JP2018157636A - Power conversion control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To urge a user to exchange an electrolytic capacitor at an appropriate time point by accurately grasping timing in which the electrolytic capacitor should be exchanged.SOLUTION: A power conversion control device 10 comprises: an electrostatic capacity calculation unit 11 configured to calculate electrostatic capacity of an electrolytic capacitor 21 from a current flowing to the electrolytic capacitor 21 and a terminal voltage applied to the electrolytic capacitor 21; and a lifetime judging unit 12 by which, at a time point when the electrostatic capacity becomes smaller than a specific value, it is judged that the lifetime of the electrolytic capacitor 21 is exhausted.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power conversion control device that transmits and receives power to and from an electrolytic capacitor, and particularly relates to a life determination of the electrolytic capacitor.

  2. Description of the Related Art Conventionally, a power conversion device including an electrolytic capacitor and a power converter that performs power conversion using a voltage-type PWM inverter or the like is widely used in railway vehicles, industrial fields, and the like. In this power conversion device, switching elements that constitute a power converter generally have a long life because they are semiconductors, while electrolytic capacitors are said to have a short life due to deterioration over time. In particular, deterioration is accelerated when the temperature of the apparatus increases by passing a high temperature or a large current. Therefore, conventionally, the lifetime of the electrolytic capacitor is calculated in advance assuming the worst state, and the replacement of the electrolytic capacitor is urged when the lifetime has elapsed.

  In Non-Patent Document 1, the replacement time of the electrolytic capacitor is assumed to be an average 12 hours of operation per day at an average ambient temperature of 35 ° C. or less. As a guideline, if the accumulated operation time exceeds 43800 hours, an alarm is used. It is described that the LED is turned on and the replacement of the electrolytic capacitor is recommended.

Toyo Electric Manufacturing Co., Ltd., “VF66B Instruction Manual”, [online], [Search February 28, 2017], Internet <URL: https://www.toyodenki.co.jp/products/download/manual/pdf /industrial/TIM002M_201611.pdf>

  However, the life time of electrolytic capacitors is set assuming the worst condition, and in most cases it is much shorter than the actual one. And there was a problem that it would be a big loss of energy. Moreover, since it needs to be replaced frequently, there is a problem that it takes time and effort for replacement.

  An object of the present invention made in view of such circumstances is to provide a power conversion control device capable of accurately grasping the timing to replace an electrolytic capacitor and prompting the replacement of the electrolytic capacitor at an appropriate time. .

  In order to solve the above problems, a power conversion control device according to the present invention is a power conversion control device that controls a power converter that exchanges power with an electrolytic capacitor, the current flowing in the electrolytic capacitor, and the A capacitance calculating unit for calculating the capacitance of the electrolytic capacitor from a terminal voltage applied to the electrolytic capacitor, and a lifetime for determining the lifetime of the electrolytic capacitor when the capacitance becomes smaller than a specified value And a determination unit.

  In order to solve the above problem, the power conversion control device according to the present invention operates the power converter so as to change the terminal voltage when the fluctuation amount of the terminal voltage of the electrolytic capacitor is smaller than a threshold value. An active power fluctuation unit is provided.

  In order to solve the above problem, the power conversion control device according to the present invention operates the power converter so as to limit the maximum value of the power when the life determination unit determines that the life of the electrolytic capacitor is reached. A power control unit is provided.

  According to the present invention, it is possible to accurately grasp the timing for replacing the electrolytic capacitor, and it is possible to replace the electrolytic capacitor at an appropriate time. Therefore, the loss of resources and energy can be greatly reduced. In general, since the exchange cycle becomes longer, the labor required for exchange can be reduced.

It is a figure which shows the structural example of the power conversion control apparatus which concerns on one Embodiment of this invention.

  Hereinafter, a power conversion control device according to an embodiment of the present invention will be described in detail with reference to FIG.

  FIG. 1 shows a configuration example of a power conversion control device according to the first embodiment of the present invention. In this example, the power conversion control device 10 is applied to a reactive power compensation system. That is, the power conversion control device 10 may be a reactive power compensation device. The power conversion control device 10 controls the power conversion device 20 connected to the power system 40 via the three-phase reactor 30.

  The power conversion device 20 includes an electrolytic capacitor 21, a power converter 22, a voltage sensor 23, and a current sensor 24.

  The electrolytic capacitor 21 is connected in parallel with the power converter 22.

  The power converter 22 has a switching element, and exchanges power with the electrolytic capacitor 21.

Voltage sensor 23 detects the terminal voltage V _C applied between the electrolytic capacitor 21 terminal, and outputs the electric power conversion control system 10.

Current sensor 24 detects a current I _C flowing through the electrolytic capacitor 21, and outputs the electric power conversion control system 10.

  The power conversion control device 10 includes a capacitance calculation unit 11, a life determination unit 12, a warning unit 13, an active power fluctuation unit 14, and a power control unit 15.

The capacitance calculating unit 11 inputs the terminal voltage V _C detected by the voltage sensor 23 and the current I _C detected by the current sensor 24, and the capacitance C of the electrolytic capacitor 21 is expressed by, for example, equation (1). ) And output to the life determination unit 12.

C = I _C / (dV _C / dt) (1)

If the power converter 20 does not include the current sensor 24, the capacitance calculation unit 11 may estimate the current I _C. For example, it is possible to estimate the current I _C from the output current of the power converter 20.

  The life determination unit 12 outputs a capacitor replacement notification for prompting replacement of the electrolytic capacitor to the warning unit 13 when the capacitance C calculated by the capacitance calculation unit 11 becomes smaller than a specified value.

  In addition, when the capacitance C calculated by the capacitance calculation unit 11 becomes smaller than a specified value, the life determination unit 12 outputs capacitance decrease information indicating that to the power control unit 15. It may be.

  When the warning unit 13 obtains the capacitor replacement notification from the life determination unit 12, the warning unit 13 issues a warning that prompts replacement of the electrolytic capacitor 21. The warning prompting the replacement of the electrolytic capacitor 21 can be performed by any method such as displaying a message on the display, turning on the LED, or generating a warning sound. The user replaces the electrolytic capacitor 21 in accordance with the warning from the warning unit 13.

Active power variation section 14 generates a active power command based on the terminal voltage V _C which is detected by the voltage sensor 23, and outputs to the power control unit 15.

When the fluctuation of the terminal voltage V _C of the electrolytic capacitor 21 detected by the voltage sensor 23 is small, as is clear from equation (1), the capacitance at the capacitance calculation unit 11 with sufficient precision It becomes impossible to calculate. Therefore, it is preferable that the active power fluctuation unit 14 operates the power converter 22 so as to intentionally vary the terminal voltage V _C when the fluctuation amount of the terminal voltage V _C is smaller than the threshold value. Specifically, the active power command is set to a value other than zero. That is, by passing a three-phase unbalanced current to actively increase the amount of variation of the terminal voltage V _C.

  Since the capacitance of the electrolytic capacitor 21 does not change suddenly, it is not necessary to perform the calculation of the capacitance of the electrolytic capacitor 21 by the capacitance calculation unit 11 as needed. Therefore, the terminal voltage Vc is intentionally changed by the active power changing unit 14 only once, for example, once a day.

  The power control unit 15 controls the power conversion device 20 in accordance with the active power command generated by the active power fluctuation unit 14. That is, a PWM signal is generated according to the active power command, and is output to the switching elements constituting the power converter 22. By performing on / off control of the switching element, it is possible to cause an effective current and a reactive current to flow through the three-phase reactor 30, and it is possible to control voltage fluctuation suppression of the power system 40 and power factor of the power system by the reactive current.

  In addition, when the power control unit 15 receives the capacitance decrease information from the life determination unit 12, the power control unit 15 operates the power converter 22 so as to limit the maximum value of power exchanged with the electrolytic capacitor 21. . Thereby, since the burden of the electrolytic capacitor 21 can be reduced, the operation of the power converter 20 can be continued until the electrolytic capacitor 21 is replaced.

As described above, the power conversion control device 10 calculates the capacitance C from the current I _C and the terminal voltage V _C of the electrolytic capacitor 21, and determines that the lifetime is reached when the capacitance C becomes smaller than the specified value. To do. As described above, since the capacitance C of the electrolytic capacitor 21 is directly obtained, it is not necessary to consider the temperature, and the life of the electrolytic capacitor 21 can be accurately determined. Therefore, it is possible to minimize the cost for replacing the electrolytic capacitor and to maintain the performance of the power conversion device 20.

Further, when the variation amount of the terminal voltage V _C of the electrolytic capacitor 21 is smaller than the threshold, the active power command may be a value other than 0. With this configuration, the capacitance C can be calculated with high accuracy even when the fluctuation of the terminal voltage V _C is small.

  Although the above embodiments have been described as representative examples, it will be apparent to those skilled in the art that many changes and substitutions can be made within the spirit and scope of the invention. Therefore, the present invention should not be construed as being limited by the above-described embodiments, and various modifications and changes can be made without departing from the scope of the claims. For example, a plurality of constituent blocks described in the embodiments can be combined into one, or one constituent block can be divided.

  In the above-described embodiment, the power converter 22 is described as a three-phase voltage source inverter. However, the power converter 22 may be a single-phase inverter or a chopper.

  According to the present invention, the electrolytic capacitor can be replaced at an appropriate timing, which is useful for controlling a power conversion device including the electrolytic capacitor.

DESCRIPTION OF SYMBOLS 10 Power conversion control apparatus 11 Capacitance calculation part 12 Life judgment part 13 Warning part 14 Active power fluctuation part 15 Power control part 20 Power converter 21 Electrolytic capacitor 22 Power converter 23 Voltage sensor 24 Current sensor 30 Three-phase reactor 40 Power system

Claims (3)

A power conversion control device that controls a power converter that exchanges power with an electrolytic capacitor,
A capacitance calculator that calculates the capacitance of the electrolytic capacitor from the current flowing through the electrolytic capacitor and the terminal voltage applied to the electrolytic capacitor;
A life determination unit that determines the life of the electrolytic capacitor when the capacitance is smaller than a specified value;
A power conversion control device comprising:   2. The power according to claim 1, further comprising an active power fluctuation unit that operates the power converter to vary the terminal voltage when the fluctuation amount of the terminal voltage of the electrolytic capacitor is smaller than a threshold value. Conversion control device. 3. The power control unit according to claim 1, further comprising: a power control unit that operates the power converter so as to limit a maximum value of the power when the life determination unit determines the life of the electrolytic capacitor. Power conversion control device.

Images