Motor drive device

Abstract

To provide a motor drive device with less energy loss.SOLUTION: Provided is a motor drive device to be connected to a circuit including an inverter and a motor, the motor drive device including: a DC link connected to the inverter; a power storage device connected to the DC link; and a control device that measures a voltage of the DC link and controls charging / discharging of the power storage device according to the value of the measured voltage. The control device exerts control of charging the power storage device when the value of the voltage is more than a predetermined value, and exerts control of discharging the power storage device when the value of the voltage is less than the predetermined value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a motor drive device having a power storage device. [Background technology]

[0002] A known example of a motor drive device is disclosed in Japanese Patent Application Laid-Open No. 2022-19798. This motor drive device includes a control device that adds up the power losses in the motor, converter, and inverter, calculates an estimated value for a predetermined time period from the current value, and determines whether to supply power to or discharge power from a power storage device based on the estimated amount of power. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-19798 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional motor drives can result in lost energy. The present disclosure has been made in an attempt to solve the above problems. [Means for solving the problem]

[0005] In order to solve the above problems, the present disclosure provides the following motor drive device.

[0006] 1. A motor drive device connected to a circuit having an inverter and a motor, the motor drive device comprising: a DC link connected to the inverter; a power storage device connected to the DC link; a voltage meter that measures a voltage of the DC link; and a control device that controls charging and discharging of the power storage device in accordance with a value of the voltage measured by the voltage meter, wherein the control device controls the power storage device to be charged when the value of the voltage is greater than a predetermined value, and controls the power storage device to be discharged when the value of the voltage is smaller than the predetermined value.

[0007] The motor drive device, wherein the storage device further has a passing power meter that measures the charging power, and the control device controls the storage device to discharge an amount of power equal to the value of the charging power measured by the passing power meter when the value of the voltage is smaller than the predetermined value.

[0008] The motor drive device, wherein the predetermined value is greater than the voltage of the system power supply.

[0009] The circuit includes a plurality of inverters and a plurality of motors. [Effects of the Invention]

[0010] According to the invention of the present disclosure, it is possible to provide a motor drive device with low energy loss. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram of one embodiment of the disclosed invention. [Figure 2] FIG. 2 is a flowchart of the operation of one embodiment of the disclosed invention. [Figure 3] FIG. 3 is a graph showing the relationship between the DC link voltage, the motor drive current input / output to / from the capacitor, and the regenerative current in one embodiment according to the invention of the present disclosure. [Figure 4]FIG. 4 is a graph comparing the power of the system power supply consumed to drive the motor in a conventional system and one embodiment according to the invention of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In this specification, "converting power" includes at least one of "rectification" (changing DC to AC or AC to DC) and "conversion" (changing voltage to an arbitrary value).

[0013] As shown in Fig. 1, motor drive device 1 according to the invention of the present disclosure is connected to a power system 2 and includes a converter 3, an inverter 5 connected to a DC link 4, a motor 6 connected to inverter 5, and a power storage device 7 connected to DC link 4. Two types of power flow through motor drive device 1: "motor drive power" that is supplied from at least one of power system 2 and power storage device 7 and drives motor 6, and "regenerative power" that is regenerative power generated by motor 6 during deceleration, etc. and supplied to power storage device 7.

[0014] 1 shows a configuration in which regenerative power generated from one motor 6 is charged into one power storage device 7. Motor drive device 1 may, for example, be provided with one power storage device 7 for a plurality of inverters 5 and motors 6. Motor drive device 1 may, for example, be provided with a plurality of power storage devices 7 for a pair of inverters 5 and motors 6. The number of power storage devices 7 does not limit this embodiment, and may be one or more.

[0015] The system power supply 2 is a commercial power supply. The system power supply 2 may be, for example, an AC power supply. The AC power supply may be, for example, a three-phase AC power supply or a single-phase AC power supply. The voltage of the system power supply 2 may be, for example, 200 V. The voltage of the system power supply 2 may be, for example, 100 to 200 V.

[0016] The converter 3 converts AC power supplied from the system power supply 2 into DC power. For example, when three-phase AC is supplied from the system power supply 2, the converter 3 may be configured with a three-phase bridge circuit. For example, when single-phase AC is supplied from the system power supply 2, the converter 3 may be configured with a single-phase bridge circuit. For example, a rectifier circuit of a PWM (Pulse Width Modulation) switching control type may be used for the converter 3. For example, a unipolar transistor, a bipolar transistor, an IGBT (Insulated Gate Bipolar Transistor), a thyristor, or the like may be used as the switching element.

[0017] The DC link 4 is located between the converter 3, the inverter 5, and the power storage device 7. DC power flows through the DC link 4. When motor drive power flows to the motor drive device 1, the DC power output from the converter 3 is supplied to the inverter 5 via the DC link 4 to drive the motor 6. When motor regenerative power flows, regenerative power generated by the motor 6 is supplied to the power storage device 7 via the inverter 5 and the DC link 4. When motor drive power is supplied from the power storage device 7 to the motor 6, it is supplied from the power storage device 7 to the motor 6 via the DC link 4 and the inverter 5.

[0018] The inverter 5 converts the DC power output from the converter 3 into AC power to drive the motor 6. The inverter 5 converts regenerative AC power generated when the motor 6 decelerates, for example, into DC power to supply the regenerative power to the power storage device 7. As shown in FIG. 1 , the inverters 5 may be provided in one-to-one correspondence with the motors 6. For example, if the motor 6 is a three-phase motor, the inverter 5 may be a three-phase bridge circuit. For example, if the motor 6 is a single-phase motor, the inverter 5 may be a single-phase bridge circuit.

[0019] The inverter 5 is a bridge circuit having a switching element and a diode connected in antiparallel to the switching element. The switching element of the inverter 5 may be controlled based on, for example, a triangular wave comparison type PWM switching control. The switching element may be, for example, a unipolar transistor, a bipolar transistor, an IGBT, a thyristor, or the like.

[0020] The motor 6 is driven by the converted AC power supplied from the inverter 5. In other words, by controlling the switching elements of the inverter 5, the motor 6 rotates forward to drive the motor 6 and rotates reversely to decelerate the motor 6. The motor 6 supplies the power generated during reverse rotation to the inverter 5 as regenerative power, and the power is supplied to the power storage device 7 via the DC link 4.

[0021] The power storage device 7 is a device that stores surplus power generated in the motor drive device 1 and supplies power to drive the motor drive device 1 from a source other than the grid power supply 2. In this embodiment, the description focuses on regenerative power generated by the motor 6, but is not limited to regenerative power, and may also include power generated by other factors. The power storage device 7 includes a power storage device 8, a power converter 9, a passing power meter 10, a voltage meter 11, and a control device 12.

[0022] The capacitor 8 stores the power supplied to the power storage device 7 by charging it, and drives the motor 6 by discharging the stored power. The capacitor 8 can be repeatedly charged and discharged. For example, an electric double layer capacitor may be used as the capacitor 8. The electric double layer capacitor may use an electrolytic solution such as an aqueous solution, an organic solution, or an ionic liquid. For example, a secondary battery may be used as the capacitor 8. The secondary battery may be, for example, a lithium ion secondary battery or a nickel-metal hydride battery. For example, the capacitor 8 may be a fuel cell. In this case, the capacitor 8 may, for example, electrolyze water using the supplied power, store the hydrogen, and extract electricity from the fuel cell when needed.

[0023] The capacitor 8 may store electric energy using a flywheel as rotational energy, for example. In this case, the capacitor 8 may have a separate motor and inverter for rotating the flywheel.

[0024] The power converter 9 is connected to the DC link 4 as shown in FIG. 1 and converts the voltage of the DC power. In other words, the power converter 9 is a DC-DC converter. The power converter 9 may use, for example, a DC chopper circuit. The power converter 9 may also be an isolated DC-DC converter using a transformer. The power converter 9 can step up or step down the voltage of the power input / output to / from the power storage device 7. The power converter 9 is controlled by a control device 12, which will be described later.

[0025] The passing power meter 10 measures the power charged to the capacitor 8. The passing power meter 10 measures the power discharged from the capacitor 8. As shown in FIG. 1, the passing power meter 10 is connected in series between the capacitor 8 and the power converter 9. The passing power meter 10 may measure the DC power supplied to the capacitor 8, for example, by measuring the magnitude of the power passing through the passing power meter 10 and integrating it over time.

[0026] The voltage meter 11 measures the voltage of the DC link 4. The voltage meter 11 is connected in parallel to the DC link 4. The voltage meter 11 outputs information about the measured voltage to the control device 12, which will be described later.

[0027] The control device 12 controls the charging and discharging of the battery 8. The control device 12 measures the voltage of the DC link 4, and if the voltage is greater than a predetermined value stored in the control device 12, controls the power converter 9 to charge the battery 8. If the voltage of the DC link 4 is smaller than a predetermined value, the control device 12 controls the power converter 9 to discharge the battery 8. Information on the voltage of the DC link 4 measured by a voltage meter 11 is input to the control device 12. Information on the charging power or discharging power measured by a passing power meter 10 is input to the control device 12. The control device 12 controls the power converter 9 based on the various pieces of input information, thereby controlling the charging or discharging operation of the battery 7.

[0028] The predetermined value of the voltage of the DC link 4 may be set to, for example, a value greater than the voltage of the grid power supply 2. As a result, when a voltage greater than that of the grid power supply 2 is applied to the DC link 4, i.e., when regenerative power is generated, power is immediately stored in the battery 8. This reduces the possibility of energy loss. The predetermined value of the voltage of the DC link 4 may be, for example, 220 V. The predetermined value of the voltage of the DC link 4 may be, for example, 110 to 220 V.

[0029] The control performed by the control device 12 will be described in detail below with reference to FIG.

[0030] In step S101, the control device 12 acquires information about the voltage of the DC link 4 measured by the voltage measuring instrument 11, and determines whether the measured value of the voltage of the DC link 4 differs from a predetermined value. If the measured value of the voltage of the DC link 4 differs from the predetermined value, the process proceeds to step S102. If the measured value of the voltage of the DC link 4 is the same as the predetermined value, the process returns to step S101.

[0031] In step S102, the control device 12 acquires information about the voltage of the DC link 4 measured by the voltage measuring instrument 11, and determines whether the measured value of the voltage of the DC link 4 is greater than a predetermined value. If the measured value of the voltage of the DC link 4 is greater than the predetermined value, the process proceeds to step S103. If the measured value of the voltage of the DC link 4 is smaller than the predetermined value, the process proceeds to step S107.

[0032] In step S103, the control device 12 controls the power converter 9 to charge the capacitor 8 with power. As shown in Fig. 3, the control device 12 refers to the voltage (solid line) of the DC link 4, and when the measured value of the voltage of the DC link 4 is greater than a predetermined value, the control device 12 charges the capacitor 8 with regenerative power (dashed line). Once charging of the capacitor 8 has started, the process proceeds to step S104.

[0033] In step S104, the passing power meter 10 measures the regenerative power that is charged into the capacitor 8. The measured value of the regenerative power is output to and recorded by the control device 12. Then, the process proceeds to step S105.

[0034] In step S105, the control device 12 acquires the value of the voltage of the DC link 4 measured by the voltage measuring instrument 11, and determines whether the measured value of the voltage of the DC link 4 is equal to or less than a predetermined value. If the measured value of the voltage of the DC link 4 is equal to or less than the predetermined value, the process proceeds to step S106. If the voltage of the DC link 4 is greater than the predetermined value, the process returns to step S103.

[0035] In step S106, the control device 12 controls the power converter 9 to terminate the charging operation to the capacitor 8. After the charging operation is completed, the process returns to step S101.

[0036] In step S107, the control device 12 controls the power converter 9 to discharge power from the capacitor 8. As shown in Fig. 3, the control device 12 refers to the voltage (solid line) of the DC link 4, and discharges power from the capacitor 8 (dashed line) if the measured value of the DC link 4 is smaller than a predetermined value. Once discharge from the capacitor 8 has started, the process proceeds to step S108.

[0037] In step S108, the passing power meter 10 measures the motor driving power discharged from the capacitor 8. The measured value of the motor driving power is recorded in the control device 12. Then, the process proceeds to step S109.

[0038] In step S109, the control device 12 acquires information about the voltage of the DC link 4 measured by the voltage meter 11, determines whether the measured value of the voltage of the DC link 4 is equal to or greater than a predetermined value, and further compares it with the discharge amount measured by the passing power meter 10 to determine whether the discharge amount is equal to or greater than the charge amount. If at least one of the cases where the measured value of the voltage of the DC link 4 is equal to or greater than the predetermined value and the discharge amount is equal to or greater than the charge amount is met, the process proceeds to step S110. If the measured value of the voltage of the DC link 4 is smaller than the predetermined value and the discharge amount is smaller than the charge amount, the process returns to step S107.

[0039] In step S110, the control device 12 controls the power converter 9 to terminate the discharging operation to the capacitor 8. After the discharging operation is completed, the process returns to step S101.

[0040] As described above, motor drive device 1 controls the charging and discharging of battery 8 in accordance with the voltage of DC link 4. This allows regenerative power to be charged to battery 8 without the need to control inverter 5 or separately calculate the amount of regenerative power generated by motor 6. As a result, it becomes possible to take in the generated regenerative power into battery 8 at an appropriate timing, and as shown in FIG. 4, energy loss can be reduced compared to conventional systems, and motor 6 can be driven with a smaller amount of power supplied from grid power supply 2.

[0041] In another embodiment of the motor drive device 1, for example, instead of using the passing power meter 10, charging and discharging may be controlled by measuring the SOC (State Of Charge) of the capacitor 8. The SOC of the capacitor 8 may be measured, for example, by measuring the open circuit voltage of the capacitor 8. The SOC of the capacitor 8 may be measured, for example, by measuring the temperature of the capacitor 8 with a thermistor or the like, and used for calculation.

[0042] In step S105, the control device 12 may terminate the charging operation by, for example, referring to the SOC of the capacitor 8 instead of the voltage value of the DC link 4. That is, in step S105, the control device 12 may terminate the charging operation when, for example, the SOC of the capacitor 8 is 80% to 90% or more. This can reduce the possibility that the capacitor 8 will be overcharged.

[0043] In step S109, the control device 12 may terminate the discharging operation by, for example, referring to the SOC of the capacitor 8 instead of the voltage value of the DC link 4. That is, in step S109, the control device 12 may terminate the discharging operation when the SOC of the capacitor 8 is 10% to 20% or less, for example. This can reduce the possibility of the capacitor 8 being over-discharged.

[0044] In another embodiment of the motor drive device 1, for example, power generated by a solar power generation device may be supplied in addition to the grid power supply 2. In this case, the solar power generation device may be connected to a DC link (not shown). This allows the power supplied from the solar power generation device to be stored in the power storage device 7, making it possible to drive the motor 6 with a smaller amount of power supplied from the grid power supply 2. As a result, carbon dioxide emissions can be reduced.

[0045] The present disclosure has been described in detail above, but the present disclosure is not limited to the above-described embodiments, and various modifications, improvements, etc. are possible within the scope that does not deviate from the gist of the present disclosure. [Explanation of symbols]

[0046] 1. Motor drive unit 2 power supplies 3 Converter 4 DC Link 5 inverters 6 motors 7. Energy storage device 8. Capacitor 9 Power Converter 10. Pass-through power meter 11 Voltage measuring instrument 12 Control device

Claims

1. A motor drive device connected to a circuit having an inverter and a motor, a DC link connected to the inverter; a power storage device connected to the DC link; a control device that measures a voltage of the DC link and controls charging and discharging of the power storage device in accordance with the value of the measured voltage, The control device controls the storage device to charge when the voltage value is greater than a predetermined value, and controls the storage device to discharge when the voltage value is less than the predetermined value.

2. the power storage device further includes a passing power meter that measures charging power; 2. The motor drive device according to claim 1, wherein the control device controls the storage device to discharge an amount of power equal to the value of the charged power measured by the passing power meter when the voltage value is smaller than the predetermined value.

3. 2. The motor drive device according to claim 1, wherein the predetermined value is greater than the voltage of the system power supply.

4. 2. The motor drive device according to claim 1, wherein the circuit includes a plurality of inverters and a plurality of motors.

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