JP2014222995A - Power conversion apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion apparatus capable of suppressing distortion of a current waveform while an interconnection point voltage is lowering.SOLUTION: The power conversion apparatus includes: a voltage value acquisition section that acquires a voltage value at an interconnection point to a power system for each predetermined cycle; a control gain setting section that sets a control gain according to the voltage value acquired by the voltage value acquisition section; and a PLL control section that synchronizes a current phase with a voltage phase at the interconnection point on the basis of the control gain set by the control gain setting section.

Description

  Embodiments described herein relate generally to a power conversion apparatus.

  In a power conversion device that converts AC power and DC power to each other, the phase of current at a connection point where the power conversion device and the power system are connected by using PLL (Phase Locked Loop) control A technique for synchronizing the voltage phase with the voltage is known.

Japanese Patent Application Laid-Open No. 2005-261055

  When the control gain of the PLL control is large, when the voltage at the connection point (connection point voltage) decreases, the harmonic voltage included in the connection point voltage becomes relatively large. Susceptible to noise.

  Therefore, the current waveform may be distorted, and a current including many harmonic currents flows in the power system. This adversely affects the power system and the devices connected to the power system.

  Therefore, in order to solve these problems, an embodiment of the present invention provides a power conversion device that can suppress distortion of a current waveform when a connection point voltage is lowered.

  In order to achieve the above object, the power conversion device according to the embodiment includes a voltage value acquisition unit that acquires a voltage value at a connection point with the power system every predetermined period, and the voltage acquired by the voltage value acquisition unit. A control gain setting unit that sets a control gain according to a value, and a PLL control unit that synchronizes the current phase and the voltage phase at the interconnection point based on the control gain set by the control gain setting unit And have.

The block diagram which shows the structure of the power converter device and its peripheral device which concern on 1st Embodiment. The block diagram which shows the structure of the power converter device which concerns on 1st Embodiment. An example of the control gain setting by the control gain setting part of the power converter device which concerns on 1st Embodiment. The flowchart which shows operation | movement of the power converter device which concerns on 1st Embodiment. The block diagram which shows the structure of the power converter device which concerns on 2nd Embodiment. An example of the control gain setting by the control gain setting part of the power converter device which concerns on 2nd Embodiment. The flowchart which shows operation | movement of the power converter device which concerns on 2nd Embodiment. The block diagram which shows the structure of the power converter device which concerns on 3rd Embodiment. An example of the control gain setting by the control gain setting part of the power converter device which concerns on 3rd Embodiment. An example of the control gain setting by the control gain setting part of the power converter device which concerns on 3rd Embodiment. The block diagram which shows the structure of the power converter device which concerns on 4th Embodiment. The flowchart which shows operation | movement of the power converter device which concerns on 4th Embodiment. An example of the control gain setting by the control gain setting part of the power converter device which concerns on 4th Embodiment.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing the configuration of the power conversion device and its peripheral devices according to the first embodiment.

  The power conversion device 1 is a device or means that is connected to the power system 2 and converts DC power and AC power to each other.

  The solar power generation device 3 is a device or means for converting sunlight into DC power and outputting it to the booster 4.

  The boosting unit 4 is a device or means for acquiring the DC power output from the solar power generation device 3, boosting the voltage of the acquired DC power, and outputting the boosted voltage to the power conversion device 1.

  The power conversion device 1 is connected to the power system 2, acquires the DC power output by the booster 4, converts it to AC power, and outputs the AC power to the power system 2.

  The capacitor 5 is installed between the power converter 1 and the booster 4.

  Instead of the solar power generation device 3, a secondary battery such as a lithium ion battery, a lead battery, or a sodium sulfur battery, or a fuel cell may be used.

  Moreover, when the output of sufficient voltage is obtained from the solar power generation device 3, the booster 4 is not necessary and is not an essential component.

  FIG. 2 is a block diagram illustrating a configuration of the power conversion device according to the first embodiment.

  As shown in FIG. 2, the power conversion device 1 includes a voltage value acquisition unit 11, a control gain setting unit 12, a PLL control unit 13, a device control unit 14, and a main circuit unit 15.

  The voltage value acquisition unit 11 is a processing unit that acquires a voltage value (connection point voltage value) at a connection point with the power system 2.

  The control gain setting unit 12 is a processing unit that sets the control gain of the PLL control unit 13 in accordance with the interconnection point voltage value acquired by the voltage value acquisition unit 11.

  Specifically, the control gain setting unit 12 associates a storage device such as a hard disk drive (HDD) or a semiconductor memory (not shown), a calculation formula stored in the storage means, a connection point voltage value, and a control gain value. By referring to the obtained table, as shown in FIG. 3, the control gain is reduced according to the decrease in the interconnection voltage.

  FIG. 3 shows an example in which the control gain is linearly reduced in accordance with a decrease in the interconnection point voltage value. For example, the gain can be obtained by using a linear function as a calculation formula.

  The calculation formula stored in the storage device or the storage means is not limited to a linear function, but may be a multidimensional function such as a quadratic function or a cubic function, an exponential function, a logarithmic function, or the like.

  In FIG. 3, when the interconnection point voltage value is zero, the control gain is zero, but it may not be zero.

  The PLL control unit 13 performs PLL control based on the control gain set by the control gain setting unit 12, and synchronizes the current phase and the voltage phase at the connection point between the power conversion device 1 and the power system 2. It is a processing unit.

  The device control unit 14 is a processing unit that acquires the phase information of the voltage at the interconnection point from the PLL control unit 13 and controls the power conversion device 1 to keep the voltage of the capacitor 5 constant based on the acquired phase information. is there.

  The main circuit unit 15 is a processing unit that converts DC power and AC power to each other based on control by the device control unit 14.

  The processes in the voltage value acquisition unit 11, the control gain setting unit 12, the PLL control unit 13, the device control unit 14, and the main circuit unit 15 described above are performed by a processor such as a CPU (Central Processing Unit), for example.

  Next, the operation of each component will be described with reference to FIG. FIG. 4 is a flowchart showing the operation of the power conversion apparatus according to the first embodiment.

  The voltage value acquisition unit 11 acquires a connection point voltage value for each predetermined period (step S101).

  The control gain setting unit 12 sets the control gain of the PLL control unit according to the interconnection point voltage value acquired by the voltage value acquisition unit 11 (step S102).

  The PLL control unit 13 performs PLL control based on the control gain set by the control gain setting unit 12, and synchronizes the current phase and the voltage phase at the connection point between the power conversion device 1 and the power system 2. (Step S103).

  The device control unit 14 acquires voltage phase information at the interconnection point from the PLL control unit 13 and controls the power conversion device 1 based on the acquired phase information (step S104).

  The main circuit unit 15 mutually converts DC power and AC power based on the control by the device control unit 14 (step S105).

  As described above, according to the power conversion device of the first embodiment, the harmonic voltage included in the interconnection point voltage is relatively reduced by reducing the control gain when the interconnection point voltage is reduced. Even when it becomes larger, it is possible to reduce the influence of vibration and noise due to the harmonic voltage applied to the PLL control.

  As a result, distortion of the current waveform can be suppressed, and a current with less harmonic current can be supplied to the power system 2.

  This leads to a reduction in adverse effects on the power system and the devices connected to the power system, and a reduction in loss of the power conversion device 1 due to harmonic current.

  In addition, when a multidimensional function or exponential function is used as a calculation formula referred to by the control gain setting unit 12, the control gain can be rapidly reduced when the interconnection point voltage value is decreased. The influence of high frequency in can be further reduced.

(Second Embodiment)
The configuration of the second embodiment will be described with reference to the drawings. In addition, the same part as 1st Embodiment is shown with the same code | symbol, and description is abbreviate | omitted. Hereinafter, a different part from 1st Embodiment is demonstrated.

  FIG. 5 is a block diagram illustrating a configuration of the power conversion device according to the second embodiment.

  The second embodiment is different from the first embodiment in the first voltage value determination unit 21 and the control gain setting unit 22.

  The first voltage value determination unit 21 is a processing unit that determines whether or not the interconnection point voltage value acquired by the voltage value acquisition unit has fallen below a gain reduction threshold.

  The control gain setting unit 22 is a processing unit that decreases the control gain when the first voltage value determination unit determines that the interconnection point voltage value is below the gain reduction threshold.

  FIG. 6 shows an example of a case where the control gain is linearly decreased when the first voltage value determination unit 21 determines that the interconnection point voltage value is below the gain reduction threshold. It is obtained by using the following function.

  The processing in the first voltage value determination unit 21 and the control gain setting unit 22 described above is performed by a processor such as a CPU (Central Processing Unit), for example.

  Next, the operation of each component will be described with reference to FIG. FIG. 7 is a flowchart showing the operation of the power conversion apparatus according to the second embodiment.

  The first voltage value determination unit 21 determines whether or not the interconnection point voltage value acquired by the voltage value acquisition unit is lower than the first predetermined value (step S201).

  The control gain setting unit 22 reduces the control gain when the first voltage value determination unit determines that the interconnection point voltage value is below the gain reduction threshold (YES in step S201) (step S202).

  The control gain setting unit 22 does not change the value of the control gain when the first voltage value determination unit does not determine that the interconnection point voltage value is lower than the gain reduction threshold (NO in step S201).

  When the control gain is changed in accordance with the fluctuation of the system voltage value, there is a possibility that a beat may occur due to the fluctuation appearing in the current. As described above, the power conversion device according to the second embodiment According to the above, since the value of the control gain is not changed until the interconnection point voltage value falls below the gain reduction threshold, it is possible to suppress the occurrence of beats in addition to the effect obtained in the first embodiment.

  In FIG. 6, there is one gain reduction threshold value, but a plurality of gain reduction threshold values may be provided.

(Third embodiment)
The configuration of the third embodiment will be described with reference to the drawings. In addition, the same part as 1st Embodiment and 2nd Embodiment is shown with the same code | symbol, and description is abbreviate | omitted. Hereinafter, parts different from the first embodiment and the second embodiment will be described.

  FIG. 8 is a block diagram illustrating a configuration of a power conversion device according to the third embodiment.

  The third embodiment is different from the first embodiment and the second embodiment in the control gain setting unit 31.

  The control gain setting unit 31 is a processing unit that decreases the control gain step by step when the first voltage value determination unit determines that the interconnection point voltage value is below the gain reduction threshold.

  FIG. 9 shows the connection point voltage after the control gain setting unit 31 decreases the control gain stepwise when the first voltage value determination unit determines that the connection point voltage value is below the gain reduction threshold. This is an example in which the control gain is linearly reduced in accordance with the decrease in the value.

  FIG. 10 is an example in the case of having a plurality of gain reduction thresholds.

  As described above, according to the power conversion device according to the third embodiment, when the interconnection point voltage value falls below the gain reduction threshold, the control gain is drastically reduced. As compared with the above, distortion of the current waveform can be further suppressed.

(Fourth embodiment)
The configuration of the fourth embodiment will be described with reference to the drawings. The same parts as those in the first to third embodiments are denoted by the same reference numerals, and the description thereof is omitted. Hereinafter, a different part from 1st Embodiment thru | or 3rd Embodiment is demonstrated.

  FIG. 11 is a block diagram illustrating a configuration of a power conversion device according to the fourth embodiment.

  The fourth embodiment differs from the first to third embodiments in the second voltage value determination unit 41 and the control gain setting unit 42.

  The second voltage value determination unit 41 is a processing unit that determines whether the interconnection point voltage value acquired by the voltage value acquisition unit exceeds a gain increase threshold value.

  The control gain setting unit 42 is a processing unit that increases the control gain when the second voltage value determination unit determines that the interconnection point voltage value exceeds the gain increase threshold.

  Next, the operation of each component will be described with reference to FIG. FIG. 12 is a flowchart showing the operation of the power conversion apparatus according to the fourth embodiment.

  The second voltage value determination unit 41 determines whether or not the interconnection point voltage value acquired by the voltage value acquisition unit exceeds the gain increase threshold (step S401).

  The control gain setting unit 42 increases the control gain when the second voltage value determination unit determines that the interconnection point voltage value exceeds the gain increase threshold (YES in step S401) (step S402).

  Note that the gain decrease threshold and the gain increase threshold may be the same value or different values.

  An example of the time-series operation of the control gain setting unit 42 in this embodiment is shown in FIG. FIG. 13 shows an example in which the gain decrease threshold and the gain increase threshold are set to the same value.

  As described above, according to the power conversion device of the fourth embodiment, after the connection point voltage falls below the gain reduction threshold due to an accident or the like of the power system 2, the connection point voltage is restored and the gain is increased. The response speed is increased by temporarily increasing the control gain when the increase threshold is exceeded.

  Therefore, the phase of the current at the interconnection point can be quickly followed by the phase of the voltage, and the phase can be synchronized at an early stage.

  Although several embodiments of the present invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof in the same manner as included in the scope and gist of the invention.

  For example, in the above embodiment, the control gain may be reduced equivalently by calculating the amplitude or effective value from the interconnection point voltage and lowering the cutoff frequency of the filter.

DESCRIPTION OF SYMBOLS 1 ... Power converter 2 ... Electric power system 3 ... Solar power generation device 4 ... Booster part 5 ... Capacitor 11 ... Voltage value acquisition part 12, 22, 31, 42 ... Control gain setting part 13 ... PLL control part 14 ... Apparatus control part 15 ... main circuit unit 21 ... first voltage value determination unit 41 ... second voltage value determination unit

Claims (10)

A voltage value acquisition unit for acquiring a voltage value at a connection point with the electric power system every predetermined period;
A control gain setting unit that sets a control gain according to the voltage value acquired by the voltage value acquisition unit;
A power conversion apparatus comprising: a PLL control unit configured to synchronize a current phase and a voltage phase at the interconnection point based on the control gain set by the control gain setting unit.   The power conversion device according to claim 1, wherein the control gain setting unit reduces the control gain according to the decrease in the voltage value when the voltage value acquired by the voltage value acquisition unit decreases.   The power conversion according to claim 2, wherein when the voltage value acquired by the voltage value acquisition unit decreases, the control gain setting unit linearly decreases the control gain according to a decrease in the voltage value. apparatus. A first voltage value determination unit that determines whether or not the voltage value acquired by the voltage value acquisition unit falls below a gain reduction threshold;
2. The power conversion device according to claim 1, wherein the control gain setting unit decreases the control gain when the first voltage value determination unit determines that the voltage value has fallen below a gain reduction threshold.   The control gain setting unit linearly decreases the control gain in response to a decrease in the voltage value when the first voltage value determination unit determines that the voltage value is below a gain reduction threshold. Item 5. The power conversion device according to Item 4.   5. The power conversion device according to claim 4, wherein the control gain setting unit reduces the control gain stepwise when the first voltage value determination unit determines that the voltage value is below a gain reduction threshold. .   The control gain setting unit responds to a decrease in the voltage value after stepwise decreasing the control gain when the first voltage value determination unit determines that the voltage value is below a gain reduction threshold. The power converter according to claim 6, wherein the control gain is reduced.   The control gain setting unit responds to a decrease in the voltage value after stepwise decreasing the control gain when the first voltage value determination unit determines that the voltage value is below a gain reduction threshold. The power converter according to claim 7, wherein the control gain is linearly reduced. A second voltage value determination unit that determines whether or not the voltage value acquired by the voltage value acquisition unit exceeds a gain increase threshold;
9. The control gain setting unit according to claim 1, wherein the control gain setting unit increases the control gain when the second voltage value determination unit determines that the voltage value exceeds the gain increase threshold. 10. The power converter device described in 1.   The power conversion device according to claim 3, wherein the power conversion device includes a plurality of gain decrease thresholds or gain increase thresholds.

Images