JP7199262B2 - Series multiplex power converter - Google Patents

Description

The present invention relates to a one-pulse multiplexing serial multiplexed power converter in which two or more single-phase inverter units are connected in series, and more particularly to a gate generation method for suppressing the influence of a minimum on-pulse width.

Patent Literature 1 describes an example of a series multiple power converter in which two single-phase inverter units are connected in series.

FIG. 6 shows the configuration of a series multiplex power converter in which six inverter units are connected in series to multiplex voltages. As a method for generating a gate signal in such a serial multiplex power converter, there is a one-pulse control method in which a gate signal is obtained by comparing a voltage command value Vref and a fixed gate threshold as shown in FIG.

The relationship between the gate threshold values Vth1a and Vth1b of the unit 1 and the gate signals GU1, GV1, GX1 and GY1 (that is, the ON/OFF states of the switching elements) is as follows.
・If Vref>Vth1a, GU1 is ON and GX1 is OFF. If Vref<Vth1a, GU1 is OFF and GX1 is ON.
If Vref>Vth1b, GY1 is turned on and GV1 is turned off, and if Vref<Vth1b, GY1 is turned off and GV1 is turned on.

Other units 2 to 6 similarly generate gate signals. With this method, a stepwise output voltage Vout is obtained as the sum of the output voltages (hereinafter referred to as unit output voltages) Vo1 to Vo6 of each unit. When the absolute value of the voltage command value Vref is less than the gate threshold corresponding to that unit, the output voltage of that unit becomes zero.

In the example of FIG. 6, there are six units, but as the number of units increases, an output voltage Vout closer to a sine wave can be obtained.

JP-A-2000-324845

Consider a case where the voltage command value Vref increases, exceeds the gate threshold value corresponding to the unit that has not output voltage until then, and the number of units outputting voltage increases (the number of operating units increases).

FIG. 8 shows the output voltage when the operation of two units is changed to the operation of three units. When the absolute value of the voltage command value Vref exceeds the gate threshold values Vth3a and Vth3b of the unit 3, the unit output voltage Vo3 is output and three units are operated.

The switching element cannot be driven with an on-time shorter than the minimum on-pulse width for protection of the element. Therefore, the minimum voltage width that one unit can output is limited by the minimum on-pulse width.

Therefore, even if the comparison result between the voltage command value Vref and the gate thresholds Vth3a and Vth3b results in a pulse width less than the minimum on-pulse width, the unit output voltage Vo3 can only output a voltage equal to or greater than the minimum on-pulse width. There is a problem of outputting a voltage higher than

FIG. 9 shows a comparison between the voltage command value Vref in FIG. 8 and the gate threshold value Vth3a in the unit 3, and an enlarged view of the unit output voltage Vo3. Ideally, it is desirable that the unit output voltage Vo3 is output only while the voltage command value Vref exceeds the gate threshold Vth3a. end up

A similar problem occurs even when the number of operating vehicles decreases. In addition, it occurs not only between 2 and 3 machines, but all the number of machines in operation.

As described above, it is a problem to output a voltage less than the minimum on-pulse width in the series multiple power converter.

The present invention has been devised in view of the above-mentioned conventional problems, and one aspect thereof is a one-pulse multiplexing series bridge cell unit in which a plurality of bridge cell units are connected in series and a single-phase voltage with an output frequency of 1 kHz or higher is output. A multiplex power converter, comprising: a phase determination unit that determines a peak time point and a zero crossing time point of a voltage command value and outputs them as updating timing of a gate threshold; and comparing the gate threshold of each unit with the voltage command value. and an operating unit determination unit that determines the number of units currently operating and outputs it as an operating unit determination value; The positive side gate threshold of the unit operating at the peak point is exchanged, the negative side gate threshold of the unit operating at the negative side peak point of the voltage command value is exchanged, and at the zero crossing point of the voltage command value A threshold controller that restores the replaced gate threshold to the original value, and compares the voltage command value and the positive and negative gate thresholds output from the threshold controller for each unit to generate a gate signal for the switching element. and a PWM control unit.

In addition, as one aspect thereof, the threshold control unit selects only the top two positive gate thresholds having a large absolute value of the gate threshold among the operating units at the time of the positive peak of the voltage command value. The switching is characterized in that only the two highest negative gate thresholds having the largest absolute value of the gate threshold among the operating units are replaced at the negative peak point of the voltage command value.

In another aspect, the threshold control unit rearranges the absolute values of the positive gate thresholds of all operating units in reverse order at the positive peak point of the voltage command value, The magnitude of the absolute value of the gate threshold value on the negative side of all the operating units is rearranged in reverse order at the peak point of the voltage command value on the negative side.

According to the present invention, it is possible to output a voltage less than the minimum on-pulse width in a series multiple power converter.

FIG. 2 is a configuration diagram of a serial multiplex power converter according to Embodiments 1 and 2; 4 is a time chart showing voltage command values, gate thresholds, unit output voltages, and output voltages in Embodiment 1 (when the number of operating units is three); 4 is a time chart showing voltage command values, gate thresholds, unit output voltages, and output voltages in Embodiment 1 (in the case of 6 operating units); 8 is a time chart showing voltage command values, gate thresholds, unit output voltages, and output voltages in Embodiment 2 (when the number of operating units is 3); 6 is a time chart showing voltage command values, gate threshold values, unit output voltages, and output voltages in Embodiment 2 (when the number of units in operation is 6); Schematic which shows an example of a series multiplex power converter. The time chart of each signal in the conventional 1-pulse multiplex system. The time chart which shows each signal at the time of the conventional operating number increase (2 -> 3 units). FIG. 9 is an enlarged view of FIG. 8;

Embodiments 1 and 2 of the series multiplex power converter according to the present invention will be described in detail below with reference to FIGS. 1 to 5. FIG.

[Embodiment 1]
Embodiment 1 describes a method of outputting a voltage less than the minimum on-pulse width, taking the series multiplex power converter shown in FIG. 1 as an example. First, the main circuit configuration of the series multiple power converter shown in FIG. 1 will be described.

As shown in FIG. 1, the series multiplex power converter in Embodiment 1 includes six first to sixth units (bridge cells) 1 to 6. In FIG. In the first unit 1, switching elements U1, V1, X1 and Y1 are bridge-connected. A DC voltage source C1 is connected between the common connection point of the switching elements U1 and V1 and the common connection point of the switching elements X1 and Y1.

A common connection point of the switching element U1 and the switching element X1 of the first unit 1 is connected to one end of the reactor L. A common connection point of the switching elements V1 and Y1 of the first unit 1 and a common connection point of the switching elements U2 and X2 of the second unit 2 are connected. Similarly, the second unit 2 and the third unit 3, the third unit 3 and the fourth unit 4, the fourth unit 4 and the fifth unit 5, and the fifth unit 5 and the sixth unit 6 are connected. A capacitor C is connected between the other end of the reactor L and a common connection point of the switching elements V6 and Y6 of the sixth unit 6 .

A unit output voltage Vo1 is the voltage between the common connection point of the switching elements U1 and X1 and the common connection point of the switching elements V1 and Y1. Similarly, the unit output voltages of the second to sixth units 2 to 6 are Vo2 to Vo6. Further, the total output voltage between the common connection point of the switching elements U1 and X1 of the first unit 1 and the common connection point of the switching elements V6 and Y6 of the sixth unit 6 is Vout. In the first embodiment, for example, a single-phase voltage with an output frequency of 1 kHz or more is output.

The serial multiplex power conversion device also includes a phase determination unit 10, an operating number determination unit 20, a threshold control unit 30, and a PWM control unit PWM.

The phase determination unit 10 determines update timings (phases 0°, 90°, 180°, 270°) of the gate threshold based on the phase θ of the voltage command value Vref, and outputs the determination to the threshold control unit 30 .

The operating number determining unit 20 determines the number of units currently operating by comparing the gate threshold value of each unit and the voltage command value Vref, and outputs the operating number determination value to the threshold control unit 30 .

The threshold control unit 30 controls the gate threshold of each unit at the gate threshold update timing (phase 0°, 90°, 180°, 270°) based on the gate threshold update timing and the operating number determination value. At the point of phase 90°270° (peak) of the voltage command value Vref, the gate threshold value is switched according to the number of operating units. At the phases of 0° and 180° (zero crossing) of the voltage command value Vref, the exchanged gate threshold is restored.

The PWM control section PWM performs pulse width modulation control of the one-pulse control method. The PWM controller PWM compares the voltage command value Vref and the gate threshold output from the threshold controller 30 to generate a gate signal. The gate threshold is a positive or negative gate threshold that takes a constant value for at least a quarter period of the voltage command value Vef. Dead-time processing and minimum on-pulse processing are performed during the comparison.

Next, a method of outputting a voltage less than the minimum on-pulse width will be described. In the first embodiment, the uppermost pulse of the output voltage Vout is output by overlapping the output voltages of the two units, thereby avoiding the pulse width limitation due to the minimum ON pulse width of each unit.

In the first embodiment, a method of changing only the gate thresholds of the top two units having the largest absolute values of the gate thresholds among the units in operation will be described.

In the PWM control section PWM, comparison between the voltage command value Vref and the gate threshold value of each unit is performed in the same manner as in the conventional art. The operating number determining unit 20 determines the operating number at the peak portion (phase 90°, 270°) of the voltage command value Vref. The threshold control unit 30 selects the unit having the largest positive gate threshold absolute value among the units operating at the time of the phase 90° (peak portion) of the voltage command value Vref and the positive gate threshold absolute value. Swap the gate threshold of the unit with the second largest . In addition, among the units operating at the time of the phase 270° (peak portion) of the voltage command value Vref, the unit with the largest negative gate threshold absolute value and the negative gate threshold absolute value second. Swap gate thresholds for larger units. In addition, the gate thresholds that have been switched at the phases of 0° and 180° of the voltage command value Vref are restored. After that, the voltage command value Vref and the gate threshold are compared in the same manner as when the output is started.

FIG. 2 shows an example of three-unit operation. A case of outputting a positive voltage will be described. When voltage command value Vref exceeds positive-side gate thresholds Vth1a, Vth2a, and Vth3a of units 1-3, units 1-3 output positive voltages, respectively. The number of operating units is determined at the time of the phase 90° (peak portion) of the voltage command value Vref, and the top two gate thresholds having the largest absolute value among the positive side gate thresholds Vth1a, Vth2a, and Vth3a of the units 1 to 3 in operation. to select. Here, the gate thresholds Vth3a and Vth2a are the top two gate thresholds having the largest absolute values, so the gate thresholds Vth3a and Vth2a are interchanged (underlined portion in FIG. 2).

After the phase 90° of the voltage command value Vref, the gate threshold after switching is compared with the voltage command value Vref, and the output of unit 2, unit 3, and unit 1 becomes 0 in this order. As a result, the voltage at the top of the output voltage Vout is composed of the unit output voltages Vo2 and Vo3 of the units 2 and 3 superimposed. Since the pulse width of each unit output voltage Vo1-Vo6 is sufficiently larger than the minimum on-pulse width, the output voltage Vout can be configured without being restricted by the minimum on-pulse width.

It should be noted that the gate threshold values are returned to the original order at the point of phase 180° (zero cross) of the voltage command value Vref. Similarly, when a negative voltage is output, among the units operating at the phase 270° (peak portion) of the voltage command value Vref, the two highest absolute values of the gate thresholds on the negative side (gate thresholds Vth3b, Vth2b ). Thereafter, the gate thresholds are returned to the original order at the point of phase 360° (zero crossing) of the voltage command value Vref.

FIG. 3 shows an example of the case of 6 units. A case of outputting a positive voltage will be described. When voltage command value Vref exceeds gate thresholds Vth1a, Vth2a, Vth3a, Vth4a, Vth5a, and Vth6a of units 1-6, units 1-6 output positive voltages, respectively. The operating number determination unit 20 determines the operating number at the voltage command value Vref=90° (peak portion). The threshold controller 30 selects two gate thresholds having a large absolute value from the positive side gate thresholds Vth1a, Vth2a, Vth3a, Vth4a, Vth5a, and Vth6a of the units 1 to 6 in operation. Here, since the two positive side gate threshold values having the larger absolute values are the gate threshold values Vth6a and Vth5a, the gate threshold value Vth6a and the gate threshold value Vth5a are exchanged (underlined portion in FIG. 3).

The gate threshold after replacement is compared with the voltage command value Vref, and the output becomes 0 in the order of unit 5, unit 6, unit 4, unit 3, unit 2, and unit 1. FIG. As a result, the uppermost voltage of the output voltage Vout is composed of the unit output voltages Vo5 and Vo6 of the units 5 and 6 superimposed. Since the pulse width of each unit output voltage Vo1-Vo6 is sufficiently larger than the minimum on-pulse width, the output voltage Vout can be configured without being restricted by the minimum on-pulse width.

It should be noted that the gate threshold values are returned to the original order at the point of phase 180° (zero cross) of the voltage command value Vref. Similarly, in the case of outputting a negative voltage, among the units operating at the phase 270° (peak portion) of the voltage command value Vref, the two highest absolute values of the gate thresholds on the negative side (gate thresholds Vth6b, Vth5b ). Thereafter, the gate thresholds are returned to the original order at the point of phase 360° (zero crossing) of the voltage command value Vref.

As described above, according to the first embodiment, since each unit is not subject to the limitation of the output voltage width due to the minimum on-pulse width, it is possible to output the output voltage Vout less than the minimum on-pulse width as a series multiplex power converter. Become. Further, in the first embodiment, the output voltage waveform is the same as that of the conventional gate generation method, except for the portion of the minimum on-pulse width.

[Embodiment 2]
In the first embodiment, the method of exchanging the gate thresholds of the top two units having the largest absolute value of the gate threshold among the units in operation has been described. A method for changing the threshold will be described.

Comparison between the voltage command value Vref and the gate threshold value of each unit in the PWM control section PWM is performed in the same manner as in the conventional art. The operating number determination unit 20 determines the operating number at the time of the phase 90° (peak portion) of the voltage command value Vref. The threshold control unit 30 rearranges the positive side gate thresholds of the units operating at the time of the phase 90° (peak portion) of the voltage command value Vref in reverse order. In addition, the negative side gate thresholds of the units operating at the time of the phase 270° (peak portion) of the voltage command value Vref are rearranged in reverse order. In addition, the gate thresholds that have been switched at the phases of 0° and 180° of the voltage command value Vref are restored. After that, the voltage command value Vref and each gate threshold value are compared in the same manner as usual to generate a gate signal.

FIG. 4 shows an example of three-unit operation. A case of outputting a positive voltage will be described. When voltage command value Vref exceeds gate thresholds Vth1a, Vth2a, and Vth3a of units 1-3, units 1-3 output positive voltages, respectively.

The number of operating units is determined when the phase of the voltage command value is 90°. Since three units are operated, the magnitudes of the absolute values of the positive gate thresholds Vth1a, Vth2a, and Vth3a of units 1 to 3 are reversed. Specifically, the gate thresholds Vth1a, Vth2a, and Vth3a in ascending order of the absolute value of the positive gate threshold are reversed to Vth3a, Vth2a, and Vth1a in ascending order of the absolute value of the positive gate threshold. (underlined in FIG. 4).

The rearranged positive gate thresholds Vth3a, Vth2a, Vth1a are compared with the voltage command value Vref, and the unit output voltages Vo1, Vo2, Vo3 become 0 in the order of unit 1, unit 2, unit 3.

As a result, the uppermost voltage of the output voltage Vout is composed of the unit output voltages Vo1 and Vo3 of the units 1 and 3 superimposed. Since the pulse width of each of the unit output voltages Vo1-Vo6 is sufficiently larger than the minimum on-pulse width, the output voltage Vout can be configured without being restricted by the minimum on-pulse width.

It should be noted that the gate threshold values are returned to the original order at the point of phase 180° (zero cross) of the voltage command value Vref. Similarly, when outputting a negative voltage, the magnitude of the absolute value of the gate threshold on the negative side of the unit that is operating at the time of the phase 270° of the voltage command value Vref is reversed. Thereafter, the gate thresholds are returned to the original order at the phase 360° (zero cross) of the voltage command value Vref.

FIG. 5 shows an example of operation of six units. A case of outputting a positive voltage will be described. When voltage command value Vref exceeds positive gate thresholds Vth1a, Vth2a, Vth3a, Vth4a, Vth5a and Vth6a of units 1-6, units 1-6 output positive voltages, respectively.

The operating number determination unit 20 determines the operating number at the time of phase 90° (peak portion) of the voltage command value Vref. Since six units are operated, the threshold control unit 30 reverses the absolute values of the positive gate thresholds Vth1a, Vth2a, Vth3a, Vth4a, Vth5a, and Vth6a of the units 1 to 6. FIG. Specifically, the gate thresholds Vth1a, Vth2a, Vth3a, Vth4a, Vth5a, and Vth6a are reversed in ascending order of the absolute value of the positive gate threshold value, and are reversed in ascending order of the positive gate threshold absolute value. to Vth6a, Vth5a, Vth4a, Vth3a, Vth2a, and Vth1a (underlined parts in FIG. 5).

The rearranged positive gate threshold values Vth6a, Vth5a, Vth4a, Vth3a, Vth2a, and Vth1a are compared with the voltage command value Vref. output becomes 0.

As a result, the voltage at the top of the output voltage Vout is formed by superimposing the outputs of the unit output voltages Vo1 and Vo6 of the units 1 and 6. FIG. Since the pulse width of each of the unit output voltages Vo1-Vo6 is sufficiently larger than the minimum on-pulse width, the output voltage Vout can be configured without being restricted by the minimum on-pulse width.

It should be noted that the gate threshold values are returned to the original order at the point of phase 180° (zero crossing) of the voltage command value Vref. Similarly, when outputting a negative voltage, the magnitude of the absolute value of the gate threshold on the negative side of the unit operating at the phase 270° (peak) of the voltage command value Vref is reversed. Thereafter, the gate thresholds are returned to the original order at the phase 360° (zero cross) of the voltage command value Vref.

As described above, according to the second embodiment, the same effects as those of the first embodiment are obtained. Further, in the second embodiment, all the unit output voltage widths are more uniform than in the first embodiment.

Although the present invention has been described in detail only with respect to the specific examples described above, it is obvious to those skilled in the art that various modifications and modifications are possible within the scope of the technical idea of the present invention. Such variations and modifications are, of course, covered by the claims.

10: Phase determination unit 20: Number of operating units determination unit 30: Threshold control unit PWM: PWM control unit Vth1a to Vth6a, Vth1b to Vth6b ... Gate threshold Vo1 to Vo6: Unit output voltage Vout: Output voltage Vref: Voltage command value U1 to U6 , V1 to V6, X1 to X6, Y1 to Y6: Switching element C1 to C6: DC voltage source C: Capacitor L: Reactor GU1, GV1, GX1, GY1: Gate signal

Claims (3)

A one-pulse multiplexing serial multiplex power converter that connects a plurality of bridge cell units in series and outputs a single-phase voltage with an output frequency of 1 kHz or higher,
a phase determination unit that determines the peak time point and the zero crossing time point of the voltage command value and outputs them as update timings of the gate threshold;
an operating number determination unit that determines the number of units that are currently operating by comparing the gate threshold value of each unit with the voltage command value, and outputs the number as an operating number determination value;
Based on the update timing of the gate threshold and the determination value of the number of operating units, the positive side gate threshold of the unit operating at the time of the positive side peak of the voltage command value is replaced, and the negative side peak of the voltage command value is replaced. a threshold control unit that replaces the gate threshold on the negative side of the unit that is operating at the time and restores the replaced gate threshold at the zero crossing point of the voltage command value;
a PWM control unit that compares the voltage command value and a positive or negative gate threshold output from the threshold control unit for each of the units to generate a gate signal for a switching element;
A series multiplex power converter, comprising: The threshold control unit is
At the time of the peak on the positive side of the voltage command value, among the operating units, only the top two positive gate thresholds with the largest absolute values of the gate thresholds are exchanged,
2. The series multiplexing according to claim 1, wherein at the negative peak of said voltage command value, only the two highest negative gate thresholds having a larger absolute value of the gate threshold among the operating units are exchanged. Power converter. The threshold control unit is
At the positive peak point of the voltage command value, the absolute values of the positive gate threshold values of all the units in operation are rearranged in reverse order,
2. The series multiplex power conversion according to claim 1, wherein the magnitudes of the absolute values of the gate thresholds on the negative side of all the units in operation are rearranged in reverse order at the point of peak on the negative side of the voltage command value. Device.

Images