JP6047425B2 - Isolated operation detection device and isolated operation detection method - Google Patents

Description

  The present invention relates to an isolated operation detection device and an isolated operation detection method for detecting isolated operation of a distributed power source that operates in conjunction with a commercial power supply system.

  2. Description of the Related Art In recent years, a power supply device that supplies power from a distributed power source such as a solar cell or a fuel cell to an AC load in conjunction with a commercial power supply system is used. In order to efficiently supply the power of the distributed power source and the power of the commercial power source system to the AC load, a power conditioner is connected between the distributed power source and the commercial power source system.

  A power conditioner is a device that converts generated electric power so that it can be used commercially when using solar cells or fuel cells. The power conditioner supplies surplus power to the commercial power supply system if the generated power is larger than the required power of the AC load. Conversely, if the generated power of the distributed power source is smaller than the required power of the AC load, the power conditioner There are those that receive power from the power supply system and those that supplement only the consumed power and do not supply power to the commercial power supply system.

  Since the power conditioner is connected to the commercial power system and can supply the power generated by the distributed power source to the commercial power system, if the power conditioner does not detect the power outage quickly due to an accident or construction, Electric power is supplied from the side to the commercial power supply system side.

  For this reason, the power conditioner is provided with an isolated operation detection device that detects that the distributed power supply is operating independently when the commercial power supply system fails. For example, there is a conventional isolated operation detection apparatus as shown in Patent Document 1 below.

  The islanding operation detection device of Patent Document 1 has two functions of an active detection function and a passive detection function. The active detection function externally adds disturbance factors such as frequency, reactive power fluctuation and active power fluctuation to the AC power currently output, and based on this externally added disturbance element, This is a function to detect driving. The passive detection function is a function for detecting islanding based on various elements of the AC power currently output, for example, elements of output current and system voltage.

  The isolated operation detection device of Patent Document 1 determines that the distributed power supply is operating independently when it detects isolated operation with at least one of the active detection function and the passive detection function.

Patent No. 4073387

  In the conventional isolated operation detection device as described above, the isolated operation of the distributed power source is determined based on whether or not the frequency fluctuation of the currently output AC power exceeds the reference value. However, the detection of an isolated operation is required to be performed as quickly as possible as well as being as accurate as possible. However, there is still room for improvement in these respects even with the conventional isolated operation detection device as described above.

  An object of the present invention is to provide an isolated operation detection device and an isolated operation detection method that can detect an isolated operation more accurately and quickly.

  An isolated operation detection device for achieving the above object is an isolated operation detection device that detects an isolated operation of a distributed power source that operates in conjunction with a commercial power supply system, and includes a reactive power injection unit, an electric power change period detection unit, an electric power It has a change cycle storage unit, an average power change cycle calculation unit, a power change cycle prediction unit, a deviation calculation unit, and an active islanding determination unit.

  The reactive power injection unit injects reactive power into the commercial power system. The power change period detection unit detects the power change period of the commercial power system. The power change cycle storage unit stores the detected power change cycle. The average power change period calculation unit calculates the average of the past m power change periods. The power change cycle prediction unit predicts the next power change cycle from the past n power change cycles. The deviation calculating unit calculates an average deviation between the predicted power change period and the calculated power change period. The active isolated operation determination unit compares the calculated deviation with a predetermined threshold value and determines that the distributed power source is isolated operation if the deviation exceeds the threshold value. Judge that there is no.

  An isolated operation detection method for achieving the above object is an isolated operation detection method for detecting an isolated operation of a distributed power source that operates in conjunction with a commercial power supply system. It includes a detection step, a power change cycle storage step, an average power change cycle calculation step, a power change cycle prediction step, a deviation calculation step, and an active islanding determination step.

  In the reactive power injection stage, reactive power is injected into the commercial power system. In the power change cycle detection stage, the power change cycle of the commercial power supply system is detected. In the power change cycle storage stage, the detected power change cycle is stored. In the average power change cycle calculation stage, the average of the past m power change cycles is calculated. In the power change cycle prediction stage, the next power change cycle is predicted from the past n power change cycles. In the deviation calculation stage, an average deviation between the predicted power change period and the calculated power change period is calculated. In the active isolated operation determination stage, the calculated deviation is compared with a predetermined threshold, and if the deviation exceeds the threshold, it is determined that the distributed power source is operating alone, and if the deviation does not exceed the threshold, Judge that there is no.

  According to the isolated operation detection device and the isolated operation detection method according to the present invention having the above-described configuration, the next power change cycle is predicted from the past power change cycle, and the distributed power Since the single operation is determined, the single operation of the distributed power source can be detected more accurately and quickly.

It is a block diagram of a power conditioner provided with an isolated operation detection device according to the present invention. It is a block diagram of the isolated operation detection apparatus of FIG. 3 is an operation flowchart of a reactive power injection unit, a power change cycle detection unit, and a power change cycle storage unit shown in FIG. 2. 3 is an operation flowchart of an average power change cycle calculation unit, a power change cycle prediction unit, a deviation calculation unit, a deviation storage unit, and an active islanding determination unit shown in FIG. 2. 5 is a subroutine flowchart of a normal pattern detection process of FIG. It is a subroutine flowchart of the negative pattern detection process of FIG. 3 is an operation flowchart of an average power change period calculation unit, a power change period prediction unit, a frequency change rate calculation unit, and a passive isolated operation determination unit illustrated in FIG. 2. It is a figure where it uses for operation | movement description of the active detection function of the independent operation detection apparatus of FIG. It is a figure which shows the threshold value of the positive pattern and negative pattern which are memorize | stored in the threshold value memory | storage part of FIG. It is a figure with which it uses for operation | movement description of the passive detection function of the isolated operation detection apparatus of FIG.

  Next, an isolated operation detection device and an isolated operation detection method according to the present invention will be described in detail with reference to the drawings.

[Configuration of power conditioner]
FIG. 1 is a block diagram of a power conditioner provided with an isolated operation detection device according to the present invention. The isolated operation detection device detects an isolated operation of a distributed power supply that operates in conjunction with a commercial power supply system.

  The power conditioner 10 is connected to the distributed power supply 20 and the commercial power supply system 30. The distributed power source 20 is a DC power source that can supply DC power, such as a solar cell panel or a fuel cell. The commercial power supply system 30 is a commercial power supply of 50 Hz or 60 Hz connected to a power plant. The power conditioner 10 converts the DC power from the distributed power source 20 into AC power and supplies the AC power to a load (not shown), and converts the DC power from the distributed power source 20 into AC power to convert the load. An interconnected operation function that supplies surplus power to the commercial power supply system, converts DC power from the distributed power supply 20 to AC power, supplies AC power to the load, and supplies insufficient power from the commercial power system And has two functions.

  The power conditioner 10 includes a DC / DC converter 12 that boosts the output voltage of the distributed power source 20 and a DC / AC inverter 14 that converts the boosted voltage into an AC voltage in order to exhibit an independent operation function and an interconnected operation function. And have. The DC / AC inverter 14 is connected to the commercial power supply system 30 via the interconnection relay 16.

  The power conditioner 10 performs an interconnected operation according to the power generation status of the distributed power supply 20 or performs an independent operation according to the power transmission status of the commercial power supply system 30. The power conditioner 10 has an islanding operation detection device 100, quickly recognizes the interconnection operation and the islanding operation, and disconnects the interconnection relay 16 when the islanding operation is detected. For example, if a power failure due to construction occurs in the commercial power supply system 30, the isolated operation detection device 100 quickly detects this power failure so that power is not supplied from the distributed power supply 20 toward the commercial power supply system 30. In addition, the isolated operation detection device 100 disconnects the interconnection relay 16 and disconnects the DC / AC inverter 14 and the commercial power supply system 30.

[Configuration of single operation detection device]
FIG. 2 is a block diagram of the isolated operation detection device of FIG. The isolated operation detection apparatus 100 includes a reactive power injection unit 110, a power change cycle detection unit 120, a power change cycle storage unit 125, an average power change cycle calculation unit 130, a power change cycle prediction unit 140, a deviation calculation unit 150, and a threshold storage unit. 155, deviation storage unit 160, active isolated operation determination unit 165, frequency change rate calculation unit 170, and passive isolated operation determination unit 180.

  The reactive power injection unit 110 injects reactive power into the commercial power supply system 30 so that a power failure in the commercial power supply system 30 can be detected quickly. Reactive power injection uses a commonly used technique.

  The power change cycle detector 120 individually detects both the rise cycle of the voltage of the commercial power supply system 30 and the fall cycle of the voltage, and detects the power change cycle of the commercial power supply system 30. In the present specification, the power change period is detected based on the voltage change of the commercial power supply system 30. In the case of three-phase alternating current, it may be detected by a voltage change of one phase of the three phases, or may be detected by a voltage change of two phases.

  The power change cycle storage unit 125 stores the power change cycle detected by the power change cycle detection unit 120. The power change period stores the rising period of the voltage of the commercial power supply system 30 and the falling period of the voltage separately in time series.

  The average power change cycle calculation unit 130 extracts m power change cycles stored in time series in the power change cycle storage unit 125, and calculates an average of the past m power change cycles. The detailed operation of the average power change period calculation unit 130 will be described later.

  The power change cycle prediction unit 140 takes out n power change cycles stored in time series in the power change cycle storage unit 125, and weights a specific power change cycle among the past n power change cycles. The next power change cycle is predicted by calculating the average of the n power change cycles after weighting. The detailed operation of the power change period prediction unit 140 will be described later.

  The deviation calculation unit 150 calculates a deviation between the power change cycle predicted by the power change cycle prediction unit 140 and the average of the power change cycles calculated by the average power change cycle calculation unit 130. The detailed operation of the deviation calculating unit 150 will be described later.

  The threshold storage unit 155 stores a plurality of thresholds corresponding to each of the plurality of deviations calculated by the deviation calculation unit 150. As shown in FIG. 9, the threshold value storage unit 155 uses a plurality of threshold values corresponding to each of a plurality of deviations as a positive pattern threshold value used when the deviation calculated by the deviation calculation unit 150 is positive, and the deviation is negative. Are stored separately for the negative pattern threshold used. A plurality of threshold values corresponding to each of the plurality of deviations are individually different, and an absolute value of a plurality of threshold values corresponding to each of the plurality of deviations is made smaller as a threshold corresponding to a past deviation is smaller. is there. Further, the threshold storage unit 155 stores a threshold value (frequency change rate and number of times) for comparing the frequency change rate calculated by the frequency change rate calculation unit 170 by the passive islanding operation determination unit 180.

  The deviation storage unit 160 stores a plurality of deviations calculated by the deviation calculation unit 150 in time series.

  The active isolated operation determination unit 165 compares the deviation calculated by the deviation calculation unit 150 with a predetermined threshold value stored in the threshold value storage unit 155, and if the deviation exceeds the threshold value, the distributed power source 20 operates independently. If the deviation does not exceed the threshold value, it is determined that the distributed power source 20 is not operating alone. In addition, the active islanding determination unit 165 compares the plurality of deviations stored in the deviation storage unit 160 in time series with a plurality of threshold values corresponding to each of the plurality of deviations stored in the threshold storage unit 155. If all of the plurality of deviations exceed a plurality of thresholds corresponding to each of the plurality of deviations, it is determined that the distributed power source 20 is operating independently, and one of the plurality of deviations also corresponds to the deviation. If it does not exceed the threshold value, it is determined that the distributed power source 20 is not operating alone. Further, when the deviation calculated by the deviation calculating unit 150 is positive, the active isolated operation determination unit 165 uses the positive pattern threshold value stored in the threshold value storage unit 155 to determine whether the distributed power source 20 is operated independently. When the deviation calculated by the deviation calculation unit 150 is negative, the judgment of whether or not the distributed power source 20 is operated independently is determined using the negative pattern threshold value stored in the threshold value storage unit 155.

  The frequency change rate calculation unit 170 calculates the frequency change rate from the average power change cycle calculated by the average power change cycle calculation unit 130 and the next power change cycle predicted by the power change cycle prediction unit 140. Moreover, the frequency change rate calculation unit 170 calculates the frequency change rate with respect to each power change cycle using the power change cycle predicted by the power change cycle prediction unit 140.

  The passive islanding determination unit 180 stores the frequency change rate calculated every time the next power change cycle predicted by the power change cycle prediction unit 140 is stored in the threshold storage unit 155 a plurality of times. The frequency change rate calculated every time the next power change period is calculated, it is determined that the distributed power source 20 is in a single operation if the frequency change direction is the same for a plurality of times. If the threshold value is not exceeded continuously for a plurality of times or the direction of frequency change for a plurality of times is not the same, it is determined that the distributed power source 20 is not in a single operation. Moreover, the passive isolated operation determination unit 180 determines whether the distributed power supply 20 is operated independently using the frequency change rate calculated individually for the power change period predicted by the power change period prediction unit 140.

[Operation of isolated operation detector]
The general configuration of the isolated operation detection device 100 is as described above. Next, the operation of the isolated operation detection device 100 will be described with reference to FIGS. The operation of the isolated operation detection device 100 described below is the same as the procedure of the isolated operation detection method according to the present invention.

<Active detection function>
FIG. 3 is an operation flowchart of the reactive power injection unit 110, the power change cycle detection unit 120, and the power change cycle storage unit 125.

  The reactive power injection unit 110 injects reactive power toward the commercial power supply system 30 (step S100). The reactive power is injected by the following procedure. First, the difference between the moving average of the power change period detected by the power change period detection unit 120, for example, for 80 msec before 200 msec, and the moving average of the power change period from the present to 40 msec is obtained as a frequency deviation. Next, the reactive power injection amount corresponding to the magnitude of the frequency deviation is calculated, and the calculated reactive power injection amount is injected toward the commercial power supply system 30 while changing the current phase in order to keep the active power constant. To do.

  The power change period detection unit 120 detects the power change periods Ta and Tb of the commercial power supply system 30 (step S110). As shown in FIG. 8, the power change cycle detection unit 120 detects a cycle from a voltage rise from the zero cross of the commercial power supply system 30 to a voltage rise from the next zero cross as a Ta-based power change cycle. Then, the period from the fall of the voltage from the zero cross of the commercial power supply system 30 to the fall of the voltage from the next zero cross is detected as a Tb system power change period. That is, the power change period detection unit 120 individually detects the Ta-based power change period and the Tb-based power change period.

  The power change cycle storage unit 125 stores the detected Ta-based and Tb-based cycles (step S120). The power change cycle storage unit 125 individually stores the Ta-based power change cycle and the Tb-based power change cycle detected by the power change cycle detection unit 120 in time series.

  FIG. 4 is an operation flowchart of the average power change period calculation unit 130, the power change period prediction unit 140, the deviation calculation unit 150, the deviation storage unit 160, and the active isolated operation determination unit 165.

  The average power change period calculation unit 130 calculates an average period of m power change periods up to a predetermined time (step S200). In the present embodiment, m is 7. The average power change cycle calculation unit 130 separately extracts the Ta-based power change cycle and the Tb-based power change cycle stored in the power change cycle storage unit 125. Specifically, as shown in FIG. 8, with respect to the Ta system, data of power change period for 7 times from 200 msec before (corresponding to 10 times of power change period at 50 Hz), Ta (N-10), Ta Seven power change periods of (N-11),..., Ta (N-15), Ta (N-16) are taken out. At the same time, for the Tb system, seven power change periods of Tb (N-10), Tb (N-11),..., Tb (N-15), Tb (N-16) are taken out.

  Next, the average power change period calculation unit 130 calculates [Ta (N−10) + Ta (N−11) +... + Ta (N−15) + Ta (N−16)] / 7 for the Ta system. The average Taave of the Ta-based power change period is calculated. At the same time, the average power change period calculation unit 130 calculates [Tb (N−10) + Tb (N−11) +... + Tb (N−15) + Tb (N−16)] / 7 for the Tb system to calculate Tb. The average Tbave of the power change period of the system is calculated. In the above example, the average of the power change periods is obtained using all of the seven power change periods. However, in order to improve reliability, the maximum and minimum two power change periods of the seven power change periods are obtained. And the average of the power change periods may be calculated using the remaining five power change periods.

  The power change cycle prediction unit 140 calculates a prediction cycle from n power change cycles before the current time (step S210). In this embodiment, n is 5. The power change cycle prediction unit 140 separately extracts the Ta-based power change cycle and the Tb-based power change cycle stored in the power change cycle storage unit 125. Specifically, as shown in FIG. 8, for the Ta system, data of the power change period for five times from the present time, Ta (N), Ta (N-1), Ta (N-2), Ta (N- 3) Five power change periods of Ta (N-4) are taken out. At the same time, five power change periods of Tb (N), Tb (N-1), Tb (N-2), Tb (N-3), and Tb (N-4) are extracted from the Tb system.

Next, the power change cycle prediction unit 140 performs the following calculation to calculate a power change prediction cycle. In particular,
The Ta-based prediction cycle Ta (N + 1) is
Prediction period Ta (N + 1) = Ta (N) + [{Ta (N) -Ta (N-1)} +
2 * {Ta (N-1) -Ta (N-2)} + 2 * {Ta (N-2) -Ta (N-3)} +
{Ta (N-3) -Ta (N-4)}] / 6
By calculating
The prediction period Tb (N + 1) of the Tb system is
Prediction period Tb (N + 1) = Tb (N) + [{Tb (N) -Tb (N-1)} +
2 * {Tb (N-1) -Tb (N-2)} + 2 * {Tb (N-2) -Tb (N-3)} +
{Tb (N-3) -Tb (N-4)}] / 6
Is calculated by calculating

  The above calculation refers to the Lung Getter quartic equation, weights a specific power change period, and predicts a future power change period from a past power change period by a differential equation.

  The deviation calculation unit 150 calculates the deviation between the average period and the prediction period (step S220).

Specifically, for the Ta system, since the average of the power change period is Taave and the prediction period is Ta (N + 1), the deviation diffTa (N) is
Calculate by calculating diffTa (N) = Taave−Ta (N + 1). For the Tb system, the average of the power change period is Tbave and the prediction period is Tb (N + 1), so the deviation diffTb (N) is
Calculate by calculating diffTb (N) = Tbave−Tb (N + 1).

  The deviation diffTa (N) and the deviation diffTb (N) have positive or negative values.

  The deviation calculation unit 150 stores the deviation diffTa (N) and the deviation diffTb (N) obtained in step S220 in the deviation storage unit 160 in time series (step S230).

  The deviation calculation unit 150 determines whether the deviation diffTa (N) and the deviation diffTb (N) calculated in step S220 are positive or negative (step S240).

  If the deviation diffTa (N) and the deviation diffTb (N) are positive (step S240: YES), the active isolated operation determination unit 165 executes the positive pattern detection process of step S250, and if negative (step S240). : NO), the negative pattern detection process of step S260 is executed. When the deviation diffTa (N) is positive and the deviation diffTb (N) is negative, the positive pattern detection processing in step S250 is executed for the deviation diffTa (N), and the negative diffTb (N) is negative in step S260. Perform pattern detection processing. When the deviation diffTa (N) is negative and the deviation diffTb (N) is positive, the negative pattern detection process of step S260 is executed for the deviation diffTa (N), and the positive pattern detection of step S250 is performed for diffTb (N). Execute the process.

  FIG. 5 is a subroutine flowchart of the normal pattern detection process of FIG. FIG. 6 is a subroutine flowchart of the negative pattern detection process of FIG.

  When the deviation diffTa (N) and the deviation diffTb (N) are positive, the active islanding determination unit 165 extracts p deviations before the current time from the deviation storage unit 160, and sets the extracted p deviations as a threshold value. The threshold value stored in the storage unit 155 is compared (step S250-1). In this embodiment, p is 5.

  Specifically, as shown in FIG. 8, the active islanding operation determination unit 165 receives, as a Ta system, diffTa (N), diffTa (N−1), diffTa (N−2), diffTa (N-3) and diffTa (N-4) are Tb systems, and diffTb (N), diffTb (N-1), diffTb (N-2), diffTb (N-3), diffTb (N-4) ).

  Next, the active islanding determination unit 165 stores the threshold values Thp (N), Thp (N−1), Thp (N−2) of the positive patterns as shown in FIG. 9 stored in the threshold storage unit 155. ), Thp (N-3), Thp (N-4), and these are extracted from the deviation storage unit 160 as diffTa (N), diffTa (N-1), diffTa (N-2), diffTa (N -3), diffTa (N-4) and diffTb (N), diffTb (N-1), diffTb (N-2), diffTb (N-3), and diffTb (N-4).

  Specifically, for the Ta system, the magnitude relation between the threshold Thp (N) and the deviation diffTa (N) is compared, and the magnitude relation between the threshold Thp (N-1) and the deviation diffTa (N-1) is compared. Similarly, the threshold Thp (N−2) and the deviation diffTa (N−2), the threshold Thp (N−3) and the deviation diffTa (N−3), the threshold Thp (N−4) and the deviation diffTa (N− Compare 4).

  For the Tb system, the magnitude relationship between the threshold Thp (N) and the deviation diffTb (N) is compared, and the magnitude relationship between the threshold Thp (N-1) and the deviation diffTb (N-1) is compared. Threshold Thp (N-2) and deviation diffTb (N-2), threshold Thp (N-3) and deviation diffTb (N-3), threshold Thp (N-4) and deviation diffTb (N-4). Compare.

  The active isolated operation determination unit 165 determines whether or not all of the compared deviations are larger than the corresponding threshold values (step S250-2).

  When all the compared deviations are larger than the threshold value (step S250-2: YES), the active isolated operation determination unit 165 determines that a power failure has occurred in the commercial power supply system 30 and that the distributed power supply 20 is in isolated operation. Then, the interconnection relay 16 is disconnected and the commercial power supply system 30 is disconnected (step S250-3). On the other hand, if any of the compared deviations is not greater than the threshold value (step S250-2: NO), it is determined that the operation is not an independent operation, and the connection of the interconnection relay 16 is maintained (step S250-). 4).

  When the deviation diffTa (N) and the deviation diffTb (N) are negative, the active islanding determination unit 165 extracts p deviations before the current time from the deviation storage unit 160, and sets the extracted p deviations as a threshold value. The threshold value stored in the storage unit 155 is compared (step S260-1).

  Specifically, as shown in FIG. 8, the active islanding operation determination unit 165 receives, as a Ta system, diffTa (N), diffTa (N−1), diffTa (N−2), diffTa (N-3) and diffTa (N-4) are Tb systems, and diffTb (N), diffTb (N-1), diffTb (N-2), diffTb (N-3), diffTb (N-4) ).

  Next, the active islanding determination unit 165 stores the negative pattern threshold values Thn (N), Thn (N−1), and Thn (N−2) as shown in FIG. 9 stored in the threshold value storage unit 155. ), Thn (N-3), Thn (N-4), and these are extracted from the deviation storage unit 160 as diffTa (N), diffTa (N-1), diffTa (N-2), diffTa (N -3), diffTa (N-4) and diffTb (N), diffTb (N-1), diffTb (N-2), diffTb (N-3), and diffTb (N-4).

  Specifically, for the Ta system, the magnitude relationship between the threshold value Thn (N) and the deviation diffTa (N) is compared, and the magnitude relationship between the threshold value Thn (N-1) and the deviation diffTa (N-1) is compared. Similarly, the threshold value Thn (N-2) and the deviation diffTa (N-2), the threshold value Thn (N-3) and the deviation diffTa (N-3), the threshold value Thn (N-4) and the deviation diffTa (N- Compare 4).

  For the Tb system, the magnitude relation between the threshold Thn (N) and the deviation diffTb (N) is compared, the magnitude relation between the threshold Thn (N-1) and the deviation diffTb (N-1) is compared, and the same Threshold value Thn (N-2) and deviation diffTb (N-2), threshold value Thn (N-3) and deviation diffTb (N-3), threshold value Thn (N-4) and deviation diffTb (N-4) Compare.

  The active isolated operation determination unit 165 determines whether or not all of the compared deviations are smaller than the corresponding threshold values (step S260-2).

  When all of the compared deviations are smaller than the threshold (step S260-2: YES), the active isolated operation determination unit 165 determines that a power failure has occurred in the commercial power supply system 30 and that the distributed power supply 20 is in isolated operation. Thus, the interconnection relay 16 is disconnected and the commercial power supply system 30 is disconnected. Further, the gate of the DC / AC inverter 14 (see FIG. 1) is blocked. That is, no switching signal is given to the gate of the inverter 14 (step S260-3). On the other hand, when any one of the compared deviations is not smaller than the threshold value (step S260-2: NO), it is determined that the operation is not an independent operation, and the connection of the interconnection relay 16 is maintained. Further, the gate of the DC / AC inverter 14 (see FIG. 1) is switched as usual without blocking (step S260-4).

  As described above, the active detection function forcibly injects reactive power into the commercial power supply system 30, detects a power failure in the commercial power supply system 30 due to fluctuations in the voltage change of the commercial power supply due to the injection of reactive power, and distributes the power. An isolated operation of the power supply 20 is detected.

<Passive detection function>
FIG. 7 is an operation flowchart of the average power change cycle calculation unit 130, the power change cycle prediction unit 140, the frequency change rate calculation unit 170, and the passive islanding operation determination unit 180.

  The average power change period calculation unit 130 calculates an average period of q power change periods before the current time (step S300). In the present embodiment, q is 25. The average power change cycle calculation unit 130 separately extracts the Ta-based power change cycle and the Tb-based power change cycle stored in the power change cycle storage unit 125. Specifically, as shown in FIG. 10, for the Ta system, data on the power change period for 25 times from the present time, Ta (N), Ta (N−1),..., Ta (N-23), Ta ( N-24), 25 power change periods. At the same time, 25 power change periods of Tb (N), Tb (N-1),..., Tb (N-23), Tb (N-24) are extracted from the Tb system.

  Next, the average power change period calculation unit 130 calculates [Ta (N) + Ta (N−1) +... + Ta (N−23) + Ta (N−24)] / 25 with respect to the Ta system. The average Taave of the power change period is calculated. At the same time, the average power change period calculation unit 130 calculates [Tb (N) + Tb (N−1) +... + Tb (N−23) + Tb (N−24)] / 25 for the Tb system. The average Tbave of the power change period is calculated.

  The power change cycle prediction unit 140 calculates a prediction cycle from q power change cycles before the current time (step S310). The calculation of the prediction cycle is the same as step S210 in FIG. 4 except that the number of power change cycles is different.

  The frequency change rate calculation unit 170 calculates the frequency change rate from the average period and the prediction period (step S320). The frequency change rate is obtained for each of the Ta system and the Tb system. It is calculated by calculating Ta-based frequency change rate A = (average period−predicted period) / average period. The frequency change rate B of the Tb system is calculated in the same way.

  The passive islanding determination unit 180 compares each of the Ta-based and Tb-based frequency change rates A and B calculated by the frequency change rate calculation unit 170 with the threshold value stored in the threshold value storage unit 155. (Step S330). The threshold storage unit 155 stores a plurality of thresholds such as 0.2%, 0.3%, 0.4%, and 0.5%. The threshold used for comparison is selected by a selection switch. In this embodiment, 0.3% is selected. Accordingly, it is compared whether each of the Ta-based and Tb-based frequency change rates A and B is greater than 0.3%.

  If each of the frequency change rate A and the frequency change rate B is larger than 0.3% of the threshold (step S330: YES), the passive islanding determination unit 180 proceeds to the next step. The large frequency change rate is because the possibility that the commercial power supply system 30 has failed is high. On the other hand, if it is not larger than 0.3% of the threshold (step S330: NO), it is determined that it is not an independent operation, and the DC / AC inverter 14 (see FIG. 1) is switched as usual without blocking the gate. (Step S360).

  If each of the frequency change rate A and the frequency change rate B is larger than 0.3% of the threshold (step S330: YES), the passive islanding determination unit 180 changes the change direction of the frequency change rate A and the frequency change rate B. It is determined whether or not the number of consecutive times r stored in the threshold value storage unit 155 has been reached with the same (positive and negative signs) (step S340). When the frequency change rate A and frequency change rate B in the same change direction exceeding the threshold value continue r times (S340: YES), a power failure occurs in the commercial power supply system 30, and the distributed power supply 20 is operating independently. The interconnection relay 16 is disconnected and the commercial power supply system 30 is disconnected. Further, the gate of the DC / AC inverter 14 (see FIG. 1) is blocked. That is, no switching signal is given to the gate of the inverter 14 (step S350). On the other hand, when the frequency change rate A and the frequency change rate B in the same change direction exceeding the threshold value do not continue r times, it is determined that the operation is not an independent operation, and the connection of the interconnection relay 16 is maintained. Further, the gate of the DC / AC inverter 14 (see FIG. 1) is switched as usual without blocking (step S360). The reason for confirming that the frequency change rate exceeding the threshold value exceeds a certain number is to remove noise and prevent uncertain isolated operation. However, if the number of times is set large, the detection timing of the isolated operation is delayed. Therefore, the number of times to be stored in the threshold storage unit 155 is set to a number that satisfies the detection reliability and the detection speed.

  As described above, in order to detect an isolated operation, the frequency of the commercial power supply system is measured to detect a change in the frequency of a minute time. Up to now, the past average and the latest average of frequency change are compared to determine whether the frequency is increasing or decreasing, and it is determined that the vehicle is operating independently when the frequency is increasing or decreasing. To do. However, in the present invention described above, the isolated operation is determined by comparing the past average frequency change and the future frequency change after one cycle. For this reason, the detection time of an isolated operation becomes short. Further, since the isolated operation is detected by comparing the frequency deviation with the threshold value, the detection accuracy of the isolated operation is improved. Furthermore, since the isolated operation is detected using the two functions of the active detection function and the passive detection function, it is possible to reliably detect the isolated operation.

10 Power conditioner,
12 DC / DC converter,
14 DC / AC inverter,
16 interconnection relay,
20 Distributed power supply,
30 Commercial power system,
100 islanding detection device,
110 reactive power injection unit,
120 power change period detector,
130 power change cycle storage unit,
130 average power change period calculation unit,
140 Power change period prediction unit,
150 deviation calculator,
155 threshold storage unit,
160 deviation storage unit,
165 Active isolated operation determination unit,
170 Frequency change rate calculation unit,
180 Passive islanding determination unit.

Claims (12)

An isolated operation detection device for detecting isolated operation of a distributed power supply that operates in conjunction with a commercial power supply system,
A reactive power injection unit for injecting reactive power into the commercial power supply system;
A power change period detector for detecting a power change period of the commercial power system;
A power change cycle storage unit for storing the detected power change cycle;
An average power change period calculating unit for calculating an average of the past m power change periods;
A power change period prediction unit that predicts the next power change period from the past n power change periods;
A deviation calculating unit that calculates an average deviation between the predicted power change period and the calculated power change period;
The calculated deviation is compared with a predetermined threshold value, and if the deviation exceeds the threshold value, it is determined that the distributed power source is operating alone, and if the deviation does not exceed the threshold value, it is determined that it is not operating independently. An active islanding determination unit that
An isolated operation detection device comprising: A deviation storage unit for storing a plurality of deviations calculated by the deviation calculation unit in time series;
A threshold storage unit that stores a plurality of thresholds corresponding to each of the plurality of deviations;
Further comprising
The active islanding determination unit includes:
Comparing a plurality of deviations stored in time series with a plurality of thresholds corresponding to each of the plurality of deviations, if all of the plurality of deviations exceed a plurality of thresholds corresponding to each of the plurality of deviations, the distributed power source is independent 2. The isolated operation detection device according to claim 1, wherein it is determined that the operation is performed, and if one of the plurality of deviations does not exceed a threshold corresponding to the deviation, it is determined that the operation is not performed independently. . The threshold storage unit
A plurality of threshold values corresponding to each of the plurality of deviations, a positive pattern threshold value used when the deviation calculated by the deviation calculation unit is positive, and a negative pattern threshold value used when the deviation is negative, Divided into memory,
The active islanding determination unit includes:
When the deviation calculated by the deviation calculation unit is positive, it is determined whether the single operation is performed using the positive pattern threshold value. When the calculated deviation is negative, the determination is performed based on the negative pattern threshold value. The isolated operation detection device according to claim 2, wherein:   The isolated operation detection apparatus according to claim 2 or 3, wherein the plurality of threshold values corresponding to each of the plurality of deviations are individually different.   The isolated operation detection apparatus according to claim 4, wherein an absolute value of a plurality of threshold values corresponding to each of the plurality of deviations is smaller as the threshold value corresponds to a past deviation. The power change period prediction unit
Weighting a specific power change cycle among the past n power change cycles, and predicting the next power change cycle by calculating an average of the n power change cycles after weighting The isolated operation detection device according to any one of claims 1 to 5. further,
A frequency change rate calculating unit that calculates a frequency change rate from an average of the power change cycle calculated by the average power change cycle calculating unit and a next power change cycle predicted by the power change cycle predicting unit;
If the frequency change rate calculated each time the next power change period is calculated exceeds the threshold value continuously for a plurality of times and the direction of the frequency change for a plurality of times is the same, the distributed power source is operated independently. A passive single operation determination unit that determines that it is not a single operation unless the threshold is continuously exceeded multiple times or the direction of frequency change of multiple times is not the same, and
The isolated operation detection device according to any one of claims 1 to 6, further comprising: The power change period detector is
The islanding operation detection device according to any one of claims 1 to 7, wherein both the period of rise of the voltage of the commercial power supply system and the period of fall of the voltage are individually detected. The power change cycle storage unit is
9. The islanding operation detection device according to claim 8, wherein a rise period of the voltage of the commercial power supply system and a fall period of the voltage are separately stored in time series.   The average power change cycle calculation unit, the power change cycle prediction unit, and the deviation calculation unit are individually detected from both the rising cycle of the voltage of the commercial power supply system and the falling cycle of the voltage 2 Using one power change period, the average of the power change period, the prediction of the next power change period, and the average deviation of the power change period for each power change period are calculated. The isolated operation detection device according to claim 9, wherein whether or not an isolated operation is performed is determined using a deviation calculated individually for each of the two power change periods. The frequency change rate calculation unit includes:
The frequency change rate for each power change cycle is calculated using the two power change cycles, and the passive islanding determination unit uses the frequency change rates calculated individually for the two power change cycles. The isolated operation detection device according to claim 7 , wherein whether or not isolated operation is appropriate is determined. An isolated operation detection method for detecting isolated operation of a distributed power supply that operates in conjunction with a commercial power supply system,
A reactive power injection step of injecting reactive power into the commercial power system;
A power change period detecting step for detecting a power change period of the commercial power supply system;
A power change cycle storage stage for storing the detected power change cycle;
A power cycle average calculation stage for calculating an average of the past m power change cycles;
A power change period prediction step for predicting a next power change period from the past n power change periods;
Deviation calculation stage for calculating an average deviation between the predicted power change period and the calculated power change period;
The calculated deviation is compared with a predetermined threshold value, and if the deviation exceeds the threshold value, it is determined that the distributed power source is operating alone, and if the deviation does not exceed the threshold value, it is determined that it is not operating independently. An independent operation determination stage to perform,
An islanding operation detection method comprising:

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