CN1336715A - Mixed bridge-type zero-voltage and zero-current switch three level DC converter - Google Patents

Abstract

The invention relates to a zero-voltage zero-current switching hybrid full-bridge three-level direct-current converter, which belongs to direct-current converters. It includes an input voltage dividing capacitor circuit 1, a blocking capacitor 4, an isolation transformer 5, and a rectification and filtering circuit 6. It is characterized in that it also includes a three-level bridge arm 2 and a two-level bridge arm 3. The voltage stress of the switch tube of the three-level bridge arm is half of the input voltage, which can realize zero-voltage switching in a wide load range, and MOSFET can be selected; the voltage stress of the switch tube of the two-level bridge arm can be input voltage, which can be Realize zero-current switching in a wide load range, and IGBT can be selected, and has the advantages of small size, light weight, and good dynamic characteristics.

Description

Zero-Voltage Zero-Current Switching Hybrid Full-Bridge Three-Level DC Converter

technical field

The zero-voltage zero-current switching hybrid full-bridge three-level DC converter of the present invention belongs to the DC converter of an electric energy conversion device.

Background technique

With the development of power electronics technology, the requirements for power converters are getting higher and higher, especially the requirements for input power factor are getting higher and higher. After three-phase power factor correction, the output voltage of the circuit can generally reach 760-800V, sometimes even 1000V, which requires increasing the switching tube voltage rating of the subsequent DC converter, making it difficult to choose a suitable power switching tube. However, the voltage stress of the switching tube of the three-level DC converter is half of the input DC voltage, so it is easy to select a suitable switching tube.

In order to reduce the volume and weight of the converter, the switching frequency must be increased, which requires the soft switching of the switching tube (that is, zero-voltage switching or zero-current switching) to reduce switching losses. At present, the soft-switching three-level DC converters can be divided into two categories: zero-voltage switching and zero-voltage zero-current switching. The two outer switching tubes of the zero-voltage switching three-level DC converter can realize zero-voltage switching in a wide load range, but the two inner switching tubes cannot achieve zero-voltage switching when the load is light; for zero-voltage zero Current switch three-level DC converter (patent number: 00219197.0), the two outer switch tubes can realize zero voltage switching in a wide load range, and the inner two switch tubes can realize zero current in a wide load range switch. MOSFET can be used for the two switch tubes outside, and IGBT can be used for the two switch tubes inside. For the current device level, it is easy to buy high-voltage IGBTs (such as 1200V), so IGBTs do not play their advantages here.

Contents of the invention

The purpose of the present invention is to provide a soft switch that realizes switching in a wide load range, can make full use of the high-voltage switch tube IGBT, and at the same time can reduce the volume and weight of the input and output filters, and can improve the zero voltage of the dynamic characteristics of the converter Zero-current switching hybrid full-bridge three-level DC converter. This DC converter includes an input voltage dividing capacitor circuit, a blocking capacitor circuit, an isolation transformer, and a rectification and filtering circuit. It is characterized in that the inverter bridge circuit is composed of a three-level inverter bridge arm and a two-level inverter bridge arm. . Since one bridge arm of the DC converter is a three-level bridge arm, the voltage stress of the switching tube is half of the input voltage, and zero-voltage switching can be realized in a wide load range, so MOSFET can be selected; the other bridge arm It is a two-level bridge arm, which is composed of two switch tubes. The voltage stress of the switch tube is the input voltage, which can realize zero current switching in a wide load range, so IGBT can be selected; the converter outputs the rectified voltage waveform The AC component is very small, so the output filter can be greatly reduced, thereby reducing the size and weight of the filter, and improving the dynamic characteristics of the converter; the input current ripple of the converter is small, so the input filter can be reduced.

Description of drawings

Accompanying drawing 1, the circuit composition schematic diagram of the present invention.

Accompanying drawing 2-6, the circuit embodiment figure of several different composition forms of the present invention.

Accompanying drawing 7, the main waveform schematic diagram of the present invention.

Figures 8-15 are schematic diagrams of equivalent circuits of each switch mode of the present invention.

Label names in each dotted line box in attached drawing 1: 1, input voltage dividing capacitor circuit, 2, three-level inverter bridge arm, 3, two-level inverter bridge arm, 4, blocking capacitor circuit, 5, isolation Transformer, 6, rectification filter circuit.

Detailed ways

Describe the concrete composition of the present invention according to accompanying drawing 1-6.

Accompanying drawing 1 is a schematic diagram of basic circuit composition of the present invention, in input voltage dividing capacitor circuit 1, the capacity of voltage dividing capacitor Cin ₁ and Cin ₂ is equal, and very large, their voltages are half of the input supply voltage Vin, i.e. Vcin ₁ =Vcin ₂ =Vin/2.

The composition of the three-level inverter bridge arm 2 is that the four switching tubes Q ₁ , Q ₂ , Q ₃ , and Q ₄ are respectively antiparallel connected with diodes D ₁ , D ₂ , D ₃ , and D ₄ and then connected in parallel with capacitors (or externally connected Capacitors) C ₁ , C ₂ , C ₃ , C ₄ , in which the switching tubes Q ₁ and Q ₄ form the leading tube, and the lagging tube composed of Q ₂ and Q ₃ are respectively connected in parallel with two series freewheeling diodes D ₇ and D ₈ and connecting capacitor C _ss , the function of parallel capacitor C _ss is to connect the switching process of two pairs of switching tubes Q ₁ and Q ₄ and Q ₂ and Q ₃ . When the converter works in a steady state, the voltage on the capacitor C _ss is constant as Vin/2. The voltage stresses of Q ₁ , Q ₂ , Q ₃ , and Q ₄ are all half of the input voltage, and can realize zero-voltage switching in a wide load range, so MOSFET switches can be used.

The two-level inverter bridge arm 3 is composed of two switch tubes _Q5 and _Q6 and two diodes _D5 and _D6 . The two diodes D ₅ and D ₆ can be connected in series with the corresponding switching tubes Q ₅ and Q ₆ respectively (as shown in Figure 1), or can be connected in parallel with Q ₅ and Q ₆ respectively (as shown in Figures 2-6) , the voltage stress of the switching tube is the input voltage, which can realize zero-current switching in a wide load range, so the high-voltage switching tube IGBT can be selected.

The blocking capacitor circuit 4 is used to realize zero-current switching of _Q5 and _Q6 .

Both the isolation transformer 5 and the rectification filter circuit 6 can adopt the prior art.

Accompanying drawing 2 is that a saturated inductance L _s is connected in series with the primary side of the isolation transformer 5 in Fig. 1 .

Attached Figure 3 is to move the blocking capacitor C _b in Figure 1 to the secondary side of the isolation transformer 5, and connect it in series with a switch tube Q _b , and the S pole of Q _b is connected to the cathodes of the two output rectifier diodes D _R1 and D _R2 , the other end of the blocking capacitor C _b is connected to the center tap of the secondary winding of the isolation transformer 5 .

Accompanying drawing 4 removes the blocking capacitor C _b in Fig. 1 , and adds two diodes D _b1 and D _b2 and a capacitor C _b1 in the rectification filter circuit 6 . That is, a diode D _b1 is connected in series with a capacitor C _b1 and then connected in parallel to the output terminal of the secondary side of the isolation transformer, and another diode D _b2 is connected across the series connection point of the diode D _b1 and the capacitor C _b1 and the filter inductance L _f and filter Between the series connection points of the capacitor C _f .

Figure 5 also removes the blocking capacitor C _b in Figure 1, and adds two capacitors C _b1 and C _b2 and three diodes D _b1 , D _b2 , and D _b3 to the rectification filter circuit 6, that is, a diode D _b1 is connected in series with a capacitor C _b1 and connected to the output terminal of the secondary side of the isolation transformer, and the other capacitor C _b2 . It is connected in series with the second diode D _b2 and connected to the input end of the rectification filter circuit, and the third diode D _b3 is connected across the series connection point of the above two series circuits.

Accompanying drawing 6 moves the blocking capacitor C _b in Fig. 1 to the rectification and filtering circuit, and at the same time adds two secondary windings to the isolation transformer 5 to form a current reset together with three diodes D _a1 , D _a2 , and D _a3 circuit.

Figures 2-6 have no essential difference compared with Figure 1, but Figure 3, Figure 4 and Figure 5 can better suppress the voltage spike on the output rectifier.

Taking accompanying drawing 1 as an example, the specific working principle of the present invention is described in conjunction with accompanying drawings 7 to 15. From accompanying drawing 7, it can be known that the entire converter has 14 switching modes in one switching cycle, respectively [t ₀ moment], [t0 t1], [t ₁ t ₂ ], [t ₂ t ₃ ], [t ₃ t ₄ ], [t ₄ t ₅ ], [t ₅ t ₆ ], [t ₆ t ₇ ], [t ₇ t ₈ ], [t ₈ t ₉ ], [t ₉ t ₁₀ ], [t ₁₀ t ₁₁ ], [t ₁₁ t ₁₂ ], [t ₁₂ t ₁₃ ] [t ₁₃ t ₁₄ ] (see attached drawing 7) , wherein, [t ₀ t ₇ ] is the first half cycle, and [t ₇ t ₁₄ ] is the second half cycle. The working conditions of each switch mode of [t ₀ t ₇ ] are specifically analyzed below. In the accompanying drawing 7 , made the following assumptions: a) The two input divider capacitors are replaced by two voltage sources whose voltage is V _in /2, and the output filter circuit is replaced by a current source whose output current is I ₀ . 1. Switch mode 0 [before time t ₀ ] (corresponding to Figure 8)

Before time t ₀ , Q ₁ , Q ₂ and Q ₆ are turned on, v _AB =V _in , the primary side supplies power to the load, and the primary side current _ip charges the blocking capacitor C _b . The output rectifier D _R1 is turned on, and D _R2 is cut off. At time t ₀ , i _p =I _p0 =I ₀ /K, where K is the primary and secondary turns ratio of the transformer. The voltage of C _b is V _cb (t ₀ ). 2. Switching mode 1 [t ₀ t ₁ ] [corresponding to Figure 9]

Turn off Q ₁ at t ₁ moment, i _p charges C ₁ , and discharges C ₄ through capacitor C _ss at the same time. Due to C ₁ and C ₄ , Q ₁ is zero voltage off. At this time, L _1k and L _f are connected in series, and _ip approximately keeps I _p0 unchanged. i _p continues to charge C _b . The voltage of _C1 increases linearly and the voltage of _C4 decreases linearly. At time t ₁ , when the voltage of C ₁ rises to V _in /2, the voltage of C ₄ drops to 0, the potential of point A is V _in /2, and D ₇ is naturally turned on. 3. Switch mode 2 [t ₁ t ₂ ] [corresponding to accompanying drawing 10]

When D ₇ is turned on, the voltage of C ₄ is clamped at 0, so Q ₄ can be turned on with zero voltage. The dead time t _d (14)>t ₀₁ between Q ₄ and Q ₁ driving signals. During this period of time, v _AB =V _in /2, the primary side continues to supply power to the load, and i _p charges C _b . 4. Switching mode 3 [t ₂ t ₃ ] [corresponding to Figure 11] Turn off Q ₂ at time t ₂ , charge C ₂ with i _p , and discharge C ₃ through capacitor C _ss at the same time. Due to C ₂ and C ₃ , Q ₂ is zero voltage off. At this time, L _1k and L _f are connected in series, i _p =I _p0 . I _p continues to charge C _b , because C _b is very large, it can be considered that its voltage is basically unchanged during this time. The voltage of _C2 increases linearly and the voltage of _C3 decreases linearly. At time _t3 , the voltage of _C2 rises to V _in /2, the voltage of _C3 drops to 0, and _D3 turns on naturally. 5. Switch mode 4 [t ₃ t ₄ ] [corresponding to accompanying drawing 12]

When D ₃ is turned on, the voltage of C ₃ is clamped at 0, so Q ₃ can be turned on with zero voltage. During this time, D ₃ , D ₆ and Q ₆ are on, and v _AB =0. v _cb makes i _p begin to decrease, i _p is not enough to provide load current, so _DR1 and _DR2 are turned on at the same time, so the voltage of the primary and secondary windings of the transformer is zero. At this moment, v _cb is all added to L _lk , i _p decreases, and v _cb rises. Because L _lk is small and C _b is large, it can be considered that v _cb is basically unchanged in this switching mode, and the approximate line of i _p decreases. drops to zero at _ip . The duration of the switching mode is: 6. Switching mode 5 [t ₄ t ₅ ] [corresponding to accompanying drawing 13]

In this switching mode, i _p has a tendency to flow in the opposite direction, but the presence of D ₆ keeps i _p at zero, and v _B = -V _cbp at this time. The two rectifiers are turned on at the same time to share the load current equally. 7. Switch mode 6 [t ₅ t ₆ ] [corresponding to accompanying drawing 14]

Turn off Q ₆ at time t ₅ , and no current flows in Q ₆ at this time, so Q ₆ is turned off with zero current. After a small time delay, Q ₅ is turned on, because of the existence of L _lk , i _p cannot change abruptly, and Q ₆ is turned on with zero current. Because _ip is not enough to provide load current, the two rectifiers are still turned on at the same time, and the primary and secondary windings of the transformer are clamped at zero voltage. At this time, the voltage applied to L _lk is -(V _in +V _cbp ), and i _p starts from zero and increases linearly in the opposite direction. At time t ₆ , i _p increases in the opposite direction to the load current I ₀ /K converted to the primary side. The time of the switch mode is: 8, switch mode 7 [t ₆ t ₇ ] (corresponding to Figure 14)

From time t ₆ onwards, the primary side provides energy for the load and reverse charges _Cb at the same time. D _R1 turns off and all load current flows through D _R2 .

At t ₇ moment, turn off Q ₄ , start another half cycle [t ₇ t ₁₄ ], its working situation is similar to [t ₀ t ₇ ] described above.

A specific example of the present invention is as follows: the input AC voltage is 380V/50HZ AC, and the DC voltage obtained after rectification and filtering is V _in =530VDC; the output DC voltage is V ₀ =54VDC; the output current I ₀ =50A; the primary and secondary turns of the transformer The _ratio K=7; the output filter inductance is L _f =10μH; the output filter capacitor is C _f = _10000μF ; the connection capacitance C _ss is _{2.2μF ;} Junction capacitance C ₁ -C ₄ ) is MOSFET (model is IRF460); switch tubes Q ₅ and Q ₆ are IGBT (model is CT60AM-20); diodes D ₅ , D ₆ , D ₇ , and D ₈ are DSEI130-06A ; The output rectifier diodes _DR1 and _DR2 are MEK95-06DA; the switching frequency is f _s =50kHZ.

It can be seen from the above description that the three-level zero-voltage switching DC converter with clamping diodes proposed by the present invention has the following advantages:

1. One bridge arm of the converter is a three-level bridge arm, and the voltage stress of the switching tube is half of the input voltage, which can realize zero-voltage switching in a wide load range, so MOSFET can be selected;

2. The other bridge arm is a two-level bridge arm, which is composed of two switch tubes. The voltage stress of the switch tube is the input voltage, which can realize zero current switching in a wide load range, so IGBT can be used.

3. The AC component of the output rectified voltage waveform of the converter is very small, so the output filter can be greatly reduced, thereby reducing the size and weight of the filter, and improving the dynamic characteristics of the converter.

4. The input current ripple of the converter is very small, so the input filter can be reduced.

Claims (3)

1, a kind of zero-voltage and zero-current switch mixed type full-bridge three-level DC converter comprises input dividing potential drop condenser network, blocking capacitor circuit, isolating transformer, current rectifying and wave filtering circuit, it is characterized in that, also comprise the tri-level inversion brachium pontis and the two-level inverter arm that are connected between input dividing potential drop condenser network and the isolating transformer.

2, according to the described zero-voltage and zero-current switch mixed type of claim 1 full-bridge three-level DC converter, it is characterized in that, the composition of tri-level inversion brachium pontis is, four switching tubes are distinguished reverse parallel connection diode and electric capacity separately, two diodes of connect mutually in parallel between the anode of the negative electrode of second switching tube and the 3rd switching tube, the serial connection point of two diodes is connected in the serial connection point of two electric capacity importing the dividing potential drop condenser network.

3, according to claim 1 or 2 described zero-voltage and zero-current switch mixed type full-bridge three-level DC converters, it is characterized in that, the two-level inverter arm by two switching tubes separately respectively diode of serial or parallel connection formed.

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