A multi-loop nested PV control method

Abstract

This invention discloses a multi-loop nested PV control method, comprising the following steps: loop configuration; the core architecture of the MPPT system includes an input current loop, an input voltage loop, an output voltage loop, and an output current loop; calculating the output target value of the input current loop and transmitting the output result to the output voltage loop; calculating the output target value of the output current loop and transmitting the output result to the output voltage loop; calculating the output target value of the input voltage loop and transmitting the output result to the output voltage loop; calculating the output target value of the output voltage loop; and adjusting the duty cycle of the PWM modulation control switching device based on the output target value of the output voltage loop. The above-mentioned four-loop nested control scheme applies the calculation results of the three loops to one loop as an influencing factor for single-voltage loop calculation, thereby outputting a single control result. This eliminates competition and makes loop tracking control more stable.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic power generation system technology, and specifically to a multi-loop nested PV control method. Background Technology

[0002] With the growth of global energy demand and the increasing awareness of environmental protection, photovoltaic (PV) power generation, as a clean and renewable energy technology, has become an important component of the new energy system. PV power generation systems directly convert light energy into electrical energy through photovoltaic cells. Their core components include PV arrays, inverters, and maximum power point tracking (MPPT) controllers. The power output characteristics of a PV array are significantly affected by factors such as light intensity, temperature, and shading. Its PV curve has a unique maximum power point (MPPT) under specific environmental conditions. When external conditions change, if the actual operating point of the PV array deviates from the MPPT, the power generation efficiency will decrease significantly. Therefore, MPPT technology, by adjusting the system's operating voltage or current in real time, ensures that the PV array always operates at its maximum power point, making it a key technology for improving the overall power generation of the system.

[0003] For traditional single-loop control methods, such as Figure 1 As shown, the traditional method uses four loops to calculate separately and takes the minimum value after competition. This can lead to loop switching under critical conditions, resulting in unstable loop tracking control. Summary of the Invention

[0004] Therefore, it is necessary to provide a more stable multi-loop nested PV control method for loop tracking control.

[0005] A multi-loop nested PV control method, the method comprising the following steps:

[0006] Step 1, Loop Configuration; The core architecture of the MPPT system includes the input current loop, input voltage loop, output voltage loop, and output current loop;

[0007] Step 2: Calculate the target output value of the input current loop and transmit the output result to the output voltage loop;

[0008] Step 3: Calculate the target output value of the output current loop and transmit the output result to the output voltage loop;

[0009] Step 4: Calculate the target output value of the input voltage loop and transmit the output result to the output voltage loop;

[0010] Step 5: Calculate the target output value of the output voltage loop;

[0011] Step 6: Adjust the duty cycle of the PWM modulation control switching device according to the target output value of the output voltage loop.

[0012] Preferably, the loop functions of the input current loop, input voltage loop, output voltage loop, and output current loop in step one are as follows:

[0013] The input current loop is used to monitor whether the input current of the PV exceeds the maximum limit that the power module with PV can withstand, limit the maximum input current of the PV, and make the power module with PV operate within the normal range.

[0014] The input voltage loop is used to monitor the input voltage of the PV and stabilize the system output near the maximum power point by comparing it with the preset maximum power point voltage.

[0015] The output voltage loop is used to stabilize the output voltage of the power module with PV. It obtains the error value by comparing the target value and the actual value of the output voltage, and controls the output voltage to be stable through PI calculation to ensure that the battery is not over-voltaged.

[0016] The output current loop is used to stabilize the output current of the PV power module. It compares the set target current value with the actual value and uses PI calculation to stabilize the current and protect the battery cells from impact.

[0017] Preferably, the specific steps for calculating the output target value of the input current loop in step two include:

[0018] Step 2.1: Sample the input current value in real time; obtain the actual input current value ADC_PV_Iin through the ADC analog-to-digital converter;

[0019] Step 2.2, calculate the error value; compare the sampled value ADC_PV_Iin with the preset maximum allowable input current PV_Iinref to obtain the error value Error_Iin, as shown in equation (1);

[0020] Error_Iin = PV_Iinref - ADC_PV_Iin (1);

[0021] Step 2.3: PI operation generates control signal; PI operation is performed on the error value Error_Iin, as shown in equation (2):

[0022] PV_Iinresult = Kp⋅Error_Iin + Ki⋅∫Error_Iindt (2);

[0023] Where PV_Iinresult is the final result of the input current loop, Error_Iin is the error value, Kp is the coefficient of the proportional part, and Ki is the coefficient of the integral part;

[0024] Step 2.4, Output target value transfer; obtain the final result of the input current loop PV_Iinresult, and transfer the final result of the input current loop PV_Iinresult into the output voltage loop.

[0025] Preferably, the specific steps for calculating the target output value of the output current loop in step three include:

[0026] Step 3.1: Sample the output current value in real time; obtain the actual output current value ADC_Iout at the battery terminal or load terminal through the ADC analog-to-digital converter;

[0027] Step 3.2, calculate the error value; compare the sampled value ADC_Iout with the preset target output current value Ioutref to obtain the error value Error_Iout, as shown in equation (3):

[0028] Error_Iout = Ioutref - ADC_Iout (3);

[0029] Step 3.3: PI operation generates control signal; PI operation is performed on the error value Error_Iout, as shown in equation (4):

[0030] Ioutresult = Kp⋅Error_Iout + Ki⋅∫Error_Ioutdt (4);

[0031] Where Ioutresult is the final result of the output current loop, Error_Iout is the error value, Kp is the coefficient of the proportional part, and Ki is the coefficient of the integral part;

[0032] Step 3.4, Output target value transfer; obtain the final result Ioutresult of the output current loop, and transfer the final result Ioutresult of the output current loop into the output voltage loop.

[0033] Preferably, the specific steps for calculating the target output value of the input voltage loop in step four include:

[0034] Step 4.1: Calculate the instantaneous power Pin using the input voltage and input current of PV sampled in real time by the ADC;

[0035] Step 4.2: Track the maximum power point using the perturbation observation method. Compare the calculated instantaneous power Pin with the previously tracked instantaneous power Pre_Pin. If Pin is higher than Pre_Pin, increase the target value PV_Vinref; otherwise, decrease the target value PV_Vinref. Drive the system toward the maximum power point and dynamically estimate the target voltage PV_Vinref corresponding to the maximum power point.

[0036] Step 4.3: Subtract the PV input voltage ADC_PV_Vin sampled by the ADC in real time from the target value PV_Vinref that the system needs to achieve to obtain the error value Error_PV_Vin, as shown in equation (6):

[0037] Error_PV_Vin = ADC_PV_Vin - PV_Vinref(6);

[0038] Step 4.4: After PI calculation, the final result of the input voltage loop, PV_Vinresult, is obtained; the final result of the input voltage loop, PV_Vinresult, is then sent into the output voltage loop.

[0039] The calculation of the final result PV_Vinresult of the input voltage loop is shown in equation (7):

[0040] PV_Vinresult = Kp⋅Error_PV_Vin + Ki⋅∫Error_PV_Vindt(7);

[0041] Where PV_Vinresult is the final result of the input voltage loop, Error_PV_Vin is the error value, Kp is the coefficient of the proportional part, and Ki is the coefficient of the integral part.

[0042] Preferably, the specific steps for calculating the target output value of the output voltage loop in step five include:

[0043] Step 5.1: Sample the output voltage value in real time; obtain the actual output voltage ADC_Vout at the battery terminal or load terminal through the ADC analog-to-digital converter;

[0044] Step 5.2, calculate the error value; compare the sampled value ADC_Vout with the preset target output voltage value Voutref, add the final result of the input current loop PV_Iinresult, the final result of the input voltage loop PV_Vinresult, and the final result of the output current loop Ioutresult to obtain the error value Error_Vout, and perform nested processing;

[0045] The formula for calculating the error value Error_Vout is shown in equation (8):

[0046] Error_Vout = Voutref - ADC_Vout + PV_Iinresult

[0047] + Ioutresult + PV_Vinresult(8);

[0048] Step 5.3: PI calculation generates control signals; PI calculation is performed on the error value Error_Vout to obtain the final output voltage loop result Voutresult;

[0049] The PI operation is shown in equation (9):

[0050] Voutresult = Kp⋅Error_Vout + Ki⋅∫Error_Voutdt(9);

[0051] Where Voutresult is the final result of the output voltage loop, Error_Vout is the error value, Kp is the coefficient of the proportional part, and Ki is the coefficient of the integral part.

[0052] Preferably, step six, adjusting the duty cycle of the PWM modulation control switching device based on the target output value of the output voltage loop, includes the following specific steps:

[0053] Step 6.1: Multiply the target output value of the output voltage loop by the counting period of the PWM module to obtain the adjustment coefficient of the PWM signal;

[0054] Step 6.2: The adjustment coefficient of the PWM signal is transmitted to the PWM module to obtain the adjusted modulation signal PWM, so as to adjust the duty cycle of the control switching device.

[0055] The aforementioned multi-loop nested PV control method overcomes the limitations of traditional methods through multi-level collaborative control, dynamic parameter optimization, and intelligent algorithm integration, achieving efficient and stable power point tracking in complex scenarios and providing a new path for improving the performance of photovoltaic power generation systems. The four-loop nested control scheme in this application applies the calculation results of three loops to one loop as an influencing factor for single-voltage loop calculation, thereby outputting a single control result. This eliminates competition and makes loop tracking control more stable. The method of this invention is simple, easy to implement, low-cost, and easy to promote. Attached Figure Description

[0056] Figure 1 This is a flowchart of the traditional four-ring road calculation process in existing technologies.

[0057] Figure 2 This is a flowchart of a multi-loop nested PV control method according to an embodiment of the present invention. Detailed Implementation

[0058] This embodiment takes a multi-loop nested PV control method as an example. The invention will be described in detail below with reference to specific embodiments and accompanying drawings.

[0059] Please see Figure 2This illustrates a multi-loop nested PV control method provided by an embodiment of the present invention, the method comprising the following steps:

[0060] Step S10, Loop Configuration; The core architecture of the MPPT system includes an input current loop, an input voltage loop, an output voltage loop, and an output current loop.

[0061] The input current loop, input voltage loop, output voltage loop, and output current loop are the four software control loops in the core architecture of the MPPT system. They achieve stable power output by controlling the interaction between the sampled signal and the target output value. The functions of each loop are as follows:

[0062] The input current loop is used to monitor whether the input current of the PV exceeds the maximum limit that the power module with PV can withstand, limit the maximum input current of the PV, and make the power module with PV operate within the normal range.

[0063] The input voltage loop is used to monitor the input voltage of the PV and stabilize the system output near the maximum power point by comparing it with the preset maximum power point voltage.

[0064] The output voltage loop is used to stabilize the output voltage of the power module with PV. It obtains the error value by comparing the target value and the actual value of the output voltage, and controls the output voltage to be stable through PI calculation to ensure that the battery is not over-voltaged.

[0065] The output current loop is used to stabilize the output current of the PV power module. It compares the set target current value with the actual value and uses PI calculation to stabilize the current and protect the battery cells from impact.

[0066] Specifically, the power module with PV is used to provide a stable AC output or DC output. The battery is located at the DC input port of the power module and plays the role of providing DC voltage in the module, so that the power module outputs a stable AC voltage.

[0067] Specifically, PI control is a closed-loop control method (proportional-integral) provided by software. It reduces the error of the power supply module by adjusting the control output, thereby enabling the output to track the given reference signal.

[0068] Specifically, in this embodiment, the PI calculation is used to achieve stable control of the system and realize dynamic parameter optimization by adjusting the PI coefficient. The PI calculation is combined with the MPPT tracking algorithm to control the loop, achieving intelligent algorithm fusion.

[0069] Step S20: Calculate the target output value of the input current loop and transmit the output result to the output voltage loop.

[0070] The specific steps include:

[0071] Step S21: Sample the input current value in real time; obtain the actual input current value ADC_PV_Iin through the ADC analog-to-digital converter;

[0072] Specifically, the input current value is sampled in real time to monitor the real-time status of the system and ensure that the current does not exceed the hardware safety limit.

[0073] Step S22, calculate the error value; compare the sampled value ADC_PV_Iin with the preset maximum allowable input current PV_Iinref to obtain the error value Error_Iin, as shown in equation (1);

[0074] Error_Iin = PV_Iinref - ADC_PV_Iin(1);

[0075] Specifically, calculate the error value. If Error_Iin>0 (actual current not exceeded the limit), the current needs to be increased to the target value; if Error_Iin<0 (actual current exceeded the limit), the current needs to be forcibly reduced.

[0076] Step S23: PI operation generates control signal; PI operation is performed on the error value Error_Iin, as shown in equation (2):

[0077] PV_Iinresult = Kp⋅Error_Iin + Ki⋅∫Error_Iindt (2);

[0078] Where PV_Iinresult is the final result of the input current loop, Error_Iin is the error value, Kp is the coefficient of the proportional part, and Ki is the coefficient of the integral part.

[0079] Specifically, a PI controller, short for proportional-integral controller, aims to make the system's process variable (PV) track the setpoint (SP) as closely as possible. Its output consists of two parts: a proportional element and an integral element. Kp is the coefficient of the proportional element, determining the strength of the proportional action. Ki is the coefficient of the integral element, determining the strength of the integral action.

[0080] Step S24: Output target value transmission; obtain the final result PV_Iinresult of the input current loop, and transmit the final result PV_Iinresult of the input current loop into the output voltage loop.

[0081] Step S30: Calculate the target output value of the output current loop and transmit the output result to the output voltage loop.

[0082] The specific steps include:

[0083] Step S31: Sample the output current value in real time; obtain the actual output current value ADC_Iout at the battery terminal or load terminal through the ADC analog-to-digital converter;

[0084] Specifically, by monitoring the battery charging current in real time, overcurrent can be prevented from impacting the battery cells.

[0085] Step S32, calculate the error value; compare the sampled value ADC_Iout with the preset target output current value Ioutref to obtain the error value Error_Iout, as shown in equation (3):

[0086] Error_Iout = Ioutref - ADC_Iout(3);

[0087] Specifically, the error value is calculated. If Error_Iout>0 (actual current is less than target current), the current needs to be increased; if Error_Iout<0 (actual current exceeds target current), the current needs to be forcibly reduced.

[0088] Step S33: PI operation generates control signal; PI operation is performed on the error value Error_Iout, as shown in equation (4):

[0089] Ioutresult = Kp⋅Error_Iout + Ki⋅∫Error_Ioutdt(4);

[0090] Where Ioutresult is the final result of the output current loop, Error_Iout is the error value, Kp is the coefficient of the proportional part, and Ki is the coefficient of the integral part.

[0091] Step S34: Output target value transmission; obtain the final result Ioutresult of the output current loop, and transmit the final result Ioutresult of the output current loop into the output voltage loop.

[0092] Step S40: Calculate the target output value of the input voltage loop and transmit the output result to the output voltage loop.

[0093] The specific steps include:

[0094] Step S41: Calculate the instantaneous power Pin using the input voltage and input current of PV sampled in real time by the ADC.

[0095] Specifically, the sampling data includes: PV input voltage ADC_PV_Vin and PV input current ADC_PV_Iin; the instantaneous power Pin is calculated using the formula (5):

[0096] Pin = ADC_PV_Vin × ADC_PV_Iin(5);

[0097] Equation (5) provides real-time power data for the MPPT algorithm.

[0098] Step S42: Track the maximum power point using the perturbation observation method. Compare the calculated instantaneous power Pin with the previously tracked instantaneous power Pre_Pin. If Pin is higher than Pre_Pin, increase the target value PV_Vinref; otherwise, decrease the target value PV_Vinref. Drive the system toward the maximum power point and dynamically estimate the target voltage PV_Vinref corresponding to the maximum power point.

[0099] Specifically, PV_Vinref is the estimated value of the maximum power point voltage dynamically calculated by the MPPT algorithm.

[0100] Step S43: Subtract the PV input voltage ADC_PV_Vin sampled by the ADC in real time from the target value PV_Vinref that the system needs to achieve to obtain the error value Error_PV_Vin, as shown in equation (6):

[0101] Error_PV_Vin = ADC_PV_Vin - PV_Vinref (6);

[0102] Specifically, when the error value Error_PV_Vin > 0, there is a positive error, and the actual voltage is higher than the target, so the voltage needs to be reduced; when the error value Error_PV_Vin < 0, there is a negative error, and the actual voltage is lower than the target, so the voltage needs to be increased.

[0103] Step S44: After PI calculation, the final result of the input voltage loop, PV_Vinresult, is obtained; the final result of the input voltage loop, PV_Vinresult, is then sent into the output voltage loop.

[0104] The calculation of the final result PV_Vinresult of the input voltage loop is shown in equation (7):

[0105] PV_Vinresult = Kp⋅Error_PV_Vin + Ki⋅∫Error_PV_Vindt(7);

[0106] Where PV_Vinresult is the final result of the input voltage loop, Error_PV_Vin is the error value, Kp is the coefficient of the proportional part, and Ki is the coefficient of the integral part.

[0107] The Perturb and Observe (P&O) method is one of the commonly used algorithms for achieving maximum power point tracking (MPPT) in photovoltaic (PV) systems. Its core idea is to actively perturb the system's operating point and observe power changes to gradually approach the maximum power point (MPP). The following is a complete analysis:

[0108] I. Algorithm Principles

[0109] Basic logic: Hill Climbing

[0110] Imagine the PV power-voltage (PV) curve as a "mountain", with MPP at the summit.

[0111] By periodically perturbing the PV operating voltage (ΔV), the direction of power change is observed to determine the next perturbation direction:

[0112] Power increases → Continue perturbation in the same direction ("uphill");

[0113] Power reduction → reverse disturbance ("downhill").

[0114] II. Key Parameter Design

[0115] 1. The disturbance step size ΔV is used to control the voltage adjustment amplitude. Too large a step size results in fast tracking, but severe oscillations near the MPP; too small a step size results in slow tracking and susceptibility to noise interference.

[0116] Adaptive step size: automatically decreases when approaching MPP (e.g., ΔV = k·|dP / dV|).

[0117] 2. The sampling period T is the time interval between two disturbances. It needs to be much longer than the system response time (usually 100 ms to 1 s); if it is too fast, the system will not be in steady state, and the direction of power change will be misjudged.

[0118] 3. The initial direction is the direction of voltage increase or decrease during the first disturbance.

[0119] III. Mathematical Expression and Decision Logic

[0120] Let the current voltage be V_k and the power be P_k; after the disturbance, the voltage is V_{k+1} and the power is P_{k+1}:

[0121] 1. Calculate the power change: ΔP = P_{k+1} - P_k

[0122] Decision rule: ΔP>0 (power increases):

[0123] If V_{k+1} > V_k (the voltage was increased last time), then the voltage will continue to be increased next time (V_{k+2} = V_{k+1} + ΔV);

[0124] If \(V_{k + 1}<V_k\) (voltage decreased last time), then decrease the voltage next time (\(V_{k + 2}=V_{k + 1}-\Delta V\)).

[0125] \(\Delta P<0\) (power decreased):

[0126] If \(V_{k + 1}>V_k\) (voltage increased last time), then reverse and decrease the voltage next time (\(V_{k + 2}=V_{k + 1}-\Delta V\));

[0127] If \(V_{k + 1}<V_k\) (voltage decreased last time), then reverse and increase the voltage next time (\(V_{k + 2}=V_{k + 1}+\Delta V\)).

[0128] IV. Implementation in the four - loop control

[0129] In the input voltage loop, the P&O algorithm dynamically updates the target voltage \(PV\_Vinref\):

[0130] 1. Sampling: Obtain \(ADC\_PV\_Vin\) (voltage) and \(ADC\_PV\_Iin\) (current);

[0131] 2. Calculate power: \(P_{in}=\{ADC\_PV\_Vin\}\times\{ADC\_PV\_Iin\}\);

[0132] 3. Compare historical power:

[0133] If \(P_{in}>P_{pre}\), then maintain the current disturbance direction (such as continue to increase \(PV\_Vinref\));

[0134] If \(P_{in}<P_{pre}\), then reverse the disturbance direction (such as change to decrease \(PV\_Vinref\));

[0135] 4. Update the reference value: \(PV\_Vinref = PV\_Vinref\pm\Delta V\)

[0136] 5. Store the current power: \(P_{pre}=P_{in}\).

[0137] V. Summary

[0138] The perturbation observation method drives the operating point of the PV system to move towards the maximum power point through the closed - loop control of "probe - observe - decision".

[0139] The steps of S50 calculate the output target value of the output voltage loop.

[0140] The specific steps include:

[0141] Step S51: Sample the output voltage value in real time; obtain the actual output voltage ADC_Vout at the battery terminal or load terminal through the ADC analog-to-digital converter.

[0142] Step S52: Calculate the error value; compare the sampled value ADC_Vout with the preset target output voltage value Voutref, add the final result of the input current loop PV_Iinresult, the final result of the input voltage loop PV_Vinresult, and the final result of the output current loop Ioutresult to obtain the error value Error_Vout, and perform nested processing;

[0143] The formula for calculating the error value Error_Vout is shown in equation (8):

[0144] Error_Vout = Voutref - ADC_Vout + PV_Iinresult

[0145] + Ioutresult + PV_Vinresult(8).

[0146] Step S53: PI operation generates control signal; PI operation is performed on the error value Error_Vout to obtain the final output voltage loop result Voutresult;

[0147] The PI operation is shown in equation (9):

[0148] Voutresult = Kp⋅Error_Vout + Ki⋅∫Error_Voutdt(9);

[0149] Where Voutresult is the final result of the output voltage loop, Error_Vout is the error value, Kp is the coefficient of the proportional part, and Ki is the coefficient of the integral part.

[0150] Specifically, in the above formula, the error value Error_Vout is calculated using the ADC sampled value, and the final results of each control loop need to be normalized.

[0151] Step S60: Adjust the duty cycle of the PWM modulation control switching device according to the output target value of the output voltage loop.

[0152] The specific steps include:

[0153] Step S61: Multiply the target output value of the output voltage loop by the counting period of the PWM module to obtain the adjustment coefficient of the PWM signal.

[0154] Step S62: The adjustment coefficient of the PWM signal is transmitted to the PWM module to obtain the adjusted modulation signal PWM, so as to adjust the duty cycle of the control switching device.

[0155] The aforementioned four-loop nested control scheme applies the results of the three loops to a single loop as an influencing factor in the single-voltage loop calculation, thus outputting a single control result. This eliminates competition and makes loop tracking control more stable. The advantages of the four-loop nested control scheme are mainly reflected in the following aspects:

[0156] 1. Dynamic response and stability: The fast response of the output current loop can quickly cope with sudden load changes, while the nested four-loop regulation ensures that the system is always close to the maximum power point in steady state, avoiding efficiency loss caused by frequent "optimization".

[0157] 2. Anti-interference capability: The four-loop nested structure has the ability to adapt to external disturbances such as sudden changes in light intensity, temperature drift, and component aging. For example, when cloud cover causes a decrease in light intensity, the input voltage loop will recalculate a new target value, and the current loop will quickly adjust the output current to adapt to the new power curve.

[0158] 3. Accuracy and efficiency optimization: Through a closed-loop feedback mechanism, the system can compensate for PV open-circuit voltage fluctuations caused by external conditions in real time, thereby maintaining the best working state.

[0159] 4. Algorithm fusion:

[0160] The input voltage loop can be controlled by the perturbation and observation method, while the other loops are controlled by PI. The proportional coefficient (Kp) and integral coefficient (Ki) need to be optimized to avoid overshoot or slow response.

[0161] 5. Summary:

[0162] The four-loop control structure is the core of PV tracking technology. Through nested loop adjustment, it can respond quickly to unexpected external situations and stabilize rapidly, achieving a balance between efficiency and stability. With the development of science and technology, this solution has even better application prospects in the field of new energy.

[0163] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can be modified and varied in various ways. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-loop nested PV control method, characterized in that, The method includes the following steps: Step 1, Loop Configuration; The core architecture of the MPPT system includes the input current loop, input voltage loop, output voltage loop, and output current loop; Step 2: Calculate the target output value of the input current loop and transmit the output result to the output voltage loop; Step 3: Calculate the target output value of the output current loop and transmit the output result to the output voltage loop; Step 4: Calculate the target output value of the input voltage loop and transmit the output result to the output voltage loop; Step 5: Calculate the target output value of the output voltage loop; Step 6: Adjust the duty cycle of the PWM modulation control switching device according to the target output value of the output voltage loop; The loop functions of the input current loop, input voltage loop, output voltage loop, and output current loop in step one are as follows: The input current loop is used to monitor whether the input current of the PV exceeds the maximum limit that the power module with PV can withstand, limit the maximum input current of the PV, and make the power module with PV operate within the normal range. The input voltage loop is used to monitor the input voltage of the PV and stabilize the system output near the maximum power point by comparing it with the preset maximum power point voltage. The output voltage loop is used to stabilize the output voltage of the power module with PV. It obtains the error value by comparing the target value and the actual value of the output voltage, and controls the output voltage to be stable through PI calculation to ensure that the battery is not over-voltaged. The output current loop is used to stabilize the output current of the PV power module. It compares the set target current value with the actual value and uses PI calculation to stabilize the current and protect the battery cells from impact.

2. The multi-loop nested PV control method as described in claim 1, characterized in that, The specific steps for calculating the target output value of the input current loop in step two include: Step 2.1: Sample the input current value in real time; obtain the actual input current value ADC_PV_Iin through the ADC analog-to-digital converter; Step 2.2, calculate the error value; compare the sampled value ADC_PV_Iin with the preset maximum allowable input current PV_Iinref to obtain the error value Error_Iin, as shown in equation (1); Error_Iin = PV_Iinref - ADC_PV_Iin(1); Step 2.3: PI operation generates control signal; PI operation is performed on the error value Error_Iin, as shown in equation (2): PV_Iinresult = Kp⋅Error_Iin + Ki⋅∫Error_Iindt (2); Where PV_Iinresult is the final result of the input current loop, Error_Iin is the error value, Kp is the coefficient of the proportional part, and Ki is the coefficient of the integral part; Step 2.4, Output target value transfer; obtain the final result of the input current loop PV_Iinresult, and transfer the final result of the input current loop PV_Iinresult into the output voltage loop.

3. The multi-loop nested PV control method as described in claim 1, characterized in that, The specific steps for calculating the target output value of the output current loop in step three include: Step 3.1: Sample the output current value in real time; obtain the actual output current value ADC_Iout at the battery terminal or load terminal through the ADC analog-to-digital converter; Step 3.2, calculate the error value; compare the sampled value ADC_Iout with the preset target output current value Ioutref to obtain the error value Error_Iout, as shown in equation (3): Error_Iout = Ioutref - ADC_Iout(3); Step 3.3: PI operation generates control signal; PI operation is performed on the error value Error_Iout, as shown in equation (4): Ioutresult = Kp⋅Error_Iout + Ki⋅∫Error_Ioutdt (4); Where Ioutresult is the final result of the output current loop, Error_Iout is the error value, Kp is the coefficient of the proportional part, and Ki is the coefficient of the integral part; Step 3.4, Output target value transfer; obtain the final result Ioutresult of the output current loop, and transfer the final result Ioutresult of the output current loop into the output voltage loop.

4. The multi-loop nested PV control method as described in claim 1, characterized in that, The specific steps for calculating the target output value of the input voltage loop in step four include: Step 4.1: Calculate the instantaneous power Pin using the input voltage and input current of PV sampled in real time by the ADC; Step 4.2: Track the maximum power point using the perturbation observation method. Compare the calculated instantaneous power Pin with the previously tracked instantaneous power Pre_Pin. If Pin is higher than Pre_Pin, increase the target value PV_Vinref; otherwise, decrease the target value PV_Vinref. Drive the system toward the maximum power point and dynamically estimate the target voltage PV_Vinref corresponding to the maximum power point. Step 4.3: Subtract the PV input voltage ADC_PV_Vin sampled by the ADC in real time from the target value PV_Vinref that the system needs to achieve to obtain the error value Error_PV_Vin, as shown in equation (6): Error_PV_Vin = ADC_PV_Vin - PV_Vinref (6); Step 4.4: After PI calculation, the final result of the input voltage loop, PV_Vinresult, is obtained; the final result of the input voltage loop, PV_Vinresult, is then sent into the output voltage loop. The calculation of the final result PV_Vinresult of the input voltage loop is shown in equation (7): PV_Vinresult = Kp⋅Error_PV_Vin + Ki⋅∫Error_PV_Vindt(7); Where PV_Vinresult is the final result of the input voltage loop, Error_PV_Vin is the error value, Kp is the coefficient of the proportional part, and Ki is the coefficient of the integral part.

5. The multi-loop nested PV control method as described in claim 1, characterized in that, The specific steps for calculating the target output value of the output voltage loop in step five include: Step 5.1: Sample the output voltage value in real time; obtain the actual output voltage ADC_Vout at the battery terminal or load terminal through the ADC analog-to-digital converter; Step 5.2, calculate the error value; compare the sampled value ADC_Vout with the preset target output voltage value Voutref, add the final result of the input current loop PV_Iinresult, the final result of the input voltage loop PV_Vinresult, and the final result of the output current loop Ioutresult to obtain the error value Error_Vout, and perform nested processing; The formula for calculating the error value Error_Vout is shown in equation (8): Error_Vout = Voutref - ADC_Vout + PV_Iinresult + Ioutresult + PV_Vinresult (8); Step 5.3: PI calculation generates control signals; PI calculation is performed on the error value Error_Vout to obtain the final output voltage loop result Voutresult; The PI operation is shown in equation (9): Voutresult = Kp⋅Error_Vout + Ki⋅∫Error_Voutdt (9); Where Voutresult is the final result of the output voltage loop, Error_Vout is the error value, Kp is the coefficient of the proportional part, and Ki is the coefficient of the integral part.

6. The multi-loop nested PV control method as described in claim 1, characterized in that, Step six, which involves adjusting the duty cycle of the PWM modulation control switching device based on the target output value of the output voltage loop, includes the following specific steps: Step 6.1: Multiply the target output value of the output voltage loop by the counting period of the PWM module to obtain the adjustment coefficient of the PWM signal; Step 6.2: The adjustment coefficient of the PWM signal is transmitted to the PWM module to obtain the adjusted modulation signal PWM, so as to adjust the duty cycle of the control switching device.

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