JP5788540B2 - Electric motor drive device and refrigeration air conditioner - Google Patents

Description

  The present invention relates to an electric motor drive device and a refrigeration air conditioner.

  As variable voltage / variable frequency inverters are put into practical use, various application fields of power converters have been developed. For example, a three-phase voltage source inverter or the like is used for a drive circuit used in an electric motor drive device or the like. The three-phase voltage source inverter includes a three-phase bridge circuit using a power semiconductor switching element such as a thyristor, transistor, IGBT, or MOSFET. In this circuit, the switching element of each phase can be realized by directly connecting the positive terminal and the negative terminal to the positive terminal and the negative terminal of the DC voltage source, respectively. In recent years, as the efficiency of devices has been improved, such standard circuits have been improved to further increase the efficiency.

  In the prior art, for example, “a pair of main circuit switching elements connected in series to a DC voltage source and supplying power to a load, freewheeling diodes connected in reverse parallel to these main circuit switching elements, and each of these freewheeling diodes A power conversion device comprising a reverse voltage application circuit that applies a reverse voltage smaller than that of the DC voltage source to each of the freewheeling diodes when shutting off ”has been proposed (see, for example, Patent Document 1). .

JP-A-10-327585 (Claim 1)

  The conventional device as described above has a problem that a high-function and expensive control device is required to control the reverse voltage application timing due to dv / dt variations of the switching elements. In addition, since the reverse voltage is applied by the additional circuit, there is a problem that the inverter efficiency is remarkably lowered when the additional circuit fails.

  Further, the conventional inverter device has a problem in that recovery loss occurs due to a switching element having a parasitic diode during switching.

The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain an electric motor drive device and a refrigeration air conditioner that can reduce recovery loss.
It is another object of the present invention to obtain an electric motor drive device and a refrigeration air conditioner that can improve energy efficiency with a relatively simple configuration.

An electric motor drive device according to the present invention is an electric motor drive device that drives an electric motor, and includes an inverter device that drives the electric motor and a second inverter device that drives the electric motor, and a current that flows in a winding of the electric motor Current detecting means for detecting current and control means for controlling the inverter device and the second inverter device, wherein the inverter device bridges six arms for conducting and interrupting current to connect a three-phase inverter. Among the six arms, three arms connected to the high voltage side or the low voltage side of the DC voltage supplied to the inverter device have parasitic diodes and a plurality of switching elements connected in series to each other. A free-wheeling diode connected in parallel with the plurality of switching elements, and the switching element includes the switching element. The polarity of the parasitic diode of the switching element is connected to be opposite to the polarity of the parasitic diode of another adjacent switching element, and the polarity of the parasitic diode of the plurality of switching elements is opposite to that of the freewheeling diode. The switching element has a short reverse recovery time of the parasitic diode compared to other switching elements, and the conduction path of the parasitic diode flowing to the switching element having the same polarity as the free-wheeling diode is blocked, The time for forming an equivalent short circuit is reduced, and the other three arms include one second switching element and a second free- wheeling diode connected in parallel with the second switching element. And the second inverter device has one switching element and one free-wheeling diode. And at least one of the control means, the control means, based on the current detected by the current detection means, the inverter device in an inverter rotation angle section in which the combination of the basic voltage vectors for generating the voltage command vector is the same. Phase with no switching operation among the three phases, two-phase modulation with extension that keeps the switching element of the arm connected to the high voltage side on, or a phase with no switching operation among the three phases Based on the current detected by the current detection means, the PWM control is performed by two-phase modulation with under tension that maintains the switching element of the arm connected to the low-voltage side in an ON state, and the motor is driven. Each phase voltage command value is obtained, the inverter device is PWM controlled based on each phase voltage command value, and the voltage polarity of each phase voltage command value is set. Based on this, the second inverter device is controlled.

  A refrigerating and air-conditioning apparatus according to the present invention includes the above-described electric motor driving device and an electric motor driven by the electric motor driving device.

  According to the present invention, since the plurality of switching elements having the parasitic diode include the arms connected in series with each other, recovery loss at the time of switching of the arms can be reduced. Moreover, energy efficiency can be improved with a relatively simple configuration.

FIG. 3 is a diagram illustrating a configuration of an arm of the inverter circuit according to the first embodiment. 1 is a diagram illustrating a configuration of an inverter circuit according to a first embodiment. 1 is a schematic diagram showing a structure of a MOSFET having an SJ structure according to a first embodiment. It is a figure which shows an example of the relationship between the drain-source voltage regarding on MOSFET of SJ structure, and ON resistance. It is a figure which shows the structure of the electric motor drive device which concerns on Embodiment 2. FIG. 10 is a flowchart showing a PWM creation sequence according to the second embodiment. It is a figure which shows an example of the PWM switching pattern of the electric motor drive device which concerns on Embodiment 2. FIG. It is a figure which shows the structure of the electric motor drive device which concerns on Embodiment 3. FIG. It is a figure showing the upper arm logic state of a PWM inverter. It is a figure which shows the relationship between the inverter rotation angle of a PWM inverter, and a voltage command vector. 10 is a diagram illustrating an example of a PWM switching pattern in underlined two-phase modulation of an inverter circuit according to Embodiment 3. FIG. It is a figure which shows the structure of the electric motor drive device which concerns on Embodiment 3. FIG. FIG. 10 is a diagram illustrating an example of a PWM switching pattern in two-phase modulation with an overlay on an inverter circuit according to a third embodiment. It is a figure which shows the structure of the electric motor drive device which concerns on Embodiment 4. FIG. It is a figure showing an example of the U phase voltage command and slave side inverter U phase electric potential of the electric motor drive device which concerns on Embodiment 4. FIG. It is a figure which shows the structure of the electric motor drive device which concerns on Embodiment 5. FIG. FIG. 10 is a diagram showing a configuration of a grid-connected photovoltaic power generation system according to Embodiment 6. It is a figure which shows the structure of the refrigeration air conditioning apparatus which concerns on Embodiment 7. FIG. It is a figure which shows the structure of the conventional inverter circuit. It is a figure which shows an example of the equivalent short circuit formation by the parasitic diode of the conventional MOSFET. It is the figure which showed an example of the short circuit current concerning the conventional inverter circuit.

Embodiment 1 FIG.
<Configuration of arm 4>
FIG. 1 is a diagram illustrating a configuration of an arm of an inverter circuit according to the first embodiment.
As shown in FIG. 1, the arm 4 includes an upper switching element 5, a lower switching element 6, and a free wheel diode 9. This arm 4 conducts and cuts off current.

  The upper switching element 5 is configured by, for example, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) having a super junction structure (hereinafter referred to as “SJ structure”). The upper switching element 5 has a parasitic diode 7. The SJ structure will be described later.

The lower switching element 6 is configured by a MOSFET. The lower switching element 6 has a parasitic diode 8.
The parasitic diode 8 of the lower switching element 6 has a shorter reverse recovery time than the parasitic diode 7 of the upper switching element 5.
The lower switching element 6 is not necessarily required to have a high breakdown voltage, and may have a low breakdown voltage. For example, the lower switching element 6 may have a lower withstand voltage than the upper switching element 5.

  The upper switching element 5 and the lower switching element 6 correspond to the “switching element” in the present invention.

The upper switching element 5 and the lower switching element 6 are connected in series with each other.
For example, an upper switching element 5 constituted by an n-channel MOSFET and a lower switching element 6 constituted by a p-channel MOSFET are connected in series.
Further, for example, an upper switching element 5 constituted by a p-channel MOSFET and a lower switching element 6 constituted by an n-channel MOSFET are connected in series.
That is, the upper switching element 5 and the lower switching element 6 are connected in series with a MOSFET having a channel different from that of the MOSFET.

Further, for example, the upper switching element 5 configured by an n-channel MOSFET and the lower switching element 6 configured by an n-channel MOSFET are connected in reverse series as a source common.
That is, the upper switching element 5 and the lower switching element 6 are connected in reverse series with a MOSFET having the same channel as that of the MOSFET.

  By connecting the upper switching element 5 and the lower switching element 6 in this way, the polarity of the parasitic diode 7 of the upper switching element 5 and the polarity of the parasitic diode 8 of the lower switching element 6 are reversed in series. Connected.

The freewheeling diode 9 is connected in parallel with the upper switching element 5 and the lower switching element 6. The free wheeling diode 9 is connected so as to have the same polarity as the parasitic diode 7 of the upper switching element 5.
The freewheeling diode 9 has a shorter reverse recovery time than the parasitic diode 7 and the parasitic diode 8.
The freewheeling diode 9 functions to flow a freewheeling current when the upper switching element 5 and the lower switching element 6 are in the off state.

  In the present embodiment, a mode in which a MOSFET is used as the “switching element” will be described. However, the present invention is not limited to this, and any switching element having a parasitic diode may be used. it can.

  In the present embodiment, the case where the arm 4 is provided with two switching elements will be described. However, the present invention is not limited to this, and two or more switching elements may be provided.

<Configuration of inverter circuit 2>
FIG. 2 is a diagram illustrating a configuration of the inverter circuit according to the first embodiment.
As shown in FIG. 2, the inverter circuit 2 is configured by bridge-connecting six arms 4a to 4f.
The inverter circuit 2 conducts and cuts off the current by the arms 4 a to 4 f, converts the DC voltage from the DC voltage source 12 into a three-phase AC having an arbitrary voltage and an arbitrary frequency, and supplies the converted voltage to the load device 16. Is.

The inverter circuit 2 corresponds to the “inverter device” in the present invention.
The inverter device is also referred to as a power conversion device.

One end of each of the arms 4a, 4b, and 4c is connected to the high voltage side (P side) of the DC voltage source 12.
One end of each of the arms 4d, 4e, and 7f is connected to the low voltage side (N side) of the DC voltage source 12.
The connection point between the arms 4 a and 4 d, the connection point between the arms 4 b and 4 e, and the connection point between the arms 4 c and 4 f are connected to the load device 16.

In the following description, the arms 4a, 4b, and 4c are also referred to as “upper arms”.
In the following description, the arms 4d, 4e, and 4f are also referred to as “lower arms”.

Each arm 4a-4f is provided with upper switching elements 5a-5f, lower switching elements 6a-6f, and freewheeling diodes 9a-9f.
The upper switching elements 5a to 5f include parasitic diodes 7a to 7f. The lower switching elements 6a to 6f include parasitic diodes 8a to 8f.

The configuration of the arm 4 and the inverter circuit 2 including the arm 4 in the present embodiment has been described above.
Next, the characteristics of the SJ structure MOSFET used for the upper switching element 5 and the problems of the conventional inverter circuit using the SJ structure MOSFET will be described.

<SJ structure MOSFET>
Power devices such as IGBTs and MOSFETs have been used in various applications from consumer equipment to industrial equipment. Currently, device development using SiC (silicon carbide), GaN (gallium nitride) and the like has been performed in various forms.
On the other hand, power MOSFETs having an SJ structure have emerged, and devices having a low on-resistance (ultra-low on-resistance) compared to conventional structures have been realized.

FIG. 3 is a schematic diagram showing the structure of the SJ-structure MOSFET according to the first embodiment.
As shown in FIG. 3, the MOSFET having the SJ structure includes a gate 21, a source 22, a drain 23, a substrate (polarity n +) 24, a p layer 25, and an n layer 26.
The MOSFET having the SJ structure has an advantage that the on-resistance can be reduced and the breakdown voltage can be improved by balancing the charge of the p layer 25 and the n layer 26.

FIG. 4 is a diagram showing an example of the relationship between the drain-source voltage and the on-resistance for the SJ-structure MOSFET.
As shown in FIG. 4, in the conventional MOSFET, the on-resistance increases as the drain-source voltage increases. In the MOSFET having the SJ structure, the on-resistance can be kept low.
However, the SJ-structure MOSFET has a characteristic that the reverse recovery time of the parasitic diode is longer than that of the conventional MOSFET.

<Problems with conventional inverter circuits>
A problem in applying the SJ structure MOSFET having the above characteristics to an inverter circuit will be described.

FIG. 19 is a diagram showing a configuration of a conventional inverter circuit.
As shown in FIG. 19, the conventional inverter circuit 2 bridge-connects switching elements 101a to 101f made of MOSFETs having an SJ structure. The inverter circuit 2 performs switching control of the switching elements 101a to 101f based on, for example, a PWM signal from the control unit 11.
Thereby, the DC voltage from the DC voltage source 12 is converted into a three-phase AC having an arbitrary voltage and an arbitrary frequency, and supplied to the electric motor 1, for example.

As described above, the configuration of the conventional inverter circuit 2 is generally a circuit having one switching element 101a to 101f on each of the upper arm and the lower arm.
When the motor driving operation using PWM is performed with such a circuit configuration, the recovery loss of the parasitic diodes 102a to 102f associated with the switching elements 101a to 101f cannot be ignored.

FIG. 20 is a diagram showing an example of forming an equivalent short circuit using a parasitic diode of a conventional MOSFET.
For example, focus on the U phase. Now, both the U-phase upper switching element 101a and the U-phase lower switching element 101d are turned off. A case where the switching element 101a on the upper side of the U phase is turned on when a load current (return current) flows through the parasitic diode 102d on the lower side of the U phase will be considered.
In this case, even if a reverse bias is applied to the parasitic diode 102d, the accumulated carriers (charges) can be energized during the reverse recovery time (recovery time).
That is, since the parasitic diode 102d can be regarded as a kind of capacitor, the parasitic diode 102d is in a conductive state until the stored charge amount is completely discharged, that is, until the parasitic diode 102d is turned off.
For this reason, as shown in FIG. 20, when the switching element 101a on the upper side of the U phase is turned on, a circuit for short-circuiting the DC voltage source 12 is formed during the reverse recovery time of the parasitic diode 102d. That is, during this period, the switching element 101a on the upper side of the U phase and the parasitic diode 102d on the lower side of the U phase can be equivalently regarded as a short circuit.
The time for forming such an equivalent short circuit depends on the reverse recovery time of the parasitic diode 102 of the MOSFET, and the recovery loss increases as the reverse recovery time increases.
As in this example, in the conventional inverter circuit 2, when an SJ-structure MOSFET having a long reverse recovery time is used for the switching element 101, the time required for forming an equivalent short circuit due to the presence of the parasitic diode 102 when switching is switched. The recovery loss was large because

FIG. 21 is a diagram showing an example of a short-circuit current according to a conventional inverter circuit.
FIG. 21 shows a short circuit current on the main circuit side (DC voltage source 12 side) due to an equivalent short circuit at turn-on.
As shown in FIG. 21, when an arbitrary switching element 101 is turned off and the switching element 101 on the opposite side is turned on, it is equivalent in the loop path to the main circuit side until the charge of the parasitic diode 102 is completely discharged. Since a short circuit current flows, loss is worsened.

<Operation of inverter circuit 2>
Next, the operation of the inverter circuit 2 that prevents the short-circuit current as described above and reduces the recovery loss will be described.

This will be described with reference to FIG. 2 again.
In the present embodiment, the upper switching element 5 and the lower switching element 6 of the arm 4 are supplied with gate signals of the same logic. That is, the upper switching element 5 and the lower switching element 6 in the same arm 4 are controlled to the on state and the off state at the same timing.

For example, focus on the U phase. Now, both the U-phase upper arm 4a and the U-phase lower arm 4d are turned off. In this case, a load current (return current) flows through the return diode 9d of the U-phase lower arm 4d.
At this time, since the parasitic diode 8d of the lower switching element 6d is connected so as to have a reverse polarity to the freewheeling diode 9d, the parasitic diode 8d blocks a conduction path through which the load current flows to the upper switching element 5. Yes. For this reason, the load current does not flow through the parasitic diode 7d having a long reverse recovery time.
Next, when the U-phase upper arm 4a is turned on, even if a reverse bias is applied to the parasitic diode 7d, no load current flows through the parasitic diode 7d, so that no recovery current flows.

  As in this example, the inverter circuit 2 according to the present embodiment does not turn on the upper switching element 5 at the time of switching switching even when the upper switching element 5 having the parasitic diode 7 having a long reverse recovery time is used. .

  Since the load current flows through the freewheeling diode 9, the arm 4 can be conducted only during the reverse recovery time (recovery time) of the freewheeling diode 9.

As described above, in the present embodiment, the arm 4 of the inverter circuit 2 is connected in series so that the parasitic diode 7 of the upper switching element 5 and the parasitic diode 8 of the lower switching element 6 are opposite in polarity. Has been.
For this reason, the load current does not flow to the upper switching element 5 and the lower switching element 6, and it is possible to suppress the recovery current from flowing to the upper switching element 5 and the lower switching element 6 during switching.
Therefore, even when the upper switching element 5 having the parasitic diode 7 having a long reverse recovery time is used, the recovery loss can be reduced.
Therefore, the efficiency of the inverter circuit 2 can be improved.

  Further, the parasitic diode 8 of the lower switching element 6 has a shorter reverse recovery time than the parasitic diode 7 of the upper switching element 5. For this reason, the conduction path through which the load current flows to the upper switching element 5 when the arm 4 is switched can be blocked, the time for forming the equivalent short circuit can be shortened, and the recovery loss can be reduced.

The arm 4 includes a free wheeling diode 9 connected in parallel with the upper switching element 5 and the lower switching element 6. For this reason, a load current can be passed through the freewheeling diode 9.
The reverse recovery time of the free wheeling diode 9 is shorter than that of the parasitic diode 7 of the upper switching element 5. For this reason, the time for forming an equivalent short circuit during switching of the arm 4 can be shortened, and recovery loss can be reduced.

  Further, an SJ structure MOSFET is used as the upper switching element 5. As a result, the on-resistance can be reduced, and the recovery loss can be reduced without impairing the merit that the breakdown voltage can be improved.

  Further, when a low-breakdown-voltage MOS-FET is used for the lower switching element 6, the channel resistance is low and the built-in potential (potential difference generated by the electric field in the depletion layer region) is low. Therefore, a decrease in efficiency due to an increase in the number of switching elements can be minimized.

  In the present embodiment, the case of the inverter circuit 2 using the SJ-structure MOSFET is shown, but any switching element having a parasitic diode or parasitic inductance can be used.

  In addition, by using a high-speed type that has a short reverse recovery time for the freewheeling diode 9, a short circuit can be further formed due to a difference in reverse recovery time characteristics between the upper switching element 5 in the arm 4 and the lower switching element 6. Can be prevented.

  Note that at least one or all of the arms 4 constituting the inverter circuit 2 may be modularized. By mounting such a module on the inverter circuit 2, it is possible to remove noise factors such as an increase in lead inductance. In addition, the mounting area can be reduced.

Embodiment 2. FIG.
In the present embodiment, a description will be given of an electric motor drive device including the inverter circuit 2 of the first embodiment.

<Configuration>
FIG. 5 is a diagram illustrating a configuration of the electric motor drive device according to the second embodiment.
As shown in FIG. 5, the electric motor drive device includes an inverter circuit 2, a current detection unit 3 a, a current detection unit 3 b, a voltage detection unit 10, a control unit 11, and a DC voltage source 12.
This electric motor driving device is for driving the electric motor 1.

  The control unit 11 corresponds to a “control unit” in the present invention.

  The electric motor 1 is constituted by, for example, a three-phase synchronous motor. The electric motor 1 is connected to the inverter circuit 2.

  The inverter circuit 2 has the same configuration as that of the first embodiment described above. In addition, the same code | symbol is attached | subjected to the structure similar to the said Embodiment 1. FIG.

  The current detection means 3 a and 3 b detect a current (hereinafter also referred to as “motor current”) flowing through the winding of the electric motor 1. The current detection means 3a and 3b are constituted by, for example, a current detection element, and detect a voltage corresponding to the motor current. Then, the voltage obtained by the current detection element is input to the control unit 11.

  The voltage detection means 10 detects a DC voltage (bus voltage) supplied to the inverter circuit 2. The voltage detection means 10 is composed of, for example, a voltage dividing circuit composed of a resistor / capacitor, an A / D converter, an amplifier, and the like. The voltage detection means inputs the detected voltage to the control unit 11.

  The control part 11 is comprised by CPU (Central Processing Unit), for example. The controller 11 controls the inverter circuit 2 by PWM (Pulse Width Modulation) to drive the electric motor 1. Details of the operation will be described later.

In addition, the control unit 11 converts the voltage input from the current detection means 3a and 3b into numerical data corresponding to the voltage value by a built-in A / D converter or the like, and the current flowing through the motor 1 is converted. Convert to data (information). The current detection is not limited to this.
Further, the control unit 11 converts the voltage input from the voltage detection means 10 into numerical data corresponding to the voltage value by using a built-in A / D converter or the like, and converts it into DC bus voltage data (information). To do. Note that the bus voltage detection is not limited to this.

In the above, the structure of the electric motor drive device in this Embodiment was demonstrated.
Next, the operation of the electric motor drive device in the present embodiment will be described.

<Operation>
Here, the motor drive operation using PWM (Pulse Width Modulation) will be described.
In the present embodiment, a case will be described in which the motor 1 is driven and operated based on data (information) of a current flowing in the winding without adding a magnetic pole position sensor.

  In the motor drive device according to the present embodiment, the control unit 11 can obtain motor current data using the current detection units 3a and 3b. The control unit 11 can also obtain bus voltage data via the voltage detection means 10. The controller 11 performs an operation based on these data to generate a PWM duty signal (hereinafter referred to as a PWM signal), and operates the upper switching elements 5a to 5f and the lower switching elements 6a to 6f in the arm 4. Thus, a voltage is applied to the electric motor 1 to control the driving operation of the electric motor 1.

  Here, a process in which the control unit 11 creates a PWM signal to be output to the inverter circuit 2 based on the motor currents Iu and Iw will be described.

FIG. 6 is a flowchart showing a PWM creation sequence according to the second embodiment.
Hereinafter, the operation will be described based on each step of FIG.

(S201)
The control unit 11 uses the characteristics of the three-phase balanced inverter such as “the sum of the three-phase currents becomes zero” from the two-phase currents (Iu, Iw) obtained based on the detection by the current detection means 3a and 3b. Then, the current flowing through each UVW phase is calculated.

(S202)
Next, the means for obtaining the excitation current and torque current of the control unit 11 performs coordinate conversion of each phase current value, and the excitation current component (γ-axis current) I _γ and torque current component (δ-axis current) I _δ are obtained. calculate. Specifically, the excitation current Iγ and the torque current Iδ are calculated by substituting and converting the motor currents Iu to Iw into the conversion matrix [C1] as shown in the following equation (1). However, (theta) in (1) shows an inverter rotation angle, and the case where a rotation direction is clockwise.

When a sensor for detecting the rotor position such as a pulse encoder is used, the electrical angular frequency of the rotor and the rotational frequency of the inverter circuit substantially coincide with each other. Therefore, the inverter circuit has the same frequency as the electrical angular frequency of the rotor. A rotating coordinate system is generally referred to as a dq coordinate system.
On the other hand, when a sensor for detecting the rotor position such as a pulse encoder is not used, the control unit 11 cannot accurately capture the dq axis coordinates, and is actually shifted from the dq coordinate system by a phase difference Δθ to be an inverter circuit. Is rotating. Assuming such a case, a coordinate system that rotates at the same frequency as the output voltage of the inverter circuit is generally referred to as a γδ coordinate system, and is handled separately from the rotating coordinate system. Since this embodiment shows an example in which no sensor is used, γ and δ are used as subscripts following this convention.

(S203)
Next, various vector controls including speed control are performed from the excitation current Iγ, the torque current Iδ, and the frequency command f * by the γ-axis voltage / δ-axis voltage command calculation means included in the control unit 11, and the next γ-axis voltage command V _γ ^* and δ-axis voltage command V _δ ^* are obtained.

(S204)
Next, the respective phase voltage commands Vu * to Vv * are obtained by the respective phase voltage command calculation means of the control unit 11 using the following formula (2) which is the inverse matrix [C1] ⁻¹ of the formula (1).

(S205)
Next, the ratio of each phase voltage command Vu * to Vv * of the inverter circuit 2 and the bus voltage Vdc obtained from the voltage detection means 10 (each phase voltage with respect to Vdc) by the PWM signal duty creating means included in the control unit 11. On the basis of the command ratio), the ON times (or OFF times) Tup to Twn of the switching elements in each arm 4 are calculated.
As described above, in the present embodiment, the switching element in each arm 4 is composed of two each of the upper switching element 5 and the lower switching element 6, but the gate signal of the two elements in the arm 4 The logic is the same. That is, by processing the gate signals for the two elements in the arm 4 as the same, compatibility with the conventional model can be maintained and a simple control method can be realized.

  The calculation of the ON times (or OFF times) Tup to Twn of the switching elements in each arm 4 is not limited to the method described above, and may be calculated using a conventional method such as space vector modulation. .

(S206)
Next, a PWM signal generating means included in the control unit 11 transmits a PWM signal obtained by converting a switching time in one carrier cycle to the inverter circuit 2 as PWM signals Up to Wn.
The inverter circuit 2 is based on the PWM signals Up to Wn from the control unit 11, and the upper switching element 5 and the lower switching element 6 in each arm 4 operate with the same gate signal, and a pulse voltage corresponding to the operation is supplied to the motor. 1 is applied to drive the electric motor 1. As an example, FIG. 7 shows the logic of the PWM signal of the switching element.

As described above, the present embodiment includes the same inverter circuit 2 as in the first embodiment, and drives the electric motor 1 by PWM control of the inverter circuit 2 based on the electric motor current.
For this reason, the load current (return current) from the electric motor 1 does not flow to the upper switching element 5 and the lower switching element 6, and it is possible to suppress the recovery current from flowing to the upper switching element 5 at the time of switching. .
Therefore, even when the upper switching element 5 having the parasitic diode 7 having a long reverse recovery time is used, the recovery loss can be reduced.
Therefore, the efficiency of the inverter circuit 2 can be improved, and the energy efficiency of the electric motor drive device can be improved.

Embodiment 3 FIG.
FIG. 8 is a diagram illustrating the configuration of the electric motor drive device according to the third embodiment.
As shown in FIG. 8, the electric motor drive device in the present embodiment is different from the second embodiment in the configuration of the lower arm of the inverter circuit 2. Other configurations are the same as those of the second embodiment, and the same reference numerals are given to the same portions.

The lower arms (arms 4d to 4f) of the inverter circuit 2 in the present embodiment are respectively configured by one switching element 13d to 13f and free-wheeling diodes 9d to 9f connected in parallel to the switching elements 13d to 13f, respectively. The
The configuration of the upper arms (arms 4a to 4c) of the inverter circuit 2 is the same as that of the second embodiment.

The switching elements 13d to 13f are configured by an element such as an IGBT having a low switching speed, for example .

The switching elements 13d to 13f in the present embodiment correspond to “second switching elements” in the present invention.
The freewheeling diodes 9d to 9f in the present embodiment correspond to the “second freewheeling diode” in the present invention.

  Next, the operation of the electric motor drive device in the present embodiment will be described.

FIG. 9 is a diagram showing the upper arm logic state of the PWM inverter.
FIG. 10 is a diagram showing the relationship between the inverter rotation angle of the PWM inverter and the voltage command vector.
First, the upper arm logic of the inverter circuit 2 and the relationship between the inverter rotation angle and the voltage command vector will be described.
Also in this embodiment, the gate signal logics of the two switching elements in the arms 4a to 4c are the same. As a result, the logic of the gate signal supplied to each arm 4a to 4f is either when the upper arm connected to the positive side of the DC bus is turned on or the lower arm connected to the negative side is turned on. is there. Since there are three phases, there are a total of eight (2 ³ = 8) upper arm logic states. That is, there are eight types of output states (hereinafter referred to as “voltage vectors”). Here, as the switching state notation of each arm 4, the upper arm logic is set to “1” for the ON state, “0” for the OFF state, and each switching mode voltage vector (hereinafter, “basic voltage vector”). Is defined as follows.

That is, as shown in FIG. 9, when the DC bus (W-phase upper arm logic state, V-phase upper arm logic state, U-phase upper arm logic state) = (0, 0, 1), vector V ₁ , ( 0,1,0) is a vector V ₂ , (0,1,1) is a vector V ₃ , (1,0,0) is a vector V ₄ , (1,0,1) Is a vector V ₅ , and the case of (1,1,0) is referred to as a vector V ₆ .
A voltage vector having no vector length (hereinafter referred to as “zero vector”) is referred to as follows. That is, the case of the DC bus (W-phase upper arm logic state, V-phase upper arm logic state, U-phase upper arm logic state) = (0, 0, 0) is represented by the vector V ₀ , (1, 1, 1). case is referred to as a vector _{V 7.}

In order to rotate the electric motor 1 smoothly, it is necessary to obtain a magnetic flux corresponding to a desired voltage and frequency. This can be realized by appropriately combining the above eight types of voltage vectors.
FIG. 10 shows the relationship between the inverter rotation angle θ and the voltage command vector V ^* with reference to the vector V1 direction (U-phase direction).

  Next, PWM control of the control part 11 in this Embodiment is demonstrated.

FIG. 11 is a diagram illustrating an example of a PWM switching pattern in underlined two-phase modulation of the inverter circuit according to the third embodiment.
FIG. 11 shows an example of the gate signal pattern of the upper arm at the time of two-phase modulation with underlining.
As shown in FIG. 11, the control unit 11 according to the present embodiment performs two-phase modulation with underlining by combining the voltage vectors described above.
With such an operation, in the present embodiment, in combination with the configuration of the inverter circuit 2 described above, high efficiency can be achieved without increasing the number of elements by devising the PWM pattern.

As described above, in the present embodiment, a plurality of MOSFETs with low conduction loss in the upper arm are combined, the recovery loss is reduced, and underlaying two-phase modulation with a small number of switching is used in the lower arm. .
Thereby, it is possible to improve the efficiency of the electric motor drive device.
Further, since the lower arm is constituted by one switching element 13, it is possible to reduce the cost and reduce the global environmental load by suppressing the increase in the number of elements as much as possible.

  In the above description, the lower arm is configured by one switching element 13, but the upper arm may be configured by one switching element 13. In this case, the control unit 11 performs PWM control of the inverter circuit 2 by the two-phase modulation with the overlay. Specific examples will be described below.

FIG. 12 is a diagram illustrating the configuration of the electric motor drive device according to the third embodiment.
As shown in FIG. 12, the motor drive device is different from the second embodiment in the configuration of the upper arm of the inverter circuit 2. Other configurations are the same as those of the second embodiment, and the same reference numerals are given to the same portions.

The upper arms (arms 4a to 4c) of the inverter circuit 2 are respectively configured by one switching element 13a to 13c and free-wheeling diodes 9a to 9c connected in parallel to the switching elements 13a to 13c, respectively.
The configuration of the lower arms (arms 4d to 4f) of the inverter circuit 2 is the same as that of the second embodiment.

The switching elements 13a to 13c are configured by an element such as an IGBT having a low switching speed, for example .

The switching elements 13a to 13c in the present embodiment correspond to the “second switching element” in the present invention.
The freewheeling diodes 9a to 9c in the present embodiment correspond to the “second freewheeling diode” in the present invention.

  Next, PWM control of the control part 11 in this Embodiment is demonstrated.

FIG. 13 is a diagram illustrating an example of a PWM switching pattern in the two-phase modulation with an overlay on the inverter circuit according to the third embodiment.
FIG. 13 shows an example of the gate signal pattern of the upper arm at the time of two-phase modulation with an overcoating.
As shown in FIG. 13, the control unit 11 performs two-phase modulation with a superposition by combining the voltage vectors described above.
With such an operation, in the present embodiment, in combination with the configuration of the inverter circuit 2 described above, high efficiency can be achieved without increasing the number of elements by devising the PWM pattern.

As described above, a combination of a plurality of MOSFETs with low conduction loss in the lower arm is used to reduce the recovery loss, and further, two-phase modulation with an extension with a small number of switching is used in the upper arm.
Thereby, it is possible to improve the efficiency of the electric motor drive device.
Further, since the upper arm is constituted by one switching element 13, it is possible to reduce the cost and reduce the environmental load by suppressing the increase in the number of elements as much as possible.

  In the present embodiment, the case where all the lower arms of the inverter circuit 2 are configured by one switching element 13 or the case where all the upper arms are configured by one switching element 13 has been described. The present invention is not limited to this, and at least one of the upper arm or the lower arm may be configured by one switching element. Even in such a configuration, the cost can be reduced by suppressing the increase in the number of elements.

  Also in the present embodiment, an example in which an SJ-structure MOSFET is used as the upper switching element 5 of the arm 4 of the inverter circuit 2 is shown. The present invention is not limited to this, and any switching element having a parasitic diode or parasitic inductance can be used.

  Also in the present embodiment, it is possible to eliminate noise factors such as an increase in lead inductance by mounting any at least one arm 4 of the inverter circuit 2 or all the arms 4 in one module. is there. In addition, the mounting area can be reduced.

Embodiment 4 FIG.
FIG. 14 is a diagram illustrating a configuration of an electric motor drive device according to the fourth embodiment.
As shown in FIG. 14, the motor driving device in the present embodiment detects the DC current source 12, the inverter circuit 2 a (master side) and the inverter circuit 2 b (slave side), the motor 1, and the motor current flowing through the motor 1. For example, a control unit 11 for driving the electric motor 1 by PWM control of the current detection units 3 a and 3 b, the voltage detection unit 10, and the inverter circuits 2 a and 2 b is provided.

The inverter circuit 2a on the master side has the same configuration as that of the first embodiment.
The slave-side inverter circuit 2b is configured by bridging the arms 15a to 15f.

  Each of the arms 15a to 15f of the inverter circuit 2b includes one switching element 14a to 14f and a free wheel diode 9a to 9f connected in parallel to the switching element 14a to 14f, respectively.

  The switching elements 14a to 14f are composed of elements such as an IGBT having a slow switching speed, for example. A MOSFET may be used in consideration of various conditions (carrier frequency, switching speed, degree of recovery loss, availability, etc.).

  The inverter circuit 2b in the present embodiment corresponds to a “second inverter device” in the present invention.

In the present embodiment, the PWM control of the inverter circuit 2a on the master side by the control unit 11 performs the PWM output by the method shown in the first embodiment.
In the slave-side inverter circuit 2b, an operation in which the output is made constant at the P-side potential according to the polarity of each phase output voltage command of the master-side inverter circuit 2a (hereinafter also referred to as “pasting to the P side”), or An operation in which the output is constant at the N side potential (hereinafter also referred to as “pasting to the N side”) is performed.

FIG. 15 is a diagram illustrating an example of the U-phase voltage command and the slave-side inverter U-phase potential of the electric motor drive device according to the fourth embodiment.
For example, for the U phase, when the command voltage of the inverter circuit 2a on the master side is positive, the upper arm of the inverter circuit 2b on the slave side is always turned off (applied to the N side). In addition, when the command voltage of the inverter circuit 2a on the master side is negative, the upper arm of the inverter circuit 2b on the slave side is always turned on (attached to the P side).

  When the command voltage of the master-side inverter circuit 2a is 0, the upper arm and the lower arm of the slave-side inverter circuit 2b are always turned off (not output). Alternatively, the upper arm of the inverter circuit 2b on the slave side may be attached to either the P side or the N side.

As described above, in the present embodiment, the operation of making the output of the slave-side inverter circuit 2b constant at the P-side potential or the N-side potential according to the polarity of each phase output voltage command of the master-side inverter circuit 2a. Do. For this reason, the switching frequency of the inverter circuit 2b on the slave side can be reduced, and recovery loss in the inverter circuit 2b on the slave side can be reduced.
In the inverter circuit 2b on the slave side, each arm 15 is composed of one switching element 14. For this reason, the number of parts of the inverter circuit 2b can be reduced, and the cost can be reduced.

  In addition, it has a circuit configuration that can be applied to a system that drives two electric motors by using two inverter circuits and a power supply device, and is a relatively simple and highly versatile system that is an extension of conventional control. Can be realized.

  In the present embodiment, the SJ structure MOSFET is used as the upper switching element 5 of the arm 4 of the inverter circuit 2a. However, any switching element having a parasitic diode or parasitic inductance is used. The present invention can be applied to the cooperative operation of a plurality of inverter circuits.

  Also in this embodiment, at least one arm 4 or all the arms 4 of the master-side inverter circuit 2a, or all of the arms 4 or the slave-side inverter circuit 2b are integrated into at least one module for mounting. Anyway. Thereby, it is possible to remove noise factors such as an increase in lead inductance. In addition, the mounting area can be reduced.

Embodiment 5 FIG.
FIG. 16 is a diagram illustrating a configuration of an electric motor drive device according to the fifth embodiment.
As shown in FIG. 16, the motor drive device according to the present embodiment includes a DC voltage source 12, an inverter circuit 2, a load device 16, a current detection unit 3 that detects a load current flowing through the load device 16, and a voltage detection unit 10. The control section 11 includes a PWM control of the inverter circuit 2 to control the load device 16.
In addition, the same code | symbol is attached | subjected to the structure similar to the said Embodiment 1-4.

  The inverter circuit 2 of the present embodiment is a circuit that configures a single-phase bridge by four arms 4a to 4d. Each of the arms 4a to 4d has the same configuration as that of the first embodiment.

With the configuration as described above, not only in the three-phase device, but also in the inverter circuit 2 having a single-phase bridge configuration as in the present embodiment, as in the first to fourth embodiments, the effect of suppressing the reduction in recovery of the MOSFET Can be obtained.
Therefore, energy efficiency can also be improved in the electric motor drive device according to the present embodiment.

  In the present embodiment, a case has been described in which each of the arms 4a to 4e is configured by the arm 4 configured by two switching elements. The present invention is not limited to this, and at least one of the arms 4 may be constituted by one switching element and one free-wheeling diode depending on the element type. By combining these circuits, cost optimization can be achieved while maintaining necessary efficiency.

  In the present embodiment, the SJ structure MOSFET is used as the upper switching element 5 of the arm 4 of the inverter circuit 2. However, any switching element having a parasitic diode or a parasitic inductance is used. Even in this case, the present invention can be applied.

  Also in this embodiment, any at least one arm 4 or all the arms 4 of the inverter circuit 2 may be integrated and mounted in one module. Thereby, it is possible to remove noise factors such as an increase in lead inductance. In addition, the mounting area can be reduced.

Embodiment 6 FIG.
In the present embodiment, as an example of a power generation system, an example of a grid-connected solar power generation system that supplies power by linking power generated by a solar battery to a commercial power system will be described.

FIG. 17 is a diagram showing a configuration of a grid-connected photovoltaic power generation system according to the sixth embodiment.
As shown in FIG. 17, the grid-connected photovoltaic power generation system converts a solar cell array 51 including a plurality of solar cell modules and DC power generated by the solar cell array 51 into AC power, and single-phase. And a grid-connected inverter device 53 that supplies power to the commercial power grid 52.

  The solar cell array 51 corresponds to the “power generation device” in the present invention.

The grid interconnection inverter device 53 includes a booster circuit 61, an inverter circuit 2, a filter circuit 62, a linkage relay 63, a current detection unit 3a, a current detection unit 3c, and an arithmetic processing unit 64.
The booster circuit 61 boosts the input DC voltage. The inverter circuit 2 converts a DC voltage into a high frequency AC voltage. The filter circuit 62 attenuates the high frequency switching component included in the output voltage of the inverter circuit 2. The interconnection relay 63 connects / disconnects the output voltage of the filter circuit 62 to / from the single-phase commercial power system 52. The current detection means 3a detects the output current of the inverter circuit 2. The current detection unit 3 c detects the output current of the filter circuit 62. The arithmetic processing unit 64 outputs a PWM signal for driving the inverter circuit 2 based on the information of the current detection means 3a, 3b.

The inverter circuit 2 of the present embodiment is a bridge-structured inverter circuit as in the fourth embodiment, and includes the arms 4a to 4d.
SJ structure MOSFETs are used for the upper switching elements 5a to 5d in the arm 4. Low-voltage MOSFETs are used for the lower switching elements 6a to 6d in the arm 4. As the free-wheeling diodes 9a to 9f, high-speed diodes having a short reverse recovery time are used.

  In the present embodiment, the case where the inverter circuit 2 has the same configuration as that of the fourth embodiment will be described. However, the present invention is not limited to this, and the inverter described in any of the first to fifth embodiments. The circuit 2 may be used.

As described above, the present embodiment includes the inverter circuit 2 described in any of the first to fifth embodiments, and therefore, in the photovoltaic power generation system, the inverter circuit is similar to the first to fifth embodiments. The recovery current at the time of switching 2 can be reduced, and high-efficiency driving is possible.
In the solar power generation system, an increase in power conversion efficiency in the inverter circuit 2 leads to an increase in the amount of generated power. Therefore, the user can obtain a larger amount of generated power by increasing the power conversion efficiency.
Further, in this embodiment, since loss during power conversion can be reduced, heat generation in the inverter circuit 2 can be suppressed, and there are advantages such as downsizing of the heat radiating device and improvement in reliability of components due to reduction in temperature rise.

  As described above, the present invention is applied not only to the inverter device connected to the independent load such as the electric motor 1 and the load device 16 as in the first to fifth embodiments, but also to the commercial power system as in the sixth embodiment. It can also be used for a grid-connected inverter device that is linked.

  In the present embodiment, a grid-connected photovoltaic power generation system linked to a single-phase commercial power system is shown, but a grid-connected photovoltaic power generation system linked to a three-phase commercial power grid, The same effect can also be obtained in an independent solar power generation system that supplies power to an independent load without being linked to each other.

  In the present embodiment, a solar power generation system using a solar cell module as a power generation element is shown. However, the same applies to a power generation system using any power generation element that generates DC power, such as a fuel cell or a wind power generator. Needless to say, the same effect can be obtained.

Embodiment 7 FIG.
FIG. 18 is a diagram showing a configuration of a refrigeration air conditioner according to Embodiment 7.
18, the refrigerating and air-conditioning apparatus according to the present embodiment includes an outdoor unit 201 and an indoor unit 204. The outdoor unit 201 is connected to a refrigerant circuit (not shown) and constitutes a refrigerant compressor 202 constituting a refrigeration cycle. A blower 203 for an outdoor unit that blows air to the chamber is provided.
The refrigerant compressor 202 and the blower 203 are rotationally driven by the electric motor 1 controlled by the electric motor drive control device according to any one of the above-described second to fifth embodiments.
Needless to say, even if the electric motor 1 is operated with such a configuration, the same effects as those of the first to fifth embodiments can be obtained.

  DESCRIPTION OF SYMBOLS 1 Electric motor, 2 inverter circuit, 2a inverter circuit, 2b inverter circuit, 3 current detection means, 3a current detection means, 3b current detection means, 3c current detection means, 4 arm, 4a-4f arm, 5 upper side switching element, 5a- 5f upper switching element, 6 lower switching element, 6a to 6f lower switching element, 7 parasitic diode, 7a to 7f parasitic diode, 8 parasitic diode, 8a to 8f parasitic diode, 9 freewheeling diode, 9a to 9f freewheeling diode, 10 Voltage detection means, 11 control unit, 12 DC voltage source, 13 switching element, 13a to 13f switching element, 14 switching element, 14a to 14f switching element, 15 arm, 15a to 15f arm, 16 load device, 21 gate, 2 source, 23 drain, 24 substrate (polarity n +), 25 p layer, 26 n layer, 51 solar cell array, 52 single-phase commercial power system, 53 system interconnection inverter device, 61 boost circuit, 62 filter circuit, 63 series System relay, 64 arithmetic processing unit, 101 switching element, 101a to 101f switching element, 102 parasitic diode, 102a to 102f parasitic diode, 201 outdoor unit, 202 refrigerant compressor, 203 blower, 204 indoor unit.

Claims (12)

An electric motor drive device for driving an electric motor,
An inverter device for driving the electric motor;
A second inverter device for driving the electric motor;
Current detecting means for detecting a current flowing in the winding of the motor;
Control means for controlling the inverter device and the second inverter device,
The inverter device is
Six arms that conduct and interrupt current are bridged to form a three-phase inverter,
Of the six arms, three arms connected to the high voltage side or the low voltage side of the DC voltage supplied to the inverter device are:
A plurality of switching elements having parasitic diodes and connected in series with each other;
A reflux diode connected in parallel with the plurality of switching elements;
The switching element is connected so that the polarity of the parasitic diode of the switching element is opposite to the polarity of the parasitic diode of another adjacent switching element, and the polarity of the parasitic diode of the plurality of switching elements is the The switching element having the reverse polarity to the freewheeling diode has a shorter reverse recovery time of the parasitic diode than the other switching elements, and the conduction of the parasitic diode flowing to the switching element having the same polarity as the freewheeling diode. Block the path to reduce the time to form an equivalent short circuit,
The other three arms are
One second switching element;
A second freewheeling diode connected in parallel with the second switching element,
The second inverter device includes:
Comprising at least one arm having one switching element and one free-wheeling diode;
The control means includes
Based on the current detected by the current detection means, the inverter device,
In the inverter rotation angle section where the combination of the basic voltage vectors for generating the voltage command vector is the same,
Two-phase modulation with extension that maintains the switching element of the arm connected to the high voltage side of the phase that does not perform the switching operation among the three phases, or
Of the three phases that do not perform the switching operation, the two-phase modulation with extension that maintains the switching element of the arm connected to the low voltage side in the on state is PWM-controlled to drive the electric motor,
Based on the current detected by the current detection means, determine each phase voltage command value,
PWM control of the inverter device based on each phase voltage command value,
An electric motor driving device that controls the second inverter device based on a voltage polarity of each phase voltage command value. The electric motor drive device according to claim 1, wherein the switching element is a MOSFET. The MOSFET is
3. The electric motor drive device according to claim 2, wherein the MOSFET is connected in series with a MOSFET of a channel different from the channel of the MOSFET. The MOSFET is
3. The electric motor driving device according to claim 2, wherein the channel of the MOSFET is connected in reverse series with the MOSFET of the same channel. 5. The electric motor drive device according to claim 2, wherein at least one of the plurality of MOSFETs is a MOSFET having a super junction structure. 6. Among the plurality of MOSFETs, the MOSFET whose polarity of the parasitic diode is the same as that of the freewheeling diode is:
The electric motor driving device according to any one of claims 2 to 4, wherein the electric motor driving device is a MOSFET having a super junction structure. Among the plurality of MOSFETs, the parasitic diode has a polarity opposite to that of the freewheeling diode.
The electric motor driving device according to any one of claims 2 to 6, wherein the electric motor driving device has a lower withstand voltage than other MOSFETs. The motor driving device according to any one of claims 1 to 7, wherein the freewheeling diode has a shorter reverse recovery time than the parasitic diode. The second switching element, motor driving device according to any one of claims 1-8, characterized in that the IGB T. The motor driving device according to claim 1, wherein at least one of the plurality of arms is modularized. The motor drive device according to any one of claims 1 to 10, wherein at least one of the inverter device and the second inverter device is modularized. The motor drive device according to any one of claims 1 to 11,
A refrigerating and air-conditioning apparatus comprising: an electric motor driven by the electric motor driving device.

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