JP6505261B2 - Power converter - Google Patents

Description

  The present invention relates to a power converter provided with a short circuit portion that shorts an AC power supply.

  The prior art disclosed in Patent Document 1 below discloses a power factor correction circuit that improves the power factor and reduces harmonic components contained in the input current, and selects a full wave rectification mode or a voltage doubler rectification mode. An open loop control of the short circuit start timing and the short circuit time of the short circuit element realizes a power factor improvement function and a boost function. That is, according to the prior art disclosed in Patent Document 1, the rectifier circuit is controlled to a full wave rectification mode or a voltage doubler rectification mode by turning on and off a rectifier circuit switching switch, and the DC output voltage of the power factor improvement circuit is divided into two stages. This two-step divided region is further divided into two steps with no power factor improvement and with power factor improvement by variable control of the short circuit in the open loop of the short circuit element, to form a DC output voltage region of four steps in total. Thereby, the power factor at the high load side can be improved while expanding the output range of the DC output voltage.

  Further, in the prior art disclosed in Patent Document 2 below, a DC voltage that outputs a DC voltage control signal corresponding to a deviation value between a DC output voltage reference value set corresponding to a load and a voltage between terminals of the smoothing capacitor A control unit is provided, and a current reference operation unit is provided which outputs a current reference signal from the product of a control signal from a direct current voltage control unit and a sine wave synchronous signal synchronized with an alternating current power supply. By comparing the current reference signal with the AC side current of the rectifying element, the switch element is turned on and off at high frequency, and the DC output voltage is controlled to a desired value while controlling the AC input current in a sine wave shape. The power factor can be set to 1, and the generation of harmonics can be suppressed.

Japanese Patent Application Laid-Open No. 11-206130 Patent No. 2140103

  However, according to the prior art of the said patent document 1, 2, the control pattern of a short circuiting element is limited. That is, in these conventional techniques, the control pattern of the short circuit element is limited to either the high frequency switching mode in which the current is fed back in the entire load region or the partial switching mode of the current open loop control. Thus, these prior art techniques do not operate the shorting elements to avoid over boosting the DC output voltage in the low load region, and power factor correction is not performed. Therefore, in the low load region, waveform distortion of the input current is large, and a current containing a large amount of harmonic components flows through the reactor, resulting in an increase in reactor iron loss, which reduces the AC / DC conversion efficiency of the power factor correction circuit. .

  In the prior art of Patent Document 1 described above, the short circuit control of the short circuiting element at the time of performing the power factor improvement controls the short circuit start timing and the short circuit time by open loop, and performs the short circuit operation only for a certain section with respect to the power supply cycle. Although the switching system can improve the power factor and boost the DC output voltage, the effect is small on the high load side where the amount of generated harmonics increases. Therefore, a reactor having a large inductance value is required to obtain a sufficient power factor improvement effect, that is, a harmonic suppression ability in the prior art, along with the future strengthening of harmonic regulation, and therefore, the ac / dc conversion efficiency decreases. There is a problem that the size of the circuit is increased and the cost is increased. In addition, when boosting DC output voltage while suppressing the amount of generated harmonics to a fixed level, there is a limit to the boosting capacity, so operation on the high load side may become unstable or stable operation on the high load side. If it thinks, the choice of load will become narrow.

  The present invention has been made in view of the above, and it is an object of the present invention to obtain a power conversion device capable of satisfying high boost performance and harmonic standards while achieving high efficiency across the entire operation range of a load. Do.

In order to solve the problems described above and achieve the object, the power conversion device of the present invention includes a rectifier circuit that converts AC power from an AC power source to DC power, and DC power from the rectifier circuit to AC power. An inverter for supplying a load, a shorting part for shorting the AC power supply via the reactor, and a control part for outputting a plurality of switching pulses for controlling the on / off operation of the shorting part; in the value of the power supply current before Symbol AC power source outputs a plurality of first switching pulse in a first current control range, in the second load range, value before Symbol supply current of the second outputting a plurality of second switching pulse in the current control range, when the operating state of the motor is the load is in the load area does not require a boosting of the output voltage of the rectifier circuit, the plurality of second scan Outputs Tchinguparusu, the first load applied to the load region, the second higher than the load applied to the load region, the second current control range wider than the first current control range, said plurality of The number of second switching pulses is less than the number of the plurality of first switching pulses.

  According to the present invention, it is possible to satisfy the high boost performance and the harmonic standard while achieving high efficiency over the entire operating range of the load.

A figure showing an example of composition of a power converter concerning an embodiment of the invention Diagram for explaining the relationship between the operating state of the load and the boost operation First configuration diagram of pulse control reference voltage generation circuit Second configuration diagram of pulse control reference voltage generation circuit Diagram showing a simplified circuit consisting of a reactor, a short circuit, a rectifier circuit and a smoothing capacitor The figure which shows the waveform of the power supply current when switching a short circuiting element once in the positive electrode side half cycle of AC power supply in partial switching pulse mode. Explanatory drawing of operation when pulse conversion is not performed in the pulse conversion part Explanatory drawing of operation in case pulse conversion is performed by the pulse conversion part A diagram showing a configuration example of a pulse converter Explanatory drawing of the operation at the time of using the pulse conversion part shown by FIG. Explanatory drawing of the operation when the pulse conversion is not performed when the operating condition is in the boost unnecessary region. Explanatory diagram of the operation when pulse conversion is performed at the time of start-up when the operating condition is in the step-up unnecessary region Explanatory drawing of operation at the time of performing pulse conversion at the time of a fall when an operating condition is in a boost unnecessary area. Explanatory diagram of the operation when pulse conversion is performed at the time of start-up and operation when the operation state is in the step-up unnecessary region Explanatory drawing of operation at the time of performing pulse conversion, changing a reference voltage at the time of start-up when a driving | running state is in a step-up unnecessary area | region Explanatory drawing of operation at the time of performing pulse conversion, changing reference voltage at the time of a fall when a driving | running state is in a step-up unnecessary area | region Explanatory drawing of operation at the time of performing pulse conversion, changing a reference voltage at the time of start-up when driving | running state is an area | region where a boost is unnecessary, and falling.

  Hereinafter, an embodiment of a power conversion device according to the present invention will be described in detail based on the drawings. The present invention is not limited by the embodiment.

Embodiment.
FIG. 1 is a view showing a configuration example of a power conversion device 100 according to an embodiment of the present invention. FIG. 2 is a diagram for explaining the relationship between the operating state of the load and the boosting operation. FIG. 3 is a first block diagram of a pulse control reference voltage generation circuit. FIG. 4 is a second configuration diagram of the pulse control reference voltage generation circuit. FIG. 5 is a diagram showing a simplified circuit composed of the reactor 2, the short circuit portion 30, the rectifier circuit 3, and the smoothing capacitor 4. FIG. 6 is a diagram showing the waveform of the power supply current Is when the short circuiting element 32 is switched once in the positive electrode side half cycle of the AC power supply 1 in the partial switching pulse mode. FIG. 7 is an explanatory diagram of an operation when pulse conversion is not performed by the pulse conversion unit 22. FIG. 8 is an explanatory diagram of an operation when pulse conversion is performed by the pulse conversion unit 22. FIG. 9 is a view showing a configuration example of the pulse conversion unit 22. As shown in FIG. FIG. 10 is an explanatory diagram of an operation when the pulse conversion unit 22 shown in FIG. 9 is used.

  The power conversion device 100 shown in FIG. 1 includes a reactor 2, a rectification circuit 3, a smoothing capacitor 4, a DC voltage detection unit 5, a power supply voltage detection unit 6, a current detection unit 9, a control unit 20, a pulse transmission unit 24, and a shorting unit 30. , An inverter circuit 40, an inverter control unit 41, and an alternating current detection unit 60.

  The reactor 2 is connected to the AC power supply 1 side more than the short circuit portion 30, and is inserted, for example, between one input end of the rectifier circuit 3 and the AC power supply 1. The rectifier circuit 3 is connected to the AC power supply 1 through the reactor 2 and converts the AC voltage of the AC power supply 1 into a DC voltage. Although the rectifier circuit 3 in the illustrated example is configured by a diode bridge in which four diodes are combined, the present invention is not limited to this. A combination of metal oxide semiconductor field effect transistors that are diode-connected unidirectional conduction elements is used. It may be configured.

  The smoothing capacitor 4 is connected between the output terminals of the rectifier circuit 3, and the smoothing capacitor 4 smoothes the voltage of the full-wave rectified waveform output from the rectifier circuit 3. An inverter circuit 40 is connected to both ends of the smoothing capacitor 4. The inverter circuit 40 is composed of a plurality of switching elements, operates according to the switching signal from the inverter control unit 41 to convert DC power from the rectifier circuit 3 into AC power and supplies it to the motor 50 which is a load. Motor 50 receives supply of AC power from inverter circuit 40 and is driven.

  An alternating current detection unit 60 is disposed between the inverter circuit 40 and the motor 50, and the current value detected by the alternating current detection unit 60 is input to the inverter control unit 41. The inverter control unit 41 controls the switching elements constituting the inverter circuit 40 based on the value of the DC output voltage Vdc detected by the DC voltage detection unit 5 and the value of the current detected by the alternating current detection unit 60. Generate control signals.

  The current detection means 9 comprises a current detection element 8 and a current detection unit 7. The current detection element 8 is connected between the reactor 2 and the rectifier circuit 3 to detect the current value at the connection position. A current transformer or a shunt resistor is used as the current detection element 8 in one example. The current detection unit 7 is realized by an amplifier or a level shift circuit, and converts a voltage in direct proportion to the current detected by the current detection element 8 into a current detection voltage Vis within a low voltage range that the control unit 20 can handle. Do. The DC voltage detection unit 5 is realized by an amplifier or a level shift circuit, detects the voltage across the smoothing capacitor 4, converts the detected voltage into a voltage detection value within a low voltage range that the control unit 20 can handle, and outputs it. Do.

  The short circuit part 30 which is a bidirectional switch is comprised from the diode bridge 31 connected in parallel with AC power supply 1 through the reactor 2, and the short circuiting element 32 connected to the both output ends of the diode bridge 31. When the shorting element 32 is a metal oxide semiconductor field effect transistor, the gate of the shorting element 32 is connected to the pulse transfer unit 24 and the shorting element 32 is turned on / off by the drive signal Sa2 which is a gate drive signal from the pulse transfer unit 24. In the configuration, when the shorting element 32 is turned on, the AC power supply 1 is shorted through the reactor 2 and the diode bridge 31.

  The control unit 20 has a drive signal generation unit 21 and a pulse conversion unit 22, and is configured by a microcomputer or a central processing unit.

  Drive signal generation unit 21 receives the value of DC output voltage Vdc detected by DC voltage detection unit 5, the value of power supply voltage Vs detected by power supply voltage detection unit 6, and inverter control information 41a from inverter control unit 41. The drive signal Sa which is a switching pulse which controls the short circuiting element 32 of the short circuit part 30 is generated based on.

  The inverter control information 41a includes operating state information indicating the operating state of the motor 50 which is a load. An example of the driving state information is the modulation rate or the motor speed. The modulation factor is a voltage ratio between the DC voltage from the rectifier circuit 3 and the effective value of the AC voltage applied to the motor 50. The motor speed is calculated based on the current value detected by the alternating current detection unit 60. In the present embodiment, the inverter control information 41a is used as an example of the operating state information, but the operating state information is not limited to this. For example, motor speed information detected by a speed information detector (not shown) of the motor 50 or the power supply current Is of the AC power supply 1 detected by the current detection means 9 may be used as the operating state information. By using the information used to drive the motor 50, it is possible to control the shorting part 30 corresponding to the operating condition without separately providing a detector for obtaining the operating condition information. In the present embodiment, the motor speed generated by the inverter control unit 41, the modulation factor generated by the inverter control unit 41, the motor speed information detected by the speed information detector, or the current detection means 9 Although the generated power supply current Is is used, the means for generating these operating state information is not limited to these.

Further, the drive signal generation unit 21 generates a hysteresis reference voltage which is a threshold for limiting the value of the power supply current Is of the AC power supply 1. In the following description, the hysteresis reference voltage is referred to as a reference voltage V _ref, and the reference voltage V _ref is a threshold that limits the value of the power supply current Is of the AC power supply 1.

The reference voltage V _ref is generated by the circuit shown in FIG. 3 or FIG. The circuit of FIG. 3 generates a reference voltage V _ref by converting a pulse width modulation signal which is the port output Sb of the drive signal generation unit 21 into a DC value by a low pass filter. In this case, the value of the reference voltage V _ref can be varied seamlessly by controlling the duty ratio of the pulse width modulation signal. The circuit of FIG. 4 can change the value of the reference voltage V _ref in stages by the voltage dividing ratio of the resistors Rb and Rc by driving the switch TR with the port output Sb of the drive signal generation unit 21. The circuit that generates the reference voltage V _ref is not limited to this, and may be generated by a known circuit other than the circuit shown in FIG. 3 or FIG. These reference voltages V _ref may be used.

The pulse conversion unit 22 drives the switching pulse to bring the peak value of the power supply current Is detected in the on period t of the drive signal Sa into the current control range w, which is the target control range of the power supply current Is of the AC power supply 1. Output as Sa1. Specifically, in the pulse conversion unit 22, an upper limit threshold and a lower limit threshold of the current control range w centering on the reference voltage V _ref from the drive signal generation unit 21 are set. Then, the pulse conversion unit 22 divides the drive signal Sa into a plurality of switching pulses in order to keep the peak value of the power supply current Is detected in the on period t of the drive signal Sa between the upper threshold and the lower threshold. The plurality of divided switching pulses become the drive signal Sa1. The on period t is a period from when the drive signal Sa is turned on to when it is turned off. The upper limit threshold is a threshold that regulates the upper limit of the short circuit current flowing when the short circuit portion 30 is turned on, and the lower limit threshold is a threshold set to a value smaller than the upper limit threshold. The pulse division operation by the pulse conversion unit 22 is performed at the positive electrode and the negative electrode of the AC power supply 1.

  The pulse transfer unit 24 is configured by a level shift circuit, converts a voltage level shift so that gate driving can be performed, converts the drive signal Sa1 into a drive signal Sa2, and outputs it. The open / close operation of the short circuit portion 30 is performed by the drive signal Sa2 thus obtained.

  The motor rotation speed N of the motor 50 which is a load is shown on the horizontal axis of FIG. 2, and the motor voltage V applied to the motor 50 is shown on the vertical axis. The region of symbol A represents the high rotation region of the motor 50, the region of symbol B represents the middle rotation region of the motor 50, and the region of symbol C represents the low rotation region of the motor 50.

  When the inverter circuit 40 and the motor 50 are connected to the rectifier circuit 3, the motor voltage V applied to the motor 50 rises with the rise of the motor rotational speed N of the motor 50. However, the motor voltage V that can be applied to the motor 50 is restricted by the value of the DC output voltage Vdc applied to the inverter circuit 40. Therefore, the motor voltage V may be insufficient in the high rotation range A which is a high load range. When the motor current supplied to the motor 50 is increased to compensate for the shortage of the motor voltage V in the high rotation range A, the loss accompanying the increase of the motor current increases.

  Control unit 20 according to the present embodiment determines whether motor rotation number N is in high rotation range A or not based on the operating state information included in inverter control information 41 a, and motor rotation number N is in the high rotation range A. When it is determined that boosting of the DC output voltage Vdc of the rectifier circuit 3 is necessary, the DC output voltage Vdc is boosted by turning on and off the shorting unit 30. That is, the control unit 20 outputs a plurality of first switching pulses so that the value of the power supply current Is falls within the current control range w. This makes it possible to compensate for the insufficient motor voltage V while suppressing the increase in motor current in the high rotation range A.

  On the other hand, in the middle rotation range B which is the middle load range and the low rotation range C which is the low load range, boosting of the DC output voltage Vdc, that is, on / off of the shorting portion 30 is unnecessary because the motor voltage V is not insufficient. . However, when the shorting portion 30 is not turned on / off, the waveform distortion of the power supply current Is becomes large, and the power supply current Is containing many harmonic components flows to the reactor 2 and iron loss of the reactor 2 increases. It will decrease.

  Control unit 20 according to the present embodiment determines whether motor rotation number N is in high rotation range A or not based on the operating state information included in inverter control information 41 a, and motor rotation number N is in the middle rotation range B. When it is determined that boosting of the DC output voltage Vdc of the rectifier circuit 3 is unnecessary because it is in the low rotation range C, the current control range w is expanded more than the current control range w in the high rotation range A, and this current control range w A plurality of second switching pulses are output so as to keep the value of the power supply current Is in. Hereinafter, the current control range w in the high rotation range A will be referred to as a first current control range w. The current control range w in the middle rotation range B or the low rotation range C is referred to as a second current control range w. The second current control range is wider than the first current control range, and the number of the plurality of second switching pulses is smaller than the number of the plurality of first switching pulses. Thus, the DC output voltage Vdc in the middle rotation range B or the low rotation range C can be prevented from being excessively boosted, and harmonic components included in the power supply current Is in the middle rotation range B or the low rotation range C are suppressed. Since the iron loss of the reactor 2 is suppressed, the power factor is also improved.

  The electric power supplied to the motor 50 in the low rotation range C is smaller than the electric power supplied to the motor 50 in the middle rotation range B and the high rotation range A, so that the motor rotation speed N is in the low rotation range C Even if the harmonic components contained in the power supply current Is are suppressed, the effect of power factor improvement is small. Therefore, when the motor rotation number N is in the low rotation range C, that is, when it is determined that boosting is unnecessary and the output of a plurality of switching pulses is unnecessary, the control unit 20 has the second current control range w. Increase the upper threshold. With this configuration, the generation of the drive signal Sa is stopped in the low rotation range C, and the loss associated with the on / off of the short circuit portion 30 can be reduced.

  Hereinafter, the operation of power converter 100 of the present embodiment will be described in detail. First, an operation when the pulse conversion unit 22 does not perform the pulse conversion operation will be described. The pulse conversion operation is an operation of dividing the drive signal Sa into a plurality of switching pulses. In the current open loop control, turning on and off the short circuit portion 30 once to a plurality of times in a power supply half cycle is referred to as a partial switching pulse mode.

The current path at the time of on-off of the short circuit part 30 is shown by FIG. When the short circuit 30 is turned on, the AC power supply 1, the reactor 2, and the short circuit 30 form a closed circuit, and the AC power supply 1 is short circuited through the reactor 2. Therefore, the power supply current Is flows in the closed circuit, and the magnetic energy obtained by (1/2) × LI ² is accumulated in the reactor 2.

  The stored energy is released to the load side at the same time as the short circuit portion 30 is turned off, rectified by the rectifier circuit 3, and transferred to the smoothing capacitor 4. By this series of operations, the power supply current Is as shown in FIG. 6 flows, so that the conduction angle of the power supply current Is can be wider than in the passive mode without power factor improvement, and the power factor can be improved.

  In the partial switching pulse mode, the energy stored in the reactor 2 can be controlled by controlling the short circuit start time and the short circuit continuation time of the short circuit portion 30, and the DC output voltage Vdc can be steplessly boosted. Further, FIG. 6 shows the drive signal Sa1 which is a single pulse in the case of switching the short circuit part 30 once during the power supply half cycle as an example of the operation in the partial switching pulse mode. The number of switching the short circuit portion 30 may be two or more.

  Next, the waveform of the power supply current Is when the pulse conversion unit 22 is not operating and the waveform of the power supply current Is when the pulse conversion unit 22 is operating will be described in comparison.

  FIG. 7 shows the waveform of the power supply current Is when the drive signal Sa which is a single pulse from the drive signal generation unit 21 is not converted into a plurality of switching pulses. When pulse conversion is not performed by the pulse conversion unit 22, the drive signal Sa1 is turned on at the timing when the drive signal Sa is turned on, and the on period t of the drive signal Sa is also the on period t of the drive signal Sa. It turns on for a period equal to. Therefore, when the power supply voltage Vs is boosted, the short circuit time of the short circuiting element 32 increases in direct proportion to the on period t of the drive signal Sa, and the power supply current Is increases as shown in the illustrated example. When the power supply current Is reaches the set value, the drive signal Sa is turned off, and the drive signal Sa1 is turned off at the timing when the drive signal Sa is turned off.

  When the short-circuit time of the short-circuiting element 32 is thus lengthened, although more energy can be stored in the reactor 2, the peak of the power supply current Is increases, so the power factor deteriorates and the harmonic component increases. Problems such as increased circuit loss.

  FIG. 8 shows the waveform of the power supply current Is when the drive signal Sa which is a single pulse from the drive signal generation unit 21 is converted into a plurality of switching pulses. When pulse conversion is performed by the pulse converter 22, the drive signal Sa1 is turned on at the timing when the drive signal Sa is turned on, and the power supply current Is increases. As the power supply current Is increases, the current detection voltage Vis output from the current detection unit 7, that is, the current detection value detected by the current detection unit 7 rises. When the current detection value exceeds the upper limit threshold while the drive signal Sa is on, the pulse conversion unit 22 turns off the drive signal Sa1.

  As a result, the power supply current Is decreases and the current detection value decreases. After that, when the current detection value falls below the lower limit threshold while the drive signal Sa is on, the pulse conversion unit 22 turns on the drive signal Sa1 again. As a result, the power supply current Is increases again, and the current detection value detected by the current detection unit 7 rises.

  As described above, as the on / off of the drive signal Sa1 is repeated in the on period t of the drive signal Sa, the peak value of the power supply current Is in the on period t of the drive signal Sa is controlled within the current control range w. . Therefore, even when DC output voltage Vdc is boosted to a relatively high value, the peak value of power supply current Is within on period t of drive signal Sa shown in FIG. 8 is the peak value when drive signal Sa1 is turned off. It is suppressed more.

  Note that by adjusting the upper limit threshold and the lower limit threshold of the current control range w, it is possible to control the number of switchings of the drive signal Sa1 in the on period t of the drive signal Sa, that is, the switching frequency of the drive signal Sa1.

If the switching frequency is relatively high, switching losses, radiated noise, and noise terminal voltage may be problematic. In order to solve such a problem, the number of switching times of the drive signal Sa1 is reduced by widening the current control range w with the reference voltage V _ref as a central value. Therefore, the switching frequency is lowered, and loss increase, radiation noise and noise terminal voltage can be suppressed.

On the other hand, when the switching frequency is relatively low, noise in the audio frequency band may be a problem. In order to solve such a problem, the number of switching times of the drive signal Sa1 is increased by narrowing the current control range w with the reference voltage V _ref as a central value. Therefore, the switching frequency can be increased and noise can be suppressed.

  Next, a configuration example of the pulse converter 22 will be described. The pulse conversion unit 22 illustrated in FIG. 9 includes a positive hysteresis comparator HCH, a negative hysteresis comparator HCL, and a plurality of logic ICs.

The current detection voltage Vis which is the output of the current detection unit 7 and the positive reference voltage V _refH from the drive signal generation unit 21 are input to the positive hysteresis comparator HCH. The current detection voltage Vis and the negative reference voltage V _refL from the drive signal generation unit 21 are input to the negative hysteresis comparator HCL.

  The current detection unit 7 shown in FIG. 1 has a level shift circuit and an amplifier provided at the output stage of the current detection element 8, and 1⁄2 Vd, that is, a half value of the low voltage system power supply Vd is equivalent to 0 amperes. The current waveform of the alternating current detected by the current detection element 8 is converted into a current waveform of only the positive side and output. As a result, the pulse converter 22 of FIG. 9 can generate the drive signal Sa1 regardless of the current polarity.

  Next, the operation of the pulse converter 22 will be described with reference to FIG.

In the positive side hysteresis comparator HCH, the positive side upper limit threshold V _THH (H) calculated by the formula (1), the positive side lower limit threshold V _THH (L) calculated by the formula (2), and the positive side reference voltage V _The hysteresis Δ corresponding to the current control range w on the positive electrode side is determined by the relationship with _refH, and the AND logic of the output of the positive electrode hysteresis comparator HCH and the drive signal Sa is taken in the AND logic IC2 'to obtain the positive electrode drive signal SaH. Is output. Note that _{V d} of equation (1) represents a low-voltage power supply, (2) the _{V OL} represents the output saturation voltage of the comparator.

Similarly, in the negative electrode side hysteresis comparator HCL, the negative electrode side upper limit threshold value V _THL (H) is calculated by equation (1), and the negative electrode side lower limit threshold voltage V _THL (L) is calculated by equation (2).

Hysteresis Δ is determined by the relationship between the negative electrode side lower limit threshold V _THL (L) and the negative electrode side upper limit threshold voltage V _refL , the output of the negative electrode side hysteresis comparator HCL is inverted by NOT logic IC3, and AND logic IC2 is the NOT logic IC3. The AND logic of the output and the drive signal Sa is taken, and the negative side drive signal SaL is output. Then, in the AND logic IC4, the AND logic of the positive side drive signal SaH and the negative side drive signal SaL is taken, and the result of the AND logic is output as the drive signal Sa1.

  By using the pulse converter 22 having a plurality of hysteresis comparators, the drive signal Sa1 can be generated regardless of the current polarity, and the waveform of the power supply current Is, that is, the current detection voltage Vis can be controlled. Therefore, it is possible to boost the DC output voltage Vdc while suppressing the peak value of the short circuit current flowing when the short circuit portion 30 is turned on.

  Further, the hysteresis comparator of FIG. 9 can change the width of the hysteresis Δ by changing the resistance values of the resistors R1, R2, and R3. For example, a series circuit of a switch and a resistor is connected in parallel to the resistor R2 or the resistor R2 ', and the combined resistance value can be switched by opening and closing the switch. By performing a part of the processing in the control unit 20 with a hysteresis comparator, the calculation load in the control unit 20 is reduced, and the power conversion device 100 can be manufactured with an inexpensive central processing unit.

  In FIG. 10, for example, the motor rotation number N is in the high rotation range A, and the operation in the case of boosting the DC output voltage Vdc has been described. The operation in the low rotation range C will be described.

  FIG. 11 is an explanatory diagram of the operation in the case where pulse conversion is not performed when the operating state is in the step-up unnecessary region. For example, when the motor rotation speed N is in the low rotation range C, the control unit 20 turns off both the drive signals Sa and Sa1 as in the illustrated example in order to reduce the loss associated with the on / off of the short circuit portion 30. Stop the pulse conversion operation.

  FIG. 12 is an explanatory diagram of an operation in the case where pulse conversion is performed at the time of start-up when the operating state is in the step-up unnecessary region. FIG. 13 is an explanatory diagram of an operation in the case where pulse conversion is performed at the time of falling when the operating state is in the step-up unnecessary region. FIG. 14 is an explanatory diagram of an operation in the case where pulse conversion is performed at the time of start-up and at the time of start-up when the operation state is in the step-up unnecessary region.

  The control unit 20 that has determined that the motor rotation number N is in the middle rotation range B based on the driving state information turns on the driving signal Sa when, for example, a predetermined time T1 has elapsed from the zero cross point t0. In addition, the drive signal Sa is turned off when a predetermined time T2 has elapsed from the time when the predetermined time T1 has elapsed. The on period t of the drive signal Sa at this time is shorter than the on period t of the drive signal Sa at the time of boosting.

  In addition, table information in which the operating state of the load, the on timing of the drive signal Sa and the on period t are associated with each other is prepared in advance, and the table information is externally input to the control unit 20 or the table information is previously controlled By being held at 20, it is possible to set the timing for turning on the drive signal Sa and the on period t of the drive signal Sa.

  By this operation, drive signal Sa is divided into a plurality of switching pulses in a period shorter than on period t of drive signal Sa at the time of boosting, so that DC output voltage Vdc is prevented from being excessively boosted. The power factor can be improved by suppressing the included harmonic components. The timing at which the drive signal Sa is divided into a plurality of switching pulses may be either when the power supply current Is rises as shown in FIG. 12 or when the power supply current Is falls as shown in FIG. In FIG. 14, the on / off operation is not performed until the predetermined time T3 elapses after the predetermined time T2 elapses, and the on / off operation is performed again during the predetermined time T4 elapses from the predetermined time T3 An example is shown. By performing the on / off operation before and after the peak value of the power supply current Is as shown in FIG. 14, the effects of harmonic suppression and power factor improvement can be further enhanced when the operating state is in the step-up unnecessary region. 12, 13 and 14, although the on / off operation is not performed near the zero crossing point, when the motor rotation number N is in the low rotation range C, the harmonic component contained in the power supply current Is is suppressed to Also because the effect of power factor improvement is small.

  FIG. 15 is an explanatory diagram of an operation in the case where pulse conversion is performed while changing the reference voltage at the time of start-up when the operating state is in the area not requiring boosting. FIG. 16 is an explanatory diagram of an operation in the case where pulse conversion is performed while changing the reference voltage at the time of falling when the operating state is in the area not requiring boosting. FIG. 17 is an explanatory diagram of an operation in the case where pulse conversion is performed while changing the reference voltage at the rising and the falling when the operating state is in the region not requiring boosting.

12, 13 and 14 described the operation example in the case where the reference voltage V _ref is constant. 15, 16 and 17 show an operation example in the case where the first current control range w and the second current control range w, that is, the reference voltage V _ref is changed with time. By changing the reference voltage V _ref with time, the waveform of the power supply current Is becomes closer to a sine wave. Therefore, the effects of harmonic suppression and power factor improvement can be further enhanced when the operating condition is in the step-up unnecessary region. In the present embodiment, the reactor 2 is inserted between the AC power supply 1 and the rectifier circuit 3 and the rectifier circuit 3 is connected to the AC power supply 1 via the reactor 2, but the power converter 100 is a reactor. The positional relationship between the rectifier circuit 3, the reactor 2, and the short circuit portion 30 is not limited to the configuration of the illustrated example, as long as the power supply can be short-circuited and opened via the line 2. That is, the power conversion device 100 may have a configuration in which the power supply current Is flows in the order of the AC power supply 1, the reactor 2, the short circuit 30, and the AC power supply 1 at the time of short circuit. The circuit 3 may be inserted, and the reactor 2 may be connected to the AC power supply 1 via the rectifier circuit 3.

  As described above, the power conversion device 100 according to the present embodiment includes the rectifier circuit 3, the inverter circuit 40 which is an inverter, the short circuit portion 30, and a plurality of switching pulses for controlling the on / off operation of the short circuit portion 30. And, in the first load region, the control unit 20 performs the plurality of first switching pulses in which the value of the power supply current Is of the AC power supply 1 is in the first current control range. In the second load region, the control unit 20 outputs a plurality of second switching pulses in which the value of the power supply current Is is in the second current control range, or a plurality of second switching pulses The load applied to the first load area is higher than the load applied to the second load area, and the second current control range is wider than the first current control range, and the plurality of second load ranges switch The number of Guparusu is less than the number of the plurality of first switching pulse.

  With this configuration, the short circuit portion 30 is controlled by the plurality of first switching pulses when the load operating state is a high load region, and the short circuit portion 30 is controlled by the second switching pulse when the load operating state is other than the high load region. It is possible to control or to stop the output of the plurality of second switching pulses. Therefore, high boost performance and harmonic specifications can be satisfied while achieving high efficiency over the entire operating range of the load. Further, compared to the conventional simple switching converter, it is possible to boost the DC output voltage Vdc while suppressing the peak of the power supply current Is. Further, since the peak of the power supply current Is can be suppressed, distortion of the power supply current Is can be suppressed when the short circuit portion 30 is turned on, and harmonic components can be suppressed. Further, since the peak of the power supply current Is can be suppressed, the conduction period of the power supply current Is can be extended, and the power factor can be improved. Further, since the peak of the power supply current Is can be suppressed, the capacity increase of the filter circuit and other components constituting the AC power supply 1 can be suppressed, and the cost increase can be suppressed. Further, according to power conversion apparatus 100 of the present embodiment, even when switching is performed a plurality of times in a half cycle of the power supply, design of the setting time of each switching pulse becomes unnecessary, and current upper and lower limits corresponding to positive and negative electrodes Control design becomes relatively easy because the threshold design at Further, according to power conversion apparatus 100 of the present embodiment, control can be performed with a suitable number of switching times and pulse timing regardless of load conditions, so design load can be reduced.

  In addition, the control unit 20 according to the present embodiment may be configured to output the plurality of second switching pulses as the drive signal Sa1 when the operating state of the motor 50 is in a load region that does not require boosting. With this configuration, when the load is the motor 50, it is possible to compensate for the insufficient motor voltage V in the high rotation range A while suppressing the increase in the motor current. Further, in the middle rotation range B or the low rotation range C, the DC output voltage Vdc can be prevented from being excessively boosted, and the harmonic components contained in the power supply current Is are suppressed, and the power factor is also improved.

  In addition, the control unit 20 according to the present embodiment may be configured to provide hysteresis in the threshold value for determining the operating state of the load to determine whether or not boosting is necessary. With this configuration, for example, it is possible to prevent chattering of the boosting operation at the boundary between the high load region requiring boosting and the region other than the high load region not requiring boosting.

  Moreover, although the example which controls the short circuit part 30 using the power supply current Is detected by the electric current detection part 7 was demonstrated in this Embodiment, it is not limited to this. The power supply current Is is associated with the plurality of first switching pulses and the plurality of second switching pulses by a test in advance, and the correspondence relationship is held by the external input or the control unit 20, whereby the power supply current Is is obtained. Control of the short circuit portion 30 is possible without detection. As described above, the necessity of detection of the power supply current Is may be selected according to the system specification to be constructed.

  Although power conversion device 100 of the present embodiment is configured to output drive signal Sa1 using the current detection value detected by current detection unit 7, direct control unit 20 does not use current detection unit 7. The drive signal Sa1 may be output by detecting the value of the power supply current Is.

  The configuration shown in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and one of the configurations is possible within the scope of the present invention. Parts can be omitted or changed.

  DESCRIPTION OF SYMBOLS 1 AC power supply, 2 reactors, 3 rectification circuits, 4 smoothing capacitors, 5 DC voltage detection parts, 6 power supply voltage detection parts, 7 current detection parts, 8 current detection elements, 9 current detection means, 20 control parts, 21 drive signal generation Unit, 22 pulse conversion unit, 24 pulse transmission unit, 30 short circuit unit, 31 diode bridge, 32 short circuit element, 40 inverter circuit, 41 inverter control unit, 50 motor, 60 alternating current detection unit, 100 power conversion device.

Claims (8)

A rectifier circuit that converts AC power from an AC power source into DC power;
An inverter that converts DC power from the rectifier circuit into AC power and supplies the AC power to the load;
A short circuit that shorts the AC power supply via a reactor;
A control unit that outputs a plurality of switching pulses for controlling the on / off operation of the short circuit portion;
Equipped with
In the first load range, the value of the power supply current before Symbol AC power source outputs a plurality of first switching pulse in a first current control range,
In the second load range, and the output value before Symbol power supply current a plurality of second switching pulse in the second current control range,
When the operating condition of the motor which is the load is in a load region where boosting of the output voltage of the rectifier circuit is not required, the plurality of second switching pulses are output;
The load applied to the first load area is higher than the load applied to the second load area,
The second current control range is wider than the first current control range,
The power converter device, wherein the number of the plurality of second switching pulses is smaller than the number of the plurality of first switching pulses. A rectifier circuit that converts AC power from an AC power source into DC power;
An inverter that converts DC power from the rectifier circuit into AC power and supplies the AC power to the load;
A short circuit that shorts the AC power supply via a reactor;
A control unit that outputs a plurality of switching pulses for controlling the on / off operation of the short circuit portion;
Equipped with
In the first load range, the value of the power supply current before Symbol AC power source outputs a plurality of first switching pulse in a first current control range,
In the second load range, it stops the output of the first switching pulse of multiple,
When the operating state of the motor which is the load is in a load region where boosting of the output voltage of the rectifier circuit is not required, a plurality of second switching pulses whose value of the power supply current is in a second current control range are output ,
The load applied to the first load area is higher than the load applied to the second load area,
The second current control range is wider than the first current control range,
The power converter device, wherein the number of the plurality of second switching pulses is smaller than the number of the plurality of first switching pulses. The control unit may power converter according to claim 1 or 2 over time alter the first current control range and the second current control range. The controller is configured to increase the upper limit threshold value of the second current control range when it is determined that boosting of the output voltage of the rectifier circuit is unnecessary and output of the plurality of switching pulses is unnecessary. The power converter device according to any one of claims 1 to 3 . The power conversion device according to any one of claims 1 to 4 , wherein an operating state of the load is a modulation factor, a motor speed, motor speed information, or a power supply current of the AC power supply. The controller according to any one of claims 1 to 5 , wherein the control unit provides hysteresis to a threshold for determining the operating state of the load to determine whether boosting of the output voltage of the rectifier circuit is necessary. Power converter. In the control unit, correspondence relationships among the plurality of first switching pulses, the plurality of second switching pulses, and the power supply current are set.
The power conversion device according to any one of claims 1 to 6 , wherein the control unit controls the short circuit portion using the correspondence relationship. The control unit controls the short circuit portion using a power supply current detected by a current detection unit provided outside the control unit, or directly detects the power supply current without using the current detection unit. The power converter according to any one of claims 1 to 6 , which controls the short circuit portion.

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