Three-phase ac-three-phase ac converter

Abstract

Provided is a three-phase AC-three-phase AC converter that is small and high-density. The three-phase AC-three-phase AC converter includes a number of rectifier circuit modules that is a multiple of 3, the rectifier circuit modules converting a three-phase AC input voltage supplied from a three-phase AC power supply into a DC voltage, and a number of inverter circuit modules that is the same as the number of rectifier circuit modules, the inverter circuit modules converting the DC voltage into a three-phase AC output voltage. The three input terminals of each of the rectifier circuit modules are connected to the output terminal of each phase of the three-phase AC power supply and the input terminal of a rectifier circuit module different from the rectifier circuit module via an inductor.

Description

Technical Field

[0001] This invention relates to a three-phase AC to three-phase AC converter. Background Technology

[0002] Three-phase motors are widely used in industrial equipment such as fans, pumps, and FA (fabrication, assembly, and distribution) equipment. Motor drive systems used to drive such three-phase motors typically include a three-phase AC-to-three-phase AC converter, which consists of a rectifier circuit that rectifies the three-phase AC voltage to generate DC voltage (rectified voltage), a DC link following the rectifier circuit, and an inverter circuit that generates the three-phase AC voltage based on the DC link voltage.

[0003] Existing technical documents

[0004] Non-patent literature

[0005] Non-patent document 1: M.Guacci, D.Bortis, and JWKolar, "High-Eciency Weight-Optimized Fault-Tolerant Modular Multi-Cell Three-Phase GaN Inverter for NextGeneration Aerospace Applications," in Proc.of IEEE Energy Conversion Congressand Exposition (ECCE-USA), Portland, OR, USA, Sept. 2018, pp.1334-1341.

[0006] Non-patent document 2: JWKolar and T.Friedli "The Essence of Three-Phase PFCRectifir Systems-Part I," IEEE Transactions on Power Electronics, vol.28, no.1,1, pp.176-198, Jan.2013.

[0007] Non-patent document 3: J.Wen and K.Smedley, "A New Multilevel Inverter-HexagramInverter for Medium Voltage Adjustable Speed ​​Drive Systems PartII.Three-phase Motor Drive," in Proc.of the IEEE Power Electronics Specialists Conference (PESC), Orlando, FL, USA, June 2007, pp.1571-1577.

[0008] Non-patent document 4: J.Wen and KMSmedley, "Synthesis of Multilevel ConvertersBased on Single-and / or Three-Phase Converter Building Blocks," IEEETransactions on Power Electronics, vol.23, no.3, pp.1247-1256, May 2008. Summary of the Invention

[0009] The problem the invention aims to solve

[0010] In motor drive systems, miniaturization and high density are required to enable the use of low-voltage components, reduce design time, and share components. One technique for achieving this is a "modular motor drive (MMD)" (see, for example, Non-Patent Document 1), which modularizes the inverter circuit to construct the motor using independent modular motors for each segment of the three-phase windings and drives each segment with each module. However, in this type of MMD, while the inverter circuit is modularized, the rectifier circuit is not. In this case, because high-voltage semiconductor components are required in the rectifier circuit, miniaturization and high density of the overall motor drive system are difficult.

[0011] As a method for modularizing a three-phase bridge rectifier circuit, a 6-switch boost rectifier circuit is proposed (see, for example, Non-Patent Document 2). In this circuit, a filter inductor is used as a boost inductor. In this case, to achieve boost operation, the output voltage of the rectifier circuit (i.e., the sum of the DC link voltages of the inverter circuit) must be obtained that is greater than the line-to-line peak voltage of the input voltage. Therefore, the rectifier circuit must operate at high voltage, requiring high-voltage-resistant components. As a result, the overall motor drive system is difficult to miniaturize and increase density, and requires a dedicated design corresponding to the input voltage, thus increasing design and manufacturing costs.

[0012] As another method of modularizing the rectifier circuit, there exists a back-to-back hexagram converter (see, for example, non-patent document 3) that uses the same low-voltage components in both the rectifier and inverter circuits. However, this structure requires an open delta connection after insulation, which is disadvantageous in terms of miniaturization, high density, and cost.

[0013] As another method of modularizing the rectifier circuit, there is a structure that uses several interconnected three-phase AC-DC rectifier units (see, for example, Non-Patent Document 4). Since this interconnection reduces the withstand voltage of the rectifier units, the same units can be used for both the rectifier units and the inverter. However, in order to drive a single load using an inverter unit connected in parallel with the input, an additional, insulated DC-DC converter is required. This additional DC-DC converter hinders the miniaturization and high-density scaling of the overall motor drive system.

[0014] As mentioned above, conventional rectifier circuits have limitations in achieving sufficient miniaturization and high density for motor drive systems. This invention addresses these issues, aiming to miniaturize and increase the density of motor drive systems.

[0015] Solution for solving the problem

[0016] To address the aforementioned problems, a three-phase AC-to-three-phase AC converter according to one aspect of the present invention comprises: a number of rectifier circuit modules that are multiples of three, the rectifier circuit modules converting a three-phase AC input voltage supplied from a three-phase AC power supply into a DC voltage; and an inverter circuit module of the same number as the rectifier circuit modules, the inverter circuit modules converting the DC voltage into a three-phase AC output voltage. Each rectifier circuit module has three input terminals that are respectively connected via inductors to the output terminals of each phase of the three-phase AC power supply and to the input terminals of a different rectifier circuit module.

[0017] Alternatively, the three-phase AC to three-phase AC converter in the embodiment may also include a control unit that controls the switching elements constituting the rectifier circuit module and the inverter circuit module to make the DC voltage a fixed DC voltage and to make the phase of the three-phase input current from the AC power supply consistent with the phase of the three-phase AC voltage.

[0018] Alternatively, the control unit controls the switching elements that constitute the rectifier circuit module and the inverter circuit module, so that the load of an external motor can be used to remove the pulsation of the three-phase AC power related to the three-phase AC input voltage and the pulsation of the DC power related to the DC voltage.

[0019] Alternatively, the control unit calculates the target capacitor power based on the difference between the DC link voltage of the DC link set in the downstream stage of the rectifier circuit module and the target link voltage. The target motor power is calculated by subtracting the target capacitor power from the target DC power. Based on the target capacitor power and the target motor power, the control unit controls the switching elements constituting the rectifier circuit module and the inverter circuit module to make the voltage ripple of the DC link become zero.

[0020] Alternatively, the DC stage may include a capacitor, which is used to remove pulsations in the three-phase AC power related to the three-phase AC voltage and pulsations in the DC power related to the DC voltage.

[0021] Alternatively, the number of rectifier circuit modules can be 3.

[0022] Alternatively, each rectifier circuit module may have an energy buffer circuit, which is connected to one of the three input terminals to buffer the energy of the three-phase AC input power supplied from the three-phase AC power source, thereby preventing excessive power from being input to the rectifier circuit module.

[0023] Alternatively, a low-pass filter can be set in the front stage of the rectifier circuit module.

[0024] Alternatively, the low-pass filter could be an LC low-pass filter.

[0025] Alternatively, each inverter circuit module can be modularized together with two three-phase AC to three-phase AC conversion submodules.

[0026] Alternatively, the rectifier circuit module and the inverter circuit module may be composed of the same circuit.

[0027] Furthermore, any combination of the above structural elements, or the substitution of the structural elements and forms of the present invention among methods, apparatus, programs, temporary or non-temporary storage media recording programs, systems, etc., is also valid as a mode of the present invention.

[0028] The effects of the invention

[0029] According to the present invention, motor drive systems can be miniaturized and made more dense. Attached Figure Description

[0030] Figure 1 This is a functional block diagram of the three-phase AC to three-phase AC converter according to the first embodiment.

[0031] Figure 2 This is a functional block diagram of the three-phase AC to three-phase AC converter involved in the comparative example.

[0032] Figure 3 (a) is a graph showing the time variation of the first three-phase AC voltage. Figure 3 (b) is Figure 3 The phasor display of the three-phase AC voltage in (a) is shown.

[0033] Figure 4 (a) is the phasor display of the first three-phase AC voltage when there are 3 rectifier circuit modules. Figure 4 (b) is the phasor display of the first three-phase AC voltage when there are 6 rectifier circuit modules. Figure 4 (c) is the phasor display of the first three-phase AC voltage when there are 9 rectifier circuit modules.

[0034] Figure 5 This is a functional block diagram of the three-phase AC to three-phase AC converter according to the second embodiment.

[0035] Figure 6 This is a functional block diagram of the control unit in the three-phase AC to three-phase AC converter according to the third embodiment.

[0036] Figure 7 This is a functional block diagram of the three-phase AC to three-phase AC converter according to the fourth embodiment.

[0037] Figure 8 This is a functional block diagram of the rectifier circuit, including the energy buffer circuit, in the three-phase AC to three-phase AC converter according to the fifth embodiment.

[0038] Figure 9 This is a functional block diagram of the rectifier circuit in the three-phase AC to three-phase AC converter according to the sixth embodiment.

[0039] Figure 10 This is a functional block diagram of the three-phase AC-to-three-phase AC conversion submodule in the three-phase AC-to-three-phase AC converter according to the seventh embodiment.

[0040] Figure 11This is a diagram illustrating the circuit structure of the rectifier circuit module in a three-phase AC to three-phase AC converter according to multiple embodiments. Detailed Implementation

[0041] Below, based on the preferred embodiments, refer to the appendix. Figure 1 The invention is described below. The embodiments are not limiting but illustrative. All features described in the embodiments, and combinations thereof, are not necessarily essential features of the invention. Identical or equivalent structural elements, components, and processes shown in the various figures are labeled with the same reference numerals, and redundant descriptions are appropriately omitted. Furthermore, the scales and shapes of the parts shown in the figures are appropriately set for ease of explanation and are not to be interpreted limitingly unless specifically mentioned. Additionally, where terms such as "first," "second," etc., are used in this specification or claims, unless specifically mentioned, these terms do not indicate any order or importance, but are only used to distinguish one structure from others. Furthermore, in the figures, parts of components that are not important in illustrating the embodiments are omitted.

[0042] [First Implementation]

[0043] Figure 1 This is a functional block diagram of the three-phase AC-to-three-phase AC converter 1 according to the first embodiment. The three-phase AC-to-three-phase AC converter 1 includes a rectifier circuit 100 and an inverter circuit 300. The rectifier circuit 100 generates a DC voltage based on a three-phase AC input voltage (hereinafter referred to as "first three-phase AC input voltage") from a three-phase AC power source such as a commercial power supply. This DC voltage is output to the inverter circuit 300. The inverter circuit 300 converts the DC voltage output from the rectifier circuit 100 into a three-phase AC input voltage (hereinafter referred to as "second three-phase AC voltage"). The second three-phase AC output voltage is used to drive a three-phase motor.

[0044] The rectifier circuit 100 is modular. That is, the rectifier circuit 100 includes a first rectifier circuit module 11, a second rectifier circuit module 12, a third rectifier circuit module 13, and inductors 20, 21, 22, 23, 24, and 25. As described later, the first rectifier circuit module 11, the second rectifier circuit module 12, and the third rectifier circuit module 13 are, for example, three-phase bridge circuits composed of six switching elements, each having three input terminals and two output terminals. The first rectifier circuit module 11, the second rectifier circuit module 12, and the third rectifier circuit module 13 are all connected to each other using inductors. Specifically, the first rectifier circuit module 11 is connected to the second rectifier circuit module 12 via inductor 23, and to the third rectifier circuit module 13 via inductor 25. The second rectifier circuit module 12 is connected to the third rectifier circuit module 13 via inductor 24, and to the first rectifier circuit module 11 via inductor 23. The third rectifier circuit module 13 is connected to the first rectifier circuit module 11 via inductor 25, and to the second rectifier circuit module 12 via inductor 24. Hereinafter, this connection method, in which all components and circuits are interconnected with all other components and circuits, will be referred to as a "mesh connection." That is, in this embodiment, the first rectifier circuit module 11, the second rectifier circuit module 12, and the third rectifier circuit module 13 are connected in a mesh manner using inductors.

[0045] One of the input terminals of the first rectifier circuit module 11 is connected to the output terminal of phase U of the three-phase AC power supply via inductor 20. Phase U of the three-phase power supply 500U is input to the first rectifier circuit module 11 via inductor 20. The input voltage to the first rectifier circuit module 11 is set to v. u Set the input current to i u One of the input terminals of the second rectifier circuit module 12 is connected to the output terminal of the V phase of the three-phase AC power supply via an inductor 21. The V phase of the three-phase power supply (500V) is input to the second rectifier circuit module 12 via the inductor 21. The input voltage to the second rectifier circuit module 12 is set to V... v Set the input current to i v One of the input terminals of the third rectifier circuit module 13 is connected to the output terminal of phase W of the three-phase AC power supply via inductor 22. A 500W phase W power supply is input to the third rectifier circuit module 13 via inductor 22. The input voltage to the third rectifier circuit module 13 is set to V. w Set the input current to i w .

[0046] DC stages are respectively provided after the first rectifier circuit module 11, the second rectifier circuit module 12, and the third rectifier circuit module 13. dc1 vdc2 and v dc3 .

[0047] The first rectifier circuit module 11 removes the input voltage v u and input current i u The power ripples caused by the input voltage are used to generate the first DC voltage. The second rectifier circuit module 12 removes the power ripples caused by the input voltage v. v and input current i v The resulting power ripple is used to generate the second DC voltage. The third rectifier circuit module 13 removes the power ripple caused by the input voltage v. w and input current i w The resulting power ripples are used to generate the third DC voltage. The first DC voltage, the second DC voltage, and the third DC voltage are output to the first DC link, the second DC link, and the third DC link located outside the rectifier circuit 101, respectively. The voltages of the first DC link (DC link voltage), the second DC link (DC link voltage), and the third DC link (DC link voltage) are respectively set to v. dc1 v dc2 and v dc3 The first rectifier circuit module 11, the second rectifier circuit module 12, and the third rectifier circuit module 13 are meshed together using inductors, thereby increasing the voltage v of each DC link. dc1 v dc2 and v dc3 equal.

[0048] The first external DC link voltage v dc1 The second external DC link voltage v dc2 and the third external DC link voltage v dc3 The input is given to inverter circuit 300. Inverter circuit 300 is modular and includes a first inverter circuit module 31, a second inverter circuit module 32, and a third inverter circuit module 33. The first external DC link voltage v dc1 The second external DC link voltage v dc2 and the third external DC link voltage v dc3 The inputs are respectively fed into the first inverter circuit module 31, the second inverter circuit module 32, and the third inverter circuit module 33 of the inverter circuit 300. The first inverter circuit module 31 is based on the first DC link voltage v. dc1 To generate three-phase AC voltage v 11a v 11b and v 11c The second inverter circuit module 32 is based on the voltage v of the second DC link. dc2 To convert and generate three-phase AC voltage v 12a v 12b and v 12cThe third inverter circuit module 33 is based on the third DC stage voltage v. dc3 To generate three-phase AC voltage v 13a v 13b and v 13c .

[0049] Three-phase AC voltage V 11a v 11b and v 11c The first winding WS1 of the three-phase motor 600 is supplied. Three-phase AC voltage v 12a v 12b and v 12c The second winding WS2 of the three-phase motor 600 is supplied. Three-phase AC voltage v 13a v 13b and v 13c The third winding WS3 of the three-phase motor 600 is supplied. In this way, the three-phase motor 600 is driven by the three-phase output supplied to the first winding WS1, the second winding WS2 and the third winding WS3.

[0050] In the aforementioned implementation, both the rectifier circuit module and the inverter circuit module consist of three units. However, this is not a limitation; the number of rectifier circuit modules and inverter circuit modules can be the same, or any multiple of three.

[0051] [Comparative Example]

[0052] Figure 2 This is a functional block diagram of the three-phase AC-to-three-phase AC converter 2 according to the comparative example. The three-phase AC-to-three-phase AC converter 2 was developed during the development of this invention. The three-phase AC-to-three-phase AC converter 2 according to the comparative example includes a rectifier 120 instead of the first rectifier circuit module 11, the second rectifier circuit module 12, and the third rectifier circuit module 13 of the three-phase AC-to-three-phase AC converter 1 according to the embodiment. That is, the rectifier 120 of the comparative example differs from that of the embodiment in that it is not modularized and is composed of a single DC bus. The other structures of the three-phase AC-to-three-phase AC converter 2 are the same as those of the three-phase AC-to-three-phase AC converter 1, therefore repeated descriptions are omitted.

[0053] Three-phase power supplies, U-phase 500U, V-phase 500V, and W-phase 500W, are respectively input to rectifier 120 via inductors 20, 21, and 22. Rectifier 120 removes the input voltage V of U-phase 500U. u and input current i u The resulting power pulsation, due to the 500V input voltage of phase V. v and input current i v The resulting power ripple and the 500W input voltage V of phase W.w and input current i w The resulting power pulsation is used to generate DC voltage.

[0054] As previously described, rectifier 120 is not modularized and consists of a single DC bus. In this case, the input and output peak voltages are high, thus requiring the circuit components used in rectifier 120 to have high voltage withstand capability. In contrast, by modularizing rectifier circuit 100 using three rectifier circuit modules 11, 12, and 13, the voltage withstand capability of each module can be reduced to one-third of the input and output peak voltages. Therefore, all modules, including the inverter circuit, can use low-voltage circuit components. This enables miniaturization and high density of the entire motor drive system. Thus, according to this embodiment, the motor drive system can be miniaturized and made more dense.

[0055] The number of rectifier circuit modules is a multiple of 3. This will be explained below. Figure 3 Figure (a) is a graph showing the time variation of the first three-phase AC voltage. As shown in the figure, the first three-phase AC voltage v RiA v RiB v RiC The phases are offset from each other by 120 degrees. Figure 3 (b) is Figure 3 (a) Phasor display of the three-phase AC voltage. The phasor display shows the voltage over time at the power supply frequency f. G Rotate. Figure 3 (b) shows setting the power cycle to T. G Time, t=T G The three-phase AC voltage at that time. Note the following: Figure 3 The sides of the equilateral triangle in (b) are the line voltages.

[0056] Figure 4 (a) is a phasor display of the first three-phase AC voltage when the first rectifier circuit module 11, the second rectifier circuit module 12, and the third rectifier circuit module 13 are meshed using inductors in the first embodiment. The graph is formed by combining three equilateral triangles R1, R2, and R3. This indicates that the sides of the line-to-line voltage are aligned symmetrically in a straight line. Figure 4 (b) is a phasor display of the first three-phase AC voltage when the six rectifier circuit modules are meshed together using inductors. The graph is formed by combining six equilateral triangles R1, R2, R3, R4, R5, and R6. In this case, the sides representing the line-to-line voltages are also aligned symmetrically in a straight line. Figure 4(c) shows the phasor display of the first three-phase AC voltage when nine rectifier circuit modules are meshed together using inductors. This graph is formed by combining nine equilateral triangles R1, R2, R3, R4, R5, R6, R7, R8, and R9. In this case, the sides representing the line-to-line voltages are also aligned symmetrically in a straight line. By setting the number of rectifier circuit modules to a multiple of three, it is possible to ensure that the sides of the phasor display representing the line-to-line voltages are aligned symmetrically in a straight line. This allows for the smooth maintenance of each phase of the input voltage without disturbance.

[0057] In particular, when driving a three-phase motor using a motor drive device employing the rectifier circuit described in this embodiment, by setting the number of rectifier circuit modules to a multiple of 3, it is possible to generate a drive voltage that is an integer multiple of the number of motor windings. This enables smooth motor drive. Furthermore, the more the number of rectifier circuit modules is increased to 3, 6, 9, ..., the lower the withstand voltage of each module becomes to 1 / 3, 1 / 6, 1 / 9, ... Therefore, circuit components with lower withstand voltages can be used.

[0058] Specifically, the number of rectifier circuit modules can also be three. In this case, smooth motor drive can be achieved with a minimal number of rectifier circuit modules. This reduces the number of components.

[0059] [Second Implementation]

[0060] Figure 5 This is a functional block diagram of the three-phase AC to three-phase AC converter 3 according to the second embodiment. The three-phase AC to three-phase AC converter 3... Figure 1 A control unit 40 is added to the structure of the three-phase AC to three-phase AC converter 1. The other structures of the three-phase AC to three-phase AC converter 3 are the same as those of the three-phase AC to three-phase AC converter 1, so repeated descriptions are omitted.

[0061] The control unit 40 controls the switching elements constituting the rectifier circuit modules 11, 12, and 13, and the inverter circuit modules 31, 32, and 33, to keep the DC voltage fixed and to ensure that the phase of the three-phase input current from the AC power supply is consistent with the phase of the first three-phase AC voltage. Figure 5 The diagram illustrates a configuration where a single control unit 40 comprehensively controls the switching elements constituting rectifier circuit modules 11, 12, and 13, and inverter circuit modules 31, 32, and 33. However, this is not the only possibility. For example, six control units could be provided, each independently controlling the switching elements constituting rectifier circuit modules 11, 12, and 13, and inverter circuit modules 31, 32, and 33.

[0062] In this way, the control unit 40 controls the switching elements constituting the rectifier circuit modules 11, 12, and 13, and the inverter circuit modules 31, 32, and 33, thereby eliminating the power pulsation generated by the DC voltage produced by the rectifier circuit modules 11, 12, and 13. This enables the rectifier circuit 100 to be a PFC rectifier circuit, thereby achieving a power factor of 1.

[0063] [Third Implementation]

[0064] In the third embodiment, Figure 5 The control unit 40 controls the switching elements constituting the rectifier circuit module and the inverter circuit module, so that the pulsation of the three-phase AC power related to the first three-phase AC voltage and the DC power related to the DC voltage can be removed by using an external motor load. According to this embodiment, power pulsation can be removed without using a large-capacity DC link capacitor.

[0065] Next, use Figure 6 The structure and operation of the control unit 40 in the third embodiment will be explained in detail. Figure 6 This is a detailed functional block diagram of the control unit 40. The control unit 40 includes a DC link voltage control unit 42, a rectifier circuit control unit 44, a speed control unit 46, and an inverter control unit 48. The control unit 40 controls the switching elements constituting the rectifier circuit modules 11, 12, 13 and the inverter circuit modules 31, 32, 33 to adjust the generated DC voltage and three-phase AC voltage.

[0066] The DC link voltage control unit 42 has a first input terminal 42b, a second input terminal 42c, and an output terminal 42d. The rectifier circuit control unit 44 has an input terminal 44b and an output terminal 44c. The speed control unit 46 has a first input terminal 46b, a second input terminal 46c, and an output terminal 46d. The inverter control unit 48 has an input terminal 48b, a first output terminal 48c, a second output terminal 48d, and a third output terminal 48e. The control unit 40 provides a low-pass filter 43a between the output terminal 42d of the DC link voltage control unit 42 and the input terminal 44b of the rectifier circuit control unit 44. The control unit 40 provides a low-pass filter 43b before the second input terminal 46c of the speed control unit 46.

[0067] The target DC link voltage v is input to the first input terminal 42b of the DC link voltage control unit 42. DC * Input the current DC stage voltage V to the second input terminal 42c. DC DC link voltage control unit 42 is based on v DC *and v DC The difference Δv DC (Not shown) To calculate the target capacitor power P C* and output it from output terminal 42d.

[0068] The target capacitor power P output from the output terminal 42d of the DC link voltage control unit 42 C *At branch point v3, the circuit splits into two, one of which is input to low-pass filter 43a. Low-pass filter 43a is fed from P... C High-frequency components are removed to generate the target average capacitor power. <P C >*, and output it. The output from low-pass filter 43a. <P C At branch point v4, the inverter is split into two branches, one of which is the target average inverter output from the output terminal 46d of the speed control unit 46. <P INV >* Add them together. The result is the target average rectified power. <P PFC >* is calculated as <P PFC >*= <P C >*+ <P INV >*. Calculated <P PFC >*The input is given to the input terminal 44b of the rectifier circuit control unit 44. P is branched off at branch point v3. C The other subtraction of the branch at branch point v4 is also included. <P C Another one is to generate input power ripple P. C,AC That is, the input power ripple P C,AC From the target capacitor power P C *This is obtained by extracting only the pulsating portion. From the target rectified power p PFC *Subtract input power ripple P C,AC To calculate the target motor power p M *(p M *=p PFC *-P C,AC ). Calculated p M *The input is fed to input terminal 48b of the inverter control unit 48.

[0069] Thus, the target motor power p input to the inverter control unit 48 M * is from the target rectified power p PFC *Subtract input power ripple P C,AC And thus obtained. That is, the pulsation Δp input to the DC link of the three-phase motor 600. DC The three-phase motor 600 utilizes the inertia of the load connected to it to compensate for this pulsation. As a result, the pulsation in the DC link becomes zero, p M =p G This is true. That is, the motor power p... M With input power p G Consistent.

[0070] The cause is a three-phase motor with 600 pairs of input power p G The compensation, the speed ω of the three-phase motor 600 is equal to the input power p G frequency f G 2 times the frequency 2f G The motor is pulsated. Therefore, a low-pass filter is used to remove the high-frequency components of ω as follows: The current motor speed ω is input to the low-pass filter 43b. The low-pass filter 43b removes the high-frequency components from ω to generate the current average motor speed <ω>, and inputs it to the second input terminal 46c of the speed control unit 46. The target average speed <ω>* of the three-phase motor 600 is input to the first input terminal 46b of the speed control unit 46. The speed control unit 46 calculates the target average inverter output based on the difference Δω (not shown) between <ω>* and <ω>. <P INV >*, and output it from output terminal 46d.

[0071] The rectifier circuit control unit 44 controls the rectifier circuit 10 in a feedforward manner to make the DC link voltage v DC The target average inverter output is maintained at a constant value. This is achieved from the output terminal 46d of the speed control unit 46. <P INV >*Target average capacitor power output from low-pass filter 43a <P C >* Add them together. The result is the target average rectified power. <P PFC >* is calculated as <P PFC >*= <P C >*+ <P INV >*. Calculated <P PFC The input is sent to input terminal 44b of the rectifier circuit control unit 44. The rectifier circuit control unit 44, based on the input... <P PFC >*To calculate the target input current i G *(Not shown), the output duty cycle d is determined based on the inductor current difference. B It is then output from output terminal 44c. The output duty cycle d B The desired control is achieved by inputting the pulse width modulator (not shown) to the rectifier circuit 100.

[0072] According to this embodiment, power pulsations can be eliminated using the motor load by utilizing the control unit specifically configured as described above. Therefore, without the need for large-capacity DC link capacitors, further miniaturization, high density, low cost, and long lifespan of the motor drive system can be achieved.

[0073] [Fourth Implementation]

[0074] Figure 7This is a functional block diagram of the three-phase AC-to-three-phase AC converter 4 according to the fourth embodiment. The three-phase AC-to-three-phase AC converter 1 includes a rectifier circuit 101 and an inverter circuit 300. Compared to... Figure 1 The rectifier circuit 100 and rectifier circuit 101 are respectively provided with DC stages equipped with capacitors C1, C2, and C3 after each rectifier circuit module 11, 12, and 13. The capacitors C1, C2, and C3 are used to remove the power pulsation generated by the input three-phase AC voltage and the DC power pulsation generated by the rectifier circuit modules 11, 12, and 13.

[0075] In a typical example, when the rectifier circuit 103 operates at several kW and hundreds of V, the capacitance of these capacitors is in the mF range. According to this embodiment, power ripple can be eliminated without the need for a special control unit.

[0076] [Fifth Implementation]

[0077] In the fifth embodiment, the three-phase AC to three-phase AC converter includes an energy buffer circuit. Figure 8 This is a functional block diagram of the rectifier circuit, including the energy buffer circuit 14. The energy buffer circuit 14 is connected to one of the three input terminals of the rectifier circuit modules 11, 12, and 13. Like the rectifier circuit modules, the energy buffer circuit 14 is, for example, a three-phase bridge circuit composed of six switching elements.

[0078] Energy buffer circuit 14 buffers the energy from the three-phase AC input power supplied by the three-phase AC power source to prevent excessive power input to the rectifier circuit modules 11, 12, and 13. According to this embodiment, energy can be buffered before the input power is input to the rectifier circuit module, thus enabling smoother voltage control.

[0079] [Sixth Implementation]

[0080] Figure 9 This is a functional block diagram of the rectifier circuit 102 in the three-phase AC-to-three-phase AC converter according to the sixth embodiment. In the rectifier circuit 102, in... Figure 1The first rectifier circuit module 11, the second rectifier circuit module 12, and the third rectifier circuit module 13 of the rectifier circuit 100 are respectively equipped with a first low-pass filter 71, a second low-pass filter 72, and a third low-pass filter 73 in the pre-stage. The first low-pass filter 71 is a π-type filter composed of inductors L11, L12, and L13 and capacitors C11, C12, C13, C14, and C15. The second low-pass filter 72 is a π-type filter composed of inductors L21, L22, and L23 and capacitors C21, C22, C23, C24, and C25. The third low-pass filter 73 is a π-type filter composed of inductors L31, L32, and L33 and capacitors C31, C32, C33, C34, and C35. The other structures of the rectifier circuit 102 are the same as those of the rectifier circuit 100, so repeated descriptions are omitted.

[0081] The first low-pass filter 71, the second low-pass filter 72, and the third low-pass filter 73 remove high-frequency components from the input AC voltage to generate a noise-removed input AC voltage. The first rectifier circuit module 11, the second rectifier circuit module 12, and the third rectifier circuit module 13 generate a DC voltage based on the noise-removed input AC voltage. According to this embodiment, a DC voltage with less noise can be generated.

[0082] Figure 9 The low-pass filters 71, 72, and 73 shown are simple LC low-pass filters composed of inductors and capacitors. In this case, low-pass filters 71, 72, and 73 can be implemented at low cost and simply. However, they are not limited to this; the low-pass filters can also be implemented using other preferred methods such as operational amplifiers. Figure 6 The LC low-pass filter is a π-type low-pass filter, but it is not limited to this. It can also be an L-type, T-type, or any other preferred type of LC low-pass filter.

[0083] [Seventh Implementation]

[0084] In the three-phase AC to three-phase AC converter of the seventh embodiment, each inverter circuit module is modularized together with two three-phase AC to three-phase AC conversion sub-modules. Figure 10 This is a functional block diagram of the three-phase AC-to-three-phase AC conversion submodules 801 and 802 according to the seventh embodiment. The three-phase AC-to-three-phase AC conversion submodule 801 includes a rectifier circuit submodule PFC 11 and an inverter submodule INV 11. The three-phase AC-to-three-phase AC conversion submodule 802 includes a rectifier circuit submodule PFC 12 and an inverter submodule INV 12. The three-phase AC-to-three-phase AC conversion submodules 801 and 802 are respectively connected to… Figure 7 The inverter circuit module 31 is modularized together.

[0085] Rectifier circuit submodules PFC 11 and PFC 12 are constructed using the same circuitry as rectifier circuit module 11. Inverter submodules INV 11 and INV 12 are constructed using the same circuitry as inverter circuit module 31. Three-phase AC to three-phase AC conversion submodules 801 and 802 generate three-phase AC voltages based on the three-phase AC voltage generated by inverter circuit module 31. The three-phase AC voltages generated by three-phase AC to three-phase AC conversion submodules 801 and 802 are supplied to the dual windings WS of the motor. 11 and WS 12 .

[0086] Inverter circuit modules 32 and 33 (see, for example) Figure 7 It is also modularized together with two other three-phase AC-to-three-phase AC conversion submodules, which have the same structure as the three-phase AC-to-three-phase AC conversion submodules 801 and 802. The operation of the three-phase AC-to-three-phase AC conversion submodule is the same as that of the three-phase AC-to-three-phase AC conversion submodules 801 and 802 mentioned above.

[0087] According to this embodiment, a small and high-density motor drive device for a motor having dual windings can be realized.

[0088] exist Figure 11 Examples of the circuit structures of the rectifier circuit module 11 according to the aforementioned embodiments are shown. The rectifier circuit module 11 is a three-phase bridge circuit composed of switching elements SW1, SW2, SW3, SW4, SW5, and SW6. However, it is not limited to this; the rectifier circuit module may also be composed of other preferred circuits such as a bridgeless circuit.

[0089] In one implementation, all rectifier circuit modules and inverter circuit modules are constructed using the same circuitry. This implementation allows for the sharing of circuit components, thereby reducing design and manufacturing costs.

[0090] The above description is based on embodiments of the present invention. These embodiments are illustrative, and those skilled in the art will understand that various modifications and alterations can be made within the scope of the claims of the present invention. Furthermore, those skilled in the art will understand that such modifications and alterations are also within the scope of the claims of the present invention. Therefore, the descriptions and drawings in this specification should not be considered limiting, but rather illustrative.

[0091] The following describes modified examples. In the accompanying drawings and descriptions of the modified examples, structural elements and components that are the same as or equivalent to those in the embodiment are labeled with the same reference numerals. Descriptions that are repeated in the embodiment are omitted where appropriate, and the focus is on describing structures that differ from the embodiment.

[0092] The rectifier circuit modules in this embodiment are meshed using inductors. However, diodes can also be used to mesh the rectifier circuit modules. In this case, a smaller, higher-density rectifier circuit can be achieved at a lower cost.

[0093] The modified examples achieve the same function and effect as the implementation methods.

[0094] Any combination of the above-described embodiments and modifications is also useful as an embodiment of the present invention. New embodiments resulting from such combinations combine the effects of each of the combined embodiments and modifications.

[0095] Explanation of reference numerals in the attached figures

[0096] 1, 2, 3, 4: Three-phase AC to three-phase AC converter; 11: First rectifier circuit module; 12: Second rectifier circuit module; 13: Third rectifier circuit module; 20, 21, 22, 23, 24, 25: Inductors; 31: First inverter circuit module; 32: Second inverter circuit module; 33: Third inverter circuit module; 40: Control unit; 100, 101, 102: Rectifier circuit; 300: Inverter circuit; 600: Three-phase motor; 801, 802: Three-phase AC to three-phase AC conversion sub-modules.

Claims

1. A three-phase AC to three-phase AC converter, comprising: A number of rectifier circuit modules, multiples of 3, which convert the three-phase AC input voltage supplied from a three-phase AC power source into DC voltage; and The same number of inverter circuit modules as the rectifier circuit module, which convert the DC voltage into a three-phase AC output voltage. in, Each of the rectifier circuit modules has three input terminals, which are connected to the output terminals of each phase of the three-phase AC power supply and the input terminals of a different rectifier circuit module via inductors. Each rectifier circuit module has an energy buffer circuit, which is connected to one of the three input terminals of the rectifier circuit module. The energy buffer circuit is used to buffer the energy of the three-phase AC input power supplied from the three-phase AC power source to prevent excessive power from being input to the rectifier circuit module.

2. The three-phase AC to three-phase AC converter according to claim 1, characterized in that, It also includes a control unit that controls the switching elements constituting the rectifier circuit module and the inverter circuit module to make the DC voltage a fixed DC voltage and to make the phase of the three-phase input current from the AC power supply consistent with the phase of the three-phase AC input voltage.

3. The three-phase AC to three-phase AC converter according to claim 2, characterized in that, The control unit controls the switching elements constituting the rectifier circuit module and the inverter circuit module to remove the pulsation of three-phase AC power related to the three-phase AC input voltage and the pulsation of DC power related to the DC voltage by using an external motor load.

4. The three-phase AC to three-phase AC converter according to claim 3, characterized in that, The control unit calculates the target capacitor power based on the difference between the DC link voltage of the DC link provided after the rectifier circuit module and the target link voltage. It calculates the target motor power by subtracting the target capacitor power from the target DC power. Based on the target capacitor power and the target motor power, it controls the switching elements constituting the rectifier circuit module and the inverter circuit module to make the voltage ripple of the DC link zero.

5. The three-phase AC to three-phase AC converter according to claim 1, characterized in that, The DC link has a capacitor. The capacitor is used to remove pulsations in the three-phase AC power related to the three-phase AC input voltage and pulsations in the DC power related to the DC voltage.

6. The three-phase AC to three-phase AC converter according to claim 1, characterized in that, The number of rectifier circuit modules is 3.

7. The three-phase AC-to-three-phase AC converter according to any one of claims 1 to 6, characterized in that, A low-pass filter is provided in the front stage of the rectifier circuit module.

8. The three-phase AC to three-phase AC converter according to claim 7, characterized in that, The low-pass filter is an LC low-pass filter.

9. The three-phase AC-to-three-phase AC converter according to any one of claims 1 to 6, characterized in that, Each inverter circuit module of the inverter circuit module is modularized together with two three-phase AC to three-phase AC conversion submodules.

10. The three-phase AC-to-three-phase AC converter according to any one of claims 1 to 6, characterized in that, The rectifier circuit module and the inverter circuit module are composed of the same circuit.

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