JP2008141937A - Power converter and power conversion method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress output fluctuation caused by error voltage between an instruction value and an output voltage when the frequency of carrier waves is changed. <P>SOLUTION: The power converter compensates an instruction value according to changes in frequency of carrier waves, to suppress output fluctuation caused by error voltage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power converter and a power conversion method for converting an output of a DC power source into AC power by PWM (Pulse Width Modulation) modulation and supplying the AC power to a load.

  A power conversion device that converts DC power into three-phase AC power has a basic unit of an arm in which switching elements are connected in series, and the upper switching element and the lower switching element are alternately turned on / off. The

  In the conventional power converter, in order to prevent the upper switching element and the lower switching element from being simultaneously turned on and short-circuited, the upper and lower switching elements are simultaneously switched on and off. A short-circuit prevention time (also referred to as a dead time) for turning off is provided.

Due to the existence of this dead time, an error (hereinafter referred to as an error voltage) occurs between the voltage command value output from the control device and the actually output voltage, and the output voltage may be distorted. For this reason, a technique for compensating for an error voltage by adding a constant compensation voltage to a voltage command value is known (see Patent Document 1 below).
JP 2002-95262 A

  However, the conventional power converter compensates the error voltage by adding a constant compensation voltage to the voltage command value, but when applied to a power converter that changes the carrier frequency, There is a problem that the error voltage is not sufficiently compensated, ripples appear in the current supplied to the load, and the output of the load fluctuates.

  The present invention has been made in view of the above problems, and an object of the present invention is to suppress output fluctuation caused by an error voltage when the frequency of a carrier wave is changed.

  In the present invention, the command value is compensated according to a change in the frequency of the carrier wave.

  According to the present invention, since the command value is compensated according to the change in the frequency of the carrier wave, the output fluctuation caused by the error voltage can be suppressed.

  Below, the power converter device which concerns on the 1st thru | or 5th embodiment of this invention is demonstrated with reference to FIG. 1 thru | or FIG.

(First embodiment)
First, the power converter device which becomes the 1st Embodiment of this invention is demonstrated with reference to FIGS.

  FIG. 1 is a diagram illustrating a configuration of a power conversion device according to a first embodiment of the present invention.

  The power converter includes a battery (DC power supply) 1 that can charge and discharge DC power, an inverter 2 that converts DC power stored in the battery 1 into AC power, and outputs the AC power to the motor 6. A current detection unit 3 that detects the output current I of the AC power output to the current detection value, a current detection value detected by the current detection unit 3, and a current command value output from the current command generator 5; And a control device 4 that controls the inverter 2 based on the above.

  In the power converter shown in FIG. 1, the control device 4 and the current command generator 5 are shown as different configurations, but may be mounted on a single controller. Therefore, they are divided as different configurations for convenience.

  As shown in FIG. 2, the inverter 2 is supplied with DC voltages V + and V− from the battery 1. The inverter 2 includes a parallel circuit of six transistors Tu +, Tu−, Tv +, Tv−, Tw +, Tw− and six diodes. The transistors Tu +, Tu−, Tv +, Tv−, Tw +, and Tw− are configured by a semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor).

  The current detection unit 3 includes three current sensors 3a, 3b, and 3c that detect output currents Iu, Iv, and Iw of the u-phase, v-phase, and w-phase of the inverter 2 as current detection values. The detected current value is output to the control device 4. In the following description, when it is not necessary to distinguish the current sensors 3a, 3b, and 3c of the respective phases, the current sensor 3 is simply referred to as the current detection unit 3 and will be described.

  As shown in FIG. 3, the control device 4 includes a voltage command generation unit that generates a voltage command based on the current command value output from the current command generation device 5 and the current detection value output from the current detection unit 3. 41, a carrier signal generation unit 42 for generating a carrier signal, a dead time compensation unit 44 for outputting a dead time compensation correction voltage ΔV, which will be described later, and a command value signal obtained by adding the dead time compensation correction voltage ΔV and a voltage command. The adder 46 to output, the command value signal and the carrier wave signal are compared (PWM comparison), the control signal generator 43 for generating a control signal for turning on / off the transistor of the inverter 2, and the frequency of the carrier wave signal (carrier wave) A carrier frequency changing unit 45 that changes the frequency fc.

  The carrier signal generation unit 42 modulates the carrier signal based on the carrier frequency fc output from the carrier frequency changing unit 45 to generate a carrier signal.

  The control signal generation unit 43 generates a pulsed control signal by comparing the magnitude relationship between the command value signal output from the adder 46 and the carrier wave signal using a comparator, and outputs the pulsed control signal to the inverter 2.

  As shown in FIG. 4, the dead time compensation unit 44 is synchronized with the carrier time fc of the dead time compensation voltage generation unit 441 that generates the constant dead time compensation voltage ΔV1 and the carrier frequency change unit 45, A carrier correction voltage generator 442 that generates a carrier correction voltage ΔV 2 and an adder 443 that adds the dead time compensation voltage ΔV 1 and the carrier correction voltage ΔV 2 and outputs the dead time compensation correction voltage ΔV to the adder 46. Is done.

  Here, the reason why the dead time compensator 44 is provided in the control device 4 will be described below with reference to FIGS. FIG. 5 is a simplified diagram of inverter 2 shown in FIG. As described above, the battery 1 supplies the DC voltages V + and V− to the inverter 2. The control signal generated by the control signal generator 43 (see FIG. 3) is input to the gate terminals of the transistors Tu + and Tu−.

  This control signal is an on / off pulse signal generated by comparing the command value signal and the carrier wave signal (PWM comparison) in the control signal generation unit 43 and based on the magnitude relationship of the compared signals. Based on this control signal, the transistors Tu + and Tu− are turned on and off to supply power from the inverter 2 to the motor 6.

  FIG. 6 is a time chart of control signals input to the gate terminals of the transistors Tu + and Tu− shown in FIG. FIG. 6A shows a time chart of control signals input to the gate terminals of ideal transistors Tu + and Tu− when it is assumed that there is no operation delay. However, when the on / off operation as shown in FIG. 6 (a) is performed, the transistors Tu + and Tu− that are actually used have an operation delay, so the on / off switching between the positive side and the negative side is possible. Occasionally, the transistors Tu + and Tu− may be turned on at the same time.

  In this case, the power supply is short-circuited and the transistors Tu + and Tu− may be destroyed. In order to prevent this short-circuit state, as shown in FIG. 6B, the timing at which the transistors Tu + and Tu− are turned on is delayed by several μsec from the timing shown in FIG. -Is prevented from turning on at the same time. This time delay of about several μsec is set as a dead time Td which is a short circuit prevention time.

  During this dead time Td, the transistors Tu + and Tu− are both off, so that the output voltage of the inverter 2 is in an uncontrolled state, and during this period, a voltage determined only by the direction of the output current I is output. Therefore, the output voltage of the inverter 2 during this dead time Td acts as an error voltage. A dead time compensation voltage generator 441 is provided in the dead time compensator 44 in order to obtain a command value in consideration of the error voltage in advance so that the error voltage does not occur.

  FIG. 7 is a diagram illustrating the output voltage and the dead time compensation voltage ΔV1 when the carrier frequency fc is constant. In FIG. 7, when the carrier frequency fc is constant, the dead time Td is provided and the dead time compensation is performed, and the dead time Td is provided and the dead time compensation is performed. The output voltage for one cycle of the carrier signal and the dead time compensation voltage ΔV1 when there is no carrier signal are shown.

In FIG. 7A, A represents a command value, B represents an output voltage when dead time compensation is not performed, and C represents an output voltage when dead time compensation is performed. FIG. 7B shows the dead time compensation voltage ΔV1 when dead time compensation is performed. The dead time compensation voltage ΔV1 is a constant voltage.
FIG. 7 shows that the output voltage is lower than the command value when dead time compensation is not performed. On the other hand, when dead time compensation is performed, the output voltage becomes substantially equal to the command value.

  However, when the carrier frequency fc is changed with time, a current ripple appears in the output current I of the inverter 2 even if the above-described dead time compensation is performed. In particular, when the motor 6 is operated at low speed and light load, There was a problem that output fluctuation and rotation unevenness were increased due to ripple. Therefore, in the first embodiment, the dead time compensation shown in FIG. 7B is further corrected to suppress the current ripple, the output fluctuation caused by the current ripple, and the rotation unevenness. .

  FIG. 8 is a diagram illustrating a carrier signal output from the carrier signal generation unit 42 (see FIG. 3). FIG. 8A shows a carrier signal (broken line) when the carrier frequency fc is constant, and a carrier signal (solid line) where the carrier frequency fc changes with time. FIG. 8B shows the change over time of the carrier frequency fc of the carrier signal represented by the solid line in FIG. 8A and 8B show waveforms for one cycle of the carrier frequency fc.

  FIG. 9 is a diagram illustrating the carrier wave correction voltage ΔV2 output from the carrier wave correction voltage generation unit 442 (see FIG. 4). FIG. 9A shows a time change of the carrier frequency fc output from the carrier frequency changing unit 45. FIG. 9B shows the dead time compensation voltage ΔV1 generated from the dead time compensation voltage generator 441. The dead time compensation voltage ΔV1 is a constant value. FIG. 9C shows the carrier wave correction voltage ΔV 2 generated from the carrier wave correction voltage generation unit 442. As shown in FIG. 9C, the carrier wave correction voltage ΔV2 is synchronized with the carrier wave frequency fc of the carrier wave frequency changing unit 45. Specifically, when the carrier frequency is fc (t), the power supply voltage is Vdc, and the average value of the carrier frequency fc (t) is fa, each is expressed as follows.

ΔV1 = fa × Td × Vdc
ΔV2 (t) = {fc (t) −fa} × Td × Vdc
ΔV (t) = ΔV1 + ΔV2 (t) = fc (t) × Td × Vdc
The dead time compensation correction voltage ΔV (t), which is an output from the adder 443 that adds the dead time compensation voltage ΔV1 of the dead time compensation voltage generator 441 and the carrier wave correction voltage ΔV2 of the carrier wave correction voltage generator 442, is the dead time compensation unit. 44 output signals.

  In other words, since the dead time compensation correction voltage ΔV (t) is proportional to the carrier frequency fc (t), the dead time compensation unit 44 does not change the carrier frequency fc (t) even if the carrier frequency fc (t) changes with time. The dead time compensation correction voltage ΔV (t) corresponding to the time change can be output.

  FIG. 10 is a diagram illustrating the waveform of the output current I output from the inverter 2 shown in FIG. In FIG. 10, a waveform D shows an ideal output current waveform from the command value. A waveform E represents an output current waveform when the carrier frequency fc is changed with time and the dead time compensation correction voltage ΔV is set to a constant dead time compensation voltage ΔV1. A waveform F represents an output current waveform when the dead time compensation correction voltage ΔV changes according to the time change of the carrier frequency fc. When the error between the waveform D and the waveform E is compared with the error between the waveform D and the waveform F, the error with respect to the waveform D is reduced by about 10% in the waveform F compared with the waveform E. Further, when the ripples of the waveform E and the waveform F are compared, the waveform F is smaller.

  As described above, the dead time compensation voltage ΔV1 generated from the dead time compensation voltage generator 441 and the carrier wave correction voltage ΔV2 generated from the carrier wave correction voltage generator 442 and synchronized with the time-varying carrier frequency fc are added. The dead time compensation correction voltage ΔV (t) added at 443 is output from the dead time compensation unit 44, and the dead time compensation correction voltage ΔV (t) and the voltage command generated from the voltage command generation unit 41 are added to the adder 46. Is output to the control signal generation unit 43, the control signal generation unit 43 compares the command value signal with the carrier signal output from the carrier signal generation unit 42, and generates a control signal. Since this control signal is output to the gate terminals of the transistors Tu +, Tu−, Tv +, Tv−, Tw +, Tw− of the inverter 2 Even when changing the carrier frequency fc, while suppressing the occurrence of the error voltage, the output variation due to current ripple and the current ripple, an effect is obtained that the non-uniform rotation can be restrained.

  Further, by changing the dead time compensation correction voltage ΔV according to the time change of the carrier frequency fc, an error with respect to the ideal output current I from the command value of the output current I actually supplied from the inverter 2 to the motor 6. Can be reduced. Furthermore, since the carrier frequency fc is changed, switching noise having a spectral component having a high noise level with respect to the carrier frequency fc and the frequency of the n-th harmonic can be reduced.

(Second Embodiment)
Next, the power converter device which becomes 2nd Embodiment is demonstrated with reference to FIGS. 11-13 centering on a different point from the power converter device of 1st Embodiment. Note that in the second embodiment, the same reference numerals are given to the same configurations as those in the first embodiment.

  The power conversion device of the second embodiment differs from the power conversion device of the first embodiment in that the dead time compensation unit of the control device is different, and this will be described in detail below.

  FIG. 11 is a diagram illustrating the control device 14 of the power conversion device according to the second embodiment of the present invention.

  As shown in FIG. 11, the controller 14 generates a voltage command based on the current command value output from the current command generator 5 and the detected current value output from the current detector 3. 41, a carrier signal generation unit 42 that generates a carrier signal, a dead time compensation unit 144 that outputs a dead time compensation correction voltage ΔV, and a command value signal obtained by adding the dead time compensation correction voltage ΔV and a voltage command. An adder 46, a control signal generator 43 that compares the command value signal and the carrier wave signal, generates a control signal for turning on / off the transistor of the inverter 2, and a carrier frequency changer 45 that changes the carrier frequency fc. It is composed of Unlike the first embodiment, the control device 14 receives the current detection value of the current detector 3 in the dead time compensator 144 in addition to the voltage command generator 41.

  As shown in FIG. 12, the dead time compensation unit 144 includes a current polarity discrimination unit 1444 that discriminates the polarity of the output current I based on the current detection value of the current detection unit 3, and a dead time that generates a dead time compensation voltage ΔV1. The time compensation voltage generator 1441, the carrier wave correction voltage generator 1442 that generates the carrier wave correction voltage ΔV2 in synchronization with the carrier wave frequency fc of the carrier wave frequency change unit 45, and the dead time compensation voltage ΔV1 and the carrier wave correction voltage ΔV2 are added. The adder 443 outputs the dead time compensation correction voltage ΔV to the adder 46.

  The current polarity discriminating unit 1444 discriminates the polarity of the output current I using the current detection value output from the current detecting unit 3, and the current polarity signal as a result of the discrimination is used as the dead time compensation voltage generating unit 1441 and the carrier wave The correction voltage is output to the correction voltage generator 1442.

  When the polarity of the current polarity signal output from the current polarity determination unit 1444 is positive, the dead time compensation voltage generation unit 1441 generates a positive constant value as the dead time compensation voltage ΔV1. On the other hand, when the polarity of the current polarity signal output from the current polarity determination unit 1444 is negative, a negative constant value is generated as the dead time compensation voltage ΔV1.

  When the polarity of the current polarity signal output from the current polarity discriminating unit 1444 is positive, the carrier wave correction voltage generation unit 1442 generates a carrier wave correction voltage ΔV2 that changes over time with the same inclination as the inclination of the carrier frequency fc that changes over time. . On the other hand, when the polarity of the current polarity signal output from the current polarity discriminating unit 1444 is negative, a carrier wave correction voltage ΔV2 that changes in time with the same slope as the slope of the carrier frequency fc that changes with time and the sign is generated. .

  FIG. 13 is a diagram illustrating the dead time compensation correction voltage ΔV shown in FIG. Here, FIG. 13A shows the time change of the current detection value detected by the current detector 3, and FIG. 13B shows the dead time compensation voltage ΔV1. FIG. 13C shows the time change of the carrier frequency fc, and FIG. 13D shows the carrier correction voltage ΔV2. FIG. 13E shows the dead time compensation correction voltage ΔV. FIGS. 13A to 13E show waveforms for one cycle of the current detection value.

  As shown in FIG. 13A, when the current polarity determination unit 1444 determines that the polarity is positive from the current detection value of the current detection unit 3 (right side in FIG. 13), the dead time compensation voltage generation unit 1441 The compensation voltage ΔV1 is set to a positive constant value (see FIG. 13B), and the carrier wave correction voltage generator 1442 changes over time with the same inclination as the inclination of the carrier frequency fc that changes over time (see FIG. 13C). A carrier wave correction voltage ΔV2 (see FIG. 13D) is generated.

  On the other hand, as shown in FIG. 13A, when the current polarity determination unit 1444 determines that the polarity of the current detection value of the current detection unit 3 is negative (left side in FIG. 13), the dead time compensation voltage generation unit 1441 The dead time compensation voltage ΔV1 is set to a negative negative value (see FIG. 13B), and the carrier wave correction voltage generation unit 1442 has the slope and the sign of the carrier frequency fc that change with time (see FIG. 13C) reversed. A carrier wave correction voltage ΔV2 (see FIG. 13D) whose numerical value changes with time at the same inclination is generated.

  Further, the adder 443 outputs the dead time compensation correction voltage ΔV (see FIG. 13E) obtained by adding the dead time compensation voltage ΔV1 and the carrier wave correction voltage ΔV2 to the adder 46. Similarly to the first embodiment, the adder 46 adds the dead time compensation correction voltage ΔV and the voltage command, and outputs the command value signal to the control signal generation unit 43. The control signal is generated from the command value and the carrier wave signal output from the carrier wave signal generation unit 42, and this control signal is applied to the gate terminals of the transistors Tu +, Tu−, Tv +, Tv−, Tw +, Tw− of the inverter 2. Output.

  As described above, in the control device 14 of the second embodiment, the dead time compensation unit 144 determines the polarity based on the current detection value of the current detection unit 3, and the dead time compensation voltage generation unit 1441 and the carrier wave correction voltage are determined. The generation unit 1442 is provided with a current polarity determination unit 1444 that outputs a current polarity signal indicating the polarity of the current detection value. When the polarity of the current detection value is positive, the dead time compensation voltage generation unit 1441 generates the dead time compensation voltage ΔV1. While generating a positive constant value, the carrier correction voltage generator 1442 generates a carrier correction voltage ΔV2 that changes over time with the same inclination as the inclination of the carrier frequency fc that changes over time, while the polarity of the current detection value is negative. In this case, the dead time compensation voltage generator 1441 generates a constant negative value as the dead time compensation voltage ΔV1, and the carrier correction voltage Since the carrier wave correction voltage ΔV2 that changes in time with the same slope as the slope of the carrier frequency fc that changes with time is generated from the raw unit 1442, the carrier frequency is changed as in the first embodiment. Even when fc is changed, it is possible to suppress the generation of the error voltage and to suppress the current ripple and the output fluctuation and the rotation unevenness due to the current ripple.

(Third embodiment)
Next, the power converter device which becomes 3rd Embodiment is demonstrated with reference to FIGS. 14-16 centering on a different point from the power converter device of 1st Embodiment. In addition, the same number is attached | subjected to the structure similar to 1st Embodiment.

  The power conversion device of the third embodiment is different from the power conversion device of the first embodiment in that the dead time compensation unit of the control device is different, and this will be described in detail below.

  FIG. 14 is a diagram illustrating the control device 24 of the power conversion device according to the third embodiment of the present invention.

  As shown in FIG. 14, the control device 24 includes a voltage command generation unit that generates a voltage command based on the current command value output from the current command generation device 5 and the current detection value output from the current detection unit 3. 41 and a carrier signal generator 42 for generating a carrier signal. A dead time compensation unit 244 that outputs the dead time compensation correction voltage ΔV and an adder 46 that outputs a command value signal obtained by adding the dead time compensation correction voltage ΔV and the voltage command are provided. Further, the command value signal and the carrier wave signal are compared (PWM comparison), a control signal generator 43 that generates a control signal for turning on / off the transistor of the inverter 2, and a carrier frequency changer 45 that changes the carrier frequency fc. And. The dead time compensation unit 244 includes a voltage compensation unit 2441 that generates the dead time compensation correction means voltage ΔV in synchronization with the carrier frequency fc of the carrier frequency change unit 45.

FIG. 15A shows the time change of the carrier frequency fc output from the carrier frequency changing unit 45 in the third embodiment. FIG. 15B shows the dead time compensation correction voltage ΔV generated from the voltage compensator 2441 in FIG. The dead time compensation correction voltage ΔV is synchronized with the carrier frequency fc of the carrier frequency changing unit 45. Specifically, when the time change of the carrier frequency fc is fc (t), the minimum value of the carrier frequency fc is fc1, the maximum value of the carrier frequency fc is fc2, the dead time is Td, and the power supply voltage is Vdc, the dead time compensation The correction voltage ΔV (t) is expressed as follows.
ΔV (t) = | fc (t) −fc1 | × Td × Vdc (1)
Or
ΔV (t) = | fc (t) −fc2 | × Td × Vdc (2)
The dead time Td is a constant value.

  As shown in FIG. 15B, in the third embodiment, the dead time compensation correction voltage ΔV (t) calculated from the equation (2) is used. However, the dead time compensation correction voltage ΔV (t) calculated from the equation (1) may be used. Thus, as shown in FIG. 15B, the dead time compensation correction voltage ΔV (t) is synchronized with the carrier frequency fc (t). Therefore, the voltage compensation unit 2441 can output the dead time compensation correction voltage ΔV (t) synchronized with the time change of the carrier frequency fc (t) even if the carrier frequency fc (t) changes with time.

  Next, FIG. 16 is a diagram for explaining the waveform of the output voltage output from the inverter 2 in the third embodiment, and FIG. 16A is output from the carrier frequency changing unit 45 in the third embodiment. Represents the time change of the carrier frequency fc.

  FIG. 16B shows an output voltage waveform of the inverter 2 in the third embodiment. In FIG. 16B, a waveform G represents an output voltage waveform when the carrier frequency fc is changed with time as shown in FIG. On the other hand, the waveform H represents an output voltage waveform when the dead time compensation correction voltage ΔV of the voltage compensator 2441 is changed as shown in FIG. 15B in accordance with the time change of the carrier frequency fc. When the waveform G and the waveform H are compared, a voltage ripple synchronized with the change in the carrier frequency fc is seen in the waveform G.

  However, by generating the dead time compensation correction voltage ΔV corresponding to the time change of the carrier frequency fc, ripples generated by changing the carrier frequency fc seen in the waveform G can be suppressed. Yes. That is, even when an error voltage is included in the output voltage, the error voltage can be set to a substantially constant value.

  As described above, the dead time compensation unit 244 of the third embodiment changes the dead time compensation correction voltage ΔV based on the maximum value fc2 or the minimum value fc1 of the carrier frequency fc so that the error voltage becomes a constant value. . That is, the dead time compensation unit 244 (voltage compensation unit 2441) outputs the dead time compensation correction voltage ΔV (t) synchronized with the time change of the carrier frequency fc (t). As a result, the output error of the inverter 2 due to the fluctuation of the carrier frequency fc, that is, the generation of voltage (current) ripple can be suppressed. Furthermore, since the carrier frequency fc is changed as in the first embodiment, it is possible to reduce switching noise having a spectral component having a high noise level with respect to the carrier frequency fc and its n-th harmonic frequency.

(Fourth embodiment)
Next, the power converter device which becomes 4th Embodiment is demonstrated with reference to FIGS. 17-18 centering on a different point from 3rd Embodiment. In addition, about the 4th Embodiment, the same number is attached | subjected to the structure similar to 3rd Embodiment. Here, since the power conversion device of the fourth embodiment is different from the power conversion device of the third embodiment in that the dead time compensation unit of the control device is different, this point will be described in detail below.

  FIG. 17 is a diagram illustrating the control device 34 of the power conversion device according to the fourth embodiment of the present invention.

  As shown in FIG. 17, the controller 34 generates a voltage command based on the current command value output from the current command generator 5 and the detected current value output from the current detector 3. 41 and a carrier signal generator 42 for generating a carrier signal. Furthermore, a dead time compensation unit 344 that outputs the dead time compensation correction voltage ΔV, and an adder 46 that outputs a command value signal obtained by adding the dead time compensation correction voltage ΔV and the voltage command are provided. Further, a control signal generating unit 43 that generates a control signal from the command value signal and the carrier wave signal, and a carrier frequency changing unit 45 that changes the carrier frequency fc are provided.

  Also, as shown in FIG. 17, the dead time compensation unit 344 includes a current polarity determination unit 3441 that determines the polarity of the current detection value based on the current detection value output from the current detection unit 3, and a carrier frequency change unit. The voltage compensation unit 3442 generates a dead time compensation correction voltage ΔV in synchronization with the 45 carrier frequency fc.

  The current polarity determination unit 3441 determines the polarity of the current detection value of the current detection unit 3. The discriminated current polarity signal is output to the voltage compensator 3442. Then, when the polarity of the current detection value output from the current polarity discriminating unit 3441 is positive, the voltage compensator 3442 generates a dead time compensation correction voltage ΔV that changes over time with the same inclination as the inclination of the carrier frequency fc that changes over time. appear. On the other hand, when the polarity of the current detection value output from the current polarity discriminating unit 3441 is negative, the dead time compensation correction voltage ΔV whose time changes with the same slope as the slope of the carrier frequency fc, which changes with time, is opposite. appear.

  FIG. 18 is a diagram illustrating the dead time compensation correction voltage ΔV in the fourth embodiment.

  18A shows the time change of the current detection value detected by the current detector 3, FIG. 18B shows the time change of the carrier frequency fc, and FIG. 18C shows the dead time compensation correction voltage ΔV. Represents. 18A to 18C show waveforms for one cycle of the current detection value.

  As shown in FIG. 18A, when the current polarity determination unit 3441 determines that the polarity of the current detection value of the current detection unit 3 is positive (left side in FIG. 18), the voltage compensation unit 3442 changes with time. A dead time compensation correction voltage ΔV (see FIG. 18C) that changes with time at the same slope as the carrier frequency fc (see FIG. 18B) is generated. On the other hand, as shown in FIG. 18A, when the current polarity determination unit 3441 determines that the polarity of the current detection value of the current detection unit 3 is negative (right side in FIG. 18), the voltage compensation unit 3442 A dead time compensation correction voltage ΔV (see FIG. 18 (c)) is generated that changes in time with the same slope as the slope of the changing carrier frequency fc (see FIG. 18 (b)) but with the opposite sign.

Specifically, when the time change of the carrier frequency fc is fc (t), the minimum value of the carrier frequency fc is fc1, the maximum value of the carrier frequency fc is fc2, the dead time is Td, and the power supply voltage is Vdc, the dead time compensation The correction voltage | ΔV (t) | is expressed as follows.
| ΔV (t) | = | fc (t) −fc1 | × Td × Vdc (3)
Or
| ΔV (t) | = | fc (t) −fc2 | × Td × Vdc (4)
The dead time Td is a constant value.

  As shown in FIG. 18C, in the fourth embodiment, the dead time compensation correction voltage ΔV (t) calculated from the equation (3) is used. However, the dead time compensation correction voltage ΔV (t) calculated from the equation (4) may be used. Thus, as shown in FIG. 18, the dead time compensation correction voltage ΔV (t) is synchronized with the carrier frequency fc (t). Therefore, the voltage compensation unit 3442 can output the dead time compensation correction voltage ΔV (t) synchronized with the time change of the carrier frequency fc (t) even if the carrier frequency fc (t) changes with time. Therefore, even when an error voltage is included in the output voltage, the error voltage can be set to a constant value.

  As described above, the dead time compensation unit 344 of the fourth embodiment performs the dead time compensation correction voltage ΔV based on the maximum value fc2 or the minimum value fc1 of the carrier frequency fc so that the error voltage becomes a constant value. To change. That is, the dead time compensation unit 344 outputs a dead time compensation correction voltage ΔV (t) synchronized with the time change of the carrier frequency fc (t). From this, similarly to the third embodiment, it is possible to suppress the output error of the inverter 2, that is, the generation of voltage (current) ripple due to the fluctuation of the carrier frequency fc. Furthermore, the dead time compensation unit 344 determines the dead time compensation correction voltage ΔV (t) based on the determination result from the current polarity determination unit 3441 that determines the polarity of the output current I based on the current detection value of the current detection unit 3. Change the polarity. Therefore, even when the polarity of the current detection value of the current detector 3 changes, it is possible to reduce the occurrence of output error of the inverter 2 due to the fluctuation of the carrier frequency fc, that is, the occurrence of voltage (current) ripple.

  Further, since the carrier frequency fc is changed as in the third embodiment, switching noise having a spectral component having a high noise level with respect to the carrier frequency fc and the frequency of the n-th harmonic can be reduced.

(Fifth embodiment)
Next, the power converter device which becomes 5th Embodiment is demonstrated with reference to FIGS. 19-23 centering on a different point from 4th Embodiment. In addition, about the 5th Embodiment, the same number is attached | subjected to the structure similar to 4th Embodiment. Here, the power conversion device of the fifth embodiment is different from the power conversion device of the fourth embodiment in that the motor becomes the synchronous motor 16 and the synchronous motor 16 includes the position detector 8. Since the current detection unit 3 is not provided between the inverter 12 and the synchronous motor 16, this point will be described in detail below.

  FIG. 20 is a diagram illustrating the inverter 12 in the fifth embodiment.

  As shown in FIG. 20, the inverter 12 of the fifth embodiment includes a shunt resistor 7 and a current estimation device 9.

  The shunt resistor section 7 includes shunt resistors 7a, 7b, and 7c connected in series on the negative side of the transistors Tu−, Tv−, and Tw−.

  The current estimation device 9 estimates the output current I of the inverter 12 based on the terminal voltages of the shunt resistors 7a, 7b, and 7c. Further, in order to change the control signal supplied to the inverter 12 with time in synchronization with the change of the carrier frequency fc, the carrier information of the carrier frequency changing unit 45 is supplied from the control device 54 to the current estimating device 9.

  FIG. 21 is a diagram for explaining the relationship between the terminal voltage of the shunt resistor 7 shown in FIG. 20 and the carrier wave signal. Note that the terminal voltage of the shunt resistor 7 indicates one (one phase) of the terminal voltages (three phases) of the shunt resistors 7a, 7b, and 7c. FIG. 21A shows a carrier wave signal for generating a control signal for turning on / off the transistors Tu +, Tu−, Tv +, Tv−, Tw +, and Tw− of the inverter 12. FIG. 21B shows terminal voltages (for one phase) of the shunt resistors 7a, 7b, and 7c. FIG. 21C shows the output current I of the inverter 12.

  In the current estimation device 9, the output current I in FIG. 21C is estimated from the terminal voltages of the shunt resistors 7a, 7b, and 7c. As shown by the dotted line in FIG. 21B, the current estimation device 9 detects the terminal voltages of the shunt resistors 7a, 7b, and 7c at the time of the peak of the carrier wave signal. Even when the carrier frequency fc is changed, the current estimation device 9 always detects the terminal voltage of the shunt resistors 7a, 7b, 7c at the time of the peak of the carrier signal by using carrier information of the carrier frequency changing unit 45 described later. is doing.

  FIG. 22 is a diagram illustrating the control device 54 according to the fifth embodiment.

  The control device 54 uses a position detection value from the position detector 8 to convert a three-layer current command value output from the current command generator 5 into a two-phase current command value. I have.

  Further, a coordinate conversion unit 5402 that converts the current estimation value of the three-phase quantity output from the current estimation device 9 into the current estimation value of the two-phase quantity using the position detection value from the position detector 8 is provided.

  In addition, a voltage command generation unit 5404 that generates a voltage command via the q-axis component converted by the coordinate conversion unit 5401 and the coordinate conversion unit 5402, a carrier wave signal generation unit 42 that generates a carrier wave signal, and dead time compensation described later A dead time compensator 544 that outputs a correction voltage ΔVq.

  The dead time compensation unit 544 outputs a dead time compensation correction voltage ΔVq of a q-axis voltage that compensates for a voltage command of the q-axis component among the dq-axis components of the synchronous motor 16 shown in FIG.

  Also, an adder 46 that outputs a command value signal obtained by adding the dead time compensation correction voltage ΔVq and the voltage command, and converts the two-layer command value signal output from the adder 46 into a three-phase command value signal. A coordinate conversion unit 5403.

  The control signal generator 43 that generates a control signal based on the command value signal output from the coordinate converter 5403 and the carrier signal output from the carrier signal generator 42, and the carrier frequency that changes the carrier frequency fc And a change unit 45. Here, the position detector 8 detects the position of the magnetic pole of the permanent magnet synchronous motor 16 using an encoder, and outputs a position detection value. The dead time compensation unit 544 includes a voltage compensation unit 5441 that generates a dead time compensation correction voltage ΔVq in synchronization with the carrier frequency fc of the carrier frequency change unit 45. The carrier frequency changing unit 45 outputs the carrier frequency fc as carrier information to the current estimation device 9.

  FIG. 23 is a diagram for explaining a dead time compensation correction voltage ΔVq in the fifth embodiment. FIG. 23A shows a time change of the carrier frequency fc output from the carrier frequency changing unit 45 in FIG. FIG. 23B shows a dead time compensation correction voltage ΔVq (t) generated from the voltage compensation unit 5441 in FIG. The dead time compensation correction voltage ΔVq (t) is synchronized with the carrier frequency fc output by the carrier frequency changing unit 45.

Specifically, when the time change of the carrier frequency fc is fc (t), the minimum value of the carrier frequency fc is fc1, the maximum value of the carrier frequency fc is fc2, the dead time is Td, and the power supply voltage is Vdc, the dead time compensation The correction voltage ΔVq (t) is expressed as follows.
ΔVq (t) = √ (3/2) × | fc (t) −fc1 | × Td × Vdc (5)
Or
ΔVq (t) = √ (3/2) × | fc (t) −fc2 | × Td × Vdc (6)
The dead time Td is a constant value.

  The motor is a synchronous motor 16 and corrects only the q-axis voltage.

  As shown in FIG. 23B, in the fifth embodiment, the dead time compensation correction voltage ΔVq (t) calculated from the equation (6) is used. However, the dead time compensation correction voltage ΔVq (t) calculated from the equation (5) may be used.

  Thus, as shown in FIG. 23, the dead time compensation correction voltage ΔVq (t) is synchronized with the carrier frequency fc (t). The voltage compensation unit 5441 can output the dead time compensation correction voltage ΔVq (t) synchronized with the time change of the carrier frequency fc (t) even if the carrier frequency fc (t) changes with time. Therefore, even when an error voltage is included in the output voltage, the error voltage can be set to a constant value.

  As described above, the dead time compensation unit 544 of the fifth embodiment changes the dead time compensation correction voltage ΔVq based on the maximum value fc2 or the minimum value fc1 of the carrier frequency fc so that the error voltage becomes a constant value. . That is, the dead time compensation unit 544 outputs the dead time compensation means output ΔVq (t) synchronized with the time change of the carrier frequency fc (t). As in the fourth embodiment, the output error of the inverter 12, that is, the generation of voltage (current) ripple due to the fluctuation of the carrier frequency fc can be suppressed. Furthermore, in the fifth embodiment, since the motor is the synchronous motor 16, even when the carrier frequency fc is changed without adding the current polarity discriminating unit 3441 by compensating only the q-axis voltage, the voltage ( Current) ripple can be suppressed. Further, since the carrier frequency fc is changed as in the fourth embodiment, switching noise having a spectral component having a high noise level with respect to the carrier frequency fc and the frequency of the n-th harmonic can be reduced.

  The embodiment described above is an example of the implementation of the present invention, and the scope of the present invention is not limited thereto, and other various embodiments are within the scope described in the claims. It is applicable to. For example, in the first to fifth embodiments, the battery is shown as the DC power supply. However, the present invention is not particularly limited to this, and a converter circuit that rectifies an AC voltage from a commercial power supply to obtain a DC voltage may be used.

  In the first to fifth embodiments, the motor 6 is shown as a load. However, the present invention is not particularly limited to this and can be applied to other loads.

  In the first to fifth embodiments, the voltage command is output to the adder 46 from the voltage command generators 41 and 5404 provided in the control devices 4, 14, 24, 34, and 54. It is not limited to this, and it may be input from the outside in the form of a voltage command.

  In the first to fourth embodiments, the control signal generation unit 43 compares the magnitude relationship between the command value signal of the adder 46 and the carrier wave signal using a comparator, but the present invention is particularly limited to this. Instead, the command value signal and the carrier wave signal may be compared by calculation. Similarly, in the fifth embodiment, the control signal generation unit 43 compares the magnitude relationship between the command value signal from the coordinate conversion unit 5403 and the carrier wave signal using a comparator, but the present invention is particularly limited to this. Instead, the command value signal and the carrier wave signal may be compared by calculation.

  In the first to fifth embodiments, the carrier wave signal generation unit 42 modulates the carrier wave frequency fc of the carrier wave frequency changing unit 45 to generate a carrier wave signal. However, the present invention is not limited to this. Instead, a carrier wave signal may be generated by using a voltage controlled oscillator (VCO) based on the voltage waveform from the carrier wave frequency changing unit 45.

  In the first to fourth embodiments, the current sensors 3a, 3b, and 3c are provided as the current detection unit 3 between the inverter 2 and the motor 6, but the present invention is not particularly limited thereto. A current may be detected by inserting a shunt resistor between the motor 6 and the motor 6. Furthermore, although the current sensors 3a, 3b, and 3c are provided in each phase, two current sensors may be provided, and the remaining phases may be obtained by calculation.

  In the fifth embodiment, as the shunt resistor section 7, shunt resistors 7a, 7b, and 7c are connected in series to the transistors Tu−, Tv−, and Tw− of the inverter 12, and the terminals of the shunt resistors 7a, 7b, and 7c are connected. Although the case where the voltage is detected and the output current I of the inverter 12 is estimated by the current estimation device 9 has been shown, the present invention is not particularly limited to this, and the inverter 2 as in the first to fourth embodiments. The current detection unit 3 may be provided between the motor 6 and the motor 6.

  In the fifth embodiment, the position detector 8 detects the position of the magnetic pole of the synchronous motor 16 using an encoder. However, the position detector 8 is not particularly limited to this, and detects the position using a resolver or the like. Also good.

  In the first to fifth embodiments, the case where the carrier frequency fc is changed in time in a triangular wave shape has been described. However, the present invention is not limited to this, and the carrier frequency fc may be changed in time at random. good.

  In the first to fifth embodiments, the dead time compensation correction voltages ΔV and ΔVq are calculated from the calculation formula and controlled. However, the present invention is not particularly limited to this, and a map is prepared in advance to the microcomputer. It may be read and controlled.

  The inverters 2 and 12 of the first to fifth embodiments may include a reactor L and a capacitor C.

The figure explaining the control apparatus of the power converter device which becomes the 1st Embodiment of this invention The figure explaining the inverter shown in FIG. The figure explaining the control apparatus shown in FIG. The figure explaining the dead time compensation part shown in FIG. A simplified diagram of the inverter shown in FIG. Time chart of control signal input to transistor shown in FIG. Diagram explaining output voltage and dead time compensation voltage when carrier frequency is constant The figure explaining the carrier wave signal output from the carrier wave signal generation part shown in FIG. The figure explaining the carrier wave correction voltage shown in FIG. The figure explaining the waveform of the output current output from the inverter shown in FIG. The figure explaining the control apparatus of the 2nd Embodiment of this invention The figure explaining the dead time compensation part shown in FIG. The figure explaining the dead time compensation part output shown in FIG. The figure explaining the control apparatus of the 3rd Embodiment of this invention The figure explaining the dead time compensation correction voltage shown in FIG. The figure explaining the waveform of the output voltage output from the inverter shown in FIG. The figure explaining the control apparatus of the 4th Embodiment of this invention The figure explaining the dead time compensation correction voltage shown in FIG. The figure explaining the control apparatus of the power converter device which becomes the 5th Embodiment of this invention. The figure explaining the power converter device shown in FIG. The figure explaining the relationship between the terminal voltage of a shunt resistance part shown in FIG. 20, and a carrier wave signal The figure explaining the control apparatus shown in FIG. The figure explaining the dead time compensation correction voltage shown in FIG.

Explanation of symbols

1 DC power supply,
2, 12 inverter,
3 Current detector,
3a, 3b, 3c current sensor,
4, 14, 24, 34, 56 control device,
5 Current command generator,
6 motor,
7 Shunt resistor,
7a, 7b, 7c Shunt resistor,
8 position detector,
9 Current estimation device,
16 Synchronous motor,
41 Voltage command generator,
42 Carrier wave signal generator,
43 control signal generator,
44, 144, 244, 344, 544 dead time compensator,
45. Carrier frequency change unit,
46 adder,
441 Dead time compensation voltage generator,
442 carrier wave correction voltage generator,
443 adder,
1441 Dead time compensation voltage generator,
1442 Carrier wave correction voltage generator,
1444 current polarity discriminator,
2441, 5441 Voltage compensation unit,
3441 current polarity discriminator,
3442 voltage compensator,
5401, 5402, 5403 coordinate conversion unit,
5404 voltage command generator,

Claims (14)

A power supply that outputs a DC voltage;
Command value output means for outputting the command value;
Compensating means for compensating the command value output by the command value output means, and outputting a command value signal;
Carrier wave output means for outputting a carrier wave;
Frequency changing means for changing the frequency of the carrier;
Control signal generating means for comparing the command value signal with the carrier wave and generating a control signal according to the comparison;
Based on the control signal generated by the control signal generating means, the switching element is controlled to open and close, thereby converting the DC voltage output from the power source into an AC voltage and outputting it to the load, and
With
The power converter according to claim 1, wherein the compensation means compensates the command value in correspondence with a carrier frequency changed by the frequency changing means. The power conversion device according to claim 1,
The power conversion apparatus, wherein the compensation means compensates the command value in synchronization with a change in the carrier frequency. The power conversion device according to claim 1, wherein
The command value signal output by the compensation means is a voltage amount,
The compensation means includes
Compensation voltage generating means for generating a constant compensation voltage for the command value;
Carrier correction voltage generating means for generating a carrier correction voltage corresponding to the change in the carrier frequency;
An adding means for outputting a compensation correction voltage obtained by adding the compensation voltage and the carrier wave correction voltage to the command value as a command value signal;
A power conversion device comprising: The power conversion device according to claim 3,
The carrier wave correction voltage is a power conversion device synchronized with a change in the carrier wave frequency. The power conversion device according to claim 3,
Current detection means for detecting current output from the inverter;
A current polarity discriminating unit for discriminating the polarity based on the current detected by the current detecting unit;
The power conversion apparatus according to claim 1, wherein the carrier wave correction voltage generation unit changes the polarity of the carrier wave correction voltage based on the polarity determination determined by the current polarity determination unit. The power conversion device according to claim 5,
When the polarity determination is positive, the carrier correction voltage generation means generates the carrier correction voltage that changes with the same inclination as the change in the frequency of the carrier that changes with time, and the polarity determination is negative. In this case, the power conversion apparatus generates the carrier wave correction voltage in which the slope of the frequency of the carrier wave changing with time is opposite to the sign of the frequency and the numerical value changes with the same slope. The power conversion device according to claim 3,
The switching elements are connected in series,
The compensation correction voltage is ΔV (t), the change in the carrier frequency is fc (t), the short-circuit prevention time set so that the switching elements are simultaneously opened, Td, and the DC voltage output by the power supply is Vdc. Then,
A power converter represented by ΔV (t) = fc (t) × Td × Vdc. The power conversion device according to claim 3,
The carrier wave correction voltage ΔV2 (t) has an average value of the carrier wave frequency fa, a change in the carrier wave frequency fc (t), and a short-circuit prevention time set so that the switching elements are simultaneously opened. Td, where the DC voltage output by the power source is Vdc,
ΔV2 (t) = {fc (t) −fa} × Td × Vdc
A power converter represented by The power conversion device according to claim 3,
When the compensation voltage is ΔV1, the average frequency of the carrier wave is fa, the short-circuit prevention time set so that the switching elements are simultaneously opened is Td, and the DC voltage output by the power supply is Vdc,
A power converter represented by ΔV1 = fa × Td × Vdc. The power conversion device according to claim 3,
The compensation correction voltage is ΔV (t), the time variation of the carrier frequency is fc (t), the minimum value of the carrier frequency is fc1, the maximum value of the carrier frequency is fc2, and the switching elements are simultaneously open. If the short-circuit prevention time set to be Td and the DC voltage output by the power source is Vdc,
ΔV (t) = | fc (t) −fc1 | × Td × Vdc,
Or
ΔV (t) = | fc (t) −fc2 | × Td × Vdc,
A power converter represented by The power conversion device according to claim 3,
The load is a synchronous motor;
Position detecting means for detecting the magnetic pole position of the synchronous motor;
Based on the magnetic pole position detected by the position detection means, comprising coordinate conversion means for coordinate conversion of the two-phase amount and the three-phase amount of the synchronous motor;
The compensation means is a power converter that compensates the q-axis voltage of the synchronous motor. The power conversion device according to claim 11,
The compensation correction voltage ΔVq (t) for compensating the q-axis voltage is fc (t) for the time variation of the frequency of the carrier wave, fc1 for the minimum value of the carrier wave frequency, and the switching element is open at the same time. When the short-circuit prevention time set to be Td and the DC voltage output from the power source is Vdc,
ΔVq (t) = √ (3/2) × | fc (t) −fc1 | × Td × Vdc,
Or
ΔVq (t) = √ (3/2) × | fc (t) −fc2 | × Td × Vdc
A power converter represented by A power conversion control device according to any one of claims 1 to 12,
The carrier wave frequency changing means is a power conversion device that changes the frequency of the carrier wave at a constant period. Comparing the carrier frequency at which the frequency changes with the compensated command value corresponding to the change in the carrier frequency,
Based on the control signal generated according to this comparison, the switching element is controlled to open and close, thereby converting the DC voltage output from the power source into an AC voltage and outputting it to the load.
The power conversion method characterized by the above-mentioned.

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