阅读说明：本技术 电力变换装置以及电力变换系统 (Power conversion device and power conversion system ) 是由 嘉藤贵洋 泉喜久夫 田渕朗子 于 2018-02-19 设计创作，主要内容包括：电力变换系统的各电力变换装置(21)的控制部(31)根据流过滤波电抗器(4)的电抗器电流的检测值、向滤波电容器(5)的端子间输出的输出电压的检测值以及流过输出电抗器(6)的输出电流的检测值,控制开关元件部(3)。控制部(31)根据输出电流以及输出电压来生成电压指令,并且根据去除基准频率分量的输出电流来生成电压指令的校正量。控制部(31)根据电压指令和校正量的相加值来生成电流指令,以使电抗器电流与电流指令一致的方式控制开关元件部(3)。(A control unit (31) of each power conversion device (21) of the power conversion system controls a switching element unit (3) on the basis of a detected value of a reactor current flowing through a filter reactor (4), a detected value of an output voltage output between terminals of a filter capacitor (5), and a detected value of an output current flowing through an output reactor (6). A control unit (31) generates a voltage command from the output current and the output voltage, and generates a correction amount of the voltage command from the output current from which the reference frequency component is removed. A control unit (31) generates a current command from the sum of the voltage command and the correction amount, and controls the switching element unit (3) so that the reactor current matches the current command.)

1. A power conversion device is provided with:

an input terminal connected to a DC power supply;

an output terminal connected to a load;

a switching element unit that converts dc power supplied from the dc power supply to the input terminal into ac power and outputs the ac power to the output terminal;

a filter reactor and a filter capacitor for smoothing an output of the switching element unit;

an output reactor disposed between the filter reactor and the load;

a1 st current sensor that detects a reactor current flowing through the filter reactor;

a1 st voltage sensor for detecting an output voltage to be output between terminals of the smoothing capacitor;

a2 nd current sensor that detects an output current flowing through the output reactor; and

a control unit for controlling the switching element unit based on the detection values of the 1 st and 2 nd current sensors and the 1 st voltage sensor,

in the control section, the control section controls the operation of the motor,

generating a voltage command from the output current and the output voltage,

generating a correction amount of the voltage command based on the output current with the reference frequency component attenuated,

generating a current command from an added value of the voltage command and the correction amount,

the switching element unit is controlled so that the reactor current coincides with the current command.

2. The power conversion device according to claim 1,

the control unit has a filter for attenuating the reference frequency component of the output current, and generates the correction amount based on an output of the filter.

3. The power conversion device according to claim 2,

the filter has the following frequency characteristics: the gain of the reference frequency is the lowest, and at least one of a gain of a high frequency higher than the reference frequency and a gain of a low frequency lower than the reference frequency is higher than the gain of the reference frequency.

4. The power conversion device according to any one of claims 1 to 3,

in the control section, the control section controls the operation of the motor,

calculating the effective power output from the output terminal based on the output current, the output voltage, and the internal phase,

generating the internal phase based on the internal frequency corrected according to the effective power,

generating the voltage command according to the internal phase.

5. The power conversion device according to any one of claims 1 to 3,

in the control section, the control section controls the operation of the motor,

calculating reactive power output from the output terminal based on the output current, the output voltage, and the internal phase,

the voltage command is generated based on the amplitude corrected in accordance with the reactive power.

6. The power conversion device according to any one of claims 1 to 3,

in the control section, the control section controls the operation of the motor,

calculating the active power and the reactive power output from the output terminal based on the output current, the output voltage, and the internal phase,

generating the internal phase based on the internal frequency corrected according to the effective power,

the voltage command is generated based on the amplitude corrected in accordance with the reactive power and the internal phase.

7. The power conversion device according to any one of claims 1 to 6,

the power conversion device includes:

a dc bus capacitor for smoothing the dc voltage supplied to the input terminal and supplying the smoothed dc voltage to the switching element unit; and

a2 nd voltage sensor that detects an inter-terminal voltage of the DC bus capacitor,

the control unit limits the current command to an initial limit current value when a detected value of the inter-terminal voltage of the dc bus capacitor is higher than a lower limit voltage, and limits the current command to a current value lower than the initial limit current value when the detected value of the inter-terminal voltage of the dc bus capacitor is lower than the lower limit voltage.

8. A power conversion system including a plurality of power conversion devices connected in parallel to a load,

the plurality of power conversion devices each include:

an input terminal connected to a DC power supply;

an output terminal connected to the load;

a switching element unit that converts dc power supplied from the dc power supply to the input terminal into ac power and outputs the ac power to the output terminal;

a filter reactor and a filter capacitor for smoothing an output of the switching element unit;

an output reactor disposed between the filter reactor and the load;

a1 st current sensor that detects a reactor current flowing through the filter reactor;

a1 st voltage sensor for detecting an output voltage to be output between terminals of the smoothing capacitor;

a2 nd current sensor that detects an output current flowing through the output reactor; and

a control unit for controlling the switching element unit based on the detection values of the 1 st and 2 nd current sensors and the 1 st voltage sensor,

in the control section, the control section controls the operation of the motor,

generating a voltage command from the output current and the output voltage,

generating a correction amount of the voltage command based on the output current with the reference frequency component attenuated,

generating a current command from an added value of the voltage command and the correction amount,

the switching element unit is controlled so that the reactor current coincides with the current command.

9. The power conversion system according to claim 8,

the control unit is configured to have a filter for attenuating the reference frequency component of the output current, the control unit is configured to generate the correction amount based on an output of the filter,

the frequency characteristics of the filters are different from each other among the plurality of power conversion devices.

10. The power conversion system according to claim 8,

the control unit is configured to have a filter for attenuating the reference frequency component of the output current, the control unit is configured to generate the correction amount by multiplying an output of the filter by a gain,

the gains are different from each other among the plurality of power conversion devices.

11. The power conversion system according to any one of claims 8 to 10,

the control unit is configured to: calculating an effective power output from the output terminal based on the output current, the output voltage, and an internal phase, generating the internal phase based on an internal frequency corrected using a multiplication value of the effective power and a droop characteristic gain, and generating the voltage command based on the internal phase,

the droop characteristic gain is set according to a residual capacity of the dc power supply.

12. The power conversion system according to claim 11,

the droop characteristic gains are different from each other among the plurality of power conversion devices.

Technical Field

The present invention relates to a technique for suppressing a circulating current in a power conversion system including a plurality of power conversion devices connected in parallel.

Background

A power conversion system including a plurality of power conversion devices connected in parallel is known. In such a power conversion system, when a plurality of power conversion devices are operated in parallel to supply power to a load, if a deviation occurs in the amplitude or phase of the output voltage of each power conversion device, a circulating current may occur between the power conversion devices.

In order to suppress the occurrence of a circulating current, for example, the following method is disclosed in japanese patent application laid-open No. 2010-288437 (patent document 1): the current detector detects a current (hereinafter also referred to as a "load current") supplied from the power conversion system to the load, and the output current of each power conversion device is controlled by dividing the detected load current by the number of parallel-connected power conversion devices as an average output current command for 1 power conversion device.

Disclosure of Invention

According to patent document 1, a load current is extracted for each order of the fundamental wave component and the harmonic component, and an output current command is generated from a current obtained by dividing the extracted current by the number of parallel-operated power converters, so that imbalance of output currents between power conversion devices is reduced, and as a result, circulating currents of the fundamental wave component and the harmonic component are suppressed.

However, in patent document 1, it is necessary to detect the load current in order to generate the output current command. Therefore, when some of the power conversion devices are stopped due to a failure or the like and the number of parallel-operated devices is changed, a delay in detection of the load current or a delay in generation of the output current command occurs, and thus there is a problem that a deviation between the output current command and the load current becomes large. As a result, it may be impossible to stably supply an appropriate current to the load.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a technique for stably supplying an appropriate current to a load even when the number of parallel-operated power converters is changed in a power conversion system including a plurality of power conversion devices connected in parallel.

Another object of the present invention is to realize the above-described technique without providing a higher-level control device that totally controls a plurality of power conversion devices or a power conversion device that becomes a master of the plurality of power conversion devices.

The power conversion device according to the present disclosure includes: an input terminal connected to a DC power supply; an output terminal connected to a load; a switching element unit that converts dc power supplied from a dc power supply to the input terminal into ac power and outputs the ac power to an output terminal; a filter reactor and a filter capacitor for smoothing an output of the switching element unit; the output reactor is arranged between the filter reactor and the load; a1 st current sensor; a1 st voltage sensor; a2 nd current sensor; and a control section. The 1 st current sensor detects a reactor current flowing through the filter reactor. The 1 st voltage sensor detects an output voltage to be output between terminals of the smoothing capacitor. The 2 nd current sensor detects an output current flowing through the output reactor. The control unit controls the switching element unit based on the detection values of the 1 st and 2 nd current sensors and the 1 st voltage sensor. The control unit generates a voltage command from the output current and the output voltage, and generates a correction amount of the voltage command from the output current from which the reference frequency component is removed. The control unit generates a current command from the sum of the voltage command and the correction amount, and controls the switching element unit so that the reactor current matches the current command.

The power conversion system according to the present disclosure includes a plurality of power conversion devices connected in parallel to a load. Each of the plurality of power conversion devices includes: an input terminal connected to a DC power supply; an output terminal connected to a load; a switching element unit that converts dc power supplied from a dc power supply to an input terminal into ac power and outputs the ac power to an output terminal; a filter reactor and a filter capacitor for smoothing an output of the switching element unit; the output reactor is arranged between the filter reactor and the load; a1 st current sensor; a1 st voltage sensor; a2 nd current sensor; and a control section. The 1 st current sensor detects a reactor current flowing through the filter reactor. The 1 st voltage sensor detects an output voltage to be output between terminals of the smoothing capacitor. The 2 nd current sensor detects an output current flowing through the output reactor. The control unit controls the switching element unit based on the detection values of the 1 st and 2 nd current sensors and the 1 st voltage sensor. The control unit generates a voltage command from the output current and the output voltage, and generates a correction amount of the voltage command from the output current from which the reference frequency component is removed. The control unit generates a current command from the sum of the voltage command and the correction amount, and controls the switching element unit so that the reactor current matches the current command.

According to the present disclosure, in a power conversion system in which a plurality of power conversion devices are operated in parallel to supply power to a load, circulating currents of a fundamental wave component and a harmonic component can be suppressed without detecting a load current. Thus, in the power conversion system, even if the number of parallel-connected devices varies, appropriate current can be stably supplied to the load. Further, according to the present disclosure, such a power conversion system can be realized without providing a higher-level control device that totally controls a plurality of power conversion devices or a power conversion device that becomes a master of the plurality of power conversion devices.

Drawings

Fig. 1 is a diagram schematically showing a configuration example of a power conversion system to which a power conversion device according to an embodiment of the present invention is applied.

Fig. 2 is a diagram schematically showing a configuration example of a power conversion system to which the power conversion device according to the embodiment of the present invention is applied.

Fig. 3 is a diagram schematically showing the configuration of the power conversion device shown in fig. 1 and 2.

Fig. 4 is a functional block diagram for explaining the overall configuration of the control unit shown in fig. 3.

Fig. 5 is a block diagram showing an internal configuration of the electric power arithmetic unit shown in fig. 4.

Fig. 6 is a block diagram showing an internal configuration of the effective power operator shown in fig. 5.

Fig. 7 is a block diagram showing an internal configuration of the reactive power operator shown in fig. 5.

Fig. 8 is a block diagram showing an internal configuration of the sine wave voltage measuring instrument shown in fig. 7.

Fig. 9 is a block diagram showing an internal configuration of the cosine wave voltage measuring instrument shown in fig. 7.

Fig. 10 is a block diagram showing an internal configuration of the sine wave current measuring instrument shown in fig. 7.

Fig. 11 is a block diagram showing an internal configuration of the cosine wave current measuring instrument shown in fig. 7.

Fig. 12 is a block diagram showing an internal configuration of the phase generating section shown in fig. 4.

Fig. 13 is a diagram showing an example of droop characteristics of the frequency command generated by the phase generation unit.

Fig. 14 is a block diagram showing an internal configuration of the voltage command generation unit shown in fig. 4.

Fig. 15 is a diagram showing an example of droop characteristics of the effective voltage command generated by the voltage command generation unit.

Fig. 16 is a block diagram showing an internal configuration of the voltage command correction unit shown in fig. 4.

Fig. 17 is a graph showing the frequency characteristics of the filter shown in fig. 16.

Fig. 18 is a block diagram showing an internal configuration of the voltage control section shown in fig. 4.

Fig. 19 is a block diagram showing an internal configuration of the current control section shown in fig. 4.

Fig. 20 is a timing chart for explaining the operation of the PWM signal generation unit shown in fig. 19.

Fig. 21 is a diagram schematically showing the configuration of a power conversion system according to an embodiment and a comparative example.

Fig. 22 is a diagram schematically showing the configuration of a power conversion device according to a comparative example.

Fig. 23 is a timing chart for explaining the operation of each power conversion device in the power conversion system according to the comparative example and the power conversion system according to the embodiment.

Fig. 24 is a diagram showing the result of FFT analysis of the output current of each power conversion device shown in fig. 23.

Fig. 25 is a diagram schematically showing a relationship between a current flowing through the filter reactor and an inductance of the filter reactor.

Fig. 26 is a diagram schematically showing a configuration of a power conversion device applied to a power conversion system according to embodiment 2 of the present invention.

Fig. 27 is a functional block diagram for explaining the overall configuration of the control unit shown in fig. 26.

Fig. 28 is a block diagram showing an internal configuration of the voltage command generation unit shown in fig. 27.

Fig. 29 is a block diagram showing an internal configuration of the voltage command correction unit shown in fig. 27.

Fig. 30 is a graph showing the frequency characteristics of the filter shown in fig. 29.

Fig. 31 is a block diagram showing an internal configuration of the voltage control section shown in fig. 27.

Fig. 32 is a block diagram showing an internal configuration of the output current adjusting section shown in fig. 27.

Fig. 33 is a block diagram showing an internal configuration of the current command limiting unit shown in fig. 27.

Fig. 34 is a block diagram showing an internal configuration of the current control section shown in fig. 27.

Fig. 35 is a block diagram illustrating an internal configuration of the INV voltage command generation unit illustrated in fig. 27.

Fig. 36 is a block diagram showing an internal configuration of the PWM signal generation section shown in fig. 27.

(symbol description)

1: an input terminal; 2: a DC bus capacitor; 3: a switching element section; 4: a filter reactor; 5: a filter capacitor; 6: an output reactor; 7: an output terminal; 11. 13: a voltage sensor; 12. 14: a current sensor; 21. 21a, 21b, 21c, 210a, 210b, 210c, 500: a power conversion device; 31. 501: a control unit; 32. 511: a power calculation unit; 33: a phase generation unit; 34. 512: a voltage command generation unit; 35. 513: a voltage command correction unit; 36. 514: a voltage control unit; 37. 515: an output current adjusting part; 38: an insufficient voltage suppression unit; 39. 516: a current command limiting unit; 40. 517: a current control unit; 41. 518: an INV voltage command generation unit; 42. 520, the method comprises the following steps: a PWM signal generation unit; 51-54: a semiconductor switching element; 60: a direct current power supply; 61: a load; 101. 225: a sine wave generator; 102: a cosine wave generator; 103: an effective power arithmetic unit; 104: an invalid power calculator; 111. 131: a zero-crossing signal outputter; 112. 132, 214: a signal delayer; 113. 140, 141, 151, 161, 171, 181, 226, 562, 563, 570, 571: a multiplier; 114. 117, 134, 152, 162, 172, 182, 245, 255, 284: an integrator; 115. 118, 153, 163, 173, 183: a sample and hold unit; 116. 133: a fixed signal output; 119. 154, 164, 174, 184, 569: a divider; 136: a sine wave voltage measurer; 137: a cosine wave voltage measurer; 138: a sine wave current measurer; 139: a cosine wave current measurer; 142. 204, 211, 241, 242, 252, 260, 281, 549, 551, 566, 581: a subtractor; 155. 165, 175, 185, 224, 232, 262, 544, 545, 546, 547: a booster; 201. 221: a droop characteristic calculator; 202: a change limiter; 203: a reference frequency command unit; 205: a phase generator; 212. 246, 248, 256, 258, 273, 285, 287, 567: an amplitude limiter; 213. 223, 247, 257, 271, 286, 290, 548, 552, 560, 561, 564, 568, 582, 590, 591: an adder; 222: a reference voltage effective value; 231. 261, 540, 541, 542, 543: a filter; 243. 253, 282: a proportional booster; 244. 254, 283: an integral gain device; 251: a lower limit voltage; 259: initially limiting the current; 291: a carrier signal generator; 292: a comparator; 293: an inverter; 301: a switch; 1000. 2000: a power conversion system; t1: an input terminal; t2: an output terminal; 530. 531, 532: a dq conversion unit; 519: an inverse dq conversion unit; 535: a d-axis reference voltage commander; 536: a q-axis reference voltage commander; 550: a capacitor current correction booster; 565: square root; 580: and a reactor current correction gain device.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference characters, and description thereof will not be repeated.