Bidirectional resonant DC-DC converter considering wide-range voltage change and modulation method

Abstract

The invention discloses a bidirectional resonant DC-DC converter considering wide-range voltage variation and a modulation method. The modulation method comprises the following steps: S1, considering wide-range voltage change, and constructing a corresponding working mode according to a voltage relationship between bidirectional resonant DC-DC converter power supplies; s2, according to the equivalent circuit of the bidirectional resonant DC-DC converter, generating an optimized modulation scheme corresponding to the working mode; and S3, modulating the bidirectional resonant DC-DC converter based on the optimized modulation scheme to enable the bidirectional resonant DC-DC converter to enter a corresponding working mode, and meanwhile, realizing soft switching of the device by utilizing excitation current flowing through the excitation inductor. According to the invention, the wide-range change of the voltage of the energy storage battery is fully considered, the soft switching of the device is realized by using the exciting current of the transformer, all switching tubes can realize zero-voltage switching on, and the switching off is always realized by only two tubes with loss.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a bidirectional resonant DC-DC converter and a modulation method taking into account wide voltage range variations. Background Art

[0002] In recent years, bidirectional isolated DC-DC converters have developed rapidly and are widely used in electric vehicles, DC power supplies, new energy grid-connected and energy storage systems. At present, the mainstream bidirectional isolated DC-DC converters include dual active bridge DC-DC converters and bidirectional resonant DC-DC converters. Dual active bridge DC-DC converters can achieve flexible energy regulation, bidirectional voltage wide range gain, and many optimized modulation algorithms, but they also have limitations, such as reflux power, large shutdown current, and narrow soft switching range.

[0003] Bidirectional resonant DC-DC converter (BRDC for short) is a power conversion device that can realize bidirectional energy transmission between two DC power sources. Its core is to utilize the characteristics of the resonant circuit to realize the conversion and transmission of electric energy by controlling the on and off of the switch tube. BRDC is usually composed of components such as high-frequency transformer, resonant inductor, resonant capacitor and switch tube, and has the advantages of compact structure, high efficiency and flexible control. However, BRDC has some problems in that it cannot realize bidirectional buck-boost and narrow voltage gain range, which limits its application scope.

[0004] When working in reverse, bidirectional resonant DC-DC converters can usually only achieve the step-down function, but not the step-up function. This limitation limits the application of bidirectional resonant DC-DC converters in situations where the voltage variation range is large. For example, in the bidirectional interaction between electric vehicles and power grids, if the grid voltage fluctuates greatly, while the electric vehicle battery voltage is relatively stable, then when the bidirectional resonant DC-DC converter transmits grid power to the electric vehicle battery, it may not be able to increase the low voltage of the grid to the high voltage required by the battery, resulting in low energy transmission efficiency or inability to complete the transmission.

[0005] The voltage gain range of a bidirectional resonant DC-DC converter is usually narrow, which limits its application in wide output voltage applications. The narrow voltage gain range means that when the input voltage of the bidirectional resonant DC-DC converter changes, the output voltage has a limited range of change, which cannot meet some applications with high requirements for output voltage. For example, in a DC microgrid, the voltage of the supercapacitor may fluctuate over a wide range, and the voltage gain range of the bidirectional resonant DC-DC converter is narrow, which may not be able to stably convert the voltage of the supercapacitor to the voltage range required by the DC microgrid bus.

[0006] Therefore, how to design a bidirectional resonant DC-DC converter modulation method that can achieve bidirectional buck-boost and has a wider voltage gain range is a technical problem that needs to be solved urgently. Summary of the invention

[0007] In view of the deficiencies of the above-mentioned prior art, the technical problem to be solved by the present invention is: how to provide a bidirectional resonant DC-DC converter and modulation method that takes into account wide-range voltage changes, fully considers the wide-range changes in the voltage of the energy storage battery, and formulates different optimized modulation schemes under different primary and secondary power supply voltage conditions; at the same time, the transformer excitation current is used to realize the soft switching of the device, and the soft switching range is expanded by optimizing the modulation scheme, reducing the operating loss of the converter and improving the overall efficiency. In addition, all switch tubes can achieve zero voltage switching, and only two tubes have losses when they are turned off, and the others all achieve zero current shutdown, and the overall loss is small.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] Considering the wide voltage range change, the bidirectional resonant DC-DC converter includes:

[0010] The primary half-bridge circuit is set at the power supply U s The primary side includes the primary switch tube S connected in series 1 And the primary side lower switch tube S 2 A half bridge is formed;

[0011] Secondary full-bridge circuit, set at power supply U p The secondary side includes the first secondary switch tube Q connected in series 1 And the first secondary side lower switch tube Q 2 And the second secondary switch tube Q 3 And the second secondary side lower switch tube Q 4 The H full bridge is formed by connecting two phases in parallel;

[0012] The transformer is connected between the primary half-bridge circuit and the secondary full-bridge circuit; the transformer's magnetizing inductance is L m ;

[0013] The resonant circuit is connected between the primary half-bridge circuit and the transformer, including a series resonant inductor L r and resonant capacitor C r .

[0014] A bidirectional resonant DC-DC converter modulation method considering wide voltage range variation is implemented based on the bidirectional resonant DC-DC converter of the present invention, comprising:

[0015] S1: Considering the wide range of voltage changes, according to the bidirectional resonant DC-DC converter power supply Us and U p The voltage relationship between them builds the corresponding working mode;

[0016] S2: Generate an optimized modulation scheme corresponding to the working mode according to the equivalent circuit of the bidirectional resonant DC-DC converter;

[0017] S3: Based on the optimized modulation scheme, the bidirectional resonant DC-DC converter is modulated to enter the corresponding working mode, and the excitation current flowing through the excitation inductor is used to realize the soft switching of the device.

[0018] Preferably, in step S1, the working mode includes working mode 1 in which power is transmitted from the primary half-bridge circuit to the secondary full-bridge circuit in a forward boost direction.

[0019] Preferably, in step S2, the optimized modulation scheme of working mode 1 is:

[0020] By phase shifting, the switch tube S on the primary side is 1 The falling edge of the PWM drive signal and the second secondary switch Q 3 The falling edge of the PWM drive signal is aligned, so that the primary side lower switch tube S 2 The falling edge of the PWM drive signal and the second secondary side lower switch tube Q 4 The falling edge of the PWM drive signal is aligned; the first secondary side lower switch tube Q 2 The rising edge of the PWM drive signal lags behind the primary switch S 1 The rising edge of the PWM drive signal, the switch tube Q on the first secondary side 1 The rising edge of the PWM drive signal lags behind the primary side switch S 2 The rising edge of the PWM drive signal;

[0021] The second secondary switch tube Q 3 After shutdown, the resonant current flows through the excitation inductor, and the second secondary side lower switch tube Q 4 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0022] The second secondary side lower switch tube Q 4 After shutdown, the resonant current flows through the excitation inductor, and the switch tube Q on the second secondary side 3 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0023] The first secondary switch tube Q 1 Turn off, resulting in turn-off loss, the first secondary side switch tube Q 2 Achieve zero voltage turn-on; the first secondary side lower switch tube Q 2 Turn off, resulting in turn-off loss, the switch tube Q on the first secondary side 1 Achieve zero voltage switching.

[0024] Preferably, in step S1, the working mode includes working mode 2 in which power is transmitted from the primary half-bridge circuit to the secondary full-bridge circuit in a forward step-down manner.

[0025] Preferably, in step S2, the optimized modulation scheme of working mode 2 is:

[0026] By phase shifting, the switch tube S on the primary side is 1 The rising edge of the PWM drive signal and the first secondary side lower switch tube Q 2 The rising edge of the PWM drive signal is aligned, so that the primary side lower switch tube S 2 The rising edge of the PWM drive signal and the first secondary switch Q 1 The rising edge of the PWM drive signal is aligned; the switch tube Q on the second secondary side 3 The falling edge of the PWM drive signal lags behind the primary switch S 1 The falling edge of the PWM drive signal, the second secondary side lower switch tube Q 4 The falling edge of the PWM drive signal lags behind the primary side switch S 2 The falling edge of the PWM drive signal;

[0027] The second secondary switch tube Q 3 After shutdown, the resonant current flows through the excitation inductor, and the second secondary side lower switch tube Q 4 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0028] The second secondary side lower switch tube Q 4 After shutdown, the resonant current flows through the excitation inductor, and the switch tube Q on the second secondary side 3 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0029] The first secondary side lower switch tube Q 2 After shutdown, the resonant current flows through the excitation inductor, and the switch tube Q on the first secondary side 1 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0030] The first secondary switch tube Q 1 After shutdown, the resonant current flows through the excitation inductor, and the first secondary side lower switch tube Q 2 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on.

[0031] Preferably, in step S1, the working mode includes working mode three in which power is transmitted from the secondary full-bridge circuit to the primary half-bridge circuit in reverse step-down.

[0032] Preferably, in step S2, the optimized modulation scheme of working mode three is:

[0033] By phase shifting, the switch tube S on the primary side is 1 The rising edge of the PWM drive signal and the first secondary side lower switch tube Q 2 The rising edge of the PWM drive signal is aligned, so that the primary side lower switch tube S 2 The rising edge of the PWM drive signal and the first secondary switch Q 1 The rising edge of the PWM drive signal is aligned; the switch tube Q on the second secondary side 3 The falling edge of the PWM drive signal is ahead of the primary switch S 1 The falling edge of the PWM drive signal, the second secondary side lower switch tube Q 4 The falling edge of the PWM drive signal is ahead of the primary side lower switch S 2 The falling edge of the PWM drive signal;

[0034] The first secondary side lower switch tube Q 2 After shutdown, the resonant current flows through the excitation inductor, and the switch tube Q on the first secondary side 1 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0035] The first secondary switch tube Q 1 After shutdown, the resonant current flows through the excitation inductor, and the first secondary side lower switch tube Q 2 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0036] The second secondary switch tube Q 3 After shutdown, the turn-off loss is generated, and the second secondary side switch tube Q 4 Achieve zero voltage turn-on; the second secondary side lower switch tube Q 4 After shutdown, turn-off loss occurs, and the switch tube Q on the second secondary side 3 Achieve zero voltage switching.

[0037] Preferably, in step S1, the working mode includes working mode 4 in which power is reversely boosted and transmitted from the secondary full-bridge circuit to the primary half-bridge circuit.

[0038] Preferably, in step S2, the optimized modulation scheme of working mode 4 is:

[0039] By phase shifting, the switch tube S on the primary side is 1 The rising edge of the PWM drive signal and the first secondary switch Q 1 The rising edge of the PWM drive signal is aligned, so that the primary side lower switch tube S 2 The rising edge of the PWM drive signal and the first secondary side lower switch tube Q 2 The rising edge of the PWM drive signal is aligned; the second secondary side lower switch tube Q 4 The falling edge of the PWM drive signal lags behind the primary switch S1 The falling edge of the PWM drive signal, the second secondary switch tube Q 3 The falling edge of the PWM drive signal lags behind the primary side switch S 2 The falling edge of the PWM drive signal;

[0040] The first secondary side lower switch tube Q 2 After shutdown, the resonant current flows through the excitation inductor, and the switch tube Q on the first secondary side 1 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0041] The first secondary switch tube Q 1 After shutdown, the resonant current flows through the excitation inductor, and the first secondary side lower switch tube Q 2 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0042] The second secondary switch tube Q 3 After shutdown, the resonant current flows through the excitation inductor, and the second secondary side lower switch tube Q 4 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0043] The second secondary side lower switch tube Q 4 After shutdown, the resonant current flows through the excitation inductor, and the switch tube Q on the second secondary side 3 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on.

[0044] Compared with the prior art, the bidirectional resonant DC-DC converter and modulation method considering wide voltage range variation in the present invention have the following beneficial effects:

[0045] The modulation method of the present invention fully considers the wide range variation of the energy storage battery voltage, and formulates different optimized modulation schemes under different primary and secondary power supply voltage conditions. At the same time, the transformer excitation current is used to realize the soft switching of the device, and the soft switching range is expanded by optimizing the modulation scheme, the converter operation loss is reduced, and the overall efficiency is improved. In addition, all switch tubes can achieve zero voltage opening, and only two tubes have losses when they are turned off, and the others achieve zero current shutdown, and the overall loss is small. In addition, the modulation algorithm is similar to ordinary buck / boost modulation, without complex multiple phase shift control, the algorithm and control method are simple, and by changing the pulse width of the primary switch tube and the phase shift of the secondary switch tube, the bidirectional resonant DC-DC converter is realized without relying on the high-frequency transformer ratio. The bidirectional wide range voltage gain and flexible bidirectional energy flow are realized, and the no reflux power and low transformer ratio reduce the effective value of the resonant current, and the converter has high operating efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to make the purpose, technical solution and advantages of the invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings, in which:

[0047] Figure 1 This is the circuit diagram of a bidirectional resonant DC-DC converter.

[0048] Figure 2 This is the driving state waveform timing diagram of the working mode.

[0049] Figure 3 The following is the current flow diagram from t0 to t1 in the working mode.

[0050] Figure 4 The following is the current flow diagram from t1 to t2 in the working mode.

[0051] Figure 5 The following is the current flow diagram from t2 to t3 in the working mode.

[0052] Figure 6 The following is the current flow diagram from t3 to t4 in the working mode.

[0053] Figure 7 This is the driving state waveform timing diagram under working mode 2.

[0054] Figure 8 This is the current flow diagram from t0 to t1 in working mode 2.

[0055] Fig. 9 This is the current flow diagram from t1 to t2 in working mode 2.

[0056] Fig.10 This is the current flow diagram from t2 to t3 in working mode 2.

[0057] Fig.11 This is the current flow diagram from t3 to t4 in working mode 2.

[0058] Fig.12 This is the current flow diagram from t4 to t5 in working mode 2.

[0059] Fig.13 This is the driving state waveform timing diagram under working mode three.

[0060] Fig.14 This is the current flow diagram from t0 to t1 in working mode three.

[0061] Fig.15 This is the current flow diagram from t1 to t2 in working mode three.

[0062] Fig.16 This is the current flow diagram from t2 to t3 in working mode three.

[0063] Fig.17 This is the current flow diagram at time t3~t4 in working mode three.

[0064] Fig.18 This is the driving state waveform timing diagram under working mode 4.

[0065] Fig.19 This is the current flow diagram at time t0~t1 in working mode 4.

[0066] Fig. 20 This is the current flow diagram from t1 to t2 in working mode 4.

[0067] Fig.21 This is the current flow diagram from t2 to t3 in working mode 4.

[0068] Fig. 22 This is the current flow diagram at time t3~t4 in working mode 4.

[0069] Fig.23 This is the current flow diagram at time t4~t5 in working mode 4. DETAILED DESCRIPTION

[0070] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but only represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0071] It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In the description of the present invention, it should be noted that the orientation or position relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the invention product is usually placed when used, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance. In addition, the terms "horizontal", "vertical", etc. do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0072] The following is a further detailed description through specific implementation methods:

[0073] Embodiment 1:

[0074] This embodiment discloses a bidirectional resonant DC-DC converter that takes into account wide voltage range changes.

[0075] like Figure 1 As shown, a bidirectional resonant DC-DC converter considering a wide range of voltage changes is characterized by comprising:

[0076] The primary half-bridge circuit is set on the primary power supply U s The primary side includes the primary switch tube S connected in series 1 And the primary side lower switch tube S 2 A half bridge is formed;

[0077] Secondary full-bridge circuit, set on the secondary power supply U p The secondary side includes the first secondary switch tube Q connected in series 1 And the first secondary side lower switch tube Q 2And the second secondary switch tube Q 3 And the second secondary side lower switch tube Q 4 The H full bridge is formed by connecting two phases in parallel;

[0078] The transformer is connected between the primary half-bridge circuit and the secondary full-bridge circuit. The transformer's magnetizing inductance is L m ;The turns ratio of the transformer is n (n is a natural number);

[0079] The resonant circuit is connected between the primary half-bridge circuit and the transformer, including a series resonant inductor L r and resonant capacitor C r .

[0080] in:

[0081] Power supply s The primary side is equipped with a voltage stabilizing capacitor C S , power supply U p A voltage stabilizing capacitor C is provided on the secondary side. p .

[0082] The switch tube S on the primary side 1 , primary side lower switch tube S 2 , the first secondary switch tube Q 1 , the first secondary side lower switch tube Q 2 , the second secondary switch tube Q 3 And the second secondary side lower switch tube Q 4 The corresponding anti-parallel diodes and parasitic capacitors are respectively arranged on the S1 and C S1 , D S2 and C S2 , D Q1 and C Q1 , D Q2 and C S2 , D Q3 and C Q3 , D Q4 and C Q4 .

[0083] In this embodiment, the power supply U s To power supply U p The transmission is in the forward direction.

[0084] Embodiment 2:

[0085] This embodiment discloses a bidirectional resonant DC-DC converter modulation method taking into account wide range voltage changes, which is implemented based on the bidirectional resonant DC-DC converter of the first embodiment.

[0086] A modulation method for a bidirectional resonant DC-DC converter considering wide voltage range variation includes:

[0087] S1: Considering the wide voltage range, according to the bidirectional resonant DC-DC converter external power supply U s and U p The voltage relationship between them builds the corresponding working mode;

[0088] S2: Generate an optimized modulation scheme corresponding to the working mode according to the equivalent circuit of the bidirectional resonant DC-DC converter;

[0089] S3: Based on the optimized modulation scheme, the bidirectional resonant DC-DC converter is modulated to enter the corresponding working mode, and the excitation current flowing through the excitation inductor is used to realize the soft switching of the device.

[0090] The modulation method of the present invention fully considers the wide range variation of the energy storage battery voltage, and formulates different optimized modulation schemes under different primary and secondary power supply voltage conditions. At the same time, the transformer excitation current is used to realize the soft switching of the device, and the soft switching range is expanded by optimizing the modulation scheme, the converter operation loss is reduced, and the overall efficiency is improved. In addition, all switch tubes can achieve zero voltage opening, and only two tubes have losses when they are turned off, and the others achieve zero current shutdown, and the overall loss is small. In addition, the modulation algorithm is similar to ordinary buck / boost modulation, without complex multiple phase shift control, the algorithm and control method are simple, and by changing the pulse width of the primary switch tube and the phase shift of the secondary switch tube, the bidirectional resonant DC-DC converter is realized without relying on the high-frequency transformer ratio. The bidirectional wide range voltage gain and flexible bidirectional energy flow are realized, and the no reflux power and low transformer ratio reduce the effective value of the resonant current, and the converter has high operating efficiency.

[0091] In order to better introduce the technical solution of the present invention, this embodiment is described through the following parts.

[0092] 1. Working Mode 1

[0093] In this embodiment, the working mode includes working mode 1 in which the primary half-bridge circuit transmits power to the secondary full-bridge circuit in a forward boost mode. In working mode 1, the secondary battery voltage increases, U s <2*nU p .

[0094] The optimized modulation scheme for working mode 1 is:

[0095] Control the secondary switch Q 1 To Q 4 The duty cycle of the PWM drive signal is 0.5, and the upper and lower switches of the same bridge arm in the secondary full-bridge circuit are complementary turned on; the switch S 1 And the primary side lower switch tube S 2 The duty cycle of the PWM drive signal is equal and less than 0.5.

[0096] By phase shifting, the switch tube S on the primary side is 1 The falling edge of the PWM drive signal and the second secondary switch Q 3 The falling edge of the PWM drive signal is aligned, so that the primary side lower switch tube S 2 The falling edge of the PWM drive signal and the second secondary side lower switch tube Q 4 The falling edge of the PWM drive signal is aligned; the first secondary side lower switch tube Q 2 The rising edge of the PWM drive signal lags behind the primary switch S 1 The rising edge of the PWM drive signal, the switch tube Q on the first secondary side 1 The rising edge of the PWM drive signal lags behind the primary side switch S 2 The rising edge of the PWM drive signal.

[0097] The second secondary switch tube Q 3 After shutdown, the resonant current flows through the excitation inductor, and the second secondary side lower switch tube Q 4 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0098] The second secondary side lower switch tube Q 4 After shutdown, the resonant current flows through the excitation inductor, and the switch tube Q on the second secondary side 3 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0099] The first secondary switch tube Q 1 Turn off, resulting in turn-off loss, the first secondary side switch tube Q 2 Achieve zero voltage turn-on; the first secondary side lower switch tube Q 2 Turn off, resulting in turn-off loss, the switch tube Q on the first secondary side 1 Achieve zero voltage switching.

[0100] Figure 2 The PWM driving waveform, the current flowing through the switch tube, and the resonant inductor L in the forward boost power transmission mode from the primary half-bridge circuit to the secondary full-bridge circuit are shown in FIG. r , resonant current i Lr .

[0101] In working mode 1, the mode of the bidirectional resonant DC-DC converter in half a PWM control cycle (t0~t4) is as follows: Figures 3 to 6 shown.

[0102] like Figure 3 Description, Mode 1 [t0, t1]: At time t0, the switch S 1 , Q 1 and Q 3 Open, inductance Lr The resonant current i Lr There are the following expressions:

[0103]

[0104] like Figure 4 Description, Mode 2 [t1, t2]: At time t1, the switch S 1 , Q 2 and Q 3 Open, where Q 2 Zero voltage turn-on, inductance L r The resonant current i Lr There are the following expressions:

[0105]

[0106] like Figure 5 Description, Mode 3 [t2, t3]: At t2, the switch tube Q 3 Shutdown, where Q 3 Near zero current shutdown.

[0107] like Figure 6 Description, Mode 4 [t3, t4]: At t3, the switch tube Q 2 and Q 4 Open, where Q 4 Zero voltage turn-on, current flows through Q 2 and Q 4 The current is the excitation current i Lm .

[0108] 2. Working Mode 2

[0109] In this embodiment, the working mode includes working mode 2 in which the primary half-bridge circuit transfers power to the secondary full-bridge circuit in a forward step-down manner. In working mode 2, the secondary battery voltage decreases, U s ≥2*nU p .

[0110] The optimized modulation scheme for working mode 2 is:

[0111] Control the secondary switch Q 1 To Q 4 The duty cycle of the PWM drive signal is 0.5, and the upper and lower switches of the same bridge arm in the secondary full-bridge circuit are complementary turned on; the switch S 1 And the primary side lower switch tube S 2 The duty cycle of the PWM drive signal is equal and less than 0.5.

[0112] By phase shifting, the switch tube S on the primary side is 1 The rising edge of the PWM drive signal and the first secondary side lower switch tube Q2 The rising edge of the PWM drive signal is aligned, so that the primary side lower switch tube S 2 The rising edge of the PWM drive signal and the first secondary switch Q 1 The rising edge of the PWM drive signal is aligned; the switch tube Q on the second secondary side 3 The falling edge of the PWM drive signal lags behind the primary switch S 1 The falling edge of the PWM drive signal, the second secondary side lower switch tube Q 4 The falling edge of the PWM drive signal lags behind the primary side switch S 2 The falling edge of the PWM drive signal.

[0113] The second secondary switch tube Q 3 After shutdown, the resonant current flows through the excitation inductor, and the second secondary side lower switch tube Q 4 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0114] The second secondary side lower switch tube Q 4 After shutdown, the resonant current flows through the excitation inductor, and the switch tube Q on the second secondary side 3 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0115] The first secondary side lower switch tube Q 2 After shutdown, the resonant current flows through the excitation inductor, and the switch tube Q on the first secondary side 1 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0116] The first secondary switch tube Q 1 After shutdown, the resonant current flows through the excitation inductor, and the first secondary side lower switch tube Q 2 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on.

[0117] Figure 7 The PWM driving waveform, the current flowing through the switch tube, and the resonant inductor L in the forward buck power transmission mode from the primary half-bridge circuit to the secondary full-bridge circuit are shown in FIG. r , resonant current i Lr .

[0118] In the second working mode, the mode of the bidirectional resonant DC-DC converter in half a PWM control cycle (t0~t5) is as follows: Figures 8 to 12 shown.

[0119] like Figure 8 Description, Mode 1 [t0, t1]: At time t0, the switch S 1 , Q 2 and Q 3 Open, inductance L r The resonant current iLr There are the following expressions:

[0120]

[0121] like Fig. 9 Description, Mode 2 [t1, t2]: At time t1, the switch tube Q 2 and Q 3 Open, switch tube S 1 Turn off, inductor L r The resonant current i Lr There are the following expressions:

[0122]

[0123] like Fig.10 Description, Mode 3 [t2, t3]: At t2, the switch tube Q 2 Open, switch tube Q 3 Shut down.

[0124] like Fig.11 Description, Mode 4 [t3, t4]: At t3, the switch tube Q 2 and Q 4 Open, where Q 4 Zero voltage turn-on, current flows through Q 2 and Q 4 The current is the excitation current i Lm .

[0125] like Fig.12 Description, Mode 5 [t4, t5]: At t4, the switch tube Q 4 Open, switch tube Q 2 Shut down.

[0126] 3. Working Mode 3

[0127] In this embodiment, the working mode includes working mode 3 where the secondary full-bridge circuit transfers power to the primary half-bridge circuit in reverse step-down. In working mode 3, the secondary battery voltage increases, 2*nU p ≥U s .

[0128] The optimized modulation scheme for working mode three is:

[0129] Control the secondary switch Q 1 To Q 4 The duty cycle of the PWM drive signal is 0.5, and the upper and lower switches of the same bridge arm in the secondary full-bridge circuit are complementary turned on; the switch S 1 And the primary side lower switch tube S 2 The duty cycle of the PWM drive signal is equal and less than 0.5.

[0130] By phase shifting, the switch tube S on the primary side is 1 The rising edge of the PWM drive signal and the first secondary side lower switch tube Q 2 The rising edge of the PWM drive signal is aligned, so that the primary side lower switch tube S 2 The rising edge of the PWM drive signal and the first secondary switch Q 1 The rising edge of the PWM drive signal is aligned; the switch tube Q on the second secondary side 3 The falling edge of the PWM drive signal is ahead of the primary switch S 1 The falling edge of the PWM drive signal, the second secondary side lower switch tube Q 4 The falling edge of the PWM drive signal is ahead of the primary side lower switch S 2 The falling edge of the PWM drive signal.

[0131] The first secondary side lower switch tube Q 2 After shutdown, the resonant current flows through the excitation inductor, and the switch tube Q on the first secondary side 1 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0132] The first secondary switch tube Q 1 After shutdown, the resonant current flows through the excitation inductor, and the first secondary side lower switch tube Q 2 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0133] The second secondary switch tube Q 3 After shutdown, the turn-off loss is generated, and the second secondary side switch tube Q 4 Achieve zero voltage turn-on; the second secondary side lower switch tube Q 4 After shutdown, turn-off loss occurs, and the switch tube Q on the second secondary side 3 Achieve zero voltage switching.

[0134] Fig.13 The PWM driving waveform, the current flowing through the switch tube, and the resonant inductor L in the reverse buck transmission mode from the secondary full-bridge circuit to the primary half-bridge circuit are shown in FIG. r , resonant current i Lr .

[0135] In working mode 3, the mode of the bidirectional resonant DC-DC converter in half a PWM control cycle (t0~t4) is as follows: Figures 14 to 17 shown.

[0136] like Fig.14 Description, Mode 1 [t0, t1]: At time t0, the switch S 1 , Q 2 and Q 3 Open, inductance L r The resonant current i LrThere are the following expressions:

[0137]

[0138] like Fig.15 Description, Mode 2 [t1, t2]: At time t1, the switch S 1 , Q 2 , Q 4 Open, switch tube Q 3 Shutdown, where Q 4 Zero voltage turn-on, inductance L r The resonant current i Lr There are the following expressions:

[0139]

[0140] like Fig.16 Description, Mode 3 [t2, t3]: At time t2, the switch S 1 Turn off, switch tube Q 2 and Q 4 Open, flow through Q 2 and Q 4 The current is the excitation current i Lm .

[0141] like Fig.17 Description, Mode 4 [t3, t4]: At t3, the switch tube Q 2 Turn off, switch tube Q 4 Open.

[0142] 4. Working Mode 4

[0143] In this embodiment, the working mode includes working mode 4 in which the secondary full-bridge circuit reversely boosts the power transmission to the primary half-bridge circuit. In working mode 4, the secondary battery voltage decreases, 2*nU p s .

[0144] The optimized modulation scheme for working mode 4 is:

[0145] Control the secondary switch Q 1 To Q 4 The duty cycle of the PWM drive signal is 0.5, and the upper and lower switches of the same bridge arm in the secondary full-bridge circuit are complementary turned on; the switch S 1 And the primary side lower switch tube S 2 The duty cycle of the PWM drive signal is equal and less than 0.5.

[0146] By phase shifting, the switch tube S on the primary side is 1 The rising edge of the PWM drive signal and the first secondary switch Q 1 ​The rising edge of the PWM drive signal is aligned, so that the primary side lower switch tube S 2 The rising edge of the PWM drive signal and the first secondary side lower switch tube Q 2 The rising edge of the PWM drive signal is aligned; the second secondary side lower switch tube Q 4 The falling edge of the PWM drive signal lags behind the primary switch S 1 The falling edge of the PWM drive signal, the second secondary switch tube Q 3 The falling edge of the PWM drive signal lags behind the primary side switch S 2 The falling edge of the PWM drive signal.

[0147] The first secondary side lower switch tube Q 2 After shutdown, the resonant current flows through the excitation inductor, and the switch tube Q on the first secondary side 1 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0148] The first secondary switch tube Q 1 After shutdown, the resonant current flows through the excitation inductor, and the first secondary side lower switch tube Q 2 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0149] The second secondary switch tube Q 3 After shutdown, the resonant current flows through the excitation inductor, and the second secondary side lower switch tube Q 4 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on;

[0150] The second secondary side lower switch tube Q 4 After shutdown, the resonant current flows through the excitation inductor, and the switch tube Q on the second secondary side 3 The anti-parallel diode is turned on in advance to achieve zero voltage turn-on.

[0151] Fig.18 The PWM driving waveform, the current flowing through the switch tube, and the resonant inductor L in the reverse boost power transmission mode from the secondary full-bridge circuit to the primary half-bridge circuit are shown in FIG. r , resonant current i Lr .

[0152] In working mode 4, the mode of the bidirectional resonant DC-DC converter in half a PWM control cycle (t0~t5) is as follows: Figures 19 to 23 shown.

[0153] like Fig.19 Description, Mode 1 [t0, t1]: At time t0, the switch S 2 , Q 2 and Q 3 Open, inductance L r The resonant current i Lr There are the following expressions:

[0154]

[0155] like Fig. 20 Description, Mode 2 [t1, t2]: At time t1, the switch tube Q 2 and Q 3 Open, switch tube S 2 Turn off, inductor L r The resonant current i Lr There are the following expressions:

[0156]

[0157]

[0158] like Fig.21 Description, Mode 3 [t2, t3]: At t2, the switch tube Q 2 Open, switch tube Q 3 Shut down.

[0159] like Fig. 22 Description, Mode 4 [t3, t4]: At t3, the switch tube Q 2 and Q 4 Open, where Q 4 Zero voltage turn-on, current flows through Q 2 and Q 4 The current is the excitation current i Lm .

[0160] like Fig.23 Description, Mode 5 [t4, t5]: At t4, the switch tube Q 4 Open, switch tube Q 2 Shut down.

[0161] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A bidirectional resonant DC-DC converter considering wide voltage range variation, characterized in that: include: The primary half-bridge circuit is set at the power supply U s The primary side includes a half bridge consisting of a primary upper switch tube S1 and a primary lower switch tube S2 connected in series; Secondary full-bridge circuit, set at power supply U p The secondary side includes an H full bridge formed by connecting a first secondary upper switch tube Q1 and a first secondary lower switch tube Q2 in series, and a second secondary upper switch tube Q3 and a second secondary lower switch tube Q4 in parallel; The transformer is connected between the primary half-bridge circuit and the secondary full-bridge circuit; the transformer's magnetizing inductance is L m ; The resonant circuit is connected between the primary half-bridge circuit and the transformer, including a series resonant inductor L r and resonant capacitor C r .

2. A bidirectional resonant DC-DC converter modulation method considering wide voltage range variation, characterized in that: The bidirectional resonant DC-DC converter according to claim 1 is implemented as follows: S1: Considering the wide range of voltage changes, according to the bidirectional resonant DC-DC converter power supply U s and U p The voltage relationship between them builds the corresponding working mode; S2: Generate an optimized modulation scheme corresponding to the working mode according to the equivalent circuit of the bidirectional resonant DC-DC converter; S3: Based on the optimized modulation scheme, the bidirectional resonant DC-DC converter is modulated to enter the corresponding working mode, and the excitation current flowing through the excitation inductor is used to realize the soft switching of the device.

3. The modulation method of a bidirectional resonant DC-DC converter considering wide voltage range variation as claimed in claim 2, characterized in that: In step S1 , the working mode includes working mode 1 in which power is forward-boosted and transmitted from the primary half-bridge circuit to the secondary full-bridge circuit.

4. The modulation method of a bidirectional resonant DC-DC converter considering wide voltage range variation as claimed in claim 3, characterized in that: In step S2, the optimized modulation scheme of working mode 1 is: By means of phase shifting, the falling edge of the PWM drive signal of the switch tube S1 on the primary side is aligned with the falling edge of the PWM drive signal of the switch tube Q3 on the second secondary side, and the falling edge of the PWM drive signal of the switch tube S2 on the primary side is aligned with the falling edge of the PWM drive signal of the switch tube Q4 on the second secondary side; the rising edge of the PWM drive signal of the switch tube Q2 on the first secondary side lags behind the rising edge of the PWM drive signal of the switch tube S1 on the primary side, and the rising edge of the PWM drive signal of the switch tube Q1 on the first secondary side lags behind the rising edge of the PWM drive signal of the switch tube S2 on the primary side; After the switch tube Q3 on the second secondary side is turned off, the resonant current flows through the excitation inductor, and the anti-parallel diode of the switch tube Q4 on the second secondary side is turned on in advance to achieve zero voltage turn-on; After the second secondary side lower switch tube Q4 is turned off, the resonant current flows through the excitation inductor, and the anti-parallel diode of the second secondary side upper switch tube Q3 is turned on in advance to achieve zero voltage turn-on; The switch tube Q1 on the first secondary side is turned off, generating turn-off loss, and the switch tube Q2 on the first secondary side is turned on with zero voltage; the switch tube Q2 on the first secondary side is turned off, generating turn-off loss, and the switch tube Q1 on the first secondary side is turned on with zero voltage.

5. The modulation method of a bidirectional resonant DC-DC converter considering wide voltage range variation as claimed in claim 2, characterized in that: In step S1 , the working mode includes working mode 2 in which power is transmitted from the primary half-bridge circuit to the secondary full-bridge circuit in a forward step-down manner.

6. The modulation method of a bidirectional resonant DC-DC converter considering wide voltage range variation as claimed in claim 5, characterized in that: In step S2, the optimized modulation scheme of working mode 2 is: By means of phase shifting, the rising edge of the PWM drive signal of the primary switch tube S1 is aligned with the rising edge of the PWM drive signal of the first secondary switch tube Q2, so that the rising edge of the PWM drive signal of the primary switch tube S2 is aligned with the rising edge of the PWM drive signal of the first secondary switch tube Q1; The falling edge of the PWM drive signal of the second secondary switch tube Q3 lags behind the falling edge of the PWM drive signal of the primary switch tube S1, and the falling edge of the PWM drive signal of the second secondary lower switch tube Q4 lags behind the falling edge of the PWM drive signal of the primary lower switch tube S2; After the switch tube Q3 on the second secondary side is turned off, the resonant current flows through the excitation inductor, and the anti-parallel diode of the switch tube Q4 on the second secondary side is turned on in advance to achieve zero voltage turn-on; After the second secondary side lower switch tube Q4 is turned off, the resonant current flows through the excitation inductor, and the anti-parallel diode of the second secondary side upper switch tube Q3 is turned on in advance to achieve zero voltage turn-on; After the lower switch tube Q2 of the first secondary side is turned off, the resonant current flows through the excitation inductor, and the anti-parallel diode of the upper switch tube Q1 of the first secondary side is turned on in advance to achieve zero voltage turn-on; After the switch tube Q1 on the first secondary side is turned off, the resonant current flows through the excitation inductor, and the anti-parallel diode of the switch tube Q2 on the first secondary side is turned on in advance to achieve zero voltage turn-on.

7. The modulation method of a bidirectional resonant DC-DC converter considering wide voltage range variation as claimed in claim 2, characterized in that: In step S1, the working mode includes working mode 3 in which power is transmitted from the secondary full-bridge circuit to the primary half-bridge circuit in reverse step-down.

8. The modulation method of a bidirectional resonant DC-DC converter considering wide voltage range variation as claimed in claim 7, characterized in that: In step S2, the optimized modulation scheme of working mode three is: By means of phase shifting, the rising edge of the PWM drive signal of the primary switch tube S1 is aligned with the rising edge of the PWM drive signal of the first secondary switch tube Q2, so that the rising edge of the PWM drive signal of the primary switch tube S2 is aligned with the rising edge of the PWM drive signal of the first secondary switch tube Q1; The falling edge of the PWM drive signal of the second secondary switch tube Q3 is ahead of the falling edge of the PWM drive signal of the primary switch tube S1, and the falling edge of the PWM drive signal of the second secondary lower switch tube Q4 is ahead of the falling edge of the PWM drive signal of the primary lower switch tube S2; After the lower switch tube Q2 of the first secondary side is turned off, the resonant current flows through the excitation inductor, and the anti-parallel diode of the upper switch tube Q1 of the first secondary side is turned on in advance to achieve zero voltage turn-on; After the switch tube Q1 on the first secondary side is turned off, the resonant current flows through the excitation inductor, and the anti-parallel diode of the switch tube Q2 on the first secondary side is turned on in advance to achieve zero voltage turn-on; After the switch tube Q3 on the second secondary side is turned off, turn-off loss is generated, and the switch tube Q4 on the second secondary side is turned on with zero voltage; after the switch tube Q4 on the second secondary side is turned off, turn-off loss is generated, and the switch tube Q3 on the second secondary side is turned on with zero voltage.

9. The modulation method of a bidirectional resonant DC-DC converter considering wide voltage range variation as claimed in claim 2, characterized in that: In step S1, the working mode includes working mode 4 in which power is reversely boosted and transmitted from the secondary full-bridge circuit to the primary half-bridge circuit.

10. The modulation method of a bidirectional resonant DC-DC converter considering wide voltage range variation as claimed in claim 9, characterized in that: In step S2, the optimized modulation scheme of working mode 4 is: By means of phase shifting, the rising edge of the PWM drive signal of the switch tube S1 on the primary side is aligned with the rising edge of the PWM drive signal of the switch tube Q1 on the first secondary side, and the rising edge of the PWM drive signal of the switch tube S2 on the primary side is aligned with the rising edge of the PWM drive signal of the switch tube Q2 on the first secondary side; the falling edge of the PWM drive signal of the switch tube Q4 on the second secondary side lags behind the falling edge of the PWM drive signal of the switch tube S1 on the primary side, and the falling edge of the PWM drive signal of the switch tube Q3 on the second secondary side lags behind the falling edge of the PWM drive signal of the switch tube S2 on the primary side; After the lower switch tube Q2 of the first secondary side is turned off, the resonant current flows through the excitation inductor, and the anti-parallel diode of the upper switch tube Q1 of the first secondary side is turned on in advance to achieve zero voltage turn-on; After the switch tube Q1 on the first secondary side is turned off, the resonant current flows through the excitation inductor, and the anti-parallel diode of the switch tube Q2 on the first secondary side is turned on in advance to achieve zero voltage turn-on; After the switch tube Q3 on the second secondary side is turned off, the resonant current flows through the excitation inductor, and the anti-parallel diode of the switch tube Q4 on the second secondary side is turned on in advance to achieve zero voltage turn-on; After the switch tube Q4 on the second secondary side is turned off, the resonant current flows through the excitation inductor, and the anti-parallel diode of the switch tube Q3 on the second secondary side is turned on in advance to achieve zero voltage turn-on.

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