JPH0591754A - Protecting method for inverter device against overvoltage - Google Patents

Abstract

PURPOSE:To avoid an overvoltage protecting operation for a temporary overvoltage state of a device DC intermediate voltage when an inverter device is energized by a power source. CONSTITUTION:When an inverter device having an AC input rectifier, a smoothing capacitor, an inverter and a damper having a switching element and a damping resistor is energized by a power source, if an overvoltage state of a device DC intermediate voltage occurs, a predetermined overvoltage protecting operation is not immediately conducted, but an intermediate voltage dropping state after a predetermined time is decided while operating the damper, etc. If the overvoltage state is eliminated at the time of deciding or the reducing gradient of the intermediate voltage is compared with a reducing gradient corresponding to a time constant to be decided according to the load condition of a DC intermediate circuit of the device while similarly operating the damper so that the gradient of the former is larger than that of the latter, the overvoltage state is decided to be temporary, and the predetermined overvoltage protecting operation is not conducted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overvoltage protection method for an inverter device for temporarily avoiding an overvoltage protection operation under a transient overvoltage condition when the power is turned on.

[0002]

2. Description of the Related Art As a conventional overvoltage protection method for this type of inverter device, it is detected that the DC intermediate voltage of the inverter device, that is, the terminal voltage of a smoothing capacitor in the device exceeds a predetermined value. It is known that when the overvoltage relay means is operated, a predetermined overvoltage protection operation such as operation stop of the inverter device is immediately performed by the output signal thereof.

[0003]

When the AC power supply of the inverter device as described above is turned on, the total inductance on the input power supply side of the device, the electrostatic capacitance of the smoothing capacitor, and the parallel connection to the capacitor at the time of turning on the power supply. Depending on the mutual numerical relationship with the equivalent resistance of the load that consumes and consumes electric power, the terminal voltage of the capacitor, that is, the DC intermediate voltage, may abnormally increase due to the rapid rising of the capacitor due to the rising speed according to the three values. There is.

In this case, the charging of the capacitor from the side of the AC power supply after the time point when the maximum charging state is reached is cut off, and the accumulated charge is discharged and consumed through the load parallel to the capacitor, Therefore, the DC intermediate voltage is attenuated according to the time constant given by the product of the electrostatic capacity of the capacitor and the equivalent resistance of the load from the value corresponding to the maximum state of charge of the capacitor. For this reason, the DC intermediate voltage transiently exceeds the overvoltage determination level during the transition from the initial rise to the attenuation.

However, in the conventional overvoltage protection method as described above, it should be asked whether the cause of the abnormal occurrence of the DC intermediate voltage rises, and therefore whether the abnormal rise is continuous or transient. As soon as it is detected that the DC intermediate voltage exceeds the predetermined value, a predetermined overvoltage protection operation such as operation stop of the inverter device is started, and a transient DC intermediate voltage when the power is turned on. Due to the occurrence of the voltage overvoltage state, the inverter device may not be able to shift to its normal inverter operation.

In view of the above, the present invention, when an overvoltage state occurs when the power of the inverter device is turned on, determines the nature of the overvoltage state and can avoid the unnecessary stoppage of the operation of the inverter device. It is intended to provide a method.

[0007]

In order to achieve the above object, an overvoltage protection method for an inverter device according to the present invention comprises an AC input rectifying section, a smoothing capacitor for the output rectified voltage of the rectifying section, An inverter unit that receives a smoothed rectified voltage as an input and outputs a desired AC; a braking unit that has a braking resistor and a switching element connected in series to the resistor and that is connected in parallel to the capacitor; A method for overvoltage protection of an inverter device, which is directed to a DC intermediate voltage in the inverter device, that is, a terminal voltage of the capacitor, wherein the inverter unit is activated when the power of the inverter device is turned on. If the DC intermediate voltage is in the overvoltage state and the overvoltage relay section having the intermediate voltage as the detection input outputs the overvoltage protection signal, The predetermined overvoltage protection operation for the inverter device is temporarily stopped for a predetermined time from the time when the protection signal is generated, and when the protection signal is still output after the predetermined time has elapsed, the predetermined overvoltage protection operation is performed. If the protection signal disappears within the predetermined time, on the other hand, the normal inverter operation is started immediately after the disappearance of the protection signal. Further, within the predetermined time, the switching element in the braking unit is operated. To discharge the accumulated charge of the capacitor through the braking resistor, or to replace the operation of the braking portion with a bridge structure to form the whole of the upper arm or the lower arm of the inverter. The switching element is caused to conduct so as to reduce the DC intermediate voltage, or, similarly to the above, the overvoltage relay section outputs the overvoltage protection signal. If you force,
The predetermined overvoltage protection operation for the inverter device by the protection signal is temporarily stopped and the temporal fluctuation state of the DC intermediate voltage is confirmed, and the intermediate voltage tends to decrease, and the decrease gradient is the intermediate voltage. Time constant given by the product of the equivalent resistance equivalent to the sum of various electric powers such as the control electric power excluding the AC output power of the inverter part in the electric power consumed as the input and the electrostatic capacitance of the smoothing capacitor. If it is equal to or greater than the decreasing gradient according to the above, the temporary stop of the overvoltage protection operation is released to shift to the normal inverter operation, while if it is less, the predetermined overvoltage protection operation is performed. Further, in this case, with the generation of the overvoltage protection signal, the switching element in the braking unit is made conductive, and the power consumption in the braking resistor is changed to various powers such as the control power. Either by addition to the sum, or by the same inverter - motor unit each A - made to perform a connection operation for the arm and attempt to increase the decreasing gradient of the intermediate voltage.

[0008]

When an AC power supply voltage is applied to the inverter device having the above-mentioned structure before the start of the inverter operation, the terminal voltage of the rectified voltage smoothing capacitor of the DC intermediate circuit of the apparatus is the rated value of the terminal voltage. A value larger than the value is rapidly increased as the final value and then the final value is maintained thereafter, or after the maximum value larger than the rated value is rapidly reached, the capacitance of the smoothing capacitor and the power source are increased. The terminal voltage of the capacitor is attenuated to a rectified DC voltage value of the AC power supply voltage which is a steady value according to a time constant given as a product with a resistance value corresponding to power consumption of the power supply when the voltage is applied, or In addition, either the constant value or the uniform increase without excessive increase is followed. In addition, the temporal voltage rise rate and the final value or the maximum value of the terminal voltage in each of the respective passages are the total inductance of the AC input side of the inverter device, the capacitance of the capacitor, and the terminal voltage of the capacitor. It is determined according to the resistance value corresponding to the total power consumption of the loads other than the inverter main circuit load among the loads used as the power source and the value of the AC power supply voltage.

As described above, when the AC power supply voltage is applied to the inverter device before the start of the inverter operation, if the fluctuation of the capacitor terminal voltage is referred to the overvoltage protection level, the overvoltage protection level is set. The first case in which the overvoltage protection state continues, and the second case in which the overvoltage protection level is temporarily exceeded but is thereafter attenuated below the protection level according to the time constant of the smoothing capacitor and its load circuit. Can be roughly divided into Here, the first case corresponds to a case where the abnormal increase state of the AC power supply voltage continues and is a state to be the target of the overvoltage protection, and the second case has the power supply voltage. The abnormal rising state of 1 is transient, and unless the overvoltage state becomes extremely abnormal, the start of the overvoltage protection operation should be waited for a certain time.

According to the above, according to the present invention, when an AC power supply voltage is applied to the inverter device before the start of the inverter operation, if an overvoltage protection signal targeting the capacitor terminal voltage is issued, an overvoltage state confirmation is performed. In order to absorb the regenerative electric power from the load induction motor of the inverter device, the braking is waited for a certain period of time before the start of the overvoltage protection operation by the protection signal, and is parallel to the capacitor within the certain period of time. When the terminal voltage drops below the overvoltage protection level within the certain time by attempting to operate the section to discharge the accumulated charge of the capacitor through the braking resistance, etc. −
If the terminal voltage is still at or above the overvoltage protection level after the elapse of the certain time, the overvoltage state is determined to be due to a continuous abnormal increase in the AC power supply voltage, and a predetermined overvoltage protection operation is performed. Alternatively, or with the suspension of the overvoltage protection operation as described above,
Confirming the time-varying state of the DC intermediate voltage, the intermediate voltage tends to decrease and the decreasing gradient excludes the AC output power of the inverter part in the power consumed with the intermediate voltage as an input. When the value is equal to or greater than the decreasing gradient according to the time constant given by the product of the equivalent resistance corresponding to the sum of various electric power such as control power and the electrostatic capacitance of the smoothing capacitor, the overvoltage protection operation is performed. Is canceled to shift to the normal inverter operation, and when it is smaller, the predetermined overvoltage protection operation is performed. Further, in this case, the decreasing gradient is performed by operating the braking unit. Is intended to increase.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A flow chart of FIG. 1 showing a first example of the embodiment of the present invention, a flow chart of FIG. 2 showing a second example thereof, and an inverter shown in FIG. And a block circuit diagram of the device. First, in FIG. 3, 1 is a rectifier for rectifying, for example, a three-phase AC input, 2 is a smoothing capacitor for the rectified voltage output from the rectifier, 3 is a braking resistor, a transistor connected in series to the resistor, and the like. And a switching element 4 connected in parallel to the capacitor 2 having a switching element of the above-mentioned type and a switching element such as a transistor having an anti-parallel diode as an arm element of the bridge structure. An inverter section 5 for receiving the rectified voltage and converting and outputting it into a desired three-phase AC, for example, is an intermediate voltage detecting circuit for detecting the terminal voltage of the capacitor 2, that is, the DC intermediate voltage of the inverter device. Reference numeral 6 denotes a control circuit for the entire inverter device, which receives a detection signal of the intermediate voltage by the voltage detection circuit 5 and detects an overvoltage state of the intermediate voltage when the AC power supply voltage is applied or when the load regenerative power is absorbed. It has a function of an overvoltage relay section for performing the processing, and also performs various calculations for creating a required alternating current output from the inverter section 4. Further, 7 is a braking unit drive circuit which receives a command signal from the control circuit 6 and outputs an opening / closing command signal to the switching element of the braking unit 3, and 8 is an inverter unit 4 which receives a command signal from the control circuit 6. Is a base drive circuit for outputting an opening / closing command signal to the switching element of each arm, and the above-mentioned elements constitute the inverter device.

Next, FIGS. 1 and 2 show the protection operation when the intermediate voltage is in an overvoltage state even when the inverter unit is not operated when the power of the inverter device is turned on. It shows the flow chart,
The contents processed by the overvoltage relay function in the control circuit 6 are shown. First, in FIG. 1, it is determined whether or not the intermediate voltage is in the overvoltage state in the "overvoltage?" Step, and if it is in the overvoltage state (Y: YES), N (NO) in the next "time UP?" Step. And the next step "overvoltage reset" step, the above-mentioned overvoltage protection operation is temporarily stopped for a predetermined time from the point of occurrence of the overvoltage state, and the "brake circuit ON" step is entered to switch elements of the braking unit 3. Is conducted to accelerate the reduction of the intermediate voltage by continuing to consume power in the braking resistor, and then the above operations are circulated within the predetermined time, and the overvoltage state is eliminated during the circulation. In other words, if the result of the above-mentioned "overvoltage?" Step judgment is N (NO), the above-mentioned temporary stop of the overvoltage protection operation is released and the "normal operation" -Up in the usual inverter - to shift the data operation, or also if also continue the overvoltage condition after elapse of the predetermined time, that is, the Y in step "Time UP?"
If the determination result is (YES), it is determined that there is a continuous overvoltage state on the AC power source side of the inverter device, and a predetermined overvoltage protection operation is performed in the "protection operation" step.

Next, in FIG. 2, in each step of "overvoltage?", "Overvoltage reset", and "braking circuit ON", the same operation as in FIG. 1 is performed, and the reduction gradient of the intermediate voltage is changed. The judgment result in the next step "current voltage value-previous voltage value: decrease value due to time constant" is negative, that is, the AC power supply voltage is in an overvoltage state and exceeds the power consumption by the braking resistor or the like. When the supply is continuously performed from the AC power supply side, a predetermined overvoltage protection operation is performed in the "protection operation" step, and the determination result is positive or zero, that is, the increase of the AC power supply voltage is transient. If the power is not continuously supplied from the AC power supply side, the temporary stop of the overvoltage protection operation is canceled and the normal inverter is operated in the “normal operation” step. It is intended to transition to work.

[0014]

According to the present invention, an AC input rectifying section,
An inverter device comprising a rectified voltage smoothing capacitor, an inverter unit, a braking unit having a braking resistor and a switching element connected in series to the resistor, and connected in parallel to the capacitor. When the power supply of the inverter device is turned on, a predetermined overvoltage is immediately generated when the terminal voltage of the capacitor, that is, the DC intermediate voltage of the device is in the overvoltage state even though the inverter unit is not operated. The overvoltage state is maintained without performing a protective operation by determining the voltage drop state after a certain period of time accompanying the operation of the braking unit or the like, or by comparing the voltage decrease gradients associated with the operation of the braking unit or the like. By determining the personality of a transient type or a transient type, it is possible to detect a transient type when an overvoltage state occurs when the power of the inverter device is turned on as described above. The situation of the device operation stop of use can be easily avoided, the inverter - it is possible to improve the reliability of operation of the motor device.

[Brief description of drawings]

FIG. 1 is a flow chart showing a first embodiment of the present invention.

FIG. 2 is a flow chart showing a second embodiment of the present invention.

FIG. 3 is a block circuit diagram of an inverter device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rectification part 2 Smoothing capacitor 3 Braking part 4 Inverter part 5 Intermediate voltage detection circuit 6 Control circuit 7 Braking part drive circuit 8 Base drive circuit

Claims (6)

[Claims] 1. An AC input rectifying unit, a smoothing capacitor for the output rectified voltage of the rectifying unit, an inverter unit for inputting the smoothed rectified voltage and outputting a desired AC, a braking resistor, and An inverter device for a DC intermediate voltage, that is, a terminal voltage of the capacitor, in an inverter device having a switching element connected in series to a resistor and connected in parallel to the capacitor. The overvoltage protection method of claim 1, wherein the DC intermediate voltage is in an overvoltage state even when the inverter unit is not operated when the power of the inverter device is turned on. When the electric power unit outputs the overvoltage protection signal, a predetermined overvoltage protection operation for the inverter device by the protection signal is carried out for a predetermined time from the time when the protection signal is generated. If the protection signal is paused and the protection signal is still output after the predetermined time has elapsed, the predetermined overvoltage protection operation is performed, while if the protection signal disappears within the predetermined time, Immediately the normal inverter
A method for overvoltage protection of an inverter device, characterized by shifting to an inverter operation. 2. The overvoltage protection method for an inverter device according to claim 1, wherein the switching element in the braking section is made conductive within the predetermined time when the overvoltage protection signal is generated, and the switching resistor is connected via the braking resistor. An overvoltage protection method for an inverter device, characterized in that the stored intermediate charge is discharged to reduce the DC intermediate voltage. 3. The overvoltage protection method for an inverter device according to claim 2, wherein the upper part of the inverter part forming a bridge structure is replaced with the actuation of the braking part by the conduction of the switching element in the overvoltage state. A method for overvoltage protection of an inverter device, characterized in that all switching elements in either the arm or the lower arm are conducted. 4. An AC input rectifying section, a smoothing capacitor for the output rectified voltage of the rectifying section, an inverter section for inputting the smoothed rectified voltage and outputting a desired AC, a braking resistor, and An inverter device for a DC intermediate voltage, that is, a terminal voltage of the capacitor, in an inverter device having a switching element connected in series to a resistor and connected in parallel to the capacitor. The overvoltage protection method of claim 1, wherein the DC intermediate voltage is in an overvoltage state even when the inverter unit is not operated when the power of the inverter device is turned on, and the intermediate voltage is used as a detection input. When the electric power unit outputs the overvoltage protection signal, the predetermined overvoltage protection operation for the inverter device by the protection signal is temporarily stopped and the time of the DC intermediate voltage is increased. After confirming the fluctuation state, the intermediate voltage tends to decrease and the decreasing gradient of the various kinds of electric power such as the control power other than the inverter AC output power among the various electric power consumed by inputting the intermediate voltage. If it is equal to or greater than the decreasing slope according to the time constant given by the product of the equivalent resistance equivalent to the sum and the electrostatic capacitance of the smoothing capacitor, the temporary stop of the overvoltage protection operation is canceled. The inverter is characterized in that it shifts to a normal inverter operation, and on the other hand, if it becomes smaller, the predetermined overvoltage protection operation is performed.
Overvoltage protection method for power supply equipment. 5. The overvoltage protection method for an inverter device according to claim 4, wherein at the same time as the generation of the overvoltage protection signal, a switching element in the braking section is rendered conductive to reduce the power consumption in the braking resistor to various powers such as the control power. To increase the decrease gradient of the intermediate voltage, the overvoltage protection method for the inverter device. 6. An overvoltage protection method for an inverter device according to claim 5, wherein in place of the operation of said braking portion due to conduction of its switching element in the above-mentioned overvoltage state, an upper gate of said inverter portion forming a bridge structure. A method for overvoltage protection of an inverter device, characterized in that all switching elements in either the arm or the lower arm are conducted.