JP2007124732A - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a power converter in which total harmonic distortion rate of AC output voltage is minimized, basic wave component is maximized and the size and weight of an output filter can be reduced. <P>SOLUTION: The power converter comprises two three-level single phase output inverter bridges 9 and 10 receiving different voltages, and a control circuit 23 for switching the output voltage level of two three-level single phase output inverter bridges 9 and 10 every time determined by dividing one period of an AC output voltage output by connecting the output terminals of the two three-level single phase output inverter bridges 9 and 10 in series by a division number 2n which is an even number of 14 or above, and a DC power supply 2 having a transformer 3 which supplies a voltage according to the ratio between the amplitudes V1 and V2 of output voltages from the two three-level single phase output inverter bridges 9 and 10 where the total harmonic distortion rate of AC output voltage is set to have a predetermined value or less depending on the division number. The amplitude ratio is set by turn ratio of the transformer 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power conversion device that converts DC power into AC power.

A conventional power conversion device includes n three-level single-phase output inverter bridges each capable of three-level output, each having an isolated DC power supply, and a series connection in which output terminals of the three-level single-phase output inverter bridge are connected in series. An n-stage single-phase output is obtained, and the amplitude ratios of the amplitudes V1, V2, V3 and Vn of the output voltages of the n three-level single-phase output inverter bridges are expressed as V1: V2: V3:. 1: 2: 4: ...: 2 ^{(n-1) The} voltage amplitude ratio distribution means and the voltage closest to the output voltage command to be given to the n-stage power converter are set to the output voltage amplitude of V2 to Vn. Command voltage generating means that is generated by a combination of output voltages of a three-level single-phase output inverter bridge having the same (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 11-89242 (page 3, FIG. 1)

  Conventional power converters have n three-level single-phase output inverter bridges each capable of three-level output, each having an isolated DC power supply, and n-stage output terminals of the three-level single-phase output inverter bridge are connected in series. It was. For example, when the output power is small, a configuration in which two three-level single-phase output inverter bridges are connected in series has been used. However, when a DC power supply having a voltage ratio of V1: V2 = 1: 2 is provided and two three-level single-phase output inverter bridges are connected in series, each output of the two three-level single-phase output inverter bridges Since the voltage amplitude ratio is V1: V2 = 1: 2, the total harmonic distortion factor of the AC output voltage cannot be reduced, and the harmonic component of the AC output voltage cannot be sufficiently reduced. was there. In addition, it is necessary to provide a large output filter in order to attenuate the harmonic component of the AC output voltage.

  The present invention has been made to solve the above-described problems, and reduces the total harmonic distortion of the AC output voltage and increases the fundamental wave component, thereby reducing the size and weight of the output filter. A conversion device is obtained. Moreover, the power converter device with which switching control of a 3 level single phase output inverter bridge is simple is obtained.

  The power conversion device according to the present invention is an AC output that is output by connecting two three-level single-phase output inverter bridges to which different voltages are input and the output terminals of two three-level single-phase output inverter bridges in series. Inverter control means for switching the level of the output voltage of two three-level single-phase output inverter bridges every time when one period of voltage is equally divided by 2n, which is an even number of 14 or more, and AC output according to the number of divisions Two three levels according to the amplitude ratio between the amplitude V1 and the amplitude V2 of the output voltage of each of the two three-level single-phase output inverter bridges set so that the total harmonic distortion of the voltage is not more than a predetermined value. And a DC power supply device having a transformer for supplying a voltage to each of the single-phase output inverter bridges, wherein the amplitude ratio is set by the turns ratio of the transformer A.

  The power conversion device according to the present invention is an AC output that is output by connecting two three-level single-phase output inverter bridges to which different voltages are input and the output terminals of two three-level single-phase output inverter bridges in series. Inverter control means for switching the level of the output voltage of two three-level single-phase output inverter bridges every time when one period of voltage is equally divided by 2n, which is an even number of 14 or more, and AC output according to the number of divisions Two three levels according to the amplitude ratio between the amplitude V1 and the amplitude V2 of the output voltage of each of the two three-level single-phase output inverter bridges set so that the total harmonic distortion of the voltage is not more than a predetermined value. DC power supply device having a transformer for supplying a voltage to each of the single-phase output inverter bridges, and the amplitude ratio is set by the turns ratio of the transformer. Together reduce the harmonic distortion, to increase the fundamental wave component, can be smaller and lighter output filter to obtain a power conversion apparatus capable. Moreover, the power converter device with easy control is obtained. Furthermore, the power converter device in which the zero cross point of the AC output voltage is clear is obtained.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a power conversion device according to Embodiment 1 for carrying out the present invention. In FIG. 1, an input power source 1 such as a battery is connected to a DC power source device 2 that supplies two different output voltages V1 and V2 that are insulated. The first three-level single-phase output inverter bridge 9 that can output + V1, 0, and −V1 and three levels of + V2, 0, and −V2 can be output to the two output terminals of the DC power supply device 2, respectively. A second three-level single-phase output inverter bridge 10 is connected.

  In the first embodiment, the DC power supply device 2 is a flyback converter, and includes a transformer 3, a switching element 4, diodes 5 and 6, voltage detection means 13, and a control drive circuit 14 that is power supply control means. The transformer 3 is wound with a primary winding 3a, a first output winding 3b, and a second output winding 3c. The number of windings of the first output winding 3b is N1, the number of windings of the second output winding 3c is N2, and the relationship between N1 and N2 is N1 <N2. Two different output voltages V1 and V2 insulated from the input power supply 1 are obtained by controlling on / off of the switching element 4 composed of a MOSFET (field effect transistor) or the like by the control drive circuit 14. The first DC output 7 and the second DC output 8 are output. The DC outputs 7 and 8 are constituted by electrolytic capacitors, for example. The output voltage V1 and the output voltage V2 have a relationship of V1 <V2. When the switching element 4 is on, energy is stored in the transformer 3. When the switching element 4 is in the OFF state, the diodes 5 and 6 are conducted, and the energy accumulated in the transformer 3 is transmitted to the first DC output 7 and the second DC output 8, respectively.

  The feedback of the output voltage of the DC power supply device 2 is performed by the voltage detection means 13 using the resistance voltage dividing method or the like for the voltage V2 of the second DC output 8 that outputs an output voltage higher than the voltage V1 of the first DC output 7. The detection is performed by sending the detected output voltage signal to the control drive circuit 14. That is, of the two three-level single-phase output inverter bridges 9, 10, the voltage detection means 13 for detecting the input voltage of the three-level single-phase output inverter bridge having a high input voltage is provided. The output is fed back to the control drive circuit 14 which is a power supply control means of the DC power supply device, and the control drive circuit 14 controls the output voltage of the DC power supply device.

  The voltage V1 of the first DC output 7 that outputs a low output voltage is determined by the turn ratio between the first output winding 3b and the second output winding 3c of the transformer 3. Here, if feedback is performed with the voltage V2 of the second DC output 8, which is a high output voltage, the output voltage control error is output as a low output voltage as an error voltage reduced by the ratio of the transformer turns ratio N1 / N2. This only affects the voltage V1 of the first DC output 7. On the other hand, when the voltage V1 of the first DC output 7 that outputs a low output voltage is used for feedback, the control error of the output voltage is increased by the ratio of the turns ratio N2 / N1 of the transformer, and the second high output voltage. A large voltage error may occur in the voltage V2 of the DC output 8. For this reason, the feedback with the voltage V2 of the second DC output 8 which is a high output voltage can increase the output voltage accuracy.

  A first three-level single-phase output inverter bridge 9 capable of three-level output of + V1, 0, −V1 is connected to the first DC output 7, and + V2, 0, −V2 is connected to the second DC output 8. A second three-level single-phase output inverter bridge 10 capable of three-level output is connected. The output terminal of the first three-level single-phase output inverter bridge 9 that is two three-level single-phase output inverter bridges and the output terminal of the second three-level single-phase output inverter bridge 10 are connected in series and connected in series. A two-stage single-phase AC output power converter is configured.

  FIG. 2 shows a circuit diagram of a control device for two three-level single-phase output inverter bridges 9 and 10 constituting the power conversion device according to Embodiment 1 for carrying out the present invention. In FIG. 2, the first three-level single-phase output inverter bridge 9 includes switching elements 9a, 9b, 9c, and 9d such as MOSFETs (field effect transistors). 10 is constituted by switching elements 10a, 10b, 10c and 10d such as MOSFETs. The first drive circuit 21 controls on / off of the switching elements 9a to 9d, and the second drive circuit 22 controls on / off of the switching elements 10a to 10d. The first driving circuit and the second driving circuit perform on / off control in response to a driving signal from a control circuit 23 including a microcomputer, a digital signal processor, and the like.

  Between the output terminals 11 and 12 of the power converter in which the output terminal of the first three-level single-phase output inverter bridge 9 and the output terminal of the second three-level single-phase output inverter bridge 10 are connected in two stages in series. AC output voltage having a voltage effective value of and a desired output frequency is output. The control circuit 23 performs the first three-level single-phase output inverter bridge 9 and the second three-level single-phase output inverter every time when one cycle of the AC output voltage is equally divided by the division number 2n that is an even number of 14 or more. Inverter control means for switching the level of each output voltage of the bridge 10.

  The amplitude V1 of the output voltage of the first three-level single-phase output inverter bridge 9 and the second three-level single-phase output inverter so that the total harmonic distortion of the AC output voltage is not more than a predetermined value according to the number of divisions. The first three levels are set by setting the amplitude ratio of the output voltage of the bridge 10 to the amplitude V2 and receiving the drive signal from the control circuit 23 to control the switching elements 9a to 9d and 10a to 10d on and off. An AC output voltage in which the output voltage of the single-phase output inverter bridge 9 and the output voltage of the second three-level single-phase output inverter bridge 10 are superimposed can be obtained. The transformer 3 of the DC power supply device 2 outputs the outputs of the two three-level single-phase output inverter bridges 9 and 10 that are set so that the total harmonic distortion of the AC output voltage is a predetermined value or less according to the number of divisions. A voltage is supplied to each of the two three-level single-phase output inverter bridges 9 and 10 in accordance with the amplitude ratio between the amplitude V1 and the amplitude V2. That is, the amplitude ratio between the amplitude V1 and the amplitude V2 of the output voltage is set by the turns ratio of the transformer 3.

  By controlling the switching elements 9a to 9d and 10a to 10d for each equally divided time, the control by the control circuit 23 becomes very easy, and the processing load of the microcomputer, the digital signal processor, etc. can be reduced. 23 can be simplified.

  FIG. 3 is a waveform diagram showing the relationship between the AC output voltage and the switching sequence of the switching elements 9a to 9d and 10a to 10d in the first embodiment. FIG. 3A is a waveform diagram of an AC output voltage of a pseudo sine wave output having a desired voltage effective value and a desired output frequency output between the output terminals 11 and 12. One cycle of the desired AC output voltage is equally divided into 14, for example, equally divided every 1.4286 ms when the output frequency is 50 Hz, and equally divided every 1.1905 ms when the output frequency is 60 Hz. FIG. 3B is an example of an on / off signal for switching the switching elements 9a to 9d and 10a to 10d for obtaining an AC output voltage, where High is an on signal and Low is an off signal.

  The output voltages of the first three-level single-phase output inverter bridge 9 and the second three-level single-phase output inverter bridge 10 are switched by switching the switching elements 9a to 9d and 10a to 10d in FIG. The combination of three levels of +,-, and 0 is changed during one cycle of the AC output voltage (+ V1, 0), (-V1, + V2), (0, + V2), (+ V1, + V2), (0, + V2). ), (-V1, + V2), (+ V1, 0), (-V1, 0), (+ V1, -V2), (0, -V2), (-V1, -V2), (0, -V2) , (+ V1, -V2), (-V1, 0), and (+ V1, + V2) and (-V1, -V2) in the order of m times (m = n-6) Inverter control every time divided equally to become Switched by a drive signal from the control circuit 23 is stepped.

  In the first embodiment, the number of divisions 2n is 14, and n = 7. Therefore, the time corresponding to the combination of (+ V1, + V2) and (−V1, −V2) is equal to one time of equal division. Switching is performed by a drive signal from the control circuit 23 which is an inverter control means at every equally divided time. As a result, as shown in FIG. 3A, the output voltage is + V1, + V2-V1, + V2, + V1 + V2, + V2, + V2-V1, + V1, -V1, -V2 + V1, -V2, -V1 during one cycle. It changes to -V2, -V2, -V2 + V1, and -V1. When the voltage changes from + V1 to -V1 and from -V1 to + V1, it passes through the zero cross point of the voltage, and the zero cross point is uniquely determined and clearly determined. The present invention can also be applied to a load device using a zero cross point as a signal or a load device using phase control.

  FIG. 4 is a relationship diagram between the amplitude ratio (turn ratio K) and the total harmonic distortion of the AC output voltage in the first embodiment. The voltage ratio V2 / V1 between the voltage V1 of the first input power supply 1 and the voltage V2 of the second input power supply 2, that is, the first output winding N1 and the second output winding N2 of the transformer 3 The turn ratio K (= N2 / N1 = V2 / V1) is related to the total harmonic distortion THD of the AC output voltage as shown in FIG. There is a turns ratio K). The THD can be minimized by determining the amplitude ratio (turn ratio K) according to the equal number of divisions. In the prior art, V2 / V1 = 2. However, when the AC output voltage is equally divided into 14 as in the present embodiment, V2 / V1 = 2 does not minimize the THD, and V2 / V1 ≠ 2.

  FIG. 5 is a relationship diagram between the amplitude ratio (turn ratio K) and the magnitude of the fundamental wave component of the AC output voltage in the first embodiment. When the output frequency is 50 Hz, the fundamental wave component is a 50 Hz component. The fundamental wave component becomes maximum in the amplitude ratio (turn ratio K) at point B. The point B and the point A shown in FIG. 4 are the same, and can be uniquely determined for an equal number of divisions.

  FIG. 6 is a relationship diagram between the amplitude ratio (turn ratio K) and the standard deviation in the first embodiment. The standard deviation is obtained from the desired ideal sine wave output voltage and the output voltage obtained by this embodiment. The standard deviation is minimized in the amplitude ratio (turn ratio K) at the point C, and can be brought close to the ideal sine wave. The amplitude ratio (turn ratio K) at point C is the same value as point A in FIG. 4 and point B in FIG.

  The division number 2n is set so as to satisfy Expression (1) which is a conditional expression for matching the effective value of the pseudo sine wave output voltage and the effective value Vrms of the AC output voltage with respect to the effective value Vrms of the desired AC output voltage. By setting the amplitude V1 and the turns ratio K (= N2 / N1 = V2 / V1), an AC output voltage having a desired effective value Vrms can be easily obtained.

  In the first embodiment, the number of divisions 2n is 14, and n = 7. Therefore, the amplitude V1 and the amplitude V2 or the turn ratio are set so as to satisfy Expression (2) in which 7 is substituted for n in Expression (1). By setting K (= N2 / N1 = V2 / V1), an AC output voltage having a desired effective value Vrms can be easily obtained.

  In the case of equal division with the division number 14 as shown in FIG. 3A, the amplitude ratio (turn ratio K) at points A to C shown in FIGS. 4 to 6 is K = 4.0567. That is, V1: V2 = 1: 4.0567, and by setting the amplitude ratio (turn ratio K) to a value of about 4.1, the total harmonic distortion of the AC output voltage is minimized and the basic Wave components can be maximized. Practically, it is set in the vicinity of K = 4.0567. When an LC filter is provided at the output so as to be close to the ideal sine wave output, the waveform distortion is the smallest, so that the LC filter can be reduced in size and weight.

  Even if the total harmonic distortion of the AC output voltage is not minimized, the waveform distortion can be reduced as long as the total harmonic distortion of the AC output voltage is not more than a predetermined value. Thereby, the LC filter can be reduced in size and weight. When the specified value of the total harmonic distortion is the value obtained by adding + 1% to the minimum value of the total harmonic distortion, that is, when the distortion is allowed up to + 1% with respect to the minimum value of the total harmonic distortion The amplitude ratio (turn ratio K) may be set in the range of 3.35 ≦ K ≦ 5.14. When the specified value of the total harmonic distortion is added to the minimum value of the total harmonic distortion by + 2%, that is, when the distortion is allowed up to + 2% with respect to the minimum value of the total harmonic distortion. The amplitude ratio (turn ratio K) may be set in a range of 3.11 ≦ K ≦ 5.83. When the specified value of the total harmonic distortion is a value obtained by adding + 3% to the minimum value of the total harmonic distortion, that is, when + 3% is allowed with respect to the minimum value of the total harmonic distortion, the amplitude The ratio (turn ratio K) may be set in the range of 2.94 ≦ K ≦ 6.52. In the conventional technique, K = 2 and it can be seen that a completely different amplitude ratio (turn ratio K) is the optimum value.

  In the case of K = 4.0567 in which the total harmonic distortion of the AC output voltage is minimum and the fundamental wave component is maximum, the desired effective value Vrms of the AC output voltage and two stages of 3 are obtained from Equation (2). When the amplitude ratio with the amplitude V1 of the output voltage of the first three-level single-phase output inverter bridge 9 is Vrms: V1 = 1: 0.2973, the desired effective An alternating output voltage having the value Vrms is easily obtained. For example, V1 = 29.73V for effective value 100V output, V1 = 59.47V for effective value 200V output, V1 = 65.42V for effective value 220V output, and V1 = 71.36V for effective value 240V output. It is better to set.

  Further, when K = 4.0567 in which the total harmonic distortion of the output voltage is minimum and the fundamental wave component is maximum, the desired effective value Vrms of the AC output voltage and two-stage three-level single-phase output When the amplitude ratio with the amplitude V2 of the output voltage on the high voltage side in the inverter bridge is set to Vrms: V2 = 1: 1.2063, an output voltage having a desired effective value can be easily obtained. For example, V2 = 120.63V for effective value 100V output, V2 = 241.25V for effective value 200V output, V2 = 265.38V for effective value 220V output, and V2 = 289.50V for effective value 240V output. It is better to set.

  Furthermore, since the crest factor ((V1 + V2) / Vrms) of the AC output voltage is as shown in Equation (3), if the crest factor is 1.5036, the total harmonic distortion of the output voltage is minimized. Thus, K = 4.0567, which maximizes the fundamental wave component, can be obtained.

  As described above, the amplitude V1 and the amplitude V2 of the output voltage of each of the two three-level single-phase output inverter bridges set so that the total harmonic distortion factor of the AC output voltage is not more than a predetermined value according to the number of divisions. And a DC power supply device having a transformer for supplying a voltage to each of the two three-level single-phase output inverter bridges, and the amplitude ratio is set according to the turns ratio of the transformer. It is possible to obtain a power conversion device that can reduce the total harmonic distortion factor, increase the fundamental wave component, and reduce the size and weight of the output filter. Further, a desired effective value of the AC output voltage can be easily output, and the control of the power converter can be simplified. Furthermore, there is an effect that the zero cross point of the AC output voltage is clearly determined.

  In the first embodiment, the amplitude of each output voltage of the two-stage three-level single-phase output inverter bridges 9 and 10 is large, and the amplitude of the output voltage of the second three-level single-phase output inverter bridge 10 that is the upper stage is large. Explained the case. However, the amplitude of the output voltage of the first three-level single-phase output inverter bridge 9 in the lower stage may be large, and the upper three-level single-phase output inverter bridge and the lower three-level single-phase output inverter bridge are interchanged. The same effect can be obtained.

Embodiment 2. FIG.
FIG. 7 is a waveform diagram showing the relationship between the output voltage and the switching sequence of switching elements 9a to 9d and 10a to 10d in the second embodiment for carrying out the present invention. The power converter in the present embodiment has a configuration other than the number of divisions of one cycle of the AC output voltage and the combination of three levels of +, −, and 0 of the output voltages of each of the two three-level single-phase output inverter bridges. The same as in the first embodiment.

  In the second embodiment, a first three-level single-phase output inverter bridge 9 and a second three-level single-phase output inverter bridge 10 which are two three-level single-phase output inverter bridges to which different voltages are input, Every time when one cycle of the AC output voltage output by connecting the output terminals of the first three-level single-phase output inverter bridge 9 and the second three-level single-phase output inverter bridge 10 in series is equally divided by the division number 16 And a control circuit 23 which is inverter control means for switching the output voltage levels of the first three-level single-phase output inverter bridge 9 and the second three-level single-phase output inverter bridge 10.

  FIG. 7A is a waveform diagram of an AC output voltage of a pseudo sine wave output having a desired voltage effective value and a desired output frequency output between the output terminals 11 and 12. One cycle of the desired AC output voltage is equally divided into 16, for example, when the output frequency is 50 Hz, equally divided every 1.25 ms, and when the output frequency is 60 Hz, equally divided every 1.0417 ms. FIG. 7B is an example of an on / off signal for switching the switching elements 9a to 9d and 10a to 10d to obtain an AC output voltage, where High is an on signal and Low is an off signal.

  The output voltages of the first three-level single-phase output inverter bridge 9 and the second three-level single-phase output inverter bridge 10 are changed by switching the switching elements 9a to 9d and 10a to 10d in FIG. The combination of three levels of +,-, and 0 is changed during one cycle of the AC output voltage (+ V1, 0), (-V1, + V2), (0, + V2), (+ V1, + V2), (0, + V2). ), (-V1, + V2), (+ V1, 0), (-V1, 0), (+ V1, -V2), (0, -V2), (-V1, -V2), (0, -V2) , (+ V1, -V2), (-V1, 0), and (+ V1, + V2) and (-V1, -V2) in the order of m times (m = n-6) Inverter control every time divided equally to become Switched by a drive signal from the control circuit 23 is stepped.

  In the second embodiment, the number of divisions 2n is 16, and n = 8. Therefore, the time corresponding to the combination of (+ V1, + V2) and (−V1, −V2) is equal to two times of equal division. Switching is performed by a drive signal from the control circuit 23 which is an inverter control means at every equally divided time.

  As a result, as shown in FIG. 7A, the output voltage is + V1, + V2-V1, + V2, + V1 + V2, + V1 + V2, + V2, + V2-V1, + V1, -V1, -V2, -V2, -V2, It changes as -V1-V2, -V1-V2, -V2, -V2 + V1, -V1. When the voltage changes from + V1 to -V1 and from -V1 to + V1, it passes through the zero cross point of the voltage, and the zero cross point is uniquely determined and clearly determined.

  As in the first embodiment, the amplitude ratio between the amplitudes V1 and V2 of each output voltage in the first three-level single-phase output inverter bridge 9 and the second three-level single-phase output inverter bridge 10, that is, the turns ratio K ( = N2 / N1 = V2 / V1) is related to the total harmonic distortion factor THD of the AC output voltage, and there exists an amplitude ratio (turn ratio K) that can minimize THD as shown in point A in FIG. To do. By determining the amplitude ratio in the two-stage three-level single-phase output inverter bridge according to the equal number of divisions, that is, by determining the turn ratio K of the transformer 3, the THD is minimized. Further, there is an amplitude ratio (turn ratio K) at which the fundamental wave component is maximum as shown by point B in FIG. Furthermore, there is also a relationship with the standard deviation obtained from the desired ideal sine wave output voltage and the output voltage obtained by this embodiment, and the amplitude ratio (number of turns) at which the standard deviation as shown in FIG. The ratio K) exists. Point C is the same value as point A and point B.

  In the second embodiment, the number of divisions 2n is 16, and n = 8. Therefore, the amplitude V1 and the amplitude V2 or the turn ratio are set so as to satisfy Expression (4) in which 8 is substituted for n in Expression (1). By setting K (= N2 / N1 = V2 / V1), an AC output voltage having a desired effective value Vrms can be easily obtained.

  In the case of even division with the division number 16 as shown in FIG. 7A, the amplitude ratio (turn ratio K) at points A to C shown in FIGS. 4 to 6 is K = 3.8172. That is, V1: V2 = 1: 3.8172, and by setting the amplitude ratio (turn ratio K) to a value of about 3.8, the total harmonic distortion of the output voltage is minimized and the fundamental wave Ingredients can be maximized. Practically, it is set in the vicinity of K = 3.8172. When an LC filter is provided at the output so as to be close to the ideal sine wave output, the waveform distortion is the smallest, so that the LC filter can be reduced in size and weight most.

  Even if the total harmonic distortion of the AC output voltage is not minimized, the waveform distortion can be reduced as long as the total harmonic distortion of the AC output voltage is not more than a predetermined value. Thereby, the LC filter can be reduced in size and weight. When the specified value of the total harmonic distortion is the value obtained by adding + 1% to the minimum value of the total harmonic distortion, that is, when the distortion is allowed up to + 1% with respect to the minimum value of the total harmonic distortion The amplitude ratio (turn ratio K) may be set in a range of 3.17 ≦ K ≦ 4.76. When the specified value of the total harmonic distortion is added to the minimum value of the total harmonic distortion by + 2%, that is, when the distortion is allowed up to + 2% with respect to the minimum value of the total harmonic distortion. The amplitude ratio (turn ratio K) may be set in the range of 2.95 ≦ K ≦ 5.33. When the specified value of the total harmonic distortion is a value obtained by adding + 3% to the minimum value of the total harmonic distortion, that is, when + 3% is allowed with respect to the minimum value of the total harmonic distortion, the amplitude The ratio (turn ratio K) may be set in the range of 2.79 ≦ K ≦ 5.91. In the conventional technique, K = 2 and it can be seen that a completely different amplitude ratio (turn ratio K) is the optimum value.

  In the case of K = 3.8172 in which the total harmonic distortion of the AC output voltage is minimum and the fundamental wave component is maximum, the desired effective value Vrms of the AC output voltage and two stages of 3 are obtained from Equation (4). When the amplitude ratio with the amplitude V1 of the output voltage of the first three-level single-phase output inverter bridge 9 in this case is Vrms: V1 = 1: 0.2926, An alternating output voltage having the value Vrms is easily obtained. For example, V1 = 29.26V for effective value 100V output, V1 = 58.53V for effective value 200V output, V1 = 64.38V for effective value 220V output, and V1 = 70.23V for effective value 240V output. It is better to set.

  In the case of K = 3.8172 where the total harmonic distortion of the output voltage is minimum and the fundamental wave component is maximum, the desired effective value Vrms of the AC output voltage and the two-stage three-level single-phase output When the amplitude ratio of the output voltage on the high voltage side in the inverter bridge to the amplitude V2 is Vrms: V2 = 1: 1.1170, an output voltage having a desired effective value can be easily obtained. For example, V2 = 111.70V for an effective value 100V output, V2 = 223.40V for an effective value 200V output, V2 = 245.74V for an effective value 220V output, and V2 = 268.08V for an effective value 240V output. It is better to set. Therefore, the voltage of V2 can be lowered as compared with the case where the number of divisions is 14.

  Furthermore, since the crest factor of the AC output voltage is as shown in Equation (5), if the crest factor is 1.4096, the total harmonic distortion of the output voltage is minimized and the fundamental wave component is maximized. K = 3.8172 can be obtained.

  As described above, the amplitude V1 and the amplitude V2 of the output voltage of each of the two three-level single-phase output inverter bridges set so that the total harmonic distortion factor of the AC output voltage is not more than a predetermined value according to the number of divisions. And a DC power supply device having a transformer for supplying a voltage to each of the two three-level single-phase output inverter bridges, and the amplitude ratio is set according to the turns ratio of the transformer. It is possible to obtain a power conversion device that can reduce the total harmonic distortion factor, increase the fundamental wave component, and reduce the size and weight of the output filter. Further, a desired effective value of the AC output voltage can be easily output, and the control of the power converter can be simplified. Furthermore, there is an effect that the zero cross point of the AC output voltage is clearly determined.

  In the second embodiment, the amplitude of each output voltage of the two-stage three-level single-phase output inverter bridges 9 and 10 is large in the amplitude of the output voltage of the second three-level single-phase output inverter bridge 10 that is the upper stage. Explained the case. However, the amplitude of the output voltage of the first three-level single-phase output inverter bridge 9 in the lower stage may be large, and the upper three-level single-phase output inverter bridge and the lower three-level single-phase output inverter bridge are interchanged. The same effect can be obtained.

Embodiment 3 FIG.
FIG. 8 is a waveform diagram showing the relationship between the output voltage and the switch switching sequence of switching elements 9a to 9d and 10a to 10d in the third embodiment for carrying out the present invention. The power converter in the present embodiment has a configuration other than the number of divisions of one cycle of the AC output voltage and the combination of three levels of +, −, and 0 of the output voltages of each of the two three-level single-phase output inverter bridges. The same as in the first embodiment.

  In the third embodiment, a first three-level single-phase output inverter bridge 9 and a second three-level single-phase output inverter bridge 10 which are two three-level single-phase output inverter bridges to which different voltages are input, Every time when one cycle of the AC output voltage output by connecting the output terminals of the first three-level single-phase output inverter bridge 9 and the second three-level single-phase output inverter bridge 10 in series is equally divided by the division number 18 And a control circuit 23 which is inverter control means for switching the output voltage levels of the first three-level single-phase output inverter bridge 9 and the second three-level single-phase output inverter bridge 10.

  FIG. 8A is a waveform diagram of an AC output voltage of a pseudo sine wave output having a desired voltage effective value and a desired output frequency output between the output terminals 11 and 12. One cycle of the desired AC output voltage is equally divided into 18, for example, when the output frequency is 50 Hz, equally divided every 1.1111 ms, and when the output frequency is 60 Hz, equally divided every 0.9259 ms. FIG. 8B shows an example of an on / off signal for switching the switching elements 9a to 9d and 10a to 10d for obtaining an AC output voltage, where High is an on signal and Low is an off signal.

  The output voltages of the first three-level single-phase output inverter bridge 9 and the second three-level single-phase output inverter bridge 10 are changed by switching the switching elements 9a to 9d and 10a to 10d in FIG. The combination of three levels of +,-, and 0 is changed during one cycle of the AC output voltage (+ V1, 0), (-V1, + V2), (0, + V2), (+ V1, + V2), (0, + V2). ), (-V1, + V2), (+ V1, 0), (-V1, 0), (+ V1, -V2), (0, -V2), (-V1, -V2), (0, -V2) , (+ V1, -V2), (-V1, 0), and (+ V1, + V2) and (-V1, -V2) in the order of m times (m = n-6) Inverter control every time divided equally to become Switched by a drive signal from the control circuit 23 is stepped.

  In the third embodiment, since the number of divisions 2n is 18 and n = 9, the time corresponding to the combination of (+ V1, + V2) and (−V1, −V2) is equal to three times of equal division. Switching is performed by a drive signal from the control circuit 23 which is an inverter control means at every equally divided time.

  As a result, as shown in FIG. 8A, the output voltages are + V1, + V2-V1, + V2, + V1 + V2, + V1 + V2, + V1 + V2, + V2, + V2-V1, + V1, -V1, -V2 + V1, -V during one cycle. V2, -V1-V2, -V1-V2, -V1-V2, -V2, -V2 + V1, and -V1 change. When the voltage changes from + V1 to -V1 and from -V1 to + V1, it passes through the zero cross point of the voltage, and the zero cross point is uniquely determined and clearly determined.

  As in the first embodiment, the amplitude ratio between the amplitudes V1 and V2 of each output voltage in the first three-level single-phase output inverter bridge 9 and the second three-level single-phase output inverter bridge 10, that is, the turns ratio K ( = N2 / N1 = V2 / V1) is related to the total harmonic distortion factor THD of the AC output voltage, and there exists an amplitude ratio (turn ratio K) that can minimize THD as shown in point A in FIG. To do. By determining the amplitude ratio in the two-stage three-level single-phase output inverter bridge according to the equal number of divisions, that is, by determining the turn ratio K of the transformer 3, the THD is minimized. Further, there is an amplitude ratio (turn ratio K) at which the fundamental wave component is maximum as shown by point B in FIG. Furthermore, there is also a relationship with the standard deviation obtained from the desired ideal sine wave output voltage and the output voltage obtained by this embodiment, and the amplitude ratio (number of turns) at which the standard deviation as shown in FIG. The ratio K) exists. Point C is the same value as point A and point B.

  In the third embodiment, since the number of divisions 2n is 18 and n = 9, the amplitude V1 and the amplitude V2 or the turn ratio are set so as to satisfy Equation (6) in which 9 is substituted for n in Equation (1). By setting K (= N2 / N1 = V2 / V1), an AC output voltage having a desired effective value Vrms can be easily obtained.

  In the case of even division with 18 divisions as shown in FIG. 8A, the amplitude ratio (turn ratio K) at points A to C shown in FIGS. 4 to 6 is K = 3.5039. That is, V1: V2 = 1: 3.5039, and by setting the amplitude ratio (turn ratio K) to a value of about 3.5, the total harmonic distortion of the output voltage is minimized and the fundamental wave Ingredients can be maximized. Practically, it is set in the vicinity of K = 3.5039. When an LC filter is provided at the output so as to be close to the ideal sine wave output, the waveform distortion is the smallest, so that the LC filter can be reduced in size and weight most.

  Even if the total harmonic distortion of the AC output voltage is not minimized, the waveform distortion can be reduced as long as the total harmonic distortion of the AC output voltage is not more than a predetermined value. Thereby, the LC filter can be reduced in size and weight. When the specified value of the total harmonic distortion is the value obtained by adding + 1% to the minimum value of the total harmonic distortion, that is, when the distortion is allowed up to + 1% with respect to the minimum value of the total harmonic distortion The amplitude ratio (turn ratio K) may be set in the range of 2.92 ≦ K ≦ 4.32. When the specified value of the total harmonic distortion is added to the minimum value of the total harmonic distortion by + 2%, that is, when the distortion is allowed up to + 2% with respect to the minimum value of the total harmonic distortion. The amplitude ratio (turn ratio K) may be set in a range of 2.72 ≦ K ≦ 4.81. When the specified value of the total harmonic distortion is a value obtained by adding + 3% to the minimum value of the total harmonic distortion, that is, when + 3% is allowed with respect to the minimum value of the total harmonic distortion, the amplitude The ratio (turn ratio K) may be set in a range of 2.57 ≦ K ≦ 5.29. In the conventional technique, K = 2 and it can be seen that a completely different amplitude ratio (turn ratio K) is the optimum value.

  In the case of K = 3.5039, where the total harmonic distortion of the AC output voltage is minimum and the fundamental wave component is maximum, the desired effective value Vrms of the AC output voltage and two stages of 3 are obtained from Equation (6). When the amplitude ratio with the amplitude V1 of the output voltage of the first three-level single-phase output inverter bridge 9 is Vrms: V1 = 1: 0.3001, the desired effective An alternating output voltage having the value Vrms is easily obtained. For example, V1 = 30.01V for effective value 100V output, V1 = 60.01V for effective value 200V output, V1 = 66.02V for effective value 220V output, and V1 = 72.02V for effective value 240V output. It is better to set.

  When K = 3.5039, where the total harmonic distortion of the output voltage is minimum and the fundamental component is maximum, the desired effective value Vrms of the AC output voltage and two-stage three-level single-phase output When the amplitude ratio of the output voltage on the high voltage side in the inverter bridge to the amplitude V2 is Vrms: V2 = 1: 1.0514, an output voltage having a desired effective value can be easily obtained. For example, V2 = 105.14V for effective value 100V output, V2 = 210.29V for effective value 200V output, V2 = 231.32V for effective value 220V output, and V2 = 252.35V for effective value 240V output. It is better to set. Therefore, the voltage of V2 can be made lower than 14 divisions and 16 divisions.

  Furthermore, since the crest factor of the AC output voltage is as shown in Equation (7), if the crest factor is 1.3515, the total harmonic distortion of the output voltage is minimized and the fundamental wave component is maximized. K = 3.5039 can be obtained.

  As described above, the amplitude V1 and the amplitude V2 of the output voltage of each of the two three-level single-phase output inverter bridges set so that the total harmonic distortion factor of the AC output voltage is not more than a predetermined value according to the number of divisions. And a DC power supply device having a transformer for supplying a voltage to each of the two three-level single-phase output inverter bridges, and the amplitude ratio is set according to the turns ratio of the transformer. It is possible to obtain a power conversion device that can reduce the total harmonic distortion factor, increase the fundamental wave component, and reduce the size and weight of the output filter. Further, a desired effective value of the AC output voltage can be easily output, and the control of the power converter can be simplified. Furthermore, there is an effect that the zero cross point of the AC output voltage is clearly determined.

  In the third embodiment, the amplitude of each output voltage of the two-stage three-level single-phase output inverter bridges 9 and 10 is larger than the amplitude of the output voltage of the second three-level single-phase output inverter bridge 10 that is the upper stage. Explained the case. However, the amplitude of the output voltage of the first three-level single-phase output inverter bridge 9 in the lower stage may be large, and the upper three-level single-phase output inverter bridge and the lower three-level single-phase output inverter bridge are interchanged. The same effect can be obtained.

Embodiment 4 FIG.
In the third embodiment, the case where the number of divisions is 18 has been described. However, when the number of divisions is 20, the time of (+ V1, + V2) and (-V1, -V2) is divided into four equal divided times. Even if it does in this way, the same effect can be acquired.

  In the fourth embodiment, the number of divisions 2n is 20, and n = 10. Therefore, the amplitude V1 and the amplitude V2 or the transformer 3 are set so as to satisfy Expression (8) in which 10 is substituted for n in Expression (1). By setting the turn ratio K (= N2 / N1 = V2 / V1), an AC output voltage having a desired effective value Vrms can be easily obtained.

  In the case of even division with 20 divisions, the amplitude ratio (turn ratio K) is K = 3.2203, that is, V1: V2 = 1: 3.2203, and the amplitude ratio (turn ratio K) is 3. By setting the value to about 2, it is possible to minimize the total harmonic distortion of the output voltage and maximize the fundamental wave component. Practically, it is set in the vicinity of K = 3.2203. When an LC filter is provided at the output so as to be close to the ideal sine wave output, the waveform distortion is the smallest, so that the LC filter can be reduced in size and weight most.

  Even if the total harmonic distortion of the AC output voltage is not minimized, the waveform distortion can be reduced as long as the total harmonic distortion of the AC output voltage is not more than a predetermined value. Thereby, the LC filter can be reduced in size and weight. When the specified value of the total harmonic distortion is the value obtained by adding + 1% to the minimum value of the total harmonic distortion, that is, when the distortion is allowed up to + 1% with respect to the minimum value of the total harmonic distortion The amplitude ratio (turn ratio K) may be set in a range of 2.67 ≦ K ≦ 3.97. When the specified value of the total harmonic distortion is added to the minimum value of the total harmonic distortion by + 2%, that is, when the distortion is allowed up to + 2% with respect to the minimum value of the total harmonic distortion. The amplitude ratio (turn ratio K) may be set in a range of 2.48 ≦ K ≦ 4.43. When the specified value of the total harmonic distortion is a value obtained by adding + 3% to the minimum value of the total harmonic distortion, that is, when + 3% is allowed with respect to the minimum value of the total harmonic distortion, the amplitude The ratio (turn ratio K) may be set in a range of 2.33 ≦ K ≦ 4.86. In the conventional technique, K = 2 and it can be seen that a completely different amplitude ratio (turn ratio K) is the optimum value.

  As described above, the amplitude V1 and the amplitude V2 of the output voltage of each of the two three-level single-phase output inverter bridges set so that the total harmonic distortion factor of the AC output voltage is not more than a predetermined value according to the number of divisions. And a DC power supply device having a transformer for supplying a voltage to each of the two three-level single-phase output inverter bridges, and the amplitude ratio is set according to the turns ratio of the transformer. It is possible to obtain a power conversion device that can reduce the total harmonic distortion factor, increase the fundamental wave component, and reduce the size and weight of the output filter. Further, a desired effective value of the AC output voltage can be easily output, and the control of the power converter can be simplified. Furthermore, there is an effect that the zero cross point of the AC output voltage is clearly determined.

Embodiment 5. FIG.
Embodiments in which the number of divisions is 2n, and the times corresponding to the combinations of (+ V1, + V2) and (−V1, −V2) are equally divided into m times (m = n−6), respectively. The effect similar to 1-4 can be acquired.

  With the number of divisions being 2n, the amplitude V1 and the amplitude V2 or the turn ratio K of the transformer 3 so as to satisfy the formula (1) with respect to the effective value Vrms of the desired AC output voltage (= N2 / N1 = V2 / V1) By setting these, an AC output voltage having a desired effective value Vrms can be easily obtained. In the case where the number of divisions is evenly divided, in order to minimize the total harmonic distortion of the output voltage and maximize the fundamental wave component, the amplitude ratio K is close to a value satisfying Equation (9). If it is in.

  By setting the turns ratio K to satisfy Equation (9), the total harmonic distortion of the AC output voltage can be minimized and the fundamental component can be maximized, so an LC filter is provided at the output. Thus, when approaching the ideal sine wave output, the LC filter can be most reduced in size and weight. Even if the total harmonic distortion of the AC output voltage is not minimized, the waveform distortion can be reduced as long as the total harmonic distortion of the AC output voltage is not more than a predetermined value. As in the first to fourth embodiments, a value of + 1%, + 2%, or + 3% is added to the minimum value of the total harmonic distortion factor to set a predetermined value of the total harmonic distortion factor, and accordingly The winding ratio K may be set.

  As described above, the amplitude V1 and the amplitude V2 of the output voltage of each of the two three-level single-phase output inverter bridges set so that the total harmonic distortion factor of the AC output voltage is not more than a predetermined value according to the number of divisions. And a DC power supply device having a transformer for supplying a voltage to each of the two three-level single-phase output inverter bridges, and the amplitude ratio is set according to the turns ratio of the transformer. It is possible to obtain a power conversion device that can reduce the total harmonic distortion factor, increase the fundamental wave component, and reduce the size and weight of the output filter. Further, a desired effective value of the AC output voltage can be easily output, and the control of the power converter can be simplified. Furthermore, there is an effect that the zero cross point of the AC output voltage is clearly determined.

Embodiment 6 FIG.
FIG. 9 shows a configuration diagram of the power conversion device according to the sixth embodiment for carrying out the present invention. In FIG. 9, a solar cell (PV) 15 is connected to the input power source 1 via a charging circuit 16. The charging circuit 16 includes a diode 17 and a switching element 18. The generated power from the solar cell 15 is charged into the input power source 1 composed of a battery, an electric double layer capacitor and the like via the diode 17. When the input power supply 1 is in a fully charged state, the switching element 18 is turned on to prevent overcharging, and the generated power from the solar cell 15 is returned.

  In the first to fifth embodiments, a DC power supply device that supplies two different output voltages V1 and V2 that are insulated from an input power source 1 such as a battery that can be applied to an inverter mounted on a car or an inverter for outdoor use is provided. Showed about. In the sixth embodiment, the photovoltaic cell (PV) 15 may be a non-electrification photovoltaic power generation system or an independent photovoltaic power generation system that serves as an energy supply source, and the same effects as in the first to fifth embodiments are obtained. can get.

It is a block diagram of the power converter device which shows Embodiment 1 of this invention. It is a circuit diagram of the control apparatus of two 3 level single phase output inverter bridges in Embodiment 1 of this invention. It is a wave form diagram which shows the relationship between the alternating current output voltage in Embodiment 1 of this invention, and the switch switching sequence of a switching element. FIG. 3 is a relationship diagram between an amplitude ratio and a total harmonic distortion factor of an AC output voltage in Embodiment 1 of the present invention. It is a relationship diagram between the amplitude ratio in Embodiment 1 of this invention and the magnitude | size of the fundamental wave component of alternating current output voltage. FIG. 5 is a relationship diagram between an amplitude ratio and a standard deviation according to Embodiment 1 of the present invention. It is a wave form diagram which shows the relationship between the alternating current output voltage in Embodiment 2 of this invention, and the switch switching sequence of a switching element. It is a wave form diagram which shows the relationship between the alternating current output voltage in Embodiment 3 of this invention, and the switch switching sequence of a switching element. It is a block diagram of the power converter device which shows Embodiment 6 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Input power supply, 2 DC power supply device, 3 Transformer, 4, 9a-9d, 10a-10d, 18 Switching element, 5, 6, 17 Diode, 7 1st direct current output, 8 2nd direct current output, 9, 10 Three-level single-phase inverter bridge, 11, 12 output terminal, 13 voltage detection means, 14 control drive circuit, 15 solar cell, 16 charging circuit, 21 first drive circuit, 22 second drive circuit, 23 control circuit.

Claims (9)

Two 3-level single-phase output inverter bridges to which different voltages are input;
The two three-level single-phase output inverter bridges are connected in series with each other by dividing one cycle of an AC output voltage output in series by an even number of divisions 2n that is an even number of 14 or more. Inverter control means for switching the level of the output voltage of the level single-phase output inverter bridge;
According to the number of divisions, the output voltage amplitude V1 and amplitude V2 of each of the two three-level single-phase output inverter bridges set so that the total harmonic distortion factor of the AC output voltage is a predetermined value or less. And a DC power supply having a transformer for supplying a voltage to each of the two three-level single-phase output inverter bridges according to an amplitude ratio, wherein the amplitude ratio is set according to a turns ratio of the transformer. Power conversion device. Among the two three-level single-phase output inverter bridges, voltage detection means for detecting the input voltage of the three-level single-phase output inverter bridge having a high input voltage is provided, and the detected value of the voltage detection means is used for power control of the DC power supply device. The power converter according to claim 1, wherein the output voltage of the DC power supply device is controlled by the power supply control means. The combination of the three levels of the output voltage of each of the two three-level single-phase output inverter bridges, that is, +, −, and 0 is (+ V1, 0), (−V1, + V2) during one cycle of the AC output voltage, (0, + V2), (+ V1, + V2), (0, + V2), (−V1, + V2), (+ V1, 0), (−V1, 0), (+ V1, −V2), (0, −V2) ), (−V1, −V2), (0, −V2), (+ V1, −V2), (−V1, 0), and (+ V1, + V2) and (−V1, −V2) 3. The inverter control means switches over each of the equally divided times so as to be m times (m = n−6) of the equally divided times for each combination time. The power converter described. 4. The power conversion apparatus according to claim 3, wherein the amplitude V1 and the amplitude ratio K (= V2 / V1) are set so as to satisfy the expression (1) with respect to an effective value Vrms of a desired AC output voltage.

5. The power converter according to claim 4, wherein when the number of divisions 2n is 14, the amplitude ratio K is in the range of 2.94 to 6.52. The power converter according to claim 4, wherein when the number of divisions 2n is 16, the amplitude ratio K is in the range of 2.79 or more and 5.91 or less. 5. The power converter according to claim 4, wherein when the number of divisions 2n is 18, the amplitude ratio K is in a range of 2.57 to 5.29. 5. The power converter according to claim 4, wherein when the number of divisions 2n is 20, the amplitude ratio K is in the range of 2.33 to 4.86. The power conversion apparatus according to claim 4, wherein the amplitude ratio K is a value in the vicinity of a value derived from the expression (2).

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