Control method for power conversion device, control device for power conversion device, and power conversion device

Abstract

This control method for a power conversion device includes: a step for outputting a first control signal that is applied to a first switching device and serves to connect the first switching device to a motor for the same length of time as the time from a first cross point to a second cross point between a carrier wave and a voltage command value; and a step for outputting a second control signal that is applied to the other of the first switching device and a second switching device and in which a waiting time is set for dead time during which the first switching device and the second switching device are simultaneously placed in a disconnected state.

Description

Control method for a power converter, control device for a power converter, and power converter

[0001] This disclosure relates to a control method for a power converter, a control device for a power converter, and a power converter.

[0002] A power converter, also known as an inverter, converts direct current (DC) power into alternating current (AC) power. An inverter consists of a circuit made up of multiple switching devices, and it converts DC power to AC power by turning each of these switching devices on or off.

[0003] Japanese Patent Publication No. 2022-187420 Japanese Patent Publication No. 2014-147200

[0004] When a power converter is operating, if two interconnected switching devices are turned on simultaneously, a power short circuit will occur. Therefore, a period is provided during which both interconnected switching devices are turned off simultaneously. This period is called the dead time. Patent documents 1 and 2 disclose technology related to the dead time of a power converter.

[0005] However, during the dead time period, power is not supplied from the power converter to the load device. As a result, introducing a dead time can cause a decrease in the voltage output from the power converter.

[0006] Therefore, this disclosure describes a control method for a power converter, a control device for a power converter, and a power converter that can suppress a drop in the voltage output from the power converter while providing a dead time.

[0007] One embodiment of the present disclosure is a control method for a power converter having a first switching device that switches between electrically connecting and disconnecting the positive terminal of a power supply to a load device, and a second switching device that switches between electrically connecting and disconnecting the negative terminal of a power supply to a load device. The control method for the power converter includes the steps of: outputting a first control signal given to one of the first switching device and the second switching device for a period of time equal to the time from a first crossover point to a second crossover point between the carrier wave and the voltage command value, to connect one of the first switching device and the second switching device to the load device; and outputting a second control signal given to the other of the first switching device and the second switching device, with a waiting time set for a dead time that simultaneously disconnects the first switching device and the second switching device.

[0008] According to this control method, the first control signal connects one of the first and second switching devices to the load device for the same amount of time as the time between the first and second crossover points of the carrier wave and the voltage command value. As a result, the length of the period during which voltage is output from the power converter can be set to a desired length, thereby suppressing a drop in the voltage output from the power converter. Furthermore, the second control signal can be used to set a waiting time for a dead time in the operation of the other of the first and second switching devices, in which the first and second switching devices are simultaneously disconnected. As a result, a drop in the voltage output from the power converter can be suppressed while incorporating a dead time.

[0009] In the control method described above, when current flows from the power supply to the load device, the first control signal may be supplied to the first switching device in the step of outputting the first control signal, and the second control signal may be supplied to the second switching device in the step of outputting the second control signal. This method makes it possible to suppress the voltage drop output from the power converter while providing a dead time when current flows from the power supply to the load device.

[0010] In the control method described above, when current flows from the load device to the power supply, the first control signal may be supplied to the second switching device in the step of outputting the first control signal, and the second control signal may be supplied to the first switching device in the step of outputting the second control signal. This method makes it possible to suppress the decrease in voltage output from the power converter while providing a dead time when current flows from the load device to the power supply.

[0011] In the control method described above, when current flows from the power supply to the load device, in the step of outputting the first control signal, the first switching device may be connected at the time of the first crossover point and disconnected at the time of the second crossover point. In the step of outputting the second control signal, the second switching device may be disconnected at the time of the first crossover point after a first waiting time has elapsed, and the second switching device may be connected at a time delayed by the first waiting time from the time of the second crossover point. This method makes it possible to coincide the timing of the first crossover point with the timing of voltage output from the power converter. Furthermore, this method makes it possible to coincide the timing of the second crossover point with the timing of stopping the voltage output from the power converter.

[0012] In the control method described above, when current flows from the power supply to the load device, the first control signal may be output in the step of outputting a first control signal that connects the first switching device at a time delayed by a first waiting time from the time of the first crossover point, and disconnects the first switching device at a time delayed by a first waiting time from the time of the second crossover point. The second control signal may be output in the step of outputting a second control signal that disconnects the second switching device at the time of the first crossover point, and connects the second switching device after a second waiting time, which is longer than the first waiting time, has elapsed from the second crossover point. This method makes it possible to control the first and second switching devices based on the detection of the first and second crossover points. As a result, the control of the first and second switching devices can be made easier.

[0013] Another embodiment of the present disclosure is a control device for a power converter having a first switching device that switches between electrically connecting and disconnecting the positive terminal of a power supply to a load device, and a second switching device that switches between electrically connecting and disconnecting the negative terminal of a power supply to a load device. The control device for the power converter has a first control signal output unit that outputs a first control signal to one of the first and second switching devices for a period of time equal to the time from a first crossover point to a second crossover point between the carrier wave and the voltage command value, for connecting one of the first and second switching devices to the load device, and a second control signal output unit that outputs a second control signal to the other of the first and second switching devices, with a waiting time set for a dead time that simultaneously disconnects the first and second switching devices. With this control device, similar to the control method for the power converter described above, it is possible to suppress a drop in the voltage output from the power converter while providing a dead time.

[0014] A power converter in yet another form of the present disclosure includes a first switching device that switches the positive terminal of a power supply between being electrically connected to and disconnected from a load device, a second switching device that switches the negative terminal of a power supply between being electrically connected to and disconnected from a load device, and a control unit that outputs a first control signal that switches the connection state between the positive terminal and the first switching device and a second control signal that switches the connection state between the negative terminal and the second switching device. The control unit outputs a first control signal given to one of the first and second switching devices, which connects one of the first and second switching devices to the load device for the same amount of time as the time from a first crossover point to a second crossover point between the carrier wave and the voltage command value, and a second control signal given to the other of the first and second switching devices, which sets a waiting time for a dead time that simultaneously disconnects the first and second switching devices. With this power converter, a decrease in the output voltage can be suppressed while providing a dead time, similar to the control method of the power converter described above.

[0015] According to the control method for a power converter, the control device for a power converter, and the power converter of this disclosure, it is possible to suppress a decrease in the voltage output from the power converter while providing a dead time.

[0016] Figure 1 is a diagram showing the configuration of a power converter equipped with a control device for the power converter that implements the control method of the power converter of the first embodiment. Figure 2(a) is a diagram showing the carrier wave and voltage command value in the control method of the power converter to explain the dead time. Figure 2(b) is a diagram showing the operation of the high-side switching device to explain the dead time. Figure 2(c) is a diagram showing the operation of the low-side switching device to explain the dead time. Figure 2(d) is a diagram showing the output voltage of the power converter to explain the dead time. Figure 3 is a flowchart showing the control method of the power converter to explain the dead time. Figure 4(a) is a diagram showing the operation of the high-side switching device when it is in the first state. Figure 4(b) is a diagram showing the operation of the low-side switching device when it is in the first state. Figure 4(c) is a diagram showing the output voltage of the power converter when it is in the first state. Figure 4(d) is a diagram showing the current flowing through the conversion circuit when it is in the first state. Figure 5(a) is a diagram showing the operation of the high-side switching device when it is in the second state. Figure 5(b) is a diagram showing the operation of the low-side switching device when it is in the second state. Figure 5(c) shows the output voltage of the power converter when it is in the second state. Figure 5(d) shows the current flowing through the conversion circuit when it is in the second state. Figure 6(a) shows the operation of the high-side switching device when it is in the third state. Figure 6(b) shows the operation of the low-side switching device when it is in the third state. Figure 6(c) shows the output voltage of the power converter when it is in the third state. Figure 6(d) shows the current flowing through the conversion circuit when it is in the third state. Figure 7(a) shows the operation of the high-side switching device when it is in the fourth state. Figure 7(b) shows the operation of the low-side switching device when it is in the fourth state. Figure 7(c) shows the output voltage of the power converter when it is in the fourth state. Figure 7(d) shows the current flowing through the conversion circuit when it is in the fourth state. Figure 8(a) shows the carrier wave and voltage command value in the control method of the power converter according to the first embodiment.Figure 8(b) is a diagram showing the operation of the high-side switching device in the first embodiment of the power converter control method. Figure 8(c) is a diagram showing the operation of the low-side switching device in the first embodiment of the power converter control method. Figure 8(d) is a diagram showing the output voltage of the power converter in the first embodiment of the power converter control method. Figure 9 is a flowchart showing the first embodiment of the power converter control method. Figure 10(a) is a diagram showing the carrier wave and voltage command value when current flows from the power source to the load device in the second embodiment of the power converter control method. Figure 10(b) is a diagram showing the operation of the high-side switching device when current flows from the power source to the load device in the second embodiment of the power converter control method. Figure 10(c) is a diagram showing the operation of the low-side switching device when current flows from the power source to the load device in the second embodiment of the power converter control method. Figure 10(d) is a diagram showing the output voltage of the power converter when current flows from the power source to the load device in the second embodiment of the power converter control method. Figure 11 is a flowchart showing the control method executed in the second embodiment of the power converter when current flows from the power source to the load device. Figure 12(a) is a diagram showing the carrier wave and voltage command value when current flows from the load device to the power source in the control method of the second embodiment of the power converter. Figure 12(b) is a diagram showing the operation of the high-side switching device when current flows from the load device to the power source in the control method of the second embodiment of the power converter. Figure 12(c) is a diagram showing the operation of the low-side switching device when current flows from the load device to the power source in the control method of the second embodiment of the power converter. Figure 12(d) is a diagram showing the output voltage of the power converter when current flows from the load device to the power source in the control method of the second embodiment of the power converter. Figure 13 is a flowchart showing the control method executed in the second embodiment of the power converter when current flows from the load device to the power source.

[0017] The control method for the power converter, the control device for the power converter, and the power converter of this disclosure will be described in detail below with reference to the attached drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted.

[0018] <Power Conversion Device> The power conversion device 1 shown in Figure 1 converts the DC power received from the power source 21 into three-phase AC power. The power conversion device 1 then outputs the three-phase AC power to the motor 9 (load device). The power conversion device 1 has a conversion circuit section 2 and a control section 3. In other words, the power conversion device 1 shown in Figure 1 is a so-called three-phase PWM inverter.

[0019] The conversion circuit 2 converts the DC power received from the power supply 21 into three-phase AC power based on the control signal provided by the control unit 3. In Figure 1, the thick solid lines connecting each electrical element indicate that they are power lines for supplying power to the motor 9.

[0020] The conversion circuit section 2 includes a power supply 21 and six switching devices 221, 222, 231, 232, 241, and 242. The six switching devices 221, 222, 231, 232, 241, and 242 may be so-called MOS transistors. The power supply 21 may be defined as a component of the conversion circuit section 2, or as a component separate from the conversion circuit section 2. The power supply 21 is a DC power supply that generates DC power.

[0021] Of the six switching devices 221, 222, 231, 232, 241, and 242, two switching devices 221 and 222 constitute a U-phase unit 22 corresponding to the U-phase of the motor 9. Switching devices 231 and 232 constitute a V-phase unit 23 corresponding to the V-phase of the motor 9. Switching devices 241 and 242 constitute a W-phase unit 24 corresponding to the W-phase of the motor 9.

[0022] For example, the high-side switching device 221 of the U-phase unit 22 is arranged between the positive electrode 211 of the power supply 21 and the motor 9. The low-side switching device 222 of the U-phase unit 22 is arranged between the negative electrode 212 of the power supply 21 and the motor 9. In the high-side switching device 221, the drain is connected to the positive electrode 211 of the power supply 21, the source is connected to the low-side switching device 222, and the gate is connected to the gate drive circuit 331. In the low-side switching device 222, the drain is connected to the high-side switching device 221, the source is connected to the negative electrode 212 of the power supply 21, and the gate is connected to the gate drive circuit 332. A power line connecting the source of the high-side switching device 221 and the drain of the low-side switching device 222 is provided with an output point for supplying current to the U-phase of the motor 9.

[0023] The V-phase unit 23 and the W-phase unit 24 differ only in that they are connected to the V-phase and W-phase of the motor 9, respectively, and the connection configuration of the switching devices is the same as that of the U-phase unit 22. Therefore, detailed descriptions of the V-phase unit 23 and the W-phase unit 24 are omitted.

[0024] The control unit 3 supplies control signals to each of the switching devices 221, 222, 231, 232, 241, 242. In FIG. 1, the broken lines connecting each functional block indicate that they are signal lines for PWM signals and control signals.

[0025] The control unit 3 includes several sensor circuits that measure voltage and current in the conversion circuit unit 2. Specifically, the control unit 3 includes a DC voltage sensor circuit 311, a U-phase current sensor circuit 312, a V-phase current sensor circuit 313, and a W-phase current sensor circuit 314. The DC voltage sensor circuit 311 measures the DC voltage output by the power supply 21. The U-phase current sensor circuit 312 measures the current supplied to the U-phase of the motor 9. The V-phase current sensor circuit 313 measures the current supplied to the V-phase of the motor 9. The W-phase current sensor circuit 314 measures the current supplied to the W-phase of the motor 9. The measurement values obtained by these sensor circuits are provided to a CPU 32 included in the control unit 3.

[0026] The CPU 32 implements a plurality of functional components by executing programs. For example, the CPU 32 includes a first control signal output unit 321 and a second control signal output unit 322. Further, the control method for the power conversion device 1 according to the present embodiment is implemented by the CPU 32 executing a control program that defines a control procedure. The CPU 32 outputs a PWM signal by executing the control program. The PWM signal is provided to gate drive circuits 331 to 336.

[0027] The control unit 3 includes six gate drive circuits 331 to 336. The gate drive circuits 331 to 336 receive PWM signals from the CPU 32. Then, based on the PWM signals, the gate drive circuits 331 to 336 generate control signals defined by a voltage for turning on switching devices 221, 222, 231, 232, 241, and 242 and a voltage for turning off said switching devices. Then, the gate drive circuits 331 to 336 provide the control signals to the switching devices 221, 222, 231, 232, 241, and 242. For example, the first gate drive circuit 331 is connected to the high-side switching device 221 in the U-phase unit 22, and provides a control signal to the switching device 221.

[0028] <Dead Time> The PWM signal output by the CPU 32 is supplied to the switching devices 221, 222, 231, 232, 241, and 242 via the gate drive circuits 331 to 336. As a result, the power converter 1 provides a voltage corresponding to the PWM signal to the three-phase motor 9. The CPU 32 determines the ratio of the time when the switching devices 221, 222, 231, 232, 241, and 242 are on (connected) and the time when they are off (disconnected) so that the desired current is supplied to the motor 9. Furthermore, the CPU 32 provides a period during which both switching devices 221 and 222 are turned off simultaneously to prevent a short circuit between the high-side switching device 221 and the low-side switching device 222. This period is called the so-called dead time.

[0029] Here, the dead time will be explained with reference to Figures 2 and 3. The control method of the power converter 1 is based on a general triangular wave comparison method. In the triangular wave comparison method, a carrier wave CW having a predetermined period is compared with a voltage command value CV. For example, during the period from the first crossover point Rd to the second crossover point Ru, the voltage command value CV is greater than the carrier wave CW. During this period, the high-side switching device 221 is turned on. Also, during the period from the second crossover point Ru to the first crossover point Rd, the voltage command value CV is less than the carrier wave CW. During this period, the low-side switching device 222 is turned on. The turn-on timing for both the high-side and low-side is delayed by a certain amount of time. As a result, a dead time DT is set.

[0030] The operation for introducing a dead time is shown in the flowchart in Figure 3. First, the first crossover point Rd is detected (S11, see Figure 2(a)). The first crossover point Rd is the starting point of the period in which the voltage command value CV is greater than the carrier wave CW. Next, immediately after detecting the first crossover point Rd, the low-side switching device 222 is switched from on to off (S12, indicated by the symbol L in Figure 2). ｏｆｆ(See reference). At this time, the output voltage of the power converter 1 is low (see Figure 2(d)). Next, after a predetermined waiting time has elapsed since the detection of the first cross point Rd, the high-side switching device 221 is switched from off to on (S13, indicated by the symbol H in Figure 2). ｏｎ (See reference). The period until a predetermined waiting time has elapsed is the dead time DT. This operation (S13) causes the output voltage of the power converter 1 to switch to the high voltage V1 (see Figure 2(d)).

[0031] Next, the second crossover point Ru is detected (S21, see Figure 2(a)). The second crossover point Ru is the starting point of the period when the voltage command value CV is smaller than the carrier wave CW. Immediately after detecting the second crossover point Ru, the high-side switching device 221 is switched from on to off (S22, indicated by the symbol H in Figure 2). ｏｆｆ (See reference). At this time, the output voltage of the power converter 1 switches from high to low (see Figure 2(d)). Next, after a predetermined waiting time has elapsed since the detection of the second cross point Ru, the low-side switching device 222 is switched from off to on (S23, see reference numeral Lon in Figure 2). The period until the predetermined waiting time has elapsed is the dead time DT.

[0032] Refer to Figure 2(d) here. Ideally, the voltage supplied from the power converter 1 to the motor 9 should be continuously output over the period from the first crossover point Rd to the second crossover point Ru. However, due to the high-side switching device 221 being switched from off to on by a predetermined delay time from the time Cd of the first crossover point Rd (see Figure 2(b)), the time at which the voltage supplied from the power converter 1 to the motor 9 switches from low to high is delayed compared to the time of the first crossover point Rd. As a result, the voltage supplied from the power converter 1 to the motor 9 is output over the period from when the predetermined delay time has elapsed from the first crossover point Rd to the second crossover point Ru. In other words, the time during which the voltage is output is shortened by the amount of the dead time set by the delay time. This is the cause of the decrease in the voltage output from the power converter.

[0033] In contrast, the control methods for the power converters of the first and second embodiments can suppress the voltage drop shown in Figure 2(d) while setting a dead time.

[0034] <Detailed Operation of the Conversion Circuit> The effect of the dead time DT mentioned above on the voltage output by the power converter 1 will be explained using Figures 4, 5, 6, and 7. These diagrams illustrate the operation when current is flowing from the power converter 1 to the motor 9. In the following explanation, we define the first state as high-side turn-on, the second state as high-side turn-off, the third state as low-side turn-on, and the fourth state as low-side turn-off. The definitions of the first, second, third, and fourth states are as follows: First state: high-side (Low to High), low-side (Low to Low) Second state: high-side (High to Low), low-side (Low to Low) Third state: high-side (Low to Low), low-side (Low to High) Fourth state: high-side (Low to Low), low-side (High to Low)

[0035] When in the first state (high-side turn-on), the high-side switching device 221 receives the first control signal V shown in Figure 4(a). ＨＳ A predetermined delay time is given. At time t2, which is delayed by a predetermined delay time from time t1, the high-side switching device 221 switches from low to high. The low-side switching device 222 receives the second control signal V shown in Figure 4(b). ＬＳ The voltage V shown in Figure 4(c) is given. The low-side switching device 222 maintains a low state. The power converter 1 is given a voltage V shown in Figure 4(c). ＯＵＴ The power converter 1 outputs the high voltage V1 at time t2, which is delayed by a predetermined time from time t1.

[0036] In the first state, in the U-phase unit 22 of the conversion circuit section 2, current IP1 flows toward the motor 9 via the high-side switching device 221.

[0037] In the second state (high-side turn-off), the first control signal V shown in Fig. 5(a) is applied to the high-side switching device 221 ＨＳ . At time t1, the high-side switching device 221 switches from high to low. The second control signal V shown in Fig. 5(b) is applied to the low-side switching device 222 ＬＳ . The low-side switching device 222 maintains a low (Low) state. The power converter 1 outputs the voltage V shown in Fig. 5(c) ＯＵＴ . At time t1, the power converter 1 outputs a low voltage V0.

[0038] In the second state, in the U-phase unit 22 of the conversion circuit unit 2, the current IP1 flowing through the high-side switching device 221, which was generated in the first state, does not occur. Further, in the U-phase unit 22 of the conversion circuit unit 2, since the low-side switching device 222 also maintains a low state, no current flows through the low-side switching device 222. Here, a diode 224 is connected to the low-side switching device 222. The diode 224 is provided in a direction that allows generation of a current flowing from the source to the drain of the low-side switching device 222. As a result, in the second state, in the U-phase unit 22 of the conversion circuit unit 2, the current IP2 flows toward the motor 9 through the diode 224 associated with the low-side switching device 222.

[0039] In the third state (low-side turn-on), the first control signal V shown in Fig. 6(a) is applied to the high-side switching device 221 ＨＳ . The high-side switching device 221 maintains a low (Low) state. The second control signal V shown in Fig. 6(b) is applied to the low-side switching device 222 ＬＳA voltage V is given. At time t2, which is delayed by a predetermined time from time t1, the low-side switching device 222 switches from low to high. The power converter 1 receives the voltage V shown in Figure 6(c). ＯＵＴ It outputs a low voltage V0. When in the third state, the power converter 1 outputs a low voltage V0.

[0040] In the third state, in the U-phase unit 22 of the conversion circuit section 2, current IP3 flows toward the motor 9 via the low-side switching device 222.

[0041] When in the fourth state (low-side turn-off), the high-side switching device 221 receives the first control signal V shown in Figure 7(a). ＨＳ The high-side switching device 221 maintains a low state. At time t1, the low-side switching device 222 switches from high to low. The power converter 1 receives the voltage V shown in Figure 7(c). ＯＵＴ It outputs a low voltage V0. When in the fourth state, the power converter 1 outputs a low voltage V0.

[0042] From the explanation so far, it can be seen that the decrease in output voltage caused by the setting of the dead time DT is due to the dead time DT set on the high-side switching device 221, assuming that current is flowing from the power converter 1 to the motor 9. For example, comparing Figure 2(b) and Figure 2(d), it can be seen that setting the dead time DT on the high-side switching device 221 causes a decrease in output power, as shown in Figure 2(d). On the other hand, assuming that current is flowing from the power converter 1 to the motor 9, the dead time DT set on the low-side switching device 222 does not cause a decrease in output power, as shown in Figure 2(d). Therefore, when current is flowing from the power converter 1 to the motor 9, the dead time DT is not set on the high-side switching device 221, but on the low-side switching device 222.

[0043] <Control Method of Power Converter in the First Embodiment> The control method of the power converter in the first embodiment will be described with reference to Figures 8 and 9. First, when the first cross point Rd is reached after the first waiting time has elapsed, the low-side switching device 222 is switched from on to off (S31). The time when the first cross point Rd is reached after the waiting time has elapsed is the time Cb shown in Figure 8(c). Next, the first cross point Rd is detected (S32). Immediately after the first cross point Rd is detected, the high-side switching device 221 is switched from off to on (S33). With this operation (S33), the power converter 1 starts outputting a high voltage (V1) (see Figure 8(d)). In other words, the output of a high voltage (V1) is started at the same time as the time Cd when the first cross point Rd is detected.

[0044] In this series of operations, from time Cb shown in Figure 8(c) until time Cd, when the high-side switching device 221 switches from off to on, both the high-side switching device 221 and the low-side switching device 222 are off. In other words, a dead time DT is set.

[0045] Next, the second crossover point Ru is detected (S41). Immediately after the detection of the second crossover point Ru, the high-side switching device 221 is switched from on to off (S42). This operation (S42) causes the power converter 1 to start outputting a low voltage (V0) (see Figure 8(d)). In other words, the output of the low voltage (V0) starts simultaneously with the time Cu when the second crossover point Ru is detected. Then, after a waiting time has elapsed since the detection of the second crossover point Ru, the low-side switching device 222 is switched from off to on (S43).

[0046] In this series of operations, from the time Cu when the high-side switching device 221 is switched from on to off, to the time Ca when the waiting time has elapsed after the detection of the second cross point Ru, both the high-side switching device 221 and the low-side switching device 222 are off. In other words, a dead time DT is set.

[0047] Thus, according to the control method of the first embodiment, while setting the dead time DT, the power converter 1 can output a high voltage (V1) for the same duration as the period from the first cross point Rd to the second cross point Ru. In other words, the decrease in output voltage is suppressed.

[0048] Here, if the period from the second crossover point Ru to the first crossover point Rd, in other words, the period during which the voltage command value CV is smaller than the carrier wave CW, is relatively long, a period occurs during which the low-side switching device 222 is turned on (see state E1 in Figure 8(c)). Specifically, if the period from the second crossover point Ru to the first crossover point Rd is longer than twice the waiting time, a period occurs during which the low-side switching device 222 is turned on.

[0049] On the other hand, if the period from the second crosspoint Ru to the first crosspoint Rd is shorter than twice the waiting time, there is no period during which the low-side switching device 222 is turned on (see state E2 in Figure 8(c)). In other words, the low-side switching device 222 remains in the off state.

[0050] <Effects> The control method of the power converter 1 is a first control signal V that is given to the first switching device 221. ＨＳ The first control signal V for connecting the first switching device 221 to the motor 9 is set for the same duration as the time from the first crossover point Rd to the second crossover point Ru between the carrier wave CW and the voltage command value CV. ＨＳ The steps include outputting a signal and giving a second control signal V to the other of the first switching device 221 and the second switching device 222. ＬＳThe second control signal V is set to a waiting time for a dead time DT which simultaneously disconnects the first switching device 221 and the second switching device 222. ＬＳ The process includes the step of outputting a value.

[0051] According to this control method, the first control signal V ＨＳ This connects the first switching device 221 to the motor 9 for the same amount of time as the time from the first crossover point Rd to the second crossover point Ru between the carrier wave CW and the voltage command value CV. As a result, the length of the period during which voltage is output from the power converter 1 can be set to the desired length, and thus the voltage drop output from the power converter 1 can be suppressed. Furthermore, the second control signal V ＬＳ This allows setting a waiting time for a dead time DT in the operation of the second switching device 222, which simultaneously disconnects the first switching device 221 and the second switching device 222. As a result, it is possible to suppress a drop in the voltage output from the power converter 1 while maintaining the dead time DT.

[0052] When current flows from the power supply 21 to the motor 9, the first control signal V ＨＳ In the step of outputting the first signal V, the first switching device 221 receives the first control signal V ＨＳ Given, the second control signal V ＬＳ In the step of outputting the second control signal V, the second switching device 222 is given the second control signal V ＬＳ This may be provided. This method makes it possible to suppress the drop in voltage output from the power converter 1 while providing a dead time DT when current flows from the power supply 21 to the motor 9.

[0053] When current flows from motor 9 to power supply 21, the first control signal V ＨＳ In the step of outputting the first control signal V, the second switching device 222 is given the first control signal V ＨＳ Given, the second control signal V ＬＳ In the step of outputting the second control signal V, the first switching device 221 receives the second control signal V. ＬＳThis may be provided. This method makes it possible to suppress the drop in voltage output from the power converter 1 while providing a dead time DT when current flows from the motor 9 to the power supply 21.

[0054] When current flows from the power supply 21 to the motor 9, the first control signal V ＨＳ In the step of outputting the second control signal V, the first switching device 221 is connected at the time of the first crossover point Rd, and disconnected at the time of the second crossover point Ru. ＬＳ In the step of outputting the signal, the second switching device 222 is disconnected at the time of the first crossover point Rd, after a first waiting period has elapsed, and the second switching device 222 is connected at a time delayed by the first waiting period from the time of the second crossover point Ru. This method makes it possible to synchronize the timing of the first crossover point Rd with the timing of outputting voltage from the power converter 1. Furthermore, this method makes it possible to synchronize the timing of the second crossover point Ru with the timing of stopping the output of voltage from the power converter 1.

[0055] The control unit 3 provides a first control signal V to one of the first switching device 221 and the second switching device 222. ＨＳ The first control signal V for connecting the first switching device 221 to the motor 9 is set for the same duration as the time from the first crossover point Rd to the second crossover point Ru between the carrier wave CW and the voltage command value CV. ＨＳ A first control signal output unit 321 outputs a second control signal V, and a second control signal V is supplied to the second switching device 222. ＬＳ The second control signal V is set to a waiting time for a dead time DT which simultaneously disconnects the first switching device 221 and the second switching device 222. ＬＳ It has a second control signal output unit 322 that outputs a signal. With this control device, similar to the control method of the power converter 1 described above, it is possible to suppress the decrease in voltage output from the power converter 1 while providing a dead time DT.

[0056] The power converter 1 includes a first switching device 221 that switches between electrically connecting and disconnecting the positive terminal of the power supply 21 to the motor 9, a second switching device 222 that switches between electrically connecting and disconnecting the negative terminal of the power supply 21 to the motor 9, and a first control signal V that switches between connecting and disconnecting the positive terminal and the first switching device 221. ＨＳ and a second control signal V that switches between the connected state and the disconnected state of the negative electrode and the second switching device 222. ＬＳ The control unit 3 comprises a control unit that outputs a first control signal V supplied to the first switching device 221. ＨＳ The first control signal V for connecting the first switching device 221 to the motor 9 is set for the same duration as the time from the first crossover point Rd to the second crossover point Ru between the carrier wave CW and the voltage command value CV. ＨＳ , and the second control signal V given to the second switching device 222 ＬＳ The second control signal V is set to a waiting time for a dead time DT which simultaneously disconnects the first switching device 221 and the second switching device 222. ＬＳ This power converter 1 outputs a voltage drop while providing a dead time DT, similar to the control method for the power converter 1 described above.

[0057] Next, the control method for the power converter according to the second embodiment will be described. The basic concept of the control method for the power converter in the second embodiment is the same as that of the power converter in the first embodiment. That is, when current is flowing from the power source to the motor, a dead time DT is set only for the low-side switching device 222, and no dead time DT is set for the high-side switching device 221. In the second embodiment, the control method when current is flowing from the power source to the motor will be described first, and then the control method when current is flowing from the motor to the power source will be described.

[0058] <When current is flowing from the power supply to the motor> The control method of the power converter according to the second embodiment will be explained with reference to Figures 10 and 11. First, the first cross point Rd is detected (S51). Next, immediately after detecting the first cross point Rd, the low-side switching device 222 is switched from on to off (S52). Next, after a first waiting time has elapsed since the detection of the first cross point Rd, the high-side switching device 221 is switched from off to on (S53). With this operation (S53), the power converter 1 starts outputting a high voltage (V1). Also, during the period from the time Cd when the low-side switching device 222 is switched from on to off to the time Cu when the high-side switching device 221 is switched from off to on, both the low-side switching device 222 and the high-side switching device 221 are in the off state. In other words, a dead time DT is set.

[0059] The second cross point Ru is detected (S61). Then, after a first waiting time has elapsed since the detection of the second cross point Ru, the high-side switching device 221 is switched from on to off (S62). Here, the time at which the high-side switching device 221 was switched from off to on was when the first waiting time had elapsed since the first cross point Rd. Also, the time at which the high-side switching device 221 was switched from on to off was when the first waiting time had elapsed since the second cross point Ru. Thus, although the timing of switching the states of the switching devices 221 and 222 for each cross point is different, the period during which the high-side switching device 221 is in the on state is the same as the period from the first cross point Rd to the second cross point Ru. Therefore, the power converter 1 can continue to output voltage to the motor 9 for the desired period of time.

[0060] Next, after a second waiting time has elapsed since the detection of the second crosspoint Ru, the low-side switching device 222 is switched from off to on (S63). This second waiting time is longer than the first waiting time. For example, the length of the second waiting time is twice the length of the first waiting time. When the low-side switching device 222 is switched from off to on after such a second waiting time has elapsed, the high-side switching device 221 is switched from on to off before the low-side switching device 222 is switched from off to on. The period during which the high-side switching device 221 is in the off state and the period during which the low-side switching device 222 is in the off state overlap. In other words, a dead time DT is set.

[0061] In the control method of the first embodiment, it was necessary to set the time Cb to reach the first cross point Rd when the first waiting time had elapsed. In other words, it was necessary to control the operation of the switching devices 221 and 222 before the first cross point Rd was detected. In contrast, the advantage of the control method of the second embodiment is that the operation of the switching devices 221 and 222 can be controlled based on the detection of the first cross point Rd and the second cross point Ru.

[0062] <When current flows from the motor to the power supply> Next, the control method when current flows from the motor 9 to the power supply 21 will be explained with reference to Figures 12 and 13. As mentioned above, when current flows from the power supply 21 to the motor 9, a dead time DT is set only for the low-side switching device 222, and no dead time DT is set for the high-side switching device 221. In contrast, when current flows from the motor 9 to the power supply 21, a dead time DT is set only for the high-side switching device 221, and no dead time DT is set for the low-side switching device 222.

[0063] First, the first crossover point Rd is detected (S71). After detecting the first crossover point Rd, when the first waiting time has elapsed, the low-side switching device 222 is switched from on to off (S72). As a result, the power converter 1 starts outputting a high voltage (V1) (see Figure 12(d)). After detecting the first crossover point Rd, when the second waiting time has elapsed, the high-side switching device 221 is switched from off to on (S73). When the switching operation of the high-side switching device 221 (S73) is performed, the low-side switching device 222 is already in the off state. Therefore, by performing the switching operation (S73), both the high-side switching device 221 and the low-side switching device 222 can be turned off. In other words, a dead time DT can be set.

[0064] Next, the second crosspoint Ru is detected (S81). Immediately after detecting the second crosspoint Ru, the high-side switching device 221 is switched from off to on (S82). Then, after detecting the second crosspoint Ru and after the first waiting time has elapsed, the low-side switching device 222 is switched from on to off (S83). As a result, the power converter 1 starts outputting a low voltage (V0) (see Figure 12(d)).

[0065] Here, the time at which the low-side switching device 222 was switched from on to off was when the first waiting time had elapsed from the first crossover point Rd. Also, the time at which the low-side switching device 222 was switched from off to on was when the first waiting time had elapsed from the second crossover point Ru. In other words, although the period during which voltage is supplied from the power converter 1 to the motor 9 due to the low-side switching device 222 is delayed by the first waiting time from each crossover point, the period during which voltage is supplied from the power converter 1 to the motor 9 is the same as the period from the first crossover point Rd to the second crossover point Ru. Therefore, the decrease in output voltage is suppressed.

[0066] <Effects> The control method of the power converter 1 is such that when current flows from the power source 21 to the motor 9, the first control signal V ＨＳ In the step of outputting the first switching device 221, a first control signal is output to connect the first switching device 221 at a time delayed by a first waiting time from the time of the first crosspoint Rd, and to disconnect the first switching device 221 at a time delayed by a first waiting time from the time of the second crosspoint Ru. In the step of outputting the second control signal, a second control signal is output to disconnect the second switching device 222 at the time of the first crosspoint Rd, and to connect the second switching device 222 after a second waiting time, which is longer than the first waiting time, has elapsed from the second crosspoint Ru. This method makes it possible to control the first switching device 221 and the second switching device 222 based on the detection of the first crosspoint Rd and the second crosspoint Ru. As a result, control of the first switching device 221 and the second switching device 222 can be made easier.

[0067] <Modification> The control method for a power converter, the control device for a power converter, and the power converter of the present disclosure have been described above. However, the control method for a power converter, the control device for a power converter, and the power converter of the present disclosure are not necessarily limited to the embodiments described above, and various modifications can be made without departing from the gist of the invention.

[0068] 1 Power conversion device 2 Conversion circuit section 3 Control section 9 Motor (load device) 21 Power supply 211 Positive electrode 212 Negative electrode 22 U-phase unit 23 V-phase unit 24 W-phase unit 32 CPU 221 First switching device 222 Second switching device 224 Diode 311 DC voltage sensor circuit 312 U-phase current sensor circuit 313 V-phase current sensor circuit 314 W-phase current sensor circuit 321 First control signal output section 322 Second control signal output section 331-336 Gate drive circuit 332 Gate drive circuit CV Voltage command value CW Carrier wave DT Dead time Rd First crossover point Ru Second crossover point V ＨＳFirst control signal V ＬＳ Second control signal

Claims

1. A control method for a power converter having a first switching device that switches between electrically connecting and disconnecting the positive terminal of a power supply to a load device, and a second switching device that switches between electrically connecting and disconnecting the negative terminal of the power supply to the load device, the method comprising: a step of outputting a first control signal given to one of the first switching device and the second switching device for a period of time equal to the time from a first crossing point to a second crossing point between the carrier wave and the voltage command value, to connect one of the first switching device and the second switching device to the load device; and a step of outputting a second control signal given to the other of the first switching device and the second switching device, which has a waiting time set for a dead time that simultaneously disconnects the first switching device and the second switching device.

2. A control method for a power converter according to claim 1, wherein, when current flows from the power supply to the load device, the first control signal is supplied to the first switching device in the step of outputting the first control signal, and the second control signal is supplied to the second switching device in the step of outputting the second control signal.

3. A control method for a power converter according to claim 1 or 2, wherein, when current flows from the load device to the power supply, the first control signal is supplied to the second switching device in the step of outputting the first control signal, and the second control signal is supplied to the first switching device in the step of outputting the second control signal.

4. A control method for a power converter according to claim 2, wherein, when current flows from the power supply to the load device, in the step of outputting the first control signal, the first switching device is connected at the time of the first crossover point, and the first switching device is disconnected at the time of the second crossover point, and in the step of outputting the second control signal, the second switching device is disconnected at the time of the first crossover point after a first waiting time has elapsed, and the second switching device is connected at a time delayed by the first waiting time from the time of the second crossover point.

5. A control method for a power converter according to claim 2, wherein, when current flows from the power supply to the load device, the first control signal is output to connect the first switching device at a time delayed by a first waiting time from the time of the first crossover point, and to disconnect the first switching device at a time delayed by a first waiting time from the time of the second crossover point; and the second control signal is output to disconnect the second switching device at the time of the first crossover point, and to connect the second switching device after a second waiting time longer than the first waiting time has elapsed from the second crossover point.

6. A control device for a power converter, comprising: a first switching device for switching between electrically connected and disconnected states of the positive terminal of a power supply to a load device; and a second switching device for switching between electrically connected and disconnected states of the negative terminal of the power supply to the load device, the control device comprising: a first control signal output unit that outputs a first control signal to one of the first and second switching devices for a period of time equal to the time from a first crossing point to a second crossing point between the carrier wave and the voltage command value, for connecting one of the first and second switching devices to the load device; and a second control signal output unit that outputs a second control signal to the other of the first and second switching devices, for which a waiting time for a dead time is set to simultaneously disconnect the first and second switching devices.

7. A power converter comprising: a first switching device that switches the positive terminal of a power supply between being electrically connected to and disconnected from a load device; a second switching device that switches the negative terminal of the power supply between being electrically connected to and disconnected from a load device; and a control unit that outputs a first control signal that switches the positive terminal between being connected to and disconnected from the first switching device, and a second control signal that switches the negative terminal between being connected to and disconnected from the second switching device, wherein the control unit outputs a first control signal that is given to one of the first switching device and the second switching device, for connecting one of the first switching device and the second switching device to the load device for the same amount of time as the time from a first crossover point to a second crossover point between the carrier wave and the voltage command value; and a second control signal that is given to the other of the first switching device and the second switching device, for which a waiting time for a dead time is set to simultaneously disconnect the first switching device and the second switching device.

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