JP2010160001A - Capacitance calculator and degradation detector of main circuit capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitance calculator and a degradation detector of a main circuit capacitor which calculate a capacitance of the main circuit capacitor, and detect its degradation even when an inverter is operated. <P>SOLUTION: The capacitance calculator for calculating the capacitance of the main circuit capacitor 3 connected to the DC side of an inverter circuit 4 includes: a voltage detector 3a for detecting a voltage of the main circuit capacitor 3; a voltage change rate calculator 5 for calculating a voltage change rate of the main circuit capacitor 3 from the detected voltage; an operation timing generator 6 for outputting a calculation instruction while the voltage change rate is negative and fixed; and a capacitance calculator 7 using the voltage and the voltage change rate of the main circuit capacitor 3 and power generated from the inverter circuit 4, and calculating the capacitance of the main circuit capacitor 3 according to the calculation instruction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a capacity calculating device for a main circuit capacitor connected to a DC intermediate circuit of an inverter device, and a deterioration detecting device for detecting deterioration of the main circuit capacitor from the calculated capacitance value.

Conventionally, as a main circuit capacitor deterioration detection device, those described in Patent Document 1 and Patent Document 2 are known.
The prior art according to Patent Document 1 compares the discharge characteristics of a main circuit capacitor when it is new with the discharge characteristics of the main circuit capacitor measured each time the inverter is stopped after aged operation. The deterioration of the main circuit capacitor is detected by comparing the discharge time until the voltage reaches the attenuation tolerance.
Further, in the prior art according to Patent Document 2, the operation stop of the inverter is detected by the breaking operation of the breaker provided on the system side of the inverter, and the discharge time of the main circuit capacitor is measured. This is to detect deterioration.

JP-A-7-92212 (paragraphs [0007] to [0012], FIG. 1 and the like) JP-A-6-165523 (paragraph [0018], FIG. 1 etc.)

As described above, all the prior arts are based on the principle of measuring the discharge time of the main circuit capacitor every time the inverter stops operating.
However, there are also facilities that operate the inverter continuously for a long period of half a year or one year, and there are cases where the operation of the inverter is frequently stopped and the discharge time of the main circuit capacitor cannot be detected. If the degradation detection method according to the prior art is applied to such equipment, the main circuit capacitor may reach the end of its life and be damaged during operation of the inverter, which may cause an accident.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a main circuit capacitor capacity calculation device and a deterioration detection device which can detect deterioration of a main circuit capacitor even during operation of an inverter.

In order to solve the above-described problem, a capacity calculation apparatus according to claim 1 is a capacity calculation apparatus that calculates the capacity of a main circuit capacitor connected to the DC side of an inverter circuit.
Voltage detection means for detecting the voltage of the main circuit capacitor;
Voltage change rate calculating means for calculating a voltage change rate from the voltage of the main circuit capacitor detected by the voltage detecting means;
Calculation timing generating means for outputting a calculation command during a period in which the voltage change rate is negative and a constant value;
Capacitance calculating means for calculating the capacity of the main circuit capacitor using the voltage of the main circuit capacitor, the voltage change rate, and the generated power of the inverter circuit according to the calculation command.

  According to a second aspect of the present invention, there is provided the capacity calculation device according to the first aspect, further comprising a calculation value stabilizing unit that stabilizes the capacity calculation value calculated by the capacity calculation unit.

According to a third aspect of the present invention, there is provided a deterioration detection apparatus comprising a comparison means for comparing the output of the capacity calculation means according to the first aspect or the calculation value stabilization means according to the second aspect and a life judgment threshold value of the main circuit capacitor. ,
The comparison means outputs a deterioration detection signal of the main circuit capacitor when the output of the capacity calculation means or the calculation value stabilization means falls below the lifetime determination threshold value.

According to the present invention, the capacity of the main circuit capacitor can be obtained by the capacity calculation device even during operation of the inverter, and this capacity calculation value can be used as maintenance information.
In addition, the deterioration detection device outputs an alarm or the like when the calculated capacity value falls below a preset threshold value, so that preventive maintenance can be performed before the main circuit capacitor deteriorates and an accident such as breakage occurs. Is possible.

It is a circuit block diagram which shows 1st Embodiment of this invention. It is a circuit block diagram which shows 2nd Embodiment of this invention. It is a circuit block diagram which shows 3rd Embodiment of this invention. It is a wave form diagram which shows operation | movement of embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall circuit configuration diagram of an inverter device showing a first embodiment of the present invention. First, in the main circuit of the inverter device, 1 is an AC power source, 2 is a rectifier circuit that rectifies the AC voltage of the AC power source 1 and converts it into a DC voltage, 3 is a main circuit capacitor connected to a DC intermediate circuit, and 4 is a main circuit capacitor. An inverter circuit that converts a DC voltage smoothed by the circuit capacitor 3 into an AC voltage having an arbitrary frequency and magnitude by an on / off operation of the semiconductor switching element, and M is a load such as a motor. Incidentally, 3a is a voltage detector for detecting the voltage V _c across the main circuit capacitor 3.

Next, 20A is a capacity calculator for the main circuit capacitor.
The voltage V _c of the main circuit capacitor 3 detected by the voltage detector 3a is input to the voltage change rate calculator 5 in the capacity calculation device 20A, and the voltage change rate (dV _c / dt) of the voltage V _c is calculated. . This voltage change rate (dV _c / dt) is input to the operation timing generator 6, and the operation timing generator 6 has a period during which (dV _c / dt) is a negative value and is stable at a constant value. Detect and output calculation command. This calculation command is input to the main circuit capacitor capacity calculator 7.

Here, FIG. 4 is a waveform diagram showing the operation of the present embodiment.
In FIG. 4, a period Δt in which the voltage change rate (dV _c / dt) is negative and constant is a period during which the main circuit capacitor 3 is discharged to the load M through the inverter circuit 4, and the AC power supply 1 side This is a period during which stable calculation can be performed because there is no current flow from the terminal. On the other hand, during the period Δt ′ in which the voltage change rate (dV _c / dt) is positive, the voltage V _c varies due to the voltage variation of the AC power source 1 and the influence of the power source impedance, and the calculation accuracy is higher than that during the period Δt. May decrease.

Therefore, in the present embodiment, the capacitance C of the main circuit capacitor 3 is obtained by paying attention to the period Δt.
That is, the voltage change rate (dV _c / dt) in the period Δt is expressed by Equation 1 using the voltage V _c , the generated power P of the inverter circuit 4 and the capacitance C of the main circuit capacitor 3.

  When Formula 1 is solved for the capacity C, Formula 2 is obtained.

The main circuit capacitor capacity calculator 7 in FIG. 1 uses dV _c / dt (= V _c ′), the voltage V _c and the generated power P of the inverter circuit 4 in accordance with a calculation command from the calculation timing generator 6. The capacitance C of the main circuit capacitor 3 is calculated by Equation 2.
The generated power P is calculated by the inverter power calculator 8 and is a value obtained by adding the power consumption of the load M and the internal power consumption of the inverter circuit 4. When the internal power consumption of the inverter circuit 4 is negligible compared to the power consumption of the load M, the generated power P may be calculated using only the power consumption of the load M.

As described above, in this embodiment, the capacity C of the main circuit capacitor 3 can be calculated while the inverter circuit 4 is operated. Since it is well known that the capacity decreases when the capacitor deteriorates, according to the present embodiment, the main circuit capacitor capacity calculator 7 displays the capacity calculation value and uses it as maintenance information. If the capacitor 3 is replaced before reaching the end of its life, accidents such as breakage can be prevented.
Therefore, there is no inconvenience that the main circuit capacitor 3 is overlooked and is damaged during the operation of the inverter device as in the prior art.

Next, FIG. 2 is an overall circuit configuration diagram of an inverter device showing a second embodiment of the present invention.
The capacity calculation device 20B of this embodiment inputs the capacity calculation value of the main circuit capacitor 3 in the first embodiment to a first-order lag filter calculator 9 as a calculation value stabilization means, and outputs the output as a final capacity. It is configured to output as a calculated value. The calculation command in the period Δt shown in FIG. 4 is also input to the first-order lag filter calculator 9.

  In the present embodiment, even when the capacity calculation value of the main circuit capacitor 3 fluctuates due to a transient load fluctuation, a stable capacity calculation value can be obtained by passing through the primary delay filter calculator 9. Although not shown in the drawing, as the calculation value stabilizing means, a calculator for obtaining a moving average of the capacitance calculation values may be provided in place of the primary delay filter calculator 9.

Next, FIG. 3 is an overall circuit configuration diagram of an inverter device showing a third embodiment of the present invention.
In FIG. 3, reference numeral 20 </ b> C denotes a deterioration detection device, which is a capacity at which the output of the first-order lag filter calculator 9 in the second embodiment is input to the comparator 10 and it is determined that the main circuit capacitor 3 has reached the end of its life. Compared with the life judgment threshold value 11, when the capacity calculation value falls below the life judgment threshold value 11, a deterioration detection signal is output to notify that the main circuit capacitor 3 has reached the life. The deterioration detection signal is used for generating an alarm.
Here, as a configuration of the deterioration detection device 20C, the capacity calculation value in the first embodiment may be directly input to the comparator 10 and compared with the life determination threshold value 11 to obtain a deterioration detection signal.

1: AC power supply 2: Rectifier circuit 3: Main circuit capacitor 3a: Voltage detector 4: Inverter circuit 5: Voltage change rate calculator 6: Calculation timing generator 7: Main circuit capacitor capacity calculator 8: Inverter power calculator 9 1st order lag filter computing unit 10: Comparator 11: Life judgment threshold 20A, 20B: Capacity computing device 20C: Degradation detecting device M: Load

Claims (3)

In the capacity calculation device that calculates the capacity of the main circuit capacitor connected to the DC side of the inverter circuit,
Voltage detection means for detecting the voltage of the main circuit capacitor;
Voltage change rate calculating means for calculating a voltage change rate from the voltage of the main circuit capacitor detected by the voltage detecting means;
Calculation timing generating means for outputting a calculation command during a period in which the voltage change rate is negative and a constant value;
Capacitance calculating means for calculating the capacity of the main circuit capacitor using the voltage of the main circuit capacitor, the voltage change rate, and the generated power of the inverter circuit according to the calculation command;
A capacity calculation device for a main circuit capacitor. The capacity calculation apparatus according to claim 1,
An apparatus for calculating a capacity of a main circuit capacitor, comprising: an operation value stabilizing means for stabilizing an operation value calculated by the capacity operation means. Comparing means for comparing the output of the capacity calculating means according to claim 1 or the calculated value stabilizing means according to claim 2 and a life judgment threshold value of the main circuit capacitor;
The comparison means outputs a deterioration detection signal of the main circuit capacitor when the output of the capacity calculation means or the calculation value stabilization means falls below the lifetime judgment threshold value. apparatus.

Images