JP2012070611A - Isolated operation detection method, power conditioner and distributed power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect isolated operation reliably.SOLUTION: The isolated operation detection method for detecting isolated operation of a distributed power supply in a distributed power supply system comprising a distributed power supply and a power conditioner includes a first step for dividing each period of the system voltage or the system output current output from the power conditioner and linked with a system power supply into multiple time intervals, a second step for feeding a system output current from the power conditioner during the multiple time intervals of each period so as to produce a difference between system interconnection operation and isolated operation, a third step for measuring the difference of the time intervals by the magnitude or including the code, and a fourth step for determining that it is not isolated operation but system interconnection operation when the number of times of continuous measurement is less than a predetermined number of times, otherwise determining that it is isolated operation.

Description

  The present invention relates to an isolated operation detection method for detecting whether or not a distributed power source is disconnected from a commercial power source and is operating alone, converts the direct current power of the distributed power source into alternating current power, and connects the power system to the power system. The present invention relates to a power conditioner that supplies power to a power source and a distributed power supply system including the power conditioner.

  The isolated operation in the distributed power supply system is a state in which power is supplied from the distributed power supply to the system load while the commercial power supply is stopped. In this way, when a single operation for supplying power to a load with only a distributed power source is performed, a system that should be essentially voltageless is charged, which may cause various problems in terms of security. Therefore, it is necessary to prevent the occurrence of the above problem by detecting the isolated operation of the distributed power source.

  As a method of detecting the isolated operation of such a distributed power source, a system that monitors the system voltage and detects a change that appears during an isolated operation in the event of a system power failure, and a variation in the system voltage from the distributed power source side. There is an active method in which a disturbance signal (active signal) is applied to give a change, and a change that appears at the time of a single operation in the case of a system power failure is detected. In addition, there are many patent documents of isolated operation detection.

JP 2010-074943 A

  A typical example of the active method is a frequency shift method. In this method, the output frequency is shifted in a period lower than the period of the fundamental wave of the system, and if there is a change in the system frequency, the shift direction is fixed. .If it lasts for 5 seconds, the gate block and the interconnection relay will be disconnected.

  Another representative example of the active method is a reactive power fluctuation method. In this method, the reactive power is changed at a period lower than the fundamental wave of the system, and if the system frequency change of a predetermined value or more continues for a predetermined time or more, it is determined as an independent operation, and the gate block and the interconnection relay are disconnected. It is.

  However, in these systems, when a plurality of them are connected to the distributed power source, there is a concern that the isolated operation detection performance deteriorates when the active signals interfere with each other.

  Another example of the active method is a slip mode frequency shift method. In this method, by giving a characteristic that shifts the frequency of the output current according to the frequency change from the rated frequency, the frequency is changed by positively feeding back the minute frequency change that occurs even when active and reactive power are balanced, When a predetermined frequency is reached, it is determined that the operation is independent, and the gate block and the interconnection relay are disconnected.

  However, in the case of this method, since there is no active signal, when the power generated by the distributed power source is equal to the load power and no current is flowing through the system, there is a possibility that the isolated operation cannot be detected because the frequency does not change. On the other hand, when there is no frequency fluctuation and an increase in voltage or harmonic is detected, a method is adopted in which reactive power is step-injected to generate a frequency change. If no increase is detected, this cannot be done, and there is a possibility that isolated operation cannot be detected.

  The present invention has been made to solve the above-described problems of the active method, and includes an isolated operation detection method capable of reliably detecting an isolated operation, a power conditioner that implements this method, and the power conditioner. A distributed power supply system is provided.

The isolated operation detection method according to the first aspect of the present invention includes:
A distributed power source and a power conditioner that converts the DC power of the distributed power source into AC power, and the AC power converted by the power conditioner is connected to the power of the power system line and supplied to the system load Type power supply system,
A method for detecting isolated operation of the distributed power source, comprising first to fourth steps,
The first step is a step of dividing each cycle of the system voltage or system output current output from the power conditioner and linked to the system power source into a plurality of time intervals.
The second step is a step of causing the grid output current to flow from the power conditioner so that a difference occurs between the grid interconnection operation or the single operation in the plurality of time intervals within each cycle.
The third step is a step of measuring the difference or sum of the time intervals in magnitude, or measuring the difference of the time intervals including a sign,
In the fourth step, when the measurement is measured by the difference or the sum of the time intervals, when the measured number of times that the measured value is greater than or equal to a predetermined value is less than the predetermined number, While it is determined that it is connected to the grid rather than driving, it is determined to be an independent operation when it is more than a predetermined number of times,
When measuring including the sign,
When the sign of the measured value is positive, the upper limit value of the positive value is a predetermined value, and when the number of continuous measurements that the value is equal to or greater than the predetermined value is less than the predetermined number, While it is determined that the system is connected
When the sign of the measured value is negative, the negative lower limit value is a predetermined value, and when the measured number of times that the measured value is less than or equal to the predetermined value is less than the predetermined number, it is not an isolated operation. While it is determined that the grid is connected, when it is a predetermined number of times or more, it is a step to determine that it is an independent operation,
It is characterized by that.

The isolated operation detection method according to the second aspect of the present invention includes:
A distributed power source and a power conditioner that converts the DC power of the distributed power source into AC power, and the AC power converted by the power conditioner is connected to the power of the power system line and supplied to the system load Type power supply system,
A method for detecting isolated operation of the distributed power source, comprising first to fourth steps,
The first step is a step of dividing each cycle of the system voltage or system output current output from the power conditioner and linked to the system power source into a plurality of time intervals.
The second step is a step of causing the grid output current to flow from the power conditioner so that a difference occurs between the grid interconnection operation or the single operation in the plurality of time intervals within each cycle.
The third step is a step of measuring the difference or sum of the time intervals by a magnitude or measuring the difference of the time intervals including a sign,
In the fourth step, when the measurement is performed with the difference between the time intervals or the sum, the number of measurements that the measured value is greater than or equal to a predetermined value is less than the predetermined number within a predetermined time. When it is determined that the system is connected to the grid rather than a single operation, when the number of times is a predetermined number of times or more within the predetermined time, it is determined to be a single operation,
When measuring including the sign,
When the sign of the measured value is positive, the upper limit value of the positive value is a predetermined value, and the number of times that the value is greater than or equal to the predetermined value is less than the predetermined number of times within a predetermined time. On the other hand, when the number of times is more than a predetermined number within the predetermined time, it is determined that the operation is independent,
When the sign of the measured value is negative, the lower limit of the negative value is a predetermined value, and the number of times that the measured value is less than or equal to the predetermined value is less than the predetermined number of times within a predetermined time. On the other hand, it is determined that the system is connected to the grid instead of the operation.
It is a step.

The isolated operation detection method according to the third aspect of the present invention includes:
A distributed power source and a power conditioner that converts the DC power of the distributed power source into AC power, and the AC power converted by the power conditioner is connected to the power of the power system line and supplied to the system load Type power supply system,
A method for detecting isolated operation of the distributed power source, comprising first to fourth steps,
The first step is a step of dividing each cycle of the system voltage or system output current output from the power conditioner and linked to the system power source into a plurality of time intervals.
The second step is a step of causing the grid output current to flow from the power conditioner so that a difference occurs between the grid interconnection operation or the single operation in the plurality of time intervals within each cycle.
The third step is a step of measuring the difference or sum of the time intervals by a magnitude or measuring the difference of the time intervals including a sign,
In the fourth step, when the measurement is measured by the difference or sum of the time intervals, the measurement time is determined to be greater than or equal to the predetermined value, and the measurement time is less than the predetermined time within the predetermined time. Is determined to be grid-connected rather than isolated, while it is determined to be isolated when it is greater than or equal to a predetermined time within the predetermined time,
When measuring including the sign,
When the sign of the measured value is positive, the upper limit value of the positive value is a predetermined value, and when the time of measurement that the value is equal to or greater than the predetermined value is less than the predetermined time within the predetermined time, the operation is performed independently. On the other hand, when it is determined that it is grid-connected, when it is a predetermined time or more within the predetermined time, it is determined as an isolated operation,
When the sign of the measured value is negative, the lower limit value of the negative value is a predetermined value, and when the measured time is less than the predetermined time within the predetermined time On the other hand, it is determined that it is connected to the grid instead of driving, and when it is not less than a predetermined time within the above predetermined time, it is determined that it is a single operation.
It is a step.

In the first to third aspects of the present invention,
Preferably, the first step is divided into two, that is, a first time interval in which a positive voltage continues continuously and a second time interval in which a negative voltage continues continuously in one cycle of the system voltage. It is a step.

  Preferably, in the second step, in each one period of the system voltage, the system output current is set to the sum of the fundamental current and the harmonic current each having one period as one period. In this step, the current to be output is supplied to the system so that a difference occurs between the grid connection operation and the single operation.

  Preferably, in the second step, a grid output current that changes the amplitude of the grid output current at the first time interval and the second time interval for each cycle of the grid output current is supplied.

  Preferably, the second step is a step in which, within each period of the system output current, the system output current is a sum of a fundamental wave current having one period as one period and the even-order harmonic current. It is.

  Preferably, when the second step is the sum of the fundamental current and the even-order harmonic current, each of which is one cycle, within each cycle of the grid output current. The step of increasing the even-order harmonic current so that a difference occurs between the grid interconnection operation and the single operation in the plurality of time intervals in each cycle.

  Preferably, the third step measures the difference or sum of the first time interval and the second time interval in magnitude, or measures the difference between the first time interval and the second time interval including a sign. It is.

A power conditioner according to a fourth aspect of the present invention is a power conditioner that converts DC power of a distributed power source into AC power,
An inverter unit that converts a DC input voltage output from a distributed power source into an AC voltage and outputs the AC voltage;
An LC filter unit that smoothes the AC output voltage of the inverter unit and shapes the output waveform into a sinusoidal waveform;
A disconnecting relay interposed between the inverter unit and the power source of the power system line;
Each cycle of the system voltage from the inverter section is divided into a plurality of time intervals, and the power conditioner produces a difference between the grid connection operation or the single operation at the plurality of time intervals within each cycle. A control unit for controlling on / off of the plurality of switching elements in the inverter unit so as to flow the system output current,
The difference or sum of the time intervals is measured from the system output current flowing from the LC filter unit in synchronization with each cycle of the system voltage, or the difference of the time intervals is measured including a sign. A measurement unit;
In the execution of the isolated operation detection method according to the first to third aspects of the present invention, an isolated operation determination unit that performs at least the disconnection operation of the disconnect relay when it is determined that the operation is independent based on the measurement from the measurement unit;
It is characterized by comprising.

In the fourth invention,
Preferably, the control unit divides the control unit into two, a first time interval in which the positive voltage continues in the one cycle and a second time interval in which the negative voltage continues.

  Preferably, the control unit performs control so as to flow a system output current that changes the amplitude of the system output current at the first time interval and the second time interval for each cycle of the system output current.

  A distributed power supply system according to a fifth aspect of the present invention includes a distributed power supply and the power conditioner.

  According to the present invention, each cycle of the system voltage output from the power conditioner and connected to the power supply of the power system line is divided into at least two different time intervals, and the grid connection operation is performed in the two time intervals. The grid output current is passed from the inverter so that a difference may occur in the independent operation, and the difference is measured with the magnitude or the sign, and the measurement is performed with the difference in the time interval. When measuring, the number of consecutive measurements that the measured value is greater than or equal to a predetermined value, and when measuring the measurement including the sign, the sign of the measured value is positive If the positive upper limit value is a predetermined value, and the value is equal to or greater than the predetermined value and the sign is negative, the negative lower limit value is the predetermined value, and the measured value is equal to or smaller than the predetermined value. Measurement When the number of continuous times is less than the predetermined number, it is determined that the system is connected to the grid instead of the single operation. On the other hand, when the number of continuous times is equal to or more than the predetermined number, the single operation is determined. Unlike the frequency shift method, which is one of the typical examples of the method, and the reactive power fluctuation method, which is another one of the typical examples of the active method, a plurality of connected distributed power sources are caused by mutual interference of active signals. There is no concern that the isolated operation detection performance will deteriorate, and, unlike another slip mode frequency shift method, which is a typical example of the active method, the generated power and load power of the distributed power source are equal to the current in the system. Even when there is no flow, the isolated operation can be detected, and the isolated operation can be reliably detected.

FIG. 1 is a diagram showing a distributed power supply system according to an embodiment of the present invention. FIG. 2 is a diagram showing a table regarding the time of each period and the maximum absolute value in the first half of the system output current, that is, the period in which the system output current is positive and the second half, that is, the period in which the system output current is negative. is there. FIG. 3 (a) is a diagram showing a system output current Is waveform from the power conditioner, FIG. 3 (b) is a diagram showing a waveform of the system voltage Es during system interconnection, and FIG. 3 (c) is a diagram during independent operation. It is a figure which shows the waveform of the system voltage Es. FIG. 4 is a flowchart showing the operation. FIGS. 5A to 5C are diagrams showing waveforms for explaining the generation process of the system output current. 6A and 6B are diagrams for explaining another generation process of the system output current, and are diagrams in which the system output current is decomposed into a fundamental current and a harmonic current. FIG. 7 is a diagram showing a flowchart used for explaining the operation of another embodiment of the present invention. FIG. 8 is a diagram showing a flowchart used for explaining the operation of still another embodiment of the present invention. FIG. 9 shows a flowchart corresponding to FIG. 4 according to still another embodiment of the present invention. FIG. 10 shows a flowchart corresponding to FIG. 7 according to still another embodiment of the present invention. FIG. 11 shows a flowchart corresponding to FIG. 8 according to still another embodiment of the present invention.

  Hereinafter, an isolated operation detection method, a power conditioner, and a distributed power supply system according to embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a distributed power supply system that implements the isolated operation detection method of the embodiment. This system includes a distributed power source 1, a power conditioner (system interconnection device) 2, a commercial (system) power source 3, and a load 4. 5 is a power distribution breaker, and 6 is a power distribution switch. In addition, illustration of a pole transformer etc. is omitted for convenience of illustration.

  The distributed power source 1 is, for example, a solar cell or a fuel cell.

  The power conditioner 2 converts the DC power output from the distributed power source 1 into AC power, and supplies the AC power to the load 4 in conjunction with the commercial power source 3. The inverter unit 7, LC A filter unit 8, a disconnection relay 9, a control unit 10, a measurement unit 11, and an isolated operation determination unit 12 are provided.

  The inverter unit 7 includes a plurality of switching elements such as IGBTs connected in a full bridge, for example, and is an inverter that is a DC voltage input from the distributed power source 1 by turning on / off the switching element by a PWM switching control signal S1 from the control unit 10 The input voltage Ed can be DC / AC converted and output as an inverter output voltage Ei, and when the operation stop signal S3 from the single operation determination unit 12 is input to the control unit 10, the switching is performed through the control unit 10. The gate can be blocked (stopped) by controlling the on / off operation of the element to stop.

  In the power conditioner 2, when the distributed power source 1 is a solar cell, for example, a step-up circuit for boosting the DC voltage can be provided before the inverter unit 7, but the illustration thereof is omitted.

  The LC filter unit 8 includes a reactor L and a capacitor C. The inverter output voltage Ei from the inverter unit 7 smoothes the ripple component of the carrier frequency caused by the PWM switching control to make a sine wave, and the commercial power system line The waveform is shaped into the system voltage Es linked to the commercial power supply 3 of the system. Note that the control unit 10 described later controls the output of the PWM switching control signal S1 to the inverter unit 7 so that the system voltage Es and the system output current (current output to the system side) Is are synchronized.

  The disconnect relay 9 is connected to the commercial power source 3 on the rear stage side of the LC filter unit 8 and is turned off by the relay disconnect signal S2 from the independent operation determination unit 12 to the commercial power source 3 in the commercial power system line. Thus, the inverter 2 is disconnected.

  The control unit 10 outputs a PWM switching control signal S1 for controlling on / off of the plurality of switching elements in the inverter unit 7, and outputs the PWM switching control signal S1 to the inverter unit 7 so that the power condition is controlled. The first half of the current is the positive period and the second half of the current is the negative period for each period of the system output current Is that is the current output from the power source 2 to the system side. Control each time to change.

  For example, when each period of the system output current Is is Tn (the reciprocal number is each frequency fn), the reciprocal frequency f1 of the system output current Is in the period when the first half current is positive (Is> 0) is f + Δf (formula 1) and the second half. The frequency f2 of the system output current Is during a period in which the current is negative (Is <0) is represented by the following equation 2. Note that the “first half” and “second half” do not mean the division of one cycle in half, but merely the front and rear in terms of time within one cycle, and the same applies to the following.

  Further, the control unit 10 determines the absolute value of the system output current Is in a period in which the current in the first half is positive (Is> 0) with respect to each period (0 to 2π rad) of the system output current Is of the inverter unit 7. Control is performed so that the amplitude at the absolute value of the system output current Is in the period in which the amplitude A1 is larger than the original amplitude A0 and the latter half current is negative (Is <0) is changed to the amplitude A2 smaller than the original amplitude A0. To do.

  For example, when the original amplitude of the system output current Is is A0, the amplitude A1 of the system output current Is during the period when the first half current is positive (Is> 0) is [(f + Δf) / f] times the amplitude A0 (* formula 3 ), The amplitude A2 of the system output current Is during a period in which the latter half of the current is negative (Is <0) is A1 (equation 4) times the original amplitude A0.

  The frequency and amplitude are shown in Table 1 of FIG. Referring to Table 1, f is 50 Hz, and Δf is 1 Hz, 1.5 Hz, and 2 Hz. Of course, this example is for illustrative purposes only and is not intended to limit the present invention.

  In each period (0 to 2π rad) of the system output current Is, Δf is “1 Hz”, “1.5 Hz”, and “2 Hz” in the period in which the current in the first half is positive (Is> 0), the frequency is expressed by the above formula 1. In the above equation, “51 Hz”, “51.5 Hz”, and “52 Hz” are set, and the amplitudes are set to “51/50”, “51.5 / 50”, and “52/50”, respectively, in Equation 2 above.

  In the period when the current in the latter half is negative (Is <0), the frequency is “49.04 Hz”, “48.58 Hz” and “48.15 Hz” in the above equation 3 when Δf is “1 Hz”, “1.5 Hz” and “2 Hz”. In the above equation 4, the amplitudes are “49.04 / 50”, “48.58 / 50”, and “48.15 / 50”, respectively.

  Note that when the system output current Is becomes smaller than a certain value, the frequency Δf may be increased so that the single operation can be detected without decreasing the harmonic component.

  The measurement unit 11 inputs the system voltage Es, and at the first time interval in which a positive voltage continuously continues in each cycle of the system voltage Es during system interconnection and in isolated operation, and continuously negative. The voltage is divided into second time intervals followed by voltage, the difference between the first and second time intervals is measured in magnitude, and the measured output result is output to the isolated operation determination unit 12.

  The islanding operation determination unit 12 is connected to the grid instead of the islanding operation when the continuous number of measurements that the value measured by the measurement unit 11 is equal to or greater than the predetermined value is less than the predetermined number. On the other hand, when the number of consecutive times is equal to or greater than the predetermined number of times, it is determined as an isolated operation, and when it is determined as an isolated operation, the signals S2 and S3 are input to the control unit 10 and the disconnecting relay 9. The inverter unit 7 is operated through the control unit 10 to cause the gate block (the operation of the inverter unit 7 to be stopped), and the disconnecting relay 9 is operated to perform the disconnecting operation, thereby stopping the operation of the power conditioner 2.

  When the measurement unit 11 measures the difference in time interval including the sign, the isolated operation determination unit 12 sets a positive upper limit value when the sign of the value measured by the measurement unit 11 is positive. When the value is equal to or greater than the predetermined value and the sign is negative, the lower limit of the negative value is the predetermined value, and the number of consecutive measurements is less than the predetermined value is less than the predetermined number Is determined not to be an isolated operation but to be connected to the grid, while it is determined to be an isolated operation when the number of continuous times is equal to or greater than a predetermined number.

  FIG. 3A shows the waveform of the system output current Is flowing from the power conditioner 2 to the system side, and FIG. 3B shows the waveform of the system voltage Es input to the measuring unit 11 of the power conditioner 2 when the system is connected. FIG. 3C shows a waveform of the system voltage Es input to the measuring unit 11 of the power conditioner 2 during the single operation. Operations of the control unit 10, the measurement unit 11, and the isolated operation determination unit 12 will be described with reference to these drawings.

  The control unit 10 inputs a PWM switching control signal S1 to the inverter unit 7 to turn on and off a plurality of switching elements in the inverter unit 7 to convert the DC input voltage Ed into an AC output voltage Ei. In this conversion, data of inverter input voltage Ed, inverter output current Ii, system voltage Es, and system output current Is are input and output from the inverter unit 7 to the system side via the LC filter unit 8 based on these data. On / off control of the plurality of switching elements in the inverter unit 7 is performed so that the system output current Is having the waveform shown in FIG.

  The waveform of the grid output current Is will be described with reference to FIG. 3A. Each cycle (0 to 2πrad) of the grid output current Is Tn−2, Tn−1, Tn,. The first time interval (referred to as the first half time interval) followed by the second voltage is divided into the second time interval (referred to as the second half time interval) followed by the negative voltage continuously. For example, the first half time interval is ΔTn−2 to 1, ΔTn−1 to 1 and ΔTn to 1, and the second half time interval is ΔTn−2 to 2, ΔTn−1 to 2 and ΔTn to 2, and the first half time interval is less than the second half time interval. Set to be. Thereby, a set time difference is generated between the first half time interval and the second half time interval in any one cycle. Thus, the system output current Is having the waveform shown in FIG. 3A is output from the power conditioner 2 to the system. The set time difference in this case is a time difference that is larger than the predetermined time difference.

  Here, the predetermined time difference will be explained. For example, one period at 50 Hz is 0.02 seconds, and in this period, the first half time interval is 0.008 seconds and the second half time interval is 0.012 seconds, for example. For example, the set time difference that is the time difference between the first half time interval and the second half time interval is 0.004 seconds. In such a case, the predetermined time difference can be set to 0.003 seconds, for example.

  Note that the amplitude of the grid output current Is in the first half time interval is A1, and the amplitude of the grid output current Is in the second half time interval is A2, so that A1> A2 is satisfied, so that no DC component is generated.

  Next, a description will be given of the time of grid interconnection. In the grid interconnection, even if the grid output current Is shown in FIG. 3A described above is output from the power conditioner to the commercial power supply 3 side of the grid, On the third side, the system output current Is output from the power conditioner 2 is almost unaffected, and the system voltage Es synchronized with the voltage of the commercial power source 3 shown in FIG. Is done. The system voltage Es having the waveform shown in FIG. 3B is represented by the first half time intervals ΔTn-2 ′ to 1 and ΔTn-1 ′ to 1 in each of the periods Tn-2 ′, Tn-1 ′, Tn ′. , ΔTn′˜1 and the latter half time intervals ΔTn−2′˜2, ΔTn−1′˜2, and ΔTn′˜2 are substantially equal. In this case, the amplitudes A1 ′ and A2 ′ of the system voltage Es at the first half time interval and the second half time interval are substantially equal.

  Therefore, the difference in the time interval between the first half time interval and the second half time interval is almost zero in each one cycle Tn-2 ′, Tn-1 ′, Tn ′.

  Therefore, in each of the periods Tn-2 ′, Tn-1 ′, Tn ′..., There is no predetermined time difference in the set time difference between the first half time interval and the second half time interval. The number of times the above measurement is continuously performed does not exceed a predetermined number. Such a measurement output result is input to the isolated operation determination unit 12. The predetermined number of times can be determined by the minimum value of the disconnection time period by the isolated operation detection function defined in the grid connection provision JEAC9701.

  For example, the disconnection time limit in the above rule is 0.5 seconds or more and 1 second or less after the occurrence of the independent operation. Therefore, the minimum value of the disconnection time limit is 0.5 seconds, and the predetermined number of times is 0. .Number of times over 5 seconds. However, in some cases, the measurement where the set time difference is equal to or greater than the predetermined time difference may be continuously performed.For example, the influence of the injection signal of the power conditioner that employs other active method islanding detection connected to the system. Others may be discontinuous. The predetermined number of times is 0.5 × frequency or more, but the frequency is not always constant, and when trying to cope with both 50 Hz and 60 Hz, the frequency is set to ± 2 Hz. , 48 Hz to 62 Hz must be supported, and the predetermined number of times is 31 times or more for 0.5 seconds or more.

  On the other hand, when a single operation is performed due to the interruption of the breaker 6 due to a power failure or failure of the commercial power supply 3, the system voltage Es in FIG. During the single operation, the system voltage Es has a waveform reflected on the system output current Is shown in FIG. Of course, although it does not correspond as it is to Fig.3 (a), it receives to the influence of the load.

  In the system voltage Es of FIG. 3C, the first half time intervals ΔTn-2 ″ to 1 and ΔTn-1 ″ to 1 for each one period Tn−2 ″, Tn−1 ″, Tn ″. , ΔTn ″ to 1 and the latter half time intervals ΔTn−2 ″ to 2, ΔTn−1 ″ to 2 and ΔTn ″ to 2, respectively, the time difference that is the difference between the above time intervals is equal to or greater than a predetermined time difference, and the time difference is The number of times that the measurement that exceeds the predetermined time difference is continuously performed exceeds the predetermined number. Such a measurement output result is input to the isolated operation determination unit 12. This predetermined number of times can be determined, for example, by experiments. The amplitude does not directly correspond to A1 and A2 in FIG. 3A, but is A1 ″ and A2 ″ in FIG. 3C and, of course, is affected by the load.

  In the isolated operation determination unit 12, when the measurement output result shown in FIG. 3B is input, it is determined that the operation is not the isolated operation but the grid connection, and the operation stop signal S3 and the relay disconnection signal S2 are not output. When the measurement output result shown in FIG. 3C is input, it is determined that the operation is a single operation, and the signals S3 and S2 are output.

  The operation will be described with reference to the flowchart of FIG.

  In step n1, each cycle of the system voltage Es output from the power conditioner 2 and linked to the commercial power source 3 of the power system line is divided into the first half time interval (the first time interval in which a positive voltage continues continuously). And the latter half time interval (second time interval in which negative voltage continues continuously) is divided into two time intervals.

  Next, in step n2, the grid output current Is is supplied from the power conditioner 2 so that a difference occurs between the grid interconnection operation and the isolated operation at each time interval of the first half and the latter half in each cycle.

  In step n3, the magnitude of the difference is measured.

  Then, when the number of consecutive measurements that the magnitude of the value measured in step n4 is greater than or equal to a predetermined value is less than the predetermined number N1 within a predetermined time, in step n5, the system is connected to the grid instead of being isolated. On the other hand, when the number of continuous times is equal to or greater than the predetermined number N1 within the predetermined time, it is determined that the single operation is performed in Step n6.

  When the difference is measured including the sign at step n3, if the sign of the value measured at step n4 is positive, the positive upper limit value is set to a predetermined value, and the value is equal to or greater than the predetermined value. When the sign is negative, the lower limit value of the negative value is a predetermined value, and the number of consecutive measurements that the measured value is less than the predetermined value is less than the predetermined number of times, the system is not operated independently at step n5. On the other hand, when it is determined that the system is linked, when the number of consecutive times is equal to or greater than a predetermined number, it may be determined that the single operation is performed in Step n6.

  For example, in the system output current Is within one cycle (0.02 seconds) at 50 Hz, the first half time is, for example, 0.0085 seconds, for example, positive current, the second half time, for example, 0.0115 seconds is a negative negative. The current is passed from the power conditioner to the grid as a grid output current Is so as to become a current. Then, in the voltage within one cycle of the system voltage Es, the difference between the first half time interval and the second half time interval is measured by the measuring unit 11, and the measured value becomes the first half time interval> the second half time interval. When the sign of the value of the time interval is positive, the above determination is made based on whether or not the positive value exceeds an upper limit value that is a predetermined value.

  The same applies when the sign is negative.

  Thus, the sign of “when measuring including the sign of the difference” is a sign of time obtained by subtracting the latter half time interval from the first half time interval in one cycle of the system voltage Es, and the sign is a plus. When the first half time interval in one cycle of the system voltage Es> the second half time interval. If the time relationship between the first half time interval and the second half time interval is reversed, the sign becomes negative. The time difference is not necessarily constant because the system voltage Es is affected by various changing factors of the system and the power conditioner 2, but it is small in a normal state, and it will continue even if the time difference exceeds a predetermined value. Absent. In order for the time difference to exceed the predetermined value continuously or in a considerable amount in one second, the system to which the power conditioner 2 is connected is brought into an independent operation state, and the output of the power conditioner 2 This is when the time difference between the positive time and the negative time s of the current Is is greater than or equal to a predetermined value. The predetermined value does not exceed in the normal state as described above, and even if the time difference exceeds the predetermined value, it does not continue, and the system to which the power conditioner 2 is connected enters the single operation state. And the time difference between the first half time interval and the second half time interval of the output voltage (equal to the system voltage) of the power conditioner 2 due to the influence of the time difference between the first half time interval and the second half time interval of the output current Is of the power conditioner 2 Set to a value that is longer than a certain time. Therefore, the fact that this time difference is equal to or greater than the predetermined value indicates the possibility that the inverter 2 has become a single operation, and when it is continuous or intermittent, but the frequency is high, the single operation is performed. It can be determined that the state has been reached.

  Another method for generating the system output current Is will be described with reference to FIGS. FIG. 5A shows the waveform of the fundamental current Io. For example, the waveform of the second harmonic current I1 is shown as an even order in FIG. The system output current Is shown in FIG. 5C can be generated by synthesizing the waveforms shown in FIGS. 5A and 5B. The system output current Is in FIG. 5C is obtained by dividing the first half time intervals ΔTn-2 to 1, ΔTn-1 to 1, ΔTn to 1, and the latter half time interval ΔTn in each cycle Tn-2, Tn-1, Tn. The time interval between −2 to 2, ΔTn−1 to 2 and ΔTn to 2 is shorter in the first half and longer in the second half. Further, the amplitude of the system output current Is is also made larger in the first half time interval than in the second half time interval so that no DC component is generated.

  The present invention is not limited to this second harmonic current.

  The harmonics included in the system output current Is are set so as not to exceed a predetermined value.

  When the amplitude of the fundamental wave current io decreases from a certain value, the amplitude of the secondary harmonic current I1 is also reduced so that the waveform of the secondary harmonic current I1 does not affect the isolated operation detection. It may be maintainable.

  In each one period Tn-2, Tn-1, Tn,... Of the system output current Is, the system output current Is is a fundamental wave current I0 having one period as one period and its second harmonic. In the case where the sum of the current I1 and the current I1 is increased, the second harmonic current I1 is increased in order to improve sensitivity so that a difference occurs between the grid interconnection operation and the single operation at a plurality of time intervals in each cycle. preferable.

  With reference to FIG. 6, another method for generating the system output current Is will be described. The control unit 10 controls the inverter unit 7 so that the system output current Is at the system output point flows a sinusoidal current Is1 shown in FIGS. 6A and 6B and Is2 described below. May be. That is, in FIG. 6A, a system output current Is2 having a waveform indicated by hatching A1, A2, and A3 is generated, and the generated system output current Is2 is combined with the system output current Is1 to flow. In FIG. 6B, a system output current Is2 having a waveform indicated by hatching A1, A2, A3, and A2 ′ is generated, and the generated system output current Is2 is combined with the system output current Is1 to flow. The combined system output current Is is supplied from the power conditioner 2 to the system.

  In the above-described embodiment, each cycle of the grid output current is divided into the first half and the second half of the time interval. However, the present invention is not limited to this, and each cycle of the grid voltage is divided into the first half and the second half of the time. It may be divided into intervals, or may be divided into time intervals sandwiching 0V in the above-mentioned one cycle instead of a half cycle, and may include more than two divisions. .

  In addition, in order to detect the independent operation of the distributed power source, each cycle of the system voltage Es or the system output current Is output from the power conditioner 2 and linked to the commercial power source 2 is divided into a plurality of time intervals. In this case, it is preferable to limit the frequency of the one cycle so as not to exceed a predetermined frequency range with respect to the rated frequency of the commercial power source (system power source) 3. That is, when the rated frequency of the system power supply 3 is 50 Hz or 60 Hz, limiting the frequency of each cycle of the system voltage Es or the system output current Is so that it does not exceed ± 3% thereof is to prevent a malfunction in detecting an independent operation. Then, it is preferable.

  Further, within each cycle of the system voltage (power conditioner output voltage) Es or the power conditioner output current Is, the time interval of one cycle is divided into a first half time interval and a second half time interval. The difference in time interval between the first half and the second half is measured by size or by including a sign. When measuring the difference in the time interval by the magnitude, the number of consecutive measurements that the measured value is equal to or greater than a predetermined value, and when measuring the measurement including a sign, the measurement When the sign of the value is positive, the upper limit value of the positive value is a predetermined value and the above value is equal to or greater than the predetermined value. When the sign is negative, the lower limit value of the negative value is a predetermined value and the measured value is less than the predetermined value. If the number of consecutive measurements is determined to be equal to or greater than the predetermined number and is determined to be an independent operation, even after the determination, the change in the sum of the first half time and the second half time is equal to or greater than the predetermined value. For example, it is more preferable to determine that the single operation is continuing. The change in the sum of the first half time and the second half time means that the sum of the first half time and the second half time, that is, the period change for each cycle is directly or moving averaged.

  Next, another embodiment of the present invention will be described with reference to FIG. In FIG. 7, steps n11, n12, and n13 correspond to steps n1, n2, and n3 in FIG. In step n14, when the number of times that the measured value is greater than or equal to the predetermined value within a predetermined time is less than the predetermined number N1, it is determined in step n15 that the system is not isolated but connected to the grid. When the number of times N1 is equal to or greater than the predetermined number of times within the predetermined time, it is determined at step n16 that the single operation is performed.

  In step n13, when the difference is measured including the sign, if the sign of the value measured in step n14 is positive, a positive upper limit value is set as a predetermined value, and the value is equal to or greater than the predetermined value. Is negative, the lower limit value of the negative value is a predetermined value, and the number of consecutive measurements that the measured value is less than or equal to the predetermined value is less than the predetermined number N1, the system connection is not performed in step n15. On the other hand, when the number of continuous times is equal to or greater than the predetermined number N1, the single operation may be determined in step n16.

  Still another embodiment of the present invention will be described with reference to FIG. In FIG. 8, steps n21, n22, and n23 correspond to steps n1, n2, and n3 in FIG. In step n24, when the measurement time that the measured value is equal to or greater than the predetermined value within the predetermined time T1 is less than the predetermined time, it is determined in step n25 that the system is connected to the grid instead of being operated alone. When it is not less than the predetermined time within the predetermined time T1, it is determined in step n26 that it is an independent operation.

  When the difference is measured including the sign at step n23, when the sign of the value measured at step n24 is positive, the positive upper limit value is a predetermined value, and the value is equal to or greater than the predetermined value. When the sign is negative, the lower limit value of the negative value is a predetermined value, and when the number of consecutive measurements that the measured value is less than or equal to the predetermined value is less than the predetermined number of times, it is determined that the system connection is not performed in step n25. On the other hand, when the number of continuous times is equal to or greater than a predetermined number, it may be determined that the single operation is performed in Step n26.

  In step n4 of the flowchart of FIG. 4, when the output current variation of the other power conditioners in the system is large, the measured value is equal to or greater than the predetermined value within a predetermined time despite the single operation. In some cases, the number of continuous measurements does not exceed a predetermined number and is not detected as an isolated operation. Therefore, in order to prevent such erroneous detection, the flowchart of FIG. 9 may be used instead of the flowchart of FIG. In the flowchart of FIG. 9, Steps n1 and n2 are the same as Steps n1 and n2 of FIG. 4. In Step n3, the magnitude of the difference between the first half time interval and the second half time interval is measured, and the process proceeds to Step n4. In step n3 ″, the sum of the first half time interval and the second half time interval is measured, and the process proceeds to step n4 ′.

  In steps n4 and n4 ′, when the number of continuous measurements that the measured value is equal to or greater than the predetermined value exceeds N1, the process proceeds to step n2 ′, and otherwise, the process proceeds to step n5.

  In step n2 ′, the grid output current is supplied so that a larger difference than in step n2 is generated between the time interval of the first half and the latter half of the time interval between grid connection and single operation. In step n3 ′, the time of the first half When the difference between the interval and the second half time interval is measured, and the number of consecutive measurements that the measured value is greater than or equal to a predetermined value greater than step n4 in step n4 ″ does not exceed the predetermined number N1-N2 When the grid interconnection operation is performed at step n5 ′ and the number of measurement is added and the predetermined number of times is exceeded, it is determined at step n6 that the operation is independent.

  Similarly, in step n14 of the flowchart of FIG. 7, when the fluctuation of the output current of the other power conditioner in the system is large, the measurement value is determined to be greater than or equal to the predetermined value despite the single operation. May not exceed a predetermined number of times within a predetermined time. Therefore, in such a case, the process may be executed with the flowchart of FIG. 10 instead of the flowchart of FIG. In the flowchart of FIG. 10, the magnitude of the difference between the first half time interval and the second half time interval is measured in steps n11 and n12 to step n13, and the process proceeds to step n14. In step n13 ″, the first half time interval is determined. The sum of the latter half of the time interval is measured, and the process proceeds to step n14 ′. In steps n14 and n14 ′, when the number of continuous measurements that the measured value is equal to or greater than the predetermined value at the predetermined time T exceeds N1, the process proceeds to step n12 ′, and otherwise, the process proceeds to step n15.

  In step n12 ′, a grid output current is passed between the first half time interval and the second half time interval so that there is a greater difference than in step n12 between grid connection and single operation. In step n13 ′, the first half time interval The magnitude of the difference between the interval and the time interval of the latter half is measured, and the number of consecutive times that the measured value is greater than or equal to a predetermined value larger than step n14 within the predetermined time T at step n14 ″ is the predetermined number of times N1-N2. If not, system interconnection operation is performed at step n15 ', and if it exceeds, the operation is performed independently at step n16.

  Similarly, in step n24 of the flowchart of FIG. 8, when the fluctuation of the output current of the other power conditioner in the system is large, the measurement time is measured to be equal to or longer than the predetermined time despite the single operation. May not. Therefore, in such a case, the process may be executed with the flowchart of FIG. 11 instead of the flowchart of FIG. In the flowchart of FIG. 11, the magnitude of the difference between the first half time interval and the second half time interval is measured in steps n21 and n22 to step n23, and the process proceeds to step n24. In step n23 ″, the first half time interval is determined. The sum of the latter half time interval is measured, and the process proceeds to step n24 ′. In Steps n24 and n24 ′, when the measurement time that the measured value is equal to or greater than the predetermined value within the predetermined time T exceeds the predetermined time, the process proceeds to Step n22 ′, and otherwise, the process proceeds to Step n25.

  In step n22 ′, a grid output current is passed between the first half time interval and the second half time interval so that a larger difference than that in step n22 occurs between grid connection and single operation. In step n23 ′, the first half When the magnitude of the difference between the time interval and the latter time interval is measured, and the measurement time is not greater than the predetermined time in step n24 ″, the measured value is greater than or equal to the predetermined value within the predetermined time T Is connected to the grid at step n25 ', and if it is longer than the predetermined time, it is set to stand alone at step n26.

DESCRIPTION OF SYMBOLS 1 Distributed type power supply 2 Power conditioner 7 Inverter part 8 LC filter part 10 Measurement part 11 Control part 12 Independent operation determination part 3 Commercial power supply 4 Load

Claims (11)

A distributed power source and a power conditioner that converts the DC power of the distributed power source into AC power, and the AC power converted by the power conditioner is connected to the power of the power system line and supplied to the system load Type power supply system,
A method for detecting isolated operation of the distributed power source, comprising first to fourth steps,
The first step is a step of dividing each cycle of the system voltage or system output current output from the power conditioner and linked to the system power source into a plurality of time intervals.
The second step is a step of causing the grid output current to flow from the power conditioner so that a difference occurs between the grid interconnection operation or the single operation in the plurality of time intervals within each cycle.
The third step is a step of measuring the difference or sum of the time intervals in magnitude, or measuring the difference of the time intervals including a sign,
In the fourth step, when the measurement is measured by the difference or the sum of the time intervals, when the measured number of times that the measured value is greater than or equal to a predetermined value is less than the predetermined number, While it is determined that it is connected to the grid rather than driving, it is determined to be an independent operation when it is more than a predetermined number of times,
When measuring including the sign,
When the sign of the measured value is positive, the upper limit value of the positive value is a predetermined value, and when the number of continuous measurements that the value is equal to or greater than the predetermined value is less than the predetermined number, While it is determined that the system is connected
When the sign of the measured value is negative, the negative lower limit value is a predetermined value, and when the measured number of times that the measured value is less than or equal to the predetermined value is less than the predetermined number, it is not an isolated operation. While it is determined that the grid is connected, when it is a predetermined number of times or more, it is a step to determine that it is an independent operation,
An isolated operation detection method characterized by the above. A distributed power source and a power conditioner that converts the DC power of the distributed power source into AC power, and the AC power converted by the power conditioner is connected to the power of the power system line and supplied to the system load Type power supply system,
A method for detecting isolated operation of the distributed power source, comprising first to fourth steps,
The first step is a step of dividing each cycle of the system voltage or system output current output from the power conditioner and linked to the system power source into a plurality of time intervals.
The second step is a step of causing the grid output current to flow from the power conditioner so that a difference occurs between the grid interconnection operation or the single operation in the plurality of time intervals within each cycle.
The third step is a step of measuring the difference or sum of the time intervals in magnitude, or measuring the difference of the time intervals including a sign,
In the fourth step, when the measurement is performed with the difference between the time intervals or the sum, the number of measurements that the measured value is greater than or equal to a predetermined value is less than the predetermined number within a predetermined time. When it is determined that the system is connected to the grid rather than a single operation, when the number of times is a predetermined number of times or more within the predetermined time, it is determined to be a single operation,
When measuring including the sign,
When the sign of the measured value is positive, the upper limit value of the positive value is a predetermined value, and the number of times that the value is greater than or equal to the predetermined value is less than the predetermined number of times within a predetermined time. On the other hand, when the number of times is more than a predetermined number within the predetermined time, it is determined that the operation is independent,
When the sign of the measured value is negative, the lower limit of the negative value is a predetermined value, and the number of times that the measured value is less than or equal to the predetermined value is less than the predetermined number of times within a predetermined time. On the other hand, it is determined that the system is connected to the grid instead of the operation.
An isolated operation detection method characterized by being a step. A distributed power source and a power conditioner that converts the DC power of the distributed power source into AC power, and the AC power converted by the power conditioner is connected to the power of the power system line and supplied to the system load Type power supply system,
A method for detecting isolated operation of the distributed power source, comprising first to fourth steps,
The first step is a step of dividing each cycle of the system voltage or system output current output from the power conditioner and linked to the system power source into a plurality of time intervals.
The second step is a step of causing the grid output current to flow from the power conditioner so that a difference occurs between the grid interconnection operation or the single operation in the plurality of time intervals within each cycle.
The third step is a step of measuring the difference or sum of the time intervals in magnitude, or measuring the difference of the time intervals including a sign,
In the fourth step, when the measurement is measured by the difference or sum of the time intervals, the measurement time is determined to be greater than or equal to the predetermined value, and the measurement time is less than the predetermined time within the predetermined time. Is determined to be grid-connected rather than isolated, while it is determined to be isolated when it is greater than or equal to a predetermined time within the predetermined time,
When measuring including the sign,
When the sign of the measured value is positive, the upper limit value of the positive value is a predetermined value, and when the time of measurement that the value is equal to or greater than the predetermined value is less than the predetermined time within the predetermined time, the operation is performed independently. On the other hand, when it is determined that it is grid-connected, when it is a predetermined time or more within the predetermined time, it is determined as an isolated operation,
When the sign of the measured value is negative, the lower limit value of the negative value is a predetermined value, and when the measured time is less than the predetermined time within the predetermined time On the other hand, it is determined that it is connected to the grid instead of driving, and when it is not less than a predetermined time within the above predetermined time, it is determined that it is a single operation.
An isolated operation detection method characterized by being a step.   The first step is a step of dividing into two, a first time interval in which a positive voltage continues continuously and a second time interval in which a negative voltage continues continuously in one cycle of the system voltage. 4. The method according to any one of claims 1 to 3.   In the second step, within each period of the system voltage, the system output current is set to the sum of the fundamental current and the harmonic current each having one period as one period. The method according to claim 4, wherein the method includes a step of supplying a current to be output to the grid so that a difference occurs between the interconnection operation and the single operation.   5. The method according to claim 4, wherein the second step passes a grid output current that changes an amplitude of the grid output current between the first time interval and the second time interval for each cycle of the grid output current.   The said 2nd step makes the system | strain output current into the sum of the fundamental wave current which makes each 1 period 1 period, and its even-order harmonic current within 1 period of each system | strain output current. The method described in 1.   In the case where the second step is the sum of the fundamental current and the even-order harmonic current, each of which is one cycle, in each cycle of the grid output current, 5. The method according to claim 4, wherein the even-order harmonic current is increased so that a difference occurs between the grid connection operation and the single operation in the plurality of time intervals within one period.   The third step is a step of measuring the difference or sum of the first time interval and the second time interval in magnitude, or measuring the difference between the first time interval and the second time interval including a sign, 9. A method according to any one of claims 5 to 8. In the power conditioner that converts the DC power of the distributed power source into AC power,
An inverter unit that converts a DC input voltage output from a distributed power source into an AC voltage and outputs the AC voltage;
An LC filter unit that smoothes the AC output voltage of the inverter unit and shapes the output waveform into a sinusoidal waveform;
A disconnecting relay interposed between the inverter unit and the power source of the power system line;
Each cycle of the system voltage from the inverter section is divided into a plurality of time intervals, and the power conditioner produces a difference between the grid connection operation or the single operation at the plurality of time intervals within each cycle. A control unit for controlling on / off of the plurality of switching elements in the inverter unit so as to flow the system output current,
The difference or sum of the time intervals is measured from the system output current flowing from the LC filter unit in synchronization with each cycle of the system voltage, or the difference of the time intervals is measured including a sign. A measurement unit;
In the execution of the method according to any one of claims 1 to 3, an isolated operation determination unit that performs at least the disconnection operation of the disconnect relay when it is determined as an isolated operation based on measurement from the measurement unit;
A power conditioner comprising:   A distributed power supply system comprising: a distributed power supply; and the power conditioner according to claim 10.

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