CN204442168U - A kind of based on without bridge CUK isolated form Three Phase Power Factor Correction Converter - Google Patents

Abstract

The utility model provides a bridgeless CUK-based isolated three-phase power factor correction converter. The converter of the present invention includes a star-connected three-phase AC power supply, three bridgeless CUK isolated converters, output filter capacitors and loads, and the input ends of the three bridgeless CUK isolated converters are respectively connected to the three-phase AC The A phase, B phase, and C phase voltage of the power supply are connected, and the three bridgeless CUK isolated converters are connected to each other through interconnection terminals; the outputs of the three bridgeless CUK isolated converters are connected to two terminals of the output filter capacitor. The two ends of the output filter capacitor are connected to the load. The utility model has the functions of step-down and step-down output, realization of power factor correction, isolation of input and output, and elimination of circulation caused by phase-to-phase coupling. The circuit parameters of the utility model are simple in design and easy to control.

Description

An isolated three-phase power factor correction converter based on bridgeless CUK

technical field

The utility model relates to the field of power factor correction of three-phase alternating current, in particular to a three-phase power factor correction converter for buck-boosting and isolation input and output.

Background technique

The power of the switching power supply converter is greater than 75W, and a power factor correction converter is added before it is connected to the grid, so as to reduce the pollution of harmonics to the grid. In medium and high power (above a few kilowatts) applications, a three-phase power supply is generally used for power supply. The use of traditional three-phase uncontrolled rectifiers will cause distortion of the input current and increase the harmonic content, threatening the safe operation of the power grid. The output voltage of the widely used three-phase BOOST PWM rectifier is as high as 500V, which requires a high voltage stress on the subsequent load. When low voltage output is required, a DC/DC converter is added to the output end to reduce the voltage to the final voltage. This increases the cost and difficulty of power supply design and reduces the efficiency of the whole machine. The PWM rectifier circuit of the three-phase BUCK structure can realize step-down, but cannot realize step-up. When high-voltage output is required, a DC/DC converter is added to the output, which increases the cost and difficulty of power supply design and reduces the efficiency of the whole machine. Neither the PWM rectifier circuit with the three-phase BOOST structure nor the PWM rectifier circuit with the three-phase BUCK structure can realize electrical isolation. Although the three-phase BUCK-BOOST PWM rectifier circuit can realize buck-boost, it cannot realize electrical isolation, and transmits the interference of the subsequent load to the input AC power side, which increases the difficulty of power factor correction. If three traditional single-stage non-isolated BOOSTs are directly connected in parallel to the three phases, there will be a circulating current between phases, which will affect the operation of the non-isolated BOOST converter. Each phase consists of a non-isolated BOOST and a post-stage isolated DC/DC converter in parallel to form a three-phase power factor correction converter. Although it has the functions of buck-boost and isolation, it needs to design a two-stage circuit. The efficiency of the whole machine is low, and each stage circuit needs a control circuit, which increases the design cost and difficulty. For the traditional CUK and SEPIC isolated converters, three-phase parallel connection can also be realized, but since the front stage generally uses an uncontrolled diode rectifier bridge, two diodes are turned on every half power frequency cycle and there is a reverse recovery of the rectifier diode The problem is that the diode uncontrolled rectifier bridge and the switch tube in the traditional isolated CUK and SEPIC converters are hard-switched, and the loss of the switch tube is large, which reduces the working efficiency of the whole machine.

Utility model content

The purpose of this utility model is to overcome the shortcomings of the above-mentioned prior art and provide a bridgeless CUK-based isolated three-phase power factor correction converter. The specific technical solution is as follows.

A bridgeless CUK isolated three-phase power factor correction converter, which includes a star-connected three-phase AC power supply, three bridgeless CUK isolated converters with the same structure, an output filter capacitor and a load, the three described The input ends of the bridgeless CUK isolated converters are respectively connected to the A-phase, B-phase, and C-phase voltages of the three-phase AC power supply, and the three bridgeless CUK isolated converters are connected to each other through interconnection terminals; The output terminal of the bridgeless CUK isolated converter is connected to the two ends of the output filter capacitor, and the two ends of the output filter capacitor are connected to the load.

Further, among the three bridgeless CUK isolated converters with the same structure, each bridgeless CUK isolated converter includes an input inductor, a first primary diode and a second primary diode, a first switch tube and The second switching tube, primary side capacitor, high frequency transformer, secondary side capacitor, secondary side diode and secondary side inductance are composed of one end of the input inductance as the input end of the bridgeless CUK isolated converter, and the other end of the input inductance is connected to the first The anode of a primary side diode and the cathode of the second primary side diode, the other end of the first primary side diode is connected to the source of the first switch tube and one end of the primary side capacitor; the drain of the first switch tube is connected to the second switch tube The source of the high-frequency transformer is connected, and one end is drawn out at the connection point as an interconnection end to connect to another converter; the other end of the primary side capacitor is connected to the same name end of the primary side of the high-frequency transformer; the anode of the second primary side diode is connected to the second The drain of the switch tube is connected to the non-identical end of the primary side of the high-frequency transformer; the non-identical end of the secondary side of the high-frequency transformer is connected to one end of the secondary capacitor; the other end of the secondary capacitor is connected to the cathode of the secondary diode and the secondary inductance The other end of the secondary inductance is used as the positive terminal of the output terminal, and is connected to the output filter capacitor and the positive terminal of the load; the same name terminal of the secondary side of the high frequency transformer is connected to the anode of the secondary diode, and at this connection One end is drawn out as the common ground end of the output end.

Further, each of the three bridgeless CUK isolated converters has a separate controller or is controlled simultaneously by the same controller.

Further, the load is a pure resistive load, a resistive-inductive load, a resistive-capacitive load or a switching converter.

Further, all the diodes are ordinary diodes, power diodes, thyristors or full-control switch tubes.

Further, all the switch tubes are MOSFETs, IGBTs with parasitic anti-parallel diodes or unidirectional conduction switch tubes with anti-parallel diodes.

Compared with the existing technology, the utility model has the advantages of: realizing a power factor close to 1, realizing the step-down and step-down of the input voltage, meeting various electrical requirements of the subsequent load, and the connection between the input AC power supply side and the output load end. electrical isolation. When the three converters all work in the discontinuous mode, the utility model only needs one voltage loop to control the three isolated converters and realize power factor correction. Compared with the traditional BOOST PWM rectifier circuit, the control method is very simple. The two switching tubes used in the previous stage replace the diodes in the rectifier bridge. In the positive half cycle of the input power supply, the upper switching tube S _{1_i} (i=1,2,3) of each converter realizes zero current turn-on, and the lower switching tube S _{2_i} (i=1, 2, 3) realizes zero-voltage turn-on, and the efficiency of the whole machine is relatively high. The three converters in the bridgeless CUK isolated three-phase power factor correction converter proposed by the utility model have the same structure and the same parameters, and reduce the design difficulty and cost of the whole machine, and have great advantages in industrial assembly line production. big advantage.

Description of drawings

Figure 1 is a structural diagram of a bridgeless CUK isolated three-phase power factor correction converter.

Figure 2 is a three-phase AC waveform diagram of a power frequency cycle.

Fig. 3 is a working principle diagram of a three-phase power factor correction converter when six switching tubes are turned on at the same time.

Fig. 4 is a working schematic diagram of the converter when the six switching tubes are turned off and the secondary diodes _{ID3_i} (i=1, 2, 3) are all zero.

Fig. 5 is a working schematic diagram of the converter when the six switch tubes are turned off, the secondary diode current _{ID3_i} (i=1, 3) is not zero, and _{ID3_2} is zero.

Fig. 6 is a working schematic diagram of the converter when the six switch tubes are turned off, the secondary diode current _{ID3_3} is not zero, and _{ID3_i} (i=1, 2) is zero.

Fig. 7 is a working schematic diagram of the converter when the six switching tubes are turned off and the secondary diodes _{ID3_i} (i=1, 2, 3) are all zero.

Fig. 8 shows the input inductor current and output voltage waveforms when the design of the embodiment of the utility model is 400V.

Fig. 9 is a 150-times enlarged waveform of the voltage and current of the upper and lower switch tubes of the bridgeless CUK isolated converter (3).

Figure 10 shows each input inductor current and the corresponding AC phase voltage waveform.

Fig. 11 shows a short segment of the corresponding three-phase AC voltage waveform and three secondary diode current waveforms of the intercept mode 5.

Detailed ways

In order to further illustrate the content and characteristics of the present utility model, the specific embodiments of the present utility model are described in detail below in conjunction with the accompanying drawings, but the implementation and protection of the present utility model are not limited thereto. Those skilled in the art can use existing technology to realize.

The basic topology of the utility model is shown in Figure 1. As an embodiment, a bridgeless CUK-based isolated three-phase power factor correction converter is provided, including a star-connected three-phase AC power supply and three bridgeless bridges with the same structure. CUK isolated converter, output filter capacitor and load. The i-th (i=1,2,3) bridgeless CUK isolated converter consists of input inductor L _{1_i} , primary side diodes D _{1_i} and D _{2_i} , switch tubes S _{1_i} and S _{2_i} , primary side capacitor C _{1_i} , high frequency The transformer T _i , the secondary capacitor C _{2_i} , the secondary diode D _{3_i} and the secondary inductor L _{2_i} are composed. All the diodes can be ordinary diodes, power diodes, thyristors and full-control switch tubes, and all switch tubes can be MOSFETs and unidirectional switch parallel diodes. The phase A voltage is connected to the node where the anode of the primary diode D _{1_1} and the cathode of the _primary diode D _{2_1} are connected through the input inductor L _{1_1} , and the phase B voltage is connected to the anode of the primary diode D 1_2 and the cathode of the primary diode D _{2_2} through the input inductor L _{1_2} The node connected, the phase C voltage is connected to the node where the anode of the primary diode D _{1_3} and the cathode of the primary diode D _{2_3} are connected through the input inductor L _{1_3} . The node between the switch tube S _{1_1} and the switch tube S _{2_1} of the first bridgeless CUK isolated converter 1, the node between the switch tube S _{1_2} and the switch tube S _{2_2} of the second bridgeless CUK isolated converter 2 and Nodes between the switch tube S _{1_3} and the switch tube S _{2_3} of the third bridgeless CUK isolated converter 3 are connected to each other. The same-named ends of the primary winding of the high-frequency transformer T _i (i=1,2,3) are respectively connected to the primary capacitor C _{1_i} (i=1,2,3), and the different-named ends of the secondary winding are connected to the secondary capacitor One end of C _{2_i} (i=1,2,3).

The primary capacitor C _{1_i} and the secondary capacitor C _{2_i} (i=1, 2, 3) are both non-polar capacitors. One end of the secondary inductor L _{2_i} (i=1,2,3) is connected to the secondary capacitor C _{2_i} (i=1,2,3), and the other end is connected to each other and then connected to the filter capacitor and the load. The filter capacitor C _out is a large-capacity capacitor. Loads can be purely resistive loads, resistive inductive loads, capacitive loads and switching converters. In the embodiment of the utility model, each bridgeless CUK isolated converter works in a discontinuous mode, and one voltage loop controller is used to control three bridgeless CUK isolated converters.

As shown in Figure 2 in the appendix, according to the amplitude and positive and negative of the A-phase, B-phase, and C-phase voltages of a three-phase AC power supply in a power frequency cycle, it is divided into 12 modes, and the switching actions of all switching tubes in each mode are consistent. The analysis method of the working principle of each mode converter is similar, and the working principle of the embodiment of the present invention will be analyzed below taking the fifth mode as an example. As shown in Figure 2 of the appendix, in the fifth mode, phase A voltage u _a >0, phase B voltage u _b >0, phase C voltage u _c <0, the amplitudes of phase A, phase B and phase C voltages The relationship is |u _c | > |u _a | > |u _b |.

The input inductor current is represented by I _{L1_i} (i=1,2,3), the primary capacitor voltage is represented by V _{C1_i} (i=1,2,3), and the primary voltage of the high-frequency transformer is represented by V _{P_i} (i=1,2 ,3), the high-frequency transformer secondary voltage is represented by V _{S_i} (i=1,2,3), the secondary capacitor voltage is represented by V _{C2_i} (i=1,2,3), and the secondary inductor current is represented by I _{L2_i} ( i = 1, 2, 3), and the secondary diode current is represented by I _{D3_i} (i = 1, 2, 3). The reference directions of all voltage and current variables are shown in Figure 1 in the appendix.

The six switch tubes are turned on at the same time, and the working principle diagram of the converter of the embodiment of the utility model is shown in Fig. 3 in the appendix. The input voltage charges the input inductance through the switch tubes. The primary capacitance C _{1_i} (i=1,2,3) passes through the switch tubes S _{1_i} (i=1,2,3) and S _{2_i} (i=1,2,3), and then passes through the high-frequency transformer T _i (i =1,2,3) The non-identical end of the primary side charges the excitation inductance, so the primary side voltage V _{P_i} (i=1,2,3) of the high-frequency transformer T _i (i=1,2,3) is a negative value , the secondary voltage V _{S_i} (i=1,2,3) of the high-frequency transformer T _i (i=1,2,3) is induced to be greater than zero, and the secondary diode D _{3_i} (i=1,2,3) bears The secondary side diode current I _{D3_i} (i=1,2,3) is zero, and the secondary side capacitor supplies power to the load through the secondary side inductor current I _{L2_i} (i=1,2,3).

After the six switching tubes are turned off at the same time, when the secondary diode current I _{D3_i} (i=1, 2, 3) is not equal to zero, the working principle diagram of the converter of the embodiment of the utility model is shown in Fig. 4 in the appendix. On the primary side of the high-frequency transformer, the current I _{L1_i} (i=1,2) of the input inductors L _{1_1} and L _{1_2} passes through the primary diode D _{1_i} (i=1,2), the primary capacitor C _{1_i} (i=1, 2), the high-frequency transformer T _i (i=1,2) primary terminal with the same name and the switch tube S _{2_i} (i=1,2) freewheeling diode sequentially flow into the switch tube S _{1_3} freewheeling diode, primary capacitor C _{1_3} , the same-named terminal of the primary side of the high-frequency transformer T ₃ and the primary side diode D _{2_3} are returned to the input inductor L _{1_3} and the C-phase voltage. Therefore, the sum of the input inductor currents I _{L1_1} and I _{L1_2} is equal to I _{L1_3} , and the input inductors L _{1_1} and L _{1_2} are subjected to positive voltages, so the current is a positive value of I _{L1_1} and I _{L1_2} , which is consistent with the reference direction, and the input inductor L _{1_3} is due to Withstand negative voltage, so its current is I _{L1_3} negative, that is, opposite to the reference direction. On the secondary side of the high-frequency transformer, the secondary voltage V _{S_i} (i=1,2,3) of the high-frequency transformer is greater than zero, and the secondary diode D _{3_i} (i=1,2,3) is cut off due to forward voltage. The secondary diode current I _{D3_i} (i=1, 2, 3) is not zero, but because the amplitude relationship of the A-phase, B-phase and C-phase voltages is |u _c |＞|u _a |＞|u _b |, Therefore _{ID3_2} , _{ID3_1} and _{ID3_3} decrease to zero in turn, and the last three are zero at the same time. The corresponding working principles are shown in Figures 5, 6 and 7 in the appendix. After _{ID3_2} , _{ID3_1} and _{ID3_3} are zero, the working process of the next switching cycle in mode 5 is restarted.

Carry out simulation verification to the implementation of the utility model below. The output power of each module is 200W, and the total output power is 600W. The design parameters are as follows:

Output power: P _o ＝200W*3

Input voltage: 220V/50Hz

Efficiency: η=95%

Power factor: PF＝0.99

Total harmonic content: THD≤5%

Output voltage: 400V

The main circuit and the control circuit are designed according to the above parameters, and the embodiment of the utility model is simulated. The simulation results are shown in Figures 8, 9, 10 and 11 in the appendix. Since the input inductors are connected in series with the three-phase power supply, the input inductor current is also the input current of the three-phase power supply. As shown in Figure 8 in the appendix, the waves of the input inductor currents I _{L1_1} , I _{L1_2} and I _{L1_3} form sinusoidal changes, and in The total harmonic content THD values of the input inductor currents I _{L1_1} , I _{L1_2} and I _{L1_3} measured in the simulation software are 2.947%, 2.950% and 2.947%, respectively, which are far less than the 10% specified in the domestic standard. The output voltage is stable at 400V. As shown in Fig. 9 in the appendix, the upper switch tube of the bridgeless CUK isolated converter (3) realizes zero-current turn-on, and the lower switch tube realizes zero-voltage turn-on. In Figure 9, the current is magnified 150 times. Appendix Figure 10 shows the waveforms of each phase voltage and the corresponding input inductor current, the current I _{L1_1} of the input inductor L _{1_1} and the voltage u _a of phase A, the current I _{L1_2} of the input inductor L _{1_2} and the voltage of phase B and the input inductor L The current I _{L1_3} of _{1_3} and the power factor of the C-phase voltage are both 0.999. Figure 11 in the appendix is the two and a half switching cycles of mode 5 in the intercepted simulation results, phase A voltage u _a >0, phase B voltage u _b >0, phase C voltage u _c <0, phase A, phase B and phase C The amplitude relationship of the voltage is |u _c |＞|u _a |＞|u _b |. It can be seen from Figure 11 in the appendix that _{ID3_2} , _{ID3_1} and _{ID3_3} decrease to zero in turn, and the last three are zero at the same time. All simulation results have fully verified that the utility model can realize power factor correction under the control of only one voltage loop.

Claims (6)

1. A bridgeless CUK isolated three-phase power factor correction converter is characterized in that comprising star-connected three-phase AC power supply (4), three structurally identical bridgeless CUK isolated converters (1, 2 and 3), the output filter capacitor (C _out ) and the load (R _laod ), the input terminals of the three bridgeless CUK isolated converters (1, 2 and 3) are connected to the three-phase AC power supply (4) respectively Phase A, phase B, and phase C are voltage-connected, and the three bridgeless CUK isolated converters (1, 2 and 3) are connected to each other through interconnection terminals; the three bridgeless CUK isolated converters (1, The output terminals of 2 and 3) are connected to both ends of the output filter capacitor (C _out ), and both ends of the output filter capacitor (C _out ) are connected to the load (R _laod ). 2. A kind of bridgeless CUK isolated three-phase power factor correction converter based on claim 1, characterized in that in three bridgeless CUK isolated converters with the same structure, each bridgeless CUK isolated converter The device consists of an input inductor, a first primary diode and a second primary diode, a first switch tube and a second switch tube, a primary capacitor, a high-frequency transformer, a secondary capacitor, a secondary diode and a secondary inductor, where the input One end of the inductor is used as the input end of the bridgeless CUK isolated converter, the other end of the input inductor is connected to the anode of the first primary diode and the cathode of the second primary diode, and the other end of the first primary diode is connected to the first switch tube The source is connected to one end of the primary side capacitor; the drain of the first switch tube is connected to the source of the second switch tube, and one end is drawn out at the connection point as an interconnection terminal to be connected to another converter; the other end of the primary side capacitor One end is connected to the primary end of the high-frequency transformer with the same name; the anode of the second primary diode is connected to the drain of the second switching tube and the primary end of the high-frequency transformer with the same name; the secondary end of the high-frequency transformer with the same name is connected to the secondary One end of the side capacitor is connected; the other end of the secondary capacitor is connected to the cathode of the secondary diode and one end of the secondary inductor; the other end of the secondary inductor is used as the positive terminal of the output terminal, and is connected to the output filter capacitor (C _out ) and the load (R _laod ) positive terminals are connected; the same-named terminal of the secondary side of the high-frequency transformer is connected to the anode of the secondary diode, and one terminal is drawn out at this connection point as the common ground terminal of the output terminal. 3. A kind of bridgeless CUK isolated three-phase power factor correction converter based on claim 1, characterized in that each converter in the three bridgeless CUK isolated converters has a separate controller or is controlled by Simultaneous control by the same controller. 4. A bridgeless CUK-based isolated three-phase power factor correction converter according to claim 1, characterized in that the load is a purely resistive load, a resistive-inductive load, a resistive-capacitive load or a switching converter. 5. A bridgeless CUK-based isolated three-phase power factor correction converter according to claim 2, characterized in that all diodes are ordinary diodes, power diodes, thyristors or full-control switches. 6. A kind of isolated three-phase power factor correction converter based on bridgeless CUK according to claim 2, characterized in that all switching tubes are MOSFETs, unidirectional conduction with parasitic anti-parallel diode IGBT or anti-parallel diode turning tube.