JPH11160372A - Measuring method for harmonics characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a measuring method in which the influence of a noise is excluded and in which a harmonics characteristic can be measured with good accuracy by a method wherein the voltage and the current, of a noise existing in a power system, at respective frequencies are subtracted and corrected from a voltage and a current at respective intermediate harmnics in the power system measured by injecting currents at the respective intermdiate harmonics. SOLUTION: A current injection device 3 repeats, at every 30 minutes, an operation in which a current at an intermediate harmnics is generated so as to be injected into an injection point (a). The infected current in the injection point (a) is measured by a current transformer 4. The voltage of a power system 1 is measured by a transformer 5, and a current on the side of a load in the injection point (a) of the system 1 is measured by a current transformer 6. Then, the analog measured output of the current transformer 4, that of the current transformer 6 and that of the transformer 5 are converted into digital signals by an A/D converter 7 in a harmonics measuring apparatus so as to be supplied to a signal processor 8. The processor 8 analyzes digital frequencies of the measured outputs by the current transformers 4, 6 and the transformer 5 so as to detect the voltage and the current of the system 1. In addition, the analyzed result of the processor 8 is supplied to a processor module 9. The processor module 9 subtracts the vector of a noise, and it computes a harmonics characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injecting a current having a frequency which is a non-integer multiple of the system fundamental frequency into a power system, obtaining a harmonic equivalent circuit of the power system based on the measurement result, The present invention relates to a method for measuring harmonic characteristics for measuring the characteristics.

[0002]

2. Description of the Related Art Conventionally, from the viewpoint of power supply and the like, it is important to measure and grasp momentarily harmonic characteristics of a power system.

The harmonic equivalent circuits on the load side and the upstream side of the power system can be regarded as, for example, a parallel circuit of an admittance expressed by Norton's theorem and a current source.
IEEJ Transactions on Electronics, Vol. 101, No. 8, p. 451-45
8, (Showa 56-8) describes the voltage and current of the fundamental wave of the system with respect to the harmonic characteristics of the fifth harmonic, which is a typical harmonic of the distribution line, and from the result, the fifth harmonic. Admittance of harmonic equivalent circuit for harmonics, size of current source,
It describes that the phase and the like are calculated, estimated, and measured.

However, in the case of the harmonic measurement method described in the above-mentioned journal, the admittance and current source of the equivalent circuit for the harmonic to be measured are not actually measured and found, but the measurement results of the fundamental wave voltage and current of the system are obtained. Thus, the harmonic admittance, the size and phase of the harmonic current source are estimated to determine the harmonic equivalent circuit, and therefore the admittance and the like of this equivalent circuit cannot be obtained with high accuracy.

Therefore, the present applicant has filed Japanese Patent Application No. 8-31019.
With the application of No.2, the power system will be
Injecting each non-integer multiple of the frequency of the current of the system fundamental frequency f _s of the lower as an intermediate harmonic currents, the load side of the voltage and the injection point of the injection frequency of the injection point, the injection frequency flowing through the upstream side of the current Based on the measurement results, the admittance of the harmonic equivalent circuit for the intermediate harmonic of the injection frequency is determined for each of the load side and the upstream side of the injection point of the system, and the harmonics to be measured before interpolation using this admittance are calculated. Has already invented to determine the admittance and the current source of the equivalent circuit and to find its harmonic equivalent circuit.

In this case, the current of the intermediate harmonic is a current having a frequency that does not originally exist in the system, and the admittance of the harmonic equivalent circuit with respect to this injection frequency can be determined accurately by actually measuring the voltage and the current. Thus, the admittance and the like of the equivalent circuit with respect to the harmonic to be measured can be accurately obtained, and the harmonic equivalent circuit can be grasped.

[0007]

In the case of the measuring method of the above-mentioned application, if a frequency component of the intermediate harmonic exists in the system, this frequency component becomes noise and causes a measurement error.

Therefore, conventionally, the injection current of the intermediate harmonic is set to a relatively large appropriate level and injected into the power system.

For this reason, a large-capacity and large-sized current injection device is required for the injection of the intermediate harmonic, and there is a problem that the harmonic characteristics of the power system cannot be measured with a small injection capacity.

In addition, the system at the injection point of the intermediate harmonic (injection system) and the system at the measurement point (measurement system) are made different from each other, so that the system is upstream (upper) of the injection system or downstream of this higher system. It is conceivable that another branch system other than the above is used as a measurement system, the harmonic characteristics of the upstream system and other branch systems are measured, and the measurement range is extended outside the injection system.

However, the farther the injection point of the intermediate harmonic is from the measurement point, the lower the measurement level of the injection current.

[0012] In addition, the measurement level of the injected current is further reduced due to a substation transformer or the like between the systems, particularly in an upstream system.

Therefore, if a measurement point is set in an upstream system or another branch system, the influence of noise becomes extremely large, a measurement error becomes large, and the measurement range cannot be actually expanded.

An object of the present invention is to eliminate the influence of the existing noise of the system, to enable accurate measurement of the harmonic characteristics of the power system with a small injection capacity, and to expand the measurement range. As an issue.

[0015]

In order to solve the above-mentioned problems, in the method of measuring harmonic characteristics according to the present invention, in the case of claim 1, the power system before and after the injection of the current of each intermediate harmonic is described. Measures the voltage and current at the frequency of each intermediate harmonic as the voltage and current of the existing intermediate harmonic noise, and measures the voltage and measurement of each intermediate harmonic in the power system based on the injection of the current of each intermediate harmonic. The current is corrected by subtracting the voltage and current of the noise of each intermediate harmonic.

Therefore, the voltage and current of the existing noise at each frequency are subtracted from the voltage and current of each intermediate harmonic of the power system measured by injecting the current of each intermediate harmonic, and their influences are reduced. Is removed.

Therefore, it is possible to accurately measure the voltage and the current based on the injection of each intermediate harmonic in the power system with a small-capacity current injection regardless of the existing noise level of the system at the frequency of each intermediate harmonic. It is possible to accurately measure the harmonic characteristics with a small injection capacity.

In addition, when the measurement system is different from the injection system such as the upstream system of the injection system, the voltage and current of the existing noise at the frequency of each intermediate harmonic of the measurement system are measured. The voltage and current of each intermediate harmonic in the measurement system based on injection can be accurately measured to measure its harmonic characteristics, and the measurement range can be expanded.

In the case of claim 2, the voltage and the current of the frequency of each intermediate harmonic of the power system before and after the injection of the current of each intermediate harmonic are used as the voltage and the noise voltage of the existing intermediate harmonic, respectively. The current is measured a plurality of times, the average of the measurement results of the noise voltage and the current of each of the intermediate harmonics is obtained, and the measurement of each of the intermediate harmonics of the power system based on the injection of the current of each of the intermediate harmonics The voltage and the measured current are respectively corrected by subtracting the average of the noise current and the voltage of each intermediate harmonic.

Therefore, in this case, the voltage and the current of the noise at the frequency of each of the existing intermediate harmonics can be more accurately measured by averaging a plurality of measurements to prevent transient fluctuations, etc. Voltage and current based on the injection of each intermediate harmonic in the power system can be measured more accurately, and the harmonic characteristics of the power system can be measured very accurately with a small injection capacity, and the measurement range can be further expanded. be able to.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
This will be described with reference to FIG. (One Embodiment) First, one embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a single-wire system diagram of a power system 1 to be measured. A current injection device 3 formed by an inverter or the like of a harmonic measurement device 2 is connected to an injection point a of an intermediate harmonic current.

Then, the harmonic to be measured is converted to a frequency n · f
_s and the intermediate harmonic that is a non-integer multiple of the system fundamental frequency f _s sandwiching this harmonic is divided into two frequencies f ₁ and f ₂ (f
₁ <When intermediate harmonics _{n · f s <f 2)} , current injection device 3, for example, injected into the injection point a generated sequentially or simultaneously intermediate harmonic current of a frequency f _1, f ₂ Do it every 30 minutes. The injection current at the injection point a is measured by the current transformer 4 for the instrument.

The voltage of the power system 1 is measured by a transformer 5 for a meter, and the current on the load side of the injection point a of the power system 1 is measured by a current transformer 6 for a meter.

Then, the analog measurement outputs of the current transformers 4 and 6 and the transformer 5 are converted into digital signals by the A / D converter 7 of the harmonic measuring device 2 and then supplied to the signal processing device 8.

The signal processing device 8 executes digital frequency analysis such as DFT and FFT of measurement outputs of the current transformers 4 and 6 and the transformer 5 to detect a voltage and a current of each frequency of the power system 1.

Further, the voltage and current vector values obtained as a result of the analysis by the signal processing device 8 are supplied to an arithmetic processing device 9. The processing device 9 performs a vector subtraction of the existing system noise and a calculation of the harmonic characteristic, which will be described later. Then, for example, an equivalent circuit (harmonic equivalent circuit) 10 for the harmonic to be measured on the downstream side (load side) of the injection point a is obtained and determined.

By the way, this kind of intermediate harmonic having a frequency which is a non-integer multiple of the system fundamental frequency f _s is not originally present in the power system 1, and usually, the voltage of the existing intermediate harmonic noise, The current is very small, and it can be considered that the current does not change during current injection by the current injection device 3 and before and after the current injection.

Therefore, before and after the injection of the currents of the two intermediate harmonics of the frequencies f ₁ and f ₂ , the voltage and current of the respective frequencies of the two intermediate harmonics of the power system 1 are converted to the noise of the existing frequency sources of the system. Measured as voltage and current.

Before and after a series of injection periods during which the currents of both intermediate harmonics are injected, before and after the injection of both intermediate harmonics, in this embodiment, the harmonics as shown in the flow chart of the procedure 2 of the measuring device 2 is provided with a step S ₁ pre-injection measured before a series of injection period of the.

In this step S ₁ , the digital frequency analysis of the signal processing device 8 immediately before the current injection device 3 starts the injection, the frequency f ₁ included in the measurement output of the transformer 5 and the current transformer 6, The component of f ₂ is measured as the voltage and current of the existing noise of the system of each frequency, and the measured voltage and current vector values of the noise of frequencies f ₁ and f ₂ are stored, for example, in the latter stage of the arithmetic processing unit 9. It is stored in the device 11.

Next, the routine goes to Step S ₂ of injection and measurement for each middle harmonic of FIG. 2, step S _2, the current injection device 3 frequencies f ₁ to the injection point a from, f ₂ intermediate harmonic The currents are sequentially injected, and the measured outputs of the current transformers 4, 6 and the transformer 5 at that time are subjected to digital frequency analysis by the signal processing device 8, and the voltage of both intermediate harmonics of the power system 1 based on the injection and the injection point a The current of both intermediate harmonics on the load side is detected.

At this time, if the currents of the two intermediate harmonics of the difference between the measured outputs of the current transformers 4 and 6 are obtained, the currents of the two intermediate harmonics shunted upstream from the injection point a can be simultaneously detected.

[0033] Then, after a series of injection period, the vector value of the detection result of the signal processing device 8 is supplied to the arithmetic processing unit 9, the arithmetic processing unit 9 by the subtraction of the noise removal step S _3, the storage unit Recently strains existing frequency f _1, f ₂ of the noise voltage held in the 11, current and the frequency f ₁ of based on the injection measured power system 1, f ₂
Is subtracted from the voltage and the current by a vector subtraction (complex operation), and as shown in the vector diagram of FIG. 3, the harmonics of the frequencies f ₁ and f ₂ are systematized from the voltage or current detection vector a including the noise based on the injection. The voltage or current vector b of the existing noise is subtracted, and the voltage and current vector c corrected by eliminating the influence of the existing noise is obtained. The voltage and current of the vector c are measured based on the injection voltage. Current.

Further, based on the measured voltage and measured current from which the noises of the frequencies f ₁ and f ₂ have been removed, the arithmetic processing unit 9
Constant of the equivalent circuit 10 for the running operation of the harmonic characteristics of the step S ₄ in FIG. 2, the harmonic to be measured (the equivalent circuit constant), i.e. the admittance Y _(n), the current source I _{G (n)}
To determine its harmonic characteristics.

[0035] That is, step S measured voltage having a frequency f _1, f ₂ after the resulting noise removal by ₃ V _1, V _2, the measured current and I _1, I _2, respectively voltage V _i, the current I _i
When expressed by (i = 1, 2), since those intermediate harmonics do not originally exist in the power system 1, the equivalent circuit on the load side as viewed from the injection point a has frequencies f ₁ , f corresponding to the admittance Y _(n). The admittance Y _{i for 2} (= Y ₁ ,
Y ₂ ), and the admittance Y _{i is}
It is obtained from the operation of the expression

[0036]

## EQU1 ## Y _i = I _i / V _i

Note that, also on the upstream side of the injection point a, the equivalent circuit of the frequencies f ₁ and f ₂ is only admittance and can be obtained from the calculation of the same equation as the equation (1).

When the admittances Y ₁ and Y ₂ for the intermediate harmonics of the frequencies f ₁ and f ₂ are obtained, the admittance Y _(n) for the harmonic to be measured is most simply Y _n = ｛. It is obtained from the interpolation calculation of (Y ₁ + Y ₂ ) / 2}.

Next, the harmonic voltage to be measured of the power system 1 obtained by the digital frequency analysis of the signal processing device 8 is represented by V
_(n), and the current of the harmonic to be measured flowing on the load side of the injection point a is represented by I _{(n).
G (n)} is obtained.

[0040]

_{IG (n)} = I _(n) −V _(n) · Y _(n)

The admittance Y _n and the current source I
_{When (n)} is determined, the equivalent circuit 10 is determined, and the characteristic (harmonic characteristic) of the harmonic to be measured on the load side of the injection point a is determined and measured.

At this time, from the measurement results of the voltage and the current of each frequency based on the injection of the current of the intermediate harmonic of the frequencies f ₁ and f ₂ , the respective frequency components existing in the system measured immediately before are removed. Since the harmonic characteristic is obtained and measured using the measurement result based only on the injected current, even if the injection amount is smaller than the existing components of the system, it is not affected by the injection amount and the current injection device 3 can be reduced in capacity and capacity. The size can be reduced and the harmonic characteristics can be determined and measured accurately with a small injection capacity.

The measurement results are stored in the storage device 11 and displayed on a screen on a display device 12 such as a CRT.

Also, on the upstream side of the injection point a, the admittance and the current source for the harmonic to be measured can be obtained by the same method to measure the harmonic characteristics.

The frequency components of the existing two intermediate harmonics may be measured before and after the injection of the currents of the two intermediate harmonics, that is, when the currents of the two intermediate harmonics are not injected.

[0046] Thus, instead of measuring them before a series of injection of both intermediate harmonic current step S ₂ in FIG. 2, the step S ₂ in step S ₅ measuring after injection of the broken line in FIG. 2 May be measured after a series of injections is completed.

The term “before and after the injection of the current of each intermediate harmonic” in the present invention means the time when the current of each intermediate harmonic is not injected.

When the currents of the intermediate harmonics of the frequencies f ₁ and f ₂ are sequentially injected, the currents of the intermediate harmonics of the frequency f ₁ are calculated before and after step S ₂ in step S _2.
1, not only the period of S _5, injection is stopped from the end of the injection of frequency f ₁ or f ₂ in a series of injection period in step S ₂ to the start of injection of the frequency f ₂ or f ₁ infusion period of the current of which frequency switching period or frequency f ₂ is also included in the front and rear injection.

Similarly, before and after the injection of the current of the intermediate harmonic having the frequency f ₂ , not only the periods of steps S ₁ and S ₅ but also
Infusion period of said frequency switching period or frequency f ₁ of the current step S ₂ are included.

Therefore, in some cases, the measurement in step S ₁ or S ₅ is omitted, and during the series of injection and measurement in step S ₂ , the frequency f is determined based on the frequency analysis of the signal processing device 8.
Frequency f ₂ when the current of the intermediate harmonic of ₁ is injected
The measurement result, the frequency measurement result of f _1, each line existing frequency f _2, f ₁ noise voltage while injecting an intermediate harmonic current of a frequency f _2, is detected as a current, these You may make it measure simultaneously with injection | pouring and measurement.

(Another Embodiment) Next, another embodiment of the present invention will be described with reference to FIG. FIG. 4 shows a flowchart of a processing procedure in this embodiment of the harmonic measurement device 2 of FIG.

In this embodiment, in order to accurately measure the existing noise of the system, for example, the pre-injection measurement and the post-injection measurement in FIG. 4 corresponding to steps S ₁ and S ₅ in FIG. In steps Q ₁ and Q ₃ , the frequencies f ₁ and f are determined from the digital frequency analysis result of the signal processing device 8 in FIG.
The frequency component of the _second intermediate harmonic is detected, and the voltage and current of the noise of the two existing intermediate harmonics are measured a plurality of times and stored in the storage device 11.

Then, in step Q ₂ of the injection and measurement of the intermediate harmonic in FIG. 4 corresponding to step S ₂ in FIG. 2, the current of the intermediate harmonics of the frequencies f ₁ and f ₂ is injected from the current injection device 3 to the injection point. a into the signal processing device 8
The voltage and current of both intermediate harmonics of the power system 1 based on the injection are measured from the result of digital frequency analysis of
To hold.

[0054] Further, by calculating the average value of the step Q _4, the frequency f _1, each time a series of injections of middle harmonic current of f ₂ is ended, the immediately preceding, immediately after step Q _1, Q ₃
Performs vector averaging for each of the measurement results of the voltage and current of the two intermediate harmonics based on the measurement of the two intermediate harmonics, and averages the voltage and current of the noise of both the intermediate harmonics existing in the system and averages each Find a vector of values.

With the vectors of these average values, the transient (instantaneous) fluctuations of the noise and voltage of the two intermediate harmonics of the power system 1 are averaged, and each of them is more accurate than when measuring only once. I get it.

[0056] Then, step S of FIG. 2 in the step Q ₅
By treatment ₃ with similar vector subtraction, both intermediate harmonics of the voltage obtained by injection and measurement of step Q _2, the vector of the current measurement result, the average of each strain existing noise obtained in Step Q ₄ The value vector is subtracted to eliminate the influence of the existing noise in the system, and the measured voltage and measured current based on the injection of both intermediate harmonics are obtained.

[0057] Furthermore, these removal was measured voltage noise, based on the measured current, the calculation of the harmonic characteristics of the step Q _6, as in step S ₄ in FIG. 2, for example the injection point a load side The equivalent circuit constant such as the admittance Y _{(n) in} FIG. 1 for the harmonic to be measured is determined, and the equivalent circuit 10 in the figure is obtained.

In this case, the admittance Y is determined based on the averaged voltage and current of the noise of the existing two intermediate harmonics of the system.
_{(n) and the} like can be obtained extremely accurately without being affected by the transient fluctuation of the noise, and the harmonic characteristics of the power system 1 can be measured very accurately by injecting a small amount of current.

When the accuracy of averaging is improved by further increasing the number of times of measuring the noise of both intermediate harmonics existing in the system, the number of times of measurement in each of steps Q ₁ and Q ₃ may be increased to a plurality of times, _1, not only measured in Q _3, a frequency different from that of the frequency switching period or noise from the injection end of the current frequency f ₁ or f ₂ of step Q ₂ until the start of the infusion of the current frequency f ₁ or f ₂ May be measured also during the current injection period.

Further, steps Q ₁ and Q ₃ in FIG.
In Step Q _2, the noise voltage of the frequency f _1, for current repeatedly measured during injection and measurement of the frequency switching period and the frequency f ₂ of the current, the noise of the voltage frequency f _2, wherein for current frequency switching period and it may be repeated measured during injection and measurement of the frequency f ₁ of the current, in this case, the injection and measuring the strain existing voltage of each of the two intermediate harmonic currents, and the measurement of the current at the same time Done,
There is an advantage that the measurement time is shortened and no error is caused due to the deviation of the measurement time.

In each of the above embodiments, the intermediate harmonic current is described as a current having two frequencies f ₁ and f _2. However, the current of the intermediate harmonic is the system fundamental frequency between the harmonics to be measured. may be a non-integer multiple of the plurality of frequency of the current of f _s, it is not limited to two frequencies f _1, f ₂ currents.

The current of each intermediate harmonic is, for example, as shown in FIG.
In step S ₂ or step Q ₂ in FIG. 4, instead of sequentially injected, it may be injected by all or part simultaneously.

Further, the order and combination of the injection frequencies of the currents of the respective intermediate harmonics may be set arbitrarily.

Next, for example, the transformer 5 and the current transformer 6 are connected to an injection system such as an upper system of the system (injection system) provided with the injection point a or another system of the same level branched from the upper system. The system may be provided in a system other than the above, and measurement may be performed by making the injection system of the intermediate harmonic different from the measurement system.

[0065] The components of the case, for example, in step S ₂ or noise removal step Q ₂ in FIG. 4 in FIG. 2, each intermediate harmonics of the voltage injected and measurement, each existing intermediate harmonics from the current measurement system For example, even if the injected current is reduced by a substation transformer between systems and injected into a higher-level measurement system, the measurement results are not affected by noise, and the harmonic characteristics can be measured accurately. And the measurement range can be expanded.

Then, for example, the harmonic characteristic circuit on the load side and the upstream side of the injection point a can be measured as a series circuit of an impedance and a voltage source, and in this case, the harmonic characteristics can be measured. The admittance of the above-described embodiment may be replaced with impedance and the current source may be replaced with a voltage source.

[0067]

The present invention has the following effects. First, in the case of claim 1, the current at the frequency of each intermediate harmonic of the power system 1 before and after the injection of the current of each intermediate harmonic is measured as the voltage and current of the noise of each existing intermediate harmonic in the system, The voltage and current of the existing noise at each frequency were subtracted from the voltage and current of each intermediate harmonic of the power system 1 measured by injecting the current of each intermediate harmonic, and their effects were removed. Regardless of the magnitude of the existing noise at the frequency of each intermediate harmonic of the power system 1, the voltage based on the injection of each intermediate harmonic of the power system with a small-capacity current injection,
The current can be accurately measured, and its harmonic characteristics can be accurately measured with a small injection capacity.

Further, when the measurement system is a system different from the injection method such as the system upstream of the injection system, the voltage and current of the existing noise at the frequency of each intermediate harmonic of the measurement system are measured, so that the current is measured. The voltage and current of each intermediate harmonic in the measurement system based on injection can be accurately measured to measure its harmonic characteristics, and the measurement range can be expanded.

In the case of claim 2, the voltage and the current of the noise of the frequency of each intermediate harmonic existing in the system are more accurately measured by averaging a plurality of measurements to prevent transient fluctuations and the like. The voltage and the current based on the injection of each intermediate harmonic of the power system 1 can be measured with higher accuracy by small-capacity current injection, and the harmonic characteristics of the power system can be extremely accurately measured with a small injection capacity. Measurement can be performed, and the measurement range can be further expanded.

[Brief description of the drawings]

FIG. 1 is a single-wire system diagram of one embodiment of the present invention.

FIG. 2 is a flowchart of a measurement process of FIG. 1;

FIG. 3 is a vector diagram illustrating subtraction of noise removal in FIG. 2;

FIG. 4 is a flowchart of a measurement process according to another embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 power system 2 harmonic measurement device 3 current injection device 8 signal processing device 9 arithmetic processing device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shoji Nishimura, 47, Takane-cho, Umezu, Ukyo-ku, Kyoto-shi Inside Nisshin Electric Co., Ltd. Inside

Claims (2)

[Claims] 1. An electric current having a frequency which is a non-integer multiple of a system fundamental frequency sandwiching a harmonic to be measured is injected into an electric power system as an intermediate harmonic current. The equivalent circuit constant for each intermediate harmonic of the power system is obtained from the measured voltage and current of the harmonic, and the equivalent circuit constant for the target harmonic of the power system is interpolated from the equivalent circuit constant for each intermediate harmonic. In the harmonic characteristic measurement method determined by calculation, the voltage and current of the frequency of each intermediate harmonic of the power system before and after the injection of the current of each intermediate harmonic are converted to the voltage of the noise of each existing intermediate harmonic in the system. , And measuring the current and correcting the measured voltage and measured current of each intermediate harmonic of the power system based on the injection of the current of each intermediate harmonic by subtracting the voltage and current of the noise of each intermediate harmonic. A method for measuring harmonic characteristics. 2. An electric current having a frequency which is a non-integer multiple of a system fundamental frequency sandwiching a harmonic to be measured is injected into the electric power system as an intermediate harmonic current, and each intermediate current of the electric power system based on the injection is injected. The equivalent circuit constant for each intermediate harmonic of the power system is obtained from the measured voltage and current of the harmonic, and the equivalent circuit constant for the target harmonic of the power system is interpolated from the equivalent circuit constant for each intermediate harmonic. In the harmonic characteristic measurement method determined by calculation, the voltage and current of the frequency of each intermediate harmonic of the power system before and after the injection of the current of each intermediate harmonic are converted to the voltage of the noise of each existing intermediate harmonic, The current is measured a plurality of times, the average of the measurement results of the noise voltage and the current of each of the intermediate harmonics is obtained, and the measured voltage of each intermediate harmonic of the power system based on the injection of the current of each intermediate harmonic And a measurement current is corrected by subtracting an average of the noise current and voltage of each intermediate harmonic.