JP6432832B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device, and more particularly to a power conversion device capable of converting at least a DC voltage into an AC voltage.

  Conventionally, a power conversion device that converts a DC voltage of a solar cell or the like into an AC voltage has been provided (see, for example, Patent Document 1). The power conversion device described in Patent Document 1 includes two booster circuit units that boost an input voltage of a magnitude that is input from a solar cell to a predetermined magnitude, and input voltages from the two booster circuit units. And an inverter circuit unit for converting into commercial AC voltage.

  Each booster circuit unit includes a switch element and a capacitor. One end of the switch element is connected to one end of the output of the solar cell through the reactor, and the other end is connected to the other end of the output of the solar cell. Further, one end of the capacitor is connected to one end of the switch element via a diode, and the other end is connected to the other end of the output of the solar cell. Each booster circuit unit outputs a DC voltage having a magnitude corresponding to the switching operation to the inverter circuit unit by controlling the switching operation of the switch element by the PWM control unit.

  The inverter circuit unit includes a bridge circuit composed of four switch elements, two reactors and capacitors connected to both ends of the output of the bridge circuit, and an inverter control unit. The inverter circuit unit converts the DC voltage output from each booster circuit unit into an AC voltage and outputs it to the load by controlling the switching operation of the four switch elements by the inverter control unit.

Japanese Patent Laid-Open No. 10-14258

  In the power conversion device described in Patent Document 1 described above, the booster circuit unit is configured by a chopper circuit having a switch element and a capacitor, and the ripple of the input current to the inverter circuit unit may increase.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a power conversion device in which a ripple of an input current to a circuit that converts direct current into alternating current is reduced.

The power conversion device of the present invention is a power conversion device capable of converting at least a DC voltage into an AC voltage, and includes a first power conversion unit, a second power conversion unit, the first power conversion unit, and the second power. A control unit that controls the conversion unit, wherein the first power conversion unit includes at least two conversion circuits connected in parallel to each other between a DC power source and the second power conversion unit, and the DC power source The DC voltage output from the first power converter is boosted to a DC voltage having a desired voltage value and output to the second power converter. The second power converter converts the DC voltage output from the first power converter into an AC The first power conversion unit outputs a current obtained by combining the output currents of the at least two conversion circuits to the second power conversion unit as a combined current, and the control unit outputs the power The power conversion device more than the life of the conversion device The first power conversion unit is controlled to reduce the ripple current output by the first power conversion unit when the life is prioritized over the conversion efficiency compared to the case where the conversion efficiency is prioritized. Features.

  According to the configuration of the present invention, there is an effect that it is possible to provide a power conversion device in which a ripple of an input current to a circuit that converts direct current into alternating current is reduced.

It is a schematic block diagram which shows an example of the power converter device which concerns on embodiment of this invention. It is a schematic circuit diagram which shows an example of the power converter device which concerns on embodiment of this invention. It is a block diagram which shows the principal part of the control part of the power converter device which concerns on embodiment of this invention. It is a block diagram which shows another principal part of the control part of the power converter device which concerns on embodiment of this invention. 5A and 5B are waveform diagrams of a carrier wave output from the carrier wave generation unit of the power conversion device according to the embodiment of the present invention. FIG. 6A is a waveform diagram of a current flowing through each conversion circuit in the power conversion device according to the embodiment of the present invention, and FIG. 6B is a waveform diagram of a combined current obtained by combining the currents flowing through the two conversion circuits. 7A and 7B are waveform diagrams of currents flowing through the respective conversion circuits in the power conversion device according to the embodiment of the present invention. 8A and 8B are timing charts for explaining the operation of the control unit of the power conversion device according to the embodiment of the present invention. It is a schematic block diagram which shows another example of the power converter device which concerns on embodiment of this invention.

  A power converter 10 according to an embodiment of the present invention will be specifically described with reference to FIGS. However, the configuration described below is merely an example of the present invention, and the present invention is not limited to the following embodiment. Therefore, various modifications other than this embodiment can be made according to the design and the like as long as they do not depart from the technical idea of the present invention.

  The power conversion device 10 of the present embodiment has a DC-AC conversion function that converts, for example, a DC voltage output from the DC power supply 1 into an AC voltage. As shown in FIG. A second power conversion unit 3, a control unit 5, and switches 6A and 6B (see FIG. 2) are provided.

  The first power conversion unit 2 includes at least two conversion circuits 21,..., 2 n (n = 2, 3,...) Connected in parallel with each other between the DC power source 1 and the second power conversion unit 3. Moreover, the 2nd power converter 3 is electrically connected with the alternating current power supply 4 via the interconnection breaker.

  FIG. 2 is a schematic circuit diagram illustrating an example of the power conversion apparatus 10 according to the present embodiment. Hereinafter, a case where the first power conversion unit 2 includes two conversion circuits 21 and 22 will be described.

  The DC power supply 1 includes a power supply unit 11 made of, for example, a solar battery or a fuel cell, and a power supply unit 12 made of a storage battery. The power supply unit 11 is electrically connected to a pair of input terminals 111 and 112 provided in the power conversion device 10. The power supply unit 12 is electrically connected to a pair of input terminals 113 and 114 provided in the power conversion apparatus 10.

  Here, a switch 6A having a pair of contacts 61 is inserted between the pair of input terminals 111, 112 and the first power converter 2, and the pair of contacts 61 of the switch 6A is closed. A DC voltage is input from the power supply unit 11 to the first power converter 2. In addition, a switch 6B having a pair of contacts 62 is inserted between the pair of input terminals 113, 114 and the first power conversion unit 2, and the power source is closed by closing the pair of contacts 62 of the switch 6B. A DC voltage is input from the unit 12 to the first power converter 2.

  In the present embodiment, a DC voltage is not simultaneously input from both of the power supply units 11 and 12, but by switching to the switch 6A or 6B by a switching signal output from the control unit 5, A DC voltage is input from one of 12.

  As shown in FIG. 2, the first power conversion unit 2 includes two conversion circuits 21 and 22, a capacitor C <b> 1 connected between input terminals of the first power conversion unit 2, and an output of the first power conversion unit 2. It has the capacitor | condenser C2 connected between ends, and the voltage measurement part 200. FIG.

  The conversion circuit 21 is, for example, a step-up / step-down chopper circuit that boosts or lowers a DC voltage output from the DC power supply 1, and includes two switching elements Q1 and Q2, a reactor L1, and a current measurement unit 211 (measurement unit). It comprises.

  The switching elements Q1, Q2 are, for example, NPN bipolar transistors, and are connected in series by connecting the emitter of the switching element Q1 and the collector of the switching element Q2. In addition, one end of the reactor L1 is connected to the connection point of the switching elements Q1 and Q2, and the other end of the reactor L1 is connected to one end of the capacitor C1 via the current measuring unit 211.

  Furthermore, the other end of the capacitor C1 is connected to the emitter of the switching element Q2. Further, a capacitor C2 is connected between the collector of the switching element Q1 and the emitter of the switching element Q2, and a voltage measuring unit 200 is further connected. That is, in this embodiment, the voltage measurement unit 200 measures the output voltage of the first power conversion unit 2.

  Here, the current measurement unit 211 includes, for example, a shunt resistor, a current transformer (CT), and the like, detects a current flowing through the reactor L1, and outputs the detected current to the control unit 5.

  The conversion circuit 22 is a step-up / step-down chopper circuit similar to the conversion circuit 21, and includes two switching elements Q3 and Q4, a reactor L2, and a current measurement unit 221 (measurement unit).

  The switching elements Q3 and Q4 are NPN type bipolar transistors like the switching elements Q1 and Q2, and are connected in series by connecting the emitter of the switching element Q3 and the collector of the switching element Q4. Further, one end of the reactor L2 is connected to the connection point of the switching elements Q3, Q4, and the other end of the reactor L2 is connected to one end of the capacitor C1 via the current measuring unit 221.

  Further, the other end of the capacitor C1 is connected to the emitter of the switching element Q4. Further, a capacitor C2 is connected between the collector of the switching element Q3 and the emitter of the switching element Q4, and the voltage measuring unit 200 is further connected.

  The current measuring unit 221 is configured with a shunt resistor, a current transformer (CT), and the like, similar to the current measuring unit 211, detects the current flowing through the reactor L2, and outputs the detected current to the control unit 5.

  In the conversion circuit 21, when the voltage value of the DC voltage output from the DC power source 1 is lower than the target voltage, the voltage is increased by controlling the switching element Q2, and the voltage value of the DC voltage output from the DC power source 1 is the target voltage. When higher, the voltage is stepped down by controlling the switching element Q1. In the conversion circuit 22, when the voltage value of the DC voltage output from the DC power source 1 is lower than the target voltage, the voltage is increased by controlling the switching element Q4, and the voltage value of the DC voltage output from the DC power source 1 is the target voltage. When it is higher, the voltage is stepped down by controlling the switching element Q3.

  The second power conversion unit 3 is a so-called full bridge type inverter circuit composed of four switching elements Q5 to Q8 made of NPN type bipolar transistors. Switching elements Q5 and Q6 are connected in series by connecting the emitter of switching element Q5 and the collector of switching element Q6. Switching elements Q7 and Q8 are connected in series by connecting the emitter of switching element Q7 and the collector of switching element Q8.

  The switching elements Q5 and Q6 connected in series and the switching elements Q7 and Q8 connected in series are connected in parallel to form a bridge circuit.

  One end of reactor L3 is connected to the connection point of switching elements Q5 and Q6, and the other end of reactor L3 is connected to output terminal 115. Further, one end of reactor L4 is connected to the connection point of switching elements Q7 and Q8, and the other end of reactor L4 is connected to output terminal 116. Further, a capacitor C3 is connected between the output terminals 115 and 116.

  The control unit 5 includes, for example, a microcomputer, and controls the switching elements Q1 and Q2 of the conversion circuit 21, the switching elements Q3 and Q4 of the conversion circuit 22, and the switching elements Q5 to Q8 of the second power conversion unit 3, respectively. Output a signal. Thereby, on / off of each switching element is controlled. Further, the measurement results of the current measurement units 211 and 221 and the measurement result of the voltage measurement unit 200 are input to the control unit 5, respectively.

  FIG. 3 is a block diagram showing a main part of the control unit 5. The control unit 5 realizes the two comparators 52 and 53 and the carrier generation unit 51 that outputs the carrier waves W1 and W2 to the comparators 52 and 53 by executing a program stored in advance.

  After obtaining the output voltage V2 of the first power conversion unit 2 from the voltage measurement unit 200, the control unit 5 calculates a difference ΔV between the preset target voltage V1 and the output voltage V2. Then, the control unit 5 calculates the reference value K1 of the carrier waves W1 and W2 output from the carrier wave generation unit 51 based on the difference ΔV, and outputs it to one input terminal of each of the comparators 52 and 53.

  The comparator 52 compares the carrier wave W1 from the carrier wave generator 51 input to the other input terminal with the reference value K1, and outputs a control signal Sig1 according to the comparison result to the switching element Q1 or Q2. The comparator 53 compares the carrier wave W2 from the carrier wave generation unit 51 input to the other input terminal with the reference value K1, and outputs a control signal Sig2 corresponding to the comparison result to the switching element Q3 or Q4.

  FIG. 4 is a block diagram showing another main part of the control unit 5. In the present embodiment, the switching elements Q1 to Q4 of the conversion circuits 21 and 22 are turned on by the control signals Sig1 and Sig2 that are comparison results between the carrier waves W1 and W2 output from the carrier wave generation unit 51 of the control unit 5 and the reference value K1. / Off is controlled. As a result, the current I1 is output from the conversion circuit 21 and the current I2 is output from the conversion circuit 22.

  FIG. 5A is a waveform diagram of carrier waves W1 and W2 output from the carrier wave generation unit 51 to the comparators 52 and 53. FIG. In the present embodiment, the phase of the carrier wave W2 (solid line a2 in FIG. 5A) output to the comparator 53 is shifted by 180 ° with respect to the carrier wave W1 (solid line a1 in FIG. 5A) output to the comparator 52.

  Thereby, the current output from the conversion circuit 21 changes as indicated by a solid line a3 in FIG. 6A, and the current output from the conversion circuit 22 changes as indicated by a solid line a4 in FIG. 6A. As a result, the combined current obtained by combining the current output from the first power conversion unit 2, that is, the current output from the conversion circuit 21 and the current output from the conversion circuit 22, is as indicated by a solid line a5 in FIG. 6B. Change. FIG. 5B is a waveform diagram of carrier waves output from the carrier wave generation unit 51 to the three conversion circuits, respectively, and will be described in detail later.

  Further, in the present embodiment, the control unit 5 switches the switching elements Q1 and Q2 of the conversion circuit 21 and the switching circuit 22 so that the amplitude h1 of the ripple (pulsation) of the combined current falls within a predetermined value set in advance. Controls on / off of the elements Q3 and Q4.

  Therefore, according to this embodiment, the ripple of the input current (synthetic current) to the 2nd power converter 3 can be reduced compared with the conventional power converter device. In addition, since at least two conversion circuits 21,..., 2n are connected in parallel to each other, the amount of current flowing through each conversion circuit 21,.

  Table 1 is a table showing the relationship between the number of conversion circuits constituting the first power conversion unit 2, the conversion efficiency of the first power conversion unit 2, and the ripple current. In addition, the design index in Table 1 is an index representing which of the conversion efficiency of the conversion circuit or the life of the capacitor used in the conversion circuit is prioritized.

  Here, in the interleave control in which the operations of at least two conversion circuits are shifted little by little to perform parallel processing, the ripple current decreases as the number of conversion circuits increases, and the burden on the capacitors C1 and C2 decreases. The lifetime of C2 can be extended. On the other hand, as the number of conversion circuits performing interleave control increases, circuit loss increases and conversion efficiency decreases.

  In case 1, since there is one conversion circuit, the circuit loss is small and the conversion efficiency is high, but since the interleave control is not performed, the ripple current is large and the lifetimes of the capacitors C1 and C2 are shortened.

  In Case 2, since there are four conversion circuits, the circuit loss is large and the conversion efficiency is low. However, since the interleave control is performed, the ripple current is small and the lifetimes of the capacitors C1 and C2 are extended.

  In case 3, since there are four conversion circuits, the circuit loss is large and the conversion efficiency is low. However, since the interleave control is performed and the output power is 2 kW, which is half of that in case 2, the ripple current is larger than that in case 2. The lifetime of the capacitors C1 and C2 is longer than that of the case 2 because it is small.

  In Case 4, since there are two conversion circuits, the circuit loss is large and the efficiency is low. However, since the interleave control is performed, the ripple current is small and the lifetimes of the capacitors C1 and C2 are extended.

  From the results of cases 2 and 4, the number of conversion circuits that perform interleave control is increased as the output power (combined current) from the first power conversion unit 2 to the second power conversion unit 3 increases. Is preferred. Thereby, it is possible to suppress a decrease in conversion efficiency as compared with the case where the number of conversion circuits is not increased while reducing the ripple of the input current to the second power conversion unit 3.

  By the way, in the above-described interleave control, the phase of the carrier wave W2 used to generate the control signal Sig2 to the conversion circuit 22 is shifted by 180 ° with respect to the carrier wave W1 used to generate the control signal Sig1 to the conversion circuit 21. It is. Therefore, due to the quality error of circuit components (such as switching elements and reactors) constituting the conversion circuits 21 and 22, the amount of current I1 output from the conversion circuit 21 and the amount of current I2 output from the conversion circuit 22 There may be a deviation between the two (see FIG. 7A).

  A broken line a6 in FIG. 7A indicates the current I1, and a broken line a7 in FIG. 7A indicates the current I2. Further, a solid line a8 in FIG. 7A represents an average value of the current I1, and a solid line a9 in FIG. 7A represents an average value of the current I2.

  At this time, a carrier wave W1 indicated by a solid line a10 in FIG. 8A is output to the comparator 52, and a carrier wave W2 indicated by a broken line a11 in FIG. As a result, the control signal Sig1 in FIG. 8A is output from the comparator 52 to the conversion circuit 21, and the control signal Sig2 in FIG. 8A is output from the comparator 53 to the conversion circuit 22.

  As described above, when there is a difference between the current amount of the current I1 output from the conversion circuit 21 and the current amount of the current I2 output from the conversion circuit 22, the synthesis input to the second power conversion unit 3 The amplitude of current ripple increases. As a result, the load on the capacitors C1 and C2 increases, and the lifetime of the capacitors C1 and C2 may be shortened.

  Therefore, in the present embodiment, the carrier waves W1 and W1 output from the carrier wave generation unit 51 are set so that the current amount of the current I1 output from the conversion circuit 21 and the current amount of the current I2 output from the conversion circuit 22 are equal. W2 is controlled.

  In the present embodiment, as shown in FIG. 4, the control unit 5 calculates the difference ΔI between the current amount of the current I1 output from the conversion circuit 21 and the current amount of the current I2 output from the conversion circuit 22, An offset amount of the carrier wave W2 is obtained based on the difference ΔI.

  Specifically, as illustrated in FIG. 8B, the control unit 5 maintains the carrier wave W1 output to the comparator 52 (solid line a10 in FIG. 8B) as it is, and the carrier wave W2 output to the comparator 53 (FIG. 8B). The middle broken line a11) is offset by d1. As a result, the control signal Sig1 output to the conversion circuit 21 remains unchanged, and the control signal Sig2 output to the conversion circuit 22 has a large duty ratio.

  Thereby, as shown in FIG. 7B, the current amount of the current I1 output from the conversion circuit 21 is equal to the current amount of the current I2 output from the conversion circuit 22, and the amplitude of the ripple of the combined current is reduced. Can do. As a result, the burden on the capacitors C1 and C2 is reduced, so that the lifetime of the capacitors C1 and C2 can be extended. Further, as described above, by performing equal control of the currents I1 and I2 output from the conversion circuits 21 and 22, the output voltage of the first power conversion unit 2 is smoothed, and harmonic distortion of the output current is reduced. be able to.

  Here, when the current amount of the current I1 flowing through the conversion circuit 21 and the current amount of the current I2 flowing through the conversion circuit 22 are not equal, as described above, the conversion circuit 21 having the largest flowing current is used as the reference circuit, and the conversion circuit It is preferable to make the amount of current I2 flowing through the current 22 close to the current I1. In this case, the control unit 5 controls the conversion circuits 21 and 22 so that the amount of the current I2 flowing through the conversion circuit 22 falls within a specified range with the current I1 flowing through the conversion circuit 21 as an upper limit. preferable.

  When the conversion circuit 21 serving as the reference circuit fails, the control unit 5 changes the phase difference of the control signals output to the remaining conversion circuits according to the number of conversion circuits that are operated simultaneously. Is preferred. For example, in the case where the first power conversion unit 2 includes three conversion circuits 21, 22, and 23, it is assumed that the conversion circuit 21 has failed. In this case, interleave control is performed by the remaining conversion circuits 22 and 23.

  When the interleave control is performed by the three conversion circuits 21, 22, and 23, the phase of the carrier wave output from the carrier wave generation unit 51 is shifted by 120 ° as shown in FIG. 5B. When the conversion circuit 21 fails from this state, the remaining two conversion circuits 22 and 23 perform interleave control. At this time, the carrier wave output from the carrier wave generation unit 51 is a carrier wave whose phase is shifted by 180 ° as shown in FIG. 5A.

  That is, in this embodiment, when the conversion circuit 21 serving as the reference circuit fails, the phase difference of the carrier wave is changed from 120 ° to 180 ° according to the number of conversion circuits 22 and 23 that perform interleave control thereafter. As a result, an increase in the ripple of the input current to the second power conversion unit 3 can be suppressed, so that the capacitors C1 and C2 having small capacities can be used, and the conversion circuits 21, 22, and 23 can be downsized. Can be planned.

  At this time, it is preferable that the conversion circuit having the larger current flowing in the remaining conversion circuits 22 and 23 is used as a new reference circuit, so that power conversion from DC to AC can be continuously performed. .

  Furthermore, the control unit 5 determines the upper limit value (current upper limit value) of the combined current output from the first power conversion unit 2 and the first power conversion unit so that the combined current is less than or equal to the set upper limit value. 2 is preferably controlled. If the upper limit value of the combined current is not set, the operating voltage of the DC power supply 1 is greatly lowered, and the operation may become unstable. On the other hand, when the upper limit value of the combined current is set, there is an advantage that the operation voltage of the DC power supply 1 is not greatly lowered and the operation is not easily unstable.

  FIG. 9 is a schematic block diagram illustrating another example of the power conversion apparatus 10 according to the present embodiment.

  The power conversion device 10 includes a first power conversion unit 201 (2), a second power conversion unit 3, a control unit 5, and at least one third power conversion unit 202, ..., 20k (k = 2, 3, …). The DC power source 1 includes a plurality of power supply units 101,..., 10m (m = 2, 3,...).

  In the present embodiment, the plurality of power supply units 101,..., 10m are electrically connected to the first power conversion unit 201 and at least one third power conversion unit 202,. ing. Therefore, there is an advantage that the operation is less likely to become unstable even when the DC voltage output from each of the power supply units 101,.

  Moreover, it is preferable that the numbers of the first power conversion unit 2 and the third power conversion units 202,..., 20k are registered in advance in the storage unit 54 of the control unit 5. Then, the control unit 5 compares the number of the first power conversion unit 2 and the third power conversion unit 202,..., 20k registered in the storage unit 54 with the number of power conversion units that are currently in operation. It is possible to know the number of power conversion units that have been used.

  In this embodiment, one capacitor C1 is connected between the input terminals of the conversion circuits 21 and 22. However, for example, a capacitor may be connected between the input terminals of the conversion circuit 21 and between the input terminals of the conversion circuit 22, respectively. Good. In this case, since the current flowing through each capacitor can be reduced, a capacitor having a small capacity can be used, and the cost can be reduced.

  Further, in the present embodiment, the case where there are two conversion circuits configuring the first power conversion unit 2 has been described as an example, but the number of conversion circuits may be at least two and may be three or more. . Furthermore, although this embodiment demonstrated the power converter device 10 which has only the DC-AC conversion function which converts a DC voltage into an AC voltage, the power converter device which has the AC-DC conversion function which converts an AC voltage into a DC voltage. It may be 10. That is, the power converter device 10 having a bidirectional conversion function may be used.

  Further, in the present embodiment, the conversion circuits 21,..., 2n are composed of the step-up / step-down chopper circuit, but may be composed of a step-up chopper circuit or a step-down chopper circuit by the connected DC power source 1. Good.

  As described above, the power conversion device 10 of the present embodiment can convert at least a DC voltage into an AC voltage, and includes the first power conversion unit 2, the second power conversion unit 3, and the first power conversion unit 2. And a control unit 5 that controls the second power conversion unit 3. The first power conversion unit 2 includes at least two conversion circuits 21,..., 2n (n = 1, 2,...) Connected in parallel with each other between the DC power source 1 and the second power conversion unit 3. The DC voltage of the DC power source 1 is converted into a DC voltage having a desired voltage value and output to the second power conversion unit 3. The second power conversion unit 3 converts the DC voltage output from the first power conversion unit 2 into an AC voltage and outputs the AC voltage. The first power conversion unit 2 outputs a current obtained by combining the output currents of at least two conversion circuits 21, ..., 2n to the second power conversion unit 3 as a combined current. The control unit 5 controls the first power conversion unit 2 so that the amplitude of the ripple of the combined current falls below a specified value.

  According to the said structure, the ripple of the input current to the 2nd power converter 3 can be reduced compared with the conventional power converter device. That is, it is possible to provide the power conversion device 10 in which the ripple of the input current to the circuit that converts direct current to alternating current is reduced. In addition, since at least two conversion circuits 21,..., 2n are connected in parallel to each other, the amount of current flowing through each conversion circuit 21,.

  Further, like the power conversion device 10 of the present embodiment, the control unit 5 increases the number of conversion circuits to be operated among the at least two conversion circuits 21,. Is preferred.

  According to the above configuration, the number of conversion circuits to be operated is increased as the combined current increases, thereby reducing the ripple of the input current to the second power conversion unit 3 and reducing the number of conversion circuits. A decrease in conversion efficiency can be suppressed compared to a case where the increase is not made.

  Further, like the power conversion device 10 of the present embodiment, the control unit 5 controls at least two conversion circuits by controlling the switching elements Q1, Q2,... Of each of the at least two conversion circuits 21,. It is preferable to adjust the output voltage of each of 21,. In this case, the control unit 5 compares the reference value K1 with each of at least two carrier waves W1 and W2 whose phase angles are shifted according to the number of conversion circuits to be operated among at least two conversion circuits 21,. It is preferable to do this. Then, the control unit 5 outputs at least two control signals Sig1, Sig2 based on the comparison result between each of the at least two carrier waves W1, W2 and the reference value K1 to at least two conversion circuits 21,. Is preferred.

  According to the above configuration, the ripple of the input current to the second power conversion unit 3 can be reduced by shifting the phase angle of the carrier waves W1, W2 to the at least two conversion circuits 21,. Accordingly, a circuit component having a small capacity can be used as a circuit component constituting each of the conversion circuits 21,..., 2n, and the conversion circuits 21,.

  Further, like the power conversion device 10 of the present embodiment, each of the at least two conversion circuits 21,..., 2n measures current amounts per unit time flowing through the current measurement units 211 and 221 (measurement units). It is preferable to have. In this case, the control unit 5 uses the first power so that the amount of current flowing through the operating conversion circuit among the at least two conversion circuits 21, ..., 2n is equal based on the measurement results of the current measurement units 211 and 221. It is preferable to control the converter 2.

  According to the above-described configuration, the output voltage of the first power conversion unit 2 can be smoothed by equalizing the currents flowing through the operating conversion circuit, and harmonic distortion of the output current can be reduced.

  Further, like the power conversion device 10 of the present embodiment, the control unit 5 controls at least two conversion circuits by controlling the switching elements Q1, Q2,... Of each of the at least two conversion circuits 21,. It is preferable to adjust the output voltage of each of 21,. In this case, the control unit 5 determines whether or not the amount of current flowing in the operating conversion circuit among the at least two conversion circuits 21,..., 2n is equal based on the measurement results of the current measurement units 211 and 221. Is preferred. When the control unit 5 determines that the current amounts are not equal, it is preferable to adjust the duty ratio of the control signal output to the operating conversion circuit among the at least two conversion circuits 21,..., 2n.

  According to the above configuration, the amount of current flowing through the operating conversion circuit can be made equal, and as a result, the output voltage of the first power conversion unit 2 can be smoothed and the harmonic distortion of the output current can be reduced. it can.

  Moreover, like the power converter device 10 of this embodiment, the control part 5 flows into the conversion circuit in operation among at least two conversion circuits 21, ..., 2n based on the measurement result of the current measurement parts 211,221. It is preferable to determine whether the current amounts are equal. In this case, when the control unit 5 determines that the current amounts are not equal, it is preferable that the conversion circuit having the largest flowing current amount among the at least two conversion circuits 21,. Then, the control unit 5 has a current amount flowing through the conversion circuit in operation excluding the reference circuit among the at least two conversion circuits 21,..., 2n within a specified range with an upper limit of the current amount flowing through the reference circuit. It is preferable to control the first power conversion unit 2 so as to be accommodated.

  According to the above configuration, the amount of current flowing through the converter circuit in operation excluding the reference circuit among the at least two conversion circuits 21,..., 2n is within a specified range with the amount of current flowing through the reference circuit as an upper limit. By storing, the output voltage of the first power converter 2 is smoothed. Thereby, the harmonic distortion of the output current can be reduced.

  Further, like the power conversion device 10 of the present embodiment, the control unit 5 controls at least two conversion circuits by controlling the switching elements Q1, Q2,... Of each of the at least two conversion circuits 21,. It is preferable to adjust the output voltage of each of 21,. In this case, when the reference circuit fails, the control unit 5 preferably changes the phase difference of the control signal output to the conversion circuit excluding the reference circuit among the at least two conversion circuits 21,..., 2n. . At this time, it is preferable that the control unit 5 changes the phase difference of the control signal in accordance with the number of conversion circuits to be operated among at least two conversion circuits 21,.

  According to the above configuration, the phase difference of the control signal output to the conversion circuit excluding the reference circuit among the at least two conversion circuits 21,..., 2n is changed according to the number of conversion circuits to be operated. 2 It is possible to suppress the ripple of the input current to the power conversion unit 3 from increasing. As a result, a circuit component having a small capacity can be used as a circuit component constituting each of the conversion circuits 21,..., 2n, and the conversion circuits 21,.

  Further, like the power conversion device 10 of the present embodiment, when the reference circuit fails, the control unit 5 has the largest amount of flowing current among at least two conversion circuits 21, ..., 2n excluding the reference circuit. The conversion circuit is preferably a new reference circuit.

  According to the above configuration, even if the reference circuit fails, the conversion circuit having the largest flowing current among the at least two conversion circuits 21,. Power conversion to can be continued.

  Moreover, like the power converter device 10 of this embodiment, it is preferable that the control part 5 determines an electric current upper limit value according to the number of the conversion circuits in operation among at least two conversion circuits 21, ..., 2n. . In this case, it is preferable that the control unit 5 controls the first power conversion unit 2 so that the combined current falls below the current upper limit value.

  When the current upper limit value is not set, the operating voltage of the DC power supply 1 is greatly reduced, and the operation may become unstable. On the other hand, when the current upper limit value is set, the operating voltage of the DC power supply 1 is not greatly reduced, and the operation is not likely to be unstable.

  In addition, the above-described power conversion device 10 includes at least one third power conversion unit 202,..., 20k (k = 2, 3,...) (2) having the same configuration as that of the first power conversion unit 201 (2). It is preferable to further provide. In this case, the DC power supply 1 preferably includes a plurality of power supply units 101,..., 10m (m = 2, 3,...). And it is preferable that a plurality of power supply units 101,..., 10m are electrically connected to the first power conversion unit 201 and at least one third power conversion unit 202,. .

  According to the above configuration, the first power conversion unit 201 and the third power conversion unit 202,..., 20k are provided for each power supply unit 101,. Even when the voltage is different, the operation is not likely to be unstable.

  Moreover, the power converter 10 of this embodiment is further provided with the memory | storage part 54 by which the number of the 1st power converter 201 and the at least 1 3rd power converter 202, ..., 20k is registered previously. Is preferred.

  According to the above configuration, the control unit 5 compares the number of the first power conversion unit 2 and the third power conversion unit 202,..., 20k registered in the storage unit 54 with the number of power conversion units currently in operation. Thus, the number of failed power conversion units can be known.

DESCRIPTION OF SYMBOLS 1 DC power supply 2,201 1st power conversion part 3 2nd power conversion part 5 Control part 10 Power conversion device 21, ..., 2n Conversion circuit 54 Memory | storage part 101, ..., 10m Power supply unit 202, ..., 2k 3rd power conversion Units 211 and 221 Current measurement unit (measurement unit)
Q1, Q2, ... Switching element

Claims (11)

A power conversion device capable of converting at least a DC voltage into an AC voltage,
A first power converter, a second power converter, and a controller that controls the first power converter and the second power converter;
The first power conversion unit includes at least two conversion circuits connected in parallel with each other between a DC power supply and the second power conversion unit, and converts the DC voltage output from the DC power supply to a desired voltage value. Is boosted to a direct current voltage and output to the second power converter,
The second power conversion unit converts the DC voltage output from the first power conversion unit into an AC voltage and outputs the AC voltage,
The first power conversion unit outputs a combined current of the output currents of the at least two conversion circuits to the second power conversion unit as a combined current,
The control unit outputs a ripple current output by the first power conversion unit when the life is prioritized over the conversion efficiency compared to when the conversion efficiency of the power conversion device is prioritized over the life of the power conversion device. The power converter is configured to control the first power converter so as to reduce the power consumption.   2. The power conversion device according to claim 1, wherein the control unit increases the number of conversion circuits to be operated among the at least two conversion circuits as the combined current increases. The control unit adjusts the output voltage of each of the at least two conversion circuits by controlling each switching element of the at least two conversion circuits,
The control unit outputs at least two control signals based on a comparison result between each of at least two carrier waves shifted in phase angle according to the number of conversion circuits to be operated among the at least two conversion circuits and a reference value. The power converter according to claim 1, wherein the power converter is configured to output to at least two converter circuits. Each of the at least two conversion circuits has a measurement unit that measures the amount of current per unit time flowing through the conversion circuit,
The control unit controls the first power conversion unit based on a measurement result of the measurement unit so that the amount of current flowing through an operating conversion circuit among the at least two conversion circuits becomes equal. The power converter device according to any one of claims 1 to 3. The control unit adjusts the output voltage of each of the at least two conversion circuits by controlling each switching element of the at least two conversion circuits,
When the control unit determines that the amount of current flowing in the operating conversion circuit among the at least two conversion circuits is not equal based on the measurement result of the measurement unit, the conversion in operation of the at least two conversion circuits The power conversion apparatus according to claim 4, wherein the duty ratio of the control signal output to the circuit is adjusted. When the control unit determines that the amount of current flowing in the operating conversion circuit among the at least two conversion circuits is not equal based on the measurement result of the measurement unit, the amount of current flowing in the at least two conversion circuits is The largest conversion circuit is the reference circuit,
The control unit is configured so that an amount of current flowing through an operating conversion circuit excluding the reference circuit out of the at least two conversion circuits falls within a predetermined range with an upper limit of the amount of current flowing through the reference circuit. The power converter according to claim 4 or 5, wherein one power converter is controlled. The control unit adjusts the output voltage of each of the at least two conversion circuits by controlling each switching element of the at least two conversion circuits,
The control unit converts a phase difference of a control signal output to a conversion circuit other than the reference circuit among the at least two conversion circuits when the reference circuit fails, and operates the phase difference of the at least two conversion circuits. The power conversion device according to claim 6, wherein the power conversion device is changed according to the number of circuits.   7. The control unit according to claim 6, wherein when the reference circuit fails, the conversion circuit having the largest amount of flowing current among the at least two conversion circuits excluding the reference circuit is set as a new reference circuit. Power converter.   The control unit determines a current upper limit value according to the number of operating conversion circuits among the at least two conversion circuits, and sets the first power conversion unit so that the combined current falls below the current upper limit value. It controls, The power converter device of any one of Claims 1-8 characterized by the above-mentioned. And further comprising at least one third power conversion unit having the same configuration as the first power conversion unit,
The DC power supply has a plurality of power supply units,
The plurality of power supply units are electrically connected to the first power conversion unit and the at least one third power conversion unit in a one-to-one correspondence. The power converter device of Claim 1.   The power converter according to claim 10, further comprising a storage unit in which the numbers of the first power conversion unit and the at least one third power conversion unit are registered in advance.

Images