JP5323426B2 - Power converter - Google Patents

Description

  The present invention relates to a power converter that converts AC power supplied from a single-phase AC power source into DC power.

  A DC circuit (converter) equipped with a general diode full bridge full-wave rectifier circuit can convert an AC voltage supplied from an AC power source into a DC voltage. It is difficult to keep the harmonic content of alternating current current below a desired specified value.

  Therefore, in the prior art, when converting AC voltage to DC voltage, the harmonic current content of AC current at the time of DC voltage conversion is desired so that the current waveform of AC current becomes a sine waveform synchronized with the AC voltage waveform. Has been proposed (see, for example, Patent Document 1 below).

  In the power conversion device of Patent Document 1, a reactor and a full-bridge inverter are connected in series to an AC power source, and a voltage AC / DC converter is connected, whereby a harmonic of an AC current during DC voltage conversion is obtained. While suppressing the content rate below a desired specified value, it is possible to change the boost rate by changing the duty ratio of the positive and negative output voltages of each inverter arm constituting the full bridge inverter.

JP 2008-61322 A

  However, this type of conventional boost type power conversion device still has the following problems. (A) Since a smoothing reactor provided between the AC power supply and the full-bridge inverter is applied with a switching voltage having a PWM waveform having the same magnitude as the boosted voltage, As a result, the specifications of the reactor increase and the cost increases.

(B) Moreover, the conventional power converter cannot obtain the boosted voltage below the maximum instantaneous voltage value of AC power supply on a circuit structure. In addition, since there is a restriction on the reactor as described in (a) above, the step-up rate cannot be increased. As a result, the selection range of the boosted voltage is narrowed.

(C) Since each inverter arm constituting the full-bridge inverter switches the boosted voltage at a high frequency, the switching loss increases, and the efficiency of the entire apparatus decreases.

  The present invention has been made to solve the problems shown in the above (a) to (c), and has a low cost, a wide selection range of boosted voltage, and a small switching loss. An object of the present invention is to provide a power conversion device having excellent conversion efficiency.

In the power converter of the present invention, a reactor and a single-phase full-bridge inverter operating at a high frequency are sequentially connected in series to one power line of a single-phase AC power supply, and the series-connected power line and the AC power supply On the premise of a configuration in which a voltage AC / DC converter that operates with one pulse drive signal applied every half cycle of the AC power supply and converts AC to DC is connected between the other power line and the following configuration: Adopted.
That is, in the present invention, the reactor, the full bridge inverter, and the voltage AC / DC converter are individually provided corresponding to the positive and negative polarities of the AC power supply, and the power balance per cycle of the full bridge inverter is the pulse width of the voltage applied to said voltage AC-DC converter such that the zero you are being controlled.

According to the power conversion device of the present invention, a low-voltage switching voltage by the full bridge inverter is applied to the reactor. For this reason, the reactor may have a small inductance value, and the cost can be reduced. In addition, by providing a voltage AC / DC converter that operates with a drive signal of one pulse, a high step-up ratio can be obtained and current control with high accuracy can be achieved. Furthermore, even when a difference occurs between the positive electrode side and the negative electrode side of the AC voltage of the AC power source, by independently controlling the ON period of the switching element and changing the pulse width, Ru can be zero independently of the power balance.

Embodiment 1 FIG.
FIG. 1 is a circuit diagram showing a configuration of a power conversion device according to Embodiment 1 of the present invention.

  In the power conversion device according to the first embodiment, a reactor Lo and a single-phase full-bridge inverter IV operating at a high frequency are sequentially connected in series to one power line 11 of a single-phase AC power supply AC. Further, an AC current is operated between the power line 11 connected in series with the reactor Lo and the full-bridge inverter IV and the other power line 12 of the AC power supply AC by a one-pulse drive signal applied every half cycle of the AC power supply AC. Is connected to a voltage doubler converter CV1 as a voltage AC / DC converter for converting DC to DC. Hereinafter, the single-phase full-bridge inverter IV is referred to as a bit inverter.

  Here, the bit inverter IV is configured by bridging four switching elements Q1 to Q4 in which the diodes D1 to D4 are connected in antiparallel, and providing a DC capacitor Co as a DC unit for holding a DC voltage. Has been.

  The voltage doubler converter CV1 outputs a DC voltage having a voltage Vout (≈2Vp) that is approximately twice the maximum voltage Vp of the AC power supply AC, and is a pair of upper and lower diodes connected in antiparallel with the diodes Da and Db. Switching elements Qa and Qb are connected in series with each other, and a pair of upper and lower smoothing output capacitors Ca and Cb connected in series with each other are connected in parallel with the series circuit of these switching elements Qa and Qb. ing. Then, one power line 11 of the AC power supply AC is connected to a connection point between both switching elements Qa and Qb, and the other power line 12 of the AC power supply AC is connected to a connection point between both output capacitors Ca and Cb. Further, this voltage doubler converter CV1 is provided with a bidirectional switch SW formed by connecting a pair of upper and lower switching elements Qc each having a diode Dc connected in antiparallel to each other in series on the output side of the bit inverter IV. A switch SW is connected between both power lines 11 and 12 of the AC power supply AC.

  The switching elements Q1 to Q4 and Qa to Qc constituting the bit inverter IV and the voltage doubler converter CV1 are subjected to switching control by a drive signal supplied from a control circuit (not shown). Here, as each of the switching elements Q1 to Q4 and Qa to Qc, a self-extinguishing type such as an IGBT is applied here. However, the present invention is not limited to this, and may be constituted by, for example, a MOSFET or a bipolar transistor. Is possible.

  Next, the operation of the power conversion device having the above configuration will be described with reference to the operation waveform diagrams shown in FIGS.

Here, first, the operation of the voltage doubler converter CV1 will be described with reference to FIG.
In the positive half cycle of the AC power supply AC, the switching element Qb is kept off. By turning on the switching element Qc of the bidirectional switch SW at the rising and falling portions of the voltage in the positive half cycle, the two power lines l1 and l2 of the AC power supply AC are short-circuited. When the voltage between them is Vx, Vx (indicated by a thick solid line in FIG. 2) becomes zero. In the other period within the positive half cycle of the AC power supply AC, the switching element Qc is off, and the switching element Qa is turned on at this time, so that the upper output capacitor Ca is charged to Vx. Is done.

  Further, in the negative half cycle of the AC power supply AC, the switching element Qa is kept off. Since the switching element Qc of the bidirectional switch is turned on at the rising and falling portions of the voltage in the negative half cycle, the two power lines l1 and l2 of the AC power supply AC are short-circuited. Voltage Vx (indicated by a thick solid line in FIG. 2) becomes zero. In the other period within the negative half cycle of the AC power supply AC, the switching element Qc is off, and the switching element Qb is turned on at this time, so that the lower output capacitor Cb becomes Vx. Charged.

  Thus, in the positive half cycle, the upper output capacitor Ca is charged to Vx, and in the negative half cycle, the lower output capacitor Cb is charged to Vx. The voltage Vx is charged, and this becomes the output voltage Vout of the voltage doubler converter CV1.

Next, the operation of the bit inverter IV will be described.
The bit inverter IV fills the voltage difference between the voltage Vx determined by the switching elements Qa and Qc of the voltage doubler converter CV1 and the voltage Vp · sin (ωt) of the AC power supply AC in the positive half cycle of the AC power supply AC. A constant voltage Viv (indicated by a thick broken line in FIG. 2) is always generated. That is, the voltage Viv generated by the bit inverter IV is controlled to satisfy the following relational expression.
Viv = Vx−Vp · sin (ωt) (1)

Therefore, the voltage Vx applied to the voltage doubler converter CV1 is
Vx = Vp · sin (ωt) + Viv (2)
It becomes.
The inductance value of the reactor Lo is a small value that hardly generates a voltage in the frequency region of the AC power supply AC.

  In the bit inverter IV, the voltage Vx determined by the switching elements Qb and Qc of the voltage doubler converter CV1 and the voltage Vp of the AC power supply AC are the same as in the positive half cycle even when the AC power supply AC is in the negative half cycle. A voltage Viv that fills the voltage difference from sin (ωt) is generated.

  Therefore, in each of the positive half cycle and the negative half cycle of the AC power supply AC, the voltage Viv output from the bit inverter IV is added near the maximum value of the voltage Vp · sin (ωt) of the AC power supply AC to obtain Vx. If it is made to correspond with the voltage of this, the voltage higher than the maximum voltage Vp of AC power supply AC will be obtained. Therefore, the output voltage Vout (= 2 · Vx) of the voltage doubler converter CV1 can be set to a value more than twice the maximum voltage Vp of the AC power supply AC.

  Next, a specific operation of the bit inverter IV will be described with reference to an operation waveform diagram shown in FIG. In general, the inverter circuit is often PWM controlled so that the current of the AC power supply AC becomes approximately a sine wave. However, also in the first embodiment, the current of the AC power supply AC approximates a sine wave. A case where PWM control is performed will be described.

  As described above, the bit inverter IV operates to generate the voltage Viv that fills the difference between the voltage Vx applied to the voltage doubler converter CV1 and the voltage Vp · sin (ωt) of the AC power supply AC. Generates an output voltage so that the current io of the AC power supply AC is approximately a sine wave.

  FIG. 3 shows an example of a voltage waveform output from the bit inverter IV. As shown in FIG. 5A, if the switching element Q3 is turned on / off while the switching elements Q1 and Q2 are off and the switching element Q4 is on, the output voltage becomes a positive rectangular waveform. As shown in FIG. 5B, if the switching element Q1 is turned on / off while the switching elements Q3 and Q4 are turned off and the switching element Q2 is turned on, the output voltage has a negative rectangular waveform. Become. Then, PWM control is performed to change the duty ratio of the rectangular wave so that the switching elements Q1 to Q4 are switched by a drive signal by a control circuit (not shown) and the current of the AC power supply AC becomes approximately a sine wave. .

  At this time, since the voltage of the rectangular wave as described above is applied to the reactor Lo and smoothed, the voltage Viv generated as a result of the bit inverter IV has a waveform indicated by a thick broken line in FIG. In this case, the voltage Viv only needs to fill a difference between the voltage Vx applied to the voltage doubler converter CV1 and the voltage Vp · sin (ωt) of the AC power supply AC (see the above-described equation (1)). The voltage Vo that becomes the peak value (peak value) of the rectangular wave for generating the voltage Viv is sufficiently smaller than the value of the voltage Vout output from the voltage doubler converter CV1. For this reason, the inductance value of the reactor L can be reduced. As a result, the cost can be reduced as compared with the conventional boost type inverter, and the switching loss of the bit inverter IV can be kept low.

Next, the power balance handled by the bit inverter IV will be described.
In FIG. 2, when paying attention to the positive half cycle of the AC power supply AC, the power handled by the bit inverter IV is negative power (when the current is positive) during the period when the switching element Qc is on. The period during which Qc is off and switching element Qa is on is positive power. If the two positive and negative electric power amounts are equal, the power balance handled by the bit inverter IV in the positive half cycle becomes zero, and there is no need to provide a special DC power source in the DC capacitor Co portion.

  Thus, in order to make the power balance in the bit inverter IV zero, the pulse width of the voltage Vx applied to the voltage doubler converter CV1 or the value of the voltage Vout output from the voltage doubler converter CV1 may be controlled. That is, if the pulse width of the voltage Vx is increased by controlling the on / off period of the switching element Qc of the bidirectional switch SW and the switching element Qa of the voltage doubler converter CV1, the positive electric energy increases. Further, even if the output voltage Viv of the bit inverter IV is controlled by the PWM control of the bit inverter IV to increase the voltage value of the voltage Vout output from the voltage doubler converter CV1, the positive power value increases. Therefore, the power balance can be adjusted to be zero. In addition, since it becomes the same operation | movement also about a negative half cycle, description is abbreviate | omitted. In this way, if the power balance per cycle of the bit inverter IV operating at a high frequency becomes zero, the bit inverter IV does not require a DC power source, and the cost can be reduced. Note that when the current polarities are opposite (in the case of regenerative operation), the polarities of the respective expressions are opposite.

  As described above, in the first embodiment, by inserting the bit inverter IV into one power line 11 of the single-phase AC power supply AC, the current is made a sine waveform in both the positive and negative periods of the AC power supply AC. It is possible. For this reason, the effective value of the current flowing through the AC power supply AC is reduced, and loss can be reduced.

  In addition, the boosting function can be provided in either the positive or negative period of the AC power supply AC. At that time, since a voltage sufficiently smaller than the value of the voltage Vout output from the voltage doubler converter CV1 is applied to the reactor Lo, the step-up rate can be set large. Then, by controlling the output voltage Viv by PWM control of the bit inverter IV and adjusting the voltage value of the voltage Vout output from the voltage doubler converter CV1, the output voltage Vout of the voltage doubler converter CV1 is obtained from the AC power supply AC. It can be higher than twice the maximum value Vp of the voltage waveform, and a higher voltage can be obtained compared to the conventional one. On the other hand, if the voltage value of the voltage Vout output from the voltage doubler converter CV1 is adjusted by controlling the output voltage Viv of the bit inverter IV, the output voltage Vout of the voltage doubler converter CV1 is the maximum value of the voltage waveform of the AC power supply AC. It can also be lower than twice Vp.

  In the first embodiment, the description has been made on the assumption that when the AC power supply AC is a positive voltage, the current also flows positive. However, if the AC power supply AC is controlled so as to be negative. A regenerative operation from the DC side to the AC side is obtained.

  FIG. 4 is a block diagram showing an example for setting the current io flowing in the AC power supply AC.

  In this example, the error detector 11 detects the difference ΔV between the output voltage Vout boosted by the voltage doubler converter CV1 and the target voltage Vref, and the value ΔV is proportionally amplified by the proportional amplifier 12 (or integratedly amplified by the integrator). The target level iop of the sine wave is determined so as to be proportional to the voltage. On the other hand, the reference phase of the sine wave is created based on the phase information θ obtained from the phased lock loop (PLL) 13. Then, the multiplier 14 obtains the current iop · sin (ωt + θ) of the AC power supply AC and sets it as the target current Iref. Then, the current io input to the AC power supply AC is detected by a current detector (not shown), the difference Δi between the current io and the target current Iref is obtained by the subtractor 15, and then the difference value Δi is obtained as a proportional amplifier. After proportional amplification by 16 or the like, the PWM controller 17 performs PWM control for changing the duty ratio of the drive signal applied to the switching elements Q1 to Q4 of the bit inverter IV.

  As described above, when the output voltage Vout of the voltage doubler converter CV1 becomes larger than the target boosted voltage Vref, the current target value Iref is changed so that the current io flowing through the AC power supply AC becomes small. Thus, simply changing the current target value Iref of the current automatically switches between the power running mode and the regenerative mode, so that the control system is simplified.

Embodiment 2. FIG.
FIG. 5 is a circuit diagram showing a configuration of the power conversion device according to the second embodiment of the present invention, and components corresponding to those in the first embodiment shown in FIG.

  In the power conversion device according to the second embodiment, a reactor Lo and a bit inverter IV operating at a high frequency are sequentially connected in series to one power line l1 of a single-phase AC power supply AC, and the power line 11 connected in series is connected. And the other power line l2 of the AC power supply AC are common to the first embodiment in that a voltage AC / DC converter is connected. However, the voltage AC / DC converter in the case of the second embodiment is not the voltage doubler converter CV1 as in the first embodiment, but a direct current having a voltage Vout (≈Vp) that is about one time the maximum voltage Vp of the AC power supply AC. It is composed of a normal converter CV2 that outputs a voltage.

That is, the converter CV2 includes a series circuit of a pair of upper and lower switching elements Qa and Qd in which diodes Da and Dd are connected in antiparallel and a pair of upper and lower switching elements Qc and Qb in which diodes Dc and Db are connected in antiparallel. And a smoothing output capacitor Cd are sequentially connected in parallel, one power line 11 of the AC power supply AC is connected to the connection point of both switching elements Qa and Qd, and the other power line 12 of the AC power supply AC is switched both. They are connected to the connection points of the elements Qc and Cb, respectively.
Since other configurations are the same as those in the first embodiment, detailed description thereof is omitted here.

  In this power converter, as shown in the operation waveform diagram of FIG. 6, in the positive half cycle of the AC power supply AC, the switching elements Qa and Qc constituting the converter CV2 are both turned on at the rising and falling portions of the voltage. As a result, the two power lines 11 and 12 of the AC power supply AC are short-circuited. Therefore, when the voltage between the two power lines 11 and 12 is Vx, Vx (shown by a thick solid line in FIG. 6) becomes zero. Further, in another period within the positive half cycle of the AC power supply AC, both the switching elements Qa and Qb are turned on to charge the output capacitor Cd, and Vx matches the output voltage Vout of the converter CV2. .

Further, in the negative half cycle of the AC power supply AC, the switching elements Qd and Qb constituting the converter CV2 are both turned on at the rising and falling portions of the voltage, thereby short-circuiting between both power lines 11 and 12 of the AC power supply AC. Therefore, the voltage Vx (shown by the thick solid line in FIG. 6) between the power lines 11 and 12 is zero. In another period within the negative half cycle of the AC power supply AC, both the switching elements Qc and Qd are turned on, so that the output capacitor Cd is charged and Vx matches the output voltage Vout of the converter CV2. .
Since other operations and effects including the bit inverter IV are the same as those in the first embodiment, detailed description thereof is omitted here.

Embodiment 3 FIG.
FIG. 7 is a circuit diagram showing a configuration of the power conversion device according to the third embodiment of the present invention, and components corresponding to those in the first embodiment shown in FIG.

  In the power conversion device having the configuration of the first embodiment shown in FIG. 1, the bit inverter IV is commonly used for the positive / negative polarity of the voltage of the single-phase AC power supply AC. In that case, when a voltage difference occurs between the positive and negative of the input voltage (that is, when the waveform of the AC power supply AC is not a perfect sine wave waveform and there is a difference between the positive and negative sides), the output voltage As a result, there is a difference between the upper and lower values, and a stable boost voltage cannot be obtained.

  In order to solve this problem, in the third embodiment, reactors Loa and Lob and bit inverters IVa and IVb are provided independently corresponding to the positive polarity and the negative polarity of AC power supply AC, respectively, and the positive electrode A positive charging circuit CPa as a voltage AC / DC converter is connected to the subsequent stage of the side bit inverter IVa, and a negative charging circuit CPb as a voltage AC / DC converter is connected to the subsequent stage of the negative bit inverter IVb. Yes. A voltage doubler converter CV3 is configured by both positive and negative charging circuits CPa and CPb.

  Here, the positive charging circuit CPa connects a switching element Qca in which the diode Dca is connected in antiparallel and a series circuit composed of the switching element Qa in which the diode Da is connected in antiparallel and the output capacitor Ca in parallel with each other. It becomes. The negative charging circuit CPb includes a switching element Qcb in which the diode Dcb is connected in antiparallel, and a series circuit including the switching element Qb in which the diode Db is connected in antiparallel and the output capacitor Cb are connected in parallel to each other. Become. A connection point between the upper and lower switching elements Qca and Qcb and a connection point between the upper and lower output capacitors Ca and Cb are commonly connected to the other power line 12 of the AC power supply AC.

  In this power conversion device, as shown in the operation waveform diagram of FIG. 8, in the positive half cycle of the AC power supply AC, the switching element Qca constituting the positive charging circuit CPa is turned on at the rising and falling portions of the voltage. As a result, the power lines 11 and 12 of the AC power supply AC are short-circuited. Therefore, when the voltage between the power lines 11 and 12 is Vxa, Vxa (indicated by a thick solid line in FIG. 8) becomes zero. In another period within the positive half cycle of the AC power supply AC, the output capacitor Ca is charged to a predetermined voltage Vxa by turning off the switching element Qca and turning on the switching element Qa.

  Further, in the negative half cycle of the AC power supply AC, the switching element Qcb constituting the negative charging circuit CPb is turned on at the rising and falling portions of the voltage, thereby short-circuiting between both power lines 11 and 12 of the AC power supply AC. Therefore, if the voltage between the power lines 11 and 12 is Vxb, Vxb (indicated by a thick solid line in FIG. 8) becomes zero. Further, in another period within the negative half cycle of the AC power supply AC, the output capacitor Cb is charged to a predetermined voltage Vxb by turning off the switching element Qcb and turning on the switching element Qb.

In this way, the upper output capacitor Ca is charged to Vxa in the positive half cycle, and the lower output capacitor Cb is charged to Vxb in the negative half cycle. ) Is charged, and this is taken out as the output voltage Vout.
Since other operations and effects including the bit inverters IVa and IVb are the same as those in the first embodiment, detailed description thereof is omitted here.

  As described above, in the third embodiment, even when a difference occurs between the positive electrode side and the negative electrode side of the AC voltage of the AC power supply AC, the ON period of the switching elements Qa and Qb is independently controlled to set the pulse width. By changing, the power balance of the bit inverters IVa and IVb in each half cycle can be made zero independently, and the degree of freedom can be greatly increased as compared with the case of the first embodiment.

  In addition, this invention is not limited to the structure of said Embodiment 1-3, A various deformation | transformation can be added in the range which does not deviate from the meaning. For example, although there are various types of voltage doubler converter systems, a configuration in which a single-phase bit inverter is connected in series to such a converter may be used, and the same effects as the present invention can be achieved.

It is a circuit diagram of the power converter device in Embodiment 1 of the present invention. It is an operation | movement waveform diagram of the same power converter device. It is an operation | movement waveform diagram of the bit inverter which comprises the same power converter device. It is a block diagram which shows an example for setting the electric current of alternating current power supply in the same power converter device. It is a circuit diagram of the power converter device in Embodiment 2 of this invention. It is an operation | movement waveform diagram of the same power converter device. It is a circuit diagram of the power converter device in Embodiment 3 of this invention. It is an operation | movement waveform diagram of the same power converter device.

Explanation of symbols

AC single-phase AC power supply, l1, l2 power line, Lo reactor,
IV, IVa, IVb bit inverter (single phase full bridge inverter),
CV1 voltage doubler converter (voltage AC / DC converter),
CV2 converter (voltage AC / DC converter), CV3 voltage doubler converter,
CPa, CPb Charging circuit (voltage AC / DC converter).

Claims (4)

A single-phase full-bridge inverter that operates at a reactor and a high frequency is sequentially connected in series to one power line of a single-phase AC power supply, and the power line connected in series and the other power line of the AC power supply Connected to a voltage AC / DC converter that operates with one pulse drive signal applied every half cycle of the AC power source and converts AC to DC,
The reactor, the full bridge inverter, and the voltage AC / DC converter are individually provided corresponding to the positive and negative polarities of the AC power supply,
A power conversion device, wherein a pulse width of a voltage applied to the voltage AC / DC converter is controlled so that a power balance per cycle of the full bridge inverter becomes zero. 2. The power converter according to claim 1, wherein a voltage of a DC portion of the full bridge inverter is smaller than an output voltage boosted by the voltage AC / DC converter. The power converter according to claim 1 or 2, wherein an output voltage of the voltage AC / DC converter is larger than twice a maximum value of a voltage waveform of the AC power supply. The power converter according to claim 1 or 2, wherein an output voltage of the voltage AC / DC converter is smaller than twice a maximum value of a voltage waveform of the AC power supply.

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