Two-stage photovoltaic inverter hybrid power tracking method and system for load power fluctuation

Abstract

This invention discloses a two-stage photovoltaic inverter hybrid power tracking method and system for load power fluctuations. Based on the inverter's reference output voltage phase angle, a three-phase modulation wave is obtained through coordinate transformation, and then converted into a PWM duty cycle signal to achieve dual droop control of DC-side voltage and frequency. The operating mode of the photovoltaic inverter is determined according to the output voltage. When the steady-state value of the photovoltaic inverter (FlagStb) is < 0, photovoltaic array mode conversion is performed based on CountStb. The control command value of the photovoltaic current is determined according to the photovoltaic inverter's operating state, and the photovoltaic port current control command value is calculated. The duty cycle of the DC / DC converter before the photovoltaic inverter is obtained based on the photovoltaic port current control command value and the photovoltaic port current, achieving rapid power tracking control of the photovoltaic inverter without energy storage during load power fluctuations. This improves the photovoltaic inverter's active support capability for new power systems and enhances the penetration level of new energy power generation.

Description

Technical Field

[0001] This invention belongs to the field of new energy power generation and converter control technology, specifically relating to a two-stage photovoltaic inverter hybrid power tracking method and system for load power fluctuation. Background Technology

[0002] Among new energy power generation technologies, photovoltaic (PV) power generation has attracted much attention due to its wide energy distribution and ease of utilization. However, the high dependence of PV power generation on the power grid, energy storage, and energy management systems severely limits its development. PV inverters are crucial in the utilization of solar energy; PV arrays convert solar energy into electrical energy, and inverters control their output to meet load requirements. Therefore, proper control of PV arrays and inverters can better utilize solar energy.

[0003] To improve the utilization rate of solar energy in photovoltaic arrays, inverters are typically controlled to maximize the output power of the array under specific conditions. However, in isolated microgrids, this contradicts the principle of source-load power matching. Furthermore, to enable the photovoltaic inverter to actively support the voltage and frequency of the AC bus, maximum power point tracking (MPPT) should be replaced by a more flexible active power control method. Active power control can match the photovoltaic output power to the load demand by controlling the inverter, adjusting the photovoltaic output power based on load power requirements rather than operating at the maximum power point.

[0004] However, although a PI regulator can track the power point of a photovoltaic inverter in islanded operation mode, its response speed is slow because it requires both a power loop and an inner loop for tracking, and it also requires an external power supply loop to track the operating point. Therefore, a more convenient and faster control method is needed to track the power of the photovoltaic inverter when the load power fluctuates. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a two-stage photovoltaic inverter hybrid power tracking method and system for load power fluctuation, which addresses the shortcomings of the prior art and solves the technical problem that photovoltaic inverters cannot achieve source-grid dual-side power adaptation when there is no energy storage on the DC side.

[0006] The present invention adopts the following technical solution:

[0007] A two-stage photovoltaic inverter hybrid power tracking method for load power fluctuations includes the following steps:

[0008] S1. Modulation wave M under the d and q axes is obtained by using voltage and current dual closed-loop control. d M q The three-phase modulation wave M of the inverter is obtained by coordinate transformation based on the phase angle θ of the inverter reference output voltage. a M b Mc Then it is converted into a PWM duty cycle signal to achieve dual droop control of DC side voltage and frequency;

[0009] S2, Based on the output power p of the photovoltaic inverter obtained in step S1 pv_ref and the output voltage u of the photovoltaic array pv Determine the operating mode of the photovoltaic inverter, if K mpp If K < 0, continue to evaluate the values ​​of FlagMpp and FlagStb; if K mpp ≥0, read in the current photovoltaic power command value p pv_ref And determine the values ​​of FlagMpp and FlagStb;

[0010] S3. When the steady-state value of the photovoltaic inverter obtained in step S2, FlagStb, is less than 0, the photovoltaic array mode conversion is performed according to CountStb.

[0011] S4. Determine the photovoltaic current control command value based on the operating status of the photovoltaic inverter obtained in step S3, and calculate the photovoltaic port current control command value i. pv_ref According to the photovoltaic port current control command value i pv_ref and photovoltaic port current i pv By obtaining the duty cycle of the DC / DC converter before the photovoltaic inverter, power tracking control of the photovoltaic inverter without energy storage can be achieved when the load power fluctuates.

[0012] Specifically, step S1 is as follows:

[0013] S101. Determine the DC-side voltage reference value U0 of the inverter and the droop factor k. d Virtual inertia J, synchronous angular frequency w ref Given the inverter's DC-side capacitor C0, the relationship coefficient G between the photovoltaic array's input power to the inverter and the inverter's DC-side voltage is calculated. u The relationship coefficient G between the DC-side voltage and the output frequency of the inverter w ;

[0014] S102. Obtain the inverter DC-side voltage reference value U0 and sample the inverter DC-side voltage u0. Calculate the difference between u0 and U0, and use the relationship coefficient G between the photovoltaic array and the inverter's input power and DC-side voltage. u The relationship coefficient G between the DC-side voltage and the output frequency of the inverter w The output power command value p of the photovoltaic array is calculated. pv_ref Phase angle θ with the inverter reference output voltage;

[0015] S103, Sample inverter port output voltage u abc Output current i abcAfter coordinate transformation, the voltages u on the d and q axes are obtained respectively. d u q and current i d i q Then, the real-time output reactive power Q of the inverter is calculated.

[0016] S104. Based on reactive power Q and droop coefficient k d The inverter's d-axis and q-axis output reference voltages u are calculated from the inverter's AC bus rated voltage amplitude U and the virtual impedance element. d_ref u q_ref ;

[0017] S105, Obtain the inverter's d-axis and q-axis reference output voltage u. d_ref u q_ref Then, the modulation wave M under the d and q axes is obtained by using voltage and current dual closed-loop control. d M q Then, using the inverter reference output voltage phase angle θ obtained in step S102, the three-phase modulation wave M of the inverter is obtained through coordinate transformation. a M b M c Then it is converted into a PWM duty cycle signal.

[0018] Furthermore, in step S105, the inverter's three-phase modulation wave M a M b M c Specifically:

[0019]

[0020] Specifically, step S2 is as follows:

[0021] S201, The photovoltaic system samples the current output voltage u of the photovoltaic array. pv Current i pv And read in the photovoltaic port voltage u of the photovoltaic system at the previous moment. old and photovoltaic output power p old Then calculate the current output power p of the photovoltaic array. pv ;

[0022] S202, Determine u pv Is it greater than 5? If u pv If the value is less than 5, determine that the photovoltaic inverter is currently operating on the left side of MPP, i.e., FlagMpp = -1 and FlagStb = -1, and then set the photovoltaic port voltage u at this time. pv and photovoltaic output power p pv Assign a value to u old and p old The test is complete; if upv If >5, proceed to step S203;

[0023] S203, Determine whether Δu = |u pv -u old |Whether it is greater than 5, if Δu<5, exit the judgment directly; if Δu>5, proceed to step S204;

[0024] S204, Determine K mpp =(u pv -u old )·(p pv -p old Is K greater than 0? mpp If K < 0, continue to evaluate the values ​​of FlagMpp and FlagStb. mpp ≥0, read in the current photovoltaic power command value p pv_ref And determine the values ​​of FlagMpp and FlagStb.

[0025] Furthermore, in step S204, if K mpp <0, when FlagMpp<0, let u mpp =u pv i mpp =i pv p mpp =p pv Set FlagStb = 1, and simultaneously set FlagMpp = 1. Finally, set the photovoltaic port voltage u at this point. pv and photovoltaic output power p pv Assign a value to u old and p old The test is complete;

[0026] When FlagMpp ≥ 0, set FlagStb = 1 and FlagMpp = 1, and set the photovoltaic port voltage u at this time. pv and photovoltaic output power p pv Assign a value to u old and p old The test is now complete.

[0027] Furthermore, in step S204, if K mpp ≥0, when FlagMpp≤0, read p pv_ref The value of p pv <p pv_ref Let FlagStb = -1 and FlagMpp = -1, then set the photovoltaic port voltage u at this time. pv and photovoltaic output power p pv Assign a value to u old and p old The test is complete;

[0028] When p pv ≥p pv_ref Then set FlagStb = 1 and FlagMpp = -1, and set the photovoltaic port voltage u at this time. pv and photovoltaic output power p pv Assign a value to u old and p old The test is complete;

[0029] When FlagMpp > 0, let u mpp =u pv i mpp =i pv p mpp =p pv Read p pv_ref The value of p pv <p pv_ref Let FlagStb = -1 and FlagMpp = -1, and then set the photovoltaic port voltage u at this time. pv and photovoltaic output power p pv Assign a value to u old and p old The test is complete; when p pv ≥p pv_ref Set FlagStb = 1 and FlagMpp = -1, and then set the photovoltaic port voltage u at this time. pv and photovoltaic output power p pv Assign a value to u old and p old The test is now complete.

[0030] Specifically, step S3 is as follows:

[0031] S301. Obtain the steady-state value FlagStb and the state delay count value CountStb of the photovoltaic system, and determine the magnitude of FlagStb.

[0032] S302. Determine whether the steady-state value FlagStb of the photovoltaic is greater than 0. If FlagStb≥0, set the state delay count value CountStb=0 and the switching ends; if FlagStb<0, proceed to step S303.

[0033] S303. Let CountStb = CountStb + 1, and determine CountStb; if CountStb ≤ Tstb, where Tstb is a preset delay time value, let i pv_left =i mpp i pv_ref =i mpp *k rgt k rgtLet i be the gain coefficient of the current; if CountStb > Tstb, where Tstb is the preset delay time value, let i pv_left =i pv_left *k rgt i pv_ref =i pv_left k rgt This is the gain coefficient for the current; the switching is now complete.

[0034] Specifically, step S4 is as follows:

[0035] S401. After determining the operating state of the photovoltaic inverter, obtain the control command value of the photovoltaic current; if the photovoltaic inverter is operating in a steady state, FlagStb = 1, and according to the command value p of the photovoltaic array output power... pv_ref The photovoltaic port voltage u obtained by sampling pv Calculate the photovoltaic port current control command value i pv_ref If the photovoltaic array operates in an unstable state, FlagStb = -1, based on the i corresponding to the maximum power point of the photovoltaic array. mpp Obtain the photovoltaic port current control command value i pv_ref ;

[0036] S402, Based on the photovoltaic port current control command value i pv_ref and photovoltaic port current i pv Obtain the duty cycle of the DC / DC converter before the photovoltaic inverter.

[0037] Furthermore, the photovoltaic port current control command value i pv_ref Specifically:

[0038]

[0039] Where, p pv_ref u is the output power command value of the photovoltaic array. pv For the photovoltaic port voltage, i mpp Let k be the current of the photovoltaic array at its maximum power point. rgt This is the gain coefficient of the current.

[0040] Secondly, embodiments of the present invention provide a two-stage photovoltaic inverter hybrid power tracking system for load power fluctuations, comprising:

[0041] The control module uses voltage and current dual closed-loop control to obtain the modulated wave M along the d and q axes. d M q The three-phase modulation wave M of the inverter is obtained by coordinate transformation based on the phase angle θ of the inverter reference output voltage. a M b M cThen it is converted into a PWM duty cycle signal to achieve dual droop control of DC side voltage and frequency;

[0042] The working module, based on the output power p of the photovoltaic inverter obtained from the control module, pv_ref and the output voltage u of the photovoltaic array pv Determine the operating mode of the photovoltaic inverter, if K mpp If K < 0, continue to evaluate the values ​​of FlagMpp and FlagStb; if K mpp ≥0, read in the current photovoltaic power command value p pv_ref And determine the values ​​of FlagMpp and FlagStb;

[0043] When the steady-state value FlagStb of the photovoltaic inverter obtained by the working module is less than 0, the conversion module performs mode conversion of the photovoltaic array according to CountStb.

[0044] The tracking module determines the control command value of the photovoltaic current based on the operating status of the photovoltaic inverter obtained from the conversion module, and calculates the photovoltaic port current control command value i. pv_ref According to the photovoltaic port current control command value i pv_ref and photovoltaic port current i pv By obtaining the duty cycle of the DC / DC converter before the photovoltaic inverter, power tracking control of the photovoltaic inverter without energy storage can be achieved when the load power fluctuates.

[0045] Compared with the prior art, the present invention has at least the following beneficial effects:

[0046] The two-stage photovoltaic inverter hybrid power point tracking method for load power fluctuations enables the photovoltaic inverter to quickly adapt to power disturbances on both the source and load sides. Compared with the traditional PI control method based on MPP, the improved control method has a wider control range, which reduces the need for mode switching. In islanded microgrids, even without the support of other energy sources, the two-stage photovoltaic inverter can actively adapt to load demands and actively support grid voltage and frequency. Relying on mode detection and mode switching strategies, the photovoltaic inverter spontaneously changes the photovoltaic operating point in non-steady-state conditions, enabling it to adjust the output power of the photovoltaic array in real time and track load power demands without the support of external energy sources.

[0047] Furthermore, the inverter side is directly responsible for regulating the DC-side capacitor voltage, based on the relationship coefficient G between the inverter-side DC voltage and the output frequency. w The relationship coefficient G between inverter-side DC voltage and inverter input power u The command value p of the inverter reference output voltage phase angle θ and the photovoltaic array output power is obtained. pv_refThis helps photovoltaic inverters cope with the fluctuations and randomness of the output power and load power of photovoltaic arrays.

[0048] Furthermore, by transforming the fundamental sinusoidal quantity in the three-phase stationary coordinate system into a DC quantity in the synchronous rotating coordinate system, the design of the control system is simplified, allowing the inverter output d-axis voltage command value to be obtained using a traditional reactive power droop control strategy. The modulation signal obtained in the synchronous rotating coordinate system is then transformed to obtain the inverter's three-phase modulation wave M. a M b M c .

[0049] Furthermore, by comparing and calculating the current output voltage and power of the photovoltaic array with the output voltage and power at the previous moment, the current operating area and operating state of the photovoltaic array can be obtained, providing a basis for further selection of control strategies for the photovoltaic inverter.

[0050] Furthermore, a more detailed classification of the situation when the photovoltaic array operates to the left of the maximum power point is beneficial for the system to correctly judge the operating conditions and select appropriate control strategies to cope with changes in environmental conditions and the conditions of the photovoltaic power source itself.

[0051] Furthermore, a more detailed classification of the situation when the photovoltaic array operates to the right of the maximum power point is beneficial for the system to correctly judge the operating conditions and select appropriate control strategies to cope with changes in environmental conditions and the conditions of the photovoltaic power source itself.

[0052] Furthermore, the detailed strategy for mode switching of photovoltaic inverters is as follows: if the photovoltaic inverter is operating in a stable region, mode switching is not required; if the photovoltaic inverter is operating in an unstable region, the operating point is moved to a stable region through a control strategy.

[0053] Furthermore, based on the operating state of the photovoltaic inverter, control command reference values ​​are given to achieve control of the upstream DC / DC converter of the photovoltaic inverter.

[0054] Furthermore, the photovoltaic port current control command value i is given. pv_ref Detailed calculation method.

[0055] It is understandable that the beneficial effects of the second aspect mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0056] In summary, this invention, by judging the working area and working mode of the photovoltaic array, achieves rapid tracking of source load power while supporting grid voltage and frequency; it reduces the photovoltaic microgrid's dependence on energy storage devices, enabling it to actively adapt to the randomness and volatility of load and photovoltaics.

[0057] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0058] Figure 1 This is a schematic diagram of the pattern detection process of the method of the present invention;

[0059] Figure 2 This is a schematic diagram of the mode switching process of the method of the present invention;

[0060] Figure 3 The following are simulation waveforms of the method of the present invention under various operating conditions, wherein (a) is the active power output of the photovoltaic cell and the inverter, (b) is the DC bus voltage of the photovoltaic inverter, (c) is the port output voltage of the photovoltaic cell, (d) is the photovoltaic inverter flag used to indicate the operating status and stability of the MPP, and (e) is the three-phase output voltage of the photovoltaic inverter. Detailed Implementation

[0061] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0063] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0064] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" relationship.

[0065] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0066] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0067] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0068] This invention provides a two-stage photovoltaic inverter hybrid power tracking method for load power fluctuations. By combining mode detection and mode switching control strategies during photovoltaic power fluctuations, it can achieve rapid power tracking when the load power changes and the characteristic curve of the photovoltaic array changes in a photovoltaic islanded microgrid. It also actively supports the voltage frequency of the AC bus, enabling the photovoltaic inverter to handle power disturbances from both the source and load sides simultaneously.

[0069] This invention discloses a hybrid power tracking method for a two-stage photovoltaic inverter with fluctuating load power, comprising the following steps:

[0070] S1, Dual droop control of DC side voltage and frequency;

[0071] S101. Determine the DC-side voltage reference value U0 of the inverter and the droop factor k. d Virtual inertia J, synchronous angular frequency w ref The inverter's DC-side capacitor C0 is used to calculate the relationship coefficient G between the photovoltaic array's input power to the inverter and the inverter's DC-side voltage. u The relationship coefficient G between the DC-side voltage and the output frequency of the inverter w The calculation formula is as follows:

[0072]

[0073] S102. Obtain the inverter DC-side voltage reference value U0 and sample the inverter DC-side voltage u0. Calculate the difference between u0 and U0, and use the relationship coefficient G between the photovoltaic array and the inverter's input power and DC-side voltage. u The relationship coefficient G between the DC-side voltage and the output frequency of the inverter w The output power command value p of the photovoltaic array is calculated. pv_ref Phase angle θ with the inverter reference output voltage;

[0074] The calculation formula is as follows:

[0075]

[0076] S103, Sample inverter port output voltage u abc Output current i abc After coordinate transformation, the voltages u on the d and q axes are obtained respectively. d u q and current i d i q Then, the real-time output reactive power Q of the inverter is calculated.

[0077] The expression for the abc / dq transformation module is as follows:

[0078]

[0079] Among them, i a i b i c These are the values ​​of the inverter output current in the abc three-phase stationary coordinate system, i. d i q Let u be the value of the inverter output current in the dq synchronous rotating coordinate system. a u b u c These are the inverter output voltage values ​​in the abc three-phase stationary coordinate system, u and u. d u q θ represents the inverter output voltage in the dq synchronous rotating coordinate system, where θ is the angle between the d-axis and the phase reference axis.

[0080] The formula for calculating reactive power is as follows:

[0081] Q = 1.5 × (v q ·i d -v d ·i q )

[0082] S104. Based on reactive power Q and droop coefficient k dThe inverter's d-axis and q-axis output reference voltages u are calculated from the inverter's AC bus rated voltage amplitude U and the virtual impedance element. d_ref u q_ref ;

[0083] The calculation formula is as follows:

[0084]

[0085] Among them, L v Here, U is the virtual impedance, U is the rated voltage amplitude of the inverter's AC bus, Q is the reactive power, and k is the voltage across the inverter. d w is the droop coefficient. ref i is the synchronization angular frequency. d i q This represents the inverter output current in the dq synchronous rotating coordinate system.

[0086] S105, Obtain the inverter's d-axis and q-axis reference output voltage u. d_ref u q_ref Then, the modulation wave M under the d and q axes is obtained by using voltage and current dual closed-loop control. d M q Then, using the inverter reference output voltage phase angle θ obtained in step S102, the three-phase modulation wave M of the inverter is obtained through coordinate transformation. a M b M c Then it is converted into a PWM duty cycle signal.

[0087] The formula for calculating the current command generated by the voltage outer loop control module is as follows:

[0088]

[0089] Among them, i d_ref with i q_ref These are the reference values ​​for the active component and reactive component of the inverter output current, respectively, k p_du k is the value of the proportional controller of the PI regulator for the active component of the inverter output voltage. i_du k is the value of the PI regulator integral controller for the active component of the inverter output voltage. p_qu k is the value of the PI regulator proportional controller for the reactive component of the inverter output voltage. i_qu The value of u is the integral controller value of the PI regulator for the reactive component of the inverter output voltage. d_ref u is the reference value for the active component of the inverter output voltage. d u is the active component of the inverter output voltage. q_ref u is the reference value for the reactive component of the inverter output voltage. q This represents the reactive component of the inverter output voltage.

[0090] The formula for calculating the modulation signal generated by the current inner loop control module is as follows:

[0091]

[0092] Among them, M d M q Generate modulation command values ​​for the d-axis current inner loop and the q-axis current inner loop, k p_di k i_di These represent the values ​​of the proportional controller and integral controller of the d-axis current inner loop PI regulator, respectively, k. p_qi k i_qi These are the values ​​of the proportional controller and integral controller of the q-axis current inner loop PI regulator, respectively.

[0093] The obtained M d and M q Perform an inverse dq / abc transform to generate the driving PWM signal. The calculation formula is as follows:

[0094]

[0095] S2, Detection of the operating modes of the photovoltaic array;

[0096] Please see Figure 1 The specific testing process is as follows:

[0097] S201, The photovoltaic system samples the current output voltage u of the photovoltaic array. pv Current i pv And read in the photovoltaic port voltage u of the photovoltaic system at the previous moment. old and photovoltaic output power p old Then calculate the current output power p of the photovoltaic array. pv ;

[0098] p pv The calculation formula is:

[0099] p pv =u pv *i pv

[0100] S202, Determine u pv Is it greater than 5? If u pv If the value is less than 5, determine that the photovoltaic inverter is currently operating on the left side of MPP, i.e., FlagMpp = -1 and FlagStb = -1, and then set the photovoltaic port voltage u at this time. pv and photovoltaic output power p pv Assign a value to u old and p old The test is complete; if u pv If >5, proceed to step S203;

[0101] S203, Determine whether Δu = |u pv -u old |Whether it is greater than 5, if Δu<5, exit the judgment directly; if Δu>5, proceed to step S204;

[0102] S204, Determine K mpp =(u pv -u old )·(p pv -p old Is it greater than 0?

[0103] S2041, if K mpp If the value is less than 0, continue to check the values ​​of FlagMpp and FlagStb.

[0104] When FlagMpp < 0, let u mpp =u pv i mpp =i pv p mpp =p pv Set FlagStb = 1, and simultaneously set FlagMpp = 1. Finally, set the photovoltaic port voltage u at this point. pv and photovoltaic output power p pv Assign a value to u old and p old The test is complete;

[0105] When FlagMpp ≥ 0, set FlagStb = 1 and FlagMpp = 1, and set the photovoltaic port voltage u at this time. pv and photovoltaic output power p pv Assign a value to u old and p old The test is complete;

[0106] S2042, if K mpp ≥0, read in the current photovoltaic power command value p pv_ref And determine the values ​​of FlagMpp and FlagStb;

[0107] When FlagMpp≤0, read p pv_ref The values ​​are as follows:

[0108] When p pv <p pv_ref Let FlagStb = -1 and FlagMpp = -1, then set the photovoltaic port voltage u at this time. pv and photovoltaic output power p pv Assign a value to u old and p old The test is complete;

[0109] When p pv ≥p pv_ref Then set FlagStb = 1 and FlagMpp = -1, and set the photovoltaic port voltage u at this time. pv and photovoltaic output power p pv Assign a value to u old and p old The test is complete;

[0110] When FlagMpp > 0, let u mpp =u pv i mpp =i pv p mpp =p pv Read p pv_ref The values ​​are as follows:

[0111] If p pv <p pv_ref Then set FlagStb = -1 and FlagMpp = -1, and set the photovoltaic port voltage u at this time. pv and photovoltaic output power p pv Assign a value to u old and p old The test is complete;

[0112] When p pv ≥p pv_ref Then set FlagStb = 1 and FlagMpp = -1, and set the photovoltaic port voltage u at this time. pv and photovoltaic output power p pv Assign a value to u old and p old The test is now complete.

[0113] S3, photovoltaic array mode conversion;

[0114] Please see Figure 2 The specific mode switching process is as follows:

[0115] S301. Obtain the steady-state value FlagStb and the state delay count value CountStb of the photovoltaic system, and determine the magnitude of FlagStb.

[0116] S302. Determine whether the steady-state value FlagStb of the photovoltaic is greater than 0. If FlagStb≥0, set the state delay count value CountStb=0 and the switching ends; if FlagStb<0, proceed to step S303.

[0117] S303. Let CountStb = CountStb + 1, and determine CountStb; if CountStb ≤ Tstb, where Tstb is a preset delay time value, let i pv_left =i mpp i pv_ref =i mpp *k rgt k rgt Let i be the gain coefficient of the current; if CountStb > Tstb, where Tstb is the preset delay time value, let i pv_left =i pv_left *k rgt i pv_ref =i pv_left k rgt This is the gain coefficient for the current; the switching is now complete.

[0118] S4, tracking of specific photovoltaic power command values ​​for the front-end Boost converter.

[0119] S401. After determining the operating state of the photovoltaic inverter, obtain the control command value of the photovoltaic current; if the photovoltaic inverter is operating in a steady state, FlagStb = 1, and according to the command value p of the photovoltaic array output power... pv_ref The photovoltaic port voltage u obtained by sampling pv Calculate the photovoltaic port current control command value i pv_ref If the photovoltaic array operates in an unstable state, FlagStb = -1, based on the i corresponding to the maximum power point of the photovoltaic array. mpp Obtain the photovoltaic port current control command value i pv_ref ;

[0120] Photovoltaic port current control command value i pv_ref The calculation is as follows:

[0121]

[0122] S402, Based on the photovoltaic port current control command value i pv_ref and photovoltaic port current i pv By obtaining the duty cycle of the DC / DC converter in front of the photovoltaic inverter, a fast power point tracking control strategy for photovoltaic inverters without energy storage can be implemented when the load power fluctuates.

[0123] In another embodiment of the present invention, a two-stage photovoltaic inverter hybrid power tracking system with load power fluctuation is provided. This system can be used to implement the above-mentioned two-stage photovoltaic inverter hybrid power tracking method with load power fluctuation. Specifically, the two-stage photovoltaic inverter hybrid power tracking system with load power fluctuation includes a control module, a working module, a conversion module, and a tracking module.

[0124] The control module utilizes dual closed-loop control of voltage and current to obtain the modulation wave M along the d and q axes. d M q The three-phase modulation wave M of the inverter is obtained by coordinate transformation based on the phase angle θ of the inverter reference output voltage. a M b M c Then it is converted into a PWM duty cycle signal to achieve dual droop control of DC side voltage and frequency;

[0125] The working module, based on the output power p of the photovoltaic inverter obtained from the control module, pv_ref and the output voltage u of the photovoltaic array pv Determine the operating mode of the photovoltaic inverter, if K mpp If K < 0, continue to evaluate the values ​​of FlagMpp and FlagStb; if K mpp ≥0, read in the current photovoltaic power command value p pv_ref And determine the values ​​of FlagMpp and FlagStb;

[0126] When the steady-state value FlagStb of the photovoltaic inverter obtained by the working module is less than 0, the conversion module performs mode conversion of the photovoltaic array according to CountStb.

[0127] The tracking module determines the control command value of the photovoltaic current based on the operating status of the photovoltaic inverter obtained from the conversion module, and calculates the photovoltaic port current control command value i. pv_ref According to the photovoltaic port current control command value i pv_ref and photovoltaic port current i pv By obtaining the duty cycle of the DC / DC converter before the photovoltaic inverter, power tracking control of the photovoltaic inverter without energy storage can be achieved when the load power fluctuates.

[0128] In another embodiment of the present invention, a terminal device is provided, comprising a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions to achieve a corresponding method flow or corresponding function. The processor described in this embodiment can be used in the operation of a two-stage photovoltaic inverter hybrid power tracking method for load power fluctuations, including:

[0129] The modulation wave M in the d and q axes is obtained by using voltage and current dual closed-loop control. d M q The three-phase modulation wave M of the inverter is obtained by coordinate transformation based on the phase angle θ of the inverter reference output voltage. a M b M c Then it is converted into a PWM duty cycle signal to achieve dual droop control of DC side voltage and frequency; based on the output power p of the photovoltaic inverter pv_ref and the output voltage u of the photovoltaic array pv Determine the operating mode of the photovoltaic inverter, if K mpp If K < 0, continue to evaluate the values ​​of FlagMpp and FlagStb; if K mpp ≥0, read in the current photovoltaic power command value p pv_ref The values ​​of FlagMpp and FlagStb are determined; when the steady-state value of the photovoltaic inverter, FlagStb, is less than 0, the photovoltaic array mode conversion is performed based on CountStb; the control command value of the photovoltaic current is determined based on the operating state of the photovoltaic inverter, and the photovoltaic port current control command value i is calculated. pv_ref According to the photovoltaic port current control command value i pv_ref and photovoltaic port current i pv By obtaining the duty cycle of the DC / DC converter before the photovoltaic inverter, power tracking control of the photovoltaic inverter without energy storage can be achieved when the load power fluctuates.

[0130] In another embodiment of the present invention, a storage medium is also provided, specifically a computer-readable storage medium (memory). This computer-readable storage medium is a memory device in a terminal device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and extended storage media supported by the terminal device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device.

[0131] One or more instructions stored in a computer-readable storage medium can be loaded and executed by a processor to implement the corresponding steps of the two-stage photovoltaic inverter hybrid power tracking method for load power fluctuations in the above embodiments; one or more instructions in the computer-readable storage medium are loaded and executed by the processor in the following steps:

[0132] The modulation wave M in the d and q axes is obtained by using voltage and current dual closed-loop control. d M q The three-phase modulation wave M of the inverter is obtained by coordinate transformation based on the phase angle θ of the inverter reference output voltage. a M b M c Then it is converted into a PWM duty cycle signal to achieve dual droop control of DC side voltage and frequency; based on the output power p of the photovoltaic inverter pv_ref and the output voltage u of the photovoltaic array pv Determine the operating mode of the photovoltaic inverter, if K mpp If K < 0, continue to evaluate the values ​​of FlagMpp and FlagStb; if K mpp ≥0, read in the current photovoltaic power command value p pv_ref The values ​​of FlagMpp and FlagStb are determined; when the steady-state value of the photovoltaic inverter, FlagStb, is less than 0, the photovoltaic array mode conversion is performed based on CountStb; the control command value of the photovoltaic current is determined based on the operating state of the photovoltaic inverter, and the photovoltaic port current control command value i is calculated. pv_ref According to the photovoltaic port current control command value i pv_ref and photovoltaic port current i pv By obtaining the duty cycle of the DC / DC converter before the photovoltaic inverter, power tracking control of the photovoltaic inverter without energy storage can be achieved when the load power fluctuates.

[0133] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0134] To test this invention, a dual-machine parallel simulation model was built in PLECS. This model operates under islanded conditions, using photovoltaic cells as the sole energy source. Electricity is fed into the grid through a two-stage inverter consisting of a boost converter, inverter, and filter. The two sets of inverters are connected in parallel to verify the control method under photovoltaic power fluctuations and load changes.

[0135] 1.5 seconds ago, both photovoltaic inverters were stably supporting the AC bus and supplying power to the load, with a load of 7.25kW for both inverters. The characteristic curve parameters of the photovoltaic array are as follows: U1 ocref 400V, U mref 320V, p mpp For 11.5kW, PV2 U ocref 400V, U mref 320V, p mpp The MPP power is 11.5kW. This is sufficient to meet the power allocation of each inverter, such as... Figure 3 As shown in (a), the output power and voltage are stable and meet the design requirements.

[0136] At 1.5s, the output characteristics of the photovoltaic array of PV1 change. ocref Upgraded to 600V, U mref Upgraded to 480V, p mpp The output power was increased to 17.8kW. Because the characteristic curve of the photovoltaic array changed, the output power at the same voltage value differed, causing the output power of the photovoltaic array to exceed the load power. Through a mode detection switching method, the inverter PV1 recalculated the photovoltaic array port current command value to track the load power, quickly bringing the output power of the photovoltaic array to match the load power, achieving stability. Figure 3 As shown in (a). Figure 3 (b) and 3(c) show that the DC bus voltage of the photovoltaic inverter and the output power of the photovoltaic array can quickly reach stable values ​​during the switching process. Figure 3 (d) shows the changes in the operating status and stability indicators during the switching process. The output characteristics of PV1's photovoltaic array recovered at 2.5s, and PV1 quickly returned to normal operating status. Between 2.5 and 4s, both photovoltaic inverters operated stably under normal conditions.

[0137] At 4 seconds, the load increased to 26.6kW, and the maximum power of PV1 (11.5kW) could not meet the allocated power (13.3kW). Therefore, inverter PV1 operated in MPP mode, and inverter PV2 provided the remaining power of PV1. Specifically, the mode detection method detected that the photovoltaic inverter was in an unstable state and updated the corresponding flags. Inverter PV1 then switched to MPP mode via a mode switching method, while inverter PV2 automatically took over the remaining load power. Figure 3 (a) It can be seen that when the load increases by 4s, photovoltaic inverters PV1 and PV2 can track the load power well and quickly maintain stability. From Figure 3 The simulation results show that the photovoltaic inverter can smoothly switch to MPP mode without introducing interference during the switching process. At 8 seconds, the load is reduced, and the power again meets the requirements of PV1. After detecting the reduced load power, the photovoltaic inverter returns to normal operation. At 7 seconds, the load is reduced again, and the load power is less than the MPP of PV1. After detecting the reduced load power, the photovoltaic inverter quickly returns to normal operation.

[0138] In summary, this invention provides a two-stage photovoltaic inverter hybrid power point tracking method and system for load power fluctuations. In islanded microgrids, when power disturbances occur on both the source and load sides due to photovoltaic randomness, the photovoltaic inverter can update the port current command tracking value through mode detection and mode switching control strategies. This achieves rapid tracking and balancing of the photovoltaic array output power with the load power, and outputs a stable AC bus voltage and frequency during the tracking process. When multiple inverters are connected in parallel, if the power of the photovoltaic inverter's MPP (Multi-Level Power Point) is insufficient to balance the load power, it can quickly switch to MPP mode, with the missing load power provided by other photovoltaic inverters in the system. This improves the flexibility of photovoltaic inverters in photovoltaic microgrids and their reliability in future renewable energy applications.

[0139] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0140] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0141] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0142] In the embodiments provided by this invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0143] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0144] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0145] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.

[0146] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0147] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0148] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0149] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A two-stage photovoltaic inverter hybrid power tracking method for load power fluctuations, characterized in that, Includes the following steps: S1, obtained using voltage and current dual closed-loop control. , Modulated wave under axis , Based on the inverter reference output voltage phase angle The three-phase modulation wave of the inverter is obtained through coordinate transformation. , , Then it is converted into a PWM duty cycle signal to achieve dual droop control of DC side voltage and frequency; S2. Based on the current photovoltaic power command value of the photovoltaic inverter obtained in step S1. and the output voltage of the photovoltaic array Determine the operating mode of the photovoltaic inverter, if Continue to judge and The value; if Read in the current photovoltaic power command value of the photovoltaic inverter. And judge and The value; S3, the steady-state operating value of the photovoltaic inverter obtained in step S2 ,according to The photovoltaic array undergoes mode conversion, specifically as follows: S301, Obtain steady-state values ​​of photovoltaic operation and state delay count value ,judge size; S302. Determine the steady-state operating value of photovoltaics. Is it greater than 0? Set the state delay count value The switch is complete; if Then proceed to step S303; S303, Order ,judge ;like , Let the preset delay time value be... , , Let be the gain coefficient of the current; if , Let the preset delay time value be... , , This is the gain coefficient for the current; the switching ends. S4. Determine the control command value of the photovoltaic current based on the operating status of the photovoltaic inverter obtained in step S3, and calculate the photovoltaic port current control command value. According to the photovoltaic port current control command value and photovoltaic port current By obtaining the duty cycle of the DC / DC converter preceding the photovoltaic inverter, power point tracking control of the photovoltaic inverter without energy storage can be achieved during load power fluctuations. Specifically: S401. After determining the operating state of the photovoltaic inverter, the control command value of the photovoltaic current is obtained; if the photovoltaic inverter is operating in a stable state, Based on the current photovoltaic power command value of the photovoltaic inverter The photovoltaic port voltage obtained by sampling Calculate the photovoltaic port current control command value If the photovoltaic array is operating in an unstable state, According to the maximum power point of the photovoltaic array Obtain the photovoltaic port current control command value ; S402, Based on the photovoltaic port current control command value and photovoltaic port current Obtain the duty cycle of the DC / DC converter before the photovoltaic inverter.

2. The two-stage photovoltaic inverter hybrid power tracking method for load power fluctuations according to claim 1, characterized in that, Step S1 is as follows: S101. Determine the reference value of the DC side voltage of the inverter. droop coefficient Virtual inertia Synchronous angular frequency DC-side capacitor of inverter The relationship coefficient between the input power of the photovoltaic array to the inverter and the DC-side voltage of the inverter was calculated. The relationship coefficient between the DC-side voltage and the output frequency of the inverter ; S102. Obtain the DC-side voltage reference value of the inverter. and sampling inverter DC side voltage ,Will and The difference is used to calculate the relationship between the input power of the inverter and the DC-side voltage of the inverter based on the photovoltaic array. The relationship coefficient between the DC-side voltage and the output frequency of the inverter The current photovoltaic power command value of the photovoltaic inverter is calculated. Phase angle with inverter reference output voltage ; S103, Sample inverter port output voltage Output current After coordinate transformation, the following were obtained: , shaft voltage , and current , Then, the real-time output reactive power of the inverter is calculated. ; S104, Based on reactive power Sag coefficient Inverter AC bus rated voltage amplitude Inverter is obtained by calculating virtual impedance. , Shaft output reference voltage , ; S105, Obtain the inverter , Shaft reference output voltage , Then, voltage and current dual closed-loop control was used to obtain... , Modulated wave under axis , Then, using the inverter reference output voltage phase angle obtained in step S102... The three-phase modulation wave of the inverter is obtained after coordinate transformation. , , Then it is converted into a PWM duty cycle signal.

3. The two-stage photovoltaic inverter hybrid power tracking method for load power fluctuations according to claim 2, characterized in that, In step S105, the inverter's three-phase modulation wave , , Specifically: 。 4. The two-stage photovoltaic inverter hybrid power tracking method for load power fluctuations according to claim 1, characterized in that, Step S2 is as follows: S201, The photovoltaic system samples the current output voltage of the photovoltaic array. Current And read in the photovoltaic port voltage of the photovoltaic system at the previous moment. and photovoltaic output power Then calculate the current output power of the photovoltaic array. ; S202. Judgment Is it greater than 5? Then it is determined that the photovoltaic inverter is currently operating on the left side of the MPP. , and the photovoltaic port voltage at this time and photovoltaic output power Assign to as well as The test is complete; if Then proceed to step S203; S203. Judgment Is it greater than 5? Then exit the judgment directly; if Then proceed to step S204; S204. Judgment Is it greater than 0? Continue to judge and The value, if Read in the current photovoltaic power command value of the photovoltaic inverter. And judge and The value of .

5. The two-stage photovoltaic inverter hybrid power tracking method for load power fluctuations according to claim 4, characterized in that, In step S204, if ,when ,make , , , At the same time, let Finally, the photovoltaic port voltage at this time and photovoltaic output power Assign to as well as The test is complete; when Then let , and the photovoltaic port voltage at this time and photovoltaic output power Assign to as well as The test is now complete.

6. The two-stage photovoltaic inverter hybrid power tracking method for load power fluctuations according to claim 4, characterized in that, In step S204, if ,when , read in The value when ,make , The photovoltaic port voltage at this time and photovoltaic output power Assign to as well as The test is complete; when Then let , and the photovoltaic port voltage at this time and photovoltaic output power Assign to as well as The test is complete; when ,make , , , read in The value, if ,make , and the photovoltaic port voltage at this time and photovoltaic output power Assign to as well as The test is over; when ,make , and the photovoltaic port voltage at this time and photovoltaic output power Assign to as well as The test is now complete.

7. The two-stage photovoltaic inverter hybrid power tracking method for load power fluctuations according to claim 1, characterized in that, Photovoltaic port current control command value Specifically: in, This refers to the photovoltaic port voltage. This refers to the current at the maximum power point of the photovoltaic array. This is the gain coefficient of the current.

8. A two-stage photovoltaic inverter hybrid power tracking system for load power fluctuations, characterized in that, include: The control module utilizes dual closed-loop control of voltage and current to obtain... , Modulated wave under axis , Based on the inverter reference output voltage phase angle The three-phase modulation wave of the inverter is obtained through coordinate transformation. , , Then it is converted into a PWM duty cycle signal to achieve dual droop control of DC side voltage and frequency; The working module, based on the current photovoltaic power command value of the photovoltaic inverter obtained from the control module, and the output voltage of the photovoltaic array Determine the operating mode of the photovoltaic inverter, if Continue to judge and The value; if Read in the current photovoltaic power command value And judge and The value; The conversion module, when the working module obtains the steady-state operating value of the photovoltaic inverter... ,according to The photovoltaic array undergoes mode conversion, specifically as follows: S301, Obtain steady-state values ​​of photovoltaic operation and state delay count value ,judge size; S302. Determine the steady-state operating value of photovoltaics. Is it greater than 0? Set the state delay count value The switch is complete; if Then proceed to step S303; S303, Order ,judge ;like , Let the preset delay time value be... , , Let be the gain coefficient of the current; if , Let the preset delay time value be... , , This is the gain coefficient for the current; the switching ends. The tracking module determines the control command value of the photovoltaic current based on the operating status of the photovoltaic inverter obtained from the conversion module, and calculates the control command value of the photovoltaic port current. According to the photovoltaic port current control command value and photovoltaic port current By obtaining the duty cycle of the DC / DC converter preceding the photovoltaic inverter, power point tracking control of the photovoltaic inverter without energy storage can be achieved during load power fluctuations. Specifically: S401. After determining the operating state of the photovoltaic inverter, the control command value of the photovoltaic current is obtained; if the photovoltaic inverter is operating in a stable state, Based on the current photovoltaic power command value of the photovoltaic inverter The photovoltaic port voltage obtained by sampling Calculate the photovoltaic port current control command value If the photovoltaic array is operating in an unstable state, According to the maximum power point of the photovoltaic array Obtain the photovoltaic port current control command value ; S402, Based on the photovoltaic port current control command value and photovoltaic port current Obtain the duty cycle of the DC / DC converter before the photovoltaic inverter.

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