AU2003204811B2 - Power-related amount measurement device - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): MITSUBISHI DENKI KABUSHIKI KAISHA Invention Title: POWER-RELATED AMOUNT MEASUREMENT DEVICE The following statement is a full description of this invention, including the best method of performing it known to us: 2 Title of the Invention Power-related Amount Measurement device Background of the Invention 1i. Field of the Invention The present invention relates to a measurement device for measuring at least one of an electric power (valid, invalid) and an electric energy (valid, invalid) (hereinafter, referred to as power-related amount measurement device), and which is equipped with compensation function to improve accuracy in measurement.

2. Description of the Related Art A power-related amount measurement device according to a prior art comprises a delta-sigma AD modulator for quantizing a voltage signal and a current signal based on an over sampling frequency respectively, moving average processing means for processing the voltage signal and current signal having been quantized by a moving average method with a digital filter respectively, multiplying means for multiplying the voltage signal and current signal having been processed by the moving average method for each sampling frequency, and digital low-pass filter means for filtering out a high-frequency component of a multiplied value.

Another conventional power-related amount measurement device further comprises shift register phase compensation means for adjusting phases between the voltage signal and the current signal, being capable of changing a data shift timing from the mentioned delta-sigma AD modulator that quantizes based on an over sampling frequency to the moving average means at a subsequent stage, and balance compensation means for adjusting balance of power-related Hi\akhoo\Keep\Temp\P49868 542530-AU-O1(spec.).doc 17/06/03 3 amounts of each phase (Japanese Patent No. 3080207).

In a further conventional power-related amount measurement device, fluctuation in signals generated by the voltage signal input means and current signal input means are suppressed by adjusting phases between the voltage signal and current signal of each phase and balance of the power-related amounts of each phase, thereby achieving a required accuracy in measurement (Japanese Patent No.

3330519) Summary of the Invention The fluctuation in signals generated by voltage signal input means and current signal input means depends on magnitude of voltage and current intended to be detected, frequency of voltage and current intended to be detected, and on temperature during operation. Furthermore, conversion characteristic of an AD converter depends on temperature as well.

However, in the conventional power-related amount measurement devices, the compensation is conducted at a rated voltage, rated current, rated frequency and at an ambient temperature before commercially shipping the device, and a compensation value thereof is set to a constant value.

Therefore, to obtain a sufficient accuracy over a wide range of input and temperature, it is necessary to employ voltage signal input means and current signal input means, and an AD converter, each being of a high accuracy, in which change in errors depending on magnitude or frequency of the voltage and current intended to be detected, and temperature during operation is small, which eventually results in a measurement device of a high cost.

The present invention has been made to solve the above-discussed problems, and has an object of obtaining a H \akhoo\Keep\Temp\P49868 542530-AU-01(spec.) .doc 17/06/03 4 power-related amount measurement device that is not much affected by magnitude and frequency in voltage and current intended to be detected and temperature during operation.

A power-related amount measurement device according to the invention includes an AD conversion circuit for performing a digital conversion respectively of current and voltage detected by a current sensor and voltage sensor mounted on a power line, a power-related amount operation section for calculating a frequency of the mentioned voltage on the basis of an output from the mentioned AD conversion circuit as well as operating an amount related to an electric power of the mentioned power line on the basis of an output from the mentioned AD conversion circuit and compensation means for compensating the mentioned amount related to an electric power, establishing at least one of the mentioned voltage, current and frequency as a parameter.

In the power-related amount measurement device according to this invention, even if respective characteristics of the voltage signal input means and current signal input means, and the AD converter are changed depending on magnitude and frequency of voltage and current intended to be detected, and temperature of the AD converter during operation, they can be compensated at a high speed and measured in high accuracy at all times requiring a small amount of operation and a small amount of memory. As a result, it is possible to measure the amount related to an electric power with a high accuracy.

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent in the course of the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

Brief Description of the Drawings H \akhoo\Keep\Temp\P49868 542530-AU-01(spec.) .doc 17/06/03 5 Fig. 1 is a block diagram showing a constitution of a power-related amount measurement device according to a first preferred embodiment of the present invention.

Fig. 2 is a partially detail block diagram of Fig. 1..

Fig. 3 is a vector chart of an electric power before and after compensation.

Fig. 4 is a block diagram showing a compensation flow.

Figs. 5(a) and are characteristic charts for explaining relation between a frequency and phase in current sensing of a CT, and a compensation line.

Fig. 6 is a graphic diagram for explaining a compensation line.

Figs. 7 and are charts for explaining relation between a frequency and phase in current sensing of an CT, and a compensation line according to a fifth embodiment of the invention.

Detailed Description of the invention Embodiment 1.

A constitution of a power-related amount measurement device according to a first preferred embodiment of the present invention is hereinafter described with reference to Figs. 1 and 2. In this regards, to show the drawings clearly, only a first phase and a third phase are shown, while omitting a second phase.

Additionally, in the following descriptions, reference numerals and letters are described without precise discrimination between lowercase and uppercase characters in the application procedure.

With reference to Fig. 1, a voltage signal 101, 103 of a power line, not shown, which voltage signal is detected by a voltage sensor (hereinafter also referred to as PT) mounted on the power line, and a current signal 201, 203 H.\akhoo\Keep\Temp\P49868 542530-AU-01(spec.) .doc 17/06/03 6 detected by a current sensor (hereinafter also referred to as CT), not shown, mounted on mentioned power line, are quantized respectively based on an over sampling frequency by an delta-sigma AD converter (hereinafter AD converter) provided for each signal, and inputted to a power-related amount operation section 100. Further, frequency is operated by frequency operation means 54 on the basis of a voltage output from an AD converter, and temperature of each AD converter is measured by temperature measurement means 56. Then these frequency and temperature are inputted to the power-related amount operation section 100.

The power-related amount operation section 100 is shown in detail in Fig. 2. With reference to Fig. 2, moving average processing means, not shown, processes by the moving average method the voltage signal and current signal having been quantized respectively by a digital filter, and thereafter inputs them to multiplication means 301, 303.

The multiplication means 301, 303 multiplies the voltage signal and current signal having been processed by the moving average method for each sampling frequency. Digital low-pass filter means 321 and 323 filters out a highfrequency component of the mentioned multiplied value.

Output from the digital low-pass filter means 321 and 323 is referred to as an electric power before compensation W inN 2, In addition, W in N becomes a positive value in the case of receiving power, and a negative value in the case of transmitting power.

Furthermore, although not shown especially in the diagrams, all the processing of the signals after having been converted from analog to digital by the AD converters 121, 123, 221, 223 of Fig. 1 could be carried out with the use of either software or hardware Hilbert transform means 191, 193, 291, 293 consisting H \akhoo\Keep\Temp\P49868 542530-AU-01(spec.) .doc 17/06/03 7 of a Hilbert transform quadrature-phase 191 (193) and a Hilbert transform in-phase 291 (293) turns by 90 degrees a phase between a voltage signal and current signal. The multiplication means 341, 343 multiplies the voltage signal and current signal having been outputted from the Hilbert transform means for each sampling frequency. The digital low-pass filter means 361, 363 filters out a high-frequency component of a multiplied value. Output form the digital low-pass filter means 361, 363 is referred to as an invalid power before compensation var in N 2, 3).

Additionally, var_in_N becomes a positive value in the case of delay in receiving and advance in transmission, and a negative value in the case of advance in receiving and delay in transmission.

Amplitude-phase compensation matrix operation means 381, 383 conducts a compensation operation as described hereinafter establishing an electric power before compensation W_in_N and an invalid electric power var in N as inputs. Then, outputs thereof are referred to as an electric power after compensation W out N 2, and an invalid electric power after compensation var out N (N=1, 2, A compensation operation by the amplitude phase compensation matrix operation means 381, 383 is shown in the following Expression W W out N (cos(9 N) -sin(O N)(W in N var out_N) sin(O cos( ){varin N (Expression 1) Gain_N IBI/IAI (Expression 2) In the above Expressions N 2, 3) indicates each phase. The Expressions are to H \akhoo\Keep\Temp\P49868 542530-AU-01(spec.) .doc 17/06/03 8 conduct a left-handed rotation in the case where 0 N is positive, and therefore they conduct rotation in a direction of delay in the case where 0_N is positive, and rotation in a direction of advance in the case where 0 N is negative.

To make clearly understandable, this relation is shown in Fig. 3.

Gain N and 0 N of a matrix of the above-mentioned Expressions are obtained at a rated voltage, rated current, rated frequency, and at an ambient temperature.

Then, phase adjustment between a voltage signal and a current signal, and a balance adjustment of power-related amounts of each phase are conducted based on the foregoing Expressions at the time of initial adjustment of the power-related amount measurement device according to the invention. The GainN and 0_N, which have been determined at the time of initial adjustment, are not changed except for at the time of adjustment, but are stored as an amplitude phase compensation matrix at the time of initial adjustment in addition to an amplitude phase compensation matrix for use in actual operation.

Amplitude phase compensation matrix at the time of initial adjustment: Gain NX (cos(ON) -sin(O_N)) sin(O N) cos(O N) Flow of compensation according to the invention is shown in Fig. 4. Concept of compensation of a phase variation due to change in power supply frequency is shown in Figs. 5(a) and Figs. 5(a) and are charts for explaining relation between frequency and phase in current sensing at CT, as well as a compensation line. Fig. 5(a) is a characteristic chart in which axis of abscissas stands for frequency (40Hz-7Hz), and an axis of ordinates stands for a H,\akho\Keep\Temp\P49868 542530-AU-O1(spec.) .doc 17/06/03 9 phase error o to +0.4 Fig. 5(a) shows an actual characteristic 90 of CT and a primary line 91 for compensation obtained by causing the actual characteristic to be approximate with a linear expression (hereinafter referred to as a primary line). Fig. 5 shows an amount of a phase error at each frequency after frequency has been compensated with the primary line 91 for compensation in the same axis of abscissas and the same axis of ordinates as those of Fig. It is shown in Fig. 5(b) that an error amount is less than 0.10 within the range of 45Hz to Example 1.

A currently effective value voltage Vrms_1, Vrms 3 is obtained by effective-value-voltage operation means 161, 163. Then amplitude compensation rate (inverse number of rate of change in amplitude) and phase variation depending on the effective value voltage are calculated with a primary line for compensation. In addition, a primary line for compensation of an amplitude compensation rate and phase variation in voltage is similar to the error example depending on frequency shown in Figs. and therefore showing characteristics thereof in the chart is omitted. Compensation expressions are hereinafter described further in detail. In the following descriptions, N denotes each phase. That is, herein N=1, 2, 3.

On the assumption that amplitude compensation rate depending on the effective value voltages Vrms 1, Vrms 3 is GainVrmsN, and phase variation thereof is PhaseVrmsN; slope of a primary line of an amplitude compensation rate is A_Gain_Vrms, and intercept thereof is B_Gain_Vrms; slope of a primary line of a phase variation is A_PhaseVrms, and intercept thereof is B_Phase_Vrms; and currently effective value voltage is Vrms_N; the following compensation H \akhoo\Keep\Temp\P49868 542530-AU-01(spec.) .doc 17/06/03 10 expressions are obtained.

GainVrmsN=AGainVrmsXVrmsN+BGain_Vrms (Vi) PhaseVrmsN=APhaseVrmsXVrms_N+B_PhaseVrms (V2) The amplitude compensation rate GainVrms_N is set to be 1 in the case where the effective value voltage is a voltage at the time of initial adjustment. Further, the Phase Vrms N is set to be 0 in the case where the effective value voltage is a voltage at the time of initial adjustment, while setting variation in the direction of advance to be positive and variation in the direction of delay to be negative. Note that the voltage at the time of initial adjustment herein means a voltage set to serve as a reference requiring no compensation) at the time of conducting an adjustment, and is not always limited to a voltage at the time of actual adjustment. To make clearly understandable, the above-mentioned Expression (V1) (V2) are shown in Fig. 6.

Additionally, it is also preferable that the mentioned rated voltage is preliminarily stored, and the intercept is calculated back and automatically operated based on the rated voltage and slope of a line. In this case, setting of intercept can be omitted. Furthermore, slope and intercept of a primary line can be set freely and changed.

Accordingly, in the case where a circuit arrangement of the voltage signal input means is changed (for example, from a PT circuit to a resistance voltage-dividing circuit), only changing values of slope and intercept of a primary line is sufficient for the mentioned compensation.

Example 2.

A currently effective value current Irml, Irm_3 is obtained by effective value current operation means 261, 263, and an amplitude compensation rate (inverse number of H.\akhoo\Keep\Temp\P49868 542530-AU-O1(spec.) .doc 17/06/03 11 rate of change in amplitude) and a phase variation depending on the effective value current are calculated using a primary line.

On the assumption that amplitude compensation rate depending on the effective value current is GainIrmsN, and a phase variation thereof is Phase_Irms_N; slope of a primary line of an amplitude compensation rate is A_GainIrms, and intercept thereof is B_GainIrms; slope of a primary line of a phase variation is APhase_Irms, and intercept thereof is B_Phase_Irms; and currently effective value current is Irms_N, the following compensation expressions are obtained: Gain Irms N=A Gain IrmsXIrms N+B Gain Irms (I1) PhaseVrms N=APhaseIrmsXIrmsN+B_PhaseIrms (12) The Gain Irms N is set to be 1 in the case where the currently effective value current is a current at the time of initial adjustment. Further, Phase_IrmsN is set to be 0 in the case where the currently effective value current is a current at the time of initial adjustment, while setting variation in the direction of advance to be positive and variation in the direction of delay to be negative. It is also preferable that current at the time of initial adjustment is preliminarily stored, and intercept is calculated back base on the current value of current and slope of the line. In this case, setting quantity of intercept can be reduced. Further, slope and intercept can be set and changed freely. Accordingly, in the case where a circuit arrangement of the current signal input means is changed (for example, from a CT circuit to a divided CT circuit), only changing values of slope and intercept of a primary line is sufficient. The Expression (II) (12) will be characteristic charts similar to Figs. 6, and therefore further description thereof with reference to the charts is H,\akhoo\Keep\Temp\P49868 542530-AU-01(spec.).doc 17/06/03 12 omitted.

Example 3.

A current power supply frequency Freq is obtained by power supply frequency operation means 54. Then, an amplitude compensation rate (inverse number of the rate of change in amplitude) and a phase variation in voltage signal input and a current signal input depending on the power supply frequency are calculated using a primary line for compensation.

On the assumption that amplitude compensation rate of a voltage signal input depending on the power supply frequency is Gain_FreqV, and a phase variation thereof is Phase_FreqV, slope of a primary line of an amplitude compensation rate is A_Gain_FreqV, and intercept thereof is B_Gain_FreqV, slope of a primary line of a phase variation is A_Phase_FreqV, and intercept thereof is B_Phase_FreqV, an amplitude compensation rate of a current signal input depending on a power supply frequency is Gain_FreqI, and a phase variation thereof is Phase_FreqI, slope of a primary line of an amplitude compensation rate is AGain_FreqI, and intercept thereof is B_Gain_FreqI, slope of a primary line of a phase variation is A_Phase_FreqI, and intercept thereof is B_Phase_FreqI, and a current power supply frequency is Freq, the following expressions of primary line for compensation is obtained: GainFreqV=A Gain_FreqVXFreq+B Gain FreqV* (FV1) GainFreqI=AGain_FreqIXFreq+BGainFreqI (FI1) Phase_FreqV=APhase_FreqVXFreq+B_Phase_FreqV (FV2) Phase_FreqI=APhase_FreqIXFreq+BPhase_FreqI (FI2) The slope and intercept of a primary line are set so that Gain_FreqV and Gain_FreqI may be 1 in the case where the current power supply frequency is a power supply HI\akhoo\Keep\Temp\P49868 542530-AU-01(spec.).doc 17/06/03 13 frequency at the time of initial adjustment. Further, the slope and intercept of a primary line are set so that Phase_FreqV and Phase_FreqI may be 0 in the case where the current power supply frequency is a power supply frequency at the time of initial adjustment, while setting variation in a direction of advance to be positive and variation in a direction of delay to be negative. It is also preferable that the power supply frequency at the time of initial adjustment is preliminarily stored, and intercept is calculated back based on the current frequency and slope of the line. In this case, setting quantity of intercept can be reduced. Further, slope and intercept can be set and changed freely. Accordingly, in the case where a circuit arrangement of the voltage signal input means and the current signal input means is changed (for example, from a PT circuit to a resistance voltage-dividing circuit, or from a CT circuit to a divided CT circuit), only changing values of slope and intercept of a primary line is sufficient. Any of the compensation Expressions (FV1)(FI) (FV2)(FI2) shows a characteristic similar to Fig. 6, and further description thereof with reference to charts is omitted.

In addition, it is also preferable that operation amount and setting amount of slope and intercept of the line are reduced, on the assumption that amplitude compensation rate obtained by summing the voltage signal input means and current signal input means is Gain_Freq, and a phase variation thereof is Phase_Freq; and that Gain_Freq=(A_GainFreqV+A_Gain_Freql) XFreq+ B_Gain_FreqV+BGainFreqI Phase_Freq=(A_Phase_FreqV+A_Phase_Freql) XFreq+ B_Gain_FreqV+B_Phase_FreqI Example 4.

Hi\akhoo\Keep\Temp\P49868 542530-AU-01(spec.) .doc 17/06/03 14 A temperature Temp of a current AD converter is obtained by temperature measurement means 56 (herein it is assumed that any AD converter is substantially at the same temperature). Then an amplitude compensation rate (inverse number of the rate of change in amplitude) and a phase variation of a voltage signal input, a current signal input and AD converter depending on temperature are calculated with a primary line.

1) For compensation of a voltage signal input depending on temperature, it is assumed that amplitude compensation rate is Gain_TempV, and phase variation thereof is Phase_TempV; slope of a primary line of an amplitude compensation rate is A_Gain_TempV, and intercept thereof is B_Gain_TmepV; and slope of a primary line of a phase variation is A_Phase_TmepV, and intercept thereof is BPhase_TmepV; 2) For compensation of a current signal input depending on temperature, it is assumed that amplitude compensation rate is Gain_TempI, and phase variation thereof is Phase_TempI; slope of a primary line of an amplitude compensation rate is A_GainTempI, and intercept thereof is B_Gain_TmepI; and slope of a primary line of a phase variation is A_Phase_TmepI, and intercept thereof is B_Phase_TmepI; 3) For compensation of an AD converter depending on temperature, it is assumed that amplitude compensation rate is Gain_TempAD, and phase variation thereof is Phase_TempAD; slope of a primary line of an amplitude compensation rate is A_Gain_TempAD, and intercept thereof is B_GainTmepAD; and H.\akhoo\Keep\Temp\P49868 542530-AU-01(spec.) .doc 17/06/03 15 slope of a primary line of a phase variation is A_Phase_TmepAD, and intercept thereof is B_Phase_TmepAD. On the assumption that the current temperature is Temp, the following compensation expressions are obtained: Gain_TempV=A_Gain_TempVXTemp+B_Gain_TempV* (TV1) Gain_TempI=A_Gain_TempIXTemp+B_Gain_TempI (Til) Gain_TempAD=A_Gain_TempADXTemp+B_Gain_TempAD (TA1) Phase_TempV=A_Phase_TempVXTemp+B_Phase_TempV (TV2) Phase_TempI=A_Phase_TempI XTemp+B_Phase_TempI (TI2) Phase_TempAD=A_Phase_TempADXTemp+B_Phase_TempAD (TA2) The slope and intercept of a primary line is set so that Gain_TempV, Gain_TempI and Gain_Temp AD may be 1 in the case where the current temperature is a temperature at initial adjustment. Further, the slope and intercept of a primary line are set so that Phase_TempV, PhaseTempI and Phase_Temp AD may be 0 in the case where the current temperature is a temperature at the time of initial adjustment, while setting variation in the direction of advance to be positive and variation in the direction of delay to be negative. It is also preferable that the temperature at the time of initial adjustment is preliminarily stored, and intercept is calculated back based on the current frequency and slope of the line. In this case, setting quantity of intercept can be reduced.

Further, slope and intercept can be set and changed freely.

Accordingly, in the case where a circuit arrangement of the voltage signal input means and the current signal input means is changed (for example, from a PT circuit to a resistance voltage-dividing circuit, or from a CT circuit to a divided CT circuit), only changing values of slope and intercept of a primary line is sufficient.

In addition, it is also preferable that operation amount and setting amount of slope and intercept of the line H,\akhoo\Keep\Temp\P49868 542530-AU-1(spec.) .doc 17/06/03 16 are reduced, on the assumption that amplitude compensation rate obtained by summing the voltage signal input means and current signal input means and the AD converter is GainTemp, and a phase variation thereof is Phase_Temp, and that Gain_Temp= (A_Gain_TempV+A_Gain_TempI+A_Gain_TempAD)X Temp+B_Gain_TempV+B_Gain_TempI+B_Gain_TempAD Phase_Temp= (A_Phase_TempV+A_PhaseTempI+A_Phase_TempAD)X Temp+B_Gain_TempV+B_Phase_TempI+B_Phase_TempAD To reflect the amplitude compensation rate and phase variation having been calculated in the mentioned manner on the operation of electric power and invalid electric power, amplitude phase compensation matrix at the time of initial adjustment (described above) is multiplied by the amplitude compensation rate and phase variation compensation matrix.

A result thus obtained is adopted as an amplitude phase compensation matrix for use in actual operation.

The amplitude compensation rate and phase variation as a whole is to be a sum of effects provided by a parameter having been selected arbitrarily and intended to be compensated out of the effective value voltage, effective value current, power supply frequency, and temperature. In the case of selecting all the parameters, assuming that the entire amplitude compensation rate is Gainall N and an entire phase variation is Phase all N, the following Expression is obtained: Gain_allN=Gain_Vrms_NXGain_Irms_NXGain_FreqXGain_Temp Phase_all_N=Phase_Vrms_N+Phase_Irms_N+PhaseFreq+Phase_ Temp Phase variation compensation matrix= (cos(Phaseall N) -sin(Phase allN) (xpression 3) sin(Phase all N) cos(Phase_ all N)) H.\akhoo\Keep\Temp\P49868 542530-AU-01(spec.).doc 17/06/03 17 Accordingly, an amplitude phase compensation matrix for use in actual operation is as shown in the following Expression Amplitude phase compensation matrix for use in operation= Gain_all_NX amplitude phase compensation matrix at the time of adjustment (cos(Phase_ all_ N) -sin(Phase_ all _N) sin(Phase_all_N) cos(Phase_all _N) Further, in the case of reflecting an amplitude compensation rate and phase variation having been calculated in the mentioned manner on the effective value voltage or effective value current, since any effective value is irrelevant to phase, an actual operation is preferably carried out in the following manner. That is, a result obtained by multiplying a transformation coefficient 181, 183, 281, 283 at the time of initial adjustment by an amplitude compensation rate of the effective value voltage Vrms-N and the effective value current Irms-N is used as a transformation coefficient in actual operation.

In addition, a coefficient of amplitude phase compensation matrix for use in actual operation is not calculated for each sampling frequency, but is preferably calculated at time intervals in which change in each effective value, temperature, etc. is recognized as a significant difference. For example, the calculation amplitude phase compensation matrix is preferably carried out at intervals of 0.5 to several seconds. Therefore, an operation amount is increased only when updated, and the operation amount to operate an amount related to electric power on a constant basis is not increased, and an operation load is not increased as well.

As described above, compensation is carried out depending on an effective value voltage, effective value HI\akhoo\Keep\Temp\P49868 542530-AU-01(spec.).doc 17/06/03 18 current, power supply frequency and AD converter temperature, which are detected at the time of measuring an amount related to electric power. As a result, it becomes possible to measure an amount related to electric power with a high degree of accuracy at all times. Although an example of conducting compensation depending on an effective value voltage, effective value current, power supply frequency and temperature is described, it is also preferable to conduct compensation depending on at least one of those parameters.

Such example is later-described in the second preferred embodiment.

Note that since phases are compensated with a rotation matrix, it becomes possible to perform compensation in a short time.

Further, the power-related amount measurement device according to this first embodiment includes: 900 phase transformation means for performing orthogonal phase transformation of current phases with respect to voltage by 900 or that of current with respect to voltage by 900 invalid power operation means for operating an invalid power based on output from the 900 phase transformation means; and valid power operation means for operating a valid power based on the current and voltage. As a result, it becomes possible to perform both rotation matrix operation function for obtaining an amplitude phase compensation matrix at the time of adjustment and rotation matrix operation function for the above-described compensation.

In addition, although the temperature is defined to that of an AD converter in this first embodiment, it is also preferable to use a temperature of an operation device for performing the above-described operation.

Ht\akhoo\Keep\Temp\P49868 542530-AU-01(spec.).doc 17/06/03 19 Embodiment 2.

In the above-mentioned first embodiment, seven amplitude compensation rates and seven phase variations are calculated with the use of four parameters of effective value voltage, effective value current, power supply frequency and AD converter temperature. It is, however, also preferable that some of those items are arbitrarily selected and operated. For example, when only any phase variation in current signal input depends largely on an effective value current and power supply frequency and it is required to conduct compensation for them, only operations of Phase_IrmsN and PhaseFreqI are preferably conducted.

Much the same is true on the other items.

Embodiment 3.

In the above-mentioned second embodiment, arbitrary items are selected and operated. However, the similar operation can be preferably achieved also by selecting all the items and then setting slope and intercept of a primary line for compensation in the following manner as to items not requiring any particular compensation.

That is, as to an amplitude compensation rate of unnecessary items, slope of a primary line is set to be 0, and intercept thereof is set to be 1. As to a phase variation of unnecessary items, slope of a primary line is set to be 0, and intercept thereof is set to be 0.

Embodiment 4.

It is preferable that coefficient of an amplitude phase compensation matrix for use in actual operation is calculated in a manner of a floating-point operation, and thereafter it is transformed from with a floating decimal point to with a fixed decimal point and set on updating an Hs\akhoo\Keep\Temp\P49868 542530-AU-01(spec.).doc 17/06/03 20 amplitude phase compensation matrix. Whereby operation on a constant basis is only multiplication and addition of values with a fixed decimal point resulting in improvement in operation speed.

Embodiment In the above-mentioned fourth embodiment, operation is done with a fixed decimal point upon updating an amplitude phase compensation matrix. However, it is possible to calculate coefficient of an amplitude phase compensation matrix for use in an actual operation with a fixed decimal point.

Practically, slope and intercept of a primary line is set with a fixed decimal point. Further, parameters of an effective value voltage, effective value of current, power supply frequency and temperature on calculating an amplitude compensation rate and phase variation are obtained with a fixed decimal point. Accordingly, calculation of an amplitude compensation rate and phase variation is done solely by multiplication and addition with a fixed decimal point.

Moreover, to reduce an operation amount with a floating decimal point of a sine value and cosine value, which become necessary upon operating a phase variation compensation matrix, it is preferable that a phase variation compensation matrix is operated as follows. In this operation, for example, coefficient of a 0.010 left-handed rotation matrix, 0.10 left-handed rotation matrix, 10 left-handed matrix have been held preliminarily in default with a fixed decimal point. A phase variation is calculated and thereafter multiplied by the above-mentioned left-handed rotation matrix.

In the above-mentioned example, in the case where a H \akhoo\Keep\Temp\P49868 542530-AU-01(spec.).doc 17/06/03 21 phase variation is 1.240 (lead), a phase variation compensation matrix can be calculated by operation of 1° left-handed rotation matrixX left-handed rotation matrix) 2X(0.01 0 left-handed rotation matrix) 4.

Embodiment 6.

As a division CT, in the case where a phase variation depending on magnitude of current intended to be detected is nonlinear, and compensation with a primary line is difficult, compensation is done in the following way. In this compensation, a large number of primary lines, e.g., two or three primary lines having different slopes and intercepts are set, and primary line for calculating a compensation amount is switched, establishing intersection of the lines as a boundary.

For example, the case where a division CT is employed as for a current signal input, and a phase variation depending on magnitude of current intended to be detected is nonlinear is described as an example. One example 95 of characteristic at this time is shown in Fig. In the characteristic 95 of Fig. with load of approximately being a boundary, a phase error becomes steeply large in a region of a lighter load as compared with a region of a heavier load. In this case, for example, two primary lines for calculating a phase variation PhaseIrms N are provided.

Slope of a first primary line 96 for calculating a phase variation is AlPhase Irms, and intercept thereof is Bl_Phase_Irms. Slope of a second primary line 97 is A2_Phase_Irms, and intercept thereof is B2_PhaseIrms. At the point of two primary lines being set, Irms of intersection of the line 96 and line 97 is calculated.

H.\akhoo\Keep\Temp\P49868 542530-AU-01(spec.) .doc 17/06/03 22 B2 Phase Irms Phase Irms Irms of intersection of lines- Phe-I -Pha Al Phase Irms A2 Phase Irms Accordingly, in the case where a current IrmsN is not less than Irms of intersection of the lines, the first primary line 96 is used, and Phase Irms N=AlPhase IrmsXIrms N+B1lPhase Irms In the case where a current Irms N is less than Irms of intersection of the lines, the second primary line 97 is used, and Phase Irms N=A2 Phase IrmsXIrms N+B2 Phase Irms By operation like this, as a phase error 98 shown in Fig. measurement of an amount related to an electric power can be carried out in high accuracy. It is a matter of course to use a larger number of lines in conformity with a curved line of the characteristic In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

Ht\akhoo\Keep\Temp\49868 542530-AU-01(spe.) .doc 17/06/03

Claims (7)

1. A power-related amount measurement device comprising: an AD conversion circuit performing a digital conversion respectively with a current signal and voltage signal detected by a current sensor and voltage sensor laid on a power line; a power-related amount operation section calculating a frequency of said voltage signal as well as operating an amount related to an electric power of said power line based on an output from said AD conversion circuit; and compensation means for compensating said amount related to an electric power, establishing at least one of said voltage signal, current signal and frequency as a parameter.

2. A power-related amount measurement device comprising: an AD conversion circuit performing a digital conversion respectively with a current signal and voltage signal detected by a current sensor and voltage sensor laid on a power line; an temperature detector detecting temperature of said AD conversion circuit; a power-related amount operation section calculating a frequency of said voltage signal as well as operating an amount related to an electric power of said power line based on an output from said AD conversion circuit; and compensation means for compensating said amount related to an electric power, establishing said temperature as a parameter.

3. The power-related amount measurement device H \akhoo\Keep\Temp\P49868 542530-AU-01(spec.) .doc 17/06/03 24 according to claim 1 or claim 2, wherein said compensation means is to conduct compensation for an amplitude and phase of said amount related to said electric power.

4. The power-related amount measurement device according to claim 3, wherein compensation for a phase of said amount related to said electric power by said compensation means is conducted with the following expression shown in operation of a rotation matrix based on an amplitude, phase compensation matrix at the time of an initial adjustment.

Var out N =amplitude phase compensation matrix at the time Var out N\ of an initial adjustment X(cos(Phase_all -sin(Phase_all W _in_ N Ssin(Phase all_ N) cos(Phase_ all Var_in N W out N :valid power after compensation Var out N :invalid power after compensation Phase all N :phase to be compensated, being obtained from parameter W in N :valid power before compensation Var in N :invalid power before compensation The power-related amount measurement device according to claim 1 or claim 2, wherein the power-related amount operation section comprising: valid power operation means for calculating a valid electric power from said current signal and voltage signal outputted from said AD conversion circuit; 900 phase transformation means for performing a 900 phase transformation with a phase of said voltage signal with respect to said current signal, or of said current H \akhoo\Keep\Temp\P4986S 542530-AU-01spec.) .doc 17/06/03 S- 25 O eC signal with respect to said voltage signal; and invalid power operation means for operating an O Z invalid power with a phase output having been transformed by said 900 phase transformation means.

6. The power-related amount measurement device according to claim 4, wherein said compensation expression 00 is set respectively in each predetermined range of said 0 parameter. m1

7. A power-related amount measurement device, substantially as herein described with reference to the accompanying drawings. Dated this llth day of November 2004 MITSUBISHI DENKI KABUSHIKI KAISHA By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia H.\jolzik\keep\Speci\2003204811.doc 11/11/04