JP2015142444A - Pwm signal controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a PWM signal controller capable of controlling information on current values for two phases from shunt current even at timing when phase currents intersect with each other.SOLUTION: In a waveform information correction unit, a first correction treatment is made to function in response to a head carrier period Tc out of a vector operation period Tn, and a short period waveform B of one shunt current Idc is expanded along a time axis. Also, in the waveform information correction unit, a second correction treatment is made to function in response other carrier period excluding the head carrier period Tc out of the vector operation period Tn and the short period waveform B of one shunt current Idc is shortened along the time axis.

Description

  The present invention relates to a PWM signal control device, and is particularly suitable for use in a one-shunt circuit device.

  For example, Japanese Unexamined Patent Application Publication No. 2007-312511 (Patent Document 1) introduces an AC motor control device using a one-shunt resistor. As shown in FIG. 6, the one-shunt control device compares the command voltages Vu to Vw calculated by the control device with the carrier wave Wc, thereby generating PWM signals Sau to Sbw, PWM signals Sau to Sbw are applied to the power transistors.

  Among the PWM signals, Sau to Saw indicate signals supplied to the high-side power transistor, and Sbu to Sbw indicate signals supplied to the low-side power transistor. In addition, each power transistor receiving Sau or Sbu is connected in series to form an arm portion, and the other power transistors similarly form an arm portion.

  In the inverter circuit, all the high-side power transistors are set to the non-energized state, or all the low-side power transistors are set to the non-energized state. Current flows. At this time, in the one-shunt type power conversion circuit, a shunt current Idc representing two phase currents flows (see FIG. 6), and the control device performs vector calculation based on this, and the command voltage calculated by the vector calculation And a carrier wave are compared to generate a new PWM signal.

  However, at the timing when the phase currents intersect (time corresponding to the point X in FIG. 7), the edges of the pair of PWM signals are very close as shown in FIG. (B section) becomes extremely short, and the value of this waveform B cannot be AD converted.

  For this reason, in the technique of Patent Document 1, updating of the shunt current Idc (new data creation) is interrupted until the distorted waveform B recovers to a shape capable of AD conversion, and the current obtained up to that point is interrupted. A vector operation is performed based on the value information to generate and output a PWM signal. Then, after the waveform B returns to normal, the update of the shunt current Idc is resumed, and vector calculation using this is performed.

JP 2007-312511 A

  However, according to the technique of Patent Document 1, since the shunt current information is quoted from the history information while the waveform of the shunt current is extremely distorted, the command voltage calculated by the vector calculation becomes inappropriate. There is a risk of causing operational problems.

  In view of the above problems, an object of the present invention is to provide a PWM signal control device that can acquire current value information for two phases from a shunt current even at the timing when the phase currents intersect.

In order to solve the above problems, the present invention has the following configuration of the PWM signal control device. That is, in a PWM signal control device that performs a vector operation based on a one-shunt current and compares each phase command voltage acquired by the operation with a carrier wave to generate a PWM signal,
The signal generation function unit that generates the PWM signal includes a vector calculation unit that acquires a calculation result of the command voltage of each phase for each of a plurality of predetermined carrier periods, and a command voltage and carrier waveform of each phase. A PWM waveform calculation unit that creates information relating to PWM signals output from each port in comparison, and a PWM waveform correction unit that corrects the waveform information created by the PWM waveform information calculation unit,
The PWM waveform correction unit includes: a first correction process for extending a short-term waveform of the one-shunt current along a time axis corresponding to a predetermined carrier period among the plurality of carrier periods; and the plurality of carrier periods The second correction process is executed to shorten the short-period waveform along the time axis in correspondence with other carrier periods excluding the predetermined carrier period.

  Preferably, the addition period given to the short period waveform by the first correction process substantially coincides with the sum of the subtraction periods given to the short period waveform by the second correction process.

  Preferably, in the PWM waveform correction unit, the correction unit functions for an intersection period including the intersection timing of two phase currents, and the function of the correction unit is canceled for other periods other than the intersection period.

  According to the PWM signal control device according to the present invention, the short-term waveform of the one-shunt current is expanded along the time axis, so even in a scene close to the timing at which the phase currents intersect, the AD conversion processing of the short-term waveform is performed. A necessary period is secured, and current value information for two phases can be acquired from one one shunt current.

The figure which shows the circuit structure of the power converter of a one shunt system. The figure which shows the structure of the signal generation function part which concerns on embodiment. The figure which shows the state of the waveform information calculated in the PWM waveform calculating part which concerns on an actual form. The figure which shows the state of the waveform information calculated in the PWM waveform correction part which concerns on an actual form. The figure which shows the period when the PWM waveform correction | amendment part which concerns on embodiment functions. The figure explaining a one shunt detection electric current (normal time). The figure explaining the characteristic of the phase current in each detection timing. The figure explaining one shunt detection current (at the time of phase current crossing).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows the configuration of a general one-shunt power converter. The power conversion circuit 10 includes a PWM signal control device 100 and an inverter circuit 200. Among these, in the inverter circuit 200, power supply lines provided on both the positive and negative sides are connected to the DC power supply unit Vdc. The DC power supply unit Vdc may be a battery or a smoothing capacitor provided in a converter circuit.

  The inverter circuit 200 includes power transistors Tua to Twa provided on the high side and power transistors Tub to Twb provided on the low side. In these, Tua and Tub are connected in series to form one arm, and the other power transistors similarly form each arm. These arms are connected in parallel via a power supply line.

  Each contact point of the arm is connected to a phase current line Lu to Lw, and is connected to a stator circuit portion of the DC brushless motor Me via this. The DC brushless motor Me includes a rotor (not shown) in which permanent magnets are embedded, and outputs a rotational torque from the rotor in accordance with switching of the energization direction of the phase current. For example, when the DC brushless motor Me is used in an outdoor unit, the output torque from the rotor is input to the compressor to drive the refrigerant system.

  In the stator circuit, the energizing direction (vector current) of the phase current is controlled by switching the switching pattern of the power transistors Tua to Twb of the inverter circuit 200. The PWM signal control device 100 plays a role of appropriately controlling this switching pattern. The power conversion device 10 according to the present embodiment is a circuit device that performs current detection by the one-shunt method, and therefore, as shown in the figure, one shunt resistor RS is provided corresponding to one power supply line. Yes. The voltage across the shunt resistor is input to the input port of the PWM signal control apparatus 100 via the signal line.

  The PWM signal control device 100 (hereinafter simply referred to as the control device 100) includes a CPU (Central Processing Unit), a memory circuit, an AD conversion circuit, a clock circuit, and other communication devices. The control device 100 acquires a predetermined processing result / calculation result by sequentially processing the programs stored in the memory circuit. That is, the control device 100 constructs various functional units by the hardware resources such as a CPU and a memory circuit and the software resources such as a control program function in cooperation.

  In the control device 100 according to the present embodiment, as shown in FIG. 1, a signal detection function unit 110, a signal generation function unit 120, and a signal output function unit 130 are constructed. Among these, the signal detection function unit 110 creates the signal value given from each signal line of the shunt resistor Rs as digital data, and transfers this data to the data register of the CPU at an appropriate timing. Then, the CPU calculates the value of the current flowing through the shunt resistor Rs (hereinafter, “one shunt current”) based on this data.

  The signal generation function unit 120 performs vector calculation based on the one-shunt current acquired as described above, compares the command voltage and the carrier wave for each phase acquired by this calculation, and information on the waveform of the PWM signal (Waveform information) is obtained as a calculation result. The carrier wave refers to a triangular wave created corresponding to the carrier frequency, and this is called a carrier wave. Further, the command voltage may be a voltage value (command voltage value) of the command voltage, or may be a modulation rate (command modulation rate) of the command voltage. The signal generation function unit 120 includes a characteristic unit according to the present embodiment, and will be described in detail later.

  The signal output function unit 130 controls and outputs the pulse waveform of the PWM signal based on the waveform information acquired as described above. More specifically, the signal output function unit 130 sets waveform information as a model for each carrier cycle, reproduces the voltage state (High / Low) of the PWM signal so as to match the waveform information, and outputs this. Output from the port. As a result, the PWM signal is shaped into a pulse wave corresponding to the waveform information and output from the output port of the control device 100. The control device 100 includes a plurality of output ports, and by setting each of these output patterns, a switching pattern can be appropriately formed and the patterns can be switched.

  Next, the processing operation of the signal generation function unit 120 will be specifically described with reference to FIG. In the signal generation function unit 120, various calculation units are functionally constructed. In the present embodiment, a vector calculation unit 121, a waveform information calculation unit 122, and a waveform information correction unit 123 are formed. As a particularly characteristic matter, the vector calculation unit 121 functions for each of a plurality of predetermined carrier periods (hereinafter, this period is referred to as a vector calculation period). Accordingly, in the waveform information calculation unit 122 and the waveform information correction unit 123, which are subsequent processes, the waveform information that is basic information of the process is updated every vector calculation cycle.

  In the vector calculation unit 121, a three-phase current calculation unit 121a, a vector current calculation unit 121b, a PI control unit 121c, and a coordinate conversion unit 121d are constructed. The vector calculation unit 121 is provided with the latest phase information, and this calculation unit can use this information.

  In the phase current, the input current component that flows into the stator circuit matches the output component that returns from the stator circuit to the inverter circuit. Therefore, using this property, the three-phase current calculation unit 121a calculates the remaining current information using the current information for two phases superimposed on the one-shunt current Idc, and the three-phase currents Iu, Iv, Iw. Prepare all the information.

  The vector current calculation unit 121b converts the three-phase currents Iu, Iv, and Iw values into a d-axis current (detected value) and a q-axis current (detected value) based on a mathematical formula using phase information. Here, the d-axis current refers to a current component that matches the magnetic flux direction of the rotor. The q-axis current refers to a current component that coincides with the axial direction orthogonal to the d-axis.

  In the vector control, the rotor is motivated by changing the vector current formed in the stator circuit in a state where it matches the q-axis direction of the rotor. In order to realize this operation, the PI control unit 121c calculates an intended d-axis current (command value) and q-axis current (command value) based on the command rotational speed ωr, and the calculated d-axis current (detected value). ) And q-axis current (detected value) are respectively compared to set a proportional value, and a d-axis command voltage and a q-axis command voltage are calculated as the calculation results.

  The coordinate calculation unit 121d converts the d-axis command voltage and the q-axis command voltage into a command voltage for each phase based on a mathematical formula using phase information. Here, the command voltage for each phase is a collective expression of the U-phase command voltage Vu, the V-phase command voltage Vv, and the W-phase command voltage Vw. As described above, the vector calculation unit 121 calculates and obtains calculation results related to the command voltage of each phase by a series of calculation processes 121a to 121d.

  As described above, the vector calculation unit 121 according to the present embodiment can obtain the calculation result of the command voltage for each vector calculation cycle Tn. In the present embodiment, as shown in FIG. 3, the vector calculation cycle Tn is set to three times the carrier cycle Tc, and the calculation result of the command voltage is obtained every time the vector calculation cycle Tn arrives. Correspondingly, the command voltage is changed sequentially. For this reason, in one vector calculation cycle Tn, each command voltage shows a fixed value.

  FIG. 3 shows a scene where the U-phase current and the V-phase current intersect. Therefore, in order to form the phase current in this scene, the U-phase command voltage Vu and the V-phase command voltage Vv are close to each other. In the figure, since the U-phase current and the V-phase current intersect just before the vector calculation cycle Tn shifts to the next cycle, the order of the command voltages Vu and Vv is switched accordingly. In such a scene, since the W-phase current reaches its peak value, the W-phase command voltage Vw hardly changes.

  When the above-described vector calculation unit 121 ends, a waveform information calculation unit 122 (PWM waveform calculation unit) is executed as shown in FIG. The calculation unit 122 compares the command voltages Vu to Vw of each phase with the carrier waveform Wc (see FIG. 3), and creates information on the PWM signal output from each port. Hereinafter, this information is referred to as waveform information.

  This waveform information is information that specifies the waveform of the PWM signal in advance, and reflects the calculation result obtained immediately before its own processing timing. As a result of the calculation, when the command voltage Vu is larger than the carrier waveform Wc, setting information is created in which the signal Sau * to be given to the power transistor Tua is a High value, and the signal Sbu * to be given to the other power transistor Tub is a Low value. Setting information is created. Further, when the command voltage Vu is smaller than the carrier waveform Wc, setting information indicating the opposite is created. For waveform information corresponding to the V phase or W phase, waveform information related to the PWM signal is created in the same manner.

  Hereinafter, the waveform information created by the waveform information calculation unit 122 may be described as Sau * to Sbw *. The waveform information Sav * is calculated corresponding to the transistor Tva. In addition, Sbv and Tvb correspond, Saw and Twa correspond, and Sbw and Twb correspond. In addition, for the waveform information Sau to Sbw in FIG. 4, the signals of the respective power transistors are set in the same correspondence relationship.

  The waveform information Sau * to Sbw * calculated here does not change within the range of the vector calculation cycle Tn, and the same information is set for each carrier cycle Tc (a cycle corresponding to one peak of the carrier waveform Wc). Is done. When the vector calculation cycle Tn arrives, the waveform information calculated in the immediately preceding cycle Tn is reflected and used as new waveform information for vector calculation.

  The waveform information correction unit 123 (PWM waveform correction unit) performs processing for correcting the waveform information Sau * to Sbw * created by the waveform information calculation unit 122. If it is a prior art, as shown in FIG. 8, the waveform information Sau * -Sbw * is output as a PWM signal, the one shunt current Idc at this time is detected, and the next control processing is performed. However, according to such a technique, when the pair of phase currents intersect, one waveform of the one shunt current Idc is eroded as shown in FIG. Disappear.

  The present embodiment solves such a problem, and the characteristic processing will be specifically described with reference to FIG. Hereinafter, among the waveforms of the one shunt current Idc, a waveform portion where the time width of the waveform is sufficiently secured and AD conversion can be performed is referred to as a normal waveform A. On the other hand, a waveform portion which is eroded and cannot perform AD conversion is referred to. It will be called a short-term waveform B.

  FIG. 4 shows a processing operation for correcting the waveform information Sau * to Sbw *, and the corrected waveform information Sau to Sbw is reflected in the next vector calculation cycle Tn. The waveform information correction unit 123 causes the first correction process to function corresponding to the leading carrier cycle Tc in the vector calculation cycle Tn, and extends the short-term waveform B of the one shunt current Idc along the time axis. Yes.

  More specifically, the first correction process is to change the edge of the waveform information Sau in the time axis direction, and the edge of the waveform information Sav formed by the intermediate command voltage Vv (hereinafter referred to as the intermediate edge). m). In the present embodiment, when the edges of the waveform information Sau to be corrected are adjacent to each other in the correction direction, the extended correction value ΔS1 is set in a range in which they do not intersect with each other. Note that the reference line p in the figure corresponds to the outer edge of the short-period waveform B before the correction is applied, and the reference line q corresponds to the outer edge of the short-period waveform B after the correction. . This correction is similarly applied to the waveform information Sbu.

  In addition, the waveform information correction unit 123 causes the second correction process to function in response to other carrier periods excluding the leading carrier period Tc in the vector calculation period Tn, so that the short-term waveform B of the one shunt current Idc is timed. It is shortened along the axis. That is, in the present embodiment, two carrier periods Tc following the latter stage of the leading carrier period Tc correspond to this.

  Specifically, in the second correction process, the shortening correction values ΔS2 and ΔS3 are set corresponding to each carrier frequency. In this process, the edge of the waveform information Sau is changed in the time axis direction so as to be close to an intermediate edge (an edge formed between the normal waveform A and the short-term waveform B). The reference line r in the figure corresponds to the outer edge of the short-term waveform B in the second correction process. In the second correction process, the waveform may be deformed beyond the intermediate edge, and the short-term waveform B may disappear.

  As described above, according to the PWM signal control apparatus 100 according to the present embodiment, the short-term waveform B of the one-shunt current is expanded along the time axis, so even in a scene close to the timing at which the phase currents intersect. A sufficient period for AD conversion processing of the short-term waveform B is secured, and it is possible to acquire current value information for two phases from one one-shunt current.

  Further, according to the present embodiment, the amount of increase in DUTY by the first correction process is decreased by the second correction process to cancel the change in DUTY as a whole of the vector calculation period Tn. . In particular, in this embodiment, the extended correction value ΔS1 (addition period) given to the short-term waveform B is set to coincide with the sum of the shortening correction values ΔS2 and ΔS3 (subtraction period), and the above-described DUTY change cancellation Has been done well.

  In the technique related to the control device 100, as shown in FIG. 5, the PWM waveform correction unit 123 is preferably caused to function in correspondence with the timing at which any phase current intersects. According to the figure, the period Dx and the period Dy are alternately set, and among these, the waveform information correction unit 123 functions only for the period Dx, and the function of the waveform information correction unit 123 is canceled in the other period Dy. ing. That is, the correction of the PWM signal is limited to the period Dx.

  This period Dx is a period including timing corresponding to the intersection X of two phase currents as shown in the figure, and is referred to as an intersection period. The period Dy is a period excluding the crossing period Dx and is a period in which the phase current is preferably detected, and is referred to as a normal period.

  In the crossing period Dx, since the waveform of the one-shunt current Idc is distorted, the waveform information correction unit 123 functions, and the one-shunt detection of the phase current is reliably performed at a timing that cannot be detected by the conventional technique. On the other hand, since the one-shunt current is not distorted in the normal period Dy, processing for updating the waveform information is performed for each carrier cycle Tc. Thereby, in the normal period Dy, control contributing to accuracy improvement is performed.

  As described above, according to the technique described in FIG. 5, an appropriate process is selected according to the crossing state of the phase currents. For example, a process that can detect this is selected in a scene where the phase currents are likely to cross, In such a scene, a PWM signal that matches the technical matter prioritized in that scene is generated, such as selecting a process for stably driving the motor.

  The above-described embodiment is merely a description of one form of the technical idea in the claims, and various changes can be made to each item. For example, the vector calculation cycle Tn is set to three times the carrier cycle Tc, but is not limited thereto, and may be increased or decreased as appropriate. In addition, the target for performing the first correction processing is the first carrier cycle Tc in the vector calculation cycle Tn, but it is needless to say that it is not limited to such a mode.

  100 PWM signal control device, 110 current detection function unit, 120 signal generation function unit, 121 to 124 vector calculation unit, 125 PWM waveform calculation unit, 126 PWM waveform correction unit, 130 signal output function unit, 200 inverter circuit, ΔS1 addition period , ΔS2 to ΔS3 Subtraction period, St PWM signal, Rs shunt resistance, Tn command voltage update cycle, Tc carrier cycle.

Claims (3)

In the PWM signal control device that performs vector calculation based on the one-shunt current and compares the command voltage of each phase acquired by the calculation with the carrier wave to generate each PWM signal,
The signal generation function unit that generates the PWM signal includes a vector calculation unit that acquires a calculation result of the command voltage of each phase for each of a plurality of predetermined carrier periods, and a command voltage and carrier waveform of each phase. A PWM waveform calculation unit that creates information relating to PWM signals output from each port in comparison, and a PWM waveform correction unit that corrects the waveform information created by the PWM waveform information calculation unit,
The PWM waveform correction unit includes: a first correction process for extending a short-term waveform of the one-shunt current along a time axis corresponding to a predetermined carrier period among the plurality of carrier periods; and the plurality of carrier periods And a second correction process for shortening the short-period waveform along the time axis in correspondence with other carrier periods excluding the predetermined carrier period.   The addition period given to the short-term waveform by the first correction process is substantially equal to the sum of subtraction periods given to the short-term waveform by the second correction process. The PWM signal control device described in 1.   2. The PWM waveform correction unit according to claim 1, wherein the correction unit functions in an intersection period including an intersection timing of two phase currents, and the correction unit is deactivated in other periods excluding the intersection period. The PWM signal control device according to claim 1 or 2.

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