JP2006166629A - Control method of power converting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method that prevents an interpole short-circuit current and that prevents an interpole short circuit to reduce the heat generation of a switch. <P>SOLUTION: This control method is for a power-converting device (30) that drives an AC motor (20). The power-converting device is connected to a plurality of DC power sources (10a, 10b). The driving voltage of the AC motor is generated by generating/synthesizing pulses from each output voltage of these DC power sources. The control method includes a short-circuit prevention step that prevents the short circuit of an interpole path of different potentials. This structure can prevent the interpole short circuit and the heat generation of each switch (including 101a, 102a) by an unnecessary short-circuit current. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is a method for controlling a power converter that drives an AC motor.

Japanese Laid-Open Patent Publication No. 2002-118981 (refer to Patent Document 1) discloses a configuration of driving a motor with high efficiency using a fuel cell as a main power source as a conventional technique. In this example, as shown in FIG. 1, the battery is connected in parallel with the fuel cell via the DCDC converter, and the output voltage of the DCDC converter is controlled to improve the output efficiency of the power source. . In addition, as a technique that eliminates the need for a DCDC converter, the inventors of the present application (in Japanese Patent Application No. 2004-200545) do not use a DCDC converter, and not only a combination of a fuel cell and a battery, but also a plurality of power sources. We are developing a power converter control method that can be used and distributed to reduce the overall volume and loss.
JP 2002-118981 A (paragraphs 0004-0005, FIG. 1)

However, in the configuration of the first example, since the DCDC converter is used, the volume of the entire system including the power source, the power conversion device, and the motor is increased, and the DCDC converter is used for charging and discharging the battery. Loss occurs due to passing through. Therefore, the present invention provides a method of controlling a power converter that can reduce and reduce the overall volume and loss by using and distributing a plurality of power sources without using a DCDC converter, and not limited to a combination of a fuel cell and a battery. For the purpose.
Moreover, in the following prior application (Application No. 2004-200545), there is a case where a short-circuit current flows between the electrodes when the power converter is turned on / off. Was not considered. Then, this invention also aims at providing the control method which prevents the short circuit current between electrodes and prevents the short circuit between electrodes which reduces the heat_generation | fever of a switch.

In order to solve the above-described problems, a method for controlling a power conversion device according to the first invention includes:
A method for controlling a power converter that is connected to a plurality of DC power supplies, generates a drive voltage by generating and synthesizing pulses from the output voltages of each of these DC power supplies, and drives an AC motor,
A short-circuit prevention step for preventing a short circuit between paths having different potentials,
It is characterized by including.

The control method of the power converter according to the second invention is
The power converter comprises a plurality of switches,
The short circuit prevention step includes:
A step of switching any one of the plurality of switches from off to on after a predetermined time has elapsed when both sets of the switches in the inter-electrode paths having different potentials are turned off.
It is characterized by that.

Furthermore, the control method of the power converter according to the third invention is
The short-circuit prevention step further comprises:
A step of preventing a short circuit between paths of the same polarity with different potentials;
Preventing short-circuiting between different-polarity interpolar paths with different potentials based on the state of the same-polarity different-polarity paths with different potentials,
It is characterized by that.

Furthermore, the control method of the power conversion device according to the fourth invention is:
The short-circuit prevention step further comprises:
A step of switching any one of the plurality of switches from off to on after a predetermined time has elapsed when both of the switches in the same-polarity path of different potentials are turned off;
An on signal generating step of generating an on signal of the switch in the interpolar path of different polarity based on the on signal of the plurality of switches in the interpolar path of the same polarity having different potentials,
It is characterized by that.

Furthermore, the control method of the power converter according to the fifth invention is:
The on signal generation step includes:
Generating a switch ON signal in the interpolar path of the different polarity based on a logical product of the ON signals of a plurality of switches in the interpolar path of the same polarity with different potentials,
It is characterized by that.

Furthermore, the control method of the power conversion device according to the sixth invention is:
The short circuit prevention step comprises:
Including a selection step of selecting at least one inter-electrode path to be prevented from being short-circuited from among a plurality of inter-electrode paths having different potentials.
It is characterized by that.

Furthermore, the control method of the power conversion device according to the seventh invention is:
The selection step comprises:
Obtaining a potential difference between poles of different potentials;
A selection step based on the potential difference, which selects at least one of the inter-electrode paths that should be prevented from being short-circuited among the plurality of inter-electrode paths having different potentials based on the obtained potential difference,
The control method is:
A step of switching any one of the plurality of switches from off to on after a predetermined time when both sets of the plurality of switches in the inter-electrode path with different selected potentials have turned off has passed.
It is characterized by that.

Furthermore, the control method of the power converter according to the eighth invention is:
The selection step based on the potential difference includes:
Use a threshold that allows hysteresis control to determine the potential difference.
It is characterized by that.
In other words, once the determination is made, the determination is switched violently, and based on the determination, a threshold value capable of performing hysteresis control is provided in order to prevent chattering of the path switch, and the determination is performed based on the threshold value.

Furthermore, the control method of the power converter according to the ninth aspect of the invention is
The selection step based on the potential difference includes:
Select at least one inter-electrode path that should prevent a short circuit based on the sign of the potential difference,
It is characterized by that.

Furthermore, the control method of the power conversion device according to the tenth invention is
Drive voltage by providing the first and second DC power supply, connecting the negative electrode of the first DC power supply and the negative electrode of the second DC power supply, and generating and synthesizing pulses from the output voltages of each of these DC power supplies Is a control method of a power converter that drives an AC motor by generating
A switch between the positive electrode of the first DC power supply and the output terminal of the power converter in a path that conducts only from the positive electrode of the first DC power supply to the positive electrode of the second DC power supply for each phase of AC Then, after a predetermined time when both of the pair of the switch between the output terminal of the power converter and the positive electrode of the second DC power supply have been turned off, the switch of any one of the pair of switches is turned off to on. A first short-circuit prevention time generation step to be switched;
For each phase of AC, between the positive electrode of the second DC power source and the output terminal of the power converter in a path that conducts only from the positive electrode of the second DC power source to the positive electrode of the first DC power source. After a predetermined time when both the switch and the positive switch between the output terminal of the power converter and the first DC power supply have been turned off has passed, one of the switch sets is switched from OFF to ON. A second short-circuit prevention time generation step;
A switch between the output terminal of the power converter and the positive electrode of the second DC power source in a path that conducts only from the positive electrode of the first DC power source to the positive electrode of the second DC power source for each phase of AC When the switch between the output terminal of the power conversion device and the positive electrode of the first DC power supply is turned on in a path that conducts only from the positive electrode of the second DC power supply to the positive electrode of the first DC power supply, Turning on a switch between the output terminal of the power converter and at least one negative electrode of the first DC power source and the second DC power source;
It is characterized by including.

Furthermore, the control method of the power converter according to the eleventh invention is
The control method further comprises:
Controlling a plurality of switches placed in inter-pole paths having different potentials by a drive signal for each switch,
The short circuit prevention step comprises:
Based on each combination of the drive signal of any one of the plurality of switches and the drive signals of all the other switches, outputting an off signal when detecting a short circuit between the electrodes;
Replacing the output signal of the switch with a drive signal of a switch placed in an inter-pole path in which the short circuit is detected,
It is characterized by that.

Furthermore, a control method for a power converter according to a twelfth aspect of the invention is
The control method further comprises:
Controlling a plurality of switches placed in inter-pole paths having different potentials by a drive signal for each switch,
The short circuit prevention step comprises:
A logical product (a logical product circuit or the like) of a drive signal of any one of the plurality of switches and a signal obtained by logically inverting the drive signals of all other switches (using a logical negation circuit or the like). Using) the generated output signal to replace the drive signal of any one of the switches.
It is characterized by that.

Furthermore, the control method of the power converter according to the thirteenth aspect of the invention is
The control method further comprises:
Controlling a plurality of switches placed in inter-pole paths having different potentials by a drive signal for each switch,
The short circuit prevention step comprises:
Obtaining a potential difference between poles of different potentials;
Generating a path selection signal (voltage discrimination signal) for selecting a path between electrodes to prevent a short circuit based on the potential difference;
Obtaining a logical product of a drive signal of each switch of the plurality of switches and the path selection signal, and generating an output signal obtained by logically inverting the logical product;
An output signal generated by a logical product of the drive signal of any one of the plurality of switches and any one of the generated output signals for all other switches, Replacing the drive signal of one switch,
It is characterized by that.

Further, as described above, the solving means of the present invention has been described as a method, but the present invention is also realized as an apparatus substantially equivalent to these, a program for executing this method by a computer, and a storage medium storing the program. It should be understood that these are included within the scope of the present invention.
For example, when the first invention is realized by the device, the control device for the power converter is
A control device for a power converter that is connected to a plurality of DC power supplies, generates a drive voltage by generating and synthesizing pulses from respective output voltages of these DC power supplies, and drives an AC motor,
Including short-circuit prevention means (circuit) for preventing short-circuiting between paths between different potentials,
It is characterized by that.
The procedure (step) as described above can be realized by using a combination of a plurality of logic circuits (AND, NOT, OR circuit, etc.). (Equivalent circuit) and a procedure using a logic operation can be realized, and such a procedure or a combination of logic circuits also falls within the scope of the present invention.

According to the first aspect of the present invention, it is possible to prevent a short circuit between the electrodes and prevent the switch from being heated due to an unnecessary short circuit current.
Further, according to the second invention, when the switch on the path is switched, a time for turning off the switch is provided, so that it is possible to prevent a short circuit between the electrodes due to a time delay of turning on and off the switch. Heat generation of the switch due to a short-circuit current can be prevented.
Furthermore, according to the third invention, since the interpolar short-circuit prevention is prevented using the same polarity inter-electrode short-circuit prevention result, there is no need to newly generate the different-polar inter-electrode short-circuit prevention. It is possible to simplify the control device or the control circuit.
Furthermore, according to the fourth aspect of the invention, the on signal of the interpolar short circuit prevention switch is generated using the on signal of the same polarity interpolar short circuit prevention switch. Therefore, the control device can be simplified.
Furthermore, according to the fifth aspect of the present invention, the on-signal of the interpolar short circuit between the same polarity is generated based on the logical product of the on signal of the same polarity polar short-circuit prevention switch. It is not necessary to generate an inter-electrode short-circuit prevention, and the control device can be simplified.

Furthermore, according to the sixth aspect, by selecting a path for performing a short circuit prevention, it is not necessary to turn on / off the switch for each switching frequency of the power converter, and the switching loss can be reduced. For example, depending on the magnitude of the voltage, there are combinations that do not require short-circuit prevention. Therefore, it is possible to select a path for performing short-circuit prevention excluding such combinations.
Furthermore, according to the seventh invention, by selecting a path for performing a short circuit prevention using the potential difference between the electrodes, it is not necessary to turn on / off the switch for each switching frequency of the power conversion device. Loss can be reduced.

Further, according to the eighth invention, when the detected voltage value includes noise, the voltage determination signal is switched by the noise and switching is performed. When these voltages are fluctuating, there is an effect that the switching loss is not increased by providing hysteresis.
Furthermore, according to the ninth aspect, by selecting the path for performing the short circuit prevention using the sign of the voltage value, it is not necessary to turn on / off the switch for each switching frequency of the power conversion device. Loss can be reduced.
Furthermore, according to the tenth invention, in order to prevent four sets of short-circuits between the five switches for each phase, the short-circuit prevention time generating means for preventing two sets of short-circuits between the poles, and the generation results thereof Since the ON signal of the remaining switch is generated, the control device can be simplified, the short circuit between the electrodes can be prevented, and the heat generation of the switch due to an unnecessary short circuit current can be prevented.

Furthermore, according to the eleventh aspect, when a set of drive signals for short-circuiting the poles is input, the current for short-circuiting the poles can be prevented by replacing those sets with off signals. It is not necessary to increase the heat generation of the switch.
Furthermore, according to the twelfth invention, when a set of drive signals for short-circuiting between the electrodes is input, by replacing these sets with off signals, it is possible to prevent a current short-circuiting between the electrodes. It is not necessary to increase the heat generation of the switch.
Furthermore, according to the thirteenth invention, it is possible to prevent a current short-circuiting between the electrodes, and it is possible to avoid the increase in heat generation of the switch. Therefore, it is not necessary to newly generate on / off switching, so that switching loss can be further reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 3 shows an example of a circuit diagram of a power converter suitable for use in the method for controlling a power converter according to the present invention. The negative electrode of the power supply 10a and the negative electrode of the power supply 10b are connected to the common negative electrode bus 15. A pair of semiconductor switches 107a, 108a, 109a and diodes 107b, 108b, 109b is connected between the common negative electrode bus 15 and each phase terminal of the motor 20 in the same manner as a generally known lower arm of an inverter. . The positive electrode bus 14 of the power supply 10a and each phase terminal of the motor 20 are connected by semiconductor switches 101a / 101b, 102a / 102b, 103a / 103b, respectively, capable of controlling bidirectional conduction. Further, semiconductor switches 104a / 104b, 105a / 105b, and 106a / 106b that can control bidirectional conduction are also connected between the positive electrode bus 16 of the power supply 10b and each phase terminal of the motor 20.

  A smoothing capacitor 12 is provided between the positive electrode bus 14 and the common negative electrode bus 15 of the power source 10a, and a smoothing capacitor 13 is also provided between the positive electrode bus 16 and the common negative electrode bus 15 of the power source 10b. The power converter 30 is a DC-AC power converter that generates a voltage to be applied to the motor based on the voltage of the above three potentials, the common negative electrode bus, the positive electrode bus of the power source 10a, and the positive electrode bus of the power source 10b. . The semiconductor switch provided in each phase of U phase (30U), V phase (30V), and W phase (30W) is a switch means that generates a voltage to be output to each phase of the AC motor. Alternatively, the necessary voltage is supplied to the motor by changing the ratio of the connection time.

  A first embodiment will be described. FIG. 2 is a configuration diagram showing an example of a motor control system suitable for use in the method for controlling the power conversion apparatus according to the present invention. First, the configuration of the control device 40 will be described. As shown in the figure, 41 is a torque control means for calculating a d-axis current command value id * and a q-axis current command value iq * from an externally provided torque command and motor rotational speed ( Circuit). Reference numeral 42 denotes current control means (circuit) for calculating voltage command values vd * and vq * for matching the dq-axis current command values id * and iq * and the dq-axis current values id and iq. id and iq are obtained from the three-phase currents iu and iv by the three-phase / dq conversion means (circuit) 48. Reference numeral 43 denotes dq / 3-phase voltage conversion means (circuit) for converting the dq-axis voltage command values vd * and vq * into three-phase voltage commands vu *, vq * and vw *. 44 is a U-phase voltage command generated from the voltage of each power supply according to the distribution target value (rto_pa, rto_pb) of the power Pa supplied from the power supply 10a and the power Pb supplied from the power supply 10b. vu_a *, vu_b *, V-phase voltage commands vv_a *, vv_b *, W-phase voltage commands vw_a *, vw_b * are voltage distribution means (circuits) (hereinafter referred to as voltage commands generated from the power supply 10a) A voltage command and a voltage command generated from the power source 10b are referred to as a power source 10b voltage command). 45, the voltage Vdc_a of the power source 10a and the voltage Vdc_b of the power source 10b are input, and the instantaneous modulation rate command mu_a *, which is a standardized voltage command, vu_a *, vu_b *, vv_a *, vv_b *, vw_a *, vw_b *, Modulation rate calculation means (circuit) for generating mu_b *, mv_a *, mv_b *, mw_a *, mw_b *. 46 is a modulation rate correction means (circuit) that performs processing before performing PWM on the instantaneous modulation rate command and generates final instantaneous modulation rate commands mu_a_c *, mu_b_c *, mv_a_c *, mv_b_c *, mw_a_c *, mw_b_c * It is. Reference numeral 47 denotes PWM pulse generation means for generating a PWM pulse for turning on / off each switch of the power converter 30 based on the final instantaneous modulation rate command, and is a main part of the present invention.

As shown in FIG. 2, the voltage distribution unit 44 and the standardized voltage command generation unit 45 generate a voltage command value for setting the power distribution to a desired value. A voltage command vu *, vv *, vw * and a distributed power command value rto_pa (= 1−rto_pb) are input to the voltage distribution unit 44. From these, the power supply 10a divided voltage command and the power supply 10b divided voltage command are obtained by the following calculation.
vu_a * = rto_pa ・ vu *
vu_b * = rto_pb ・ vu *
vv_a * = rto_pa ・ vv *
vv_b * = rto_pb ・ vv *
vw_a * = rto_pa ・ vw *
vw_b * = rto_pb ・ vu *
Hereinafter, the modulation factor calculation unit 45, the modulation factor correction unit 46, and the PWM pulse generation unit 47 will be described in detail with reference to FIGS. FIG. 5 is a flowchart showing the calculation performed by each means of FIG. FIG. 6 shows a method for generating PWM pulses. The following description is performed only for the U phase, but the same operation is performed for the V phase and the W phase.

Modulation rate calculation means 45
The modulation factor calculation means 45 performs calculation 2 shown in FIG. By normalizing the U-phase power supply 10a voltage command vu_a * and power supply 10b voltage command vu_b * by half the value of each DC voltage, the power supply 10a instantaneous modulation rate command mu_a * and the power supply 10b instantaneous modulation rate command Find mu_b *.
mu_a * = vu_a * / (Vdc_a / 2)
mu_b * = vu_b * / (Vdc_b / 2)

このように、電源10a分瞬時変調率指令ｍu_a*、電源10b分瞬時変調率指令ｍu*_bに分配電力目標値の大きさに応じた値を乗じるとともにオフセット値を減算することで、分配電力目標値の大きさが大きい電源から生成する電圧を大きくできるようにしている。 Modulation rate correction means 46
The modulation factor correction means 46 performs calculation 3 shown in FIG. In this calculation, the power supply voltages Vdc_a and Vdc_b and the distributed power target values rto_pa and rto_pb are used to correct the instantaneous modulation factor command mu_a * for the power supply 10a and the instantaneous modulation factor command mu * _b for the power supply 10b based on the following equations. Do.

In this way, the power supply 10a instantaneous modulation rate command mu_a * and the power supply 10b instantaneous modulation rate command mu * _b are multiplied by a value corresponding to the size of the distribution power target value and the offset value is subtracted to obtain the distribution power target. The voltage generated from the power supply having a large value can be increased.

PWM pulse generating means 47 (corresponding to the first to fifth inventions)
In FIG. 6, a power supply 10a carrier is a triangular wave carrier for generating a PWM pulse for driving each switch in order to output a voltage pulse from the voltage Vdc_a of the power supply 10a. Similarly, a triangular wave carrier is used as the power supply 10b carrier. Is provided. These two triangular wave carriers have values of an upper limit of +1 and a lower limit of -1, and have a phase difference of 180 degrees.
Here, the signals for driving the U-phase switches are set as follows based on FIG.
A: Switch drive signal conducting from the power supply 10a to the output terminal B: Switch drive signal conducting from the output terminal to the negative electrode C: Switch drive signal conducting from the output terminal to the power supply 10a D: Power supply Switch drive signal conducting from 10b to output terminal E: Switch drive signal conducting from output terminal to power supply 10b

First, a pulse generation method when a voltage pulse is output from the power supply 10a will be described. When outputting a PWM pulse from the power supply 10a, it is necessary to turn on A. If there is a potential difference between the positive electrode and the positive electrode and Vdc_a> Vdc_b, when both A and E are turned on, a current that short-circuits between the positive electrodes flows. When the switch is constituted by a semiconductor switch, a time delay occurs in switching from the off state to the on state. For example, when A is switched from on to off and E is switched from off to on at the same time, it takes time for A to completely turn off. At this time, a short-circuit current flows, and the amount of heat generated by the semiconductor switch installed in this path increases. In order to prevent such an increase in heat generation, A and E are switched from OFF to ON after a time during which both the drive signals A and E are turned off. In this way, pulse generation is performed by adding a short-circuit prevention time (dead time) to the drive signal.
Similarly to adding dead time to the drive signals of A and E, dead time is added to E and C in order to prevent short circuit between the positive electrodes, and furthermore, in order to prevent short circuit between the positive electrode and negative electrode, A dead time is added to A and B, and E and B.

A method for adding dead time to the A and E drive signals will be described below with reference to FIG. In order to generate a drive signal with a dead time added, mu_a_c_up * and mu_a_c_down * offset from the mu_a_c * by the dead time are obtained as follows.
mu_a_c_up * = mu_a_c * + Hd
mu_a_c_down * = mu_a_c * − Hd
Here, Hd is obtained from the amplitude of the triangular wave (from the base to the apex) Htr, the period Ttr, and the dead time Td as follows.
Hd = 2Td · Htr / Ttr
The carrier and mu_a_c *, mu_a_c_up *, mu_a_c_down * are compared, and the drive signals for the A and E switches are obtained according to the following rules.
If mu_a_c_down * ≧ carrier for power supply 10a, A = ON
If mu_a_c * ≤ carrier for power supply 10a, A = OFF
If mu_a_c * ≥ carrier for power supply 10a, E = OFF
mu_a_c_up * ≤ Carrier for power supply 10a E = ON
Thus, by generating the drive signal, a dead time of Td can be provided between A and E, and a short circuit between the positive electrodes can be prevented.

Further, the pulse generation method when outputting the voltage pulse from the power supply 10b is the same as that of the power supply 10a, and the following mu_b_c_up * and mu_b_c_down * are obtained and compared with the carrier for the power supply 10b (FIG. 9).
mu_b_c_up * = mu_b_c * + Hd
mu_b_c_down * = mu_b_c * − Hd
The drive signals for the D and C switches are obtained according to the following rules.
If mu_b_c_down * ≥ carrier for power supply 10b, D = ON
If mu_b_c * ≤ carrier for power supply 10b, D = OFF
If mu_b_c * ≥ carrier for power supply 10b, C = OFF
If mu_b_c_up * ≤ carrier for power supply 10b, C = ON
In this way, a dead time of Td can be provided between D and C, and a short circuit between the positive electrodes can be prevented.

The drive signal B is generated from the logical product of the generated drive signals E and C (corresponding to the third, fourth and fifth inventions).
B = E ・ C
E is a drive signal with a dead time added to A, and C is a drive signal with a dead time added to D. Therefore, by generating B from the logical product of E and C, dead time can also be generated for B and A and B and E. An example of pulse generation with a dead time added is shown in FIG.

  In this way, by generating a pulse with a dead time added, it is possible to prevent a short circuit between the electrodes, and it is possible to prevent the switch from being heated due to an unnecessary short circuit current. Also, according to the generation method of the present invention, dead time is added to two sets of A and E, D and C, and B is generated from the logical product, thereby generating dead times of A and B, E and B. This can be omitted, and the control device can be simplified.

In the second embodiment, only differences from the first embodiment will be described.
Means for obtaining a potential difference (equivalent to the seventh, eighth and ninth inventions)
In FIG. 11, the voltage comparator 101 receives the voltage Vdc_a of the power supply 10a and the voltage Vdc_b of the power supply 10b, compares them, and outputs a voltage determination signal. The voltage determination signal is an H signal when Vdc_a−Vdc_b> 0, and an L signal otherwise. In this voltage determination, Vdc_a-Vdc_b is determined by providing a hysteresis (for example, a threshold having a predetermined width). As shown in FIG. 12, the subtractor 103 calculates Vdc_a−Vdc_b, and the output is passed through the hysteresis controller 104 to output H / L of the voltage determination signal.

Means for selecting a path for preventing a short circuit (corresponding to the sixth, seventh, eighth and ninth inventions)
The short-circuit prevention path determination unit 102 receives the voltage determination signal and the E and C drive signals as inputs, and outputs new E and C drive signals. The internal operation of this short-circuit prevention determiner is performed by a logical operation as shown in FIG. 13, and when the voltage determination signal is H, a logical sum is calculated with C. Therefore, C is an ON signal. . When the voltage determination signal is L. E becomes an ON signal.
This operation is based on the following idea. If the voltage determination signal is H, that is, Vdc_a> Vdc_b, when both A and E are turned on, a current for short-circuiting between the positive electrodes flows, so it is necessary to provide a short-circuit prevention time between the power supplies. The generation of the short-circuit prevention time is performed in the same manner as in the first embodiment.
On the other hand, even if D and C are turned on at the same time, since Vdc_a> Vdc_b, this voltage is applied to the switch in this path, but no short-circuit current flows. For this reason, from the point of prevention of short circuit current, C may remain on, and between the positive electrodes, short circuit prevention by A and E may be performed. Similarly, when the voltage determination signal is L, E can be kept on. In this way, by receiving the voltage determination signal and turning on C or E, it is not necessary to turn on or off the C or E switch for each switching frequency of the power conversion device, thereby reducing the switching loss. Can do.

  When the potential difference is close to 0 and the detected voltage value includes noise, the voltage determination signal is switched by the noise. That is, switching between E and C is performed. In addition, when these voltages are fluctuating at values close to the voltages of the power supply 10a and the power supply 10b, providing a hysteresis has an effect of not increasing the switching loss. However, if a hysteresis is provided, a short-circuit current may flow. However, by setting the hysteresis width (threshold used for hysteresis control) appropriately, the magnitude of the short-circuit current will affect the heat generated by the switch. Has no significant effect.

A third embodiment (corresponding to the eleventh and twelfth inventions) will be described with reference to FIG. It is a logic circuit that receives drive signals A to E as inputs. When A and E are viewed as a circuit for preventing a short circuit between the positive electrodes, a new E is output from the logical product of the logically inverted signal of A and the signal of E. Conversely, since a new A is output from the logical product of the logically inverted signal of E and the signal of A, when both A and E are on signals, A and E are replaced with off signals. . A similar circuit is also provided between D and C as a circuit for preventing the other positive electrode short circuit. As a circuit for preventing a short circuit between the positive and negative electrodes, when A and B are simultaneously turned on, and when D and B are simultaneously turned on, they are replaced with an off signal by a circuit similar to the above-described logical operation.
By providing such a circuit, when a set of drive signals that short-circuit the poles is input, by replacing those sets with off-signals, the current that short-circuits the poles can be prevented, and the switch It is not necessary to increase the fever.

  In the fourth embodiment (corresponding to the thirteenth invention), only differences from the third embodiment will be described with reference to FIG. The voltage discrimination signal is an H signal when Vdc_a-Vdc_b> 0, and an L signal when not, and is generated by the voltage comparator shown in the second embodiment. The logical product of the voltage determination signal and the drive signal A or the voltage determination signal and the drive signal E is calculated. The logical product of the signal obtained by logically inverting the output of these logical products and the drive signals A and E is calculated. When Vdc_a-Vdc_b> 0, if A and E are turned on at the same time, a current for short-circuiting between the positive electrodes flows. However, by using the circuit of FIG. 15, A and E are simultaneously turned off. In the case of Vdc_a−Vdc_b ≦ 0, since the voltage determination signal is L, the drive signals A and E output from this circuit are both ON signals. In this case, a short-circuit current does not flow even when simultaneously turned on.

Similarly, a circuit having a voltage determination signal as an input is also provided for C and D. In C and D, the path through which the short-circuit current flows is opposite to that in the case of A and E described above. Therefore, a logical inversion signal of the voltage determination signal is also calculated and used for input of each logical product.
By providing such a circuit, it is possible to prevent a current short-circuiting between the electrodes, and it is not necessary to increase the heat generation of the switch, and for a path that does not need to prevent a short-circuit, a voltage determination signal is used. Therefore, it is possible to further reduce the switching loss because the on / off switching is not newly generated.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention.

It is a figure which shows the structure of the conventional motor control system. It is a block diagram which shows an example of the motor control system suitable for use of the control method of the power converter device by this invention. It is an example of the circuit diagram of the power converter device suitable for use of the control method of the power converter device by this invention. It is the figure which extracted a part of FIG. It is a flowchart which shows the calculation of each block of FIG. It is a figure which shows the calculation in the PWM pulse production | generation means of 1st Example. It is a figure which shows the structure which extracted only the U phase from FIG. It is a figure which shows the pulse generation of A and E by a triangular wave comparison. It is a figure which shows the pulse generation of D and C by a triangular wave comparison. It is a figure which shows the example of the pulse generation to which the dead time was added. It is a figure which shows a part of control block diagram in a 2nd Example. It is a figure which shows the detail of the voltage comparator of FIG. It is a figure which shows the detail of the short circuit prevention path | route determination device of FIG. It is a figure which shows the short circuit prevention circuit in a 3rd Example. It is a figure which shows the short circuit prevention circuit in a 4th Example.

Explanation of symbols

10a, 10b power supply
12,13 Smoothing capacitor
14 Positive bus of power supply 10a
15 Common negative electrode bus
16 Power supply 10b positive bus
20 Motor
101a / 101b, 102a / 102b, 103a / 103b Semiconductor switch
104a / 104b, 105a / 105b, 106a / 106b semiconductor switch
107a, 108a, 109a Semiconductor switch
107b, 108b, 109b Diode
30 Power converter
30U U-phase switch group
30V V-phase switch group
30W W phase switch group
40 Control unit
41 Torque control means
42 Current control means
43 dq / 3-phase voltage conversion means
44 Voltage distribution means
45 Modulation rate calculation means
46 Modulation rate correction means
47 PWM pulse generation means
48 Three-phase / dq voltage conversion means

Claims (13)

A method for controlling a power converter that is connected to a plurality of DC power supplies, generates a drive voltage by generating and synthesizing pulses from the output voltages of each of these DC power supplies, and drives an AC motor,
A short-circuit prevention step for preventing a short circuit between paths having different potentials,
The control method of the power converter device characterized by including. In the control method of the power converter device according to claim 1,
The power converter comprises a plurality of switches,
The short circuit prevention step includes:
A step of switching any one of the plurality of switches from off to on after a predetermined time has elapsed when both sets of the switches in the inter-electrode paths having different potentials are turned off.
A method for controlling a power conversion device. In the control method of the power converter device according to claim 1,
The short circuit prevention step further includes:
A step of preventing a short circuit between paths of the same polarity with different potentials;
Preventing short-circuiting between different-polarity interpolar paths with different potentials based on the state of the same-polarity different-polarity paths with different potentials,
A method for controlling a power conversion device. In the control method of the power converter device according to claim 3,
The short circuit prevention step further includes:
A step of switching any one of the plurality of switches from off to on after a predetermined time has elapsed when both of the switches in the same-polarity path of different potentials are turned off;
An on signal generating step of generating an on signal of the switch in the interpolar path of different polarity based on the on signal of the plurality of switches in the interpolar path of the same polarity having different potentials,
A method for controlling a power conversion device. In the control method of the power converter device according to claim 4,
The on signal generation step includes:
Generating a switch ON signal in the interpolar path of the different polarity based on a logical product of the ON signals of a plurality of switches in the interpolar path of the same polarity with different potentials,
A method for controlling a power conversion device. In the control method of the power converter device according to claim 1,
The short circuit prevention step includes:
Including a selection step of selecting at least one inter-electrode path to be prevented from being short-circuited from among a plurality of inter-electrode paths having different potentials.
A method for controlling a power conversion device. In the control method of the power converter device according to claim 6,
The selection step includes
Obtaining a potential difference between poles of different potentials;
A selection step based on the potential difference, which selects at least one of the inter-electrode paths that should be prevented from being short-circuited among the plurality of inter-electrode paths having different potentials based on the obtained potential difference,
The control method is:
A step of switching any one of the plurality of switches from off to on after a predetermined time when both sets of the plurality of switches in the inter-electrode path with different selected potentials have turned off has passed.
A method for controlling a power conversion device. In the control method of the power converter device according to claim 7,
The selection step based on the potential difference includes:
Use a threshold that allows hysteresis control to determine the potential difference.
A method for controlling a power conversion device. In the control method of the power converter device according to claim 7,
The selection step based on the potential difference includes:
Select at least one inter-electrode path that should prevent a short circuit based on the sign of the potential difference,
A method for controlling a power conversion device. Drive voltage by providing the first and second DC power supply, connecting the negative electrode of the first DC power supply and the negative electrode of the second DC power supply, and generating and synthesizing pulses from the output voltages of each of these DC power supplies Is a control method of a power converter that drives an AC motor by generating
A switch between the positive electrode of the first DC power supply and the output terminal of the power converter in a path that conducts only from the positive electrode of the first DC power supply to the positive electrode of the second DC power supply for each phase of AC Then, after a predetermined time when both of the pair of the switch between the output terminal of the power converter and the positive electrode of the second DC power supply have been turned off, the switch of any one of the pair of switches is turned off to on. A first short-circuit prevention time generation step to be switched;
For each phase of AC, between the positive electrode of the second DC power source and the output terminal of the power converter in a path that conducts only from the positive electrode of the second DC power source to the positive electrode of the first DC power source. After a predetermined time when both the switch and the positive switch between the output terminal of the power converter and the first DC power supply have been turned off has passed, one of the switch sets is switched from OFF to ON. A second short-circuit prevention time generation step;
A switch between the output terminal of the power converter and the positive electrode of the second DC power source in a path that conducts only from the positive electrode of the first DC power source to the positive electrode of the second DC power source for each phase of AC When the switch between the output terminal of the power conversion device and the positive electrode of the first DC power supply is turned on in a path that conducts only from the positive electrode of the second DC power supply to the positive electrode of the first DC power supply, Turning on a switch between the output terminal of the power converter and at least one negative electrode of the first DC power source and the second DC power source;
The control method of the power converter device characterized by including. In the control method of the power converter device according to claim 1,
The control method further includes:
Controlling a plurality of switches placed in inter-pole paths having different potentials by a drive signal for each switch,
The short circuit prevention step includes:
Based on each combination of the drive signal of any one of the plurality of switches and the drive signals of all the other switches, outputting an off signal when detecting a short circuit between the electrodes;
Replacing the output signal of the switch with a drive signal of a switch placed in an inter-pole path in which the short circuit is detected,
A method for controlling a power conversion device. In the control method of the power converter device according to claim 1,
The control method further includes:
Controlling a plurality of switches placed in inter-pole paths having different potentials by a drive signal for each switch,
The short circuit prevention step includes:
An output signal generated by a logical product of a drive signal of any one of the plurality of switches and a signal obtained by logically inverting the drive signals of all other switches, and the drive signal of any one of the switches Including the step of replacing
A method for controlling a power conversion device. In the control method of the power converter device according to claim 1,
The control method further includes:
Controlling a plurality of switches placed in inter-pole paths having different potentials by a drive signal for each switch,
The short circuit prevention step includes:
Obtaining a potential difference between poles of different potentials;
Generating a path selection signal for selecting a path between electrodes to prevent a short circuit based on the potential difference; and
Obtaining a logical product of a drive signal of each switch of the plurality of switches and the path selection signal, and generating an output signal obtained by logically inverting the logical product;
An output signal generated by a logical product of the drive signal of any one of the plurality of switches and any one of the generated output signals for all other switches, Replacing the drive signal of one switch,
A method for controlling a power conversion device.

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