JP5328313B2 - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the spread of resonance of an LC filter provided on the DC power-supply side of a power converter that converts power of a DC power supply into AC power or DC power of different voltages. <P>SOLUTION: A power converter has a configuration, wherein a battery is not grounded to any of a DC power supply, an LC filter or the ground; the battery is included in a circuit; the power converter is configured to use either a direction of charging the battery or a direction of discharging the battery in a switching mode that a current flows in the battery; and switching between the charging direction and the discharging direction of the battery is switched in the variational direction of a capacitor voltage of the LC filter so as to suppress resonance of the LC filter. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a power converter for converting power of a DC power source for operating a load with a constant output to AC power or DC power, and particularly to vibration suppression of an LC filter connected to the DC power source side. It is.

  FIG. 9 shows a configuration diagram in the case where the output is a three-phase alternating current as an example of the power converter, and the conventional technology will be described based on this diagram.

The LC filter 2 includes a reactor 21 and a capacitor 22 and is connected to the DC power source 1. A power conversion circuit 3 is connected between the outputs of the LC filter 2. In the power conversion circuit 3, three sets of two switches 31 connected in series are connected in parallel. The output point is between two switches 31 connected in series, and the output voltage of three phases
v _U , v _V , and v _W are each connected to the load 4.

  FIG. 2 shows the configuration of the switch 31. The switch 31 has a switching element 311 and a free-wheeling diode 312 connected in antiparallel, and is turned on when 1 is input from the control circuit 5 and is cut off when 0 is input.

The control circuit 5 adjusts the U-phase output voltage v _U so as to agree with the U-phase voltage command v _U * on average, and the V-phase output voltage v _V as average with the V-phase voltage command v _V *. In addition, a command is issued to each switch so that the W-phase output voltage v _W is equal to the W-phase voltage command v _W * on average.
Patent Publication 2006-94598

It is known that there is a resonance characteristic between the reactor 21 and the capacitor 22 of the LC filter 2. To keep the three-phase output voltages v _U , v _V , and v _W constant when the capacitor voltage Vc, which is the voltage of the capacitor 22 fluctuates, the output current I _LC of the LC filter 2 is reduced by the amount that the capacitor voltage Vc has decreased. Need to increase. However, when the output current I _LC of the LC filter 2 is increased, the capacitor voltage Vc tends to further decrease. On the other hand, when the capacitor voltage Vc increases, the output current I _LC of the LC filter 2 needs to be decreased in order to keep the three-phase output voltages v _U , v _V , and v _W constant. However, when the output current I _LC of the LC filter 2 is decreased, the capacitor voltage Vc further increases.

  That is, when the capacitor voltage Vc fluctuates, it acts to further amplify the fluctuation, whereby the resonance of the LC filter 2 diverges and becomes unstable.

  In order to suppress this instability, the resonance of the LC filter 2 can be suppressed by adding a resistor in the circuit of the LC filter 2 and absorbing the resonance energy of the LC filter 2. However, the resistor absorbs energy not only for the resonance energy of the LC filter 2 but also for a normal current, and thus consumes extra power. In addition, power consumption due to the resistance causes heat generation in the power converter.

  If there is no resistance and the circuit impedance and element loss are negligible, there is no element that absorbs energy between the LC filter 2 and the load 4, so the resonance energy of the LC filter 2 cannot be absorbed and resonance occurs. It is impossible to suppress the divergence.

  In addition to the power converter that converts the DC power source 1 into three-phase AC, this phenomenon also occurs in a power converter that converts single-phase AC and other phase AC voltages, or the DC power source 1 into DC voltages of different voltages. It is a problem that occurs.

According to the first aspect of the present invention, there is provided a power conversion device that takes a DC power supply as an input and converts the power of the DC power supply into AC power or DC power of a different voltage, and an LC composed of a capacitor and a reactor on the DC power supply side. a power converter a filter is connected, in a power conversion device that contains the batteries that are not grounded in any of the DC power source and the LC filter and the ground in the circuit of the power converter, the battery A power conversion device, wherein resonance of the LC filter is suppressed by a current flowing into the LC filter.

According to a second aspect of the present invention, in the power conversion device according to the first aspect, the circuit of the power conversion device is a capacitor of the LC filter in which four sets of switches in which switching elements and diodes are connected in antiparallel are connected in series. Is connected in parallel , the battery is connected between the 3rd and 4th switch from between the 1st and 2nd switch, between the 2nd and 3rd switch is the output of the power converter The power converter characterized by the above-mentioned.

According to the invention of claim 3, in the power conversion device of claim 2, a plurality of phases of the circuit constituted by the switch and the battery are connected in parallel to the capacitor between the LC filters in parallel . A power converter characterized by obtaining an output voltage.

According to a fourth aspect of the present invention, in the power conversion device according to the first aspect, the direction in which the battery is charged by using either the charging direction or the discharging direction in the switching mode in which current flows in the battery. The power conversion device is characterized in that the resonance of the LC filter is suppressed by switching between the direction of discharging and the direction of discharging in accordance with the fluctuation direction of the capacitor voltage of the LC filter.

According to a fifth aspect of the present invention, in the power conversion device of the fourth aspect, the switching between the charging current and the discharging current flowing through the battery is switched according to the polarity of the output current and the fluctuation direction of the capacitor voltage. Conversion device.

According to invention of Claim 6 , in the power converter device of Claims 1-5, the capacitor is used instead of the said battery, The power converter device characterized by the above-mentioned.

  According to the present invention, since energy can be taken in and out in the power conversion circuit, resonance of the LC filter can be suppressed.

  The circuit includes a DC power supply, an LC filter, and a battery that is not grounded to either of the earths. In the switching mode in which current flows through the battery, use either the charging direction or the discharging direction. The switching is switched in the fluctuation direction of the capacitor voltage of the LC filter, thereby suppressing the resonance of the LC filter.

  The case where the output is a three-phase alternating current will be described as an example to which the invention of claims 1 to 6 is applied using FIG. 1, but the same parts as those of the conventional technique are omitted.

In the power conversion circuit 3, four switches 31 are connected in series between the outputs of the LC filter 2. Among the switches 31 connected in series, a battery 32 is connected between the first and second switches 31 and between the third and fourth switches 31. This configuration is connected in parallel between the outputs of the LC filter 2 in three sets, and the three-phase output voltages v _U , v _V , v _W from the second and third of the switches 31 connected in series. Are output respectively.

  The detailed operation will be described below for the U phase, but the same applies to the V phase and the W phase.

It is assumed that the voltage of the battery 32 is charged to V _BAT . Note that V _BAT is 0 or more and less than or equal to the voltage Vdc of the DC power supply 1.

Here, the combination capable of generating switch 31 U-phase output voltage v _U without short-circuiting the output of the LC filter 2 is the next four. The switches are su1, su2, su3, and su4 from the high potential side, where 1 is a state in which the switch is conductive and 0 is a state in which the switch is cut off.

Mode 1: su1 = 1, su2 = 1, su3 = 0, su4 = 0
Mode 2: su1 = 1, su2 = 0, su3 = 1, su4 = 0
Mode 3: su1 = 0, su2 = 1, su3 = 0, su4 = 1
Mode 4: su1 = 0, su2 = 0, su3 = 1, su4 = 1

The path of the U-phase output current i _U in each mode state is shown in FIG. Further, U-phase output voltage v _U during each mode becomes the following value. Here, the voltage is 0 on the low potential side of the DC power supply 1.

Mode 1: v _U = V _C
Mode 2: v _U = V _C -V _BAT
Mode 3: v _U = V _BAT
Mode 4: v _U = 0

By switching the selection of the four kinds of voltages, in order to obtain an arbitrary voltage in average in a range of from 0 to V _C output voltage v _U, it can be generated if the mode 1 and mode 4, mode 2 and mode 3 are not necessarily required. Therefore, an arbitrary voltage is obtained on average using only one of mode 2 and mode 3 in addition to mode 1 and mode 4.

Next, power input / output from the battery 32 will be described. In the mode 1 and the mode 4, since the U-phase output current i _U does not flow through the battery 32, no power enters and leaves the battery. On the other hand, when the mode 2 in, U-phase output currents i _U is positive when becomes charged state, when the negative a discharged state. The case of mode 3, the discharge state, when a negative when U-phase output currents i _U is positive the charge state.

  The voltage fluctuation direction discriminator 51 receives the capacitor voltage Vc, and outputs 1 when the capacitor voltage Vc is increased and 1 when it is decreased.

  FIG. 5 is an example of the voltage fluctuation direction discriminator 51. The fluctuation component of the capacitor voltage Vc is extracted from the difference between the capacitor voltage Vc and the capacitor voltage Vc that has passed through the filter 51, and if positive, 1 is output, and if negative, -1 is output.

  FIG. 6 shows another example of the voltage fluctuation direction discriminator. The fluctuation component of the capacitor voltage Vc is extracted from the difference between the capacitor voltage Vc and the voltage Vdc of the DC power supply 1, and 1 is output if it is positive and -1 if it is negative.

The current detector 6 detects the output currents i _U , i _V , i _W. The U-phase current polarity discriminator 52 discriminates the polarity of the U-phase output current i _U detected by the current detector 6, and outputs 1 if positive and -1 if negative.

The U-phase PWM controller 55 receives the product of the output of the U-phase current detector 52 and the output of the voltage fluctuation determiner 51 and the U-phase voltage command v _u *. The U-phase PWM control device 55 issues a switching command so that the U-phase output voltage v _u coincides with the U-phase voltage command v _u * on average, but the output of the U-phase current detector 52 and the voltage fluctuation determination device 51 When the product of the outputs of 1 is 1, the switching command is generated using the three modes 1, 2, and 4, and the product of the output of the U-phase current detector 52 and the output of the voltage fluctuation determiner 51 is −1. In such a case, a switching command is generated using three modes, mode 1, mode 3, and mode 4.

  7 and 8 show an example of a U-phase switching command generation method. In this example, a triangular wave carrier is used. FIG. 7 is an example in the case of outputting three kinds of switching commands of mode 1, mode 2 and mode 4, and FIG. 8 is an example in the case of outputting three kinds of switching commands of mode 1, mode 3 and mode 4. It is.

  A switching command is similarly output for the V phase and the W phase.

  With the above configuration, when the capacitor voltage Vc is decreased, all the current passing through the battery 32 is discharged from the battery 32, so that the capacitor voltage Vc is increased, and when the capacitor voltage Vc is increased, the battery 32 is Since all of the current passing through the battery 32 is charged in the direction to charge the battery 32, the capacitor voltage Vc is lowered, so that the resonance of the LC filter 2 is suppressed. That is, the resonance energy of the LC filter 2 is absorbed by the input / output of the battery 32.

  By changing the number of circuits connected in parallel to the output of the LC filter 2, a power conversion device that converts the DC power source 1 into a single-phase AC or other phase AC voltage, or the DC power source 1 with other voltages The present invention can also be applied to a power conversion device that converts a DC voltage.

  INDUSTRIAL APPLICABILITY According to the present invention, the present invention can be applied to an inverter that is a power conversion device that converts DC power into AC power, and a chopper that converts DC power into DC power of different voltages, and can be used in various industrial fields that use power. Therefore, it is extremely effective.

It is a control circuit block diagram of one Example of this invention. It is a figure which shows the structure of a switch. It is a figure explaining the mode of the conduction state of the switch of the present invention. It is a block diagram of the control circuit in one Example of this invention. It is an example of the voltage fluctuation direction discriminator of the control circuit in one Example of this invention. It is another example of the voltage fluctuation direction discriminator of the control circuit in one Example of this invention. It is an example of the switching instruction | command generation | occurrence | production using the 3 types of the mode 1, the mode 2, and the mode 4 in one Example of this invention. It is an example of the switching instruction | command generation | occurrence | production using the 3 types of the mode 1, the mode 3, and the mode 4 in one Example of this invention. It is an example of the power converter device by a prior art

Explanation of symbols

1 DC power supply 2 LC filter 21 reactor 22 capacitor 3 power conversion circuit 31 switch 311 switching element 312 freewheeling diode 32 battery 4 load 5 control circuit 51 voltage fluctuation direction discriminator 511 filter 52 U-phase current polarity discriminator 53 V-phase current polarity discrimination 54 W-phase current polarity discriminator 55 U-phase PWM controller 56 V-phase PWM controller 57 W-phase PWM controller 6 Current detector

Claims (6)

A power conversion device that receives a DC power supply and converts the power of the DC power supply to AC power or DC power of a different voltage, and a power conversion device in which an LC filter composed of a capacitor and a reactor is connected to the DC power supply side In the power converter including a battery that is not grounded to any of the DC power supply, the LC filter, and the ground in the circuit of the power converter, the resonance of the LC filter is caused by the current flowing to the battery. The power converter characterized by suppressing. 2. The power conversion device according to claim 1, wherein the circuit of the power conversion device includes four sets of switches in which switching elements and diodes are connected in antiparallel and connected in series to the capacitor of the LC filter. Is connected between the 3rd and 4th switches from between the 1st and 2nd switches, and the space between the 2nd and 3rd switches is the output of the power conversion device. 3. The power conversion device according to claim 2, wherein a circuit configured by the switch and the battery is connected in parallel to a capacitor between the LC filters in parallel to obtain a multi-phase output voltage. Power conversion device. 2. The power conversion device according to claim 1, wherein switching between a charging direction or a discharging direction of the battery is performed using either a charging direction or a discharging direction of the battery in a switching mode in which a current flows in the battery. A power converter that suppresses resonance of the LC filter by being switched in the direction of fluctuation of the capacitor voltage of the LC filter. 5. The power conversion device according to claim 4, wherein the current flowing through the battery is switched between charging and discharging according to the polarity of the output current and the fluctuation direction of the capacitor voltage. 6. The power conversion device according to claim 1, wherein a capacitor is used instead of the battery.

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