Flyback micro inverter control method

Abstract

The invention discloses a flyback micro inverter control method, which ensures that transmitted energy does not suddenly change and that a flyback switching tube is opened at the valley bottom in light load frequency limiting (the number of jump valley bottoms changes) or when the number of interlaced paths in interlaced application changes, so that the current waveform is smooth and continuous, and the power consumption is reduced. The power factor and the total harmonic distortion of the network access current can be improved under the light load condition or when the number of interlaced paths changes.

Description

Technical Field

[0001] The invention relates to inverter technology, and in particular to a flyback micro inverter control method. Background Art

[0002] The flyback micro inverter is the most widely used inverter at present. It generally works in discontinuous mode. Due to the system parasitic parameters, the DS (drain-source) voltage of the flyback switch tube will oscillate after the secondary current continues to flow. During the oscillation process, the switch tube is controlled to be turned on, and the turn-on point is uncertain, resulting in uncertain turn-on loss. In order to improve the system efficiency, the flyback switch tube should be turned on when the DS voltage oscillates to the bottom.

[0003] ① Under light load conditions, when the grid voltage is near zero point, the switching frequency increases sharply due to the small current. In order to reduce the switching frequency of the flyback switch tube under light load conditions, the flyback switch tube is turned on after the DS voltage jumps to several valleys. The existing patent realizes the switching of the number of valleys according to the current switching frequency and the preset upper and lower limits of the frequency, but does not describe the treatment of the impact of energy fluctuations caused by the switching of the number of valleys on the current waveform and the impact of the limit of the minimum on-time of the flyback switch tube on the initial number of valleys after the grid voltage is commutated.

[0004] ② In the multi-phase interleaved flyback micro-inverter, in order to improve the system efficiency, it is necessary to determine the number of operating flyback paths based on the instantaneous output power. The strategy of directly dividing the turn-on time of the flyback switch tube commonly used in the DCM variable frequency mode will cause the output current to be unsmooth when the number of interleaved paths changes. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a flyback micro-inverter control method, which ensures that the transferred energy does not change suddenly when the frequency is limited under light load (the number of valley jumps changes) or the number of interleaving paths changes in interleaving applications, and ensures that the flyback switch tube is turned on at the valley bottom, so that the current waveform is smooth and continuous, and can improve the power factor (PF) and total harmonic distortion (THD) of the grid-connected current under light load conditions or when the number of interleaving paths changes.

[0006] In order to solve the above technical problems, the present invention provides a flyback micro-inverter control method, wherein the flyback micro-inverter includes at least one flyback converter; the output of the flyback converter of the flyback micro-inverter is connected to the grid via a full-bridge inverter circuit and a grid-connected inductor L; the flyback converter includes a power switch tube M, a transformer T and a diode D; the flyback converter, a flyback switch cycle T is composed of the switch tube M opening time T on , flyback freewheeling time T off And the delay T generated to achieve valley bottom opening delay Composition; [0,T on] period, the switch tube M is turned on and the diode D is turned off; [T on ,T on +T off ] period is the freewheeling stage, the switch tube is turned off and the diode D is turned on; [T on +T off ,T] period, the switch tube M and the diode D are both turned off; it is characterized in that the control method comprises the following steps:

[0007] S0. Monitor the grid voltage v g ;

[0008] S1. Determine the grid voltage v g Whether it is near zero crossing, it is in commutation state; if it is in commutation state, proceed to step S2, if commutation is completed, proceed to step S3;

[0009] S2.T on3 =0, proceed to step S20;

[0010] S3. Confirm the current number of valleys m and the control loop calculation output T on1 , calculate the opening time T when jumping to m valleys on3_b And the corresponding switching period T _b ;

[0011] S4. If T _b ≥T min1 , proceed to step S5; if T b <T min1 Then proceed to step S8;

[0012] S5. If the number of valley jumps m = 0, confirm the final output T on3 =T on3_b , proceed to step S20; if m≥1, proceed to step S6;

[0013] S6. Calculate the opening time T when jumping (m-1) valleys on3_a And the corresponding switching period T _a ; Go to step 7;

[0014] S7. If T _a >T min2 And T on3_a >T on_min , then confirm the final output T on3 =T on3_a , proceed to step S20; otherwise confirm the final output T on3 =T on3_b , proceed to step S20;

[0015] S8. Recalculate T when the number of valley jumps is m=m+1. on3_bAnd the corresponding switching period T _b , confirm the final output T on3 =T on3_b , proceed to step S20;

[0016] S20. Based on the third opening time parameter T on3 , get the turn-on time T of the regulating switch tube M on ;

[0017] Among them, T min is the minimum switching period specified by the system; T min2 is the switching cycle threshold to reduce the number of valleys, T min1 The switching cycle threshold for increasing the number of valleys; T min2 ≥T min1 ≥T min ; T on3 It is the third opening time parameter.

[0018] Preferably, one end of the primary winding of the transformer T is connected to one end of the source and drain of the power switch tube M;

[0019] The other end of the source and drain of the power switch tube M is grounded;

[0020] The other end of the primary winding of the transformer T is connected to the positive end of the DC power supply;

[0021] One end of the secondary winding of the transformer T is connected to the positive end of the diode D.

[0022] A bus capacitor C is connected between the other end of the secondary winding of the transformer T and the other end of the diode D.

[0023] Preferably, in step S2, the number m of initial valley bottoms of the on pulse after commutation is calculated.

[0024] Preferably, in step S2, first determine the commutation pulse angle θ x , and the minimum switching period T limited by the system components min And the minimum on-time of the switch tube T on_min Then, according to the following formula (6), formula (7) and the constraint condition m≥0, the initial number of valley bottoms m of the open pulse after commutation is determined;

[0025]

[0026] Where, T r is the resonant oscillation period of the transformer leakage inductance and the parasitic capacitance of the switch tube M, L r is the primary leakage inductance of the transformer, C oss is the equivalent parasitic capacitance of the flyback switch tube, n is the transformer ratio, v in is the DC power supply voltage, Vg is the peak value of the grid voltage, L m is the transformer primary magnetizing inductance, I ref is the peak value of the reference current of a given power grid.

[0027] Preferably, in step S2, first determine the commutation pulse angle θ x , the minimum switching period T limited by the system components min And the minimum on-time of the switch tube T on_min ;

[0028] When I ref ≤I ref_th When , the initial number of valley bottoms m of the open pulse is calculated according to formula (9) and the constraint condition m ≥ 0;

[0029] When I ref >I ref_th When , according to formula (8) and the constraint condition m ≥ 0, the initial number of valley bottoms of the open pulse m is determined;

[0030]

[0031] Among them I ref_th Calculated according to formula (10);

[0032]

[0033] Where, T r is the resonant oscillation period of the transformer leakage inductance and the parasitic capacitance of the switch tube M, n is the transformer ratio, v in is the DC power supply voltage, V g is the peak value of the grid voltage, L m is the transformer primary magnetizing inductance; I ref is the peak value of the reference current of the given power grid, I ref_th is the calculated threshold current.

[0034] Preferably, the control loop outputs the first opening time parameter T calculated by the system. on1 , current grid-connected parameters and system parameters to determine the final output switch opening time.

[0035] Preferably, in step S3, the first on-time parameter T of the control loop output is calculated. on1 The number of valley jumps before and after the change is m1 and m2. Under the constraint of ensuring that the total output power remains unchanged, the equivalent output second opening time parameter T of the control loop output when the number of valley jumps changes is obtained. on2 ;

[0036]

[0037]

[0038] Among them, T delay1 The delay corresponding to the number of valleys before the change, m1, T delay2 The delay corresponding to the number of valley jumps m2 after the change, T r is the resonant oscillation period of the transformer leakage inductance and the parasitic capacitance of the switch tube M, n is the transformer ratio, v in is the DC power supply voltage, v g is the instantaneous value of the grid voltage.

[0039] Preferably, in the second opening time parameter T on2 Add the feedforward value T calculated based on the current system parameters f , get the system's third opening time parameter T on3 :

[0040] T on3 =T on2 +T f ;

[0041]

[0042] v g is the instantaneous value of the grid voltage, i gref is the instantaneous value of the grid reference current, L m is the primary magnetizing inductance of the transformer, n is the transformer ratio, v in is the DC power supply voltage.

[0043] Preferably, in step S20, the third on-time parameter T needs to be set when considering the number of flyback paths in operation. on3 The flyback converter assigned to each target operation, under the constraint of ensuring that the total output power remains unchanged, obtains the final turn-on time parameters of the flyback switch tube assigned to each target operation by the system:

[0044]

[0045] Where p2 is the flyback path number of the target operation, v g is the instantaneous value of the grid voltage, n is the transformer ratio, v in is the DC power supply voltage, T delay The delay corresponding to the number of target valley jumps m.

[0046] Preferably, the flyback micro-inverter is a two-phase interleaved flyback micro-inverter.

[0047] The present invention also discloses a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor executes the steps of the method when executing the computer program.

[0048] The present invention also discloses a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the method are implemented.

[0049] The flyback micro-inverter control method of the present invention calculates the initial valley number m of the open pulse after commutation when the grid voltage is in the commutation state; when the voltage commutation is completed, calculates the control loop output T on1 , confirm the current number of valley jumps m, and calculate the opening time T when jumping m valleys on3_b And the corresponding switching period T _b , if T_ b <T min1 , recalculate T when the number of valley jumps is m = m + 1 on_b and T _b , confirm the final output T on3 =T on_b ; if T _b ≥T min1 , then determine whether m = 0, if it is confirmed that the final output T on3 =T on_b If m ≥ 1, then calculate the opening time T when jumping (m-1) valleys on3_a And the corresponding switching period T _a , if T on3_a ≥T on_min And T _a ≥T min2 , then confirm the final output T on3 =T on_a , otherwise confirm the final output T on3 =T on_b Where T min2 is the switching cycle threshold to reduce the number of valleys, T min1 To increase the switching cycle threshold of the number of valleys, T min is the minimum switching period specified by the system, T min2 ≥T min1 ≥T min The flyback micro-inverter control method of the present invention ensures that the transferred energy does not change suddenly when the frequency is limited at light load (the number of valley jumps changes) or the number of interleaving paths changes in interleaving applications, and ensures that the flyback switch tube is turned on at the valley bottom, so that the current waveform is smooth and continuous, and can improve the power factor (PF) and total harmonic distortion (THDi) of the grid-connected current when the light load condition is in operation or the number of interleaving paths changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0051] Figure 1 It is a two-phase interleaved flyback micro inverter circuit diagram;

[0052] Figure 2 The flyback switch tube Vds valley-turned-on operation waveform;

[0053] Figure 3 is a flow chart of an embodiment of a flyback micro-inverter control method of the present invention;

[0054] Figure 4 is a current loop control block diagram of an embodiment of a flyback micro-inverter control method of the present invention;

[0055] Figure 5a This is a comparison of experimental results with an input power of 50W;

[0056] Figure 5b This is the comparison of experimental results with an input power of 70W;

[0057] Figure 5c This is a comparison of experimental results with an input power of 200W. DETAILED DESCRIPTION

[0058] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments 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.

[0059] A flyback micro inverter control method, such as Figure 1 As shown, the flyback micro-inverter includes at least one flyback converter; the output of the flyback converter of the flyback micro-inverter is connected to the grid via a full-bridge inverter circuit and a grid-connected inductor L; the flyback converter includes a power switch tube M, a transformer T and a diode D; the flyback converter, as shown Figure 2 As shown, a flyback switching cycle T is composed of the switch tube M on time T on , flyback freewheeling time T off And the delay T generated to achieve valley bottom opening delay Composition; [0,T on ] period, the switch tube M is turned on and the diode D is turned off; [T on ,T on+T off The period is the freewheeling stage, the switch tube is turned off and the diode D is turned on; [T on +T off ,T] period, the switch tube M and the diode D are both cut off;

[0060] like Figure 3 As shown, the control method includes the following steps:

[0061] S0. Monitor the grid voltage v g ;

[0062] S1. Determine the grid voltage v g Whether it is near zero crossing, it is in commutation state; if it is in commutation state, proceed to step S2, if commutation is completed, proceed to step S3;

[0063] S2.T on3 =0, proceed to step S20;

[0064] S3. Confirm the current number of valleys m and the control loop calculation output T on1 , calculate the opening time T when jumping to m valleys on3_b And the corresponding switching period T _b ;

[0065] S4. If T _b ≥T min1 , proceed to step S5; if T b <T min1 Then proceed to step S8;

[0066] S5. If the number of valley jumps m = 0, confirm the final output T on3 =T on3_b , proceed to step S20; if m≥1, proceed to step S6;

[0067] S6. Calculate the opening time T when jumping (m-1) valleys on3_a And the corresponding switching period T _a ; Go to step 7;

[0068] S7. If T_ a >T min2 And T on3_a >T on_min , then confirm the final output T on3 =T on3_a , proceed to step S20; otherwise confirm the final output T on3 =T on3_b , proceed to step S20;

[0069] S8. Recalculate T when the number of valley jumps is m=m+1. on3_b And the corresponding switching period T_b , confirm the final output T on3 =T on3_b , proceed to step S20;

[0070] S20. Based on the third opening time parameter T on3 , get the turn-on time T of the regulating switch tube M on ;

[0071] Among them, T min is the minimum switching period specified by the system; T min2 is the switching cycle threshold to reduce the number of valleys, T min1 The switching cycle threshold for increasing the number of valleys; T min2 ≥T min1 ≥T min ; T on3 It is the third opening time parameter.

[0072] Preferably, one end of the primary winding of the transformer T is connected to one end of the source and drain of the power switch tube M;

[0073] The other end of the source and drain of the power switch tube M is grounded;

[0074] The other end of the primary winding of the transformer T is connected to the positive end of the DC power supply;

[0075] One end of the secondary winding of the transformer T is connected to the positive end of the diode D.

[0076] A bus capacitor C is connected between the other end of the secondary winding of the transformer T and the other end of the diode D.

[0077] The flyback micro-inverter is a multi-phase interleaved flyback micro-inverter suitable for valley switching or other converters requiring valley switching control. Figure 1 The figure shows a two-phase interleaved flyback micro inverter. In order to reduce system losses, the flyback output is a steamed bun wave, and the inverter uses an industrial frequency switch to modulate the steamed bun wave into a sine wave.

[0078] Preferably, the DC power supply is provided by a photovoltaic panel through a maximum power point tracking (MPPT) loop.

[0079] The flyback micro-inverter control method of the present invention has a working principle specifically analyzed as follows:

[0080] The flyback converter has three working states. A switching cycle T of the flyback converter is equal to the switch-on time T. on , also includes the flyback follow-up time T off , and the delay T generated to achieve valley bottom opening delay ,like Figure 2 As shown. [0,T on ]The switch tube is turned on and the diode is turned off, [T on ,T on +T off ] During the freewheeling phase, the switch tube is turned off and the diode is turned on, and [T on +T off ,T] the switch tube and the diode are cut off, where [0,T on ] and [T on ,T on +T off ] The state equation in the time period is as follows:

[0081]

[0082] Where L m is the transformer primary magnetizing inductance, v in is the DC power supply voltage, v g is the instantaneous value of the grid voltage, V g is the peak value of the grid voltage, L is the grid inductance, i g is the instantaneous value of the grid current, The value is much smaller than v g can be ignored, so we can get T off With T on Δi is The amount of change, is the current of the primary magnetizing inductance, n is the transformer ratio;

[0083] Transformer leakage inductance and switch tube M parasitic capacitance resonant oscillation period T r And the delay T delay The relationship is as shown in formula (2), where L r is the transformer primary leakage inductance, C oss is the equivalent parasitic capacitance of the flyback switch tube, and m is the number of valleys skipped by the switch tube:

[0084]

[0085] (I) Control loop

[0086] The micro reverse current loop control block diagram is as follows: Figure 4 As shown, the input is the grid reference current i output by the MPPT (Maximum power point tracking) loop. gref and the actual sampled grid current i g , the switch on time T is obtained through loop control calculation and compensation on In order to ensure that the transmission power does not change suddenly when the number of valley jumps changes during frequency limiting and the number of interleaving paths changes, the first opening time parameter T of the loop output is respectivelyon1 and feedforward T f Perform the equivalent to ensure the same equivalent duty cycle, and then distribute it to each flyback T on .

[0087] Ignoring the effects of losses and parasitic parameters, the input power is equal to the output power:

[0088]

[0089] where i gref The grid reference current can be simplified to obtain:

[0090] v in 2 T on 2 -2L m v g i gref (1+k)T on -2L m v g i gref T delay =0 (14);

[0091] Solving the above equation, we can get the feedforward quantity T f :

[0092]

[0093] where v g =V g sinθ,i gref =I ref sinθ,V g is the peak value of the grid voltage. When the grid voltage of the system passes through zero and the system is commutating, it is assumed that the voltage phase angle θ at the time of pulse opening after commutation is known as the commutation pulse opening angle θ x , and θ x The value is very small, so it can be approximated that sinθ x ≈θ x , then we can calculate the delay T delay Minimum value of:

[0094]

[0095] Where T min is the minimum switching cycle limited by the system.

[0096] Substitute the known quantities:

[0097]

[0098] In addition, since the switch tube generally limits the minimum on-time T of the switch tubeon_min , we also need to consider the minimum number of m under the minimum opening time:

[0099]

[0100] The values ​​of equations (17) and (18) can be directly calculated, and the initial number of valley jumps m can be obtained by adding the constraint condition m ≥ 0; or it can be determined when I ref ≤I ref_th When m is calculated according to formula (18), when I ref >I ref_th When m is calculated according to formula (17), the above constraint plus other constraints m≥0 can be used to obtain the initial number of valley jumps after system commutation. ref_th The calculation formula is as follows:

[0101]

[0102] According to the change of the number of valley jumps and the number of operating flyback paths, the smooth transition of transmission power can be obtained:

[0103]

[0104] Among them, p1 is the number of flyback operation paths before the change, p2 is the number of flyback paths currently running after the change, m1 is the number of valley jumps before the change, m2 is the number of valley jumps after the change, T on1 ,T off1 ,T delay1 is the flyback parameter before change, T on2 ,T off2 ,T delay2 is the flyback parameter after the change, T delay1 Corresponding to the delay before the number m1 of valley jump changes, T delay2 The delay of the number of valley jumps m2 after the corresponding change; after simplification, we can get:

[0105]

[0106] If only the number of valleys changes, the output power is small, and generally only one flyback is working. Let p1=p2=1, and the equivalent ratio of the duty cycle is:

[0107]

[0108] In the above formula, T on1 is the first opening time parameter, T on2 It is the second opening time parameter.

[0109] The second opening time parameter T on2 Add the feedforward T calculated from the current system parameters fGet the current third opening time parameter T on3 .

[0110] When the output power changes and the number of flyback paths changes, it is considered that the unallocated T on3 This is the loop calculation output when one flyback path is working. When the target change of the number of flyback paths is p2, the duty cycle is allocated by the following formula to ensure that the transmission power is still smoothly distributed when the number of flyback paths changes:

[0111]

[0112] Where p2 is the number of flyback converter paths to be operated, T delay is the delay corresponding to the number of target valley jumps, T on The conduction time allocated to the output switch tube is finally controlled.

[0113] (II) Valley jumping condition judgment and switching

[0114] When the grid voltage is near zero crossing and in commutation state, the preset commutation post-pulse angle θ is known. x , calculate the initial number of valleys of the open pulse after commutation according to equations (17), (18), and (19), and m ≥ 0; calculate the control loop output T on1 , confirm the current number of valley jumps m, and calculate the opening time T when jumping m valleys on3_b And the corresponding switching period T _b , if T _b <T min1 , recalculate T when the number of valley jumps is m = m + 1 on_b and T _b , confirm the final output T on3 =T on_b ; if T _b ≥T min1 , then determine whether m = 0, if it is confirmed that the final output T on3 =T on_b If m ≥ 1, then calculate the opening time T when jumping (m-1) valleys on3_a And the corresponding switching period T _a , if T on3_a ≥T on_min And T _a ≥T min2 , then confirm the final output T on3 =T on_a , otherwise confirm the final output T on3 =T on_b The judgment and switching conditions are as follows: Figure 3 . T min2 is the switching cycle threshold to reduce the number of valleys, T min1To increase the switching cycle threshold of the number of valleys, T min is the minimum switching period specified by the system, T min2 ≥T min1 ≥T min .

[0115] (III) Comparison of experimental effects between the control method of the present invention and the traditional control method

[0116] The experimental platform is a two-way interleaved anti-laser volt micro inverter, which tests the control effects of traditional control and optimized control respectively. Figure 5a , Figure 5b , Figure 5c As shown in the figure, red represents the grid current and purple represents the grid voltage. Figure 5a This is the experimental effect comparison with an input power of 50W. Figure 5b This is the experimental effect comparison with an input power of 70W. Figure 5c This is a comparison of experimental results with an input power of 200W.

[0117] The upper waveform is only the control waveform when the switching frequency is limited. The higher the switching frequency limit, the better the grid-connected current waveform. The frequency of the waveform in the figure is limited to 200kHz; the lower part is the control scheme adopted by the present invention. When the load is light, when the input power is 50W and 70W, only one flyback works. It can be seen that the present invention has better sinusoidality and is smoother than the simple control waveform; when the power increases, such as the power is 200W, within one cycle, when the instantaneous power is small, one flyback runs; when the instantaneous power is large, two flybacks run, and when one is cut to two, or two are cut to one flyback, the waveform of the present invention is smoother when switching, and there is no sudden change.

[0118] The flyback micro-inverter control method of the present invention ensures that the transferred energy does not change suddenly when the frequency is limited at light load (the number of valley jumps changes) or the number of interleaving paths changes in interleaving applications, and ensures that the flyback switch tube is turned on at the valley bottom, so that the current waveform is smooth and continuous, and can improve the power factor (PF) and total harmonic distortion (THDi) of the grid-connected current when the light load condition is applied or the number of interleaving paths changes.

[0119] The grid-connected current loop here can also be equivalent to other loops, such as the flyback primary current loop, and the loop output result can be processed in the same way to achieve the same effect. The same idea can be applied to other converters that require valley switching control, such as boost circuits.

[0120] There may be a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and wherein the processor implements the steps of the flyback micro-inverter control method when executing the computer program.

[0121] A computer-readable storage medium may be provided, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the flyback micro-inverter control method are implemented.

[0122] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A flyback micro-inverter control method, wherein the flyback micro-inverter comprises at least one flyback converter; the output of the flyback converter of the flyback micro-inverter is connected to the grid via a full-bridge inverter circuit and a grid-connected inductor L; the flyback converter comprises a power switch tube M, a transformer T and a diode D; the flyback converter, a flyback switching cycle T is composed of the switch tube M opening time T on , flyback freewheeling time T off And the delay T generated to achieve valley bottom opening delay Composition; [0,T on ] period, the switch tube M is turned on and the diode D is turned off; [T on ,T on +T off ] period is the freewheeling stage, the switch tube is turned off and the diode D is turned on; [T on +T off ,T] period switch tube M and diode D are both cut off; it is characterized by: The control method comprises the following steps: S0. Monitor the grid voltage v g ; S1. Determine the grid voltage v g Whether it is near zero crossing, it is in commutation state; if it is in commutation state, proceed to step S2, if commutation is completed, proceed to step S3; S2.T on3 =0, proceed to step S20; S3. Confirm the current number of valleys m and the control loop calculation output T on1 , calculate the opening time T when jumping to m valleys on3_b And the corresponding switching period T _b ; S4. If T _b ≥T min1 , proceed to step S5; if T b <T min1 Then proceed to step S8; S5. If the number of valley jumps m = 0, confirm the final output T on3 =T on3_b , proceed to step S20; if m≥1, proceed to step S6; S6. Calculate the opening time T when jumping (m-1) valleys on3_a And the corresponding switching period T _a ; Go to step 7; S7. If T_ a >T min2 And T on3_a >T on_min , then confirm the final output T on3 =T on3_a , proceed to step S20; otherwise confirm the final output T on3 =T on3_b , proceed to step S20; S8. Recalculate T when the number of valley jumps is m=m+1. on3_b And the corresponding switching period T _b , confirm the final output T on3 =T on3_b , proceed to step S20; S20. Based on the third opening time parameter T on3 , get the turn-on time T of the regulating switch tube M on ; Among them, T min is the minimum switching period specified by the system; T min2 is the switching cycle threshold to reduce the number of valleys, T min1 The switching cycle threshold for increasing the number of valleys; T min2 ≥T min1 ≥T min ; T on3 It is the third opening time parameter.

2. The flyback micro-inverter control method according to claim 1, characterized in that: One end of the primary winding of the transformer T is connected to one end of the source and drain of the power switch tube M; The other end of the source and drain of the power switch tube M is grounded; The other end of the primary winding of the transformer T is connected to the positive end of the DC power supply; One end of the secondary winding of the transformer T is connected to the positive end of the diode D. A bus capacitor C is connected between the other end of the secondary winding of the transformer T and the other end of the diode D.

3. The flyback micro-inverter control method according to claim 1, characterized in that: In step S2, the initial number m of valley bottoms of the on pulse after commutation is calculated.

4. The flyback micro-inverter control method according to claim 3, characterized in that: In step S2, first confirm the commutation pulse angle θ x , and the minimum switching period T limited by the system components min And the minimum on-time of the switch tube T on_min Then, according to the following formula (1), formula (2) and the constraint condition m ≥ 0, the initial number of valley bottoms m of the open pulse after commutation is determined; Where, T r is the resonant oscillation period of the transformer leakage inductance and the parasitic capacitance of the switch tube M, L r is the primary leakage inductance of the transformer, C oss is the equivalent parasitic capacitance of the flyback switch tube, n is the transformer ratio, v in is the DC power supply voltage, V g is the peak value of the grid voltage, L m is the transformer primary magnetizing inductance, I ref is the peak value of the reference current of a given power grid.

5. The flyback micro-inverter control method according to claim 3, characterized in that: In step S2, first confirm the commutation pulse angle θ x , the minimum switching period T limited by the system components min And the minimum on-time of the switch tube T on_min ; When I ref ≤I ref_th When , the initial number of valley bottoms m of the open pulse is calculated according to formula (4) and the constraint condition m ≥ 0; When I ref >I ref_th When , according to formula (3) and the constraint condition m ≥ 0, the initial number of valley bottoms of the open pulse m is determined; Among them I ref_th Calculated according to formula (5); Where, T r is the resonant oscillation period of the transformer leakage inductance and the parasitic capacitance of the switch tube M, n is the transformer ratio, v in is the DC power supply voltage, V g is the peak value of the grid voltage, L m is the transformer primary magnetizing inductance, L is the grid inductance; I ref is the peak value of the reference current of the given power grid, I ref_th is the calculated threshold current.

6. The flyback micro-inverter control method according to claim 1, characterized in that: The control loop outputs the first opening time parameter T calculated by the system on1 , current grid-connected parameters and system parameters to determine the final output switch opening time.

7. The flyback micro-inverter control method according to claim 6, characterized in that: In step S3, the first on-time parameter T of the control loop output is calculated. on1 The number of valley jumps before and after the change is m1 and m2. Under the constraint of ensuring that the total output power remains unchanged, the equivalent output second opening time parameter T of the control loop output when the number of valley jumps changes is obtained. on2 ; Among them, T delay1 The delay corresponding to the number of valleys before the change, m1, T delay2 The delay corresponding to the number of valley jumps m2 after the change, T r is the resonant oscillation period of the transformer leakage inductance and the parasitic capacitance of the switch tube M, n is the transformer ratio, v in is the DC power supply voltage, v g is the instantaneous value of the grid voltage.

8. The flyback micro-inverter control method according to claim 7, characterized in that: In the second opening time parameter T on2 Add the feedforward value T calculated based on the current system parameters f , get the system's third opening time parameter T on3 : T on3 =T on2 +T f ; v g is the instantaneous value of the grid voltage, i gref is the instantaneous value of the grid reference current, L m is the primary magnetizing inductance of the transformer, n is the transformer ratio, v in is the DC power supply voltage, T delay The delay corresponding to the target number of valley jumps m.

9. The flyback micro-inverter control method according to claim 8, characterized in that: In step S20, the third on-time parameter T on3 The flyback converter assigned to each target operation is used to obtain the final turn-on time parameter T of the flyback switch tube assigned to each target operation by the system under the constraint of ensuring that the total output power remains unchanged. on : Where p2 is the flyback path number of the target operation, v g is the instantaneous value of the grid voltage, n is the transformer ratio, v in is the DC power supply voltage, T delay The delay corresponding to the target number of valley jumps m.

10. The flyback micro-inverter control method according to claim 2, characterized in that: The flyback micro-inverter is a two-phase interleaved flyback micro-inverter.

11. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 10 are implemented.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 10 are implemented.

Images