JP2015126579A - Power conversion device, and power conversion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a current distortion factor while reducing a switching loss, in a power conversion device in hysteresis control.SOLUTION: Phases of the respective phases at a three-phase AC side are detected. During a three-phase modulation period in which a phase of any one phase is in a predetermined period including π/2 rad and in a predetermined period including 3π/2 rad, hysteresis control is performed by three-phase modulation. For each phase, during a period other than a three-phase modulation period and during a period in which the phase is from π/6 rad to 2π/6 rad and from 4π/6 rad to 5π/6 rad, two-phase modulation of turning on a switching element connected with a positive side of an arm of the phase, and turning off a switching element connected with a negative side. During a period other than the three-phase modulation period and during a period in which the phase is from 7π/6 rad to 8π/6 rad and from 10π/6 rad to 11π/6 rad, two-phase modulation of turning on the switching element connected with the negative side of the arm of the phase and turning off the switching element connected with the positive side is performed.

Description

  The present invention relates to a power conversion device and a power conversion method for performing three-phase power conversion based on a hysteresis control method.

  There are a carrier wave comparison method and a hysteresis control method as control methods when performing three-phase power conversion. The carrier wave comparison method compares a signal wave such as a sine wave based on the output voltage command value with a carrier wave such as a triangular wave that determines the switching frequency, and a gate having a predetermined pulse width depending on the magnitude of the signal wave and the carrier wave. In this method, a signal is generated and output to a switching element. In addition, the hysteresis control method compares the detected value of the output current of each phase with the output current command value of the sine wave of each phase with hysteresis characteristics, so that the output current is within a predetermined hysteresis width. The gate signal is generated and output to the switching element.

  The hysteresis control method is less affected by fluctuations in the power supply voltage than the carrier wave comparison method and can perform stable power conversion. Further, as compared with the carrier wave comparison method, the dependency of the inductance value of the reactor on the current harmonics is small, and there is an advantage that the reactor can be downsized.

  By the way, in the power conversion device based on the hysteresis control method, the switching loss increases as the number of times of switching of the switching element increases. Therefore, for example, the following proposal is made in Patent Document 1 in order to reduce the switching loss. ing. That is, the DC voltage high voltage of each phase corresponding to the current command value of the three-phase inverter circuit is not dependent on the gate signal from the hysteresis control circuit for a predetermined period including the positive peak value of the current command value of each phase. The upper switching element connected to the side is forcibly turned on, and the lower switching element connected to the DC voltage low voltage side is forcibly turned off. Furthermore, the DC voltage of each phase corresponding to the current command value of the three-phase inverter circuit is not dependent on the gate signal from the hysteresis control circuit for a predetermined period including the negative peak value of the current command value of each phase. The upper switching element connected to the high voltage side is forcibly turned off, and the lower switching element connected to the DC voltage low voltage side is forcibly turned on. In Patent Document 1, the above two-phase modulation method is proposed.

  As described above, in the conventional technique described in Patent Document 1, when the hysteresis control method is employed, the switching elements of each phase are forcibly switched only for a predetermined period including the positive and negative peak values of the current command values of each phase. Therefore, it is possible to suppress the occurrence of excessive switching loss by reducing the number of times of switching in a predetermined period including the peak value.

  On the other hand, in the carrier wave comparison method, the number of times of switching depends on the frequency of a carrier wave such as a triangular wave. For this reason, there are two-phase modulation schemes aimed at reducing switching loss. The two-phase modulation method in the carrier wave comparison method is a method in which a certain one-phase switching element is fixed and PWM control is always performed using the two-phase switching element.

  Specifically, the two-phase modulation method in the carrier wave comparison method does not modulate the phase where the absolute value of the three-phase modulation wave is maximum, outputs the DC voltage as it is, that is, the switching is fixed, and the remaining Two-phase is a method of modulating and switching so that the line voltage becomes a sine wave.

  In the carrier wave comparison method adopting the two-phase modulation method, for example, Patent Document 2 proposes the following switching method between the two-phase modulation method and the three-phase modulation method. When the signal level of each two-phase reference voltage signal enters a predetermined dead band region in the vicinity of the amplitude value of the triangular wave carrier signal, the comparison unit includes a three-phase signal having a sine waveform instead of the two-phase reference voltage signal. A reference voltage signal is input.

  As described above, in the conventional technique described in Patent Document 2, in the carrier wave comparison method adopting the two-phase modulation method, the dead band is set according to the signal level of the two-phase reference voltage signal and the switching to the three-phase modulation method is performed. An inverter device that can improve the control accuracy of the inverter can be realized in a state where the advantage of the two-phase modulation method for the inverter, which is to reduce the power consumption and extend the life of each switching element, is fully utilized.

JP 2011-120349 A JP 2006-42481 A

  In the hysteresis control method described in Patent Document 1, the period for forcibly fixing switching is a predetermined period including a peak value, and a period in which the change amount of current is small near the peak value and the number of times of switching is small in one cycle. It is. According to Patent Document 1, the number of switching operations can be reduced in the hysteresis control method, and the filter reactor can be downsized. Further, when the current distortion rate is limited, it is possible to cope with it by shortening the period for fixing the switching. However, the two-phase modulation method is continued even during a period in which two-phase modulation is difficult, and as a result, one-phase modulation may occur, and the current waveform may be distorted.

  In Patent Document 2, by adopting a two-phase modulation method in a carrier wave comparison method and switching to a three-phase modulation method in the vicinity of the amplitude value of a triangular wave carrier wave, both switching loss reduction and current distortion rate improvement are achieved. Yes. Since the hysteresis control method does not use a carrier wave, the technique described in Patent Document 2 cannot be applied as it is, and even if the modulation method is switched for a phase period equivalent to the vicinity of the amplitude value of the carrier wave, the current waveform can be improved. In addition, the number of times of switching increases.

  The present invention has been made to solve the above-described problems, and in the hysteresis control method to which the two-phase modulation method for reducing the number of switching times is applied, both reduction of switching loss and improvement of current distortion ratio are achieved. An object of the present invention is to provide a power conversion device and a power conversion method that can be performed.

  In the present invention, three arms each having two switching elements connected in series are connected between two positive and negative terminals on the DC side, and the connection points of the two switching elements in the three arms are three terminals on the three-phase AC side. A power conversion device for converting power between DC power and AC power having a smoothing filter having inductance characteristics on the three-phase AC side, wherein the output current of each phase on the three-phase AC side is A hysteresis comparator that generates gate control signals for the switching elements of the three arms to control the current command value within the hysteresis width, and detects the phase of each phase on the three-phase AC side and outputs a phase signal From the phase detector, a gate controller that outputs a gate signal for controlling the gates of the switching elements of the three arms, and a phase detector Using the phase signal, for each phase, during the period from π / 6 rad to 2π / 6 rad and 4π / 6 rad to 5π / 6 rad, the switching element connected to the positive side of the arm of the phase is turned on and on the negative side A gate control signal for turning off the connected switching element is output, and a gate control signal input from the hysteresis comparator is output as a gate control signal for the switching element of the arm other than the relevant phase, and the phase is 7π / 6 rad. During the period from 8π / 6 rad to 10π / 6 rad to 11π / 6 rad, a gate control signal for turning on the switching element connected to the negative side of the arm of the phase and turning off the switching element connected to the positive side is output. And a gate control signal for the switching element of the arm of the phase other than the phase The two-phase modulation control unit that outputs the gate control signal input from the hysteresis comparator, the gate control signal from the hysteresis comparator, and the gate control signal from the two-phase modulation control unit are input, and the phase from the phase detection unit Using a signal, a gate control signal from a hysteresis comparator is supplied to the gate control unit during a three-phase modulation period in which a phase of any phase includes a predetermined period including π / 2 rad and a predetermined period including 3π / 2 rad. A modulation method switching unit that outputs and outputs a gate control signal from the two-phase modulation control unit to the gate control unit during a period other than the three-phase modulation period.

  Also, the gate control signal from the hysteresis comparator, the gate control signal from the two-phase modulation control unit, and the gate signal output from the gate control unit are input, and the gate signal output from the gate control unit is one-phase. When it is determined that the one-phase modulation gate signal has continued for the set time set as the maximum modulation time, the gate control signal from the hysteresis comparator is output to the gate control unit for a predetermined period after the determination, and the hysteresis comparator A period other than the period in which the gate control signal is output to the gate controller is provided with a modulation system switching unit that outputs the gate control signal from the two-phase modulation controller.

  In addition, three arms each having two switching elements connected in series are connected between two positive and negative terminals on the DC side, and each of the connection points of the two switching elements in the three arms becomes three terminals on the three-phase AC side. This is a power conversion method in which power conversion between DC power and AC power is performed by hysteresis control in which the output current of each phase on the three-phase AC side is controlled within the hysteresis width with respect to the current command value of each phase. The phase of each phase on the three-phase alternating current side is detected, and hysteresis control is performed in a three-phase modulation period in which the phase of any phase is a predetermined period including π / 2 rad and a predetermined period including 3π / 2 rad. Three-phase modulation is performed in each of the three phases, and each phase is a period other than the three-phase modulation period and the phase is from π / 6 rad to 2π / 6 rad and from 4π / 6 rad to 5π / 6 rad. During this period, the switching element connected to the positive side of the arm of the phase is turned on and the switching element connected to the negative side is turned off, and the phase other than the phase is set to hysteresis control, and the period other than the three-phase modulation period In addition, the switching element connected to the negative side of the arm of the phase is turned on and the switching element is connected to the positive side during a period of 7π / 6 rad to 8π / 6 rad and 10π / 6 rad to 11π / 6 rad. The phase other than the relevant phase is subjected to two-phase modulation with hysteresis control.

  In addition, the phase of each phase on the three-phase AC side is detected, and in each phase, the phase is connected to the positive side of the arm of the phase for a period of π / 6 rad to 2π / 6 rad and 4π / 6 rad to 5π / 6 rad. The switching element connected to the negative side is turned off and the switching element connected to the negative side is turned off. The phase other than the relevant phase is controlled by hysteresis, and the phase is a period of 7π / 6 rad to 8π / 6 rad and 10π / 6 rad to 11π / 6 rad, The switching element connected to the negative side of the arm of the phase is turned on and the switching element connected to the positive side is turned off. The gate signal of each switching element is monitored, and it is determined that the one-phase modulation has continued for the time set as the maximum one-phase modulation time. When determined, three-phase modulation is performed in which hysteresis control is performed in each of the three phases without performing two-phase modulation for a predetermined period after the determination.

  According to the present invention, in the hysteresis control method to which the two-phase modulation method is applied, there is an effect that the switching loss is reduced while suppressing the current distortion rate.

It is a circuit diagram which shows the whole structure of the power converter device by Embodiment 1 of this invention. It is a block diagram which shows the structure of the hysteresis control part in the power converter device by Embodiment 1 of this invention. It is a figure explaining operation | movement of a hysteresis control system. It is a flowchart which shows the operation | movement of the modulation system switching part in the power converter device by Embodiment 1 of this invention. It is a time chart explaining operation | movement of the power converter device by Embodiment 1 of this invention. It is a block diagram which shows the structure of the hysteresis control part in the power converter device by Embodiment 2 of this invention. It is a flowchart which shows the operation | movement of the modulation system switching part in the power converter device by Embodiment 2 of this invention.

  1 is a circuit diagram showing an overall configuration of a power conversion apparatus according to Embodiment 1 of the present invention. The power conversion device 1 according to the first embodiment includes a three-phase power conversion circuit 2 configured by a three-phase full bridge converter. A DC capacitor 3 and a load 4 are connected to the three-phase power conversion circuit 2 on the DC side, and a three-phase AC power source 6 is connected to the AC side via a smoothing filter 5 having inductance characteristics. And the power converter device 1 is a system which converts electric power bidirectionally between the three-phase AC power source 6 and the load 4. The grounding point is a three-phase AC power source 6.

  The three-phase power conversion circuit 2 includes three-phase arms corresponding to the U-phase, V-phase, and W-phase, and each arm includes a pair of upper and lower switching elements 7U and 8U, 7V and 8V, and 7W and 8W. Are connected in series, and each connection point has an AC terminal for each phase. Further, the collector terminals of the switching elements 7U, 7V, 7W on the upper side of each phase are on the high voltage side of the DC capacitor 3, that is, the positive side of the DC, and the emitter terminals of the switching elements 8U, 8V, 8W on the lower side of each phase are DC. It is connected to the low voltage side of the capacitor 3, that is, the negative side of the direct current.

  In this case, each of the switching elements 7U, 8U, 7V, 8V, 7W, and 8W includes a self-extinguishing semiconductor element made of an IGBT and a reflux diode connected in reverse parallel thereto. Here, the IGBT is used as the semiconductor element, but the present invention is not limited to this, and other self-extinguishing type semiconductor elements such as MOSFETs can also be applied.

  The DC capacitor 3 is provided with a DC voltage detector 9 for detecting the DC voltage, and the voltage and current of each phase are detected between the smoothing filter 5 and the three-phase AC power source 6. Voltage detectors 10U, 10V, and 10W and current detectors 11U, 11V, and 11W are provided. Here, the detection current of each phase is positive in the direction from the three-phase AC power supply 6 side to the DC side.

  Furthermore, the power conversion device 1 according to the first embodiment includes the DC voltage detected by the DC voltage detector 9, the detections detected by the voltage detectors 10U, 10V, and 10W and the current detectors 11U, 11V, and 11W. A hysteresis control unit 12 is provided to input the voltage and the detection current and to control on / off of the six switching elements 7U, 8U, 7V, 8V, 7W, and 8W constituting the three-phase power conversion circuit 2.

  FIG. 2 is a block diagram illustrating a configuration of the hysteresis control unit 12 in the power conversion device 1. The hysteresis control unit 12 of the first embodiment includes a subtractor 21, a DC voltage control unit 22, a dq inverse converter 23, a hysteresis comparator 24, a two-phase modulation control unit 25, a modulation scheme switching unit 26, a gate control unit 27, and A phase detector 28 is included.

  Here, the subtractor 21 obtains a difference between the DC voltage Vmdc of the DC capacitor 3 detected by the DC voltage detector 9 and the target voltage Vsdc of the DC capacitor 3. Further, the DC voltage control unit 22 gives an effective current command value so that the DC voltage of the DC capacitor 3 approaches the target voltage, that is, the output of the differentiator 21 approaches zero. Note that the effective current command value in this case is not limited to that by the DC voltage control unit 22 as long as the power of the load 4 and the power of the three-phase power conversion circuit 2 are balanced. Also good.

  The phase detector 28 calculates information on the phase θ based on the detected voltages Vuac, Vvac, and Vwac of each phase detected by the voltage detectors 10U to 10W. Information on the phase θ detected by the phase detection unit 28 is supplied to the dq inverse converter 23, the two-phase modulation control unit 25, the modulation scheme switching unit 26, and the gate control unit 27, respectively.

  The dq inverse converter 23 uses the information on the phase θ detected by the phase detection unit 28 to convert the effective current command value obtained by the DC voltage control unit 22 into the voltage phases of the U phase, the V phase, and the W phase. Is converted back to a current command value for each phase in the form of a sine wave with approximately the same phase as the output.

  The hysteresis comparator 24 sets a current command upper limit value and a current command lower limit value each having a predetermined hysteresis width ± ΔI around the sine wave-shaped current command values obtained by the dq inverse converter 23, The current command upper limit value, the current command lower limit value, and the detected currents Iuac, Ivac, Iwac detected by the respective current detectors 11U, 11V, 11W are compared, and the detected current is compared with the current command upper limit value. Gate control for ON / OFF control of each switching element 7U, 8U, 7V, 8V, 7W, 8W constituting the three-phase power conversion circuit 2 so as to be within the range of the current command lower limit value, that is, within the hysteresis width ± ΔI Generate a signal.

  Therefore, for example, when the U-phase detected current reaches the current command upper limit value, this U-phase is set so that the current flows from the load 4 side to the three-phase AC power supply 6 side and the detected current falls within the hysteresis width ± ΔI. A gate control signal for turning on the high-voltage side switching element 7U and turning off the low-voltage side switching element 8U is generated. Further, when the U-phase detection current reaches the current command lower limit value, this U-phase is set so that the current flows from the three-phase AC power supply 6 side to the load 4 side and the detection current falls within the hysteresis width ± ΔI. A gate control signal for turning on the low-voltage side switching element 8U and turning off the high-voltage side switching element 7U is generated. The same applies to the switching elements 7V and 8V and 7W and 8W corresponding to the other phases. In this way, the hysteresis control is performed so that the output current of each phase of the three-phase power conversion circuit 2 falls within the range of the current command value having the hysteresis width ± ΔI. FIG. 3 schematically shows the hysteresis control operation.

Here, the above-described hysteresis width ΔI is determined by limiting current ripple (current distortion) and switching frequency. The limit of current ripple directly becomes a determining factor of ΔI, and since the current is controlled within the range of ± ΔI of the current command, ΔI is determined as the maximum value of the current ripple. Further, the voltage difference between the voltage of the three-phase AC power supply 6 and the output voltage of each phase of the three-phase power conversion circuit 2 is ΔV, the inductance value of the smoothing filter 5 is L, and the time for changing from the current command value to + ΔI or −ΔI If Δt is Δt, it can be expressed by the relationship of Expression (1).
ΔI = (ΔV / L) × Δt (1)
Δt corresponds to about ¼ of the switching period (the current fluctuates in a range of ± ΔI, so it takes four times as long as Δt to make one round trip). If the maximum switching period is set, Δt Is determined, and ΔI is determined according to the equation (1). At this time, it is desirable to apply the maximum value for ΔV for one period of the fundamental wave.

  The two-phase modulation control unit 25 sets the phase θ generated by the phase detection unit 28 as a reference phase of the current command value for the U phase, and for the V phase and the W phase, 2π / 3, 4π respectively from the U phase phase θ. The phase obtained by delaying the / 3 (rad) phase is set as the reference phase of the current command value. Then, over a predetermined positive and negative reference phase period of each phase current command value, one switching element of the pair of switching elements on the high voltage side and the low voltage side constituting the arm corresponding to each phase of the current command value is forced. The other switching element is forcibly fixed off. During other periods, based on the output of the hysteresis comparator 24, a gate control signal is generated so that the pair of switching elements 7U and 8U, 7V and 8V, and 7W and 8W constituting the arm of each phase are on / off controlled. To do.

  More specifically and ideally, the U phase, the V phase, and the W phase have high pressures in the range of π / 6 to 2π / 6 (rad) and the range of 4π / 6 to 5π / 6 (rad). The switching element on the side is turned on and the switching element on the low voltage side is turned off. In addition, the switching elements on the high voltage side are turned off in the range of 7π / 6 to 8π / 6 (rad) and the range of 10π / 6 to 11π / 6 (rad) for each of the U-phase, V-phase, and W-phase reference phases. At the same time, the switching element on the low voltage side is turned on.

  Thus, among each switching element, the pair of switching elements corresponding to one phase is fixed to the on or off state, and only the four switching elements corresponding to the remaining two phases are gated from the hysteresis comparator 24. The control operation that performs on / off control according to the control signal is referred to herein as two-phase modulation. In addition, a control operation for controlling on / off of all the switching elements of each of the three phases according to the gate control signal from the hysteresis comparator 24 is referred to as three-phase modulation.

  The modulation system switching unit 26 uses the phase θ information generated by the phase detection unit 28 as a reference phase for the current command value of the U phase, and the phase of the U phase for the V phase and the W phase. The phases delayed from θ by 2π / 3 and 4π / 3 (rad), respectively, are used as the reference phase of the current command value. Then, near the positive and negative peak values of the current command value of each phase, that is, a predetermined period including π / 2 of the reference phase of the current command value of each phase and a predetermined period including 3π / 2 (rad), three-phase modulation As a period, the output value of the hysteresis comparator 24 is input to the gate controller 27 to perform three-phase modulation. This predetermined period is a period in which the phase is in the range of the short-circuit prevention time (dead time) or more and the phase is less than π / 6 (rad). In other words, it is preferable to determine a period as small as possible through experiments or the like based on current distortion and switching loss. During a period other than the three-phase modulation period, a two-phase modulation in which the switching element of any phase is fixed to ON or OFF is performed by outputting a gate control signal from the two-phase modulation control unit 25.

  The gate control unit 27 holds dead time for preventing a short circuit between the pair of upper and lower switching elements 7U and 8U, 7V and 8V, 7W and 8W corresponding to each phase, and is output from the modulation system switching unit 26. A dead time for preventing a short circuit is added to the gate control signal, and a gate signal is output to each switching element. A specific dead time addition method is, for example, when focusing on a pair of switching elements 7U and 8U corresponding to the U phase, and when one switching element 7U or 8U is turned from on to off, the dead time period The other switching element 8U or 7U is also forcibly turned off. The same operation is performed for the V-phase and W-phase switching elements 7V and 8V, and 7W and 8W.

  In Patent Document 1, a predetermined period (for example, a 60-degree period) including positive and negative peak values of the current command value of each phase is set as a two-phase modulation period, and the switching element of the phase including the peak value is fixed to an on or off state. Only the remaining two phases are on / off controlled. As shown in FIG. 3 for explaining the operation of the hysteresis control method, the phase including the peak value of the current command value of each phase is determined by the DC voltage applied to the three-phase power conversion circuit 2 and the phase of each phase of the three-phase AC power source 6. Since the voltage difference ΔV from the output voltage is a small phase, this is a period in which the number of times of switching is small. As described in Patent Document 1, a significant reduction in switching loss cannot be expected even if the switching element is fixed to the on or off state during this period.

  On the other hand, in the present invention, the phase during which the switching element for one phase is fixed to the on or off state has a phase of π / 6 to 2π / 6, 4π / 6 to 5π / 6, 7π / 6 to 8π / 6, and The period is 10π / 6 to 11π / 6. These periods are periods in which the number of switching is large because the amount of current change is larger than the period including the positive and negative peak values of the current command value of each phase. In the first embodiment, during this period, the switching element is forcibly fixed to an on or off state, and as in Patent Document 1, 60 degrees (including positive and negative peak values of the current command value of each phase) Compared to forcibly turning on or off the (π / 6 rad) period, it is possible to significantly reduce the number of times of switching, and accordingly, switching loss can be reduced.

  Thus, in the two-phase modulation control unit 25, the two-phase modulation period is generated from the phase detection unit 28 in order to greatly reduce the number of times of switching compared to the case of the general hysteresis control method of the three-phase modulation. Using the phase θ information, the phase ranges from π / 6 to 2π / 6, 4π / 6 to 5π / 6, 7π / 6 to 8π / 6, and 10π / 6 to 11π / 6 (rad) To do.

  In the two-phase modulation method, since the sum of the three-phase output currents becomes zero, if the two-phase current control is performed, the three-phase control can be performed.

  However, when the two-phase modulation method is applied in the above period, at a timing when a certain phase is close to the peak value and the other phase is fixed so that the switching is fixed, switching other than near the peak value is fixed, and the maximum voltage phase Only switching, that is, one-phase modulation may occur. This is because the switching state and output current state during switching fixed phase switching and the switching of the maximum voltage phase affect the remaining phases due to the intermediate voltage, causing a current in the opposite direction to flow. . As a result, the current distortion may increase temporarily due to one-phase modulation. Therefore, in order to suppress the current distortion, the three-phase modulation is performed in which hysteresis control is performed in each of the three phases only during a period when there is a possibility of the one-phase modulation.

  FIG. 4 is a flowchart showing a modulation scheme switching method in modulation scheme switching section 26 of power conversion device 1 according to Embodiment 1 of the present invention. In addition, the code | symbol S in FIG. 4 means each process step.

  If the phase obtained from the phase detector 28 in each of the U-phase, V-phase, and W-phase is a phase for a predetermined period including π / 2 or 3π / 2 (S001 NO), the three-phase modulation method (S002) In other words, the gate control signal from the hysteresis comparator 24 is output. During the other period (S001 YES), the two-phase modulation method (S003) is continued, that is, the gate control signal from the two-phase modulation control unit 25 is output. It is assumed that the phase obtained from the phase detector 28 in any phase is three-phase modulation for a predetermined period including π / 2 or 3π / 2. In consideration of the determination of other phases, three-phase modulation is performed for a predetermined period including π / 6, 3π / 6, 5π / 6, 7π / 6, 9π / 6, and 11π / 6.

  FIG. 5 shows the relationship between the U-phase, V-phase, and W-phase phases in the power conversion device according to Embodiment 1 of the present invention, the timing for switching on / off the switching element, and the three-phase modulation method switching period. It is explanatory drawing which shows a relationship. In this case, the phase of each phase uses the information of the phase θ generated from the phase detector 28 as described above, and this phase θ is set as the reference phase of the U phase, and the reference phases of the V phase and the W phase are The phase is set to be delayed by 2π / 3 and 4π / 3 phases from the phase θ of the U phase, respectively.

  As described above, in the power conversion device according to Embodiment 1 of the present invention, when any phase is a phase of a predetermined period including π / 2 rad or 3π / 2 rad, the two-phase modulation method may be difficult. Therefore, hysteresis control is performed by three-phase modulation, and each phase has a phase other than the above-described predetermined period, and the phase is π / 6 rad to 2π / 6 ra, 4π / 6 rad to 5π / 6 rad, 7π / 6 to 8π. In the period of / 6 rad and 10π / 6 to 11π / 6 rad, the switching element of the arm of the phase is fixed on or off to perform two-phase modulation. As described above, in hysteresis control having a high current control response, it is possible to realize both a significant reduction in switching loss and a reduction in current distortion.

  In Patent Document 2, in the carrier wave comparison method, as in Patent Document 1, the two-phase modulation method is adopted for the purpose of reducing the switching loss, and the three-phase modulation method is switched in the vicinity of the amplitude value of the triangular wave carrier wave. Therefore, both reduction of switching loss and improvement of current distortion ratio are achieved. That is, the period near the zero cross of the phase voltage command value is the three-phase modulation period. The switching of the switching fixed phase in this region is not in the vicinity of the peak value of the current command value in the hysteresis control method, and is not a region in which one-phase modulation is performed. Since there is no triangular wave carrier wave described in Patent Document 2 in the hysteresis control method, the switching method in Patent Document 2 cannot be applied as it is. Furthermore, even if it replaces with the system which switches to the three-phase modulation in the vicinity of the current zero cross in Patent Document 1, the current distortion rate does not change and the number of switching increases because the hysteresis control system is not a region for the one-phase modulation. become.

Embodiment 2. FIG.
FIG. 6 is a block diagram showing a configuration of hysteresis control unit 12 of power conversion device 1 according to the second embodiment of the present invention. The overall configuration of the power conversion apparatus is the same as that in FIG. In the first embodiment, when switching the modulation method, the modulation method switching unit 26 may use the phase detected by the phase detection unit 28 to make the two-phase modulation method difficult π / 2, 3π / 2. However, the present invention is not limited to this and may be as follows.

  The gate signal of each phase output from the gate control unit 27 is detected, and it is detected that the one-phase modulation has been performed, and the mode is switched to the three-phase modulation. In the single-phase modulation detection method, for example, the gate signal of each phase is monitored, and detection is performed when a gate signal of two or more phases is fixed for a predetermined period or more.

  In the modulation system switching unit 26, the gate signal of each phase output from the gate control unit 27 is monitored. If a gate signal of two or more phases is fixed for a predetermined time or more, it is determined that one-phase modulation has been performed. Switch to three-phase modulation. That is, the gate control signal output from the hysteresis comparator 24 is output to the gate control unit. The predetermined time is referred to as the longest time of one-phase modulation, and based on the current distortion rate, one-phase modulation is prevented from continuing for more than this time. Conversely, one-phase modulation is continued until this time. Is determined from experiments and the like as the maximum allowable time.

  FIG. 7 is a flowchart showing a modulation method switching method in the modulation method switching unit 26 of the power conversion apparatus according to Embodiment 2 of the present invention. In addition, the code | symbol S in FIG. 7 means each process step. In the following description, when the two-phase modulation method is used, the gate control signal input from the two-phase modulation control unit 25 is output from the modulation method switching unit 26 to the gate control unit 27. When the three-phase modulation method is used, the gate control signal input from the hysteresis comparator 24 is output from the modulation method switching unit 26 to the gate control unit 27. The operation of the two-phase modulation control unit 25 and the operation of the hysteresis comparator 24 are the same as those in the first embodiment.

  The U phase, V phase, and W phase gate signals, which are the output values of the gate control unit 27, are monitored to obtain the time during which each switching is fixed. If the U-phase gate signal fixing time is equal to or longer than the predetermined maximum one-phase modulation time (Tm) (S101 YES) and the V-phase gate signal fixing time is equal to or longer than the maximum one-phase modulation time (S102 YES), one-phase modulation is performed. It is determined that there is, and the mode is switched to the three-phase modulation method (S103). If the V-phase gate signal fixing time is shorter than the one-phase modulation longest time (NO in S102), the two-phase modulation method (S104) is selected.

  Further, if the U-phase gate signal fixed time is longer than the one-phase modulation longest time (S101 YES) and the W-phase gate signal fixed time is longer than the one-phase modulation longest time (S105 YES), it is determined that the single-phase modulation is performed. Then, the mode is switched to the three-phase modulation method (S106). If the W-phase gate signal fixed time is shorter than the one-phase modulation maximum time (S105 NO), the two-phase modulation method (S107) is selected.

  The U-phase gate signal fixing time is shorter than the single-phase modulation maximum time (S101 NO), the V-phase gate signal fixing time is longer than the single-phase modulation maximum time (S108 YES), and the W-phase gate signal fixing time is one phase. When the time is longer than the longest modulation time (YES in S109), it is determined that the modulation is one-phase modulation, and the mode is switched to the three-phase modulation method (S110).

  When the U-phase gate signal fixed time is shorter than the one-phase modulation longest time (S101 NO) and the V-phase gate signal fixed time is also shorter than the one-phase modulation longest time (S108 NO), the two-phase modulation method (S112) is set. .

  The U-phase gate signal fixing time is shorter than the single-phase modulation maximum time (S101 NO), the V-phase gate signal fixing time is longer than the single-phase modulation maximum time (S108 YES), and the W-phase gate signal fixing time is one phase. When the modulation time is shorter than the longest modulation time (NO in S109), the two-phase modulation method (S111) is selected.

  In this way, it may be switched to the three-phase modulation method by detecting the one-phase modulation. After switching to three-phase modulation, switching to two-phase modulation is performed after a predetermined period, that is, after a period as small as possible determined by experiments or the like based on current distortion and switching loss, as in the first embodiment. As described above, by switching the control method by detecting one-phase modulation, it is possible to switch to three-phase modulation only for the minimum necessary period.

  In the present invention, it is possible to freely combine the respective embodiments within the scope of the invention, to appropriately modify the respective embodiments, or to omit the constituent elements thereof.

  DESCRIPTION OF SYMBOLS 1 Power converter device, 2 Three-phase power converter circuit, 3 DC capacitor, 4 Load, 5 Smoothing filter, 6 Three-phase alternating current power supply, 7U, 7V, 7W, 8U, 8V, 8W Switching element, 9 DC voltage detector, 10U 10 V, 10 W voltage detector, 11 U, 11 V, 11 W current detector, 12 hysteresis control unit, 24 hysteresis comparator, 25 two-phase modulation control unit, 26 modulation system switching unit, 27 gate control unit, 28 phase detection unit.

Claims (10)

Three arms each having two switching elements connected in series are connected between the positive and negative two terminals on the DC side, and the connection points of the two switching elements in the three arms are three terminals on the three-phase AC side, A power converter that performs power conversion between DC power and AC power, comprising a smoothing filter having inductance characteristics on the three-phase AC side,
A hysteresis comparator that generates a gate control signal for the switching elements of the three arms for controlling the output current of each phase on the three-phase AC side within a hysteresis width with respect to the current command value of each phase;
A phase detector that detects the phase of each phase on the three-phase AC side and outputs a phase signal;
A gate control unit for outputting a gate signal for controlling the gate of each switching element of the three arms;
Using the phase signal from the phase detector, for each phase, the switching connected to the positive side of the arm of the phase for a phase of π / 6 rad to 2π / 6 rad and 4π / 6 rad to 5π / 6 rad Gate control signal for turning on the element and outputting the gate control signal for turning off the switching element connected to the negative side, and inputting from the hysteresis comparator as a gate control signal for the switching element of the arm other than the phase The signal is output, and the switching element connected to the negative side of the arm of the phase is turned on and connected to the positive side during a period of 7π / 6 rad to 8π / 6 rad and 10π / 6 rad to 11π / 6 rad. A gate control signal for turning off the switching element is output, and a phase other than the relevant phase is output. As a gate control signal for the switching element of the arm, a two-phase modulation control unit that outputs a gate control signal input from the hysteresis comparator;
The gate control signal from the hysteresis comparator and the gate control signal from the two-phase modulation control unit are input, and the phase of any phase includes π / 2 rad using the phase signal from the phase detection unit. The gate control signal from the hysteresis comparator is output to the gate control unit during a three-phase modulation period that is a predetermined period and a phase of a predetermined period including 3π / 2 rad, and the two-phase is output during the period other than the three-phase modulation period A modulation system switching unit that outputs a gate control signal from a modulation control unit to the gate control unit;
A power conversion device comprising: Three arms each having two switching elements connected in series are connected between the positive and negative two terminals on the DC side, and the connection points of the two switching elements in the three arms are three terminals on the three-phase AC side, A power conversion device that performs power conversion between DC power and AC power,
A hysteresis comparator that generates a gate control signal for the switching elements of the three arms for controlling the output current of each phase on the three-phase AC side within a hysteresis width with respect to the current command value of each phase;
A phase detector that detects the phase of each phase on the three-phase AC side and outputs a phase signal;
A gate control unit for outputting a gate signal for controlling the gate of each switching element of the three arms;
Using the phase signal from the phase detector, for each phase, the switching connected to the positive side of the arm of the phase for a phase of π / 6 rad to 2π / 6 rad and 4π / 6 rad to 5π / 6 rad Gate control signal for turning on the element and outputting the gate control signal for turning off the switching element connected to the negative side, and inputting from the hysteresis comparator as a gate control signal for the switching element of the arm other than the phase The signal is output, and the switching element connected to the negative side of the arm of the phase is turned on and connected to the positive side during a period of 7π / 6 rad to 8π / 6 rad and 10π / 6 rad to 11π / 6 rad. A gate control signal for turning off the switching element is output, and a phase other than the relevant phase is output. As a gate control signal for the switching element of the arm, a two-phase modulation control unit that outputs a gate control signal input from the hysteresis comparator;
A gate control signal from the hysteresis comparator, a gate control signal from the two-phase modulation control unit, and a gate signal output from the gate control unit are input, and a gate signal output from the gate control unit is: If it is determined that the gate signal of the one-phase modulation has continued for a set time set as the longest time for one-phase modulation, the gate control signal from the hysteresis comparator is output to the gate control unit for a predetermined period after the determination, A modulation system switching unit that outputs a gate control signal from the two-phase modulation control unit during a period other than a period in which the gate control signal from the hysteresis comparator is output to the gate control unit;
A power conversion device comprising:   3. The power converter according to claim 1, wherein the predetermined period is a period that is equal to or longer than a dead time set to prevent a short circuit of the arm and whose phase is less than π / 6 rad.   The power converter according to claim 3, wherein the predetermined period is a period determined based on current distortion and switching loss.   3. The power conversion device according to claim 2, wherein the one-phase modulation longest time is a time determined as a longest time in which one-phase modulation can be allowed to continue based on current distortion. Three arms each having two switching elements connected in series are connected between two positive and negative terminals on the DC side, and the connection points of the two switching elements in the three arms are three terminals on the three-phase AC side. In this power conversion method, power conversion between DC power and AC power is performed by hysteresis control in which the output current of each phase on the three-phase AC side is controlled within the hysteresis width with respect to the current command value of each phase. There,
The phase of each phase on the three-phase AC side is detected, and the hysteresis control is performed in a three-phase modulation period in which a phase of any phase is a predetermined period including π / 2 rad and a predetermined period including 3π / 2 rad. Three-phase modulation is performed in each of the three phases, and for each phase, the phase is in a period other than the three-phase modulation period and the phase is from π / 6 rad to 2π / 6 rad and 4π / 6 rad to 5π / 6 rad. The switching element connected to the positive side of the arm is turned on and the switching element connected to the negative side is turned off, and the phase other than the phase is set as the hysteresis control, and the period other than the three-phase modulation period And the switching connected to the negative side of the arm of the phase during a period of 7π / 6 rad to 8π / 6 rad and 10π / 6 rad to 11π / 6 rad Power conversion method turns off the switching element connected to the positive side, a phase other than the phase which is characterized in that the two-phase modulation to the hysteresis control as well as on the child. Three arms each having two switching elements connected in series are connected between two positive and negative terminals on the DC side, and the connection points of the two switching elements in the three arms are three terminals on the three-phase AC side. In this power conversion method, power conversion between DC power and AC power is performed by hysteresis control in which the output current of each phase on the three-phase AC side is controlled within the hysteresis width with respect to the current command value of each phase. There,
The phase of each phase on the three-phase AC side is detected, and in each phase, the phase is connected to the positive side of the arm of the phase for a period of π / 6 rad to 2π / 6 rad and 4π / 6 rad to 5π / 6 rad The switching element connected to the negative side is turned off while the switching element is turned on, and the phase other than the phase is the hysteresis control, and the phase is a period of 7π / 6 rad to 8π / 6 rad and 10π / 6 rad to 11π / 6 rad The switching element connected to the negative side of the arm of the phase is turned on and the switching element connected to the positive side is turned off, and the phase other than the phase performs two-phase modulation with the hysteresis control,
When the gate signals of the switching elements in the three arms are monitored and it is determined that the one-phase modulation has continued for the time set as the maximum one-phase modulation time, the two-phase modulation is performed for a predetermined period after the determination. A power conversion method characterized by performing three-phase modulation in which the hysteresis control is performed for each of the three phases.   8. The power conversion method according to claim 6, wherein the predetermined period is a period that is equal to or longer than a dead time set to prevent a short circuit of the arm and whose phase is less than π / 6 rad.   The power conversion method according to claim 8, wherein the predetermined period is a period determined based on current distortion and switching loss.   The power conversion method according to claim 7, wherein the one-phase modulation longest time is a time determined as a longest time in which one-phase modulation can be allowed to continue based on current distortion.

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