JP2022174416A - Control device and control method - Google Patents

Abstract

To provide a control device and a control method capable of further enhancing the stability of current control during braking of an electric motor.SOLUTION: A control device is equipped with a current control unit and a braking control unit. The current control unit controls the magnitude of current flowing in windings of a motor by means of current control using a current feedback value for a detected value of the current flowing in the windings of the motor and a current reference, which is an index of a control target for the magnitude of the current flowing in the windings of the motor. The braking control unit outputs a braking command for braking control of the electric motor. In response to the output of the braking control command, the current control unit switches the control gain of the current control from a first gain for driving the motor to a second gain for braking the motor.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD Embodiments of the present invention relate to a control device and a control method.

In a ship driven by an electric propulsion device, a control device of the electric propulsion device controls an electric motor via a power converter, and the power generated by the electric motor is used as thrust for the ship. The control device uses the braking force of the electric motor to slow down or stop the ship. However, when the motor is braked, the magnitude of the current flowing through the windings of the motor changes oscillatingly, and an overvoltage exceeding the allowable value is applied to the DC link that connects the converter and the inverter in the power converter while the motor is being braked. This could trigger a protection circuit and stop the electric propulsion system.

Japanese Patent Application Laid-Open No. 2008-022660

The problem to be solved by the present invention is to provide a control device and a control method that can further improve the stability of current control during braking of an electric motor.

A control device according to an embodiment includes a current control section and a braking control section. The current control unit performs current control using a current feedback value for a detected value of the current flowing through the windings of the motor and a current reference that is an index of a control target for the magnitude of the current flowing through the windings of the motor. Control the magnitude of the current flowing through the windings of the motor. The braking control unit outputs a braking command for braking control of the electric motor. The current control unit changes the control gain of the current control from a first gain during driving for driving the electric motor to a second gain during braking for braking the electric motor, according to the output of the braking control command. switch.

The block diagram of the control apparatus of the electric propulsion apparatus which concerns on embodiment. FIG. 3 is a configuration diagram of a current control unit according to the embodiment; FIG. 2B is an equivalent circuit diagram of the current controller shown in FIG. 2A; FIG. 4 is a diagram for explaining the gain of the current control section of the embodiment; 4 is a flowchart related to braking control according to the embodiment;

Hereinafter, a control device and a control method according to embodiments will be described with reference to the drawings. In addition, in the following description, the same code|symbol is attached|subjected to the structure which has the same or similar function. Duplicate descriptions of those configurations may be omitted. It should be noted that being electrically connected is sometimes simply referred to as being “connected”. In the following description, "perpendicular" includes substantially perpendicular. It should be noted that the case of "having the same size" includes the case of being substantially the same.

FIG. 1 is a configuration diagram of a control device for an electric propulsion device according to an embodiment.
FIG. 1 shows a generator 2 , a power converter 3 , a thruster 4 and a control device 5 forming an electric propulsion device 1 .

The generator 2 supplies the generated AC power from the output of the generator 2 to the power converter 3 . The power converter 3 converts the AC power supplied from the generator 2 and uses it to drive the AC motor 4 a in the propeller 4 . A propeller 4b connected to the output shaft of the AC motor 4a rolls according to the rotation of the output shaft of the AC motor 4a. The AC motor 4a is, for example, an induction motor.

The power converter 3 includes, for example, a transformer 3a, a converter 3b, and an inverter 3c. The power converter 3 converts the AC power received via the transformer 3a into DC power by the converter 3b, and further converts it into AC power of the voltage and frequency required for speed control of the AC motor 4a by the inverter 3c. A connection between the converter 3b and the inverter 3c is called a DC link. The inverter 3 c is configured by, for example, bridge-connecting a plurality of switching elements (not shown). The inverter 3c may be a two-level inverter or a three-level inverter. This embodiment can be applied regardless of the type of inverter.

The output current of the inverter 3c is detected by a current detector 31 provided in the wiring between the output of the inverter 3c and the terminals of the AC motor 4a, and supplied to the control device 5. For example, the output current of the inverter 3c corresponds to the current (line current) flowing through each phase winding of the AC motor 4a. The control device 5 forms a feedback control system for current control based on the output current of the inverter 3c. A rotor position detector 41 is attached to the AC motor 4a to detect the rotor position of the AC motor 4a and provide it to the controller 5. FIG. The control device 5 forms a feedback control system for speed control using the rotor position detection result of the rotor position detector 41 .

Next, the control device 5 of the inverter 3c of the embodiment will be described.

The control device 5 uses so-called vector control for controlling the AC motor 4a by separating the current flowing through the windings of the AC motor 4a into a torque current and an excitation current. The configuration of the control device 5 will be described below with a focus on this vector control.

For example, the control device 5 includes a speed controller 5a, a speed calculator 5b, a magnetic flux calculator 5c, a magnetizing current calculator 5d, a slip frequency calculator 5e, a slip angle calculator 5f, a 3-phase/2 A phase coordinate converter 5g, a current controller 5h, a two-phase/three-phase converter 5i, a PWM controller 5j, a gate circuit 5k, a divider 5m, an adder 5n, subtractors 5r and 5s, A reverse phase braking control circuit 6 is provided.

The reverse-phase braking control circuit 6 includes, for example, a reverse-phase braking controller 6a, a control signal selector switch 6b, a current setting unit 6c, a current adjusting unit 6d, a frequency setting unit 6e, a rotation direction switcher 6f, and a reverse A selector 6g and a subtractor 6h are provided.

Each of the above units will be described below in order.

The speed controller 5a differentiates the speed reference signal ωr* from the speed setter 51 (hereinafter * indicates a target value) and the rotor position θr from the rotor position detector 41 by the speed calculator 5b. Based on the deviation from the speed feedback signal ωr received, the torque reference signal Tm* is calculated and output so that this deviation becomes zero. The magnetic flux calculator 5c calculates a secondary magnetic flux reference signal φ2* of the AC motor 4a based on the speed feedback signal ωr. The divider 5m divides the torque reference signal Tm* by the secondary magnetic flux reference signal φ2* to obtain the torque current reference signal iq*. The magnetizing current calculator 5d calculates the excitation current reference signal id* based on the secondary magnetic flux reference signal φ2*. The slip frequency calculator 5e calculates a slip frequency signal ωs based on the torque component current reference signal iq* and the secondary magnetic flux reference signal φ2*.

The torque current reference signal iq* and slip frequency signal ωs thus obtained are applied to the anti-phase braking control circuit 6 . The anti-phase braking control circuit 6 switches between several operation modes including a normal operation mode and an anti-phase braking operation mode based on at least the torque current reference signal iq* and the slip frequency signal ωs to control each section. The normal operation mode is an operation mode other than the reverse phase braking operation mode described later. The reverse-phase braking operation mode is an operation mode applied when performing reverse-phase braking of the AC motor 4a. In the reverse-phase braking operation mode, reverse-phase braking is selected to brake the ship by causing the output shaft of the AC motor 4a to generate torque in the direction opposite to the torque that drives the output shaft of the electric motor during propulsion of the ship. be done. Although the details of the reverse phase braking control circuit 6 will be described later, the reverse phase braking controller 6a in the reverse phase braking control circuit 6 determines which of the normal operation mode and the reverse phase braking operation mode is to be controlled. decide. The reverse phase braking controller 6a preferably controls the control signal changeover switch 6b, the current setting section 6c, and the current controller 5h based on the determined operation mode. Details of control over the current setting unit 6c and the current controller 5h will be described later. In addition to the above, the anti-phase braking controller 6a of the anti-phase braking control circuit 6 may use the speed reference signal ωr*, the speed feedback signal ωr, and their deviation for braking control.

For example, in the normal operation mode, the control signal selector switch 6b outputs the torque current reference signal iq*, the exciting current reference signal id*, and the slip frequency signal ωs to the anti-phase braking control circuit 6 as they are.

The slip angle calculator 5f calculates the slip angle θs based on the slip frequency signal ωs. The adder 5n adds the rotor position .theta.r and the slip angle .theta.s to obtain the secondary magnetic flux position .theta.0. When the rotor position detector 41 outputs the rotational speed instead of the rotor position θr, the rotor position θr can be obtained by integrating the rotational speed.

The three-phase/two-phase coordinate converter 5g uses the secondary magnetic flux position θ0 as a reference phase to convert the current signal from the current detector 31 into a torque current feedback signal iq and an excitation current feedback signal id orthogonal thereto. and output them.

The current controller 5h multiplies the deviation .DELTA.iq by a predetermined gain so that the deviation .DELTA.iq between the torque current reference signal iq* and the torque current feedback signal iq calculated by the subtractor 5r becomes small or zero. to calculate and output the torque voltage reference signal Eq*. The current controller 5h multiplies the deviation .DELTA.id by a predetermined gain so that the deviation .DELTA.id between the excitation current reference signal id* calculated by the subtractor 5s and the excitation current feedback signal id becomes small or zero. , to calculate and output the excitation voltage reference signal Ed*. For example, the current controller 5h uses a predetermined gain according to the operation mode selected from the normal operation mode and the reversed-phase braking operation mode, and based on the deviation input from the previous stage, the torque voltage reference signal Eq * and the excitation voltage reference signal Ed* are calculated and output. As the predetermined gain, a value is set in advance so as to ensure the stability of the control system. The predetermined gain will be described later.

The two-phase/three-phase converter 5i calculates three-phase voltage reference signals Vu*, Vv*, Vw* based on the torque voltage reference signal Eq*, the excitation voltage reference signal Ed*, and the secondary magnetic flux position θ0. Output. Here, the PWM controller 5j outputs pulse width modulated gate pulse signals based on the obtained three-phase voltage reference signals Vu*, Vv*, Vw*. The gate circuit 5k insulates and amplifies this gate pulse signal, applies a gate pulse to the main circuit switching devices of the inverter 3c, and turns these main circuit switching devices on and off to perform desired power conversion.

Next, the internal configuration of the antiphase braking control circuit 6 will be described.
The anti-phase braking controller 6a monitors the run/stop signal, the torque current reference signal iq*, the slip frequency signal ωs, the speed feedback signal ωr and the speed reference signal ωr* provided from the stop condition circuit 7, The normal operation mode and the negative phase braking operation mode are switched according to the detection result of the state of the signal. At that time, the anti-phase braking controller 6a switches the torque current reference signal iq*, the excitation current reference signal id*, and the slip frequency signal ωs by, for example, the control signal selector switch 6b.

The following description is based on the case where the reverse phase braking is performed (the reverse phase braking operation mode).
For example, the anti-phase braking controller 6a selects the anti-phase braking operation mode based on the states of the run/stop signal, torque current reference signal iq*, slip frequency signal ωs, speed feedback signal ωr, and speed reference signal ωr*. When it is detected that it should be in a state where it should be, the control signal changeover switch 6b is selected to the negative phase braking side, and the torque current reference signal iq* is switched to the negative phase torque current io* set by the current setting unit 6c. In the above case, the anti-phase braking controller 6a similarly switches the excitation current reference signal id* to the anti-phase excitation current ip* set by the current adjustment section 6d, and furthermore reverses the slip frequency signal ωs. Switch to the slip frequency ωsi during phase braking.

An example of the anti-phase excitation current ip* is zero or a very small value close to zero. This anti-phase braking slip frequency ωsi is obtained by subtracting the speed feedback signal ωr from the anti-phase braking frequency reference ωp*, for example, by a subtractor 6h.

For example, the frequency setting unit 6e sets the anti-phase damping frequency. The input of the inverting selector 6g is connected to the output of the frequency setting section 6e. Based on the identification result of the speed feedback signal ωr by the rotating direction switcher 6f, the inversion selector 6g outputs the anti-phase braking frequency set by the frequency setting unit 6e as it is or after changing the polarity. The inversion selector 6g uses this as the anti-phase damping frequency reference ωp*. For example, the rotational direction selector 6f reverses the polarity by the reversal selector 6g when the speed feedback signal ωr is positive, and does not reverse the polarity when it is negative.

The current controller 5h of the embodiment will be described with reference to FIGS. 2A, 2B, and 3. FIG.
FIG. 2A is a configuration diagram of the current controller 5h of the embodiment. FIG. 2B is an equivalent circuit diagram of the current controller 5h shown in FIG. 2A. FIG. 3 is a diagram for explaining the gain of the current controller 5h of the embodiment.

As shown in FIG. 2A, the current controller 5h includes proportional calculation units 211 and 221, integral calculation units 212 and 222, and adders 213 and 223.

First, the configuration regarding the q-axis component of the current controller 5h will be described. Refer to FIG. 3 for each gain in the description.

The deviation Δiq is supplied to the input of the proportional calculation unit 211, and the proportional calculation unit 211 multiplies the deviation Δiq by a predetermined proportional gain Kp (for example, proportional gain K11) and outputs the result. The output of the proportional calculator 211 is connected to the input of the integral calculator 212 and the first input of the adder 213 . The calculation result of the proportional calculation unit 211 is supplied to the input of the integral calculation unit 212, and the integral calculation unit 212 applies a predetermined integral gain Ki (for example, integral gain K12 ) and outputs the result. A second input of the adder 213 is connected to the output of the integral operation section 212 . The adder 213 adds the calculation result of the proportional calculation section 211 and the calculation result of the integral calculation section 212, and outputs this as the torque voltage reference signal Eq*. Each of the proportional gain K11 and the integral gain K12 is a predetermined real number.

Next, the configuration regarding the d-axis component of the current controller 5h will be described. The configuration regarding the d-axis component is also the same as the configuration regarding the q-axis component described above.

For example, the deviation Δid is supplied to the input of the proportional calculation unit 221, and the proportional calculation unit 221 multiplies the deviation Δid by a predetermined proportional gain Kp (for example, proportional gain K11) and outputs the result. The output of the proportional calculator 221 is connected to the input of the integral calculator 222 and the first input of the adder 223 . The calculation result of the proportional calculation unit 221 is supplied to the input of the integral calculation unit 222, and the integral calculation unit 222 applies a predetermined integral gain Ki (for example, integral gain K12 ) and outputs the result. A second input of the adder 223 is connected to the output of the integral operation section 222 . The adder 223 adds the calculation result of the proportional calculation section 221 and the calculation result of the integral calculation section 222, and outputs this as the torque voltage reference signal Ed*.

The apparent integral gain of the current controller 5h configured as described above is the product of the proportional gain K11 and the integral gain K12.

By the way, the proportional gain Kp of the proportional calculation units 211 and 221 of the current controller 5h is switched according to the braking command GCONT that specifies the reverse phase braking operation mode. As shown in FIG. 3, for example, the set of gains used in the normal operation mode is proportional gain K11 and integral gain K12, and the set of gains used in the reversed-phase braking operation mode is proportional gain K21 and integral gain K22. do. Comparing the proportional gain K11 and the proportional gain K21, the proportional gain K11 is set larger. As a result, the gain of the current controller 5h becomes larger in the reversed-phase braking operation mode than in the normal operation mode, and the control to make the deviation zero can be strengthened.

As shown in FIG. 2B, the current controller 5h can be represented by a configuration in which PI calculation units 231 to 234 and changeover switches 235 and 236 are combined.
For example, the PI calculator 231 includes a proportional calculator 211 set with a proportional gain K11, an integral calculator 212 with an integral gain K12, and an adder 213 shown in FIG. 2A. The PI calculation unit 232 includes a proportional calculation unit 211 set with a proportional gain K21, an integral calculation unit 212 with an integral gain K22, and an adder 213 shown in FIG. 2A.

The switch 235 switches between the calculation result of the PI calculation unit 231 and the calculation result of the PI calculation unit 232 according to the braking command GCONT. The selector switch 235 outputs the calculation result of the PI calculation unit 231 as the torque voltage reference signal Eq* when the braking command GCONT is not activated (when it is invalid), and when the braking command GCONT is activated ( valid), the calculation result of the PI calculation unit 232 is output as the torque voltage reference signal Eq*.

The PI calculator 233 includes a proportional calculator 221 set with a proportional gain K11, an integral calculator 222 with an integral gain K12, and an adder 223 shown in FIG. 2A. The PI calculator 234 includes a proportional calculator 221 set with a proportional gain K21, an integral calculator 222 with an integral gain K22, and an adder 223 shown in FIG. 2A.

The selector switch 236 switches between the computation result of the PI computation section 233 and the computation result of the PI computation section 234 . The selector switch 236 outputs the calculation result of the PI calculation unit 233 as the torque voltage reference signal Ed* when the braking command GCONT is not activated, and outputs the PI calculation unit 234 when the braking command GCONT is activated. is output as the torque voltage reference signal Ed*.
Although the configuration shown in FIG. 2B has been described as an equivalent circuit, it does not limit application to the actual configuration and may be used as appropriate.

Next, braking control of the AC motor 4a will be described with reference to FIG.
FIG. 4 is a flowchart relating to braking control according to the embodiment.
For example, when a stop command is given from the operation stop condition circuit 7 while the AC motor 4a is running, the reverse phase braking controller 6a detects this and performs the following processing according to this detection.

The anti-phase braking controller 6a identifies whether or not the speed feedback signal .omega.r indicates a non-braking rotation speed or less (ST1). If it is equal to or less than the unbraking rotation speed, the reverse phase braking controller 6a identifies whether or not the torque current reference signal iq* is equal to or less than a predetermined value (ST3).
A state in which the torque current reference signal iq* exceeds a predetermined value or a state in which the braking-disabled rotational speed is exceeded in step ST1 is a state in which reverse-phase braking is not desirable. Therefore, the antiphase braking controller 6a decelerates at a predetermined deceleration rate regardless of the value of the speed reference signal ωr* at the time when the stop command is given (ST4).

In step ST3, if the torque current reference signal iq* is equal to or less than a predetermined value, the anti-phase braking controller 6a recognizes that the conditions for performing anti-phase braking are satisfied, and validates the gate block command GB. is output to the gate circuit 5k to set the gate block state. The AC motor 4a enters a free-running state (ST5). The reverse-phase braking controller 6a continues the operation of step ST5 at least for a predetermined period of time during which the counter-electromotive voltage of the AC motor 4a moderately decreases. This predetermined time is preferably set to several times based on the time constant for the decrease of the induced voltage of the AC motor 4a.

Next, the anti-phase braking controller 6a identifies whether or not the speed feedback signal .omega.r indicates a braking maximum rotational speed (braking maximum rotational speed) or less (ST6).

When the speed feedback signal ωr becomes equal to or less than the maximum braking speed, the anti-phase braking controller 6a performs the following control to perform braking in the anti-phase braking operation mode (called anti-phase braking). .) is started (ST7).

For example, the reverse phase braking controller 6a switches the gain in the current controller 5h from the gain for the normal operation mode to the gain for the reverse phase braking operation mode, and then invalidates the gate block command GB. Cancel the gate block state. The negative-phase braking controller 6a further selects the negative-phase braking side in the control signal selector switch 6b, switches the torque current reference signal iq* to the negative-phase torque current io* whose value gradually changes, and controls the excitation current reference signal id. * is switched to the anti-phase excitation current ip* set by the current adjusting section 6d, and the slip frequency signal ωs is switched to the slip frequency ωsi during anti-phase braking.

Further, the anti-phase braking controller 6a controls the current setting section 6c to output the anti-phase torque current io*0, which is the index value for the anti-phase braking operation mode, from the current setting section 6c. The reverse-sequence torque current io*0 has a sharply changing signal component suppressed by a filter 6r provided after the current setting section 6c. As a result, the filter 6r generates the anti-phase torque current io* whose change amount (change rate) is appropriately limited. By such a method, after switching the output of the current setting section 6c, the reversed-phase torque current io* that gradually increases monotonically rather than stepwise is obtained. With regard to the negative-sequence torque current io*, it is possible to suppress sharp fluctuations that may occur in response to switching of the operation mode. The filter 6r may be configured as a primary response type low-pass filter, or may be configured as a rate limiting type circuit that limits the rate of change of the output within a predetermined range.

Note that there are cases where power cannot be regenerated from the DC link side to the generator 2 side, such as when a diode converter is used as the converter 3b, for example. In such a case, the value during the normal operation mode should normally be set to 0%. The current setting unit 6c may use this value as a reference value for the negative phase torque current io*0.

However, if the kinetic energy of the AC motor 4a has decreased after a predetermined period of time has elapsed since the start of reverse-phase braking, excessive regenerative energy may flow into the DC link side via the inverter 3c. become less sexual. In such a state, it may be possible to generate a larger braking torque by setting the reverse-phase torque current io* to a value other than 0%.

Therefore, in the current setting unit 6c, the initial value of the negative phase torque current io*0 at the start stage of the negative phase braking is set to 0%, which is the same as the reference value during the normal operation mode, and the negative phase braking operation mode is started. A desired value other than 0% may be set in advance as the target value after the adjustment. For example, when the value of the negative-sequence torque current io*0 changes from 0% to a desired value other than 0% by switching the operation mode, the filter 6r detects that the negative-sequence torque current io* changes sharply. suppress

In the embodiment, for example, the negative-phase exciting current ip* may be set to zero (0%) for the current adjusting section 6d.

Next, the anti-phase braking controller 6a compares the speed reference signal ωr* and the speed feedback signal ωr during the anti-phase braking period (ST7A). When the deviation in step ST7A becomes less than the predetermined value, the anti-phase braking controller 6a ends the anti-phase braking (ST9) and stops the operation in this state.

If the deviation in step ST7A is equal to or greater than the predetermined value, the anti-phase braking controller 6a identifies the speed feedback signal ωr and determines that the rotation speed of the AC motor 4a is the minimum rotation speed, which is the lower limit of rotation speed for continuing the braking state. (ST8). If the speed feedback signal ωr indicates that the AC motor 4a is rotating at a speed exceeding the minimum speed for braking, the anti-phase braking controller 6a repeats identification of the speed feedback signal ωr in step ST8. and waits until the rotation speed (speed) of the AC motor 4a decreases. When the speed feedback signal .omega.r becomes less than the braking minimum rotation speed, the anti-phase braking controller 6a terminates anti-phase braking (ST9) and stops driving in this state.

In the above description, the situation in which the stop command is given while the AC motor 4a is rotating at the braking minimum rotation speed or more has been described as an example. In a certain situation, there is no need to perform the free-running operation in step ST5, so the operation can be stopped directly. Also, the determination of the torque current reference in step ST3 may be omitted. When the torque current reference signal iq* exceeds a predetermined value when the torque current reference signal iq* is determined in step ST3, it is preferable that the electric propulsion device 1 regard this as an abnormal state and issue an alarm. .

Although the above is an example of braking the AC motor 4a during operation of the electric propulsion device 1, the same method as described above can also be applied to the case of decelerating the AC motor 4a.

According to the above embodiment, the current controller 5h uses the current feedback value for the detected value of the current flowing through the windings of the AC motor 4a and the index of the control target for the magnitude of the current flowing through the windings of the AC motor 4a. Current control using a certain current reference iq* controls the magnitude of the current flowing through the windings of the AC motor 4a. The reverse-phase braking controller 6a validates and outputs a braking command GCONT for braking control of the AC motor 4a. The reverse-phase braking controller 6a changes the control gain of the current control from the first gain during driving for driving the AC motor 4a to the second gain during braking for braking the AC motor 4a, according to the output of the braking control command. Switch to gain. As a result, the control device 5 can further enhance the stability of the current control when the AC motor 4a is braked by reverse-phase braking.
The driving state in which the AC motor 4a is driven is an example of a state in which the normal operation mode is selected. The normal operation mode can be applied to control during driving and during free-running described above.

Further, the current controller 5h utilizes the torque current feedback signal iq and the excitation current feedback signal id for the detected value of the current flowing through the windings of the AC motor 4a as current feedback values, and compares the current feedback value and the current reference. A proportional calculation for the deviation may be performed using the second gain for braking (for example, the above proportional gain K21) to control the deviation to be small.

The current controller 5h performs the proportional integral calculation for the difference between the current feedback value and the current reference using the second gain for braking (for example, the proportional gain K21 and the integral gain K22). may be controlled so that the deviation becomes small.

The current controller 5h may be formed so as to set the apparent gain of the integral component in the proportional integral calculation to a magnitude corresponding to the magnitude of the gain of the proportional component in the proportional integral calculation.

The current setting unit 6c generates the current reference for generating the reverse phase torque of the motor by control. The filter 6r moderates changes in the current reference during braking. The current controller 5h may control the current setting section 6c to generate a current reference during braking.

In the comparative example, since the control state during braking control is different from that during normal operation, if the gain for normal operation is applied during braking control, the control may become unstable. By dividing the gain in the normal operation mode and the gain in the reversed-phase braking operation mode as in the present embodiment, it is possible to set values suitable for each situation and control.
For example, in the reversed-phase braking operation mode, the AC motor 4a can be decelerated efficiently by increasing the compensation by the proportional component rather than the compensation by the integral component.

In addition, instead of changing the current reference stepwise, the filter 6r can be used to set a control target that matches the responsiveness of the control system, thereby suppressing the occurrence of overcurrent. . The characteristics of the filter 6r may be determined by modeling the response characteristics of the control system and applying a model predictive control method using this model.
Note that the response time of the current control system during negative-phase braking is may be determined by a method of determining the response characteristic (time constant) of the filter 6r so that .
The filter 6r is provided outside the control loop of current control. By providing the filter 6r at this position, the above control becomes possible without lowering the responsiveness to the deviation.

(Modification)
In the above embodiment, the case of reverse phase braking has been described as an example of the braking method. Alternatively, other braking methods may be applied.
Other braking methods include, for example, DC braking. In the case of DC braking, the control device 5 applies a direct voltage to the windings of the AC motor 4a instead of causing current of a predetermined frequency to flow through the windings during braking. As a result, a magnetic field is generated in the AC motor 4a to increase the mechanical loss of the AC motor 4a. A well-known method may be applied for a specific control method of DC braking, and reference may be made, for example, to International Publication WO2019/234920A1.

In the case of the comparative example, when DC braking is started and during DC braking, the magnitude of the current flowing through the windings of the AC motor 4a changes oscillatingly, and the converter 3b and the inverter in the power converter 3 change. An overvoltage exceeding the allowable value may occur in the DC link connecting 3c during reverse phase braking.

On the other hand, according to the control device 5 (current controller 5h) of the modified example, even in the case of DC braking, the vibrational change in the current as in the comparative example is reduced, and the overvoltage exceeding the allowable value is reduced. can be suppressed. In this manner, the stability of the current control during the braking control can be further enhanced in this modification as well.

According to at least one embodiment described above, the control device comprises a current controller and a braking controller. The current control unit performs current control using a detected value of the current flowing through the windings of the motor and a current reference that is an index of the control target for the magnitude of the current flowing through the windings of the motor. Controls the magnitude of the current. The braking control unit outputs a braking command GCONT for braking control of the electric motor. The current control unit switches a control gain of current control from a first gain for driving the electric motor to a second gain for braking the electric motor in accordance with an output of a braking control command. As a result, the control device can further enhance the stability of current control during braking of the electric motor.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 1... Electric propulsion apparatus, 2... Generator, 3... Power converter, 3c... Inverter, 31... Current detector, 4... Propeller, 4a... AC motor (motor), 4b... Propeller, 5... Control device, 5a Speed controller 5b Speed calculator 5c Magnetic flux calculator 5d Magnetizing current calculator 5e Slip frequency calculator 5f Slip angle calculator 5g 3-phase/2-phase coordinate converter 5h Current controller 5i 2-phase/3-phase coordinate converter 5j PWM controller 5k Gate circuit 5m Divider 5n Adder 5r, 5s Subtractor 6 Anti-phase braking control circuit 6a reverse phase braking controller (braking control unit) 6b control signal switching switch 6c current setting unit 6d current adjusting unit 6e frequency setting unit 6f rotation direction switch 6g reverse Selector 6h Subtractor 7 Operation stop condition circuit

Claims (8)

Current control using a current feedback value with respect to a detected value of the current flowing through the windings of the motor and a current reference, which is an index of the control target for the magnitude of the current flowing through the windings of the motor, allows the windings of the motor to a current control unit that controls the magnitude of the flowing current;
a braking control unit that outputs a braking command for braking control of the electric motor,
The current control unit
According to the output of the braking control command, the control gain of the current control is switched from a first gain during driving for driving the electric motor to a second gain during braking for braking the electric motor.
Control device. The current control unit
A proportional calculation for the deviation between the current feedback value and the current reference is performed using the second gain, and the deviation is controlled so as to be small.
A control device according to claim 1 . A proportional calculation gain for the first gain during driving is set smaller than a proportional calculation gain for the second gain during braking.
3. A control device according to claim 2. The current control unit
The second gain is used to perform a proportional integral operation on the deviation between the current feedback value and the current reference, and the deviation is controlled to be small.
A control device according to claim 1 . The current control unit
The gain of the integral component in the proportional-integral calculation is formed to have a magnitude corresponding to the gain of the proportional component in the proportional-integral calculation.
5. A control device according to claim 4. a current setting unit that generates the current reference for generating the reverse-sequence torque of the electric motor under control;
a filter that moderates changes in the current reference during the braking;
The current control unit
controlling the current setting unit to generate the current reference during the braking;
A control device according to claim 1 . The braking control unit brakes the electric motor by reverse-phase braking or DC braking.
The control device according to any one of claims 1 to 6. Current control using a current feedback value with respect to a detected value of the current flowing through the windings of the motor and a current reference, which is an index of the control target for the magnitude of the current flowing through the windings of the motor, allows the windings of the motor to a step in which the current control unit controls the magnitude of the flowing current;
a step in which a control device outputs a braking command for braking control of the electric motor;
According to the output of the brake control command, the control gain of the current control in the current control unit is changed from the first gain during driving for driving the electric motor to the second gain during braking for braking the electric motor. A control method comprising the step of switching the current controller.

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