JP2003250226A - Single operation detection method for distributed power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect single operation of a distributed power supply only during a system stop by surely preventing fault detection due to variation of a system fundamental harmonic, without taking into account the phase-sequence variation of a system by means of single-phase injection of an intermediate-degree harmonic, and also by duplicating the detection. <P>SOLUTION: The intermediate-degree harmonic of an injected degree is single-phase injected to the system 5: positive-phase-sequence component and negative-phase-sequence component of each of a voltage and a current, in which the intermediate-degree harmonic of the injected degree of each system is measured, are detected; and the single operation of the distributed power supply 6 is detected only when there are concurrently performed the single operation detection of the distributed power supply 6 obtained from the variation of a detected impedance or a detected admittance of a positive-phase operation side calculated from the positive-phase-sequence component, and the single operation detection of the distributed power supply 6 obtained from the variation of the detected impedance or the detected admittance of a negative-phase operation side calculated from the negative-phase-sequence component. <P>COPYRIGHT: (C)2003,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] TECHNICAL FIELD The present invention relates to a system connected to a power system.
A distributed power supply that detects islanding when the
The present invention relates to an islanding detection method. [0002] 2. Description of the Related Art Conventionally, a power system is stopped due to an accidental power failure or the like.
Sometimes it detects the islanding operation of this kind of distributed power source by the customer and
In order to stop the operation, the applicant of the present invention disclosed in, for example,
No. 248168 (H02J 3/38) and the like.
As shown in the figure, the power system has a non-integer multiple of the system fundamental.
Inject current of interharmonics (intermediate harmonics)
-Order harmonics of the injection order from the voltage and current measurement signals
Voltage and current are detected, and the system
Impedance or admittance of inter-order harmonics of in-order
And the change (fluctuation) of these
We have already filed an invention to detect the isolated operation of a distributed power source.
You. [0003] SUMMARY OF THE INVENTION The conventional islanding inspection
When applying to a three-phase system,
As described in the specification, drawings, etc. of the application,
Source (intermediate harmonic current injection device) as a three-phase power source
It is necessary to inject the three-phase current of the interharmonic between the injection orders
is there. Therefore, the power supply for injecting interharmonics is
Therefore, there is a problem that an expensive and large three-phase power source is required. Therefore, the injection power supply is changed to a single-phase power supply to reduce the cost.
Down order and miniaturization, inter-order harmonics between two phases of the system
Single-phase injection to detect the isolated operation of the distributed power source when the system is stopped
It is conceivable that this single-phase injection
The detection method of islanding was not invented, and single-phase injection was performed.
In this case, note the
The shift between the input phase and the detection phase becomes a problem. Furthermore, the voltage of the interharmonic of the injection order,
The current is affected by fluctuations in the fundamental wave due to fluctuations in the system load, etc.
Erroneous detection. [0007] In addition, erroneous detection of islanding is prevented as much as possible.
Do not accidentally disconnect the distributed power supply from the grid when the grid is normal
It is desired that The present invention provides a single phase injection of interharmonics.
Without worrying about changes in the phase sequence of the system.
To be less susceptible to fluctuations in the fundamental wave
Prevent erroneous detection without fail, and in systems with large load fluctuations
Even when the system is stopped, it is possible to detect
The task is to make it work. [0009] Means for Solving the Problems To solve the above problems,
For this reason, the method for detecting the isolated operation of the distributed power
Next to the non-integer multiple of the system fundamental
Injects inter-harmonics, and inter-harmonics
Based on the measurements, the impedance of the interharmonic
Admittance is detected and the
Detection impedance or detection admittance of interharmonics
Of the distributed power source when the system is stopped
Method for detecting the isolated operation of a distributed power source
Single-phase injection of inter-order harmonics of the order
The measured voltage and current of the interharmonics of the
The positive phase of each of the voltage and current is decomposed into symmetric components
And negative phase components, and detects whether the voltage and the current are positive phase components.
The positive-phase impedance of the interharmonic of the injection order of the system
The positive phase admittance to the detection impedance on the positive phase calculation side.
Calculated as a dance or detection admittance,
From the negative phase component of the current, the interharmonic of the injection order of the system
-Phase operation of the reverse-phase impedance or admittance of
Calculated as detected impedance or admittance
Detection impedance on the positive phase calculation side or the detection impedance
Detection of isolated operation of distributed power supply from change in dominance and reverse
Detection impedance on the phase calculation side or the detection admittance
Detection of the isolated operation of the distributed power supply from the
Only when the operation of the distributed power source is detected. Therefore, for example, even in a three-phase system,
Interharmonics only need to be injected in a single phase, and a three-phase injection power supply
A single-phase power supply that is cheaper and smaller than the power supply can be used.
You. Next, the injection of each phase of the system based on the single-phase injection
Of the measured voltage and current of the
A normal phase component or a negative phase component is detected. By the way, a system fundamental wave is generated due to a load fluctuation or the like.
When the change in the positive phase is less than the change in the negative phase,
The positive phase component of the interharmonics injected into the system is
It is hardly affected by fluctuations of the system fundamental wave.
If the change in the positive phase of the wave is greater than the change in the negative phase
In other words, the amount of change in the reverse phase of the system fundamental wave is
If the change is smaller than the
The negative phase component of the inter-harmonic is affected by the fluctuation of the system fundamental wave from the positive phase component.
It turned out to be difficult. [0013] From this, it can be seen that the
Detecting isolated operation of distributed power sources based on changes in the positive phase
For example, when the positive phase change of the system fundamental wave is large,
Misdetection is likely to occur due to fluctuations of the fundamental wave, and the order of the injection order
Operation of the distributed power source based on the change of the reverse phase of the interharmonic
Is detected, the amount of change in the positive phase of the system fundamental wave is small,
When the amount of change in the negative phase is large, the
Erroneous detection is likely to occur. Then, the positive phase I of the interharmonic of the injection order is obtained.
Singularity from changes in impedance or normal phase admittance
Phase detection and reverse phase impedance of interharmonics of the injection order
Of islanding from changes in impedance or reverse phase admittance
Occur at the same time, and the distributed power
Only when the islanding of the distributed power source is detected.
In order to detect the inversion, the detection is duplicated and the system fundamental component
Is extremely insensitive to fluctuations in
False detection is reliably prevented, and it can be used in systems with large load fluctuations.
However, the isolated operation of the distributed power source is detected only when the system is stopped.
It is. [0015] BRIEF DESCRIPTION OF THE DRAWINGS FIG.
This will be described with reference to FIGS. Figure 1 is an example of a power system
FIG. 2 is a single-line diagram of a certain three-phase distribution system, and
The primary side of one or more transformers 3 of the substation 2 is connected,
From the secondary side of the transformer 3 through the circuit breaker 4 under one or more
The system 5 is branched out. [0016] These systems 5 are provided with a distributed power source 6.
General demand without key house equipment 7 and distributed power supply 6
A plurality of customer facilities such as the house facility 8 are connected. The customer equipment 7 is connected to other customer equipment.
Similarly, the load bus is connected to the system 5 via the breaker 10 of the service line 9.
11 is connected, and each load feeder 1 is connected to this load bus 11.
Each load is connected via two transformers 13. A breaker 14 is connected to the load bus 11.
And is distributed to the circuit breaker 14 via a disconnecting switch 15.
A power supply 6 is connected, and a single-phase
The flow injection device 16 is connected. The current injection device 16 is a single-order harmonic device.
Inexpensive and compact inverters that output the phase injection current
A single-phase power supply unit 17;
Formed by a single-phase injection transformer 18 provided therebetween.
You. Further, a load bus is connected from the circuit breaker 10 of the drop line 9.
On the 11 side, a three-phase transformer 19 and a current transformer 20 are respectively provided.
Voltage and current measurement signals for each phase
In the sample and hold circuit 22 of the stop detection processing device 21
Supplied. This sample and hold circuit 22
Of the sampling command of the constant frequency of the
The voltage and current measurement signals are sampled and
The output is held by the A / D conversion circuit 24 at the subsequent stage.
Voltage and current sampling
Data, and this voltage and current sampling data
It is supplied to the arithmetic processing unit 25. The arithmetic processing unit 25 is provided with a microcomputer.
Computer, etc., and the software processing
A known digital Fourier transform of the sampling data
Execute the filter operation and note from the current injection device 16 to the system 5
Interharmonics of the injected injection order are detected and
Of the distributed power source 6 when the circuit breaker 4 opens
Monitor and detect operation. Further, when this isolated operation is detected, a calculation is performed.
The processing unit 25 supplies a disconnection command to the switch 15, and
15 is opened to disconnect the distributed power source 6 from the system 5. By the way, when the system is normal, the circuit breakers 4, 1
0, 14 and the switch 15 are both closed,
1 is supplied to the grid 5, and the grid 5 is in the power supply state.
is there. At this time, the distributed power source 6 is connected to the system 5
It is operated and its output is consumed in its own equipment 7
The surplus is output to the system 5 via the service line 9. On the other hand, the transformer 19 and the current transformer 20 are
Voltage of each phase (three phases) of power receiving point P in FIG. 1, each phase of power receiving point P
The current of the service line 9 is constantly measured. Then, the arithmetic processing unit 25 sends a timing command.
The power supply unit is synchronized with the constant frequency timing signal of the unit 23.
17 periodically outputs a start command, and based on this command,
One or more power supply units 17 synchronized with the timing signal
Of single-phase current of interharmonic of frequency (channel)
These single-phase injection currents are applied to the transformer 18, the load
From the receiving point P via the line 11 and the drop line 9
Injected between two phases. Based on this injection, the transformer 19, the current transformer 2
The measurement signal of each phase of 0 includes the measurement of the interharmonic of the injection order.
Includes measured voltage and measured current. Next, the operation of the isolated operation by the
The detection process will be described. First, by stopping system 5
When the circuit breaker 4 is opened, the voltage and current measurement points
The impedance on the upstream side of the system as viewed from the
Change from short-circuit impedance to open impedance
And the interharmonic of the injection order of the system 5 viewed from the receiving point P
Detection impedance or detection admittance for
(Hereinafter referred to as detection impedance, etc.)
When the system 5 is stopped,
In addition, the isolated operation of the distributed power source 6 can be detected. Therefore, the arithmetic processing unit 25 performs the injection of the system 5
Impedance or admittance of inter-order harmonics of order
Is detected, and from the change, the distributed power source 6 is
Monitor and detect operation. By the way, the current injected into the system in single phase is
Nth harmonic (n: an integer of 1 or more) including a fundamental wave and n + 1
Non-integer order M that does not originally exist in the system between the second harmonic
(N <M <n + 1) inter-order harmonic current, detected
Influence of turning on / off capacitor equipment whose result is in the system
For example, to avoid receiving, the secondary of 2 <M <3
The current of the interharmonic between the harmonic and the third harmonic.
You. Specifically, the injection channel of the inter-order harmonics
Base frequency which is the frequency unit interval of the₀, System base
The main wave frequency (60Hz or 50Hz) is f₁And the injection order
Let the frequency (injection frequency) of the interharmonic of M be f_MTo be
And f₁= 60 Hz, for example, f₀= 2Hz
Set, 120 (= 2.60) Hz <f_M(= 120 + 2
A) <180 (= 3 · 60) Hz, (1 ≦ A ≦ k (k =
f₁/ F₀= 60/2 = 30)) is the single-phase current
Into system 5. At this time, the injection order of A = 15 M = 2.5
(= N + (A / 30))
If the injection frequency f_MIs 150 Hz. Next, on the upstream side of the system as viewed from the power receiving point P,
Generally, the resistance such as the line impedance of the system is extremely
Because it is small, as shown in the equivalent circuit diagram of a single connection in FIG.
An inductive reactor is connected between the system power source S and the receiving point P.
Source impedance Z_S, Distribution line path impedance
Z_LAre connected in series. In the equivalent circuit diagram of FIG.
Dance Z_S, Z_LThe reactance of X _S, X_LAnd receiving power
The impedance on the upstream side of the system viewed from point P is Z_PTomorrow
If Z _S= JX_S, Z_L= JX_LAnd Z_P= R_P+ JX_P
≒ j (X_S+ X_L), (R_P: Resistance, X_P:reactance
Minutes). The admittance Y_P(= 1 / Z_P)
Y_P= G_P+ J (-B_P) ≒ -j (1 / (X_S+ X_L)),
(G_P: Conductance component, (−B_P): Susceptance
Minutes). On the other hand, the downstream side of the system (load
Side) is more impedance than the upstream side (power supply side)
large. Then, the inter-order height of the injection order M at the receiving point P is
The harmonic voltage (injection voltage) is Vi_M, The injection current Ii_MWhen
And the impedance for the interharmonic of injection order M
Su Z_P , Admittance Y_PTo Z_PM, Y_PMIf so, other demand
In an ideal case where there is no influence from the key house, etc., 2_PM, Y_PMIs it
Each Z_PM= Vi_M/ Ii_M, Y_PM= Ii_M/ Vi_MRequested from
In practice, the impedance Z_PMAs that liak
Close X_PMTo Vi _M/ Ii_MThe imaginary part I of_mage(V_M/
I_MAdmittance Y_PMAs
Susceptance (-B_PM) To Ii_M/ Vi_M(−imaginary number
Part I_mage(Ii_M/ Vi_M)) Is sufficient. At this time, the three phases of the system 5 are changed to a, b,
c, between the b-phase and c-phase from the power supply 17
When injecting a single-phase current, the
Phase equivalent circuit on the upstream side of the system viewed from the receiving point P
Is represented by a Δ-type three-phase load circuit 26 in FIG. Therefore, a single-phase current of the interharmonic is injected.
Then, on the upstream side of the system, the three-phase current of the
Flows. Then, the order harmonics of the injection order M are described.
Admittance (impedance) of all the load circuits 26
-Dance) to Yab (Zab), Ybc (Zbc), Y
ca (Zca), and the line voltage of each phase is Va, Vb, V
c, and the line currents are Ia, Ib, and Ic, respectively.
Zero-phase component Y in the symmetrical coordinate method obtained by decomposition into components₀,
V₀, I₀, Positive phase component Y₁, V₁, I₁, Reverse phase component Y_Two, V_Two, I_Two
Can be obtained as follows. The voltages Va to Vc, the currents Ia to Ic, etc.
Is a vector value having a real part and an imaginary part. The voltages Va to Vc are expressed by the following equation (1).
Where α is α = exp (j · (2π / 3))
Is a constant. [0044] (Equation 1) Therefore, each symmetric component V₀~ V_TwoIs the voltage V
a to Vc as component V₀~ V_TwoThe following equation 2
It can be obtained from arithmetic. [0046] (Equation 2)Similarly, each symmetric component I₀~ I_TwoIs the current Ia
~ Ic to component I₀~ I_TwoEquation 3
Can be obtained from [0048] [Equation 3] Further, the symmetric component V₀~ V_Two, I₀~ I_TwoSought
Then, the symmetric component Y₀~ Y_TwoIs the operation of the following equation (4)
Can be obtained from [0050] (Equation 4) [0051] Then, in an ungrounded system such as a distribution system,
The zero-phase component I₀Becomes 0, so the expression of equation 4
By calculation, the interharmonics of the injection order M viewed from the receiving point P
Admittance Yp_MAs normal phase admittance Y₁= I₁
/ V₁, Reversed-phase admittance Y_Two= I_Two/ V_TwoIs obtained. At this time, the positive phase component Y₁, Reverse phase component Y_TwoIs a system stop
Change together due to shutdown, and if this change is monitored,
The stand-alone operation of the distributed power source 6 at the time of stoppage can be detected. By the way, admittance Y₁, Y_TwoWill eventually
Has a large susceptance, and in practical use, the admittance Y
₁, Y_TwoAs the respective imaginary parts -I_mage(I₁/
V₁), -I_mage(I_Two/ V_Two). Next, the load equipment of each customer in the system 5
The impedance (admittance) due to turning on and off
Changes, the system fundamental wave fluctuates, and the system characteristics change
Is such a load setting for the interharmonics of the injection order.
For example, acts as the fluctuation source NG shown in FIG.
You. Then, as shown in FIG.
Current I of interharmonic of injection order M injected into system 5
i_MTo the system 5 equivalently from the fluctuation source NG
The current of the interharmonic of the order M of the injected_MToss
You. In this case, the injection voltage V at the receiving point P at the time of fluctuation is
i_MSince there is no fluctuation source NG, the following equation 5
Obtained from the operation. [0057] ## EQU5 ## Vi_M= Z_PM・ Ii_M Then, the susceptance component before the fluctuation is calculated by (−B
_PM), The susceptance before this change (−B_PM)
Is calculated from the following equation (6) (I_mage: Imaginary part
Function). [0059] (Equation 6)_PM= -I_mage(Ii_M/ Vi_M) On the other hand, current Ig_MIs injected
And this current Ig_MAlso impedance Z_s, Z_LFlowing through
Therefore, the current Ig_MIs given by the following equation (7).
Voltage Vg of interharmonic of injection order M_MOccurs. [0061] ## EQU7 ## Vg_M= Z_PM・ Ig_M Then, the impedance Z_PMVoltage V
i_M, Vg_MAnd the series voltage of
Injection current is Ii_MSusceptance after fluctuation
Minutes (-B_PM’), The susceptance after the change (−
B_PM') Is obtained from the operation of the following equation (8). [0063] (Equation 8) -B_PM'= -I_mage(Ii_M/ (Vi_M+ Vg_M)) Then, the absolute value (magnitude) | I of the equation (6)
i_M/ Vi_M| And the absolute value (magnitude) of equation (8) | Ii_M/
(Vi_M+ Vg_M) |
(Vi_M+ Vg_M) Is the denominator Vg of the equation (6)._MBigger
Therefore, the susceptance after the change (−B_PM’) Absolute
The value is the susceptance (-B_PM) Less than the absolute value of
And approaches the value when the system was stopped. Then, due to the fluctuation of the system fundamental wave, the power receiving point
The order harmonics of the injection order M on the upstream side of the system viewed from P
Susceptance is (-B_PM) To (-B_PM’)
Decreasing changes, diversification despite system outage
The islanding of the power supply 6 is erroneously detected. Incidentally, this erroneous detection is performed as described above.
In addition, the current of the interharmonic of the injection order M changes with the system fundamental wave.
Ii under the influence of movement_MFrom Ii_M+ Ig_MChange to
Occurs with On the other hand, in the case of single-phase injection,
From the formula, the magnitude of the current and voltage of the
Can be understood as follows. For example, when a single phase is injected between the a phase and the b phase
Indicates that the phase currents of the a-phase and b-phase line currents are inverted,
Line current is zero. At this time, this condition is applied to the equation (3).
In other words, the positive-phase current and the negative-phase current have different phases,
The magnitudes are equal. Further, the voltage is positive from the equation (4).
If phase admittance and reverse phase admittance are equal,
It can be seen that the magnitudes of the voltage and the negative phase voltage are equal. why
Then, in the case of single-phase injection, the magnitudes of the positive-phase current and the negative-phase current are
Because they are equal. In addition, the three phases of the system viewed from the receiving point P
Think of the load circuit as roughly balanced between the three phases
Admittance (impedance) positive phase and negative phase
Are almost equal. As described above, in the case of single-phase injection, the
It can be said that the magnitudes of the voltage and the current become substantially equal. The three phases of the transformer 19 and the current transformer 20
Between the orders of the injection order M of the system 5 in the Fourier transform of the measurement signal
When the voltage and current of the harmonic are detected (extracted), the detection
Specifically, the influence of the system fundamental wave in
It is necessary to devise it separately. Next, the system base in the interharmonic extraction is described.
The effect of the fluctuation of the main wave will be specifically described. First,
In the following description, the base frequency and the system
The fundamental frequency (commercial fundamental frequency) is f₀, F₁age,
Instead of the injection order M, the base frequency f ₀Based on (basic
Wave) integer order m = f_M/ F₀Using the frequency f_M
= F_mAnd (A) When there is no fluctuation of the system fundamental wave In this case, the frequency f₀, F₁, F_MEach frequency ω₀, Ω₁,
ω_mIs ω₀= 2πf₀, Ω₁= 2πf₁= Kω₀, Ω_m= 2
πf_m= Mω₀, (M, k: m> k is an integer). The current Ii of the interharmonic of order m
_MAt the time t based on the measurement signal of the current transformer 20
The three-phase measured current (line current) is converted to a vector-valued current Ia
(t), Ib (t) and Ic (t), these currents Ia (t)
~ Ic (t) is the inter-order harmonic of order m at the system fundamental frequency.
Since the wave is superimposed, it can be expressed by the following equation (3).
The first term of each right side is the component of the system fundamental wave.
The second term on the right side is the interharmonic component. [0075] (Equation 9)   Ia (t) = I_1a・ Sin (ω₁t + φ_1a) + I_ma・ Sin (ω_mt + φ_ma)   Ib (t) = I_1b・ Sin (ω₁t + φ_1b) + I_mb・ Sin (ω_mt + φ_mb)   Ic (t) = I_1c・ Sin (ω₁t + φ_1c) + I_mc・ Sin (ω_mt + φ_mc) It should be noted that I in each equation of Equation 9 is_1a, I_1b, I_1c,
I_ma, I_mb, I_mcIs the maximum value and φ_1a, Φ_1b, Φ_1c,
φ_ma, Φ_mb, Φ_mcIs the initial phase. Then, the currents Ia (t) to Ic (t) of the nine equations are obtained.
For detecting (extracting) interharmonics of the injection order M from the
In this case, the following Fourier transform is generally used. Now, the current I (t) of the vector value is transmitted to the periodic signal
And the fundamental angular frequency is ω₀Then the current I (t)
The n-th harmonic component (harmonic component) contained is the sine
Ingredient I_nS, The cosine component is I_nCThe following equation 10-2
It is calculated from the Fourier transform formula of the formula. [0079] (Equation 10) Note that ω in the equation_nIs the angular frequency of the nth harmonic
Numbers and S-shaped symbols are integral symbols. And the expression 10
Assuming that the component of the nth harmonic based on Equation 2 is I (n), this high
The harmonic component I (n) is expressed by the following complex expression of Expression 11:
Is done. [0081] (Equation 11) By the way, the current I (t) = I · sin (ωt +
φ), the current I (t) is the vector
It is represented by an equation. [0083] ## EQU12 ## I (t) = I · sin (ωt + φ) = (1 / 2j) ·
[I · exp (j (ωt + φ)) − I · exp (−j (ωt + φ))] Therefore, the following equation (13) is established. [0085] (Equation 13) Then, from the current Ia (t) in the equation (9), the order
When detecting (extracting) interharmonics of order m, the following number
The calculation of the expression 14 may be performed. [0087] [Equation 14] When the operation of the equation (14) is actually performed,
By using the relation of the equation (13), the following equation (15) is obtained.
Is obtained. [0089] (Equation 15) Further, in the equation (13), ω₁−ω_m=
(Km) ω₀, Ω₁+ Ω_m= (K + m) ω₀, Ω_m−ω_m=
0, ω_m+ Ω_m= 2mω₀, K−m, k + m, 2 m
Is an integer, so in the expression of Expression 15, the following Expression 16
The following four equations hold. [0091] (Equation 16) Therefore, the operation result of the equation (15) is I
_ma・ Exp (jφ_ma). Then, the current Ib in the equation (9)
By performing the same operation for (t) and Ic (t),
Inter-order harmonics of order m of currents Ia (t), Ib (t) and Ic (t)
The wave components Ia (m), Ib (m) and Ic (m) are components of the system fundamental wave.
If there is no variation in the minutes, the Fourier transform
Calculation without being affected by the system fundamental wave.
Can be issued. [0093] [Equation 17](B) When the system fundamental wave fluctuates Next, at time t₀Load fluctuations occur in the
If it fluctuates, t ₀Before (t <t₀) Is 3 in Equation 9 above.
The currents Ia (t) to Ic (t) of each phase represented by the equations are t₀Since
(T ≧ t₀) Is expressed by the following equation (3).
Become. [0095] (Equation 18)   I_a(t) = I_1a’· Sin (ω₁t + φ_1a’) + I_ma・ Sin (ω_mt + φ_ma)   I_b(t) = I_1b’· Sin (ω₁t + φ_1b’) + I_mb・ Sin (ω_mt + φ_mb)   I_c(t) = I_1c’· Sin (ω₁t + φ_1c’) + I_mc・ Sin (ω_mt + φ_mc) Note that the first term on the right side in each of the equations (18) varies.
Is a component of the subsequent system fundamental wave,_1a’, I_1b’, I_1c’
Is the maximum amplitude after fluctuation, φ_1a’, Φ_1b’, Φ_1c’After the change
Is the initial phase. In addition, the second term on the right side of each equation of Expression 18
The components of the interharmonics do not change. Then, the current Ia expressed by each equation of Expression 18 is obtained.
From (t) to Ic (t), (t−2π / ω)₀) ≦ t₀≦ t range
In the box, the current Ia
(m) to Ic (m) are obtained. At this time, for example, the current I of the a-phase
a (m) is expressed by the following equation (19). [0098] [Equation 19] Further, the equation (19) is related to the equation (12).
Applying the engagement, ω₁= Kω₀, Ω_m= Mω₀, Km, k
Since + m is an integer, the first rightmost
The following equation (20) holds for each term. [0100] (Equation 20)Further, the second term on the rightmost side of the equation (19) is
Then, the following equation 21 is established. [0102] (Equation 21) Therefore, the current Ia (m) in the equation (19) is
The following equation (22) is used. [0104] (Equation 22) In the equation (22), I_1a’· Exp (j
φ_1a’) -I_1a・ Exp (jφ_1a) Is the current component of the system fundamental wave.
Is the difference vector due to the change, which is ΔI_aAnd that
To the conjugate amount of *_a ^*Then, the following Expression 23
Two equations hold. [0106] (Equation 23)   ΔI_a= I_1a’· Exp (jφ_1a’) -I_1a・ Exp (jφ_1a)   ΔI_a ^*= I_1a’· Exp (−jφ_1a’) -I_1a・ Exp (−jφ_1a) Then, the b-phase current Ib (m) and the c-phase current Ib (m)
Since the same applies to c (m), t−2π / ω₀≤
t₀Detected amount of inter-order harmonic component of order m in ≦ t
The (extraction amount) is as shown in the following equation (3). [0108] (Equation 24)Note that those marked with * in each equation of Equation 24 are
Indicate the amount of conjugation.
It is a component shown in. [0110] (Equation 25) Then, the current Ia of each phase of the equation (24) is calculated.
From (m), Ib (m) and Ic (m), the interharmonic of order m
Positive phase component (positive phase detection amount) I when decomposed into symmetric components
₁(m), negative phase component (reverse phase detection amount) I_Two(m) generally gives
Positive phase component I based on three-phase currents Ia, Ib, Ic₁, Reversed phase component
I_TwoIs I₁= (1/3) (I_a+ ΑI_b+ Α^TwoI_C), I_Two= (1 /
3) (I_a+ Α^TwoI_b+ ΑI_C), (However, α = exp (j2 / 3
π), α^Two= Exp (j4 / 3π)), the following
Equation 26 shows two equations. [0112] (Equation 26) I₁(m) = ζ · (ΔI₁₁) −ξ · (ΔI₁₂)^*+ I_m1 I_Two(m) = ζ · (ΔI₁₂) −ξ · (ΔI₁₁)^*+ I_m2 In equation (26), (Δ
I₁₁)^*, (ΔI₁₂)^*Is (ΔI₁₁), (ΔI₁₂)
The first and second terms that indicate the role and include the components ζ and の on the right
Error component ΔI caused by the influence of fluctuation of the fundamental wave_m1, Δ
I_m2And the third term on the right side is the original injected component. Then, the components ζ and 演 are represented by
By the calculation, the following two equations of Expression 27 are obtained. [0115] [Equation 27]On the basis of the two equations in Expression 27, the components ζ and ξ
The magnitudes | ζ | and | ξ | are shown in the following equation (28).
Swell. [0117] [Equation 28] | ζ | ≦ | (1 / (km) π) · sin [(km) ω₀(tt₀) / 2] | ≦ (1 / (mk) π ) | ξ | ≦ | (1 / (k + m) π) · sin [(k + m) ω₀(tt₀) / 2] | ≦ (1 / (m + k) π ) Therefore, the above equation (26) is used.
Normal phase component I₁(m), reversed phase component I_Two(m) is the effect of the fluctuation of the system fundamental wave
And the magnitude of the error component due to the variation | ΔI_m1|,
| ΔI_m2Is based on the following equation (2),
9, respectively. [0119] (Equation 29) | ΔI_m1| = | Ζ · (ΔI₁₁) −ξ · (ΔI₁₂)^*|        ≤ (1 / π) (| ΔI₁₁| / (Mk) + | ΔI₁₂| / (M + k))        = (1 / π) (m (| ΔI₁₁| + | ΔI₁₂|) + K (| ΔI₁₁|-| ΔI₁₂|)) / (M- k) ・ (m + k) | ΔI_m2| = | Ζ · (ΔI₁₂) −ξ · (ΔI₁₁)^*|        ≤ (1 / π) (| ΔI₁₂| / (Mk) + | ΔI₁₁| / (M + k))        = (1 / π) (m (| ΔI₁₁| + | ΔI₁₂|) + K (| ΔI₁₂|-| ΔI₁₁|)) / (M- k) ・ (m + k) As shown on the rightmost side of the two equations of Expression 29,
Error component | ΔI_m1|, | ΔI_m2| Is the error component | ΔI_m1
| K (| ΔI₁₁|-| ΔI₁₂|) Is incorrect
Difference component | ΔI_m2|, K (| ΔI₁₂|-| ΔI₁₁｜)
Is different. Then, | ΔI in the equation (29)
₁₁|, | ΔI₁₂| Is | ΔI₁₁| For fluctuation of system fundamental wave
Is the amount of change (fluctuation amount) of the positive phase generated by |
I₁₂| Is the change in the opposite phase caused by the fluctuation of the system fundamental wave
(Variation). Further, m and k in the two equations of the above Expression 29 are f₀
= 2Hz, f₁= 60Hz, f_m= 150 Hz, m = 1
50/2 = 75, k = 60/2 = 30.
Then, mk = 45 and m + k = 105. As described above, the system basics are determined by the load fluctuation of the system 5, etc.
When the wave fluctuates, the order m of the equation
The currents Ia (m), Ib (m), Ic (m) of the interharmonics are
Affected by fundamental wave fluctuations, decompose them into symmetric components
Then, the positive phase component I expressed by equation (26)₁(m), reversed phase component I
_Two(m) is the original component I based on single phase injection._m1, I_m2Alone
No, based on the fluctuation of the system fundamental wave component shown in Equation 29
Each error component ΔI_m1, ΔI_m2It is possible to include each
Revealed. Further, the error component ΔI_m1, ΔI_m2By
For example, the susceptance (-B_Pm ') (= -B
_PM) ′) Is the susceptance (−B_Pm) (= −B
_PM), And then the susceptance Bim '
Is different between the normal phase and the negative phase.
Was. (C) Influence of system fundamental wave First, the positive phase component I expressed by the above equation (26)₁(m), reversed phase
Minute I_TwoIn (m), the original positive phase amount of the injected component I_m1And reversed phase
Quantity I_m2Is a single-phase injection, and its size | I
_m1|, | I_m2| Are equal and | I_m1| = | I_m2|. Next, the error component ΔI_m1, ΔI_m2Size of
| ΔI_m1|, | ΔI_m2| Is expressed by the above equation (29).
And the amount of change | ΔI for the positive phase of the system fundamental wave₁₁| And inverse phase
Change amount | ΔI₁₂| Depends on the magnitude relationship. Then, the positive phase component I₁(m) and inverse phase component I_Two(m) system
The effect of the fluctuation of the fundamental wave is the change ΔI₁₁, ΔI₁₂Big and small
It changes depending on the relationship, as shown in the following (i) and (ii).
You. (I) | ΔI₁₁| ≦ | ΔI₁₂When |
Normal phase component I₁Error component ΔI of (m)_m1Is reversed phase component I_TwoError component of (m)
Minute ΔI_m2Smaller, positive phase component I₁(m) is the system fundamental wave
Less susceptible to fluctuations. (Ii) | ΔI₁₁|> | ΔI₁₂|, The inverse phase I
_TwoError component ΔIm of (m)_TwoIs positive phase component I₁Error component of (m)
Minute ΔIm₁Smaller, reversed phase component I_Two(M) is more basic
Less susceptible to wave fluctuations. Then, | ΔI₁₁| ≦ | ΔI₁₂|, | ΔI
₁₁|> | ΔI₁₂｜ Regardless of the
In order not to be affected by motion,
Is the positive phase component I₁(M) Detection of islanding operation and reverse phase
Minute I_TwoIn combination with the detection of islanding using (m)
Weighting is performed, and islanding is detected by AND of the two detections. Next, the validity of this product detection (AND detection)
The nature will be described. First, the voltage Vg of the equation (7)_M
Let Vga, Vgb, Vgc be the phase components of
g_MEnergy (for convenience | Vg_M|^TwoAs
Represents each phase component as shown in the following equation (30).
Vga-Vgc can be represented by the sum of squares of the absolute values.
This is 3 pu (pu: arbitrary unit). [0131] [Equation 30] | Vg_M|^Two= | Vga |^Two+ | Vgb |^Two+ |
Vgc |^Two= 3pu Next, each of the phase components Vga to V
The sum of the squares of the absolute values of gc is the voltage Vg _MVg₁,
Vg of reverse phase_TwoThen, as shown in the following equation 31,
become. Here, zero-phase component Vg₀= 0
You. [0133] [Equation 31] | Vga |^Two+ | Vgb |^Two+ | Vgc |^Two=
Vga ・ Vga^*+ Vgb ・ Vgb^*+ Vgc · Vgc^*
= (Vg₁+ Vg_Two) ・ (Vg₁+ Vg_Two)^*+ (Α^Two・ Vg₁+ Α
・ Vg_Two) ・ (Α ・ Vg₁+ Α^Two・ Vg_Two)^*+ (Α · Vg₁+ Α
^Two・ Vg_Two) ・ (Α^Two・ Vg₁+ Α · Vg_Two)^*= 3 · (Vg₁ ^Two+
Vg_Two ^Two) = 3 (| Vg₁|^Two+ | Vg_Two|^Two) = 3pu Based on the equation (31), the positive phase component Vg₁,
Reverse phase Vg_TwoIs | Vg in FIG._M| = 1 on the circumferential line γ
Take. The effect of the fluctuation of the fundamental wave can be ignored.
Assuming that the limit level is 1 pu, the positive phase component I
₁(M), reversed phase component I_Two(M), for example, positive phase
Minute I₁When islanding detection is performed using only (m),
(Vg₁, Vg_Two) = Circle of 1pu radius passing through (0,1)
Voltage Vg of γ_M, (| Vg_M| = 1 pu)
Inversion detection is not effective, but the positive phase component I₁(M), reversed phase component I_Two
When product detection is performed using both (m), (Vg₁, V
g_Two) = Circumference γ of 2pu passing through the point of (1,1)
Voltage Vg_M, (| Vg_M| = √2 (= √ (1 + 1)) p
Until u), the detection of islanding is enabled, and
The resistance to 対 2 increases (about 1.4 times). In other words, the voltage Vg_MOf fundamental wave fluctuation
And the positive phase component I₁(M), reversed phase component I_Two(M) product detection
Is the positive phase component I₁(M), reversed phase component I_TwoAny one of (m)
, There is a margin of about 40%. Therefore, the arithmetic processing unit 25 firstly converts
Injection included in the measurement signal of each phase of the compressor 19 and the converter 20
The measured voltage and measured current of the interharmonic of order m
A digital filter of the Fourier transform to extract
As the calculation, for example, a regression type DFT calculation is executed. At this time, the past N sampling data
The sampled measurement signal of each phase is used for DFT operation.
The voltage and current of the signal are represented by voltage V (q), current I (q),
(Q: 0, 1, 2,..., N−1)
From the following operation of the two equations of Expression 30 using the result,
Measurement voltage Vm (q) of interharmonics of injection order M, measurement
The current Im (q) is obtained. [0139] (Equation 32) Vm (q) = (2 / N) · (Vm (q−1) −V (q−N) + V (q)) · x^-1 Im (q) = (2 / N) · (Im (q−1) −I (q−N) + I (q)) · x^-1 The number of data N is, for example, 1
Assuming 32 wavelengths with 64 samplings per cycle,
(64 × 32 =) 4096. Also, in equation (5)
X is a parameter of x = exp (-j2πm / N)
You. Next, extraction is performed by the operation of the equation (32).
Voltage and current of harmonics of order m of each phase
To Vam (q), Vbm (q), Vcm (q), Ia
m (q), Ibm (q), Icm (q), positive phase
Min Y₁, V₁, I₁Is Ym₁(Q), Vm₁(Q), Im
₁(Q) is calculated by the following in-phase operation of the following two equations of Expression 31.
And the positive phase component of each of the voltage Vm (q) and the current Im (q)
Vm₁(Q), Im₁Find (q). [0142] [Equation 33]   Vm₁(Q) = (Vam (q) + α · Vbm (q) + α^Two・ Vcm (q)) / 3   Im₁(Q) = (Iam (q) + α · Ibm (q) + α^Two・ Icm (q)) / 3 Also, the reverse phase component Y_Two, V_Two, I_TwoIs Ym
_Two(Q), Vm_Two(Q), Im_TwoThe following number as (q)
34, the voltage Vm (q) and the current I
m (q) each inverse phase component Vm_Two(Q), Im_Two(Q)
Ask. [0144] [Equation 34] Vm_Two(Q) = (Vam (q) + α^Two・ Vbm (q) + α · Vcm (q)) / 3 Im_Two(Q) = (Iam (q) + α^Two・ Ibm (q) + α ・ Icm (q)) / 3 Then, Im₁(Q) / Vm₁(Q) to next
Positive phase admittance Ym of interharmonics of number M₁(Q)
Can be calculated, Im_Two(Q) / Vm_Two(Q) to next
Negative phase admittance Ym of interharmonics of number M_Two(Q)
In this mode, the positive phase component Vm can be calculated.
₁(Q), Im₁Equation (35) based on (q)
From, normal phase admittance Ym₁(Q) susceptance
(-Bm₁(Q)) is the detection admittance on the positive-phase operation side and
And calculate. [0146] (-Bm)₁(Q)) =-I_mage(Im₁(Q)
/ Vm₁(Q)) Similarly, the reverse phase component Vm_Two(Q), Im_Two(Q)
From the operation of the following equation (36) based on
Su Ym_Two(Q) susceptance (-Bm_Two(Q))
It is calculated as the detection admittance on the negative phase calculation side. [0148] (36)_Two(Q)) =-I_mage(Im_Two(Q)
/ Vm_Two(Q)) The susceptance (-Bm
₁(Q)), (-Bm_Two(Q))
The calculated susceptance (-Bm₁(Q)), (−
Bm_Two(Q)) for each of the positive and negative phases
The susceptance is compared with the judgment value (−Bm
₁(Q)), (-Bm_TwoMonitor changes in (q)). That is, the calculated susceptance (-B
m₁(Q)), (-Bm_Two(Q)) is the absolute value of
Judgment values are continuously obtained for each set continuous set value.
And the impedance on the upstream side of the grid as viewed from the receiving point P
Dance increased to open impedance due to system stop
Monitors whether to convert The susceptance (-Bm
₁(Q)) Single operation of the distributed power source 6 due to a system stop from the side
Rotation detection and susceptance (-Bm_Two(Q)) From the side
Of detection of isolated operation of distributed power source 6 due to system shutdown
(And) is calculated and the susceptance (-Bm
₁(Q)) Change in the distribution power source 6 due to system shutdown
Operation is detected, and at the same time, the susceptance (-Bm
_Two(Q)) also indicates that isolated operation of the distributed power source 6 is detected.
Only when the AND condition holds,
Detecting that the distributed power source 6 is operating alone, the switch 15
To disconnect the distributed power source 6 from the system 5. The process for detecting the islanding operation is described in detail below.
The arithmetic processing unit 25 performs the normal phase detection process shown in FIG.
-Each step S of the chart₁~ S₆Realized by executing
Is done. Therefore, the islanding operation is detected in the normal phase and the reverse phase.
Side, and the positive and negative phases of the fundamental wave of system 5
System shut down so as not to be affected by any fluctuations
The isolated operation of the distributed power source 6 at the time can be reliably detected.
Even if the system 5 is a system with large load fluctuation,
Minimize false detections due to fluctuations in the system fundamental wave due to fluctuations, etc.
Thus, the isolated operation of the distributed power source 6 can be detected, and the signal
The reliability is significantly improved. Then, the current of the interharmonic of the injection order M
From the power receiving point P to a single-phase injection between the b-phase and c-phase of the system 5
Injection power supply (power supply unit 17) etc. are three-phase injection
Is much cheaper and smaller. Further, the symmetric component admittance Ym
₁(Q), Ym_Two(Q) susceptance (-Bm
₁(Q)), (-Bm_Two(Q)) and their changes
Detected the islanding operation from the
Operation of the distributed power source 6 on the system stop side without receiving
It can be detected and it is necessary to worry about phase sequence change etc. of the system
There is no. Further, by making the detection redundant, a detection processing device is provided.
The reliability of the operation unit 25, especially the failure of the arithmetic processing unit 25,
improves. By the way, the detection on the normal phase calculation side and the negative phase calculation side is performed.
As the output admittance, normal phase admittance Ym
₁(Q), reversed-phase admittance Ym_TwoThe real part of (q)
Find both the conductance and the susceptance of the imaginary part,
Domitance Ym₁(Q), Ym_Two(Q) vector change
To detect the individual operation of the distributed power source 6
Is also good. Also, the normal phase operation of the reciprocal of the detected admittance
Dispersion from changes in detection impedance on the
The isolated operation of the power supply 6 may be detected.
As the detection impedance on the calculation side and the negative-phase calculation side,
Phase impedance Zm₁(Q), reverse phase impedance Z
m_Two(Q) with Zm₁(Q) = Vm₁(Q) / Im
₁(Q), Zm_Two(Q) = Vm_Two(Q) / Im_TwoFrom (q)
What is necessary is just to calculate. Further, the susceptance Bm₁(Q), B
m_TwoReactance Xm corresponding to (q)₁(Q), Xm_Two
(Q) may be calculated from the following equation (37). [0160] (37) Xm₁(Q) = I_mage(Vm₁(Q) / Im₁(Q)) Xm_Two(Q) = I_mage(Vm_Two(Q) / Im_Two(Q)) Next, the above-described judgment on the normal phase operation side and the negative phase operation side is performed.
The fixed value may be set according to the state of the system 5 or the like.
At this time, the determination values on both calculation sides may not be the same value. The present invention relates to a multi-phase system having three or more phases.
Application to islanding detection of distributed power sources in various power systems
In this case, the single-phase power supply of the interharmonics is
It may be injected between any two phases. [0163] The present invention has the following effects.
You. First, for example, even in a three-phase system, the
Phase injection is sufficient and injection power is cheaper than three-phase power supply
In addition, a small single-phase power supply can be used. Next, the positive phase I of the interharmonics of the injection order.
Singularity from changes in impedance or normal phase admittance
Phase detection and reverse phase impedance of interharmonics of the injection order
Of islanding from changes in impedance or reverse phase admittance
Occur at the same time, and the distributed power
6 only when an islanding operation of 6 is detected
Detection was duplicated because it was detected as isolated operation of distributed power supply 6.
Has been greatly affected by the fluctuation of the fundamental wave component of system 5.
Erroneous detection due to this fluctuation is reliably prevented,
Even when the load fluctuation of the system 5 is large, etc.
The distributed power supply 6 is connected to the
5, and the reliability is remarkably improved. Therefore, cost reduction and miniaturization can be achieved.
Phase change of system 5 due to single-phase injection of harmonics
Minimize the effects of fluctuations in the system fundamental without worrying about
Eliminate the impedance of the interharmonic of the injection order of system 5
Dispersion when the system is stopped due to changes in dance or admittance
The isolated operation of the power supply 6 can be reliably detected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a single-line diagram of one embodiment of the present invention. FIG. 2 is an equivalent circuit diagram of an inter-order harmonic of FIG. FIG. 3 is an equivalent circuit diagram of a three-phase connection at the time of single-phase injection in FIG. 2; FIG. 4 is a noise voltage characteristic diagram for explaining the effectiveness of the detection of FIG. 1; FIG. 5 is a flowchart for explaining a detection process in FIG. 1; [Description of Signs] 1, 5 system 6 distributed power supply 16 current injection device 17 power supply unit 21 system stop detection processing device 25 arithmetic processing unit

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Yoshihiro Haneda             47 Nisshin Electric, Umezu Takaune-cho, Ukyo-ku, Kyoto-shi             Inside the company F-term (reference) 5G066 HA11 HB02

Claims (1)

Claims 1. An inter-order harmonic of a non-integer multiple of a system fundamental wave is injected into a system to which a distributed power source is connected, and based on measurement of an inter-order harmonic of an injection order of the system. Detecting the impedance or admittance of the inter-harmonics of the injection order of the system, and detecting the isolated operation of the distributed power supply when the system is stopped, based on a change in the detection impedance or detection admittance of the inter-harmonics of the injection order of the system. A single-phase injection of the inter-harmonic of the injection order into the system, and symmetrically measure the measured voltage and current of the inter-harmonic of the injection order of each phase of the system. The positive and negative phase components of the voltage and the current are detected by decomposing the components into positive and negative components, and the positive phase impedance or the positive order interharmonic of the injection order of the system is determined from the positive and negative phases of the voltage and the current. A phase admittance is calculated as a detection impedance or a detection admittance on the positive phase calculation side, and a reverse phase impedance or a negative phase admittance of a higher order interharmonic of the injection order of the system is calculated from the negative phase component of the voltage and the current. Calculated as the detection impedance or detection admittance on the side, and the isolated operation detection of the distributed power supply from the change in the detection impedance or detection admittance on the positive-phase calculation side, and from the change in the detection impedance or detection admittance on the negative-phase calculation side. A method for detecting an isolated operation of a distributed power source, wherein the isolated operation of the distributed power source is detected only when the isolated operation of the distributed power source occurs simultaneously.