Power conversion device, motor drive device, and refrigeration cycle application equipment

Abstract

A power conversion device (1) for performing power conversion comprises: one or more switching elements included in at least one power converter among one or more power converters that perform power conversion; and a current detector disposed on a path of current flowing through the power converter. The waveform shape of the pulse current waveform detected by the current detector changes.

Description

Power conversion devices, motor drive devices, and refrigeration cycle application equipment

[0001] The present disclosure relates to a power conversion device that performs power conversion, a motor drive device, and a refrigeration cycle application device.

[0002] Conventionally, a power conversion device that supplies power to a motor includes a converter, an inverter, etc., and controls the on / off of switching elements included in the converter and the inverter based on detection values ​​from detection units that are arranged in various locations within the device and detect current, voltage, etc. For example, Patent Document 1 discloses a technology in which a motor drive device controls the on / off of switching elements included in the converter based on zero crossings of an AC power supply detected by a power supply zero crossing detection unit, and controls the on / off of switching elements included in the inverter based on bus current detected by a bus current detection unit.

[0003] The on / off periods of switching elements included in power converters such as converters and inverters can be controlled according to the detection values ​​of each detection unit. Furthermore, the switching speed of switching elements included in power converters such as converters and inverters can also be adjusted by the circuit configuration of a drive circuit that supplies current or power to the switching elements. Ringing and other noise generated in switching elements varies depending on the switching speed of the switching elements. For example, the ringing generated in switching elements increases as the switching speed increases, and decreases as the switching speed decreases. Since the correct current value cannot be detected when ringing occurs in the switching elements, it is desirable for the current detection unit to detect the current value after the ringing has converged.

[0004] JP 2016-103886 A

[0005] However, in a power converter such as an inverter, depending on the control content, the period from when the on / off state of one switching element changes to when the on / off state of another switching element changes may be short. Therefore, if the on / off state of one switching element changes at such a switching speed that it takes time for ringing to converge in the other switching element, and then the on / off state of the other switching element also changes immediately, there is a problem in that it is not possible to accurately detect the current value when the on / off state of the one switching element changes.

[0006] The present disclosure has been made in view of the above, and has an object to provide a power conversion device that can improve the accuracy of current detection.

[0007] In order to solve the above-mentioned problems and achieve the object, the present disclosure provides a power conversion device that performs power conversion, the power conversion device including one or more switching elements included in at least one of one or more power converters that perform power conversion, and a current detector disposed on a path of a current flowing through the power converter, and the waveform shape of a pulsed current waveform detected by the current detector changes.

[0008] The power conversion device according to the present disclosure has an effect of being able to improve the accuracy of current detection.

[0009]

[0010] Hereinafter, a power conversion device, a motor drive device, and a refrigeration cycle applied device according to embodiments of the present disclosure will be described in detail with reference to the drawings.

[0011] First Embodiment. FIG. 1 is a diagram illustrating an example of the configuration of a power conversion device 1 according to a first embodiment. The power conversion device 1 is connected to a commercial power source 110 and a motor 314. The power conversion device 1 converts a first AC voltage of a power supply voltage Vs supplied from the commercial power source 110, which is an AC power source, into a second AC voltage having a desired amplitude and phase, and supplies the second AC voltage to the motor 314. In the example of FIG. 1 , the commercial power source 110 is a single-phase AC power source, but it may also be a three-phase AC power source. The power conversion device 1 includes a state quantity detection unit 501, a converter 130, a capacitor 210, a state quantity detection unit 502, an inverter 310, a state quantity detection unit 503, a state quantity detection unit 504, a state quantity detection unit 505, and a control unit 400. The power conversion device 1 and the motor 314 constitute a motor drive device 2.

[0012] The state quantity detection unit 501 detects a state quantity that indicates the operating state of the power conversion device 1. The state quantity detection unit 501 detects, for example, the voltage value of the AC voltage of the power supply voltage Vs supplied from the commercial power supply 110 to the converter 130, the current value of the AC voltage of the power supply voltage Vs supplied from the commercial power supply 110 to the converter 130, etc. The state quantity detection unit 501 may also detect a zero crossing of the power supply voltage Vs supplied from the commercial power supply 110 to the converter 130, etc.

[0013] Converter 130 is a power converter that converts the AC voltage of power supply voltage Vs supplied from commercial power supply 110 into a DC voltage. Converter 130 includes rectifying elements 131-134, a reactor 135, a switching element 136, a freewheeling diode 137, a diode 138, and a drive circuit 150. Converter 130 has a bridge circuit formed by rectifying elements 131-134, rectifies a first AC voltage of power supply voltage Vs supplied from commercial power supply 110, boosts the rectified DC voltage, and outputs it. In the following description, the rectified DC voltage may be referred to as a first DC voltage, and the boosted DC voltage, i.e., output to capacitor 210, may be referred to as a second DC voltage. Drive circuit 150 generates a drive signal for actually driving switching element 136 based on a basic pulse generated by a basic pulse generating unit 410 of control unit 400, which will be described later. The switching element 136 is, for example, an insulated gate bipolar transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET), a bipolar transistor, or the like, but is not limited to these.

[0014] In the example of FIG. 1 , converter 130 includes rectifier unit 161 of a bridge circuit configured with rectifier elements 131 to 134, and boost unit 162 configured with reactor 135, switching element 136, freewheel diode 137, and diode 138. However, the configuration of converter 130 is not limited to the example of FIG. 1 . FIG. 2 is a first diagram showing the rectifying and boosting portion of converter 130 included in power conversion device 1 according to embodiment 1. FIG. 3 is a second diagram showing the rectifying and boosting portion of converter 130 included in power conversion device 1 according to embodiment 1. FIG. 4 is a third diagram showing the rectifying and boosting portion of converter 130 included in power conversion device 1 according to embodiment 1. FIG. 5 is a fourth diagram showing the rectifying and boosting portion of converter 130 included in power conversion device 1 according to embodiment 1. FIG. 6 is a fifth diagram showing the rectifying and boosting portion of converter 130 included in power conversion device 1 according to embodiment 1.

[0015] As shown in FIG. 2, the converter 130 may be configured to include a rectifier / boost unit 163 including a reactor 135, switching elements 136a and 136b, freewheeling diodes 137a and 137b, and rectifier elements 133 and 134. The rectifier / boost unit 163 shown in FIG. 2 is a totem-pole bridgeless circuit. Alternatively, as shown in FIG. 3, the converter 130 may be configured to include a rectifier / boost unit 163 including a reactor 135, switching elements 136b and 136d, freewheeling diodes 137b and 137d, and rectifier elements 131 and 133. The rectifier / boost unit 163 shown in FIG. 3 is a half-bridgeless circuit. Alternatively, as shown in FIG. 4, the converter 130 may be configured to include a rectifier / boost unit 163 including a reactor 135, switching elements 136a to 136d, and freewheeling diodes 137a to 137d. The rectifying / boosting unit 163 shown in FIG. 4 is a full-bridgeless circuit. Alternatively, as shown in FIG. 5, the converter 130 may include a rectifying unit 161 including rectifying elements 131 to 134 and a boosting unit 162 including reactors 135a and 135b, switching elements 136a and 136b, freewheeling diodes 137a and 137b, and diodes 138a and 138b. The boosting unit 162 shown in FIG. 5 is an interleaved circuit. Alternatively, as shown in FIG. 6, the converter 130 may include a rectifying / boosting unit 163 including a reactor 135, a first rectifying circuit including rectifying elements 131 to 134, and a second rectifying circuit including switching element 136, freewheeling diode 137, and rectifying elements 131a to 134a. The rectifying and boosting unit 163 shown in FIG. 6 is a simple PAM (Pulse Amplitude Modulation) type circuit in which a first rectifying circuit and a second rectifying circuit are connected in parallel, a switching element 136 is connected to the output terminal of the first rectifying circuit, and a capacitor 210 that supplies a second DC voltage to an inverter 310 is connected to the output terminal of the second rectifying circuit.

[0016] As described above, converter 130 includes rectifier 161 that converts the first AC voltage supplied from commercial power supply 110 into a first DC voltage, and booster 162 that boosts the first DC voltage to a second DC voltage greater than the first DC voltage, or rectifier / booster 163 that rectifies the first AC voltage and boosts it to a second DC voltage having an effective value greater than the effective value of the first AC voltage. Note that, when commercial power supply 110 is a three-phase AC power supply, converter 130 is configured to include at least six elements, such as rectifiers and switching elements. In this case, power conversion device 1 may be a three-phase three-wire power conversion device or a three-phase four-wire power conversion device. In this embodiment, converter 130 is only required to have a rectification function and does not necessarily have a boost function. Hereinafter, a description will be given of a power conversion device 1 having the configuration shown in FIG. 1 as an example.

[0017] Capacitor 210 is connected to the output terminal of converter 130 and smoothes the DC voltage converted by converter 130. Capacitor 210 is, for example, an electrolytic capacitor or a film capacitor.

[0018] The state quantity detection unit 502 detects a state quantity that indicates the operating state of the power conversion device 1. The state quantity detection unit 502 detects, for example, the voltage value of the DC voltage supplied from the capacitor 210 to the inverter 310.

[0019] The inverter 310 is a power converter connected to both ends of the capacitor 210. The inverter 310 has switching elements 311a to 311f and freewheeling diodes 312a to 312f. The inverter 310 turns on and off the switching elements 311a to 311f under the control of the control unit 400, converts the DC voltage output from the converter 130 and the capacitor 210 into a second AC voltage having a desired amplitude and phase, i.e., generates a second AC voltage, and outputs it to the motor 314. In other words, the inverter 310 converts the second DC voltage into a second AC voltage and outputs it. The switching elements 311a to 311f are, for example, IGBTs, MOSFETs, bipolar transistors, etc., but are not limited to these. The circuit configuration of the inverter 310 is not particularly limited and may be a full-bridge circuit, a single-phase bridge circuit, a half-bridge circuit, or the like. Furthermore, in this embodiment, the inverter 310 includes a waveform shape modification unit 340 that can modify the waveform shapes of the switching waveforms of the switching elements 311a to 311f without physically switching gate resistors or the like. The waveform shape modification unit 340 can output two or more waveform shapes as the waveform shapes of the switching waveforms of the switching elements 311a to 311f. In the example of FIG. 1, the waveform shape modification unit 340 is configured to modify the waveform shapes of the switching waveforms of the switching elements 311a to 311f, but it is also possible to modify the waveform shape of the switching waveform of at least one of the switching elements 311a to 311f. The inverter 310 may also be configured to include a waveform shape modification unit 340 for each of the switching elements 311a to 311f. The detailed operation of the waveform shape modification unit 340 will be described later.

[0020] The state quantity detection unit 503 detects a state quantity indicating the operating state of the power conversion device 1. The state quantity detection unit 503 detects, for example, a voltage value of the second AC voltage supplied from the inverter 310 to the motor 314, which is a load, and a current value of the second AC voltage supplied from the inverter 310 to the motor 314, which is a load. The state quantity detection unit 504 detects a state quantity indicating the operating state of the power conversion device 1. The state quantity detection unit 504 detects, for example, a current value of the DC voltage supplied from the capacitor 210 to the inverter 310. The state quantity detection unit 505 detects a state quantity indicating the operating state of the power conversion device 1. The state quantity detection unit 505 detects, for example, a current flowing through the switching elements 311b, 311d, and 311f.

[0021] Among the state quantity detection units 501 to 505, methods for detecting current in the state quantity detection units capable of detecting current include, but are not limited to, a method of measuring current using a shunt resistor, a method using a DCCT (Direct Current Current Transformer), an ACCT (Alternating Current Transformer), or the like. The state quantity detection unit 501 is disposed on a path of current flowing through the converter 130, which is a power converter, and can detect the current flowing through the converter 130 as a state quantity. The state quantity detection unit 504 is disposed on a path of current flowing through the inverter 310, which is a power converter, and can detect the current flowing through the inverter 310 as a state quantity. In the example of FIG. 1, the state quantity detection unit 504 is disposed on the N line of the power conversion device 1, but it may also be disposed on the P line.

[0022] The control unit 400 acquires the state quantities detected by the state quantity detection units 501 to 505 from the state quantity detection units 501 to 505, and controls the operations of the converter 130 and the inverter 310 based on the acquired state quantities, specifically, controls the on / off of the switching element 136 of the converter 130, and controls the on / off of the switching elements 311 a to 311 f of the inverter 310. The control unit 400 includes a basic pulse generation unit 410 and a waveform shape setting unit 420.

[0023] The basic pulse generation unit 410 generates a basic pulse having a duty ratio corresponding to the state quantities detected by the state quantity detection units 501 to 505, for controlling the operation of the switching element 136 of the converter 130. The basic pulse generation unit 410 also generates a basic pulse having a duty ratio corresponding to the state quantities detected by the state quantity detection units 501 to 505, for controlling the operation of the switching elements 311a to 311f of the inverter 310. The basic pulse is, for example, a PWM (Pulse Width Modulation) signal having a duty ratio corresponding to the state quantities detected by the state quantity detection units 501 to 505. The basic pulse generation unit 410 outputs a basic pulse for controlling the operation of the switching element 136 of the converter 130 to the converter 130, and outputs a basic pulse for controlling the operation of the switching elements 311a to 311f of the inverter 310 to the waveform shape setting unit 420.

[0024] The waveform shape setting unit 420 sets the waveform shapes of the switching waveforms of the switching elements 311a to 311f when the waveform shape changing unit 340 of the inverter 310 changes the switching waveforms of the switching elements 311a to 311f in accordance with the state quantities detected by the state quantity detection units 501 to 505, and outputs a control signal for reflecting a setting value indicating the set waveform shape. Specifically, when the switching elements 311a to 311f are turned on and off based on the basic pulses for controlling the operation of the switching elements 311a to 311f of the inverter 310 generated by the basic pulse generation unit 410, the waveform shape setting unit 420 controls the magnitude of the drive signals that the waveform shape changing unit 340 of the inverter 310 outputs to the switching elements 311a to 311f to actually drive the switching elements 311a to 311f, and the timing at which the drive signals are output. The waveform shape setting unit 420 outputs a control signal for controlling the operation of the waveform shape changing unit 340 to the waveform shape changing unit 340. In the case where the inverter 310 has a waveform shape modification unit 340 for each of the switching elements 311a to 311f, i.e., six waveform shape modification units 340, the control unit 400 may be configured to have a waveform shape setting unit 420 for each waveform shape modification unit 340, i.e., six waveform shape setting units 420.

[0025] In the example of FIG. 1 , the control unit 400 acquires state quantities detected by the state quantity detection units 501 to 505 from the state quantity detection units 501 to 505 and controls the operation of the converter 130 and the inverter 310 based on the acquired state quantities. However, this is not limited to this. The control unit 400 can control the operation of the converter 130 and the inverter 310 based on state quantities acquired from at least one of the state quantity detection units 501 to 505. In the power conversion device 1, the state quantity detection units 501 to 505 detect, as state quantities, voltages or currents input to each component of the power conversion device 1 and voltages or currents output from each component of the power conversion device 1 in the above example, but the detection targets are not limited to these. Furthermore, the installation locations of the state quantity detection units 501 to 505 are not limited to the example of FIG. 1 . The power conversion device 1 does not need to have all of the state quantity detection units 501 to 505 arranged as shown in FIG. 1 . The power conversion device 1 may include a state quantity detection unit anywhere other than the locations shown in the figure as long as the state quantities can be detected. The power conversion device 1 may be provided with a state quantity detection unit at a position where it can detect state quantities such as noise generated by the power conversion device 1, the motor 314, etc., losses generated by the power conversion device 1, the motor 314, etc., and the temperature of each component of the power conversion device 1, the motor 314, etc.

[0026] Furthermore, since the basic pulse generating section 410 and the waveform shape setting section 420 both operate based on the state quantities acquired from the state quantity detecting sections 501 to 505, the control section 400 may combine the functions of the basic pulse generating section 410 and the waveform shape setting section 420 into a single configuration.

[0027] The motor 314 is a load connected to the power conversion device 1. The motor 314 is, for example, a compressor motor for driving a compressor. The motor 314 rotates in accordance with the amplitude and phase of the second AC voltage supplied from the inverter 310 to perform compression. For example, when the compressor is a hermetic compressor, the load torque of the motor 314 driving the compressor can often be considered a constant torque load. The motor 314 may have a Y-connection, a Δ-connection, or a specification that allows switching between the Y-connection and the Δ-connection, with respect to the motor windings (not shown). Furthermore, the load connected to the power conversion device 1, i.e., the inverter 310, is not limited to the motor 314 for driving the compressor and may be a fan motor or the like. Furthermore, the load connected to the power conversion device 1 is not limited to the motor 314 and may be a load other than the motor 314.

[0028] In this embodiment, the power conversion device 1 can change the waveform shapes of the switching waveforms of the switching elements 311a to 311f of the inverter 310 using the waveform shape setting unit 420 and the waveform shape changing unit 340. Specifically, the power conversion device 1 can change the switching speed, delay time, etc. of the switching elements 311a to 311f of the inverter 310.

[0029] FIG. 7 is a diagram showing examples of turn-on joule loss, turn-on current, and turn-on voltage when the switching speed of the switching elements 311a to 311f of the inverter 310 in the power conversion device 1 according to the first embodiment is slowed down. FIG. 8 is a diagram showing examples of turn-on joule loss, turn-on current, and turn-on voltage when the switching speed of the switching elements 311a to 311f of the inverter 310 in the power conversion device 1 according to the first embodiment is fastened down. In FIGS. 7 and 8 , A represents turn-on joule loss, B represents turn-on current, and C represents turn-on voltage. In FIGS. 7 and 8 , the horizontal axis represents time. For example, the turn-on current is the current flowing through the switching element 311a, the turn-on voltage is the voltage across the switching element 311a, and the turn-on joule loss is the product of the turn-on current and the turn-on voltage. However, the measurement target is not limited to the switching element 311a, and may be the other switching elements 311b to 311f. 7 and 8 show the differences in characteristics depending on the switching speed of the switching elements 311a to 311f of the inverter 310, and the specific values ​​of "slow" and "fast" switching speeds are not particularly important. As shown in FIGS. 7 and 8, slowing the switching speed reduces noise represented by the peak value of the turn-on current of B, but increases loss represented by the area of ​​the turn-on joule loss of A. Also, as shown in FIGS. 7 and 8, increasing the switching speed increases noise represented by the peak value of the turn-on current of B, but decreases loss represented by the area of ​​the turn-on joule loss of A. In other words, there is a trade-off between the noise and loss generated in the switching elements 311a to 311f.

[0030] In the power conversion device 1, the waveform shape modification unit 340 is configured by a digital gate driver. Alternatively, in the power conversion device 1, the switching elements 311a to 311f of the inverter 310 and the waveform shape modification unit 340 are configured by a digital gate driver module. This allows the power conversion device 1 to change the switching speed of the switching elements 311a to 311f of the inverter 310 by changing a command value in software without changing the hardware, and to control the noise and loss generated in the switching elements 311a to 311f to a desired state.

[0031] Fig. 9 is a diagram showing an example of the relationship between noise and loss generated in a typical switching element. As mentioned above, there is a trade-off between noise and loss generated in a switching element. Therefore, as shown in Fig. 9, in a typical switching element, increasing the switching speed increases noise but reduces loss, and decreasing the switching speed reduces noise but increases loss.

[0032] FIG. 10 is a first diagram illustrating the effect obtained by changing the switching speed of the switching elements 311a to 311f of the inverter 310 in the power conversion device 1 according to the first embodiment. Even if the power conversion device 1 is operating within the noise range specified for the product in which the power conversion device 1 is installed, when the load state of the motor 314 changes from a light load to a heavy load, the curve showing the characteristics of the noise and loss generated by the switching elements 311a to 311f shifts to the upper right as shown in FIG. 10, resulting in an increase in noise. In other words, in the power conversion device 1, the heavier the load, the more noise increases. Therefore, the power conversion device 1 can reduce the noise generated by the switching elements 311a to 311f by slowing down the switching speed of the switching elements 311a to 311f. Similarly, even if the power conversion device 1 is operating within the loss range specified for the product in which the power conversion device 1 is installed, when the load state of the motor 314 changes from a light load to a heavy load, the curve showing the characteristics of the noise and loss generated by the switching elements 311a to 311f shifts to the upper right as shown in Figure 10, resulting in an increase in loss. In other words, in the power conversion device 1, the heavier the load, the greater the loss. Therefore, the power conversion device 1 can reduce the loss generated by the switching elements 311a to 311f by increasing the switching speed of the switching elements 311a to 311f.

[0033] When the load state of the motor 314 changes from a light load to a heavy load, the waveform shape setting unit 420 changes the set values ​​of the waveform shapes of the switching waveforms of the switching elements 311a to 311f so that the noise generated in the switching elements 311a to 311f satisfies the specified requirements and the loss generated in the switching elements 311a to 311f is reduced. Alternatively, when the load state of the motor 314 changes from a light load to a heavy load, the waveform shape setting unit 420 changes the set values ​​of the waveform shapes of the switching waveforms of the switching elements 311a to 311f so that the loss generated in the switching elements 311a to 311f satisfies the specified requirements and the noise generated in the switching elements 311a to 311f is reduced.

[0034] 11 is a second diagram illustrating the effect obtained by changing the switching speed of the switching elements 311a to 311f of the inverter 310 in the power conversion device 1 according to the first embodiment. The power conversion device 1, specifically the waveform shape modification unit 340, divides, for example, the turn-on period or the turn-off period of a single switching operation of the switching elements 311a to 311f into two or more periods, and modifies the amplitude of the gate current or gate voltage for the switching elements 311a to 311f to different magnitudes in each of the divided periods. By optimizing the switching waveforms of the switching elements 311a to 311f as shown in FIG. 11, the power conversion device 1 can obtain noise and loss characteristics generated by the switching elements 311a to 311f that could not be obtained with typical switching elements such as those shown in FIG. 9.

[0035] Here, the configuration of the waveform shape modification unit 340 will be described. For ease of explanation, a case will be described in which the waveform shape modification unit 340 is capable of modifying the waveform shape of the switching waveform of one switching element 311a. FIG. 12 is a diagram showing an example of the configuration of the waveform shape modification unit 340 of the power conversion device 1 according to the first embodiment. FIG. 12 also shows an example of the configuration of one digital gate driver module configured by the waveform shape modification unit 340 and the switching element 311a. As shown in FIG. 1, the waveform shape modification unit 340 is included in the inverter 310, which is a power converter including the switching element 311a. The waveform shape changing unit 340 includes n P-channel MOSFETs (PMOSs) for turn-on, n PreDrivers for operating the n PMOSs, n N-channel MOSFETs (NMOSs) for turn-off, and n PreDrivers for operating the n NMOSs.

[0036] The waveform shape changing unit 340 is connected to a control power supply Vdd and a ground GND. The waveform shape changing unit 340 changes the number of PMOS or NMOS transistors to be operated based on a control signal from the waveform shape setting unit 420, thereby adjusting the gate current I, which is a drive signal to be output to the switching element 311a, during each of the turn-on period and the turn-off period. Ｇ The waveform shape changing unit 340 can change the amplitude value of the gate current I output to the switching element 311a in n ways, thereby adjusting the switching speed of the switching element 311a. Ｇ The absolute value of can be increased, and the switching speed of the switching element 311a can be increased. In addition, the waveform shape changing unit 340 can adjust the switching speed of the switching element 311a more precisely as the number of PMOS and NMOS included therein increases, and the gate current I Ｇ The faster the response of the increase or decrease of the gate current I Ｇ It is possible to adjust the number of PMOS or NMOS transistors operated by the waveform shape modification unit 340. The control signal from the waveform shape setting unit 420 may be an analog signal or a digital signal as long as it can change the number of PMOS or NMOS transistors operated by the waveform shape modification unit 340. In addition, the example of FIG. 12 shows that there are m parallel control signals from the waveform shape setting unit 420 to the waveform shape modification unit 340, but this is just an example, and the number of control signals is not limited to m. The number of control signals may be any number that can indicate whether each PMOS transistor and each NMOS transistor is operable or not, or it may be one signal as long as it is an analog signal that indicates a voltage or the like.

[0037] FIG. 13 shows the gate current I output by the waveform shape modification unit 340 in the power conversion device 1 according to the first embodiment. Ｇ and the gate voltage V, which indicates the rise speed of the switching element 311a. Ｇ 14 is a first diagram showing the relationship between the gate current I output by the waveform shape modification unit 340 in the power conversion device 1 according to the first embodiment. Ｇ and the gate voltage V, which indicates the rise speed of the switching element 311a. Ｇ13 and 14, the waveform shape changing unit 340 changes the gate current I Ｇ The larger the gate voltage V Ｇ 13 and 14, the waveform shape changing unit 340 can change the rise time of the output gate current I Ｇ The smaller the gate voltage V Ｇ 10, the power conversion device 1 can output a gate current I when it is desired to reduce noise generated by the switching element 311a. Ｇ When it is desired to reduce the loss occurring in the switching element 311a by decreasing the switching speed, the output gate current I Ｇ The switching speed can be increased by increasing the gate current I Ｇ and gate voltage V Ｇ The waveform of the gate current I is an ideal example, and in reality, as shown in FIGS. Ｇ It takes time for the current to reach a constant value.

[0038] FIG. 15 shows the gate current I output by the waveform shape modification unit 340 in the power conversion device 1 according to the first embodiment. Ｇ and the gate voltage V, which indicates the rise speed of the switching element 311a. Ｇ 15, the waveform shape changing unit 340 divides the turn-on period and changes the gate current I Ｇ That is, the waveform shape changing section 340 can change the magnitude of the gate current I Ｇ This allows the power conversion device 1 to finely adjust the magnitude of the gate current I Ｇ11, it is possible to perform control so as to reduce the loss generated in the switching element 311a while reducing the noise generated in the switching element 311a.

[0039] 13 to 15 have been used to explain the turn-on period of the switching element 311a as an example, but the same applies to the turn-off period of the switching element 311a. Fig. 16 shows the basic pulse output by the basic pulse generating unit 410 and the gate current I output by the waveform shape changing unit 340 in the power conversion device 1 according to the first embodiment. Ｇ 16 is a diagram illustrating an example of the relationship between |Ig2| and |Ig1|. In FIG. 16, |Ig2|>|Ig1|. The waveform shape changing unit 340 changes the gate current I Ｇ The period during which the current Ig2 having the larger amplitude is output is divided, and the gate current I Ｇ Then, the gate current I of the current Ig1 with the next smallest amplitude is output. Ｇ Alternatively, the gate current I of the current Ig1 with the small amplitude may be output first. Ｇ After outputting the gate current I of the current Ig2 with the next largest amplitude, Ｇ Similarly, the waveform shape changing unit 340 may output the gate current I Ｇ The period during which the current with the largest amplitude is output is divided, and the gate current I Ｇ Then, the gate current I of the next smallest amplitude current -Ig1 is output. Ｇ Alternatively, the gate current I of the current −Ig1 with a small amplitude may be output first. Ｇ After outputting the next largest current, the gate current Ig2 Ｇ may be output.

[0040] In this way, the waveform shape changing unit 340 divides at least one of the turn-on period and the turn-off period of the switching element 311a into two or more periods based on the control signal output from the waveform shape setting unit 420, and determines the gate current I for the switching element 311a in each divided period. ＧThe waveform shape changing section 340 includes a plurality of transistors, and by changing the number of transistors to be operated based on the control signal output from the waveform shape setting section 420, the amplitude of the gate current I Ｇ The amplitude of can be changed.

[0041] Furthermore, the waveform shape changing unit 340 changes the gate current I Ｇ The waveform shape changing unit 340 can change the switching waveform to a different waveform shape for each switching period of the switching element 311a during operation of the power conversion device 1. In this case, the waveform shape setting unit 420 can change the set value of the waveform shape of the switching waveform of the switching element 311a at the same period as the switching period of the switching element 311a. The waveform shape setting unit 420 may also change the set value of the waveform shape of the switching waveform of the switching element 311a at a period that is a positive integer multiple of the switching period of the switching element 311a.

[0042] 12 is merely an example and is not limiting. In this manner, the waveform shape modification unit 340 can adjust the switching speed of the switching element 311a more precisely by digital control using multiple MOS (Metal Oxide Semiconductor) transistors, compared to analog control that physically switches the gate resistor. Furthermore, the waveform shape modification unit 340 may use transistors other than MOS transistors for its internal transistors.

[0043] In the above example, the waveform shape changing unit 340 changes the number of PMOS or NMOS to be operated in accordance with the acquired control signal, and generates a gate current I Ｇ to the switching element 311a, but is not limited to this. The waveform shape changing unit 340 changes the gate current I ＧThe output pattern, i.e., waveform shape, of the gate current I is stored in advance, and the output pattern, i.e., waveform shape, corresponding to the acquired control signal is output. Ｇ Furthermore, the waveform shape changing unit 340 may output a previously acquired control signal and a gate current I Ｇ The output pattern, i.e., waveform shape, of the gate current I is stored in memory, and when the same control signal is acquired, the stored output pattern, i.e., waveform shape is used. Ｇ The waveform shape changing section 340 may output the gate current I Ｇ By storing the output pattern, i.e., waveform shape, of the gate current I Ｇ This reduces the processing load when outputting.

[0044] In the example of FIG. 12, the waveform shape changing unit 340 changes the gate current I Ｇ The waveform shape changing unit 340 adjusts the switching speed of the switching element 311a by changing the gate voltage V Ｇ and the gate voltage V Ｇ By changing the value of the switching speed of the switching element 311a, the switching speed of the switching element 311a can be adjusted and the waveform shape of the switching waveform of the switching element 311a can be changed.

[0045] In this way, the waveform shape changing unit 340 divides at least one of the turn-on period and the turn-off period of the switching element 311a into two or more periods based on the control signal output from the waveform shape setting unit 420, and sets the gate voltage V Ｇ The waveform shape changing section 340 includes a plurality of transistors, and by changing the number of transistors to be operated based on the control signal output from the waveform shape setting section 420, the amplitude of the gate voltage V Ｇ The amplitude of can be changed.

[0046] In this embodiment, in the power conversion device 1, the waveform shape of a pulsed current waveform detected by a current detector disposed on a path of a current flowing through the power converter changes. Specifically, the power conversion device 1 can change the waveform shape of the pulsed current waveform detected by the current detector by changing the waveform shape of the switching waveform of the switching element. The power converter is at least one of the converter 130 and the inverter 310. The current detector disposed on the path of a current flowing through the converter 130, which is a power converter, is, for example, a state quantity detection unit 501. The current detector disposed on the path of a current flowing through the inverter 310, which is a power converter, is, for example, a state quantity detection unit 504. The waveform shape of the pulsed current waveform detected by the current detector is a waveform shape that includes surges, ringing, and the like. Since the waveform shape of the pulsed current waveform detected by the current detector changes due to the influence of surges, ringing, and the like in addition to the current flowing through the power converter, the power conversion device 1 can detect the current with high accuracy by detecting the current in a range that is not affected by surges, ringing, and the like. Furthermore, the power conversion device 1 can detect current with high accuracy, and therefore can appropriately control the switching of the switching elements included in the converter 130 and the inverter 310 according to the detected current amount.

[0047] As an example, a case will be described in which a current flowing through the inverter 310 in the power conversion device 1 is detected. FIG. 17 is a diagram showing an example of a state quantity detection unit 504 that is a current detector using switching elements 311a to 311f and shunt resistors provided in the inverter 310 of the power conversion device 1 according to the first embodiment. While reference numerals indicating each component are omitted in FIG. 17 , the switching element 311a is indicated by Up, the switching element 311b is indicated by Un, the switching element 311c is indicated by Vp, the switching element 311d is indicated by Vn, the switching element 311e is indicated by Wp, and the switching element 311f is indicated by Wn. The state quantity detection unit 504 that is a current detector using a shunt resistor is indicated by the resistor in the lower left.

[0048] 18 is a diagram showing an example of a switching pattern of the switching elements of the inverter 310, which can detect currents by the state quantity detection unit 504, which is a current detector using a shunt resistor, in the power conversion device 1 according to the first embodiment. FIG. 18 is a diagram showing the on / off states of the switching elements of the inverter 310 and the state of the command voltage vector in the inverter 310. In FIG. 18, the switching elements in the on state are indicated by circles. FIG. 18(a) shows the command voltage vector V when the switching elements Un, Vn, and Wp are on and the switching elements Up, Vp, and Wn are off. １ 18(b) shows the state of the command voltage vector V ２ 18(c) shows the state of the command voltage vector V when the switching elements Un, Vp, and Wp are on and the switching elements Up, Vn, and Wn are off. ３ 18(d) shows the state of the command voltage vector V when the switching elements Up, Vn, and Wn are on and the switching elements Un, Vp, and Wp are off. ４ 18(e) shows the state of the command voltage vector V when the switching elements Up, Vn, and Wp are on and the switching elements Un, Vp, and Wn are off. ５ 18(f) shows the state of the command voltage vector V when the switching elements Up, Vp, and Wn are on and the switching elements Un, Vn, and Wp are off. ６ This shows the state of

[0049] As shown in FIG. 18, the power conversion device 1 detects phase currents that change depending on the on / off state of each switching element of the inverter 310. １ ~V ６18(c) , the state quantity detection unit 504 arranged on the N line of the power conversion device 1 can detect the current (-Iu) flowing through the switching element Un in the case of FIG. 18(c), the current (-Iv) flowing through the switching element Vn in the case of FIG. 18(e), and the current (-Iw) flowing through the switching element Wn in the case of FIG. 18(f). If the state quantity detection unit 504 were arranged on the P line of the power conversion device 1, the state quantity detection unit 504 could detect the current Iw flowing through the switching element Wp in the case of FIG. 18(a), the current Iv flowing through the switching element Vp in the case of FIG. 18(b), and the current Iu flowing through the switching element Up in the case of FIG. 18(d).

[0050] 19 is a diagram showing an example of a switching pattern of the switching elements of the inverter 310 in which the state quantity detection unit 504, which is a current detector using a shunt resistor, cannot detect current in the power conversion device 1 according to the first embodiment. FIG. 19 is a diagram showing the on / off states of each switching element of the inverter 310 and the state of the command voltage vector. In FIG. 19, the switching elements in the on state are indicated by circles. FIG. 19(a) shows the command voltage vector V when the switching elements Un, Vn, and Wn are on and the switching elements Up, Vp, and Wp are off. ０ 19(b) shows the state of the command voltage vector V when the switching elements Up, Vp, and Wp are on and the switching elements Un, Vn, and Wn are off. ７ As shown in FIG. 19, the power conversion device 1 is in a state where the command voltage vector V ０ , V ７ In this state, current detection is not possible.

[0051] Here, the power conversion device 1 cannot detect the correct current value immediately after switching of the switching elements of the inverter 310 due to surges, ringing, and the like. Therefore, the power conversion device 1 waits until the surges, ringing, and the like converge before detecting the current value. FIG. 20 is a diagram illustrating an example of a control state when there is no phase in which current detection is impossible in the power conversion device 1 according to embodiment 1. FIG. 21 is a diagram illustrating an example of a control state when there is a phase in which current detection is impossible in the power conversion device 1 according to embodiment 1. In FIGS. 20 and 21 , the left side shows the command voltage vector, and the right side shows the PWM signal, which is a control signal for each switching element, and the bus current Idc detected by the state quantity detection unit 504. FIG. 20 illustrates a state in which the U-phase and W-phase currents are detectable, while FIG. 21 illustrates a state in which the W-phase current is detectable but the U-phase current is undetectable. Although it may appear that the U-phase current can be detected in FIG. 21 , if the power conversion device 1 waits until the surges, ringing, and the like converge, as described above, the time during which the U-phase current can be detected is zero or extremely short. That is, for a certain switching element, in relation to the timing at which the switching of the next switching element begins, there are cases in which current detection cannot be performed if it is necessary to wait until the surge, ringing, etc., has subsided.

[0052] FIG. 22 is a diagram showing an example of a region of a command voltage vector that cannot be used for motor control in the power conversion device 1 according to the first embodiment. The region shown in FIG. 22 is the region of the command voltage vector that cannot be used for motor control. The command voltage vector shown on the left side of FIG. 21 is included in the region shown in FIG. 22, and therefore a period occurs in which the power conversion device 1 cannot detect current, resulting in a command voltage vector that cannot be used for motor control. Although the power conversion device 1 cannot use command voltage vectors in the region shown in FIG. 22 for motor control, by reducing surges, ringing, etc. that occur in the shunt resistor, the region shown in FIG. 22 can be made smaller, enabling more accurate motor control to be achieved.

[0053] 23 is a first diagram showing the relationship between the switching speed of the switching elements and the current detection timing in the power conversion device 1 according to the first embodiment. The upper part of FIG. 23( a) shows state quantities indicating the operating state of the first switching element when the first switching element changes from non-conductive to conductive under the first drive condition, and the lower part of FIG. 23( a) shows the detected value, i.e., the current value, detected by the state quantity detection unit, which is a current detector, when the first switching element changes from non-conductive to conductive under the first drive condition. The upper part of FIG. 23( b) shows state quantities indicating the operating state of the first switching element when the first switching element changes from non-conductive to conductive under the second drive condition, and the lower part of FIG. 23( b) shows the detected value, i.e., the current value, detected by the state quantity detection unit, which is a current detector, when the first switching element changes from non-conductive to conductive under the second drive condition. The non-conductive state of the switching element is the same as the off state of the switching element, and the conductive state of the switching element is the same as the on state of the switching element. The same applies hereafter.

[0054] The state quantity indicating the operating state of the first switching element may be any value that can indicate the operating state of the first switching element, such as a voltage or current value detectable by a state quantity detection unit, a drive signal for driving the first switching element, or a command value used within the control unit 400 to generate the drive signal. The first switching element is any of the aforementioned switching elements Up, Un, Vp, Vn, Wp, and Wn, i.e., any of the switching elements 311a to 311f. Note that the first and second drive conditions indicate the difference in switching speed of the first switching element, and here, the switching speed of the first switching element is assumed to be faster under the first drive condition than under the second drive condition. While FIG. 23 illustrates the state in which the first switching element changes from non-conductive to conductive under the first and second drive conditions, similar diagrams can also be used to illustrate the case in which the first switching element changes from conductive to non-conductive under the first and second drive conditions.

[0055] 23 , when the first switching element changes from conductive to non-conductive or from non-conductive to conductive under a first drive condition, the time until the state quantity indicating the conductive state of the first switching element reaches a specified threshold is defined as a first time t1. Also, when the first switching element changes from conductive to non-conductive or from non-conductive to conductive under a second drive condition, the time until the state quantity indicating the conductive state of the first switching element reaches a threshold is defined as a second time t2.

[0056] In this case, when the first switching element is being driven under the first drive condition, the power conversion device 1 acquires the detection value of the current detector after the first time t1 has elapsed from the time marking the start of the first time t1 and after a specified third time t3 has elapsed. That is, when the first switching element is a switching element mounted on the inverter 310, the control unit 400 of the power conversion device 1 acquires the current value detected by the state quantity detection unit 504 after the first time t1 and the third time t3 have elapsed. Similarly, when the first switching element is being driven under the second drive condition, the power conversion device 1 acquires the detection value of the current detector after the second time t2 has elapsed from the time marking the start of the second time t2 and after a specified fourth time t4 has elapsed. That is, when the first switching element is a switching element mounted on the inverter 310, the control unit 400 of the power conversion device 1 acquires the current value detected by the state quantity detection unit 504 after the second time t2 and the fourth time t4 have elapsed. As shown in FIG. 23, the first time t1 is shorter than the second time t2, and the third time t3 is longer than the fourth time t4.

[0057] 24 is a second diagram showing the relationship between the switching speed of the switching elements and the current detection timing in the power conversion device 1 according to the first embodiment. In the example of FIG. 24, the power conversion device 1 includes at least a first switching element and a second switching element as switching elements in the same power converter. The upper part of FIG. 24(a) shows state quantities indicating the operating state of the first switching element when the first switching element changes from non-conductive to conductive under the first drive condition. The middle part of FIG. 24(a) shows state quantities indicating the operating state of the second switching element when the second switching element changes from non-conductive to conductive under the first drive condition. The lower part of FIG. 24(a) shows the detection value, i.e., the current value, detected by the state quantity detection unit, which is a current detector, when the first switching element changes from non-conductive to conductive under the first drive condition. Moreover, the upper part of FIG. 24(b) shows the state quantities indicating the operating state of the first switching element when the first switching element changes from non-conducting to conducting under the second drive condition, the middle part of FIG. 24(b) shows the state quantities indicating the operating state of the second switching element when the second switching element changes from non-conducting to conducting under the second drive condition, and the lower part of FIG. 24(b) shows the detection value, i.e., the current value, detected by the state quantity detection unit, which is a current detector, when the first switching element changes from non-conducting to conducting under the second drive condition.

[0058] The state quantities indicating the operating states of the first switching element and the second switching element may be any quantity that can indicate the operating states of the first switching element and the second switching element, and may be voltage or current values ​​detectable by a state quantity detection unit, drive signals for driving the first switching element and the second switching element, or command values ​​used within the control unit 400 to generate the drive signals. The first switching element and the second switching element are any of the switching elements Up, Un, Vp, Vn, Wp, and Wn described above, i.e., any of the switching elements 311a to 311f. The first and second driving conditions indicate the difference in the switching speed of the first switching element, and here, it is assumed that the switching speed of the first switching element is faster under the first driving condition than under the second driving condition. Furthermore, although Figure 24 shows the state in which the first switching element and the second switching element change from non-conductive to conductive under the first drive condition and the second drive condition, a similar diagram can also be used to show the case in which the first switching element and the second switching element change from conductive to non-conductive under the first drive condition and the second drive condition.

[0059] 24 , when the first switching element changes from conductive to non-conductive or from non-conductive to conductive under the first drive condition, the time until the state quantity indicating the conductive state of the first switching element reaches a specified threshold is designated as a fifth time t5. Furthermore, the time from when the first switching element changes from conductive to non-conductive or from non-conductive to conductive under the first drive condition to when the second switching element next starts to change from conductive to non-conductive or from non-conductive to conductive under the first drive condition is designated as a sixth time t6. Furthermore, when the first switching element changes from conductive to non-conductive or from non-conductive to conductive under the second drive condition, the time until the state quantity indicating the conductive state of the first switching element reaches a threshold is designated as a seventh time t7. Furthermore, the time from when the first switching element changes from conductive to non-conductive or from non-conductive to conductive under the second drive condition to when the second switching element next begins to change from conductive to non-conductive or from non-conductive to conductive under the second drive condition is defined as an eighth time t8.

[0060] In this case, when the first switching element and the second switching element are being driven under the first drive condition, the power conversion device 1 acquires the detection value of the current detector after the fifth time t5 has elapsed from the time marking the start of the fifth time t5 and after a specified ninth time t9 has elapsed. That is, when the first switching element is a switching element mounted on the inverter 310, the control unit 400 of the power conversion device 1 acquires the current value detected by the state quantity detection unit 504 after the fifth time t5 and the ninth time t9 have elapsed. Similarly, when the first switching element and the second switching element are being driven under the second drive condition, the power conversion device 1 acquires the detection value of the current detector after the seventh time t7 has elapsed from the time marking the start of the seventh time t7 and after a specified tenth time t10 has elapsed. That is, when the first switching element is a switching element mounted on the inverter 310, the control unit 400 of the power conversion device 1 acquires the current value detected by the state quantity detection unit 504 after the seventh time t7 and the tenth time t10 have elapsed. As shown in FIG. 24 , the sixth time t6 and the eighth time t8 are the same, or the error between the sixth time t6 and the eighth time t8 is within a specified tolerance range. The specified tolerance range can be defined by a value corresponding to the length of the sixth time t6, the eighth time t8, etc., such as a ratio, but is not limited thereto. Furthermore, the ninth time t9 is shorter than the sixth time t6 and the eighth time t8, the tenth time t10 is shorter than the ninth time t9, and the seventh time t7 is longer than the fifth time t5.

[0061] In this way, by changing the waiting time before current detection depending on the switching speed of the switching elements, the power conversion device 1 can accurately detect current, i.e., acquire the current value, even when control is performed in which the switching speed of the switching elements changes. For example, in consideration of the command values ​​of each phase corresponding to each switching element, if the period from when one switching element becomes conductive or non-conductive until when another switching element becomes conductive or non-conductive is short, the power conversion device 1 can ensure time for current detection by slowing down the switching speed of the switching element to suppress the occurrence of surges, ringing, etc.

[0062] 25A to 25C are diagrams illustrating an example of the switching states of switching elements and the voltages detected by the shunt resistors used in the current detectors when the switching speed of the switching elements is changed in the power conversion device 1 according to the first embodiment. FIGS. 25A, 25B, and 25C illustrate the switching states of a certain switching element and the voltages detected by the shunt resistors when the switching state of the certain switching element changes. The faster the switching state changes, the faster the switching speed. Therefore, as shown in FIG. 25, the switching speed of the switching elements increases from FIG. 25A to FIG. 25C. The shunt resistor voltage fluctuates due to influences such as surges and ringing immediately after switching of the switching element. The faster the switching speed, i.e., the faster the switching speed, i.e., the faster the switching speed, i.e., the faster the switching speed, and the longer the time until convergence.

[0063] Fig. 26 is a diagram showing the amplitude and convergence time of surges, ringing, and the like that occur when switching elements of the power conversion device 1 according to embodiment 1 are switched. In Fig. 26, the horizontal axis represents the switching speed of the switching elements, the left vertical axis represents the amplitude of surges, ringing, and the like, and the right vertical axis represents the convergence time of surges, ringing, and the like. Also, in Fig. 26, the graphs indicated by circles represent the amplitude of surges, ringing, and the like, and the graphs indicated by squares represent the convergence time of surges, ringing, and the like. The graph shown in Fig. 26 is based on actual measurements and therefore contains errors. However, in reality, the faster the switching speed, i.e., toward the right side of Fig. 26, the larger the amplitude of surges, ringing, and the like, and the longer the time it takes for surges, ringing, and the like to converge.

[0064] Next, the time until the detection value of the current detector is acquired, which is the time during which the power conversion device 1 waits, taking into consideration surges, ringing, etc. that occur due to the switching of the switching elements, will be described. The time until the detection value of the current detector is acquired by the power conversion device 1 is indicated by the third time t3 and the fourth time t4 shown in FIG. 23, and the ninth time t9 and the tenth time t10 shown in FIG. 24, but all of these can be explained using the same concept, so the third time t3 will be used as an example below. FIG. 27 is a diagram showing an example of the carrier frequency of a carrier signal used in controlling the inverter 310 of the power conversion device 1 according to the first embodiment. The triangular wave shown in FIG. 27 is the carrier signal, and as shown in FIG. 27, the carrier frequency of the carrier signal is set to f １ 27, the U-phase command value is a command value for driving a switching element corresponding to the U-phase of the motor 314, the V-phase command value is a command value for driving a switching element corresponding to the V-phase of the motor 314, and the W-phase command value is a command value for driving a switching element corresponding to the W-phase of the motor 314. Here, the current detectable ratio P ｎ is defined by equation (1).

[0065]

[0066] Current detectable ratio P ｎ 28 is a diagram showing a schematic enlargement of a part of FIG. 27. In FIG. 28, the U-phase command value, V-phase command value, and W-phase command value are actually sine waves as shown in FIG. 27, but are shown as straight lines because the horizontal time axis is enlarged compared to FIG. 27. For the same reason, in FIG. 28, the carrier signal is shown so that its magnitude changes for each clock cycle. As shown in FIG. 28, the pulse width from the timing when the command value of a certain first phase and the carrier signal intersect to the timing when the command value of another second phase and the carrier signal intersect is defined as pulse width T １ The pulse width from the timing when the command value of the second phase and the carrier signal intersect to the timing when the command value of the third phase intersects with the carrier signal is defined as pulse width T ２ Pulse width T １ and pulse width T ２ Both of these have a predefined minimum pulse width T ｓｈａｎｔ If the current is greater than or equal to the value of x, it is determined that the current can be detected using a shunt resistor in the power conversion device 1. ｎ = 1. Pulse width T １ and pulse width T ２ At least one of the minimum pulse widths T ｓｈａｎｔ If the current is less than x, it is determined that current detection using a shunt resistor is not possible in the power conversion device 1. ｎ 28 only shows a part of the 360-degree period of the command value for each phase, similar determination is made within the range of 0 to 360 degrees, and the current detectable ratio P ｎ is calculated using equation (1). The range of 0 to 360 degrees is represented by N in equation (1). As an example, as shown in FIG. 27, the amplitude of the command value for each phase is set to 0.1, and the amplitude of the carrier signal, i.e., the maximum value, is set to 1.0.

[0067] In this embodiment, the current detectable ratio P is determined by the length of the current detection waiting time with respect to the carrier frequency of the carrier signal used in the control of the inverter 310. ｎ29 shows the relationship between the carrier frequency of the carrier signal used to control the inverter 310 in the power conversion device 1 according to the first embodiment and the current detectable ratio P calculated from the equation (1). ｎ 29 shows an example of the relationship between the current detection waiting time and the switching speed of the switching element. ｎ is 0, that is, the carrier frequency at which the current cannot be detected and motor control becomes impossible is plotted as shown in FIG.

[0068] FIG. 30 is a diagram showing an example of the relationship between the carrier frequency of the carrier signal used in the control of the inverter 310 in the power conversion device 1 according to the first embodiment and the maximum current detection wait time. FIG. 30 is a diagram showing the maximum current detection wait time for each carrier frequency. In the power conversion device 1, if the current detection wait time is shorter than the maximum current detection wait time shown in FIG. 30, current detection is possible even at the corresponding carrier frequency, and motor control can be achieved. Calculating the linear approximation of the curve shown in FIG. 30 gives y = -0.0008x + 8.413, as shown in FIG. 30, and therefore the power conversion device 1 performs motor control with a current detection wait time that satisfies this linear approximation. That is, in the power conversion device 1, the carrier frequency of the carrier signal used in the switching control of the switching elements is set to f １ Then, if the third time is t3, then t3<{f １ × (−0.0008) + 8.413} × 10 －６ It is sufficient that the first time t1, i.e., the switching speed of the switching element, is adjusted so as to satisfy the formula. In this way, even when the switching speed of the switching element is increased, the power conversion device 1 keeps the current detection wait time, i.e., the third time t3, within a certain value range. This allows the power conversion device 1 to achieve stable current detection in motor control.

[0069] The command values ​​for each phase are the same as those used in a general power conversion device that controls a motor. In the present embodiment, the basic pulse generating unit 410 and the waveform shape setting unit 420 of the control unit 400 may also use the command values. That is, the power conversion device 1 includes the control unit 400 that controls the waveform shape of the switching waveform of the switching element in accordance with the command value for each phase. In the power conversion device 1, the waveform shape of the switching waveform of the switching element is changed in accordance with the magnitude of the command value. Since the control unit 400 knows the command value, the power conversion device 1 can suppress surges, ringing, and the like caused by switching of the switching element by, for example, slowing down the switching speed of the switching element when the command value is small.

[0070] In the present embodiment, the power conversion device 1 includes at least one power converter, specifically the inverter 310, among the one or more power converters that perform power conversion. The inverter 310 has at least three output phases, with at least one switching element for each phase. When the switching elements of each phase sequentially change from conductive to non-conductive or from non-conductive to conductive, the power conversion device 1 controls the switching waveform of the switching element that changes first, second, and third, so that the waveform shape of the switching waveform of the switching element that changes second is different from the waveform shapes of the switching waveform of the switching element that changes first and the switching waveform of the switching element that changes third. For example, the power conversion device 1 slows the switching speed of the switching elements of only the middle phase in the three-phase inverter 310. In this way, the power conversion device 1 can minimize the increase in loss by controlling the switching speed of only the switching elements of the middle phase, whereas slowing the switching speed of the switching elements of all phases would result in excessive loss. In addition, since the inverter 310 has at least three phases as output phases and has at least one switching element for each phase, it is also applicable to a case where the inverter 310 is a four-phase inverter and has eight switching elements, for example.

[0071] 31 is a flowchart showing an operation of changing the waveform shapes of the switching waveforms of the switching elements 311a to 311f in the power conversion device 1 according to the first embodiment. In the power conversion device 1, the basic pulse generation unit 410 generates basic pulses for driving the switching elements 311a to 311f of the inverter 310 based on the state quantities acquired from the state quantity detection units 501 to 505 (step S1). As described above, in the control unit 400, the basic pulse generation unit 410 generates basic pulses based on the state quantities acquired from the state quantity detection units 501 to 505, and determines the timings for turning on and off the switching elements 311a to 311f. The basic pulse generation unit 410 outputs the generated basic pulses to the waveform shape setting unit 420.

[0072] The waveform shape setting unit 420 sets a waveform shape for changing the waveform shape of the switching waveform of the switching elements 311a to 311f of the inverter 310, based on the basic pulse obtained from the basic pulse generating unit 410 and the state quantities obtained from the state quantity detecting units 501 to 505. As described above, in the control unit 400, the waveform shape setting unit 420 sets the waveform shapes of the switching waveforms at the timings for turning on and off the switching elements 311a to 311f determined by the basic pulse generating unit 410, based on the state quantities obtained from the state quantity detecting units 501 to 505. The waveform shape setting unit 420 outputs a control signal to the waveform shape changing unit 340, which can change the magnitude and output timing of the drive signal in accordance with the set waveform shape, i.e., the set value of the waveform shape (step S2).

[0073] The waveform shape changing unit 340 changes the gate current I Ｇ The waveform shape of the gate current I after the waveform shape change is performed is changed based on the control signal obtained from the waveform shape setting unit 420 (step S3). Ｇ are output to the switching elements 311 a to 311 f of the inverter 310 .

[0074] Next, a description will be given of the hardware configuration of the control unit 400 included in the power conversion device 1. Fig. 32 is a diagram showing an example of a hardware configuration that realizes the control unit 400 included in the power conversion device 1 according to embodiment 1. The control unit 400 is realized by a processor 91 and a memory 92.

[0075] The processor 91 is a CPU (Central Processing Unit, also called a central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, or DSP (Digital Signal Processor)) or a system LSI (Large Scale Integration). Examples of memory 92 include non-volatile or volatile semiconductor memories such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), and EEPROM (Electrically Erasable Programmable Read Only Memory). Memory 92 is not limited to these, and may also be a magnetic disk, optical disk, compact disk, minidisc, or DVD (Digital Versatile Disc).

[0076] As described above, according to this embodiment, in the power conversion device 1, the waveform shape setting unit 420 of the control unit 400 outputs a control signal for reflecting a set value when the waveform shape changing unit 340 of the inverter 310 changes the switching waveforms of the switching elements 311a to 311f, in accordance with the state quantities detected by the state quantity detection units 501 to 505. The waveform shape changing unit 340 of the inverter 310 determines the gate current I to be output to the switching elements 311a to 311f based on the control signal output from the waveform shape setting unit 420. Ｇ or gate voltage V ＧBy changing the gate current I to be output to the switching elements 311a to 311f in one switching period, the waveform shapes of the switching waveforms of the switching elements 311a to 311f are changed. This allows the power conversion device 1 to change the switching speed of the switching elements 311a to 311f while suppressing an increase in the circuit size. Ｇ or gate voltage V Ｇ By finely adjusting the values, it is possible to realize a desired waveform shape for the switching waveforms of the switching elements 311a to 311f.

[0077] Furthermore, since the magnitude and convergence time of surges, ringing, etc. generated by switching of the switching elements differ depending on the switching speed of the switching elements, when measuring the current flowing through the switching elements, the power conversion device 1 appropriately changes the current detection wait time depending on the switching speed of the switching elements, thereby enabling the power conversion device 1 to improve the current detection accuracy.

[0078] Embodiment 2 In the first embodiment, a case has been described in which the set value of the waveform shape of the switching waveform of the switching elements 311a to 311f of the inverter 310 is changed in the power conversion device 1. In the second embodiment, a case will be described in which the set value of the waveform shape of the switching waveform of the switching element 136 of the converter 130 is changed in the power conversion device 1.

[0079] 33 is a diagram showing a configuration example of a power conversion device 1 according to embodiment 2. The power conversion device 1 is connected to a commercial power supply 110 and a motor 314. The power conversion device 1 converts a first AC voltage of a power supply voltage Vs supplied from the commercial power supply 110, which is an AC power supply, into a second AC voltage having a desired amplitude and phase, and supplies the second AC voltage to the motor 314. The power conversion device 1 includes a state quantity detection unit 501, a converter 130, a capacitor 210, a state quantity detection unit 502, an inverter 310, a state quantity detection unit 503, a state quantity detection unit 504, a state quantity detection unit 505, and a control unit 400. The power conversion device 1 and the motor 314 constitute a motor drive device 2.

[0080] The power conversion device 1 of the second embodiment shown in FIG. 33 is configured by removing the waveform shape modification unit 340 from the inverter 310 and adding a drive circuit 350, and by removing the drive circuit 150 from the converter 130 and adding a waveform shape modification unit 140. The power conversion device 1 of the second embodiment shown in FIG. 33 also differs from the power conversion device 1 of the first embodiment shown in FIG. 1 in that the output destinations of the basic pulse generation unit 410 and the waveform shape setting unit 420 are changed. Specifically, the basic pulse generation unit 410 outputs a basic pulse to the waveform shape setting unit 420 for controlling the operation of the switching element 136 of the converter 130, and outputs a basic pulse to the inverter 310 for controlling the operation of the switching elements 311a to 311f of the inverter 310. The waveform shape setting unit 420 also outputs a control signal to the waveform shape modification unit 140 for controlling the operation of the waveform shape modification unit 140.

[0081] In the inverter 310, the drive circuit 350 generates drive signals for actually driving the switching elements 311a to 311f based on the basic pulses generated by the basic pulse generating section 410 of the control section 400.

[0082] In this embodiment, the waveform shape setting unit 420 sets the waveform shape of the switching waveform of the switching element 136 when the waveform shape changing unit 140 of the converter 130 changes the switching waveform of the switching element 136 in accordance with the state quantities detected by the state quantity detection units 501 to 505, and outputs a control signal for reflecting a setting value indicating the set waveform shape. Specifically, when the switching element 136 is turned on and off based on the basic pulse for controlling the operation of the switching element 136 of the converter 130 generated by the basic pulse generation unit 410, the waveform shape setting unit 420 controls the magnitude of the drive signal that the waveform shape changing unit 140 of the converter 130 outputs to the switching element 136 to actually drive the switching element 136, and the timing at which the drive signal is output. The waveform shape setting unit 420 outputs a control signal for controlling the operation of the waveform shape changing unit 140 to the waveform shape changing unit 140.

[0083] The waveform shape modification unit 140 can change the waveform shape of the switching waveform of the switching element 136 without physically switching a gate resistor or the like. The waveform shape modification unit 140 can output two or more waveform shapes as the waveform shape of the switching waveform of the switching element 136. As shown in FIG. 33 , the waveform shape modification unit 140 is included in a converter 130, which is a power converter including the switching element 136. The configuration of the waveform shape modification unit 140 is the same as the configuration of the waveform shape modification unit 340 of the first embodiment shown in FIG. 12 . That is, the waveform shape modification unit 140 and the switching element 136 are configured by one digital gate driver module. As with the waveform shape modification unit 340, the waveform shape modification unit 140 also outputs the gate current I to the switching element 136 as a drive signal. Ｇ Instead, the gate voltage V output to the switching element 136 Ｇ may be adjusted.

[0084] In this way, the waveform shape changing unit 140 divides at least one of the turn-on period and the turn-off period of the switching element 136 into two or more periods based on the control signal output from the waveform shape setting unit 420, and determines the gate current I for the switching element 136 in each divided period. Ｇ or gate voltage V Ｇ The waveform shape changing section 140 includes a plurality of transistors, and by changing the number of transistors to be operated based on the control signal output from the waveform shape setting section 420, the amplitude of the gate current I Ｇ or gate voltage V Ｇ As a result, the power conversion device 1 performs the same operation as in the first embodiment, and thereby the waveform shape setting unit 420 and the waveform shape changing unit 140 can change the waveform shape of the switching waveform of the switching element 136 of the converter 130.

[0085] In the present embodiment, the power conversion device 1 can adjust noise and loss generated in the switching element 136 by changing a setting value of the waveform shape of the switching waveform of the switching element 136 mounted on the converter 130. For example, the waveform shape change unit 140 changes the switching waveform of the switching element 136 in accordance with a state quantity correlated with any of the current flowing through the converter 130, the current flowing from the commercial power supply 110, or the second DC voltage, based on the control signal. As a result, even under conditions in which the bus voltage Vdc is high, the power conversion device 1 can suppress an increase in noise and loss generated in the switching element 136 by changing the waveform shape of the switching waveform of the switching element 136. Specifically, the power conversion device 1 operates to suppress loss generated in the switching element 136 under light load conditions and to suppress loss generated in the switching element 136 under heavy load conditions, thereby contributing to an improvement in the annual performance factor (APF) and value engineering (VE) by reducing noise countermeasure costs.

[0086] As described above, according to this embodiment, in the power conversion device 1, the waveform shape setting unit 420 of the control unit 400 outputs a control signal for reflecting a set value when the waveform shape changing unit 140 of the converter 130 changes the switching waveform of the switching element 136, in accordance with the state quantities detected by the state quantity detection units 501 to 505. The waveform shape changing unit 140 of the converter 130 determines the gate current I to be output to the switching element 136 based on the control signal output from the waveform shape setting unit 420. Ｇ or gate voltage V ＧThe waveform shape change unit 140 can change the waveform shape of the switching waveform of the switching element 136 in the same way that the waveform shape change unit 340 of the first embodiment changes the waveform shape of the switching waveform of the switching element 311a. This allows the power conversion device 1 to change the switching speed of the switching element 136 while suppressing an increase in circuit size. The power conversion device 1 changes the gate current I Ｇ or gate voltage V Ｇ By finely adjusting the value of the switching waveform of the switching element 136, a desired waveform shape can be achieved.

[0087] In this embodiment, the configuration of converter 130 for which the waveform shapes of the switching elements are changed is not limited to the example in FIG. 33 . In this embodiment, the configuration of converter 130 for which the waveform shapes of the switching elements are changed can also be applied to the configurations of converter 130 shown in FIGS. 2 to 6 . In the example of FIG. 2 , waveform shape change unit 140 changes the waveform shapes of the switching waveforms of switching elements 136 a and 136 b; in the example of FIG. 3 , it changes the waveform shapes of the switching waveforms of switching elements 136 b and 136 d; in the example of FIG. 4 , it changes the waveform shapes of the switching waveforms of switching elements 136 a to 136 d; in the example of FIG. 5 , it changes the waveform shapes of the switching waveforms of switching elements 136 a and 136 b; and in the example of FIG. 6 , it changes the waveform shape of the switching waveform of switching element 136. The same applies to the embodiments described below.

[0088] Furthermore, in this embodiment, the waveform shape of the switching waveform of the switching element included in converter 130 can be changed, and therefore, when detecting a current with state quantity detection unit 501, power conversion device 1 can appropriately change the current detection wait time in accordance with the switching speed of the switching element included in converter 130. This allows power conversion device 1 to improve the current detection accuracy, similar to the case of changing the switching speed of the switching element of inverter 310 in embodiment 1.

[0089] 2 to 6, the power conversion device 1 includes a control unit 400 that controls the waveform shape of the switching waveform of the switching element in accordance with a command value for each phase when the power conversion device 1 is configured to include a switching element for each input phase of the converter. In the power conversion device 1, the waveform shape of the switching waveform of the switching element is changed in accordance with the magnitude of the command value.

[0090] Furthermore, when the commercial power supply 110 is a three-phase AC power supply, in the power conversion device 1, at least one of the one or more power converters that perform power conversion, specifically, the converter 130, has at least three phases as input phases and includes at least one switching element for each phase. When the switching elements of each phase change sequentially from conductive to non-conductive or from non-conductive to conductive, the power conversion device 1 makes the waveform shape of the switching waveform of the switching element that changes first, second, and third different from the waveform shapes of the switching waveform of the switching element that changes first and the switching element that changes third. For example, when the converter 130 is a three-phase converter, the power conversion device 1 slows down the switching speed of the switching elements only in the intermediate phase. As a result, in the power conversion device 1, when controlling to slow down the switching speed of the switching elements of the converter 130, slowing down the switching speed of the switching elements of all phases would result in excessive increase in losses, but by controlling to slow down the switching speed of only the switching elements of the middle phase, it is possible to minimize the deterioration of losses.

[0091] Embodiment 3. In the first embodiment, a case has been described in which the set value of the waveform shape of the switching waveform of the switching elements 311a to 311f of the inverter 310 is changed in the power conversion device 1. In the second embodiment, a case has been described in which the set value of the waveform shape of the switching waveform of the switching element 136 of the converter 130 is changed in the power conversion device 1. In the third embodiment, a case will be described in which the set value of the waveform shape of the switching waveform of the switching elements 311a to 311f of the inverter 310 is changed and the set value of the waveform shape of the switching waveform of the switching element 136 of the converter 130 is changed in the power conversion device 1.

[0092] 34 is a diagram showing a configuration example of a power conversion device 1 according to a third embodiment. The power conversion device 1 is connected to a commercial power supply 110 and a motor 314. The power conversion device 1 converts a first AC voltage of a power supply voltage Vs supplied from the commercial power supply 110, which is an AC power supply, into a second AC voltage having a desired amplitude and phase, and supplies the second AC voltage to the motor 314. The power conversion device 1 includes a state quantity detection unit 501, a converter 130, a capacitor 210, a state quantity detection unit 502, an inverter 310, a state quantity detection unit 503, a state quantity detection unit 504, a state quantity detection unit 505, and a control unit 400. The power conversion device 1 and the motor 314 constitute a motor drive device 2.

[0093] The power conversion device 1 of the third embodiment shown in FIG. 34 is configured by removing the drive circuit 150 from the converter 130 and adding a waveform shape modification unit 140 to the power conversion device 1 of the first embodiment shown in FIG. 1 . Furthermore, the power conversion device 1 of the third embodiment shown in FIG. 34 has output destinations of the basic pulse generation unit 410 and the waveform shape setting unit 420 changed from those of the power conversion device 1 of the first embodiment shown in FIG. 1 . Specifically, the basic pulse generation unit 410 outputs a basic pulse to the waveform shape setting unit 420 for controlling the operation of the switching elements 311a to 311f of the inverter 310, and outputs a basic pulse to the waveform shape setting unit 420 for controlling the operation of the switching element 136 of the converter 130. Furthermore, the waveform shape setting unit 420 outputs a control signal to the waveform shape modification unit 340 for controlling the operation of the waveform shape modification unit 340, and outputs a control signal to the waveform shape modification unit 140 for controlling the operation of the waveform shape modification unit 140.

[0094] In the present embodiment, the waveform shape setting unit 420 performs the operation described in the first embodiment as well as the operation described in the second embodiment. Furthermore, in the present embodiment, the waveform shape changing unit 340 performs the same operation as that described in the first embodiment, and the waveform shape changing unit 140 performs the same operation as that described in the second embodiment. As a result, the power conversion device 1 performs the same operation as in the first embodiment, thereby being able to change the waveform shapes of the switching waveforms of the switching elements 311a to 311f of the inverter 310 by the waveform shape setting unit 420 and the waveform shape changing unit 340. Furthermore, the power conversion device 1 performs the same operation as in the second embodiment, thereby being able to change the waveform shape of the switching waveform of the switching element 136 of the converter 130 by the waveform shape setting unit 420 and the waveform shape changing unit 140.

[0095] For example, if the noise caused by the inverter 310 exceeds a prescribed noise standard, the power conversion device 1 can reduce the noise caused by the inverter 310 by having the waveform shape modification unit 340 slow down the switching speed of the switching elements 311a to 311f mounted on the inverter 310, but this increases the loss in the inverter 310. In such a case, the power conversion device 1 can adjust the total loss of the power conversion device 1 by having the waveform shape modification unit 140 speed up the switching speed of the switching element 136 mounted on the converter 130. Furthermore, when it is desired to improve the APF, the power conversion device 1 can easily achieve the effect of improving loss by increasing the switching speed of the switching element 136 of the converter 130, which has a high carrier frequency. This is because, due to the high carrier frequency, the number of switching times of the switching elements 136 of the converter 130 is greater than the number of switching times of the switching elements 311a to 311f of the inverter 310. In this way, the power conversion device 1 optimizes the total noise and loss as the power conversion device 1 by taking into account the noise and loss generated in the switching element 136 of the converter 130 and the noise and loss generated in the switching elements 311a to 311f of the inverter 310, thereby contributing to the improvement of APF and the VE by reducing the cost of noise countermeasures.

[0096] Furthermore, in this embodiment, power conversion device 1 includes switching elements in at least one of converter 130 and inverter 310, and can adjust noise and loss generated by the switching elements by changing the set values ​​of the waveform shapes of the switching waveforms of the switching elements. For example, waveform shape modification unit 340 changes the switching waveforms of switching elements 311a to 311f in accordance with a state quantity correlated with the second DC voltage based on a control signal. Furthermore, waveform shape modification unit 140 changes the switching waveform of switching element 136 in accordance with a state quantity correlated with either the current flowing through converter 130, the current flowing from commercial power supply 110, or the second DC voltage based on the control signal. As a result, power conversion device 1 can suppress increases in noise and loss generated by switching elements 311a to 311f, switching element 136, etc., by changing the waveform shapes of the switching waveforms of switching elements 311a to 311f, switching element 136, etc., even under conditions where bus voltage Vdc is high.

[0097] In this embodiment, the power conversion device 1 can also perform control such that at a certain timing, one of the waveform shape modification units 140, 340 changes the waveform shape of the switching waveform of the switching element, while the other does not change the waveform shape of the switching waveform of the switching element. In this embodiment, the switching elements whose switching waveforms are changed by the waveform shape modification units 140, 340 of the power conversion device 1 are one or more switching elements included in at least one of the one or more power converters that perform power conversion in the power conversion device 1.

[0098] As described above, according to this embodiment, in the power conversion device 1, the waveform shape setting unit 420 of the control unit 400 outputs a control signal for reflecting a set value when the waveform shape changing unit 340 of the inverter 310 changes the switching waveform of the switching elements 311a to 311f, in accordance with the state quantities detected by the state quantity detection units 501 to 505, and outputs a control signal for reflecting a set value when the waveform shape changing unit 140 of the converter 130 changes the switching waveform of the switching element 136. The waveform shape changing unit 340 of the inverter 310 determines the gate current I to be output to the switching elements 311a to 311f based on the control signal output from the waveform shape setting unit 420. Ｇ or gate voltage V Ｇ The waveform shape changing unit 140 of the converter 130 changes the waveform shape of the switching waveform of the switching elements 311a to 311f based on the control signal output from the waveform shape setting unit 420. Ｇ or gate voltage V Ｇ By changing the gate current I , the waveform shape of the switching waveform of the switching element 136 is changed. This allows the power conversion device 1 to change the switching speed of the switching elements 311a to 311f and the switching element 136 while suppressing an increase in circuit size. The power conversion device 1 changes the gate current I , which is output to the switching elements 311a to 311f and the switching element 136 in one switching period. Ｇ or gate voltage V Ｇ By finely adjusting the values, it is possible to realize a desired waveform shape for the switching waveforms of the switching elements 311a to 311f and the switching element 136.

[0099] Furthermore, in this embodiment, the waveform shapes of the switching waveforms of the switching elements 311a to 311f included in the inverter 310 are changeable, and the waveform shape of the switching waveform of the switching element 136 included in the converter 130 is changeable, so that when the state quantity detection unit 504 detects a current, the power conversion device 1 can change the current detection wait time as appropriate in accordance with the switching speed of the switching elements 311a to 311f included in the inverter 310, and when the state quantity detection unit 501 detects a current, the power conversion device 1 can change the current detection wait time as appropriate in accordance with the switching speed of the switching element 136 included in the converter 130. This allows the power conversion device 1 to achieve the same effects as those of the first and second embodiments.

[0100] In the present embodiment, the power conversion device 1 includes a control unit 400 having the functions described in the first and second embodiments. In the power conversion device 1, the waveform shape of the switching waveform of the switching element is changed according to the magnitude of the command value.

[0101] In the power conversion device 1, at least one of the one or more power converters that perform power conversion has at least three phases as input phases or output phases, and includes at least one switching element for each phase. When the switching elements of each phase change sequentially from conductive to non-conductive or from non-conductive to conductive, the power conversion device 1 makes the waveform shape of the switching waveform of the switching element that changes first, second, and third different from the waveform shapes of the switching waveform of the switching element that changes first and third different. As a result, in controlling the switching speed of the switching elements of the power converter to slow down, slowing the switching speed of the switching elements of all phases would result in excessive increases in losses. However, by controlling to slow down only the switching speed of the switching elements of the middle phases, it is possible to minimize the deterioration of losses.

[0102] Fourth Embodiment In a fourth embodiment, a case will be described in which the waveform setting section 420 and the waveform modification sections 140 and 340 transmit and receive control signals via a signal transmission / reception section.

[0103] FIG. 35 is a diagram illustrating a configuration example of a power conversion device 1 according to a fourth embodiment. The power conversion device 1 illustrated in FIG. 35 is obtained by adding signal transmitter / receivers 141, 341, and 421 to the power conversion device 1 according to the third embodiment illustrated in FIG. 34 . The signal transmitter / receiver 141 is arranged in the converter 130. The signal transmitter / receiver 341 is arranged in the inverter 310. The signal transmitter / receiver 421 is arranged in the control unit 400. The signal transmitter / receiver 421 acquires a control signal output from the waveform shape setting unit 420, transmits a control signal for controlling the operation of the waveform shape modification unit 140 to the signal transmitter / receiver 141 arranged in the converter 130, and transmits a control signal for controlling the operation of the waveform shape modification unit 340 to the signal transmitter / receiver 341 arranged in the inverter 310. The signal transmitter / receiver 141 outputs the control signal received from the signal transmitter / receiver 421 arranged in the control unit 400 to the waveform shape modification unit 140. The signal transmitting / receiving unit 341 outputs the control signal received from the signal transmitting / receiving unit 421 arranged in the control unit 400 to the waveform shape modifying unit 340. The operation of the waveform shape modifying units 140 and 340 that have received the control signal is as described above.

[0104] When the waveform shape modification unit 140 is capable of generating a signal such as a control signal for the waveform shape setting unit 420, the signal transmission / reception unit 141 can transmit a control signal acquired from the waveform shape modification unit 140 to the signal transmission / reception unit 421. The control signal for the waveform shape setting unit 420 generated by the waveform shape modification unit 140 is, for example, a signal indicating whether the waveform shape modification unit 140, the switching element 136, etc. are operating normally, but is not limited to this. The signal transmission / reception unit 421 outputs the control signal received from the signal transmission / reception unit 141 to the waveform shape setting unit 420. Similarly, when the waveform shape modification unit 340 is capable of generating a signal such as a control signal for the waveform shape setting unit 420, the signal transmission / reception unit 341 can transmit a control signal acquired from the waveform shape modification unit 340 to the signal transmission / reception unit 421. The control signal for the waveform shape setting unit 420 generated by the waveform shape modification unit 340 is, for example, a signal indicating whether the waveform shape modification unit 340, the switching elements 311a to 311f, etc. are operating normally, but is not limited to this. The signal transmitting / receiving unit 421 outputs the control signal received from the signal transmitting / receiving unit 341 to the waveform shape setting unit 420 .

[0105] Note that if the waveform shape modification section 140 does not generate a signal such as a control signal for the waveform shape setting section 420, the signal transmission / reception section 141 may not have a function to transmit a signal. Similarly, if the waveform shape modification section 340 does not generate a signal such as a control signal for the waveform shape setting section 420, the signal transmission / reception section 341 may not have a function to transmit a signal. If no signal is transmitted from the signal transmission / reception sections 141 and 341, the signal transmission / reception section 421 may not have a function to receive a signal.

[0106] In this way, the waveform shape setting unit 420 and the waveform shape modification unit 140 can also exchange control signals via the signal transmission / reception units 421 and 141. In addition, the waveform shape setting unit 420 and the waveform shape modification unit 340 can also exchange control signals via the signal transmission / reception units 421 and 341.

[0107] While the power conversion device 1 of the third embodiment shown in Fig. 34 has been described as an example, the present invention is not limited to this, and the signal transmitter / receiver unit can also be applied to the power conversion device 1 of the first and second embodiments. Although not shown, for example, in the power conversion device 1 of the first embodiment, signal transmitter / receivers 341 and 421 can be added, and control signals can be transmitted and received between the waveform shape setting unit 420 and the waveform shape changing unit 340 via the signal transmitter / receivers 421 and 341. Furthermore, in the power conversion device 1 of the second embodiment, signal transmitter / receivers 141 and 421 can be added, and control signals can be transmitted and received between the waveform shape setting unit 420 and the waveform shape changing unit 140 via the signal transmitter / receivers 421 and 141.

[0108] Fifth Embodiment Fig. 36 is a diagram showing a configuration example of a refrigeration cycle-applied apparatus 900 according to a fifth embodiment. The refrigeration cycle-applied apparatus 900 according to the fifth embodiment includes the power conversion device 1 described in the first embodiment. The refrigeration cycle-applied apparatus 900 according to the fifth embodiment can also include the power conversion device 1 described in any of the second to fourth embodiments. The refrigeration cycle-applied apparatus 900 according to the fifth embodiment can be applied to products equipped with a refrigeration cycle, such as air conditioners, refrigerators, freezers, and heat pump water heaters. In Fig. 36, components having the same functions as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

[0109] The refrigeration cycle application equipment 900 includes a compressor 315 incorporating the motor 314 in embodiment 1, a four-way valve 902, an indoor heat exchanger 906, an expansion valve 908, and an outdoor heat exchanger 910, which are attached via refrigerant piping 912.

[0110] Inside the compressor 315, a compression mechanism 904 that compresses the refrigerant and a motor 314 that operates the compression mechanism 904 are provided.

[0111] The refrigeration cycle device 900 can perform heating or cooling operation by switching the four-way valve 902. The compression mechanism 904 is driven by a motor 314 that is variably controlled in speed.

[0112] During heating operation, as shown by the solid arrow, the refrigerant is pressurized by the compression mechanism 904 and sent out, passes through the four-way valve 902, the indoor heat exchanger 906, the expansion valve 908, the outdoor heat exchanger 910 and the four-way valve 902 and returns to the compression mechanism 904.

[0113] During cooling operation, as shown by the dashed arrow, the refrigerant is pressurized by the compression mechanism 904 and sent out, and returns to the compression mechanism 904 through the four-way valve 902, the outdoor heat exchanger 910, the expansion valve 908, the indoor heat exchanger 906 and the four-way valve 902.

[0114] During heating operation, the indoor heat exchanger 906 acts as a condenser to release heat, and the outdoor heat exchanger 910 acts as an evaporator to absorb heat. During cooling operation, the outdoor heat exchanger 910 acts as a condenser to release heat, and the indoor heat exchanger 906 acts as an evaporator to absorb heat. The expansion valve 908 reduces the pressure of the refrigerant to expand it.

[0115] Even if the refrigeration cycle device 900 is operating within the specified noise range, when the load state of the motor 314 changes from a light load to a heavy load, the curve showing the characteristics of the noise and losses generated by the switching elements 311a to 311f, etc., shifts upward to the upper right as shown in FIG. 10 , resulting in an increase in noise. Therefore, the refrigeration cycle device 900 can reduce the noise generated by the switching elements 311a to 311f, etc., by slowing the switching speed of the switching elements 311a to 311f, etc. Similarly, even if the refrigeration cycle device 900 is operating within the specified loss range, when the load state of the motor 314 changes from a light load to a heavy load, the curve showing the characteristics of the noise and losses generated by the switching elements 311a to 311f, etc., shifts upward to the upper right as shown in FIG. 10 , resulting in an increase in loss. Therefore, the refrigeration cycle device 900 can reduce the losses generated by the switching elements 311a to 311f, etc., by increasing the switching speed of the switching elements 311a to 311f, etc.

[0116] In the power conversion device 1 included in the refrigeration cycle device 900, the digital gate driver module, which is composed of the waveform shape changing unit 340 and switching elements 311a to 311f included in the inverter 310, generates a large surge voltage and a lot of electromagnetic noise when the switching speed is fast. When the refrigeration cycle device 900 uses a flammable refrigerant, there is a possibility that the refrigerant may leak and burn due to discharge caused by electromagnetic noise. Therefore, the refrigeration cycle device 900 sets the switching speed of the digital gate driver module included in the power conversion device 1 according to the flammability of the refrigerant used in the refrigeration cycle device 900. For example, the refrigeration cycle device 900 slows the switching speed of the digital gate driver module included in the power conversion device 1 the more flammable the refrigerant used in the refrigeration cycle device 900 is. By slowing the switching speed of the digital gate driver module, the refrigeration cycle device 900 can reduce surge voltage and suppress discharge caused by electromagnetic noise, thereby preventing refrigerant from burning even if it leaks from the refrigeration cycle device 900.

[0117] The refrigerant used in the refrigeration cycle application equipment 900 is, for example, any one of R1234yf, R1234ze(E), R1243zf, HFO1123, HFO1132(E), R1132a, CF3I, and R290 as a single refrigerant, or a mixed refrigerant containing at least two of the aforementioned refrigerants.

[0118] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0119] 1 Power conversion device, 2 Motor drive device, 91 Processor, 92 Memory, 110 Commercial power supply, 130 Converter, 131 to 134, 131a to 134a Rectifying element, 135, 135a, 135b Reactor, 136, 136a to 136d, 311a to 311f Switching element, 137, 137a to 137d, 312a to 312f Freewheeling diode, 138, 138a, 138b Diode, 140, 340 Waveform shape change unit, 141, 341, 421 Signal transmitting / receiving unit, 150, 350 Drive circuit, 161 Rectifying unit, 162 Boost unit, 163 Rectifying / boosting unit, 210 Capacitor, 310 Inverter, 314 Motor, 315 Compressor, 400 Control unit, 410 basic pulse generation unit, 420 waveform shape setting unit, 501 to 505 state quantity detection units, 900 refrigeration cycle applied equipment, 902 four-way valve, 904 compression mechanism, 906 indoor heat exchanger, 908 expansion valve, 910 outdoor heat exchanger, 912 refrigerant piping.

Claims

1. A power conversion device that performs power conversion, comprising: one or more switching elements included in at least one of one or more power converters that perform power conversion; and a current detector that is arranged on a path of current flowing through the power converter, wherein the waveform shape of the pulsed current waveform detected by the current detector changes.

2. The power conversion device according to claim 1, wherein at least one of the one or more power converters performing power conversion has at least three phases as input phases or output phases and is equipped with at least one switching element for each phase, and when the switching elements of each phase change in sequence from conductive to non-conductive or from non-conductive to conductive, for the switching element that changes first, the switching element that changes second, and the switching element that changes third, the waveform shape of the switching waveform of the switching element that changes second is different from the waveform shape of the switching waveform of the switching element that changes first and the waveform shape of the switching waveform of the switching element that changes third.

3. A power conversion device as claimed in claim 1 or 2, comprising: a waveform shape changing unit capable of changing the waveform shape of a switching waveform of the switching element; and a waveform shape setting unit that outputs a control signal to reflect a setting value when the waveform shape changing unit changes the switching waveform of the switching element, wherein the waveform shape of the pulsed current waveform is changed by changing the waveform shape of the switching waveform of the switching element.

4. The power conversion device according to claim 1 or 2, further comprising: a control unit that controls a waveform shape of the switching waveform of the switching element in accordance with a command value for each phase, wherein the waveform shape of the switching waveform of the switching element is changed in accordance with the magnitude of the command value.

5. The power conversion device according to claim 2, wherein a first time is a time until a state quantity indicating a conductive state of the switching element reaches a specified threshold value when the switching element changes from conductive to non-conductive or from non-conductive to conductive under a first drive condition; a second time is a time until a state quantity indicating a conductive state of the switching element reaches the threshold value when the switching element changes from conductive to non-conductive or from non-conductive to conductive under a second drive condition; when the switching element is driven under the first drive condition, the detection value of the current detector is obtained after the first time has elapsed from a time marking the start of the first time and a further specified third time has elapsed; and when the switching element is driven under the second drive condition, the detection value of the current detector is obtained after the second time has elapsed from a time marking the start of the second time and a further specified fourth time has elapsed.

6. The power conversion device according to claim 5, wherein the first time period is shorter than the second time period, and the third time period is longer than the fourth time period.

7. The carrier frequency of the carrier signal used in the switching control of the switching element is f １ Let the third time be t3, then t3<{f １ ×(−0.0008)+8.413}×10 －６ The power conversion device according to claim 5 or 6, wherein the first time is adjusted to satisfy the following equation.

8. The switching elements include at least a first switching element and a second switching element, wherein a fifth time is a time until a state quantity indicating a conductive state of the first switching element reaches a specified threshold value when the first switching element changes from conductive to non-conductive or from non-conductive to conductive under a first drive condition, a sixth time is a time from when the first switching element changes from conductive to non-conductive or from non-conductive to conductive under the first drive condition to when the second switching element starts to change from conductive to non-conductive or from non-conductive to conductive under the first drive condition, and a seventh time is a time until a state quantity indicating a conductive state of the first switching element reaches the threshold value when the first switching element changes from conductive to non-conductive or from non-conductive to conductive under a second drive condition, the power conversion device according to claim 2, wherein a time from when the first switching element changes from conductive to non-conductive or from non-conductive to conductive under the second drive condition to when the second switching element next starts to change from conductive to non-conductive or from non-conductive to conductive under the second drive condition is an eighth time; when the first switching element and the second switching element are being driven under the first drive condition, the detection value of the current detector is obtained after the fifth time has elapsed from a time which is a starting point of the fifth time and a further specified ninth time has elapsed; when the first switching element and the second switching element are being driven under the second drive condition, the detection value of the current detector is obtained after the seventh time has elapsed from a time which is a starting point of the seventh time and a further specified tenth time has elapsed; an error between the sixth time and the eighth time is within a specified allowable value range; the ninth time is shorter than the sixth time and the eighth time; the tenth time is shorter than the ninth time; and the seventh time is longer than the fifth time.

9. A motor drive device comprising a power conversion device according to any one of claims 1 to 8.

10. A refrigeration cycle device comprising the power conversion device according to any one of claims 1 to 8.

11. The refrigeration cycle application equipment according to claim 10, wherein the refrigerant used is any one of R1234yf, R1234ze(E), R1243zf, HFO1123, HFO1132(E), R1132a, CF3I and R290, or a mixed refrigerant containing at least two of the above refrigerants.

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