Bidirectional inverter circuit

Abstract

The inverter circuit of the bidirectional structure of the present invention relates to the field of power electronics. The charging and discharging of the energy storage unit are realized by controlling twelve switching tubes, so that the inverter circuit of the bidirectional structure of the present application can be used for both charging and discharging, which solves the problem that the existing energy storage unit charging and discharging adopts two circuits, resulting in high costs. Furthermore, by adopting a connection method in which the secondary sides of two transformers are connected in series to reduce the turns ratio of the transformer, compared with the use of a single transformer, the transformer leakage inductance and heat loss are effectively reduced, and the transformer efficiency is improved. At the same time, the total conduction loss of the switch tube is also reduced by half, which solves the problem of low efficiency caused by the high turns ratio of the transformer. The present invention is suitable for charging and discharging energy storage units.

Description

Technical Field

[0001] The invention relates to the field of power electronics, and in particular to an inverter circuit with a bidirectional structure. Background Art

[0002] With the continuous growth of energy demand, the development and utilization of new energy sources have received more and more attention, and the market demand for portable energy storage is also growing. Portable battery energy storage products need to realize two basic functions: DC / AC inverter and AC / DC charging. Since the DC voltage level at the battery end is low, generally lower than DC100V, a DC / DC boost circuit is also required before the inverter. At present, the general solution is: the inverter uses DC / DC boost and DC / AC inverter to output the mains voltage to power the electrical equipment; the charging uses AC / DC charging circuit to charge the battery. Battery inverter and charging use two circuits, which brings cost and volume problems to product design. In addition, when the battery voltage is not high (such as the car battery voltage is 12V in the application of vehicle inverter power supply, or the battery cell used in portable energy storage power supply generally has a nominal voltage of 3.6V, and for safety reasons, the battery voltage is generally not high with a small number of strings), it is still necessary to increase the battery voltage to more than DC 310V through DC / DC conversion to ensure that the AC 220V can be output normally after DC / AC inverter. For example, the battery input voltage is 12V, the output Vbus is 360V, and the DC / DC transformer turns ratio N=360 / 12=30. Such a high turns ratio will increase the transformer leakage inductance and reduce the transformer efficiency. At the same time, since the input voltage is too low, the input current is correspondingly large, which will also increase the heat loss of the transformer. Summary of the invention

[0003] The technical problem solved by the present invention is to provide an inverter circuit with a bidirectional structure to solve the problem that the existing energy storage unit uses two circuits for charging and discharging, resulting in high costs, and further solve the problem of low efficiency caused by the high turns ratio of the transformer.

[0004] The present invention adopts a technical solution to solve the above technical problems: a bidirectional inverter circuit includes an energy storage unit, a first filtering unit, a second capacitor, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, a ninth switch tube, a tenth switch tube, an eleventh switch tube, a twelfth switch tube, a first transformer, a second transformer, a resonance unit and a second filtering unit; the first filtering unit is connected between the positive and negative electrodes of the energy storage unit, the negative electrode of the energy storage unit is respectively connected to the source electrodes of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, the drain electrode of the first switch tube is connected to one end of the primary side of the first transformer, the drain electrode of the second switch tube is connected to the other end of the primary side of the first transformer, the drain electrode of the third switch tube is connected to one end of the primary side of the second transformer, the drain electrode of the fourth switch tube is connected to the other end of the primary side of the second transformer, the positive electrode of the energy storage unit is respectively connected to the center taps of the primary sides of the first transformer and the second transformer, one end of the secondary side of the first transformer is connected to one end of the resonance unit, and the resonance unit The other end of the secondary side of the first transformer is connected to the source of the eighth switch tube and the drain of the seventh switch tube, respectively. The other end of the secondary side of the first transformer is connected to one end of the secondary side of the second transformer, and the other end of the secondary side of the second transformer is connected to the source of the fifth switch tube and the drain of the sixth switch tube, respectively. The drain of the fifth switch tube is connected to the drain of the eighth switch tube, the positive electrode of the second capacitor, the drain of the ninth switch tube and the drain of the twelfth switch tube, respectively. The source of the sixth switch tube is connected to the source of the seventh switch tube, the negative electrode of the second capacitor, the source of the tenth switch tube and the eleventh switch tube, respectively. The source of the ninth switch tube is connected to the drain of the tenth switch tube as one end of the AC, the source of the twelfth switch tube is connected to the drain of the eleventh switch tube as the other end of the AC, the AC is connected to the mains or to the electrical equipment after being filtered by the second filtering unit, and the gates of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the seventh switch tube, the eighth switch tube, the ninth switch tube, the tenth switch tube, the eleventh switch tube and the twelfth switch tube are connected to the control signal.

[0005] Furthermore, the first filtering unit includes a first capacitor, one end of the first capacitor is connected to one end of the energy storage unit, and the other end of the first capacitor is connected to the other end of the energy storage unit.

[0006] Furthermore, the resonance unit includes a first inductor and a third capacitor, one end of the first inductor is connected to one end of the third capacitor, the other end of the first inductor serves as one end of the resonance unit, and the other end of the third capacitor serves as the other end of the resonance unit.

[0007] Furthermore, the second filtering unit includes a second inductor and a fourth capacitor, one end of the second inductor is connected to one end of the fourth capacitor, serving as one end for access to the mains or electrical equipment, the other end of the second inductor is connected to one end of the alternating current, and the other end of the fourth capacitor is connected to the other end of the alternating current, serving as the other end for access to the mains or electrical equipment.

[0008] Beneficial effects of the present invention: The inverter circuit of the bidirectional structure of the present invention realizes the charging and discharging of the energy storage unit through the control of twelve switching tubes, so that the inverter circuit of the bidirectional structure of the present application can be used for both charging and discharging, which solves the problem that the existing energy storage unit charging and discharging adopts two circuits resulting in high costs. Furthermore, by adopting a connection method in which the secondary sides of two transformers are connected in series to reduce the turns ratio of the transformer, compared with the use of a single transformer, the transformer leakage inductance and heat loss are effectively reduced, the transformer efficiency is improved, and the total conduction loss of the switching tube is also reduced by half, solving the problem of low efficiency caused by the high turns ratio of the transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Attached Figure 1 1 is a circuit diagram of an embodiment of an inverter circuit of a bidirectional structure of the present invention, wherein C1 represents a first filtering unit, C2 represents a second capacitor, Cr represents a third capacitor, Co represents a fourth capacitor, S1 to S12 represent a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, a ninth switch tube, a tenth switch tube, an eleventh switch tube, and a twelfth switch tube, respectively, T1 represents a first transformer, T2 represents a second transformer, Lr represents a first inductor, Lo represents a second inductor, Vdc represents an energy storage unit voltage, Vbus represents a transformer secondary voltage, and Vac represents an AC voltage. DETAILED DESCRIPTION

[0010] The inverter circuit of the bidirectional structure includes an energy storage unit, a first filtering unit, a second capacitor, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, a ninth switch tube, a tenth switch tube, an eleventh switch tube, a twelfth switch tube, a first transformer, a second transformer, a resonance unit and a second filtering unit; the first filtering unit is connected between the positive and negative electrodes of the energy storage unit, the negative electrode of the energy storage unit is respectively connected to the source electrodes of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, the drain electrode of the first switch tube is connected to one end of the primary side of the first transformer, the drain electrode of the second switch tube is connected to the other end of the primary side of the first transformer, the drain electrode of the third switch tube is connected to one end of the primary side of the second transformer, the drain electrode of the fourth switch tube is connected to the other end of the primary side of the second transformer, the positive electrode of the energy storage unit is respectively connected to the center taps of the primary sides of the first transformer and the second transformer, one end of the secondary side of the first transformer is connected to one end of the resonance unit, and the other end of the resonance unit is respectively connected to the eighth The source of the switch tube is connected to the drain of the seventh switch tube, the other end of the secondary side of the first transformer is connected to one end of the secondary side of the second transformer, the other end of the secondary side of the second transformer is respectively connected to the source of the fifth switch tube and the drain of the sixth switch tube, the drain of the fifth switch tube is respectively connected to the drain of the eighth switch tube, the positive electrode of the second capacitor, the drain of the ninth switch tube and the drain of the twelfth switch tube, the source of the sixth switch tube is respectively connected to the source of the seventh switch tube, the negative electrode of the second capacitor, the source of the tenth switch tube and the source of the eleventh switch tube, the source of the ninth switch tube is connected to the drain of the tenth switch tube as one end of the alternating current, the source of the twelfth switch tube is connected to the drain of the eleventh switch tube as the other end of the alternating current, the alternating current is filtered by the second filtering unit and then connected to the mains or supplies power to the electrical equipment, and the gates of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the seventh switch tube, the eighth switch tube, the ninth switch tube, the tenth switch tube, the eleventh switch tube and the twelfth switch tube are connected to the control signal.

[0011] Furthermore, the first filtering unit includes a first capacitor, one end of the first capacitor is connected to one end of the energy storage unit, and the other end of the first capacitor is connected to the other end of the energy storage unit.

[0012] Furthermore, the resonance unit includes a first inductor and a third capacitor, one end of the first inductor is connected to one end of the third capacitor, the other end of the first inductor serves as one end of the resonance unit, and the other end of the third capacitor serves as the other end of the resonance unit.

[0013] Furthermore, the second filtering unit includes a second inductor and a fourth capacitor, one end of the second inductor is connected to one end of the fourth capacitor, serving as one end for access to the mains or electrical equipment, the other end of the second inductor is connected to one end of the alternating current, and the other end of the fourth capacitor is connected to the other end of the alternating current, serving as the other end for access to the mains or electrical equipment.

[0014] Example:

[0015] The inverter circuit of the bidirectional structure of the present invention is as shown in the attached Figure 1As shown, the first filtering unit adopts an independent capacitor, namely, the first capacitor C1, the resonant unit adopts an inductor and a capacitor connected in series, namely, the first inductor Lr and the third capacitor Cr, the second filtering unit adopts the second inductor Lo connected in series in the main circuit, and the fourth capacitor Co is connected in parallel in the main circuit. That is, the circuit structure of this embodiment is: the negative electrode of the energy storage unit after filtering by the first filtering unit, namely, the negative electrode of the first capacitor C1 is respectively connected to the source electrodes of the first switch tube S1, the second switch tube S2, the third switch tube S3 and the fourth switch tube S4, the drain electrode of the first switch tube S1 is connected to one end of the primary side of the first transformer T1, the drain electrode of the second switch tube S2 is connected to the other end of the primary side of the first transformer T1, the drain electrode of the third switch tube S3 is connected to one end of the primary side of the second transformer T2, and the drain electrode of the fourth switch tube S4 is connected to the other end of the primary side of the second transformer T2 The positive electrode of the energy storage unit after filtering by the first filtering unit, that is, the positive electrode of the first capacitor C1, is respectively connected to the primary centers of the first transformer T1 and the second transformer T2, one end of the secondary side of the first transformer T1 is connected to one end of the first inductor Lr, the other end of the first inductor Lr is connected to one end of the third capacitor Cr, the other end of the third capacitor Cr is respectively connected to the source of the eighth switch tube S8 and the drain of the seventh switch tube S7, the other end of the secondary side of the first transformer T1 is connected to one end of the secondary side of the second transformer T2, and the other end of the secondary side of the second transformer T2 is respectively connected to The source of the fifth switch tube S5 is connected to the drain of the sixth switch tube S6. The drain of the fifth switch tube S5 is respectively connected to the drain of the eighth switch tube S8, the positive electrode of the second capacitor C2, the drain of the ninth switch tube S9 and the drain of the twelfth switch tube S12. The source of the sixth switch tube S6 is respectively connected to the source of the seventh switch tube S7, the negative electrode of the second capacitor C2, the source of the tenth switch tube S10 and the source of the eleventh switch tube S11. The source of the ninth switch tube S9 is connected to the drain of the tenth switch tube S10 as one end of the AC and is connected to the other end of the second capacitor. As the other end of the access to the mains or electrical equipment, the source of the twelfth switch tube S12 is connected to the drain of the eleventh switch tube S11 as the other end of the AC and is connected to one end of the second inductor Lo, and the other end of the second inductor is connected to one end of the fourth capacitor Co. As the other end of the access to the mains or electrical equipment, the gates of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the seventh switch tube, the eighth switch tube, the ninth switch tube, the tenth switch tube, the eleventh switch tube and the twelfth switch tube are connected to the control signal.

[0016] Specifically, in this embodiment, the first transformer T1 and the second transformer T2 are two identical transformers.

[0017] Discharge process: the control signals of the first switch tube S1 and the third switch tube S3 are the same, the control signals of the second switch tube S2 and the fourth switch tube S4 are the same, and the switch states of S1 and S3 are not turned on at the same time as the switch states of S2 and S4 in one switching cycle, and the opening time is less than 50% of the switching cycle, that is, there is a dead zone on the primary side of the transformer, and the capacitor on the secondary side is used for discharge, thereby ensuring uninterrupted power supply. When S1 and S3 are turned on, the secondary side current Isec of T1 and T2 is discharged according to the positive The current flows to the secondary winding T1, the secondary winding T2, S5, C2, S7, Cr, and Lr, thereby obtaining the secondary DC voltage Vbus. The ninth switch tube S9, the tenth switch tube S10, the eleventh switch tube S11, and the twelfth switch tube S12 form a bridge circuit through a control signal to perform AC conversion. A pulse sequence equivalent to a sine wave is output at one end of the second inductor Lo, and the high-frequency components are filtered out by the second inductor Lo and the fourth capacitor Co to obtain a pure sinusoidal AC voltage Vac for use by electrical equipment.

[0018] Charging process: A totem pole bridgeless PFC circuit is formed by the ninth switch tube S9, the tenth switch tube S10, the eleventh switch tube S11, the twelfth switch tube S12, the second inductor Lo and the fourth capacitor Co, which inputs the AC voltage Vac and rectifies the output high-voltage DC voltage Vbus; that is, in the positive half cycle of Vac, S10 remains on, S9 remains off, S11 is a high-frequency switch tube, and S12 is a high-frequency freewheeling tube. When S11 is on and S12 is off, Vac stores energy in the inductor Lo through S11 and S10; when S11 is off and S12 is on, Vac charges C2 through Lo, S12, C2, and S10, and the inductor Lo releases energy at the same time; in the negative half cycle of Vac, S9 remains on, S10 remains off, S12 is a high-frequency switch tube, and S11 is a high-frequency freewheeling tube. When S12 is on and S11 is off, Vac charges C2 through Lo, S12, C2, and S10, and the inductor Lo releases energy. When S12 is turned off and S11 is turned on, Vac stores energy in the inductor Lo through S9 and S12; when S12 is turned off and S11 is turned on, Vac charges C2 through S9, C2, S11 and Lo, and Lo releases energy at the same time, thereby obtaining a high-voltage DC voltage Vbus. The back stage is composed of S1-S8, T1, T2, C1, Lr, and Cr to form a full-bridge LLC resonant circuit, that is, the switching states of S5 and S7 are consistent, the switching states of S6 and S8 are consistent, and the switching states of S5, S7 and S6, S8 are not turned on at the same time in one switching cycle, and the opening time of S5-S8 is less than 50% of the switching cycle, the states of the rectifier tubes S1 and S3 are consistent, and the states of S2 and S4 are consistent. The synchronous rectification method can effectively reduce the loss of the rectifier tube, thereby realizing the charging of the energy storage unit. In particular, when charging the energy storage unit, the excitation inductance of the transformer needs to be considered.

Claims

1. A bidirectional inverter circuit, characterized in that: The invention comprises an energy storage unit, a first filtering unit, a second capacitor, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, a ninth switch tube, a tenth switch tube, an eleventh switch tube, a twelfth switch tube, a first transformer, a second transformer, a resonance unit and a second filtering unit; the positive and negative electrodes of the energy storage unit are connected to the first filtering unit, the negative electrode of the energy storage unit is respectively connected to the source electrodes of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, the drain electrode of the first switch tube is connected to one end of the primary side of the first transformer, the drain electrode of the second switch tube is connected to the other end of the primary side of the first transformer, and the third switch tube is connected to the positive and negative electrodes of the energy storage unit. The drain of the fourth switch tube is connected to one end of the primary side of the second transformer, the drain of the fourth switch tube is connected to the other end of the primary side of the second transformer, the positive electrode of the energy storage unit is respectively connected to the center taps of the primary sides of the first transformer and the second transformer, one end of the secondary side of the first transformer is connected to one end of the resonance unit, the other end of the resonance unit is respectively connected to the source of the eighth switch tube and the drain of the seventh switch tube, the other end of the secondary side of the first transformer is connected to one end of the secondary side of the second transformer, the other end of the secondary side of the second transformer is respectively connected to the source of the fifth switch tube and the drain of the sixth switch tube, the drain of the fifth switch tube is respectively connected to the drain of the eighth switch tube, the positive electrode of the second capacitor, the drain of the ninth switch tube and the drain of the twelfth switch tube The source of the sixth switch tube is respectively connected to the source of the seventh switch tube, the negative electrode of the second capacitor, the source of the tenth switch tube and the source of the eleventh switch tube, the source of the ninth switch tube is connected to the drain of the tenth switch tube as one end of the AC, the source of the twelfth switch tube is connected to the drain of the eleventh switch tube as the other end of the AC, the AC is filtered by the second filtering unit and then connected to the mains or to power the electrical equipment, the gates of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the seventh switch tube, the eighth switch tube, the ninth switch tube, the tenth switch tube, the eleventh switch tube and the twelfth switch tube are connected to the control signal, and the first filtering unit It includes a first capacitor, one end of which is connected to one end of an energy storage unit, and the other end of the first capacitor is connected to the other end of the energy storage unit. The resonance unit includes a first inductor and a third capacitor, one end of the first inductor is connected to one end of the third capacitor, the other end of the first inductor serves as one end of the resonance unit, and the other end of the third capacitor serves as the other end of the resonance unit. The second filtering unit includes a second inductor and a fourth capacitor, one end of the second inductor is connected to one end of the fourth capacitor, serving as one end for access to the mains or electrical equipment, the other end of the second inductor is connected to one end of the alternating current, and the other end of the fourth capacitor is connected to the other end of the alternating current, serving as the other end for access to the mains or electrical equipment.

Images