JP2019213303A - Electric power conversion device - Google Patents

Abstract

To provide an electric power conversion device performing system interconnection, in which there is no effect on a system voltage when an internal portion of a system side winding of an interconnection transformer is short-circuited with impedance due to some factor during an interconnection operation, and the interconnection operation is stopped without continuing even if a short circuit current does not reach an overcurrent level.SOLUTION: In a subtracter 1, a difference between d-axis and q-axis system current detection values and d-axis and q-axis INV current detection values or a difference between d-axis and q-axis system current command values and d-axis and q-axis INV current command values is calculated. A first absolute value block ABS1 calculates a first absolute value that is an absolute value of the difference. A first abnormality determination processing portion 2a performs determination of a short circuit abnormality by comparing the first absolute value with a first threshold value. A failure stop processing portion 3 performs failure stop processing when the first abnormality determination processing portion 2a determines that a short circuit abnormality occurs.SELECTED DRAWING: Figure 1

Description

  The present invention relates to short circuit detection in an interconnection transformer in a power converter.

  Patent Document 1 discloses a method of detecting a short circuit in a motor using an integral value of a difference between a current command value and a current detection value in a power conversion device that performs motor control.

Japanese Patent No. 6108043

  However, in the power converter connected to the grid, if the short circuit between the system side windings inside the grid transformer with impedance occurs during the grid operation, there is no effect on the grid voltage and the short circuit current If the overcurrent level is not reached, there is a problem that the interconnection operation continues.

  In such a state, the grid-side current of the interconnection transformer is an unbalanced current, and the inverter-side current is in a state of flowing a three-phase balanced current. In addition to the Δ-Y connection, the interconnection transformer includes a YY connection, a Δ-Δ connection, and a Y-Δ connection.

  As described above, in the power conversion device connected to the grid, when the internal side of the grid side of the grid transformer is short-circuited with impedance due to some factor during the grid operation, the grid voltage is not affected. Even when the short-circuit current does not reach the overcurrent level, it becomes a problem to stop the interconnection operation without continuing.

  The present invention has been devised in view of the conventional problems, and one aspect thereof is provided between a converter that performs DC-AC conversion or AC-DC conversion, and the converter and an AC system. And a control unit that controls the converter, the control unit includes a d-axis and q-axis system current detection value, a d-axis and q-axis INV current detection value, and Or a subtractor that calculates the difference between the d-axis and q-axis system current command value and the d-axis and q-axis INV current command value, and the first absolute value that calculates the first absolute value that is the absolute value of the difference A failure determination unit for determining a short-circuit abnormality by comparing the value block with the first absolute value and the first threshold, and a failure stop processing unit for performing a failure stop process when the abnormality determination unit determines that a short-circuit abnormality has occurred And.

  Further, as another aspect, a converter that performs DC-AC conversion or AC-DC conversion, an interconnection transformer provided between the converter and an AC system, and a control unit that controls the converter , The control unit is configured such that a difference between a d-axis / q-axis system current detection value and a d-axis / q-axis INV current detection value or a d-axis / q-axis system current command value and d A subtractor that calculates the difference between the axis and q-axis INV current command values, an integrator that integrates the difference, a second absolute value block that calculates a second absolute value that is an absolute value of the output of the integrator, An abnormality determination unit that determines a short circuit abnormality by comparing the second absolute value and a second threshold value, and a failure stop processing unit that performs a failure stop process when the abnormality determination unit determines that a short circuit abnormality has occurred. It is characterized by that.

  Further, as another aspect, a converter that performs DC-AC conversion or AC-DC conversion, an interconnection transformer provided between the converter and an AC system, and a control unit that controls the converter , The control unit is configured such that a difference between a d-axis / q-axis system current detection value and a d-axis / q-axis INV current detection value or a d-axis / q-axis system current command value and d A subtractor that calculates a difference between the axis and q-axis INV current command values, a first absolute value block that calculates a first absolute value that is an absolute value of the difference, and a comparison between the first absolute value and the first threshold value A first abnormality determination unit that determines whether or not a short circuit has occurred, an integrator that integrates the difference, a second absolute value block that calculates a second absolute value that is an absolute value of the output of the integrator, and the second absolute value A second abnormality determination unit that determines a short-circuit abnormality by comparing the value with a second threshold value; Abnormality determination unit and the case where the second abnormality at least one of the determination section determines that the abnormal short circuit, characterized by comprising a failure stop processing unit for performing fault stop process, the.

  According to the present invention, in the power conversion device interconnected with the grid, when the inside of the grid side winding of the grid transformer is short-circuited with an impedance due to some factor during the grid operation, the grid voltage is not affected, and Even when the short-circuit current does not reach the overcurrent level, it is possible to stop the interconnection operation without continuing.

FIG. 3 is a control block diagram illustrating a short circuit detection process in the first embodiment. 5 is a flowchart of an abnormality determination processing unit in the first embodiment. FIG. 6 is a control block diagram illustrating a short circuit detection process in the second embodiment. FIG. 10 is a control block diagram showing a short circuit detection process in the third embodiment.

  Hereinafter, Embodiments 1 to 4 of the power conversion device according to the present invention will be described in detail with reference to FIGS.

[Embodiment 1]
The power conversion device according to the first embodiment includes a converter that performs DC-AC conversion or AC-DC conversion (hereinafter referred to as an inverter), an interconnection transformer provided between the inverter and the AC system, and an inverter A control unit that performs control.

  The control unit detects a system voltage, a system current detection value which is a current on the primary side of the interconnection transformer (system side), and an INV current detection value which is a current on the secondary side of the interconnection transformer (inverter side).

  The system current detection value and the INV current detection value are determined based on the voltage phase θ1 of the system voltage and the voltage phase θ2 of the interconnection transformer secondary side, and the d-axis and q-axis system current detection values and the d-axis and q-axis INV current detection. Convert rotating coordinates to a value. In the short-circuit detection process, the d-axis and q-axis system current detection values and the d-axis and q-axis INV current detection values are used.

  A control block diagram of the short-circuit detection process in the first embodiment is shown in FIG. This is a process for instantaneously detecting an internal short circuit of the interconnection transformer. Although the d-axis control block will be described with reference to FIG. 1, the q-axis control block is configured similarly to the d-axis control block.

  As shown in FIG. 1, the subtracter 1 calculates the difference between the d-axis system current detection value and the d-axis INV current detection value. Next, the difference is averaged in the low-pass filter LPF. Next, in the first absolute value block ABS1, the absolute value of the averaged difference is calculated as the first absolute value.

  The first abnormality determination processing unit 2a performs abnormality determination based on the first absolute value and the first threshold A. FIG. 2 is a flowchart showing the processing of the first abnormality determination processing unit 2a.

  As shown in FIG. 2, in S1, the first absolute value is compared with the first threshold A. However, in order to prevent malfunction, the first threshold value A needs to be set with a margin. If the first absolute value is greater than or equal to the first threshold A, the process proceeds to S2 and counts up (+1). After the process of S2, the process proceeds to S4. If the first absolute value is smaller than the first threshold value A, the process proceeds to S3, the count is reset, and count = 0. When the process of S3 is finished, the process in the calculation cycle is finished.

  In S4, it is determined whether or not the counter has reached a predetermined value. If the counter has reached the predetermined value, the process proceeds to S5. If the counter has not reached the predetermined value, processing in the calculation cycle is performed. finish. In S5, a stop flag is set and the processing in the calculation cycle is ended.

  As shown in FIG. 1, the failure stop processing unit 3 performs failure stop processing if the first abnormality determination processing unit 2a has a stop flag. If the stop flag is not set, the normal operation is continued without performing the failure stop process.

  As described above, according to the first embodiment, in the power conversion device that is connected to the grid, when the inside of the grid-side winding of the grid transformer is short-circuited with an impedance due to some factor during the grid operation, Even when the system voltage is not affected and the short-circuit current does not reach the overcurrent level, it is possible to stop the grid operation without continuing. In the first embodiment, instantaneous detection of a short circuit is also possible.

  In the first embodiment, a short circuit cannot be detected when the short circuit impedance is small.

[Embodiment 2]
FIG. 3 shows a control block of the short circuit detection process in the second embodiment. The second embodiment is a method for detecting an internal short circuit of the interconnection transformer in a time limit. The same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

  In the second embodiment, the difference averaged by the low-pass filter LPF is input to the dead band 4. The dead band 4 is output as 0 if the output (absolute value) of the low-pass filter LPF is equal to or less than the third threshold value b. This is a process for preventing erroneous detection in a later integration process.

  The integrator 5 integrates the output of the dead band 4. The integrator 5 can be reset such as when stopped. The second absolute value block ABS2 calculates the output of the dead band 4 with the absolute value as the second absolute value. The second absolute value block ABS2 integrates the output of the dead band 4 and then performs absolute value processing, so that the positive integration amount and the negative integration amount are canceled out by fluctuations exceeding 0 that exceed the third threshold value b. To prevent that.

  The second abnormality determination processing unit 2b compares the second absolute value with the second threshold value B. Other than that, the operation is the same as that of the first abnormality determination processing unit 2a of the first embodiment. The operation of the failure stop processing unit 3 is the same as that of the first embodiment.

  As described above, according to the second embodiment, the same operational effects as those of the first embodiment can be obtained. In the first embodiment, when the short-circuit impedance is small, the short circuit cannot be detected. However, in the second embodiment, the short circuit can be detected even when the short-circuit impedance is small.

  However, in the second embodiment, since there is a time limit until short circuit detection by integration, instantaneous detection cannot be performed.

[Embodiment 3]
FIG. 4 shows a control block diagram of the short circuit detection process in the third embodiment. As illustrated in FIG. 4, the third embodiment includes a control block up to the first abnormality determination processing unit 2 a according to the first embodiment and a control block up to the second abnormality determination processing unit 2 b according to the second embodiment. Then, the outputs of the two first and second abnormality determination processing units 2 a and 2 b are output to the OR circuit 6.

  The OR circuit 6 outputs a “1” level signal to the failure stop processing unit 3 when at least one of the first abnormality determination processing unit 2a and the second abnormality determination processing unit 2b has set a failure flag. To do. The failure stop processing unit 3 performs failure stop processing when at least one of the first abnormality determination processing unit 2a and the second abnormality determination processing unit 2b determines that a short circuit abnormality has occurred.

  As described above, the third embodiment is a logical sum of the abnormality determination results of the first and second embodiments. As a result, even when the short-circuit impedance is small, it is possible to detect a short-circuit, and instantaneous detection is also possible. Therefore, the problem of Embodiment 1 and Embodiment 2 can be solved.

[Embodiment 4]
In the fourth embodiment, the d-axis, q-axis INV current detection value and the d-axis, q-axis system current detection value of the third embodiment are changed to the d-axis, q-axis INV current command value, d-axis, q-axis system current command value. It is a replacement. Since the current command value is more stable than the current detection value, it is possible to suppress erroneous detection.

  Further, the d-axis, q-axis INV current detection value and the d-axis, q-axis system current detection value of the first and second embodiments may be used as the d-axis, q-axis INV current command value, and d-axis, q-axis system current command value. .

  Although the present invention has been described in detail only for the specific examples described above, it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the technical idea of the present invention. Such variations and modifications are naturally within the scope of the claims.

DESCRIPTION OF SYMBOLS 1 ... Subtractor 2a, 2b ... Abnormality determination process part 3 ... Failure stop process part 4 ... Dead band 5 ... Integrator 6 ... OR circuit ABS1, ABS ... 1st, 2nd absolute value block LPF ... Low pass filter

Claims (3)

A power conversion device comprising: a converter that performs DC-AC conversion or AC-DC conversion; an interconnection transformer provided between the converter and an AC system; and a control unit that controls the converter. In
The controller is
The difference between the d-axis / q-axis system current detection value and the d-axis / q-axis INV current detection value or the difference between the d-axis / q-axis system current command value and the d-axis / q-axis INV current command value is calculated. A subtractor,
A first absolute value block for calculating a first absolute value that is an absolute value of the difference;
An abnormality determination unit that determines a short-circuit abnormality by comparing the first absolute value and the first threshold;
When the abnormality determination unit determines that a short circuit abnormality has occurred, a failure stop processing unit that performs failure stop processing;
A power conversion device comprising: A power conversion device comprising: a converter that performs DC-AC conversion or AC-DC conversion; an interconnection transformer provided between the converter and an AC system; and a control unit that controls the converter. In
The controller is
The difference between the d-axis / q-axis system current detection value and the d-axis / q-axis INV current detection value or the difference between the d-axis / q-axis system current command value and the d-axis / q-axis INV current command value is calculated. A subtractor,
An integrator that integrates the difference;
A second absolute value block for calculating a second absolute value that is an absolute value of the output of the integrator;
An abnormality determination unit that determines a short-circuit abnormality by comparing the second absolute value and the second threshold;
When the abnormality determination unit determines that a short circuit abnormality has occurred, a failure stop processing unit that performs failure stop processing;
A power conversion device comprising: A power conversion device comprising: a converter that performs DC-AC conversion or AC-DC conversion; an interconnection transformer provided between the converter and an AC system; and a control unit that controls the converter. In
The controller is
The difference between the d-axis / q-axis system current detection value and the d-axis / q-axis INV current detection value or the difference between the d-axis / q-axis system current command value and the d-axis / q-axis INV current command value is calculated. A subtractor,
A first absolute value block for calculating a first absolute value that is an absolute value of the difference;
A first abnormality determination unit that determines a short-circuit abnormality by comparing the first absolute value with a first threshold;
An integrator that integrates the difference;
A second absolute value block for calculating a second absolute value that is an absolute value of the output of the integrator;
A second abnormality determination unit that determines a short-circuit abnormality by comparing the second absolute value and a second threshold;
When at least one of the first abnormality determination unit and the second abnormality determination unit determines that a short circuit abnormality has occurred, a failure stop processing unit that performs a failure stop process;
A power conversion device comprising:

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