JP2015091145A - Motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor control device that blocks a battery from an inverter and protects a system while suppressing damage of components in the inverter and a contact failure of a contactor.SOLUTION: A motor control device 9 comprises: contactor control means 70 that blocks a battery 1 from an inverter 5 by opening contactors 2 and 3, and connects the battery to the inverter by closing the contactors; and inverter control means that controls supply and supply stopping of AC voltages to a motor 6. The inverter includes: switching elements for replacing DC voltages with the AC voltages; reflux diodes 400 that are connected in parallel to the switching elements respectively; and a smooth capacitor 4 for absorbing switching surge. The motor includes an exciting coil 200 for generating magnetic force. The motor control device 9 is configured to stop the inverter before blocking the battery from the inverter, wait for elapsing of prescribed time and then control the contactors between the closed state and the opened state.

Description

  The present invention relates to a motor control device.

  In a system that drives an AC motor by converting the voltage of the DC power supply into an AC voltage by an inverter and applying it to the AC motor, a contactor is arranged between the inverter and the DC power supply, and the contactor is controlled to be in an open state and a closed state. As a result, electrical disconnection and connection between the inverter and the DC power source are implemented.

  In recent years, in many motor drive systems for hybrid vehicles and electric vehicles that have been developed, the output required for a motor for driving a vehicle connected to an axle is several tens kW, and a permanent magnet is used to achieve this high output. Many motors with built-in are used.

  As a direct current power source, a battery such as a nickel metal hydride battery or a lithium ion battery is used, and the electric power taken out from the battery increases according to the output of the motor. The voltage of the battery becomes several hundred volts or more, and the battery and the inverter are connected via the contactor. The current flowing between them is several tens of A or more.

  A battery capable of storing such high energy needs to avoid a failure particularly in a state where the charge amount of the battery is high, that is, a state where energy is stored. Therefore, when there is a possibility that the motor drive system breaks down and leads to overcharging of the battery or excessive current supply, it is necessary to cut off the charging current to the battery in as short a time as possible.

  When a motor with a built-in permanent magnet is installed in an automobile, even if a system failure is detected and the inverter is stopped, the induced voltage is generated by the permanent magnet if the motor is rotating. If it is higher than the battery voltage, the battery will continue to be charged via the diode of the switching element in the inverter.

  For this reason, in order to cut off the charging current, it is necessary to open the contactor or cut off the energization path with a fuse.

  Also, in the case of a serious failure that generates an extremely large current that needs to be interrupted immediately, the inverter may be damaged and the fuse may be blown, and repair or replacement may be necessary. A slight overcurrent that only needs to be interrupted within a few seconds can be protected by opening the contactor, so it is not necessary to replace the fuse.

  Patent Document 1 discloses a configuration for protecting a battery from an overcurrent generated by a motor using such a contactor and a fuse.

  Patent Document 2 discloses a method in which a resistor is connected in parallel to a contactor interposed between a power source and a motor, and a voltage increase can be suppressed even when the contactor is opened during energization.

Japanese Patent No. 3787701 Japanese Patent No. 3759736

  In the method of Patent Document 1, when the contactor is opened or the fuse is blown in a state where the motor performs regenerative control and the battery is charged, the voltage on the motor side from the contactor rapidly increases due to the inductance of the excitation coil of the motor. There is a possibility of damaging components such as switching elements and capacitors in the inverter.

  The method of Patent Document 2 is effective in the relationship between a general power source and a motor. However, when a motor having a built-in permanent magnet is mounted on an automobile, this method can be used to rotate the motor. For example, an induced voltage caused by a permanent magnet may cause a current to continue to flow through a resistor connected in parallel to the contactor, resulting in overheating. Further, when the power source is a battery, there is a risk of overcharging.

  Therefore, the present invention detects a failure when the motor is performing regenerative power generation and when the contactor must be opened, without damaging components such as switching elements and capacitors in the inverter, An object of the present invention is to provide a motor control device capable of protecting a drive system.

  In order to solve the above problems, for example, the configuration described in the claims is adopted. The present application includes a plurality of means for solving the above-mentioned problems. To give an example, a battery and an inverter are connected via a contactor, and a DC voltage of the battery is converted into an AC voltage by the inverter and applied to an AC motor. A contactor control means for shutting off the battery and the inverter by opening the contactor, and connecting the battery and the inverter by closing the contactor; and the motor Inverter control means for controlling supply and stop of AC voltage to the inverter, the inverter comprising a switching element for converting the DC voltage into AC voltage, and a free wheel diode connected in parallel to each switching element, And a smoothing capacitor for absorbing a switching surge. Includes an exciting coil for generating magnetic force, stops the inverter before the battery and the inverter are disconnected from the connected state, and waits for a predetermined waiting time, and then The contactor is controlled from a closed state to an open state.

  ADVANTAGE OF THE INVENTION According to this invention, the motor control apparatus which interrupts | blocks a battery and an inverter and protects a system can be provided, suppressing the damage of the components in an inverter, and the contact failure of a contactor.

1 is a schematic diagram of a motor control device according to an embodiment. The flowchart from the starting of the motor control apparatus which concerns on an Example to a stop. The timing chart at the time of the stop of the motor control apparatus which concerns on an Example. The flowchart from the starting of the motor control apparatus which concerns on an Example to a stop (another example).

Embodiments of the present invention will be described below with reference to the drawings.
[Example]
FIG. 1 shows a motor control apparatus according to an embodiment of the present invention, which is a battery 1 that is a DC power source, a main contactor 2, a sub contactor 3, a capacitor 4, an inverter 5, a motor 6, and an alternating current detection circuit. 7, a magnetic pole position detection circuit 8, a control device 9, an exciting coil 200, and a fuse 300.

  The battery 1 is a secondary battery such as a nickel metal hydride battery or a lithium ion battery, and holds a high voltage of about 100V to 300V.

  The main contactor 2 is connected in series between the battery 1 and the inverter 5, the sub-contactor 3 is connected in parallel to the main contactor 2 via a resistor, and both contactors are opened by a contactor control device 70 arranged in the control device 9. Controlled to the closed state.

  The inverter 5 includes six transistors, and two transistors are connected in series to form a U-phase upper arm and a U-phase lower arm, and another two transistors are connected in series, and the V-phase upper arm and the V-phase are connected. The lower arm is configured, and the remaining two transistors are connected in series to form a W-phase upper arm and a W-phase lower arm. A diode is electrically connected in antiparallel between the collector and emitter of each transistor.

  The control device 9 outputs a control signal (PWM signal) to the gate terminals of the six transistors in the inverter 5 and controls the armature current supplied to the armature of the motor 6 by controlling each transistor on and off. Then, the torque of the motor 6 is controlled.

  The inverter 5 is provided with a capacitor 4 for smoothing the ripple of the DC voltage generated by transistor switching.

  The motor 6 is a three-phase AC synchronous motor with a built-in magnet. Although not shown, the motor 6 changes when a current flows through a stator having three phases of windings of U phase, V phase, and W phase and the windings. It is mainly composed of two parts of a rotor that generates a rotational force by magnetic flux.

  A magnetic pole position detection circuit 8 disposed in the motor 6 detects a magnetic pole position θ that changes as the rotor rotates, and the detected value is transmitted to the control device 9. In the control device 9, the rotational speed calculation circuit 80 generates the rotational speed ω of the motor 6 from the magnetic pole position θ.

  The control device 9 includes a current map circuit 10, a PI control circuit 20, a dq / 3-phase conversion circuit 30, a PWM signal generation circuit 40, a 3-phase / dq conversion circuit 50, a PWM signal changeover switch 60, a contactor The control circuit 70 and the rotation speed calculation circuit 80 are configured to receive an external start command or stop command and a torque command value.

  Based on the external torque command, the current map circuit 10 is a d-axis current command value Id * that is an excitation current command value for outputting torque as a command value and a q-axis current command value that is a torque current command value. Iq * is generated according to the rotational speed ω of the motor 6.

  The PI control circuit 20 includes a d-axis current command value Id * obtained from the current map circuit 10, a q-axis current command value Iq *, and actual current values Id and Iq of the motor 6 detected as described later. And a PI operation is performed on the difference to generate a d-axis voltage command value Vd * and a q-axis voltage command value Vq *.

  The output of the PI control circuit 20 is input to the dq / 3-phase conversion circuit 30. The dq / 3-phase conversion circuit 30 drives the motor 6 from the d-axis voltage command value Vd * and the q-axis voltage command value Vq *. Three-phase voltage command values Vu, Vv, and Vw are generated according to the magnetic pole position θ.

  The PWM signal generation circuit 40 generates a PWM drive signal for on / off control of the six transistors of the inverter 5 based on the three-phase voltage command values Vu, Vv, Vw.

  The U-phase current Iu, V-phase current Iv, and W-phase current Iw flowing through the motor 6 are detected by the AC current detection circuit 7, and the detected current values for the three phases are detected by the three-phase / dq conversion circuit 50 by the magnetic pole position θ. Accordingly, the excitation d-axis actual current Id and the torque q-axis actual current Iq are converted and supplied to the PI control circuit 20.

  By this feedback control loop, the d-axis current command value Id * and the q-axis current command value Iq * coincide with the actual current values Id and Iq of the motor 6, so that the motor 6 outputs a torque corresponding to the torque command. The response time depends on the response time constant set by the PI control circuit 20.

  In this embodiment, PI control is used as feedback control for making the current command value coincide with the actual current value of the motor 6, but other control methods such as PID control may be used.

  When the control device 9 receives the start command, the PWM signal changeover switch 60 switches the PWM signal to the side where the PWM signal from the PWM signal generation circuit 40 is input to the inverter 5. When a stop command is received, the PWM signal is switched to the OFF side.

  When the control device 9 receives the start command, the contactor control circuit 70 first charges the capacitor 4 in the inverter 5 by closing the sub contactor 3 in order to connect the battery 1 and the inverter 5. Do. When the capacitor 4 is sufficiently charged, the main contactor 2 is closed, the sub contactor 3 is controlled to be opened, and the battery 1 and the inverter 5 are connected.

  The contactor control circuit 70 opens the main contactor 2 in order to shut off the battery 1 and the inverter 5 under the conditions described later, triggered by reception of a stop command from the control device 9.

  Hereinafter, the operation of the system when the battery 1 and the inverter 5 are disconnected will be described.

  The control device 9 sends a PWM signal to the inverter 5 based on the external torque command value to control the torque of the motor 6 while receiving the start command.

  When the driver performs the key-off operation after stopping the vehicle, the control device 9 receives the stop command, the PWM signal changeover switch 60 is switched to the side where the PWM signal input to the inverter 5 is turned off, and the battery 1 Supply of current to the motor 6 is stopped. At the same time, the main contactor 2 is controlled from the contactor control 70 to the open state. The main contactor 2 is generally a contactor having a relatively large capacity capable of interrupting at least several times the maximum value of the DC current Idc in a normal state, for example, several thousand A or more, and the contactor control 70 is opened. In general, several tens of ms are required from the start of control until the actual opening state. Therefore, the contactor is opened after the current from the battery 1 to the motor 6 has already stopped. As a result, the motor drive system is safely shut down.

  On the other hand, during driving, the motor drive system operates the motor drive system from the viewpoint of diagnostic protection, for example, the current detection circuit 100 detects a current greater than a predetermined value and determines that it is abnormal. When stopping when the motor 6 is running, the phenomenon differs depending on whether the motor 6 is performing regenerative output or powering output.

  First, when the control device 9 receives a stop command while the motor 6 is performing a power running output, the control device 9 issues a stop command as in the case where the driver performs a key-off operation after stopping the vehicle. The PWM signal changeover switch 60 is switched to the side where the PWM signal input to the inverter 5 is turned OFF, the supply of current from the battery 1 to the motor 6 is stopped, and the main contactor 2 is opened from the contactor control 70 at the same time. After a few tens of ms, the main contactor 2 is opened and the motor drive system is safely stopped.

  Next, when the control device 9 receives a stop command while the motor 6 is performing regenerative output, the PWM signal selector switch 60 is switched to the side where the PWM signal input to the inverter 5 is turned off, and the battery The supply of excitation current from 1 to the motor 6 stops. When the motor 6 is performing regenerative output, the forward voltage of the diode 400 does not drop immediately due to the inductance of the exciting coil 200 even if the supply of the exciting current is stopped, and the motor 6 passes through the main contactor 2. The current in the regeneration direction is maintained in the battery 1 for a certain time.

  At this time, the contactor control 70 calculates the standby time t, which is the time during which the current in the regenerative direction is sufficiently reduced and the voltage rise generated when the main contactor 2 is opened converges to a range where the inverter 5 is not damaged. To do.

During this standby time t, the AC signal Iac and the smoothing capacitor voltage Vdc are switched from the AC current detection circuit 7 and the voltage detection circuit 500 to the side where the PWM signal input to the inverter 5 is turned off. The values I0 and V0 of the regenerative current at the moment of switching are acquired, and the predetermined capacitance C of the smoothing capacitor, the inductance L of the exciting coil, the total impedance Z of the energization path from the exciting coil 200 to the battery 1, Using the upper limit voltage Vlim of the inverter, it is calculated from the following equation. In addition, Ln in a formula represents a natural logarithm.
t = −L / Z × Ln ((Vlim−V0) × √ (C / L) / I0)

  The contactor control 70 waits until the standby time t elapses from the moment when the PWM signal changeover switch 60 is switched to the side where the PWM signal input to the inverter 5 is turned OFF, and then controls the main contactor 2 to be in an open state.

  Thereby, the main contactor 2 can be opened in the shortest time that can prevent the inverter 5 from being damaged. Note that when the main contactor 2 is opened, the current flowing through the main contactor 2 is not always zero. However, as described above, the breaking capacity of the main contactor 2 generally has a breaking capacity that is several times larger than the maximum current. Therefore, the main contactor 2 can be controlled to open without any problem. As a result, the motor drive system is safely shut down.

  For example, assuming that I0 is 1000 A in total for three phases, V0 is 500 V, C is 100 μF, L is 100 μH, Z is 10 mΩ, and Vlim is 600 V, the standby time t is calculated to be about 23 ms. This is the same time as the response time of the main contactor, which is several tens of milliseconds as described above, and is sufficiently long to be practically used as the waiting time.

  Further, if only I0 is set to 100A in total for the three phases and the above-described values are used for the other conditions, the standby time t is 0 ms, and the standby time is unnecessary.

When it is assumed that the current Iac of the motor 6 where the standby time t is just 0 is It,
It = Vlim / (√ (L / C)).

  The condition for shutting off the main contactor 2 may be set when the current Iac of the motor 6 becomes equal to or less than It using this It instead of calculating the waiting time t and waiting for the progress.

  FIG. 2 is a flowchart showing from the connection of the battery 1 and the inverter 5 by the power-on and start command to the system to the stop of the system by the disconnection of the battery 1 and the inverter 5.

  After the system is turned on, when the control device 9 receives a start command in step S1, the contactor control circuit 70 closes the main contactor 2 in step S2. Although not shown, the main contactor 2 is closed after the capacitor 4 is sufficiently charged by the sub-contactor 3, and the sub-contactor 3 is opened.

  As a result, the PWM signal output in step S3 is turned on, the PWM signal output to the inverter 50 is switched to the output side of the PWM circuit 40, and the motor 6 in step S4 is torque controlled according to the external torque command value. When the control device 9 receives the stop request in step S5, the PWM signal change-over switch 60 turns the PWM signal output to the OFF state and is switched to the side where the PWM signal output to the inverter 50 is turned OFF. Control of the motor 6 with the torque command value is continued.

  When it is confirmed in step S7 that the waiting time t calculated by the contactor control 70 has elapsed since the execution of step S6, the contactor control circuit 70 opens the main contactor 2 in step S8. .

Here, as shown in FIG. 4, instead of step S7, step S17 is used to determine whether or not the motor current Iac is equal to or less than a predetermined value using the following equation.
Iac ≦ Vlim / (√ (L / C))
After the condition is established, the contactor control circuit 70 may open the main contactor 2 in step S8.

  In FIG. 3, the control device 9 controls the motor 6 in the regenerative state while receiving the start command, and receives the stop command from the state where the current of 1000 A in total of the three phases of the exciting coil 200 is flowing, and outputs the PWM signal. The timing chart until the voltage of the capacitor 4 rises to the maximum value after turning off the main contactor 2 from the closed state to the open state is shown.

  When the stop command is received at time T1, the PWM signal input to the inverter 5 is switched from the output of the PWM circuit 40 to the OFF state at time T2, and the excitation current to the motor 6 is stopped.

  Thereafter, the current Iac of the motor 6 passes through the diode 400 and flows as a direct current to the main contactor 2 and reaches the battery 1, and decreases with the passage of time due to the resistance of these paths.

  The main contactor 2 is controlled from the closed state to the open state at time T3 23 ms after the PWM signal is switched to the OFF state according to the calculation result 23 ms of the standby time t of the contactor control circuit 70.

  When the main contactor 2 is controlled to be in an open state, a current Iac flowing through the exciting coil 200 flows through the motor 6 at 100 A. The capacitor voltage Vdc starts damped oscillation. Assuming that the resistance of the circuit is sufficiently small, Vdc starts to rise from 500V of V0, and just reaches 600V of the upper limit voltage Vlim of the inverter 5. Thereafter, the capacitor voltage Vdc oscillates repeatedly as it falls and rises, attenuates due to the resistance of the circuit, and decreases toward 0V. The motor current Iac is attenuated by the resistance of the circuit while repeatedly oscillating and descending with a maximum value of 100A, and decreases toward 0A. If the resistance of the circuit is large, it may converge without vibration. In either case, the voltage finally decreases toward 0V and current 0A.

  Since the present invention can be realized by adding a contactor control circuit for calculating a standby time to a general motor control circuit, the configuration is not complicated, and the addition of the contactor control circuit can be realized by changing a control program. Therefore, there is no increase in cost due to the addition of parts.

  Although the above description has described the case where the present embodiment is applied to a three-phase AC synchronous motor with a built-in magnet, the present embodiment can also be applied to an induction motor without a built-in magnet or a non-three-phase AC motor. Is not limited to this.

  The embodiments disclosed herein are illustrative and non-restrictive in every respect. The technical scope of the present embodiment is defined by the claims, and all modifications within the scope equivalent to the configuration described therein are also included in the technical scope of the present embodiment.

DESCRIPTION OF SYMBOLS 1 Battery 2 Main contactor 3 Sub contactor 4 Capacitor 5 Inverter 6 Motor 7 AC current detection circuit 8 Magnetic pole position detection circuit 9 Controller 10 Current map circuit 20 PI control circuit 30 dq / 3 phase conversion circuit 40 PWM signal generation circuit 50 3 phase / Dq conversion circuit 60 PWM signal changeover switch 70 Contactor control circuit 80 Speed calculation circuit 100 Current detection circuit 200 Excitation coil 300 Fuse 400 Diode 500 Voltage detection circuit

Claims (13)

A motor control device, wherein a battery and an inverter are connected via a contactor, and a DC voltage of the battery is converted into an AC voltage by the inverter and applied to an AC motor,
Contactor control means for disconnecting the battery and the inverter by opening the contactor and closing the contactor to connect the battery and the inverter, and supply and stop of AC voltage to the motor Inverter control means for controlling
The inverter includes a switching element for converting a DC voltage into an AC voltage, a reflux diode connected in parallel to each switching element, and a smoothing capacitor for absorbing a switching surge,
The motor includes an exciting coil for generating magnetic force,
Before the battery and the inverter are disconnected from the connected state,
Stop the inverter and wait for the predetermined waiting time to elapse.
Thereafter, the contactor is controlled from a closed state to an open state.
The motor control apparatus characterized by the above-mentioned. The motor control device according to claim 1,
Furthermore, it has a current detection circuit for detecting the current flowing through the exciting coil,
The standby time is a time determined from the current flowing through the excitation coil, the characteristics of the smoothing capacitor, and the characteristics of the excitation coil.
And a motor control device. The motor control device according to claim 1 or 2,
Furthermore, it has a voltage detection circuit for detecting the voltage of the smoothing capacitor,
The waiting time is
The time determined from the current flowing through the excitation coil, the characteristics of the smoothing capacitor, the characteristics of the excitation coil, the voltage of the smoothing capacitor at the time of inverter stop, and a predetermined upper limit voltage of the inverter,
And a motor control device. The motor control device according to claim 3,
The waiting time t is
The current Iac flowing through the exciting coil, the capacitance C of the smoothing capacitor, the inductance L of the exciting coil, the total impedance Z of the energization path from the exciting coil to the battery, and the voltage V0 of the smoothing capacitor when the inverter is stopped , Using the predetermined upper limit voltage Vlim of the inverter 5,
t = −L / ZXLn ((Vlim−V0) × √ (C / L) / Iac)
A motor control device characterized by the following. The motor control device according to claim 1,
Furthermore, it has a current detection circuit for detecting the current flowing through the exciting coil, a voltage detection circuit for detecting the voltage of the smoothing capacitor,
The standby time until the current flowing through the exciting coil falls below the current determined from the characteristics of the smoothing capacitor and the exciting coil,
And a motor control device. The motor control device according to claim 5,
The waiting time is
Using the current Iac flowing through the exciting coil, the capacitance C of the smoothing capacitor, the inductance L of the exciting coil, the voltage Vdc of the smoothing capacitor, and the predetermined upper limit voltage Vlim of the inverter, the following equation is established. Until
And a motor control device.
Iac ≦ (Vlim−Vdc) / (√ (L / C)) The motor control device according to any one of claims 1 to 6,
The standby time is provided only during regenerative control of the motor.
And a motor control device. The motor control device according to claim 4,
The waiting time t is
The current Iac flowing through the exciting coil, the capacitance C of the smoothing capacitor, the inductance L of the exciting coil, the voltage V0 of the smoothing capacitor when the inverter is stopped, and the predetermined upper limit voltage Vlim of the inverter are:
Iac> (Vlim−V0) × √ (C / L)
Provided only when the conditions of
And a motor control device. In the motor control device according to any one of claims 1 to 8,
Comprising a fuse electrically connected in series with the contactor;
The motor control apparatus characterized by the above-mentioned. In the motor control device according to any one of claims 1 to 9,
A current detection circuit for detecting a current between the inverter and the battery;
When the current detection circuit detects a current exceeding a predetermined overcurrent threshold,
Do not wait for the waiting time to elapse,
The motor control apparatus characterized by the above-mentioned. The motor control device according to claim 10,
The overcurrent threshold is less than the current at which the contactor is welded;
The motor control apparatus characterized by the above-mentioned. The motor control device according to claim 11, wherein
A fuse electrically connected in series with the contactor;
The current at which the fuse blows is smaller than the current at which the contactor is welded.
The motor control apparatus characterized by the above-mentioned. The motor control device according to claim 11, wherein
A fuse electrically connected in series with the contactor;
The current at which the fuse blows is smaller than the current at which the contactor is welded,
And,
The overcurrent threshold is set smaller than the current at which the fuse blows,
The motor control apparatus characterized by the above-mentioned.