JP2017093077A - Controller and control method of open winding system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resolve concentration of switching loss, while suppressing current ripple, in an open winding system including first and second inverters, and an open winding connected between the AC output terminals of these inverters.SOLUTION: A carrier signal generation unit 200 generating first and second carrier signals having a phase difference of 90°, and a voltage command conversion unit 210 converting a winding voltage command into the output voltage command of an inverter are provided. The converted output voltage commands of the first and second inverters of the same phase are then compared, any one of the first or second carrier signal is selected according to the comparison results, and when the selected carrier signal is larger than the converted output voltage command, the switching element in the upper arm of that phase of the first inverter is turned off, and the switching element in the lower arm is turned on. The second inverter is also controlled similarly.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for controlling an open winding system for driving a three-phase induction motor or the like.

  The open winding system has a configuration in which three-phase windings such as an induction motor are driven by an H-bridge inverter. 8 and 9 show circuit configuration examples of the open winding system. In FIG. 8, all the legs of the first and second H-bridge inverters 110 and 120 (Inverter 1 and Inverter 2), that is, the positive side DC input terminal and the negative side DC input terminal are connected to the common DC power supply 130. Output terminal of each AC phase (a phase, b phase, c phase) of the H-bridge inverter 110 and output terminal of each AC phase (a phase, b phase, c phase) of the second H bridge inverter 120 The windings 140a, 140b, and 140c are respectively connected between them.

  In FIG. 9, the positive DC input terminal and negative DC input terminal of the first H-bridge inverter 110 are connected to the first DC power supply 131, and the positive DC input terminal and negative side of the second H-bridge inverter 120 are connected. A DC input terminal is connected to a second DC power supply 132 that is insulated from the first DC power supply 131, and an output terminal for each AC phase (a phase, b phase, c phase) of the first H-bridge inverter 110. And windings 140a, 140b, and 140c are connected to the output terminals of the AC phases (a phase, b phase, and c phase) of the second H-bridge inverter 120, respectively.

  The H-bridge inverters 110 and 120 (hereinafter simply referred to as inverters 110 and 120) include switching devices (switching elements) such as IGBTs, and inverter output voltages (vi1 = [ vi1a, vi1b, vi1c], vi2 = [vi2a, vi2b, vi2c]).

  The winding voltage vs = [vsa, vsb, vsc] applied to the windings (140a, 140b, 140c) of each phase is a difference in output voltage between the same phases of the inverters 110, 120. Therefore, when the output voltages of the first and second inverters 110 and 120 are vi1 = [vi1a, vi1b, vi1c], vi2 = [vi2a, vi2b, vi2c], the winding voltage vs and the inverter output voltages vi1, vi2 The relational expression is expressed by the following expression.

vs = vi1-vi2 (1)
Since the output voltage of each phase of the inverters 110 and 120 is two levels of Vdc and 0 (these voltages are based on the 0 terminal in FIG. 8 or FIG. 9), the winding voltage vs is -Vdc, 0, and Vdc. Become 3rd level.

  As a prior art of the open winding system, there is, for example, Patent Document 1.

  Further, the three-phase inverter output voltage vi1 = [vi1a, vi1b, vi1c] can be converted into an α-axis component, a β-axis component, and a zero-phase component (0-axis component) by the following equation that performs three-phase / two-phase conversion.

vi1α = vi1a−1 / 2 × vi1b−1 / 2 × vi1c
vi1β = √3 / 2 × vi1b−√3 / 2 × vi1c
vi10 = vi1a + vi1b + vi1c
A similar conversion formula can be applied to vi2 = [vi2a, vi2b, vi2c] and the winding voltage vs.

  FIG. 10 shows a two-level space vector (left side) of the inverter output voltage vi and a three-level space vector (right side) of the winding voltage vs. These space vectors are indicated by α axis-β axis coordinates.

  Vectors that can be output are represented by lattice points in FIG. The 2-level space vector has 8 vectors from 0 to 7, and the 3-level space vector has 27 vectors from 0 to 26.

  These space vectors are determined by the common connection point voltages vi1a, vi1b, vi1c (vi2a, vi2b, vi2c) of the switching devices of the lower arm above each phase of the H-bridge inverter of FIG. 8 (or FIG. 9).

  The relationship between each phase output voltage of the first inverter 110 in FIG. 8 and the space vector is shown in Table 1 below.

  Each phase output voltage vi2 = [vi2a, vi2b, vi2c] of the second inverter 120 has the same relationship as in Table 1.

  Further, the three-level space vector of the winding voltage vs shown in FIG. 10 is generated by the expression (1) vs = vi1-vi2.

PWM is a technique for controlling the pulse width (duty ratio) of the output voltage so that the average voltage of the control period matches the voltage command. When viewed in terms of a space vector, the sum of the space vector output in the control cycle multiplied by the duty ratio matches the voltage command vector. This is referred to as voltage command PWM synthesis. The prior art for synthesizing this voltage when the winding voltage command is vs ^* is roughly divided into two methods.

One is to fix one of the output voltages of the two inverters to one of the two outer space vectors (1, 2,..., 6 on the left side of FIG. 10) and the other to PWM. (Non-Patent Documents 2, 3, and 4). For example, when the inverter 110 is fixed to a certain space vector vk (k = 1, 2,..., 6), the command values vi1 ^* and vi2 ^* of the output voltages of the inverters 110 and 120 are
vi1 ^* = vk (2)
vi2 ^* = vk−vs ^* (3)
When fixing the inverter 120,
vi1 ^* = vs ^* + vk (4)
vi2 ^* = vk (5)
It becomes. This is referred to as “Method 1”. An example when the output voltage of the inverter 120 is fixed by the technique 1 is shown in FIG. When the voltage command values shown in FIG. 11 are synthesized, the space vector output from the inverter 110 is indicated by ◇, the space vector output by the inverter 120 is indicated by Δ, and the space vector of the winding voltage is indicated by ○.

The other is a method in which the output voltage commands vi1 ^* and vi2 ^* of two inverters are combined by PWM with a 180 ° phase difference as shown in the following equations (6) and (7) (Non-patent Document 1). 5).

vi1 ^* = 0.5 * vs ^* (6)
vi2 ^* = − 0.5 * vs ^* (7)
This is referred to as “Method 2”. An example in which the voltage command is synthesized by the technique 2 is shown in FIG. The space vector output from the inverter 110 is indicated by ◇, the space vector output by the inverter 120 is indicated by Δ, and the space vector of the winding voltage is indicated by ○.

H. Stemmler and P.M. Guggenbach, “Configurations of high-power voltage source inverter drives”, in Power Electronics and Applications, 1993. Fifth European Conference on, Sep 1993, pp. 7-14 vol. 5. E. Shivakumar, K. et al. Gopakumar, S .; Sinha, A .; Pitter, and V.M. Ranganathan, “Space Vector Pwm control of dual invertered opef-end winding induction motor drive,“ In Applied Power Electronics 1 APEC 2001. Sixteenth Annual IEEE, vol. 1,2001, pp. 399-405 vol. 1. V. Somasekhar, S .; Srinivas, B.M. Prakash Reddy, C.I. Nagarjuna Reddy, and K.K. Sivakumar, “Pulse width-modulated switching strategy for the dynamic balancing of zero-sequence current and tentatively rented-in-fed-off. 1, no. 4, pp. 591-600, July 2007. S. Srinivas and V.M. Somasekhhar, “Space-vector-based pwm switching stagings for a three-level dual-inverter-driven-headed-motor-reader. 2, no. 1, pp. 19-31, Jan 2008. V. Somasekhar, S .; Srinivas, and K.K. Kumar, “Effect of zero-vector placement in a dual-inverter-fed open-end winding inductive pacer-electric spacepumper-vector-pumper ---------------------------- 55, no. 6, pp. 2497-2505, June 2008.

Japanese Patent Laid-Open No. 7-135797 JP2012-80753A

  In the “method 1” described in FIG. 11, since only one inverter is switched to synthesize the output voltage, the switching loss of the switching device is concentrated on one inverter, and the switching device of one inverter is The temperature rises easily and the temperature is easily destroyed.

  In order to equalize the switching loss, there is also a technique (Non-patent Document 4) in which the role of the inverter that fixes the output and the inverter that switches and synthesizes the voltage is changed according to the electrical angle. Under the condition of outputting voltage, the time during which switching loss concentrates on one side becomes longer, and the temperature of the switching device is likely to rise.

The “method 2” described with reference to FIG. 12 solves the switching loss concentration problem of the “method 1”. However, when a three-level space vector is viewed on the α-β plane, a space vector (vector at the “0” position in the center of FIG. 12) other than three near the winding voltage command value vs ^* is also used. For this reason, the voltage error increases at the moment of outputting a space vector away from the command value, and the current ripple of the current flowing through the winding increases.

  Due to the increase in current ripple, there is a problem that winding loads such as induction motors cannot be operated smoothly.

  The present invention solves the above problem, and its object is to solve the concentration of switching loss, which is a problem of “Method 1”, and to suppress current ripple, which is a problem of “Method 2”. It is an object of the present invention to provide a control device and control method for an open winding system.

The control device for an open winding system according to claim 1 for solving the above-described problems includes a first inverter and a second inverter that convert DC power of a DC power source into AC power, the first inverter, and a second inverter. In an open winding system having an open winding connected between AC output terminals of inverters of
A carrier signal generator for generating first and second carrier signals having a phase difference of 90 °;
A voltage command conversion unit that converts the winding voltage command of each phase of the alternating current of the open winding into an output voltage command of each phase of the first and second inverters having a phase difference of 180 °;
Provided for each AC phase, compare the converted output voltage command of the same phase of the first and second inverters, and the output voltage command of the first inverter is greater than the output voltage command of the second inverter Is selected, one of the first and second carrier signals is selected, and when the output voltage command of the second inverter is larger than the output voltage command of the first inverter, the first and second carriers A carrier signal selector for selecting the other of the signals;
The output voltage command of a phase of the first inverter provided for each AC phase and converted by the voltage command conversion unit is compared with the carrier signal selected by the carrier signal selection unit provided for the phase. When the output voltage command is larger than the carrier signal, the upper arm switching element of the phase of the first inverter is turned on and the lower arm switching element is turned off, and the carrier signal is larger than the output voltage command. A first pulse voltage command generation unit that generates a pulse voltage command of the first inverter that turns off the switching element of the upper arm of the phase of the first inverter and turns on the switching element of the lower arm;
The output voltage command of a phase of the second inverter provided for each AC phase and converted by the voltage command conversion unit is compared with the carrier signal selected by the carrier signal selection unit provided for the phase. When the output voltage command is larger than the carrier signal, the upper arm switching element of the second inverter is turned on and the lower arm switching element is turned off, and the carrier signal is larger than the output voltage command. A second pulse voltage command generation unit that generates a pulse voltage command of the second inverter that controls the switching element of the upper arm to be turned off and the switching element of the lower arm to be turned on;
It is characterized by having.

  According to a second aspect of the present invention, there is provided the control device for the open winding system according to the first aspect, wherein the positive and negative DC input terminals of the first and second inverters are connected to a common DC power source. It is characterized by.

  According to a third aspect of the present invention, there is provided the control device for the open winding system according to the first aspect, wherein the positive and negative DC input terminals of the first inverter are connected to the first DC power source, and the second inverter The positive and negative DC input terminals are connected to a second DC power source that is insulated from the first DC power source.

According to a fourth aspect of the present invention, there is provided an open winding system control method comprising: first and second inverters that convert DC power of a DC power source into AC power; and AC outputs of the first inverter and the second inverter. A method for controlling an open winding system comprising an open winding connected between terminals,
A voltage command conversion step of converting the winding voltage command of each phase of the alternating current of the open winding into an output voltage command of each phase of the first and second inverters having a phase difference of 180 °;
When the converted output voltage command of the same phase of the first and second inverters is compared, and the output voltage command of the first inverter is larger than the output voltage command of the second inverter, the phase difference is The first and second carrier signals are selected when one of the first and second carrier signals of 90 ° is selected and the output voltage command of the second inverter is larger than the output voltage command of the first inverter. A carrier signal selection step of executing the process of selecting the other of each of the alternating current phases;
The output voltage command of a phase of the first inverter converted in the voltage command conversion step is compared with the carrier signal selected in the carrier signal selection step in the phase, and the output voltage command is larger than the carrier signal. When the upper arm switching element of the phase of the first inverter is turned on and the switching element of the lower arm is turned off, and the carrier signal is larger than the output voltage command, the upper arm of the phase of the first inverter A first inverter control step for executing a process of turning off the switching elements of the first switch and turning on the switching elements of the lower arm in each AC phase;
The output voltage command of a phase of the second inverter converted in the voltage command conversion step is compared with the carrier signal selected in the phase by the carrier signal selection step, and the output voltage command is larger than the carrier signal. When the upper arm switching element of the second inverter is turned on and the lower arm switching element is turned off, and the carrier signal is larger than the output voltage command, the upper arm of the phase of the second inverter A second inverter control step for performing a process of turning off the switching elements of the first arm and switching on the lower arm switching elements in each AC phase;
It is characterized by having.

  In the above configuration, since the first and second inverters are driven by the output voltage command in which the polarity is inverted with the same amplitude, the switching loss of the two inverters becomes equal, and the temperature rise of the switching elements of the inverters is equalized it can. This makes it difficult for the switching element to break down in temperature, and the reliability of the system can be improved.

  Further, since the output voltage command of the first and second inverters is compared with one carrier signal that is reciprocated between two levels selected by the carrier signal selection unit (step), the two-level carrier comparison PWM is used. Each is synthesized.

  And since the difference of the output voltage of a 1st inverter and a 2nd inverter turns into a winding voltage, a winding voltage becomes a voltage based on the same pulse voltage command as the PD-PWM method.

  As a result, the winding voltage command is synthesized by using a space vector on the three neighborhoods of the winding voltage command in the α-β plane that has been converted into the three-phase / two-phase, so that the voltage error in the α-β plane Is minimized and the ripple of the winding current is reduced. Therefore, a winding load such as an induction motor can be smoothly operated.

  According to the present invention, since the first and second inverters are driven by the output voltage command with the same amplitude and the polarity reversed, the switching loss of the two inverters becomes uniform, and the temperature rise of the switching elements of the inverters is increased. Can be equalized. This makes it difficult for the switching element to break down in temperature, and the reliability of the system can be improved.

  In addition, since the winding voltage command is synthesized by using a space vector on the three neighborhoods of the winding voltage command in the α-β plane that has been subjected to the three-phase / two-phase conversion, a voltage error in the α-β plane. Is minimized and the ripple of the winding current is reduced. Therefore, a winding load such as an induction motor can be smoothly operated.

The block diagram of the control apparatus by the example of this embodiment. The carrier signal waveform figure for demonstrating the PD-PWM method. The carrier signal waveform diagram for demonstrating the relationship between the carrier voltage of 2 levels, the carrier comparison of 3 levels, and the pulse voltage command of winding voltage in the example of this embodiment. The wave form diagram which shows the experimental result of the voltage waveform in this embodiment example and the conventional method. The vector top view which shows the experimental result of the space vector in this embodiment example and the conventional method. The wave form diagram which shows the experimental result of the current waveform in this embodiment example and the conventional method. The block diagram which shows the typical example of the conventional 3 level inverter. The circuit block diagram which shows an example of the open winding system to which this invention is applied. The circuit block diagram which shows the other example of the open winding system to which this invention is applied. The space vector figure for demonstrating the 2 level space vector of the output voltage of an inverter, and the 3 level space vector of a winding voltage. The space vector figure for demonstrating an example (method 1) of the synthetic | combination method by PWM of each conventional voltage command in an open winding system. The space vector figure for demonstrating the other example (method 2) of the synthetic | combination methods by PWM of each conventional voltage command in an open winding system.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. FIG. 1 is a block diagram of a control device of an open winding system according to the present embodiment using a PD-PWM (Phase Disposition-PWM) technique. The control device of FIG. 1 is applied to the open winding system of FIGS. 8 and 9, for example.

  In the present embodiment example, two triangular wave carrier signals (first carrier signal: carrier1, second carrier signal: carrier2) output from the carrier signal generation unit 200 and having different phases are used. The first carrier signal has a phase that is 90 ° (1/4 cycle) ahead of the second carrier signal.

210, FIG. 8, the three-phase phase windings 140a of FIG. 9, 140b, winding voltage command ^{140c vs * = [vsa *,} vsb *, vsc *] a, 180 ° position in the same manner as the method 2 This is a voltage command conversion unit for converting into phase difference inverter output voltage commands vi1 ^* = [vi1a ^* , vi1b ^* , vi1c ^* ], vi2 ^* = [vi2a ^* , vi2b ^* , vi2c ^* ].

vi1 ^* = 0.5 * vs ^* (8)
vi2 ^* = − 0.5 * vs ^* (9)
220a, 220b, and 220c are output voltage commands vi1a ^* , vi1b ^* , vi1c ^* of the three-phase each phase of the first inverter 110 output from the voltage command conversion unit 210 and three-phase each phase of the second inverter 120. The comparator compares the output voltage commands vi2a ^* , vi2b ^* , and vi2c ^* for each phase.

230a, 230b, and 230c are selectors that select a triangular wave carrier signal from the carrier signal generator 200 for each phase according to the comparison outputs of the comparators 220a, 220b, and 220c, and the output voltage of the first inverter 110 command ^{vi1 * (= vi1a *, vi1b} *, vi1c *) the output voltage command of the second inverter ^{120 vi2 * (= vi2a *,} vi2b *, vi2c *) is larger than phase selects the second carrier signal, A phase in which the output voltage command vi2 ^* is larger than vi1 ^* selects the first carrier signal.

  The comparators 220a, 220b, 220c and the selectors 230a, 230b, 230c constitute a carrier signal selector.

241a, 241b, and 241c respectively compare the triangular wave carrier signal selected by the selectors 230a, 230b, and 230c of each phase with the output voltage commands vi1a ^* , vi1b ^* , and vi1c ^* of each phase of the first inverter 110. Thus, the comparator generates a pulse voltage command for each phase of the first inverter 110.

242a, 242b, and 242c respectively compare the triangular wave carrier signal selected by the selectors 230a, 230b, and 230c of each phase and the output voltage commands vi2a ^* , vi2b ^* , and vi2c ^* of each phase of the second inverter 120. The comparator generates a pulse voltage command for each phase of the second inverter 120.

  The comparators 241a, 241b, and 241c constitute a first pulse voltage command generation unit, and the comparators 242a, 242b, and 242c constitute a second pulse voltage command generation unit.

For example, in the a phase of the first pulse voltage command generation unit, when the a phase output voltage command vi1a ^* > is the triangular wave carrier signal selected by the selector 230a, 1 is output, and the upper arm of the a phase of the inverter 110 The switching device is turned on, and the lower arm switching device is turned off.

Also, when the a-phase output voltage command vi1a ^* <the triangular wave carrier signal selected by the selector 230a, 0 is output, the switching device for the upper arm of the inverter 110 is turned off, and the switching device for the lower arm is turned on. Let

  Other b-phase and c-phase pulse voltage commands perform the same operation.

Further, in the second pulse voltage command section, for example, in the a phase, when the a phase output voltage command vi2a ^* > is the triangular wave carrier signal selected by the selector 230a, 1 is output, and the upper phase of the inverter 120 is increased ^. Turn on the arm switching device and turn off the lower arm switching device.

Also, when the a-phase output voltage command vi2a ^* <the triangular wave carrier signal selected by the selector 230a, 0 is output, the switching device for the upper arm of the inverter 120 is turned off, and the switching device for the lower arm is turned on. Let

  Other b-phase and c-phase pulse voltage commands perform the same operation.

PD-PWM (in-phase disposition PWM) is a general three-level inverter PWM method. FIG. 2 shows a triangular wave carrier waveform of PD-PWM and a three-phase command voltage. In this PD-PWM method, the values of the three-phase voltage commands (va ^* , vb ^* , vc ^* ) are compared with the values of two types of triangular carrier waveforms, carrier A and carrier B, and the pulses shown in Table 2 below are compared. Generate a voltage command.

  Furthermore, based on this pulse voltage command, a gate signal for turning on / off each switching device of the three-level inverter is generated, and by controlling the switching device with the gate signal, a three-level voltage is output to the output phase of the three-level inverter. Let

  FIG. 7 shows a representative configuration of the three-level inverter described in Patent Document 2. In the case of this configuration, the relationship between the pulse voltage command and the output voltage (AB terminal voltage) in Table 2 is shown in Table 3 below.

  Next, a method for generating a gate signal using a space vector as shown in FIG. 12 will be described.

Three-phase voltage commands (va ^* , vb ^* , vc ^* ) are three-phase / two-phase converted to α-β axes. A space vector (1, 7, 8, 19 in FIG. 12) in the vicinity of the winding voltage command (vs ^* in FIGS. 11 and 12) on the α-β plane is selected. Furthermore, the voltage command is synthesized by matching the sum of the selected space vector with the duty ratio and the voltage vector. Further, since the space vector has a voltage condition of each phase as shown in Table 1 (that is, an on / off condition of the switching device), an on / off condition (gate signal) of each switching device in the inverter can be determined. In this method, only space vectors in three neighborhoods are selected, so that the voltage error on the α-β plane can be minimized.

  On the other hand, the winding voltage vs of the open winding system is also three levels. Therefore, in the open winding system, if the voltages of the inverter 110 and the inverter 120 are output so that the winding voltage vs becomes a voltage based on the same pulse voltage command as the PD-PWM, the voltage error on the α-β plane is minimized. Can be.

FIG. 3 shows the corresponding relationship of the triangular wave comparison PWM for one phase when the relationship between the inverter output voltage commands vi1a ^* and vi2a ^* and the winding voltage command vs ^* is the expressions (8) and (9). It is a thing. The numbers (0, 1, −1) between the two-level carrier comparison in the upper part of FIG. 3 and the three-level carrier comparison (PD-PWM) in the lower part of FIG. 3 are pulse voltage commands for the winding voltage vs.

(1) Two-level carrier comparison that compares the inverter output voltage command (vi1 ^* or vi2 ^* ) with one type of carrier signal (the upper method in FIG. 3)
(2) Three-level carry comparison that compares the winding voltage command vs ^* and two types of carrier signals (lower method in FIG. 3)
From any of these methods, a pulse voltage command of the same winding voltage is obtained.

  In the two-level carrier comparison method (1), the inverter pulse voltage command = 1 when the inverter output voltage command> carrier signal, and the inverter pulse voltage command = 0 when the inverter output voltage command <carrier signal.

For example, in the left end region of the left chart in the upper part of FIG. 3, since vi1 ^* > carrier signal> vi2 ^* , the pulse voltage command of the inverter 110 = 1 and the pulse voltage command of the inverter 120 = 0.

  For this reason, the pulse voltage command of the winding voltage = the pulse voltage command of the inverter 110−the pulse voltage command of the inverter 120 = 1−0 = 1.

  Therefore, in an open winding system, if the output voltage commands of the first and second inverters (110, 120) are synthesized by this two-level carrier comparison PWM, a PD-PWM pulse voltage command is output to the winding. Will be.

Furthermore, the two-level carrier comparison triangular wave carrier signal in the upper part of FIG. 3 is changed according to the magnitude relationship between vi1 ^* and vi2 ^* . Looking at the triangular wave carrier signal of the three-level carrier comparison in the lower part of FIG. 3, the carrier signal in the upper right part of FIG. 3 (vi1 ^* <vi2 ^* ) is from the carrier signal in the upper left part of FIG. 3 (vi1 ^* > vi2 ^* ). It can be seen that the phase has advanced by 90 ° (1/4 period). Therefore, as shown in FIG. 3, it is necessary to change the phase of the carrier signal based on the magnitude relationship between vi1 ^* and vi2 ^* .

Therefore, in the block diagram of FIG. 1 of the present embodiment, two carrier signals (carrier1 and carrier2) having a phase difference of 90 ° are provided, and the two carrier signals are selected based on the magnitude relationship between vi1 ^* and vi2 ^*. ing.

  Furthermore, in the method of the present invention that can output a voltage based on the pulse voltage command of PD-PWM to the winding, the winding voltage command uses only a space vector on the vicinity of the command voltage in the α-β plane.

  Further, the two inverter output voltage commands are obtained by reversing the polarity with the same amplitude from the equations (8) and (9). Therefore, both inverters are switched the same number of times, and the switching loss of the two inverters becomes equal in the method of the present invention.

  4, 5, and 6 show experimental results comparing the method 1 (PD-PWM clamped), the method 2 (APOD-PWM; Intelligent Phase Opposition Disposition PWM), and the method of the present invention (PD-PWM).

  FIG. 4 shows the a-phase winding command voltage (upper stage), the output voltage (middle stage) of the first inverter 110 (Inverter 1), and the output voltage (lower stage) of the second inverter 120 (Inverter 2). In the method 1 in the center of FIG. 4, only the switching operation of either the first inverter 110 or the second inverter 120 is performed every half cycle of the sinusoidal winding voltage command, but the method of the present invention on the right side of FIG. Then, it turns out that both inverters are switching in the whole period.

  FIG. 5 shows the winding voltage as a three-level space vector. A space vector output in a certain carrier signal period is indicated by x. In the method 2 (APOD-PWM) on the left side of FIG. 5, the center vector (vector 0) of the circle is selected, but not selected in the method (PD-PWM) of the present invention on the right side of FIG. It can be confirmed that the method of the present invention uses space vectors on three neighborhoods in the α-β plane as in the method 1 in the center of FIG.

  FIG. 6 shows the α-β-axis current flowing through the windings. The upper part shows method 2 (APOD-PWM), the middle part shows method 1 (PD-PWM clamped), and the lower part shows the method of the present invention. The sinusoidal waveform indicates the α axis winding current is. α and β axis winding current is. β. Also, THDiα is the winding current is. The distortion rate of α.

  The method of the present invention in the lower part of FIG. 6 has a lower TFDiα than the method 2 in the upper part of FIG. The same applies to the β-axis current ripple.

  As described above, according to this embodiment, in the open winding system, the output voltage commands of the first and second inverters are synthesized by the two-level carrier comparison PWM, and the pulse voltage command of PD-PWM is applied to the winding. Since it is configured to output, the first and second inverters can be driven with an output voltage command in which the polarity is inverted with the same amplitude, and the switching loss of the two inverters becomes equal, and the inverter switching The temperature rise of the element can be equalized. This makes it difficult for the switching element to break down in temperature, and the reliability of the system can be improved.

  In addition, since the winding voltage command is synthesized by using a space vector on the three neighborhoods of the winding voltage command in the α-β plane that has been subjected to the three-phase / two-phase conversion, a voltage error in the α-β plane. Is minimized and the ripple of the winding current is reduced. Therefore, a winding load such as an induction motor can be smoothly operated.

DESCRIPTION OF SYMBOLS 110 ... 1st inverter 120 ... 2nd inverter 130, 131, 132 ... DC power supply 140a, 140b, 140c ... Winding 200 ... Carrier signal generation part 210 ... Voltage command conversion part 220a, 220b, 220c, 241a, 241b, 241c, 242a, 242b, 242c ... comparators 230a, 230b, 230c ... selectors

Claims (4)

Open winding comprising: first and second inverters for converting DC power of a DC power source into AC power; and an open winding connected between the first inverter and the AC output terminal of the second inverter. In the system,
A carrier signal generator for generating first and second carrier signals having a phase difference of 90 °;
A voltage command conversion unit that converts the winding voltage command of each phase of the alternating current of the open winding into an output voltage command of each phase of the first and second inverters having a phase difference of 180 °;
Provided for each AC phase, compare the converted output voltage command of the same phase of the first and second inverters, and the output voltage command of the first inverter is greater than the output voltage command of the second inverter Is selected, one of the first and second carrier signals is selected, and when the output voltage command of the second inverter is larger than the output voltage command of the first inverter, the first and second carriers A carrier signal selector for selecting the other of the signals;
The output voltage command of a phase of the first inverter provided for each AC phase and converted by the voltage command conversion unit is compared with the carrier signal selected by the carrier signal selection unit provided for the phase. When the output voltage command is larger than the carrier signal, the upper arm switching element of the phase of the first inverter is turned on and the lower arm switching element is turned off, and the carrier signal is larger than the output voltage command. A first pulse voltage command generation unit that generates a pulse voltage command of the first inverter that turns off the switching element of the upper arm of the phase of the first inverter and turns on the switching element of the lower arm;
The output voltage command of a phase of the second inverter provided for each AC phase and converted by the voltage command conversion unit is compared with the carrier signal selected by the carrier signal selection unit provided for the phase. When the output voltage command is larger than the carrier signal, the upper arm switching element of the second inverter is turned on and the lower arm switching element is turned off, and the carrier signal is larger than the output voltage command. A second pulse voltage command generation unit that generates a pulse voltage command of the second inverter that controls the switching element of the upper arm to be turned off and the switching element of the lower arm to be turned on;
A control device for an open winding system, comprising:   2. The control device for an open winding system according to claim 1, wherein positive and negative DC input terminals of the first and second inverters are connected to a common DC power source.   The positive and negative DC input terminals of the first inverter are connected to a first DC power supply, and the positive and negative DC input terminals of the second inverter are insulated from the first DC power supply. 2. The control device for an open winding system according to claim 1, wherein the control device is connected to a direct current power source. Open winding comprising: first and second inverters for converting DC power of a DC power source into AC power; and an open winding connected between the first inverter and the AC output terminal of the second inverter. A system control method comprising:
A voltage command conversion step of converting the winding voltage command of each phase of the alternating current of the open winding into an output voltage command of each phase of the first and second inverters having a phase difference of 180 °;
When the converted output voltage command of the same phase of the first and second inverters is compared, and the output voltage command of the first inverter is larger than the output voltage command of the second inverter, the phase difference is The first and second carrier signals are selected when one of the first and second carrier signals of 90 ° is selected and the output voltage command of the second inverter is larger than the output voltage command of the first inverter. A carrier signal selection step of executing the process of selecting the other of each of the alternating current phases;
The output voltage command of a phase of the first inverter converted in the voltage command conversion step is compared with the carrier signal selected in the carrier signal selection step in the phase, and the output voltage command is larger than the carrier signal. When the upper arm switching element of the phase of the first inverter is turned on and the switching element of the lower arm is turned off, and the carrier signal is larger than the output voltage command, the upper arm of the phase of the first inverter A first inverter control step for executing a process of turning off the switching elements of the first switch and turning on the switching elements of the lower arm in each AC phase;
The output voltage command of a phase of the second inverter converted in the voltage command conversion step is compared with the carrier signal selected in the phase by the carrier signal selection step, and the output voltage command is larger than the carrier signal. When the upper arm switching element of the second inverter is turned on and the lower arm switching element is turned off, and the carrier signal is larger than the output voltage command, the upper arm of the phase of the second inverter A second inverter control step for performing a process of turning off the switching elements of the first arm and switching on the lower arm switching elements in each AC phase;
A method for controlling an open winding system, comprising:

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