Bidirectional inverter and power supply system
By setting up a parallel frequency conversion sub-circuit in the bidirectional inverter, the frequency conversion of AC signals is realized, which solves the problem of high cost caused by a large number of components and achieves cost reduction.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- 无锡微胜新能源科技有限公司
- Filing Date
- 2023-10-09
- Publication Date
- 2026-06-26
AI Technical Summary
The current bidirectional inverter has a large number of components, resulting in high costs.
A frequency conversion circuit is adopted, including a first frequency conversion sub-circuit and a second frequency conversion sub-circuit connected in parallel. The controller controls them to work alternately, directly realizing the frequency conversion of AC signals and reducing the number of components.
By reducing the number of components, the cost of bidirectional inverters has been reduced.
Smart Images
Figure CN117175967B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of power supply technology, and more specifically to a bidirectional inverter and power supply system. Background Technology
[0002] A bidirectional inverter can convert direct current (DC) to alternating current (AC) and vice versa.
[0003] When a bidirectional inverter is used to convert direct current (DC) to alternating current (AC), it can be used as a DC / AC inverter. For example, bidirectional inverters can be used to convert photovoltaic power generation, wind power generation, and fuel cell power generation in the new energy field into AC power that can be used by electrical equipment. When a bidirectional inverter is used to convert alternating current (AC) to DC, it can be used as an AC / DC inverter. For example, a bidirectional inverter can be connected to an AC power grid to convert AC power generated by the AC grid into DC power and charge batteries.
[0004] Existing bidirectional inverters use a large number of components, resulting in higher costs. Summary of the Invention
[0005] The problem this invention aims to solve is: how to reduce the number of components used in a bidirectional inverter.
[0006] To address the above problems, this invention provides a bidirectional inverter, comprising: a transformer, a rectifier circuit on the primary side of the transformer, a frequency conversion circuit on the secondary side of the transformer, and a controller; wherein:
[0007] The rectifier circuit is coupled to the DC power supply and the transformer, and is adapted to convert the DC signal output by the DC power supply into an AC signal, or to convert the AC signal output by the transformer into a DC signal.
[0008] The transformer is coupled to the rectifier circuit and the frequency conversion circuit, and is adapted to boost the AC signal output by the rectifier circuit or the AC signal output by the frequency conversion circuit.
[0009] The frequency conversion circuit is coupled to the transformer and is adapted to reduce the frequency of the AC signal output by the transformer or increase the frequency of the AC signal output by the AC power grid.
[0010] The controller is coupled to the rectifier circuit and the frequency conversion circuit, and is adapted to control the operation of the rectifier circuit and the frequency conversion circuit to convert the DC signal output by the DC power supply into an AC signal suitable for supplying to the AC power grid, or to convert the AC signal output by the AC power grid into a DC signal suitable for supplying to the DC power supply.
[0011] The frequency conversion circuit includes a first frequency conversion sub-circuit and a second frequency conversion sub-circuit connected in parallel. The first frequency conversion sub-circuit and the second frequency conversion sub-circuit are adapted to work alternately under the control of the controller to realize the frequency conversion of the AC signal.
[0012] Optionally, the first frequency conversion sub-circuit includes:
[0013] The first and second branches are connected in parallel;
[0014] And a first capacitor connected in series with the first branch and the second branch.
[0015] Optionally, the first branch includes a first diode and a first switching transistor connected in series, wherein the direction of the first diode is opposite to the direction of the body diode in the first switching transistor.
[0016] Optionally, the second branch includes: a second diode and a second switching transistor connected in series, wherein the direction of the second diode is opposite to the direction of the body diode in the second switching transistor; and the direction of the second diode is opposite to the direction of the first diode.
[0017] Optionally, the second frequency conversion sub-circuit includes:
[0018] The third and fourth branches are connected in parallel;
[0019] And a second capacitor connected in series with the third and fourth branches.
[0020] Optionally, the third branch includes a third diode and a third switching transistor connected in series, wherein the direction of the third diode is opposite to the direction of the body diode in the third switching transistor.
[0021] Optionally, the fourth branch includes a fourth diode and a fourth switching transistor connected in series, wherein the direction of the fourth diode is opposite to the direction of the body diode in the fourth switching transistor, and the direction of the fourth diode is opposite to the direction of the third diode.
[0022] Optionally, the rectifier circuit is a full-bridge circuit.
[0023] Optionally, the bidirectional inverter further includes a third capacitor located on the primary side of the transformer, the third capacitor being connected in parallel across the DC power supply.
[0024] Optionally, the number of frequency conversion circuits is three, and the transformer includes three secondary windings, which are coupled to the three frequency conversion circuits in a one-to-one correspondence.
[0025] This invention also provides a power supply system, which includes a DC power supply and a bidirectional inverter as described in any of the above embodiments.
[0026] Compared with the prior art, the technical solution of the embodiments of the present invention has the following advantages:
[0027] By applying the solution of the present invention, a frequency conversion circuit is set up, which includes a first frequency conversion sub-circuit and a second frequency conversion sub-circuit connected in parallel. The first frequency conversion sub-circuit and the second frequency conversion sub-circuit can work alternately under the control of the controller to realize the frequency conversion of AC signal. It is not necessary to first convert the received AC signal into DC signal and then convert it into AC signal of corresponding frequency, thereby reducing the number of components and reducing costs. Attached Figure Description
[0028] Figure 1 This is a schematic diagram of the structure of a bidirectional inverter according to an embodiment of the present invention;
[0029] Figure 2 This is a schematic diagram of the circuit structure of a bidirectional inverter according to an embodiment of the present invention;
[0030] Figures 3 to 6 This is a schematic diagram showing the current flow direction at different times during the process of converting DC signals to AC signals in the bidirectional inverter of this embodiment of the invention.
[0031] Figures 7 to 10 This is a schematic diagram showing the current flow direction at different times during the process of converting AC signals to DC signals in the bidirectional inverter of this invention.
[0032] Figure 11 This is a schematic diagram of the circuit structure of another bidirectional inverter in an embodiment of the present invention. Detailed Implementation
[0033] Existing bidirectional inverters require two stages of conversion on the secondary side of the transformer. Taking the conversion of DC to AC signals in a bidirectional inverter as an example, the secondary side of the transformer needs to first convert the AC output signal from the transformer into a DC signal, and then convert it into an AC signal of the corresponding frequency. This results in a large number of required components and higher costs.
[0034] To address this issue, this invention provides a bidirectional inverter, which includes a frequency conversion circuit comprising a first frequency conversion sub-circuit and a second frequency conversion sub-circuit connected in parallel. The first and second frequency conversion sub-circuits can operate alternately under the control of the controller to achieve frequency conversion of AC signals. This eliminates the need to first convert the received AC signal into a DC signal and then into an AC signal of the corresponding frequency, thereby reducing the number of components and lowering costs.
[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
[0036] Reference Figure 1 This invention provides a bidirectional inverter, which may include: a transformer 10, a rectifier circuit 12 located on the primary side of the transformer 10, a frequency conversion circuit 13 located on the secondary side of the transformer, and a controller 14. Wherein:
[0037] The rectifier circuit 12 is coupled to the DC power supply 11 and the transformer 10, and is adapted to convert the DC signal output by the DC power supply 11 into an AC signal, or to convert the AC signal output by the transformer 10 into a DC signal.
[0038] The transformer 10 is coupled to the rectifier circuit 12 and the frequency conversion circuit 13, and is adapted to boost the AC signal output by the rectifier circuit 12 or the AC signal output by the frequency conversion circuit 13.
[0039] The frequency conversion circuit 13 is coupled to the transformer 10 and is adapted to reduce the frequency of the AC signal output by the transformer 10 and output it to the AC power grid, or to increase the frequency of the AC signal output by the AC power grid.
[0040] The controller 14 is coupled to the rectifier circuit 12 and the frequency conversion circuit 13, and is adapted to control the operation of the rectifier circuit 12 and the frequency conversion circuit 13 to convert the DC signal output by the DC power supply 11 into an AC signal suitable for supplying to the AC power grid, or to convert the AC signal output by the AC power grid into a DC signal suitable for supplying to the DC power supply 11.
[0041] The frequency conversion circuit 13 includes a first frequency conversion sub-circuit and a second frequency conversion sub-circuit connected in parallel. The first frequency conversion sub-circuit and the second frequency conversion sub-circuit are adapted to work alternately under the control of the controller 14 to realize the frequency conversion of the AC signal.
[0042] After obtaining the AC signal output by the rectifier circuit 12 or the AC signal output by the AC power grid, the frequency conversion circuit 13 directly converts the frequency of the AC signal instead of performing two-stage conversion, thereby reducing the number of components and lowering the cost.
[0043] It should be noted that the "coupling" described in the embodiments of the present invention refers to a direct or indirect connection. For example, A and B are coupled, which can be either a direct connection between A and B or an indirect connection between A and B through one or more other electrical components. For example, A can be directly connected to C, and C can be directly connected to B, thereby achieving coupling between A and B through C.
[0044] In specific implementations, the DC power supply 11 can be an energy storage battery (such as a nickel-cadmium battery, a nickel-metal hydride battery, a lithium-ion battery, a lithium polymer battery, etc.), a solar panel, or some converters (such as an AC / DC converter or a DC / DC converter). There are no restrictions here, as long as it can provide DC power.
[0045] In specific implementations, the controller 14 may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.
[0046] For example, DC power supply 11 is a solar panel that converts solar energy signals into DC voltage, and controller 14 can control rectifier circuit 12 to convert the DC signal output by solar panel into AC signal of preset frequency.
[0047] In specific implementations, the first frequency conversion sub-circuit and the second frequency conversion sub-circuit can have various circuit structures, which are not limited here. The structures of the first frequency conversion sub-circuit and the second frequency conversion sub-circuit can be the same or different.
[0048] In one embodiment of the present invention, reference is made to... Figure 2 The first frequency conversion sub-circuit may include:
[0049] The first branch 131 and the second branch 132 are connected in parallel;
[0050] And a first capacitor C1 connected in series with the first branch 131 and the second branch 132.
[0051] In practice, the controller can control the first branch and the second branch to work alternately in order to achieve frequency conversion of AC signals.
[0052] In practice, the structures of the first branch 131 and the second branch 132 may be the same or different.
[0053] In one embodiment, the first branch 131 and the second branch 132 have the same structure, each consisting of a switching transistor and a diode connected in series.
[0054] Specifically, refer to Figure 2 The first branch 131 may include a first diode Q1 and a first switch M1 connected in series, wherein the direction of the first diode Q1 is opposite to the direction of the body diode in the first switch M1.
[0055] In a specific implementation, the first switching transistor M1 can be a metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated-gate bipolar transistor (IGBT) or other semiconductor devices.
[0056] When the first switching transistor M1 is a MOSFET, it can be either an NMOS or a PMOS transistor. A diode is formed between the source and drain of each MOSFET, which serves as the body diode of that MOSFET.
[0057] Reference Figure 2 The second branch 132 may include: a second diode Q2 and a second switch M2 connected in series, wherein the direction of the second diode Q2 is opposite to the direction of the body diode in the second switch M2; and the direction of the second diode Q2 is opposite to the direction of the first diode Q1.
[0058] In practical implementation, the second switch M2 can be a MOSFET or other semiconductor devices such as an IGBT. When the second switch M2 is a MOSFET, it can be an NMOS or a PMOS transistor.
[0059] Reference Figure 2 In another embodiment of the present invention, the second frequency conversion sub-circuit may include:
[0060] The third branch 133 and the fourth branch 134 are connected in parallel;
[0061] And a second capacitor C2 connected in series with the third branch 133 and the fourth branch 134.
[0062] In practice, the controller can control the third branch 133 and the fourth branch 134 to work alternately in order to achieve frequency conversion of AC signals.
[0063] In specific implementations, the structures of the third branch 133 and the fourth branch 134 may be the same or different.
[0064] In one embodiment, the third branch 133 and the fourth branch 134 have the same structure, each consisting of a switching transistor and a diode connected in series.
[0065] Specifically, refer to Figure 2 The third branch 133 may include a third diode Q3 and a third switch M3 connected in series, wherein the direction of the third diode Q3 is opposite to the direction of the body diode in the third switch M3.
[0066] In specific implementations, the third switch M3 can be a MOSFET, an IGBT, or other semiconductor devices. When the third switch M3 is a MOSFET, it can be an NMOS or a PMOS transistor.
[0067] Reference Figure 2 The fourth branch 134 may include: a fourth diode Q4 and a fourth switch M4 connected in series, wherein the direction of the fourth diode Q4 is opposite to the direction of the body diode in the fourth switch M4; and the direction of the fourth diode Q4 is opposite to the direction of the third diode Q3.
[0068] In practical implementation, the fourth switch M4 can be a MOSFET, or an IGBT, or other semiconductor devices. When the fourth switch M4 is a MOSFET, it can be an NMOS or a PMOS transistor.
[0069] For example, all four switching transistors, from the first switch M1 to the fourth switch M4, are NMOS transistors. In this case, the cathode of the first diode Q1, the anode of the second diode Q2, the anode of the third diode Q3, and the cathode of the fourth diode can be connected to the first terminal of the transformer secondary side. The anode of the first diode Q1 is connected to the source of the first switch M1, the cathode of the second diode Q2 is connected to the drain of the second switch M2, the cathode of the third diode Q3 is connected to the drain of the third switch M3, and the anode of the fourth diode Q4 is connected to the source of the fourth switch M4. The drain of the first switch M1 and the source of the second switch M2 are connected to the second terminal of the transformer secondary side via the first capacitor C1. The source of the third switch M3 and the drain of the fourth switch M4 are connected to the second terminal of the transformer secondary side via the second capacitor C2. The first and second terminals of the transformer secondary side are the two ends of the same winding of the transformer secondary side.
[0070] In specific implementation, refer to Figure 2 A transformer can include: an ideal transformer T, a primary leakage inductance Lr1, a magnetizing inductance Lm, and a secondary leakage inductance Lr2. An ideal transformer T is one in which the primary and secondary voltages are proportional and there is no power loss. The ideal transformer T, along with the primary leakage inductance Lr1, magnetizing inductance Lm, and secondary leakage inductance Lr2, can be concretely implemented as a single, actual transformer.
[0071] One end of the transformer secondary leakage inductance Lr2 is connected to the secondary terminal of the ideal transformer T, and the other end is connected to the rectifier circuit. It should be noted that one end of the transformer secondary leakage inductance Lr2 can be connected to either the same-name terminal or the opposite-name terminal of the ideal transformer T's secondary side; there is no restriction here.
[0072] It should be noted that the first terminal of the secondary side of the ideal transformer T may be either the same-name terminal or a different-name terminal of the secondary side of the ideal transformer T. When the leakage inductance Lr2 of the transformer secondary side is connected to the same-name terminal of the secondary side of the ideal transformer T, the first capacitor C1 and the second capacitor C2 are connected to the different-name terminal of the secondary side of the ideal transformer T.
[0073] The gates of the first switching transistor M1 to the fourth switching transistor M4 are all connected to the controller. The controller is adapted to control the switching transistors in the first frequency conversion sub-circuit 131 and the second frequency conversion sub-circuit 132 to work alternately to convert the frequency of the corresponding AC signal.
[0074] Specifically, the controller can turn on the switching transistors of one branch of the first frequency conversion sub-circuit 131 and the second frequency conversion sub-circuit 132, while turning off the switching transistors of the other branches. The controller can change the switching duration of the switching transistors in the first frequency conversion sub-circuit 131 and the second frequency conversion sub-circuit 132 to control the frequency of the AC signal to increase or decrease. When the on-time of the switching transistors increases, the frequency of the AC signal decreases. When the on-time of the switching transistors decreases, the frequency of the AC signal increases.
[0075] In a specific implementation, the rectifier circuit can be a full-bridge circuit composed of MOSFETs. Specifically, refer to... Figure 2 The rectifier circuit 11 may include a fifth switch M5, a sixth switch M6, a seventh switch M7, and an eighth switch M8. The fifth switch M5 and the sixth switch M6 are connected in series to form one arm of the full-bridge circuit. The seventh switch M7 and the eighth switch M8 are connected in series to form the other arm of the full-bridge circuit. One output terminal of the DC power supply 11 is connected to the drain of the fifth switch M5 and the drain of the seventh switch M7, and the other output terminal of the DC power supply 11 is connected to the source of the sixth switch M6 and the source of the eighth switch M8. Thus, the DC signal output by the DC power supply 11 can be converted into an AC signal by the full-bridge circuit and then input to the transformer 10, or the AC signal output from the AC mains can be converted into a DC signal by the full-bridge circuit and then used to charge the DC power supply 11.
[0076] In practical implementation, the controller can control the switching durations of the fifth switch M5, the sixth switch M6, the seventh switch M7, and the eighth switch M8, thereby changing the duty cycle of the signal received by the rectifier circuit and thus realizing the mutual conversion between DC and AC signals. Specifically, the controller can increase the on-time of the switches to convert AC signals to DC signals, and decrease the on-time of the switches to convert DC signals to AC signals.
[0077] In practice, the fifth switch M5, the sixth switch M6, the seventh switch M7, and the eighth switch M8 are all low-voltage MOSFETs, and their operating voltage is usually less than 60V.
[0078] In one embodiment of the present invention, reference is made to... Figure 2 The bidirectional inverter may further include a third capacitor C3 located on the primary side of the transformer, wherein the third capacitor C3 is connected in parallel across the DC power supply 11.
[0079] Specifically, the third capacitor C3 can filter the DC signal input from the DC power supply 11 and store energy. The third capacitor C3 can be an electrolytic capacitor, which has a very large capacitance, tens to hundreds of times that of ordinary capacitors, thus making it more suitable for energy storage.
[0080] In one embodiment of the present invention, the bidirectional inverter may further include: a common-mode signal suppression circuit located on the secondary side of the transformer, coupled to the frequency conversion circuit, adapted to suppress common-mode signals. Specifically, refer to... Figure 2 The common-mode signal suppression circuit may include a fourth capacitor C4 and a common-mode inductor L0. The fourth capacitor C4 and the common-mode inductor L0 are connected in parallel at the output of the bidirectional inverter to suppress common-mode signals and prevent common-mode signals from interfering with the AC power grid.
[0081] In practical implementation, under the control of the controller, the DC signal output by the DC power supply is stepped up by the transformer, then its frequency is reduced by the frequency conversion circuit before being output to the AC power grid. At this time, the AC voltage output by the frequency conversion circuit is higher than the voltage of the AC power grid, and the bidirectional inverter is used to realize the conversion of DC signal to AC signal.
[0082] Figure 3 and Figure 6 for Figure 2 A schematic diagram showing the current flow direction at different moments during the conversion of DC to AC signals in a bidirectional inverter. The following is combined with... Figures 3 to 6 The process of converting DC signals to AC signals using the bidirectional inverter is described as follows:
[0083] Reference Figure 3 At time t0, on the primary side of the transformer, the controller turns on the fifth switch M5 and the eighth switch M8, and turns off the seventh switch M7 and the sixth switch M6. On the secondary side of the transformer, the controller turns on the second switch M2, and turns off the other switches.
[0084] At this time, the current path on the primary side of the transformer is: DC power supply 11 → fifth switch M5 → transformer primary leakage inductance Lr1 → magnetizing inductance Lm → eighth switch M8 → DC power supply 11.
[0085] The current path on the secondary side of the transformer is: ideal transformer → transformer secondary leakage inductance Lr2 → second diode Q2 → second switch M2 → common mode inductor L0 → AC power grid → second capacitor C2 → ideal transformer.
[0086] Reference Figure 4At time t1 (t1 > t0), on the primary side of the transformer, the controller disconnects the fifth switch M5 and the eighth switch M8, while turning on the seventh switch M7 and the sixth switch M6. On the secondary side of the transformer, the controller turns on the fourth switch M4 and disconnects the other switches.
[0087] At this time, the current path on the primary side of the transformer is: DC power supply 11 → seventh switch M7 → magnetizing inductor Lm → primary leakage inductance of transformer → Lr1 → sixth switch M6 → transformer → DC power supply 11.
[0088] The current path on the secondary side of the transformer is: ideal transformer → first capacitor C1 → common mode inductor L0 → AC power grid → fourth switch M4 → fourth diode Q4 → transformer secondary leakage inductance Lr2 → ideal transformer.
[0089] The time sequence from time t0 to time t1 is the positive half-cycle control sequence of the AC signal.
[0090] Reference Figure 5 At time t2 (t4 > t1), on the primary side of the transformer, the controller turns on the fifth switch M5 and the eighth switch M8, and turns off the seventh switch M7 and the sixth switch M6. On the secondary side of the transformer, the controller turns on the third switch M3, and turns off the other switches.
[0091] At this time, the current path on the primary side of the transformer is: DC power supply 11 → fifth switch M5 → transformer primary leakage inductance Lr1 → magnetizing inductance Lm → eighth switch M8 → DC power supply 11.
[0092] The current path on the secondary side of the transformer is: ideal transformer → transformer secondary leakage inductance Lr2 → third diode Q3 → third switch M3 → common mode inductor L0 → AC power grid → first capacitor C1 → ideal transformer.
[0093] Reference Figure 6 At time t3 (t3 > t2), on the primary side of the transformer, the controller disconnects the fifth switch M5 and the eighth switch M8, while turning on the seventh switch M7 and the sixth switch M6. On the secondary side of the transformer, the controller turns on the first switch M1 and disconnects the other switches.
[0094] At this time, the current path on the primary side of the transformer is: DC power supply 11 → seventh switch M7 → magnetizing inductor Lm → primary leakage inductance of transformer → Lr1 → sixth switch M6 → transformer → DC power supply 11.
[0095] The current path on the secondary side of the transformer is: ideal transformer → second capacitor C2 → common mode inductor L0 → AC power grid → first switch M1 → first diode Q1 → transformer secondary leakage inductance Lr2 → ideal transformer.
[0096] The time interval from t2 to t3 is the negative half-cycle control timing for providing AC signals to the AC power grid.
[0097] In practical implementation, under the control of the controller, the AC mains outputs an AC signal, which is then frequency-increased by a frequency conversion circuit, stepped up by a transformer, rectified by a rectifier, and finally output to a DC power supply. At this point, the DC power output to the DC power supply is higher than the voltage of the DC power supply itself. The bidirectional inverter is used to convert the AC signal to a DC signal.
[0098] Figure 7 and Figure 10 for Figure 2 A schematic diagram showing the current flow direction at different moments during the AC-to-DC conversion process of a bidirectional inverter. The following is combined with... Figures 7 to 10 The process of converting AC signals to DC signals using the bidirectional inverter is described as follows:
[0099] Reference Figure 7 At time t4, on the primary side of the transformer, the controller turns on the fifth switch M5 and the eighth switch M8, and turns off the seventh switch M7 and the sixth switch M6. On the secondary side of the transformer, the controller turns on the first switch M1 and turns off the other switches.
[0100] At this time, the current path on the secondary side of the transformer is: AC power grid → first switch M1 → first diode Q1 → transformer secondary leakage inductance Lr2 → second capacitor C2 → AC power grid.
[0101] The current path on the primary side of the transformer is: magnetizing inductance Lm → transformer primary leakage inductance Lr1 → fifth switch M5 → DC power supply 11 → eighth switch M8 → magnetizing inductance Lm.
[0102] Reference Figure 8 At time t5 (t5 > t4), on the primary side of the transformer, the controller disconnects the fifth switch M5 and the eighth switch M8, while turning on the seventh switch M7 and the sixth switch M6. On the secondary side of the transformer, the controller turns on the third switch M3 and disconnects the other switches.
[0103] At this time, the current path on the secondary side of the transformer is: AC power grid → third switch M3 → third diode Q3 → transformer secondary leakage inductance Lr2 → ideal transformer → first capacitor C1 → AC power grid.
[0104] The current path on the primary side of the transformer is: magnetizing inductor Lm → seventh switch M7 → DC power supply 11 → sixth switch M6 → primary leakage inductance Lr1 → magnetizing inductor Lm.
[0105] The time interval from t4 to t5 is the positive half-cycle control timing for the DC signal supplied to the DC power supply.
[0106] Reference Figure 9 At time t6 (t6 > t5), on the primary side of the transformer, the controller turns on the fifth switch M5 and the eighth switch M8, and turns off the seventh switch M7 and the sixth switch M6. On the secondary side of the transformer, the controller turns on the second switch M2, and turns off the other switches.
[0107] At this time, the current path on the secondary side of the transformer is: AC power grid → second capacitor C2 → ideal transformer → transformer secondary leakage inductance Lr2 → second diode Q2 → second switching transistor M2.
[0108] The current path on the primary side of the transformer is: magnetizing inductor Lm → seventh switch M7 → DC power supply 11 → sixth switch M6 → primary leakage inductance Lr1 → magnetizing inductor Lm.
[0109] Reference Figure 10 At time t7 (t7 > t6), on the primary side of the transformer, the controller disconnects the fifth switch M5 and the eighth switch M8, while turning on the seventh switch M7 and the sixth switch M6. On the secondary side of the two-phase three-wire transformer, the controller turns on the fourth switch M4 and disconnects the other switches.
[0110] At this time, the current path on the secondary side of the transformer is: AC power grid → fourth switch M4 → fourth diode Q4 → transformer secondary leakage inductance Lr2 → ideal transformer → first capacitor C1 → AC power grid.
[0111] The current path on the primary side of the transformer is: magnetizing inductor Lm → eighth switch M8 → DC power supply 11 → fifth switch M5 → primary leakage inductance Lr1 → magnetizing inductor Lm.
[0112] From time t6 to time t7, the control timing is the negative half-cycle of the DC signal provided to the DC power supply.
[0113] In some embodiments, the number of frequency conversion circuits is three, and the transformer includes three secondary windings, which are coupled one-to-one with the three frequency conversion circuits.
[0114] Specifically, refer to Figure 11 The bidirectional inverter may include three frequency conversion circuits: a first frequency conversion circuit 13a, a second frequency conversion circuit 13b, and a third frequency conversion circuit 13c. Correspondingly, the transformer secondary side has three secondary windings: a first secondary winding RSA, a second secondary winding RSB, and a third secondary winding RSC. The first frequency conversion circuit 13a is coupled to both ends of the first secondary winding RSA, the second frequency conversion circuit 13b is coupled to both ends of the second secondary winding RSB, and the third frequency conversion circuit 13c is coupled to both ends of the third secondary winding RSC.
[0115] In practical implementation, when the transformer has three secondary windings, all three secondary windings are electromagnetically coupled to the primary winding. This converts the AC signal input to the primary winding into three AC signals, with a 120-degree phase difference between the AC signals generated by adjacent secondary windings. These three AC signals are then frequency-converted by different frequency conversion circuits, thereby providing three-phase power to the AC grid.
[0116] In practice, the three-phase electricity output from the AC power grid can also be frequency-converted through different frequency conversion circuits to obtain three AC signals with a phase difference of 120 degrees, which are then input to the transformer. Through electromagnetic coupling, an AC signal is generated on the primary side of the transformer. This AC signal is then rectified by a rectifier circuit to obtain a corresponding DC signal, which is then supplied to the DC power supply.
[0117] The specific operating process of each frequency conversion circuit can be referred to the above-mentioned... Figures 2 to 10 The description will not be repeated here.
[0118] By using the bidirectional inverter in this embodiment of the invention, an AC signal output to the AC power grid can be obtained with fewer components, which can effectively reduce costs.
[0119] Embodiments of the present invention also provide a power supply system, which includes the bidirectional inverter described in the above embodiments and a DC power supply. The bidirectional inverter can convert the DC signal output from the DC power supply into an AC signal and output it to the AC power grid, or it can convert the AC signal output from the AC power grid into a DC signal and provide it to the DC power supply.
[0120] It should be noted that the DC power source includes, but is not limited to, solar panels, and may also be a DC power source such as a fuel cell.
[0121] In practical applications, a power system can include multiple DC power sources, which together provide power to the AC grid. For example, in a photovoltaic power generation system, there may be multiple solar panels that can work together to provide power to the AC grid.
[0122] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.
Claims
1. A bidirectional inverter, characterized in that, Includes: a transformer, a rectifier circuit located on the primary side of the transformer, a frequency conversion circuit located on the secondary side of the transformer, and a controller; wherein: The rectifier circuit is coupled to the DC power supply and the transformer, and is adapted to convert the DC signal output by the DC power supply into an AC signal, or to convert the AC signal output by the transformer into a DC signal. The transformer is coupled to the rectifier circuit and the frequency conversion circuit, and is adapted to boost the AC signal output by the rectifier circuit or the AC signal output by the frequency conversion circuit. The frequency conversion circuit is coupled to the transformer and is adapted to reduce the frequency of the AC signal output by the transformer or increase the frequency of the AC signal output by the AC power grid. The controller is coupled to the rectifier circuit and the frequency conversion circuit, and is adapted to control the operation of the rectifier circuit and the frequency conversion circuit to convert the DC signal output by the DC power supply into an AC signal suitable for supplying to the AC power grid, or to convert the AC signal output by the AC power grid into a DC signal suitable for supplying to the DC power supply. The frequency conversion circuit includes a first frequency conversion sub-circuit and a second frequency conversion sub-circuit connected in parallel; the first frequency conversion sub-circuit and the second frequency conversion sub-circuit are adapted to work alternately under the control of the controller to realize the frequency conversion of the AC signal. The first frequency conversion sub-circuit includes: a first branch and a second branch connected in parallel; and a first capacitor connected in series with the first branch and the second branch; the first branch includes: a first diode and a first switching transistor connected in series, the direction of the first diode being opposite to the direction of the body diode in the first switching transistor; the second branch includes: a second diode and a second switching transistor connected in series, the direction of the second diode being opposite to the direction of the body diode in the second switching transistor; the direction of the second diode is opposite to the direction of the first diode; The second frequency conversion sub-circuit includes: a third branch and a fourth branch connected in parallel; and a second capacitor connected in series with the third branch and the fourth branch; the third branch includes: a third diode and a third switch connected in series, the direction of the third diode being opposite to the direction of the body diode in the third switch; the fourth branch includes: a fourth diode and a fourth switch connected in series, the direction of the fourth diode being opposite to the direction of the body diode in the fourth switch, and the direction of the fourth diode being opposite to the direction of the third diode.
2. The bidirectional inverter as described in claim 1, characterized in that, The rectifier circuit is a full-bridge circuit.
3. The bidirectional inverter as described in claim 1, characterized in that, Also includes: The third capacitor is located on the primary side of the transformer and is connected in parallel across the DC power supply.
4. The bidirectional inverter as described in claim 1, characterized in that, The frequency conversion circuits are in the form of three circuits, and the transformer includes three secondary windings, which are coupled to the three frequency conversion circuits in a one-to-one correspondence.
5. A power supply system, characterized in that, It includes a DC power supply and a bidirectional inverter as described in any one of claims 1 to 4.