JP7366571B2 - Life prediction device, air conditioning system, life prediction method and program - Google Patents

Description

The present invention relates to a lifespan prediction device, an air conditioning system, a lifespan prediction method, and a program.

An air conditioning system includes a power conversion circuit that converts three-phase AC power input from an input power source (commercial power source) into AC power for driving a motor. In this power conversion circuit, the weight ratio of passive elements such as a reactor and an electrolytic capacitor is large, and there is a demand for miniaturization and weight reduction of these electrical components. However, reducing the size of reactors and electrolytic capacitors may shorten the life of the electrolytic capacitors.

It is known that the life of an electrolytic capacitor largely depends on the ambient temperature of the electrolytic capacitor and the ripple current input to the electrolytic capacitor. This ripple current increases significantly, especially when voltage imbalance occurs in the three-phase AC power from the input power source.

Patent Document 1 describes a life extension device that can accurately determine whether or not life extension measures are necessary for a capacitor by using the amount of drop in the output voltage of a power supply circuit.

JP2016-217986A

In the above-mentioned air conditioning system, there is a need for a function that can determine the lifespan of the electrolytic capacitor mounted in the power conversion circuit.

An object of the present invention is to provide a lifespan prediction device, an air conditioning system, a lifespan prediction method, and a program that can determine the lifespan of an electrolytic capacitor mounted in a power conversion circuit.

According to the first aspect of the present invention, the life prediction device is provided between a rectifier that converts AC power from a commercial power source into DC power and an inverter that converts the DC power into AC power for driving a motor. and a first ripple current measurement unit that measures a first ripple current input to the electrolytic capacitor from the rectifier side; a second ripple current measuring unit that measures a second ripple current input into the electrolytic capacitor from the side; and a lifespan calculation part that calculates the lifespan of the electrolytic capacitor by substituting the calculation result of the total ripple current into a predetermined lifespan calculation formula.

Further, according to the second aspect of the present invention, the first ripple current measuring section acquires a DC current value through a first current sensor capable of detecting a DC current flowing from the rectifier to the inverter. A measured value of the first ripple current is calculated by subtracting a time average value of the DC current value from the DC current value.

Further, according to the third aspect of the present invention, the second ripple current measuring section acquires a motor current value through a second current sensor capable of detecting a motor current flowing through the motor, and A measured value of the second ripple current is specified with reference to a ripple current table in which a relationship between the applied modulation factor, the motor current value, and the second ripple current value is defined. .

Further, according to a fourth aspect of the present invention, an air conditioning system includes the above-described life prediction device.

Further, according to the fifth aspect of the present invention, the life prediction method includes a method for predicting the life between a rectifier that converts AC power from a commercial power source into DC power, and an inverter that converts the DC power into AC power for driving a motor. A method for estimating the life of an electrolytic capacitor for smoothing the DC power, the method comprising: measuring a first ripple current input to the electrolytic capacitor from the rectifier side; a step of measuring a second ripple current input to the electrolytic capacitor; and a step of measuring a total ripple current input to the electrolytic capacitor based on the measured value of the first ripple current and the measured value of the second ripple current. and a step of calculating the life of the electrolytic capacitor by substituting the calculated value of the total ripple current into a predetermined life calculation formula.

According to the sixth aspect of the present invention, the program is provided between a rectifier that converts AC power from a commercial power source into DC power and an inverter that converts the DC power into AC power for driving a motor. a step of measuring a first ripple current input to the electrolytic capacitor from the rectifier side to a computer that estimates the life of the electrolytic capacitor smoothing the DC power; and inputting the first ripple current to the electrolytic capacitor from the inverter side. and calculating a total ripple current input to the electrolytic capacitor based on the measured value of the first ripple current and the measured value of the second ripple current. , calculating the lifespan of the electrolytic capacitor by substituting the calculated value of the total ripple current into a predetermined lifespan calculation formula.

According to at least one of the above aspects, it is possible to grasp the lifespan of an electrolytic capacitor mounted in a power conversion circuit.

FIG. 1 is a diagram showing the overall configuration of an air conditioning system according to a first embodiment. FIG. 2 is a diagram showing a functional configuration of a system control unit according to the first embodiment. FIG. 3 is a diagram showing a functional configuration of a motor control section according to the first embodiment. It is a figure explaining the function of the low frequency ripple current measurement part concerning a 1st embodiment. It is a figure explaining the function of the high frequency ripple current measurement part concerning a 1st embodiment. FIG. 3 is a diagram for explaining the function of the cumulative life consumption rate calculating section according to the first embodiment. FIG. 3 is a diagram for explaining the function of the cumulative life consumption rate calculating section according to the first embodiment. It is a figure for explaining the function of the rotation speed command output part concerning a 1st embodiment. It is a figure for demonstrating the function of the rotation speed command output part based on the modification of 1st Embodiment.

<First embodiment>
Hereinafter, a life prediction device according to a first embodiment and an air conditioning system including the same will be described with reference to FIGS. 1 to 7.

(Overall configuration of air conditioning system)
FIG. 1 is a diagram showing the overall configuration of an air conditioning system according to a first embodiment.
The air conditioning system 1 shown in FIG. 1 is a system that is mounted on an outdoor unit and rotates a compressor. Note that in FIG. 1, illustration of the compressor and the like is omitted.

The air conditioning system 1 according to this embodiment includes a power conversion circuit 10 and a control device 11. The power conversion circuit 10 is a circuit that is connected to an AC power supply PS and converts three-phase AC power input from the AC power supply PS into AC power for driving the motor 102. The AC power supply PS is a general commercial power system that outputs three-phase AC power. The motor 102 is, for example, a three-phase AC motor that rotationally drives a compressor.
In the following description, in each configuration included in the power conversion circuit 10, the side closer to the AC power supply PS is also referred to as the "upstream side," and the side closer to the motor 102 is also referred to as the "downstream side."

The configuration of the power conversion circuit 10 will be explained.
As shown in FIG. 1, the power conversion circuit 10 includes a rectifier 100, an inverter 101, and a motor 102.

Rectifier 100 is, for example, a diode module, and converts three-phase AC power input from AC power supply PS into DC power.

The inverter 101 is, for example, an IPM (Intelligent Power Module), and generates three-phase AC power for driving a motor from DC power by switching (ON/OFF) operations of internal power transistors. The inverter 101 performs a switching operation according to a drive command (PWM (Pulse Width Modulation) signal) from the control device 11 (motor control unit 111 described later).

As shown in FIG. 1, the high potential side output of the rectifier 100 is connected to the high potential terminal Tp of the inverter 101 through a high voltage line P. Further, a low potential side output of the rectifier 100 is connected to a low potential terminal Tn of the inverter 101 through a low voltage line N. A reactor L and a smoothing capacitor FC are connected to the high voltage line P and the low voltage line N to smooth the DC power output from the rectifier 100.
The reactor L is a passive element for smoothing the DC power output from the rectifier 100, and is connected on the high voltage line P downstream of the rectifier 100 and upstream of the smoothing capacitor FC.
The smoothing capacitor FC is a passive element for smoothing the DC power output from the rectifier 100, and is connected between the high voltage line P and the low voltage line N on the downstream side of the reactor L and on the upstream side of the inverter 101. connected between. Smoothing capacitor FC is an electrolytic capacitor. A ripple current is input to the smoothing capacitor FC. It is known that the magnitude of this ripple current has a large effect on the life of the smoothing capacitor FC. The ripple current input to the smoothing capacitor FC includes a low frequency ripple current IL (first ripple current) input from the rectifier 100 side and a high frequency ripple current IH (second ripple current) input from the inverter 101 side. ). The frequency of the low frequency ripple current IL depends on the power frequency of the AC power supply PS, and varies at a frequency of about 300 Hz, for example. The high frequency ripple current IH has a frequency that depends on the frequency of the switching operation of the inverter 101, and has a frequency of, for example, several kHz to several tens of kHz.

Furthermore, a snubber capacitor SC is connected between the high potential terminal Tp and the low potential terminal Tn of the inverter 101. Snubber capacitor SC alleviates spike currents generated due to switching operations of inverter 101.

The power conversion circuit 10 further includes a current sensor SE1 (first current sensor) and current sensors SE2-1 and SE2-2 (second current sensors).
Current sensor SE1 is provided on high voltage line P connecting rectifier 100 and reactor L, and detects reactor current IDC (direct current) flowing from rectifier 100 to inverter 101.
Current sensors SE2-1 and SE2-2 are provided on two phases (U phase and W phase in the example of FIG. 1) of the wiring connecting inverter 101 and motor 102, and detect motor current IM.
The current sensor SE1 and the current sensors SE2-1 and SE2-2 may be, for example, clamp-type current sensors. Each current detection signal output from the current sensor SE1 and the current sensors SE2-1 and SE2-2 is input to the control device 11 (motor control section). The control device 11 sequentially samples and acquires a reactor current value, which is the measured value of the reactor current IDC, and a motor current value, which is the measured value of the motor current IM, based on the detection signal input from each current sensor. .

The configuration of the control device 11 will be explained.
As shown in FIG. 1, the control device 11 includes a system control section 110 and a motor control section 111 that outputs a drive command to the inverter 101 and controls the drive of the motor 102. The system control unit 110 and the motor control unit 111 may each be a processor such as a microcontroller.
The control device 11 according to the present embodiment functions as a life prediction device that predicts the life of the smoothing capacitor FC, as described later.

The system control unit 110 controls the entire operation of the air conditioning system 1. The system control unit 110 inputs the set temperature T* set by the user of the air conditioning system 1 and the current observed temperature T obtained through the temperature sensor from the outside (indoor unit controller), and adjusts the temperature according to these values. The rotation speed command RPS* is output to the motor control unit 111.

The motor control unit 111 outputs a drive command to the inverter 101 such that the rotation speed corresponds to the rotation speed command RPS* input from the system control unit 110. When outputting the drive command, the motor control unit 111 also refers to the motor current value obtained through the current sensors SE2-1 and SE2-2.

The motor control unit 111 outputs the reactor current value obtained through the current sensor SE1 and the motor current value obtained through the current sensors SE2-1 and SE2-2 to the system control unit 110. The system control unit 110 then performs a protective operation based on these current values input from the motor control unit 111. "Protective operation" is a function to prevent deterioration and damage to circuit components due to heat generated by large current. When the reactor current value or the motor current value input from the motor control unit 111 exceeds a predefined threshold value for each, the system control unit 110 controls the rotation speed to reduce the load on the power conversion circuit 10. A protective operation is executed to reduce the command RPS*.

Further, the motor control unit 111 according to the first embodiment measures the low frequency ripple current IL input to the smoothing capacitor FC and the high frequency ripple current IH input from the inverter 101 side, and calculates each measurement value. It is output to the system control unit 110. The system control unit 110 that has input the measured values of the low frequency ripple current IL and the high frequency ripple current IH predicts the life of the smoothing capacitor FC using these measured values.
The above functions of the system control section 110 and the motor control section 111 will be described in detail below.

(Functional configuration of control device)
FIG. 2 is a diagram showing the functional configuration of the system control unit according to the first embodiment.

The functional configuration of the system control unit 110 will be explained with reference to FIG. 2.
As shown in FIG. 2, the system control unit 110 functions as a rotation speed command output unit 1100, a life calculation unit 1101, and a cumulative life consumption rate calculation unit 1102 by operating according to a predetermined program.

The rotation speed command output unit 1100 outputs a rotation speed command RPS* based on the set temperature T* and the observed temperature T. Further, the rotation speed command output unit 1100 has a function of reducing the rotation speed command RPS* based on the life consumption suppression operation. Here, the "lifetime consumption suppressing operation" is an operation different from the above-mentioned protective operation, and is an operation for suppressing excessive consumption of the lifetime of the smoothing capacitor FC. Specifically, it refers to the operation of limiting the rotation speed command RPS* so that the cumulative life consumption rate does not exceed a predefined upper limit value (cumulative life consumption rate upper limit value) for each cumulative operating time. Point. Details of this life consumption suppression operation will be described later.
The life calculation unit 1101 calculates the life of the smoothing capacitor FC by substituting the total ripple current value (measured value of the total ripple current) input from the motor control unit 111 into a predetermined life calculation formula.
The cumulative life consumption rate calculation unit 1102 calculates the cumulative life consumption rate of the smoothing capacitor FC during operation, based on the life calculation results (instantaneous estimated life) sequentially calculated by the life calculation unit 1101.

FIG. 3 is a diagram showing the functional configuration of the motor control section according to the first embodiment.
The functional configuration of the motor control section 111 will be explained with reference to FIG. 3.
As shown in FIG. 3, the motor control unit 111 operates according to a predetermined program to output a drive command output unit 1110, a low frequency ripple current measurement unit 1111, a high frequency ripple current measurement unit 1112, and a total ripple current calculation unit. It functions as 1113.

The drive command output unit 1110 outputs the rotation speed command RPS* input from the system control unit 110 and the measured value of the motor current IM (motor current value) acquired through the current sensors SE2-1 and SE2-2 (FIG. 1). ), a drive command is output to the inverter 101. The drive command output unit 1110 according to this embodiment outputs the modulation factor applied as a result of the drive command output to the inverter 101 to the high frequency ripple current measurement unit 1112. Here, "modulation rate" refers to the motor voltage applied by the inverter 101 to each phase of the motor 102 with respect to the DC voltage VDC [V] (FIG. 1) applied between the high voltage line P and the low voltage line N. It means the ratio of the peak value (√2·VM) of the line voltage VM [Vrms] (FIG. 1). For example, when the peak value (√2·VM) of the motor line voltage VM matches the DC voltage VDC, the modulation rate is 100%. The drive command output unit 1110 calculates the modulation factor achieved when the inverter 101 is driven with the currently output drive command, and outputs it to the high frequency ripple current measurement unit 1112.

The low frequency ripple current measurement unit 1111 measures the low frequency ripple current IL input from the rectifier 100 side to the smoothing capacitor FC.

The high frequency ripple current measuring section 1112 measures the high frequency ripple current IH input from the inverter 101 side to the smoothing capacitor FC. Specifically, high frequency ripple current measuring section 1112 obtains a motor current value, which is a measured value of motor current IM, through current sensors SE2-1 and SE2-2. Then, the high frequency ripple current measurement unit 1112 refers to the ripple current table tb prepared in advance and specifies the measured value of the high frequency ripple current IH. Here, the ripple current table tb is an information table that defines the relationship between the modulation factor applied in the operation of the inverter 101 based on the drive command, the motor current value, and the value of the high frequency ripple current IH. .

The total ripple current calculation unit 1113 calculates the total ripple current input to the smoothing capacitor FC based on the measured value of the low frequency ripple current IL and the measured value of the high frequency ripple current IH. A specific method for calculating the total ripple current will be described later.

(Function of low frequency ripple current measurement section)
FIG. 4 is a diagram illustrating the function of the low frequency ripple current measuring section according to the first embodiment.
The function of the low frequency ripple current measuring section 1111 of the motor control section 111 will be described in detail with reference to FIG. 4.

Figure 4 shows the power output when the AC power input from the AC power supply PS is balanced (when the power supply is balanced) and when the AC power input from the AC power supply PS is unbalanced (when the power supply is unbalanced). The waveforms of the reactor current IDC, the time average value IDC_avg of the reactor current IDC, and the low frequency ripple current IL in the case of FIG.

The processing procedure of the low frequency ripple current measuring section 1111 will be explained.
First, the low frequency ripple current measurement unit 1111 sequentially samples, acquires, and accumulates the measured value [A] (reactor current value) of the reactor current IDC through the current sensor SE1 (step S1). This reactor current IDC is a current immediately after the three-phase AC power from the AC power supply PS is rectified by the rectifier 100. Therefore, the waveform of reactor current IDC includes both AC and DC components, as shown in FIG.

Next, the low frequency ripple current measurement unit 1111 calculates a time average value IDC_avg[A] which is the average value for the most recent predetermined time of the measured values of the reactor current IDC acquired and accumulated in step S1 (step S2). The above-mentioned predetermined time for calculating the average value is such that even when the power supply is unbalanced (when the AC component increases greatly) as shown on the right side of FIG. 4, the time average value IDC_avg of the reactor current is approximately equal to the time. It is preferable that the time be constant (for example, 100 msec or more). The time average value IDC_avg[A] calculated in this way has a waveform substantially equivalent to the DC component of the reactor current IDC. That is, the time average value IDC_avg obtained by the calculation can be regarded as the DC component of the reactor current IDC.

Next, the low frequency ripple current measurement unit 1111 performs a calculation to sequentially subtract the time average value IDC_avg [A] calculated in step S2 from the measured value [A] of the reactor current IDC acquired and accumulated in step S1 (step S3). As shown in FIG. 4, the value calculated in this way is equivalent to the AC component of the reactor current IDC, and can be regarded as the low frequency ripple current IL. Therefore, the low frequency ripple current measurement unit 1111 outputs the current value [Arms] obtained by subtracting the time average value IDC_avg from the measured value of the reactor current IDC as the measured value of the low frequency ripple current IL.

The low-frequency ripple current measurement unit 1111 sequentially outputs the measured value of the low-frequency ripple current IL while repeating the processing of steps S1 to S3 above.

(Function of high frequency ripple current measurement section)
FIG. 5 is a diagram illustrating the function of the high frequency ripple current measuring section according to the first embodiment.
The function of the high frequency ripple current measuring section 1112 of the motor control section 111 will be described in detail with reference to FIG.

FIG. 5 is a diagram showing an example of the ripple current table tb.
The ripple current table tb shows the relationship between the modulation factor (horizontal axis) applied to the operation of the inverter 101, the high frequency ripple current [Arms] (vertical axis), and the motor current IM [Arms] (each series of the graph). FIG. Such a ripple current table tb is created in advance by actual measurement, circuit simulation, or the like.

High frequency ripple current measuring section 1112 acquires the modulation factor from drive command output section 1110. Furthermore, the high frequency ripple current measuring section 1112 obtains the motor current value through the current sensors SE2-1 and SE2-2. Then, the high frequency ripple current measurement unit 1112 uses the obtained modulation factor and motor current value to specify the high frequency ripple current value [Arms] from the ripple current table tb. The high-frequency ripple current measuring section 1112 outputs the high-frequency ripple current value identified in this manner as the measured value.

(Function of total ripple current calculation section)
The total ripple current calculation unit 1113 of the motor control unit 111 calculates the low frequency ripple current measurement value [Arms] input from the low frequency ripple current measurement unit 1111 and the high frequency ripple current measurement value input from the high frequency ripple current measurement unit 1112. [Arms] is used to calculate the measured value [Arms] (total ripple current value) of the total ripple current. Specifically, the total ripple current calculation unit 1113 calculates the following equation (1).

In equation (1), the symbol "In" is the total ripple current value [Arms], and the symbols "IL" and "IH" are the measured value [Arms] of the low frequency ripple current and the measured value of the high frequency ripple current, respectively. The value is [Arms].

(Function of life calculation section)
Next, the functions of the life calculation section 1101 of the system control section 110 will be explained in detail.
The life calculation unit 1101 of the system control unit 110 calculates the life of the smoothing capacitor FC based on the measured value [Arms] of ripple current input from the motor control unit 111 (total ripple current calculation unit 1113). Specifically, the life calculation unit 1101 substitutes the measured value of the ripple current input from the motor control unit 111 into equations (2) and (3).

Formula (2) is an example of a life calculation formula for a smoothing capacitor FC (electrolytic capacitor). The symbol "Ln" in equation (2) is the life [Hour] of the smoothing capacitor FC, which is calculated based on "Tn", which is the ambient temperature of the smoothing capacitor FC, and "Δtn", which is a variable that depends on the ripple current. Determined. Note that "α" is a constant value. The ambient temperature Tn is acquired through a temperature sensor included in the air conditioning system 1.

The variable “Δtn” is expressed by equation (3).

In equation (3), “In” is the total ripple current value [Arms], and the measured value from the motor control unit 111 is substituted. In addition, in equation (3), "Δt0" is the temperature rise value at rated ripple, "Im" is the rated ripple current, "K(f)" is the ripple current frequency correction coefficient, and "K(r)" is the temperature correction are coefficients, and both may be constants.

The life calculation unit 1101 substitutes the total ripple current value sequentially input from the motor control unit 111 into equation (3), and sequentially calculates the life Ln [Hour] based on the total ripple current value. The life Ln calculated sequentially in this manner is also referred to as instantaneous estimated life.

(Function of cumulative life consumption rate calculation section)
6 and 7 are diagrams for explaining the functions of the cumulative life consumption rate calculating section according to the first embodiment.
Hereinafter, the functions of the cumulative life consumption rate calculating section 1102 of the system control section 110 will be described in detail with reference to FIGS. 6 and 7.

FIG. 6 shows a graph G1 showing the transition of the instantaneous estimated lifespan sequentially calculated by the lifespan calculation unit 1101. Hereinafter, the instantaneous estimated lifespan will be described as instantaneous estimated lifespan G1.
As shown in FIG. 6, the cumulative life consumption rate calculation unit 1102 divides the cumulative operating time of the air conditioning system 1 into sections of each predetermined unit time (for example, 1 hour), and also divides the cumulative operating time of the air conditioning system 1 into sections (section A, section B, Calculate the life consumption rate [%] for each section C, section D, etc. The cumulative life consumption rate calculation unit 1102 sets the minimum value of the instantaneous estimated life G1 observed in the section as the representative life of the smoothing capacitor FC in the section. In the case of the example shown in FIG. 6, since the minimum value of the instantaneous estimated life G1 observed in section A is 30,000 hours, the typical life of the smoothing capacitor FC in section A is 30,000 hours. Similarly, since the minimum value of the instantaneous estimated life G1 observed in section B is 60,000 hours, the representative life of the smoothing capacitor FC in section B is 60,000 hours. Similarly, since the minimum value of the instantaneous estimated life G1 observed in section C is 20,000 hours, the representative life of the smoothing capacitor FC in section C is 20,000 hours. Similarly, since the minimum value of the instantaneous estimated life G1 observed in the D section is 70,000 hours, the representative life of the smoothing capacitor FC in the D section is 70,000 hours.

Next, the cumulative life consumption rate calculation unit 1102 calculates the life consumption rate [%] in each section (A section, B section, C section, D section, etc.). The life consumption rate is the ratio of the consumed life to the total life (representative life for each section) of the smoothing capacitor FC. For example, in section A, one hour out of the typical life of 30,000 hours was used, so the life consumption rate of the smoothing capacitor FC is 1 [Hour]/30000 [Hour] x 100 = 0.00333%. Similarly, in section B, 1 hour out of 60,000 hours of representative life was used, so the lifetime consumption rate of smoothing capacitor FC is 1 [Hour]/60000 [Hour] x 100 = 0.00167%. . Similarly, in section C, 1 hour out of 20,000 hours of representative life was used, so the lifetime consumption rate of smoothing capacitor FC is 1 [Hour]/20000 [Hour] x 100 = 0.005%. . Similarly, in section D, 1 hour out of 70,000 hours of representative life was used, so the lifetime consumption rate of smoothing capacitor FC is 1 [Hour]/70000 [Hour] x 100 = 0.00143%. .

As shown in FIG. 7, the cumulative life consumption rate calculation unit 1102 calculates the cumulative life consumption rate by integrating the life consumption rates calculated for each section. Graph G2 shown in FIG. 7 shows changes in the cumulative lifetime consumption rate. Hereinafter, the cumulative lifetime consumption rate will also be referred to as cumulative lifetime consumption rate G2.

(Function of rotation speed command output section)
FIG. 8 is a diagram for explaining the function of the rotation speed command output section according to the first embodiment.
Hereinafter, with reference to FIG. 8, the life consumption suppression operation by the rotation speed command output section 1100 will be described in detail.

The rotation speed command output unit 1100 of the system control unit 110 determines the rotation speed command RPS* based on the life consumption suppression operation. Here, the rotation speed command output unit 1100 has a predefined cumulative life consumption rate upper limit value Gth. The cumulative life consumption rate upper limit Gth is the upper limit value of the cumulative life consumption rate G2 determined for each cumulative operating time. The cumulative life consumption rate upper limit Gth is based on the target life which is the target value of the cumulative operating time that can be operated without failure, and its slope (that is, the rate of increase of the cumulative life consumption rate upper limit Gth per unit operating time) is 100. %/Target life. For example, when the target life is set as "30,000 hours", the cumulative life consumption rate upper limit Gth is defined by a straight line with a slope of "100%/30,000 hours" as shown in FIG.

The rotation speed command output unit 1100 suppresses (reduces) and outputs the rotation speed command RPS* so that the cumulative life consumption rate G2 inputted from the cumulative life consumption rate calculation unit 1102 does not exceed the cumulative life consumption rate upper limit value Gth. do. By suppressing the rotation speed command RPS*, the rotation speed of the motor 102 is reduced, and accordingly, the reactor current IDC and the motor current IM are reduced. Furthermore, since the reactor current IDC and motor current IM are reduced, the total ripple current In is also reduced. This also suppresses the pace at which the cumulative lifetime consumption rate increases.

However, the air conditioning system 1 should operate to satisfy the user's request (set temperature T*) to the extent that the cumulative lifetime consumption rate G2 does not exceed the cumulative lifetime consumption rate upper limit value Gth. Therefore, the rotation speed command output unit 1100 takes into consideration the cumulative life consumption rate G2 accumulated up to the current section and the cumulative life consumption rate upper limit value Gth applied to the next section. The maximum rotational speed command RPS* that does not exceed the increase pace of the allowable cumulative life consumption rate G2 is output.

Furthermore, according to equation (2), the estimated instantaneous life of the smoothing capacitor FC also depends on the ambient temperature Tn. Therefore, if the ambient temperature Tn drops during operation, there is a margin for increasing the total ripple current by that amount. Therefore, in this case, the rotation speed command output unit 1100 relaxes the suppression of the rotation speed command RPS* according to the decrease in the ambient temperature Tn, as long as the cumulative life consumption rate G2 does not exceed the cumulative life consumption rate upper limit value Gth. let

(action, effect)
As described above, the control device 11 (life prediction device) according to the first embodiment includes a rectifier 100 that converts AC power from an AC power source PS, which is a commercial power source, into DC power, and a rectifier 100 that converts the AC power from the AC power source PS, which is a commercial power source, into DC power. It functions as a device that predicts the life of an electrolytic capacitor (smoothing capacitor FC) that is provided between the inverter 101 that converts into AC power and smoothes the DC power.
The control device 11 includes a low frequency ripple current measuring section 1111 that measures a low frequency ripple current IL input to the smoothing capacitor FC from the rectifier 100 side, and a high frequency ripple current IH input to the smoothing capacitor FC from the inverter 101 side. a total ripple current calculation unit 1113 that calculates the total ripple current In input to the smoothing capacitor FC based on the measured value of the low frequency ripple current IL and the measured value of the high frequency ripple current IH; It includes a life calculation unit 1101 that calculates the life of the smoothing capacitor FC by substituting the calculated value of the total ripple current In into a predetermined life calculation formula (Equation (2), Formula (3)).
By doing this, the life of the smoothing capacitor FC is predicted by considering both the low frequency ripple current input from the rectifier 100 side and the high frequency ripple current input from the inverter 101 side, so the low frequency ripple current is The prediction accuracy can be improved compared to the case where prediction is made by considering only one of the current IL and the high frequency ripple current IH.

Note that when trying to predict the life of the smoothing capacitor FC by considering both the low-frequency ripple current and the high-frequency ripple current, it is necessary to It is also possible to directly measure the total ripple current by providing a current sensor. However, in this case, it becomes necessary to additionally install a current sensor on the wiring, which increases manufacturing costs.
On the other hand, in the air conditioning system 1 according to the present embodiment, the low frequency ripple current IL is measured through the current sensor SE1 provided on the high voltage line P connecting the rectifier 100 and the reactor L. In addition, in the air conditioning system 1 according to the present embodiment, current sensors SE2-1 and SE2-2 provided in one phase (W phase in the example of FIG. 1) of the wiring connecting the inverter 101 and the motor 102 , measure the high frequency ripple current IH.
Here, the current sensor SE1 is originally a current sensor provided for a protective operation to protect the rectifier 100 and the reactor L, which are diode modules. Further, the current sensors SE2-1 and SE2-2 are originally provided for controlling the inverter 101 and for protecting the inverter 101. Therefore, according to the air conditioning system 1 according to the present embodiment, when predicting the life of the smoothing capacitor FC in consideration of both the low frequency ripple current IL and the high frequency ripple current IH, it is not necessary to additionally install a new current sensor. do not have.

The air conditioning system 1 according to the first embodiment also includes a life calculation unit 1101 that calculates the instantaneous estimated life of the smoothing capacitor FC during operation based on the measured value of the ripple current input to the smoothing capacitor FC; A cumulative life consumption rate calculation unit 1102 calculates the cumulative life consumption rate of the smoothing capacitor FC based on the instantaneous estimated life calculated by the calculation unit 1101, and outputs a rotation speed command according to the set temperature set by the user. and a rotation speed command output unit 1100 that limits the rotation speed command RPS* so that the cumulative life consumption rate does not exceed a predetermined upper limit value (cumulative life consumption rate upper limit value Gth). do.
By doing this, the rotation speed command RPS* is limited so that the cumulative life consumption rate of the smoothing capacitor FC does not exceed the predefined upper limit, so that the life of the smoothing capacitor FC is longer than the target life. It is possible to suppress failures within a short operating time.

Further, according to the air conditioning system 1 according to the first embodiment, the cumulative life consumption rate upper limit Gth is determined to be proportional to the cumulative operating time by a predetermined coefficient (100%/target life). .
By doing so, it is possible to equalize the pace of increase in the cumulative life consumption rate over the entire operating time up to the target life. Thereby, the degree of suppression of the rotation speed command RPS* can be made uniform over the entire operating time up to the target life.

Although the control device 11 (life prediction device) and the air conditioning system 1 including the same according to the first embodiment have been described above in detail, the specific aspects of the control device 11 and the air conditioning system 1 are limited to those described above. It is possible to make various design changes without departing from the spirit of the invention.

(Modified example)
FIG. 9 is a diagram for explaining the function of the rotation speed command output section according to a modification of the first embodiment.
According to the air conditioning system 1 according to the first embodiment, the cumulative life consumption rate upper limit value Gth has a slope (increase rate of the cumulative life consumption rate upper limit value Gth per unit operation time) of "100%/target life". The explanation has been made assuming that it is defined by a straight line (see FIG. 8).
However, the air conditioning system 1 according to other embodiments is not limited to this aspect. For example, in the air conditioning system 1 according to the modification, as shown in FIG. 9, the cumulative lifetime consumption rate upper limit Gth is within the range defined by the first slope and the second slope (≠ first slope). It may have a defined range. In the example shown in FIG. 9, the cumulative life consumption rate upper limit Gth is determined by applying "first slope = 100%/20,000 hours" in the cumulative operating time range from 0 hours to 10,000 hours, and "Second slope = 100%/40,000 hours" is applied in the range from 10,000 hours to 30,000 hours. In this example, after the cumulative operating time exceeds 10,000 hours, the degree of restriction of the rotation speed command RPS* increases.
Further, the air conditioning system 1 according to another embodiment may have a function of changing (editing) the cumulative lifetime consumption rate upper limit Gth. Thereby, the user can freely decide whether to prioritize the capacity or the lifespan as the usage pattern of the air conditioning system 1 for each operating time.

Furthermore, the control device 11 (life prediction device) according to the first embodiment has been described as one that predicts the life of the smoothing capacitor FC by considering both the low frequency ripple current IL and the high frequency ripple current IH. Other embodiments are not limited to this aspect. That is, the control device 11 according to another embodiment may predict the life of the smoothing capacitor FC by considering only one of the low frequency ripple current IL and the high frequency ripple current IH.

As mentioned above, several embodiments according to the present invention have been described, but all these embodiments are presented as examples and are not intended to limit the scope of the invention. The embodiments described above can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. The above-described embodiments and their modifications are included within the scope and gist of the invention as well as within the scope of the invention described in the claims and its equivalents.

1 Air conditioning system 10 Power conversion circuit 100 Rectifier 101 Inverter 102 Motor 11 Control device (life prediction device)
110 System control section 1100 Rotation speed command output section 1101 Life calculation section 1102 Cumulative life consumption rate calculation section 111 Motor control section 1110 Drive command output section 1111 Low frequency ripple current measurement section (first ripple current measurement section)
1112 High frequency ripple current measurement section (second ripple current measurement section)
1113 Total ripple current calculation unit SE1 current sensor (first current sensor)
SE2-1, SE2-2 Current sensor (second current sensor)
L Reactor FC Smoothing capacitor SC Snubber capacitor PS AC power supply

Claims (6)

Predicting the lifespan of an electrolytic capacitor that smoothes the DC power and is installed between a rectifier that converts AC power from a commercial power source into DC power and an inverter that converts the DC power to AC power for driving a motor. A device,
a first ripple current measurement unit that measures a first ripple current input to the electrolytic capacitor from the rectifier side;
a second ripple current measurement unit that measures a second ripple current input to the electrolytic capacitor from the inverter side;
a total ripple current calculation unit that calculates a total ripple current input to the electrolytic capacitor based on the measured value of the first ripple current and the measured value of the second ripple current;
a life calculation unit that calculates the life of the electrolytic capacitor by substituting the calculation result of the total ripple current into a predetermined life calculation formula;
Equipped with
The first ripple current measurement unit obtains the first ripple current through a first current sensor provided between the rectifier and a reactor connected upstream of the electrolytic capacitor.
Life prediction device. The first ripple current measurement unit acquires a DC current value flowing from the rectifier to the inverter through the first current sensor,
The life prediction device according to claim 1, wherein the measured value of the first ripple current is calculated by subtracting a time average value of the DC current value from the acquired DC current value. The second ripple current measurement unit acquires a motor current value through a second current sensor capable of detecting a motor current flowing through the motor,
The second ripple current is determined by referring to a ripple current table that defines the relationship between the modulation factor applied in the operation of the inverter, the motor current value, and the second ripple current value. The life prediction device according to claim 1 or 2, which specifies a measured value. An air conditioning system comprising the life prediction device according to any one of claims 1 to 3. Estimating the lifespan of an electrolytic capacitor that smoothes the DC power and is installed between a rectifier that converts AC power from a commercial power source into DC power and an inverter that converts the DC power into AC power for driving a motor. A method,
measuring a first ripple current input to the electrolytic capacitor from the rectifier side;
measuring a second ripple current input to the electrolytic capacitor from the inverter side;
calculating a total ripple current input to the electrolytic capacitor based on the measured value of the first ripple current and the measured value of the second ripple current;
calculating the lifespan of the electrolytic capacitor by substituting the calculated value of the total ripple current into a predetermined lifespan calculation formula;
has
In the step of measuring the first ripple current, the first ripple current is obtained through a first current sensor provided between the rectifier and a reactor connected upstream of the electrolytic capacitor.
Lifespan prediction method. Estimating the lifespan of an electrolytic capacitor that smoothes the DC power and is installed between a rectifier that converts AC power from a commercial power source into DC power and an inverter that converts the DC power into AC power for driving a motor. to the computer,
measuring a first ripple current input to the electrolytic capacitor from the rectifier side;
measuring a second ripple current input to the electrolytic capacitor from the inverter side;
calculating a total ripple current input to the electrolytic capacitor based on the measured value of the first ripple current and the measured value of the second ripple current;
calculating the lifespan of the electrolytic capacitor by substituting the calculated value of the total ripple current into a predetermined lifespan calculation formula;
A program that executes
In the step of measuring the first ripple current, the first ripple current is obtained through a first current sensor provided between the rectifier and a reactor connected upstream of the electrolytic capacitor.
program.

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