JP7833901B2 - Three-phase heater phase current detection apparatus and method - Google Patents

Description

This invention relates to a three-phase heater phase current detection device and method for detecting the phase current flowing through a three-phase heater.

Measuring the resistance of a heater is effective in diagnosing its lifespan, but the phase currents (I _rs , I _st , I _tr ) of a delta connection are often difficult to measure due to the heater's structure. One method for estimating the phase currents of a delta connection to determine the heater's resistance is disclosed in Patent Document 1.

The method disclosed in Patent Document 1 updates the estimated phase current by feeding back the estimated value when the phase difference between the phases of a three-phase power supply is known. Since the resistance value can change significantly with respect to ambient temperature depending on the type of heater, if it is necessary to perform repeated calculations to determine the phase current, as in the method disclosed in Patent Document 1, there was a possibility that the tracking of the estimated value would be slow when the resistance value changed. Furthermore, the method disclosed in Patent Document 1 had the problem of large estimation errors in the phase current when controlling the phase angle of the three-phase heater.

Japanese Patent Publication No. 2016-110732

This invention was made to solve the above problems and aims to provide a three-phase heater phase current detection device and method that can estimate the effective value of the phase current of a three-phase heater without the need for iterative calculations, even when the current and voltage are not sinusoidal.

The three-phase heater phase current detection device of the present invention comprises: a line current measurement unit configured to measure the instantaneous value of the line current flowing through three power supply lines to a three-phase heater in which three heaters are connected; a line voltage measurement unit configured to measure the instantaneous value of the line voltage between the three power supply lines; a cross-correlation function calculation unit configured to calculate the generalized cross-correlation function Dr _r between the RS lines and the instantaneous value of the line voltage between the TR lines, the generalized cross-correlation function D _s between the ST lines and the instantaneous value of the line voltage between the RS lines, and the generalized cross-correlation function D _t between the TR lines and the instantaneous value of the line voltage between the ST lines; a cross-correlation function determination unit configured to determine whether two or more of the generalized cross-correlation functions Dr _r , D _s , and D _t are less than 0; and the generalized cross-correlation functions Dr _r , D _s , and D t determined by the cross-correlation function determination unit. _The present invention is characterized by comprising: a power consumption calculation unit configured to calculate a first total power consumption, which is the sum of the power consumption of the first heater and a portion of the power consumption of the second heater among the three-phase heaters, and a second total power consumption, which is the sum of the power consumption of the third heater and the remaining power consumption of the second heater that is not included in the first total power consumption, based on the measurement results of the line current measurement unit and the measurement results of the line voltage measurement unit when two or more of t are determined to be less than 0; a current effective value calculation unit configured to calculate the effective value of the line current from the measurement results of the line current measurement unit; a voltage effective value calculation unit configured to calculate the effective value of the line voltage from the measurement results of the _{line voltage} measurement unit; and a phase current calculation unit configured to calculate _the phase current flowing through the three-phase heater based on the values of the generalized cross-correlation functions Dr, Ds, Dt, the first and second total power consumption, the effective value of the line current, and the effective value of the line voltage.

Furthermore, in one configuration example of the three- _phase heater phase current detection device of the present invention, the power consumption calculation unit determines that the generalized cross-correlation function Dr of the RS line voltage and the TR line voltage, and the generalized cross-correlation function Dt of the TR line voltage and the ST line voltage _are less than 0, and calculates the first total power consumption, which is the power consumption obtained by adding the power consumption of the RS phase heater and a portion of the power consumption of the TR phase heater based on the instantaneous value of the RS line voltage and the instantaneous value of the R phase line current, and calculates the second total power consumption, which is the power consumption obtained by adding the power consumption of the ST phase heater and the remaining power consumption of the TR phase heater that is not included in the first total power consumption, based on the instantaneous value of the ST line voltage and the instantaneous value of the T phase line current, and the phase current calculation unit calculates the first total power consumption, the effective value of the R phase line current, the effective value of the RS line voltage, and the generalized cross-correlation function D of the RS line voltage and the TR line voltage The method is characterized by calculating the effective value of the RS phase current based on _r , calculating the effective value of the ST phase current based on the second total power consumption, the effective value of the T phase line current, the effective value of the ST line voltage, and the generalized cross-correlation function Dt of the TR line voltage and the ST line voltage, and calculating the effective value of the TR phase current based on the calculated effective values of the _RS phase current and ST phase current, and the first and second total power consumption, the effective value of the RS line voltage and the effective value of the ST line voltage.

Furthermore, in one configuration example of the three- _phase heater phase current detection device of the present invention, the power consumption calculation unit determines that the generalized cross-correlation function Dr of the RS line voltage and the TR line voltage, and the generalized cross-correlation function Ds of the ST line voltage and the RS line voltage are less than 0, and calculates the first total power consumption _, which is the power consumption obtained by adding the power consumption of the ST phase heater and a portion of the power consumption of the RS phase heater based on the instantaneous value of the ST line voltage and the instantaneous value of the S phase line current, and calculates the second total power consumption, which is the power consumption obtained by adding the power consumption of the TR phase heater and the remaining power consumption of the RS phase heater that is not included in the first total power consumption, based on the instantaneous value of the TR line voltage and the instantaneous value of the R phase line current, and the phase current calculation unit calculates the first total power consumption, the effective value of the S phase line current and the effective value of the ST line voltage, and the generalized cross-correlation function D of the ST line voltage and the RS line voltage. The method is characterized by calculating the effective value of the ST phase current based on _s , calculating the effective value of the TR phase current based on the second total power consumption, the effective value of the R phase line current, the effective value of the TR line voltage, and the generalized cross-correlation function Dr of the _RS line voltage and the TR line voltage, and calculating the effective value of the RS phase current based on the calculated effective values of the ST phase current and TR phase current, the first and second total power consumption, the effective value of the RS line voltage, the effective value of the ST line voltage, and the effective value of the TR line voltage.

Furthermore, in one configuration example of the three-phase heater phase current detection device of the present invention, the power consumption calculation unit determines that the generalized cross-correlation function D _s of the ST line voltage and the RS line voltage and the generalized cross-correlation function D _t of the TR line voltage and the ST line voltage are less than 0, and calculates the first total power consumption, which is the power consumption obtained by adding the power consumption of the TR phase heater and a portion of the power consumption of the ST phase heater based on the instantaneous value of the TR line voltage and the instantaneous value of the T phase line current, and calculates the second total power consumption, which is the power consumption obtained by adding the power consumption of the RS phase heater and the remaining power consumption of the ST phase heater that is not included in the first total power consumption, based on the instantaneous value of the RS line voltage and the instantaneous value of the S phase line current, and the phase current calculation unit calculates the first total power consumption, the effective value of the T phase line current and the effective value of the TR line voltage and the generalized cross-correlation function D The method is characterized by calculating the effective value of the TR phase current based on _t , calculating the effective value of the RS phase current based on the second total power consumption, the effective value of the S phase line current, the effective value of the RS line voltage, and the generalized cross-correlation function D _s of the ST line voltage and the RS line voltage, and calculating the effective value of the ST phase current based on the calculated effective values of the TR phase current and RS phase current, the first and second total power consumption, the effective value of the RS line voltage, the effective value of the ST line voltage, and the effective value of the TR line voltage.

Furthermore, the three-phase heater phase current detection method of the present invention includes: a first step of measuring the instantaneous value of the line current flowing through three power supply lines to a three-phase heater in which three heaters are connected; a second step of measuring the instantaneous value of the line voltage between the three power supply lines; a third step of calculating the generalized cross-correlation function Dr _r between the RS lines and the instantaneous value of the line voltage between the TR lines , the generalized cross-correlation function D _s between the ST lines and the instantaneous value of the line voltage between the RS lines, and the generalized cross-correlation function D _t between the TR lines and the instantaneous value of the line voltage between the ST lines ; a fourth step of determining whether two or more of the generalized cross-correlation functions Dr _r , D _s , and D _t are less than 0 ; and the generalized cross-correlation functions Dr _r , D _s , and D t calculated in the fourth step. The method is characterized by including, if two or more of _t are determined to be less than 0, a fifth step of calculating a first total power consumption, which is the power consumption obtained by adding the power consumption of the first heater and a portion of the power consumption of the second heater among the three-phase heaters, and a second total power consumption, which is the power consumption obtained by adding the power consumption of the third heater and the remaining power consumption of the second heater that is not included in the first total power consumption, based on the measurement results of the first step and the measurement results of the second step; a sixth step of calculating the effective value of the line current from the measurement results of the first step; a seventh step of calculating the effective value of the line voltage from the measurement _results of the second step; and an eighth step of calculating the phase current flowing through the three-phase heater based on the values of the generalized cross-correlation functions Dr _, Ds _, Dt, the first and second total power consumptions, the effective values of the line currents, and the effective values of the line voltages.

Furthermore, in one configuration example of the three-phase heater phase current detection method of the present invention, the fifth _step includes the _step of calculating the first total power consumption, which is the power consumption obtained by adding the power consumption of the RS phase heater and a portion of the power consumption of the TR phase heater, based on the instantaneous value of the RS line voltage and the instantaneous value of the R phase line current, when it is determined that the generalized cross-correlation function Dr of the RS line voltage and the TR line voltage and the generalized cross-correlation function Dt of the TR line voltage and the ST line voltage are less than 0, and calculating the second total power consumption, which is the power consumption obtained by adding the power consumption of the ST phase heater and the remaining power consumption of the TR phase heater that is not included in the first total power consumption, based on the instantaneous value of the ST line voltage and the instantaneous value of the T phase line current, and the eighth step includes the first total power consumption, the effective value of the R phase line current and the effective value of the RS line voltage and the generalized cross-correlation function D of the RS line voltage and the TR line voltage The method is characterized by including the steps of: calculating the effective value of the RS phase current based on _r ; calculating the effective value of the ST phase current based on the second total power consumption, the effective value of the T phase line current, the effective value of the ST line voltage, and the generalized cross-correlation function Dt of the TR line voltage _and the ST line voltage; and calculating the effective value of the TR phase current based on the calculated effective values of the RS phase current and ST phase current, and the first and second total power consumption, the effective value of the RS line voltage and the effective value of the ST line voltage.

Furthermore, in one configuration example of the three-phase heater phase current detection method of the present invention, the fifth step includes the step of calculating the first total power consumption, which is the power consumption obtained _{by adding} the power consumption of the ST phase heater and a portion of the power consumption of the RS phase heater based on the instantaneous value of the ST line voltage and _the instantaneous value of the S phase line current, when it is determined that the generalized cross-correlation function Dr of the RS line voltage and the generalized cross-correlation function Ds of the ST line voltage and the RS line voltage are less than 0, and the step of calculating the second total power consumption, which is the power consumption obtained by adding the power consumption of the TR phase heater and the remaining power consumption of the RS phase heater that is not included in the first total power consumption based on the instantaneous value of the TR line voltage and the instantaneous value of the R phase line current, and the step of calculating the first total power consumption, which is the power consumption obtained by adding the power consumption of the TR phase heater and the remaining power consumption of the RS phase heater that is not included in the first total power consumption, based on the instantaneous value of the TR line voltage and the instantaneous value of the R phase line current, and the generalized cross-correlation function D of the ST line voltage and the RS line voltage The method is characterized by including the steps of: calculating the effective value of the ST phase current based on _s ; calculating the effective value of the TR phase current based on the second total power consumption, the effective value of the R phase line current, the effective value of the TR line voltage, and _the generalized cross-correlation function Dr of the RS line voltage and the TR line voltage; and calculating the effective value of the RS phase current based on the calculated effective values of the ST phase current and TR phase current, the first and second total power consumption, the effective value of the RS line voltage, the effective value of the ST line voltage, and the effective value of the TR line voltage.

Furthermore, in one configuration example of the three-phase heater phase current detection method of the present invention, the fifth _step includes the _step of calculating the first total power consumption, which is the power consumption obtained by adding the power consumption of the TR phase heater and a portion of the power consumption of the ST phase heater based on the instantaneous value of the TR line voltage and the instantaneous value of the T phase line current, when it is determined that the generalized cross-correlation function D s of the ST line voltage and the RS line voltage and the generalized cross-correlation function D t of the TR line voltage and the ST line voltage are less than 0, and calculating the second total power consumption, which is the power consumption obtained by adding the power consumption of the RS phase heater and the remaining power consumption of the ST phase heater that is not included in the first total power consumption based on the instantaneous value of the RS line voltage and the instantaneous value of the S phase line current, and the eighth step includes the first total power consumption, the effective value of the T phase line current and the effective value of the TR line voltage and the generalized cross-correlation function D The method is characterized by including the steps of: calculating the effective value of the TR phase current based on _t ; calculating the effective value of the RS phase current based on the second total power consumption, the effective value of the S phase line current, the effective value of the RS line voltage, and the generalized cross-correlation function D _s of the ST line voltage and the RS line voltage; and calculating the effective value of the ST phase current based on the calculated effective values of the TR phase current and RS phase current, the first and second total power consumption, the effective value of the RS line voltage, the effective value of the ST line voltage, and the effective value of the TR line voltage.

According to the present invention, by providing a line current measurement unit, a line voltage measurement unit, a cross-correlation function calculation unit, a cross-correlation function determination unit, a power consumption calculation unit, a current RMS value calculation unit, a voltage RMS value calculation unit, and a phase current calculation unit, the iterative calculation required to determine the phase current, as in conventional methods, becomes unnecessary. Furthermore, the present invention allows for the estimation of the RMS value of the phase current flowing through a three-phase heater even when the output of the three-phase AC power supply is not sinusoidal. Therefore, the present invention can be applied to the phase angle control of a three-phase heater.

Figure 1 is a block diagram showing the configuration of a three-phase heater phase current detection device according to an embodiment of the present invention. Figure 2 is a flowchart illustrating the operation of a three-phase heater phase current detection device according to an embodiment of the present invention. Figure 3 is a flowchart illustrating the operation of a three-phase heater phase current detection device according to an embodiment of the present invention. Figure 4 is a block diagram showing an example of the configuration of a computer that realizes a three-phase heater phase current detection device according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 is a block diagram showing the configuration of a three-phase heater phase current detection device according to an 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 consists of three heaters 11 to 13 connected in a delta configuration. Three power supply lines 14 to 16 extend from the heaters 11 to 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 supply lines 14 to 16 into thermal energy and outputs it.

The three-phase heater phase current detection device of this embodiment includes current transformers 5-1 to 5-3 for measuring line currents provided on each power supply line 14 to 16, a voltage transformer 6 for measuring line voltages connected between the power supply lines 14 to 16, a line current measurement unit 7 connected to the outputs of the current transformers 5-1 to 5-3 for measuring line currents and measuring the instantaneous value of the line current flowing through each power supply line 14 to 16, a line voltage measurement unit 8 connected to the output of the voltage transformer 6 for measuring line voltages and measuring the instantaneous value of the line voltages between each power supply line 14 to 16, and a first total power consumption, which is a part of the power consumption of the three-phase heater 1, and the remaining power consumption, based on the measurement results of the line current measurement unit 7 and the measurement results of the line voltage measurement unit 8. The system includes a power consumption calculation unit 9 that calculates the second total power consumption, a cross-correlation function calculation unit 100 that calculates the generalized cross-correlation function of the instantaneous value of the line voltage, a cross-correlation function determination unit 101 that determines whether the generalized cross-correlation function calculated by the cross-correlation function calculation unit 100 is less than 0, a phase current calculation unit 102 that calculates the phase current flowing through the three-phase heater 1 based on the determination result of the cross-correlation function determination unit 101, the first and second total power consumption, the effective value of the line current, and the effective value of the line voltage, an output unit 103 that outputs the calculation result of the phase current calculation unit 102, an effective current value calculation unit 104 that calculates the effective value of the line current, and an effective voltage value calculation unit 105 that calculates the effective value of the line voltage.

As shown in Figure 1, the resistance values of heaters 11, 12, and 13 are R _rs , R _st , and R _tr , respectively. Also, the R-phase line current flowing through the power supply line 14 is I _r , the S-phase line current flowing through the power supply line 15 is I _s , and the T-phase line current flowing through the power supply line 16 is I _t . The RS-phase current flowing through the RS-phase heater 11 is I _rs , the ST-phase current flowing through the ST-phase heater 12 is I _st , and the TR-phase current flowing through the TR-phase heater 13 is I _tr . Furthermore, the RS-line voltage between power supply lines 14 and 15 is E _rs , the ST-line voltage between power supply lines 15 and 16 is E _st , and the TR-line voltage between power supply lines 16 and 14 is E _tr . Each of these currents and voltages is a vector quantity. The following relationship holds for each current.

I _r = I _rs - I _tr ... (1)
I _s = I _st - _{I rs} ...(2)
I _t = I _tr - _{I st} ...(3)

Squaring both sides of equation (1), integrating over the power supply period, and dividing by the power supply period yields equation (4). In other words, equation (4) calculates the square of the effective value of both sides of equation (1).

Similarly, equations (5) and (6) can be obtained from equations (2) and (3), respectively.

I _r(e) , I _s(e) , I _t(e) , I _rs(e) , I _st(e) , and I _tr(e) are the RMS values of the currents I _r , I _s , I _t , I _rs , I _st , and I _tr , respectively. _Dr is the generalized cross-correlation function (normalized cross-correlation function) of the RS line voltage E _rs and the TR line voltage E _tr , D _s is the generalized cross-correlation function of the ST line voltage E _st and the RS line voltage E _rs , and D _t is the generalized cross-correlation function of the TR line voltage E _tr and the ST line voltage E _st . The generalized cross-correlation functions _Dr , D _s , and D _t are given by the following equations.

E_rs(e), E_st(e), E_tr(e)These are the voltage E_rs, E_st, E_trThis is the effective value. T is the power supply period. θ_rThe voltage between the RS lines is E_rsand TR line voltage E_trThe phase difference, θ_sThe ST line voltage E_stand RS line voltage E_rsThe phase difference, θ_tTR line voltage E_trand ST line voltage E_stThis is the phase difference. The total power consumption (W) of the three-phase load is given by the following equation.

In power measurement for a three-phase heater 1, the phase currents I _rs , I _st , and I _tr cannot be measured, so the power is measured using the two-wattmeter method (see, for example, <https://www.jemima.or.jp/tech/3-01-02.html>).
Therefore, we consider measuring the sum _W1 of the power consumption of heater 11 and a portion of the power consumption of heater 13, and the sum _W2 of the power consumption of heater 12 and the power consumption of heater 13 excluding the aforementioned portion.

Measure the power consumption _W1 and _W2 , and then calculate the total power consumption using the following formula.
W= _W1 + _W2 ...(13)
Since the three-phase heater 1 is a resistive load, the power consumption _W1 can be calculated as shown in equation (14).

Similarly, the power consumption _W² can be calculated as shown in equation (15).

The items that can be measured or calculated with the configuration shown in Figure 1 are the RMS value of the R-phase line current I _r(e) , the RMS value of the S-phase line current I s _(e) , the RMS value of the T-phase line current I _t(e) , the RMS value of the RS line voltage E _rs(e) , the RMS value of the ST line voltage E _st(e) , the RMS value of the TR line voltage E _tr(e) , the generalized cross-correlation functions D _r , D _s , D _t , and the power consumption _W1 , _W2. The items that cannot be measured or calculated are the RMS value of the RS-phase current I _rs(e) , the RMS value of the ST-phase current I _st(e) , and the RMS value of the TR-phase current I _tr(e) .

Therefore, if we remove the effective value I _tr(e) of the TR phase current from equations (4) and (14), for example, we obtain a quadratic equation that includes measurable or calculable items except for the effective value I _rs(e) of the RS phase current. Solving this quadratic equation yields the following relationship.

Here, assuming that tanθ _r < 0 and Dr _r < 0, then according to equation (14), the power consumption _W1 is the sum of the power consumption of heater 11 (E _rs(e) I _rs(e) ) and a portion of the power consumption of heater 13 (-D _r E _rs(e) I _tr(e) ), so I _rs(e) < _W1 / E _rs(e) . Therefore, the plus/minus sign of the solution to the quadratic equation in equation (16) is positive. Thus, the following equation is obtained from equation (16).

If the effective value I _rs(e) of the RS phase current can be calculated using equation (17), then the effective value I _st(e) of the ST phase current and the effective value I _tr(e) of the TR phase current can be determined from equations (10) and (14). As described above, the feature of the present invention lies in the use of equations (14) and (15).

In this invention, if all of the generalized cross-correlation functions _Dr , _Ds , and _Dt are negative, there are no restrictions on the power measurement location. However, simulations using SPICE (Simulation Program with Integrated Circuit Emphasis) have shown that there are cases where one of the generalized cross-correlation functions _Dr , _Ds , and _Dt is not negative, so in practice, it is necessary to change the power measurement location as follows.

(I) First, when _Dr < 0, _Ds ≥ 0, and _Dt < 0, the total power consumption W _1s , which is the sum of the power consumption of heater 11 and a portion of the power consumption of heater 13, is calculated using formula (18) based on the instantaneous value _Ers of the RS line voltage and _Ir of the R phase line current. Also, the total power consumption W _2s , which is the sum of the power consumption of heater 12 and the remaining power consumption of heater 13 that is not included in W _1s , is calculated using _formula (19) based on the instantaneous value Est of the ST line voltage and It of the _T phase line current.

The effective values I _rs(e) for the RS phase current, I _st(e) for the ST phase current, and I _tr(e) for the TR phase current can be calculated using equations (20) to (22), respectively.

(II) Next, when _Dr < 0, D _s < 0, and D _t ≥ 0, the total power consumption W 1t, which is the sum of the power consumption of heater 12 and a portion of the power consumption of heater 11, is calculated using formula (23) based on the instantaneous value _{E st of} the ST line voltage and the instantaneous value _{I s} of the S phase line current. Also, the total power consumption W _2t , which is the sum of the power consumption of heater 13 and the remaining power consumption of heater 11 that is not included in W _1t , is calculated using formula (24) based on the instantaneous value E _tr of the TR line voltage and the instantaneous value I r of the R phase line current.

The effective values I _st(e) for the ST phase current, I _tr(e) for the TR phase current, and I _rs(e) for the RS phase current can be calculated using equations (25) to (27), respectively.

(III) Next, when D _r ≥ 0, D _s < 0, and D _t < 0, the total power consumption W _1r , which is the sum of the power consumption of heater 13 and a portion of the power consumption of heater 12, is calculated using formula (28) based on the instantaneous value E _tr of the TR line voltage and the instantaneous value I _t of the T-phase line current. Also, the total power consumption W _2r , which is the sum of the power consumption of heater 11 and the remaining power consumption of heater 12 that is not included in W _1r , is calculated using formula (29) based on the instantaneous value E _rs of the RS line voltage and the instantaneous value I _{s of} the S-phase line current.

The effective values I _tr(e) for the TR phase current, I _rs(e) for the RS phase current, and I _st(e) for the ST phase current can be calculated using equations (30) to (32), respectively.

Figures 2 and 3 are flowcharts illustrating the operation of the three-phase heater phase current detection device in this embodiment. The line voltage measurement unit 8 measures the instantaneous value of the RS line voltage E _rs , the instantaneous value of the ST line voltage E _st , and the instantaneous value of the TR line voltage E _tr (Figure 2, step S100).

The line current measurement unit 7 measures the instantaneous value _Ir of the R-phase line current, the instantaneous value _Is of the S-phase line current, and the instantaneous value _It of the T-phase line current (Figure 2, step S101).

The cross-correlation function calculation unit 100 calculates generalized cross-correlation functions Dr, Ds, and Dt based on the instantaneous values of the RS line voltage E _rs , ST line voltage E _st , and _TR line voltage _{E tr} measured by the line voltage measurement unit 8 (Figure 2 _, step S102).

The cross-correlation function determination unit 101 determines whether the generalized cross-correlation functions _Dr , _Ds , and _Dt calculated by the cross-correlation function calculation unit 100 are less than 0 (Figure 2, step S103). If two or more of the generalized cross-correlation functions _Dr , _Ds , and _Dt are 0 or greater (NO in Figure 2, step S104), the phase current cannot be estimated.

If the cross-correlation function determination unit 101 determines that the generalized cross-correlation functions _Dr and _Dt are less than 0 and the generalized cross-correlation function _Ds is 0 or greater (YES in step S105 of Figure 2), the power consumption calculation unit 9 calculates the total power consumption W1s, which is the sum of the power consumption of heater 11 and a portion of the power consumption of heater 13, based on the instantaneous value _Ers of the RS line voltage and _Ir of the R phase line current, using formula (18). The power consumption calculation unit 9 also calculates the total power consumption _W2s , which is the sum of the power consumption of heater 12 and the remaining power consumption of heater 13 that is not included in _W1s , based on the instantaneous value _Est of the _ST line voltage and It of the T phase _line current, using formula (19) (step S106 of Figure 2).

The current RMS value calculation unit 104 calculates the RMS value Ir( _e) of the R-phase line current, the RMS value _Is (e) of the S-phase line current, and the RMS value It _{(e ) of the T-phase line current based on the instantaneous values Ir, Is} , and _It of the R-phase line current measured _by the line current measurement unit 7 (Figure 2, step S107).

The voltage RMS value calculation unit 105 calculates the RMS value of the RS line voltage E _rs(e) , the RMS value of the ST line voltage E _st (e), and the RMS value of the TR line voltage E _tr(e) based on the instantaneous values of the RS line voltage E _rs , ST line voltage E _st(e) , and TR line voltage E _tr(e) measured by the line voltage measurement unit 8 (Figure 2, step S108).

If the cross-correlation function determination unit 101 determines that the generalized cross-correlation functions _Dr and _Dt are less than 0 and the generalized cross-correlation function _Ds is 0 or greater, the phase current calculation unit 102 calculates the effective value of the RS phase current I _rs(e) using equation (20) based on the total power consumption W _1s calculated by the power consumption calculation unit 9, the effective value of the R phase line current I r ₍ e) calculated by the current effective value calculation unit 104, the effective value of the RS line voltage Er _{rs (e)} calculated by the voltage effective value calculation unit 105, and the tangent _tanθr of the phase difference _θr between the _RS line voltage Er _rs and the TR line voltage E tr (Figure 2, step S109). Since there is a relationship _Dr = _cosθr between the generalized cross-correlation function Dr and the phase difference _θr , it is possible to calculate _tanθr from the generalized cross-correlation function _Dr.

Furthermore, the phase current calculation unit 102 calculates the effective value of the ST phase current I _st(e) using equation (21) based on the total power consumption W _2s calculated by the power consumption calculation unit 9, the effective value of the T phase line current I t _(e) calculated by the current effective value calculation unit 104, the effective value of the ST line voltage _{E st(e) calculated} by the voltage effective value calculation unit 105, and the tangent tanθ _t of the phase difference θ _t between the TR line voltage E _tr and the ST line voltage E st (Figure 2, step S110). Since there is a relationship D _t = cosθ _t between the generalized cross-correlation function D _t and the phase difference θ _t , it is possible to calculate tanθ _t from the generalized cross-correlation function D _t .

Furthermore, the phase current calculation unit 102 calculates the effective value I tr(e) of the TR phase current using equation (22) based on the total power consumption W _1s and W _2s calculated by the power consumption calculation unit 9, the effective values E _rs(e) of the RS line voltage, E _st(e) of the ST line voltage, and E _tr(e) of the TR line voltage calculated by the voltage effective value calculation unit 105, and the effective values I _rs(e) of the RS phase current and I _{st (e)} of the ST phase current calculated in steps S109 and S110 (Figure 2, step S111).

Furthermore, if the cross-correlation function determination unit 101 determines that the generalized cross-correlation functions _Dr and _Ds are less than 0 and the generalized cross-correlation function _Dt is 0 or greater (YES in step S112 of Figure 2), the power consumption calculation unit 9 calculates the total power consumption W1t, which is the sum of the power consumption of heater 12 _and a portion of the power consumption of heater 11, based on the instantaneous value _Est of the ST _line voltage and the instantaneous value Is of the S phase line current, using formula (23). Furthermore, the power consumption calculation unit 9 calculates the total power consumption _W2t , which is the sum of the power consumption of heater 13 and the remaining power consumption of heater 11 that is not included in _W1t , based on the instantaneous value _Etr of the TR line voltage and the instantaneous value Ir of the R phase _line current, using formula (24) (step S113 of Figure 2).

The operation of the current RMS value calculation unit 104 and the voltage RMS value calculation unit 105 (steps S114 and S115 in Figure 2) is the same as in steps S107 and S108.

If the cross-correlation function determination unit 101 determines that the generalized cross-correlation functions _Dr and _Ds are less than 0 and the generalized cross-correlation function _Dt is 0 or greater, the phase current calculation unit 102 calculates the effective value Ist(e) of the ST phase current using equation (25) based on the total power consumption _W1t calculated by the power consumption calculation unit 9, the effective value _Is(e) of the S phase line current calculated by the current effective value calculation unit 104, the effective value _{Est (e)} of the ST line voltage calculated by the voltage effective value calculation unit 105, and the tangent _tanθs of the phase difference _θs between the ST line voltage _{Est and} the RS line voltage Ers (Figure 2, step S116). Since there is a relationship _Ds = _cosθs between the generalized cross-correlation function _Ds and the phase difference _θs , it is possible to calculate _tanθs from the generalized cross-correlation function _Ds .

Furthermore, the phase current calculation unit 102 calculates the effective value of the TR phase current I _tr(e) using equation (26) based on the total power consumption W _2t calculated by the power consumption calculation unit 9, the effective value of the R phase line current I r _(e) calculated by the current effective value calculation unit 104, the effective value of the TR line voltage E tr(e ₎ calculated by the voltage effective value calculation unit 105, and the tangent _tanθr of the phase difference _θr between the RS line voltage E _rs and the TR line voltage _{E tr} (Figure 2, step S117).

Furthermore, the phase current calculation unit 102 calculates the effective value I _rs( e) of the RS phase current using equation (27) based on the total power consumption W _1t and W _2t calculated by the power consumption calculation unit 9, the effective values E rs(e) of the RS line voltage, E _st(e) of the ST line voltage, and E _tr(e) of the TR line voltage calculated by the voltage effective value calculation unit 105, and the effective values I _st(e) of the ST phase current and I _{tr (e)} of the TR phase current calculated in steps S116 and S117 (Figure 2, step S118).

Furthermore, if the cross-correlation function determination unit 101 determines that the generalized cross-correlation functions D _s and D _t are less than 0 and the generalized cross-correlation function _Dr is 0 or greater (YES in step S119 of Figure 3), the power consumption calculation unit 9 calculates the total power consumption W 1r, which _is the sum of the power consumption of heater 13 and a portion of the power consumption of heater 12, based on the instantaneous value E _tr of the TR line voltage and the instantaneous value I _t of the T-phase line current, using formula (28). Furthermore, the power consumption calculation unit 9 calculates the total power consumption W _2r , which is the sum of the power consumption of heater 11 and the remaining power consumption of heater 12 that is not included in W _1r , based on the instantaneous value E _rs of the RS line voltage and the instantaneous value I s of the S- _{phase line} current, using formula (29) (step S120 of Figure 3).

The operation of the current RMS value calculation unit 104 and the voltage RMS value calculation unit 105 (steps S121 and S122 in Figure 3) is the same as in steps S107 and S108.

If the cross-correlation function determination unit 101 determines that the generalized cross-correlation functions D _s and D _t are less than 0 and the generalized cross-correlation function _Dr is 0 or greater, the phase current calculation unit 102 calculates the effective value of the TR phase current I tr(e) using equation (30) based on the total power consumption W _1r calculated by the power consumption calculation unit 9, the effective value of the T phase line current I _t(e) calculated by the current effective value calculation unit 104, the effective value of the TR line voltage E _{tr (e)} calculated by the voltage effective value calculation unit 105, and the tangent _{tanθ t of} the phase difference θt between the TR line voltage _{E tr and} the ST line voltage E st (Figure 3, step S123).

Furthermore, the phase current calculation unit 102 calculates the effective value of the RS phase current I _rs(e) using equation (31) based on the total power consumption W _2r calculated by the power consumption calculation unit 9, the effective value of the S phase line current I s(e ₎ calculated by the current effective value calculation unit 104, the effective value of the RS line voltage E _{rs (e)} calculated by the voltage effective value calculation unit 105, and the tangent tanθ _s of the phase difference θ _s between the ST line voltage E _st and the RS line voltage E rs (Figure 3, step S124).

Furthermore, the phase current calculation unit 102 calculates the effective value I st(e) of the ST phase current using equation (32) based on the total power consumption _W1r and _W2r calculated by the power consumption calculation unit 9, the effective value E _rs(e) of the RS line voltage, the effective value E st _{(e )} of the ST line voltage, and the effective value E _tr(e) of the TR line voltage calculated by the voltage effective value calculation unit 105, and the effective value I _tr (e) of the TR phase current and the effective value I _rs(e) of the RS phase current calculated in steps S123 and S124 (Figure 3, step S125).

If all generalized cross-correlation functions _Dr , _Ds , and _Dt are less than 0 (NO in step S119 in Figure 3), any of the following can be performed: steps S106 to S111, steps S113 to S118, or steps S120 to S125. However, Figure 3 shows an example where steps S126 to S131 are performed (the same as steps S106 to S111).

After any of the processes in steps S106 to S111, S113 to S118, S120 to S125, or S126 to S131 are completed, the output unit 103 outputs the calculation result of the phase current calculation unit 102 (Figure 2, step S132). Output methods include displaying the effective values of the phase currents I _rs(e) , I _st(e) , and I _tr(e) , and transmitting the calculation result to an external source.

As described above, in this embodiment, the effective values I _rs(e) , I _st(e) , and I _tr(e) of the phase currents can be estimated. In this embodiment, iterative calculations for determining the phase currents, as in the method disclosed in Patent Document 1, are unnecessary. Furthermore, in this embodiment, the effective values I _rs(e) , I _st(e) , and I _tr(e) of the phase currents can be estimated even when the output of the three-phase AC power supply is not sinusoidal. Therefore, this embodiment can be applied to the phase angle control of the three-phase heater 1 (see, for example, <https://www.compoclub.com/products/list/valve/detail/PU23.html>).

In this embodiment, by determining the effective values I _rs(e) , I _st(e) , and I _tr(e) of the phase currents flowing through the three-phase heater 1, it is possible to calculate the resistance values R _rs , R _st , and R _tr of the heaters 11, 12, and 13 as shown in the following equation.
R _rs =E _rs(e) /I _rs(e) ...(33)
R _st =E _st(e) /I _st(e) ...(34)
R _tr =E _tr(e) /I _tr(e) ...(35)

Furthermore, if the resistance value can be determined for the delta-connected three-phase heater 1 of this embodiment, the resistance value of a three-phase heater with three heaters connected in a star configuration can be determined using the well-known delta-star conversion (see, for example, <https://eleking.net/study/s-accircuit/sac-deltastar.html>).

The power consumption calculation unit 9, cross-correlation function calculation unit 100, cross-correlation function determination unit 101, phase current calculation unit 102, output unit 103, current RMS value calculation unit 104, and voltage RMS value calculation unit 105 described in this embodiment can be realized by a computer equipped with a CPU (Central Processing Unit), storage device, and interface, and a program that controls these hardware resources. An example of this computer configuration is shown in Figure 4.

The computer comprises a CPU 200, a storage device 201, and an interface device (I/F) 202. Hardware such as the line current measurement unit 7, the line voltage measurement unit 8, and the output unit 103 are connected to the I/F 202. The program for realizing the three-phase heater phase current detection method of the present invention is stored in the storage device 201. The CPU 200 executes the processing described in this embodiment according to the program stored in the storage device 201.

This invention can be applied, for example, to the technology for diagnosing the lifespan of a three-phase heater.

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 line current measurement, 6…Voltage transformer for line voltage measurement, 7…Line current measurement unit, 8…Line voltage measurement 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…Phase current calculation unit, 103…Output unit, 104…Current RMS value calculation unit, 105…Voltage RMS value calculation unit.

Claims (8)

A line current measuring unit configured to measure the instantaneous value of the line current flowing through three power supply lines to a three-phase heater, in which three heaters are connected,
A line voltage measuring unit configured to measure the instantaneous value of the line voltage between the three power supply lines,
A cross-correlation function calculation unit configured to calculate the generalized cross-correlation function Dr _r between the instantaneous line voltages between RS lines and between TR lines, the generalized cross-correlation function D _s between the instantaneous line voltages between ST lines and between RS lines, and the generalized cross-correlation function D _t between the instantaneous line voltages between TR lines and between ST lines ,
A cross-correlation function determination unit configured to determine whether two or more of _the generalized cross-correlation functions Dr , Ds _, and Dt _are less than 0,
A power consumption calculation unit is configured to calculate, based on the measurement results of the _line current measurement unit and the measurement results of the line voltage measurement unit, a first total power consumption which is _the sum of the power consumption of the first _heater and a portion of the power consumption of the second heater among the three-phase heaters, and a second total power consumption which is the sum of the power consumption of the third heater and the remaining power consumption of the second heater that is not included in the first total power consumption.
A current effective value calculation unit configured to calculate the effective value of the line current from the measurement results of the line current measurement unit,
A voltage RMS value calculation unit configured to calculate the RMS value of the line voltage from the measurement results of the line voltage measurement unit,
A three-phase heater phase current detection device is characterized by comprising a phase current calculation unit configured to calculate the phase current flowing through the three-phase heater based on the values of the generalized cross-correlation functions Dr _, Ds _, and Dt _{, the} total power consumption of the first and second, the effective value of the line current, and the effective value of the line voltage. In the three-phase heater phase current detection device according to claim 1,
The power consumption calculation unit determines _that the generalized cross-correlation function Dr of the RS line voltage and the TR line voltage, and the generalized cross-correlation function Dt of the TR line voltage and the ST line voltage are less than 0 _, and calculates the first total power consumption, which is the sum of the power consumption of the RS phase heater and a portion of the power consumption of the TR phase heater, based on the instantaneous value of the RS line voltage and the instantaneous value of the R phase line current, and calculates the second total power consumption, which is the sum of the power consumption of the ST phase heater and the remaining power consumption of the TR phase heater that is not included in the first total power consumption, based on the instantaneous value of the ST line voltage and the instantaneous value of the T phase line current.
The phase current calculation unit calculates the effective value of the RS phase current based on the first total power consumption, the effective value of the R phase line current, the effective value of the RS line voltage, and the generalized cross-correlation function Dr _of the RS line voltage and the TR line voltage. The unit also calculates the effective value of the ST phase current based on the second total power consumption, the effective value of the T phase line current, the effective value of the ST line voltage, and the generalized cross-correlation function Dt of the TR line voltage and the ST line voltage _. The unit further calculates the effective value of the TR phase current based on the calculated effective values of the RS phase current and ST phase current, and the first and second total power consumption, the effective value of the RS line voltage, and the effective value of the ST line voltage. This is a three-phase heater phase current detection device. In the three-phase heater phase current detection device according to claim 1,
The power consumption calculation unit determines _that the generalized cross-correlation function Dr of the RS line voltage and the TR line voltage, and the generalized cross-correlation _{function Ds} of the ST line voltage and the RS line voltage are less than 0, and calculates the first total power consumption, which is the power consumption obtained by adding the power consumption of the ST phase heater and a portion of the power consumption of the RS phase heater based on the instantaneous value of the ST line voltage and the instantaneous value of the S phase line current, and calculates the second total power consumption, which is the power consumption obtained by adding the power consumption of the TR phase heater and the remaining power consumption of the RS phase heater that is not included in the first total power consumption, based on the instantaneous value of the TR line voltage and the instantaneous value of the R phase line current.
The phase current calculation unit calculates the effective value of the ST phase current based on the first total power consumption, the effective value of the S phase line current, the effective value of the ST line voltage, and the generalized cross-correlation function D _s of the ST line voltage and the RS line voltage; calculates the effective value of the TR phase current based on the second total power consumption, the effective value of the R phase line current, the effective value of the TR line voltage, _and the generalized cross-correlation function Dr of the RS line voltage and the TR line voltage; and calculates the effective value of the RS phase current based on the calculated effective values of the ST phase current and TR phase current, and the first and second total power consumption, the effective value of the RS line voltage, the effective value of the ST line voltage and the effective value of the TR line voltage. This is a three-phase heater phase current detection device. In the three-phase heater phase current detection device according to claim 1,
The power consumption calculation unit determines that the generalized cross-correlation function Ds of the ST line voltage and the RS line voltage, _and the generalized cross-correlation function Dt of the TR line voltage and the ST line voltage are less than 0 _, and calculates the first total power consumption, which is the power consumption obtained by adding the power consumption of the TR phase heater and a portion of the power consumption of the ST phase heater based on the instantaneous value of the TR line voltage and the instantaneous value of the T phase line current, and calculates the second total power consumption, which is the power consumption obtained by adding the power consumption of the RS phase heater and the remaining power consumption of the ST phase heater that is not included in the first total power consumption, based on the instantaneous value of the RS line voltage and the instantaneous value of the S phase line current.
The phase current calculation unit calculates the effective value of the TR phase current based on the first total power consumption, the effective value of the T phase line current, the effective value of the TR line voltage, and the generalized cross-correlation function Dt _of the TR line voltage and the ST line voltage. The unit also calculates the effective value of the RS phase current based on the second total power consumption, the effective value of the S phase line current, the effective value of the RS line voltage, and the generalized cross-correlation function Ds of the ST line voltage and the RS line voltage _. The unit further calculates the effective value of the ST phase current based on the calculated effective values of the TR phase current and RS phase current, the first and second total power consumption, the effective value of the RS line voltage, the effective value of the ST line voltage, and the effective value of the TR line voltage. This is a three-phase heater phase current detection device. The first step is to measure the instantaneous value of the line current flowing through the three power supply lines to a three-phase heater, in which three heaters are connected,
A second step involves measuring the instantaneous value of the line-to-line voltage of the three aforementioned power supply lines,
A third step of calculating the generalized cross-correlation function Dr r between the instantaneous line voltages between RS lines and between TR lines, the generalized cross-correlation function D _s between the instantaneous line voltages between ST lines and between RS lines, and the generalized cross- correlation function _{D t between} the instantaneous line voltages between TR lines and between ST lines ,
A fourth step is to determine whether two or more of _the generalized cross-correlation functions Dr , Ds _, and Dt _are less than 0,
If, in the fourth step, it is determined that two or more of the generalized cross-correlation functions Dr _, Ds _, and Dt _are less than 0, then, based on the measurement results of the first step and the measurement results of the second step, a fifth step is to calculate a first total power consumption, which is the sum of the power consumption of the first heater and a portion of the power consumption of the second heater among the three-phase heaters, and a second total power consumption, which is the sum of the power consumption of the third heater and the remaining power consumption of the second heater that is not included in the first total power consumption.
A sixth step of calculating the effective value of the line current from the measurement results of the first step,
A seventh step involves calculating the effective value of the line voltage from the measurement results of the second step,
A method for detecting a three-phase heater phase current, comprising an eighth step of calculating the phase current flowing through the three-phase heater based on the values of the generalized cross-correlation functions Dr _, Ds _, and Dt _, the total power consumption of the first and second, the effective value of the line current, and the effective value of the line voltage. In the three-phase heater phase current detection method according to claim 5,
The fifth step includes, _if it is determined that the generalized cross-correlation function Dr of the RS line voltage and the TR line voltage and _the generalized cross-correlation function Dt of the TR line voltage and the ST line voltage are less than 0, calculating the first total power consumption, which is the power consumption obtained by adding the power consumption of the RS phase heater and a portion of the power consumption of the TR phase heater based on the instantaneous value of the RS line voltage and the instantaneous value of the R phase line current, and calculating the second total power consumption, which is the power consumption obtained by adding the power consumption of the ST phase heater and the remaining power consumption of the TR phase heater that is not included in the first total power consumption, based on the instantaneous value of the ST line voltage and the instantaneous value of the T phase line current,
The eighth step is a three-phase heater phase current detection method characterized _by including the steps of: calculating the effective value of the RS phase current based on the first total power consumption, the effective value of the R phase line current, the effective value of the RS line voltage, and the generalized cross-correlation function Dr of the RS line voltage and the TR line voltage; calculating the effective value of the ST phase current based on the second total power consumption, the effective value of the T phase line current, the effective value of the ST line voltage, and the generalized cross-correlation function Dt of _the TR line voltage and the ST line voltage; and calculating the effective value of the TR phase current based on the calculated effective values of the RS phase current and ST phase current, and the first and second total power consumption, the effective value of the RS line voltage and the effective value of the ST line voltage. In the three-phase heater phase current detection method according to claim 5,
The fifth step includes, _if it is determined that the generalized cross-correlation function Dr of the RS line voltage and the TR line voltage and the generalized cross-correlation _{function Ds} of the ST line voltage and the RS line voltage are less than 0, calculating the first total power consumption, which is the power consumption obtained by adding the power consumption of the ST phase heater and a portion of the power consumption of the RS phase heater based on the instantaneous value of the ST line voltage and the instantaneous value of the S phase line current, and calculating the second total power consumption, which is the power consumption obtained by adding the power consumption of the TR phase heater and the remaining power consumption of the RS phase heater that is not included in the first total power consumption, based on the instantaneous value of the TR line voltage and the instantaneous value of the R phase line current,
A three-phase heater phase current detection method characterized by the eighth step comprising the steps of: calculating the effective value of the ST phase current based on the first total power consumption, the effective value of the S phase line current, the effective value of the ST line voltage, and the generalized cross-correlation function D _s of the ST line voltage and the RS line voltage; calculating the effective value of the TR phase current based on the second total power consumption, the effective value of the _R phase line current, the effective value of the TR line voltage, and the generalized cross-correlation function Dr of the RS line voltage and the TR line voltage; and calculating the effective value of the RS phase current based on the calculated effective values of the ST phase current and TR phase current, and the first and second total power consumption, the effective value of the RS line voltage, the effective value of the ST line voltage and the effective value of the TR line voltage. In the three-phase heater phase current detection method according to claim 5,
The fifth step includes, if it is determined that _{the generalized cross-correlation function Ds} of the ST line voltage and the RS line voltage and _the generalized cross-correlation function Dt of the TR line voltage and the ST line voltage are less than 0, calculating the first total power consumption, which is the power consumption obtained by adding the power consumption of the TR phase heater and a portion of the power consumption of the ST phase heater based on the instantaneous value of the TR line voltage and the instantaneous value of the T phase line current, and calculating the second total power consumption, which is the power consumption obtained by adding the power consumption of the RS phase heater and the remaining power consumption of the ST phase heater that is not included in the first total power consumption, based on the instantaneous value of the RS line voltage and the instantaneous value of the S phase line current,
The eighth step is a three-phase heater phase current detection method characterized _by including the steps of: calculating the effective value of the TR phase current based on the first total power consumption, the effective value of the T phase line current, the effective value of the TR line voltage, and the generalized cross-correlation function Dt of the TR line voltage and the ST line voltage; calculating the effective value of the RS phase current based on the second total power consumption, the effective value of the S phase line current, the effective value of the RS line voltage, and _the generalized cross-correlation function Ds of the ST line voltage and the RS line voltage; and calculating the effective value of the ST phase current based on the calculated effective values of the TR phase current and RS phase current, the first and second total power consumption, the effective value of the RS line voltage, the effective value of the ST line voltage, and the effective value of the TR line voltage.