Improved three-active-bridge DC-DC converter and fault-tolerant operation method thereof

Abstract

The invention relates to an improved three-active-bridge DC-DC converter and a fault-tolerant operation method thereof, and belongs to the technical field of converters. The problems that the system structure is complex, and a fault-tolerant strategy is not researched when a switch tube has a short-circuit fault are solved. Comprising H-bridge modules and a transformer, the three H-bridge modules are connected through a three-winding transformer to form a converter, the first fault-tolerant capacitor CB1 is connected to a first port of the transformer in series, the second fault-tolerant capacitor CB2 is connected to a second port of the transformer in series, and the third fault-tolerant capacitor CB3 is connected to a third port of the transformer in series. And the third fault-tolerant capacitor CB3 is connected in series with a third port of the transformer. The capacitor with the fault-tolerant function is used for absorbing the direct-current component output by the fault full bridge, normal operation of the TAB converter can still be guaranteed, and the circuit is made to work normally; the system architecture is simplified, the physical size is reduced, the system energy efficiency and stability are improved, and the construction cost is effectively controlled.

Description

Technical Field

[0001] The invention relates to a three-active-bridge DC-DC converter and an operating method thereof, belonging to the technical field of converters. Background Art

[0002] In the rapid development of science and technology economy, energy plays a vital role, but non-renewable traditional energy is being consumed rapidly. At the same time, these traditional energy sources emit a large amount of harmful substances, which has irreversible harm to the environment. Based on this situation, countries around the world have vigorously developed green renewable energy to promote the low-carbon transformation of the economy and society, and have also vigorously promoted the development of new energy power such as photovoltaic power generation and wind power generation. The biggest problem of wind power generation and photovoltaic power generation is that they are greatly affected by environmental factors and cannot provide power normally in the absence of wind and light. To solve this problem, photovoltaic power generation equipment and energy storage devices can be combined together. Since the battery pack does not match the bus voltage, the energy storage device cannot be directly connected to the high-voltage DC bus. A DC-DC converter is required as the key interface circuit between the low-voltage energy storage system and the high-voltage DC bus. In recent years, dual active bridge (DAB) DC-DC (DC-DC) converters have been widely used in many fields such as DC power grids, renewable energy power generation systems, and aerospace applications due to their significant advantages in bidirectional power transmission, high power density, and soft switching characteristics. However, when there are a large number of independent DAB DC-DC converters in the system, the complexity of the system structure increases significantly. At the same time, in the prior art, the publication number is CN114825963B, and the invention name is TAB converter open circuit fault diagnosis and fault-tolerant operation method, which adopts the circuit topology structure of the traditional three-active bridge DC-DC converter to realize the diagnosis of open circuit faults and the fault-tolerant technology when open circuit faults occur, but the fault-tolerant strategy when the switch tube has a short circuit fault is not studied.

[0003] Therefore, it is urgent to propose an improved three-active-bridge DC-DC converter and a fault-tolerant operation method thereof to solve the above-mentioned technical problems. Summary of the invention

[0004] In order to solve the above problems, an improved three-active bridge DC-DC converter and a fault-tolerant operation method thereof are provided to solve the problem that the system structure is complex and the fault-tolerant strategy when a short-circuit fault occurs in the switch tube is not studied. A brief overview of the present invention is given below to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to determine the key or important parts of the present invention, nor is it intended to limit the scope of the present invention.

[0005] The technical solution of the present invention:

[0006] An improved three-active bridge DC-DC converter includes an H-bridge module and a transformer. Three H-bridge modules are connected through a three-winding transformer to form a converter. 11 -S 14 - The switch tube of the first H-bridge module, S 21 -S 24 - The switch tube of the second H-bridge module, S 31 -S 34 - The voltage ratio of the three-winding high-frequency transformer of the switch tube of the third H-bridge module is N 1 :N 2 :N 3 , and also includes a first fault-tolerant capacitor C B1 , the second fault tolerance capacitor C B2 And the third fault tolerance capacitor C B3 , the first fault-tolerant capacitor C B1 Connected in series to the first port of the transformer, the second fault-tolerant capacitor C B2 Connected in series to the second port of the transformer, the third fault-tolerant capacitor C B3 Connected in series to the third port of the transformer.

[0007] Preferably, each port of the transformer includes an auxiliary inductor, a fault-tolerant capacitor, and a winding connected in series in sequence.

[0008] Preferably: an improved three-active-bridge DC-DC converter is an improved three-active-bridge DC-DC converter with fault tolerance.

[0009] A fault-tolerant operation method of an improved three-active-bridge DC-DC converter, based on the improved three-active-bridge DC-DC converter, comprises the following steps:

[0010] When S 11 -S 14 , S 21 -S 24 , S 31 -S 34 Any switch tube S nj When a short circuit occurs in the (jth switch tube of the nth H-bridge), V Hn The positive DC component that appears will be transferred to the fault tolerance capacitor C Bn In the middle, V Hn The voltage waveform becomes a square wave with zero DC component, and the current I on the three sides of the transformer 1 ,I 2 ,I 3 It will no longer continue to increase, but will become a periodic current without DC component, and the circuit will enter a new equilibrium state; when the switch tube S nj When a short circuit occurs, the circuit can still operate normally, achieving fault-tolerant operation.

[0011] Preferably, the three ports (the first port, the second port, and the third port) of the converter are all bidirectional ports, and the working mode of the converter is divided into a single-input dual-output mode and a dual-input single-output mode according to the number of input and output ports.

[0012] Preferred: In order to reduce the impact of the voltage fluctuation of the fault-tolerant capacitor on the circuit, it is required that C Bn With L n The resonant frequency of the LC resonant circuit is much lower than the operating frequency of the switch tube, so C Bn The value range of is:

[0013]

[0014] Where f is the frequency.

[0015] The present invention has the following beneficial effects:

[0016] The present invention can realize that when a short circuit fault occurs in a certain switch tube in the TAB converter, the DC component of the fault full bridge output is absorbed by a capacitor with a fault tolerance function, thereby ensuring the normal operation of the TAB converter and keeping the circuit in normal operation;

[0017] The present invention adopts a triple active bridge (TAB) DC-DC converter to replace multiple independent DAB DC-DC converters, aiming to simplify the system architecture, reduce the physical size, improve the system energy efficiency and stability, and effectively control the construction cost, thereby solving the problem that the complexity of the system structure is significantly increased when there are a large number of independent DAB DC-DC converters in the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural diagram of an improved three-active-bridge DC-DC converter.

[0019] Figure 2 This is the AC voltage and inductor current diagram when TAB is operating normally.

[0020] Figure 3 It is the switch tube S 1 Voltage waveforms on both sides of a transformer without fault tolerance after a short circuit fault.

[0021] Figure 4 It is the switch tube S 1 Voltage waveforms on both sides of a fault-tolerant transformer after a short-circuit fault.

[0022] Figure 5 It is the switch tube S 1 Current waveform of non-fault-tolerant TAB converter after short-circuit fault.

[0023] Figure 6 It is the switch tube S 1Current waveform of fault-tolerant TAB converter after short-circuit fault.

[0024] Figure 7 These are the six modes of modal analysis method;

[0025] Figure (a) is mode 1;

[0026] Figure (b) is mode 2;

[0027] Figure (c) is mode three;

[0028] Figure (d) is mode four;

[0029] Figure (e) is mode five;

[0030] Figure (f) is mode six.

[0031] Figure 8 It is the voltage and current waveform diagram of fault-tolerant operation.

[0032] In the figure, S 11 -S 14 - The switch tube of the first H-bridge module, S 21 -S 24 - The switch tube of the second H-bridge module, S 31 -S 34 - The switch tube of the third H-bridge module, C 1 , C 2 , C 3 N is the filter capacitor of the three ports of the H-bridge module. 1 :N 2 :N 3 - Voltage ratio of three-winding high-frequency transformer, L 1 , L 2 , L 3 - The three ports include auxiliary inductance of leakage inductance, V H1 、V H2 、V H3 - The midpoint voltage difference of the three H-bridge arms, V 1 、V 2 、V 3 - Voltage amplitudes of the three square wave voltage sources, C B1 , C B2 , C B3 - Three fault tolerant capacitors to absorb the DC component of the faulty full-bridge output. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0034] Specific implementation method 1: Combination Figure 1 The present embodiment is described. An improved three-active-bridge DC-DC converter of the present embodiment includes an H-bridge module and a transformer. Three H-bridge modules are connected through a three-winding transformer to form a TAB converter. 1 (S 11 -S 14 ) is the switch tube of the first H-bridge module, S 2 (S 21 -S 24 ) is the switch tube of the second H-bridge module, S 3 (S 31 -S 34 ) is the switch tube of the third H-bridge module, C 1 , C 2 , C 3 is the filter capacitor of the three ports of the H-bridge module, and the voltage ratio of the three-winding high-frequency transformer is N 1 :N 2 :N 3 , where each winding is connected to a corresponding H bridge, L 1 , L 2 , L 3 The auxiliary inductance L for the three ports includes the leakage inductance n , and also includes a first fault-tolerant capacitor C B1 , the second fault tolerance capacitor C B2 And the third fault tolerance capacitor C B3 , the first fault-tolerant capacitor C B1 Connected in series to the first port of the transformer, the second fault-tolerant capacitor C B2 Connected in series to the second port of the transformer, the third fault-tolerant capacitor C B3 Connected in series to the third port of the transformer, C B1 , C B2 , C B3 The three fault-tolerant capacitors C are used to absorb the DC component of the faulty full-bridge output. Bn The research objective of the present invention is to provide a fault-tolerant technology for a short-circuit fault of a switch tube in a TAB converter, that is, to ensure that when a short-circuit fault occurs in a switch tube in the TAB, the TAB converter is not affected and can still operate normally;

[0035] The switch tube has its own parasitic diode, and each port of the transformer includes auxiliary inductance, fault-tolerant capacitor, and winding connected in series in sequence;

[0036] An improved three-active-bridge DC-DC converter is an improved three-active-bridge DC-DC converter with fault tolerance capability; a three-active-bridge (TAB) DC-DC converter is used to replace multiple independent DC-DC converters, aiming to simplify the system architecture, reduce the physical size, improve the system energy efficiency and stability, and effectively control the construction cost; phase shift control is the main control method of the TAB converter. Due to its simple implementation, good dynamic performance, and easy implementation of zero-voltage switching, single phase shift (Single Phase Shift, SPS) control is the most commonly used control strategy of the TAB converter; by adjusting the size of the external phase shift ratio between the three full bridges, the size and direction of the power flow can be adjusted;

[0037] Among them, the transmission power between any two square wave sources is:

[0038]

[0039] Among them, V 1 is the input voltage, V' 2 、V' 3 is the output voltage, f is the operating frequency of the switch tube, D is the shift phase within half a switching cycle, 0≤D≤1.

[0040] The transmission power of a single port is the sum of the powers of the two branches it is connected to, where port one is positive with injected power, and ports two and three are positive with output power:

[0041]

[0042] Among them, the actual input (output) power of each port is not only affected by the switching frequency, inductance, and port voltage, but also related to the phase shift angle between other ports; the present invention simplifies the system architecture, reduces the physical size, improves the system energy efficiency and stability, and effectively controls the construction cost.

[0043] Specific implementation method 2: Combination Figure 1-8 The present embodiment is described. The present embodiment is a fault-tolerant operation method of an improved three-active-bridge DC-DC converter. Based on the improved three-active-bridge DC-DC converter, the improved TAB converter with fault-tolerant capability is formed by connecting three H-bridge modules through a three-winding transformer. The three ports of the TAB converter are all bidirectional ports. The working mode of the TAB converter can be divided into a single-input dual-output mode and a dual-input single-output mode according to the number of input and output ports. The TAB converter contains a total of 12 switch tubes, L 1 , L 2 , L 3 is the auxiliary inductance of the three ports including leakage inductance, C 1 , C 2, C 3 is the filter capacitor of the three ports, C B1 , C B2 , C B3 are three fault-tolerant capacitors for absorbing the DC component of the fault full-bridge output, and the voltage ratio of the three-winding high-frequency transformer is N 1 :N 2 :N 3 ;

[0044] Under normal circumstances, the switches in the converter work normally, the full-bridge output is a square wave with zero DC component, and the voltage across the inductor follows the volt-second balance theorem. Therefore, the voltage across the fault-tolerant capacitor is 0, which has no effect on the normal operation of the circuit. The circuit works normally. At this time, the voltage / current waveform is as follows: Figure 2 ;

[0045] like Figure 7 (a)-(f) take the first half cycle as an example for modal analysis. The current in the second half cycle can be obtained by inverting the first half cycle. The modal analysis method is similar. The following are six modal situations:

[0046] Mode 1: at 0-t 1 When port 1: S 11 With S 14 Open, flowing through L 1 The current is in the opposite direction and flows back to V through the two parallel diodes. 1 Side, port one bridge arm output voltage V H1 =V 1 . Port 2: S 22 With S 23 In the on state, the current is negative, V H2 =-V 2 Port 3: S 32 With S 33 In the on state, the current is negative, V H3 =-V 3 ;

[0047] Mode 2: At t 1 -t 2 When the current flows through L 1 The current passes through zero and turns positive, and the current flows from V 1 Flows into the converter through the switch tube, V H1 =V 1 ; Port 2: The current path is the same as in stage 1, V H2 =-V 2 ; Port 3: The current path is the same as that of phase 1, V H3 =-V 3 ;

[0048] Mode 3: At t 2 -t3 When port 1: V 1 By S 11 With S 14 The circuit is formed, and the current flows into the converter, V H1 =V 1 ; Port 2: S 21 With S 24 On, S 22 With S 23 Shutdown, the current is still negative, V H2 =V 2 ; Port 3: V 3 By S 32 With S 33 The circuit is formed, and the current flows into the converter, V H3 =-V 3 ;

[0049] Mode 4: At t 3 -t 4 At this time, port 1: the current remains unchanged, V H1 =V 1 ; Port 2: Current flows to V 2 , V H2 =V 2 ; Port 3: The inductor current passes through zero and turns positive, V H3 =-V 3 ;

[0050] Mode 5: At t 4 -t 5 At this time, port 1: the current remains unchanged, V H1 =V 1 ; Port 2: The inductor current passes through zero and turns positive, V H2 =V 2 ; Port 3: Current flows to V 3 , V H3 =-V 3 ;

[0051] Mode 6: At t 5 -t 6 At this time, port 1: the current remains unchanged, V H1 =V 1 ; Port 2: Current passes through S 21 , S 24 Flows into the converter, V H2 =V 2 ; Port three: S 32 With S 33 Shutdown, S 31 With S 34 On, current is positive, V H3 =V 3 ;

[0052] When the switch tube in the circuit encounters a short circuit fault, even if the gate signal of the fault branch has been blocked, the TAB converter may continue to be damaged and cannot operate normally; the root cause of this problem is that a DC component is mixed in the fault full-bridge output, which acts on the inductor L and the two ends of the transformer, destroying the voltage volt-second balance principle, thereby causing the current in the fault side circuit to be unstable and continue to rise; in order to effectively deal with the above problems and enhance the overall stability of the system, the traditional TAB converter circuit topology has been optimized and improved for fault tolerance; specifically, a capacitor with fault tolerance function is connected in series on each of the three sides of the transformer on the traditional TAB converter. When the switch tube has a short circuit fault and the fault branch is isolated, the DC component of the fault full-bridge output will be absorbed by these fault-tolerant capacitors, thereby ensuring that the voltage waveform acting on the three sides of the transformer is a square wave without a DC component; in this way, the circuit can enter a new equilibrium state to ensure the normal operation of the circuit;

[0053] When a switch tube fails, the method includes the following steps:

[0054] When S 11 -S 14 , S 21 -S 24 , S 31 -S 34 Any switch tube S nj (When the jth switch tube of the nth H bridge fails short-circuited, V Hn The positive DC component that appears will be transferred to the fault tolerance capacitor C Bn In the example, n=1, 2, 3, so that V Hn The voltage waveform becomes a square wave with zero DC component, and the current I on the three sides of the transformer 1 ,I 2 ,I 3 It will no longer continue to grow. 1 ,I 2 ,I 3 Instead of the current at the corresponding port, it becomes a periodic current without DC component, and the circuit enters a new balanced state; thus, when the switch tube S nj When a short circuit occurs, the circuit can still operate normally, that is, it can achieve fault-tolerant operation; the voltage and current waveforms at this time are as follows: Figure 8 As shown:

[0055] The three ports (first port, second port, and third port) of the TAB converter are all bidirectional ports. According to the number of input and output ports, the working mode of the TAB converter can be divided into a single-input dual-output mode and a dual-input single-output mode;

[0056] In order to reduce the impact of the voltage fluctuation of the fault-tolerant capacitor on the circuit, it is required that CB1 The resonant frequency of the LC resonant circuit composed of C and L is much lower than the operating frequency of the switch tube, so B1 The value range of is:

[0057]

[0058] C B2 and C B3 The value range is the same as above.

[0059] Embodiment 1:

[0060] The present invention can realize that when a short circuit fault occurs in a switch tube in the TAB converter, the DC component of the fault full bridge output is absorbed by a capacitor with a fault tolerance function, and the normal operation of the TAB converter can still be ensured, so that the circuit can maintain normal operation. 11 Take a fault as an example, the switch tube S 12 The gate signal is blocked; under SPS control, the voltage of the fault-tolerant capacitor is V CB1 =0.5V 1 ,V CB2 =0,V CB3 =0;

[0061] Therefore, there are:

[0062] V H1 、V H2 、V H3 The subscript corresponds to the voltage difference between the midpoints of the three H-bridge arms, V 1 、V 2 、V 3 are the voltage amplitudes of the three square wave voltage sources respectively; finally, the simulation results are as follows Figure 3 , Figure 4 ;

[0063] Depend on Figure 3 , Figure 4 It can be seen that when a switch failure occurs in a TAB converter without fault tolerance, the voltage waveform on both sides of the transformer is a square wave with a DC component, and it cannot work normally; when a switch failure occurs in a TAB converter with fault tolerance, the voltage waveform acting on both sides of the transformer is a square wave with zero DC component, and the circuit enters a new balanced state.

[0064] Depend on Figure 5 , Figure 6 It can be seen that when a switch tube failure occurs in a TAB converter without fault tolerance, the current on the fault side continues to rise, and the current on the non-fault side continues to rise in the opposite direction, and cannot be stable; when a switch tube failure occurs in a TAB converter with fault tolerance, the currents on the three sides are all periodic currents without DC components, and can operate stably.

[0065] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be arranged and combined, and those skilled in the art can exhaust all possibilities based on the mathematical knowledge of arrangement and combination. Therefore, the present invention will no longer describe the technical solutions after arrangement and combination one by one, but it should be understood that the technical solutions after arrangement and combination have been disclosed by the present invention.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An improved three-active bridge DC-DC converter, comprising an H-bridge module and a transformer, wherein three H-bridge modules are connected through a three-winding transformer to form a converter, S 11 -S 14 is the switch tube of the first H-bridge module, S 21 -S 24 is the switch tube of the second H-bridge module, S 31 -S 34 It is the switch tube of the third H-bridge module, and the voltage ratio of the three-winding high-frequency transformer is N1:N2:N3, which is characterized by: Also includes a first fault-tolerant capacitor C B1 , the second fault tolerance capacitor C B2 And the third fault tolerance capacitor C B3 , the first fault-tolerant capacitor C B1 Connected in series to the first port of the transformer, the second fault-tolerant capacitor C B2 Connected in series to the second port of the transformer, the third fault-tolerant capacitor C B3 Connected in series to the third port of the transformer.

2. The improved three-active-bridge DC-DC converter according to claim 1, characterized in that: Each port of the transformer includes an auxiliary inductor, a fault-tolerant capacitor, and a winding connected in series.

3. The improved three-active-bridge DC-DC converter according to claim 1, characterized in that: An improved three-active-bridge DC-DC converter is an improved three-active-bridge DC-DC converter with fault tolerance capability.

4. A fault-tolerant operation method of an improved three-active-bridge DC-DC converter, characterized in that: An improved three-active-bridge DC-DC converter according to any one of claims 1 to 3, comprising the following steps: When the switch S nj When a short circuit occurs, V Hn The positive DC component that appears will be transferred to the fault tolerance capacitor C Bn In the middle, V Hn The voltage waveform becomes a square wave with zero DC component, and the currents I1, I2, and I3 on ​​the three sides of the transformer will no longer continue to increase, but will become periodic currents without DC components, and the circuit will enter a new balanced state. nj When a short circuit occurs, the circuit can still operate normally, achieving fault-tolerant operation.

5. The fault-tolerant operation method of an improved three-active-bridge DC-DC converter according to claim 4, characterized in that: The three ports of the converter are all bidirectional ports. According to the number of input and output ports, the working mode of the converter is divided into a single-input dual-output mode and a dual-input single-output mode.

6. The fault-tolerant operation method of an improved three-active-bridge DC-DC converter according to claim 4, characterized in that: In order to reduce the impact of the voltage fluctuation of the fault-tolerant capacitor on the circuit, it is required that C Bn With L n The resonant frequency of the LC resonant circuit is much lower than the operating frequency of the switch tube, so C Bn The value range of is: Where f is the frequency.

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