JP2001069767A - Three-phase half-bridge inverter circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To balance the voltages impressed upon capacitors with each other by connecting a fifth switching element between the junction of the second winding of a choke coil with a second diode and the other end of a DC power source in a three-phase half-bridge type inverter circuit. SOLUTION: In a three-phase half-bridge inverter circuit, a fifth switching element T5 is connected between the junction of the second winding L2 of a choke coil L with a second diode D2 and the other end 12 of a DC power source 1. When the switching element T5 is turned on, a current flows from one end 11 to the other end 12 of the power source 1 through the second winding L2 of the choke coil L and fifth switching element T5 and energy is stored in the coil L. When the element T5 is turned off, on the other hand, the energy stored in the choke coil L is discharged, but, when VC1>VC2, the energy is shifted from the coil L to a second capacitor C2. When VC1<VC2, the energy is shifted to a first capacitor C1. Therefore, the voltages impressed upon the first and second capacitors C1 and C2 can be balanced with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-phase half-bridge type inverter circuit, and more specifically, to a DC voltage boosting means interposed therebetween, thereby boosting a DC voltage and connecting the DC voltage in series. 1. A bidirectional function that can balance the voltage applied to the second capacitor and convert DC power to three-phase AC power and three-phase AC power to DC power. The present invention relates to a half-bridge type inverter circuit.

[0002]

2. Description of the Related Art A half-bridge type inverter circuit includes a DC power supply, a series connection circuit of first and second capacitors,
A series connection circuit of first and second switching elements, and a series connection point of the first and second capacitors,
A load is connected between the second switching element and the series connection point, and has an advantage that the number of switching elements is half that of a full-bridge inverter circuit. It has been widely used in inverter circuits to which a DC power supply voltage twice or more than that of the above is input, and in recent years, it has been used also as a circuit for obtaining a three-phase output by taking advantage of these advantages.

In the above-described three-phase half-bridge type inverter circuit, even in the case of an inverter circuit to which a low DC power supply voltage is input, a boosting means for boosting the DC power supply voltage is interposed, and the inverter circuit is boosted by the boosting means. By inputting the obtained DC power, a current flowing through a switching element included in an inverter circuit is reduced, the switching element is reduced in size, and a wiring material is thinned.

In a three-phase half-bridge type inverter circuit in which such boosting means is interposed, it is necessary to boost the DC voltage to at least twice the peak value of the AC voltage to be obtained. The boost chopper circuit as shown in FIG.

The boost chopper circuit shown in FIG. 5 includes a choke coil L ₀ between one end 11 and the other end 12 of the DC power supply 1.
And connecting a series circuit of a switching element T _0, one input terminal 31 of the inverter circuit 3 a series connection point between the choke coil L ₀ and the switching element T ₀ through the diode D ₀ (first capacitor C as well as connected to _one end) formed by connecting the other end 12 of the DC power source 1 to the other input terminal 32 of the inverter circuit 3 (second end of the capacitor C _2). Reference numeral 2 denotes a capacitor for absorbing ripple.

The inverter circuit 3 comprises a first series connection circuit of a first capacitor C ₁ and a second capacitor C ₂ and a first switching element T ₁ and a second switching element T ₂ . The third connection between the second series connection circuit, the third switching element T ₃ and the fourth switching element T ₄
Are connected in parallel with each other, and the series connection point of the first capacitor C ₁ and the second capacitor C ₂ is set to a three-phase S phase, and the first switching element T ₁ and the second switching element T ₂ and the series connection point of the filter circuit 4 of the reactor L of ₄₁ via a three-phase R phase city, the third filter a series connection point of the switching element T ₃ and fourth switching element T ₄ in the three-phase half-bridge type connected as T phase of the three-phase through the reactor L ₄₂ to the load 5 of the circuit 4, and a capacitor C ₄₁ of the filter circuit 4 between the output side and the S-phase of the reactor L ₄₁ a configuration in which a capacitor C ₄₂ of the filter circuit 4 between the output side and the S-phase of the reactor L _42. Since such an inverter circuit 3 and the aforementioned boost chopper circuit are known,
The description of the operation is omitted.

[0007]

In the inverter circuit 3 and the [SUMMARY OF THE INVENTION], the load 5 has unbalanced components, the voltage applied to the first capacitor C ₁ and the second capacitor C ₂ becomes unbalanced However, there has been a problem that the output voltage from the side where the voltage has decreased does not reach the peak value.

In order to solve such a problem, conventionally, a first capacitor C ₁ and a second capacitor C ₂ have
The dummy resistors were connected in parallel, and the voltage imbalance was eliminated by balancing the voltage applied to the dummy resistors with the loss caused by the dummy resistors. since this loss is larger when the voltage applied first and if the unbalance voltage larger first capacitor C ₁ and the second capacitor C ₂ large, when used in such applications, the lowering of conversion efficiency It was not preferable because of the cause.

[0009]

According to a first aspect of the present invention, there is provided a DC power supply and a first series connection in which the other end of the first capacitor is connected to one end of a second capacitor. Circuit and the other end of the first switching element to the second
A second series connection circuit connected to one end of the first switching element; and a third series connection circuit connected to the other end of the third switching element to one end of the fourth switching element. , One end of the first switching element and one end of the third switching element are connected to each other, and the other end of the second capacitor,
The other end of the second switching element and the other end of the fourth switching element are connected to each other, and the first, second, and third switching elements are connected to each other.
A three-phase half-bridge type inverter circuit configured to obtain an output of each of the three phases from each series connection point of the series connection circuit, wherein a center connection point is provided between the series connection point of the first capacitor and the second capacitor. A choke coil having a tap connected thereto, a first winding of the choke coil being connected to the other end of the second capacitor via a first diode, and a second winding connecting a second diode; One end of the DC power supply is connected to a center tap of the choke coil, a connection point between a second winding of the choke coil and a second diode, and the DC power supply. A fifth switching element is connected between the first capacitor and the second capacitor, so that the load 5 has an unbalanced component and has a first capacitor and a second capacitor. Even when it is conceivable that the imbalance of the voltage applied to the first and second capacitors is large, or when the input voltage of the half-bridge type inverter circuit is high and the voltage applied to the first and second capacitors is large. The first capacitor and the second capacitor without lowering the conversion efficiency.
Can be balanced.

According to a second aspect of the present invention, there is provided the three-phase half-bridge inverter circuit according to the first aspect, wherein a center tap is connected to a series connection point of the first capacitor and the second capacitor. Having a coil,
A first winding of the choke coil is connected to the other end of the second capacitor via a first parallel connection circuit of a first diode and a first transistor, and a second winding is connected to a second winding of the second capacitor. One end of the DC power supply is connected to one end of the first capacitor through a second parallel connection circuit of a diode and a second transistor, and one end of the DC power supply is connected to a center tap of the choke coil. A third parallel connection circuit of a third diode and a third transistor is connected between a connection point between the winding and the second parallel connection circuit and the other end of the DC power supply. With this, the voltage applied to the first capacitor and the voltage applied to the second capacitor can be balanced, and the inverter circuit can convert the DC power to the three-phase AC power. You can have the conversion and bidirectional function capable of performing conversion into DC power from three-phase AC power.

According to a third aspect of the present invention, in the three-phase half-bridge inverter circuit according to the first or second aspect, the DC power supply is a storage battery, and a photomos circuit is used as a voltage detection circuit for detecting a voltage of the storage battery. Since the voltage detection circuit can be disconnected when it is not necessary to detect the voltage of the storage battery, unnecessary discharge of the storage battery can be prevented.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on its embodiments.

FIG. 1 is a circuit diagram of a three-phase half-bridge type inverter circuit according to a first embodiment of the present invention.

The three-phase half-bridge type inverter circuit shown in FIG. 1 is characterized by a DC power supply 1 and a first capacitor C
₁ is connected to one end of a _second capacitor C2.
A series circuit of a second series connection circuit which connects the first end of the switching element T ₁ to a second end of the switching element T _2, a third of the other end of the switching element T ₃ 4 and a third series circuit connected to one end of the switching element T ₄ as well as connected in parallel, the first center tap to a series connection point of the capacitor C ₁ and the second capacitor C ₂ is connected Having a choke coil L,
The choke coil first winding L ₁ is a first diode second winding L ₂ is a second diode D ₂ is connected to the second end of the capacitor C ₂ through the D ₁ of the L One end 11 of the DC power supply 1 is connected to a center tap of the choke coil L, and a second winding L of the choke coil L is connected to one end of the first capacitor C _1
2 is that the switching element T ₅ of the fifth is connected between the second diode D ₂ and the other end 12 of the DC power source 1 and the connection point between. The two capacitor for ripple absorption, 4 reactor L _41, reactor L _42, capacitor C _41, a filter circuit comprising a capacitor C _42.

In the above-described three-phase half-bridge type inverter circuit, the input voltage, that is, the first capacitor C
An error voltage obtained by detecting a sum voltage V _C of a voltage V _C1 applied to ₁ and a voltage V _C2 applied to the second capacitor C ₂ , and amplifying an error between the detected voltage and a voltage reference value. compared with the triangular wave can be PWM control signal the sum voltage V _C by creating controls the fifth switching element T ₅ of to be constant, also detects the sum voltage V _C, which current An error voltage obtained by amplifying an error between a reference value and an error voltage obtained by amplifying the error between the current target value and the input current of the three-phase half-bridge inverter circuit by smoothing an error voltage obtained by error amplification. it is possible to control the switching element T ₅ of the fifth so that ripples of the AC power source 1 contained in the input current by creating a PWM control signal becomes smaller than the triangular wave.

Next, the operation of the above-described three-phase half-bridge type inverter circuit will be described.

(Operation mode 1) This operation mode 1 is the fifth operation mode.
Switching element T ₅ of the case on. That is, when the switching element T ₅ of the fifth is turned on, one end of the DC power source 1 11 → second winding of the choke coil L L ₂ →
Current flows through the path of the fifth switching element T ₅ → the other end 12 of the DC power supply 1 and energy is accumulated in the choke coil L.

(Operation Mode 2) This operation mode 2 is the fifth operation mode.
Switching element T ₅ of the case off. That is, the switching element T ₅ of the fifth is turned off, but the energy in the operation mode 1 have been accumulated in the choke coil L is discharged, the voltage V _C1 applied to the first capacitor C ₁ second Voltage V _C2 applied to capacitor C ₂
The release route differs depending on the magnitude relation of

That is, the first winding L of the choke coil L
If the second winding L ₂ of the number of turns of _the number of turns = choke coil L, V _C1> For V _C2 at the node between the first winding L ₁ and the first diode D ₁ of the choke coil L potential first diode D is lower than the potential of the other end of the second capacitor C ₂ (the anode side of the potential of the first diode D _1)
1 is forward biased, the first winding L ₁ of the choke coil L → the second capacitor C ₂ → the first diode D ₁
→ a current flows in the first winding L ₁ becomes the path of the choke coil L is energy of the choke coil L is transferred to the second capacitor C _2. At this time, the choke coil secondary winding L ₂ and the potential at the connection point between the second diode D ₂ second diode D ₂ is reverse biased is lower than the first end of the potential of the capacitor C ₁ of L The choke coil L
No current flows through the path of the second winding L ₂ → the second diode D ₂ → the first capacitor C ₁ → the second winding L ₂ of the choke coil L.

Similarly, when V _C1 <V _C2 , the potential at the connection point between the second winding L ₂ of the choke coil L and the second diode D ₂ is the potential at one end of the first capacitor C ₁ (the potential at one end of the first capacitor C ₁ ). The potential on the cathode side of the _second diode D2).
Since the diode D ₂ is forward biased, the second winding of the choke coil L L ₂ → second diode D ₂ → first capacitor C ₁ → second winding L ₂ consisting path current of the choke coil L energy of the choke coil L is transferred to the first capacitor C ₁ is flowing. At this time, the first winding L ₁ of the choke coil L and the potential at the connection point between the first diode D ₁ the first diode D ₁ is reverse higher than the second electric potential at the other end of the capacitor C ₂ Being biased, the first winding L ₁ of the choke coil L → the second capacitor C ₂
No current flows through the path of the first diode D ₁ → the first winding L ₁ of the choke coil L.

According to each of the above operation modes, V _C1 > V
Since in the case of _C2 energy of the choke coil L is transferred to the second capacitor C _2, the voltage V _C2 of the second voltage V _C2 of the capacitor C ₂ is applied to the second capacitor C ₂ rises first it is possible to balance the voltage V _C1 applied to the first capacitor C _1, in the case of V _C1 <V _C2 because energy of the choke coil L is transferred to the first capacitor C _1, the first capacitor C ₁ voltage V _C1 can be balanced with the voltage V _C2 applied to the first voltage V _C1 applied to the capacitor C ₁ to the second capacitor C ₂ rises.

FIG. 2 is a circuit diagram of a three-phase half-bridge type inverter circuit according to a second embodiment of the present invention.

The feature of the embodiment shown in FIG. 2 is that the first diode D ₁ is replaced with the first diode D ₁ instead of the first diode D ₁ .
The transistors S ₁ and the first parallel connection circuit connected in parallel, instead of the second diode D _2, a second parallel connection of connecting the second transistor S ₂ in parallel with the second diode D ₂ and circuitry, in place of the switching element T ₅ of the fifth, third transistor S to the third diode D _3
3 is a third parallel connection circuit connected in parallel.

According to the above-described second embodiment, the third embodiment
ON of the transistor S _3, it is possible to balance the voltage V _C2 of the first voltage V _C1 of the capacitor by the off the second capacitor, the function of converting the DC power previously described three-phase AC power, the three Since it can be made bidirectional with the function of converting phase AC power to DC power, it can be used for interconnection operation between a system that obtains three-phase AC power and a DC power supply such as a solar cell .

That is, the AC side of the above-described single-phase full-bridge type inverter circuit and the system are interconnected, and the AC power from the system is converted into DC power by the inverter circuit and supplied to the DC power supply 1 The operation is performed in the following operation modes 3 and 4.

(Operation Mode 3) This operation mode 3 is the third operation mode.
Of the transistor S ₃ is turned off, first the first parallel connection circuit
Of a case where the transistor S ₁ and the second transistor S ₂ of the second parallel connection circuit is ON, thereby, a second first end of the capacitor C ₁ → second transistor S ₂ → choke coil L Winding L ₂ → First of choke coil L
A current flows through a path from the winding L ₁ → the first transistor S ₁ → the other end of the second capacitor C ₂ , and energy is stored in the choke coil L.

(Operation Mode 4) This operation mode 4 is the third operation mode.
Of the transistor S ₃ is turned off, first the first parallel connection circuit
Transistors S ₁ and the case of the second transistor S ₂ is turned off in the second parallel connection circuit, thereby, the second winding L ₂ → DC power source 1 → the third diode → choke coil of the choke coil L of The current stored in the choke coil L is transferred to the DC power supply 1 by passing a current through the path of the second winding L _{2 of} L, so that the AC power from the system is converted into DC power by the inverter circuit 3. It can be supplied to a DC power supply 1 such as a storage battery.

Further, in each of the above-described embodiments, an inverter circuit is used in an uninterruptible power supply,
Is a storage battery, and if a voltage detection circuit 20 for detecting the voltage of the storage battery is provided, the storage battery may be continuously discharged with a very small current by the voltage detection circuit 20, and a problem that recovery of capacity due to sulfation may not be achieved may occur. 3 and 4 in which the photomos circuit 21 is interposed in the voltage detection circuit 20, so that the above-mentioned problem can be solved.

[0029]

As described above, the present invention relates to a three-phase half-bridge inverter circuit in which the load 5 has an unbalanced component and the voltage applied to the first and second capacitors is unbalanced. Is large, or when the input voltage is high and the voltage applied to the first and second capacitors is large,
The voltage applied to the first capacitor and the second capacitor can be balanced without lowering the conversion efficiency, and the DC potential with respect to the S phase can be directly connected to one end of the DC power source with the S phase as a neutral point. It has a bidirectional function that can stabilize power, reduce high-frequency leakage current and EMI noise, and convert DC power to three-phase AC power and three-phase AC power to DC power. This greatly contributes to the expansion of applications of the three-phase half-bridge type inverter circuit.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a three-phase half-bridge inverter circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a three-phase half-bridge inverter circuit according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram in a case where a voltage detection circuit is provided in the three-phase half-bridge inverter circuit according to the embodiment of FIG. 1;

FIG. 4 is a circuit diagram in the case where a voltage detection circuit is provided in the three-phase half-bridge inverter circuit according to the embodiment of FIG. 2;

FIG. 5 is a circuit diagram of a conventional three-phase half-bridge type inverter circuit.

[Explanation of symbols]

 1 DC power supply 2 Capacitor 3 Inverter circuit 4 Filter circuit 5 Load

Claims (3)

[Claims] 1. A DC power supply, a first series connection circuit in which the other end of a first capacitor is connected to one end of a second capacitor, and the other end of the first switching element is connected to one end of a second switching element. And a third series connection circuit in which the other end of the third switching element is connected to one end of the fourth switching element, and one end of the first capacitor, One end of the switching element and one end of the third switching element are connected to each other, and the other end of the second capacitor, the other end of the second switching element, and the other end of the fourth switching element are connected to each other. A three-phase half-bridge type inverter circuit configured to obtain three-phase outputs from respective series connection points of the first, second, and third series connection circuits, wherein the first capacitor and a third A choke coil having a center tap connected to a series connection point with the second capacitor, a first winding of the choke coil being connected to the other end of the second capacitor via a first diode, Second
A winding is connected to one end of the first capacitor via a second diode, one end of the DC power supply is connected to a center tap of the choke coil, and a second winding of the choke coil and a second diode A fifth switching element is connected between the connection point of the DC power supply and the other end of the DC power supply. 2. The three-phase half-bridge type inverter circuit according to claim 1, further comprising a choke coil having a center tap connected to a series connection point between said first capacitor and said second capacitor. Is connected to the other end of the second capacitor via a first parallel connection circuit of a first diode and a first transistor, and a second winding is connected to a second diode and a second transistor. The first transistor through a second parallel connection circuit with two transistors.
One end of the DC power supply is connected to a center tap of the choke coil, and a connection point between a second winding of the choke coil and a second parallel connection circuit and the other end of the DC power supply Characterized in that a third parallel connection circuit of a third diode and a third transistor is connected between the inverter and the third diode. 3. The three-phase half-bridge inverter circuit according to claim 1, wherein the DC power supply is a storage battery, and a photomos circuit is inserted in a voltage detection circuit for detecting a voltage of the storage battery. Three-phase half-bridge type inverter circuit.