Bidirectional AC / DC inverter circuit

Abstract

The utility model relates to the technical field of inverters, in particular to a bidirectional AC / DC inverter circuit, which comprises a BUS bus energy storage circuit and a bidirectional DCAC inverter circuit, the BUS bus energy storage circuit comprises a capacitor C1, two ends of the capacitor C1 are connected with a battery in parallel, the BUS bus energy storage circuit is connected with a power grid through the bidirectional DCAC inverter circuit, and the DC / DC inverter circuit is connected with the power grid. AC-DC conversion of voltage and conversion of energy storage and energy release are achieved through the bidirectional DCAC inverter circuit, the purpose of voltage boosting and bucking can be achieved, therefore, the rated voltage of the battery does not need to be 360 V, the voltage range of the battery can be expanded, the purpose of outputting rated AC voltage through inverter voltage boosting and bucking can be achieved, and the circuit is simple in structure and easy to control.

Description

Technical Field

[0001] The utility model relates to the technical field of inverters, in particular to a bidirectional AC / DC inverter circuit. Background Art

[0002] In existing energy storage systems, especially for 230V single-phase energy storage off-grid hybrid inverters, in order to achieve efficient and stable energy conversion, the DC bus (BUS) voltage of the inverter is usually required to reach 360Vdc, so as to facilitate the inverter output of 230Vac alternating current. This requirement makes the system design tend to use 360V battery packs as energy storage units to directly match the working requirements of the inverter. However, considering the mainstream energy storage batteries on the market, such as 50AH and 100AH ​​batteries, if they are connected in series to such a high voltage level, the total battery capacity will be as high as 18KWH and 36KWH respectively. Although this design meets the voltage requirements of the inverter, it also brings the following problems:

[0003] Excessive battery capacity requirements: For many practical applications, such a large battery capacity often exceeds user needs, resulting in waste of resources and increased costs.

[0004] Increased system complexity: When the voltage of the battery pack fails to meet the 360Vdc requirement, an additional DC-DC converter must be introduced to increase the voltage, such as the three-level dual-buck conversion circuit for the back stage of the energy storage inverter device disclosed in patent CN202211399434.4. This not only increases the complexity of the system, but may also introduce additional energy loss and reduce overall efficiency.

[0005] Therefore, in the prior art, how to reduce the demand for battery capacity and simplify the system structure while ensuring the normal operation of the inverter has become a key issue that needs to be solved urgently. Summary of the invention

[0006] The utility model provides a bidirectional AC / DC inverter circuit to solve the problems of the prior art, which can expand the voltage range of the battery without adding an additional DCDC converter, and achieves the purpose of outputting the rated AC voltage by inverter step-up and step-down. The circuit structure is simple and easy to control.

[0007] In order to solve the above technical problems, the utility model adopts the following technical solutions: a bidirectional AC / DC inverter circuit, including a BUS bus energy storage circuit and a bidirectional DCAC inverter circuit, the two ends of the BUS bus energy storage circuit are connected to a battery, the BUS bus energy storage circuit is connected to a power grid through the bidirectional DCAC inverter circuit, the bidirectional DCAC inverter circuit includes an AC / DC bidirectional conversion module and an energy storage filter module, the AC / DC bidirectional conversion module is used to complete bidirectional conversion between DC and AC, the energy storage filter module is used to complete energy storage, energy release and filtering, the BUS bus energy storage circuit includes a capacitor C1, and the two ends of the capacitor C1 are connected in parallel with the battery.

[0008] Preferably, the AC-DC bidirectional conversion module includes a switch tube Q1, a switch tube Q2, a switch tube Q3 and a switch tube Q4, and control ends of the switch tubes Q1, Q2, Q3 and Q4 input different PWM drive signals respectively, and the energy storage filter module includes a plurality of energy storage elements;

[0009] A switch end of the switch tube Q1 is connected to one end of the capacitor C1, and the other switch end of the switch tube Q1 is connected to one end of the third energy storage element through the first energy storage element and the second energy storage element in sequence, and the other switch end of the switch tube Q1 is also connected to the other end of the capacitor C1 through the fourth energy storage element;

[0010] A switch end of the switch tube Q2 is connected to one end of the capacitor C1, and the other switch end of the switch tube Q2 is connected to the other end of the third energy storage element through the fifth energy storage element and the sixth energy storage element in sequence, and the other switch end of the switch tube Q2 is also connected to the other end of the capacitor C1 through the seventh energy storage element;

[0011] The first energy storage element is connected to the second energy storage element via one switch end of the switch tube Q3; the other switch end of the switch tube Q3 is connected to the other end of the capacitor C1;

[0012] The fifth energy storage element is connected to the sixth energy storage element via a switch terminal of the switch tube Q4 , and the other switch terminal of the switch tube Q4 is connected to the other end of the capacitor C1 .

[0013] Preferably, the switch tube Q1 , the switch tube Q2 , the switch tube Q3 and the switch tube Q4 are all MOS tubes.

[0014] Preferably, the several energy storage elements include inductor L1, inductor L2, inductor L3, inductor L4, capacitor C2, capacitor C3 and capacitor C4, the first energy storage element is capacitor C2, the second energy storage element is inductor L2, the third energy storage element is capacitor C4, the fourth energy storage element is inductor L1, the fifth energy storage element is capacitor C3, the sixth energy storage element is inductor L4, and the seventh energy storage element is inductor L3.

[0015] Beneficial effects of the utility model:

[0016] The utility model provides a bidirectional AC / DC inverter circuit, which realizes AC / DC conversion of voltage and conversion of energy storage and release through the bidirectional DCAC inverter circuit, and can achieve the purpose of voltage step-up and step-down. Therefore, the rated voltage of the battery does not need to be 360V, the voltage range of the battery can be expanded, and there is no need to add an additional DCDC converter. The purpose of outputting the rated AC voltage is achieved through inverter step-up and step-down. The circuit structure is simple and easy to control. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a signal block diagram of the utility model;

[0018] Figure 2 It is the circuit principle diagram of the utility model;

[0019] Figure 3 This is a wave modulation diagram of the AC / DC bidirectional conversion module of the utility model. DETAILED DESCRIPTION

[0020] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with the embodiments and drawings, and the contents mentioned in the implementation modes are not intended to limit the present invention. The present invention is described in detail below in conjunction with the drawings.

[0021] This embodiment provides a bidirectional AC / DC inverter circuit, such as Figures 1 to 3 , including a BUS bus energy storage circuit and a bidirectional DCAC inverter circuit, wherein both ends of the BUS bus energy storage circuit are connected to batteries, and the BUS bus energy storage circuit is connected to the power grid through the bidirectional DCAC inverter circuit, and the bidirectional DCAC inverter circuit includes an AC / DC bidirectional conversion module and an energy storage filter module, wherein the AC / DC bidirectional conversion module is used to complete bidirectional conversion between DC and AC, and the energy storage filter module is used to complete energy storage, energy release and filtering.

[0022] Specifically, Figure 2 As shown, the bidirectional DCAC inverter circuit of this embodiment can achieve the purpose of bidirectional conversion of AC and DC and energy storage and release. The rated voltage of the battery does not have to reach 360V, and can be lower than 360V or higher than 360V. Therefore, the working range of the battery is expanded, and there is no need to add an additional DCDC converter. The purpose of outputting the rated AC voltage is achieved by inverter step-up and step-down. The circuit structure is simple and easy to control.

[0023] The specific circuit diagram of this embodiment is as follows Figure 2As shown, capacitor C1 is a BUS bus energy storage capacitor, and also includes 7 other energy storage elements, namely inductor L1, inductor L2, inductor L3, inductor L4, capacitor C2, capacitor C3 and capacitor C4. The AC-DC bidirectional conversion module includes switch tube Q1, switch tube Q2, switch tube Q3 and switch tube Q4. The specific connection method is as follows Figure 2 As shown, a switch end of the switch tube Q1 is connected to one end of the capacitor C1, and the other switch end of the switch tube Q1 is connected to one end of the third energy storage element after passing through the first energy storage element and the second energy storage element in sequence, and the other switch end of the switch tube Q1 is also connected to the other end of the capacitor C1 through the fourth energy storage element; a switch end of the switch tube Q2 is connected to one end of the capacitor C1, and the other switch end of the switch tube Q2 is connected to the other end of the third energy storage element after passing through the fifth energy storage element and the sixth energy storage element in sequence, and the other switch end of the switch tube Q2 is also connected to the other end of the capacitor C1 through the seventh energy storage element; the first energy storage element is connected to the second energy storage element through a switch end of the switch tube Q3; the other switch end of the switch tube Q3 is connected to the other end of the capacitor C1; the fifth energy storage element is connected to the sixth energy storage element through a switch end of the switch tube Q4, and the other switch end of the switch tube Q4 is connected to the other end of the capacitor C1. Among them, the first energy storage element is capacitor C2, the second energy storage element is inductor L2, the third energy storage element is capacitor C4, the fourth energy storage element is inductor L1, the fifth energy storage element is capacitor C3, the sixth energy storage element is inductor L4, and the seventh energy storage element is inductor L3.

[0024] The specific working principle of this embodiment is:

[0025] The switch tube Q1, the switch tube Q3, the inductor L1, the inductor L2, the capacitor C2, and the capacitor C4 form a positive half-cycle inverter circuit, and the switch tube Q2, the switch tube Q4, the inductor L3, the inductor L4, the capacitor C3, and the capacitor C4 form a negative half-cycle inverter circuit; in the positive half-cycle, the switch tube Q1 and the switch tube Q3 complement each other, when the switch tube Q1 is turned on, the input voltage charges the inductor L1 and the inductor L2, and the capacitor C2 releases energy, and C4 has a filtering effect, when the switch tube Q1 is turned off, the inductor L1 and the inductor L2 continue to flow, and the capacitor C2 and the capacitor C4 are charged at the same time; similarly, in the negative half-cycle, the switch tube Q2 and the switch tube Q4 complement each other, when the switch tube Q2 is turned on, the input voltage charges the inductor L3 and the inductor L4, and the capacitor C3 releases energy, and the capacitor C4 has a filtering effect, when the switch tube Q2 is turned off, the inductor L3 and the inductor L4 continue to flow, and the capacitor C3 and the capacitor C4 are charged at the same time.

[0026] Switching tube Q1, switching tube Q2, switching tube Q3, and switching tube Q4 are four inverter tubes, which are respectively input with four PWM drive signals, such as Figure 2 and Figure 3As shown, assuming that the input is Vdc and the output is Vac, in the positive half cycle, the duty cycle D1 of the switch tube Q1 is Vac / (Vdc+Vac), the duty cycle D3 of the switch tube Q3 is Vdc / (Vdc+Vac), the switch tube Q2 is turned off, and the switch tube Q4 is turned on; similarly, in the negative half cycle, the duty cycle D2 of the switch tube Q2 is -Vac / (Vdc-Vac), the duty cycle D3 of the switch tube Q4 is Vdc / (Vdc-Vac), the switch tube Q1 is turned off, and the switch tube Q3 is turned on.

[0027] The switch tubes Q1, Q2, Q3 and Q4 of this embodiment complete bidirectional conversion of DC to AC and AC to DC, wherein the switch tubes Q1 and Q3 generate waves complementary to each other, and the switch tubes Q2 and Q4 generate waves complementary to each other; the inductor L1, L2, L3, L4, the capacitor C2, the capacitor C3 and the capacitor C4 form an energy storage filter network to complete the filtering process of high-frequency signals to industrial frequency sinusoidal waves.

[0028] Therefore, in this embodiment, there is no need to add a DCDC converter, and the battery is directly connected to the capacitor C1. If the battery voltage is less than 360V, the bidirectional DCAC inverter circuit works in the buck mode. If the battery voltage is greater than the bus voltage of 360V, the bidirectional inverter DCAC circuit works in the buck-boost inverter mode. Therefore, the operating voltage range of the battery can be expanded, and there is no need to add a DCDC converter to achieve the purpose of voltage inversion. The circuit structure is simple and more conducive to control.

[0029] The above is only a preferred embodiment of the utility model, and does not limit the utility model in any form. Although the utility model is disclosed as a preferred embodiment as above, it is not used to limit the utility model. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes by using the technical content disclosed above without departing from the scope of the technical solution of the utility model. However, any simple modification, equivalent change and modification made to the above embodiments according to the technology of the utility model, which does not depart from the content of the technical solution of the utility model, belongs to the scope of the technical solution of the utility model.

Claims

1. A bidirectional AC / DC inverter circuit, characterized in that: It includes a BUS bus energy storage circuit and a bidirectional DCAC inverter circuit. The BUS bus energy storage circuit includes a capacitor C1. Both ends of the capacitor C1 are connected in parallel with a battery. The BUS bus energy storage circuit is connected to a power grid through the bidirectional DCAC inverter circuit. The bidirectional DCAC inverter circuit includes an AC / DC bidirectional conversion module and an energy storage filter module. The AC / DC bidirectional conversion module is used to complete bidirectional conversion between DC and AC. The energy storage filter module is used to complete energy storage, energy release and filtering.

2. A bidirectional AC / DC inverter circuit according to claim 1, characterized in that: The AC-DC bidirectional conversion module includes a switch tube Q1, a switch tube Q2, a switch tube Q3 and a switch tube Q4, and the control ends of the switch tubes Q1, Q2, Q3 and Q4 are respectively input with different PWM drive signals, and the energy storage filter module includes a plurality of energy storage elements; A switch end of the switch tube Q1 is connected to one end of the capacitor C1, and the other switch end of the switch tube Q1 is connected to one end of the third energy storage element through the first energy storage element and the second energy storage element in sequence, and the other switch end of the switch tube Q1 is also connected to the other end of the capacitor C1 through the fourth energy storage element; A switch end of the switch tube Q2 is connected to one end of the capacitor C1, and the other switch end of the switch tube Q2 is connected to the other end of the third energy storage element through the fifth energy storage element and the sixth energy storage element in sequence, and the other switch end of the switch tube Q2 is also connected to the other end of the capacitor C1 through the seventh energy storage element; The first energy storage element is connected to the second energy storage element via one switch end of the switch tube Q3; the other switch end of the switch tube Q3 is connected to the other end of the capacitor C1; The fifth energy storage element is connected to the sixth energy storage element via a switch terminal of the switch tube Q4 , and the other switch terminal of the switch tube Q4 is connected to the other end of the capacitor C1 .

3. The bidirectional AC / DC inverter circuit according to claim 2, characterized in that: The switch tube Q1 , the switch tube Q2 , the switch tube Q3 and the switch tube Q4 are all MOS tubes.

4. The bidirectional AC / DC inverter circuit according to claim 2, characterized in that: Some of the energy storage elements include inductor L1, inductor L2, inductor L3, inductor L4, capacitor C2, capacitor C3 and capacitor C4, the first energy storage element is capacitor C2, the second energy storage element is inductor L2, the third energy storage element is capacitor C4, the fourth energy storage element is inductor L1, the fifth energy storage element is capacitor C3, the sixth energy storage element is inductor L4, and the seventh energy storage element is inductor L3.

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