JP6291882B2 - AC-AC converter - Google Patents

Description

  The present invention relates to an AC-AC converter.

Patent document 1 etc. are well-known as a multiplex power converter to which a plurality of unit AC-AC converters are applied. FIG. 28 shows a cascade multilevel converter using a multiphase transformer Tr as an example of a typical multilevel converter. The multiphase transformer Tr in this cascade multilevel converter has a plurality of secondary windings with three-phase AC power supplies R, S, T connected to the primary winding. The secondary winding of the multiphase transformer has a number corresponding to the number of unit inverters constituting the multilevel converter, each of which includes a three-phase full-wave rectifier DC (DC ₁ , DC ₂ ) composed of a diode, a capacitor C (C _1, C ₂₎ and the switching element unit inverter INV consisting S1~S4 (INV-U1, INV- U2) are connected three-phase U-phase circuit is formed. FIG. 28 shows only the U-phase portion of the three-phase circuit, but the V and W phases are similarly configured. Each unit inverter INV-U1 to INV-W2 is Y-connected.

In the circuit shown in FIG. 28, assuming that the voltage of the capacitor C of the unit inverter INV is E, the output voltage of the unit inverter INV is three levels of E, 0, and -E depending on the combination of ON and OFF of the switching elements S1 to S4. Can be output.
Furthermore, if the number of unit inverters INV to the output terminals U, V, and W is N based on the midpoint NO of the Y connection, 2N + 1 level phase voltage can be output to the load. FIG. 28 shows a configuration example of N = 2.

JP 2001-238455 A

  In the multiplex power converter configured as shown in FIG. 28, the DC circuit voltage of the unit inverter INV is E. Therefore, if the parts inside the unit inverter such as switching elements and capacitors are selected withstand voltage components suitable for the voltage E. Good. Therefore, there is an advantage that the phase voltage of the peak voltage N × E can be output to the load with the configuration of the low withstand voltage component which is easily available.

  However, since a multi-phase transformer is required, there is a problem that the size and weight of the power converter increases. In addition, there is a problem that it cannot be applied to applications such as conversion from a high input voltage to a low output voltage.

  An object of the present invention is to provide an AC-AC converter that does not use a multiphase transformer.

Claim 1 of the present invention is an AC-AC converter for converting an AC input voltage into an AC output voltage of a plurality of levels, wherein a series body of first and second switching elements, a first capacitor, 3 and a series of four switching elements connected in parallel, wherein the first and third switching elements are defined as the positive side, and the second and fourth switching elements are defined as the negative side The H bridge circuit is provided on the input side and the output side, respectively, the common connection point of the first and third switching elements of the input side H bridge circuit and the first of the output side H bridge circuit. The fifth and sixth switching elements that control on and off of currents flowing in opposite directions are connected in series in the opposite direction between the common connection points of the third switching element and the third switching element, and the input side H-bridge circuit 7th and 8th controlling on and off currents flowing in opposite directions between the common connection point of the second and fourth switching elements and the common connection point of the second and fourth switching elements of the output side H-bridge circuit. 8 switching elements are connected in series in the opposite direction, and a first freewheeling diode is connected between a common connection point of the fifth and sixth switching elements and a common connection point of the seventh and eighth switching elements, The common connection point of the first and second switching elements of the input-side H bridge circuit is an input terminal, and the common connection point of the third and fourth switching elements of the input-side H bridge circuit is an input-side neutral point. The common connection point of the first and second switching elements of the output-side H bridge circuit is defined as the output-side neutral point, and the third and fourth switching elements of the output-side H bridge circuit are connected. Unit AC to constitute a through connection point as the output terminal - is characterized by comprising an AC converter.

According to a second aspect of the present invention, the unit AC-AC converter includes a second output-side H bridge circuit configured in the same manner as the output-side H bridge circuit, and the second output-side H bridge is provided. Between the common connection point of the first and third switching elements of the circuit and the common connection point of the first and third switching elements of the input side H-bridge circuit, currents flowing in opposite directions are turned on and off. The ninth and tenth switching elements to be controlled are connected in series in the reverse direction, and the common connection point of the second and fourth switching elements of the second output-side H bridge circuit and the second and fourth switching elements of the input-side H bridge circuit Between the common connection point of the fourth switching element, eleventh and twelfth switching elements for controlling on and off of currents flowing in opposite directions are connected in series in the opposite direction,
The common connection point of the first and second switching elements of the output-side H bridge circuit is connected to the common connection point of the third and fourth switching elements of the second output-side H bridge circuit, and the second output A common connection point of the first and second switching elements of the side H-bridge circuit is an output side neutral point .

According to a third aspect of the present invention, there is provided a second freewheeling diode between a common connection point of the ninth and tenth switching elements and a common connection point of the eleventh and twelfth switching elements of the unit AC-AC converter. Is connected .

According to a fourth aspect of the present invention, the first capacitor voltage of the input-side H bridge circuit, the first capacitor voltage of the output-side H bridge circuit, and the first capacitor voltage of the second output-side H bridge circuit are equal. In this way, the input / output voltage ratio is 1: 2 .

  According to a fifth aspect of the present invention, the unit AC-AC converter has N (N is an integer of 2 or more) multiple stages, and the input-side neutral point of the first unit AC-AC converter is a unit of the next stage. It is configured by sequentially connecting N output side neutral points of the first stage unit AC-AC converter to the output terminal of the next stage unit AC-AC converter at the input terminal of the AC-AC converter. It is characterized by that.

(1) According to the inventions described in claims 1 to 5 , since the multi-phase transformer is not required, the conversion device is downsized. In addition, the snubber circuit for absorbing the voltage surge of the fifth, sixth, seventh and eighth switching elements of the unit AC-AC converter can be omitted or downsized.
(2) According to the invention described in claim 3 , the snubber circuit for absorbing the voltage surge of the ninth, tenth, eleventh and twelfth switching elements of the unit AC-AC converter is omitted or is small. Can be

The block diagram of the unit alternating current-alternating current converter which shows embodiment of this invention. The block diagram of the three-phase alternating current-alternating current conversion system which shows embodiment of this invention. Charge mode explanatory drawing of the input side H bridge circuit capacitor. Explanatory drawing of the charge mode of an output side H bridge circuit capacitor. FIG. 3 is a control block diagram in the three-phase AC-AC conversion system of FIG. 2. Explanatory drawing showing the switching pattern of the switching element by the voltage command value and carrier comparison in the three-phase alternating current-alternating current conversion system of FIG. The circuit diagram which used the 3 level converter for each H bridge circuit of the embodiment of this invention. The block diagram of the unit alternating current-alternating current converter which shows Example 2 of this invention. The block diagram of the unit alternating current-alternating current converter which shows Example 3 of this invention. The block diagram of the three-phase alternating current- alternating current conversion system which shows Example 3 of this invention. The block diagram of the unit alternating current-alternating current converter which shows Example 4 of this invention. The block diagram which added CR snubber of the switching element of the embodiment of this invention. Explanatory drawing which shows the current pathway at the time of commutation of the switching element in the unit alternating current-alternating current converter of the embodiment of this invention. The block diagram of the unit alternating current-alternating current converter of Example 5 of this invention. Explanatory drawing which shows the current pathway at the time of commutation of the switching element in the unit alternating current-alternating current converter of Example 5 of this invention. The block diagram of the unit alternating current-alternating current converter of Example 6 of this invention. The block diagram of the unit alternating current-alternating current converter of Example 7 of this invention. The block diagram of the unit alternating current-alternating current converter of Example 8 of this invention. The block diagram of the unit alternating current-alternating current converter of Example 9 of this invention. The block diagram of the unit alternating current-alternating current converter of Example 10 of this invention. The block diagram of the unit alternating current-alternating current converter of Example 11 of this invention. The block diagram of the unit alternating current-alternating current converter of Example 12 of this invention. The block diagram of the unit alternating current-alternating current converter of Example 13 of this invention. The block diagram of the unit alternating current-alternating current converter of Example 14 of this invention. The circuit diagram which shows an example of the switching pattern in FIG. The block diagram of the unit alternating current-alternating current converter of Example 15 of this invention. (A) is a circuit diagram showing an example of a current path in a mode in which the capacitor of the input-side H bridge circuit is discharged and the capacitor of the output-side H bridge circuit is charged. ) Is a circuit diagram showing another example of the current path in the mode. The block diagram of the conventional cascade multilevel converter.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. The present invention relates to an AC-AC converter that inputs an AC power supply and supplies a plurality of levels of AC output to a load. The AC input side and output side include an input side and an output side H composed of a switching element and a capacitor. A bridge circuit is provided. A switch body is connected between the positive side and the negative side of the capacitors constituting each H-bridge circuit to turn on and off the current flowing in each direction between the H-bridge circuits. Further, the input side H bridge circuit is provided with an input terminal and a neutral point, and the output side H bridge circuit is provided with a neutral point and an output terminal.

  FIG. 1 shows a block diagram of a unit AC-AC converter according to Embodiment 1 of the present invention. In FIG. 1, a series body of first and second switching elements S1 and S2, and a first capacitor C1 and a series body of third and fourth switching elements S3 and S4 are connected in parallel to form an input side H The bridge circuit B1 is configured, and the series body of the first and second switching elements S9 and S10 and the series body of the first capacitor C2 and the third and fourth switching elements S11 and S12 are connected in parallel. The output side H bridge circuit B2 is configured.

  Among the terminals of the input side H-bridge circuit B1, IN is an input terminal and MP1 is an input side neutral point. Further, the terminal OUT of the output side H-bridge circuit B2 is an output terminal, and MP2 is an output side neutral point.

  The first and third switching elements S1 and S3 of the input side H bridge circuit B1 are defined as positive sides, and the first and third switching elements S9 and S11 of the output side H bridge circuit B2 are defined as positive sides. The second and fourth switching elements S2 and S4 of the input side H bridge circuit B1 are defined as the negative side, and the second and fourth switching elements S10 and S12 of the output side H bridge circuit B2 are defined as the negative side. ing.

  On / off control of currents flowing in opposite directions between the common connection point of the switching elements S1 and S3 of the input side H bridge circuit B1 and the common connection point of the switching elements S9 and S11 of the output side H bridge circuit B2 The fifth and sixth switching elements S5 and S7 are connected in series in the reverse direction.

  On / off control of currents flowing in opposite directions between the common connection point of the switching elements S2 and S4 of the input side H bridge circuit B1 and the common connection point of the switching elements S10 and S12 of the output side H bridge circuit B2 The seventh and eighth switching elements S6 and S8 are connected in series in the reverse direction.

  The switching elements S5 to S8 are provided for controlling the voltage E2 of the capacitor C2. The connection is made when, for example, the switching element is an IGBT, the emitters of S5 and S7 are connected to each other, and S6 and S8. Are connected to each other. That is, the current flowing between the H bridge circuits B1 and B2 is connected so that on / off control can be performed by the control signal of any of the switching elements S5 to S8.

  The unit AC-AC converter shown in FIG. 1 generates three levels of voltages E1, 0, and −E1 when the voltage of the capacitor C1 is E1 at the input terminal IN with reference to the input side neutral point MP1. . Similarly, with the output side neutral point MP2 as a reference, assuming that the voltage of the capacitor C2 is E2 at the output terminal OUT, three-level voltages E2, 0, and -E2 can be generated. Table 1 shows the relationship pattern between each switching element, the on / off state, and the generated voltage.

  FIG. 2 shows a configuration diagram of a three-phase AC-AC conversion system using the unit AC-AC converter shown in FIG. FIG. 2 shows only one phase as a representative. In the case of three phases, each of U, V, and W is constituted by the unit AC-AC converter shown in FIG. The neutral phase MP1 and the output side neutral point MP2 of the output side H-bridge circuit B2 are connected to each other in a Y-connection state, and a three-phase AC-AC conversion system is configured. Each unit AC-AC converter of each phase is connected to a power distribution network (power supply side) 1 via a reactor 4, and a load 2 is connected to the output side thereof.

Reference numeral 3 denotes a control unit. The control unit 3 has various control functions such as a capacitor voltage control function, an input current control function, an output voltage control function, and a switching pattern generation function. The control unit 3 includes detection currents IR, IS, IT of AC power supply R, S, T phases, detection voltages VCU1, VCV1, VCW1, VCU2, VCV2, VCW2 of capacitors C1, C2 for each phase, and outputs. The phase voltage command value V ^* and the DC voltage command value VDC ^* are respectively input to execute each function described above.

The voltage control in the configuration of FIG. 2 will be described.
(1) Control of voltage VCU1, VCV1, VCW1 of capacitor C1 on input side of unit AC-AC converter of each phase The control unit 3 detects the detected capacitor voltages VCU1, VCV1, VCW1 and input currents IR, IS, On / off pattern gates in Table 1 that perform control computation using the detected IT value and the DC voltage command value VDC ^* as input parameters to turn on / off the switching elements S1 to S4 of the unit AC-AC converter of each phase. The switching elements S1 to S4 are controlled so that the detection voltages VCU1, VCV1, and VCW1 become the DC voltage command value VDC ^* by generating and outputting a signal.
(2) Control of output phase voltage The control unit 3 performs control calculation using the capacitor voltage detection values of VCU2, VCV2, and VCW2 and the output phase voltage command value V ^* as input parameters, and unit AC-AC converters for each phase By generating and outputting a gate signal for turning on / off the switching elements S9 to S12, the output phase voltage is controlled to become the output phase voltage command value V ^* .

Through the control operations (1) to (2) above, the three-phase phase voltage controlled to the output phase voltage command value V ^* is output from the output-side H bridge circuit B2.

3 and 4 show an example of charging operation of C1 and C2 during voltage control of capacitors C1 and C2 of a U-phase unit AC-AC converter as a representative example of the three-phase AC-AC conversion system shown in FIG. FIG. 3 shows the charging mode of the input-side capacitor C1, and when the U-phase switching elements S1, S4, V-phase S3 and S1 are turned on, the U-phase input-side capacitor C1 is Charged.

  FIG. 4 shows the charging mode of the output-side capacitor C2. The U-phase output-side capacitor is turned on when the U-phase switching elements S1, S5, S7, S10, the V-phase S10, S8, S6 and S2 are turned on. C2 is charged.

  The voltage is controlled by charging / discharging C1 and C2 by the combination of the on / off states of the switching elements in FIGS. 3 and 4 or the combination of the on / off states of any of the switching elements.

  Therefore, according to this embodiment, one unit AC-AC converter is used for each of the U, V, and W phases, and Y-connection or delta-connection is performed at the neutral points MP1 and MP2, respectively. The AC-AC conversion system can be realized, and the configuration with the multiplexing number N = 1 enables the generation of three-level phase voltages for both input and output. This eliminates the need for a multi-phase transformer compared to the cascade multi-level converter, thereby reducing the size of the conversion device, and the components such as switching elements and capacitors that constitute the unit AC-AC converter are also conventional configurations. Since the same breakdown voltage as the part can be used, the cost can be reduced.

  Here, FIG. 5 shows an example of a control block diagram of the control unit 3 of the three-phase AC-AC conversion system of FIG. 2, and FIG. 6 shows switching patterns of the switching elements based on voltage command values and carrier comparison in the system of FIG. Shown in

FIG. 5C is a block for generating a gate signal (switching pattern) for turning on / off each of the switching elements S1 to S12. The voltage command value V ^* _CONV generated in FIG. 5A is compared with the carrier signal. The PWM signal generation unit 31 that generates a gate signal (switching pattern) for turning on and off the switching elements S1 to S4 by the above, and the switching element S9 by comparing the voltage command value V ^* _INV and the carrier signal generated in FIG. PWM signal generation unit 32 that generates a gate signal (switching pattern) for turning on and off S12, switching patterns S1 to S4 and S9 to S12 generated by the generation units 31 and 32, and capacitors C1 and C2 From the relationship between the voltages of the switching elements S5 to S8, an expression (1) described later is obtained. And a switching control signal generation unit 33 that generates a gate signal (switching pattern) for turning on and off.

  In FIG. 5A, the detection voltages VCU1, VCV1, and VCW1 of the capacitor C1 of each phase are added by the adder 11 and then calculated by the 1/3 calculator 12.

Reference numeral 13 denotes a subtractor that takes a deviation between the DC voltage command value VDC ^* and the output voltage of the 1/3 computing unit 12, and the deviation output is subjected to PI control by the PI controller 14 to obtain a d-axis current command value Id ^* . Is done. The detected currents I _R , I _S , and I _T detected from the input currents of the three-phase input side H-bridge circuits B1 are converted by the axis converter 15 into d-axis and q-axis currents Id and Iq.

The d-axis current command value Id ^* which is the output of the PI controller 14 is deviated from the d-axis output current Id of the axis converter 15 by the subtractor 16. The d-axis deviation current of the subtracter 16 is added to the d-axis voltage command value Vd ^* in the adder 18 after passing through the automatic control unit (ACR) 17 and is input to the axis converter 19.

  The q-axis output current of the axis converter 15 is deviated from the zero value by the subtractor 20, and the q-axis deviation current is input to the rear axis converter 19 through the automatic control unit (ACR) 21.

The axis converter 19 converts the biaxial voltage components from the adder 18 and the ACR 21 into three axes. A voltage command 22 of the input side H-bridge circuit B1 is obtained by multiplying and dividing the three-axis voltage component input from the axis converter 19 by the three-phase average voltage of the capacitor C1 input from the 1/3 calculator 12. Outputs the value V ^* _CONV .

  In FIG. 5B, the detection voltages VCU2, VCV2, and VCW2 of the capacitor C2 of each phase are added by the adder 23 and then calculated by the 1/3 calculator 24.

25 multiplies and divides the output phase voltage command value V ^* by the three-phase average voltage of the capacitor C2 input from the 1/3 computing unit 24 to obtain the voltage command value V ^* _INV of the output side H-bridge circuit B2. Output.

  Further, the switching control signal generation unit 33 in FIG. 5C is configured to switch the switching patterns of the switching elements S1 to S4 and S9 to S12, the voltage VCU1 of the capacitor C1, and the voltage VCU2 of the capacitor C2 as shown in the following equation (1). The switching patterns of the switching elements S5 to S8 are obtained from the relationship.

S5 = {(S2∩S4) ∩ (S9∩S11)} ∪ {(S2∩S4) ∩ (S10∩S12)} ∩ (VCU1> VCU2)
S6 = {(S1∩S3) ∩ (S9∩S11)} ∪ {(S1∩S3) ∩ (S10∩S12)} ∩ (VCU1> VCU2)
S7 = {(S2∩S4) ∩ (S9∩S11)} ∪ {(S2∩S4) ∩ (S10∩S12)} ∩ (VCU1 <VCU2)
S8 = {(S1∩S3) ∩ (S9∩S11)} ∪ {(S1∩S3) ∩ (S10∩S12)} ∩ (VCU1 <VCU2) (1)
In the above formula (1), ∩ represents an AND condition, and ∪ represents an OR condition.

  The capacitors C1 and C2 can be charged / discharged by the switching pattern of the switching elements S5 to S8 shown in Expression (1).

FIG. 6A shows the relationship between V ^* _CONV , V ^* _INV and the carrier compared by the PWM signal generators 31 and 32 of FIG. 5B, the switching patterns of the switching elements S1 to S4 and S9 to S12, Each mode 1-5 is shown.

  FIGS. 6B to 6F show the ON / OFF states of the switching elements S1 to S12 and the current paths at that time in the modes 1 to 5, respectively. 6 (c) to 6 (e), currents flow through the capacitor C1 in modes 2, 3 and 4, and current flows through the capacitor C2 in mode 3 in FIG. 6 (d). By such an operation, the capacitors C1 and C2 are charged and discharged.

  Further, the circuit of FIG. 7 may be applied to the unit AC-AC converter of each phase in FIG. FIG. 7 is a circuit configured by using three-level converters as the input-side H-bridge circuit B1 and the output-side H-bridge circuit B2 of each phase in FIG. 2, and the same parts as those in FIG.

  In FIG. 7, the capacitor C1 of FIG. 2 is a series body of two capacitors C11 and C12, and the capacitor C2 of FIG. 2 is a series body of two capacitors C13 and C14.

  Between the common connection point of the capacitors C11 and C12 and the input terminal IN, switching elements S31 and S32 that control ON / OFF of currents in opposite directions (first bidirectional switching means that can be controlled in mutually opposite withstand voltage directions) Are connected in series in the reverse direction, and switching elements S33 and S34 (first circuits) for controlling currents in opposite directions on and off between the common connection point of the capacitors C11 and C12 and the common connection point of the switching elements S3 and S4. Two bidirectional switching means) are connected in series in the opposite direction.

  Between the common connection point of the capacitors C13 and C14 and the common connection point of the switching elements S9 and S10, switching elements S35 and S36 for controlling on and off currents in opposite directions (seconds that can be controlled in reverse voltage directions opposite to each other). Switching between the capacitors C13 and C14 and the common connection point of the switching elements S11 and S12 to control on and off currents in the opposite directions. Elements S37 and S38 (second bidirectional switching means) are connected in series in the reverse direction.

  When the unit AC-AC converter having the configuration of FIG. 7 is multiplexed at an arbitrary multiplexing number N in each phase, a 4N + 1 level phase voltage can be output to the input and a 4N + 1 level phase voltage can be output to the output.

FIG. 8 shows an embodiment in which the unit AC-AC converter of FIG. 1 is expanded to have a multiplexing number (the number of multiplexing stages) of N, and the same parts as those in FIG. That is, the neutral point MP1 of the first-stage input-side H bridge circuit B1 of the multiplex number is connected to the input terminal IN- ₂ of the second-stage input-side H bridge circuit B1, and the second-stage input-side H bridge circuit B1. point neutral MP1 _-2 are sequentially connected to the input terminal iN _-3 input side H-bridge circuit B1 in the third stage.

The neutral point MP2 of the output-side H bridge circuit B2 in the first stage of the multiplexing number is connected to the output terminal OUT- ₂ of the output-side H bridge circuit B2 in the second stage, and the output side H-bridge circuit B2 in the second stage. neutral point MP2 _-2 are sequentially connected to the output terminal OUT _-3 output side H-bridge circuit B2 of the third stage.

When an AC-AC conversion system is configured by providing three units of AC / AC converters that are multiplexed in this way, the neutral point MP1 _-n of the input-side H-bridge circuit B1 in the final stage of each phase is connected. And the neutral points MP2- _n of the output side H-bridge circuit B2 in the final stage of each phase are connected to each other.

  According to this embodiment, a multi-level AC-AC converter that can output a voltage of 2N + 1 level by Y-connection at the midpoints MP1-n, MP2-n of N multiplexed unit AC-AC converters. It is composed. As a result, a three-phase AC-AC conversion system capable of outputting a higher level of voltage than the system shown in FIG. 2 can be realized. The other effects are the same as those of the first embodiment.

  FIG. 9 shows the configuration of the unit AC-AC converter of the third embodiment. A second output-side H bridge circuit B2-1 is further added to the output-side H bridge circuit B2 of the unit AC-AC converter. The same parts as those in FIG. 1 are denoted by the same reference numerals.

  In FIG. 9, the second output-side H bridge circuit B2-1 is similar to the output-side H bridge circuit B2, and includes a series body of first and second switching elements S19 and S20, a capacitor C2-1, The fourth switching elements S21 and S22 are connected in parallel to each other.

  Between the common connection point of the switching elements S19 and S21 and the common connection point of the switching elements S1 and S3 of the input side H-bridge circuit B1, the ninth and tenth currents that control on and off currents flowing in opposite directions to each other are controlled. Switching elements S15 and S17 are connected in series in the reverse direction.

  Between the common connection point of the switching elements S20 and S22 and the common connection point of the switching elements S2 and S4 of the input-side H-bridge circuit B1, the ninth and tenth currents that control the on and off of the currents flowing in opposite directions to each other are controlled. Switching elements S16 and S18 are connected in series in the reverse direction.

  The neutral point MP2 of the output side H bridge circuit B2 is connected to the common connection point of the switching elements S21 and S22 of the second output side H bridge circuit B2-1, and the switching of the second output side H bridge circuit B2-1. A common connection point of the elements S19 and S20 is an output side neutral point MP2-1.

In FIG. 9, when the voltage of the capacitor C1 is E1 at the input terminal IN with reference to the input-side neutral point MP1, the three-level voltages E1, 0, and -E1 are turned on and off by the switching elements S1 to S4. The generation of is the same as in FIG. In the H-bridge circuit B2, B 2 - 1 on the output side, based on the output-side neutral point NP2 _-1, when the voltage of the capacitor C2, C2 _-1 and E2 to the output terminal OUT, and the switching element S9~ By combining the on / off operation of S12 and the on / off operations of S19 to S22, five-level voltages 2E2, E2, 0, -E2, and -2E2 can be generated. Here, the switching element S5~S8 is for controlling the voltage E2 of the capacitor C2, the switching elements S15~S18 are those responsible for controlling the voltage E2 of the capacitor C2 _-1.

FIG. 10 shows a case where the circuit of FIG. 9 is used for a three-phase configuration. The input side neutral point MP1 of the input side H bridge circuit B1 and the output side of the second output side H bridge circuit B2-1. The sex points MP2 _-1 are each Y-connected or delta-connected. In addition to the signals shown in FIG. 2, the control unit 3 includes detection voltages VCU2 ₋₁ , VCV2 ₋₁ , and VCW2 ₋₁ of the capacitor C2 ₋₁ of the second output side H-bridge circuit of each phase. Have been entered. While the voltage controlled is performed in the same manner as in FIG. 2, it differs from FIG. 2, when controlled to be equal to the voltage of the voltage of C1 and C2 and C2 _-1, an input / output voltage ratio 1: 2 and Thus, a multi-level unit AC-AC converter or a three-phase AC-AC conversion system in which the step-up ratio can be changed according to the DC voltage ratio can be obtained.

  Depending on the application, there is a case where a step-down conversion is performed from a high input voltage to a low output voltage. Such an application can be applied by connecting the OUT terminal of the output side H bridge circuit B2 to the power source side and connecting the input terminal IN of the input side H bridge circuit B1 to a load. That is, the input / output voltage ratio can be 2: 1 by reversing the input / output terminals.

Therefore, according to this embodiment, it is possible to generate the phase voltage of the input 3 level and the output 5 level. Further, an input / output voltage ratio by controlling equally C2 and C2 _-1 voltages of the voltage and the output side of the input side of the C1 1: 2, or 2: can be 1, DC input side The boost ratio can be changed according to the voltage ratio. The other effects are the same as those of the first embodiment.

FIG. 11 shows an embodiment in which the unit AC-AC converter shown in FIG. 9 is expanded to have a multiplexing number of N, and the same parts as those in FIG. That is, the neutral point MP1 of the first-stage input-side H bridge circuit B1 of the multiplex number is connected to the input terminal IN- ₂ of the second-stage input-side H bridge circuit B1, and the second-stage input-side H bridge circuit B1. point neutral MP1 _-2 are sequentially connected to the input terminal iN _-3 input side H-bridge circuit B1 in the third stage.

The neutral point MP2 _-1 of the second output-side H-bridge circuit B2-1 multiplex number first stage is connected to the output terminal OUT _-2 of the second-stage output H-bridge circuit B2 _-2, 2-stage second output H-bridge circuit B 2 - 1 _-2 neutral MP2 _-2 of the eye are sequentially connected to the output terminal OUT _-3 on the output side of the 3-stage H-bridge circuit B2 _-3.

When an AC-AC conversion system is configured by providing three units of AC / AC converters configured in this way for the three phases, the neutral point MP1 ₋ of the input-side H-bridge circuit B1-n at the final stage of each phase. How to connect a _n, obtained by connecting a to what second output H-bridge circuit B 2 - 1 _-n neutral point of MP2 _-n of each phase of the final stage.

  And by connecting the load to the input side H-bridge circuit to which the power supply is connected by Y-connection or delta-connection at the neutral points MP1-n and MP2-n with N multiplexed numbers It is possible to realize a multilevel AC-AC converter that can generate a voltage of 4N + 1 level in the H bridge circuit on the output side.

  When a three-phase AC-AC conversion system is configured with multiple unit AC-AC converters connected to each other, each neutral is provided on the input / output side of the final stage of the U, V, W unit AC-AC converters. It is obtained by connecting points MP1-n and MP2-n.

  Further, when it is desired to obtain a device that performs step-down conversion from a high input voltage to a low output voltage, the OUT terminal of the output side H bridge circuit B2 is connected to the power supply side, and the input terminal IN of the input side H bridge circuit B1 is used as a load. It becomes possible by connecting. As a result, a phase voltage of 4N + 1 level is obtained on the power supply side (H bridge circuit B2 side), and a phase voltage of 2N + 1 level is obtained on the load side (H bridge circuit B1 side).

  According to this embodiment, by connecting the respective midpoints MP1-n and MP2-n on the input / output side of the final stage of the N unit AC-AC converters, 2N + 1 levels on the input side, Alternatively, a 4N + 1 level voltage is obtained, and a multi-level AC-AC converter or a three-phase AC-AC conversion system capable of outputting a 4N + 1 level or 2N + 1 level voltage on the output side is obtained. The other effects are the same as those of the first embodiment.

  Here, although omitted in FIGS. 2, 6, and 7, snubber circuits are connected in parallel to the switching elements S5 to S8. The snubber circuit is a circuit that suppresses a surge voltage at the time of turn-off of a switching device such as an IGBT and prevents overvoltage breakdown of the switching device. A typical example is shown in FIG. FIG. 12 shows a configuration in which a CR snubber is added to the IGBT. The larger the capacitor capacity of the snubber circuit, the more effective the surge voltage suppression.

  FIG. 13 shows an example of mode transition when the switching element S8 is switched from ON to OFF. In FIG. 13, the snubber circuit is not shown in the switching element S <b> 8 without omitting it for explaining the operation. A switching element surrounded by a circle is a switching element in an ON state.

  FIG. 13A corresponds to mode 1 in FIG. At this time, the switching element S8 is turned on in accordance with the equation S8 in the equation (1). Therefore, a current flows through the path shown in FIG. Next, the mode shifts to mode 2 in FIG. In mode 2, since the switching element S3 is turned off, the switching element S8 is turned off in accordance with S8 of the equation (1). The current path at that time is shown in FIG. In FIG. 13B, all of the current flowing in FIG. 13A flows to the snubber circuit of the switching element S8. In order to suppress the surge voltage when the switching element S8 is turned off, it is necessary to increase the capacitor capacity of the snubber circuit. This led to an increase in the size of the converter. This problem is the same when the unit AC-AC converter of FIG. 7 is applied.

  Therefore, in the following, in addition to reducing the size of the conversion device by eliminating the need for a multi-phase transformer, an embodiment in which the snubber circuit connected to the switching element is unnecessary or the capacitor capacity of the snubber circuit is reduced will be described. To do.

  In the following embodiments, switching is performed by adding a diode that circulates the current of switching elements (particularly switching elements S5 and S7 and S6 and S8 that control bidirectional current on and off) of the AC-AC converter. Configured so that the snubber circuit, which was conventionally required to absorb the voltage surge of the switching element, can be omitted or the snubber circuit can be downsized by circulating the current to the DC capacitor when the current flowing through the element is interrupted. did.

  FIG. 14 shows an embodiment in which a free-wheeling diode (first free-wheeling diode) is provided in the circuit of FIG. 1, and the same parts as those in FIG. 14 differs from FIG. 1 in that freewheeling diodes D1 and D2 having the polarities shown are connected in series between a common connection point of switching elements S5 and S7 and a common connection point of switching elements S6 and S8, and diodes D1 and D2 These common connection points are connected to the input-side neutral point MP1 and the output-side neutral point MP2, and the other parts are configured in the same manner as in FIG.

  FIG. 15 shows an example of mode transition of the circuit of FIG. In FIG. 15, when the switching elements S1 and S8 are turned on, a current flows through the antiparallel diode S1 → C1 → S6 → S8. This is the same operation as FIG.

  Next, the switching element S8 is turned off. In this case, unlike the mode of FIG. 13B in which a current flows in the snubber circuit of the switching element S8, the current can be returned to the capacitor C1 via the return diodes D2 and D1.

  Therefore, in the circuit of the fifth embodiment, a current path other than the snubber circuit shown in FIG. 13 exists when the switching element is turned off. As a result, the snubber circuit of the switching element can be eliminated or the capacity of the snubber capacitor can be reduced. Other operations are the same as those in FIG.

  Further, the fifth embodiment may be applied to the circuit of FIG. The configuration in that case is as follows.

  As in FIG. 14, freewheeling diodes D1 and D2 (first freewheeling diodes) are connected in series between the common connection point of switching elements S5 and S7 and the common connection point of switching elements S6 and S8 in FIG. And the common connection point of the diode D2 is connected to the neutral point MP2 on the input side and the neutral point MP2 on the output side H-bridge circuit B2. Further, free-wheeling diodes D3 and D4 (second free-wheeling diodes) are connected in series between the common connection point of switching elements S15 and S17 in FIG. 9 and the common connection point of switching elements S16 and S18 as in FIG. The common connection point of the diode D3 and the diode D4 is connected to the input side neutral point MP1 and the output side neutral point MP2-1 of the second output side H bridge circuit B2-1.

  Even in such a configuration, the same operation and effect as described above can be obtained.

  FIG. 16 shows a unit AC-AC converter of Example 6, in which the common connection point of the free wheel diodes D1 and D2 in the circuit of FIG. 14 is not connected to the input side neutral point MP1, but to the output side neutral point MP2. Only, and the output side neutral point MP2 is clamped by the freewheeling diode. The other parts are the same as in FIG.

  In FIG. 16, the neutral points MP1 and MP2 can be separated. Also in the configuration of FIG. 16, the operation at the time of commutation is the same as in the case of FIG. 14, and the snubber circuit can be eliminated or the capacity of the snubber capacitor can be reduced.

  Further, the sixth embodiment may be applied to the circuit of FIG. The configuration in that case is as follows.

  As in FIG. 16, free-wheeling diodes D1 and D2 (first free-wheeling diodes) are connected in series between the common connection point of switching elements S5 and S7 in FIG. 9 and the common connection point of switching elements S6 and S8, and diode D1 And the common connection point of the diode D2 is connected to the neutral point MP2 of the output side H-bridge circuit B2. Further, free-wheeling diodes D3 and D4 (second free-wheeling diodes) are connected in series between the common connection point of switching elements S15 and S17 in FIG. 9 and the common connection point of switching elements S16 and S18 as in FIG. The common connection point of the diode D3 and the diode D4 is connected to the output side neutral point MP2-1 of the second output side H bridge circuit B2-1.

  Even in such a configuration, the same operation and effect as described above can be obtained.

  FIG. 17 shows a unit AC-AC converter of Example 7, in which the common connection point of the free wheel diodes D1 and D2 in the circuit of FIG. 14 is not connected to the output side neutral point MP2, but to the input side neutral point MP1. Only, and the input side neutral point MP1 is clamped by a free-wheeling diode. The other parts are the same as in FIG.

  In FIG. 17, the neutral points MP1 and MP2 can be separated. Also in the configuration of FIG. 17, the operation at the time of commutation is the same as in the case of FIG. 14, and the snubber circuit can be eliminated or the capacity of the snubber capacitor can be reduced.

  Further, the seventh embodiment may be applied to the circuit of FIG. The configuration in that case is as follows.

  As in FIG. 17, free-wheeling diodes D1 and D2 (first free-wheeling diodes) are connected in series between the common connection point of switching elements S5 and S7 in FIG. 9 and the common connection point of switching elements S6 and S8, and diode D1 The common connection point of the diode D2 is connected to the input-side neutral point MP1. Further, free-wheeling diodes D3 and D4 (second free-wheeling diodes) are connected in series between the common connection point of switching elements S15 and S17 in FIG. 9 and the common connection point of switching elements S16 and S18 as in FIG. A common connection point of the diode D3 and the diode D4 is connected to the input side neutral point MP1.

  Even in such a configuration, the same operation and effect as described above can be obtained.

  FIG. 18 shows a unit AC-AC converter of Example 8, in which the free wheel diodes D1 and D2 in the circuit of FIG. 14 are removed, and the common connection point of the diodes D1 and D2 and the neutral points MP1 and MP2 The connection line was removed, and instead, one free-wheeling diode D1 was connected between the common connection point of the switching elements S5 and S7 and the common connection point of the switching elements S6 and S8. The other parts are the same as in FIG.

  In FIG. 18, neutral points MP1 and MP2 can be separated. Also, only one freewheeling diode D1 is required. Also in the configuration of FIG. 18, the operation at the time of commutation is the same as in the case of FIG. 14, and the snubber circuit can be eliminated or the capacity of the snubber capacitor can be reduced.

  In Example 9, as shown in FIG. 19, each unit AC-AC converter (50) of Examples 5 to 8 (FIGS. 14 to 18) is multiplexed in a number N (50-1, 50-). 2, 50-n) connected. That is, the input side neutral point MP1 of the unit AC-AC converter 50-1 at the first stage of the multiplexing number is connected to the input terminal IN of the unit AC-AC converter 50-2 at the second stage, and the unit AC-AC is connected. The input side neutral point MP1 of the converter 50-2 is connected to the unit AC-AC converter 50-3 at the third stage, and similarly connected to the unit AC-AC converter 50-n at the final stage sequentially. ing.

  The output side neutral point MP2 of the unit AC-AC converter 50-1 of the first stage multiple is connected to the output terminal OUT of the unit AC-AC converter 50-2 of the second stage, and the unit AC-AC converter is connected. The output side neutral point MP2 of 50-2 is connected to the unit AC-AC converter 50-3 at the third stage, and similarly connected to the unit AC-AC converter 50-n at the final stage in turn. .

  By using N unit AC-AC converters in this way, it is possible to output a 2N + 1 level voltage on the input terminal IN side and a 2N + 1 level voltage on the output terminal OUT side.

  FIG. 20 shows an embodiment in which a freewheeling diode is provided in the circuit of FIG. 7, and the same parts as those in FIG. 20 is different from FIG. 7 in that freewheeling diodes D1 and D2 having polarities shown in the figure are connected in series between a common connection point of switching elements S5 and S7 and a common connection point of switching elements S6 and S8, and diodes D1 and D2 are connected. These common connection points are connected to the input-side neutral point MP1 and the output-side neutral point MP2, and the other parts are configured in the same manner as in FIG.

  The commutation operation of the switching element in the circuit of FIG. 20 is the same as the operation described with reference to FIG. Other operations are the same as those in FIG.

  FIG. 21 shows a unit AC-AC converter of Example 11, in which the common connection point of the free wheel diodes D1 and D2 in the circuit of FIG. 20 is not connected to the input side neutral point MP1, but to the output side neutral point MP2. Only, and the output side neutral point MP2 is clamped by the freewheeling diode. The other parts are the same as in FIG.

  In FIG. 21, the neutral points MP1 and MP2 can be separated. Also in the configuration of FIG. 21, the operation at the time of commutation is the same as in the case of FIG. 20, and the snubber circuit can be eliminated or the capacity of the snubber capacitor can be reduced.

  FIG. 22 shows a unit AC-AC converter of Example 12, in which the common connection point of the free wheel diodes D1 and D2 in the circuit of FIG. 20 is not connected to the output side neutral point MP2, but to the input side neutral point MP1. Only, and the input side neutral point MP1 is clamped by a free-wheeling diode. The other parts are the same as in FIG.

  In FIG. 22, neutral points MP1 and MP2 can be separated. Also in the configuration of FIG. 22, the operation at the time of commutation is the same as in the case of FIG. 20, and the snubber circuit can be eliminated or the capacity of the snubber capacitor can be reduced.

  FIG. 23 shows a unit AC-AC converter of the thirteenth embodiment, in which the free-wheeling diodes D1 and D2 in the circuit of FIG. 20 are removed, and the common connection point of the diodes D1 and D2 and the neutral points MP1 and MP2 The connection line was removed, and instead, one free-wheeling diode D1 was connected between the common connection point of the switching elements S5 and S7 and the common connection point of the switching elements S6 and S8. The other parts are the same as in FIG.

  In FIG. 23, the neutral points MP1 and MP2 can be separated. Also, only one freewheeling diode D1 is required. Also in the configuration of FIG. 23, the operation at the time of commutation is the same as in the case of FIG. 20, and the snubber circuit can be eliminated or the capacity of the snubber capacitor can be reduced.

  In the fourteenth embodiment, as shown in FIG. 24, each unit AC-AC converter (60) of the tenth to thirteenth embodiment (FIGS. 20 to 23) has a multiplexing number N (60-1, 60-). 2, 60-n) connected. That is, the input side neutral point MP1 of the unit AC-AC converter 60-1 at the first stage of the multiplex number is connected to the input terminal IN of the unit AC-AC converter 60-2 at the second stage, and the unit AC-AC. The input-side neutral point MP1 of the converter 60-2 is connected to the third-stage unit AC-AC converter 60-3, and similarly connected to the final-stage unit AC-AC converter 60-n sequentially. ing.

  The output side neutral point MP2 of the unit AC-AC converter 60-1 at the first stage of the multiplex number is connected to the output terminal OUT of the unit AC-AC converter 60-2 at the second stage, and the unit AC-AC converter is connected. The output side neutral point MP2 of 60-2 is connected to the unit AC-AC converter 60-3 at the third stage, and similarly connected to the unit AC-AC converter 60-n at the final stage in turn. .

  By using N unit AC-AC converters in this way, it is possible to output a 4N + 1 level voltage on the input terminal IN side and a 4N + 1 level voltage on the output terminal OUT side.

  In the fifteenth embodiment, by providing a reactor in the charging / discharging path of each capacitor of the input side H bridge circuit and the output side H bridge circuit, the switching pattern in which a short-circuit loop occurs is eliminated, and the degree of freedom of the switching pattern is increased. Configured.

  First, the reason why a short-circuit loop occurs in the unit AC-AC converter of FIG. 14 provided with the reflux diodes D1 and D2 will be described with reference to FIG.

  FIG. 25 shows a current path at the time of charge / discharge control of the capacitor in the circuit of FIG. 14, and the input-side neutral point MP1 and the output-side neutral point MP2 are represented as one common neutral point MP.

  In the circuit of FIG. 25, in order to charge the capacitor C2 with the electric charge of the capacitor C1, the switching elements S5 to S8 for controlling the bidirectional current are controlled to be on and off.

  In general, an AC power source is connected to the input terminal IN via an input reactor, and an inductive load is connected to the output terminal OUT. Under such conditions, the input / output inductance components are used to control the switching elements S5 to S8 to be turned on and off, and the capacitors C1 to C2 or the capacitors C2 to C1 are charged / discharged. There are limitations on the switching patterns of the switching elements S1 to S4 and S9 to S12 of the circuits B1 and B2. A current path according to an example of a switching pattern that cannot be used is indicated by a dashed arrow in FIG.

  Here, the voltage of the capacitor C1 is VC1, and the voltage of the capacitor C2 is VC2. In the case of VC1> VC2, if switching elements S3 and S6 are turned on at the same time, a short-circuit loop indicated by a broken line arrow in FIG. 25 is generated, so that a switching pattern for simultaneously turning on switching elements S3 and S6 cannot be used. Such a switching pattern that cannot be used complicates charge / discharge control of the capacitor of the converter.

  Therefore, in the fifteenth embodiment, as shown in FIG. 26, the reactor L (first output) is connected between the common connection point of the switching elements S3 and S4 of the input side H-bridge circuit B1 and the common connection point of the freewheeling diodes D1 and D2. Reactor) was connected. FIG. 26 shows a circuit configuration in which the fifteenth embodiment is applied to the circuit of FIG. 17, and the same parts as those in FIG. 17 are denoted by the same reference numerals.

  FIG. 27A shows a current path in a first mode (mode in which switching elements S3 and S6 are turned on) in which capacitor C1 is discharged and capacitor C2 is charged in FIG.

  In FIG. 27A, when switching elements S3 and S6 are turned ON, switching element S3 → reactor L → return diode D1 → reverse parallel diode of switching element S7 → capacitor C2 → reverse of switching element S8 from the positive side of capacitor C1. A current is passed through the path from the parallel diode to the switching element S6, whereby the charge of the capacitor C1 can be moved to the capacitor C2. Further, the reactor L can smooth a large peak current that flows when the potential difference between the capacitors C1 and C2 is large.

  FIG. 27B shows a current path in the second mode (mode in which switching elements S4 and S5 are turned on) in which capacitor C1 is discharged and capacitor C2 is charged in FIG.

  In FIG. 27 (b), switching elements S4 and S5 are turned on, so that switching element S5 → switching element S7 antiparallel diode → capacitor C2 → switching element S8 antiparallel diode → freewheeling diode D2 → By passing a current through the path of the reactor L → the switching element S4, the charge of the capacitor C1 can be moved to the capacitor C2. Further, the reactor L can smooth a large peak current that flows when the potential difference between the capacitors C1 and C2 is large.

  In the circuit configuration shown in FIG. 25 (FIG. 14), since the reactor is not built in the unit AC-AC converter, the capacitor C1 and C2 are short-circuited, so that the switching pattern shown in FIG. The pattern in which the switching elements S3 and S6 are turned on when VC1> VC2 cannot be used. Similarly, the switching pattern shown in FIG. 27B (a pattern for turning on the switching elements S4 and S5 when VC1> VC2) cannot be used.

  However, by using the configuration of FIG. 26, the capacitor C1 can be charged from the capacitor C1 by the switching pattern.

  In addition, the insertion position of the reactor L is not restricted to the position of FIG. That is, the fifteenth embodiment is applied to the circuit of FIG. 16, and between the common connection point of the switching elements S9 and S10 of the output side H-bridge circuit B2 of the circuit of FIG. 16 and the common connection point of the free-wheeling diodes D1 and D2. A reactor L (first reactor) may be connected.

  Further, the fifteenth embodiment is applied to the circuit of FIG. 14, and between the common connection point of the switching elements S3 and S4 of the input side H-bridge circuit B1 of the circuit of FIG. 14 and the common connection point of the free-wheeling diodes D1 and D2. Reactor L (first reactor) is connected, and reactor L (first reactor) is also connected between the common connection point of free-wheeling diodes D1 and D2 and the common connection point of switching elements S9 and S10 of output side H-bridge circuit B2. (Reactor) may be connected.

  Further, the fifteenth embodiment is applied to a unit AC-AC converter in which one input-side H bridge circuit B1 and two output-side H bridge circuits B2 and B2-1 described in the third embodiment (FIG. 9) are combined. May be.

  That is, when the circuit of FIG. 9 uses the method of clamping the output-side neutral point MP2 of FIG. 16 with the freewheeling diode, the common connection point of the switching elements S5 and S7 and the common connection point of the switching elements S6 and S8. The free-wheeling diodes D1 and D2 are connected in series, and the free-wheeling diodes D3 and D4 are connected in series between the common connection point of the switching elements S15 and S17 and the common connection point of the switching elements S16 and S18. A reactor L (first reactor) is connected between a common connection point of D2 and a common connection point of switching elements S9 and S10, and a common connection point of freewheeling diodes D3 and D4 and a common connection point of switching elements S19 and S20. A reactor L (second reactor) is connected between the two.

  Further, when the circuit of FIG. 9 uses the method of clamping the input-side neutral point MP1 of FIG. 17 with a freewheeling diode, the common connection point of the switching elements S5 and S7 and the common connection point of the switching elements S6 and S8. The free-wheeling diodes D1 and D2 are connected in series, and the free-wheeling diodes D3 and D4 are connected in series between the common connection point of the switching elements S15 and S17 and the common connection point of the switching elements S16 and S18. A reactor L (first reactor) is connected between a common connection point of D2 and a common connection point of switching elements S3 and S4, and a common connection point of freewheeling diodes D3 and D4 and a common connection point of switching elements S3 and S4. A reactor L (second reactor) is connected between the two.

  Further, when the circuit of FIG. 9 uses the method of connecting the common connection point of the free wheel diodes D1 and D2 of FIG. 14 to both the input side H bridge circuit B1 and the output side H bridge circuit B2, the switching element S5, Freewheeling diodes D1 and D2 are connected in series between the common connection point of S7 and the common connection point of switching elements S6 and S8, and between the common connection point of switching elements S15 and S17 and the common connection point of switching elements S16 and S18. Are connected in series, and a reactor L (first reactor) is connected between a common connection point of the return diodes D1 and D2 and a common connection point of the switching elements S3 and S4, and the return diode D1. , D2 and a common connection point of the switching elements S9 and S10, a reactor L (first reactor) is connected and refluxed. A reactor L (second reactor) is connected between the common connection point of the diodes D3 and D4 and the common connection point of the switching elements S3 and S4, and the common connection point of the free-wheeling diodes D3 and D4 and the switching elements S19 and S20. A reactor L (second reactor) is connected between the common connection points.

  In addition, the fifteenth embodiment can be applied to the circuits of FIGS. 20, 21, and 22. That is, in the circuit of FIG. 20, the reactor L (first reactor) is connected between the common connection point of the free wheel diodes D1 and D2 and the common connection point of the switching elements S3 and S4, and the free wheel diode D1, The reactor L (first reactor) is also connected between the common connection point of D2 and the common connection point of the switching elements S9 and S10.

  In the circuit of FIG. 21, a reactor L (first reactor) is connected between the common connection point of the freewheeling diodes D1 and D2 and the common connection point of the switching elements S9 and S10.

  In the circuit of FIG. 22, a reactor L (first reactor) is connected between the common connection point of the freewheeling diodes D1 and D2 and the common connection point of the switching elements S3 and S4.

  In any configuration in which the reactor L is connected, the operation is the same as the operation described in FIGS. 27A and 27B, and a short-circuit loop occurs when charge / discharge control of the capacitor is performed as described above. Without increasing the degree of freedom of the switching pattern. Further, it is possible to smooth a large peak current that flows when the potential difference between the capacitor of the input side H bridge circuit and the capacitor of the output side H bridge circuit is large.

  In the sixteenth embodiment, three phases of single-phase AC-AC converters including the free wheel diode and the reactor L described in the fifteenth embodiment are provided, and the neutral point MP1 is provided in the same manner as in FIGS. And MP2 (MP2-1) are respectively Y-connected or delta-connected to constitute a three-phase AC-AC conversion system.

  With this configuration, in addition to the effects described with reference to FIGS. 2 and 10, a short-circuit loop does not occur when performing charge / discharge control of the capacitor, the degree of freedom of the switching pattern increases, and the input side It is possible to smooth the large peak current that flows when the potential difference between the H bridge circuit capacitor and the output H bridge circuit capacitor is large.

In the seventeenth embodiment, the single-phase AC-AC converter having the built-in freewheeling diode and reactor L described in the fifteenth embodiment is expanded, and the multiplex number (as in FIGS. 8, 11, 19, and 24). The number of multiple stages was N. That is, for example, as shown in FIG. 8, the neutral point MP1 of the input-side H bridge circuit B1 at the first stage of the multiplex number is connected to the input terminal IN- ₂ of the input stage H-bridge circuit B1 at the second stage. The neutral point MP1 _-2 of the input side H-bridge circuit B1 is sequentially connected to the input terminal IN- ₃ of the third-stage input-side H bridge circuit B1.

The neutral point MP2 of the output-side H bridge circuit B2 in the first stage of the multiplexing number is connected to the output terminal OUT- ₂ of the output-side H bridge circuit B2 in the second stage, and the output side H-bridge circuit B2 in the second stage. neutral point MP2 _-2 sequentially connected to the output terminal OUT _-3 output side H-bridge circuit B2 of the third stage.

When an AC-AC conversion system is configured by providing three units of AC / AC converters that are multiplexed in this way, the neutral point MP1 _-n of the input-side H-bridge circuit B1 in the final stage of each phase is connected. And the neutral points MP2- _n of the output side H-bridge circuit B2 in the final stage of each phase are connected to each other.

  With this configuration, in addition to the effects described in FIGS. 8, 11, 19, and 24, a short-circuit loop does not occur when performing charge / discharge control of the capacitor, and the degree of freedom of the switching pattern increases. In addition, it is possible to smooth the large peak current that flows when the potential difference between the capacitor of the input side H bridge circuit and the capacitor of the output side H bridge circuit is large.

1 ... Power 2 ... load 3 ... control unit _{B1, B2, B2-1, B2-1 -n} ... H -bridge circuit IN ... input terminal OUT ... output terminal MP1, MP2 ... neutral point C1, C2, C2 _-1 ... Capacitors D1, D2 ... Freewheeling diodes S1 to S12, S15 to S22, S31 to S38 ... Switching elements L ... Reactor

Claims (5)

An AC-AC converter that converts an AC input voltage into an AC output voltage of a plurality of levels,
A circuit in which a series body of first and second switching elements, a first capacitor, and a series body of third and fourth switching elements are connected in parallel, the first and third switching elements being Define the positive side, define the second and fourth switching elements as the negative side, and configure an H-bridge circuit,
The H bridge circuit is provided on each of the input side and the output side, and a common connection point of the first and third switching elements of the input side H bridge circuit and a common connection of the first and third switching elements of the output side H bridge circuit Between the points, fifth and sixth switching elements that control on and off of currents flowing in opposite directions are connected in series in the opposite direction, and the second and fourth switching elements of the input side H-bridge circuit are connected in common. Between the common connection point of the point and the second and fourth switching elements of the output side H-bridge circuit, seventh and eighth switching elements that control on and off of currents flowing in opposite directions are connected in series in the opposite direction. And
Connecting a first free-wheeling diode between a common connection point of the fifth and sixth switching elements and a common connection point of the seventh and eighth switching elements;
The common connection point of the first and second switching elements of the input-side H bridge circuit is an input terminal, and the common connection point of the third and fourth switching elements of the input-side H bridge circuit is an input-side neutral point. A common connection point of the first and second switching elements of the output side H bridge circuit is defined as an output neutral point, and a common connection point of the third and fourth switching elements of the output side H bridge circuit is defined as an output terminal. An AC-AC converter comprising the unit AC-AC converter. The unit AC-AC converter is provided with a second output-side H bridge circuit configured the same as the output-side H bridge circuit, and the first and third of the second output-side H bridge circuit are provided. Between the common connection point of the switching elements and the common connection point of the first and third switching elements of the input side H-bridge circuit, ninth and tenth currents that control on and off of currents flowing in opposite directions to each other are controlled. Switching elements are connected in series in the opposite direction, and a common connection point of the second and fourth switching elements of the second output side H bridge circuit and a common connection of the second and fourth switching elements of the input side H bridge circuit Between the points, the eleventh and twelfth switching elements that turn on and off the currents flowing in opposite directions are connected in series in the opposite direction,
The common connection point of the first and second switching elements of the output-side H bridge circuit is connected to the common connection point of the third and fourth switching elements of the second output-side H bridge circuit, and the second output 2. The AC-AC converter according to claim 1, wherein a common connection point of the first and second switching elements of the side H-bridge circuit is an output side neutral point. A second freewheeling diode is connected between a common connection point of the ninth and tenth switching elements and a common connection point of the eleventh and twelfth switching elements of the unit AC-AC converter. The AC-AC converter according to claim 2 .   The first capacitor voltage of the input-side H bridge circuit, the first capacitor voltage of the output-side H bridge circuit, and the first capacitor voltage of the second output-side H bridge circuit are controlled to be equal, and the input The AC / AC converter according to claim 2 or 3, wherein the / output voltage ratio is 1: 2.   The unit AC-AC converter has N (N is an integer of 2 or more) multiple stages, and the input side neutral point of the first unit AC-AC converter is the input terminal of the next unit AC-AC converter. Further, the output-side neutral point of the first unit AC-AC converter is sequentially connected to the output terminal of the next unit AC-AC converter for N units. The alternating current-alternating current converter of any one of thru | or 4.

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