Multi-loop nested PV control method

Abstract

The invention discloses a multi-loop nested PV control method. The method comprises the following steps: loop configuration; the core architecture of the MPPT system comprises an input current loop, an input voltage loop, an output voltage loop and an output current loop. Calculating an output target value of the input current loop, and transmitting an output result to an output voltage loop; calculating an output target value of the output current loop, and transmitting an output result to an output voltage loop; calculating an output target value of the input voltage loop, and transmitting an output result to an output voltage loop; calculating an output target value of the output voltage loop; and adjusting the duty ratio of the PWM modulation control switching device according to the output target value of the output voltage loop. According to the four-loop nested scheme control, three loop operation results act on one loop and serve as influence factors to carry out single voltage loop calculation, so that one result control is output, the competition condition does not exist, and loop tracking control is 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: 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.

[0006] 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: The input current loop is used to monitor whether the input current of the PV exceeds the maximum limit that the power module with the PV can bear, limit the maximum input current of the PV, and make the power module with the PV work in a normal range; The input voltage loop is used to monitor the input voltage of the PV, and make the system output stable near the maximum power point by comparing with the preset maximum power point voltage; The output voltage loop is used to stabilize the output voltage of the power module with the PV, obtain an error value by comparing the output voltage target value with the actual value, control an output stable voltage through PI operation, and ensure that the battery is not overvoltage; The output current loop is used to stabilize the output current of the power module with the PV, compare the set current target value with the actual value, and control the current to be stable through PI operation, so as to protect the battery cell from impact.

[0007] Preferably, the specific steps of calculating the output target value of the input current loop in step two include: Step 2.1, real-time sampling of input current value; the actual input current value ADC_PV_Iin is obtained through an ADC analog-to-digital converter; Step 2.2, calculating an error value; comparing the sampling value ADC_PV_Iin with the preset maximum allowed input current PV_Iinref to obtain an error value Error_Iin, as shown in equation (1); Error_Iin = PV_Iinref - ADC_PV_Iin (1); Step 2.3, PI operation to generate a 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); Wherein, 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; Ki is the coefficient of the integral part; Step 2.4, output target value transmission; the final result PV_Iinresult of the input current loop is obtained, and the final result PV_Iinresult of the input current loop is transmitted into the output voltage loop.

[0008] Preferably, the specific steps of calculating the output target value of the output current loop in step three include: Step 3.1, real-time sampling of output current value; the actual output current value ADC_Iout of the battery end or the load end is obtained through an ADC analog-to-digital converter; Step 3.2, calculating error value; comparing the sampling value ADC_Iout with the preset target output current value Ioutref to obtain error value Error_Iout, as shown in equation (3): Error_Iout = Ioutref - ADC_Iout (3); Step 3.3, PI operation to generate control signal; performing PI operation on error value Error_Iout, as shown in equation (4): Ioutresult = Kp⋅Error_Iout + Ki⋅∫Error_Ioutdt (4); Wherein, Ioutresult is the final result of output current loop, Error_Iout is error value, Kp is the coefficient of proportional part; Ki is the coefficient of integral part; Step 3.4, output target value transmission; obtaining output current loop final result Ioutresult, and transmitting output current loop final result Ioutresult into output voltage loop.

[0009] Preferably, the specific steps of calculating the output target value of the input voltage loop in the step four include: Step 4.1, calculating instantaneous power Pin through the input voltage of PV and the input current of PV sampled by ADC in real time; Step 4.2, tracking maximum power point through perturbation and observation method, comparing the calculated instantaneous power Pin with the last tracked instantaneous power Pre_Pin, if Pin is higher than Pre_Pin, increasing target value PV_Vinref; otherwise, decreasing target value PV_Vinref; pushing the system to move towards the maximum power point, and dynamically estimating the target voltage PV_Vinref corresponding to the maximum power point; Step 4.3, obtaining error value Error_PV_Vin by subtracting the PV input voltage ADC_PV_Vin sampled by ADC in real time from the target value PV_Vinref required by the system, as shown in equation (6): Error_PV_Vin = ADC_PV_Vin - PV_Vinref (6); Step 4.4, obtaining input voltage loop final result PV_Vinresult after PI operation; sending input voltage loop final result PV_Vinresult into output voltage loop; Wherein, the calculation of input voltage loop final result PV_Vinresult is shown in equation (7): PV_Vinresult = Kp·Error_PV_Vin + Ki·∫Error_PV_Vindt (7); Wherein, PV_Vinresult is the input voltage ring final result, Error_PV_Vin is the error value, Kp is the coefficient of the proportion part; Ki is the coefficient of the integral part.

[0010] Preferably, the specific steps of calculating the output target value of the output voltage ring in step five include: Step 5.1, real-time sampling output voltage value; obtaining the actual output voltage ADC_Vout of the battery end or the load end through the ADC analog-digital converter; Step 5.2, calculating the error value; comparing the sampling value ADC_Vout with the preset target output voltage value Voutref, adding the input current ring final result PV_Iinresult, the input voltage ring final result PV_Vinresult and the output current ring final result Ioutresult, to obtain the error value Error_Vout, and implementing nested processing; Wherein, the calculation formula of the error value Error_Vout is shown in formula (8): Error_Vout = Voutref - ADC_Vout + PV_Iinresult + Ioutresult + PV_Vinresult (8); Step 5.3, PI operation to generate control signal; performing PI operation on the error value Error_Vout to obtain the output voltage ring final result Voutresult; Wherein, the PI operation is shown in formula (9): Voutresult = Kp·Error_Vout + Ki·∫Error_Voutdt (9); Wherein, Voutresult is the output voltage ring final result, Error_Vout is the error value, Kp is the coefficient of the proportion part; Ki is the coefficient of the integral part.

[0011] Preferably, the specific steps of adjusting the duty cycle of the PWM modulation control switching device according to the output target value of the output voltage ring in step six include: Step 6.1, multiplying the output target value of the output voltage ring with the count period of the PWM module to obtain the adjustment coefficient of the PWM signal; Step 6.2, transmitting the adjustment coefficient of the PWM signal to the PWM module to obtain the adjusted modulation signal PWM, so as to adjust the duty cycle of the control switching device.

[0012] The multi-loop nested PV control method breaks through the limitations of traditional methods through multi-level cooperative control, dynamic parameter optimization and intelligent algorithm fusion, realizes efficient and stable power tracking in complex scenes, and provides a new path for performance improvement of a photovoltaic power generation system. The four-loop nested scheme control in the application is to apply the results of three loop operations to one loop as an influencing factor to perform single-voltage loop calculation, thereby outputting a result control, and there is no competition. The loop tracking control is more stable. The method of the application is simple, easy to implement, low in cost and convenient to popularize. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a traditional four-loop separate calculation workflow diagram in the prior art.

[0014] Figure 2 is a flowchart of the multi-loop nested PV control method of the embodiment of the application. DETAILED DESCRIPTION

[0015] The embodiment takes the multi-loop nested PV control method as an example, and the application will be described in detail below in combination with specific embodiments and drawings.

[0016] Please refer to Figure 2 , which shows a multi-loop nested PV control method provided by the embodiment of the application, and the method comprises the following steps: 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.

[0017] The input current loop, the input voltage loop, the output voltage loop and the output current loop are four software control loops of the core architecture of the MPPT system, and the purpose of stabilizing the power output is achieved through control between the sampling signal and the output target value. The functions of each loop are as follows: The input current loop is used to monitor whether the input current of the PV exceeds the maximum limit value that can be borne by the power module with the PV, limit the maximum input current of the PV, and make the power module with the PV work in a normal range; The input voltage loop is used to monitor the input voltage of the PV, and make the system output stable near the maximum power point by comparing with the preset maximum power point voltage; The output voltage loop is used to stabilize the output voltage of the power module with the PV, compare the output voltage target value with the actual value to obtain an error value, control an output stable voltage through PI operation, and ensure that the battery is not overvoltage; The output current loop is used to stabilize the output current of the PV power module, and the set current target value is compared with the actual value, and the current control is stabilized through PI operation to protect the battery cell from impact.

[0018] Specifically, the PV power module is used to provide a stable AC output or DC output, and the battery is arranged at the DC input port of the power module to provide a DC voltage in the module to output a stable AC voltage.

[0019] Specifically, the PI operation is a closed-loop control method (proportional-integral) provided by software, which adjusts the control output to reduce the error of the power module, so that the output can track the given reference signal.

[0020] Specifically, in the PI operation in this embodiment, the PI coefficient is adjusted to realize stable control of the system and realize dynamic parameter optimization. The PI operation is combined with the MPPT tracking algorithm to control the loop, and intelligent algorithm fusion is realized.

[0021] Step S20, calculate the output target value of the input current loop, and transmit the output result to the output voltage loop.

[0022] The specific steps include: Step S21, real-time sampling of input current value; the actual input current value ADC_PV_Iin is obtained through an ADC analog-to-digital converter; Specifically, the input current value is sampled in real time to realize real-time monitoring of the system state to ensure that the current does not exceed the hardware safety limit.

[0023] Step S22, calculate the error value; compare the sampling value ADC_PV_Iin with the preset maximum allowed input current PV_Iinref to obtain the error value Error_Iin, as shown in equation (1); Error_Iin = PV_Iinref - ADC_PV_Iin (1); Specifically, the error value is calculated. If Error_Iin>0 (the actual current is not over-limit), the current needs to be increased to the target value; if Error_Iin<0 (the actual current is over-limit), the current needs to be forced to decrease.

[0024] Step S23, PI operation generates a control signal; the error value Error_Iin is subjected to PI operation, as shown in equation (2): PV_Iinresult = Kp⋅Error_Iin + Ki⋅∫Error_Iindt (2); Wherein, PV_Iinresult is the input current loop final result, Error_Iin is the error value, Kp is the coefficient of the proportional part; Ki is the coefficient of the integral part.

[0025] Specifically, the PI controller is the abbreviation of "proportional-integral" controller, which makes the process variable (PV) of the system track the set value (SP) as much as possible. Its output consists of two parts: proportional and integral. Kp is the coefficient of the proportional part, which determines the strength of the proportional action. Ki is the coefficient of the integral part, which determines the strength of the integral action.

[0026] Step S24, output target value transmission; get the input current loop final result PV_Iinresult, and transmit the input current loop final result PV_Iinresult into the output voltage loop.

[0027] Step S30, calculate the output target value of the output current loop, and transmit the output result to the output voltage loop.

[0028] The specific steps include: Step S31, real-time sampling of output current value; through the ADC analog-digital converter, the actual output current value ADC_Iout of the battery end or load end is obtained; Specifically, by monitoring the battery charging current in real time, the overcurrent impact on the battery cell is prevented.

[0029] Step S32, calculate the error value; compare the sampling 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); Specifically, the error value is calculated. If Error_Iout>0 (the actual current is less than the target current value), the current needs to be increased; if Error_Iout<0 (the actual current exceeds the target current value), the current needs to be forced to decrease.

[0030] Step S33, PI operation generates a 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); Wherein, Ioutresult is the output current loop final result, Error_Iout is the error value, Kp is the coefficient of the proportional part; Ki is the coefficient of the integral part.

[0031] Step S34, output target value transmission; get the output current loop final result Ioutresult, and transmit the output current loop final result Ioutresult into the output voltage loop.

[0032] Step S40, calculate the output target value of the input voltage loop, and transmit the output result to the output voltage loop.

[0033] The specific steps include: Step S41, calculate the instantaneous power Pin by the input voltage of the PV and the input current of the PV sampled by the ADC in real time; Specifically, the sampling data includes: the PV input voltage ADC_PV_Vin and the PV input current ADC_PV_Iin; the instantaneous power Pin calculation formula is shown in equation (5): Pin = ADC_PV_Vin × ADC_PV_Iin (5); Equation (5) provides real-time power data for the MPPT algorithm.

[0034] Step S42, track the maximum power point by the perturbation and observation method, compare the calculated instantaneous power Pin with the last 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; push the system to move towards the maximum power point, and dynamically estimate the target voltage PV_Vinref corresponding to the maximum power point; Specifically, PV_Vinref is the estimated value of the maximum power point voltage dynamically calculated by the MPPT algorithm.

[0035] Step S43, get the error value Error_PV_Vin by subtracting the target value PV_Vinref required by the system from the PV input voltage ADC_PV_Vin sampled by the ADC in real time, as shown in equation (6): Error_PV_Vin = ADC_PV_Vin - PV_Vinref (6); Specifically, when the error value Error_PV_Vin > 0, there is a positive error, so the actual voltage is higher than the target, and the voltage needs to be reduced; when the error value Error_PV_Vin < 0, there is a negative error, so the actual voltage is lower than the target, and the voltage needs to be increased.

[0036] Step S44, after PI operation, get the input voltage loop final result PV_Vinresult; transmit the input voltage loop final result PV_Vinresult into the output voltage loop; Wherein, the calculation of the input voltage loop final result PV_Vinresult is shown in equation (7): PV_Vinresult = Kp⋅Error_PV_Vin + Ki⋅∫Error_PV_Vindt(7); Where PV_Vinresult is the input voltage loop final result, Error_PV_Vin is the error value, Kp is the coefficient of the proportional part; Ki is the coefficient of the integral part.

[0037] Where Perturb and Observe (P&O) is one of the commonly used algorithms for Maximum Power Point Tracking (MPPT) in photovoltaic (PV) systems. Its core idea is to gradually approach the Maximum Power Point (MPP) by actively perturbing the system operating point and observing the power change. Here is its complete analysis: I. Algorithm Principle Basic Logic: Hill Climbing Consider the PV power-voltage (P-V) curve as a "mountain", with the MPP at the peak.

[0038] By periodically perturbing the PV operating voltage (ΔV), observe the power change direction, determine the next perturbation direction: Power increases → Continue the same direction perturbation ("uphill"); Power decreases → Perturb in the opposite direction ("downhill").

[0039] II. Key Parameter Design 1. Perturbation step size ΔV is used to control the voltage adjustment amplitude. Step size too large: fast tracking, but MPP near oscillation is serious; step size too small: slow tracking, easy to be disturbed by noise.

[0040] Adaptive step size: automatically reduce when approaching MPP (e.g. ΔV = k·|dP / dV|).

[0041] 2. Sampling period T is the time interval between two perturbations. It needs to be much larger than the system response time (usually 100 ms~1 s); too fast, the system is not stable, misjudges the power change direction.

[0042] 3. Initial direction is the voltage increase or decrease direction of the first perturbation.

[0043] III. Mathematical Expression and Decision Logic Let the current voltage V_k, power P_k; perturbed voltage V_{k+1}, power P_{k+1}: 1. Calculate power change: ΔP = P_{k+1} - P_k Decision rule: ΔP>0 (power increases): If V_{k+1} > V_k (last time increase voltage) then next continue to increase voltage (V_{k+2} = V_{k+1} + ΔV); If V_{k+1} < V_k (last time decrease voltage) then next continue to decrease voltage (V_{k+2} = V_{k+1} - ΔV).

[0044] ΔP < 0 (power decrease): If V_{k+1} > V_k (last time increase voltage) then next reverse to decrease voltage (V_{k+2} = V_{k+1} - ΔV); If V_{k+1} < V_k (last time decrease voltage) then next reverse to increase voltage (V_{k+2} = V_{k+1} + ΔV).

[0045] Four, in the implementation of the four-loop control In the input voltage ring, P&O algorithm dynamic update target voltage PV_Vinref: 1, sampling: get ADC_PV_Vin (voltage), ADC_PV_Iin (current); 2, calculate power: P_{in} = {ADC_PV_Vin} * {ADC_PV_Iin}; 3, compare historical power: If P_{in} > P_{pre} then keep the current disturbance direction (such as continue to increase PV_Vinref); If P_{in} < P_{pre} then reverse the disturbance direction (such as change to decrease PV_Vinref); 4, update reference value: PV_Vinref = PV_Vinref ± ΔV 5, store the current power: P_{pre} = P_{in}.

[0046] Five, summary The perturb and observe method promotes the PV system operating point to move to the maximum power point through the closed-loop control of "trial-observation-decision".

[0047] Step S50, calculate the output target value of the output voltage ring.

[0048] The specific steps include: Step S51, real-time sampling of output voltage value; through the ADC analog-digital converter to obtain the actual output voltage ADC_Vout of the battery end or the load end.

[0049] Step S52, calculate the error value; compare the sampling value ADC_Vout with the preset target output voltage value Voutref, add the input current loop final result PV_Iinresult, the input voltage loop final result PV_Vinresult and the output current loop final result Ioutresult to obtain the error value Error_Vout, and implement nested processing; The calculation formula of the error value Error_Vout is shown in equation (8): Error_Vout = Voutref - ADC_Vout + PV_Iinresult + Ioutresult + PV_Vinresult (8).

[0050] Step S53, PI operation generates a control signal; the error value Error_Vout is subjected to PI operation to obtain the output voltage loop final result Voutresult. The PI operation is shown in equation (9): Voutresult = Kp⋅Error_Vout + Ki⋅∫Error_Voutdt (9). Wherein, Voutresult is the output voltage loop final result, Error_Vout is the error value, Kp is the coefficient of the proportional part; Ki is the coefficient of the integral part.

[0051] Specifically, in the above formula, when calculating the error value Error_Vout, the ADC sampling value is calculated, and the final results of each control loop need to be normalized.

[0052] Step S60, adjust the duty cycle of the PWM modulation control switch device according to the output target value of the output voltage loop.

[0053] The specific steps include: Step S61, multiply the output target value of the output voltage loop by the count period of the PWM module to obtain the adjustment coefficient of the PWM signal.

[0054] Step S62, transmit the adjustment coefficient of the PWM signal to the PWM module to obtain the adjusted modulation signal PWM to adjust the duty cycle of the control switch device.

[0055] The above four-loop nested scheme control is to apply the results of three loop operations to one loop as an influencing factor to perform single voltage loop calculation to output a result control, so there is no competition situation, and the loop tracking control will be more stable. The advantages of the four-loop nested control scheme mainly lie in the following aspects: 1, Dynamic response and stability: The fast response of the output current loop can quickly respond to load mutations, while the four-loop nested regulation ensures that the system is always close to the maximum power point in steady state, avoiding the efficiency loss caused by frequent "back and forth optimization".

[0056] 2, Anti-interference ability: The four-loop nested structure has self-adaptive ability to external disturbances such as light mutation, temperature drift, component aging, etc. For example, when the cloud layer blocks the light intensity, the input voltage loop will recalculate the new target value, and the current loop will quickly adjust the output current to adapt to the new power curve.

[0057] 3, Precision and efficiency optimization: Through the closed-loop feedback mechanism, the system can compensate for the open-circuit voltage fluctuations of the PV caused by external conditions in real time, thereby maintaining the optimal working state.

[0058] 4, Algorithm fusion: The input voltage loop can use the perturbation and observation method, and the remaining loops use PI control, which needs to optimize the proportional coefficient (Kp) and integral coefficient (Ki) to avoid overshoot or slow response.

[0059] 5, Summary: The four-loop control structure is the core of PV tracking technology, which can quickly respond to sudden changes in the external environment through loop nested regulation, and can quickly stabilize to achieve a balance between efficiency and stability. With the development of science and technology, the application prospect of this scheme in the field of new energy is more superior.

[0060] It should be noted that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application can be variously modified and changed. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A multi-loop nested PV control method, characterized in that, The method comprises the following steps: Step one, 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; Step two, calculating the output target value of the input current loop and transmitting the output result to the output voltage loop; Step three, calculating the output target value of the output current loop and transmitting the output result to the output voltage loop; Step four, calculating the output target value of the input voltage loop and transmitting the output result to the output voltage loop; Step five, calculating the output target value of the output voltage loop; Step six, adjusting the duty cycle of the PWM modulation control switch device according to the output target value of the output voltage loop.

2. The multi-loop nested PV control method of claim 1, wherein, The loop functions of the input current loop, the input voltage loop, the output voltage loop and the output current loop in the step one are as follows: The input current loop is used for monitoring whether the input current of the PV exceeds the maximum limit value that the power module with the PV can bear, limiting the maximum input current of the PV, and making the power module with the PV work in a normal range; The input voltage loop is used for monitoring the input voltage of the PV, and making the system output stable near the maximum power point by comparing with the preset maximum power point voltage; The output voltage loop is used for stabilizing the output voltage of the power module with the PV, obtaining an error value by comparing the output voltage target value with the actual value, and controlling an output stable voltage through PI operation to ensure that the battery is not overvoltage; The output current loop is used for stabilizing the output current of the power module with the PV, comparing the set current target value with the actual value, and controlling the current to be stable through PI operation to protect the battery cell from impact.

3. The multi-loop nested PV control method of claim 1, wherein, The specific steps of calculating the output target value of the input current loop in the step two comprise: Step 2.1, real-time sampling of the input current value; obtaining the actual input current value ADC_PV_Iin through an ADC analog-to-digital converter; Step 2.2, calculating the error value; comparing the sampling value ADC_PV_Iin with the preset maximum allowed input current PV_Iinref to obtain the error value Error_Iin, as shown in formula (1); Error_Iin = PV_Iinref - ADC_PV_Iin (1); Step 2.3, PI operation to generate a control signal; performing PI operation on the error value Error_Iin, as shown in formula (2): PV_Iinresult = Kp⋅Error_Iin + Ki⋅∫Error_Iindt (2); Wherein, 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; Ki is the coefficient of the integral part; Step 2.4, output target value transmission; obtaining the final result PV_Iinresult of the input current loop, and transmitting the final result PV_Iinresult of the input current loop into the output voltage loop.

4. The multi-loop nested PV control method of claim 1, wherein, The specific steps of calculating the output target value of the output current loop in the step three comprise: Step 3.1, real-time sampling output current value; the actual output current value of the battery end or the load end is obtained by an ADC analog-digital converter ADC_Iout; Step 3.2, calculating error value; the error value Error_Iout is obtained by comparing the sampling value ADC_Iout with the preset target output current value Ioutref, as shown in equation (3): Error_Iout = Ioutref - ADC_Iout (3); Step 3.3, PI operation to generate control signal; the error value Error_Iout is subjected to PI operation, as shown in equation (4): Ioutresult = Kp⋅Error_Iout + Ki⋅∫Error_Ioutdt (4); wherein, Ioutresult is the final result of the output current loop, Error_Iout is the error value, Kp is the coefficient of the proportional part; Ki is the coefficient of the integral part; Step 3.4, output target value transmission; the output current loop final result Ioutresult is obtained, and the output current loop final result Ioutresult is transmitted into the output voltage loop.

5. The multi-loop nested PV control method of claim 1, wherein, The specific steps of calculating the output target value of the input voltage loop in the step four include: Step 4.1, calculating the instantaneous power Pin by the input voltage of the PV and the input current of the PV sampled by the ADC in real time; Step 4.2, tracking the maximum power point by the perturbation and observation method, comparing the calculated instantaneous power Pin with the last tracked instantaneous power Pre_Pin, if Pin is higher than Pre_Pin, increasing the target value PV_Vinref; otherwise, decreasing the target value PV_Vinref; pushing the system to move towards the maximum power point, and dynamically estimating the target voltage PV_Vinref corresponding to the maximum power point; Step 4.3, obtaining the error value Error_PV_Vin by subtracting the PV input voltage ADC_PV_Vin sampled by the ADC in real time from the target value PV_Vinref required by the system, as shown in equation (6): Error_PV_Vin = ADC_PV_Vin - PV_Vinref (6); Step 4.4, obtaining the input voltage loop final result PV_Vinresult after PI operation; the input voltage loop final result PV_Vinresult is sent into the output voltage loop; wherein, the calculation of the input voltage loop final result PV_Vinresult is shown in equation (7): PV_Vinresult = Kp⋅Error_PV_Vin + Ki⋅∫Error_PV_Vindt (7); wherein, PV_Vinresult is the input voltage loop final result, Error_PV_Vin is the error value, Kp is the coefficient of the proportional part; Ki is the coefficient of the integral part.

6. The multi-loop nested PV control method of claim 1, wherein, The specific steps of calculating the output target value of the output voltage loop in the step five include: Step 5.1, sampling the output voltage value in real time; obtaining the actual output voltage ADC_Vout of the battery end or the load end through an ADC analog-to-digital converter; Step 5.2, calculating an error value; comparing the sampling value ADC_Vout with a preset target output voltage value Voutref, adding an input current loop final result PV_Iinresult, an input voltage loop final result PV_Vinresult and an output current loop final result Ioutresult to obtain the error value Error_Vout, and performing nested processing; Wherein, the calculation formula of 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 operation to generate a control signal; performing PI operation on the error value Error_Vout to obtain an output voltage loop final result Voutresult; Wherein, the PI operation is shown in equation (9): Voutresult = Kp⋅Error_Vout + Ki⋅∫Error_Voutdt (9); Wherein, Voutresult is the output voltage loop final result, Error_Vout is the error value, Kp is the coefficient of the proportional part; Ki is the coefficient of the integral part.

7. The multi-loop nested PV control method of claim 1, wherein, The step six, the specific steps of adjusting the duty cycle of the PWM modulation control switching device according to the output target value of the output voltage loop include: Step 6.1, multiplying the output target value of the output voltage loop by the counting period of the PWM module to obtain an adjustment coefficient of the PWM signal; Step 6.2, transmitting the adjustment coefficient of the PWM signal to the PWM module to obtain an adjusted modulation signal PWM to adjust the duty cycle of the control switching device.

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