Isolated resonant converter and control method thereof

Abstract

The invention discloses an isolated resonant converter and a control method thereof, and belongs to the technical field of electric energy conversion, and the method comprises the steps: comparing a primary side current i1 with a current reference value iref, carrying out PI adjustment, and adding the primary side current i1 with the current reference value iref to obtain a target current value it; comparing the external phase shift angle alpha with an external phase shift angle reference value alpha ref, and adding a feed-forward frequency fd after PI adjustment to obtain a switching frequency fs; and reactive current Irq and active current Irp of the primary side of the resonant cavity are calculated, a voltage phase difference phi and an internal phase shift angle theta are calculated according to the target current value it and the switching frequency fs, and a switch of the isolated resonant converter is driven according to the voltage phase difference phi, the internal phase shift angle theta, the external phase shift angle alpha and the switching frequency fs. According to the isolated resonant converter and the control method thereof, accurate control of transmission power and zero-voltage switching-on of all switches can be realized, and the efficiency of the converter is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric energy conversion, and in particular to an isolated resonant converter and a control method thereof. Background Art

[0002] Energy storage systems are an indispensable part of applications such as AC / DC microgrids, electric vehicles, and uninterruptible power supplies. Bidirectional isolated DC / DC converters or bidirectional isolated AC / DC converters are key devices for energy storage system interfaces. Compared with non-resonant converters, resonant converters have the following advantages: the resonant capacitor has the function of blocking DC bias and avoiding saturation of the transformer core; since the current of the resonant network is a quasi-sinusoidal wave, the resonant converter has a lower turn-off current and can reduce turn-off losses.

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

[0004] Another control strategy is a modulation strategy that combines single phase shift and frequency conversion. By changing the frequency to increase the phase shift angle, the side with low equivalent DC voltage can achieve zero voltage turn-on. However, when the DC voltages on the left and right sides are extremely mismatched, the switching frequency needs to be greatly increased to achieve zero voltage turn-on, and the hardware circuit limits the maximum switching frequency. Therefore, the converter cannot achieve zero voltage turn-on within the full power and voltage range. In addition, relying solely on increasing the switching frequency to achieve zero voltage turn-on will increase the turn-off loss.

[0005] Another control strategy is to introduce an internal phase shift on the side with higher equivalent voltage based on single phase shift modulation. However, when the mismatch between the DC voltages on the left and right sides is large, the internal phase shift angle increases, causing the switch tube itself to lose zero voltage turn-on, affecting the efficiency of the converter. Summary of the invention

[0006] In order to solve the above problems, the present invention provides an isolated resonant converter and a control method thereof, which adopts a hybrid control of extended phase shifting (combination of internal phase shifting and external phase shifting) and variable frequency modulation.

[0007] To achieve the above object, the technical solution of the present invention is:

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

[0009] Step S1, compare the primary current i1 with the current reference value i ref , after PI adjustment and current reference value i refAfter adding, we get the target current value i t ;

[0010] Step S2, comparing the external phase shift angle α with the external phase shift angle reference value α ref , after PI regulation, plus the feedforward frequency f d Get the switching frequency f s ; In the initial state, the external phase angle α is 0, and the external phase angle reference value α ref is 0, the output of PI regulation is 0, the switching frequency f s Equal to the feedforward frequency f d ;

[0011] Step S3, calculate the reactive current I of the primary side of the resonant cavity rq and active current I rp , and then according to the target current value i t and the switching frequency f s Calculate the voltage phase difference and the internal phase shift angle θ, according to the voltage phase difference Inner phase shift angle θ, outer phase shift angle α and switching frequency f s Driving the switches of an isolated resonant converter, where the voltage phase difference is the input voltage of the resonant cavity v p and the voltage across the primary winding v sn The fundamental voltage phase difference; α is the input voltage v of the resonant cavity p and the voltage across the primary winding v sn The external phase angle between the two ends of the primary winding is θ. sn The internal phase shift angle, f s is the switching frequency, T s is the switching cycle.

[0012] In a specific embodiment of the present invention, the expression of the external shift phase angle α is as follows:

[0013]

[0014] External phase angle reference value α ref The expression is as follows:

[0015]

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

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

[0018] I rp =i t π;

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

[0020]

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

[0022]

[0023] Among them, 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] Voltage phase difference The calculation formula of the internal phase shift angle θ is as follows:

[0025]

[0026]

[0027] Among them, C r is the capacitance of the resonant cavity, L r is the inductance of the resonant cavity.

[0028] Feedforward frequency f d The expression is as follows:

[0029]

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

[0031]

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

[0033]

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

[0035]

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

[0037]

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

[0039]

[0040] Among them, 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.

[0041] Voltage phase difference The calculation formula of the internal phase shift angle θ is as follows:

[0042]

[0043]

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

[0045] Feedforward frequency f d The expression is as follows:

[0046]

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

[0048]

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

[0050]

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

[0052] Beneficial effect: The isolated resonant converter and control method thereof of the present invention can realize accurate control of transmission power and zero-voltage switching of all switches, thereby significantly improving the efficiency of the converter.

[0053] In order to make the above features and advantages of the invention more obvious and easy to understand, embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 The present invention is a control block diagram of a control method for an isolated resonant converter.

[0055] Figure 2 This is a first specific embodiment of an isolated resonant converter of the present invention.

[0056] Figure 3 for Figure 2 Switching logic and voltage waveform of the circuit in Figure 2.

[0057] Figure 4 This is a second specific embodiment of an isolated resonant converter according to the present invention.

[0058] Figure 5 for Figure 4 Switching logic and voltage waveform of the circuit in Figure 2.

[0059] Figure 6 This is a third specific embodiment of an isolated resonant converter of the present invention.

[0060] Figure 7 for Figure 6 Switching logic and voltage waveform of the circuit in Figure 2.

[0061] Figure 8 This is a fourth specific embodiment of an isolated resonant converter according to the present invention.

[0062] Fig. 9 for Figure 8 Switching logic and voltage waveform of the circuit in Figure 2. DETAILED DESCRIPTION

[0063] In order to make the purpose and technical solution of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] Figure 1 FIG. 1 is a control block diagram of a control method for an isolated resonant converter according to the present invention, such as Figure 1As shown, a control method of an isolated resonant converter of the present invention includes the following steps.

[0065] Step S1, compare the primary current i1 with the current reference value i ref , after PI adjustment and current reference value i ref After adding, we get the target current value i t , ensuring accurate active power transmission. Among them, if the current reference value i ref If the current reference value i is greater than 0, the power is transferred from the primary side to the secondary side. ref If it is less than 0, the power is transferred from the secondary side to the primary side.

[0066] Step S2, comparing the external phase shift angle α with the external phase shift angle reference value α ref , after PI regulation, plus the feedforward frequency f d Get the switching frequency f s Among them, the external phase angle α is composed of the internal phase angle θ and the voltage phase difference The calculation shows that the external phase angle reference value α ref The reactive current is I rq and active current I rp In the initial state, the external phase angle α is 0, and the external phase angle reference value α ref is 0, the output of PI regulation is 0, that is, the switching frequency f s Equal to the feedforward frequency f d .

[0067] Step S3, using the fundamental wave analysis method, calculate the reactive current I of the primary side of the resonant cavity rq and active current I rp , and then according to the target current value i t and the switching frequency f s Calculate the voltage phase difference and the internal phase shift angle θ, according to the voltage phase difference Inner phase shift angle θ, outer phase shift angle α and switching frequency f s Drive the switch of the isolated resonant converter. Among them, the voltage phase difference is the input voltage of the resonant cavity v p and the voltage across the primary winding v sn The fundamental voltage phase difference; α is the input voltage v of the resonant cavity p and the voltage across the primary winding v sn The external phase angle between the two ends of the primary winding is θ. sn The internal phase shift angle, f s is the switching frequency, T s is the switching cycle.

[0068] In the first specific embodiment, Figure 2An isolated bidirectional DC / DC resonant converter with a half-bridge structure as the central bridge is taken as an example to illustrate a control method of an isolated resonant converter of the present invention.

[0069] like Figure 2 As shown, in the isolated bidirectional DC / DC resonant converter 2, the two ends of the power supply V1 are connected in parallel to the input of the bridge module 21, the bridge module 21, the resonance module 22, and the 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 includes 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 to the two ends of the power supply V1. The switch S1 and the switch S2 are connected in series in the same direction and then connected in parallel to the two ends of the power supply V1. The bridge module 23 further includes a switch Q1, a switch Q2, a switch Q3, and a switch Q4. The switch Q1 and the switch Q3 are connected in series in the same direction and then connected in parallel to the two ends of the power supply V2. The switch Q2 and the switch Q4 are connected in series in the same direction and then connected in parallel to the two ends of the power supply V2. The resonant module 22 further includes an inductor L r and capacitor C r , inductance L r The first end is connected to the source of switch S1, and the inductor L r The second end of the capacitor C r The first end of the capacitor C r The second end of the primary winding of the transformer T1 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] Furthermore, the power source V1 may be a constant bus voltage, such as 400V; or it may be a DC voltage folded from AC mains with a wide fluctuation range.

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

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

[0073] Furthermore, the bridge module 23 adopts a full-bridge structure and outputs a high-frequency voltage, which is both frequency-converting and phase-shifting.

[0074] Furthermore, the power source V2 is a DC voltage source such as an energy storage battery, a photovoltaic panel, etc.

[0075] The isolated bidirectional DC / DC resonant converter 2 adopts a hybrid control method of extended phase shift and variable frequency modulation. The modulation principle of power transmission from the primary side to the secondary side and from the secondary side to the primary side is as follows: Figure 3 (a) and 3(b), where the voltage phase difference is the input voltage v of the resonant cavity of the resonant module 22p and the voltage across the primary winding v sn The fundamental voltage phase difference; α is the input voltage v of the resonant cavity p and the voltage across the primary winding v sn The external phase angle between the two ends of the primary winding is θ. sn The internal phase shift angle, f s is the switching frequency, T s is the switching cycle.

[0076] For the isolated bidirectional DC / DC resonant converter 2, the current i1 can be either the input current or the output current according to the power transmission direction. rq and active current I rp are respectively the resonant current i of the primary side of the resonant module 22 r The reactive component and active component of the reactive current I rq The function is to realize the soft opening of the switch in the bridge module 21, and the active current I rp The function is to realize the transmission of active power, reactive current I rq and active current I rp The expression is as follows:

[0077] I rp =i t π,

[0078]

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

[0080] Furthermore, the voltage phase difference The calculation formula of the internal phase shift angle θ is as follows:

[0081]

[0082]

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

[0084] Furthermore, the expression of the outer shift phase angle α is as follows:

[0085]

[0086] Furthermore, the external phase angle reference value α ref The expression is as follows:

[0087]

[0088] Among them, 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 arm in the bridge module 23. By controlling the frequency to adjust the external phase shift angle α, the soft opening of all switches on the secondary side of the transformer can be achieved.

[0089] Furthermore, the feedforward frequency f d The expression is as follows:

[0090]

[0091] The expression of parameter x is as follows:

[0092]

[0093] In the initial state, the external phase angle α is 0, and the external phase angle reference value α ref is 0, the output of PI regulation is 0, that is, the switching frequency f in the initial state s Equal to the feedforward frequency f d .

[0094] Find the voltage phase difference Inner phase shift angle θ, outer phase shift angle α and switching frequency f s Then, according to Figure 2 The modulation logic of the switch in the circuit can be used to derive the switch driving logic of the isolated bidirectional DC / DC resonant converter and control the resonant converter.

[0095] In the second specific embodiment, Figure 4 Taking an isolated bidirectional DC / DC resonant converter with a full-bridge structure as an example, a control method of an isolated bidirectional DC / DC resonant converter of the present invention is described.

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

[0097] Furthermore, the power source V1 may be a constant bus voltage, such as 400V; or it may be a DC voltage folded from AC mains with a wide fluctuation range.

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

[0099] Furthermore, the transformer T2 is a high-frequency isolation transformer, and its transformation ratio is n:1.

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

[0101] Furthermore, the power source V2 is a DC voltage source such as an energy storage battery, a photovoltaic panel, etc.

[0102] The isolated bidirectional DC / DC resonant converter 4 adopts a hybrid control method of extended phase shift and variable frequency modulation. The modulation principle of power transmission from the primary side to the secondary side and from the secondary side to the primary side is as follows: Figure 5 (a) and 5(b), where the voltage phase difference is the input voltage v of the resonant cavity of the resonant module 42 p and the voltage across the primary winding v sn The fundamental voltage phase difference; α is the input voltage v of the resonant cavity p and the voltage across the primary winding v sn The external phase angle between the two ends of the primary winding is θ. sn The internal phase shift angle, f s is the switching frequency, T s is the switching cycle.

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

[0104]

[0105]

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

[0107] Furthermore, the voltage phase difference The calculation formula of the internal phase shift angle θ is as follows:

[0108]

[0109]

[0110] Wherein, 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 of the outer shift phase angle α is as follows:

[0112]

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

[0114]

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

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

[0117]

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

[0119]

[0120] In the initial state, the external phase angle α is 0, and the external phase angle reference value α ref is 0, the output of PI regulation is 0, that is, the switching frequency f in the initial state s Equal to the feedforward frequency fd .

[0121] Find the voltage phase difference 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 in the circuit can be used to derive the switch driving logic of the isolated bidirectional DC / DC resonant converter and control the resonant converter.

[0122] In the third specific embodiment, Figure 6 An isolated bidirectional AC / DC resonant converter with a half-bridge structure as the central bridge is taken as an example to illustrate a control method of an isolated resonant converter of the present invention.

[0123] like Figure 6 As shown, in the isolated bidirectional AC / DC resonant converter 6, the two ends of the power source V1 are connected in parallel to the input of the bridge module 61, the bridge module 61, the resonant module 62, and the bridge module 63 are connected in parallel in sequence, and the output of the bridge module 63 is connected in parallel to the power source V2. The bridge module 61 further includes a capacitor C3, a capacitor C4, a switch S7, a switch S8, a switch S9, and a switch S 10 , capacitor C3 and capacitor C4 are connected in series and then in parallel at both ends of power supply V1, switch S7 and switch S8 are connected in reverse series, switch S9 and switch S 10 Reverse series connection, the drain of switch S8 is connected to the drain of switch S9, the drain of switch S7 is connected to the positive terminal of power supply V1, and the switch S 10 The drain of the bridge module 63 is connected to the negative terminal of the power source V1. 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 at both ends of the power supply V2. The switch Q 10 With switch Q 12 The two ends of the power source V2 are connected in parallel after being connected in series in the same direction. The resonance module 62 further includes an inductor L r and capacitor C r , inductance L r The first end of the switch S8 is connected to the drain of the inductor L r The second end of the capacitor C r The first end of the capacitor C r The second end of the primary winding of the transformer T3 is connected to the first end of the primary winding of the transformer T3, the second end of the primary winding of the transformer T3 is connected to the series midpoint of the capacitor C3 and the capacitor C4, and the first end of the secondary winding of the transformer T3 is connected to the switch Q9 and the switch Q 11 The second end of the secondary winding of transformer T3 is connected to the switch Q 10 With switch Q 12The series midpoint of the switch S7 and switch S8 constitute a bidirectional switch, and the switch S9 and switch S 10 A two-way switch is formed.

[0124] Furthermore, the power source V1 is an AC voltage source, such as 220V mains electricity.

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

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

[0127] Furthermore, the bridge module 63 adopts a full-bridge structure and outputs a high-frequency voltage, which is both frequency-converting and phase-shifting.

[0128] Furthermore, the power source V2 is a DC voltage source such as an energy storage battery, a photovoltaic panel, etc.

[0129] The isolated bidirectional AC / DC resonant converter 6 adopts a hybrid control method of extended phase shift and variable frequency modulation. The modulation principle of power transmission from the primary side to the secondary side and from the secondary side to the primary side is as follows: Figure 7 (a) and Figure 7 (b), where the voltage phase difference is the input voltage v of the resonant cavity of the resonant module 62 p and the voltage across the primary winding v sn The fundamental voltage phase difference; α is the input voltage v of the resonant cavity p and the voltage across the primary winding v sn The external phase angle between the two ends of the primary winding is θ. sn The internal phase shift angle, f s is the switching frequency, T s is the switching cycle.

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

[0131] I rp =i t π,

[0132]

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

[0134] Furthermore, the voltage phase difference The calculation formula of the internal phase shift angle θ is as follows:

[0135]

[0136]

[0137] Wherein, 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 of the outer shift phase angle α is as follows:

[0139]

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

[0141]

[0142] Among them, C ossL is the drain-source junction capacitance of the switch in the bridge module 63, T dL is the dead time between the upper and lower switches of the bridge arm in the bridge module 63. By controlling the frequency to adjust the external phase shift angle α, the soft opening 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 of parameter x is as follows:

[0146]

[0147] In the initial state, the external phase angle α is 0, and the external phase angle reference value α ref is 0, the output of PI regulation is 0, that is, the switching frequency f in the initial state s Equal to the feedforward frequency f d .

[0148] Find the voltage phase difference 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 in the converter can be used to derive the switch driving logic of the isolated bidirectional AC / DC resonant converter and control the resonant converter.

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

[0150] like Figure 8 As shown, in the isolated bidirectional AC / DC resonant converter 8, the two ends of the power source V1 are connected in parallel to the input of the bridge module 81, the bridge module 81, the resonant module 82, and the bridge module 83 are connected in parallel in sequence, and the output of the bridge module 83 is connected in parallel to the power source V2. The 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, switch S 13 With switch S 14 Reverse series, switch S 12 The drain of the switch S 13 The drain connection of the switch S 11 The drain of the switch S is connected to the positive terminal of the power supply V1. 14 The drain of the switch S is connected to the negative terminal of the power supply V1. 15 With switch S 16 Reverse series, switch S 17 With switch S 18 Reverse series, switch S 16 The drain of the switch S 17 The drain connection of the switch S 15 The drain of the switch S is connected to the positive terminal of the power supply V1. 18 The drain of is connected to the negative terminal of the power source V1. The 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 at both ends of the power supply V2. The switch Q 14 With switch Q 16 The two ends of the power source V2 are connected in parallel after being connected in series in the same direction. The resonant module 82 further includes an inductor L r and capacitor C r , inductance L rThe first end of the switch S 16 The drain inductor L r The second end of the capacitor C r The first end of the capacitor C r The second end of the primary winding of the transformer T4 is connected to the first end of the primary winding of the transformer T4, and the second end of the primary winding of the transformer T4 is connected to the switch S 12 With switch S 13 The first end of the secondary winding of transformer T4 is connected to the switch Q 13 With switch Q 15 The second end of the secondary winding of transformer T4 is connected to the switch Q 14 With switch Q 16 The series midpoint of the switch S 11 With switch S 12 Constitute a bidirectional switch, switch S 13 With switch S 14 Constitute a bidirectional switch, switch S 15 With switch S 16 Constitute a bidirectional switch, switch S 15 With switch S 16 A two-way switch is formed.

[0151] Furthermore, the power source V1 is an AC voltage source, such as 220V mains electricity.

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

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

[0154] Furthermore, the bridge module 83 adopts a full-bridge structure and outputs a high-frequency voltage, which is both frequency-converting and phase-shifting.

[0155] Furthermore, the power source V2 is a DC voltage source such as an energy storage battery, a photovoltaic panel, etc.

[0156] The isolated bidirectional AC / DC resonant converter 8 adopts a hybrid control method of extended phase shift and variable frequency modulation. The modulation principle of power transmission from the primary side to the secondary side and from the secondary side to the primary side is as follows: Fig. 9 (a) and Fig. 9 (b), where the voltage phase difference is the input voltage v of the resonant cavity of the resonant module 82 p and the voltage across the primary winding v sn The fundamental voltage phase difference; α is the input voltage v of the resonant cavity p and the voltage across the primary winding v sn The external phase angle between the two ends of the primary winding is θ. sn The internal phase shift angle, f s is the switching frequency, Ts is the switching cycle.

[0157] For the isolated bidirectional AC / DC resonant converter 8, the current i1 can be either the input current or the output current according to the power transmission direction. rq and active current I rp are respectively the resonant current i of the primary side of the resonant module 82 r The reactive component and active component of the reactive current I rq The function is to realize the soft opening of the switch in the bridge module 81, and the active current I rp The function is to realize the transmission of active power, and the reactive current is I rq and active current I rp The expression is as follows:

[0158]

[0159]

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

[0161] Furthermore, the voltage phase difference The calculation formula of the internal phase shift angle θ is as follows:

[0162]

[0163]

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

[0165] Furthermore, the expression of the outer shift phase angle α is as follows:

[0166]

[0167] Furthermore, the external phase angle reference value α ref The expression is as follows:

[0168]

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

[0170] Furthermore, the feedforward frequency f d The expression is as follows:

[0171]

[0172] The expression of parameter x is as follows:

[0173]

[0174] In the initial state, the external phase angle α is 0, and the external phase angle reference value α ref is 0, the output of PI regulation is 0, that is, the switching frequency f in the initial state s Equal to the feedforward frequency f d .

[0175] Find the voltage phase difference Inner phase shift angle θ, outer phase shift angle α and switching frequency f s Then, according to Fig. 9 The modulation logic of the switch in the converter can be used to derive the switch driving logic of the isolated bidirectional AC / DC resonant converter and control the resonant converter.

[0176] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Any person having ordinary knowledge in the technical field may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope of the attached patent application.

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 adjustment and current reference value i ref After adding, we get the target current value i t ; Step S2, comparing the external phase shift angle α with the external phase shift angle reference value α ref , after PI regulation, plus the feedforward frequency f d Get the switching frequency f s ; In the initial state, the external phase angle α is 0, and the external phase angle reference value α ref is 0, the output of PI regulation is 0, the switching frequency f s Equal to the feedforward frequency f d ; Step S3, calculate the reactive current I of the primary side of the resonant cavity rq and active current I rp , and then according to the target current value i t and the switching frequency f s Calculate the voltage phase difference and the internal phase shift angle θ, according to the voltage phase difference Inner phase shift angle θ, outer phase shift angle α and switching frequency f s Driving the switches of an isolated resonant converter, where the voltage phase difference is the input voltage of the resonant cavity v p and the voltage across the primary winding v sn The fundamental voltage phase difference; α is the input voltage v of the resonant cavity p and the voltage across the primary winding v sn The external phase angle between the two ends of the primary winding is θ. sn The internal phase shift angle, f s is the switching frequency, T s is the switching cycle.

2. A control method for an isolated resonant converter as claimed in claim 1, characterized in that: The expression of the outward shift phase angle α is as follows: External phase angle reference value α ref The expression is as follows: Where n is the turns ratio of the transformer of the isolated resonant converter, C ossL is the drain-source junction capacitance of the switch in the secondary bridge, T dL is the dead time between the upper and lower switches of the bridge arm in the secondary bridge, and V2 is the output voltage of the isolated resonant converter.

3. A control method for an isolated resonant converter as claimed in claim 2, 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 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.

4. A control method for an isolated resonant converter as claimed in claim 3, characterized in that: Voltage phase difference The calculation formula of the internal phase shift angle θ is as follows: Among them, C r is the capacitance of the resonant cavity, L r is the inductance of the resonant cavity.

5. A control method for an isolated resonant converter as claimed in claim 4, 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 of parameter x is as follows: If the isolated resonant converter is an AC / DC resonant converter, the expression of parameter x is as follows:

6. A control method for an isolated resonant converter as claimed in claim 2, 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 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.

7. A control method for an isolated resonant converter as claimed in claim 6, characterized in that: Voltage phase difference The calculation formula of the internal phase shift angle θ is as follows: Among them, C r is the capacitance of the resonant cavity, L r is the inductance of the resonant cavity.

8. A control method for an isolated resonant converter as claimed in claim 7, 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 of parameter x is as follows: If the isolated resonant converter is an AC / DC resonant converter, the expression of parameter x is as follows:

9. An isolated resonant converter, characterized in that: A control method for an isolated resonant converter as claimed in any one of claims 1 to 8 is applied, comprising a resonant cavity, wherein the resonant cavity comprises an inductor and a capacitor, wherein the inductor and the capacitor are connected in series.

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