JP2011004464A - Power conversion equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase system power generation efficiency by bringing out the maximum power generation capability in each of the positive and negative DC power supplies even if a power generation capability differs between the positive and negative DC power supplies.SOLUTION: A neutral point clamping system inverter 5 (NPC inverter) is used as an inverter for converting a DC power to an AC, and the neutral point of the NPC inverter 5 is connected to that of a positive-side DC power supply 1P and a negative-side DC power supply 1N that are connected in series. Then, the NPC inverter 5 controls a sharing ratio of positive and negative powers of a DC circuit.

Description

  The present invention relates to a power conversion device that converts direct current power such as solar power generation, thermal power generation, or a fuel cell into alternating current power, and in particular, a neutral point clamp method suitable for realizing a large capacity, high efficiency power system. The present invention relates to a power conversion device using a three-level inverter.

  As shown in a conventional solar power conditioner, a distributed power source output such as a solar cell is boosted by a booster circuit, and an AC voltage output is generated by an inverter (see, for example, Non-Patent Document 1). Such a method of boosting is generally used, but when the boosting rate is increased, there is a problem that power loss due to switching elements and diodes of the booster circuit is increased, and the efficiency of the entire power conditioner is reduced.

  In recent years, large-capacity solar power generation has also become widespread, and a system that directly supplies a solar cell output to an inverter without a booster circuit has been commercialized (for example, Non-Patent Documents 2 and 3). reference).

“Development of Solar Power Conditioner Type KP40F” OMRON TECHNICS, Vol.42, No.2 (Vol.142), 2002 "Design considerations for three-phase grid connected photovoltaic inverters" Photovoltaic Specialists Conference, 2002. Conference Record of the Twenty-Ninth IEEE, 19-24 May 2002, Page: 1396-1401 Xantrex Manual “GT100E 100 kW Grid-Tied Photovoltaic Inverter-Planning and Installation Manual” Page: 2-5

  One of the key points for high capacity and high efficiency is to increase the voltage of the power supply by increasing the number of DC power modules connected in series such as solar battery panels. However, when the DC power supply modules are connected in series, the current is suppressed to be equal to or lower than the power supply current having the smaller output possible current, or the power supply having the smaller output possible current is bypassed with a diode. The former lowers the output of the power supply with the higher current output capability, and the latter sets the power supply output with the lower current output capability to zero. In either case, when power supplies are connected in series, there is a problem that the output capability of the power supply cannot be fully utilized.

  In addition, for the purpose of expanding the power generation possible voltage range, the method of boosting only when the voltage of the DC power supply is low has a problem that the circuit becomes complicated and the control becomes complicated.

  Furthermore, even if the DC circuit is planned to have a higher voltage for higher capacity and higher efficiency, the current withstand voltage of the solar cell panel is about 600 V, and there is a limit to increasing the voltage of the power source. It is a hindrance.

  The present invention has been made to solve the above-described problems. Even when the power generation capacities of the positive and negative DC power supplies are different, the maximum power generation capacities of the positive and negative DC power supplies can be extracted, thereby improving the system power generation efficiency. An object of the present invention is to provide a power conversion device that can be realized.

  In order to achieve the above object, the present invention uses a neutral point clamp type inverter (hereinafter simply referred to as an NPC inverter) as an inverter that converts DC power into AC, and is connected in series with the neutral point of the inverter. The configuration is such that the neutral point of the power supply is connected, and then the share ratio of the positive and negative power of the DC circuit is controlled by the NPC inverter.

  Even in a device including a booster circuit, a backflow prevention diode connected in series with the DC power supply is bypassed so that the loss when supplying the inverter directly from the DC power supply does not increase compared to the case without the booster circuit. Used as a circuit.

  Further, by grounding the neutral point of the DC power supply connected in series, a high voltage DC power supply that is about twice the power supply module withstand voltage is realized while ensuring the withstand voltage of the power supply.

  According to the present invention, since the NPC inverter can control the positive and negative power sharing of the DC circuit, even when the power generation capacities of the positive and negative DC power sources are different, the maximum power generation capacities of the positive and negative DC power sources can be extracted. become. As a result, the system power generation efficiency can be improved.

  Since the voltage ripple on the AC side is increased by increasing the voltage of the DC circuit, an AC filter with a large smoothing power is required. However, in the present invention, an NPC inverter capable of outputting three levels is used as the inverter, so the output voltage step The amount of change can be reduced to half of the DC voltage, and the AC filter can be reduced.

  In addition, in a device having a booster circuit, the backflow prevention diode is used as a bypass circuit of the booster circuit, so that the booster operation of the booster circuit is stopped when the DC power supply voltage is high, and the output current of the DC power supply is reduced. And supplied to the inverter. In this state, there is no booster circuit, and it is almost the same energized state as when directly supplying DC power output to the inverter, there is no increase in loss due to the provision of the booster circuit, high efficiency operation can be realized, and the booster circuit is bypassed This eliminates the need for complicated circuits and control.

  Further, by grounding the neutral point of the distributed power supply, the DC circuit voltage can be used up to a positive / negative withstand voltage range. That is, a DC power supply voltage that is twice the distributed power supply withstand voltage can be obtained, and the inverter output can also obtain a high-voltage AC. Moreover, the voltage drop of the semiconductor switch which comprises an inverter can be made relatively small by making high voltage, and high efficiency can be implement | achieved. Moreover, since the alternating current can be made relatively small by increasing the pressure on the alternating current side, the copper loss can be reduced. Of course, since a high voltage is possible, a large-capacity system can be easily realized.

It is a circuit block diagram which shows 1st Embodiment of the power converter device by this invention. It is a connection diagram which shows the structural example of the three-phase circuit of the NPC inverter used by this invention. It is a connection diagram which shows the structural example of the single phase circuit of the NPC inverter used by this invention. It is a circuit block diagram which shows 2nd Embodiment of the power converter device by this invention. It is a circuit block diagram which shows 3rd Embodiment of the power converter device by this invention. It is a circuit block diagram equivalent to FIG. 3 which shows the other example in 3rd Embodiment. It is a circuit block diagram which shows 4th Embodiment of the power converter device by this invention. It is a circuit block diagram which shows the other example in 4th Embodiment. It is a circuit block diagram which shows the further another example in 4th Embodiment. It is a circuit block diagram which shows 5th Embodiment of the power converter device by this invention. It is a circuit block diagram equivalent to FIG. 10 which shows the other example in 5th Embodiment. It is a circuit block diagram which shows 6th Embodiment of the power converter device by this invention. It is a circuit block diagram which shows 7th Embodiment of the power converter device by this invention. It is a circuit block diagram which shows 8th Embodiment of the power converter device by this invention. It is a circuit block diagram which shows 9th Embodiment of the power converter device by this invention. It is a circuit block diagram which shows 10th Embodiment of the power converter device by this invention. It is a circuit block diagram which shows 11th Embodiment of the power converter device by this invention. It is a circuit block diagram which shows 12th Embodiment of the power converter device by this invention. It is a circuit block diagram which shows 13th Embodiment of the power converter device by this invention. It is a circuit block diagram which shows 14th Embodiment of the power converter device by this invention. It is a circuit block diagram which shows 15th Embodiment of the power converter device by this invention. It is a circuit block diagram which shows 16th Embodiment of the power converter device by this invention. It is a circuit block diagram which shows 17th Embodiment of the power converter device by this invention. It is a model figure of the reactor couple | bonded magnetically. It is a circuit block diagram which shows 18th Embodiment of the power converter device by this invention. It is a circuit block diagram which shows 19th Embodiment of the power converter device by this invention. It is a connection diagram which shows the circuit structural example which shows the electricity supply state of an NPC inverter. It is explanatory drawing of the instantaneous waveform which shows the relationship between the output voltage of a NPC inverter, and DC circuit power. It is a figure which shows the characteristic of positive / negative DC power when the output voltage of an NPC inverter is biased. It is a characteristic view which shows the example of electric power generation of a solar panel. It is an equivalent model figure which shows the 1st example for demonstrating that a positive / negative power supply can be controlled independently by this invention. It is an equivalent model figure which shows the 2nd example for demonstrating that a positive / negative power supply can be controlled independently by this invention. It is an equivalent model figure which shows the 3rd example for demonstrating that a positive / negative power supply can be controlled independently by this invention. It is an equivalent model figure which shows the 4th example for demonstrating that a positive / negative power supply can be controlled independently by this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a circuit configuration diagram showing a first embodiment of a power converter according to the present invention.

  In FIG. 1, 1P and 1N are positive and negative DC power sources such as solar panels, and 2P and 2N are provided in series with DC power sources 1P and 1N, respectively, to prevent current from flowing back to DC power sources 1P and 1N. Therefore, they constitute a DC power supply module.

  4P and 4N are positive and negative smoothing capacitors that smooth the DC outputs of the DC power supplies 1P and 1N, and 5 is a single unit that converts the DC smoothed by the smoothing capacitors 4P and 4N into AC power and supplies it to the load or the power system 6. It is a phase or multiphase NPC inverter.

  Here, the neutral point of the positive side and negative side DC power supplies 1P and 1N, the neutral point of the smoothing capacitors 4P and 4N, and the neutral point of the NPC inverter 5 are respectively connected to the positive side and negative side DC. The power supplies 1P and 1N output positive voltages upward in the figure, respectively.

  In the above configuration, even if the positional relationship between the positive side DC power supply 1P and the backflow prevention diode 2P and the negative side DC power supply 1N and the backflow prevention diode 2N are switched, that is, the backflow prevention diodes 2P and 2N are provided on the neutral point side, It is clear that the circuit operation does not change.

  2 and 3 are connection diagrams showing configuration examples of a three-phase circuit and a single-phase circuit of the NPC inverter 5 used in the present invention.

  The NPC inverter 5 shown in FIG. 2 and FIG. 3 has a feature of being capable of outputting a high voltage and having low output voltage harmonics, and has a well-known circuit configuration widely used for motor drive applications. Also, the output voltages of the DC power supplies 1P and 1N are input to the NPC inverter 5 to the positive and negative buses P and N and the neutral point bus 0 via the smoothing capacitors 4P and 4N.

  This NPC inverter 5 has a basic configuration part in which four switching elements S1 to S4 are connected in series, and a connection point between S1 and S2 and a connection point between S3 and S4 are connected via clamp diodes Dp and Dn. The basic components 51, 52 and 53 are called legs. The only difference between the three-phase and single-phase is the difference in the number of legs. A series circuit of the switching elements S1 to S4 is connected to the positive and negative buses P and N, and a connection point of the two clamp diodes Dp and Dn is connected to the neutral point bus 0.

  In this embodiment, as shown in FIG. 2 and FIG. 3, the neutral point of the power source, the smoothing capacitor, and the NPC inverter 5 is connected. Can be driven.

  The NPC inverter 5 is one of the features that can control the ratio of the positive side DC power Pp and the negative side DC power Pn. By using this feature, the currents of the positive and negative power sources 1P and 1N can be independently supplied. Can be controlled. As a result, even when there is a difference in power generation capacity between the positive and negative power supplies 1P and 1N, it is possible to operate at each maximum power generation capacity point. By controlling in this way, the system power generation efficiency is improved.

  The ratio control between the positive side DC power Pp and the negative side DC power Pn by the NPC inverter and the effect thereof will be described in detail at the end, including the configuration of other embodiments.

(Second Embodiment)
FIG. 4 is a circuit configuration diagram showing a second embodiment of the power conversion device according to the present invention, which is a configuration when a plurality of DC power supply modules are connected in parallel. The same parts as those of the power converter of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and detailed description of the overlapping parts is omitted.

  In the second embodiment, as shown in FIG. 4, two sets of direct currents comprising a series circuit of backflow prevention diodes 2Pa and 2Na, DC power supplies 1Pa and 1Na, and backflow prevention diodes 2Pb and 2Nb, and a series circuit of DC power supplies 1Pb and 1Nb. The power supply modules are connected in parallel and the neutral points of both DC power supply modules are grounded.

  When a plurality of DC power supply modules are connected in parallel in this way, a reverse current prevention diode is required for each DC power supply module in order to prevent backflow from flowing to a low voltage power supply due to voltage imbalance between the parallel power supplies. Become.

  Since the output currents of these two sets of DC power supply modules are combined and supplied to the NPC inverter 5 side, it is clear that the current capacity as a power supply increases.

  Although FIG. 4 shows the case where the number of DC power supply modules is 2, there is no upper limit to the number of parallel modules, and the power supply capacity can be increased by increasing the number of modules.

  When a plurality of DC power supply modules are connected in parallel as described above, the voltages of the DC power supply modules are equal to each other, so that each DC power supply connected in parallel cannot be operated at the maximum power point. However, the ratio of the positive and negative powers Pp and Pn can be controlled by the NPC inverter 5 and can be operated at the maximum power point as the positive side parallel power source and the maximum power point as the negative side parallel power source.

  Therefore, even when the power generation capacities of the positive and negative DC power supplies connected in parallel are different, the maximum power generation capacities of the positive and negative DC power supplies can be derived, thereby improving the system power generation efficiency. be able to.

(Third embodiment)
FIG. 5 is a circuit configuration diagram showing a third embodiment of the power conversion apparatus according to the present invention. The same parts as those in FIG.

  In the third embodiment, as shown in FIG. 5, the reactor Lc, the positive-side and negative-side DC power supplies 1 </ b> P and 1 </ b> N connected in series with the backflow prevention diodes 2 </ b> P and 2 </ b> N are connected to the neutral point, respectively. A known booster circuit 7 composed of a switch Sc and a chopper diode Dc is added.

  Here, the booster circuit 7 boosts the voltage Vs across the positive and negative DC power supplies 1P and 1N, and supplies the boosted voltage to the NPC inverter 5 side.

  In FIG. 5, when the switch Sc of the booster circuit 7 is OFF, the output current Is of the DC power supplies 1P and 1N is generated from the backflow prevention diode 2P and the series circuit of the reactor Lc and the chopper diode Dc of the booster circuit 7. To the inverter 5 side. However, because of the resistance of the reactor Lc, most of the DC power supply current Is flows on the backflow prevention diode 2P side. At this time, the backflow prevention diode 2P becomes a bypass circuit of the booster circuit 7.

  If the DC voltage Vd on the NPC inverter 5 side becomes higher than the voltage sum Vs of the positive side, negative side DC power supplies 1P and 1N when the switch Sc of the booster circuit 7 is turned on and off, the DC power supply current Is is increased. Flows through the booster circuit 7 and does not flow through the backflow prevention diode 2P.

  As described above, the current path of the DC power supply is controlled by the control of the switch Sc of the booster circuit 7, and when the booster circuit 7 is stopped, the backflow prevention diode 2P is used as a bypass circuit of the booster circuit 7. The current path when the booster circuit 7 is stopped is almost the same as in FIG. 1, and there is no increase in loss due to the addition of the booster circuit 7.

  Thus, even when boosting is performed by the booster circuit 7, the ratio of the positive and negative powers Pp and Pn is controlled by the NPC inverter 5, and the positive and negative power supplies 1P and 1N can be operated at the maximum power point. Details thereof will be described after the configuration of each embodiment is described.

  Now, the loss when the switch Sc of the booster circuit 7 is turned off and the DC power supply current Is is divided into the backflow prevention diode 2P and the series circuit of the reactor Lc and the chopper diode Dc of the booster circuit 7 will be described.

  When the current of the backflow prevention diode 2P is Idb, the electric current Ic on the booster circuit side is Is-Idb. If the voltage drop of the backflow prevention diode 2P when Idb flows is Vdb (Idb), the loss Pdb of the backflow prevention diode 2P is expressed by the following equation.

Pdb = Vdb (Idb) · Idb (1)
Since the voltage drop of the series circuit of the reactor Lc and the chopper diode Dc is also Vdb (Idb), the loss Pc of the series circuit is expressed by the following equation.

Pc = Vdb (Idb) .Ic = Vdb (Idb). (Is-Idb) (2)
The loss sum of both circuits is as follows.

Pdb + Pc = Vdb (Idb) * Idb + Vdb (Idb) * (Is-Idb)
= Vdb (Idb) ・ Is (3)
Since Idb is smaller than Is, the voltage Vdb (Idb) of the backflow prevention diode 2P is smaller than the voltage Vdb (Is) when all Is flows through the backflow prevention diode 2P. That is, the loss Pdb + Pc in the equation (3) indicates that the DC power supply current Is is less than the loss Vdb (Is) · Is when all of the DC power supply current Is flows through the backflow prevention diode 2P. Actually, since most of Is flows through the backflow prevention diode 2P, the loss is slightly smaller than the loss when all Is flows through the backflow prevention diode 2P.

  There is no backflow prevention diode 2P, and when compared with the loss when all the DC power supply current Is flows through the series circuit of the reactor Lc and the chopper diode Dc, the loss is reduced by at least the loss of the reactor Lc.

  Since the loss of the switch Sc is further added when boosting by the booster circuit 7, the boosting operation of the booster circuit 7 is stopped when the DC power supply voltage Vs is high so that most of the current flows through the backflow prevention diode 2P. Thus, the loss can be greatly reduced compared with the case where the booster circuit 7 is always operated, and high efficiency can be realized.

  Further, when the DC power supply voltage Vs is low, the voltage needs to be boosted by the booster circuit 7. However, when the DC power supply is a solar panel, the voltage is low when the amount of solar radiation is small and the amount of power generation is small. It is. In such a case, since the current Is is small, the current rating of the booster circuit 7 that operates only when the amount of power generation is small may be small, and a small and low-cost booster circuit can be obtained. Further, since the current is small, the loss is small.

  FIG. 6 is a circuit configuration diagram showing a modification of the third embodiment, and only the parts different from FIG. 5 will be described here.

  In FIG. 6, the switch Sc and the chopper diode Dc in the booster circuit 7 shown in FIG. 5 are replaced, and the chopper diode Dc is connected in parallel with the negative side backflow prevention diode 2N. In this case, when the booster circuit 7 is stopped, the negative side backflow prevention diode 2N becomes a bypass circuit of the booster circuit 7, and it goes without saying that the operation and effect are exactly the same as those in FIG.

(Fourth embodiment)
FIGS. 7 to 9 are circuit configuration diagrams showing a fourth embodiment of the power conversion device according to the present invention. The same parts as those in FIG. 5 are denoted by the same reference numerals, and detailed description of the overlapping parts is omitted.

  FIG. 7 is a circuit configuration diagram when DC power supplies including a plurality of booster circuits are connected in parallel.

  As shown in FIG. 7, two circuit modules comprising backflow prevention diodes 2Pa and 2Na (2Pb and 2Nb) and booster circuit 7a (7b) corresponding to positive and negative DC power supplies 1Pa and 1Na (1Pb and 1Nb) are provided, as in FIG. This is a configuration in which a DC output circuit to the NPC inverter 5 side is connected in parallel. In this case, it is obvious that the output currents of the two sets of circuit modules are combined and supplied to the NPC inverter 5 side.

  Although FIG. 7 shows the case where the number of parallel circuit modules is 2, there is no upper limit to the number of parallel modules. FIG. 7 shows each parallel module in the configuration shown in FIG. 5, but all or some of the modules may have the configuration shown in FIG.

  Further, the start / stop timing control of the boosting operation of the boosting circuits 7a and 7b can be performed independently for each module, or all modules can be performed simultaneously.

  With such a configuration, a configuration suitable for realizing a large capacity can be achieved by parallel connection of a plurality of DC power supply modules and a booster circuit.

  FIG. 8 is a diagram illustrating another circuit configuration example according to the fourth embodiment.

  As shown in FIG. 8, two series of positive and negative DC power supplies 1Pa and 1Na (1Pb and 1Nb) and backflow prevention diodes 2Pa and 2Na (2Pb and 2Nb) are connected in parallel.

  Then, the voltage at both ends of the two sets of positive and negative DC power supplies 1Pa, 1Na and 1Pb, 1Nb arranged on the neutral point side is boosted via the booster circuit backflow prevention diodes 8Pa, 8Pb, 8Na and 8Nb, respectively. 7 is connected to both ends of the reactor Lc and the switch Sc. That is, only one booster circuit 7 is provided for two DC power supply modules.

  The backflow prevention diodes 8Pa, 8Pb, 8Na and 8Nb for the booster circuit are used when the output voltage between the positive DC power supplies 1Pa and 1Pb connected in parallel or between the negative DC power supplies 1Na and 1Nb is different. It is provided to prevent the current from flowing backward.

  In such a circuit configuration, when the switch Sc of the booster circuit 7 is OFF, most of the DC power supply current flows through the backflow prevention diodes 2Pa and 2Pb. When the voltage is boosted by the booster circuit 7 and the capacitor voltage Vd is higher than the voltage of the DC power supply, the current flows through the booster circuit 7, the reverse voltage is applied to the backflow prevention diodes 2Pa and 2Pb, and no current flows.

  Although FIG. 8 shows the case where the number of parallel power supply modules is 2, there is no upper limit to the number of parallel modules, and the power supply capacity can be increased by increasing the number of power supply modules. 8 shows the DC power supply and the booster circuit with the configuration shown in FIG. 5, the DC power supply and the booster circuit may be configured as shown in FIG.

  Such a configuration can also be a configuration suitable for realizing a large capacity by parallel connection of a plurality of DC power supply modules and a booster circuit.

  FIG. 9 is a diagram illustrating another example of another circuit configuration according to the fourth embodiment.

  In this example, as shown in FIG. 9, two series of positive and negative DC power supplies 1Pa and 1Na (1Pb and 1Nb) and backflow prevention diodes 2Pa and 2Na (2Pb and 2Nb) are connected in parallel, The voltage at both ends of the two sets of positive and negative DC power supplies 1Pa, 1Na and 1Pb, 1Nb arranged via the booster circuit backflow prevention diodes 8Pa, 8Pb, 8Na and 8Nb, respectively, and the reactor Lc of the booster circuit 7a and the switch Sc Are connected to both ends in the same manner as in FIG.

  In FIG. 9, two series of positive and negative DC power supplies 1Pc and 1Nc (1Pd and 1Nd) and backflow prevention diodes 2Pc and 2Nc (2Pd and 2Nd) are connected in parallel and arranged on the neutral point side. The voltages at both ends of the two positive and negative DC power supplies 1Pc, 1Nc and 1Pd, 1Nd thus generated are connected to the reactor Lc of the booster circuit 7b and the switch Sc via the booster circuit backflow prevention diodes 8Pc, 8Pd, 8Nc and 8Nd, respectively. A circuit connected to both ends is added.

  In this example, a circuit group having a basic unit of a parallel circuit of a plurality of DC power supplies and one booster circuit is combined, and the operation and effect are the same as those in FIG.

  Although FIG. 9 shows the case where the number of parallel power supply modules is 2, there is no upper limit to the number of parallel modules, and a single power supply may be used. Further, there is no limit on the number of booster circuits, and the power supply capacity can be increased by increasing the number of power supply modules and the number of booster circuits.

(Fifth embodiment)
FIG. 10 is a circuit configuration diagram showing a fifth embodiment of the power conversion apparatus according to the present invention. The same parts as those in FIG.

  In FIG. 5, the input voltage to the booster circuit 7 is the voltage sum of the positive side and negative side DC power supplies 1P and 1N, whereas in the fifth embodiment, as shown in FIG. And the voltage sum of the negative side DC power source 1N including the backflow prevention diode 2N is boosted.

  Even in such a configuration, the basic circuit operation, operation, and effect are the same as in FIG.

  In the above description, the negative-side backflow prevention diode 2N is provided on the side opposite to the neutral point. However, the same applies when the negative-side backflow prevention diode 2N is provided on the neutral point side.

  FIG. 11 is a diagram illustrating another circuit configuration example according to the fifth embodiment.

  In this example, as shown in FIG. 11, the switch Sc and the chopper diode Dc in the booster circuit 7 of FIG. 10 are replaced, and the chopper diode Dc is connected in parallel with the negative side backflow prevention diode 2N. is there. In this case, when the booster circuit 7 is stopped, the negative-side backflow prevention diode 2N becomes a bypass circuit of the booster circuit, and the same operation and effect as in FIG. 10 can be obtained.

  10 and FIG. 11 can be easily understood by those skilled in the art that both circuits are equivalent, as in the relationship between FIG. 5 and FIG. 6 showing the third embodiment. Is also included in the fifth embodiment.

(Sixth embodiment)
FIG. 12 is a circuit configuration diagram showing a sixth embodiment of the power conversion device according to the present invention. The same parts as those in FIG.

  In the sixth embodiment, as shown in FIG. 12, the circuit shown in FIG. 10 is a basic configuration, and a plurality of DC power supply modules and booster circuits are connected in parallel to achieve a large capacity.

  That is, two sets of a DC power supply module including positive and negative DC power supplies 1Pa and 1Na (1Pb and 1Nb), backflow prevention diodes 2Pa and 2Na (2Pb and 2Nb), and a circuit module including a booster circuit 7a (7b). And these are connected in parallel as a DC output circuit to the inverter 5 side.

  In the above configuration, a plurality of DC power supply modules in which positive and negative DC power supplies 1Pb and 1Nb (1Pc and 1Nc) and backflow prevention diodes 2Pb and 2Nb (2Pc and 2Nc) are connected in series are boosted by one booster circuit 7b. In this case, the voltage is input via the booster circuit backflow prevention diodes 8Pb and 8Pc.

  With such a configuration, the output currents of the two sets of circuit modules are combined and supplied to the inverter 5 side.

  FIG. 12 shows the case where the parallel number of DC power supply modules is 1 and 2. However, since there is no upper limit to the parallel number of DC power supply modules and there is no limit on the number of booster circuits, the number of DC power supply modules and booster circuits By increasing the number as necessary, the power supply capacity can be increased.

(Seventh embodiment)
FIG. 13 is a circuit configuration diagram showing a seventh embodiment of the power conversion apparatus according to the present invention. The same parts as those in FIG.

  In the seventh embodiment, as shown in FIG. 13, a bypass diode 9 for bypassing the positive side and negative side backflow prevention diodes 2P and 2N provided on the neutral point side is added.

  That is, in the configuration of FIG. 1, positive and negative backflow prevention diodes 2P and 2N are provided on the neutral point side, and the positive side and negative side backflow prevention diodes 2P and 2N connected in series across the neutral point The bypass diode 9 is connected in parallel.

  Even with such a configuration, the basic operation of FIGS. 13 and 1 with the addition of the bypass diode 9 is the same. Further, in the configuration of FIG. 1 without the bypass diode 9, the DC power supply current flows through the two backflow prevention diodes 2P and 2N, so that naturally two diode losses occur. However, in the configuration of FIG. Since the bypass diode 9 is connected in parallel with 2P and 2N, most of the DC power supply current flows through the bypass diode 9.

  Therefore, when the characteristics of the three diodes 2P, 2N and 9 are the same, the diode loss of FIG. 13 is less than half that of the configuration of FIG. The reason why the loss is less than half is that the current is shunted to the series circuit of the diodes 2P and 2N and the bypass diode 9, and the loss when the booster circuit is bypassed by the backflow prevention diode is expressed by the equations (1) to (3). This is the same as explained in.

  As described above, the diode loss can be reduced by adding the bypass diode 9, and a high-efficiency system can be realized.

(Eighth embodiment)
FIG. 14 is a circuit configuration diagram showing an eighth embodiment of the power conversion apparatus according to the present invention. The same parts as those in FIG.

  In the eighth embodiment, when a plurality of DC power supply modules are connected in parallel as shown in FIG. 14, the backflow prevention diodes 2Pa (2Pb) and 2Na (2Nb) of each power supply module are respectively connected in parallel with bypass diodes 9a and 9b. It is set as the structure connected to.

  Even in such a configuration, by adding the bypass diodes 9a and 9b as in the case of FIG. 13, the diode loss can be reduced, and a high-efficiency system can be realized.

  In the above embodiment, there is no upper limit to the number of parallel DC power supply modules, and the number of parallel DC power supply modules may be increased as necessary.

(Ninth embodiment)
FIG. 15 is a circuit configuration diagram showing a ninth embodiment of the power converter according to the present invention. The same parts as those in FIG.

  In the ninth embodiment, as shown in FIG. 15, a booster circuit 7 including a reactor Lc, a switch Sc and a chopper diode Dc is added to the configuration of FIG. 13, and the reactor Lc and the chopper diode of the booster circuit 7 are further added. A bypass diode 10 is provided in parallel with the series circuit of Dc.

  Even in such a configuration, the basic circuit operation is the same as the configuration shown in FIG. 5 or FIG. 10, but in FIG. 5 and FIG. 10, the backflow prevention diode is used as a bypass circuit of the booster circuit. 15 is different in that a boost circuit bypass diode 10 dedicated to bypass is used.

  That is, in order to use the backflow prevention diode as a bypass circuit of the booster circuit, it is necessary to provide the backflow prevention diode outside the DC power supply series circuit. In FIG. 15, since it is necessary to provide the positive side and negative side backflow prevention diodes 2P and 2N on the neutral point side, the backflow prevention diode cannot be used as a bypass circuit of the booster circuit. Therefore, a diode 10 dedicated for bypassing is added so that the booster circuit 7 can be bypassed.

  If the diode bypass diode 9 is not connected in FIG. 15, the loss increases due to the voltage drop caused by the two backflow prevention diodes 2P and 2N as described above. However, the bypass diode 9 is not indispensable for basic operation, and the same operation is performed without the diode 9. Therefore, a configuration without the bypass diode 9 is also included in the present invention. The same applies to the following embodiments.

  In FIG. 15, it goes without saying that it is equivalent to the above configuration even if the positions of the switch Sc and the diode Dc in the booster circuit 7 are switched and the bypass diode 10 is provided on the negative bus of the DC circuit.

(Tenth embodiment)
FIG. 16 is a circuit configuration diagram showing a tenth embodiment of a power conversion device according to the present invention. The same parts as those in FIG.

  In the tenth embodiment, as shown in FIG. 16, the circuit shown in FIG. 15 described in the ninth embodiment is used as a basic configuration, and a plurality of DC power supply modules and booster circuits are connected in parallel to realize a large capacity. It is a configuration.

  That is, a DC power supply module including positive and negative DC power supplies 1Pa and 1Na (1Pb and 1Nb), backflow prevention diodes 2Pa and 2Na (2Pb and 2Nb), and a bypass diode 9a (9b), and a bypass dedicated diode 10a (10b) ) Including two booster circuits 7a (7b), and these are connected in parallel as a DC output circuit to the inverter 5 side.

  With such a configuration, the output currents of the two sets of circuit modules are combined and supplied to the inverter 5 side.

  In the above configuration, a plurality of DC power supply modules in which positive and negative DC power supplies 1Pb and 1Nb (1Pc and 1Nc), backflow prevention diodes 2Pb and 2Nb (2Pc and 2Nc), and bypass diode 9b (9c) are connected in series. The voltage can be boosted by one booster circuit 7b including a diode 10b dedicated to bypass.

(Eleventh embodiment)
FIG. 17 is a circuit configuration diagram showing an eleventh embodiment of the power converter according to the present invention. The same parts as those in FIG.

  In the eleventh embodiment, as shown in FIG. 17, in the configuration of FIG. 13, a positive side booster circuit constituted by a reactor Lcp, a switch Scp and a chopper diode Dcp, a reactor Lcn, a switch Scn and a chopper diode A booster circuit 71 is provided which is connected in parallel with a negative booster circuit composed of Dcn. The positive booster circuit supplies the voltage across the positive DC power supply 1P, and the negative booster circuit supplies the voltage across the negative DC power supply 1N. The pressure is increased. That is, the booster circuit 71 has a configuration in which a booster circuit for the output voltage of the positive DC power supply 1P and a booster circuit for the output voltage of the negative DC power supply 1N are connected in parallel.

  In such a configuration, when the switches Scp and Scn of the booster circuit 71 are turned off, almost no current flows through the booster circuit 71, and most of the DC power supply current flows bypassing the booster circuit 71. In this case, the backflow prevention diodes 2P and 2N or the bypass diode 9 functions as a bypass circuit of the booster circuit 71.

  Therefore, the current path when the booster circuit 71 is off is substantially the same as that in FIG. 13, and a device with less diode loss can be realized as in FIG.

(Twelfth embodiment)
FIG. 18 is a circuit configuration diagram showing a twelfth embodiment of the power conversion apparatus according to the present invention. The same parts as those in FIG.

  In the twelfth embodiment, as shown in FIG. 18, the circuit shown in FIG. 17 described in the eleventh embodiment is used as a basic configuration, and a plurality of DC power supply modules and booster circuits are connected in parallel to realize a large capacity. It is a configuration.

  That is, two sets of circuit modules including a DC power supply module including positive and negative DC power supplies 1Pa and 1Na (1Pb and 1Nb), backflow prevention diodes 2Pa and 2Na (2Pb and 2Nb), and a booster circuit 71a (71b) are provided. These are connected in parallel as a DC output circuit to the inverter 5 side.

  In the above configuration, a single booster circuit 71b boosts a DC power supply module in which a plurality of positive and negative DC power supplies 1Pb and 1Nb (1Pc and 1Nc) and backflow prevention diodes 2Pb and 2Nb (2Pc and 2Nc) are connected in series. In this case, the voltage is input via the backflow prevention diodes 8Pb, 8Pc and 8Nb, 8Nc for the booster circuit.

  With such a configuration, the output currents of the two sets of circuit modules are combined and supplied to the inverter 5 side.

(13th Embodiment)
FIG. 19 is a circuit configuration diagram showing a thirteenth embodiment of the power converter according to the present invention. The same parts as those in FIG.

  In the thirteenth embodiment, as shown in FIG. 19, the chopper diodes Dcp and Dcn of the booster circuit 71 shown in FIG. 17 are replaced with a booster circuit 72 integrated into one chopper diode Dc.

  That is, as shown in the figure, a freewheeling diode is generally connected in reverse parallel to the positive side and negative side switches Scp and Scn. The function of the positive chopper diode Dcp of the booster circuit 71 shown in FIG. 17 is realized by the chopper diode Dc of the booster circuit 72 and the freewheeling diode of the negative switch Scn shown in FIG. Similarly, the function of the negative chopper diode Dcn is realized by the chopper diode Dc and the free wheel diode of the positive switch Scn.

  Therefore, even with the configuration as shown in FIG. 19, the same operation as in FIG. 17 is possible, and the configuration of the booster circuit 72 can be simplified.

(Fourteenth embodiment)
FIG. 20 is a circuit configuration diagram showing a fourteenth embodiment of a power converter according to the present invention. The same parts as those in FIG.

  In the fourteenth embodiment, as shown in FIG. 20, the circuit of FIG. 19 described in the thirteenth embodiment has a basic configuration, and a plurality of DC power supply modules and booster circuits are connected in parallel.

  That is, a DC power supply module including positive and negative DC power supplies 1Pa and 1Na (1Pb and 1Nb), backflow prevention diodes 2Pa and 2Na (2Pb and 2Nb), a bypass diode 9a (9b), and a booster circuit 72a (72b) Two sets of circuit modules are provided, and these are connected in parallel as a DC output circuit to the inverter 5 side.

  In the above configuration, a DC power supply module in which a plurality of positive and negative DC power supplies 1Pb and 1Nb (1Pc and 1Nc) and backflow prevention diodes 2Pb and 2Nb (2Pc and 2Nc) are connected in series is boosted by one booster circuit 72b. In this case, the voltage is input via the backflow prevention diodes 8Pb, 8Pc and 8Nb, 8Nc for the booster circuit.

  With such a configuration, the output currents of the two sets of circuit modules are combined and supplied to the inverter 5 side.

(Fifteenth embodiment)
FIG. 21 is a circuit configuration diagram showing a fifteenth embodiment of the power converter according to the present invention. The same parts as those in FIG. 17 and FIG.

  The booster circuit 71 of FIG. 17 and the booster circuit 72 of FIG. 19 have two sets of booster circuits connected in parallel, whereas in the fifteenth embodiment, as shown in FIG. The circuit is configured to be connected in series.

  Here, the positive booster circuit including the reactor Lcp, the switch Scp, and the chopper diode Dcp of the booster circuit 73 boosts the voltage across the positive DC power supply 1P and charges the positive capacitor 4P. Further, the negative booster circuit composed of the reactor Lcn, the switch Scn, and the chopper diode Dcn boosts the voltage across the negative DC power supply 1N and charges the negative capacitor 4N.

  With this configuration, the boosting rate of the two booster circuits of the booster circuit 73 can be lowered, and the efficiency of the booster circuit can be increased.

(Sixteenth embodiment)
FIG. 22 is a circuit configuration diagram showing a sixteenth embodiment of the power converter according to the present invention. The same parts as those in FIG.

  In the sixteenth embodiment, as shown in FIG. 22, the circuit of FIG. 21 described in the fifteenth embodiment has a basic configuration, and a plurality of DC power supply modules and booster circuits are connected in parallel.

  That is, a DC power supply module including a positive side, a negative DC power supply positive side 1Pa and 1Na (1Pb and 1Nb), a backflow prevention diode 2Pa and 2Na (2Pb and 2Nb), and a bypass diode 9a (9b), and a booster circuit 73a (73b) 2 sets of circuit modules are provided, and these are connected in parallel as a DC output circuit to the inverter 5 side.

  In the above configuration, a DC power supply module in which a plurality of positive and negative DC power supplies 1Pb and 1Nb (1Pc and 1Nc), a backflow prevention diodes 2Pb and 2Nb (2Pc and 2Nc), and a bypass diode 9a (9b) are connected in series. When the voltage is boosted by the booster circuit 73b, the voltage is input via the backflow prevention diodes 8Pb and 8Pc and 8Nb and 8Nc for the booster circuit.

  With such a configuration, the output currents of the two sets of circuit modules are combined and supplied to the inverter 5 side.

(Seventeenth embodiment)
FIG. 23 is a circuit configuration diagram showing a seventeenth embodiment of the power converter according to the present invention. The same parts as those in FIG.

  In the seventeenth embodiment, as shown in FIG. 23, a configuration using a reactor Lcc magnetically coupled instead of the positive side and negative side reactors Lcp and Lcn of the booster circuit 73 having the configuration shown in FIG. It is.

  FIG. 24 is a model diagram of a magnetically coupled reactor Lcc. (A) is a magnetic flux addition type in which the magnetic fluxes generated by the positive and negative currents Iip and Iin are in the same direction, and (b) is a magnetic flux of both currents. This is a magnetic flux subtraction type reactor that cancels each other out.

  The current equation of FIG. 24A when the self-inductance of the two sets of windings is Lc, the mutual inductance is Mc, and the resistance of the circuit is ignored is as follows. Since the positive and negative currents are equivalent, only the positive current Iip is shown. P is the differential operator d / dt.

Iip = (LcVcp-McVcn) / p (Lc2-Mc2) (4)
When rewritten using the magnetic coupling rate Km = Mc / Lc of both inductances, it becomes as follows.

p (1−Km2) Lc Iip = Vcp−KmVcn (5)
The above expression is an expression of the current Iip that flows when the voltage Vcp-KmVcn is applied to the equivalent inductance (1-Km2) Lc. That is, the positive side current Iip is affected not only by the positive side reactor voltage Vcp but also by the negative side reactor voltage Vcn. Since Vcp and Vcn have substantially the same waveform, Vcp−KmVcn decreases as Km approaches 1, and the inductance value can be reduced for current smoothing.

  However, when Km approaches 1, the equivalent inductance (1-Km2) Lc also approaches 0 and the smoothing effect decreases. By selecting an appropriate coupling rate Km, it is possible to achieve both equivalent inductance value reduction and voltage ripple reduction.

  The current in the case of the magnetic flux subtractor type reactor of FIG. 24B is as follows.

Iip = Vcp + KmVcn) / p (1-km2) Lc (6)
When the magnetic flux addition type is used, the polarity of the negative side voltage Vcn changes, and the equivalent applied voltage becomes Vcp + KmVVcn.

  Therefore, when Vcp and Vcn have the same waveform, only the amplitude increases and the current ripple reduction effect cannot be obtained. In order to obtain the current ripple reduction effect in the magnetic flux addition type, it is necessary to shift the on / off timing of the switches Scp and Scn between the positive side and the negative side. For example, in the case of using a well-known PMW system that determines on / off timing as compared with a triangular wave carrier, the positive and negative carriers may be shifted by a half of the carrier period. As a result, the equivalent carrier frequency is doubled and current ripple can be reduced.

  The magnetic flux addition type is somewhat less effective in reducing ripple than the magnetic flux subtraction type. However, since the magnetic flux generated by the positive and negative currents cancels out, the combined magnetic flux becomes small. Therefore, there is an advantage that the cross-sectional area of the magnetic path can be reduced and the reactor can be reduced in size.

  As described above, the case where the positive and negative reactors Lcp and Lcn are magnetically coupled in FIG. 21 of the fifteenth embodiment has been described. It is clear that the effect of can be obtained.

(Eighteenth embodiment)
FIG. 25 is a circuit configuration diagram showing an eighteenth embodiment of the power converter according to the present invention. The same parts as those in FIG. 21 and FIG.

  In the eighteenth embodiment, as shown in FIG. 25, the positive and negative reactors Lcp and Lcn are further connected in series to the reactor Lcc provided in the booster circuit 74 shown in FIG. 23 described in the seventeenth embodiment. It is what.

  Such a configuration is equivalent to the case where the leakage inductance of the magnetically coupled reactor is increased by Lcp and Lcn, and the ripple reduction effect can be obtained as in FIG.

  Further, as in the case of the seventeenth embodiment, it is obvious that the same effect can be obtained with the configurations of the eleventh embodiment to the sixteenth embodiment.

(Nineteenth embodiment)
FIG. 26 is a circuit configuration diagram showing a nineteenth embodiment of the power converter according to the present invention. The same parts as those in FIG.

  In the nineteenth embodiment, as shown in FIG. 26, a ground circuit 3 for grounding the neutral point shown in FIG. 1 directly or via an impedance element is provided.

  By grounding the neutral points of the positive and negative DC power supplies 1P and 1N in this way, the ground potentials of the positive and negative DC power supplies 1P and 1N can be suppressed to within the respective power supply voltages Vsp and −Vsn. If the voltage drop of the backflow prevention diodes 2P and 2N is ignored, the inverter DC voltage Vd becomes the sum Vsp + Vsn of both power supply voltages. If Vsp and Vsn are increased to the withstand voltage limit, a DC voltage twice the withstand voltage can be obtained. .

  Therefore, the voltage of the DC circuit can be increased, and a highly efficient power conversion device can be realized.

  FIG. 26 shows the case where the neutral point is grounded in the configuration of FIG. 1, but also in each of the above-described embodiments, the DC voltage is increased to about twice the power source withstand voltage by grounding the neutral point. Obviously we can do it.

  The configuration and operation of each embodiment to which the NPC inverter 5 is applied have been described above. Finally, the positive DC power source 1P and the negative DC power source are controlled by the shared control of the NPC inverter 5 and the independent control of the positive and negative power sources. A description will be given of the fact that each 1N power generation capacity can be maximized.

  FIG. 27 is a diagram showing the relationship between the on / off of the switching elements S1 to S4 and the output potential E in each leg of the NPC inverter 5 shown in FIGS. 2 and 3, and two of S1 to S4 are The state which turns on simultaneously is shown.

  In FIG. 27, (a) shows a case where the switching elements S1 and S2 are turned on, and the output E becomes the DC circuit positive potential Ep regardless of the current polarity. (B) is when the switching elements S2 and S3 are on, and (c) is when the switching elements S3 and S4 are on, and the output potentials are the neutral potential Eo and the negative potential En, respectively.

  In this way, since three types of potentials can be output depending on the on / off state of the switching element, it is also called a three-level inverter. When the voltage v with respect to the neutral point 0 is positive, the energization states of FIGS. 27A and 27B are alternately repeated, and when v is negative, the energization states of (b) and (c) are alternated. The PWM control is repeated so that the average value of the output voltage follows the command value.

  When the voltage v is positive and the energized states of FIGS. 27A and 27B are alternately repeated, no current flows through the DC circuit negative bus, so only the positive power supply transmits and receives power. Pn becomes zero. On the other hand, when v is negative and the energized states of FIGS. 27B and 27C are alternately repeated, the positive power Pp is 0 and only the negative side performs power transfer.

  Thus, when the output voltage v is positive, the negative power Pn is 0, and when v is negative, the positive power Pp is 0, which is the basis of the positive and negative power ratio control.

  Here, the fact that the positive and negative power ratios can be controlled will be described in detail with reference to the waveform diagram shown in FIG.

  FIG. 28 shows instantaneous waveforms of (a) output voltage v, (b) output current i, and (c) power P of a leg, and also shows a waveform when a constant bias Vb is added to voltage v.

  When the bias Vb is not added, the waveform of the power P = v · i is equal between the positive period and the negative period of the voltage v = Vsinθ. When v is positive, transmission / reception is performed with the positive bus, and when v is negative, transmission / reception is performed with the positive and negative power sharing in one cycle.

  On the other hand, the power P when the bias Vb is added is superimposed on the power Vb · i, which is the product of Vb and i, and the power transfer amount Pp (first half) with the positive bus as shown in FIG. ) And the negative power supply amount Pn (second half), and the positive power Pp becomes larger during one cycle. When the bias voltage Vb is negative, the relationship is reversed, and the power for one cycle is greater on the negative side Pn. If the output voltage of each leg is biased by the same amount in both the single-phase inverter and the three-phase inverter, the voltage between the output terminals is the same as before the bias, so that even if biased, operation can be performed without any problem.

  The relationship between the positive and negative power Pp and Pn and the bias voltage Vb is shown below. If the voltage v and the current i are expressed by the equations (7) and (8), the power P, which is the product thereof, becomes the equation (9). φ is the power factor angle.

v = Vsinθ + Vb (7)
i = Isin (θ-φ) (8)
P = v · i = VIsinθsin (θ−φ) + VbIsin (θ−φ) (9)
If the bias Vb is positive, the phase range when v is positive is increased, and the increased phase angle δ is expressed by the following equation.

δ = sin ⁻¹ (Vb / V) (10)
Therefore, the positive and negative average values Pp and Pn of P during one cycle are obtained by the following equations, respectively.

By substituting P in equation (9) and solving equations (11) and (12), Pp and Pn are obtained as follows. However, Kb is a bias coefficient Vb / V.

  The sum of Pp and Pn is the output power average value Po and is given by the following equation.

Po = Pp + Pn = VIcosφ / 2 (15)
(13) and (14) can be expressed as follows using Po.

It is obvious that dP is ½ of the positive / negative power difference Pp−Pn that can be controlled by the bias voltage Vb. When the equation (16) is normalized by Po, the following equation is obtained and can be approximated by 2 Kb / π in a small Kb range.

  FIG. 29 is a graph of the above equation. If Kb <0.5 (δ <30 °), the error of the approximate solution is small.

  However, it is necessary to consider that the polarity of dP in the equation (16) is equal to the polarity of Po. When cosφ becomes negative, even if the bias voltage Vb is increased to the positive side, dP becomes negative and the positive side power Pp decreases. This indicates that when the power sharing between the positive side and the negative side is controlled, the addition polarity of the bias voltage Vb needs to be changed according to the polarity of the power Po.

  As described above, the NPC inverter can control the ratio of the positive power Pp and the negative power Pn with the bias voltage Vc. By utilizing this, even when there is a difference in power generation capacity between the positive and negative power supplies 1P and 1N, it is possible to operate at each maximum power generation capacity point.

  This will be described in more detail with reference to an example in which a solar panel is used as the DC power supplies 1P and 1N.

  FIG. 30 is a curve diagram showing the power generation characteristics of the solar cell called VI characteristics and VP characteristics. In FIG. 30, the horizontal axis represents the generated voltage V, the vertical axis represents the generated current I and the generated power P = V · I, and shows two types of characteristic curves with different irradiation amounts.

  Each power P curve has maximum power points Pm1 and Pm2, and it is a condition for high-efficiency power generation to always operate at the maximum power point. In order to operate at the maximum power point Pm1 of the characteristic 1, it is necessary to set the voltage to Vm1 and the current to Im1. Further, in order to operate at the maximum power point Pm2 of the characteristic 2, it is necessary to set the voltage to Vm2 and the current to Im2.

  However, when two DC power supplies 1P and 1N are simply connected in series and there is no neutral current path, only the same current can flow through both power supplies.

  For example, if the power generation characteristic of the positive power supply 1P is the characteristic 1 in FIG. 30 and the negative power supply 1N is the characteristic 2, the negative power supply 1N cannot pass a current such as an Im1 phase. It cannot be operated at a maximum power point Pm1 of 1. It is necessary to reduce the current of the positive power source 1P to a level that allows the negative power source 1N to flow, and as a result, the generated power of the positive power source 1P must be smaller than the maximum power Pm1 that can be generated.

  In the present invention, even when there is a difference in power generation capacity between the positive and negative power supplies 1P and 1N, both power supplies can be operated at the maximum power point. As described above, when the power generation capability of the positive / negative power source 1P is high, the bias voltage Vb may be adjusted so that the positive power Pp of the NPC inverter 5 is larger than the negative power Pn.

  As a result, the current of the positive power source 1P becomes larger than that of the negative power source 1N, and it becomes possible to operate at the respective maximum power points. Thus, the maximum power generation capacity of the solar panel can be exhibited, and the system power generation efficiency can be improved by the present invention.

  In order to operate the positive and negative power supplies 1P and 1N at their maximum power points, it is a condition that the voltage or current of 1P and 1N can be controlled independently.

  Next, the fact that the currents of both power sources can be independently controlled in the configuration of each embodiment of the present invention will be described using the equivalent models of FIGS.

  FIG. 31 shows an equivalent model without a booster circuit. However, even when the booster circuit is present, the case where the boosting operation is stopped corresponds to this equivalent model, and is therefore applied to all configurations of the present invention. In the equivalent model, diodes and the like are ignored, and the inverter is represented by positive and negative DC current sources Ip and In.

  In the case of system linkage, an inverter generally performs feedback control of an output AC current. Since the active current component in phase with the system voltage of the AC current is proportional to the DC circuit source flow, the inverter can be regarded as an equivalent current source. Further, as described above, since the positive and negative power sharing can be controlled by the bias voltage Vb, it can be regarded as a controllable current source that is independent of positive and negative, as shown in FIG.

  In FIG. 31, since no current flows through the smoothing capacitors 4P and 4N in the steady state, 4P and 4N can be ignored. The same applies to the following FIG. 32 to FIG. Therefore, the inverter currents Ip and In flow to the power sources 1P and 1N, respectively, and the currents of both power sources can be controlled by the inverter, and the operation at the optimum operating point of each power source becomes possible.

  The voltages of the smoothing capacitors 4P and 4N are equal to the voltages of the power supplies 1P and 1N and cannot be controlled.

  FIG. 32 is an equivalent model in the case where the voltages at both ends of the positive and negative power supplies are boosted together. FIG. 32A shows a case where the booster circuit output current is output to the positive bus as shown in FIGS. 32 (b) is a model when the booster circuit output current is output to the negative bus as shown in FIGS.

  As shown in FIG. 32, the booster circuit can be equivalently represented by two current sources Ic1 and Ic2. The input current Ic to the booster circuit can be controlled by the on / off ratio of the switch Sc in the booster circuit, and is divided into Ic1 and Ic2 according to the on / off ratio.

  In FIG. 32A, since the input current Ic of the booster circuit is the current of the power supply 1P, the current of the power supply 1P can be controlled by the booster circuit. The current of the power supply 1N is In + Ic2, indicating that it can be controlled by the negative inverter current In.

  In order for the current of the smoothing capacitor 4P to be 0, the two controllable currents Ic1 and Ip must be controlled to be equal, but the voltage of the smoothing capacitor 4P can be controlled by the difference current between Ic1 and Ip. It also shows that there is. In this case, the voltage of the negative side smoothing capacitor 4N becomes equal to the voltage of the power source 1N and cannot be controlled.

  Similarly in FIG. 32B, the current of the power source 1N can be controlled by the booster circuit, and the current of the power source 1P can be controlled by the positive-side inverter current Ip. In this case, the voltage of the negative side smoothing capacitor 4N can be controlled, but the voltage of the positive side smoothing capacitor 4P becomes equal to the voltage of the power source 1P and cannot be controlled.

  FIG. 33 is an equivalent model of a configuration in which the outputs of the positive and negative booster circuits are connected in parallel, and FIG. 34 is an equivalent model of a configuration in which the outputs of the positive and negative booster circuits are connected in series.

  Obviously, the currents of the positive and negative power supplies 1P and 1N can be controlled independently by the positive and negative booster circuits, respectively.

  In FIG. 33, the voltage across the smoothing capacitors 4P and 4N can be controlled by a booster circuit, and the voltage sharing ratio between the positive side and the negative side can be controlled by an inverter.

  The voltages of the smoothing capacitors 4P and 4N can be controlled independently by the booster circuit and the inverter.

1P, 1Pa, 1Pb, 1Pc, 1Pd ... Positive side DC power supply 1N, 1Na, 1Nb, 1Nc, 1Nd ... Negative side DC power supply 2, 2a, 2b, 2c, 2d ... Backflow prevention diode 2P, 2Pa, 2Pb, 2Pc, 2Pd ... Positive side backflow prevention diode 2N, 2Na, 2Nb, 2Nc, 2Nd ... Negative side backflow prevention diode 3 ... Ground circuit 4 ... Smoothing capacitor 5 ... Single-phase or multi-phase inverter 6 ... Load or power system 7, 7a, 7b, 71, 71a, 71b, 72, 72a, 72b, 73, 73a, 73b, 74, 75... Booster circuit 8Pa, 8Pb, 8Pc, 8Pd... Positive side reverse current prevention diode for booster circuit 8Na, 8Nb, 8Nc, 8Nd. Negative side reverse current prevention diode 9, 9a, 9b, 9c, 9d ... Diode bypass diode 1 , 10a, 10b ... boosting circuit bypass diode

Claims (20)

A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
A direct current DC power supply circuit in which a positive DC power supply and a positive backflow prevention diode are connected in series, and a negative DC power supply circuit in which a negative DC power supply and a negative backflow prevention diode are connected in series. A power conversion device comprising a power supply module. A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
A plurality of DC power supply circuits in which a positive DC power supply and a positive backflow prevention diode are connected in series, and a negative DC power supply circuit in which a negative DC power supply and a negative backflow prevention diode are connected in series are connected in series. A power conversion apparatus comprising: a plurality of DC power supply modules connected in parallel. A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
A positive DC power supply circuit comprising a positive DC power supply and a reverse current prevention diode connected in series to the positive potential side, and a negative DC power supply circuit comprising a negative DC power supply and a reverse current prevention diode connected in series to the negative potential side. A DC power supply module that is connected in series,
A booster circuit comprising a reactor, a switching element and a diode, and boosting a voltage across a series circuit formed by a positive side DC power source and a negative side DC power source in the DC power source module;
A power converter comprising: a parallel circuit that is formed of the DC power supply module and the booster circuit and outputs the outputs of both in parallel. A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
A positive DC power supply circuit comprising a positive DC power supply and a reverse current prevention diode connected in series to the positive potential side, and a negative DC power supply circuit comprising a negative DC power supply and a reverse current prevention diode connected in series to the negative potential side. A plurality of DC power supply modules connected in series,
A plurality of boosting circuits that boost the voltage across the series circuit of the positive side DC power source and the negative side DC power source in each of the DC power source modules, comprising a reactor, a switching element, and a diode;
A power conversion device comprising: a plurality of DC power supply modules and a plurality of booster circuits; and a parallel circuit that outputs these outputs in parallel. A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
A positive DC power supply circuit comprising a positive DC power supply and a reverse current prevention diode connected in series to the positive potential side, and a negative DC power supply circuit comprising a negative DC power supply and a reverse current prevention diode connected in series to the negative potential side. A plurality of DC power supply modules connected in series,
A booster circuit comprising a reactor, a switching element, and a diode, and boosting the voltage across each of the series circuits of the positive side DC power source and the negative side DC power source in each DC power source module;
A plurality of booster circuit backflow prevention diodes inserted in voltage input paths to the booster circuits of the positive DC power supply and the negative DC power supply in each DC power supply module;
A power converter comprising: a plurality of DC power supply modules and the booster circuit; and a parallel circuit that outputs each of these outputs in parallel. A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
A positive DC power supply circuit comprising a positive DC power supply and a reverse current prevention diode connected in series to the positive potential side, and a negative DC power supply circuit comprising a negative DC power supply and a reverse current prevention diode connected in series to the negative potential side. A DC power supply module that is connected in series,
A reactor, a switching element, and a diode. In the DC power supply module, the voltage between the positive terminal of the positive DC power supply circuit and the negative terminal of the negative DC power supply or the positive terminal of the positive DC power supply and the negative A step-up circuit for stepping up the voltage across the negative side terminal of the side DC power supply circuit;
A power conversion device comprising: a parallel circuit that is formed of the DC power supply module and the booster circuit and outputs each of these outputs in parallel. A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
A positive DC power supply circuit comprising a positive DC power supply and a reverse current prevention diode connected in series to the positive potential side, and a negative DC power supply circuit comprising a negative DC power supply and a reverse current prevention diode connected in series to the negative potential side. A plurality of DC power supply modules connected in series,
A voltage between the positive terminal of the positive DC power supply and the negative terminal of the negative DC power supply circuit in each DC power supply module, or the positive terminal of the positive DC power supply circuit, comprising a reactor, a switching element, and a diode. One booster circuit for boosting the voltage between the negative terminal of the negative DC power supply and the negative terminal;
A plurality of booster circuit backflow prevention diodes inserted in a voltage input path to the booster circuit of the positive DC power supply or the negative DC power supply in each of the DC power supply modules;
A power converter comprising: a plurality of DC power supply modules and the booster circuit; and a parallel circuit that outputs each of these outputs in parallel. A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
Consists of a positive-side DC power supply circuit composed of a positive-side DC power supply and a positive-side backflow prevention diode connected in series to the negative potential side, and a negative-side DC power supply and a negative-side backflow prevention diode connected in series to the positive potential side A DC power supply module formed by connecting a negative DC power supply circuit in series;
A power conversion device comprising: a bypass diode connected in parallel to a series circuit formed by the positive side backflow prevention diode and the negative side backflow prevention diode. A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
Consists of a positive-side DC power supply circuit composed of a positive-side DC power supply and a positive-side backflow prevention diode connected in series to the negative potential side, and a negative-side DC power supply and a negative-side backflow prevention diode connected in series to the positive potential side A plurality of DC power supply modules formed by connecting negative DC power supply circuits in series;
A power conversion device comprising a bypass diode connected in parallel to a series circuit formed by a positive side reverse current prevention diode and a negative side reverse current prevention diode of each DC power supply module. A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
Consists of a positive-side DC power supply circuit composed of a positive-side DC power supply and a positive-side backflow prevention diode connected in series to the negative potential side, and a negative-side DC power supply and a negative-side backflow prevention diode connected in series to the positive potential side A DC power supply module formed by connecting a negative DC power supply circuit in series;
One booster circuit comprising a reactor, a switching element and a diode, and boosting the voltage across the DC power supply module;
A power conversion device comprising: a bypass diode that bypasses the booster circuit with respect to the DC power supply module when the booster circuit is not operating. A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
Consists of a positive-side DC power supply circuit composed of a positive-side DC power supply and a positive-side backflow prevention diode connected in series to the negative potential side, and a negative-side DC power supply and a negative-side backflow prevention diode connected in series to the positive potential side A plurality of DC power supply modules formed by connecting negative DC power supply circuits in series;
One booster circuit comprising a reactor, a switching element and a diode, and boosting the voltage across the DC power supply module;
A bypass diode that bypasses the booster circuit with respect to the DC power supply module when the booster circuit is not operating;
A power conversion apparatus comprising: a parallel circuit that outputs in parallel the output of each DC power supply module and the output of the booster circuit. A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
Consists of a positive-side DC power supply circuit composed of a positive-side DC power supply and a positive-side backflow prevention diode connected in series to the negative potential side, and a negative-side DC power supply and a negative-side backflow prevention diode connected in series to the positive potential side A DC power supply module formed by connecting a negative DC power supply circuit in series;
A positive side boosting circuit that boosts the voltage across the positive side DC power source, and a negative side that boosts the voltage across the negative side DC power source consisting of a reactor, a switching element, and a diode. A booster circuit in which a booster circuit is connected in parallel;
A power conversion device comprising: a parallel circuit that outputs in parallel the output of the DC power supply module and the output of the booster circuit. A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
Consists of a positive-side DC power supply circuit composed of a positive-side DC power supply and a positive-side backflow prevention diode connected in series to the negative potential side, and a negative-side DC power supply and a negative-side backflow prevention diode connected in series to the positive potential side A plurality of DC power supply modules formed by connecting negative DC power supply circuits in series;
A positive-side booster circuit that boosts the voltage across the positive-side DC power supply in each DC power supply module, a reactor, a switch element, and a diode. A booster circuit connected in parallel with a negative booster circuit that boosts the voltage at both ends of the side DC power supply;
A power conversion apparatus comprising: a parallel circuit that outputs in parallel the outputs of the plurality of DC power supply modules and the output of the booster circuit. A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
Consists of a positive-side DC power supply circuit composed of a positive-side DC power supply and a positive-side backflow prevention diode connected in series to the negative potential side, and a negative-side DC power supply and a negative-side backflow prevention diode connected in series to the positive potential side A DC power supply module formed by connecting a negative DC power supply circuit in series;
A booster composed of a positive-side reactor and a negative-side reactor that are connected in series with a positive-side switch element, a diode, and a negative-side switch element, and are connected to both ends of a series circuit of backflow prevention diodes in the DC power supply module Circuit,
A power conversion device comprising: a parallel circuit that outputs in parallel the output of the DC power supply module and the output of the booster circuit. A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
Consists of a positive-side DC power supply circuit composed of a positive-side DC power supply and a positive-side backflow prevention diode connected in series to the negative potential side, and a negative-side DC power supply and a negative-side backflow prevention diode connected in series to the positive potential side A plurality of DC power supply modules formed by connecting negative DC power supply circuits in series;
A positive side switch element and a negative side switch element are connected in series via a diode, and positive and negative backflow prevention diodes for a boost circuit are provided at both ends of the series circuit of backflow prevention diodes and both ends of the diodes in each DC power supply module. One booster circuit consisting of a positive side reactor and a negative side reactor connected through each of them;
A power conversion apparatus comprising: a parallel circuit that outputs in parallel the output of each DC power supply module and the output of the booster circuit. A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
Consists of a positive-side DC power supply circuit composed of a positive-side DC power supply and a positive-side backflow prevention diode connected in series to the negative potential side, and a negative-side DC power supply and a negative-side backflow prevention diode connected in series to the positive potential side A DC power supply module formed by connecting a negative DC power supply circuit in series;
A positive side switch element, two series diodes and a negative side switch element are connected in series, and a positive side reactor and a negative side reactor are connected to both ends of the reverse current prevention diode series circuit of the DC power supply module and both ends of the series diode, respectively. And a booster circuit formed by connecting a series connection point of the two series diodes and a neutral point of the positive and negative smoothing capacitors;
A power conversion device comprising: a parallel circuit that outputs in parallel the output of the DC power supply module and the output of the booster circuit. A DC power supply having a neutral point, a positive and negative smoothing capacitor that smoothes the DC power output from this DC power supply, and a DC power that is smoothed by the positive and negative smoothing capacitors is converted to AC. With neutral point clamp type inverter to supply to load or power system,
The neutral point of the DC power source and the positive side, the neutral point of the negative side smoothing capacitor and the neutral point of the neutral point clamp system inverter are connected, respectively.
The DC power source having the neutral point is
Consists of a positive-side DC power supply circuit composed of a positive-side DC power supply and a positive-side backflow prevention diode connected in series to the negative potential side, and a negative-side DC power supply and a negative-side backflow prevention diode connected in series to the positive potential side A DC power supply module formed by connecting a negative DC power supply circuit in series;
A positive side switch element, two series diodes and a negative side switch element are connected in series, and positive and negative backflow prevention for a booster circuit are provided at both ends of the series circuit of the backflow prevention diode and both ends of the series diode in each DC power supply module. A booster circuit formed by connecting a positive side reactor and a negative side reactor via diodes, and connecting a series connection point of the two series diodes and a neutral point of the positive side and negative side smoothing capacitors;
A power conversion device comprising: a parallel circuit that outputs in parallel the output of the DC power supply module and the output of the booster circuit.   The power converter according to any one of claims 12 to 17, wherein a magnetically coupled reactor is used instead of the positive side reactor and the negative side reactor of the booster circuit.   The power converter according to any one of claims 12 to 17, wherein a positive side reactor and a negative side reactor of the booster circuit are connected in series with a magnetically coupled reactor.   The power converter according to any one of claims 1 to 19, wherein a neutral point of the DC power supply is grounded directly or via an impedance element.

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