A bidirectional dc-dc converter and control method

Abstract

The application discloses a bidirectional DC-DC converter and a control method, the converter adopts a magnetic integration technology and a switching multiplexing technology to combine a Boost circuit and a series resonant circuit, and realizes single-stage bidirectional DC-DC power conversion; compared with a two-stage converter composed of a traditional Boost and series connection, the number of power switching devices is reduced, and the efficiency and power density of the converter are improved; through the Boost interleaved parallel technology on the low-voltage side, the input current ripple is almost zero, the application occasions of the converter are increased, and the converter is particularly suitable for various applications such as a battery energy storage system and a new energy vehicle.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, and in particular relates to a bidirectional DC-DC converter and its control method. Background Technology

[0002] With the rapid development of renewable energy, battery energy storage systems have become an important means of balancing renewable energy and the power grid, and will be a key component of future smart power systems. The bidirectional DC-DC converter is a crucial component connecting the battery energy storage system and the DC bus for charging or discharging. The bidirectional DC-DC converter itself should possess high efficiency, high power density, and high safety characteristics. From an external perspective, reducing input current ripple can significantly extend the lifespan of the battery energy storage system, and high voltage gain can broaden its application range.

[0003] Existing isolated bidirectional DC-DC converters can be divided into two categories: voltage-source and current-source. Voltage-source bidirectional DC-DC converters excel in voltage stress and efficiency; however, current stress and current ripple limit their application in battery energy storage systems. In contrast, current-source bidirectional DC-DC converters are a good choice for applications requiring high boost / buck ratios and low current ripple. Current-source half-bridge DC-DC converters have simple circuits and ensure zero-current switching of the primary-side switches and secondary-side diodes. To further extend the voltage conversion range, existing technologies have also proposed boost full-bridge and buck-boost full-bridge converters. However, these converters still exhibit input current ripple, which can be reduced through interleaving techniques and push-pull transformer structures, but this also increases the number of power switches and magnetic components. Therefore, a new technical solution is urgently needed to address the shortcomings of traditional converters in terms of low efficiency and power density. Summary of the Invention

[0004] The present invention aims to provide a bidirectional DC-DC converter and control method, which realizes single-stage bidirectional DC-DC power conversion, improves the efficiency and power density of the converter, and expands the application scenarios of the converter.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a bidirectional DC-DC converter, comprising: an input terminal for receiving an input voltage; an output terminal for outputting a converted voltage; a controller electrically connected to the power conversion circuit for controlling the operating state of the power conversion circuit; and a power conversion circuit connected between the input terminal and the output terminal for converting the input voltage into an output voltage.

[0006] The power conversion circuit includes: a first isolation transformer and a second isolation transformer. The primary and secondary sides of the first and second isolation transformers are single windings. One end of the primary side of the first isolation transformer is connected to one end of the primary side of the second isolation transformer, and the positive terminal of the input voltage is connected between them. The primary magnetizing inductance of the first isolation transformer and the primary magnetizing inductance of the second isolation transformer are two boost inductors of an interleaved parallel Boost circuit. One end of the secondary side of the first isolation transformer is connected to one end of the secondary side of the second isolation transformer. The sum of the leakage inductance of the secondary side of the first isolation transformer and the leakage inductance of the secondary side of the second isolation transformer is the resonant inductance of an LC series resonant circuit. The LC series resonant circuit is connected to a half-bridge three-level topology unit.

[0007] The interleaved parallel Boost circuit includes the primary side of the first isolation transformer, the primary side of the second isolation transformer, a first half-bridge circuit, a second half-bridge circuit, and a clamping capacitor. The first half-bridge circuit includes a first switch and a second switch connected in series, and the second half-bridge circuit includes a third switch and a fourth switch connected in series. The other end of the primary side of the first isolation transformer is connected to the series connection point of the first switch and the second switch, and the other end of the primary side of the second isolation transformer is connected to the series connection point of the third switch and the fourth switch. The drain of the first switch is connected to the drain of the third switch, and the positive terminal of the clamping capacitor is connected between them. The negative terminal of the clamping capacitor is connected to the negative terminal of the input voltage. The source of the second switch is connected to the source of the fourth switch, and the negative terminal of the input voltage is connected between them.

[0008] The LC series resonant circuit includes the secondary side of the first isolation transformer, the secondary side of the second isolation transformer, and a resonant capacitor. The other end of the secondary side of the first isolation transformer is connected to one end of the resonant capacitor.

[0009] The half-bridge three-level topology unit includes a fifth switch, a sixth switch, a seventh switch, an eighth switch, a first voltage divider capacitor, a second voltage divider capacitor, and an output capacitor. The source of the fifth switch is connected to the drain of the sixth switch, the source of the sixth switch is connected to the drain of the seventh switch, and the source of the seventh switch is connected to the drain of the eighth switch. The positive terminals of the first voltage divider capacitor, the output capacitor, and the output voltage are connected to the drain of the fifth switch. The negative terminal of the first voltage divider capacitor is connected to the source of the sixth switch. The positive terminal of the second voltage divider capacitor is connected to the drain of the seventh switch, and the negative terminals of the second voltage divider capacitor, the output capacitor, and the output voltage are connected to the source of the eighth switch.

[0010] The other end of the resonant capacitor is connected to the connection point of the fifth and sixth switching transistors, and the other end of the secondary side of the second isolation transformer is connected to the connection point of the seventh and eighth switching transistors.

[0011] The first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, and the eighth switch are all equipped with anti-parallel diodes.

[0012] The power conversion circuit of the bidirectional DC-DC converter provided by this invention includes two isolation transformers. The magnetizing inductance of the primary side of the two isolation transformers serves as the boost inductance of the Boost circuit, and the sum of the leakage inductance of the secondary side of the two isolation transformers serves as the inductance of the LC series resonant circuit. The low-voltage side on the left of the isolation transformers has a Boost interleaved parallel structure, and the right side of the LC series resonant circuit has a half-bridge three-level topology. The bidirectional DC-DC converter uses magnetic integration technology and switch multiplexing technology to combine the Boost circuit and the series resonant circuit, realizing single-stage bidirectional DC-DC power conversion. Compared with the traditional two-stage converter composed of Boost + series, it only requires two magnetic components, reducing the number of power devices and magnetic devices, thereby improving the efficiency and power density of the converter. Moreover, through the Boost interleaved parallel technology on the low-voltage side, the input current ripple is almost zero, increasing the application range of the converter, especially suitable for various applications such as battery energy storage systems and new energy vehicles.

[0013] According to embodiments of the present invention, the present invention can be further optimized, and the optimized technical solution is as follows:

[0014] Based on the same concept, the present invention also provides a control method for a bidirectional DC-DC converter, the control method being applied to the bidirectional DC-DC converter described above, comprising:

[0015] The input and output voltages of the converter are collected;

[0016] The controller generates drive signals;

[0017] Based on the collected input and output voltages, the controller adjusts the duty cycle of the drive signal through closed-loop control.

[0018] The driving signal is used to control the switching transistors in the power conversion circuit to turn on and off, thereby converting the input voltage into a stable output voltage.

[0019] This invention magnetically integrates the boost inductor, the leakage inductance of the LC resonator, and the leakage inductance of the high-frequency transformer. It integrates the traditional two-phase interleaved boost circuit, full-bridge LC series resonant circuit, and dual active bridge current-mode DC-DC converter into a single-stage topology, achieving magnetic integration of the boost inductor, high-frequency transformer, and resonant inductor. This invention combines a half-bridge three-level converter with a bidirectional DC-DC converter, reducing the voltage stress on the high-voltage side power switch and making it possible to use low-voltage rated power components on the high-voltage side.

[0020] This invention achieves single-stage bidirectional DC-DC power conversion through magnetic integration technology and switch multiplexing technology, realizing zero-voltage turn-on and turn-off of switching devices, reducing the number of power devices and magnetic components, and improving the efficiency and power density of the converter. On the low-voltage side, through Boost interleaved parallel technology, the input current ripple is almost zero, increasing the application range of the converter, which can be used in various applications such as battery energy storage systems and new energy vehicles.

[0021] In power electronics, the core criterion for classifying a "level" is an independent power conversion functional unit, which possesses a complete "energy input-conversion processing-energy output" process, and this unit can independently control a type of electrical parameter (voltage, current, frequency, phase). This invention implements voltage control.

[0022] In one preferred embodiment, the controller operates in a fixed-frequency mode to generate drive signals at a constant frequency.

[0023] The control method provided by this invention adopts a fixed frequency mode, which is beneficial for smooth transition during bidirectional switching and avoids control instability or transient impact caused by frequency changes. It is particularly suitable for applications such as battery energy storage systems and new energy vehicles.

[0024] In one preferred embodiment, the converter operates in quadruple voltage mode.

[0025] This invention significantly improves the output voltage and increases the voltage gain range without increasing the size of the magnetic components, while reducing device voltage stress, improving efficiency, and reducing electromagnetic interference, thereby achieving high power density and high reliability voltage conversion.

[0026] In one preferred embodiment, the converter's quadruple voltage mode includes both forward and reverse directions;

[0027] When the converter operates in the quadruple forward mode, it includes four operating states within half a switching cycle, as follows:

[0028] Mode 1: The seventh switch is continuously on, the fifth switch is on with zero current, and the resonant current is... The direction of current flow is from right to left, representing the primary current of the first isolation transformer. Reverse flow, the second switch is turned on with zero voltage, and the primary current of the second isolation transformer... With forward flow, the third switch is turned on with zero voltage, and the resonant capacitor voltage... decline;

[0029] Mode 2: The fifth switch is turned off, and the resonant current... Positive flow;

[0030] Mode 3: The fifth switch is turned off, and the resonant current... The value is zero, indicating that the transformer series resonant circuit is open.

[0031] Mode 4: The second and third switches are turned off, and the resonant current... The current is zero, the transformer series resonant circuit is open, and the primary current of the first isolation transformer is zero. Reverse flow, the first switch is turned on at zero voltage, and the primary current of the second isolation transformer... In the forward flow, the fourth switch is turned on with zero voltage;

[0032] When the converter operates in quadruple voltage inverting mode, it includes four operating states within half a switching cycle, as follows:

[0033] Mode 5: Primary current of the first isolation transformer With forward flow, the second switch is turned on with zero voltage, and the primary current of the second isolation transformer... Reverse flow, the third switch is turned on with zero voltage, resonant current. The current is zero, so the sixth switch is turned on with zero current.

[0034] Mode 6: The sixth switch is turned off, its reverse diode freewheels, and the resonant current... Flowing in reverse from left to right;

[0035] Mode 7: The sixth switch is turned off, and the resonant current... The value is zero, indicating that the transformer series resonant circuit is open.

[0036] Mode 8: The second and third switches are turned off, and the resonant current... The current is zero, the transformer series resonant circuit is open, and the primary current of the first isolation transformer is zero. Reverse flow, the first switch is turned on at zero voltage, and the primary current of the second isolation transformer... With forward flow, the fourth switch is turned on at zero voltage.

[0037] This invention enables operation over a wide voltage range, adapting to significant voltage variations on both the high-voltage and low-voltage sides, and reducing voltage stress on switching devices. It is particularly suitable for applications such as battery energy storage systems and new energy vehicles.

[0038] In one preferred embodiment, the capacitance value of the resonant capacitor of the bidirectional DC-DC converter is calculated using the following formula:

[0039] ;

[0040] in, This is the resonant capacitance value. This is the clamping capacitor voltage. For output voltage, For output power, The switching cycle.

[0041] This invention achieves soft switching of the switching transistor through the constraint conditions of resonant modes: zero-voltage switching (ZVS) and zero-current switching (ZCS), that is, turning on or off when the voltage is zero, or turning on or off when the current is zero. This eliminates losses caused by voltage and current overlap, reduces switching losses and voltage spikes, improves electromagnetic interference performance, and supports high-frequency designs.

[0042] Compared with the prior art, the beneficial effects of the present invention are:

[0043] This invention provides a bidirectional DC-DC converter and its control method. The converter combines a Boost circuit and a series resonant circuit using magnetic integration technology and switch multiplexing technology to achieve single-stage bidirectional DC-DC power conversion. Compared with the traditional two-stage converter composed of Boost + series, it reduces the number of power switching devices and improves the converter's efficiency and power density. On the low-voltage side, through Boost interleaved parallel technology, the input current ripple is almost zero, increasing the converter's application range, and making it particularly suitable for various applications such as battery energy storage systems and new energy vehicles. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the structure of an interleaved Boost integrated series resonant bidirectional DC-DC converter according to an embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram of the topology of the power conversion circuit of an interleaved Boost integrated series resonant bidirectional DC-DC converter according to an embodiment of the present invention;

[0046] Figure 3This is a mode diagram of mode 1 of an interleaved Boost integrated series resonant bidirectional DC-DC converter in the quadruple forward mode according to an embodiment of the present invention.

[0047] Figure 4 This is a mode 2 operating mode diagram of an interleaved Boost integrated series resonant bidirectional DC-DC converter in the quadruple forward mode according to an embodiment of the present invention;

[0048] Figure 5 This is a mode 3 operating mode diagram of an interleaved Boost integrated series resonant bidirectional DC-DC converter in the quadruple forward mode according to an embodiment of the present invention.

[0049] Figure 6 This is a mode 4 diagram of the interleaved Boost integrated series resonant bidirectional DC-DC converter in the quadruple forward mode according to an embodiment of the present invention.

[0050] Figure 7 This is a mode 5 diagram of the interleaved Boost integrated series resonant bidirectional DC-DC converter in the quadruple voltage inverting mode according to an embodiment of the present invention.

[0051] Figure 8 This is a mode 6 diagram of the interleaved Boost integrated series resonant bidirectional DC-DC converter in the quadruple forward mode according to an embodiment of the present invention.

[0052] Figure 9 This is a mode 7 diagram of the interleaved Boost integrated series resonant bidirectional DC-DC converter in the quadruple forward mode according to an embodiment of the present invention.

[0053] Figure 10 This is a mode 8 diagram of the interleaved Boost integrated series resonant bidirectional DC-DC converter in the quadruple forward mode according to an embodiment of the present invention.

[0054] Figure 11 This is a waveform diagram of the interleaved Boost integrated series resonant bidirectional DC-DC converter in the quadruple forward mode according to an embodiment of the present invention.

[0055] Figure 12 This is a waveform diagram of the interleaved Boost integrated series resonant bidirectional DC-DC converter in the quadruple voltage inverting mode according to an embodiment of the present invention.

[0056] Figure 13 This is a flowchart illustrating the control method of an interleaved Boost integrated series resonant bidirectional DC-DC converter according to an embodiment of the present invention. Detailed Implementation

[0057] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0058] Example 1

[0059] like Figure 1 As shown, this embodiment of the invention provides an interleaved Boost integrated series resonant bidirectional DC-DC converter, including: an input terminal for receiving an input voltage; an output terminal for outputting the converted voltage; a power conversion circuit connected between the input terminal and the output terminal for converting the input voltage into an output voltage; and a controller electrically connected to the power conversion circuit for controlling the operating state of the power conversion circuit. The converter can reduce the number of magnetic and switching devices while increasing the voltage gain of the bidirectional DC-DC converter and reducing current ripple.

[0060] like Figure 2 As shown, the power conversion circuit includes two isolation transformers T1 and T2. The primary magnetizing inductance Lm1 of isolation transformer T1 and the primary magnetizing inductance Lm2 of isolation transformer T2 serve as the two boost inductors for the left low-voltage side interleaved Boost circuit. The sum of the secondary leakage inductance Lr1 of isolation transformer T1 and the secondary leakage inductance Lr2 of isolation transformer T2 serves as the resonant inductance for the LC series resonant circuit. The left low-voltage side of the isolation transformers has a Boost interleaved parallel structure, while the right high-voltage side of the isolation transformers has an LC series resonant circuit. The right side of the LC series resonant circuit has a half-bridge three-level topology.

[0061] like Figure 2 As shown, the interleaved Boost circuit includes switching transistors S1, S2, S3, and S4 with anti-parallel diodes, a clamping capacitor Cc, the primary windings of isolation transformers T1 and T2. Switches S1, S2, S3, and S4 form an H-bridge topology. One end of the primary winding of isolation transformer T1 and one end of the primary winding of isolation transformer T2 are connected to the positive terminal of the input power supply VL. The other end of the primary winding of isolation transformer T1 is connected to the midpoint A of the half-bridge circuit formed by switches S1 and S2. The other end of the primary winding of isolation transformer T2 is connected to the midpoint B of the half-bridge circuit formed by switches S3 and S4. The drains of switches S1 and S3 are connected and connected to one end of the clamping capacitor Cc. The other end of the clamping capacitor Cc is connected to the negative terminal of the input power supply VL.

[0062] like Figure 2As shown, the LC series resonant circuit includes the secondary side of isolation transformer T1, the secondary side of isolation transformer T2, and a resonant capacitor Cr. The secondary side of isolation transformer T1, the secondary side of isolation transformer T2, and the resonant capacitor Cr are connected in series to form an LC network. The sum of the leakage inductance Lr1 of the secondary side of isolation transformer T1 and the leakage inductance Lr2 of the secondary side of isolation transformer T2 constitutes the resonant inductance.

[0063] like Figure 2 As shown, the half-bridge three-level topology includes switching transistors S5, S6, S7, and S8, voltage dividing capacitors C1 and C2, and output capacitor C3. The source of switching transistor S5 and the drain of switching transistor S6 are connected at point C. The source of switching transistor S6 and the drain of switching transistor S7 are connected at point D. The half-bridge circuit composed of switching transistors S5 and S6 is connected in parallel with voltage dividing capacitor C1, and the half-bridge circuit composed of switching transistors S7 and S8 is connected in parallel with voltage dividing capacitor C2. The two ends of output capacitor C3 are connected to the drain of switching transistor S5 and the source of switching transistor S8, respectively. One end of the LC series resonant network is connected to point C, and the other end is connected to point D.

[0064] like Figure 2 As shown, the gates of switching transistors S1, S2, S3, S4, S5, S6, S7, and S8 receive external control drive signals. The controller operates in a fixed-frequency mode, including an oscillator that generates a constant-frequency clock signal, ensuring the converter operates in a fixed-frequency mode with a constant switching period. The output voltage is adjusted by regulating the on-time of the switching transistors. The parallel boost circuit operates in an interleaved buck-boost mode. The half-bridge three-level topology operates in a quadruple voltage multiplier mode.

[0065] The interleaved Boost integrated series resonant bidirectional DC-DC converter uses the primary inductance Lm1 of isolation transformer T1 as one of the boost inductors in the interleaved parallel Boost circuit, and the primary inductance Lm2 of isolation transformer T2 as the other boost inductor in the interleaved parallel Boost circuit. This bidirectional DC-DC converter requires only two magnetic components.

[0066] The interleaved parallel Boost circuit and the LC series resonant circuit share the switching transistors S1, S2, S3, and S4. The switching transistors S1, S2, S3, and S4 switch at a fixed switching frequency, simultaneously achieving both Boost and high-frequency square wave output functions.

[0067] In the interleaved Boost integrated series resonant bidirectional DC-DC converter, switches S1, S2, S3, and S4 all operate in zero-voltage turn-on mode, while switches S5, S6, S7, and S8 operate in zero-current turn-on and turn-off modes.

[0068] In this embodiment of the invention, the interleaved Boost integrated series resonant bidirectional DC-DC converter can operate in a forward mode (power from left to right) and a reverse mode (power from right to left). The conduction logic of the switching transistors differs between the two modes. For example... Figure 11 The diagram shown illustrates the waveform of the converter controlling the on / off state of the switch in forward mode. Figure 12 The figure shows a waveform diagram of the converter controlling the on / off state of the switch in reverse mode.

[0069] In this embodiment of the invention, the half-bridge three-level topology operates in a quadruple voltage multiplier modulation mode to increase the gain range of the DC-DC converter. The quadruple voltage multiplier modulation mode includes both forward and reverse modulation, and belongs to the modulation stage in the converter control flow. Input and output voltages are acquired through a voltage sampling circuit, and after noise processing by a conditioning circuit, the data is sent to the controller. The difference between the acquired input and output voltages and the reference voltage is used by a PI controller to determine the duty cycle, which is then output to the modulation stage.

[0070] like Figure 11 The figure shows the waveform of the interleaved Boost integrated series resonant bidirectional DC-DC converter in the fourth voltage multiplier forward mode according to an embodiment of the present invention. The time period is shown in the figure. This corresponds to half a switching cycle.

[0071] When the converter operates in quadruple forward mode, half a switching cycle contains four operating states, as follows:

[0072] Mode 1: such as Figure 3 and Figure 11 The time period As shown, switch S7 is always on, switch S5 is on with zero current, and the resonant current is... The direction of current flow is from right to left; this represents the primary current of the first isolation transformer. With the flow reversed, the anti-parallel diode of switch S2 is already conducting, switch S2 is conducting with zero voltage, and the primary current of the second isolation transformer... With forward flow, the anti-parallel diode of switch S3 is already conducting, switch S3 is conducting with zero voltage, and the resonant capacitor voltage... decline.

[0073] like Figures 3 to 6 As shown, gray indicates that the switching transistor is in a non-operating state and no current flows through it; the direction of the current arrows in the figure is only a reference direction, and the actual flow direction is determined by the actual adjustment direction of each mode.

[0074] Mode 2: such as Figure 4 and Figure 11 The time period in As shown, when switch S5 is turned off, the resonant current... With forward flow, the anti-parallel diode of switch S6 is turned on.

[0075] Mode 3: such as Figure 5 and Figure 11 The time period in As shown, when switch S5 is turned off, the resonant current... The value is zero, the transformer series resonant circuit is open, and the switching transistor S6 is turned off.

[0076] Mode 4: such as Figure 6 and Figure 11 The time period in As shown, with switches S2 and S3 off, the resonant current... The current is zero, the transformer series resonant circuit is open; the primary current of the first isolation transformer is zero. With the flow reversed, the anti-parallel diode of switch S1 is already conducting, switch S1 is turned on with zero voltage, and the primary current of the second isolation transformer... With forward flow, the anti-parallel diode of switch S4 is already conducting, and switch S4 is turned on with zero voltage.

[0077] Figure 12 This is a waveform diagram of the interleaved Boost integrated series resonant bidirectional DC-DC converter operating in quadruple voltage inverting mode according to an embodiment of the present invention. The time period is... This corresponds to half a switching cycle.

[0078] When the converter operates in quadruple voltage inverting mode, half a switching cycle contains four operating states, as detailed below:

[0079] Mode 5: such as Figure 7 and Figure 12 The time period in As shown, the primary current of the first isolation transformer With forward flow, switch S2 conducts at zero voltage, and the primary current of the second isolation transformer... Reverse flow, switch S3 conducts with zero voltage, resonant current. With zero current, switch S6 conducts with zero current.

[0080] like Figures 7 to 10 As shown, gray indicates that the switching transistor is in a non-operating state and no current flows through it; the direction of the current arrows in the figure is only a reference direction, and the actual flow direction is determined by the actual adjustment direction of each mode.

[0081] Modal 6: such as Figure 8 and Figure 12 The time period in As shown, switch S6 is off, but the anti-parallel diode continues to flow, resulting in a resonant current. The flow is reversed from left to right.

[0082] Modal 7: such as Figure 9 and Figure 12 The time period in As shown, when switch S6 is turned off, the resonant current... The value is zero, indicating that the transformer series resonant circuit is open.

[0083] Modal 8: such as Figure 10 and Figure 12 The time period in As shown, with switches S2 and S3 off, the resonant current... The current is zero, the transformer series resonant circuit is open, and the primary current of the first isolation transformer is zero. With a negative voltage, switch S2 is off, the anti-parallel diode of switch S1 is conducting, switch S1 is turned on with zero voltage, and the primary current of the second isolation transformer... When the value is positive, switch S3 is turned off, and the anti-parallel diode of switch S4 is already conducting, so switch S4 conducts with zero voltage.

[0084] like Figure 11 and 12 As shown, ~ This represents the corresponding switching transistor drive waveform, where, and Same driver and Same driver The voltage between points A and B in the interleaved parallel Boost circuit. This is the primary current of the first isolation transformer T1. The primary current of the second isolation transformer T2 is [value], and the average value of the resonant capacitor voltage is [value]. , This is the output voltage.

[0085] For the interleaved Boost integrated series resonant bidirectional DC-DC converter to operate normally, the resonant capacitor should satisfy the following calculation formula:

[0086] ;

[0087] in, This is the resonant capacitance value. This is the clamping capacitor voltage. For output voltage, For output power, The switching cycle.

[0088] Compared to traditional two-stage converters composed of Boost+series circuits, the interleaved Boost integrated series resonant bidirectional DC-DC converter provided in this embodiment combines the Boost circuit and the series resonant circuit using magnetic integration technology and switch multiplexing technology, achieving single-stage bidirectional DC-DC power conversion. This converter can reduce the number of magnetic and switching devices, while increasing the voltage gain of the bidirectional DC-DC converter and reducing current ripple.

[0089] like Figure 13 The diagram shown is a control flowchart of the interleaved Boost integrated series resonant bidirectional DC-DC converter provided in an embodiment of the present invention. The controller acquires the input and output voltages of the converter, generates the conduction time of each switching device through a closed-loop control strategy, and stabilizes the output voltage near a given value by controlling the turn-on and turn-off of the power devices.

[0090] The above embodiments should be understood as being used only to illustrate the present invention more clearly, and not to limit the scope of the present invention. After reading the present invention, any modifications of the present embodiments by those skilled in the art will fall within the scope defined by the appended claims.

Claims

1. A control method for a bidirectional DC-DC converter, characterized in that, The bidirectional DC-DC converter includes: an input terminal for receiving input voltage; an output terminal for outputting the converted voltage; a power conversion circuit connected between the input terminal and the output terminal for converting the input voltage into an output voltage; and a controller electrically connected to the power conversion circuit for controlling the operating state of the power conversion circuit. The power conversion circuit includes: a first isolation transformer and a second isolation transformer, both with single windings on their primary and secondary sides. One end of the primary winding of the first isolation transformer is connected to one end of the primary winding of the second isolation transformer, and the positive terminal of the input voltage is connected between them. The primary magnetizing inductance of the first isolation transformer and the second isolation transformer... The primary-side magnetizing inductance of the transformer consists of two boost inductors in an interleaved parallel Boost circuit. One end of the secondary side of the first isolation transformer is connected to one end of the secondary side of the second isolation transformer. The sum of the leakage inductance of the secondary side of the first isolation transformer and the leakage inductance of the secondary side of the second isolation transformer is the resonant inductance of the LC series resonant circuit, which is connected to a half-bridge three-level topology. The interleaved parallel Boost circuit includes the primary side of the first isolation transformer, the primary side of the second isolation transformer, a first half-bridge circuit, a second half-bridge circuit, and a clamping capacitor. The first half-bridge circuit includes a first and a second switch connected in series, and the second half-bridge circuit includes a third and a fourth switch connected in series. The first isolation transformer... The other end of the primary side of the second isolation transformer is connected to the series connection point of the first and second switching transistors. The other end of the primary side of the second isolation transformer is connected to the series connection point of the third and fourth switching transistors. The drain of the first switching transistor is connected to the drain of the third switching transistor, and the positive terminal of the clamping capacitor is connected between them. The negative terminal of the clamping capacitor is connected to the negative terminal of the input voltage. The source of the second switching transistor is connected to the source of the fourth switching transistor, and the negative terminal of the input voltage is connected between them. The LC series resonant circuit includes the secondary side of the first isolation transformer, the secondary side of the second isolation transformer, and a resonant capacitor. The other end of the secondary side of the first isolation transformer is connected to one end of the resonant capacitor. The half-bridge three-level topology unit... The device includes a fifth switch, a sixth switch, a seventh switch, an eighth switch, a first voltage divider capacitor, a second voltage divider capacitor, and an output capacitor. The source of the fifth switch is connected to the drain of the sixth switch, the source of the sixth switch is connected to the drain of the seventh switch, and the source of the seventh switch is connected to the drain of the eighth switch. The positive terminals of the first voltage divider capacitor, the output capacitor, and the output voltage are connected to the drain of the fifth switch. The negative terminal of the first voltage divider capacitor is connected to the source of the sixth switch. The positive terminal of the second voltage divider capacitor is connected to the drain of the seventh switch, and the negative terminals of the second voltage divider capacitor, the output capacitor, and the output voltage are connected to the source of the eighth switch.The other end of the resonant capacitor is connected to the connection point of the fifth and sixth switching transistors, and the other end of the secondary side of the second isolation transformer is connected to the connection point of the seventh and eighth switching transistors; the first, second, third, fourth, fifth, sixth, seventh, and eighth switching transistors are all equipped with anti-parallel diodes; The control method is applied to the bidirectional DC-DC converter and includes: The input and output voltages of the converter are acquired; the controller generates a drive signal; based on the acquired input and output voltages, the controller adjusts the duty cycle of the drive signal through closed-loop control; the drive signal is used to control the switching transistors in the power conversion circuit to convert the input voltage into a stable output voltage; the converter operates in a four-voltage multiplier mode; the four-voltage multiplier mode of the converter includes forward and reverse directions; When the converter operates in the quadruple forward mode, it includes four operating states within half a switching cycle, as follows: Mode 1: The seventh switch is continuously on, the fifth switch is on with zero current, and the resonant current is... The direction of current flow is from right to left, representing the primary current of the first isolation transformer. Reverse flow, the second switch is turned on with zero voltage, and the primary current of the second isolation transformer... With forward flow, the third switch is turned on with zero voltage, and the resonant capacitor voltage... decline; Mode 2: The fifth switch is turned off, and the resonant current... Positive flow; Mode 3: The fifth switch is turned off, and the resonant current... The value is zero, indicating that the transformer series resonant circuit is open. Mode 4: The second and third switches are turned off, and the resonant current... The current is zero, the transformer series resonant circuit is open, and the primary current of the first isolation transformer is zero. Reverse flow, the first switch is turned on at zero voltage, and the primary current of the second isolation transformer... In the forward flow, the fourth switch is turned on with zero voltage; When the converter operates in quadruple voltage inverting mode, it includes four operating states within half a switching cycle, as follows: Mode 5: Primary current of the first isolation transformer With forward flow, the second switch is turned on with zero voltage, and the primary current of the second isolation transformer... Reverse flow, the third switch is turned on with zero voltage, resonant current. The current is zero, so the sixth switch is turned on with zero current. Mode 6: The sixth switch is turned off, its reverse diode freewheels, and the resonant current... Flowing in reverse from left to right; Mode 7: The sixth switch is turned off, and the resonant current... The value is zero, indicating that the transformer series resonant circuit is open. Mode 8: The second and third switches are turned off, and the resonant current... The current is zero, the transformer series resonant circuit is open, and the primary current of the first isolation transformer is zero. Reverse flow, the first switch is turned on at zero voltage, and the primary current of the second isolation transformer... With forward flow, the fourth switch is turned on at zero voltage.

2. The control method for the bidirectional DC-DC converter according to claim 1, characterized in that, The controller operates in a fixed-frequency mode, generating drive signals at a constant frequency.

3. The control method for the bidirectional DC-DC converter according to claim 1, characterized in that, The formula for calculating the capacitance of the resonant capacitor in the bidirectional DC-DC converter is as follows: ； in, This is the resonant capacitance value. This is the clamping capacitor voltage. For output voltage, For output power, The switching cycle.

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