JP2022046712A - Distributed power supply unit, and control method and abnormality determination method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine whether a current sensor is operating normally or abnormally at lower cost.

SOLUTION: A distributed power supply unit comprises: a power supply unit that supplies power to a line connected to a circuit; a sensor that detects a current flowing through the line; and a control unit that controls the power supply unit based on the current detected by the sensor. The control unit comprises a first determination unit that determines whether the sensor is operating normally or abnormally based on at least a current frequency of the current detected by the sensor, and a power supply unit control unit that controls the power supply unit to stop the operation of the power supply unit in response to the fact that the first determination unit detects an abnormality in the operation of the sensor.

SELECTED DRAWING: Figure 3

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a distributed power supply unit, a control method thereof, and an abnormality determination method.

Distributed power supply units consisting of fuel cells, photovoltaic power generation devices, storage batteries, etc. are becoming widespread. The distributed power supply unit is connected to a line (cable) from the grid to the load, and supplies power to the load according to the power supplied from the grid to the load. This function of the distributed generation unit can reduce the transmission loss due to the grid. In addition, by supplying power to the load from the distributed power supply unit when the power supply from the grid drops, the operation of the equipment corresponding to the load can be maintained normally, so the number of distributed power supply units installed is increasing. ..

When the generated power of such a distributed power supply unit increases and exceeds the power consumption of the load, surplus power is generated. If nothing is done, this surplus power will flow back to the grid. However, in order to ensure the power quality of the grid, such reverse power flow is often not allowed. Therefore, it is necessary to prevent the occurrence of reverse power flow.

Therefore, it is common practice to provide a current sensor on the line from the grid to the load. This current sensor monitors the current between the system and the load and controls the distributed power supply unit so that reverse power flow does not occur.

As such a current sensor, a clamp type current sensor is often used. The clamp type current sensor has a measurement line consisting of windings, and by attaching it to the line with a clamp, it outputs the current generated in the measurement line due to the coupling between the AC current flowing through the line and the measurement line due to mutual inductance. .. By knowing the magnitude of this current, it is possible to know the magnitude of the current flowing through the line.

Since such a clamp type current sensor can measure the magnitude of the current flowing through the line simply by attaching it to the line with a clamp, there is an advantage that the installation and maintenance of the current sensor can be easily performed. However, on the other hand, the clamp type current sensor has a problem that the current may not be detected correctly due to dropping from the line, incomplete mounting, or incorrect connection direction. If the current cannot be detected correctly, there is an increased risk of reverse power flow, etc., so it is necessary to immediately detect these problems and take appropriate measures.

A proposal for solving such a problem is made in Patent Document 1 described later. The distributed power supply system disclosed in Patent Document 1 includes a distributed power supply, a first current sensor to be connected to a first voltage line, and a second current sensor to be connected to a second voltage line. And a determination unit. The determination unit supplies a plurality of power supplies from the system power supply to the power load connected to the first and second voltage lines between the planned connection positions of the first and second current sensors and the distributed power supply for a predetermined time. It is repeated, and based on the result, the presence / absence of connection of the first and second current sensors, the connection position, and the correctness of the connection direction are determined.

JP-A-2015-122819

However, the technique disclosed in Patent Document 1 energizes the internal power load and determines whether or not the current sensor is connected based on the amount of change in the current measured value by the current sensor before and after energization. Therefore, a power load and a switch must be provided. Since the number of parts increases, there is a problem that the cost increases.

Therefore, an object of the present invention is to provide a distributed power supply unit capable of determining whether the operation of a current sensor is normal or abnormal at a lower cost, a control method thereof, and an abnormality determination method.

The distributed power supply unit according to the first aspect of the present invention is a distributed power supply unit connected to a line connected to the system, and detects a power supply unit that supplies power to the line and a current flowing through the line. It includes a sensor and a control unit that controls the power supply unit based on the current detected by the sensor, and the control unit operates the sensor normally based on at least one of the current effective value and the current frequency of the current detected by the sensor. Includes a first determination unit for determining whether an abnormality is present, and a control unit for controlling the power supply unit so that the operation of the power supply unit is stopped in response to the detection of the abnormality in the operation of the sensor by the first determination unit. ..

The method for controlling a distributed power supply unit according to a second aspect of the present invention is a method for controlling a distributed power supply unit connected to a line connected to a system, and the distributed power supply unit supplies electric power to the line. It includes a power supply unit to supply and a sensor to detect the current flowing through the line, and the method determines whether the sensor is operating normally or abnormally based on at least one of the current effective value and the current frequency of the current detected by the sensor. The first determination step includes a control step of controlling the power supply unit so as to stop the operation of the power supply unit in response to the detection of an abnormality in the operation of the sensor in the first determination step.

The abnormality determination method of the distributed power supply unit according to the third aspect of the present invention is the abnormality determination method in the distributed power supply unit connected to the line connected to the system, and the distributed power supply unit is connected to the line. A first determination that includes a power supply unit that supplies power and a sensor that detects the current flowing through the line, and the method determines whether the current effective value of the current detected by the sensor is less than the first threshold value. The step, the second determination step of determining whether or not the current frequency of the current detected by the sensor is out of the first range, and the determination in the first determination step are affirmative and the determination in the second determination step. The present invention includes a third determination step of determining that the operation of the sensor is abnormal in response to the continuation of the affirmative period for the predetermined detection time or longer.

According to the present invention, it is possible to provide a distributed power supply unit capable of determining whether the operation of a current sensor is normal or abnormal at a lower cost, a control method thereof, and an abnormality determination method.

FIG. 1 is a block diagram of a distributed power supply system including a distributed power supply unit according to a first embodiment of the present invention. FIG. 2 is a block diagram showing a hardware configuration of the distributed power supply unit shown in FIG. FIG. 3 is a flowchart showing a control structure of a program for determining whether the operation of the CT (Current Transformer) sensor is normal or abnormal, which is executed in the control unit shown in FIG. 2. FIG. 4 is a part of the program shown in FIG. 3, and shows a control structure of a routine for acquiring information for determining whether the operation of the CT sensor is normal or abnormal based on the current effective value detected by the CT sensor. It is a flowchart which shows. FIG. 5 shows a control structure of a routine that is a part of the program shown in FIG. 3 and acquires information for determining whether the operation of the CT sensor is normal or abnormal based on the current frequency detected by the CT sensor. It is a flowchart. FIG. 6 is a graph showing an example of fluctuations in the CT sensor current under no load. FIG. 7 is a graph showing an example of fluctuations in the CT sensor current when the distributed power supply unit is discharged to a predetermined size. FIG. 8 is a graph showing an example of fluctuation of the CT sensor current at the time of abnormality such as the CT sensor falling off the line. FIG. 9 is a flowchart showing a control structure of a program for determining whether the operation of the CT sensor is normal or abnormal, which is executed in the distributed power supply unit according to the second embodiment of the present invention. FIG. 10 is a graph showing changes in electric power when forced charging is started from the distributed power supply unit to the storage battery in the distributed power supply system including the distributed power supply unit according to the second embodiment. FIG. 11 is a flowchart showing the control structure of the routine for determining whether the operation of the CT sensor is normal or abnormal by forced charging in the program showing the control structure in FIG. FIG. 12 is a flowchart showing a control structure of a program for determining whether the operation of the CT sensor is normal or abnormal, which is executed in the distributed power supply unit according to the third embodiment of the present invention.

In the following description and drawings, the same parts are given the same reference numbers. Therefore, detailed explanations about them will not be repeated. In addition, at least a part of the embodiments described below may be arbitrarily combined.

[Explanation of Embodiment of the present invention]
The distributed power supply unit according to the first aspect of the present invention is a distributed power supply unit connected to a line connected to the grid, and detects a power supply unit that supplies power to the line and a current flowing through the line. It includes a sensor and a control unit that controls the power supply unit based on the current detected by the sensor, and the control unit operates the sensor normally based on at least one of the current effective value and the current frequency of the current detected by the sensor. A first determination unit that determines whether an abnormality occurs, and a power supply unit control unit that controls the power supply unit so that the operation of the power supply unit is stopped in response to the detection of an abnormality in the operation of the sensor by the first determination unit. including.

With this configuration, it is possible to detect sensor dropout, disconnection, mounting failure, etc. without adding a component for detecting an abnormality of the sensor.

Preferably, the first determination unit includes a second determination unit that determines whether the operation of the sensor is normal or abnormal based on both the current effective value and the current frequency.

Since the judgment is made based on both the current effective value and the current frequency, the reliability of the judgment is improved.

More preferably, the second determination unit includes a third determination unit that determines whether or not the current effective value is less than the first threshold value, and a second determination unit that determines whether or not the current frequency is out of the first range. The sensor operation is abnormal in response to the period in which the determination by the determination unit 4 and the determination unit 3 is affirmative and the determination by the fourth determination unit is affirmative continues for a predetermined detection time or longer. Includes a fifth determination unit for determining that.

Since the sensor abnormality is determined only when the abnormality of the current effective value and the abnormality of the current frequency continue for a predetermined detection time or longer at the same time, the risk of erroneously detecting the abnormality of the sensor can be reduced.

More preferably, at least one of the first threshold and the first range is determined according to the specifications of the power supply unit.

Since the conditions for abnormality detection are determined according to the specifications of the power supply, it is possible to optimally detect sensor abnormalities according to various power supplies without adding parts.

Preferably, the power supply unit includes at least one of a storage battery, a photovoltaic power generation device and a wind power generation device.

In a distributed power supply unit including any of a storage battery, a photovoltaic power generation device, and a wind power generation device, the present invention can detect a sensor abnormality without adding parts. The power supply unit may include a combination of two or more of a storage battery, a photovoltaic power generation device and a wind power generation device. Further, two or more of these may be included.

Preferably, the power supply unit comprises a storage battery that can be recharged by the power supplied from the line, and the control unit further charges the storage battery in response to the first determination unit detecting an abnormality in the operation of the sensor. The power supply unit control unit includes an abnormality determination unit by charging that forcibly changes the power and determines whether the sensor operation is normal or not based on the change in the detected power based on the output of the sensor due to the change. A stop control unit that controls the power supply unit to stop the operation of the power supply unit in response to detection of an abnormality in the operation of the sensor by both the first determination unit and the abnormality determination unit is included.

Even if the first determination unit detects an abnormality, the operation of the power supply unit is not stopped by itself. The electric power is detected based on the output of the sensor accompanying the charging electric power to the storage battery, and it is further determined whether or not the operation of the sensor is abnormal based on the change. The operation of the power supply unit is stopped only when both judgments are abnormal. The possibility of accidentally stopping the power supply unit due to false detection of sensor abnormality can be reduced.

More preferably, the first determination unit constantly monitors the output of the sensor and determines in real time whether the operation of the sensor is normal or abnormal based on at least one of the current effective value and the current frequency of the current detected by the sensor. Includes real-time determination unit.

The real-time determination unit determines in real time whether or not the operation of the sensor is abnormal. The power supply unit can be stopped immediately when an abnormality occurs, and the adverse effects of the sensor abnormality can be limited.

More preferably, the first determination unit monitors the output of the sensor at any time for a specified predetermined time, and the sensor is based on at least one of the current effective value and the current frequency of the current detected by the sensor within the predetermined time. Includes an occasional determination unit that determines whether the operation of is normal or abnormal.

The occasional determination unit can determine at any time whether or not the operation of the sensor is abnormal within a designated predetermined time. When there is no risk that the judgment process will adversely affect the system operation or the judgment result will be adversely affected by the system operation, it is possible to judge the operation abnormality of the sensor, improve the reliability of detection, and adversely affect the system operation. Can be prevented from reaching.

The method for controlling a distributed power supply unit according to a second aspect of the present invention is a method for controlling a distributed power supply unit connected to a line connected to a system, and the distributed power supply unit supplies electric power to the line. It includes a power supply unit to supply and a sensor to detect the current flowing through the line, and the method determines whether the sensor is operating normally or abnormally based on at least one of the current effective value and the current frequency of the current detected by the sensor. The first determination step includes a control step of controlling the power supply unit so as to stop the operation of the power supply unit in response to the detection of an abnormality in the operation of the sensor in the first determination step.

It is possible to detect sensor dropout, disconnection, mounting failure, etc. without adding parts for detecting sensor abnormalities.

The abnormality determination method of the distributed power supply unit according to the third aspect of the present invention is the abnormality determination method in the distributed power supply unit connected to the line connected to the system, and the distributed power supply unit is connected to the line. A first determination that includes a power supply unit that supplies power and a sensor that detects the current flowing through the line, and the method determines whether the current effective value of the current detected by the sensor is less than the first threshold value. The step, the second determination step of determining whether or not the current frequency of the current detected by the sensor is out of the first range, and the determination in the first determination step are affirmative and the determination in the second determination step. The present invention includes a third determination step of determining that the operation of the sensor is abnormal in response to the continuation of the affirmative period for the predetermined detection time or longer.

Abnormalities such as sensor dropout, disconnection, and improper installation can be detected without adding any parts.

[Details of Embodiments of the present invention]
<Structure>
The embodiment described below is an example of a single-phase three-wire distributed power supply system. Further, in this example, a CT sensor is used as an example of the sensor.

With reference to FIG. 1, the distributed generation system 50 is connected to the system 60, the loads 62, 64 and 66 receiving power from the system 60 via the lines W, О and U, respectively, and the lines U and W. It has two CT sensors 70 and 72 that are attached and detect currents flowing through these lines U and W, respectively, and outputs connected to the lines U, О and W, and a load 62 based on the outputs of the CT sensors 70 and 72. , 64 and 66 include a distributed power supply unit 68 for supplying power.

The distributed power supply unit 68 includes a power supply unit (not shown) so that the distributed power supply unit 68 can cover the load power consumption that changes every moment based on the CT sensor currents from the CT sensors 70 and 72 by the output from the power supply unit. It is controlled to improve the overall economic efficiency of the distributed power supply system 50. In order for the distributed power supply unit 68 to control the output, the distributed power supply unit 68 has a control unit 80 that receives the outputs of the CT sensors 70 and 72, and the control units 80 control the outputs of the CT sensor 70 and the CT sensor 72. The system current from the system 60 is measured based on the above, and the power supplied from the power supply unit of the distributed power supply unit 68 to the load 62, the load 64, and the load 66 is controlled based on the value. Although a storage battery is assumed as the power supply unit in this embodiment, the present invention can also be applied to a distributed power generation unit including, for example, a solar power generation device, a wind power generation device, and the like.

If the CT sensor 70 or 72 falls off the line or the measurement line of the CT sensor 70 or 72 is disconnected, the control unit 80 of the distributed power supply unit 68 cannot normally measure the system current. Then, the control unit 80 cannot normally perform power control. In this case, it is necessary to protect and stop the distributed power supply unit 68. Therefore, there is a need for a mechanism for determining whether the operation of the CT sensors 70 and 72 is normal or abnormal.

When there is no load, a reactive current flows through the CT sensor, and when there is a load, a current that is a combination of the active current and the reactive current flows. In this embodiment, the control unit 80 determines whether the operation of the CT sensors 70 and 72 is normal or abnormal based on such properties of the outputs of the CT sensors 70 and 72, and when it is determined to be abnormal, the distributed generation unit 80. It has a function to stop the operation of the type power supply unit 68. In this embodiment, the effective value of the sensor current from the CT sensors 70 and 72 and the current frequency are used as the conditions for that purpose. Specifically, when the following conditions are satisfied, it is determined that the operation of the CT sensor is abnormal. That is, when the condition that the effective value of the CT sensor current is less than the threshold value and the frequency of the CT sensor current is out of the predetermined range continues for the detection time or longer, the operation of the CT sensor is determined to be abnormal. The threshold value of the current effective value and the range of the current frequency at this time depend on the specifications of the system to which the CT sensor is connected. The current frequency can be calculated by measuring the time between the zero crossing points of the current and obtaining the reciprocal of the time.

In order to detect the operation abnormality of the CT sensor as described above, the control unit 80 has the following configuration. FIG. 2 shows the hardware configuration of the control unit 80. With reference to FIG. 2, the control unit 80 receives an input / output interface (hereinafter referred to as “I / F”) 100 that receives CT sensor currents from the CT sensors 70 and 72 and performs AD conversion, and an input / output I / F 100. The bus 102, which is connected to the bus 102 and serves as a path for transmitting and receiving signals between the components of the control unit 80, and the CPU (Central Processing Unit) 104, ROM (Read-Only Memory) 106, both of which are connected to the bus 102. It is connected to the input / output I / F 108, timer 110, RAM (Random Access Memory) 112, input / output I / F 114, and input / output I / F 114, and displays an error code or the like as a double-digit number according to the control of the CPU 104. Includes a 7-segment display 116.

Of these, the input / output I / F 100 is for receiving the sensor currents from the CT sensors 70 and 72 shown in FIG. 1, AD converting them, and inputting them to the CPU 104. The input / output I / F 108 is for transmitting a control signal from the CPU 104 to a power supply unit (not shown). The input / output I / F 114 sends a control signal to the 7-segment display 116 so as to display a code indicating the content when the operation of the CT sensor 70 or the CT sensor 72 is determined to be abnormal according to the control from the CPU 104. It is for giving.

FIG. 3 shows a control structure of a program for realizing a function of determining whether the operation of the CT sensors 70 and 72 is normal or abnormal by being executed by the CPU 104 shown in FIG. 2 in a flowchart format. Here, a program for determining whether the operation of one CT sensor (for example, CT sensor 70) is normal or abnormal is shown for the sake of easy understanding of explanation and illustration, but the same processing is performed for the CT sensor 72. Just do it.

With reference to FIG. 3, this program is started at the same time as the power-on of the distributed power supply unit 68 and includes steps 140 and 142 to reset the first flag and the second flag, respectively. The first flag is set when the current effective value of the CT sensor 70 is less than a predetermined threshold value for a period of longer than the first duration (first threshold value), and is reset when the condition disappears. Will be done. The second flag is set when the current frequency of the CT sensor 70 is out of the predetermined range for a period longer than the second duration (second threshold value), and is reset when the condition disappears. In this embodiment, the first threshold value = the second threshold value, but both may be different. If they are different, the smaller threshold is the actual detection time limit.

Further, after step 142, this program determines whether or not the current effective value of the sensor current from the CT sensor 70 satisfies the above-mentioned conditions, and sets or resets the first flag according to the result. After step 144, it is determined whether or not the current frequency of the sensor current from the CT sensor 70 satisfies the above-mentioned conditions, and the second flag is set or reset according to the result, and steps 146 and 146. After, it is determined whether or not the first flag is set, and if the determination is negative, the control is returned to step 144. Step 148, and when the determination of step 148 is affirmative, whether or not the second flag is set. Includes step 150, which determines whether or not, and if the determination is negative, returns control to step 144. In this process, the first timer is used. The first timer can be realized by using the timer 110 shown in FIG.

The program further protects the distributed power supply unit 68 after step 152, which controls the 7-segment display 116 shown in FIG. 2 to display a predetermined error code when the determination in step 150 is affirmative, and after step 152. Includes step 154, which stops, stops the distributed generation output, and ends the execution of this program.

FIG. 4 shows the control structure of the routine executed in step 144 of FIG. With reference to FIG. 4, this routine determines whether the effective sensor current value from the CT sensor 70 is less than a predetermined threshold value, and steps 180 to branch the control flow according to the determination result. When the determination of 180 is negative, the first flag is reset, the first timer is reset (stopped), and the execution of this routine is terminated.

This routine further determines whether or not the first timer is timing when the determination in step 180 is affirmative, and when the determination in step 184 and step 184 is negative, the control flow is branched according to the result. In step 186, which sets the first timer to the first duration, step 188, which activates the first timer and starts subtraction timing, after step 188, and when the determination in step 184 is affirmative. In step 190, which determines whether or not the first timer has expired and terminates the execution of this routine when the determination is negative, and when the determination in step 190 is affirmative, the first flag is set. Includes step 192 and the end of routine execution.

FIG. 5 shows the control structure of the routine executed in step 146 of FIG. In this process, the second timer is used as in the process shown in FIG. The second timer can be realized by using the timer 110 shown in FIG. 2, similarly to the first timer. With reference to FIG. 5, this routine determines whether the sensor current frequency from the CT sensor 70 is out of a predetermined range, and determines in step 220 and step 220 that branch the control flow according to the determination result. Includes step 222, which resets the second flag, resets (stops) the second timer, and ends the execution of this routine when is negative.

This routine further determines whether or not the second timer is timing when the determination in step 220 is affirmative, and when the determination in step 224 and step 224 to branch the control flow according to the result is negative. In step 226 to set the second timer to the second duration, step 228 to start the second timer and start subtraction timing, after step 228, and when the determination in step 224 is affirmative. In step 230, which determines whether or not the second timer has expired and terminates the execution of this routine when the determination is negative, and when the determination in step 230 is affirmative, the second flag is set. Includes step 232 and the end of routine execution.

<Example of determining the threshold value for the current effective value>
Assuming that F is the system voltage frequency (Hz), C is the system side capacitor capacity (F) of the distributed power supply unit, and V is the system voltage effective value (V), the reactive current (A) measured by the CT sensor is as follows. Is calculated by.

Reactive current = 2πFCV
In the case of a single-phase three-wire system AC200V / 50Hz and the capacitor capacity on the system side is 6.6μF, the reactive current is 0.42A. The threshold value is 0.105 A, which is a margin of 75% of the reactive current value.

<Example of determining the frequency range of the CT sensor current>
In this embodiment, ± 5% (not including both ends) of the voltage frequency of the system is set as a normal range, and the other range is set as abnormal. That is,
When the system voltage is 50 Hz, the CT sensor current frequency is 47.5 Hz or less or 52.5 Hz or more and is out of the range.

When the system voltage is 60 Hz, the CT sensor current frequency is 57 Hz or less or 63 Hz or more and is out of the range.

Of course, this is only one example, and both ends of the range may be included in the normal range.

<Example of determination of detection time period>
The detection time period needs to be longer than the system voltage cycle. In this embodiment, the detection time is set to 5 seconds as an example.

<Operation>
In the distributed power supply unit 68 of the distributed power supply system 50 described above, the control unit 80 operates as follows.

With reference to FIG. 1, the CT sensors 70 and 72 input CT sensor currents corresponding to the currents flowing in the lines U and W to the control unit 80, respectively. The control unit 80 normally adjusts the output power according to this value so as to cover the power consumption of each load from the distributed power supply unit 68 and to prevent reverse power flow.

With reference to FIG. 3, when the power of the distributed power supply unit 68 is turned on, the control unit 80 resets the first flag in step 140, resets the second flag in step 142, and then repeatedly executes the following processing. Although the following description uses the CT sensor 70 as an example, the same processing is executed for the CT sensor 72 as well.

First, the current effective value check process (FIG. 4) is executed in step 144, and then the current frequency check process (FIG. 5) is executed in step 146.

-Normal-
In a normal case, with reference to FIG. 4, in the check process of the current effective value, it is determined in step 180 whether or not the current effective value of the CT sensor 70 is less than the threshold value. If no abnormality has occurred in the CT sensor 70, the current effective value is equal to or higher than the threshold value, and the control proceeds to step 182. In step 182, the first flag is reset, the first timer is reset, and this process ends. Similarly, with reference to FIG. 5, in the current frequency check process, it is determined in step 220 whether or not the current frequency of the CT sensor is out of the predetermined range. In the normal case, the current frequency is within a predetermined range, and the determination in step 220 is negative. As a result, in step 222, the second flag is reset, the second timer is reset, and this process ends.

With reference to FIG. 3 again, in the normal case, the determination in step 148 is negative, and the control returns to step 144 without executing the process of step 150. That is, if there is no abnormality in the CT sensor 70, the processes of step 144, step 146 and step 148 are repeatedly executed. The process runs normally without any errors being detected.

-In case of temporary error-
For some reason, the current effective value of the CT sensor 70 may temporarily fall below the threshold value (a time shorter than the detection time limit). The operation of the control unit 80 in that case is as follows.

With reference to FIG. 4, the determination in step 180 becomes affirmative, and in step 184, it is determined whether or not the first timer is timing. If it is in a normal state until just before this, the determination in step 184 is negative, and the control proceeds to step 186. In step 186, the first timer is set to the first duration, and in step 188, the first timer is activated and the subtraction of the first timer is started. In the following step 190, it is determined whether or not the first timer has expired. Here, the first timer has not expired, the determination is negative, and the execution of this subroutine ends.

With reference to FIG. 3, the first flag is still reset. Therefore, in this case, the determination in step 148 is still negative and control returns to step 144.

With reference to FIG. 4 again, if the current effective value of the CT sensor 70 is still less than the threshold value in the next iteration, the control proceeds to step 184. The determination in step 184 is affirmative, the processes in steps 186 and 188 are not executed, and control proceeds directly to step 190. In step 190, it is determined whether or not the first timer has expired, but here, since it has not expired due to the assumption, the determination is negative, and the execution of this subroutine ends. That is, at this point, the state in which the first flag is off is maintained.

With reference to FIG. 3, while the current effective value of the CT sensor 70 is less than the threshold value and until the first timer expires, both the first flag and the second flag remain off, and step 144 146 and 148 are repeatedly executed.

It is assumed that the current effective value of the CT sensor 70 returns to a value equal to or higher than the threshold value within the detection time limit. In this case, referring to FIG. 4, the determination in step 180 is negative. Control proceeds to step 182, the first flag is reset, the first timer is reset, and the execution of this routine ends.

Returning to FIG. 3, as a result of the processing in step 144, both the first flag and the second flag are reset, the timer also returns to the reset state (normal state), and the processing of steps 144, 146 and 148 is repeatedly executed. Will be.

The same applies when the current frequency of the CT sensor 70 temporarily falls out of the predetermined range. Specifically, referring to FIG. 5, since the determination in step 220 is usually negative, the second flag is reset. If the current frequency of the CT sensor 70 is out of the predetermined range, the second timer is activated via the route of step 220 → step 224 (NO) → step 226 → step 228, and this step 230 (NO) activates the second timer. The execution of the routine ends. That is, at this point, the second flag is not set and only the second timer is activated.

After the second timer is started, the routine of FIG. 5 ends through the route of step 220 (YES) → step 224 (YES) → step 230 (NO) of FIG. 5 until it expires. That is, the first flag and the second flag are still reset, and the control unit 80 does not detect any abnormality.

-When the current effective value is less than the threshold value for the detection period or more-
In this case, the processing of the control unit 80 is the same as the case where such a state temporarily occurs as described above. However, in the repetition of the route of step 180 (YES) → step 184 (YES) → step 190 shown in FIG. 4, if the state where the current effective value is less than the threshold value continues for the detection time or more, the determination of step 190 is made. Is affirmative, and the first flag is set in step 192. However, unless the second flag is set, the determination in step 150 in FIG. 3 is negative, so the control returns to step 144, the control unit 80 does not detect an abnormality, and on the surface, the same operation as usual is performed.

-When the current frequency is out of the specified range for the detection period or longer-
In this case as well, the processing of the control unit 80 is the same as when this state temporarily occurs, as described above. However, in the repetition of the route of step 220 (YES) → step 224 (YES) → step 230 shown in FIG. 5, if the current frequency is out of the predetermined range beyond the detection time period, the determination of step 230 becomes affirmative, and in step 232. The second flag is set. However, in this case as well, unless the first flag is set, the determination in the third step 148 is negative, so the control returns to step 144, the control unit 80 does not detect an abnormality, and the operation is the same as usual on the surface. I do.

-When the abnormality of the current effective value and the abnormality of the current frequency continue for more than the detection time at the same time-
As is clear from the above description, in this case, the time when both the first flag and the second flag are turned on continues for the detection time or longer. With reference to FIG. 3, the determinations of step 148 and step 150 are both affirmative. As a result, in step 152, the code indicating the abnormality of the CT sensor 70 is displayed by the 7-segment display 116 shown in FIG. 2, and in step 154, the output of the distributed power source in the distributed power supply unit 68 is stopped. As a result, for example, when the CT sensor 70 falls off the line or the measurement line is disconnected and normal measurement cannot be performed, the distributed power supply unit 68 is protected and stopped.

<Application example>
Actually, the control unit 80 according to the above embodiment was realized by using the above threshold value and the detection time for the single-phase three-wire system AC200V / 50Hz. For the distributed power supply unit 68 including the control unit 80, the capacitor capacity on the system side is 6.6 μF, the minimum charge / discharge power is 50 W, the CT sensor current is sampled in a 20 kHz cycle, and the CT sensor current is effective for each system voltage cycle. The value was calculated. When the CT sensor current can be measured normally and there is no load, the CT sensor current as shown in Graph 250 shown in FIG. 6 was obtained. As can be seen from FIG. 6, this graph 250 draws a beautiful sine curve. In this case, the effective value of the reactive current was 0.58 A, and the frequency of the CT sensor current was 50.01 Hz. Therefore, no abnormality was detected in the CT sensor.

The CT sensor current when 50 W is discharged from the distributed power supply unit 68 is shown in Graph 252 shown in FIG. 7. Graph 252 is not a clean sine curve but is deformed, but has a shape generally close to that of a sine curve. In FIG. 7, since the measured value from the vicinity of 0A toward the positive is set as the plot start position, the phase does not match with FIG. In this case, the effective current value was 0.33 A, and the frequency of the CT sensor current was 50.02 Hz. Therefore, even in this case, no abnormality was detected in the CT sensor.

Further, the CT sensor current obtained when the CT sensor was dropped from the line and the CT sensor current could not be measured normally is shown in Graph 254 shown in FIG. As is clear from FIG. 8, the graph 254 changes almost around the time axis, and its current value is close to zero. The current effective value at this time was 0.07 A, and the current frequency was 0 Hz. In this state, the control unit 80 detected the CT sensor abnormality, and 5 seconds after the CT sensor fell off, the distributed power supply unit 68 was protected and stopped. Although the effective current value is not completely 0A in FIG. 8, this is due to the measurement accuracy of the current.

In the above embodiment, special hardware such as specific parts is not required in order to detect defects such as the CT sensor falling off and the measurement line being broken. Therefore, it is possible to prevent an increase in the cost of the control unit 80 and the distributed power supply unit 68.

In the above embodiment, when the abnormality of the current effective value of the CT sensor current and the abnormality of the current frequency continue at the same time for a predetermined detection time or longer, it is determined as an abnormality. However, the invention is not limited to such embodiments. An abnormality may be determined when either the abnormality of the current effective value or the abnormality of the current frequency continues for a predetermined detection time or longer. Further, only the abnormality of the current effective value or only the abnormality of the current frequency may be detected, and when the abnormality continues for a predetermined detection time or longer, the operation of the CT sensor may be determined to be an abnormality.

[Second Embodiment]
<Summary>
In the first embodiment, the operation of the CT sensor is abnormal when the condition that the effective value of the CT sensor current is less than the threshold value and the frequency of the CT sensor current is out of the predetermined range continues for the detection time or longer. Is determined. By combining the two conditions in this way, the accuracy of the determination is improved as compared with the case where only the individual conditions are used, and the possibility of erroneous detection of the abnormality determination is reduced. However, if a load or power generation device that cancels the active current or reactive current flowing through the CT sensor is connected to the grid and happens to meet the above-mentioned abnormality determination conditions, it is determined that an abnormality has occurred by mistake. There is also a risk of being struck. If there is such an erroneous determination, it is conceivable that the distributed power supply unit will be protected and stopped even though it is not necessary to protect and stop it.

Therefore, even if it is determined that an abnormality has occurred in the above-mentioned abnormality determination processing, it is conceivable to stop the distributed power supply system only when it is similarly determined that an abnormality has occurred in another abnormality determination processing. The distributed power supply system according to the second embodiment is such a system.

In this second embodiment, when an abnormality is determined by the same method as in the first embodiment, the output of the distributed power supply system is temporarily stopped, and then the distributed power supply system is forced into the storage battery. Abnormality determination of the CT sensor is performed based on the change in power due to charging. By performing the double determination in this way, it is possible to prevent erroneous detection of an abnormality.

<Structure>
The hardware configuration used in this embodiment is the same as that of the first embodiment. What is different is the program for anomaly detection. The control structure of the program is shown in FIG. 9 in the form of a flowchart. Before explaining the flowchart of FIG. 9, the principle of abnormality detection of the operation of the sensor in this embodiment will be described with reference to FIG. It is assumed that the peak power of alternating current to the load at the start of forced charging of the storage battery is _P01 . This peak power can be calculated based on the detected currents of the CT sensor 70 and the CT sensor 72 shown in FIG. 1 and the voltage of the system 60. When the forced charging of the storage battery is started, the peak power increases as shown in Graph 330, and the value of the peak power of the charging power + the load power becomes _P02 after the lapse of a predetermined time. Since this forced charging is for a short time (for example, 1 second or less), it is possible even if the storage battery is fully charged. If this forced charge is 1 kW, the amount of change from the peak power P ₀₁ to the peak power P ₀₂ is about 1 kW ± 0.3 kW. If the peak power P ₀₂ after the start of charging is not within this range, it is determined that an abnormality has occurred and the distributed power supply system is protected and stopped. If the peak power P ₀₂ is within this range, it is determined to be normal, and the output of the distributed power supply system is restarted to return to the normal state.

With reference to FIG. 9, this program comprises steps 140-150 similar to the program of the first embodiment shown in FIG. Unlike FIG. 3, the program shown in FIG. 9 shows that when the determination in step 150 is affirmative, that is, the effective value of the CT sensor current is less than the threshold value and the frequency of the CT sensor current is out of the predetermined range. When the condition is continued for the detection time or longer, the distributed power supply unit is not immediately stopped, but includes a processing portion for detecting an abnormality of the CT sensor by the above-mentioned forced charging.

This processing portion stops the output of the distributed power supply unit and step 300 of resetting the third flag indicating whether or not an abnormality of the CT sensor due to forced charging is detected when the determination of step 150 becomes affirmative. A step 302 for performing a check by forced charging and a step 304 for executing a check by forced charging are included. In this forced charge check, the third flag is set when an abnormality is detected, and the third flag is kept reset otherwise.

This program further branches the control flow depending on whether or not the third flag is set after the processing of step 304 is completed, and when the determination of step 306 is YES, 7 shown in FIG. Step 152 to control the segment display 116 to display a predetermined error code, and after step 152, the distributed power supply unit 68 is protected and stopped, the distributed power output is stopped, and the execution of this program is terminated. And include.

The program further resumes and controls the output of the distributed generation unit when the determination in step 306 is negative, that is, when the forced charging check performed in step 304 does not detect an abnormality in the CT sensor. Includes step 308 to return to step 140.

FIG. 11 shows a control structure of a routine that realizes step 304 of FIG. With reference to FIG. 11, this routine uses step 350 to set the repeat control variable i, which stores the number of repeats of detection in a process described below, to 0, and uses the CT sensor 70 and CT sensor 72 before the start of charging. Step 352 for measuring the peak power, step 354 for starting the forced charging of the storage battery at 1 kW, and step 356 for measuring the peak power after the start of charging after a predetermined time has elapsed from the start of the forced charging by the step 354. Includes step 358 to stop forced charging.

The program further determines, after step 358, whether the difference between the peak power before the start of forced charging and the peak power after the start of forced charging is within the range of 1 kW ± 0.3 kW, and the difference is within that range. Step 360, which ends the execution of this routine without doing anything if it is inside, step 362, which adds 1 to the repetition variable i when the determination of step 360 is negative, and step 362, which is the result of the processing of the variable i. Includes step 364 to determine if the value is greater than 5. Since the variable i was initially 0, its value after the processing of step 362 indicates how many times steps 352 to 360 were repeated. In step 364, it is determined whether or not the value of the variable i is larger than 5, and the determination in step 364 is YES when the processes of steps 352 to 360 are repeated 6 times.

If the determination in step 364 is negative (that is, the number of repetitions of steps 352 to 360 is less than 6), the control returns to step 352. If affirmative, control proceeds to step 366, sets the third flag, and ends the execution of this routine.

According to the above processing, if the determination in step 360 continues to be negative while the processing in steps 352 to 364 is repeated 6 times, the determination in step 364 becomes affirmative and the third flag is set. At other times, for example, when the determination in step 360 becomes affirmative in the middle, the execution of this routine ends with the third flag reset.

<Operation>
The control unit 80 (see FIG. 1) of the distributed power supply unit according to the second embodiment operates as follows. With reference to FIG. 9, the operation of the control unit 80 from step 140 to step 150 is the same as that of the first embodiment. When the determination in step 150 is YES, the third flag is reset in step 300, and the output of the distributed power supply unit is temporarily stopped in step 302. In step 304, the operation of the CT sensor is checked by forced charging.

With reference to FIG. 11, the value of the repeat control variable indicating the number of retries is initialized to 0 in the first step 350 of the routine for realizing step 304. In step 352, the peak power before the start of charging is measured, and in step 354, forced charging of 1 kW to the storage battery is started. The peak power after the start of charging is measured in step 356, and forced charging is stopped in step 358.

In step 360, it is determined whether or not the value of the peak power measured in step 356 is within the range of the peak power measured in step 352 + 1 kW ± 0.3 kW. If this determination is affirmative, the execution of this routine ends with the third flag reset. On the other hand, if the determination in step 360 is negative, 1 is added to the value of the repeat control variable i in step 362, and it is determined in step 364 whether the value of the variable i is larger than 5. If the determination in step 364 is negative, the control returns to step 352, and the above processing is repeated again.

If the determination in step 364 is affirmative, it is said that the determination that the value of the peak power measured in step 356 is not within the range of the peak power measured in step 352 + 1 kW ± 0.3 kW was repeated 6 times in step 360. It will be. Therefore, in this case, it is considered that an abnormality has occurred in the CT sensor, and the third flag is set in step 366 to end this routine.

With reference to FIG. 9 again, in step 306, it is determined whether the third flag remains reset or is set. If the third flag is reset, the operation of the CT sensor is normal. Therefore, the control proceeds to step 308, restarts the output from the distributed generation unit, and returns the control to step 140. The following is a repetition of normal processing.

On the other hand, if the determination in step 306 is affirmative, it means that an abnormality in the CT sensor was detected in step 304. Therefore, in step 152, the code indicating the connection abnormality of the CT sensor is displayed on the 7-segment display 116 shown in FIG. 2, and in step 154, the distributed power supply unit is protected and stopped, and the execution of the program is terminated.

As described above, in the second embodiment, even when the condition that the effective value of the CT sensor current is less than the threshold value and the frequency of the CT sensor current is out of the predetermined range continues for the detection time or longer, immediately. It is not determined that the operation of the CT sensor is abnormal. Further, the distributed power supply unit is protected and stopped only when an operation abnormality of the CT sensor is similarly detected by the check by forced charging represented by step 304 of FIG. 9 described above. If this is not the case, the output of the distributed generation system will stop once, but will resume immediately and return to the normal state. It is possible to reduce the possibility of erroneously detecting an abnormality in the CT sensor and performing unnecessary protection stop for the distributed power supply unit.

In this embodiment, the amount of change between the power measured before the start of charging and the power measured after the start of charging is within an appropriate range corresponding to the charging power (1 kW) of the CT sensor. It is determined whether or not there is an abnormality in the operation. However, the present invention is not limited to such embodiments. The charging power may be divided into several stages, the same processing may be performed, and the operation abnormality of the CT sensor may be determined by observing the amount of change in power for each of the stages. Further, in the above embodiment, the peak power is measured in the power measurement. However, the present invention is not limited to such embodiments. For example, instead of the peak power, the average power for a predetermined time or the moving average of the power may be used.

[Third Embodiment]
<Structure>
In the first and second embodiments, the CT sensor abnormality detection process is constantly performed. Such processing has the advantage that abnormality detection of the CT sensor can be performed in real time. However, for example, when a photovoltaic power generation device is incorporated in the system, it is preferable to execute the photovoltaic power generation when the photovoltaic power generation is not performed (at night). In the second embodiment, when photovoltaic power generation is performed, the power measurement result at the time of forced charging may be affected by the power generated by the photovoltaic power generation, and the reliability of abnormality detection of the CT sensor may be lowered. be. As a result, there is a possibility that the distributed power supply unit will be protected and stopped even though it is not originally necessary.

In order to avoid such a problem, it is desirable to perform the same treatment as in the second embodiment a predetermined number of times (for example, only once) a day, for example, at night when solar power generation is not performed. Therefore, the third embodiment is an embodiment in which processing for determining an abnormality in the operation of the CT sensor can be performed at any time within a predetermined time at a designated time.

FIG. 12 shows the control structure of the program executed by the control device 80 in the third embodiment in the form of a flowchart. The flowchart shown in FIG. 12 differs from that shown in FIG. 9 in that the third timer for regulating the execution time of the processes from step 144 to step 150 has a third duration (the third timer). Step 380 to be set to (maximum execution time of processing from step 144 to step 150), step 382 to start the third timer, when the determination in step 148 is NO, and the determination in step 150 is NO. In the case of, it is determined whether or not the third timer has expired, and if it has not expired, the control is returned to step 144, including step 384. If the determination in step 384 is affirmative, the execution of this program ends.

In other respects, the program shown in FIG. 12 is the same as that shown in FIG.

In this third embodiment, the upper limit (third duration) of the time required for the processing from step 144 to step 150 is set in advance. This time needs to be longer than either the first duration and the second duration in the first embodiment. By setting the upper limit of the processing time in this way, it is possible to make a determination more than the operation of the CT sensor only once at a desired time.

<Operation>
In this third embodiment, the process of step 380 and step 382 initiates a third duration countdown. One of the conditions that the determination in step 148 is NO and the determination in step 150 is NO is satisfied while the iterative processing of steps 144 to 150 is being executed until the third duration expires. Then, after the expiration of the third duration of step 384, the determination in step 384 becomes YES, and the abnormality determination process of the CT sensor ends. In this case, no abnormality is detected in the operation of the CT sensor. The processes of steps 300 to 308 and steps 152 and 154 are not executed either.

On the other hand, if both the first flag and the second flag are set at any time until the third timer expires, the process of step 300 or less is executed. That is, the third flag is reset in step 300, the output of the distributed power supply unit is stopped in step 302, and the check for abnormal operation of the CT sensor by forced charging is executed in step 304 as in the second embodiment. To. After the processing of step 304 is completed, it is determined in step 306 whether or not the third flag is set. If the third flag is set, the condition that the effective value of the CT sensor current is less than the threshold value and the frequency of the CT sensor current is out of the predetermined range continues for the detection time or longer, and an abnormality due to forced charging is continued. It means that an abnormality was detected in the CT sensor even in the detection process. Therefore, in this case, the processes of step 152 and step 154 are executed, and the distributed power supply unit is protected and stopped. If the third flag is not set, it means that the abnormality detection process by forced charging did not detect the abnormality of the CT sensor, and in step 308, the output of the distributed power supply unit is restarted and the execution of the program is terminated. .. As a result, the distributed generation system returns to normal operation.

In this third embodiment, the abnormality detection process of the CT sensor is always completed within a certain time. If an abnormality is detected in the process, the distributed power supply unit is protected and stopped, and if it is not detected, the distributed power supply unit operates normally. Therefore, instead of constantly monitoring the state of the system in real time, it is possible to perform a process of detecting an abnormality of the CT sensor only a predetermined number of times (for example, once) at night.

In the above description, the third embodiment is suitable when the photovoltaic power generation device is incorporated in the system, but the system of this embodiment is used even when the photovoltaic power generation device is not incorporated. Needless to say, you can do it.

Further, in the program shown in FIG. 12, when steps 300 to 308, steps 152 and 154 are deleted, the program has the same function as that of the first embodiment, and is not in real time, but once within the third timer expiration time. Only the control unit 80 that can detect the operation abnormality of the CT sensor can be realized.

The embodiments disclosed this time are merely examples, and the present invention is not limited to the above-described embodiments. The scope of the present invention is indicated by each claim of the scope of claims, taking into consideration the description of the detailed description of the invention, and all changes within the meaning and scope equivalent to the wording described therein. include.

50 Distributed power supply system 60 systems 62, 64, 66 Load 68 Distributed power supply unit 70, 72 CT sensor 80 Control unit 100, 108, 114 I / O I / F
102 Bus 104 CPU
106 ROM
110 timer 112 RAM
1167 7-segment display 140, 142, 144, 146, 148, 150, 152, 154, 180, 182, 184, 186, 188, 190, 192, 220, 222, 224, 226, 228, 230, 232, 300 , 302, 304, 306, 308, 350, 352, 354, 356, 358, 360, 362, 364, 366, 380, 382, 384 Step 250, 252, 254, 330 Graph

Claims (8)

A power supply unit that supplies power to the lines connected to the grid,
A sensor that detects the current flowing through the line and
Including a control unit that controls the power supply unit based on the current detected by the sensor.
The control unit
A first determination unit that determines whether the operation of the sensor is normal or abnormal based on at least the current frequency of the current detected by the sensor.
A distributed power supply unit including a power supply unit control unit that controls the power supply unit so that the operation of the power supply unit is stopped in response to the detection of an abnormality in the operation of the sensor by the first determination unit. The first determination unit is
A second determination unit for determining whether or not the current frequency is out of the first range, and
1. The first aspect of the present invention includes a third determination unit that determines that the operation of the sensor is abnormal in response to a period in which the determination by the second determination unit is affirmative continues for a predetermined detection time or longer. Distributed power supply unit described in. The distributed power supply unit according to claim 2, wherein the first range is determined according to the specifications of the power supply unit. The distributed power supply unit according to any one of claims 1 to 3, wherein the power supply unit includes at least one of a storage battery, a solar power generation device, and a wind power generation device. The first determination unit includes a real-time determination unit that constantly monitors the output of the sensor and determines in real time whether the operation of the sensor is normal or abnormal based on at least the current frequency of the current detected by the sensor. The distributed power supply unit according to claim 1. The first determination unit monitors the output of the sensor at any time for a specified predetermined time, and the operation of the sensor is normal or abnormal based on at least the current frequency of the current detected by the sensor within the predetermined time. The distributed power supply unit according to claim 1, which includes an occasional determination unit for determining whether or not. It is a control method of a distributed power supply unit connected to a line connected to a system, and the distributed power supply unit includes a power supply unit that supplies electric power to the line and a sensor that detects a current flowing through the line. Including,
The method is
The first determination step of determining whether the operation of the sensor is normal or abnormal based on at least the current frequency of the current detected by the sensor, and
Control of a distributed power supply unit including a control step of controlling the power supply unit to stop the operation of the power supply unit in response to the detection of an abnormality in the operation of the sensor in the first determination step. Method. It is an abnormality determination method in a distributed power supply unit connected to a line connected to a system, and the distributed power supply unit includes a power supply unit that supplies power to the line and a sensor that detects a current flowing through the line. Including
The method is
The first determination step of at least determining whether or not the current frequency of the current detected by the sensor is out of the first range, and
A distributed power source including a second determination step in which the operation of the sensor is determined to be abnormal in response to a period in which the determination in the first determination step is affirmative continues for a predetermined detection time or longer. How to determine the abnormality of the unit.

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