[0195] Supplementary information is provided regarding the above equations (50) to (53). When looking at the numerical values ​​in the brackets on the right side of the above equations (41) to (45), all SW_W1 values ​​are "0", and all SW_W3 values ​​are "1". That is, the switch element 15a is always off, and the switch element 15c is always on. Therefore, there is no need to set tW1on, tW1off, tW3on, and tW3off. In addition, SW_W2 changes from "1" to "0" at time t2', and changes from "0" to "1" at time t3'+td. Therefore, it is set as in the above equation (51). In addition, SW_W4 changes from "0" to "1" at time t2'+td, and changes from "1" to "0" at time t3'. Therefore, it is set as in the above equation (53).

[0196] The switching signal generating unit 50 generates a switching signal based on the on-time and off-time of each switching element determined in the above-described process.

[0197] In the above description, an example of outputting a specific voltage vector is shown, but the present invention is not limited to this example. Even when outputting an arbitrary voltage vector, the method of the above embodiment can be applied to generate a switching signal.

[0198] Figure 8 This is a block diagram illustrating the functional configuration of the switching signal generator 50 in the embodiment. The switching signal generator 50 is divided into four functional blocks according to the aforementioned functions. Specifically, the switching signal generator 50 includes a change timing determination unit 51, a current estimation unit 52, a switching timing calculation unit 53, and a switching signal output unit 54.

[0199] In addition, Figure 8 In the diagram, symbols are used to represent the input signals to each component. "vphREF" represents the phase voltage command, and "iph" represents the phase current. "Ts" represents the "control period," and "td" represents the "dead time." The control period Ts is the update period for the phase voltage command vphREF.

[0200] The change timing determination unit 51 determines the change timing of the terminal voltage. The "change timing of the terminal voltage" referred to here means the rising timing and falling timing of the terminal voltage of each phase. Figure 5As shown, the change timing determination unit 51 determines the rising and falling timings of the terminal voltages of each phase by determining the output order and phase of the voltage vectors. The key point in this process is to synchronize the rising timing of the terminal voltage at the first connection point of the first phase branch with the falling timing of the terminal voltage at the second connection point of the second phase branch. Alternatively, the falling timing of the terminal voltage at the first connection point of the first phase branch with the rising timing of the terminal voltage at the second connection point of the second phase branch can be synchronized.

[0201] In the above description, the first-phase branch is a branch for any one of the U-phase, V-phase, and W-phase. The second-phase branch is a branch for a different phase from the first-phase branch. For example, if the first-phase branch is the "U-phase" and the second-phase branch is the "V-phase," the first connection point is "connection point 13e" and the second connection point is "connection point 14e."

[0202] Figure 5 The moment t1 in the equation is the moment when the terminal voltage of the U phase rises, and the moment when the terminal voltage of the V phase falls. At the moment t1, the phase current iu_t1 of the U phase and the phase current iv_t1 of the V phase are in a reverse phase relationship. Therefore, when iu_t1>0, iv_t1<0 becomes, and when iu_t1<0 becomes iv_t1>0. In the former case, the relationship is as shown in the equations (20) and (34), and in the latter case, the relationship is as shown in the equations (21) and (33). It can be seen that in either case, the time is synchronized. In the case of the moment t2, the relationship is as shown in the equations V and W, and in the case of the moment t3, the relationship is as shown in the equations U and W, but the same explanation can be given for either case.

[0203] As described above, the change timing determination unit 51 determines the rising and falling timings of the terminal voltages between the two different phases so that they are synchronized. By synchronizing the timings, fluctuations in the neutral point potential can be suppressed. This suppresses electromagnetic noise caused by synchronization shifts corresponding to the dead time. Furthermore, since electromagnetic noise caused by synchronization shifts corresponding to the dead time is suppressed, the noise filter can be made more compact.

[0204] Furthermore, in this embodiment, within a control cycle, the timing within a first group (based on the rising timing of the terminal voltage of the first phase leg and the falling timing of the terminal voltage of the second phase leg) and a second group (based on the falling timing of the terminal voltage of the first phase leg and the rising timing of the terminal voltage of the second phase leg) are synchronized with each other. However, this is not limiting. The timing within any of the groups can be synchronized with each other. Even with this control, the electromagnetic noise caused by synchronization deviation corresponding to the dead time can be suppressed.

[0205] The current estimation unit 52 estimates the phase current during switching based on the rising and falling timings of the terminal voltage of each phase. The current estimation unit 52 also determines the current polarity of the estimated phase current value and outputs the determination result to the switching timing calculation unit 53.

[0206] The current estimation unit 52 estimates the phase current at the rising and falling times of the terminal voltage based on the detected values ​​of the phase current in the past control cycle. Figure 6 As an example, it is preferable to perform the estimation based on the detected values ​​of the phase current at least two control cycles prior, or the detected values ​​of the phase current detected at least twice within a control cycle. This improves the accuracy of the estimated value. Furthermore, based on past and current detected values, it is possible to estimate the current at the switching timing in the next control cycle and determine the current polarity.

[0207] Alternatively, the phase current can be estimated based on the detected phase current value in the current control cycle, the voltage applied to the rotating machine 20, and the impedance of the path through which the phase current flows. This allows the current at the switching timing in the next control cycle to be estimated based on the current detected value, and the current polarity to be determined.

[0208] Furthermore, when estimating phase currents, it is preferable to estimate the phase current at the rising moment of the terminal voltage and the phase current at the falling moment of the terminal voltage for each branch of the same phase. This allows the current polarity during the dead time period to be determined based on the individual currents during both the on and off operations of the switching element, enabling more accurate current polarity determination. This prevents degradation of noise suppression due to erroneous current polarity determination.

[0209] The switching timing calculation unit 53 calculates the on-time and off-time of the switching signal. Specifically, when the polarity of the phase current during switching is positive, the switching timing calculation unit 53 controls the off-time of the switching element that switches the terminal voltage to the low potential side and the on-time of the switching element that switches the terminal voltage to the high potential side by the amount of the dead time. Furthermore, when the polarity of the phase current during switching is negative, the switching timing calculation unit 53 controls the off-time of the switching element that switches the terminal voltage to the high potential side and the on-time of the switching element that switches the terminal voltage to the low potential side by the amount of the dead time.

[0210] By performing the above control, a switching signal is generated that compensates for the synchronization deviation during the dead time, thereby reducing electromagnetic noise caused by the synchronization deviation corresponding to the dead time.

[0211] Figure 9 : is a flowchart showing the flow of operations in the control device 30 of the embodiment. Figure 9, the flow of the above-mentioned processing in the control device 30 of the embodiment is shown.

[0212] The voltage command generator 40 calculates a phase voltage command as a voltage command for each phase for each control cycle Ts (step S101 ). The change timing determiner 51 determines the rising and falling timings of the terminal voltages between two different phases so as to synchronize them (step S102 ).

[0213] The current estimation unit 52 estimates the phase current during switching based on the rising and falling times of the terminal voltage of each phase and determines the current polarity of the estimated value (step S103). The switching timing calculation unit 53 determines the turning-on and turning-off times of each switching element based on the rising and falling times of the terminal voltage of each phase, taking into account the current polarity during switching (step S104).

[0214] Then, the switching signal output unit 54 generates and outputs a switching signal based on the on-time and off-time of each switching element determined in step S104 (step S105 ).

[0215] Figure 10 This is a comparison diagram of the action waveforms before and after the application of the control method based on the embodiment. Figure 10 In the figure, the waveforms before application are shown on the left side of the paper, and the waveforms after application are shown on the right side. The changes in the terminal voltages vun, vvn, and vwn are shown above each, and the changes in the common-mode voltage vcm are shown below. The horizontal axis represents time, and the vertical axis represents voltage. Furthermore, the waveforms for the U-phase, V-phase, and W-phase are shown in the upper portion using solid, dashed, and dashed lines, respectively.

[0216] When observing the waveform before application, synchronization offset occurs in the second half of the pulse-shaped waveform. This causes fluctuations in the common-mode voltage, as shown in the lower portion. In contrast, when observing the waveform after application, synchronization offset is eliminated, and the fluctuations in the common-mode voltage are reduced. This result demonstrates the usefulness of the control method of this embodiment.

[0217] As described above, according to the power conversion device of the embodiment, the control device generates switching signals that synchronize the timing within at least one of a first set based on the timing of increasing the terminal voltage at the first connection point of the first phase branch and decreasing the terminal voltage at the second connection point of the second phase branch, or a second set based on the timing of decreasing the terminal voltage at the first connection point and increasing the terminal voltage at the second connection point. The control device determines the timing of turning on or off the upper arm switching element and the timing of turning on or off the lower arm switching element based on the phase current at the rising and falling terminal voltages. This control suppresses fluctuations in the neutral point potential. Consequently, electromagnetic noise caused by synchronization shifts corresponding to the dead time can be suppressed. Furthermore, since electromagnetic noise caused by synchronization shifts corresponding to the dead time is suppressed, the noise filter can be made more compact.

[0218] In addition, in this embodiment, the case where the power conversion device 80 is a T-type three-level inverter is exemplified, but it is not limited to this structure. Figures 11 to 13 As shown, other types of inverters are used. Figure 11 1 is a diagram showing a configuration of a rotary machine drive system 100A according to a first modified example of the embodiment. Figure 12 It is a diagram showing the configuration of a rotary machine drive system 100B according to a second modified example of the embodiment. Figure 13 100C is a diagram showing a configuration of a rotary machine drive system according to a third modified example of the embodiment.

[0219] exist Figure 11 In the rotating machine drive system 100A shown, Figure 1 The illustrated power converter 80 is replaced with a power converter 80A. In power converter 80A, power converter 10 is replaced with power converter 110, capacitors 12a and 12b are replaced with capacitor 12, and control device 30 is replaced with control device 130. Power converter 110 has a circuit structure known as a three-phase full-bridge inverter. A three-phase full-bridge inverter is a two-level inverter.

[0220] The control method of the above embodiment can also be applied to the rotating machine drive system 100A including the above-described power converter 110. Therefore, by incorporating the function of the switching signal generating unit 50 into the control device 130, the effects of the above embodiment can be obtained.

[0221] In addition, Figure 12 In the rotating machine drive system 100B shown, Figure 1The power converter 80 shown is replaced with a power converter 80B. In the power converter 80B, the power converter 10 is replaced with a power converter 210, the capacitors 12a and 12b are replaced with the capacitor 12, and the control device 30 is replaced with a control device 230. The rotating machine 220, which is the driven object, is a six-phase motor, which is an example of a multi-phase motor. Power converter 210 and rotating machine 220 use a six-phase full-bridge inverter. A six-phase full-bridge inverter is an example of a multi-phase inverter. A six-phase full-bridge inverter has a circuit structure in which two three-phase full-bridge inverters are connected in parallel.

[0222] The control method of the above embodiment can also be applied to the rotating machine drive system 100B including the power converter 210 described above. Therefore, by incorporating the function of the switching signal generating unit 50 into the control device 230, the effects of the above embodiment can be obtained.

[0223] In addition, Figure 13 In the rotating machine drive system 100C shown, Figure 1 The illustrated power conversion device 80 is replaced with a power conversion device 80C. In power conversion device 80C, one power converter 10 is replaced with two power converters 310a and 310b connected in parallel, capacitors 12a and 12b are replaced with capacitor 12, and control device 30 is replaced with control device 330. Power converters 310a and 310b, which are three-phase full-bridge inverters, are connected in parallel with respect to capacitor 12. A rotating machine 320a is connected to power converter 310a, and a rotating machine 320b is connected to power converter 310b.

[0224] The control method of the above embodiment can also be applied to the rotating machine drive system 100C including the power converters 310a and 310b described above. Therefore, by incorporating the function of the switching signal generating unit 50 into the control device 330, the effects of the above embodiment can be obtained.

[0225] Furthermore, while the present embodiment describes a converter that converts DC power to AC power, the present invention is not limited to this converter. The present invention can also be applied to power converters that convert AC power to DC power, DC power to DC power, and AC power to AC power, and can achieve the same effects as those of the above-described embodiment.

[0226] In addition, various exemplary embodiments are described in this manuscript, but one or more of the various features, schemes, and functions described are not limited to application in specific embodiments and can be applied alone or in various combinations. Therefore, within the scope of the technology disclosed in this manuscript, countless variations that are not illustrated can be envisioned. For example, this includes the case where at least one component is modified, added, or omitted, and further the case where at least one component is extracted and combined with components from other embodiments.

Claims

1. A power conversion device that converts DC power into three-phase AC power for a load, characterized in that: have: a power converter connected in parallel to a plurality of single-phase branches, wherein the single-phase branches are formed by connecting an upper branch switching element and a lower branch switching element in series, and a connection point between the upper branch switching element and the lower branch switching element is connected to the load; as well as a control device for controlling the switching actions of the upper branch switching element and the lower branch switching element, The control device includes a switching signal generating unit that generates a switching signal that synchronizes timings within at least one of a first group or a second group, wherein the first group is a group of rising timings for increasing a terminal voltage at a first connection point of a first-phase branch connected to the load and a falling timing for decreasing a terminal voltage at a second connection point of a second-phase branch connected to the load, and the second group is a group of falling timings for decreasing the terminal voltage at the first connection point and a rising timing for increasing the terminal voltage at the second connection point. The switching signal generating unit determines the timing of turning on or off the upper arm switching element and the timing of turning on or off the lower arm switching element based on the phase current at the rising and falling timings of the terminal voltage. The switching signal generating unit advances the cut-off moment of the switching element that switches the terminal voltage to the low potential side and the turn-on moment of the switching element that switches the terminal voltage to the high potential side by the dead time when the polarity of the phase current during switching is positive. When the polarity of the phase current during switching is negative, the switching signal generating unit advances the cut-off moment of the switching element that switches the terminal voltage to the high potential side and the turn-on moment of the switching element that switches the terminal voltage to the low potential side by the dead time.

2. The power conversion device according to claim 1, wherein: The switching signal generating unit includes a current estimating unit that estimates the phase current at the rising timing and the falling timing of the terminal voltage based on the detected value of the phase current in the past control cycle.

3. The power conversion device according to claim 2, characterized in that The current estimation unit estimates the phase current at the rising and falling timings of the terminal voltage based on the detected value of the phase current at least two control cycles before.

4. The power conversion device according to claim 2, wherein: The current estimation unit estimates the phase current at the rising and falling timings of the terminal voltage based on the detection values ​​of the phase current detected at least twice within one control cycle.

5. The power conversion device according to claim 3, characterized in that The current estimation unit estimates the phase current at the rising and falling timings of the terminal voltage based on the detection values ​​of the phase current detected at least twice within one control cycle.

6. The power conversion device according to claim 1, wherein: The switching signal generating unit includes a current estimating unit that estimates the phase current at the rising and falling times of the terminal voltage based on the detected value of the phase current in the current control cycle, the applied voltage to the load, and the impedance of the path through which the phase current flows.

7. The power conversion device according to any one of claims 2 to 6, characterized in that: The current estimation unit estimates, in each branch of the same phase, the phase current at the rising timing of the terminal voltage and the phase current at the falling timing of the terminal voltage individually.

8. The power conversion device according to any one of claims 1 to 6, characterized in that: The switching signal generating unit determines the switching signal so that, within one control cycle, the sum of the low-level state times of all phases in which the terminal voltage changes in the order of decreasing and increasing is the same as the sum of the high-level state times of all phases in which the terminal voltage is switched in the order of increasing and decreasing.

9. A rotating machine drive system, wherein: A power conversion device according to any one of claims 1 to 8, The load is a rotating machine, The rotating machine is driven by the electric power supplied from the power conversion device.

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