JPH09121559A - Inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a compact high-efficiency inverter device which can obtain a single-phase three-wire or two-wire type AC voltage from one DC power source by outputting an AC voltage between the connecting point of two switch elements which are connected in series and a neutral point. SOLUTION: An inverter device is provided with boosting choppers 4-7 and 30 which obtain DC voltages P1 and N1 from one DC power source 1 and has a neutral point C and half bridge inverters 8 and 9 which are respectively connected between the positive sides and negative sides of the voltages P1 and N1 and composed of serial circuits of two switches. The inverter device outputs an AC voltage between the connecting point of the two switch elements which are connected in series and the neutral point. Therefore, a compact high- efficiency inverter device which can convert the DC voltage from one low- voltage DC power source 1 into a single-phase three-wire or two-wire type AC voltage without using any transformer, does not generate much noise nor leak current, and does not fluctuate the DC input voltage against the earth can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for obtaining a single-phase, three-wire type or a single-phase, two-wire type AC voltage from one DC power source.

[0002]

2. Description of the Related Art There is an inverter device which obtains a DC voltage having a neutral point from one DC power source and operates by connecting to a single-phase three-wire type AC system. The applicant of the present invention has previously proposed this type of device (Japanese Patent Application No. 5-239432), and its configuration will be shown in FIG. 6 and its outline will be described.

The output terminals P and N of the solar cell 1 are capacitors
It is connected to 7 and functions as one DC power supply. One end of the reactor 3 is connected to the P side of the DC power supply and the other end is connected to the N side of the DC power supply via the switch element (IGBT) 4, and the reactor is turned on and off by turning the IGBT 4 on and off.
The charging current flows through the capacitor 3 and the discharging current of the reactor 3 through the diode 5 and the capacitor 6,
It operates as a chopper circuit to charge 6 and a capacitor
Control charge voltage of 6. Capacitor 6 and Capacitor 7
Are connected in series so that the voltages are added, and DC voltages P1 and N1 having a neutral point C are obtained.

The neutral point C is connected to the neutral point of a single-phase three-wire AC system (AC power supplies 13a and 13b), and the IGBTs 8a and 8b are connected between P1 and N1 of the DC voltage having the neutral point C. 1st half-bridge inverter 8 consisting of a series circuit of
The second half-bridge inverter 9 consisting of a series circuit of T9a and 9b is connected. The AC output terminals of the first and second half-bridge inverters 8 and 9 are the reactor 10a and the current detector 11a, the reactor 10b and the current 10b. The detectors 11b are connected to one ends of the AC power supplies 13a and 13b, respectively. The capacitors 12a and 12b connected in parallel to the AC power supplies 13a and 13b are for absorbing the ripple voltage contained in the AC output voltage due to the PWM control.

The voltage control unit 17 includes a voltage reference Vdr and a voltage detector.
The voltage detection value Vd of the capacitor 6 detected through 15 is compared, and the current reference Idr is output so as to reduce the error, and the current control unit 18 is detected through the current reference Idr and the current detector 2. The current control signal I is compared with the detected current value Id flowing through the reactor 3 to reduce the error.
Output c. The PWM control circuit 19 outputs the PWM signal G1 based on the current control signal Ic, and as described above, the IGB
The charging voltage of the capacitor 6 is controlled so as to match the voltage reference by turning on and off T 4.

The maximum power control (MPPT) circuit 20 outputs an output current reference Imr for extracting the maximum output power from the solar cell 1, but since it is not related to the present invention, its detailed description will be omitted. The current reference circuit 21 uses the output current reference Imr and the transformer 14 to detect the AC power supply 13a or
Based on the detected voltage value Va of 13b, an AC current reference Ir having an amplitude Imr synchronized with the voltage phase of the AC power source is output, and the inverting circuit 22 inverts the polarity of the current reference Ir to obtain a current reference with a phase difference of 180 degrees. -Ir is output. The current control units 23, 24 compare the current references Ir, -Ir with the AC output currents I1a, I1b of the half-bridge inverters 8, 9 detected via the current detectors 11a, 11b, respectively, and reduce the error. The control signals are output as described above, the PWM signals G2 and G3 are output through the PWM control circuits 25 and 26, and the AC output currents I1a and I1b of the half bridge inverters 8 and 9 are the current reference Ir.
, -Ir, and PWM control is performed. As a result, the maximum output power drawn from the solar cell 1 is supplied to the AC system side and the interconnection operation is performed.

[0007]

In the system shown in FIG. 6, the output voltage of the solar cell 1 is used as it is as the DC power supply on one side, so this DC voltage is higher than the peak value of the voltage of the AC power supplies 13a and 13b. Must be voltage. However, when the cell area of the solar cell is increased or the power capacity is small, if the voltage of the solar cell is designed to be less than 160 V, the AC voltage becomes less than the peak value of 110 V, and the current control becomes impossible. In such a case, a method has been adopted in which a DC voltage is once converted into a high frequency by an inverter, boosted by a transformer, and then rectified to obtain a boosted DC voltage. This method complicates the circuit, reduces the magnetic flux density in order to avoid the magnetic flux saturation of the transformer, and thus the transformer is relatively large, and the power loss of the switch element for power conversion is small. However, there are drawbacks such as an increase in conversion efficiency, a decrease in conversion efficiency, and an increase in cost. The present invention aims to solve these problems.

[0008]

In order to achieve the above object, the inverter device of the present invention is constructed as follows. A boost chopper that obtains a DC voltage having a neutral point from one DC power source, and a half-bridge inverter that is connected between the positive and negative sides of the DC voltage and that is a series circuit of two switching elements, and is provided with two switching elements. An AC voltage is output between the series connection point and the neutral point. (Claim 1) (FIGS. 1 and 3) Further, two sets of the half bridge inverters are provided, and a single-phase three-wire type AC voltage is output between the AC outputs of the two sets of the half bridge inverters and the neutral point. To do. (Claim 2)
(FIGS. 1 and 3) Further, a voltage control unit for controlling the boost chopper so as to reduce the error by comparing the voltage reference with the DC voltage is provided, and the DC voltage is controlled to be constant. (Claim 3) (FIGS. 1 and 3) Further, the boost chopper turns on / off a reactor having a first winding and a second winding and a current supplied from the DC power supply to the first winding. A switch element is provided, the switch element is turned on, a current is supplied to the first winding from the DC power source to store energy in the reactor, and the switch element is turned off to store the stored energy. The line and the second winding are connected in series via a diode and discharged into two sets of capacitors to obtain a DC voltage having a neutral point. (Claim 4) (Figs. 1 and 5)
(a) (b)) Furthermore, the boost chopper includes a series circuit of a reactor and a switch element connected between the positive and negative sides of the DC power supply,
Energy is accumulated in the reactor by a current supplied from the DC power source by turning on the switch element,
The switch element is turned off to discharge the accumulated energy to two sets of capacitors connected in series via a diode to obtain a DC voltage having a neutral point.
(Claim 5) (FIG. 3) Further, the boost chopper includes a reactor having a winding with an intermediate tap and a switch element for turning on / off a current flowing from the DC power supply to the winding between one end of the winding and the intermediate tap. Energy is stored in the reactor by a current supplied from the DC power supply by turning on the switching element, and the energy stored by turning off the switching element is connected in series from the entire winding through a diode. The two sets of capacitors are discharged to obtain a DC voltage having a neutral point. (Claim 6) (FIGS. 4 (a) (c) and 5 (c)) Further, two sets of current references having a phase difference of 180 ° and output current detection values of the two sets of half bridge inverters are provided. Two sets of current control units are provided to respectively control the two sets of half-bridge inverters so as to reduce the error by comparing them. (Claim 7) (Fig. 3) Further, the energy stored in the reactor is supplied to the two sets of capacitors connected in series from the first winding and the second winding with predetermined energy distribution, respectively, and 2 Balance the voltage on the pair of capacitors. (Claim 8) (Fig. 1, Fig. 4 (c), Fig. 5 (a) (b) (c)) Furthermore, a correction signal is generated according to the fluctuation of the neutral point potential of the DC voltage, and the current reference is generated. Is provided, and a DC component is caused to flow in the output current of the half bridge inverter so as to suppress the fluctuation of the neutral point potential by the correction signal. (Claim 9) (FIG. 3) Further, a switch for turning on / off a current flowing between the positive electrode or the negative electrode and the neutral point according to the fluctuation of the neutral point potential of the direct current voltage is provided to change the neutral point potential. The current supplied from the positive side and the negative side of the DC power supply is changed according to the above, and the fluctuation of the neutral point potential is suppressed. (Claim 10) (Fig. 5 (a) (b))

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment corresponding to claims 1 to 4 and 8 of the present invention. Fig. 1 shows the configuration of the main parts. 30 is a reactor having a primary winding n1 and a secondary winding n2, 31 is a capacitor connected in parallel with the solar cell 1, 32 is a control power supply, and 33 is a current. A peak detection circuit that detects the maximum detection value, and 35 is a diode. Others are the same as those of the conventional one (FIG. 6), the same reference numerals are given and the description thereof is omitted.

One end of the primary winding n1 of the reactor 30 is connected to one end (P side) of a capacitor 31 (solar cell 1), and the other end of the primary winding n1 is connected via a switch element (IGBT) 4 to the capacitor 31. Is connected to the other end (N side) of. The anode side of the diode 35 is connected to the connection point of the primary winding n1 and the IGBT 4, the cathode side is connected to the connection point of the capacitors 6 and 7, and is also connected to one end of the secondary winding n2 of the reactor 30. The other end of the line n2 is connected to one end of a capacitor 6 via a diode 5.

In the above-mentioned structure, when the IGBT 4 is turned on, a current flows through the primary winding n 1, a predetermined electric power (energy) supplied from the solar cell 1 is accumulated in the reactor 30, and when the IGBT 4 is turned off, the energy is stored. Is discharged as a discharge current from the primary winding n1 and the secondary winding n2 to charge the capacitors 6 and 7, and the IGBT 4 is turned on / off to function as a chopper circuit. The capacitor 31 is always charged by the solar cell 1, and releases a charge when supplying a current to suppress the fluctuation of the DC voltage between P and N.

The voltage controller 17 includes a voltage reference Vdr and a voltage detector.
The voltage reference value Vd of the capacitor 6 detected via 15 is compared and the current reference Idr is output so as to reduce the error. The peak detection circuit 33 is the primary winding n of the reactor 30.
The peak value Idp of the current Id flowing in 1 is detected, the current controller 18 compares the current reference Idr with the peak value Idp of the current Id, and outputs the control signal Ic so as to reduce the error.
The PWM control circuit 19 outputs the PWM signal G1 based on the control signal Ic, turns on and off the IGBT 4 to perform pulse width modulation control, and controls so that the voltage of the capacitor 6 becomes equal to the voltage reference.

FIG. 2 (a) is an equivalent circuit diagram for explaining the function of the chopper circuit, and FIG. 2 (b) is an operation waveform diagram when the switch element 4 is turned on / off. When the switching element 4 is turned on for a predetermined time T1 during the pulse width modulation period T0, the voltage E1 of the solar cell 1 is applied to the primary winding n1 of the reactor 30 and the current change rate (E1 / increased current i1 at L) a predetermined energy (Li ²⁾ are accumulated. During this predetermined period T1,
The voltage e2 of the secondary winding n2 is equal to the primary winding n1 and the secondary winding n2.
Of the voltage (-E1 //) determined by the turn ratio a (= n1 / n2) of
Although a) is induced, it is blocked by the diode 5 and the current i2 does not flow. When the switch element 4 is turned off, the reactor 30
The energy stored in the primary winding n1 and the secondary winding n2
Is discharged from the primary winding n1 to the capacitor 7 via the diode 35 to the capacitor 7, the secondary winding n2 to the capacitor 6 via the diode 5 to charge current i2, and the voltage e3 of the primary winding n1. Is clamped to the charging voltage E3 of the capacitor 7, and the voltage e2 of the secondary winding n2 is clamped to the charging voltage E2 of the capacitor 6. Capacitor 6,
Since the discharge time constant determined by 7 and the load is set sufficiently larger than the pulse width modulation period T0, each charging voltage E2, E3 becomes a substantially constant value.

When the switching element 4 is turned off, the current i1 of the primary winding n1 flows through the secondary winding n2, so that the current i1 sharply decreases according to the equal ampere-turn law, and the reduced current i1 causes the capacitor 7 to decrease. To charge. If the current i2 is flowing through the secondary winding n2 when the switch element 4 is turned on, the current i1 is instantaneously increased by the equal ampere-turn law at the same time when the switch element 4 is turned on.

In this embodiment, the case where the voltage E1 of the solar cell 1 is lower than the peak value of the voltage of the AC power supplies 13a and 13b is taken into consideration. Therefore, the voltage E3 of the capacitor 7 is also boosted and the voltage E2 of the capacitor 6 is changed as before. Have control. To control the voltage E1 of the solar cell 1 to 100 V, the voltage E2 of the capacitor 6 to 200 V, and the voltage E3 of the capacitor 7 to 200 V, set the turns ratio a to 1/2 and set the voltage E2 of the capacitor 6 to 200 V. V
When controlled to, the voltage of the secondary winding n2 is 200 V (peak value)
The voltage of the primary winding n1 becomes 100 V and the capacitor
The voltage E3 of 7 is 100 V of the solar cell 1 and the primary winding n1.
The voltage of 100 V is added and the voltage is controlled to 200 V. Therefore,
The voltage E3 of the capacitor 7 is controlled to E1 + aE2.

As described above, the capacitor 6 functions as a double boost chopper, and the capacitor 7 functions as a single boost chopper. The efficiency of the boost chopper changes depending on the boost ratio, but when the boost ratio is 1, the efficiency approaches 100%. In the case of this embodiment,
3/4 will be controlled by the boost chopper.

The control power supply 32 is for supplying electric power to the control circuit. In the present embodiment, an example in which it is connected to the capacitor 7 side is shown, but it may be connected to the capacitor 6 side. Further, this embodiment can be carried out by reversing the polarities as shown in FIG.

According to the present embodiment, when a high voltage DC voltage having a neutral point is obtained from one low voltage DC power source,
It is possible to perform efficient DC / DC conversion. FIG. 3 shows the configuration of an embodiment corresponding to claims 5, 7, and 9 of the present invention.
Shown in

In this embodiment, the reactor 3 and the IGBT are used.
4, the normal boost chopper circuit consisting of diode 5 charges the series circuit of capacitor 6 and capacitor 7 to control the voltage (between P1 and N1) of the entire series circuit to be constant, and the series connection point of capacitor 6 and capacitor 7 (Neutral point) The output currents of the half-bridge inverters 8 and 9 are corrected and controlled according to the potential change of C, and FIG. 3 (a) shows the main part thereof.

In FIG. 3 (a), the voltage of the solar cell 1 is DC voltage P1, N1 having a neutral point C by a chopper circuit.
Is converted to A series circuit of resistors 40 and 41 is connected between the DC voltages P1 and N1, and the voltage detecting unit 42 connects the series connection point C1 of the resistances 40 and 41 and the series connection point (neutral point) C of the capacitor 6 and the capacitor 7. The voltage error ΔV between them is detected, and the correction unit 44 outputs the correction signal Idc based on the voltage error ΔV. Adder
45 and 46 are correction signals Idc for the current references Ir and -Ir, respectively.
Then, the corrected current references Ir1 and -Ir1 are output.
The current control units 23 and 24 control the AC output currents of the half-bridge inverters 8 and 9 based on the corrected current references Ir1 and -Ir1 in the same manner as in the conventional case, and the single-phase 3 consisting of the pole transformer 43.
It supplies power to a line AC power supply.

If the resistance values of the resistors 40 and 41 are set equal,
When the voltage of the capacitor 6 and the voltage of the capacitor 7 are equal, the value of the correction signal Idc output from the voltage detecting unit 42 becomes zero, so that the current reference I output from the adding units 45 and 46 is obtained.
r1 and -Ir1 have the same values as the current reference Ir and -Ir on the input side, and the AC output currents of the half-bridge inverters 8 and 9 are controlled as before without any correction.

However, due to a slight difference in the output power of the half-bridge inverters 8 and 9 (difference in output current, system voltage, efficiency, etc.), the voltages of the capacitors 6 and 7 become unbalanced, and the potential of the neutral point C is increased. If the value fluctuates by a certain value or more, waveform distortion or DC component of the output current may occur. In this case, in this embodiment, when the potential of the neutral point C fluctuates and the voltage error ΔV is detected by the voltage detection unit 42, the correction unit Idc outputs a correction signal Idc corresponding to the voltage error ΔV and the current The correction signal Idc is added to the references Ir and -Ir, the output currents I1a and I1b of the half-bridge inverters 8 and 9 are corrected and controlled, the charge amount discharged from the capacitors 6 and 7 is controlled, and the voltage error ΔV becomes zero. Controlled to be.

For example, when the voltage of the capacitor 6 increases and the voltage of the capacitor 7 decreases, the correction signal Idc transiently generates a direct current component Idc in the AC output currents I1a and I1b of the half-bridge inverters 8 and 9 to generate the capacitor Idc. The discharge charge amount of 6 is increased and the discharge charge amount of the capacitor 7 is decreased, so that the voltages of the capacitors 6 and 7 are balanced.

FIG. 3 (b) shows a half bridge inverter 8,9.
In the waveform diagrams of the AC output currents I1a and I1b of (1), (a) shows the case where the correction is not carried out, and (b) shows the case where the correction is carried out. When the correction is performed, the correction signal Idc causes a direct-current component Idc of the same phase in both the AC output currents I1a and I1b as shown in (B). DC component I for clarity
Although dc is expressed largely, less than 1% is actually sufficient. When the DC component Idc is output in the same phase to the pole transformer 43 with the center tap, the DC exciting magnetic flux is canceled, so that the magnetic flux saturation does not occur and the balance control of the capacitor voltage can be performed without any adverse effect. .

An embodiment corresponding to claims 6 and 10 of the present invention is shown in FIG. 4 (a). In this embodiment, a tap is provided in the winding of the reactor 30, the IGBT 4 is turned on, a current is passed from the DC power supply 1 to a part of the winding n1 of the reactor 30, energy is accumulated in the reactor 30, and the IGBT 30 is stored. 4 is turned off and the stored energy is discharged from all the windings (n1 + n2) through the diode 5 to the series circuit of the capacitors 6 and 7 to obtain the DC voltages P1 and N1 having the neutral point C. It functions as a boost chopper.

In this method, when the step-up ratio is increased, the IGB
The on-time T1 of T4 can be determined by the turn ratio of the windings n1 and n2, which has the advantage that the current flowing through the diode 5 can be reduced.

Also, a series circuit of resistors 40 and 41 is connected between P1 and N1 of the DC voltage, the emitters of transistors 47 and 48 are connected to the neutral point C, and the collectors of the DC voltage are connected via resistors 49 and 50. A voltage balance control circuit 57 is constructed by connecting P1 and N1 and connecting the base to the series connection point C1 of the resistors 40 and 41. The voltage of the capacitors 6 and 7 becomes unbalanced and the potential of the neutral point C fluctuates. At this time, a current flows through the base of the transistor 47 or 48, and a current flows through the resistor 49 or 50 so that the voltages of the capacitors 6 and 7 are balanced. For example, when the voltage of the capacitor 6 becomes higher than the voltage of the capacitor 7, a current flows through the base of the transistor 47, the transistor 47 is turned on, the charge of the capacitor 6 is discharged to the resistor 49, the voltage is lowered, and the voltage balance is maintained. .

Further, the voltage balance control circuit 57 described above can be implemented by modifying it into a circuit using the photo MOS relays 55, 56 instead of the transistors 47, 48 as shown in FIG. 4 (b). The photoMOS relay has a structure in which the FET of the switch section is turned on when a predetermined current flows to the photodiode side, and the operation time is somewhat slow (several milliseconds), but it is sufficient for balance control of the capacitor voltage.

According to the embodiment shown in FIGS. 4 (a) and 4 (b), there is an advantage that the direct current component for controlling the voltage balance does not flow out to the alternating current side. FIG. 4 shows another embodiment corresponding to claim 6 of the present invention.
This is shown in (c). In this embodiment, when the energy stored in the reactor 30 is supplied to the capacitors 7 and 6, the energy distribution is determined by the turns ratio of the windings n1 and n2 of the reactor 30, and the voltage is balanced. ,
The basic idea is the same as in FIG. Connect the anode of the diode 51 and the emitter of the switch element 52 to the tap of the winding of the reactor 30, and connect the cathode of the diode 51 and the collector of the switch element 52 to the series connection point (neutral point C) of the capacitors 6 and 7. The base of the switch element 52 is connected to one end of the winding n2 of the reactor 30 via the resistor 54. Then, the switching element 4 is turned on for a predetermined time, a current is passed through the winding n1 to store energy in the reactor 30, and then the switching element 4 is turned off and the switching element 52 is turned on by the voltage induced in the winding n2. The discharge current of n2 is passed through the diode 5 and the switch element 52 to the capacitor 6, the discharge current of winding n1 is passed through the diode 51 to the capacitor 7, and the predetermined energy is supplied from the winding n2 and the winding n1. To balance the voltage of capacitors 6 and 7. In this circuit, the voltage of the capacitor 7 is charged to the voltage of the solar cell 1 before the chopper circuit operates, so when the chopper circuit operates, the capacitor 7
So that the voltage on the
The discharge current of the winding n2 is made to flow through the switch element 52. The bidirectional Zener diode 53 is for suppressing the gate voltage applied to the switch element 52 to a predetermined voltage.

According to this embodiment, the withstand voltage of the switch element 4 can be lowered, the MOSFET can be used, and the efficiency can be improved. FIG.
As shown in (b), the discharge routes of the windings n1 and n2 of the reactor 30 are changed so that one end (P side) of the solar cell 1 has the same potential as the neutral point C of the DC voltages P1 and N1. Can be connected and implemented. The basic technical idea is the same as in Fig. 1, but winding n1 supplies energy to capacitor 6, winding n2 supplies energy to capacitor 7, and the winding ratio between windings n1 and n2 is It is the opposite of the case of 1. (Claims 4 and 8) Further, as shown in Fig. 5 (c), a center tap is provided on the winding of the reactor 30 so that the energy accumulated in the reactor 30 is evenly distributed to the capacitors 6 and 7. It can be carried out. In this embodiment, since all the electric power supplied to the load is transmitted through the chopper circuit, the efficiency is slightly lowered, but one end (P side) of the solar cell 1 is connected to the DC voltage P1, N.
The neutral point C of 1 can be set to the same potential, which has the advantage of simplifying the circuit configuration. (Claims 6 and 8)

[0031]

According to the present invention, a single-phase three-wire system or a single-phase two-phase system can be used without using a transformer from one DC power source of a low voltage.
It is possible to provide a highly efficient and compact inverter device that can be converted into a line-type AC voltage and that has no fluctuation in the DC input voltage with respect to ground and has little noise or leakage current.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram of an embodiment corresponding to claims 1 to 4 and 8 of the present invention.

FIG. 2 is a diagram for explaining the operation of the embodiment, and FIG.
Is an equivalent circuit diagram and (b) is a waveform diagram.

FIG. 3 is a main part configuration diagram of an embodiment corresponding to claims 3, 7, and 9 of the present invention.

4 (a) is an embodiment corresponding to claims 6 and 10 of the present invention, (b) is an embodiment corresponding to claim 10 of the present invention, (c)
Is a main part configuration diagram of an embodiment corresponding to claims 6 and 8 of the present invention.

5 (a) is an embodiment corresponding to claims 4 and 8 of the present invention, (b) is an embodiment corresponding to claims 4 and 8 of the present invention,
(c) is a main part configuration diagram of an embodiment corresponding to claims 6 and 8 of the present invention.

FIG. 6 is a configuration diagram of a conventional inverter device.

[Explanation of symbols]

1 ... Solar cell 2 ... Current detector 3 ... Reactor 4,8a, 8b, 9a, 9b
… IGBT 5… Diodes 6, 7… Capacitors 10a, 10b… Reactors 11a, 11b… Current detectors 12a, 12b… Capacitors 13a, 13b… AC power supply 14… Transformer 15… Voltage detectors 17, 18, 23, 24… Amplifier 19,25,26… PW
M circuit 20 ... Maximum power point control circuit 21 ... Current reference circuit 22 ... Inversion circuit 30 ... Reactor (with tap or secondary winding) 31 ... Capacitor 32 ... Control power supply 33 ... Peak detector 35 ... Diode 40, 41 … Resistor 42… Voltage detector 43… Pole transformer 44… Correction unit 45,46… Addition circuit

Claims (10)

[Claims] 1. A step-up chopper that obtains a DC voltage having a neutral point from one DC power source, and a half-bridge inverter that is connected between the positive and negative sides of the DC voltage and that is a series circuit of two switch elements. An inverter device which outputs an AC voltage between a series connection point of the individual switch elements and the neutral point. 2. The inverter device according to claim 1, wherein two sets of the half bridge inverters are provided, and a single-phase three-wire type AC voltage is provided between the AC outputs of the two sets of the half bridge inverters and the neutral point. An inverter device characterized by outputting 3. The inverter device according to claim 1, further comprising a voltage control unit for controlling the boost chopper so as to reduce a difference between a voltage reference and the DC voltage and reduce an error thereof. An inverter device characterized in that a DC voltage is controlled to be constant. 4. The inverter device according to claim 1, wherein the boost chopper includes a reactor having a first winding and a second winding, and the DC power supply in the first winding. A switch element for turning on and off a current supplied from the DC power source to supply current to the first winding to store energy in the reactor and turn off the switch element. An inverter device characterized in that the stored energy is discharged from two coils, which are connected in series from the first winding and the second winding via a diode, to obtain a DC voltage having a neutral point. 5. The inverter device according to any one of claims 1 to 3, wherein the boost chopper includes a series circuit of a reactor and a switch element connected between the positive and negative sides of the DC power supply, and the switch element. Is turned on to store energy in the reactor by a current supplied from the DC power source, the switch element is turned off to discharge the stored energy to two sets of capacitors connected in series via a diode, and An inverter device having a configuration for obtaining a DC voltage having a characteristic. 6. The inverter device according to any one of claims 1 to 3, wherein the boost chopper includes a reactor having a winding with an intermediate tap, and between the DC power source and one end of the winding and the intermediate tap. A switch element for turning on / off a current flowing through the winding, and turning on the switch element to store energy in the reactor by a current supplied from the DC power source, turning off the switch element to store the stored energy. The entire winding is connected in series via a diode and discharged into two sets of capacitors,
An inverter device having a configuration for obtaining a DC voltage having a neutral point. 7. The inverter device according to any one of claims 4 to 6, wherein the inverter device has a phase difference of 180 °.
Two sets of current control units are provided to respectively control the two sets of half-bridge inverters so as to reduce the error by comparing the set current reference with the output current detection values of the two sets of half-bridge inverters. An inverter device characterized in that 8. The inverter device according to claim 4, wherein the energy stored in the reactor is converted to the first energy.
An inverter device characterized in that the two sets of capacitors connected in series from a winding and a second winding are respectively supplied with a predetermined energy distribution to balance the voltages of the two sets of capacitors. 9. The inverter device according to claim 7, further comprising a correction unit that generates a correction signal in response to a change in neutral point potential of the DC voltage and adds the correction signal to the current reference, and the neutral point is generated by the correction signal. An inverter device, wherein a direct current component is caused to flow in an output current of the half bridge inverter so as to suppress a potential change. 10. The inverter device according to claim 7, further comprising a switch for turning on / off a current flowing between a positive electrode or a negative electrode and a neutral point according to a change of a neutral point potential of the DC voltage. An inverter device, characterized in that the current supplied from the positive side and the negative side of the DC power supply is changed according to the change of the point potential to suppress the change of the neutral point potential.