JP5348484B2 - Load drive system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it easy to select elements and to reduce cost by equalizing withstand voltages of switching elements used in a main converter and auxiliary power converters. <P>SOLUTION: A system that drives a main motor M includes the auxiliary power converters Conv<SB>1</SB>, Conv<SB>2</SB>, which drive auxiliary motors M<SB>1</SB>, M<SB>2</SB>. At least one of the converters includes a voltage raising function of rasing a power source voltage and supplying the raised voltage to a DC intermediate circuit. A main power converter INV is connected to the DC intermediate circuit between optional positive and negative poles including the DC intermediate circuit. In this system, both ends of the DC intermediate circuit of the main converter INV are connected to both ends of a DC circuit of the DC intermediate circuit of the auxiliary power converters Conv<SB>1</SB>, Conv<SB>2</SB>. The number of semiconductor switching elements connected in series in each phase of the main power converter INV is made equal to that of switching elements connected in series in each phase of the series circuit of the DC intermediate circuit of the auxiliary power converters Conv<SB>1</SB>, Conv<SB>2</SB>. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a load driving system that individually drives a load such as a motor by a plurality of power converters including inverters.

FIG. 16 shows the first prior art, which is a system for driving a load M such as an electric motor by a power converter Conv comprising a three-phase inverter. In FIG. 16, B is a DC power source (its voltage is V _d ), C _d is a DC intermediate capacitor (its voltage, ie, DC intermediate voltage is E _d ), Q _u , Q _v , Q _w , Q _x , Q _y , Q _z are semiconductor switching elements, U, V, W are output terminals of the power converter Conv, and a load M represented by a three-phase coil is connected to these output terminals U, V, W. Yes.
In this prior art, the DC power of the DC power source B is converted into three-phase AC power by arbitrarily turning on and off the switching elements Q _u , Q _v , Q _w , Q _x , Q _y , and Q _z of the power converter Conv. And supplied to the load M.

Here, the DC intermediate capacitor C _d because it is directly connected to the DC power supply B, appears as the fluctuation of the power supply voltage V _d variation as the DC intermediate voltage E _d of. Thus, the three-phase AC output of the power converter Conv fluctuates, it is necessary to output control of the power converter Conv after compensating the fluctuation of the DC intermediate voltage E _d.

FIG. 17 shows a second prior art in which a normal boost chopper Chop is added to the circuit of FIG.
In this prior art, a step-up chopper Chop composed of semiconductor switching elements Q _p and Q _n and a reactor L _c is connected between a DC power source B and a DC intermediate capacitor C _d . In this circuit, by turning on and off the switching element Q _p, the Q _n alternately, the DC intermediate voltage E _d can be made higher adjusted than the supply voltage V _d, for example, lowering the voltage of the constructed direct current power supply B by the battery when the even, to a constant DC intermediate voltage E _d of the three-phase inverter by the step-up chopper Chop, the output of the three-phase inverter can be stabilized.

FIG. 18 shows the third prior art, which is described in Patent Document 1, for example. In this prior art, between one end of the DC intermediate capacitor C _d of the neutral and power converter Conv load M, DC power supply B is connected.
In this prior art, without using the step-up chopper Chop shown in FIG. 17, all the switching elements of the upper arm or the lower arm among the switching elements Q _{u to} Q _z are turned on to output a zero voltage vector, and the load M by utilizing the inductance is obtained by adjustable DC intermediate voltage E _d to a value higher than the power supply voltage V _d. Further, by supplying the three-phase alternating current to the load M, for example, when the load M and the electric motor, it is also possible to simultaneously boosts the power supply voltage V _d is supplied to the DC intermediate capacitor C _d, drives the electric motor is there.

According to this prior art, the step-up chopper Chop shown in FIG. 17 is not necessary, which can contribute to the reduction in the number of parts and the cost.
It is also described in Patent Document 1 that FIGS. 18 (a) and 18 (b) only change the connection position of the DC power supply B and the basic operation does not change.
Moreover, the application example of this prior art is described in patent documents 2-4, for example.

Next, FIG. 19 shows a fourth prior art, in which a three-phase AC power source V _s is connected to a rectifier circuit in the power converter Conv, and the main motor is connected to the output terminal of the three-phase inverter in the power converter Conv. This is an example in which M is connected.
The CTRL is a control device that controls the power converter Conv. Power is supplied from the control device CTRL to the cooling fan F ₁ and the auxiliary motor M ₁ that cool the semiconductor switching elements such as IGBTs constituting the three-phase inverter. ing. Further, the cooling fan F ₂ and the auxiliary motor M ₂ for cooling the main motor M are directly driven by the three-phase AC power source V _s .

FIG. 20 shows the fifth prior art, and is an example in which the DC power source B is connected to the DC intermediate circuit of the power converter Conv, as in FIG.
In this prior art, the power converter Mcon the control unit CTRL by converting the power voltage _{V d} to a DC voltage or AC voltage is supplied to the auxiliary motor _M 1, _{M 2,} and drives the cooling fan _F 1, _{F 2} ing.

Japanese Patent No. 3219039 (FIG. 22 etc.) Japanese Patent No. 3721116 (FIGS. 1, 8, etc.) Japanese Patent Laid-Open No. 2002-10670 (FIGS. 1 and 5 etc.) Japanese Unexamined Patent Application Publication No. 2004-112903 (FIGS. 2, 4, etc.)

In the prior art shown in FIG. 20, when the rated voltage of the main motor M is high, a DC power source B having a large rated voltage is required.
Further, as shown in FIGS. 19 and 20, a cooling fan for a system for driving a main motor M using the power converter such as an inverter, to cool the cooling fan F ₂ and switching elements for cooling the main motor M peripheral components such as F ₁ is required. These cooling fans F ₁ and F ₂ are respectively driven by the auxiliary motors M ₁ and M ₂ as described above, and the ratings of the motors M ₁ and M ₂ are selected in order to select appropriate fans and motors. The specifications are also different. Even consists for driving these auxiliary motor M _1, M ₂ electric power is necessary, in terms of the overall drive system, causing reduced efficiency.
In order to improve the efficiency of the entire drive system, the power consumption of the auxiliary motors M ₁ and M ₂ can be reduced by turning on and off the cooling fans F ₁ and F ₂ according to the temperatures of the main motor M and the switching elements. Although it is conceivable, there is a problem that an inrush current flows every time the cooling fan is started.

  Therefore, the problem to be solved by the present invention is to prevent the DC power supply from becoming higher voltage by using the boost function of the power converter, and to reduce the power consumption of peripheral circuits such as the auxiliary motor, thereby improving the overall efficiency of the system. It is an object of the present invention to provide a load drive system that enables the above.

In order to solve the above-described problem, the invention according to claim 1 includes a plurality of auxiliary power converters each having an auxiliary load connected to the AC side, and the neutral point of each auxiliary load and the auxiliary driving the auxiliary load. A load drive system in which a power source is connected between a positive electrode or a negative electrode of a DC intermediate circuit of a power converter and a DC intermediate circuit of each auxiliary power converter is connected in series,
At least a part of the plurality of auxiliary power converters has a boosting function of boosting the power supply voltage by turning on and off the semiconductor switching element and supplying the boosted power to the DC intermediate circuit of the auxiliary power converter,
The main power converter is connected to the DC intermediate circuit between any positive and negative electrodes including the DC intermediate circuit of the auxiliary power converter having the boosting function, and the main load connected to the AC side by this main power converter In the load drive system to drive,
Connect both ends of the DC intermediate circuit of the main power converter to both ends of the series circuit of the DC intermediate circuit of each auxiliary power converter, and determine the number of semiconductor switching elements connected in series in each phase of the main power converter. The number of semiconductor switching elements connected in series in each phase of the series circuit of the DC intermediate circuit of each auxiliary power converter is made equal.

The invention according to claim 2 is the load drive system according to claim 1,
The main power converter is constituted by a power converter capable of outputting voltages of three or more levels.

The invention according to claim 3 is the load drive system according to claim 1 or 2,
Voltage detecting means for detecting the voltage of each DC intermediate circuit of each auxiliary power converter is provided, and the operation of each auxiliary power converter is controlled so that the voltages of each DC intermediate circuit detected by these voltage detecting means are equal. Is.

According to the present invention, a main power converter is connected to a DC intermediate circuit between any positive and negative electrodes including a DC intermediate circuit of an auxiliary power converter having a boost function, and the main load such as a motor is connected by the main power converter. Therefore, even when the DC power supply voltage is low, the main load having a high rated voltage can be driven.
In addition, auxiliary loads such as auxiliary motors used in peripheral circuits can be driven by an auxiliary power converter using their neutral points, and auxiliary depending on the temperature of the main load and power converter. By adjusting the output of the load and the boosting operation of the auxiliary power converter, the power consumption can be reduced and the efficiency of the entire drive system can be improved.
Furthermore, by selecting the elements by configuring the circuit so that the voltages applied to the individual semiconductor switching elements constituting the main power converter and the individual semiconductor switching elements constituting the auxiliary converter are the same. This contributes to cost reduction.

It is a circuit block diagram which shows the 1st reference form of this invention. It is a schematic block diagram of the load drive system which concerns on a 1st reference form. It is a figure which shows the voltage command and carrier of each motor in a 1st reference form. It is a schematic block diagram of the load drive system which concerns on the 2nd reference form of this invention. It is a figure which shows the voltage command with respect to each motor in a 2nd reference form. It is a figure which shows the square diminishing characteristic of a cooling fan. It is a circuit block diagram of the load drive system which concerns on the 3rd reference form of this invention. It is explanatory drawing of the DC power supply in each reference form. It is explanatory drawing of the voltage command and carrier of each motor in each reference form. It is a circuit block diagram of the load drive system which concerns on the 4th reference form of this invention. It is a schematic block diagram of the load drive system which concerns on the 5th reference form of this invention. It is a circuit block diagram of the load drive system which concerns on 1st Embodiment of this invention. It is a schematic block diagram for preventing voltage imbalance in 1st Embodiment. It is explanatory drawing of the voltage command and carrier of each motor in 1st Embodiment. It is a circuit block diagram of the load drive system which concerns on 2nd Embodiment of this invention. It is a circuit block diagram which shows 1st prior art. It is a circuit block diagram which shows a 2nd prior art. It is a circuit block diagram which shows a 3rd prior art. It is a circuit block diagram which shows 4th prior art. It is a circuit block diagram which shows 5th prior art.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 is a circuit configuration diagram showing a first reference embodiment as a premise of the present invention, and Conv ₁ and Conv ₂ are auxiliary power converters having a boosting function shown in FIG. These auxiliary power converters Conv ₁ and Conv ₂ include a DC intermediate capacitor C _d1 (voltage is assumed to be E _d1 ), C _d2 (also assumed to be E _d2 ), and semiconductor switching elements Q _u1 , Q _v1 , Q _w1 , Q _{x1, Q y1, Q z1,} Q u2, Q v2, Q w2, Q x2, Q y2, Q z2 are composed of a DC intermediate circuit (DC intermediate capacitor _{C d1, C d2)} so is in series It is connected. P ₁ and P ₂ are positive poles of each DC intermediate circuit, N ₁ and N ₂ are negative poles, U ₁ , V ₁ , W ₁ , U ₂ , V ₂ , and W ₂ are AC output terminals. Auxiliary motors M ₁ and M ₂ as auxiliary loads are connected to the output terminals U ₁ , V ₁ , W ₁ , U ₂ , V ₂ and W ₂ , respectively.
Auxiliary Between neutral point of stator coils of the motor M ₁ and the negative electrode N _{1 (the} voltage V _{d /} 2) DC power supply B ₁ is connected, in the stator coil of the auxiliary motor M ₂ A direct current power source B ₂ (with a voltage of V _d / 2) is connected between the sex point and the positive electrode P ₂ .

Note that the boosting function of the auxiliary power converters Conv ₁ and Conv ₂ is described in the above-mentioned Patent Document 1 and the like and will not be described in detail here, but the upper one of the switching elements of each power converter Conv ₁ and Conv ₂ Each of the power converters Conv ₁ and Conv ₂ operates as a boost chopper by turning on all the switching elements of the arm or lower arm to output a zero voltage vector and using the inductance of the coils of the auxiliary motors M ₁ and M _2. It is something to be made.

On the other hand, a three-phase inverter comprising semiconductor switching elements Q _u , Q _v , Q _w , Q _x , Q _y , Q _z is connected between the positive electrode P and the negative electrode N connected to the positive electrode P ₁ and the negative electrode N ₂ , respectively. A main power converter INV as a main load is connected to AC output terminals U, V, and W thereof. The voltage between the positive electrode P and the negative electrode N is E _d (= E _d1 + E _d2 ).
Here, when only _one of the auxiliary power converters Conv ₁ and Conv ₂ has a boosting function, the main power converter INV is connected between the positive electrode and the negative electrode of the DC intermediate circuit of the power converter. good.

FIG. 2 is a schematic configuration diagram of a load driving system using the circuit of FIG. 1, and the same reference numerals are given to the same components as those in FIG.
The main motor M outputs a shaft according to the operating state of the main power converter INV. Also, one of the auxiliary motor _{M 1} is the power converter _INV, Conv 1, used to drive the cooling fan _{F 1} for cooling the switching element or the like constituting the Conv _2, other auxiliary motor _{M 2,} the main motor It is used to drive the cooling fan F ₂ for cooling the M.

According to this embodiment, as described above, the DC intermediate voltages obtained by boosting the respective power supply voltages V _d / 2 from the DC power supplies B ₁ and B ₂ by the auxiliary power converters Conv ₁ and Conv ₂ are respectively expressed as E _d1 and E _d2 . Then, since the DC intermediate voltage E _d of the main power converter INV becomes E _d1 + E _d2 , the main motor M having a rated voltage higher than the voltage V _{d of the} entire DC power supplies B ₁ and B ₂ can be driven. .

For example, as shown in FIG. 3, assuming that the DC voltage modulation rates of the auxiliary motors M ₁ and M ₂ are d ₁ and d ₂ , respectively, the voltages (DC intermediate voltages) E _d1 and E of the DC intermediate capacitors C _d1 and C _{d2 d2} becomes Formula 1 and Formula 2, respectively.
[Formula 1]
E _d1 = (V _d / 2) / d ₁
[Formula 2]
E _d2 = (V _d / 2) / d ₂

Thus, the DC intermediate voltage _{E d} of the main power converter INV is expressed by Equation 3.
[Formula 3]
E _d = E _d1 + E _d2 = (V _d / 2) d ₁ + (V _d / 2) d ₂
That is, the main power converter INV, the DC based on the DC intermediate voltage E _d expressed by Equation 3 - performs AC conversion, it is possible to output the AC voltage.

Here, if the positive phase modulation factor in the case of performing sinusoidal modulation as shown in FIG. 3 is λ, the output voltage V _o of the main power converter INV is generally expressed by Equation 4.
[Formula 4]
V _o = √3 · E _d / (2 · √2) · λ
= √3 · (E _d1 + E _d2 ) / (2 · √2) · λ
= √3 · {(V _d / 2) / d ₁ + (V _d / 2) / d ₂ } / (2 · √2) · λ
In general trapezoidal wave modulation, Equation 5 is obtained.
[Equation 5]
V _o = (E _d / √2) · λ
= {(E _d1 + E _d2 ) / √2} · λ
{(V _d / 2) / d ₁ + (V _d / 2) / d ₂ } / √2 · λ
Therefore, in any case, it is possible to DC link voltage of the main power converter INV drives the high pressure of the motor as compared with the case of V _d.

Next, FIG. 4 is a schematic configuration diagram of the load driving system according to the second reference embodiment.
This embodiment is provided with a temperature detection sensor T _s1 for detecting the temperature of the main motor M and a temperature detection sensor T _s2 for detecting the temperature of the main power converter INV in the circuit configuration shown in FIG. Means for fetching the detected value into the control device CTRL are added.
Note that the temperature detection sensor T _s2 detects the temperature of the power converter (switching element) that is the object to be cooled, so even if it detects the temperature of the auxiliary power converters Conv ₁ and Conv ₂ as necessary. good.

By controlling the operation of the auxiliary power converters Conv ₁ and Conv ₂ based on the temperature detection values by the temperature detection sensors T _s1 and T _s2 , for example, as shown in FIG. 5, the auxiliary power converters Conv ₁ and Conv ₂ The output frequency (the rotation speed of the motors M ₁ and M ₂ ) can be varied to change the air volume of the cooling fans F ₁ and F ₂ .
In general, the cooling fan has a square reduction characteristic shown in FIG. 6, and when the air volume is reduced, the pressure is reduced by the square characteristic. Thus, if driving an auxiliary motor _M 1, _{M 2} so as to reduce the air volume of the cooling fan _F 1, _{F 2} when the detected temperature by the temperature sensor _{T s1, T s2} is low, the cooling fan _F 1, F ₂ can be reduced, and as a result, the efficiency of the entire drive system can be increased.
That is, since the cooling fan F _1, F ₂ and by turning on or off frequently auxiliary motor M _1, there is no need to adopt a method of reducing power consumption of M _2, there is no possibility inrush current flows.

In the circuit of FIG. 1, the DC intermediate voltage E _d of the main power converter INV is the sum of the voltages of the capacitors C _d1 and C _d2 (E _d1 + E _d2 ), but is found in a general voltage doubler rectifier circuit. Thus, it goes without saying that there is no problem even if another capacitor C _d is connected in parallel with the series circuit of the capacitors C _d1 and C _d2 as shown in the third embodiment of FIG.
In the above embodiments, the voltages of the DC power sources B ₁ and B ₂ have been described as being equal to V _d / 2. However, the voltages may be distributed to the DC power source voltages corresponding to the rated voltages of the auxiliary motors M ₁ and M _2. . In particular, when the DC power supplies B ₁ and B ₂ are constituted by a battery or the like, there are many cases where a plurality of cells of about several volts are connected in series and used. For example, as shown in FIG. 8, the DC power supply B ₁ it is easy voltage _{B 2} is to pull the terminal from any series connection point so that the condition of _V d1 _{<V d2} from the state of both _{V d / 2 (V d1 =} V d2).

Further, in FIGS. 3 and 5, voltage commands are given to the motors M, M ₁ and M ₂ on the same carrier. As shown in FIGS. 9A to 9C, the motors M and M _{1 are provided.} , M ₂ may be individually controlled using a carrier having a different frequency.
Further, when a plurality of DC power sources B ₁ , B _{2 and the} like can be distributed from the viewpoint of installation space, the auxiliary motor M ₁ and the DC power source B ₁ are connected as in the fourth reference embodiment shown in FIG. that the auxiliary power converter Conv _1, the auxiliary power converter Conv ₂ the auxiliary motor M ₂ and DC power supply B ₂ is connected, it may be connected in series with the DC intermediate circuit side.
As a matter of course, the number of auxiliary power converters connected in series in each embodiment is not limited to two. In general, n (n is a plurality) auxiliary power converters are connected in series and are individually supported by each power converter. The motor may be driven.

Next, FIG. 11 shows a fifth reference embodiment, in which n auxiliary power converters Conv ₁ , Conv ₂ ,..., Conv _n are connected in series on the DC intermediate circuit side, and the auxiliary power converter Conv ₁ , Conv ₂ uses power supplies B ₁ and B _{2 obtained} by dividing the DC power supply B ₁₂ into two parts, and the auxiliary power converter Conv _n seems to combine FIG. 1 and FIG. 10 by using a single DC power supply B _n . Even if it is a simple circuit configuration, there is no problem.
In this case, the DC intermediate circuit of the main power converter INV that drives the main motor M is taken out from arbitrary positive and negative electrodes at the series connection point of the _n auxiliary power converters Conv ₁ , Conv ₂ ,. However, the auxiliary power converter sharing the DC intermediate circuit with the main power converter INV needs to have the boosting function described above.

Next, FIG. 12 is a circuit configuration diagram showing the first embodiment of the present invention.
In the form shown in FIG. 1, FIG. 7, FIG. 10, etc., since the DC intermediate voltage value of the auxiliary power converters Conv ₁ and Conv _{2 and} the DC intermediate voltage value of the main power converter INV are different, the auxiliary power converter Conv ₁ and Conv ₂ , the semiconductor switching elements Q _{u1 to} Q _z1 and Q _{u2 to} Q _z2 constituting the main power converter INV and the semiconductor switching elements Q _{u to} Q _z constituting the main power converter INV are different in voltage. The semiconductor switching element must be selected in consideration of the breakdown voltage according to the type of converter (main or auxiliary). Further, since the main power converter INV has a higher voltage than the auxiliary power converters Conv ₁ and Conv ₂ , the loss generated on the main power converter INV side becomes large, reducing the carrier frequency and reducing the switching loss. Measures such as reduction are necessary.
Therefore, the present invention has been made in view of the above points.

The connection configuration of the auxiliary power converters Conv ₁ and Conv ₂ , the auxiliary motors M ₁ and M _2, and the DC power supplies B ₁ and B ₂ in the first embodiment of the present invention is the same as that in FIG. Explained.
In the main power converter INV of FIG. 12, a series circuit of semiconductor switching elements Q _u11 , Q _u12 , Q _u13 , and Q _u14, a series circuit of Q _v11 , Q _v12 , Q _v13 , and Q _v14 , and Q _w11 , Q _v , A series circuit of Q _w12 , Q _w13 , and Q _w14 is connected in parallel, a connection point between the switching elements Q _u12 , Q _u13, a connection point between Q _v12 , Q _v13 , and Q _w12 , Q _w13 The connection point between them is connected to the main motor M via AC output terminals U, V, and W, respectively. Both ends of the three series circuits described above, are connected to the auxiliary power converter Conv _1, Conv ₂ side positive electrode _{P 1} and the negative electrode _{N 2} as a positive electrode P and a negative electrode N of the main power converter INV.

Furthermore, a series circuit of diodes D _u1 and D _u2 is connected in parallel to the series circuit of the switching elements Q _u12 and Q _{u13, and} a series circuit of diodes D _v1 and D _v2 is also connected to the series circuit of Q _v12 and Q _v13. are connected in parallel, also the series circuit of the _{Q w12,} diode _D in series circuit of a _{Q w13 w1, D w2} are connected in parallel. The connection point between the diodes D _u1 and D _u2, the connection point between the D _v1 and D _v2 , and the connection point between the D _w1 and D _w2 are the neutral point m and the auxiliary power converter Conv _1. Are connected to a connection point between the DC power sources B ₁ and B ₂ via the negative electrode N _{1 of the A} and the positive electrode P ₂ of the auxiliary power converter Conv ₂ .

Here, the main power converter INV constitutes a three-level inverter capable of outputting three levels of voltage, and the series circuit of U, V, and W-phase semiconductor switching elements each has four switching elements. It is comprised by. The voltage of the DC intermediate circuit of the main power converter INV (the voltage between the positive electrode P and the negative electrode N) is the voltage of the DC intermediate circuit of the auxiliary power converter Conv ₁ (the positive electrode P ₁ and the negative electrode N _{1 voltage) E d1} between equal to the sum of the _{voltage) E d2} between the auxiliary power converter Conv ₂ of the DC intermediate circuit voltage (positive electrode _{P 2} and the negative electrode _{N 2.} Further, the auxiliary power converters Conv ₁ and Conv ₂ are configured by connecting a series circuit of two semiconductor switching elements in parallel to each DC intermediate circuit for three phases.

For this reason, the same voltage is applied to the individual switching elements constituting the main power converter INV and the individual switching elements constituting the auxiliary power converters Conv ₁ and Conv ₂ . Since elements having the same breakdown voltage can be used for the switching elements Q _{u11 to} Q _w14 , Q _{u1 to} Q _z1 , and Q _{u2 to} Q _z2 , the complexity of element selection is eliminated, and the cost due to the different breakdown _{voltages of} the elements Can be avoided.
Further, a voltage higher than that of the auxiliary motors M ₁ and M ₂ is applied to the main motor M, but the surge voltage generated at the terminal of the main motor M is supplemented by making the main power converter INV a three-level inverter. It becomes almost the same as the power converters Conv ₁ and Conv ₂ side, and there is no fear that the loss on the main power converter INV side increases.

Incidentally, in the first embodiment, since the DC intermediate voltage _{E d1, E d2} of the auxiliary power converter Conv _1, Conv ₂ is prevented from becoming unbalanced, as shown in FIG. 13, the voltage _E d1, E It is desirable that the calculation unit 10 in the control device CTRL adjusts the DC voltage modulation rates d ₁ and d ₂ (see FIG. 14) so that the difference between _d2 becomes zero.
In FIG. 14, voltage commands for the main motor M and the auxiliary motors M ₁ and M ₂ are given on the same carrier. However, as shown in FIG. 9, individual motors M, M ₁ and M ₂ have individual carriers. May be given.

FIG. 15 is a circuit configuration diagram showing a second embodiment of the present invention.
This embodiment connects the circuit shown in FIG. 12 into two series, in which so as to drive the auxiliary motor _M 1 ~M _4, respectively, by the four auxiliary power converter Conv ₁ ~Conv _4. Note that the number of series connections of the circuit shown in FIG. 12 may be further increased.
In the present embodiment, the individual switching elements constituting the main power converter assist the individual switching elements constituting the INV power converter Conv ₁ ~Conv _4, will be the same voltage is applied, all An element having the same breakdown voltage can be used as the switching element.
Further, by controlling such DC intermediate voltage _E d1 _{to E d4} in FIG. 13 similarly to the auxiliary power converter Conv ₁ ~Conv ₄ are equal, the auxiliary motor _M 1 ~M ₄ be stably driven Is possible.

Also in the first and second embodiments described above, the main motor having a high rated voltage can be driven by the boosting operation of the auxiliary power converter even when the DC power supply voltage is low. In the boosting operation, all the semiconductor switching elements constituting the upper arm or lower arm of the auxiliary power converter are turned on to output a zero voltage vector, and the power supply voltage is boosted using the inductance of the auxiliary motor. Can be realized.
Similarly to the second reference embodiment, the temperature of the main motor and the main power converter may be detected to control the operation of the auxiliary power converter, and the rotation speed of the auxiliary motor may be adjusted. Furthermore, the auxiliary motor may be a main motor, a main power converter, or a driving motor for a cooling fan that cools the auxiliary power converter.

  In each of the above-described embodiments, the inductance necessary for boosting the power supply voltage is obtained by the coil of the three-phase motor. However, by using a single-phase transformer or the like, such as an insulating transformer for the gate power supply inside the power converter. As for the DC power supply, a DC voltage generated by a DC-DC converter or the like may be used as the power supply.

INV: Main power converters Conv ₁ , Conv ₂ , Conv ₃ , Conv ₄ , Conv _n : Auxiliary power converter M: Main motors M ₁ , M ₂ , M ₃ , M ₄ , M _n : Auxiliary motors C _d , C _{d1, C d2:} DC intermediate capacitor _{B 1, B 2, B 12} , B n: DC power supply _{Q u, Q v, Q w} , Q x, Q y, Q z, Q u1, Q v1, Q w1, Q _{x1, Q y1, Q z1,} Q u2, Q v2, Q w2, Q x2, Q y2, Q z2, Q u11, Q v11, Q w11, Q u12, Q v12, Q w12, Q u13, Q v13, _{Q w13, Q u14, Q v14} , Q w14: semiconductor switching element _{D u1, D v1, D w1} , D u2, D v2, D w2: diode _{T s1,} T _s2: temperature sensor CT L: control device

Claims (3)

A plurality of auxiliary power converters each having an auxiliary load connected to the AC side are provided, and between the neutral point of each auxiliary load and the positive or negative electrode of the DC intermediate circuit of the auxiliary power converter that drives the auxiliary load. A load driving system in which a power source is connected and a DC intermediate circuit of each auxiliary power converter is connected in series,
At least a part of the plurality of auxiliary power converters has a boosting function of boosting the power supply voltage by turning on and off the semiconductor switching element and supplying the boosted power to the DC intermediate circuit of the auxiliary power converter,
The main power converter is connected to the DC intermediate circuit between any positive and negative electrodes including the DC intermediate circuit of the auxiliary power converter having the boosting function, and the main load connected to the AC side by this main power converter In the load drive system to drive,
Connect both ends of the DC intermediate circuit of the main power converter to both ends of the series circuit of the DC intermediate circuit of each auxiliary power converter, and determine the number of semiconductor switching elements connected in series in each phase of the main power converter. A load driving system characterized in that the number of semiconductor switching elements connected in series in each phase of the series circuit of the DC intermediate circuit of each auxiliary power converter is equal. The load drive system according to claim 1,
A load driving system, wherein the main power converter is constituted by a power converter capable of outputting a voltage of three or more levels. In the load drive system according to claim 1 or 2,
Voltage detecting means for detecting the voltage of each DC intermediate circuit of each auxiliary power converter is provided, and the operation of each auxiliary power converter is controlled so that the voltages of each DC intermediate circuit detected by these voltage detecting means are equal. A load drive system characterized by that.

Images