Three-phase heater current detection apparatus and method

Abstract

To estimate the effective value of phase current of a three-phase heater even when the current and voltage are not a sinusoidal wave.SOLUTION: A three-phase heater current detection device comprises: a line current measurement unit 7 for measuring the instantaneous value of a line current flowing in three feeder lines 14-16 to a three-phase heater 1; a line-to-line voltage measurement unit 8 for measuring the instantaneous value of a line-to-line voltage of the three feeder lines 14-16; a power consumption calculation unit 9 for calculating the power consumption of the three-phase heater 1; a cross correlation function calculation unit 100 for calculating the generalization cross correlation function of instantaneous value of the line-to-line voltage; an effective current value calculation unit 104 for calculating the effective value of the line current; an effective voltage value calculation unit 105 for calculating the effective value of the line-to-line voltage; a cross correlation function assessment unit 101 for assessing whether or not all of generalization cross correlation functions are less than 0; and a phase current calculation unit 102 for calculating a phase current flowing in the three-phase heater 1 on the basis of the effective value of line current, the effective value of line-to-line voltage, power consumption and the generalization cross correlation function when all of the generalization cross correlation functions are less than 0.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a three-phase heater current detection device and method for detecting phase currents flowing through a three-phase heater. [Background technology]

[0002] Measuring the heater resistance is effective for diagnosing the life of the heater, but the phase current (I rs ,I st ,I tr ) is often not measurable due to the structure of the heater. Patent Document 1 discloses a method for estimating the phase current of a delta connection in order to know the resistance value of the heater.

[0003] In the method disclosed in Patent Document 1, when the phase difference between the phases of a three-phase power supply is known, the estimated value of the phase current is fed back to update the estimated value. Depending on the type of heater, the resistance value may change significantly with the ambient temperature, so if repeated calculations are required to obtain the phase current as in the method disclosed in Patent Document 1, there is a possibility that the tracking of the estimated value may be slow when the resistance value changes.

[0004] Furthermore, as a method for detecting the resistance value of a three-phase heater, there is a method disclosed in Patent Document 2. However, the method disclosed in Patent Document 2 has hardware limitations, such as the need for instantaneous values ​​of current and voltage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-110732 A [Patent Document 2] JP 2020-148697 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve the above-mentioned problems, and has an object to provide a three-phase heater current detection device and method that can estimate the effective value of the phase current of a three-phase heater even when the current and voltage are not sine waves. [Means for solving the problem]

[0007] A three-phase heater current detection device of the present invention includes a line current measurement unit configured to measure an instantaneous value of a line current flowing through three power feeders to a three-phase heater to which three heaters are connected, a line voltage measurement unit configured to measure an instantaneous value of a line voltage of the three power feeders, and a power consumption calculation unit configured to calculate a power consumption of the three-phase heater based on a measurement result of the line current measurement unit and a measurement result of the line voltage measurement unit. The instantaneous value E of the line voltage between the RS lines rs The instantaneous value of the line voltage between the lines E and TR tr The generalized cross-correlation function D r , the instantaneous value E of the line voltage between the ST lines st The instantaneous value of the line voltage between the and RS lines E rs The generalized cross-correlation function D s , and the instantaneous value E of the line voltage between the TR lines tr The instantaneous value E of the line voltage between the ST line and st The generalized cross-correlation function D t a current effective value calculation unit configured to calculate an effective value of the line current from the measurement result of the line current measurement unit; a voltage effective value calculation unit configured to calculate an effective value of the line voltage from the measurement result of the line voltage measurement unit; and D r ,D s ,D t a phase current calculation unit configured to calculate a phase current flowing through the three-phase heater based on , the generalized cross-correlation function D r ,D s ,D t a cross-correlation function determination unit configured to determine whether Equipped with , the phase current calculation unit calculates the generalized cross-correlation function D r ,Ds ,D t are all determined to be less than 0, the effective value I r(e) and the effective value I of the S-phase line current s(e) The effective value of the line voltage between the and RS lines is E rs(e) and the effective value E of the line voltage between the ST line st(e) and the effective value E of the line voltage between the TR line tr(e) and the power consumption W and the generalized cross-correlation function D r ,D s Based on this, the effective value of the RS phase current I rs(e) Calculate the effective value of the RS phase current I rs(e) and the effective value I of the S-phase line current s(e) and the generalized cross-correlation function D s Based on this, the effective value of the ST phase current I st(e) Calculate the effective value of the RS phase current I rs(e) and the effective value I of the R-phase line current r(e) and the generalized cross-correlation function D r Based on this, the effective value of the TR phase current I tr(e) Calculate It is characterized by the above.

[0009] The three-phase heater current detection device of the present invention The present invention relates to a three-phase heater having three heaters connected thereto, the three-phase heater having three heaters connected thereto, a line current measuring unit configured to measure an instantaneous value of a line current flowing through three power feeders to the three heaters connected thereto, a line voltage measuring unit configured to measure an instantaneous value of a line voltage of the three power feeders, a power consumption calculating unit configured to calculate the power consumption of the three-phase heater based on a measurement result of the line current measuring unit and a measurement result of the line voltage measuring unit, and rs The instantaneous value of the line voltage between the lines E and TR tr The generalized cross-correlation function D r , the instantaneous value E of the line voltage between the ST lines st The instantaneous value of the line voltage between the and RS lines E rs The generalized cross-correlation function D s , and the instantaneous value E of the line voltage between the TR lines tr The instantaneous value E of the line voltage between the ST line and st The generalized cross-correlation function D t a current effective value calculation unit configured to calculate an effective value of the line current from the measurement result of the line current measurement unit; a voltage effective value calculation unit configured to calculate an effective value of the line voltage from the measurement result of the line voltage measurement unit; and a cross-correlation function calculation unit configured to calculate the effective value of the line current, the effective value of the line voltage, the power consumption, and the generalized cross-correlation function D r ,D s ,D t and a phase current calculation unit configured to calculate a phase current flowing through the three-phase heater based on the phase current calculation unit. The phase current calculation unit With unknown parameters x, measured data y, and sensitivity matrix H, the effective value I rs(e) and the effective value I of the ST phase current st(e) and the effective value I of the TR phase current tr(e) and the effective value I of the line current of the R phase r(e) and the effective value I of the line current of the S phase s(e) and the effective value I of the line current of the T phase t(e) and the effective value E of the line voltage between the RS lines. rs(e) and the effective value E of the line voltage between the ST lines st(e) and the effective value E of the line voltage between the TR lines tr(e) , the power consumption W, and the generalized cross-correlation function D r ,D s ,D t The effective value of the RS phase current is calculated by solving the nonlinear simultaneous equations that define the relationship between I rs(e) Calculate the effective value of the RS phase current I rs(e) and the effective value I of the S-phase line current s(e) and the generalized cross-correlation function D s Based on this, the effective value of the ST phase current I st(e) Calculate the effective value of the RS phase current I rs(e) and the effective value I of the R-phase line current r(e) and the generalized cross-correlation function D r Based on this, the effective value of the TR phase current I tr(e) Calculate It is characterized by the above.

[0010] A three-phase heater current detection method of the present invention includes a first step of measuring instantaneous values ​​of line currents flowing through three power feeders to a three-phase heater having three heaters connected thereto, a second step of measuring instantaneous values ​​of line voltages of the three power feeders, and a third step of calculating power consumption of the three-phase heater based on a measurement result of the first step and a measurement result of the second step. The instantaneous value E of the line voltage between the RS lines rs The instantaneous value of the line voltage between the lines E and TR tr The generalized cross-correlation function D r , the instantaneous value E of the line voltage between the ST lines st The instantaneous value of the line voltage between the and RS lines E rs The generalized cross-correlation function D s , and the instantaneous value E of the line voltage between the TR lines tr The instantaneous value E of the line voltage between the ST line and st The generalized cross-correlation function D ta fourth step of calculating an effective value of the line current from the measurement result of the first step; a fifth step of calculating an effective value of the line voltage from the measurement result of the second step; and a sixth step of calculating an effective value of the line current, an effective value of the line voltage, the power consumption, and the generalized cross-correlation function D r ,D s ,D t a seventh step of calculating a phase current flowing through the three-phase heater based on , the generalized cross-correlation function D r ,D s ,D t The eighth step is to determine whether all are less than zero. Including The seventh step is to calculate the generalized cross-correlation function D r ,D s ,D t are all determined to be less than 0, the effective value I r(e) and the effective value I of the S-phase line current s(e) The effective value of the line voltage between the and RS lines is E rs(e) and the effective value E of the line voltage between the ST line st(e) and the effective value E of the line voltage between the TR line tr(e) and the power consumption W and the generalized cross-correlation function D r ,D s Based on this, the effective value of the RS phase current I rs(e) Calculate the effective value of the RS phase current I rs(e) and the effective value I of the S-phase line current s(e) and the generalized cross-correlation function D s Based on this, the effective value of the ST phase current I st(e) Calculate the effective value of the RS phase current I rs(e) and the effective value I of the R-phase line current r(e) and the generalized cross-correlation function D r Based on this, the effective value of the TR phase current I tr(e) Calculating It is characterized by the above.

[0012] The three-phase heater current detection method of the present invention The method includes a first step of measuring instantaneous values ​​of line currents flowing through three power feeders to a three-phase heater having three heaters connected thereto, a second step of measuring instantaneous values ​​of line voltages of the three power feeders, a third step of calculating the power consumption of the three-phase heater based on the measurement results of the first step and the second step, and a third step of calculating an instantaneous value E of the line voltage between the RS lines. rs The instantaneous value of the line voltage between the lines E and TR tr The generalized cross-correlation function D r , the instantaneous value E of the line voltage between the ST lines st The instantaneous value of the line voltage between the and RS lines E rs The generalized cross-correlation function D s , and the instantaneous value E of the line voltage between the TR lines tr The instantaneous value E of the line voltage between the ST line and st The generalized cross-correlation function D t a fourth step of calculating an effective value of the line current from the measurement result of the first step; a fifth step of calculating an effective value of the line voltage from the measurement result of the second step; and a sixth step of calculating an effective value of the line current, an effective value of the line voltage, the power consumption, and the generalized cross-correlation function D r ,D s ,D t and a seventh step of calculating a phase current flowing through the three-phase heater based on The seventh step includes: With unknown parameters x, measured data y, and sensitivity matrix H, the effective value I rs(e) and the effective value I of the ST phase current st(e) and the effective value I of the TR phase current tr(e) and the effective value I of the line current of the R phase r(e) and the effective value I of the line current of the S phase s(e) and the effective value I of the line current of the T phase t(e) and the effective value E of the line voltage between the RS lines. rs(e) and the effective value E of the line voltage between the ST lines st(e) and the effective value E of the line voltage between the TR lines tr(e) , the power consumption W, and the generalized cross-correlation function D r ,D s ,D t The effective value of the RS phase current is calculated by solving the nonlinear simultaneous equations that define the relationship between I rs(e) Calculate the effective value of the RS phase current I rs(e) and the effective value I of the line current of the S phase s(e) and the generalized cross-correlation function D s Based on this, the effective value of the ST phase current I st(e) Calculate the effective value of the RS phase current I rs(e) and the effective value I of the R-phase line current r(e) and the generalized cross-correlation function D r Based on this, the effective value of the TR phase current I tr(e) Calculating It is characterized by the above. Effect of the Invention

[0013] According to the present invention, even if the output of the three-phase AC power supply is not a sine wave, it is possible to estimate the effective value of the phase current flowing through the three-phase heater. Furthermore, the present invention can reduce hardware restrictions compared to the conventional method. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a block diagram showing the configuration of a three-phase heater current detection device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a flowchart illustrating the operation of the three-phase heater current detecting device according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is a block diagram showing a configuration of a three-phase heater current detecting device according to a second embodiment of the present invention. [Figure 4] FIG. 4 is a flowchart illustrating the operation of the three-phase heater current detecting device according to the second embodiment of the present invention. [Diagram 5] FIG. 5 is a flowchart illustrating a method for calculating the effective value of the RS phase current using an extended Kalman filter. [Figure 6] FIG. 6 is a block diagram showing an example of the configuration of a computer that realizes the three-phase heater current detection device according to the first and second embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a block diagram showing the configuration of a three-phase heater current detection device according to a first embodiment of the present invention. The three-phase AC power supply 2 and the power control device 3 constitute a three-phase power regulator 4 that adjusts the power supplied to the three-phase heater 1. The three-phase heater 1 has three heaters 11-13 connected in a delta configuration. Three power feeders 14-16 extend from the heaters 11-13 and are connected to the output side of the power control device 3. The input side of the power control device 3 is connected to the three-phase AC power supply 2. The three-phase heater 1 converts the power supplied via the three power feeders 14-16 into thermal energy and outputs it.

[0016] The three-phase heater current detection device of this embodiment includes current transformers 5-1 to 5-3 for measuring line currents provided in the respective power feeders 14 to 16, a voltage transformer 6 for measuring line voltages connected between the lines of the power feeders 14 to 16, a line current measurement unit 7 connected to the output of the current transformers 5-1 to 5-3 for measuring line currents and for measuring instantaneous values ​​of line currents flowing through the respective power feeders 14 to 16, a line voltage measurement unit 8 connected to the output of the voltage transformer 6 for measuring line voltages and for measuring instantaneous values ​​of line voltages of the respective power feeders 14 to 16, a power consumption calculation unit 9 for calculating the power consumption of the three-phase heater 1, and a generalized cross-correlation calculation unit 10 for calculating the instantaneous values ​​of the line voltages. the cross-correlation function calculation unit 100 calculating a cross-correlation function; a cross-correlation function determination unit 101 determining whether the generalized cross-correlation functions calculated by the cross-correlation function calculation unit 100 are all less than 0; a phase current calculation unit 102 calculating a phase current flowing through the three-phase heater 1 based on the effective value of the line current, the effective value of the line voltage, the power consumption, and the generalized cross-correlation function when it is determined that the generalized cross-correlation functions are all less than 0; an output unit 103 outputting the calculation result of the phase current calculation unit 102; a current effective value calculation unit 104 calculating the effective value of the line current; and a voltage effective value calculation unit 105 calculating the effective value of the line voltage.

[0017] As shown in FIG. 1, the resistance values ​​of heaters 11, 12, and 13 are R rs ,R st ,R tr In addition, the R-phase current flowing through the power supply line 14 is I r , the S-phase current flowing through the power supply line 15 is I s , the T-phase current flowing through the power supply line 16 is I t The RS-phase current flowing through the heater 11 is I rs , the ST-phase current flowing through the heater 12 is I st , the TR phase current flowing through the heater 13 is I tr In addition, the RS line voltage between the power feeders 14 and 15 is E rs ,ST line voltage between feeders 15 and 16 is E st , the TR line voltage between feeders 16 and 14 is E tr Each of these currents and voltages is a vector quantity. The following relationship exists between the currents:

[0018] I r =I rs -I tr (1) I s =I st -I rs (2) I t =I tr -I st (3)

[0019] If we square both sides of equation (1), integrate it over the power supply period, and divide it by the power supply period, we get the following equation (4). In other words, equation (4) calculates the square of the effective value of both sides of equation (1).

[0020]

number

[0021] I r(e) ,I s(e) ,I t(e) ,I rs(e) ,I st(e) ,I tr(e) are the currents I r ,I s ,I t ,I rs ,I st ,I tr is the effective value of D r is the RS line voltage E rs and TR line voltage E tr The generalized cross-correlation function (normalized cross-correlation function) of Equation (4) shows the result of the following calculation:

[0022]

number

[0023] E rs(e) ,E st(e) ,E tr(e) are the voltages E rs ,E st ,E tr The effective value of the RS line voltage Ers and TR line voltage E tr The generalized cross-correlation function D r , ST line voltage E st and RS line voltage E rs The generalized cross-correlation function D s , TR line voltage E tr and ST line voltage E st The generalized cross-correlation function D t is expressed as follows:

[0024]

number

[0025]

number

[0026]

number

[0027] In equations (5) to (8), T is the power supply period. The generalized cross-correlation function D r -1≦D r If the three-phase AC power source 2 is in a balanced state and the power control device 3 controls the load (three-phase heater 1) by phase angle control using a thyristor, D r <0 and D s <0 and D t It was confirmed by simulation using the circuit simulator SPICE that the power consumption W of the entire three-phase load is expressed by the following equation.

[0028]

number

[0029] Here, from equation (4), the effective value I tr(e) When this is calculated, the following equation (10) is obtained.

[0030]

number

[0031] In particular, D r <0, I rs(e) ≧0 and I tr(e) ≧0, the effective value of the TR phase current I tr(e) is expressed as follows:

[0032]

number

[0033] In addition, the effective value of the ST phase current I st (e) is expressed as follows:

number

[0034] From equations (9), (11), and (12), the following nonlinear equation (13) can be obtained.

[0035]

number

[0036] If the power consumption W of the three-phase heater 1 can be measured, the unknown value in the above equation (13) is the effective value I of the RS phase current. rs(e) The effective value I of the RS phase current can be calculated by various methods (e.g., Newton's method). rs(e) Thus, the effective value of the RS phase current I rs(e) If it is possible to calculate the ST phase current effective value I st(e) The effective value of the TR phase current I tr(e) can be calculated.

[0037] 2 is a flow chart for explaining the operation of the three-phase heater current detection device of the present embodiment. The line voltage measurement unit 8 measures an instantaneous value E rs, ST instantaneous value of line voltage E st , instantaneous value of TR line voltage E tr is measured (Step S100 in FIG. 2).

[0038] The line current measuring unit 7 measures the instantaneous value I r , instantaneous value of S-phase wire current I s , instantaneous value of T-phase wire current I t is measured (Step S101 in FIG. 2).

[0039] The power consumption calculation unit 9 calculates the instantaneous value I of the R-phase line current measured by the line current measurement unit 7. r , instantaneous value of S-phase wire current I s and the instantaneous value E of the ST line voltage measured by the line voltage measuring unit 8 st , instantaneous value of TR line voltage E tr Based on the above, the power consumption W of the three-phase heater 1 is calculated by the two-wattmeter method (FIG. 2, step S102). Note that the method of calculating the power consumption W is not limited to the method of this embodiment.

[0040] The cross-correlation function calculation unit 100 calculates the instantaneous value E rs , ST instantaneous value of line voltage E st , the instantaneous value of the TR line voltage E tr Based on the generalized cross-correlation function D r ,D s ,D t (Step S103 in FIG. 2).

[0041] The current effective value calculation unit 104 calculates the instantaneous value I of the R-phase line current measured by the line current measurement unit 7. r , instantaneous value of S-phase wire current I s , instantaneous value of T-phase wire current I t Based on this, the effective value of the R-phase wire current I r(e) , the effective value of the S-phase wire current I s(e) , the effective value of the T-phase current I t(e) (Step S104 in FIG. 2).

[0042] The voltage effective value calculation unit 105 calculates the instantaneous value Ers , ST instantaneous value of line voltage E st , the instantaneous value of the TR line voltage E tr Based on this, the effective value of the RS line voltage E rs(e) , ST line voltage effective value E st(e) , the effective value of the TR line voltage E tr(e) (Step S105 in FIG. 2).

[0043] The cross-correlation function determination unit 101 determines the generalized cross-correlation function D calculated by the cross-correlation function calculation unit 100. r ,D s ,D t But, D r <0, D s <0, D t <0, i.e., whether all are less than 0 (step S106 in FIG. 2). r ,D s ,D t If at least one of is equal to or greater than 0 (NO in step S106), the phase current cannot be estimated.

[0044] The phase current calculation unit 102 calculates a generalized cross-correlation function D r ,D s ,D t If all of are less than 0 (YES in step S106), the power consumption W calculated by the power consumption calculation unit 9 and the effective value I of the R-phase line current calculated by the current effective value calculation unit 104 are r(e) , the effective value of the S-phase wire current I s(e) and the effective value E of the RS line voltage calculated by the voltage effective value calculation unit 105. rs(e) , ST line voltage effective value E st(e) , the effective value of the TR line voltage E tr(e) and the generalized cross-correlation function D calculated by the cross-correlation function calculation unit 100. r ,D s Based on this, the effective value I of the RS phase current is calculated by equation (13). rs(e) (Step S107 in FIG. 2).

[0045] Then, the phase current calculation unit 102 calculates the effective value I rs(e)and the effective value I of the S-phase wire current calculated by the current effective value calculation unit 104. s(e) and the generalized cross-correlation function D calculated by the cross-correlation function calculation unit 100. r ,D s Based on this, the effective value I of the ST phase current is calculated by equation (12). st(e) (Step S108 in FIG. 2).

[0046] Furthermore, the phase current calculation unit 102 calculates the effective value I rs(e) and the effective value I of the R-phase line current calculated by the current effective value calculation unit 104. r(e) and the generalized cross-correlation function D calculated by the cross-correlation function calculation unit 100. r Based on this, the effective value I of the TR phase current is calculated by equation (11). tr(e) (Step S109 in FIG. 2).

[0047] The output unit 103 outputs the calculation result of the phase current calculation unit 102 (step S110 in FIG. 2). rs(e) ,I st(e) ,I tr(e) These include displaying the results and sending the calculation results externally.

[0048] As described above, in this embodiment, the effective value I rs(e) ,I st(e) ,I tr(e) In this embodiment, even if the output of the three-phase AC power supply is not a sine wave, the effective value I rs(e) ,I st(e) ,I tr(e) can be estimated. In addition, in the method disclosed in Patent Document 2, since instantaneous values ​​(current and voltage), effective values ​​(current and voltage), and power consumption are mixed, it is necessary to synchronize each of the values. On the other hand, in this embodiment, although it is necessary to pre-calculate the effective values, cross-correlation functions, and power consumption, since these are values ​​integrated over the power supply cycle, it is not necessary to synchronize the instantaneous values, and it is possible to reduce hardware constraints.

[0049] [Second Example] Next, a second embodiment of the present invention will be described. In the first embodiment, a generalized cross-correlation function D r ,D s ,D t The phase current flowing through the three-phase heater can be estimated only when all of are less than 0. However, when solving the equation using an extended Kalman filter, D r <0, D s <0, D t The <0 condition can be eliminated.

[0050] FIG. 3 is a block diagram showing the configuration of a three-phase heater current detection device according to a second embodiment of the present invention, and the same components as those in FIG. 1 are given the same reference numerals. The three-phase heater current detection device of this embodiment includes current transformers 5-1 to 5-3 for measuring line current provided in each of the power feeders 14 to 16, a voltage transformer 6 for measuring line voltage connected between the lines of the power feeders 14 to 16, a line current measurement unit 7 connected to the output of the current transformers 5-1 to 5-3 for measuring line current and measuring an instantaneous value of the line current flowing through each of the power feeders 14 to 16, and a line voltage measurement unit 8 connected to the output of the voltage transformer 6 for measuring line voltage and measuring an instantaneous value of the line voltage of each of the power feeders 14 to 16. The system includes a power consumption calculation unit 9 that calculates the power consumption of the three-phase heater 1, a cross-correlation function calculation unit 100 that calculates a generalized cross-correlation function of the instantaneous values ​​of the line voltages, a phase current calculation unit 102a that calculates the phase current flowing through the three-phase heater 1 based on the effective value of the line current, the effective value of the line voltage, the power consumption, and the generalized cross-correlation function, an output unit 103 that outputs the calculation result of the phase current calculation unit 102a, a current effective value calculation unit 104 that calculates the effective value of the line current, and a voltage effective value calculation unit 105 that calculates the effective value of the line voltage.

[0051] The currents shown in FIG. 3 are related by the following equation:

[0052]

number

[0053] Here, we define the following equations (17) to (20), and apply the method described in the reference book "Tanaka, Masataka, "Application of Boundary Element Method and Filter Theory to Inverse Heat Conduction Problems", Applied Mathematics, vol. 10, No. 2, pp. 130-140, 2000" to these nonlinear simultaneous equations.

[0054]

number

[0055] 4 is a flow chart for explaining the operation of the three-phase heater current detection device of this embodiment. As in the first embodiment, the line voltage measurement unit 8 measures the instantaneous value E rs , ST instantaneous value of line voltage E st , the instantaneous value of the TR line voltage E tr is measured (Step S100 in FIG. 4).

[0056] As in the first embodiment, the line current measuring unit 7 measures the instantaneous value I r , instantaneous value of S-phase wire current I s , instantaneous value of T-phase wire current I t is measured (Step S101 in FIG. 4).

[0057] As in the first embodiment, the power consumption calculation unit 9 calculates the instantaneous value I of the R-phase line current measured by the line current measurement unit 7. r , instantaneous value of S-phase wire current I s and the instantaneous value E of the ST line voltage measured by the line voltage measuring unit 8 st , instantaneous value of TR line voltage E tr Based on this, the power consumption W of the three-phase heater 1 is calculated by the two-wattmeter method (FIG. 4, step S102).

[0058] As in the first embodiment, the cross-correlation function calculation unit 100 calculates the instantaneous value E rs , ST instantaneous value of line voltage E st , instantaneous value of TR line voltage E tr Based on the generalized cross-correlation function D r ,D s ,D t(Step S103 in FIG. 4).

[0059] As in the first embodiment, the current effective value calculation unit 104 calculates the instantaneous value I of the R-phase line current measured by the line current measurement unit 7. r , instantaneous value of S-phase wire current I s , instantaneous value of T-phase wire current I t Based on this, the effective value of the R-phase wire current I r(e) , the effective value of the S-phase wire current I s(e) , the effective value of the T-phase current I t(e) (Step S104 in FIG. 4).

[0060] As in the first embodiment, the voltage effective value calculation unit 105 calculates the instantaneous value E rs , ST instantaneous value of line voltage E st , the instantaneous value of the TR line voltage E tr Based on this, the effective value of the RS line voltage E rs(e) , ST line voltage effective value E st(e) , the effective value of the TR line voltage E tr(e) (Step S105 in FIG. 4).

[0061] Next, the phase current calculation unit 102a calculates the effective value I of the RS phase current by a method using an extended Kalman filter. rs(e) (Step S107a in FIG. 4) FIG 5 is a flowchart illustrating the details of the process in step S107a.

[0062] In this embodiment, the unknown parameter x (state vector) is defined as in equation (17), and the measurement data y (observation vector) is defined as in equation (18). The quantities at a certain stage are represented by the subscript k, and the observation vector y k noise (measurement error) vector v k The following equation is added to the state vector x k Consider this as the observation equation for y k =h k (x k )+v k ···(twenty one)

[0063] In this embodiment, it is assumed that there is no error generated by the system. In this case, the state equation representing the step-by-step change of the state quantity is expressed as follows: x k+1 =I x k (22)

[0064] Here, I is the unit matrix. Filter theory is applied to the observation equation (21) and state equation (22) shown above. First, the phase current calculation unit 102a calculates the initial value x of the unknown parameter. 0 / -1 Hereinafter, the "^" above a letter will be referred to as "^". In addition, the phase current calculation unit 102a assumes that the estimation error covariance matrix P 0 / -1 (Step S200 in FIG. 5). These initial values ​​are set in advance.

[0065] Next, the phase current calculation unit 102a calculates the observed data y k (The effective value of the line current I r(e) 2 ,I s(e) 2 ,I t(e) 2 , power consumption W) and the measurement error covariance matrix R k (Step S201 in FIG. 5).

[0066] The phase current calculation unit 102a calculates the estimated value x of the unknown parameter k / k-1 Calculation values ​​at the measurement points for the hat and the sensitivity matrix H are calculated by the boundary element method (step S202 in FIG. 5). The sensitivity matrix H is calculated using equations (19) and (20).

[0067] The phase current calculation unit 102a calculates a filter gain K k is calculated by the following formula (step S203 in FIG. 5). K k =P k / k-1 +H T [H.P. k / k-1 H T +R k ] -1 ···(twenty three)

[0068] H in Eq. (23) T is a transposed matrix of the sensitivity matrix H. The phase current calculation unit 102a updates the estimated values ​​of the parameters as shown in the following equation (Step S204 in FIG. 5).

[0069]

number

[0070] The phase current calculation unit 102a performs a convergence determination of the calculation (step S205 in FIG. 5). When it is determined that the calculation has not converged (NO in step S205), the phase current calculation unit 102a calculates the estimated value x of the unknown parameter as shown in the following equations (25) and (26). k+1 / k Hat and error covariance matrix estimate P k+1 / k The hat is updated (step S206 in FIG. 5), and the process returns to step S201.

[0071]

number

[0072] If the convergence is achieved in step S205, the process is completed. In this manner, the phase current calculation unit 102a calculates the unknown parameter, i.e., the effective value I rs(e) can be calculated.

[0073] As in the first embodiment, the effective value I rs(e) After calculating the effective value I rs(e) and the effective value I of the S-phase wire current calculated by the current effective value calculation unit 104. s(e) and the generalized cross-correlation function D calculated by the cross-correlation function calculation unit 100. r ,D s Based on this, the effective value I of the ST phase current is calculated by equation (12). st(e) (Step S108 in FIG. 4).

[0074] As in the first embodiment, the phase current calculation unit 102a calculates the effective value I rs(e)and the effective value I of the R-phase line current calculated by the current effective value calculation unit 104. r(e) and the generalized cross-correlation function D calculated by the cross-correlation function calculation unit 100. r Based on this, the effective value I of the TR phase current is calculated by equation (11). tr(e) (Step S109 in FIG. 4).

[0075] As in the first embodiment, the output unit 103 outputs the calculation result of the phase current calculation unit 102a (step S110 in FIG. 4).

[0076] In this way, the present embodiment can obtain the same effect as the first embodiment. r <0, D s <0, D t The <0 condition can be eliminated.

[0077] The method of estimating the unknown parameters is not limited to the extended Kalman filter inverse analysis method of this embodiment, and any method may be used as long as it can solve the nonlinear simultaneous equations of equations (17) to (20).

[0078] In the first and second embodiments, the effective value I rs(e) ,I st(e) ,I tr(e) By calculating the resistance R of the heaters 11, 12, and 13, rs ,R st ,R tr It is possible to calculate R rs =E rs(e) / I rs(e) (27) R st =E st(e) / I st(e) (28) R tr =E tr(e) / I tr(e) (29)

[0079] In addition, if the resistance value can be obtained for the delta-connected three-phase heater 1 of the first and second embodiments, the resistance value of a three-phase heater in which three heaters are star-connected can be obtained by the well-known delta-star conversion (for example,<https: / / eleking.net / study / s-accircuit / sac-deltastar.html> reference).

[0080] The power consumption calculation unit 9, the cross-correlation function calculation unit 100, the phase current calculation units 102, 102a, the output unit 103, the current effective value calculation unit 104, and the voltage effective value calculation unit 105 described in the first and second embodiments can be realized by a computer equipped with a CPU (Central Processing Unit), a storage device, and an interface, and a program that controls these hardware resources. An example of the configuration of this computer is shown in FIG.

[0081] The computer includes a CPU 200, a storage device 201, and an interface device (I / F) 202. Hardware such as a line current measuring unit 7, a line voltage measuring unit 8, and an output unit 103 are connected to the I / F 202. A program for implementing the three-phase heater current detection method of the present invention is stored in the storage device 201. The CPU 200 executes the processes described in the first and second embodiments in accordance with the program stored in the storage device 201. [Industrial Applicability]

[0082] The present invention can be applied to, for example, a technology for diagnosing the life span of a three-phase heater. [Explanation of symbols]

[0083] 1...three-phase heater, 2...three-phase AC power supply, 3...power control device, 4...three-phase power regulator, 5-1 to 5-3...current transformer for measuring line current, 6...voltage transformer for measuring line voltage, 7...line current measuring unit, 8...line voltage measuring unit, 9...power consumption calculation unit, 11 to 13...heater, 14 to 16...power supply line, 100...cross-correlation function calculation unit, 101...cross-correlation function determination unit, 102, 102a...phase current calculation unit, 103...output unit, 104...current effective value calculation unit, 105...voltage effective value calculation unit.

Claims

1. a line current measuring unit configured to measure instantaneous values ​​of line currents flowing through three power supply lines to a three-phase heater to which three heaters are connected; a line voltage measuring unit configured to measure instantaneous values ​​of line voltages of the three power feeders; a power consumption calculation unit configured to calculate the power consumption of the three-phase heater based on a measurement result of the line current measurement unit and a measurement result of the line voltage measurement unit; a cross-correlation function calculation unit configured to calculate a generalized cross-correlation function D r between an instantaneous value E rs of the line voltage between RS lines and an instantaneous value E tr of the line voltage between TR lines, a generalized cross-correlation function D s between an instantaneous value E st of the line voltage between ST lines and an instantaneous value E rs of the line voltage between RS lines, and a generalized cross-correlation function Dt between an instantaneous value E tr of the line voltage between TR lines and an instantaneous value E st of the line voltage between ST lines; a current effective value calculation unit configured to calculate an effective value of the line current from a measurement result of the line current measurement unit; a voltage effective value calculation unit configured to calculate an effective value of the line voltage from a measurement result of the line voltage measurement unit; a phase current calculation unit configured to calculate a phase current flowing through the three-phase heater based on the effective value of the line current, the effective value of the line voltage, the power consumption, and the generalized cross-correlation functions D r , D s , and D t; a cross-correlation function determination unit configured to determine whether the generalized cross-correlation functions D r , D s , and D t are all less than 0; When it is determined that the generalized cross-correlation functions D r , D s , and D t are all less than 0, the phase current calculation unit calculates a formula (1) based on the effective value I r(e) of the line current of R phase, the effective value I s(e) of the line current of S phase, the effective value E rs(e) of the line voltage between RS lines, the effective value E st(e) of the line voltage between ST lines, the effective value E tr(e) of the line voltage between TR lines, the power consumption W, and the generalized cross-correlation functions D r and D s : [0010] and based on the effective value I rs(e) of the RS-phase current, the effective value I s(e) of the S-phase line current, and the generalized cross-correlation function D s , [0025] The effective value I st(e) of the ST-phase current is calculated based on the effective value I rs(e) of the RS-phase current, the effective value I r(e) of the R-phase line current, and the generalized cross-correlation function D r , as follows: [0030] The three-phase heater current detection device calculates an effective value I tr(e) of a TR phase current by:

2. A line current measuring unit configured to measure instantaneous values ​​of line currents flowing through three power supply lines to a three-phase heater to which three heaters are connected; a line voltage measuring unit configured to measure instantaneous values ​​of line voltages of the three power feeders; a power consumption calculation unit configured to calculate the power consumption of the three-phase heater based on a measurement result of the line current measurement unit and a measurement result of the line voltage measurement unit; a cross-correlation function calculation unit configured to calculate a generalized cross-correlation function D r between an instantaneous value E rs of the line voltage between RS lines and an instantaneous value E tr of the line voltage between TR lines, a generalized cross-correlation function D s between an instantaneous value E st of the line voltage between ST lines and an instantaneous value E rs of the line voltage between RS lines, and a generalized cross-correlation function D t between an instantaneous value E tr of the line voltage between TR lines and an instantaneous value E st of the line voltage between ST lines; a current effective value calculation unit configured to calculate an effective value of the line current from a measurement result of the line current measurement unit; a voltage effective value calculation unit configured to calculate an effective value of the line voltage from a measurement result of the line voltage measurement unit; a phase current calculation unit configured to calculate a phase current flowing through the three-phase heater based on the effective value of the line current, the effective value of the line voltage, the power consumption, and the generalized cross-correlation functions D r , D s , and D t ; The phase current calculation unit, with an unknown parameter designated as x, measurement data designated as y, and a sensitivity matrix designated as H, calculates a set of nonlinear simultaneous equations that define relationships among the effective value I rs(e) of an RS-phase current, the effective value I st(e) of an ST-phase current, the effective value I tr(e) of a TR-phase current, the effective value I r(e) of the line current of the R-phase, the effective value I s(e) of the line current of the S-phase, the effective value I t(e) of the line current of the T-phase, the effective value E rs(e) of the line voltage between the RS lines, the effective value E st(e) of the line voltage between the ST lines, and the effective value E tr(e) of the line voltage between the TR lines, the power consumption W, and the generalized cross-correlation functions D r , D s , and D t. [0045] and based on the effective value I rs(e) of the RS-phase current, the effective value I s(e) of the S-phase line current, and the generalized cross-correlation function D s , [0050] The effective value I st(e) of the ST-phase current is calculated based on the effective value I rs(e) of the RS-phase current, the effective value I r(e) of the R-phase line current, and the generalized cross-correlation function D r , as follows: [006] The three-phase heater current detection device calculates an effective value I tr(e) of a TR phase current by:

3. A first step of measuring instantaneous values ​​of line currents flowing through three power supply lines to a three-phase heater having three heaters connected thereto; a second step of measuring instantaneous values ​​of line voltages of the three power feeders; a third step of calculating the power consumption of the three-phase heater based on the measurement results of the first step and the second step; a fourth step of calculating a generalized cross-correlation function D r between the instantaneous value E rs of the line voltage between RS lines and the instantaneous value E tr of the line voltage between TR lines, a generalized cross-correlation function D s between the instantaneous value E st of the line voltage between ST lines and the instantaneous value E rs of the line voltage between RS lines, and a generalized cross-correlation function D t between the instantaneous value E tr of the line voltage between TR lines and the instantaneous value E st of the line voltage between ST lines; a fifth step of calculating an effective value of the line current from the measurement result of the first step; a sixth step of calculating an effective value of the line voltage from the measurement result of the second step; a seventh step of calculating phase currents flowing through the three-phase heater based on the effective values ​​of the line currents, the effective values ​​of the line voltages, the power consumption, and the generalized cross-correlation functions D r , D s , and D t; and an eighth step of determining whether the generalized cross-correlation functions D r , D s , and D t are all less than zero; The seventh step, when it is determined that all of the generalized cross-correlation functions D r , D s , and D t are less than 0, calculates a formula (1) based on the effective value I r(e) of the line current of R phase, the effective value I s(e) of the line current of S phase, the effective value E rs(e) of the line voltage between RS lines, the effective value E st(e) of the line voltage between ST lines, the effective value E tr(e) of the line voltage between TR lines, the power consumption W, and the generalized cross-correlation functions D r and D s : [0070] and based on the effective value I rs(e) of the RS-phase current, the effective value I s(e) of the S-phase line current, and the generalized cross-correlation function D s , [0080] The effective value I st(e) of the ST-phase current is calculated based on the effective value I rs(e) of the RS-phase current, the effective value I r(e) of the R-phase line current, and the generalized cross-correlation function D r , as follows: [0090] Calculating an effective value I tr(e) of a TR phase current by using the above formula:

4. A method for measuring instantaneous values ​​of line currents flowing through three power supply lines to a three-phase heater having three heaters connected thereto; a second step of measuring instantaneous values ​​of line voltages of the three power feeders; a third step of calculating the power consumption of the three-phase heater based on the measurement results of the first step and the second step; a fourth step of calculating a generalized cross-correlation function D r between the instantaneous value E rs of the line voltage between RS lines and the instantaneous value E tr of the line voltage between TR lines, a generalized cross-correlation function D s between the instantaneous value E st of the line voltage between ST lines and the instantaneous value E rs of the line voltage between RS lines, and a generalized cross-correlation function D t between the instantaneous value E tr of the line voltage between TR lines and the instantaneous value E st of the line voltage between ST lines; a fifth step of calculating an effective value of the line current from the measurement result of the first step; a sixth step of calculating an effective value of the line voltage from the measurement result of the second step; a seventh step of calculating phase currents flowing through the three-phase heater based on the effective values ​​of the line currents, the effective values ​​of the line voltages, the power consumption, and the generalized cross-correlation functions D r , D s , and D t ; The seventh step, where an unknown parameter is x, measurement data is y, and a sensitivity matrix is ​​H, solves a nonlinear simultaneous equation that defines relationships among the effective value I rs(e) of the RS-phase current, the effective value I st(e) of the ST-phase current, the effective value I tr(e) of the TR-phase current, the effective value I r(e) of the line current of the R-phase, the effective value I s(e) of the line current of the S-phase, the effective value I t(e) of the line current of the T-phase, the effective value E rs(e) of the line voltage between the RS lines, the effective value E st(e) of the line voltage between the ST lines, the effective value E tr(e) of the line voltage between the TR lines, the power consumption W, and the generalized cross-correlation functions D r , D s , and D t. [0010] and based on the effective value I rs(e) of the RS-phase current, the effective value I s(e) of the S-phase line current, and the generalized cross-correlation function D s , ##EQU00011## The effective value I st(e) of the ST-phase current is calculated based on the effective value I rs(e) of the RS-phase current, the effective value I r(e) of the R-phase line current, and the generalized cross-correlation function D r , as follows: ##EQU00012## Calculating an effective value I tr(e) of a TR phase current by using the above formula:

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