JP2017005859A - Isolated operation detection device for distributed power source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an isolated operation detection device capable of achieving both reliable detection of isolated operation and prevention of erroneous detection when a system disturbance occurs. The isolated operation detection device 10a controls an inverter 6, and then converts the fundamental wave current of the same frequency as the fundamental wave of the power distribution system 2 to a non-integer multiple order m of the fundamental wave. A control device 30a having a function of superimposing and outputting the interharmonic current Im in a single phase, and measuring the interharmonic voltage Vm of the non-integer multiple order m at the measurement point 24 on the interconnection line 22. And an isolated operation monitoring device 32 for detecting that the distributed power supply 8 has been operated independently from the change in the voltage Vm. The control device 30a calculates the rate of change of the magnitude of the inter-order harmonic current Im flowing through the measurement point 24 from the value before a predetermined time, and calculates the inter-order harmonic current Im output from the inverter 6 as described above. An inter-order harmonic current correction circuit 72 that increases in inverse proportion to the calculated rate of change is provided. [Selection] Figure 3

Description

  The present invention relates to a system in which a distributed power supply facility having a distributed power source having a power source that outputs DC power and an inverter that converts the DC power into AC power and outputs the power is connected to a distribution system (this is The present invention relates to an isolated operation detection device that can be referred to as a distributed power supply interconnection system (hereinafter the same applies) and detects that the distributed power supply is in an isolated operation.

  For example, a power generation facility having a power source that outputs DC power, such as a solar battery or a storage battery, and an inverter that converts the DC power into AC power and outputs the power has become popular. Such a power generation facility is called a distributed power source.

  When operating with a distributed power supply connected to the distribution system (this is called interconnection operation), the circuit breaker of the power company's substation was opened due to a system failure, etc., and the power supply from the upper system was stopped. If the distributed power supply continues to operate (ie, single operation), the voltage will continue to be applied to the distribution line even though the power supply from the higher-level system is stopped. There is. Therefore, as a first step, it is necessary to reliably detect such a stop of power supply from the host system, that is, a single operation of the distributed power source. Furthermore, as the second step, it is necessary to disconnect (disconnect) the distributed power source from the distribution system. This application relates to the apparatus of this first step.

  FIG. 1 shows an example of a system having a configuration in which a distributed power source possessing facility having a conventional isolated operation detection device for detecting isolated operation of a distributed power source is connected to a distribution system.

  A distributed power supply facility 36 is connected to the power distribution system 2 via the interconnection line 22. The distributed power supply facility 36 includes a distributed power supply 8 having a power supply 4 that outputs DC power and an inverter 6 that converts the DC power into AC power and outputs the AC power. The power source 4 that outputs DC power is, for example, a solar battery, a storage battery, or other batteries. It may have an AC power source and a converter that converts AC power from the AC power source into DC power.

  In this example, the output unit of the inverter 6 is connected to the power distribution system 2 via the LC filter 14, the insulation transformer 16, the electromagnetic contactor 18, the circuit breaker 20, and the interconnection line 22. However, the present invention is not limited to such a configuration (the same applies to the embodiments of the present invention described later).

A control device 30 is provided that controls the inverter 6 by supplying a control signal CS to the inverter 6 (for example, PWM control). The DC voltage V _dc on the input side of the inverter 6 passes through the voltage detector 9, the AC current I _ac on the output side passes through the current transformer 12, and the voltage V _{s at} the measurement point 24 of the interconnection line 22 is These are taken into the control device 30 via the instrument transformer 26. The AC current I _ac, similar to the current I _s to be described later through the measurement point 24, in which interharmonic current I _m to the fundamental wave current I ₁ is superimposed.

The control device 30 controls the inverter 6 so that a three-phase fundamental current I ₁ having the same frequency as the fundamental wave of the distribution system 2 (for example, 60 Hz or 50 Hz) is supplied from the inverter 6 by a factor of 1 of the fundamental wave. and an order between the harmonic current I _m of the non-integer multiple order m is large (e.g., 2.25 order 2.75 order) have a function to output the superimposed single-phase. That has a current injection function of the single-phase injection of interharmonic current I _m to tie line 22.

Accordingly, the current I _s flowing through the measurement point 24 of the tie-line 22 is overlapped with the fundamental wave current I interharmonic current I _m to _1. Further, the voltage generated by the flow of such a current, that is, the voltage V _{s at the} measurement point 24 is obtained by superimposing the inter-order harmonic voltage V _m on the fundamental wave voltage V ₁ .

  In this example, the isolated operation detection device 10 that detects that the distributed power source 8 has been operated independently includes the control device 30 and the isolated operation monitoring device 32 having the functions described above.

  In addition, the apparatus 34 including the element enclosed with the broken line from the inverter 6 vicinity in FIG. 1 to the circuit breaker 20 vicinity is normally called the power conditioner (abbreviation PCS). The same applies to embodiments of the present invention described later.

  An example of the configuration of the control device 30 is shown in FIG. In this example, simply speaking, the range from the output part of the 3-phase / 2-phase converter 38 to the input part of the 2-phase / 3-phase converter 60 is handled in two phases.

This control device 30 generates a command value I ₁ ′ of the fundamental current I ₁ using the waveform of the voltage V _{s at} the measurement point. That is, the three-phase voltage V _s is converted into a two-phase voltage by the three-phase / two-phase converter 38, phase information is calculated from the fundamental wave voltage V ₁ by the voltage phase calculator 40, and the fundamental wave is converted to the fundamental wave. The current command value generator 44 is given. Further, the DC voltage constant controller 42 calculates information that makes the DC voltage V _dc constant, and _supplies it to the fundamental wave current command value generator 44. The fundamental wave command value generator 44 generates a command value I ₁ ′ of the fundamental current I ₁ output from the inverter 6 based on the above information.

On the other hand, the inter-order harmonic current command value generator 46 generates the command value I _m ′ of the inter-order harmonic current I _m output from the inverter 6 and adds the both command values I ₁ ′ and I _m ′. Adder 48

The signal from the adder 48 is converted into a voltage signal by multiplying the feed forward coefficient jωL by the amplifier 52, while being subtracted from the DC current I _ac by the subtractor 50 and then multiplied by the feedback coefficient K _p by the amplifier 54. The two voltage signals are added by the adder 56 and the voltage converted into the two phases from the three-phase / two-phase converter 38 is added by the adder 58, and then the two-phase / three-phase converter 60 is added. Is converted into three phases to form the control signal CS, which is supplied to the inverter 6.

With the configuration as described above, the control device 30 controls the inverter 6 so that the fundamental current I ₁ output therefrom is in accordance with the command value I ₁ ′. That is, even if the impedance on the power distribution system 2 side changes, control is performed so that a constant fundamental wave current I ₁ is output.

The isolated operation monitoring device 32 measures the inter-order harmonic voltage V _m of the non-integer multiple order m included in the voltage V _s at the measurement point 24, and determines the change in the inter-order harmonic voltage V _m . Then, it detects that the distributed power source 8 has become an isolated operation, and outputs an isolated operation detection signal S ₁ representing it. For example, the inter-order harmonic voltage V _m or the rate of change thereof is compared with a predetermined determination value, and when the inter-order harmonic voltage V _m or the rate of change exceeds the determination value, the isolated operation detection signal S ₁ is output. . Thereafter, for example, based on the isolated operation detection signal S ₁ , the distributed power supply 8 may be disconnected from the distribution system 2 by gate-blocking the inverter 6 to stop the output and opening the electromagnetic contactor 18. .

  In addition, as described above, an independent operation detection device that detects the independent operation of the distributed power source from the change in the harmonic voltage between the orders at the measurement points on the interconnection line by injecting the interharmonic current into the interconnection line. An example is described in Patent Document 1.

JP 2000-287362 A

In the case of the conventional isolated operation detection device 10 described above, when the circuit breaker (not shown; see the circuit breaker 154 in FIG. 11) in the distribution system 2 is opened and the isolated operation occurs, the distribution system viewed from the measurement point 24. Since the impedance on the second side increases, the inter-order harmonic voltage V _m included in the voltage V _s at the measurement point 24 also increases, but at the same time, between the orders included in the current I _s flowing through the interconnection line 22. Since the harmonic current I _m decreases, the inter-order harmonic voltage V _m does not increase as much as the increase in the impedance, and there is a problem that the change in the inter-order harmonic voltage V _m at the time of isolated operation is small.

More specifically, as described above, the control device 30 normally operates so that the fundamental wave current I ₁ output from the inverter 6 maintains a constant value even if the impedance on the distribution system 2 side changes (this is Called constant current control). As a control element for that purpose, the feedback coefficient K _p set by the amplifier 54 greatly contributes, and its value is usually set with a focus on the fundamental current I ₁ which is the original output of the distributed power supply 8.

Meanwhile, since the harmonic current I _m between orders is a non-integer multiple order m of the fundamental wave (for example, 2.25 order 2.75 order), the command value I _m interharmonic current 'also of fundamental wave current The waveform is higher than the command value I ₁ ′. To tentatively correspond to the control interharmonic current I _m, when trying to enlarge the control amount of feedback by increasing the feedback coefficient K _p, for the fundamental current I ₁ which is the original output of the distributed power supply 8 Since the fundamental wave current I ₁ becomes unstable because the feedback amount becomes too large, the feedback coefficient K _p cannot be increased as such.

Usually Therefore, and set the feedback coefficient K _p focuses on the fundamental wave current I _1, as described above, since the feedback coefficient K _p is the feedback amount is small small for interharmonic current I _m, If the impedance of the power distribution system 2 side alone operation viewed from the measurement point 24 occurs is increased, the harmonic current I _m between orders is reduced can not be kept constant. When the harmonic current I _m is reduced between orders, since interharmonic voltage V _m generated by the interharmonic current I _m also decreases, as described above, the harmonic voltage V _m between orders of the impedance It does not increase as much as the increase, and the change in the inter-order harmonic voltage V _m when the isolated operation occurs is small (see also FIGS. 14 and 18 described later and the description thereof).

If the change in the inter-order harmonic voltage V _m when the isolated operation occurs is small, it is difficult to detect the isolated operation in the isolated operation monitoring device 32. That is, if the detection value in the isolated operation monitoring device 32 is reduced to increase the detection sensitivity, erroneous detection occurs when a system disturbance such as an instantaneous decrease in the system voltage or fluctuation in the system frequency occurs (that is, it is not an isolated operation but an isolated operation. The possibility of unnecessary detection) is increased. Conversely, if the detection value is lowered by increasing the determination value in the isolated operation monitoring device 32, it will be difficult to reliably detect the isolated operation. Therefore, it is difficult to achieve both reliable detection of isolated operation and prevention of erroneous detection when a system disturbance occurs.

  Accordingly, the main object of the present invention is to provide an isolated operation detection device that can improve the above-described points and achieve both reliable detection of isolated operation and prevention of erroneous detection when a system disturbance occurs. It is said.

  In the isolated operation detection device according to the present invention, a distributed power supply facility having a distributed power source having a power source that outputs DC power and an inverter that converts the DC power into AC power and outputs the power is connected to the distribution system. An isolated operation detection device that is applied to a system having a configuration and detects that the distributed power supply is in an isolated operation, and controls the inverter so that the inverter has the same frequency as the fundamental wave of the distribution system. A control device having a function of superimposing a non-integer multiple order harmonic current greater than 1 times the fundamental wave in a single phase on a three-phase fundamental current and outputting the same; Measure the harmonic voltage between the orders of the non-integer multiple order at the measurement point on the interconnection line between the facility and the power distribution system, and the distributed power source has become an independent operation from the change in the harmonic voltage between the orders Inspect And the control device calculates a rate of change of the magnitude of the interharmonic current flowing through the measurement point on the interconnection line from a value before a predetermined time. And an inter-order harmonic current correction circuit for increasing the inter-order harmonic current output from the inverter in inverse proportion to the calculated rate of change.

  According to this isolated operation detection device, when isolated operation occurs, the impedance on the distribution system side as viewed from the measurement point increases, and the interharmonic current flowing through the measurement point decreases. The harmonic current correction circuit calculates the rate of change of the harmonic current between the orders, and increases the harmonic current between orders output from the inverter in inverse proportion to the calculated rate of change. Reduction of inter-harmonic current is kept small. As a result, the change in the harmonic voltage between the orders at the measurement point when the isolated operation occurs increases, so that the determination value can be easily selected in the isolated operation monitoring device. As a result, it is possible to achieve both reliable detection of isolated operation and prevention of erroneous detection when a system disturbance occurs.

  The inter-order harmonic current correction circuit outputs a current obtained by removing a fundamental wave of the distribution system and an integral multiple of the harmonic from the current flowing through the measurement point on the interconnection line, and the comb filter Using the instantaneous value of the current that is output, the instantaneous negative phase calculator that calculates and outputs the amplitude of the instantaneous negative phase current of the current, and the amplitude of the instantaneous negative phase current from the instantaneous negative phase calculator A change rate calculator that calculates and outputs a change rate from a predetermined time before, a correction gain calculator that calculates and outputs a correction gain that is the reciprocal of the change rate from the change rate calculator, and the inverter And a command value corrector that increases a command value of the interharmonic current to be given to output the interharmonic current with the correction gain from the correction gain calculator.

  The inter-order harmonic current correction circuit further includes a correction gain expander that expands and outputs the rate of change of the correction gain from the correction gain calculator while maintaining a steady-state value of 1, The command value corrector may employ a configuration in which the command value of the inter-order harmonic current given to the inverter is increased by an enlarged correction gain from the correction gain expander.

  According to the first aspect of the present invention, when an independent operation occurs, the impedance on the distribution system side as viewed from the measurement point increases and the interharmonic current flowing through the measurement point decreases. The interharmonic current correction circuit calculates a change in the interharmonic current and increases the interharmonic current output from the inverter in inverse proportion to the calculated rate of change, so that it flows through the measurement point. The decrease in interharmonic current is kept small. As a result, the change in the harmonic voltage between the orders at the measurement point when the isolated operation occurs increases, so that the determination value can be easily selected in the isolated operation monitoring device. As a result, it is possible to achieve both reliable detection of isolated operation and prevention of erroneous detection when a system disturbance occurs.

  According to invention of Claim 2, there exists the following further effect. That is, the inter-order harmonic current correction circuit includes an instantaneous anti-phase calculator and a comb filter as a pre-processing thereof, and the rate of change of the inter-order harmonic current is expressed as the rate of change of the amplitude of the instantaneous anti-phase current. Since it can be detected at a higher speed than when using a discrete Fourier transformer or the like, it is possible to more quickly suppress a decrease in interharmonic current output from the inverter when an isolated operation occurs. it can. As a result, the change in the inter-order harmonic voltage at the measurement point when the isolated operation occurs becomes larger, so that it becomes easier to select the determination value in the isolated operation monitoring device. As a result, it is possible to more reliably achieve both reliable detection of isolated operation and prevention of erroneous detection when a system disturbance occurs.

  According to invention of Claim 3, there exists the following further effect. That is, by using the enlarged correction gain, it is possible to more reliably suppress the decrease in the inter-order harmonic current output from the inverter when the single operation occurs. As a result, the change in the harmonic voltage between the orders at the measurement point when the isolated operation occurs is further increased, so that the selection of the judgment value in the isolated operation monitoring device is further facilitated. As a result, it is possible to more reliably achieve both reliable detection of isolated operation and prevention of erroneous detection when a system disturbance occurs.

It is a single line connection figure which shows an example of the system of the structure by which the distributed power supply equipment which has the conventional isolated operation detection apparatus was connected to the power distribution system. It is a block diagram which shows an example of a structure of the control apparatus in FIG. 1 is a single line connection diagram illustrating an example of a system having a configuration in which a distributed power supply facility having an isolated operation detection device according to an embodiment of the present invention is connected to a power distribution system. It is a block diagram which shows an example of a structure of the independent operation monitoring apparatus in FIG. It is a block diagram which shows an example of a structure of the control apparatus in FIG. FIG. 6 is a block diagram illustrating an example of a configuration of a correction gain calculation circuit in FIG. 5. It is a block diagram which shows an example of a structure of the harmonic current command value generator between orders in FIG. FIG. 7 is a block diagram showing an example of the configuration of a comb filter in FIG. 6 and an example of its characteristics. It is a block diagram which shows an example of a structure of the instantaneous reverse phase calculator in FIG. It is the schematic which shows an example of the change of the correction gain which is the rate of change of the amplitude of the instantaneous reverse phase current in FIG. It is a single line connection figure which shows the system | strain model used for the simulation at the time of islanding generation | occurrence | production. Is a diagram showing an example of independent operation simulating the correction gain G ₁ is the change rate dI _n and its inverse of the amplitude of the instantaneous anti-phase current in Figure 6 in the event the result. Instead of the instantaneous anti-phase current in FIG. 6 is a diagram showing an example of a simulation result of the correction gain G ₁ is the change rate dI _p and its inverse of the amplitude of the instantaneous positive-phase current during isolated operation occurs. It is a figure which shows an example of the change of the harmonic current between orders and the harmonic voltage between orders in a measurement point when it has a conventional islanding operation detection apparatus, and the time of an islanding operation is simulated. It is a figure which shows an example of the change of the harmonic current between orders and the harmonic voltage between orders in a measurement point when it has the islanding operation detection apparatus of the 1st Embodiment of this invention, and the time of an islanding operation is simulated. . FIG. 6 is a block diagram showing another example of the configuration of the correction gain calculation circuit in FIG. 5. FIG. 17 is a schematic diagram for explaining an enlarged correction gain G ₄ in FIG. 16. It is a figure which shows an example of the change of the harmonic current between orders and the harmonic voltage between orders in a measurement point when simulating the time of an isolated operation generation | occurrence | production on the conditions which are hard to produce an impedance change when it has the conventional isolated operation detection apparatus. . Changes in inter-order harmonic current and inter-order harmonic voltage at measurement points when a single operation occurrence is simulated under conditions where impedance change does not easily occur when the isolated operation detection device according to the first embodiment of the present invention is provided. It is a figure which shows an example. Changes in inter-order harmonic current and inter-harmonic voltage at measurement points when simulating the occurrence of isolated operation under conditions where impedance change is unlikely to occur when the isolated operation detection device of the second embodiment of the present invention is provided It is a figure which shows an example.

(1) First Embodiment of Isolated Operation Detection Device FIG. 3 shows an example of a system having a configuration in which a distributed power supply facility having an isolated operation detection device according to an embodiment of the present invention is connected to a distribution system. Parts identical or corresponding to those in the conventional example shown in FIGS. 1 and 2 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below.

The isolated operation detection device 10a of this embodiment includes a control device 30a corresponding to the above-described conventional control device 30 and the isolated operation monitoring device 32 described above. The control unit 30a, via a current transformer 28, the current I _s flowing through the measurement points 24 on the tie-line 22 is fetched. The current I _s are those as described above, the fundamental wave current I interharmonic current I _m to ₁ superimposed.

Control device 30a, the size of interharmonic current I _m flowing through the measurement points 24 on the tie-line 22, to calculate the rate of change from the value before the predetermined time, harmonic between orders to be output from the inverter 6 wave current I _m, and has a interharmonic current correction circuit 72 to increase in inverse proportion to the calculated rate of change. This will be described in detail below.

Prior to that, an example of the configuration of the isolated operation monitoring device 32 will be described with reference to FIG. This isolated operation monitoring device 32 is an example in which the rate of change dV _m of the inter-order harmonic voltage V _m included in the voltage V _s at the measurement point 24 is determined. A value calculator 64, a moving average calculator 66, a change rate calculator 68, and a comparator 70 are provided.

The discrete Fourier transformer 62 extracts the inter-order harmonic voltage V _m from the voltage V _s by discrete Fourier transform and outputs it.

The absolute value calculator 64 calculates and outputs the absolute value | V _m | of the inter-order harmonic voltage V _m given from the discrete Fourier transformer 62.

The moving average calculator 66 calculates and outputs a moving average value V _mav for a predetermined time in the past for the absolute value | V _m | given from the absolute value calculator 64. For example, the moving average value V _mav for one second in the past from the present is calculated.

The change rate calculator 68 calculates and outputs the change rate dV _m of the absolute value | V _m | according to the following equation. That is, the change rate dV _m is a ratio of | V _m | to V _{mav in} this example.

[Equation 1]
dV _m = | V _m | / V _mav

The comparator 70 compares the rate of change dV _m given from the rate of change calculator 68 with a predetermined judgment value J _1, and when the former dV _m exceeds the latter J ₁ , the distributed power source 8 is put into a single operation. An isolated operation detection signal S ₁ indicating that the failure has occurred is output.

However, instead of determining the rate of change dV _m of the inter-order harmonic voltage V _m , the isolated operation monitoring device 32 has a large inter-order harmonic voltage V _m as described in, for example, Patent Document 1 described above. Saga when exceeds a predetermined judgment value, may be adopted that outputs the isolated operation detecting signal S _1.

The isolated operation detection signal S ₁ may be output from the isolated operation monitoring device 32 as it is. However, the isolated operation detection signal S ₁ is output after determining that the signal S ₁ continues for a predetermined time (for example, about 20 milliseconds). May be. By doing so, it becomes easy to prevent erroneous detection due to instantaneous fluctuations of the voltage V _s or the like due to some cause other than the occurrence of isolated operation.

  In this embodiment, as shown in FIG. 5, the control device 30a further includes a three-phase / two-phase converter 74 and a correction gain calculation circuit 76 as compared with the one shown in FIG. Command value correctors 124 to 126 (see FIG. 7) are provided in the harmonic current command value generator 46a, and in this embodiment, these constitute the inter-order harmonic current correction circuit 72 described above. These are described in detail below.

The three-phase / two-phase converter 74 orthogonally converts the three-phase current I _s (that is, I _su , I _sv , I _sw ) flowing through the measurement point 24 of the interconnection line 22 according to the following formula, The phase α component current I _s α and β component current I _s β are converted. As described above, the command value I _m ′ and the like of the inter-order harmonic current is handled in two phases, so that it corresponds to it.

[Equation 2]
I _s α = √ (2/3) {I _su − (1/2) I _sv − (1/2) I _sw }
I _s β = √ (2/3) {(√3 / 2) I _sv − (√3 / 2) I _sw }

Incidentally, the two-phase / three-phase converter 60 described above performs conversion from two phases to three phases according to the following equation, and outputs three-phase control signals CS (ie, CS _u , CS _v , CS _w ). Vα is an α component voltage supplied from the adder 58 to the 2-phase / 3-phase converter 60, and Vβ is a β component voltage.

[Equation 3]
CS _u = √ (2/3) · Vα
CS _v = √ (2/3) {− (1/2) · Vα + (√3 / 2) · Vβ}
CS _w = √ (2/3) {− (1/2) · Vα− (√3 / 2) · Vβ}

  An example of the configuration of the correction gain calculation circuit 76 is shown in FIG. The correction gain calculation circuit 76 includes comb filters 78 and 80, an instantaneous reverse phase calculation unit 82, a low-pass filter 84, a change rate calculation unit 86, and a correction gain calculation unit 94.

The comb filters 78 and 80 respectively obtain the currents obtained by removing the fundamental wave of the distribution system 2 and the harmonics of the integral multiple thereof from the α component current I _s α and β component current I _s β obtained by the orthogonal transformation. Output.

An example of the configuration and characteristics of the comb filters 78 and 80 is shown in FIG. Each of the comb filters 78 and 80 calculates a fundamental wave one cycle before by the delay unit 130, subtracts it from the current value by the subtracter 132, and outputs the gain by halving by the amplifier 134. As a result, as shown in FIG. 8B, the fundamental wave of the power distribution system 2 and its integral multiple harmonics can be removed. Interharmonics current I _m which is included in the current I _s flowing through the measuring points, because the order is a non-integer multiple order m is greater than 1 times the fundamental wave of the power distribution system 2 as described above, comb The filters 78 and 80 pass through without being removed.

  The non-integer multiple order (in other words, the sub-order number) m is, for example, 1 <m <when the voltage of the interconnected distribution system 2 is a high voltage of 7 kV or less, in order to increase the detection accuracy of isolated operation. 2.75 (however, m ≠ 2) is preferable, and in the case of extra high voltage where the voltage of distribution system 2 exceeds 7 kV, it is within the range of 1 <m <3.6 (where m ≠ 2, m ≠ 3) Has been confirmed by experiments. In this embodiment, the range of 2.25 to 2.75 order is used as an example.

Referring again to FIG. 6, the instantaneous reverse phase calculator 82 uses the instantaneous values of the currents I _s α and I _s β output from the comb filters 78 and 80, and instantaneous instantaneous phase of the current according to the following equation: The current amplitude | I _n | is calculated and output. Here, I _n α is the α component of the instantaneous reverse phase current, I _n α ′ is the component 90 degrees before, I _n β is the β component of the instantaneous reverse phase current, and I _n β ′ is the component 90 degrees before It is.

[Equation 4]
I _n α = (1/2) (I _s α + I _s β ′)
I _n β = (1/2) (I _s β−I _s α ′)
| I _n | = √ (I _n α ² + I _n β ² )

The reverse phase component (or normal phase component) of the alternating current is normally calculated according to the symmetric coordinate method using the effective value, but here, instead of using the instantaneous value of the current, The symmetrical coordinate method is defined approximately, and the instantaneous negative phase current (specifically, its α component and β component) and the amplitude of the instantaneous negative phase current | I _n | are calculated according to the above formula. Since the instantaneous reverse phase current is calculated using the instantaneous value as described above, it can be calculated at a higher speed than when the effective value is used. This will be described in more detail later.

An example of the configuration of the instantaneous reverse phase calculator 82 is shown in FIG. The β component current I _s β is delayed by 90 degrees by the delay unit 138 to calculate the β component current I _s β ′, which is added to the α component current I _s α by the adder 140, and the gain is set to 1 by the amplifier 144. Then, the α component I _n α of the instantaneous reverse phase current is calculated and supplied to the coordinate converter 148. This is the operation of the first row in the above equation 4. Further, the α component current I _s α is delayed by 90 degrees by the delay unit 136 to calculate the α component current I _s α ′, subtracted from the β component current I _s β by the subtractor 142, and gained by the amplifier 146. and 1/2, and supplies the coordinate converter 148 calculates the instantaneous negative sequence current beta component I _n beta. This is the operation of the second row in the above equation 4.

The coordinate converter 148 performs the calculation on the third row in the above equation 4, calculates the amplitude | I _n | of the instantaneous reverse phase current, and outputs it. The amplitude | I _n | represents the magnitude of the interharmonic current I _m which is included in the current I _s flowing through the measurement point 24 (amplitude). This is further explained below.

That is, when the interphase harmonic current Im of non-integer multiple order _m is single-phase injected into the interconnection line 22 as in this embodiment, the single-phase injection is an unbalanced injection. as also described in 1 (see especially 945-946 pages), the harmonic current I _m among the orders is calculated as a positive phase current, or reverse-phase current of the flow measurement point 24 non-integer multiple order m be able to. Among them, this embodiment deals with a reverse phase current. The reason will be described in detail later.

  Non-Patent Document 1: Yamamoto Fumio, 3 others, “Development of an independent operation detection device for distributed power sources-Harmonic injection method between orders”, The Journal of the Institute of Electrical Engineers of Japan, The Institute of Electrical Engineers of Japan, December 10, 2004 24, No. 12, pp. 943 (57) -952 (66)

The Interharmonics current I _m, because its degree is non-integral multiple order m of the system fundamental wave as described above, almost absent in nature in the distribution system 2, thus, flows through the measurement point 24 By passing the current I _s (current converted into the α component current I _s α and β component current I _s β by the three-phase / two-phase converter 74 in this example) through the comb filters 78, 80, an instantaneous Only the α component current I _s α and β component current I _s β of the non-integer multiple order m injected by the own equipment are supplied to the negative phase computing unit 82, where the amplitude | I _n | Is calculated. Therefore, the amplitude | I _n | represents between the orders are included in the current I _s flowing through the measurement point 24 the magnitude of the harmonic current I _m (amplitude).

Referring to FIG. 6 again, the low-pass filter 84 is for removing noise such as a DC component from the calculated amplitude | I _n |, and although it is preferable to provide it, it is not essential. The time constant of the low-pass filter 84 is preferably about 100 milliseconds or less. By the above process, the amplitude | I _n | can be calculated at a high speed of about 100 msec or less.

The rate-of-change calculator 86 calculates and outputs the rate of change dI _n from a predetermined time before the amplitude | I _n | of the instantaneous anti-phase current output from the instantaneous anti-phase calculator 82 and passed through the low-pass filter 84. To do. The calculation of the change rate dI _n, as in this example, it is preferable to use a moving average.

More specifically, in this example, the change rate calculator 86 delays the amplitude | I _n | from the low-pass filter 84 by a delay unit 88 for a predetermined time (for example, about 1 second), and the moving average calculator 90 calculating a moving average I _nav of the predetermined time (for example, about 0.5 seconds), and calculates the change rate dI _n accordance with still following expressions divider 92.

[Equation 5]
dI _n = | I _n | / I _nav

By delaying a predetermined time by the delaying unit 88, it is possible to increase the change rate dI _n when islanding occurs. The rate of change dI _n represents the same reason as described above, the magnitude of the rate of change of the interharmonic current I _m which is included in the current I _s flowing through the measurement points 24.

Correction gain calculator 94, the correction gain G ₁ is the reciprocal of the rate of change dI _n from the change rate calculator 86 calculates and outputs. More specifically, in this example, the correction gain calculator 94 includes a constant setting unit 96 that generates a constant 1.0, and a divider 98 that calculates and outputs the correction gain G ₁ according to the following equation. ing.

[Equation 6]
G ₁ = 1 / dI _n

FIG. 10 shows a schematic example of the change rate dI _n of the amplitude of the instantaneous reverse phase current in FIG. 6 and the change of the correction gain G ₁ which is the reciprocal number when the isolated operation occurs. As shown in FIG. 10A, since there is almost no change in the amplitude | I _n | at all times, the rate of change dI _n is almost 1, and when the single operation occurs, it flows through the interconnection line 22 as described above. since the current I _s interharmonic current I _m that is being included in the decreases, the change rate dI _n is smaller than 1, finally 1 / n (n is greater than 1.0 number) settled in the vicinity. As shown in FIG. 10 (B), the correction gain G ₁ varies in reverse the change rate dI _n. That is, changes so as to cancel the change in the change rate dI _n.

The correction gain G ₁ from the correction gain calculation circuit 76 (more specifically, the correction gain calculation unit 94) is applied to the inter-order harmonic current command value generator 46a as shown in FIG. Interharmonics current command value generator 46a is a command value of the interharmonic current I _m 'to give in order to output the interharmonic current I _m to the inverter 6, from the correction gain calculator 94 has the correction gain G ₁ command value corrector that increases with the (reference command value corrector 124 to 126 in FIG. 7). An example of the configuration of the inter-order harmonic current command value generator 46a is shown in FIG.

The frequency f _m interharmonic current I _m of the non-integer multiple order m output from the inverter 6 is set by the frequency setting unit 100, which in the angular frequency omega _m according to Equation 7 by an amplifier 103 of the phase generator 102 Then, it is converted into an angle θ _m in a discrete time system by the accumulator 104 according to Equation 8. n is a data number.

[Equation 7]
ω _m = 2πf _m

[Equation 8]
θ _m = Σω _m [n]

Further, the remainder calculator 105 calculates the remainder when the angle θ _m is divided by 2π, and sets the angle θ _m in the range of 0 to 2π.

In the initial phase setter 112 to 114, u interharmonic current I _m, v, w-phase of the initial phase θ _mu, θ _mv, θ Set _mw, the angle theta _m them in adder 108 to 110 Add to. For example, in this embodiment, since it is a single-phase injection into the uv phase, θ _mu = 0 and θ _mv = π are set. In the example of FIG. 7, the w-phase circuit is also provided in the same manner as the u and v-phase circuits so that the injection phase can be arbitrarily selected, and the output of the w-phase circuit other than the injection phase is set to 0. . If the injection phase is fixed (for example, fixed to the uv phase), it is not necessary to provide a circuit for the other phase (for example, w phase), and the phase (w phase) converts the 0 signal to 3 phase / 2 phase. What is necessary is to give to the container 128. The same applies to the following description.

Using the signals from the adders 108 to 110, the sine wave function generators 116 to 118 generate non-integer multiple order m sine wave signals, and the amplifiers 120 to 122 set their amplitudes according to the following equations: The harmonic currents I _mu , I _mv , and I _mw of the u, v, and w phases are generated. However, the output of the w-phase circuit is 0 as described above. In this example, the interharmonic current I _mu is the interharmonic current command value I _m ′ and the _{interharmonic} current I _mv. Is the command value −I _m ′.

[Equation 9]
I _mu = G _mu · sin (θ _m + θ _mu )
I _mv = G _mv · sin (θ _m + θ _mv )
I _mw = G _mw · sin (θ _m + θ _mw )

The frequency setter 100 to the amplifiers 120 to 122 can also be referred to as a generation circuit for the command value I _m ′ of the interharmonic current.

The command value correctors 124 to 126 are multipliers in this example, and the command value correctors 124 to 126 are added to the command value I _m ′ (specifically, the inter-order harmonic currents I _mv and I _mw ) of the inter-order harmonic current. is multiplied by the correction gain G _1, i.e., the command value I _m 'is increased by the correction gain G _1, it gives the 3-phase / 2-phase converter 128. However, as described above, the w-phase command value corrector 126 may not be provided.

The three-phase / two-phase converter 128 converts the three-phase input into two phases according to the same equation as the equation 2 in the same manner as in the case of the three-phase / two-phase converter 74, and the corrected order. An inter-harmonic current command value I _m ′ is converted into an α component I _m α and a β component I _m β and output, and these are added to an adder 48 shown in FIG. 5 (also for two phases as described above). To give. Figure adder 48 after at 5 is the same as that of FIG. 2, thereby, the interharmonic current I _m that is output from the inverter 6 can be increased by the correction gain G _1.

According to the independent operation detecting apparatus 10a as described above, when the isolated operation occurs, the impedance viewed from the measurement point 24 the power distribution system 2 side is increased, the interharmonic current I _m flowing through the measuring point 24 Although decreasing, interharmonic current correction circuit 72 in the control device 30a, in this embodiment, the rate of change of the interharmonic current I _m (specifically, the rate of change of interharmonic current I _m to calculate the instantaneous rate of change of the negative sequence current dI _n) representing the a interharmonic current I _m output from the inverter 6, the embodiment in (specifically to increase in inverse proportion to the rate of change calculated above so it is allowed) since increasing the correction gain G ₁ is the inverse of the change rate dI _n, reduction of interharmonic current I _m flowing through the measuring point 24 is suppressed. As a result, the change in the inter-order harmonic voltage V _m at the measurement point 24 at the time of isolated operation is increased, so that the determination value J ₁ can be easily selected by the isolated operation monitoring device 32.

That is, since the judgment value J ₁ does not need to be made too small, erroneous detection is performed when a system disturbance such as an instantaneous drop in system voltage or a change in system frequency occurs (that is, unnecessary detection that determines that the system is operating independently but not operating independently). Can be prevented. In addition, when the single operation occurs, the change in the inter-order harmonic voltage V _m becomes large and reliably exceeds the determination value J ₁ , so that the single operation can be reliably detected. Further, although the feedback coefficient K _p set by the amplifier 54 has been described in the problem of the prior art, in this isolated operation detection device 10a, the feedback coefficient K _p is the original output of the distributed power source 8 as before. since the fundamental wave current I ₁ may be set focuses it, it is possible to prevent the control of the fundamental wave current I ₁ becomes unstable.

  As a result, according to this isolated operation detection device 10a, it is possible to achieve both reliable detection of isolated operation and prevention of erroneous detection when a system disturbance occurs.

Further, in this embodiment, interharmonic current correction circuit 72 have the comb filter 78, 80 or the like as an instantaneous anti-phase calculator 82 and its pre-treatment, the rate of change of interharmonic current I _m and by detecting the amplitude of the change rate dI _n instantaneous negative sequence current, can be detected at high speed as compared with the case of using a discrete Fourier transformer or the like, output from the inverter 6 during isolated operation occurs order it can be more rapidly suppressed decrease between harmonic current I _m. As a result, since the change in the inter-order harmonic voltage V _m at the measurement point 24 when the isolated operation occurs becomes larger, the selection of the judgment value J ₁ in the isolated operation monitoring device 32 becomes easier. As a result, it is possible to more reliably achieve both reliable detection of isolated operation and prevention of erroneous detection when a system disturbance occurs.

This will be explained in more detail, the extraction of interharmonic current I _m of the non-integer multiple order m as described above, although conventionally the discrete Fourier transformer is often used, when using a discrete Fourier transformer since it is necessary to increase the frequency resolution (30 degree period sentence of example systems fundamental) by increasing the number of samples, the extraction of interharmonic current I _m becomes slow. If this happens, it is slow operation to increase the interharmonic current I _m which detects a change in interharmonic current I _m output from the inverter 6, interharmonic voltage at the measurement point 24 at the time of islanding occurs V _The operation for increasing the change of _m is also delayed, and the isolated operation detection in the isolated operation monitoring device 32 is delayed. On the other hand, in this embodiment, since the amplitude of the instantaneous reverse phase current is calculated using the instantaneous value, high speed calculation is possible, and therefore detection of the change in the inter-order harmonic current _Im etc. is delayed. The generation | occurrence | production of a problem can be prevented.

Further, the calculation of the reverse phase component of interharmonic current I _m, the use of conventional symmetric coordinate method using an effective value, since it requires the measurement of one or more cycles of the system fundamental wave for calculation of the effective value, In this case as well, even if not as much as when a discrete Fourier transformer is used, the calculation is slowed down and the same problem as described above occurs. On the other hand, in this embodiment, since the amplitude of the instantaneous reverse phase current is calculated using the instantaneous value, high speed calculation is possible, and therefore detection of the change in the inter-order harmonic current _Im etc. is delayed. The generation | occurrence | production of a problem can be prevented.

As described above, if the interharmonic current I _m of the non-integer multiple order m and single phase injected harmonic current I _m between the orders, positive phase of non-integer multiple order m flowing measuring point 24 Although it can be calculated as a current or a negative phase current, it is preferable to handle the negative phase current as in this embodiment rather than the positive phase current. Specifically, it is preferable to handle instantaneous reverse phase current. The advantages of handling instantaneous values are as described above. The fact that it is preferable to handle the instantaneous negative phase current rather than the instantaneous positive phase current will be described using the following simulation results.

(2) Example of simulation The system model shown in FIG. 11 was used for the simulation. This is a more specific example of the power distribution system 2 of the system shown in FIG. In other words, the high-voltage distribution line 152 is connected to the upper system 156 via the circuit breaker 154 of the substation, and the above-described distributed power supply facility 36 is connected to the upper system 156 via the transformer 150 and the interconnection line 22. A high voltage customer facility 158 having a transformer 160 and a load 162 is connected to the high voltage distribution line 152. Here, assuming the standard high-voltage system, the simulation conditions were as follows.

Host system 156: 60 Hz system, 3-phase 6.6 kV, impedance j8% (10 MVA base)
High-voltage distribution line 152: impedance 30 + j40% (10 MVA base), equivalent to 5 km in length Transformer 150, 160: three-phase 6.6 kV / 210 V, 110 kVA, impedance (% Z) 2.5% (self-capacitance base), reactance ( X) / resistance (R) ratio = 1.11
Distributed power supply 8 (solar power generation): Capacity 100 kW
High voltage customer load 162: resistance load 100 kW, motor load 30 kVar, power factor improving capacitor 30 kVar (quality factor Qf = 0.3)
Impedance change at the time of isolated operation: 20 times Injected harmonic current I _m : Order m = 2.73, 2% of rated current is output from inverter 6

  In the system model described above, the simulation results when the distributed power source 8 is operated independently by opening the circuit breaker 154 in the substation in a state where the distributed power source 8 and the customer load 162 are balanced with the same capacity are shown in FIG. 12 to FIG.

First, FIGS. 12 and 13 will be described. When the circuit breaker 154 is opened and a single operation occurs, if the Q balance (reactive power balance) with the consumer load 162 is slightly different from the output of the distributed power supply 8, the power conditioner 34 changes the output frequency. In order to balance reactive power by raising and lowering, the frequency of the fundamental voltage V ₁ in the isolated operation system downstream from the circuit breaker 154 changes. The direction of this frequency change (up and down) depends on the superiority or inferiority of L and C constituting the customer load 162, and the magnitude of the frequency change depends on how the Q balance is broken.

As described above with reference to FIG. 2 (and FIG. 5), the fundamental wave current I ₁ from the distributed power supply 8 is output according to the command value I ₁ ′ created based on the phase information of the fundamental wave voltage V _1. Therefore, when the frequency of the fundamental wave voltage V ₁ changes as described above, the frequency of the fundamental wave current I ₁ also changes. Since this frequency change is of the fundamental wave current I ₁ , it appears as a change in the normal phase when viewed from the symmetrical component, and does not occur in the reverse phase.

Accordingly, the rate of change dI _n of the amplitude of the instantaneous reverse-phase current in FIG. 6 and the correction gain G ₁ that is the reciprocal thereof in FIG. 6 when the single operation occurs are not affected by the frequency change of the fundamental current I ₁ . As shown in FIG. 12, the change is the same as that described above with reference to FIG. Therefore, it is possible to exhibit the operational effect described above, to successfully correct the magnitude of interharmonic current I _m output from the inverter 6 during isolated operation occurs.

On the other hand, if the correction gain calculating circuit 76 shown in FIG. 6, instead of the instantaneous anti-phase currents, treats instantaneous positive-phase current, the amplitude variation of the instantaneous positive phase current instead of the rate of change dI _n instantaneous negative sequence current When the rate dI _p is calculated and the reciprocal thereof is set as the correction gain G ₁ , it is affected by the fluctuation of the positive phase accompanying the frequency change of the fundamental wave current I ₁ , so that an isolated operation occurs as shown in FIG. The rate of change of the harmonic current between orders and the correction gain cannot be calculated correctly. That is, as shown in FIG. 13 (A), when an isolated operation occurs, the impedance on the distribution system 2 side is originally increased, so that the harmonic current between the orders decreases, but on the contrary, the instantaneous positive phase current of and increased the rate of change dI _p. as a result, the correction gain G ₁ is being reduced as shown in FIG. 13 (B). This is the reverse operation of reducing it to a situation that must really increase the interharmonic current I _m. In addition, the variation rate of the instantaneous positive phase current change rate dI _p and the reciprocal correction gain G ₁ vary depending on how the Q balance is lost. 6 can not be successfully corrected the magnitude of interharmonic current I _m to be output from.

  For the above reasons, it is preferable to handle the instantaneous negative phase current as in this embodiment rather than the instantaneous positive phase current.

Next, FIGS. 14 and 15 will be described. The simulation conditions are as described above. In the figure, for reference, an example of a determination value J _{2 in} the case where the change in the inter-order harmonic voltage V _m is determined based on the magnitude of the voltage V _m is shown. However, it is not limited to this. The same applies to other figures described later.

Figure 14 is a diagram when having 1 to FIG. 2 reference conventional independent operation detecting apparatus 10 described and islanding operation between orders at the measuring point 24 when the simulated time of occurrence harmonic current I _m and between orders is a diagram showing an example of a change in the harmonic voltage V _m. When breaker 154 of the substation is opened islanding occurs, and decreased to about 1/3 of the harmonic current I _m between orders with increasing system impedance, in its effects, interharmonic The change in the voltage V _m is much smaller than the original impedance change (this is 20 times as shown in the simulation conditions) and is limited to about 6 to 7 times. Depending on the system conditions, the change in inter-order harmonic voltage V _m may be smaller than this (see, for example, FIG. 18 and its description). Therefore, as described above, it becomes difficult to select the judgment value J ₂ so that the interharmonic voltage V _m surely exceeds the judgment value J ₂ only when the single operation occurs. It becomes difficult to achieve both prevention of erroneous detection at the time of occurrence.

FIG. 15 shows the inter-order harmonics at the measurement point 24 when simulating the occurrence of isolated operation when the isolated operation detection device 10a of the first embodiment of the present invention described with reference to FIGS. is a diagram showing an example of a change in the wave currents I _m and interharmonic voltage V _m. When breaker 154 of the substation is opened by islanding operation occurs, is fastened to 2/3 but the harmonic current I _m decreases between orders with increasing system impedance, whereby interharmonic The change in the voltage V _m increases to about 12 times. Therefore, as described above, it becomes easy to select the judgment value J ₂ so that the interharmonic voltage V _m surely exceeds the judgment value J ₂ only when the single operation occurs. It is possible to achieve both prevention of erroneous detection when a disturbance occurs.

(3) Second Embodiment of Isolated Operation Detection Device Next, the second embodiment of the isolated operation detection device 10a will be described mainly with respect to differences from the previous first embodiment.

In this embodiment, the inter-order harmonic current correction circuit 72 in the control device 30a is more specifically the correction gain calculation circuit 76 constituting the same, as in the example shown in FIG. The correction gain expander 164 further expands the rate of change of the correction gain G ₁ from the adjuster 94 while maintaining the steady-state value at 1, and outputs it as the correction gain G ₄ .

Then, instead of the correction gain G ₁ , the enlarged correction gain G ₄ is given to the command value correctors 124 to 126 in the inter-order harmonic current command value generator 46a shown in FIG. the command value I _m 'interharmonic current applied to, so that increase in the correction gain G ₄ which is enlarged from the correction gain expander 164.

In this example, the correction gain expander 164 includes an amplifier 166 that amplifies the correction gain G ₁ from the correction gain calculator 94 with a gain G ₂ , and a constant setting unit 170 that sets a constant (G ₂ −1.0). And a subtractor 168 that subtracts the output of the constant setting unit 170 from the output of the amplifier 166 and outputs a correction gain G ₄ expressed by the following equation.

[Equation 10]
G ₄ = G ₂ · G ₁ − (G ₂ −1)

The reason for using the correction gain G ₄ with reference to FIG. 17 will be described. The correction gain G ₁ in FIG. 17A is the same as the correction gain G ₁ shown in FIG. If the gain G ₂ is simply multiplied to increase the rate of change of the correction gain G _1, the correction gain G ₃ (= G ₂ · G ₁ ) shown in FIG. It becomes G ₂ instead of 1. In contrast, when the above correction gain G _4, as shown in FIG. 17 (B), while keeping the value of the steady state 1, it is possible to enlarge the rate of change of the correction gain G _4. Correcting Keeping the value in the steady state gain G ₄ to 1, requires without changing the size of the interharmonic current I _m output from the inverter 6 during steady, interharmonic at the measurement point 24 in the steady state and thus Since it is not necessary to change the magnitude of the voltage V _m , it is not necessary to change the judgment value J ₁ (or J ₂ ) in the isolated operation monitoring device 32, and the change in the inter-order harmonic voltage V _m in the isolated operation monitoring device 32 can be avoided. Detection is easy.

Moreover, by using the correction gain G ₄ which is enlarged, it is possible to more reliably suppress the decrease of interharmonic current I _m which is output from the inverter 6 during isolated operation occurs. As a result, since the change in the inter-order harmonic voltage V _m at the measurement point 24 when the isolated operation occurs is further increased, the selection of the judgment value in the isolated operation monitoring device 32 is further facilitated. As a result, it is possible to more reliably achieve both reliable detection of isolated operation and prevention of erroneous detection when a system disturbance occurs.

(2) the effect of using the correction gain G ₄ which is enlarged as in other examples the second embodiment of the simulation will be described with reference to the following simulation results. Also in this case, the system model shown in FIG. 11 was used. The simulation conditions were the following conditions in which impedance change hardly occurs when an isolated operation occurs.

Host system 156: 60 Hz system, 3-phase 6.6 kV, impedance j8% (10 MVA base)
High-voltage distribution line 152: impedance 180 + j 240% (10 MVA base), equivalent to 30 km in length Transformer 150: 3-phase 6.6 kV / 210 V, 110 kVA, impedance (% Z) 7.5% (self-capacitance base), reactance (X) / Resistance (R) ratio = 1.11
Transformer 160: 3-phase 6.6 kV / 210 V, 120 kVA, impedance (% Z) 7.5% (self-capacitance base), reactance (X) / resistance (R) ratio = 1.11.
Distributed power supply 8 (solar power generation): Capacity 100 kW
High voltage customer load 162: resistance load 100 kW, motor load 60 kVar, power factor improving capacitor 60 kVar (quality factor Qf = 0.6)
Impedance change at the time of isolated operation: 2.3 times Injected order harmonic current I _m : Order m = 2.73, 2% of rated current is output from inverter 6

  In the system model described above, the simulation results when the distributed power source 8 is operated independently by opening the circuit breaker 154 in the substation in a state where the distributed power source 8 and the customer load 162 are balanced with the same capacity are shown in FIG. 18 to 20.

Figure 18 is the result when the conventional independent operation detecting apparatus 10 described above, the interharmonic current I _m when the single operation has been reduced to about 1/2, with the effect, harmonics between orders The change in the wave voltage V _m is smaller than the original impedance change (which is 2.3 times as shown in the simulation conditions) and is limited to less than 2 times. Therefore, it is very difficult to select the judgment value J ₂ so that the inter-order harmonic voltage V _m surely exceeds the judgment value J ₂ only when the single operation occurs.

Figure 19 is a case having a first embodiment of the independent operation detecting apparatus 10a described above, a decrease in interharmonic current I _m when islanding operation is suppressed, with it, the order The change of the inter-harmonic voltage V _m is also increased to nearly twice. Accordingly, the determination value J ₂ can be easily selected.

Figure 20 is the result when the independent operation detecting apparatus 10a of the second embodiment, interharmonic current I _m when islanding operation is to recover quickly but decreases very short time, The output is almost constant. As a result, the change in the inter-order harmonic voltage V _m is as large as the original change in impedance (2.3 times). Therefore, even in a system in which an impedance change is unlikely to occur when an isolated operation occurs, it becomes easier to select the determination value J ₂ so that the inter-order harmonic voltage V _m surely exceeds the determination value J ₂ only when the isolated operation occurs. It is possible to more reliably achieve both reliable detection of isolated operation and prevention of erroneous detection when a system disturbance occurs.

2 Power distribution system 4 Power supply that outputs DC power 6 Inverter 8 Distributed power supply 10, 10a Independent operation detection device 22 Interconnection line 24 Measuring point 30, 30a Control device 32 Independent operation monitoring device 36 Distributed power supply equipment 46, 46a Interharmonic Wave current command value generator 72 Interharmonic current correction circuit 76 Correction gain calculation circuit 78, 80 Comb filter 82 Instantaneous antiphase calculator 86 Change rate calculator 94 Correction gain calculator 124-126 Command value corrector 164 Correction gain Expander m Non-integer multiple order I _m Harmonic current between _m orders V _m Harmonic voltage between orders _m dIn _n Rate of change in instantaneous negative phase current amplitude G ₁ , G ₄ correction gain

Claims (3)

The distributed power supply facility comprising a distributed power source having a power source that outputs DC power and an inverter that converts the DC power into AC power and outputs the same is applied to a system having a configuration in which the distributed power source is connected to a distribution system. An isolated operation detection device for detecting that the power supply has been operated independently,
By controlling the inverter, a single-phase harmonic current having a non-integer multiple order larger than 1 times the fundamental wave is simply applied from the inverter to a three-phase fundamental current having the same frequency as the fundamental wave of the distribution system. A control device having a function of superimposing and outputting in phase;
Measure the harmonic voltage between the orders of the non-integer multiple order at the measurement point on the connection line between the distributed power supply facility and the distribution system, and the distributed power supply operates independently from the change in the harmonic voltage between the orders. With an isolated operation monitoring device that detects that
The control device calculates a rate of change from a value before a predetermined time of the magnitude of the interharmonic current flowing through the measurement point on the interconnection line, and outputs the interharmonic harmonic output from the inverter. An isolated operation detection apparatus for a distributed power source, comprising: an inter-order harmonic current correction circuit that increases current in inverse proportion to the calculated rate of change. The inter-harmonic current correction circuit is
A comb filter that outputs a current obtained by removing a fundamental wave of the distribution system and a harmonic of an integral multiple thereof from a current flowing through a measurement point on the interconnection line;
Using the instantaneous value of the current output from the comb filter, the instantaneous negative phase calculator for calculating and outputting the amplitude of the instantaneous negative phase current of the current,
A change rate calculator that calculates and outputs the rate of change of the amplitude of the instantaneous negative phase current from the instantaneous negative phase calculator from a predetermined time; and
A correction gain calculator that calculates and outputs a correction gain that is the reciprocal of the change rate from the change rate calculator;
A command value corrector that increases a command value of an interharmonic current to be supplied to the inverter to output the interharmonic current with the correction gain from the correction gain calculator. The isolated operation detection apparatus for a distributed power source according to 1. The inter-order harmonic current correction circuit further includes a correction gain expander that expands and outputs the rate of change of the correction gain from the correction gain calculator while maintaining a steady-state value of 1,
The distributed operation of the distributed power supply according to claim 2, wherein the command value corrector increases the command value of the inter-order harmonic current to be supplied to the inverter with an increased correction gain from the correction gain expander. Detection device.

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