Power conversion device

Abstract

To perform smooth adjustment of a voltage.SOLUTION: A power conversion device includes a multi-phase transformer that converts three-phase power to low-voltage AC power, a rectification unit that converts the low-voltage AC power obtained by the conversion at the multi-phase transformer, to DC power, a voltage adjustment unit that adjusts the three-phase power to be inputted to the multi-phase transfer, a voltage adjustment driving unit that drives the voltage adjustment unit to adjust the three-phase power, and a control unit. The control unit includes an output voltage detection unit that detects an output voltage of the low-voltage AC power obtained by the conversion at the multi-phase transformer or an output voltage of the DC power obtained by the conversion at the rectification unit, and a feedback control unit that calculates a control amount for controlling the driving of the voltage adjustment driving unit on the basis of the difference between the output voltage detected by the output voltage detection unit and a target voltage.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power conversion device. [Background technology]

[0002] Conventionally, there is known a voltage regulator that automatically regulates the line voltage of a distribution line that transmits a three-phase AC voltage within a target voltage range (see, for example, Patent Document 1). The voltage regulator described in Patent Document 1 outputs a plurality of regulation voltages corresponding to a plurality of taps by switching the taps. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-057135 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the voltage adjustment device described in Patent Document 1, the voltage is adjusted stepwise by switching taps, and therefore smooth voltage adjustment cannot be performed.

[0005] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to achieve smooth voltage adjustment. [Means for solving the problem]

[0006] One aspect of the present invention is a power conversion device comprising: a multi-phase transformer that converts three-phase power into low-voltage AC power; a rectification unit that converts the low-voltage AC power converted by the multi-phase transformer into DC power; a voltage adjustment unit that adjusts the three-phase power input to the multi-phase transformer; a voltage adjustment drive unit that drives the voltage adjustment unit to adjust the three-phase power; and a control unit, wherein the control unit comprises an output voltage detection unit that detects the output voltage of the low-voltage AC power converted by the multi-phase transformer or the output voltage of the DC power converted by the rectification unit; and a feedback control unit that calculates a control amount for controlling the drive of the voltage adjustment drive unit based on a difference between the output voltage detected by the output voltage detection unit and a target voltage. One aspect of the present invention is a power conversion device in which, in the above-mentioned power conversion device, the voltage adjustment unit is composed of a three-phase transformer whose primary winding is connected in series to the input side of the three-phase power, the voltage adjustment drive unit is composed of a three-phase inverter whose secondary winding is connected to the output of the three-phase transformer, and the control unit further includes a phase detection unit that detects the phase at the input side of the three-phase power, and the control unit drives the three-phase inverter with the control amount based on the phase detected by the phase detection unit. One aspect of the present invention is a power conversion device, wherein the control unit drives the three-phase inverter using the control variable in accordance with a phase shifted by 30 degrees from the line phase detected by the phase detection unit. One aspect of the present invention is the power conversion device, wherein a power supply power of the three-phase inverter is obtained from the three-phase power. One aspect of the present invention is the power conversion device, wherein the power supply power of the control unit is obtained from the three-phase power. One aspect of the present invention is a power conversion device in which, in the above-mentioned power conversion device, the output voltage detection unit detects the output voltage of the low-voltage AC power converted by the multi-phase transformer and the output voltage of the DC power converted by the rectification unit, and the control unit does not adjust the three-phase power by the voltage adjustment unit when the output voltage of the low-voltage AC power deviates from a predetermined voltage range. Here, low-voltage AC power refers to low-voltage (600V or less) AC power as defined in the "Ministry Ordinance Prescribing Technical Standards for Electrical Equipment" established by the Ministry of Economy, Trade and Industry. Effect of the Invention

[0007] According to the present invention, an effect is obtained in that voltage can be smoothly adjusted. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram showing a configuration example of a power conversion device according to an embodiment; [Diagram 2] FIG. 2 is a diagram illustrating an example of a specific circuit configuration of a power conversion device according to an embodiment. [Diagram 3] 4 is a flowchart illustrating an example of an operation of a power conversion device according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a block diagram showing a configuration example of a power conversion device according to an embodiment. The power conversion device 1 shown in Fig. 1 includes a power conversion unit 20, a low-voltage AC output unit 30, a voltage adjustment unit 40, a voltage adjustment drive unit 50, and a control unit 60.

[0010] The power conversion unit 20 includes a multi-phase transformer 21 and a rectification unit 22. The multi-phase transformer 21 converts three-phase power supplied from the three-phase power source 10 via the voltage adjustment unit 40 into low-voltage AC power of a specific voltage. The rectification unit 22 converts the low-voltage AC power converted by the multi-phase transformer 21 into DC power of a specific voltage. The DC power converted by the rectification unit 22 becomes DC output A.

[0011] The low-voltage AC output unit 30 extracts and outputs three-phase power and single-phase power from the low-voltage AC output B of the multi-phase transformer 21. The low-voltage AC output unit 30 includes a three-phase three-wire AC output unit 31, a three-phase four-wire AC output unit 32, and a single-phase three-wire AC output unit 33. The three-phase three-wire AC output unit 31 outputs three-phase three-wire AC power from the low-voltage AC output B (three-phase three-wire AC output B1). The three-phase four-wire AC output unit 32 outputs three-phase four-wire AC power from the low-voltage AC output B (three-phase four-wire AC output B2). The single-phase three-wire AC output unit 33 outputs single-phase three-wire AC power from the low-voltage AC output B (single-phase three-wire AC output B3).

[0012] The voltage adjustment unit 40 adjusts the three-phase power input to the multi-phase transformer 21. The voltage adjustment unit 40 adjusts the three-phase power "three-phase three-wire 200V AC" supplied from the three-phase power source 10. The three-phase power adjusted by the voltage adjustment unit 40 is input to the multi-phase transformer 21.

[0013] The voltage adjustment drive unit 50 drives the voltage adjustment unit 40 to adjust the three-phase power (power adjustment drive).

[0014] The control unit 60 controls the power adjustment drive of the voltage adjustment drive unit 50, thereby controlling the adjustment of the three-phase power by the voltage adjustment unit 40.

[0015] The DC output A, the three-phase three-wire AC output B1, the three-phase four-wire AC output B2, and the single-phase three-wire AC output B3 are connected to the control unit 60 as feedback signals. The control unit 60 calculates a control amount (power adjustment drive control amount) for controlling the power adjustment drive of the voltage adjustment drive unit 50 based on a difference between the output voltage of the DC output A, the three-phase three-wire AC output B1, the three-phase four-wire AC output B2, or the single-phase three-wire AC output B3 and a target voltage.

[0016] Fig. 2 is a diagram showing an example of a specific circuit configuration of the power conversion device according to the present embodiment. In the example of Fig. 2, the DC output A is used as a feedback signal to the control unit 60. Note that in Fig. 2, the low voltage AC output unit 30 is omitted, and the low voltage AC output unit 30 may or may not be present.

[0017] The voltage adjustment unit 40 is configured using a three-phase transformer 41. The voltage adjustment drive unit 50 is configured using a three-phase inverter 51. A primary winding of the three-phase transformer 41 is connected in series to the input side of the three-phase power between the three-phase power source 10 and the multi-phase transformer 21. A secondary winding of the three-phase transformer 41 is connected to the output of the three-phase inverter 51.

[0018] The control unit 60 includes an output voltage detection unit 61 , a phase detection unit 62 , a feedback control unit 63 , and a gate drive unit 64 .

[0019] The control unit 60 may be realized by dedicated hardware, or may be composed of an arithmetic processing unit such as a CPU and a memory, and the arithmetic processing unit may execute a program to realize the functions of the control unit 60, thereby realizing its functions.

[0020] The output voltage detector 61 detects the output voltage of the DC output A. The phase detector 62 detects the phase of the three-phase power input from the three-phase power source 10.

[0021] The feedback control unit 63 calculates a power adjustment drive control amount based on the difference between the output voltage detected by the output voltage detection unit 61 and the target voltage. The target voltage is set in advance in the control unit 60. The feedback control unit 63 drives the three-phase inverter 51 with the power adjustment drive control amount based on the phase detected by the phase detection unit 62. Specifically, the feedback control unit 63 drives the three-phase inverter 51 with the power adjustment drive control amount in accordance with a phase shifted by 30 degrees from the line phase detected by the phase detection unit 62. Specifically, the feedback control unit 63 controls the gate drive unit 64 to send gate signals "A,A" corresponding to the power adjustment drive control amount to the three-phase inverter 51. - ", "B,B - ", "C,C - " is output. As a result, the power adjustment drive in the three-phase inverter 51 is controlled by the power adjustment drive control amount.

[0022] In voltage adjustment unit 40, when a voltage in phase with the input phase voltage is generated in the primary winding, the voltage applied to multi-phase transformer 21 becomes higher than the three-phase three-wire input voltage of three-phase power. On the other hand, when a voltage in phase opposite to the input phase voltage is generated in the primary winding, the voltage applied to multi-phase transformer 21 becomes lower than the three-phase three-wire input voltage of three-phase power. For this reason, feedback control unit 63 calculates a power adjustment drive control amount by calculating PID control (P (proportional control), I (integral control), D (differential control)) so that there is no difference between the output voltage of DC output A (voltage detected by output voltage detection unit 61) and the target voltage.

[0023] The capacity of the three-phase transformer 41 of the voltage adjustment unit 40 and the three-phase inverter 51 of the voltage adjustment drive unit 50 is "(voltage generated in the primary winding of the three-phase transformer 41)×phase current×√3." This allows the voltage adjustment unit 40 and the voltage adjustment drive unit 50 to be configured with a smaller capacity compared to the capacity of the power conversion unit 20 (multi-phase transformer 21, rectification unit 22) because the voltage is smaller.

[0024] A specific example will be given for explanation. When the power conversion unit 20 is composed of a 35 kW multi-phase transformer 21 and a rectification unit 22, "200 V × 100 A × √3 ≈ 35 kW." In this case, when the voltage adjustment unit 40 adjusts to a maximum of ±10 V, "10 V × 100 A × √3 ≈ 1.7 kW" is obtained, so that a low-capacity three-phase transformer 41 and a three-phase inverter 51 can be used.

[0025] In this specific example, the input from the three-phase power supply 10 is "three-phase, three-wire 200V AC," but if high-voltage components are used for the multi-phase transformer 21, the voltage adjustment unit 40, and other components connected to the primary side line, it can also be applied to higher voltages (e.g., 6600V AC).

[0026] The transformer of the voltage adjusting unit 40 may be an autotransformer.

[0027] 2, DC output A is used as a feedback signal to control unit 60, but any of DC output A, three-phase three-wire AC output B1, three-phase four-wire AC output B2, and single-phase three-wire AC output B3 may be used as a feedback signal to control unit 60. Since the output voltages of DC output A, three-phase three-wire AC output B1, three-phase four-wire AC output B2, and single-phase three-wire AC output B3 are determined by the winding ratio of the polyphase transformer with respect to the input voltage in polyphase transformer 21, feedback control can be performed based on the output voltage of any one of DC output A, three-phase three-wire AC output B1, three-phase four-wire AC output B2, and single-phase three-wire AC output B3.

[0028] 2, the power supply for the three-phase inverter 51 and the control unit 60 is obtained from three-phase power input from a three-phase power supply 10. Note that a separate power supply such as a battery may be provided as the power supply for the three-phase inverter 51 and the control unit 60. Also, the power supply for the three-phase inverter 51 and the control unit 60 may be configured to be obtained from the DC output A.

[0029] An example of the operation of the power conversion device 1 according to this embodiment will be described with reference to Fig. 3. Fig. 3 is a flowchart showing an example of the operation of the power conversion device according to this embodiment.

[0030] For example, when a DC-connected device such as a solar power generation system or a storage battery is connected to the DC output A, the DC voltage detected by the control unit 60 (output voltage detection unit 61) rises due to the output of the DC-connected device. If feedback control is performed to lower the voltage of the DC output A in response to the adjustment of the three-phase power in the voltage adjustment unit 40 due to this increased DC voltage, the AC voltage of the AC output (three-phase three-wire AC output B1, three-phase four-wire AC output B2, single-phase three-wire AC output B3, etc.) from the multi-phase transformer 21 may drop too much.

[0031] To address this problem, in the operation example of FIG. 3, when the control unit 60 performs feedback control using the DC output A, the control unit 60 monitors the AC output and controls the AC output so that the AC output does not deviate from a predetermined AC voltage range. The AC output to be monitored may be any one, any two or all of the three-phase three-wire AC output B1, the three-phase four-wire AC output B2 and the single-phase three-wire AC output B3. This is because the voltages of the DC output A, the three-phase three-wire AC output B1, the three-phase four-wire AC output B2 and the single-phase three-wire AC output B3 are determined by the winding ratio of the polyphase transformer of the polyphase transformer 21 with respect to the input voltage to the polyphase transformer 21. In the operation example of FIG. 3, only the single-phase three-wire AC output B3 is an example of the object to be monitored.

[0032] (Step S1) The control unit 60 (output voltage detection unit 61) measures the voltage of the single-phase three-wire AC output B3.

[0033] (Step S2) The control unit 60 (feedback control unit 63) determines whether the measurement result of the voltage of single-phase three-wire AC output B3 exceeds the upper limit threshold. The upper limit threshold is set in advance in the control unit 60. If the measurement result of the voltage of single-phase three-wire AC output B3 exceeds the upper limit threshold, the process returns to step S1. In this case, feedback control by DC output A is not executed. On the other hand, if the measurement result of the voltage of single-phase three-wire AC output B3 is equal to or lower than the upper limit threshold, the process proceeds to step S3.

[0034] (Step S3) The control unit 60 (feedback control unit 63) determines whether the measurement result of the voltage of single-phase three-wire AC output B3 is less than the lower threshold. The lower threshold is set in advance in the control unit 60. If the measurement result of the voltage of single-phase three-wire AC output B3 is less than the lower threshold, the process returns to step S1. In this case, feedback control by DC output A is not executed. On the other hand, if the measurement result of the voltage of single-phase three-wire AC output B3 is equal to or greater than the lower threshold, the process proceeds to step S4.

[0035] In step S4 and after, feedback control using DC output A is executed.

[0036] (Step S4) The control unit 60 (output voltage detection unit 61) measures the voltage of the DC output A.

[0037] (Step S5) The control unit 60 (feedback control unit 63) calculates an AC control value (power adjustment drive control amount) from the difference between the measurement result of the voltage of the DC output A and the target voltage.

[0038] (Step S6) The control unit 60 (phase detection unit 62) detects the phase of the three-phase power input from the three-phase power source 10 (input phase).

[0039] (Step S7) The control unit 60 (feedback control unit 63) performs a correction (30 degree phase correction) on the input phase detected by the phase detection unit 62 to shift it by 30 degrees.

[0040] (Step S8) The control unit 60 (feedback control unit 63) performs phase correction to match the phase of the AC control value with the result of the 30 degree phase correction.

[0041] (Step S9) The control unit 60 (gate driver 64) generates a gate signal “A, A” according to the phase-corrected AC control value. - ", "B,B - ", "C,C - " is output. After that, the process returns to step S1.

[0042] 3, when the measurement result of the voltage of the single-phase three-wire AC output B3 is within a predetermined voltage range (a range below an upper threshold and above a lower threshold), feedback control is performed by the DC output A, but when the measurement result deviates from the voltage range, feedback control is not performed by the DC output A. This makes it possible to prevent the voltages of the AC outputs (three-phase three-wire AC output B1, three-phase four-wire AC output B2, single-phase three-wire AC output B3, etc.) from the multi-phase transformer 21 from deviating from a desired voltage range.

[0043] As described above, according to this embodiment, a voltage adjustment drive unit 50 is provided that drives the voltage adjustment unit 40, which adjusts the three-phase power input to the multi-phase transformer 21, to adjust the three-phase power. Based on the difference between the output voltage of the low-voltage AC power converted by the multi-phase transformer 21 or the output voltage of the DC output A converted by the rectifier unit 22 and a target voltage, a control amount for controlling the drive of the voltage adjustment drive unit 50 is calculated, thereby achieving the effect of smooth voltage adjustment.

[0044] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like that do not deviate from the gist of the present invention are also included.

[0045] In addition, a computer program for implementing the functions of the control unit 60 described above may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed. Note that the "computer system" referred to here may include hardware such as an OS and peripheral devices. In addition, the term "computer-readable recording medium" refers to writable non-volatile memory such as a flexible disk, an optical magnetic disk, a ROM, or a flash memory, a portable medium such as a DVD (Digital Versatile Disc), or a storage device such as a hard disk built into a computer system.

[0046] Furthermore, the term "computer-readable recording medium" includes devices that retain a program for a certain period of time, such as volatile memory (e.g., DRAM (Dynamic Random Access Memory)) within a computer system that serves as a server or client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. The program may be transmitted from a computer system in which the program is stored in a storage device or the like to another computer system via a transmission medium, or by a transmission wave in the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for implementing some of the functions described above, or may be a so-called differential file (differential program) that can implement the functions described above in combination with a program already recorded in the computer system. [Explanation of symbols]

[0047] 1...power conversion device, 20...power conversion section, 30...low-voltage AC output section, 31...three-phase three-wire AC output section, 32...three-phase four-wire AC output section, 33...single-phase three-wire AC output section, 40...voltage adjustment section, 50...voltage adjustment drive section, 60...control section, 61...output voltage detection section, 62...phase detection section, 63...feedback control section, 64...gate drive section

Claims

1. A multi-phase transformer that converts three-phase power into low-voltage AC power; a rectification unit that converts the low-voltage AC power converted by the multi-phase transformer into DC power; a voltage adjusting unit that adjusts the three-phase power input to the multi-phase transformer; a voltage adjustment drive unit that drives the voltage adjustment unit to adjust the three-phase power; A control unit, The control unit is an output voltage detection unit that detects an output voltage of the low-voltage AC power converted by the multi-phase transformer or an output voltage of the DC power converted by the rectification unit; a feedback control unit that calculates a control amount for controlling the driving of the voltage adjustment driving unit based on a difference between the output voltage detected by the output voltage detection unit and a target voltage. Power conversion equipment.

2. the voltage adjustment unit is composed of a three-phase transformer having a primary winding connected in series to an input side of the three-phase power, the voltage adjustment drive unit is composed of a three-phase inverter having a secondary winding of the three-phase transformer connected to an output thereof; The control unit further includes a phase detection unit that detects a phase on the input side of the three-phase power, The control unit drives the three-phase inverter with the controlled variable based on the phase detected by the phase detection unit. The power conversion device according to claim 1 .

3. the control unit drives the three-phase inverter using the control amount in accordance with a phase shifted by 30 degrees from the line phase detected by the phase detection unit. The power conversion device according to claim 2 .

4. The power supply of the three-phase inverter is obtained from the three-phase power. The power conversion device according to claim 2 .

5. The power supply power of the control unit is obtained from the three-phase power. The power conversion device according to claim 2 .

6. the output voltage detection unit detects an output voltage of the low-voltage AC power converted by the multi-phase transformer and an output voltage of the DC power converted by the rectification unit; When an output voltage of the low-voltage AC power deviates from a predetermined voltage range, the control unit does not adjust the three-phase power by the voltage adjustment unit. The power conversion device according to claim 1 .

Images