An isolated resonant converter and a control method thereof

Abstract

The application discloses an isolated resonant converter and a control method thereof, and belongs to the technical field of electric energy conversion. ref The target current value i t is obtained after the PI regulation and addition of the current reference value i ref ; the shift-out phase angle alpha is compared with the shift-out phase angle reference value alpha ref , PI regulation is performed, and then the feedforward frequency f d is added to obtain the switching frequency f s ; the reactive current I rq and the active current I rp of the primary side of the resonant cavity are calculated, and then the voltage phase difference phi and the shift-in phase angle theta are calculated according to the target current value i t and the switching frequency f s ; and the switching of the isolated resonant converter is driven according to the voltage phase difference phi, the shift-in phase angle theta, the shift-out phase angle alpha and the switching frequency f s . The application discloses an isolated resonant converter and a control method thereof, and can realize accurate control of transmission power and zero-voltage turn-on of all switches, and significantly improves the efficiency of the converter.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electric energy conversion, and particularly to an isolated resonant converter and a control method thereof. BACKGROUND

[0002] Energy storage system is an indispensable part in the application occasions such as AC / DC microgrid, electric vehicle and uninterruptible power supply, and the bidirectional isolated DC / DC converter or bidirectional isolated AC / DC converter is a key device for the interface of the energy storage system. Compared with the non-resonant converter, the resonant converter has the following advantages: the resonant capacitor has the function of blocking DC bias, avoiding the saturation of the transformer magnetic core; and the resonant converter has lower turn-off current due to the quasi-sinusoidal current of the resonant network, thereby reducing the turn-off loss.

[0003] A commonly used control strategy for the resonant converter is the single phase-shift modulation strategy. For the bidirectional isolated DC / DC converter, the single phase-shift modulation strategy will generate a large reactive circulating current when the left and right DC voltages are not matched, and the side with the lower equivalent DC voltage will easily lose zero voltage turn-on, greatly reducing the efficiency of the converter.

[0004] Another control strategy is the modulation strategy combining single phase-shift and frequency variation, which increases the phase-shift angle by changing the frequency, so that the side with the lower equivalent DC voltage realizes zero voltage turn-on. However, when the left and right DC voltages are extremely mismatched, the switching frequency needs to be greatly increased to realize zero voltage turn-on, and the maximum switching frequency is limited by the hardware circuit, so that the converter cannot realize zero voltage turn-on in the full power and voltage range. In addition, relying only on the increase of the switching frequency to realize zero voltage turn-on will increase the turn-off loss.

[0005] Another control strategy is to introduce internal phase-shift on the side with the higher equivalent voltage on the basis of single phase-shift modulation. However, when the left and right DC voltages are greatly mismatched, the increase of the internal phase-shift angle will cause the loss of zero voltage turn-on of the self switch, affecting the efficiency of the converter. SUMMARY

[0006] To solve the above problems, the present application provides an isolated resonant converter and a control method thereof, which adopts the hybrid control of extended phase-shift (internal phase-shift and external phase-shift combination) and frequency variation modulation.

[0007] To achieve the above purpose, the technical scheme of the present application is as follows:

[0008] A control method of an isolated resonant converter, comprising,

[0009] Step S1, comparing the primary current i1 with the current reference value i ref , and then adjusting the primary current i1 through PI regulation and comparing the primary current i1 with the current reference value i refThe target current value i is obtained after addition t ;

[0010] In step S2, the phase shift angle a is compared with the phase shift angle reference value a ref , and the PI regulation is added to the feedforward frequency f d to obtain the switching frequency f s ; in the initial state, the phase shift angle a is 0, the phase shift angle reference value a ref is 0, the output of the PI regulation is 0, and the switching frequency f s is equal to the feedforward frequency f d ;

[0011] In step S3, the reactive current I rq and the active current I rp of the primary side of the resonant cavity are calculated, and the voltage phase difference t and the phase shift angle θ are calculated according to the target current value i s and the switching frequency f s , and the switches of the isolation type resonant converter are driven according to the voltage phase difference , the phase shift angle θ, the phase shift angle a and the switching frequency f p , wherein the voltage phase difference is the fundamental voltage phase difference between the input voltage v sn of the resonant cavity and the voltage v p across the primary side winding; a is the phase shift angle between the input voltage v sn of the resonant cavity and the voltage v sn across the primary side winding; θ is the phase shift angle of the voltage v s across the primary side winding, f s is the switching frequency, and T ref is the switching period.

[0012] In one embodiment of the present application, the expression of the phase shift angle a is as follows:

[0013]

[0014] The expression of the phase shift angle reference value a ossL is as follows:

[0015]

[0016] wherein n is the turns ratio of the transformer of the isolation type resonant converter, C dL is the drain-source junction capacitance of the switch in the secondary side bridge, T rp is the dead time between the upper and lower switches of the bridge arm in the secondary side bridge, and V2 is the output voltage of the isolation type resonant converter.

[0017] If the primary side bridge of the isolation type resonant converter is a half-bridge structure, the active current Irp The expression of I is as follows:

[0018] I rp =i t ·π;

[0019] If the isolated resonant converter is a DC / DC resonant converter, the expression of the reactive current I rq is as follows:

[0020]

[0021] If the isolated resonant converter is an AC / DC resonant converter, the expression of the reactive current I rq is as follows:

[0022]

[0023] Wherein, C ossH is the drain-source junction capacitance of the switch in the primary bridge, T dH is the dead time between the upper and lower switches of the bridge arm in the primary bridge, and V1 is the input voltage of the isolated resonant converter.

[0024] The calculation formula of the voltage phase difference and the internal phase shift angle θ is as follows:

[0025]

[0026]

[0027] Wherein, C r is the capacitance of the resonant cavity, and L r is the inductance of the resonant cavity.

[0028] The expression of the feedforward frequency f d is as follows:

[0029]

[0030] If the isolated resonant converter is a DC / DC resonant converter, the expression of the parameter x is as follows:

[0031]

[0032] If the isolated resonant converter is an AC / DC resonant converter, the expression of the parameter x is as follows:

[0033]

[0034] In an embodiment of the present application, if the primary bridge of the isolated resonant converter is a full-bridge structure, the expression of the active current I rp is as follows:

[0035]

[0036] If the isolated resonant converter is a DC / DC resonant converter, the expression of the reactive current I rq is as follows:

[0037]

[0038] If the isolated resonant converter is an AC / DC resonant converter, the expression of the reactive current I rq is as follows:

[0039]

[0040] Wherein, C ossH is the drain-source junction capacitance of the switch in the primary side bridge, T dH is the dead time between the upper and lower switches of the bridge arm in the primary side bridge, V1 is the input voltage of the isolated resonant converter.

[0041] The voltage phase difference and the calculation formula of the internal phase shift angle θ are as follows:

[0042]

[0043]

[0044] Wherein, C r is the capacitance of the resonant cavity, L r is the inductance of the resonant cavity.

[0045] The expression of the feedforward frequency f d is as follows:

[0046]

[0047] If the isolated resonant converter is a DC / DC resonant converter, the expression of the parameter x is as follows:

[0048]

[0049] If the isolated resonant converter is an AC / DC resonant converter, the expression of the parameter x is as follows:

[0050]

[0051] The application also provides an isolated resonant converter, which applies the control method of the above-mentioned isolated resonant converter, and comprises a resonant cavity, wherein the resonant cavity comprises an inductor and a capacitor, and the inductor and the capacitor are connected in series.

[0052] Beneficial effects, the isolation type resonant converter and the control method thereof can realize accurate control of transmission power and zero voltage opening of all switches, and significantly improve the efficiency of the converter.

[0053] To make the above features and advantages of the invention more obvious and easy to understand, the following specific examples are described in detail below, and the accompanying drawings are described as follows. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 The control block diagram of the control method of the isolation type resonant converter of the present application.

[0055] Figure 2 The first specific embodiment of the isolation type resonant converter of the present application.

[0056] Figure 3 The switch logic and voltage waveform diagram of the circuit. Figure 2

[0057] The second specific embodiment of the isolation type resonant converter of the present application. Figure 4

[0058] The switch logic and voltage waveform diagram of the circuit. Figure 5 Figure 4 The third specific embodiment of the isolation type resonant converter of the present application.

[0059] Figure 6 The switch logic and voltage waveform diagram of the circuit.

[0060] Figure 7 Figure 6 The fourth specific embodiment of the isolation type resonant converter of the present application.

[0061] Figure 8 The switch logic and voltage waveform diagram of the circuit.

[0062] Figure 9 The switch logic and voltage waveform diagram of the circuit. Figure 8 DETAILED DESCRIPTION

[0063] To make the above features and advantages of the invention more obvious and easy to understand, the following specific examples are described in detail below, and the accompanying drawings are described as follows.

[0064] Figure 1 The control block diagram of the control method of the isolation type resonant converter of the present application, as shown in Figure 1 ​​​As shown, the control method of the isolation type resonant converter comprises the following steps.

[0065] Step S1, comparing the primary side current i1 with the current reference value i ref , and adding the current reference value i ref after PI regulation to obtain the target current value i t , which ensures accurate active power transmission. If the current reference value i ref is greater than 0, the power is transmitted from the primary side to the secondary side; if the current reference value i ref is less than 0, the power is transmitted from the secondary side to the primary side.

[0066] Step S2, comparing the phase shift angle α with the phase shift angle reference value α ref , and adding the feedforward frequency f d after PI regulation to obtain the switching frequency f s . The phase shift angle α is calculated from the internal shift angle θ and the voltage phase difference , and the phase shift angle reference value α ref is calculated from the reactive current I rq and the active current I rp . In the initial state, the phase shift angle α is 0, the phase shift angle reference value α ref is 0, and the output of PI regulation is 0, i.e. the switching frequency f s is equal to the feedforward frequency f d .

[0067] Step S3, calculating the reactive current I rq and the active current I rp of the primary side of the resonant cavity by using the fundamental analysis method, and calculating the voltage phase difference and the internal shift angle θ according to the target current value i t and the switching frequency f s , and driving the switches of the isolation type resonant converter according to the voltage phase difference , the internal shift angle θ, the phase shift angle α, and the switching frequency f s . The voltage phase difference is the fundamental voltage phase difference of the input voltage v p of the resonant cavity and the voltage v sn across the primary side winding; α is the phase shift angle between the input voltage v p of the resonant cavity and the voltage v sn across the primary side winding; θ is the internal shift angle of the voltage v sn across the primary side winding, f s is the switching frequency, and T s is the switching period.

[0068] In the first specific embodiment, the phase shift angle α is calculated as follows: Figure 2The application discloses a control method of an isolated resonant converter.

[0069] As shown in the drawings, Figure 2 the input of a bridge module 21 is connected in parallel across the power supply V1, the bridge module 21, a resonant module 22 and a bridge module 23 are connected in parallel in sequence, and the output of the bridge module 23 is connected in parallel to the power supply V2. The bridge module 21 further comprises a capacitor C1, a capacitor C2, a switch S1 and a switch S2, the capacitor C1 and the capacitor C2 are connected in series and then connected in parallel across the power supply V1, and the switch S1 and the switch S2 are connected in series and then connected in parallel across the power supply V1. The bridge module 23 further comprises a switch Q1, a switch Q2, a switch Q3 and a switch Q4, the switch Q1 and the switch Q3 are connected in series and then connected in parallel across the power supply V2, and the switch Q2 and the switch Q4 are connected in series and then connected in parallel across the power supply V2. The resonant module 22 further comprises an inductor L r and a capacitor C r , the first end of the inductor L r is connected to the source of the switch S1, the second end of the inductor L r is connected to the first end of the capacitor C r , the second end of the capacitor C r is connected to the first end of the primary winding of the transformer T1, the second end of the primary winding of the transformer T1 is connected to the series midpoint of the capacitor C1 and the capacitor C2, the first end of the secondary winding of the transformer T1 is connected to the series midpoint of the switch Q1 and the switch Q3, and the second end of the secondary winding of the transformer T1 is connected to the series midpoint of the switch Q2 and the switch Q4.

[0070] Further, the power supply V1 can be a constant bus voltage, such as 400V, or a DC voltage with a large fluctuation range obtained by folding an AC mains voltage.

[0071] Further, the bridge module 21 adopts a half-bridge structure.

[0072] Further, the transformer T1 is a high-frequency isolation transformer, and the transformation ratio of the transformer T1 is n:1.

[0073] Further, the bridge module 23 adopts a full-bridge structure and outputs a high-frequency voltage, which is frequency-converted and phase-shifted.

[0074] Further, the power supply V2 is a DC voltage source such as an energy storage battery or a photovoltaic cell panel.

[0075] The isolated bidirectional DC / DC resonant converter 2 adopts a hybrid control method of extended phase shift and frequency conversion modulation, and the modulation principle of power transmission from the primary side to the secondary side and from the secondary side to the primary side is shown in Figure 3 (a) and 3(b), wherein the voltage phase difference is the input voltage vp and the primary winding voltage v sn ; α is the lead-out phase angle between the input voltage v p and the primary winding voltage v sn ; θ is the lag-in phase angle of the primary winding voltage v sn , f s is the switching frequency, and T s is the switching period.

[0076] For the isolated bidirectional DC / DC resonant converter 2, the current i1may be the input current or the output current according to the transmission direction of the power. The reactive current I rq and the active current I rp are the reactive component and the active component of the resonant current i r of the primary side of the resonant module 22, respectively. The function of the reactive current I rq is to realize the soft turn-on of the switch in the bridge module 21, and the function of the active current I rp is to realize the transmission of the active power. The reactive current I rq and the active current I rp are expressed as follows:

[0077] I rp = i t ·π,

[0078]

[0079] where C ossH is the drain-source junction capacitance of the switch in the bridge module 21, and T dH is the dead time between the upper and lower switches of the bridge arm in the bridge module 21.

[0080] Further, the calculation formulas of the voltage phase difference α and the lag-in phase angle θ are as follows:

[0081]

[0082]

[0083] where n is the turns ratio of the transformer T1, V1is the voltage of the power supply V1, and V2is the voltage of the power supply V2.

[0084] Further, the expression of the lead-out phase angle α is as follows:

[0085]

[0086] Further, the expression of the lead-out phase angle reference value α ref is as follows:

[0087]

[0088] wherein C ossL is the drain-source junction capacitance of the switch in the bridge module 23, T dL is the dead time between the upper and lower switches of the bridge leg in the bridge module 23. By controlling the frequency to adjust the phase shift angle a, the soft turn-on of all switches in the secondary side of the transformer can be achieved.

[0089] Further, the feedforward frequency f d is expressed as follows:

[0090]

[0091] wherein the expression of the parameter x is as follows:

[0092]

[0093] In the initial state, the phase shift angle a is 0, the phase shift angle reference value a ref is 0, and the output of the PI regulation is 0, i.e. the switching frequency f s in the initial state is equal to the feedforward frequency f d .

[0094] After the voltage phase difference , the phase shift angle θ, the phase shift angle a and the switching frequency f s are obtained, the switching drive logic of the isolated bidirectional DC / DC resonant converter can be obtained according to the modulation logic of the switch in Figure 2 , and the resonant converter is controlled.

[0095] In the second specific embodiment, the isolated bidirectional DC / DC resonant converter with the primary side bridge in the full-bridge structure in Figure 4 is taken as an example to illustrate the control method of the isolated bidirectional DC / DC resonant converter.

[0096] As shown in Figure 4 , in the isolated bidirectional DC / DC resonant converter 4, the two ends of the power supply V1 are connected in parallel with the input of the bridge module 41, the bridge module 41, the resonant module 42 and the bridge module 43 are connected in parallel in sequence, and the output of the bridge module 43 is connected in parallel with the power supply V2. The bridge module 41 further comprises switches S3, S4, S5 and S6, the switches S3 and S5 are connected in series in the same direction and then connected in parallel at the two ends of the power supply V1, and the switches S4 and S6 are connected in series in the same direction and then connected in parallel at the two ends of the power supply V1. The bridge module 43 further comprises switches Q5, Q6, Q7 and Q8, the switches Q5 and Q7 are connected in series in the same direction and then connected in parallel at the two ends of the power supply V2, and the switches Q6 and Q8 are connected in series in the same direction and then connected in parallel at the two ends of the power supply V2. The resonant module 42 further comprises an inductor L r and a capacitor C rInductor L r The first terminal is connected to the source of switch S4, and the inductor L r The second terminal is connected to capacitor C r The first terminal, capacitor C r The second end is connected to the first end of the primary winding of transformer T2. The second end of the primary winding of transformer T2 is connected to the midpoint of the series connection of switch S3 and switch S5. The first end of the secondary winding of transformer T2 is connected to the midpoint of the series connection of switch Q5 and switch Q7. The second end of the secondary winding of transformer T2 is connected to the midpoint of the series connection of switch Q6 and switch Q8.

[0097] Furthermore, the power supply V1 can be a constant bus voltage, such as 400V; or it can be a DC voltage with a wide fluctuation range, which is formed by folding AC mains power.

[0098] Furthermore, bridge module 41 adopts a full-bridge structure.

[0099] Furthermore, transformer T2 is a high-frequency isolation transformer with a turns ratio of n:1.

[0100] Furthermore, bridge module 43 adopts a full-bridge structure and outputs high-frequency voltage, which is both frequency-converting and phase-shifting.

[0101] Furthermore, power source V2 is a DC voltage source for energy storage batteries, photovoltaic panels, etc.

[0102] The isolated bidirectional DC / DC resonant converter 4 employs a hybrid control method combining extended phase shift and frequency conversion modulation. The modulation principle for power transfer from the primary side to the secondary side and from the secondary side to the primary side is as follows: Figure 5 As shown in (a) and 5(b), the voltage phase difference The input voltage V of the resonant cavity of resonant module 42. p and the voltage v across the primary winding sn The fundamental voltage phase difference; α is the input voltage v of the resonant cavity. p and the voltage v across the primary winding sn The outward phase shift angle between them; θ is the voltage v across the primary winding. sn The inward phase angle, f s T is the switching frequency. s The switching cycle.

[0103] For the isolated bidirectional DC / DC resonant converter 4, depending on the direction of power transmission, the current i1 can be either the input current or the output current. Reactive current I... rq and active current I rp The resonant current i on the primary side of the resonant module 42 are respectively r The reactive and active components, with reactive current I. rq Its function is to achieve soft-start of the switch in bridge module 41, with active current Irp Its function is to realize the transfer of active power and reactive current I. rq and active current I rp The expression is as follows:

[0104]

[0105]

[0106] Among them, C ossH T is the drain-source junction capacitance of the switch in bridge module 41. dH This refers to the dead time between the upper and lower switches of the bridge arm in bridge module 41.

[0107] Furthermore, voltage phase difference The formula for calculating the inward phase angle θ is as follows:

[0108]

[0109]

[0110] Where n is the turns ratio of transformer T2, V1 is the voltage of power supply V1, and V2 is the voltage of power supply V2.

[0111] Furthermore, the expression for the outward phase angle α is as follows:

[0112]

[0113] Furthermore, the outward phase angle reference value α ref The expression is as follows:

[0114]

[0115] Among them, C ossL T is the drain-source junction capacitance of the switch in bridge module 43. dL This refers to the dead time between the upper and lower switches of the bridge arm in bridge module 43.

[0116] Furthermore, the feedforward frequency f d The expression is as follows:

[0117]

[0118] The expression for parameter x is as follows:

[0119]

[0120] In the initial state, the outward phase shift angle α is 0, and the reference value of the outward phase shift angle α is... ref When the value is 0, the output of the PI regulator is 0, meaning the switching frequency f is 0 in the initial state. s Equal to feedforward frequency fd .

[0121] Calculate the voltage phase difference mentioned above. Inner phase shift angle θ, outer phase shift angle α, and switching frequency f s Then, according to Figure 5 The modulation logic of the switch can be used to derive the switching drive logic of the isolated bidirectional DC / DC resonant converter, which controls the resonant converter.

[0122] In the third specific embodiment, with Figure 6 Taking the isolated bidirectional AC / DC resonant converter with a half-bridge structure as an example, this invention illustrates a control method for an isolated resonant converter.

[0123] like Figure 6 As shown, in the isolated bidirectional AC / DC resonant converter 6, the input of bridge module 61 is connected in parallel across the two ends of power supply V1. Bridge module 61, resonant module 62, and bridge module 63 are connected in parallel in sequence, and the output of bridge module 63 is connected in parallel with power supply V2. Bridge module 61 further includes capacitors C3 and C4, switches S7, S8, S9, and S1. 10 Capacitors C3 and C4 are connected in series and then in parallel across power supply V1. Switches S7 and S8 are connected in series in reverse. Switch S9 and S8 are connected in parallel across power supply V1. 10 In reverse series connection, the drain of switch S8 is connected to the drain of switch S9, and the drain of switch S7 is connected to the positive terminal of power supply V1. 10 The drain of the circuit is connected to the negative terminal of power supply V1. Bridge module 63 further includes switch Q9 and switch Q... 10 Switch Q 11 Switch Q 12 Switch Q9 and switch Q 11 After being connected in series in the same direction, they are connected in parallel across the two ends of power supply V2, and switch Q... 10 With switch Q 12 After being connected in series in the same direction, they are connected in parallel across the power supply V2. The resonant module 62 further includes an inductor L. r and capacitor C r Inductor L r The first terminal is connected to the drain of switch S8, and the inductor L r The second terminal is connected to capacitor C r The first terminal, capacitor C r The second terminal is connected to the first terminal of the primary winding of transformer T3. The second terminal of the primary winding of transformer T3 is connected to the midpoint of the series connection between capacitor C3 and capacitor C4. The first terminal of the secondary winding of transformer T3 is connected to switch Q9 and switch Q. 11 The series midpoint, the second terminal of the secondary winding of transformer T3 is connected to switch Q. 10 With switch Q 12The switch S7 and the switch S8 constitute a bidirectional switch, and the switch S9 and the switch S 10 constitute a bidirectional switch.

[0124] Further, the power supply V1 is an alternating voltage source, such as a mains voltage of 220 V.

[0125] Further, the bridge module 61 adopts a half-bridge structure.

[0126] Further, the transformer T3 is a high-frequency isolation transformer, and its transformation ratio is n:1.

[0127] Further, the bridge module 63 adopts a full-bridge structure, and outputs a high-frequency voltage, which is both frequency-converted and phase-shifted.

[0128] Further, the power supply V2 is a direct-current voltage source, such as an energy storage battery or a photovoltaic panel.

[0129] The isolation type bidirectional AC / DC resonant converter 6 adopts a hybrid control method of extended phase shift and frequency conversion modulation, and the modulation principles of power transmission from the primary side to the secondary side and from the secondary side to the primary side are shown in Figure 7 (a) and Figure 7 (b), wherein the voltage phase difference is the fundamental voltage phase difference between the input voltage v p of the resonant cavity of the resonant module 62 and the voltage v sn across the primary winding; α is the external phase shift angle between the input voltage v p of the resonant cavity and the voltage v sn across the primary winding; θ is the internal phase shift angle of the voltage v sn across the primary winding, f s is the switching frequency, and T s is the switching period.

[0130] For the isolation type bidirectional AC / DC resonant converter 6, according to the direction of power transmission, the current i1 can be an input current or an output current. The reactive current I rq and the active current I rp are respectively the reactive component and the active component of the resonant current i r on the primary side of the resonant module 62. The function of the reactive current I rq is to realize the soft turn-on of the switches in the bridge module 61, and the function of the active current I rp is to realize the transmission of active power. The expressions of the reactive current I rq and the active current I rp are as follows:

[0131] I rp =i t ·π,

[0132]

[0133] Among them, C ossH T is the drain-source junction capacitance of the switch in bridge module 61. dH This refers to the dead time between the upper and lower switches of the bridge arm in bridge module 61.

[0134] Furthermore, voltage phase difference The formula for calculating the inward phase angle θ is as follows:

[0135]

[0136]

[0137] Where n is the turns ratio of transformer T3, V1 is the voltage of power supply V1, and V2 is the voltage of power supply V2.

[0138] Furthermore, the expression for the outward phase angle α is as follows:

[0139]

[0140] Furthermore, the outward phase angle reference value α ref The expression is as follows:

[0141]

[0142] Among them, C ossL T is the drain-source junction capacitance of the switch in bridge module 63. dL This refers to the dead time between the upper and lower switches of the bridge arm in bridge module 63. By controlling the frequency and adjusting the outward phase shift angle α, soft-start of all switches on the secondary side of the transformer can be achieved.

[0143] Furthermore, the feedforward frequency f d The expression is as follows:

[0144]

[0145] The expression for parameter x is as follows:

[0146]

[0147] In the initial state, the outward phase shift angle α is 0, and the reference value of the outward phase shift angle α is... ref When the value is 0, the output of the PI regulator is 0, meaning the switching frequency f is 0 in the initial state. s Equal to feedforward frequency f d .

[0148] Calculate the voltage phase difference mentioned above. Inner phase shift angle θ, outer phase shift angle α, and switching frequency f s Then, according to Figure 7The modulation logic of the switch can be used to derive the switching drive logic of the isolated bidirectional AC / DC resonant converter, which controls the resonant converter.

[0149] In the fourth specific embodiment, with Figure 8 Taking the isolated bidirectional AC / DC resonant converter with a full-bridge structure as an example, this invention illustrates a control method for an isolated resonant converter.

[0150] like Figure 8 As shown, in the isolated bidirectional AC / DC resonant converter 8, the input of bridge module 81 is connected in parallel across the two ends of power supply V1. Bridge module 81, resonant module 82, and bridge module 83 are connected in parallel in sequence, and the output of bridge module 83 is connected in parallel with power supply V2. Bridge module 81 further includes a switch S. 11 Switch S 12 Switch S 13 Switch S 14 Switch S 15 Switch S 16 Switch S 17 Switch S 18 Switch S 11 With switch S 12 Reverse series connection, switch S 13 With switch S 14 Reverse series connection, switch S 12 The drain and switch S 13 The drain connection, switch S 11 The drain of the circuit is connected to the positive terminal of power supply V1, and switch S... 14 The drain of the circuit is connected to the negative terminal of power supply V1, and switch S... 15 With switch S 16 Reverse series connection, switch S 17 With switch S 18 Reverse series connection, switch S 16 The drain and switch S 17 The drain connection, switch S 15 The drain of the circuit is connected to the positive terminal of power supply V1, and switch S... 18 The drain of the circuit is connected to the negative terminal of power supply V1. Bridge module 83 further includes a switch Q. 13 Switch Q 14 Switch Q 15 Switch Q 16 Switch Q 13 With switch Q 15 After being connected in series in the same direction, they are connected in parallel across the two ends of power supply V2, and switch Q... 14 With switch Q 16 After being connected in series in the same direction, they are connected in parallel across the power supply V2. The resonant module 82 further includes an inductor L. r and capacitor C r Inductor L rthe first end of the switch S 16 the drain of the switch S r the second end of the switch S r the first end of the switch S r the second end of the switch S 12 the series midpoint of the switch S 13 the first end of the secondary winding of the transformer T4 13 the series midpoint of the switch Q 15 the second end of the secondary winding of the transformer T4 14 the series midpoint of the switch Q 16 the switch S 11 the switch S 12 forms a bidirectional switch 13 the switch S 14 forms a bidirectional switch 15 the switch S 16 forms a bidirectional switch 15 the switch S 16 forms a bidirectional switch.

[0151] Further, the power supply V1 is an alternating voltage source, such as a mains voltage of 220 V.

[0152] Further, the bridge module 81 adopts a full-bridge structure.

[0153] Further, the transformer T4 is a high-frequency isolation transformer, and its transformation ratio is n:1.

[0154] Further, the bridge module 83 adopts a full-bridge structure, and outputs a high-frequency voltage, which is both frequency-converted and phase-shifted.

[0155] Further, the power supply V2 is a direct-current voltage source, such as an energy storage battery or a photovoltaic panel.

[0156] The isolation type bidirectional AC / DC resonant converter 8 adopts a hybrid control method of extended phase shift and frequency conversion modulation, and the modulation principles of power transmission from the primary side to the secondary side and from the secondary side to the primary side are shown in Figure 9 (a) and Figure 9 (b), wherein the voltage phase difference is the fundamental voltage phase difference between the input voltage v p of the resonant cavity of the resonant module 82 and the voltage v sn across the primary winding; α is the external phase shift angle between the input voltage v p of the resonant cavity and the voltage v sn across the primary winding; θ is the internal phase shift angle of the voltage v sn across the primary winding, and f s is the switching frequency, Ts is the switching period.

[0157] For the isolated bidirectional AC / DC resonant converter 8, the current il can be the input current or the output current according to the transmission direction of the power. The reactive current is I rq and the active current is I rp are the reactive component and the active component of the resonant current il of the primary side of the resonant module 82 respectively. r The function of the reactive current I rq is to realize the soft turn-on of the switches in the bridge module 81, and the function of the active current I rp is to realize the transmission of the active power. The reactive current is I rq and the active current is I rp The expressions of I

[0158]

[0159]

[0160] wherein C ossH is the drain-source junction capacitance of the switches in the bridge module 81, and T dH is the dead time between the upper and lower switches of the bridge arm in the bridge module 81.

[0161] Further, the voltage phase difference and the inner displacement phase angle θ are calculated as follows:

[0162]

[0163]

[0164] wherein n is the turns ratio of the transformer T4, V1 is the voltage of the power supply V1, and V2 is the voltage of the power supply V2.

[0165] Further, the expression of the outer displacement phase angle α is as follows:

[0166]

[0167] Further, the expression of the outer displacement phase angle reference value α ref is as follows:

[0168]

[0169] wherein C ossL is the drain-source junction capacitance of the switches in the bridge module 83, and T dL is the dead time between the upper and lower switches of the bridge arm in the bridge module 83.

[0170] Further, the expression of the feedforward frequency f d is as follows:

[0171]

[0172] wherein the expression of parameter x is as follows:

[0173]

[0174] In the initial state, the outer phase angle a is 0, the outer phase angle reference value a ref is 0, and the output of the PI regulation is 0, i.e. the switching frequency f s equals the feedforward frequency f d in the initial state.

[0175] After the voltage phase difference , the inner phase angle θ and the outer phase angle a and the switching frequency f s are obtained, the switching drive logic of the isolated bidirectional AC / DC resonant converter can be obtained according to the modulation logic of the switches in Figure 9 , and the resonant converter is controlled.

[0176] Although the present application has been disclosed with the above embodiments, it is not intended to limit the present application, and any person skilled in the art can make some changes and modifications without departing from the spirit and scope of the present application, and the protection scope of the present application is defined by the following patent claim scope.

Claims

1. A control method for an isolated resonant converter, characterized in that, include, Step S1: Compare the primary current i1 with the current reference value i ref After PI regulation, it is then compared with the current reference value i ref The target current value i is obtained by adding them together. t ; Step S2: Compare the outward phase shift angle α with the outward phase shift reference value α. ref After PI regulation, a feedforward frequency f is added. d Obtain the switching frequency f s In the initial state, the outward phase shift angle α is 0, and the reference value of the outward phase shift angle α is... ref When the value is 0, the output of the PI regulator is 0, and the switching frequency f is 0. s Equal to feedforward frequency f d ; Step S3: Calculate the reactive current I on the primary side of the resonant cavity. rq and active current I rp Then, based on the target current value i t and switching frequency f s Calculate the voltage phase difference And the inner phase shift angle θ, based on the voltage phase difference Inner phase shift angle θ, outer phase shift angle α, and switching frequency f s The switch drives the isolated resonant converter, where the voltage phase difference It is the input voltage v of the resonant cavity. p and the voltage v across the primary winding sn The fundamental voltage phase difference; α is the input voltage v of the resonant cavity. p and the voltage v across the primary winding sn The outward phase shift angle between them; θ is the voltage v across the primary winding. sn The inward phase angle, f s T is the switching frequency. s For switching cycles; The expression for the outward phase angle α is as follows: Outward phase angle reference value α ref The expression is as follows: Where n is the turns ratio of the transformer in the isolated resonant converter, and C ossL T is the drain-source junction capacitance of the switch in the secondary bridge. dL V1 is the dead time between the upper and lower switches of the secondary bridge arm, and V2 is the output voltage of the isolated resonant converter.

2. The control method for an isolated resonant converter as described in claim 1, characterized in that, If the primary bridge of the isolated resonant converter is a half-bridge structure, the active current I rp The expression is as follows: AND rp =and t ·π; If the isolated resonant converter is a DC / DC resonant converter, the reactive current I... rq The expression is as follows: If the isolated resonant converter is an AC / DC resonant converter, the reactive current I rq The expression is as follows: Among them, C ossH T is the drain-source junction capacitance of the switch in the primary bridge. dH V1 is the dead time between the upper and lower switches of the bridge arm in the original side bridge, and V2 is the input voltage of the isolated resonant converter.

3. The control method for an isolated resonant converter as described in claim 2, characterized in that, Voltage phase difference The formula for calculating the inward phase angle θ is as follows: Among them, C r L is the capacitance of the resonant cavity. r The inductance of the resonant cavity.

4. The control method for an isolated resonant converter as described in claim 3, characterized in that, Feedforward frequency f d The expression is as follows: If the isolated resonant converter is a DC / DC resonant converter, the expression for parameter x is as follows: If the isolated resonant converter is an AC / DC resonant converter, the expression for parameter x is as follows:

5. The control method for an isolated resonant converter as described in claim 1, characterized in that, If the primary bridge of the isolated resonant converter is a full-bridge structure, the active current I... rp The expression is as follows: If the isolated resonant converter is a DC / DC resonant converter, the reactive current I... rq The expression is as follows: If the isolated resonant converter is an AC / DC resonant converter, the reactive current I rq The expression is as follows: Among them, C ossH T is the drain-source junction capacitance of the switch in the primary bridge. dH V1 is the dead time between the upper and lower switches of the bridge arm in the original side bridge, and V2 is the input voltage of the isolated resonant converter.

6. The control method for an isolated resonant converter as described in claim 5, characterized in that, Voltage phase difference The formula for calculating the inward phase angle θ is as follows: Among them, C r L is the capacitance of the resonant cavity. r The inductance of the resonant cavity.

7. The control method for an isolated resonant converter as described in claim 6, characterized in that, Feedforward frequency f d The expression is as follows: If the isolated resonant converter is a DC / DC resonant converter, the expression for parameter x is as follows: If the isolated resonant converter is an AC / DC resonant converter, the expression for parameter x is as follows:

8. An isolated resonant converter, characterized in that, The control method for an isolated resonant converter as described in any one of claims 1-7 includes a resonant cavity, wherein the resonant cavity includes an inductor and a capacitor, and the inductor and the capacitor are connected in series.

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