Power supply system and control method thereof

Abstract

To provide a power supply system which can appropriately suppress inrush current due to voltage fluctuation in an AC power supply system by a simple configuration and a control method thereof.SOLUTION: A power supply system comprises: a rectifier connected with an AC power supply system via first AC wiring to rectify first AC power in the AC power supply system to DC power; an inverter connected with the rectifier via DC wiring, connected with an electric motor via second AC wiring to convert the DC power into second AC power and to supply the second AC power to the second AC wiring; a controller comprising a processing circuit to control the inverter; and a voltage detection circuit to detect voltage in the first AC wiring, wherein the processing circuit corrects a current command value to the second AC wiring so that current flowing from the inverter to the electric motor becomes small or current flows from the electric motor to the inverter when voltage in the first AC wiring rises.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power supply system and a control method thereof. [Background technology]

[0002] Systems equipped with electric motors as power sources are known for use in mobile objects such as automobiles, ships, and aircraft, as well as in fixed facilities such as houses. For example, a mobile object may be equipped with a generator that supplies electric power to the motor, and the electric power generated by the generator is supplied to the motor via a rectifier and an inverter. However, when the installation space for the system is limited, such as when the system is mounted on a mobile object, the capacity of the generator cannot be increased and may be limited to a capacity equivalent to that of the load.

[0003] In this case, fluctuations in the load connected to the AC power supply system may cause fluctuations in the system voltage. If the system voltage rises due to such load fluctuations, the potential difference between the system voltage and the DC voltage in the DC wiring between the rectifier and the inverter may increase, and an inrush current may occur in the DC wiring through the rectifier.

[0004] In this regard, Patent Document 1 listed below discloses a configuration in which an AC power supply system is provided with an inrush current prevention resistor, an inrush current prevention relay, and a relay circuit connected in parallel with a power relay, and the relay circuit is switched depending on the DC voltage in the DC wiring. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-242081 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the configuration of Patent Document 1 requires the addition of a relay circuit, which complicates the system. Furthermore, the need for physical circuit switching results in poor responsiveness, which may make it difficult to adequately suppress inrush currents caused by voltage fluctuations.

[0007] The present disclosure is intended to solve the above-mentioned problems, and aims to provide a power supply system and a control method thereof that can appropriately suppress inrush current caused by voltage fluctuations in an AC power supply system with a simple configuration. [Means for solving the problem]

[0008] A power supply system according to one embodiment of the present disclosure is a power supply system for supplying power from an AC power supply system to an electric motor, the power supply system including: a rectifier connected to the AC power supply system via a first AC wiring and rectifying first AC power in the AC power supply system into DC power; an inverter connected to the rectifier via a DC wiring and connected to the electric motor via a second AC wiring and converting the DC power to second AC power and supplying the second AC power to the second AC wiring; a controller including a processing circuit and controlling the inverter; and a voltage detection circuit that detects a voltage in the first AC wiring, wherein when the voltage in the first AC wiring increases, the processing circuit corrects a current command value for the second AC wiring so that a current flowing from the inverter to the electric motor becomes smaller or so that a current flows from the electric motor to the inverter.

[0009] A control method for a power supply system according to another aspect of the present disclosure is a control method for a power supply system for supplying power from the AC power supply system to the electric motor, the control method comprising: a rectifier connected to an AC power supply system via a first AC wiring and rectifying first AC power in the AC power supply system into DC power; and an inverter connected to the rectifier via a DC wiring and connected to an electric motor via a second AC wiring and converting the DC power to second AC power and supplying the second AC power to the second AC wiring, the control method acquiring a voltage on the first AC wiring, and correcting a current command value for the second AC wiring when the voltage on the first AC wiring increases so that the current flowing from the inverter to the electric motor becomes smaller or so that current flows from the electric motor to the inverter. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to appropriately suppress inrush current caused by voltage fluctuations in an AC power supply system with a simple configuration. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of a power supply system according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a block diagram showing the configuration of a voltage command value calculation unit in the processing circuit shown in FIG. [Figure 3] FIG. 3 is a block diagram showing a configuration of an active current command value corrector in the processing circuit shown in FIG. [Figure 4] FIG. 4 is a block diagram showing a schematic configuration of a power supply system according to a modification of the embodiment shown in FIG. [Figure 5] FIG. 5 is a graph showing changes in the system voltage vr, the input current ir, the DC voltage vdc, and the motor rotation speed ωr with respect to time t in the first simulation. [Figure 6] FIG. 6 is a graph showing changes in the system voltage vr, the input current ir, the DC voltage vdc, and the motor rotation speed ωr with respect to time t in the second simulation. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following, elements that are identical or have the same function will be designated by the same reference numerals throughout the drawings, and redundant description thereof will be omitted.

[0013] [System Configuration] Fig. 1 is a block diagram showing a schematic configuration of a power supply system according to an embodiment of the present disclosure. As shown in Fig. 1, power supply system 1 according to the present embodiment is configured to supply power from an AC power supply system 2 to an electric motor 3. Power supply system 1 includes a rectifier 4, an inverter 5, and a controller 11 that controls inverter 5.

[0014] The rectifier 4 is connected to the AC power supply system 2 via a first AC wiring 6. In this embodiment, a generator 7, which is a power supply source in the AC power supply system 2, is directly connected to the first AC wiring 6. The rectifier 4 rectifies the first AC power in the AC power supply system 2, i.e., the first AC power generated by the generator 7, into DC power. The rectifier 4 includes at least one diode. The rectifier 4 may also include an LC filter or a transformer arranged on the AC side to remove harmonic noise.

[0015] The inverter 5 is connected to the rectifier 4 via a DC wiring 8, and is connected to the electric motor 3 via a second AC wiring 9. The inverter 5 converts the DC power in the DC wiring 8 into second AC power and supplies the second AC power to the second AC wiring 9. The electric motor 3 is driven by the second AC power supplied to the second AC wiring 9. The inverter 5 includes a switching circuit including a switching element such as a MOSFET. The inverter 5 adjusts the second AC power supplied to the second AC wiring 9 by switching the switching circuit based on a control signal from a controller 11. A capacitor 10 that smoothes the DC power rectified by the rectifier 4 is connected to the DC wiring 8.

[0016] The controller 11 includes a processing circuit 20 that performs various types of signal processing. The processing circuit 20 includes a computer such as a microcontroller, a personal computer, or a programmable logic controller (PLC). For example, the processing circuit 20 includes a processor, a memory, and peripheral circuits.

[0017] The processor includes, for example, a CPU or an MPU. The memory includes volatile memory such as ROM, RAM, and registers, and non-volatile memory such as flash memory. A control program for the inverter 5 is stored in advance in the memory. The peripheral circuit includes an input / output interface, etc. The processor, memory, and peripheral circuit communicate with each other via a bus. The processor executes the control program to perform arithmetic processing (described below) based on various information stored in the memory.

[0018] It should be noted that the functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuitry. In this specification, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. Where hardware is a processor, which is considered a type of circuit, the circuit, unit, means, or section is a combination of hardware and software, and software is used to configure the hardware or processor.

[0019] Furthermore, the power supply system 1 includes a voltage detection circuit 12, a current detection circuit 13, and a phase detector 14 in order to control the inverter 5 by the controller 11. The voltage detection circuit 12 detects the voltage in the first AC wiring 6. The current detection circuit 13 detects the current in the second AC wiring 9. The phase detector 14 detects the angular velocity ω and phase φ of the electric motor 3. The phase detector 14 includes a rotation speed sensor and a phase sensor.

[0020] The controller 11 includes control blocks, namely, a three-phase / two-phase conversion unit 21, a voltage command value calculation unit 22, a drive signal generation unit 23, an active current command value generation unit 24, a reactive current command value generation unit 25, an effective voltage value calculation unit 26, and an active current command value correction unit 27. As described above, each of these control blocks is considered to be a processing circuit or circuit. The controller 11 controls the power output by the inverter 5 to the second AC wiring 9 by executing processing in each control block. Each control block will be described in detail below.

[0021] [Three-phase / two-phase conversion section] The current detection circuit 13 detects the instantaneous value i of the current in the second AC wiring 9. a ,i b ,i c The phase detector 14 detects the phase φ. The three-phase / two-phase converter 21 detects the instantaneous current value i a ,i b ,i c The active current Iq and reactive current Id are calculated from the phase φ. The active current is also called the q-axis current or torque current, and the reactive current is also called the d-axis current or magnetic flux current. The active current Iq and reactive current Id can be calculated using the following formula. Note that k is a coefficient, for example, k=(2 / 3) 1 / 2 is.

[0022]

number

[0023] [Voltage command value calculation section] Fig. 2 is a block diagram showing the configuration of a voltage command value calculation unit in the processing circuit shown in Fig. 1. A voltage command value calculation unit 22 obtains a corrected active current command value Iqc and a corrected reactive current command value Ido, which will be described later, and compares them with the active current Iq and the reactive current Id calculated by the three-phase / two-phase conversion unit 21, respectively.

[0024] The voltage command value calculation unit 22 includes subtractors 31 and 33 and PI calculators 32 and 34 that perform proportional and integral calculations. The subtractor 31 calculates a difference value ΔId by subtracting the reactive current Id from the reactive current command value Ido. The PI calculator 32 calculates a d-axis voltage command value Vdo by performing proportional and integral calculations on the difference value ΔId. Similarly, the subtractor 33 calculates a difference value ΔIq by subtracting the active current Iq from the corrected active current command value Iqc. The PI calculator 34 calculates a q-axis voltage command value Vqo by performing proportional and integral calculations on the difference value ΔIq. In this way, the voltage command value calculation unit 22 automatically adjusts the voltage command values ​​Vqo and Vdo so that the deviations between the current command values ​​Iqc and Ido and the corresponding currents Iq and Id become zero. Note that decoupling control, etc., may be applied after the proportional and integral calculations.

[0025] [Drive signal generation section] The drive signal generator 23 generates a drive signal So such that the voltages Vq and Vd in the second AC wiring 9 become the voltage command values ​​Vqo and Vdo. More specifically, the drive signal generator 23 performs two-phase / three-phase conversion as shown in the following equation from the phase φ and the voltage command values ​​Vqo and Vdo, and generates command values ​​v of each instantaneous voltage in the second AC wiring 9, which is a three-phase AC. ao ,v bo ,v co Calculate.

[0026]

number

[0027] The drive signal generator 23 generates the calculated instantaneous voltage command value v ao ,v bo ,v coThe drive signal generator 23 generates a drive signal So for switching the inverter 5 based on the above. For example, the drive signal generator 23 generates a PWM control signal as the drive signal So. The drive signal generator 23 generates a modulated wave for each phase by dividing the command value of each instantaneous voltage by the intermediate value Ed / 2 of the DC voltage Ed. The drive signal generator 23 generates the drive signal So such that the inverter 5 is switched at the intersection of the modulated wave for each phase and a predetermined carrier signal such as a triangular wave. The drive signal So is input to the inverter 5, and the output voltage to the second AC wiring 9 is controlled based on the drive signal So.

[0028] [Active current command value generator] The active current command value generation unit 24 generates an active current command value Iqo that serves as a basis for the corrected active current command value Iqc to be input to the voltage command value calculation unit 22. For example, the active current command value generation unit 24 may output the active current command value Iqo that is stored in advance in a memory. Alternatively, the memory may store a data table that indicates different active current command values ​​Iqo depending on other predetermined control parameters such as the angular velocity ω of the electric motor 3. In this case, the active current command value generation unit 24 may acquire the values ​​of the control parameters and refer to the data table to output the active current command value Iqo that corresponds to the values ​​of the control parameters.

[0029] Alternatively, the active current command value generation unit 24 may obtain an angular velocity ω corresponding to the rotation speed of the electric motor 3, and calculate an active current command value Iqo corresponding to the difference between the angular velocity ω and the angular velocity command value ωo. In this case, the active current command value generation unit 24 may calculate the active current command value Iqo by performing a proportional integral calculation of the difference between the angular velocity ω and the angular velocity command value ωo. Instead of the proportional integral calculation, a PID calculation including a proportional calculation, an integral calculation, and a differential calculation may be performed.

[0030] Furthermore, when the electric motor 3 is an induction motor, the active current command value generating unit 24 may use a value obtained by proportional-plus-integral calculation of the difference between the angular velocity ω and the angular velocity command value ωo as a torque command value τo, and convert the torque command value τo into an active current command value Iqo using the theoretical equation of the induction motor. The conversion equation is expressed by the following equation.

[0031]

number

[0032] Note that L2 is the secondary self-inductance of the induction motor, M is the mutual inductance of the induction motor, and φ2 is the secondary magnetic flux of the induction motor. These values ​​may be fixed values ​​or may be values ​​obtained from a data table that change depending on other parameters. Furthermore, the secondary magnetic flux φ2 may be determined from the reactive current Id by magnetic flux calculation as shown in the following equation. Note that r2 is the secondary winding resistance of the induction motor. This value may also be a fixed value or may be a value obtained from a data table that changes depending on other parameters.

[0033]

number

[0034] [Reactive current command value generation part] The reactive current command value generating unit 25 generates a reactive current command value Ido to be input to the voltage command value calculating unit 22. For example, the reactive current command value generating unit 25 may output a reactive current command value Ido stored in advance in a memory. Alternatively, the memory may store a data table indicating different reactive current command values ​​Ido depending on other predetermined control parameters such as the angular velocity ω of the electric motor 3. In this case, the reactive current command value generating unit 25 may acquire the value of the control parameter and refer to the data table to output the reactive current command value Ido depending on the value of the control parameter.

[0035] Alternatively, the reactive current command value generating unit 25 may calculate the reactive current command value Ido from the magnetic flux command value φ2o. For example, when the electric motor 3 is an induction motor, the conversion equation from the magnetic flux command value φ2o to the reactive current command value Ido can be expressed as follows:

[0036]

number

[0037] The magnetic flux command value φ2o may be a fixed value or may be calculated using equation (4).

[0038] [Voltage effective value calculation section] The voltage detection circuit 12 detects the instantaneous voltage v in the first AC wiring 6. a ,v b ,v c The voltage effective value calculation unit 26 detects the voltage instantaneous value v a ,v b ,v c to the voltage effective value v in the first AC wiring 6 r For example, the effective voltage v r is the instantaneous voltage value v a ,v b ,v c It is calculated using the following formula:

[0039]

number

[0040] Or, the effective voltage v r is the instantaneous voltage value v of each phase as shown in the following equation. a ,v b ,v c Alternatively, the average value may be calculated from the root mean square of one period of the signal.

[0041]

number

[0042] Or, the effective voltage v r is the instantaneous voltage value v a ,v b ,v c Alternatively, the voltages Vα and Vβ may be calculated by performing a three-phase / two-phase conversion on the r is expressed as follows using three-phase / two-phase conversion without using the phase θ in the first AC wiring 6. Here, m is a coefficient, and for example, m=3.

number

[0043] Alternatively, the voltage effective value v is obtained by three-phase / two-phase conversion using the phase θ in the first AC wiring 6. r In this case, the voltage effective value calculation unit 26 performs three-phase / two-phase conversion as shown in the following equation. The phase θ at this time is calculated by performing a PLL (Phase Locked Loop) operation on the voltages Vα and Vβ obtained by the following equation. The voltage effective value calculation unit 26 calculates the voltage effective value v from the obtained voltages Vα and Vβ using equation (9). r Calculate.

[0044]

number

[0045] [Active current command value correction part] When the voltage in the first AC wiring 6 increases, the processing circuit 20 corrects the current command value for the second AC wiring 9 so that the current flowing from the inverter 5 to the electric motor 3 decreases or so that a current flows from the electric motor 3 to the inverter 5. For this purpose, the active current command value corrector 27 calculates the active current command value Iqo by multiplying the effective voltage value v r Correction is made based on the

[0046] 3 is a block diagram showing the configuration of the active current command value corrector 27 in the processing circuit shown in FIG. 1. The active current command value corrector 27 includes a high-pass filter 35, a subtractor 36, and limiters 37 and 38. The active current command value corrector 27 calculates the effective voltage value v r Applying a high-pass filter 35 to the voltage effective value v r In the transfer function of the high-pass filter 35 shown in FIG.

[0047] The active current command value corrector 27 subtracts the voltage effective value v from the active current command value Iqo using a subtractor 36. r The active current command value Iqo is corrected by subtracting the fluctuation component of

[0048] Here, when the voltage in the first AC wiring 6 drops, no inrush current flows through the rectifier 4. Therefore, the active current command value corrector 27 does not correct the active current command value Iqo when the voltage in the first AC wiring 6 drops. Furthermore, no inrush current flows through the rectifier 4 even in response to a small fluctuation in the voltage in the first AC wiring 6. Therefore, the active current command value corrector 27 does not correct the active current command value Iqo when the fluctuation in the voltage in the first AC wiring 6 is small.

[0049] More specifically, the active current command value corrector 27 calculates the effective voltage value v r For example, the first limiter 37 applies a first limit to the fluctuation component of the voltage effective value v r The first limiter 37 is a lower limiter that passes fluctuation components equal to or greater than a predetermined correction reference value and sets fluctuation components below the correction reference value to 0. The correction reference value is set to a value equal to or greater than 0. The first limiter 37 may include a dead band circuit instead of a lower limiter.

[0050] The first limiter 37 prevents the current command value from being corrected unnecessarily even when there is no risk of an inrush current flowing, thereby preventing the drive control performance of the electric motor 3 from deteriorating.

[0051] Furthermore, if the corrected active current command value Iqc becomes excessively larger than the original active current command value Iqo, the current in the second AC wiring 9 may be excessively corrected, which may deteriorate the drive control performance of the electric motor 3. For this reason, the active current command value corrector 27 applies a second limiter 38 to the output Iqb of the subtractor 36. For example, the second limiter 38 is configured by an upper / lower limiter or a lower limiter.

[0052] The active current command value corrector 27 outputs the output of the second limiter 38 as a corrected active current command value Iqc. The corrected active current command value Iqc is input to the voltage command value calculator 22.

[0053] [effect] As described above, according to the present embodiment, when the voltage in the first AC wiring 6 increases, the current command value for the second AC wiring 9 is corrected so that the current flowing from the inverter 5 to the motor 3 decreases or so that a current flows from the motor 3 to the inverter 5. When the current flowing from the inverter 5 to the motor 3 decreases, the current flowing from the capacitor 10 to the inverter 5 decreases, and a drop in the DC voltage in the DC wiring 8 is suppressed. Furthermore, when a current flows from the motor 3 to the inverter 5, the motor 3 enters a regenerative state, and a reverse power flow occurs from the motor 3 to the inverter 5. Therefore, a current flows from the inverter 5 to the capacitor 10 via the DC wiring 8, and the DC voltage in the DC wiring 8 increases.

[0054] A decrease in the DC voltage in the DC wiring 8 is suppressed, or when the DC voltage increases, the potential difference between the DC voltage and the voltage in the first AC wiring 6 decreases. As a result, even if the voltage in the first AC wiring 6 increases, the current flowing from the first AC wiring 6 to the DC wiring 8 via the rectifier 4 can be suppressed. Therefore, the inrush current due to voltage fluctuations in the AC power supply system 2 can be suppressed.

[0055] Furthermore, according to this embodiment, unlike the conventional technique, it is not necessary to add a relay circuit or the like, and the occurrence of inrush current can be suppressed with a simple configuration. Furthermore, since physical switching of a relay circuit or the like is not required, the response speed is fast and the occurrence of inrush current can be suppressed even in response to abrupt voltage fluctuations in the AC power supply system 2. Note that while the operating speed of a relay circuit or the like is on the order of several milliseconds, the operating speed of the inverter 5 is generally 1 millisecond or less. In this way, the inrush current caused by voltage fluctuations in the AC power supply system 2 can be appropriately suppressed with a simple configuration.

[0056] Furthermore, in the conventional configuration, it is necessary to switch the control mode before and after switching the relay circuit. Furthermore, switching the relay circuit makes it impossible to maintain the DC voltage in the DC wiring, making it impossible to continue inverter control for driving the electric motor. In contrast, according to the present embodiment, there is no need to add a relay circuit or the like, and there is no need to switch the control mode in response to switching of the relay circuit. Furthermore, since there is no need to stop the power supply from the AC power supply system 2 in response to switching of the relay circuit or the like, it is possible to continue operation of the power supply system 1 even if voltage fluctuations occur in the AC power supply system 2.

[0057] Furthermore, according to this embodiment, since there is no need to add a relay circuit or the like, it is possible to suppress an increase in the size and weight of the power supply system 1. Furthermore, since the inrush current is suppressed, the allowable current of the rectifier 4 can be reduced, thereby enabling the power supply system 1 to be made smaller and lighter. The occurrence of inrush current significantly affects the circuit configuration between the AC power supply system 2 and the DC wiring 8. In particular, inrush current can cause failure of the diodes that make up the rectifier 4. By suppressing the inrush current, the rectifier 4 can be made up of diodes with a small allowable current. Since the larger the allowable current of a diode, the larger and heavier it becomes, so by reducing the allowable current of the diode, the rectifier 4 can be made smaller and lighter. In particular, when the power supply system 1 is installed in a mobile object, fuel efficiency can be improved. Furthermore, the degree of freedom in designing the mobile object can be increased.

[0058] Furthermore, according to this embodiment, since the inrush current is suppressed, it is possible to prevent the generator 7 from becoming transiently overloaded, and the burden on the generator 7 can also be reduced.

[0059] [Variations] Fig. 4 is a block diagram showing a schematic configuration of a power supply system according to a modification of the embodiment shown in Fig. 1. In power supply system 1B shown in Fig. 4, components similar to those in power supply system 1 shown in Fig. 1 are assigned the same reference numerals, and descriptions thereof will be omitted. Power supply system 1B according to this modification differs from power supply system 1 shown in Fig. 1 in that, instead of phase detector 14 that measures angular velocity ω and phase φ of electric motor 3, processing circuit 20 of controller 11 includes, as a control block, a phase estimator 28 that estimates angular velocity ω and phase φ of electric motor 3. Phase estimator 28 is also considered to be a processing circuit or circuit.

[0060] [Phase estimation section] A phase estimation unit 28 generates a phase φ from voltage command values ​​Vqo, Vdo generated by a voltage command value calculation unit 22 and an active current Iq and a reactive current Id generated by a three-phase / two-phase conversion unit 21. A general voltage equation for the electric motor 3 is expressed as nω·sinΔθ=−Vd+rId−ωσLIq, where Δθ is the phase deviation, r is the armature resistance, L is the inductance, and n and σ are coefficients.

[0061] The phase estimation unit 28 substitutes the voltage command value Vdo for Vd of the above voltage equation, and substitutes the active current Iq and reactive current Id generated by the three-phase / two-phase conversion unit 21 for Iq, Id. Furthermore, the phase estimation unit 28 performs a PI calculation on the calculation result of the right-hand side of the above voltage equation, to calculate an angular velocity ω such that the phase deviation Δθ on the left-hand side becomes 0. The phase estimation unit 28 calculates the phase φ by integrating the calculated angular velocity ω. Note that the method for estimating the phase φ is not limited to the above, and various estimation modes are applicable.

[0062] Alternatively, instead of the above-described embodiment, the phase estimation unit 28 may acquire the angular velocity ω from a fixed angular velocity setting value or an angular velocity table stored in advance in a memory, and calculate the phase φ by integrating the angular velocity ω.

[0063] [Simulation Results] (1) Simulation based on the system configuration in Figure 1 Below, as a first simulation, the results of a simulation performed when the voltage of the first AC wiring 6 increases in the system configuration of Fig. 1 according to the above embodiment are shown. In the first simulation, an active current command value Iqo is generated according to the difference between the angular velocity ω detected by the phase detector 14 and the angular velocity command value ωo.

[0064] Figure 5 shows the system voltage v r , input current i r , DC voltage v dc and the motor rotation speed ω r This is a graph showing the change in the system voltage v r and the input current i r are all effective values. At time t, the voltage of the first AC wiring 6, that is, the system voltage v r changes from v1 to v2, where v2 is approximately 1.13 times v1.

[0065] In this way, when the system voltage vr rises, the input current i r rises significantly at time t0, and the maximum current value without correction is i co is nearly double the current i0 up to time t0. On the other hand, when the power supply system 1 according to the above embodiment is applied and the current command value is corrected, the maximum current value i ex is the maximum current value without compensation i co In this simulation, the input current i r The increase in the rate is limited to about half of what it would be without the correction.

[0066] DC voltage v dc In the graph, the DC voltage v dc It is shown that the input current i r Graph of and DC voltage v dc From the graph, DC voltage v dc By increasing the input current i rIt can be seen that the increase in

[0067] In addition, the motor rotation speed ω r In the graph, even if the current command value is corrected, the motor rotation speed ω r It is shown that the rotational speed of the electric motor ω is almost the same as that before time t0. For example, in a hydraulic system equipped with an accumulator, when the drive motor of the hydraulic pump is driven using the power supply system 1 of the above embodiment, the hydraulic pressure is maintained by the action of the accumulator, and the rotational speed of the electric motor ω r It can be seen that small fluctuations in pressure do not affect the operation of the hydraulic system.

[0068] (2) Simulation based on the system configuration in Figure 4 Below, as a second simulation, the results of a simulation performed when the voltage of the first AC wiring 6 increases in the system configuration of Fig. 4, which is a modification of the above embodiment, are shown. In the second simulation, an active current command value Iqo is generated according to the difference between the angular velocity ω estimated by the phase estimator 28 and the angular velocity command value ωo.

[0069] Figure 6 shows the grid voltage v r , input current i r , DC voltage v dc and the motor rotation speed ω r This is a graph showing the change in the system voltage v r and the input current i r are all effective values. At time t, the voltage of the first AC wiring 6, that is, the system voltage v r changes from v1 to v2, where v2 is approximately 1.13 times v1.

[0070] In the second simulation, as in the first simulation, the system voltage v r With the increase in input current i r It is shown that the increase in DC voltage v is suppressed compared to the case without correction. dc and the motor rotation speed ω rThe same tendency as in the first simulation is also observed.

[0071] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various improvements, changes, and modifications are possible within the scope of the spirit of the present disclosure.

[0072] For example, the power supply system may include both the phase detector 14 shown in Fig. 1 and the phase estimation unit 28 shown in Fig. 4. In this case, the controller 11 determines whether to set the phase φ to the value detected by the phase detector 14 or the value estimated by the phase estimation unit 28, based on a predetermined condition.

[0073] The processing circuit 20 also calculates the effective voltage v r If the fluctuation component of Iqc is equal to or greater than a correction reference value, the corrected active current command value Iqc may be corrected to a negative value. For example, the correction reference value may be set to a value greater than the active current command value Iqo. As a result, the output Iqb of the subtractor 36 becomes 0 or a negative value. As a result, the corrected active current command value Iqc becomes a negative value, so that current can flow from the electric motor 3 to the inverter 5 when the voltage in the first AC wiring 6 increases.

[0074] Summary of this disclosure [Item 1] A power supply system according to one embodiment of the present disclosure is a power supply system for supplying power from an AC power supply system to an electric motor, the power supply system including: a rectifier connected to the AC power supply system via a first AC wiring and rectifying first AC power in the AC power supply system into DC power; an inverter connected to the rectifier via a DC wiring and connected to the electric motor via a second AC wiring and converting the DC power to second AC power and supplying the second AC power to the second AC wiring; a controller including a processing circuit and controlling the inverter; and a voltage detection circuit that detects a voltage in the first AC wiring, wherein when the voltage in the first AC wiring increases, the processing circuit corrects a current command value for the second AC wiring so that a current flowing from the inverter to the electric motor becomes smaller or so that a current flows from the electric motor to the inverter.

[0075] According to the above configuration, when the voltage in the first AC wiring increases, the current command value for the second AC wiring is corrected so that the current flowing from the inverter to the motor decreases or so that current flows from the motor to the inverter. When the current flowing from the inverter to the motor decreases, the current flowing from the capacitor to the inverter decreases, thereby suppressing a drop in the DC voltage in the DC wiring. Furthermore, when current flows from the motor to the inverter, the motor enters a regenerative state, causing a reverse power flow from the motor to the inverter. As a result, the DC voltage in the DC wiring increases.

[0076] When the DC voltage in the DC wiring increases, the potential difference between the DC voltage and the voltage in the first AC wiring decreases. As a result, even if the voltage in the first AC wiring increases, the current flowing from the first AC wiring to the DC wiring via the rectifier can be suppressed. Therefore, the inrush current caused by voltage fluctuations in the AC power supply system can be suppressed.

[0077] As described above, according to the present embodiment, it is not necessary to add a relay circuit or the like as in the conventional case, and it is possible to suppress the occurrence of inrush current with a simple configuration. Furthermore, since physical switching of a relay circuit or the like is not required, the response speed is fast and it is possible to suppress the occurrence of inrush current even in response to abrupt voltage fluctuations in the AC power supply system 2. Therefore, it is possible to appropriately suppress the inrush current caused by voltage fluctuations in the AC power supply system 2 with a simple configuration.

[0078] [Item 2] In the power supply system of item 1, the voltage detection circuit may detect an instantaneous voltage value in the first AC wiring, and the processing circuit may calculate an effective voltage value in the first AC wiring from the instantaneous voltage value, apply a high-pass filter to the effective voltage value to extract a fluctuation component of the effective voltage value, and correct the active current command value by subtracting the fluctuation component of the effective voltage value from an active current command value in the second AC wiring.

[0079] [Item 3] In the power supply system of item 2, the processing circuit may correct the active current command value when the fluctuation component of the effective voltage value is equal to or greater than a predetermined correction reference value. This prevents the current command value from being corrected unnecessarily even when there is no risk of an inrush current flowing. This prevents the drive control performance of the electric motor from deteriorating.

[0080] [Item 4] In the power supply system of item 3, the processing circuit may correct the active current command value to a negative value when the fluctuation component of the effective voltage value is equal to or greater than the correction reference value. This makes it possible to allow a current to flow from the motor to the inverter 5 when the voltage in the first AC wiring increases.

[0081] [Item 5] In the power supply system according to any one of items 1 to 4, the processing circuit may be configured not to correct the current command value in the second AC wiring when the voltage in the first AC wiring drops.

[0082] [Item 6] A control method for a power supply system according to another aspect of the present disclosure is a control method for a power supply system for supplying power from the AC power supply system to the electric motor, the control method comprising: a rectifier connected to an AC power supply system via a first AC wiring and rectifying first AC power in the AC power supply system into DC power; and an inverter connected to the rectifier via a DC wiring and connected to an electric motor via a second AC wiring, converting the DC power to second AC power and supplying the second AC power to the second AC wiring, the control method acquiring a voltage on the first AC wiring, and correcting a current command value for the second AC wiring when the voltage on the first AC wiring increases so that current flows from the electric motor to the inverter. [Explanation of symbols]

[0083] 1,1B Power Supply System 2 AC power system 3 Electric motor 4 rectifier 5 inverters 6 1st AC wiring 8 DC wiring 9 2nd AC wiring 11 Controller 12 Voltage detection circuit 20 Processing circuit

Claims

1. A power supply system for supplying power from an AC power supply system to an electric motor, a rectifier connected to the AC power supply system via a first AC wiring and configured to rectify first AC power in the AC power supply system into DC power; an inverter connected to the rectifier via a DC wiring and to the electric motor via a second AC wiring, converting the DC power into second AC power and supplying the second AC power to the second AC wiring; a controller including a processing circuit for controlling the inverter; a voltage detection circuit that detects a voltage in the first AC wiring, The processing circuit corrects a current command value for the second AC wiring so that, when the voltage in the first AC wiring increases, the current flowing from the inverter to the electric motor decreases, or so that current flows from the electric motor to the inverter.

2. the voltage detection circuit detects an instantaneous value of a voltage in the first AC wiring; The processing circuitry calculating an effective voltage value in the first AC wiring from the instantaneous voltage value; applying a high-pass filter to the effective voltage value to extract a fluctuation component of the effective voltage value; The power supply system according to claim 1 , wherein the active current command value in the second AC wiring is corrected by subtracting a fluctuation component of the voltage effective value from the active current command value in the second AC wiring.

3. The power supply system according to claim 2 , wherein the processing circuit corrects the active current command value when the fluctuation component of the effective voltage value is equal to or greater than a predetermined correction reference value.

4. 4. The power supply system according to claim 3, wherein the processing circuit corrects the active current command value to a negative value when the fluctuation component of the effective voltage value is equal to or greater than the correction reference value.

5. 5. The power supply system according to claim 1, wherein the processing circuit does not correct the current command value in the second AC wiring when a voltage drop occurs in the first AC wiring.

6. A control method for a power supply system for supplying power from an AC power supply system to an electric motor, the control method comprising: a rectifier connected to an AC power supply system via a first AC wiring and rectifying first AC power in the AC power supply system into DC power; and an inverter connected to the rectifier via a DC wiring and connected to an electric motor via a second AC wiring, converting the DC power into second AC power and supplying the second AC power to the second AC wiring, the method comprising: acquiring a voltage on the first AC wiring; a control method for correcting a current command value for the second AC wiring so that, when a voltage in the first AC wiring increases, a current flowing from the inverter to the electric motor decreases or a current flows from the electric motor to the inverter.

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