Power conversion control device

Abstract

A semiconductor switch (204R) is provided, which connects the output of each phase of the three-phase AC power supply (201) to the DC intermediate potential terminal via a reactor (203R). A positive-side diode (205R) and a negative-side diode (206R) are configured to connect the reactor (203R) to the DC positive and DC negative potential terminals, respectively, and supply power to the DC side. The semiconductor switch (204R) is switched on / off, causing the current from the three-phase AC power supply to become a similar waveform to the voltage. Even when the polarity of the output voltage of the three-phase AC power supply (201) is inconsistent with the polarity of the short-time average voltage during the on / off control of the connection point of the reactor (203R) and the semiconductor switch (204R), the same voltage is applied to the ideal voltage of each phase.

Description

Technical Field

[0001] This invention relates to a power conversion control device that rectifies AC power into DC power and uses the DC power to drive an electric motor at a variable speed. Background Technology

[0002] Patent document 1 discloses a three-phase rectifier that converts three-phase alternating current into direct current in a single direction.

[0003] This three-phase rectifier has three sets of bidirectional switching circuits, constructed by connecting semiconductor switching elements between the DC output terminals of a single-phase rectifier circuit consisting of four diodes connected in a single-phase bridge configuration. The three-phase rectifier also includes three AC-side reactors connected to one of the respective AC input terminals of the three sets of bidirectional switching circuits and to the three output terminals of the three-phase AC power supply. The three-phase rectifier further includes three positive-side diodes with anodes connected to the positive DC output terminals of the three sets of bidirectional switching circuits and cathodes connected to the positive DC bus; and three negative-side diodes with cathodes connected to the negative DC output terminals of the three sets of bidirectional switching circuits and anodes connected to the negative DC bus. The three-phase rectifier also includes a smoothing capacitor consisting of two capacitors connected in series between the positive and negative DC buses, with its midpoint terminal connected to the other AC input terminal of each of the three sets of bidirectional switching circuits. The three-phase rectifier also includes a control circuit that controls the semiconductor switching elements of the three sets of bidirectional switching circuits.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 9-182441 Summary of the Invention

[0007] The present invention provides a power conversion control device that, in a power conversion control device that converts three-phase alternating current to direct current in one direction, can reduce the distortion of the current waveform on the AC side, even when using a reactor with a large inductance to achieve a smoother input current.

[0008] The power conversion control device of the present invention includes: a semiconductor circuit group comprising multiple semiconductor circuits; each semiconductor circuit having: a reactor connected to the output side of a three-phase AC power supply; a semiconductor switch for connecting the reactor to a DC intermediate potential terminal; and multiple diodes for supplying power to the DC side by connecting the reactor to a DC positive potential terminal or the reactor to a DC negative potential terminal; and a controller for controlling the on / off ratio of the semiconductor switches. In the semiconductor circuit group, each of the multiple semiconductor circuits, for each phase of the three-phase AC power supply, uses a semiconductor switch and multiple diodes to selectively allow current to flow from the three outputs of the three-phase AC power supply through the reactor, through the DC positive potential terminal, the DC negative potential terminal, and the DC intermediate potential terminal, thereby converting AC power into DC power. To make the waveform of the current flowing from the three-phase AC power supply to each of the multiple semiconductor circuits similar to the waveform of the voltage of the three-phase AC power supply, the controller calculates the ideal voltage at the connection point of multiple diodes and semiconductor switches for each of the multiple semiconductor circuits. Based on the absolute value of the ideal voltage, the controller controls the on / off ratio of the semiconductor switches to make the short-time average voltage at the connection point the ideal voltage. If the polarity of the output voltage of the three-phase AC power supply is inconsistent with the polarity of the ideal voltage at the connection point, the controller adds the same equivalent voltage value to the ideal voltage of each phase to make the polarity of the short-time average voltage zero or the same as the polarity of the output voltage of the three-phase AC power supply. Attached Figure Description

[0009] Figure 1 This is a control block diagram illustrating the control process flow of the power conversion control device in Embodiment 1 of the present invention.

[0010] Figure 2 This is a circuit block diagram showing the overall structure of the power conversion control device in Embodiment 1.

[0011] Figure 3 This is a circuit block diagram showing a portion of the structure of the power conversion control device in Embodiment 1.

[0012] Figure 4 The waveform diagrams are of the power conversion control device in Implementation 1. (a) represents the power supply voltage waveform of phase R, (b) represents the node potential waveform of phase R, (c) represents the node potential waveform of phase S, and (d) represents the node potential waveform of phase T.

[0013] Figure 5 The waveform diagrams are of the power conversion control device in Implementation 1. (a) represents the power supply voltage waveform of phase R, (b) represents the other potential waveforms of the node of phase R, (c) represents the other potential waveforms of the node of phase S, and (d) represents the other potential waveforms of the node of phase T.

[0014] Figure 6 This is a control block diagram illustrating the control process of the power conversion control device in Embodiment 2 of the present invention.

[0015] Figure 7 The waveform diagrams are for the power conversion control device in Embodiment 2. (a) represents the power supply voltage waveform of phase R, (b) represents the node potential waveform of phase R, (c) represents the node potential waveform of phase S, and (d) represents the node potential waveform of phase T.

[0016] Figure 8 This is a control block diagram illustrating the control process of the power conversion control device in Embodiment 3 of the present invention.

[0017] Figure 9 This is a circuit block diagram showing the structure of the power phase calculation section of the power conversion control device in Embodiment 3.

[0018] Figure 10 This is a waveform diagram showing the operation of the power phase calculation unit of the power conversion control device in Embodiment 3.

[0019] Figure 11 It is a waveform diagram showing other operations of the power phase calculation unit of the power conversion control device in Embodiment 3. Detailed Implementation

[0020] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, sometimes unnecessary detailed descriptions will be omitted. For example, there may be omissions of detailed descriptions of matters that are already known, or repetitions of descriptions of substantially the same structures. This is to avoid the following description becoming excessively lengthy and to facilitate understanding by those skilled in the art.

[0021] Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the invention, and are not intended to limit the subject matter described in the claims.

[0022] (Implementation Method 1)

[0023] The following uses Figures 1-4 Description of Implementation Method 1.

[0024] [1-1. Structure]

[0025] [1-1-1. Structure of the Power Conversion Control Device]

[0026] Figure 2 This is a block diagram showing the overall structure of the power conversion control device 1000 according to Embodiment 1. Figure 3This is a block diagram showing a portion of the structure of the power conversion control device according to Embodiment 1.

[0027] exist Figure 3 The diagram shows the output line of phase R of the three-phase AC power supply 201. The output line of phase R is connected to node Vr of phase R via reactor 203R. A positive diode 205R, a negative diode 206R, and a semiconductor switch 204R are connected to node Vr.

[0028] The positive-side diode 205R allows the charging current to flow through the positive-side smoothing capacitor 207. The negative-side diode 206R allows the charging current to flow through the negative-side smoothing capacitor 208.

[0029] In addition, the semiconductor switch 204R is connected to the midpoint of the two smoothing capacitors 207 and 208.

[0030] The load on the DC side is connected to the positive terminal of the smoothing capacitor 207 on the positive side and the negative terminal of the smoothing capacitor 208 on the negative side.

[0031] That is, such as Figure 3 As shown, the power conversion control device 1000 has a first semiconductor circuit 202R as an R-phase circuit (refer to...). Figure 2 The R-phase circuit includes: a reactor 203R; a semiconductor switch 204R that connects the reactor 203R to the DC intermediate potential terminal; and a positive-side diode 205R and a negative-side diode 206R that connect the reactor 203R to the DC positive potential terminal or to the DC negative potential terminal to supply power to the DC side, respectively.

[0032] Specifically, when the phase voltage (Er) is positive, if the semiconductor switch 204R of the first semiconductor circuit 202R is turned on, the current flowing through the reactor 203R increases in the direction of the current flowing from the semiconductor switch 204R to the midpoint of the DC current.

[0033] Next, if the semiconductor switch 204R is turned off, the current flowing through the reactor 203R cannot change drastically, so it flows through node Vr and via the positive-side diode 205R connected to the positive-side DC to the positive-side DC (+Vdc).

[0034] On the other hand, when the phase voltage (Er) is negative and the direction of the current flowing through the reactor 203R is back to the three-phase AC power supply 201, if the semiconductor switch 204R is turned off, the current flowing through the reactor 203R cannot change drastically. Therefore, the current flows from the DC negative side (-Vdc) through the negative side diode 206R connected to the DC negative side, through node Vr, and through the reactor 203R to the three-phase AC power supply 201.

[0035] like Figure 2 As shown, multiple semiconductor circuits are provided as a semiconductor circuit group, such as the first semiconductor circuit 202R as the R-phase circuit, the second semiconductor circuit 202S as the S-phase circuit, and the third semiconductor circuit 202T as the T-phase circuit.

[0036] In addition, reactors, semiconductor switches, positive-side diodes, and negative-side diodes are respectively installed in the second semiconductor circuit 202S, which serves as the S-phase circuit, and the third semiconductor circuit 202T, which serves as the T-phase circuit. Figure 2 The image is not shown in the image.

[0037] In the semiconductor circuit group, semiconductor switches, positive-side diodes and negative-side diodes are used to convert AC power into DC power from the three outputs of the three-phase AC power supply 201 through reactors, so that the current selectively flows through the DC positive potential terminal, the DC negative potential terminal and the DC intermediate potential terminal according to each phase.

[0038] That is, the detected values ​​of the power phase, phase current and DC voltage output of the three-phase AC power supply 201 are input to the controller 210, and the controller 210 controls the conduction / discontinuation of the semiconductor switches of each phase.

[0039] Thus, while achieving high power factor control that makes the phase current have the same waveform as the power supply voltage, the desired DC voltage can be obtained.

[0040] Specifically, the controller 210 is implemented using a microcomputer or similar device. In addition to the central processing unit (CPU) that executes the control program, the controller 210 also includes an AD converter (Analog-digital converter) and a timer capable of performing PWM (pulse width modulation). The control method of the controller 210 will be explained in detail later.

[0041] [1-1-2. Processing Structure in the Controller]

[0042] Figure 1 It means Figure 2 The control block diagram of the control processing flow of controller 210.

[0043] To drive a DC load, a DC voltage command (Vdc*) is set to the desired value. The actual DC voltage (Vdc) is detected, and the difference between the DC voltage command (Vdc*) and the DC voltage (Vdc) is obtained by the comparison unit 101. For the obtained DC voltage difference, a stable and rapid calculation of DC voltage control, such as PI (Proportional-Integral) control, is performed by the compensation calculation element 102. The calculation result of the compensation calculation element 102 is obtained as the q-axis current command (Iq*).

[0044] The q-axis current command is the command for the effective current component in the three-phase AC input. Adjusting the DC voltage by increasing or decreasing the q-axis current command allows for the control of the DC voltage. The d-axis current, the other axis, represents the ineffective current component in the three-phase AC input. Therefore, if the d-axis current component is zero, high power factor rectification can be achieved.

[0045] That is, by appropriately controlling the actual q-axis current and the d-axis current, which is orthogonal to it, AC power can be utilized with a high power factor. The d-axis current and q-axis current can be calculated using the instantaneous current and instantaneous phase of the three-phase AC power supply.

[0046] exist Figure 1 In the rotating coordinate (dq) transformation processing block 104, the d-axis current and q-axis current are calculated based on at least two phase currents from the detected phase currents (Ir, Is, It) of the three-phase AC power supply and the calculated value (θ^) of the instantaneous power supply phase.

[0047] The comparison units 103 and 105 compare the obtained d-axis current (Id) and q-axis current (Iq) with their respective current commands (Iq*, Id*). For the errors between the d-axis current and q-axis current and the current commands (Iq*, Id*), stable and rapid compensation calculations using current control, such as PI control, are performed in the q-axis current compensation calculation block 106 and the d-axis current compensation calculation block 107. The calculation results are then sent as node voltage commands to the fixed coordinate transformation (inverse dq transformation) unit 108.

[0048] In the fixed coordinate transformation (inverse dq transformation) unit 108, the calculated value (θ^) of the instantaneous power supply phase is used to obtain the node voltage commands (Vr0*, Vs0*, Vt0*) for fixed coordinates (r / s / t axes). The obtained node voltage commands (Vr0*, Vs0*, Vt0*) are sent to the zero-sequence voltage adjustment unit 109, and the zero-sequence voltage is added as needed to obtain the corrected node voltage commands (Vr*, Vs*, Vt*).

[0049] Here, the method for adjusting the zero-sequence voltage is explained. The phase voltage calculation values ​​(Er, Es, Et) and node potential commands (Vr0*, Vs0*, Vt0*) are sent to the polarity comparison & correction calculation unit 114. The phase voltage calculation values ​​are obtained by inputting the power supply phase calculation value (θ^) to the fixed coordinate (inverse dq) transformation unit 113.

[0050] In the polarity comparison and correction calculation unit 114, the polarity reversal value of the node potential command (Vr0*, Vs0*, Vt0*) for the phase with inconsistent polarity is used as the zero-sequence voltage to adjust the phase.

[0051] If the zero-sequence voltage obtained in this way is input to the zero-sequence voltage adjustment unit 109 to adjust the zero-sequence voltage, the node potential command (Vr*, Vs*, Vt*) of that phase becomes zero. This eliminates the inconsistency between the polarity of the node potential command and the polarity of the phase voltage or phase current command.

[0052] The absolute values ​​of the obtained modified node voltage commands (Vr*, Vs*, Vt*) are converted by the 1-switching unit 110 to obtain the re-modified node potential commands (|Vr*|, |Vs*|, |Vt*|).

[0053] In the PWM conversion unit 111, the revised node potential command (|Vr*|, |Vs*|, |Vt*|) is converted into a PWM signal, and the semiconductor switches in each semiconductor circuit are turned on / off. As a result, while maintaining a current waveform with a high power factor, the desired DC voltage can be obtained, and the DC load can be driven appropriately.

[0054] [1-2. Control Actions and Node Potential Waveforms]

[0055] Figure 4 This indicates that it is done through controller 210. Figure 1 The result after processing, and the waveform diagram of the generated node potential waveform.

[0056] exist Figure 4 In each waveform diagram, taking the power supply voltage waveform of phase R shown in (a) as the reference, the phase when the phase R voltage changes from zero to positive polarity is set to zero, and when it changes to zero again, the phase when it changes to negative polarity is set to 180 degrees (deg).

[0057] Furthermore, since the current waveforms of each phase are also controlled to be the same waveform with the same phase as the power supply voltage waveforms of each phase, the phase voltage waveform of phase R shown in (a) is the same as the phase current waveform of phase R. For phases S and T, the phase voltage waveforms and phase current waveforms are the same, respectively. The phase current of phase S is a sine wave that is 120 degrees delayed compared to the phase current of phase R, and the phase current of phase T is a sine wave that is 120 degrees earlier (or 240 degrees delayed) compared to the phase current of phase R. Additionally, in Figure 4 The phase voltage waveforms and phase current command waveforms of the S-phase and T-phase are omitted.

[0058] Next, the node waveforms of each phase, which are the processing results of the controller 210, will be explained.

[0059] The current flowing through the reactors in each phase is a sinusoidal wave in phase with the phase voltage. The current phase delay caused by the inductance of the reactors must be eliminated. Therefore, the phase of the node potential is delayed compared to the phase voltage.

[0060] Figure 4 The waveform in (b) represents the node potential waveform of phase R. If an arbitrary path is used to allow current to flow from the node to the DC portion, it becomes a waveform with a phase slightly later than the phase voltage, as shown by the dashed lines in the waveforms immediately following 0 degrees or immediately following 180 degrees. If the node potential can be provided in this way, the current flowing through reactor 203R, i.e., the phase current, can become a current in phase with the phase voltage.

[0061] However, within the interval shown by the dashed line, the polarity of the phase voltage is inconsistent with the polarity of the node potential. Therefore, an ideal node potential waveform like the one shown by the dashed line cannot be obtained, and the actual waveform becomes a dotted line. As a result, the node potential is significantly distorted.

[0062] At this point, within this interval, a zero-sequence voltage is applied with the node potential at zero, forming the node potential represented by the thick solid line. This reduces the distortion of the node potential.

[0063] At this time, since the same voltage is applied to other phases as well, therefore... Figure 4 As shown in (c) and (d), the waveforms of the S-phase and T-phase with thick solid lines are obtained.

[0064] In phase S, there exists a region where the polarity of the phase voltage and the node potential are inconsistent, immediately following the phases of 120 degrees and 300 degrees. Within this region, a zero-sequence voltage is applied with the node potential of phase S set to zero.

[0065] At this point, just as the R-phase and T-phase are surrounded by thin dashed lines at the four corners, the same voltage is applied, so the node potential becomes a distorted waveform with the thick solid lines shown.

[0066] Similarly, for phase T, immediately after 60 degrees and 240 degrees, there is a range where the polarity of the phase voltage is inconsistent with the polarity of the node potential. In this range, a zero-sequence voltage is applied with the node potential of phase T being zero.

[0067] At this point, just as the R phase and S phase are surrounded by thin dashed lines at the four corners, the same voltage is applied, so the node potential becomes a distorted waveform with thick solid lines.

[0068] However, even with these processing steps, the phase currents remain almost undistorted because the phase potentials remain in a three-phase sinusoidal state. As a result, high power factor DC-DC conversion can be achieved.

[0069] Figure 5 It is a waveform diagram showing the strain when the node potential exceeds the range of DC voltage after the processing of the present invention.

[0070] Figure 5 waveform and Figure 4 The waveforms are similar. The actual node potential must be within the range of the highest (+Vdc) and lowest (-Vdc) values ​​of the DC section. Therefore, if the node potential of any phase exceeds this range, the node potential must be limited.

[0071] For example, in Figure 5 In waveform (b), in order to eliminate the polarity inconsistency of the S phase near 120 degrees, the node potential of the R phase exceeds the upper limit after the node potential of the S phase is corrected. Therefore, the node potential of the R phase is limited to the upper limit.

[0072] Similarly, near temperatures exceeding 300 degrees Celsius, since the node potential of phase R is below the lower limit, the node potential of phase R is limited to reach the lower limit. Furthermore, if this potential limit is expressed in terms of the conduction width of a semiconductor switch, it is 0%, which is equivalent to complete shutdown, or in other words, to turning on the diode, and is also equivalent to allowing the semiconductor switch to conduct for a period of time that is variable from 0% to 100%.

[0073] [1-3. Effects, etc.]

[0074] As described above, in this embodiment, the power conversion control device is connected to the three-phase AC power supply 201 via a reactor to a positive-side diode connected to the positive side of the DC current, a negative-side diode connected to the negative side of the DC current, and a semiconductor switch connected to the DC midpoint. Then, the phase current is detected, and the semiconductor switch is turned on / off to achieve the desired current waveform. A zero-sequence voltage adjustment unit 109, which applies a zero-sequence voltage, eliminates the inconsistency in the polarity of the average voltage at the connection point between the diode and the semiconductor switch if the polarity is inconsistent with the desired current waveform.

[0075] Therefore, the polarity of the average voltage at the connection point will not be different from the polarity of the desired current waveform, so the phase current flowing during the period when the semiconductor switch is turned off has the same polarity as the desired current waveform.

[0076] Therefore, by repeatedly turning the semiconductor switch on and off, a high-precision and high-power-factor current waveform can be achieved.

[0077] The power conversion control device of the present invention, by applying a zero-sequence voltage to the average potential of the node, enables the diode through which current flows when the semiconductor switch is turned off to become the desired diode. Therefore, the desired node potential can be achieved, and a power conversion control device with reduced phase current distortion can be provided.

[0078] (Implementation Method 2)

[0079] The following uses Figure 6 and Figure 7 Description of Implementation Method 2.

[0080] [2-1. Structure]

[0081] [2-1-1. Structure of the Power Conversion Control Device]

[0082] The structure of the power conversion control device in Embodiment 2 is the same as that in Embodiment 1, the difference being the processing in the controller 210.

[0083] [2-1-2. Processing Structure in the Controller]

[0084] Figure 6 This is a control block diagram illustrating the processing of the controller 210 in Embodiment 2.

[0085] As a basic control, and in accordance with implementation method 1 Figure 1 Same. The difference is the processing of polarity comparison and midpoint fixing instruction sending centered on the polarity comparison & midpoint fixing instruction sending unit 414.

[0086] In the polarity comparison & midpoint fixing command output unit 414, if the polarity of the phase voltage and the node potential is not consistent, the node potential of the phase is fixed at the midpoint potential.

[0087] The following is based on Figure 7 The waveform diagram illustrates this process.

[0088] [2-2. Control Actions and Node Potential Waveforms]

[0089] Figure 7 This indicates that it is performed by controller 210. Figure 6 The result after processing, and the waveform diagram of the generated node potential waveform.

[0090] exist Figure 7 In, with Figure 4 Similarly, for waveform (a), with the power supply voltage waveform of phase R as the reference, the phase when the phase voltage of phase R changes from zero to positive polarity is set to zero, and when it changes to zero again, the phase when it changes to negative polarity is set to 180 degrees.

[0091] Furthermore, since the current waveforms of each phase are also controlled to be the same waveform with the same phase as the power supply voltage waveforms of each phase, the phase voltage waveform of phase R shown in (a) is the same as the phase current waveform of phase R. For phases S and T, the phase voltage waveforms and phase current waveforms are the same, respectively. The phase current of phase S is a sine wave that is 120 degrees delayed compared to the phase current of phase R, and the phase current of phase T is a sine wave that is 120 degrees earlier (or 240 degrees delayed) compared to the phase current of phase R. Additionally, in Figure 7 The phase voltage waveforms and phase current command waveforms of the S-phase and T-phase are omitted.

[0092] Next, the node waveforms of each phase, which are the processing results of the controller 210, will be explained.

[0093] The current flowing through the reactors in each phase is a sinusoidal wave in phase with the phase voltage. The current phase delay caused by the inductance of the reactors must be eliminated. Therefore, the phase of the node potential is delayed compared to the phase voltage.

[0094] Figure 7 The waveform in (b) represents the node potential waveform of phase R. If an arbitrary path is used to allow current to flow from the node to the DC portion, the waveform becomes a waveform with a phase slightly later than the phase voltage, as shown by the dashed line in the waveform immediately following 0 degrees or immediately following 180 degrees.

[0095] If the node potential can be provided in this way, the current flowing through reactor 203R, i.e. the phase current, can become a current in phase with the phase voltage.

[0096] However, in the interval shown by the dashed line, the polarity of the phase voltage is inconsistent with the polarity of the node potential. Therefore, it is impossible to obtain an ideal node potential waveform like the one shown by the dashed line, resulting in a significant distortion of the node potential.

[0097] At this point, within this interval, the node potential of that phase is changed to zero. For example, immediately after 0 degrees, the node potential "Vr" of phase R is made zero.

[0098] Similarly, even immediately after 180 degrees, the node potential "Vr" of phase R is made zero. In addition, immediately after 120 degrees and 300 degrees, the node potential "Vs" of phase S is made zero, and immediately after 60 degrees and 240 degrees, the node potential "Vt" of phase T is made zero.

[0099] Therefore, it is possible to improve the actual occurrence of dotted lines (refer to...). Figure 7 The large deformation shown in the figure can produce a current waveform with fewer high-order harmonics.

[0100] [2-3. Effects, etc.]

[0101] As described above, in this embodiment, the power conversion control device connects each phase of a three-phase AC power supply via a reactor to a positive-side diode connected to the positive side of the DC current, a negative-side diode connected to the negative side of the DC current, and a semiconductor switch connected to the DC midpoint. Then, it detects the phase current and turns the semiconductor switch on / off in a manner that produces the desired current waveform. The device includes a polarity comparison and midpoint fixing command output unit 414, which, if the polarity of the average voltage at the connection point between the diode and the semiconductor switch is inconsistent with the polarity of the desired current waveform, sets the average voltage of that phase to zero to eliminate the inconsistency in the polarity of the average voltage at the connection point.

[0102] Therefore, following a simpler processing flow than Embodiment 1, the average voltage at the connection point will not differ from the polarity of the desired current waveform, so the phase current flowing during the period when the semiconductor switch is turned off is consistent with the polarity of the desired current waveform.

[0103] Therefore, by repeatedly turning the semiconductor switch on and off, a current waveform with a high power factor can be achieved.

[0104] (Implementation Method 3)

[0105] The following uses Figures 8-11 The third implementation method will be described below.

[0106] [3-1. Structure]

[0107] Figure 9 This is a circuit diagram showing the overall structure of the power supply phase calculation unit 612. The three-phase AC power supply 201 has phases R, S, and T. Light-emitting diodes (LEDs) on the primary side of optocouplers 903 and 902 are connected via resistors between phase R and phase S and between phase S and phase T, respectively.

[0108] The output of the phototransistor on the secondary side is input to the power phase calculation unit 612, and then the calculation result (θ^) of the power phase and the calculation error information are output. Figure 10 The waveform represents the relationship between the line-to-line voltage of the R-phase and S-phase of the three-phase AC power supply 201 and the output of the secondary side of the optocoupler 903.

[0109] like Figure 10 As shown, if the voltage on the AC side becomes a certain value higher than that on the positive side, the output on the secondary side of the optocoupler becomes high. This is consistent with... Figure 9 The meaning of "ON" for optocoupler 903 in the text is the same.

[0110] The duration of the high-level signal varies depending on the circuit's threshold. In the optocoupler 903, the primary side is an LED, and current flows through the LED in only one direction, so the high-level period is shorter than 180 degrees. For example... Figure 11 As shown, the period from high level to the next high level is the AC power supply cycle "tac".

[0111] Furthermore, the threshold voltage of the circuit during binarization only needs to be between a voltage close to zero and the maximum voltage of the instantaneous AC voltage. Specifically, considering the variation of the AC power supply voltage, it is preferable to set it to be below the maximum voltage of the instantaneous AC voltage within the minimum value of the varying power supply voltage.

[0112] Furthermore, such as Figure 11 As shown, if we find the midpoint between the high-level moment "ton(2)" and the low-level moment "toff(2)", i.e. ("ton(2)" + "toff(2)") / 2, we can calculate the maximum value of the AC power supply voltage, i.e. the moment when the sine wave reaches 90 degrees.

[0113] Similarly, the zero-crossing moment of the power supply voltage can be determined from the same waveform. If 3 / 4 of the period “tac” is added to the 90-degree moment (“ton(2)”+“toff(2)”) / 2, the 0-degree moment of the sine wave can be calculated.

[0114] That is, if this method is used, it is possible to calculate the timing of any phase of the AC power supply. Moreover, it is unaffected by the deviation of the threshold level of the binarization circuit.

[0115] Here, if a sinusoidal voltage is no longer output, the periodic disruption of the turn-on / turn-off timing of the optocoupler 903 will result in the detection of some kind of abnormality in the AC power supply.

[0116] In addition, Figure 9 The detailed circuitry for the current control section is omitted, but it can be utilized... Figure 2 The structure is obvious.

[0117] [3-2. Controlling Actions]

[0118] Figure 8 This is a control block diagram representing the control actions in implementation method 3.

[0119] Many parts and Figure 1 The same boxes are labeled with the same number.

[0120] exist Figure 8In the power phase calculation unit 612 shown, the power phase is calculated based on the voltage information of the three-phase AC circuit.

[0121] One method for calculating the power supply phase is as follows: The phase voltage is converted to the line-to-line voltage. The line-to-line voltage is then binarized. The period of the binarized signal is used as the power supply period. The phase lead of the semiconductor switch 204R for each PWM cycle is calculated. Then, the center moment of the high-level period of the binarized signal is set as the moment corresponding to a 90-degree phase (or a 270-degree phase) of the line-to-line voltage.

[0122] The moment equivalent to 90 degrees phase is generated according to the power cycle, i.e., a certain time interval. Therefore, if the interval of the moment equivalent to 90 degrees phase deviates from a certain time interval, the phase calculation can be considered abnormal.

[0123] Examples include situations where the power supply frequency changes drastically, the power supply phase jumps, or the phase voltage that forms the basis of the binarized signal decreases significantly.

[0124] When the node potential of this phase is fixed at the midpoint, the semiconductor switch 204R is turned on for an extended period. Therefore, if the operations of Embodiment 1 and Embodiment 2 are performed in this state, it is possible that the semiconductor switch 204R will remain on for an extended period.

[0125] If the semiconductor switch 204R is kept in a conducting state for a long time, the increased current flowing through the semiconductor switch 204R may damage it. Therefore, the current capacity of the semiconductor switch must have a margin.

[0126] Therefore, in Embodiment 3, if the power supply voltage phase calculation is not performed properly in the power supply phase calculation unit 612, the detection unit detects the situation and cuts off the zero-sequence voltage to be corrected in the cut-off unit 620.

[0127] As a result, since the zero-sequence voltage is not adjusted in the zero-sequence voltage adjustment section 109, prolonged conduction of the semiconductor switch 204R can be avoided. Therefore, there is no need to excessively increase the current capacity of the semiconductor switch 204R.

[0128] [3-3. Effects, etc.]

[0129] As described above, in this embodiment, the detection unit detects when the power supply phase calculation unit 612 fails to properly perform power supply voltage phase calculation. When the failure to properly perform power supply voltage phase calculation is detected, the unit does not perform the processing for cases where the polarity of the phase voltage shown in Embodiments 1 and 2 is inconsistent with the polarity of the node potential; that is, it maintains the node potential of that phase at zero.

[0130] Therefore, in situations such as unstable AC power, the semiconductor switch can be prevented from remaining continuously on, thus preventing damage to the semiconductor switch caused by high current. Furthermore, since it is not necessary to use a large current-capacity switch in the semiconductor switch, the power conversion control device can be miniaturized.

[0131] Furthermore, in Embodiment 3, an example based on the processing flow of Embodiment 1 was described, but it is obvious that the same effect can be obtained by implementing the processing flow based on Embodiment 2.

[0132] In addition, through Figure 9 The voltage detection performed by optocouplers 902 and 903 illustrates an example of detecting the line-to-line voltage of a three-phase AC circuit. In this case, the moment when the line-to-line voltage changes to 90 degrees is calculated. However, since the line-to-line voltage maintains a certain phase relationship with the phase voltage, it is obvious to those skilled in the art that the phase transition to the phase voltage can be easily achieved.

[0133] Furthermore, the above embodiments are for illustrative purposes only, and various changes, substitutions, additions, omissions, etc., can be made within the scope of the claims or their equivalents.

[0134] Industrial availability

[0135] This invention is applicable to conversion devices in which each phase of a three-phase AC power supply is composed of a semiconductor switch, which rectify and converts the AC power supply to DC power with a high power factor.

[0136] Explanation of reference numerals in the attached figures

[0137] 109 Zero-sequence voltage regulation section

[0138] 114 Polarity Comparison & Correction Calculation Department

[0139] 201 Three-phase AC power supply

[0140] 202R First Semiconductor Circuit

[0141] 202S Second Semiconductor Circuit

[0142] 202T Third Semiconductor Circuit

[0143] 203R reactor

[0144] 204R Semiconductor Switch

[0145] 205R forward diode

[0146] 206R negative-side diode

[0147] 207, 208 Smoothing Capacitors

[0148] 210 Controller

[0149] 414 Polarity Comparison & Midpoint Fixed Command Output Unit

[0150] 612 Power Phase Calculation Unit

[0151] 620 Cut-off section

[0152] 902, 903 optocouplers

[0153] 1000 Power conversion control device.

Claims

1. A power conversion control device, characterized in that, include: A semiconductor circuit group that contains multiple semiconductor circuits; The semiconductor circuit includes: a reactor connected to the output side of a three-phase AC power supply; a semiconductor switch that connects the reactor to a DC intermediate potential terminal; and multiple diodes that connect the reactor to a DC positive potential terminal or to a DC negative potential terminal to supply power to the DC side. and The controller controls the on / off ratio of the semiconductor switch. In the semiconductor circuit group, each of the plurality of semiconductor circuits, for each phase of the three-phase AC power supply, uses the semiconductor switches and the plurality of diodes to selectively allow current to flow from the three outputs of the three-phase AC power supply through the reactor, through the DC positive potential terminal, the DC negative potential terminal, and the DC intermediate potential terminal, thereby converting AC power into DC power. The controller aims to make the waveform of the current flowing from the three-phase AC power supply to each of the plurality of semiconductor circuits similar to the waveform of the voltage of the three-phase AC power supply. The controller calculates the ideal voltage at the connection point between the plurality of diodes and the semiconductor switch for each of the plurality of semiconductor circuits. The on / off ratio of the semiconductor switch is controlled based on the absolute value of the ideal voltage, so that the average voltage at the connection point becomes the ideal voltage. If the polarity of the output voltage of the three-phase AC power supply is inconsistent with the polarity of the ideal voltage at the connection point, the same zero-sequence voltage is applied to the ideal voltage of each phase to make the polarity of the average voltage zero or the same as the polarity of the output voltage of the three-phase AC power supply. Alternatively, if the polarity of the output voltage of the three-phase AC power supply is inconsistent with the polarity of the average voltage during the on / off control of the connection point of the plurality of diodes and the semiconductor switch, the on / off ratio of the semiconductor switch of that phase is set to 100% on.

2. The power conversion control device as described in claim 1, characterized in that: The controller controls each phase of the three-phase AC power supply. Voltage and current information are calculated or detected based on a certain time interval shorter than the cycle of the three-phase AC power supply. Based on the calculated or detected voltage and current information, the ideal voltage at each connection point at a given time interval is calculated. The on / off ratio of the semiconductor switch within a certain time period is determined based on the absolute value of the ideal voltage, so that the average voltage at the connection point within that time period becomes the ideal voltage. When the polarity of the output voltage of the three-phase AC power supply is inconsistent with the polarity of the ideal voltage at the connection point, the on / off ratio of the semiconductor switches of the plurality of semiconductor circuits is increased or decreased by an amount of on time of the same width, so that the polarity of the average voltage at the connection point within a certain time period becomes zero or the same polarity as the output voltage of the three-phase AC power supply.

3. The power conversion control device as described in claim 2, characterized in that: If the average voltage at the connection point, after adding or subtracting the conduction time, exceeds the positive or negative potential of the DC current, the ideal voltage of each phase shall be replaced by the positive or negative potential.

4. The power conversion control device as described in claim 2, characterized in that: When the on / off ratio of the semiconductor switch, after adding the on-time amount, exceeds the width of 0 to 100%, the on / off ratio of the semiconductor switch is replaced by 0% or 100%.

5. The power conversion control device as described in any one of claims 1 to 4, characterized in that, Also includes: The phase calculation unit uses the output voltage of each phase of the three-phase AC power supply to calculate the phase of the three-phase AC power supply. and The detection unit detects whether the phase calculated by the phase estimation unit is stable. The controller stops the processing in cases where the polarity of the output voltage of the three-phase AC power supply is inconsistent with the polarity of the voltage between the reactor and the semiconductor circuit group when the detection unit detects the calculated phase instability.

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