JP2737262B2 - Control method of regenerative power discharge transistor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a method for controlling a discharge transistor in a regenerative power discharge circuit of a voltage type inverter having a regenerative braking function for a load AC motor.

[Conventional technology]

As a method of controlling a discharging transistor in a conventional regenerative power discharge circuit of this type, a terminal voltage of a DC intermediate circuit output side smoothing capacitor which is boosted in accordance with a regenerative power amount at the time of braking a load motor of a voltage type inverter is set to a predetermined value. It is known that the discharge transistor is continuously turned on or off in accordance with both the larger and smaller states. In other words, the regenerative electric power in which the terminal voltage of the smoothing capacitor is increased in the discharging resistor connected in series to the transistor by the conduction operation of the transistor is continuously consumed to restore the capacitor terminal voltage to the original. is there.

[Problems to be solved by the invention]

However, the conduction control of the transistor for regenerative power discharge in the conventional method as described above is based on the result of the voltage comparison as to whether the terminal voltage of the smoothing capacitor is greater than the set value or not, as the only condition. The resistance value of the discharge resistor during the conduction control period is constant, and therefore, whether the resistance value is a value suitable for consuming the regenerative electric energy during the motor braking within the required braking time There is no restriction from both the resistance value compatibility and the capacity compatibility of whether or not the power consumption at the resistance value is within the allowable applied power amount corresponding to the short-time allowable loss characteristic of the discharge resistor itself. Therefore, when the resistance value of the discharge resistor becomes inappropriately large, the shortage of the power consumption leads to a further rise in the voltage of the capacitor terminal, and the shortage of the resistance value causes the power consumption of the capacitor to decrease. The discharge resistor when the amount exceeds the allowable applied power amount leads to burnout.

In view of the above, it is an object of the present invention to provide a regenerative motor that enables a stable inverter operation by variably controlling an equivalent discharge resistance value so as to optimize a capacitor terminal voltage increase during the motor braking and optimize power consumption at the discharge resistor. It is an object of the present invention to provide a method for controlling a power discharging transistor.

[Means for solving the problem]

In order to achieve the above object, a method of controlling a transistor for regenerative power discharge of the present invention includes a regenerative power discharge circuit connected to a DC intermediate circuit output side smoothing capacitor of a voltage source inverter in parallel when braking a load motor of the inverter. A method for controlling a discharging transistor in a series circuit of a regenerative power discharging resistor and a transistor, the voltage detecting unit detecting a terminal voltage of the smoothing capacitor,
Setting means for setting various data of the resistance value of the resistor, the repetitive allowable loss characteristic and the short-time allowable loss characteristic, wherein when the terminal voltage of the smoothing capacitor becomes larger than the set value, the various data and The smoothing capacitor terminal voltage value and the required deceleration time are input, and the duty ratio of the transistor is calculated such that the rising value of the smoothing capacitor terminal voltage is within the set value and the resistance loss is within the allowable loss. According to the result of the operation, the transistor is controlled to be turned on / off.

[Action]

At the time of deceleration braking of the motor in the series configuration of the DC intermediate circuit output side smoothing capacitor, the voltage source inverter and its load AC motor, the motor operates as an AC generator and the direction of power flow in the series configuration is reversed, The rotational energy of the motor corresponding to the rotational speed deceleration amount is regenerated as an inflow current to the smoothing capacitor, and the terminal voltage is increased as a value proportional to a time integrated value of the inflow current. Therefore, the terminal voltage rise changes according to the amount of regenerative electric power from the electric motor at the time of deceleration, and the voltage rise ends with the end of power regeneration due to the completion of deceleration.

Therefore, if a variable resistor circuit is connected in parallel to the smoothing capacitor, and if the resistance value is changed in accordance with the deceleration pattern of the motor and power consumption corresponding to the regenerative power is performed, the smoothing capacitor is used. Of the terminal voltage can be appropriately suppressed.

The general in the series circuit of the resistance value of the resistor and the switching element R _0, if the OFF period of the switching element and the ON period and t ₁ was intermittently controlled at t ₂ become conduction ratio alpha, the series circuit Is the equivalent resistance R _e given by the following equation (1)
Can be regarded as a variable resistance circuit having

Therefore, the average power consumed in the above variable resistor circuit
P _av and the power consumption WH _av in the period T becomes as the following equation to the applied voltage of the variable resistance circuit as V _c (2).

Thus connecting the variable resistor circuit in parallel with the smoothing capacitor, when the deceleration time of formula (2) and the voltage V _c at the integration time T and the terminal voltage of each smoothing capacitor the electric motor is pressurized in accordance with the regenerated electric energy so that the voltage V _c changes according to the difference between the power consumption WH _av consumed by the terminal voltage rise value of the smoothing capacitor and a variable resistor that. Therefore, the conduction ratio α is adjusted to make the difference power amount between the regenerative power amount and the power consumption amount WH _av at the elapse of the time T zero, that is, the terminal voltage rise value of the smoothing capacitor is changed by the variable resistor. As a result, it is possible to suppress an increase in the voltage of the smoothing capacitor terminal during the deceleration of the electric motor, and to make the voltage zero when the deceleration is completed.

Further, the resistance of the resistor is such that the smaller the resistance value, the larger the power consumption becomes, and the resistance becomes suitable for power consumption as described above.
On the other hand, the power applied to the resistor and the duration thereof are restricted by a repetitive allowable loss characteristic or a short-time allowable loss characteristic determined by the heat resistance characteristic of the resistor. Therefore, for a resistor used in the variable resistor circuit as described above and having a small resistance value in order to widen the variable resistance range of the resistor circuit, the duty ratio control focusing only on the suppression of the rise of the capacitor terminal voltage as described above. Performing the above operation may cause a risk of resistance burnout, and accordingly, it may be necessary to correct the conduction ratio determined from the terminal voltage rise suppression surface in accordance with the two allowable loss characteristics.

The present invention relates to the suppression of the rise of the terminal voltage started after the rise time of the capacitor terminal voltage is equal to or more than a predetermined value,
From the deceleration amount of the electric motor, the required deceleration time, and the capacitor terminal voltage, an optimum duty ratio for suppressing the rise of the terminal voltage is calculated, and if necessary, the duty ratio is set to the repetitive allowable loss characteristic of the resistor and the short-time. Based on the allowable loss characteristics, the microcomputer circuit performs a duty ratio designating operation that corrects the condition that the resistance is within the allowable loss of the resistor. It is possible to reduce the required capacity of the resistor by application.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

In Figure 1, 1 is a rectifier for rectifying the AC power supply voltage, C _f capacitor for output smoothing the rectifier, 2 denotes a voltage-source inverter, the 3 is an AC motor as a load of the inverter, the rectifier 1 And the smoothing capacitor C _f form a DC intermediate circuit of the inverter 2.
The terminal voltage V _c of the capacitor C _f is during deceleration braking becomes a rated value corresponding to the AC power supply voltage the electric motor 3 at the time of steady boosts receives the regenerative power.

Next, R _d is a discharging resistor for the regenerative power stored in the capacitor, T _d is a discharging transistor that performs switching operation at the calculated duty ratio α, and the transistor T _d and the resistor R _d Form a variable resistance circuit, and its equivalent resistance and average power consumption change in accordance with the conduction ratio α.

Furthermore, 4 and outputs a difference voltage between a predetermined voltage for the voltage rise and the detection is a circuit the terminal voltage V _c suppression operation start time determination of the capacitor terminal voltage V _c, the resistance 5 R _d A setting circuit for providing various data such as the resistance value of the resistor and the repetitive permissible loss characteristic and short-term permissible loss characteristic thereof to the microcomputer circuit 6. The transistor T _{d is provided in} accordance with the conduction ratio α calculated by the microcomputer circuit 6. Is a base drive circuit that outputs a control signal for

The microcomputer circuit 6 receives various data from the voltage detection circuit 4 and the setting circuit 5 and further various data such as a deceleration amount and a required deceleration time during the motor braking, and a capacitor terminal during the motor braking. the resistor R _d in suppressing and its operational duty ratio to increase value to the within a predetermined value of the voltage V _c
The duty ratio α that satisfies various conditions such as that the loss of the resistor is within the allowable loss of the resistor is calculated to control the discharge transistor _Td .

〔The invention's effect〕

According to the present invention, it relates to control of a discharging transistor in a regenerative power discharge circuit of a voltage type inverter having a regenerative braking function for the load AC motor, and suppresses a rise in a terminal voltage of a smoothing capacitor on the inverter input side to an appropriate value. The microcomputer circuit calculates a duty ratio at which the power consumption of the regenerative power discharge resistor at the calculated duty ratio can be within the allowable value, and performs switching control of the discharge transistor based on the calculated duty ratio, thereby obtaining Moderate suppression of the capacitor terminal voltage and prevention of burnout of the discharge resistor at the time of braking of the motor can be reliably performed, and the capacity of the resistor is reduced by effective use of the capacity of the resistor, and stable operation of the inverter is achieved. be able to.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. 1 rectifier, 2 (voltage-type) inverter, 3 AC motor, 4 voltage detection circuit, 5 setting circuit, 6
... microcomputer circuit, 7 ... base drive circuit, C _f ... smoothing capacitor, R _d ... discharge resistor, T _d ... discharge transistor.

Claims (1)

(57) [Claims] 1. A series circuit of a resistor and a transistor for regenerative power discharge connected in parallel to a DC intermediate circuit output side smoothing capacitor of a voltage type inverter and constituting a regenerative power discharge circuit for braking a load motor of the inverter. A method of controlling a discharging transistor, comprising: voltage detecting means for detecting a terminal voltage of the smoothing capacitor; and setting means for setting various data of a resistance value of the resistor, a repetitive allowable loss characteristic and a short-time allowable loss characteristic. When the terminal voltage of the smoothing capacitor is larger than the set value, the data, the smoothing capacitor terminal voltage value and the required deceleration time are input, and the rising value of the smoothing capacitor terminal voltage is set to the set value. The duty ratio of the transistor is calculated so that the resistance is within the allowable loss and the resistance loss is within the allowable loss. Control method for regenerative power discharging transistor, which comprises conductive or shut off control Njisuta.