Photovoltaic DC conversion method, storage medium and computer equipment

Abstract

The invention discloses a photovoltaic direct current conversion method, a storage medium and computer equipment, and the method comprises the steps: obtaining the duty ratio of a first pulse width modulation signal through a voltage proportional-integral algorithm when an actual output voltage is adjusted to a preset target output voltage; through a maximum power point tracking control algorithm and the actual output power, obtaining a control output voltage when the photovoltaic power generation system works at the maximum photovoltaic power point and a duty ratio of a second pulse width modulation signal when the photovoltaic power generation system is adjusted to a preset target output voltage; based on the target pulse width modulation signal corresponding to the minimum duty ratio, the on-off states of the first switching device and the second switching device are controlled at the same time until the direct current of the preset target output voltage is obtained. By combining the maximum power point tracking control and the voltage proportional integral algorithm, the first switching device and the second switching device are controlled at the same time, the structure is simplified, and meanwhile direct current can be directly output.

Description

Technical Field

[0001] This application relates to the field of power technologies, and particularly to a photovoltaic DC conversion method, a storage medium, and a computer device. Background Art

[0002] With the rapid development of new energy technologies and the continuous progress of DC power distribution technologies, the emerging DC power generation and DC power consumption system of "photovoltaic-storage-direct-current-soft" has received increasing attention. It can not only reduce the dependence on traditional energy sources, but also consume a large amount of green electricity, reduce environmental pollution, lower electricity costs, and achieve intelligent management and safe and reliable control of the system energy.

[0003] However, to achieve efficient and reliable power generation of photovoltaic requires the configuration of a photovoltaic DC conversion device. Existing photovoltaic converters are basically inverters that output alternating current. If applied to the photovoltaic-storage-direct-current-soft system, the alternating current needs to be converted back into direct current, adding an additional intermediate conversion, increasing the system volume, high cost, low efficiency, complex control, poor adaptability, and poor current sharing effect. At the same time, the multi-stage circuit topology is also relatively complex. Summary of the Invention

[0004] In view of this, this application provides a photovoltaic DC conversion method, a storage medium, and a computer device. By combining the maximum power point tracking control and the voltage proportional integral algorithm, while controlling the first switching device and the second switching device, the structure is simplified and at the same time, it can directly output direct current.

[0005] According to one aspect of this application, a photovoltaic DC conversion method is provided, which is applied to a DC converter. The DC converter is installed in a photovoltaic-storage-direct-current-soft system. The photovoltaic-storage-direct-current-soft system includes a photovoltaic power generation system. The electric energy generated by the photovoltaic power generation system is converted by the DC converter and then output as direct current. The DC converter internally includes a first switching device and a second switching device. The method includes:

[0006] Real-time obtain the actual output voltage and the actual output current of the photovoltaic power generation system, and based on the actual output voltage and the actual output current, obtain the actual output power;

[0007] Through the voltage proportional integral algorithm, obtain the duty cycle of the first pulse width modulation signal inside the DC converter when the actual output voltage is adjusted to a preset target output voltage after being converted by the DC converter;

[0008] Determine the maximum photovoltaic power point of the photovoltaic power generation system and the control output voltage when the photovoltaic power generation system always operates at the maximum photovoltaic power point through the maximum power point tracking control algorithm and the actual output power, and obtain the duty cycle of the second pulse width modulation signal inside the DC converter when the control output voltage is adjusted to the preset target output voltage after being converted by the DC converter;

[0009] Based on the target pulse width modulation signal corresponding to the minimum duty cycle and the target duty cycle corresponding to the target pulse width modulation signal, control the on-off states of the first switching device and the second switching device simultaneously until the direct current with the preset target output voltage is obtained, where the conduction phase difference between the first switching device and the second switching device is 180 degrees.

[0010] Optionally, the target pulse width modulation signal includes a high level state and a low level state, the target pulse width modulation signal corresponds to a signal period, and the high level state and the low level state alternate in any signal period. The controlling the on-off states of the first switching device and the second switching device simultaneously based on the target pulse width modulation signal corresponding to the minimum duty cycle and the target duty cycle corresponding to the target pulse width modulation signal includes:

[0011] Determine the target pulse width modulation signal corresponding to the minimum duty cycle, and determine the target conduction time and the target turn-off time based on the target duty cycle corresponding to the target pulse width modulation signal, where the target duty cycle is the proportion of the time when the high level state of the target pulse width modulation signal is located in the entire signal period;

[0012] When the target pulse width modulation signal is in the high level state, control the first switching device to be in the on state during the target conduction time and the second switching device to be in the off state during the target conduction time based on the target pulse width modulation signal;

[0013] When the target pulse width modulation signal is in the low level state, control the first switching device to be in the off state during the target turn-off time and the second switching device to be in the on state during the target turn-off time based on the target pulse width modulation signal.

[0014] Optionally, after determining the target pulse width modulation signal corresponding to the minimum duty cycle, the method further includes:

[0015] If the target duty cycle corresponding to the target pulse width modulation signal is greater than the preset maximum duty cycle, control the on-off states of the first switching device and the second switching device simultaneously based on the target pulse width modulation signal and the preset maximum duty cycle.

[0016] Optionally, before obtaining the duty cycle of the first pulse width modulation signal inside the DC converter when the actual output voltage is adjusted to the preset target output voltage after being converted by the DC converter through the voltage proportional integral algorithm, the method further includes:

[0017] When there are multiple parallel DC converters in the photovoltaic-storage DC-AC flexible system, the droop control algorithm is used to stabilize the current sharing of each DC converter respectively.

[0018] Optionally, obtaining the duty cycle of the first pulse width modulation signal inside the DC converter when the actual output voltage is adjusted to the preset target output voltage after being converted by the DC converter through the voltage proportional integral algorithm includes:

[0019] Based on the actual output voltage and the preset target output voltage, a voltage error is obtained;

[0020] A proportional part control quantity proportional to the voltage error is obtained, and the voltage error is integrated to obtain an integral part control quantity proportional to the accumulated quantity of the integrated voltage error;

[0021] Based on the proportional part control quantity and the integral part control quantity, the duty cycle of the first pulse width modulation signal inside the DC converter is obtained when the actual output voltage is adjusted to the preset target output voltage after being converted by the DC converter.

[0022] Optionally, determining the maximum photovoltaic power point of the photovoltaic power generation system and the control output voltage when the photovoltaic power generation system always operates at the maximum photovoltaic power point through the maximum power point tracking control algorithm and the actual output power includes:

[0023] The output voltage and output current of the photovoltaic power generation system are respectively perturbed to obtain the change situation of the output photovoltaic power after perturbation;

[0024] Based on the change situation of the output photovoltaic power, the maximum photovoltaic power point of the photovoltaic power generation system and the control output voltage perturbed at the maximum photovoltaic power point are determined.

[0025] Optionally, obtaining the duty cycle of the second pulse width modulation signal inside the DC converter when the control output voltage is adjusted to the preset target output voltage after being converted by the DC converter includes:

[0026] Based on the proportional integral control method, the duty cycle of the second pulse width modulation signal inside the DC converter is obtained when the control output voltage is adjusted to the preset target output voltage after being converted by the DC converter.

[0027] Optionally, the DC converter internally includes a first boost topology circuit unit and a second boost topology circuit unit that are interleaved and paralleled; the first boost topology circuit unit includes a first inductor, a first capacitor, a second capacitor, and a first switching device, and the second boost topology circuit unit includes a second inductor, a first capacitor, a second capacitor, and a second switching device.

[0028] According to another aspect of the present application, there is provided a storage medium on which a computer program is stored, and when the program is executed by a processor, the above-mentioned photovoltaic DC conversion method is implemented.

[0029] According to yet another aspect of the present application, there is provided a computer device, including a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor. When the processor executes the program, the above-mentioned photovoltaic DC conversion method is implemented.

[0030] By means of the above technical solution, a photovoltaic DC conversion method, a storage medium, and a computer device provided by the present application obtain the duty cycle of the first pulse width modulation signal when the actual output voltage is adjusted to the preset target output voltage through a voltage proportional integral algorithm; obtain the control output voltage when the photovoltaic power generation system operates at the maximum photovoltaic power point and the duty cycle of the second pulse width modulation signal when it is adjusted to the preset target output voltage through a maximum power point tracking control algorithm and the actual output power; based on the target pulse width modulation signal corresponding to the minimum duty cycle, simultaneously control the on-off states of the first switching device and the second switching device until direct current electricity with the preset target output voltage is obtained. By combining the maximum power point tracking control and the voltage proportional integral algorithm, and simultaneously controlling the first switching device and the second switching device, while simplifying the structure, it can also directly output direct current electricity.

[0031] The above description is only an overview of the technical solution of the present application. In order to be able to understand the technical means of the present application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features, and advantages of the present application more obvious and understandable, the specific embodiments of the present application are specifically given below. Description of the Drawings

[0032] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application. In the drawings:

[0033] Figure 1 A flowchart showing a photovoltaic DC conversion method provided by an embodiment of the present application is shown;

[0034] Figure 2 A schematic structural diagram of a DC converter provided by an embodiment of the present application is shown

[0035] Figure 3 shows a schematic flowchart of another photovoltaic DC conversion method provided by an embodiment of the present application;

[0036] Figure 4 shows a schematic flowchart of yet another photovoltaic DC conversion method provided by an embodiment of the present application. Detailed implementation manners

[0037] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other.

[0038] In this embodiment, a photovoltaic DC conversion method is provided. As Figure 1 shown, it is applied to a DC converter. The DC converter is installed in a photovoltaic-storage-direct-current-flexible system. The photovoltaic-storage-direct-current-flexible system includes a photovoltaic power generation system. The electric energy generated by the photovoltaic power generation system is converted by the DC converter and then output as direct current. The DC converter internally includes a first switching device and a second switching device. The method includes:

[0039] Step 101, obtain the actual output voltage and actual output current of the photovoltaic power generation system in real time, and obtain the actual output power based on the actual output voltage and the actual output current.

[0040] The photovoltaic conversion device in the existing system is basically an AC grid-connected inverter, and the output is alternating current, which cannot meet the high-performance requirements of the photovoltaic-storage-direct-current-flexible system. If it is applied to the photovoltaic-storage-direct-current-flexible system, the alternating current needs to be converted into direct current again. Since an additional intermediate conversion is added, the system volume is increased, the cost is high, the efficiency is low, the control is complex, the adaptability is poor, and the current sharing effect is not good.

[0041] In the above embodiment of the present application, it is applied to a DC converter. The aforementioned DC converter is installed in a photovoltaic-storage-direct-current-flexible system. The aforementioned photovoltaic-storage-direct-current-flexible system includes a photovoltaic power generation system. The electric energy generated by the aforementioned photovoltaic power generation system is converted by the DC converter and then output as direct current. The aforementioned DC converter internally includes a first switching device and a second switching device. Regarding the internal structure of the DC converter, as Figure 2 shown, it includes a first boost topology circuit unit and a second boost topology circuit unit that are interlaced and connected in parallel. The first boost topology circuit unit includes a first inductor L1, a first capacitor C1, a second capacitor C2, and a first switching device Q2. The second boost topology circuit unit includes a second inductor L2, a first capacitor C1, a second capacitor C2, and a second switching device Q1. Among them, the first capacitor C1 and the second capacitor C2 are shared by the first boost topology circuit unit and the second boost topology circuit unit. In addition, in Figure 2In it, the DC converter further includes a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4. By adding a pair of diodes D3 and D4 at the output end, fault isolation between the output end and the external DC bus can be achieved. Figure 2 On the left side in it is the input end, which is responsible for receiving the electrical energy of photovoltaic power generation output by the photovoltaic power generation system. Figure 2 On the right side in it is the output end, which is directly connected to the DC bus and is responsible for directly outputting direct current.

[0042] The interleaved parallel circuit is a special circuit structure. It realizes higher efficiency and better performance by paralleling multiple identical circuit units in an interleaved manner. This structure enables the current in the circuit to flow on multiple paths, thus optimizing the overall performance of the circuit.

[0043] Specifically, the actual output voltage and actual output current of the photovoltaic power generation system are obtained in real time. The acquisition frequency can be set to kHz, and based on the actual output voltage and actual output current, the actual output power is obtained. Among them, the actual output power is the product of the actual output voltage and the actual output current.

[0044] Step 102: Through the voltage proportional-integral algorithm, obtain the duty cycle of the first pulse-width modulation signal inside the DC converter when the actual output voltage is adjusted to the preset target output voltage after being transformed by the DC converter.

[0045] Step 103: Through the maximum power point tracking control algorithm and the actual output power, determine the maximum photovoltaic power point of the photovoltaic power generation system and the control output voltage when the photovoltaic power generation system always operates at the maximum photovoltaic power point. Obtain the duty cycle of the second pulse-width modulation signal inside the DC converter when the control output voltage is adjusted to the preset target output voltage after being transformed by the DC converter.

[0046] Then, through the voltage proportional-integral algorithm (voltage PI algorithm), obtain the duty cycle of the first pulse-width modulation signal inside the DC converter when the actual output voltage is adjusted to the preset target output voltage after being transformed by the DC converter, and through the maximum power point tracking control algorithm (MPPT control algorithm) and the actual output power, determine the maximum photovoltaic power point of the photovoltaic power generation system and the control output voltage when the photovoltaic power generation system always operates at the maximum photovoltaic power point. Obtain the duty cycle of the second pulse-width modulation signal inside the DC converter when the control output voltage is adjusted to the preset target output voltage after being transformed by the DC converter, so as to prepare for the on-off control of the subsequent switching devices.

[0047] Step 104: Based on the target pulse width modulation signal corresponding to the minimum duty cycle and the target duty cycle corresponding to the target pulse width modulation signal, control the on-off states of the first switching device and the second switching device simultaneously until direct current with a preset target output voltage is obtained, where the conduction phase difference between the first switching device and the second switching device is 180 degrees.

[0048] Next, based on the target pulse width modulation signal corresponding to the minimum duty cycle and the target duty cycle corresponding to the target pulse width modulation signal, control the on-off states of the first switching device and the second switching device simultaneously until direct current with a preset target output voltage is obtained. The preset target output voltage can be set to 750V. Therefore, while achieving MPPT (Maximum Power Point Tracking), it can also achieve DC voltage conversion and adaptive output control. Combining two interleaved parallel BOOST (boost) topologies, it can not only achieve MPPT tracking control of the photovoltaic panel (photovoltaic power generation system), but also convert the uncontrollable DC voltage output by the photovoltaic power generation system into the DC voltage required by the optical storage direct current flexible system. Compared with the traditional PFC (Power Factor Correction) + inverter bridge combination form, the above embodiment of the present application uses a single DC converter to achieve MPPT tracking and DC voltage conversion, reducing the system volume, reducing the investment cost, improving the power generation and power consumption efficiency, with flexible control and strong adaptive output ability.

[0049] Specifically, the conduction phase difference between the first switching device and the second switching device is 180 degrees. The driving frequencies and duty cycles of the two switching devices are the same, but the conduction phase difference of 180 degrees means that the driving signals of the two switching devices are completely opposite in time. Specifically, assume there are two switching devices S1 and S2, and their driving signals are both square waves with a period of T. If the driving signal of S1 is high level (conducting state) at a certain moment, then the driving signal of S2 must be low level (off state) at the same moment, and vice versa. Moreover, this high-level and low-level state will alternate within each period T, maintaining a 180-degree conduction phase difference. In topologies such as DC-AC inverters and push-pull circuits, it is often necessary for two switching devices to work alternately to generate an AC output. By ensuring that the driving signals of the two switching devices have a 180-degree conduction phase difference, their complementary conduction can be achieved, thus avoiding short-circuit problems caused by simultaneous conduction and ensuring the stability and efficiency of the circuit.

[0050] By applying the technical solution of this embodiment, a two-way interleaved parallel BOOST circuit topology is adopted. Through the voltage proportional integral algorithm, the duty cycle of the first pulse width modulation signal is obtained when the actual output voltage is adjusted to the preset target output voltage. Through the maximum power point tracking control algorithm and the actual output power, the control output voltage when the photovoltaic power generation system operates at the maximum photovoltaic power point and the duty cycle of the second pulse width modulation signal when it is adjusted to the preset target output voltage are obtained. Based on the target pulse width modulation signal corresponding to the minimum duty cycle, the on-off states of the first switch device and the second switch device are simultaneously controlled until the direct current with the preset target output voltage is obtained. By combining the maximum power point tracking control and the voltage proportional integral algorithm, while controlling the first switch device and the second switch device simultaneously, the structure is simplified and the direct current can be directly output.

[0051] Further, as a refinement and extension of the specific implementation manner of the above embodiment, in order to fully illustrate the specific implementation process of this embodiment, another photovoltaic DC conversion method is provided, which is applied to a DC converter. The DC converter is installed in a photovoltaic-storage-direct-current flexible system, and the photovoltaic-storage-direct-current flexible system includes a photovoltaic power generation system. The electric energy generated by the photovoltaic power generation system is converted by the DC converter and output as direct current. The DC converter internally includes a first switch device and a second switch device; as Figure 3 shown, this method includes:

[0052] Step 201, obtain the actual output voltage and the actual output current of the photovoltaic power generation system in real time, and based on the actual output voltage and the actual output current, obtain the actual output power.

[0053] In the above embodiment of the present application, the actual output voltage and the actual output current of the photovoltaic power generation system are obtained in real time, and the actual output power is obtained based on the actual output voltage and the actual output current, so as to prepare for subsequent DC conversion.

[0054] Step 202, when there are multiple parallel DC converters in the photovoltaic-storage-direct-current flexible system, use the droop control algorithm to perform current sharing and stabilization on each DC converter respectively.

[0055] Step 203, based on the actual output voltage and the preset target output voltage, obtain the voltage error, obtain the proportional part control quantity proportional to the voltage error, and integrate the voltage error to obtain the integral part control quantity proportional to the integrated voltage error cumulative quantity.

[0056] When there are multiple parallel DC converters in the photovoltaic-storage-direct-current flexible system, use the droop control algorithm to perform current sharing and stabilization on each DC converter respectively. Then, set the target output voltage, for example, 750V, which is the stable value of the expected output voltage of the photovoltaic power generation system.

[0057] Step 204: Based on the proportional part control quantity and the integral part control quantity, obtain the duty cycle of the first pulse width modulation signal inside the DC converter when the actual output voltage is adjusted to the preset target output voltage after being converted by the DC converter.

[0058] Compare the current actual output voltage of the photovoltaic power generation system with the set target output voltage value to obtain a voltage error, that is, voltage error = target output voltage - actual output voltage.

[0059] Apply the PI algorithm to obtain the duty cycle of the first pulse width modulation signal inside the DC transformer. The PI algorithm (Proportional-Integral algorithm) is a commonly used control algorithm for eliminating errors and reaching the desired steady state, where:

[0060] Proportional part (P): According to the magnitude of the voltage error, directly generate a control quantity proportional to the error, which helps to quickly respond to voltage changes.

[0061] Integral part (I): Integrate the voltage error to generate a control quantity proportional to the error accumulation, which helps to eliminate the static error in the system.

[0062] Add the proportional part and the integral part to obtain the control output of the PI algorithm, that is, the first pulse width modulation signal, including the duty cycle.

[0063] Then, adjust the output voltage, that is, use the control output of the PI algorithm (the duty cycle of the first pulse width modulation signal) to adjust the output voltage of the photovoltaic power generation system. Finally, through the DC transformer, continuously measure the actual voltage, calculate the voltage error, apply the PI algorithm, and adjust the output voltage until the actual voltage approaches or reaches the target output voltage.

[0064] It should be noted that the specific implementation of the voltage proportional integral algorithm may vary due to different systems, and factors such as the dynamic characteristics of the system, stability requirements, and parameter tuning of the controller also need to be considered. In addition, the output result of the voltage proportional integral algorithm is a control signal used to adjust the output voltage of the photovoltaic power generation system. This control signal may be a current command, a voltage command, or the duty cycle of a pulse width modulation signal, etc., depending on the control method of the system and the actuator.

[0065] Step 205: Perturb the output voltage and output current of the photovoltaic power generation system respectively, obtain the change in the output photovoltaic power after perturbation, and based on the change in the output photovoltaic power, determine the maximum photovoltaic power point of the photovoltaic power generation system and the control output voltage at the maximum photovoltaic power point when perturbed.

[0066] Step 206: Based on the proportional-integral control method, obtain the duty cycle of the second pulse width modulation signal inside the DC converter when the controlled output voltage is adjusted to a preset target output voltage after being converted by the DC converter.

[0067] Next, in a photovoltaic power generation system, the main objective of the MPPT (Maximum Power Point Tracking) control algorithm is to operate the photovoltaic cells at the maximum power point, thereby maximizing the conversion of light energy into electrical energy. MPPT control is essentially an automatic optimization process. It adds an impedance converter (such as a DC-DC converter) between the photovoltaic cells and the load to control the voltage at the photovoltaic cell terminals, so that the converted operating point coincides exactly with the maximum power point of the photovoltaic cells. This process involves real-time monitoring and adjustment of the output characteristics of the photovoltaic cells. The process of determining the reference voltage using the MPPT algorithm is as follows:

[0068] The MPPT algorithm (such as the constant voltage tracking method, the perturbation and observation method, the conductance increment method, etc.) calculates the voltage value corresponding to the maximum power point of the photovoltaic cells under the current environmental conditions (such as light intensity and temperature), that is, the reference voltage Vref. During the operation of the MPPT algorithm, the system continuously collects the voltage and current values of the photovoltaic panels in the photovoltaic power generation system and calculates the current output power. Then, the algorithm compares the current output power with the maximum output power stored at the previous moment. If the current output power is greater, the value of the maximum output power is updated. This process is dynamic and changes continuously with changes in external environments such as light intensity and temperature. Finally, the maximum output photovoltaic power value is determined. The purpose of the MPPT algorithm is to track this maximum power point in real time, so that the photovoltaic panels always operate at the maximum power output state, thereby maximizing the utilization of solar energy.

[0069] The specific process of the maximum power point tracking control algorithm (MPPT) is as follows: Collect the initial voltage and current values of the photovoltaic panel. According to the characteristic curve or mathematical model of the photovoltaic panel, estimate an initial operating point (voltage and current). Continuously collect the current voltage and current values of the photovoltaic panel, and calculate the current output power, which is the voltage multiplied by the current. Compare the current output power with the previously stored maximum output power. If the current output power is greater than the previously stored maximum output power, update the value of the maximum output power and record the operating point at this time. Make a small perturbation (increase or decrease) to the operating voltage or current of the photovoltaic panel. Observe the change in the output power of the photovoltaic panel after the perturbation. If the output power increases after the perturbation, it means the perturbation direction is correct, and continue to perturb in this direction. If the output power decreases after the perturbation, it means the perturbation direction is wrong, and a reverse perturbation is required. Through continuous perturbation and observation, make the operating point of the photovoltaic panel gradually approach the maximum power point. When the operating point is close to the maximum power point, reduce the amplitude and frequency of the perturbation to avoid excessive oscillation near the maximum power point. Through fine adjustment, make the photovoltaic panel always operate near the maximum power point, thereby maximizing the output power. Since the external environment (such as light intensity, temperature, etc.) will change continuously, the MPPT algorithm needs to continuously adapt to these changes. By real-time monitoring the changes in the external environment and adjusting the control parameters of the MPPT algorithm (such as perturbation step size, observation time, etc.), to keep the photovoltaic panel always operating near the maximum power point. Commonly used MPPT algorithms include the constant voltage method, the perturbation and observation method, the incremental conductance method, etc. Each algorithm has its own advantages and disadvantages in terms of efficiency, tracking speed, steady-state accuracy, complexity, etc., and a suitable algorithm can be selected according to the actual application scenario and requirements.

[0070] Finally, determine the maximum photovoltaic power point of the photovoltaic power generation system, and the control output voltage perturbed at the maximum photovoltaic power point, and based on the proportional-integral control method, obtain the duty cycle of the second pulse width modulation signal inside the DC converter when the control output voltage is adjusted to the preset target output voltage after being converted by the DC converter.

[0071] Step 207, determine the target pulse width modulation signal corresponding to the minimum duty cycle, and determine the target conduction time and the target turn-off time based on the target duty cycle corresponding to the target pulse width modulation signal, where the target duty cycle is the proportion of the time when the high-level state of the target pulse width modulation signal is located in the entire signal period, the target pulse width modulation signal includes a high-level state and a low-level state, the target pulse width modulation signal corresponds to a signal period, and the high-level state and the low-level state alternate in any signal period.

[0072] Step 208, when the target pulse width modulation signal is in the high level state, control the first switching device to be in the on state within the target conduction time and the second switching device to be in the off state within the target conduction time based on the target pulse width modulation signal.

[0073] Step 209, when the target pulse width modulation signal is in the low level state, control the first switching device to be in the off state within the target turn-off time and the second switching device to be in the on state within the target turn-off time until the direct current of the preset target output voltage is obtained, wherein the conduction phase difference between the first switching device and the second switching device is 180 degrees.

[0074] Next, the duty cycle of the pulse width modulation signal can be determined by comparing its high level time with the total period time. Specifically, the duty cycle refers to the proportion of the time in the high level state within one pulse cycle, and the calculation formula is: duty cycle = high level time / total signal period × 100%.

[0075] For example, if there are two PWM signals, the high level time of signal A is 5 milliseconds and the total period is 10 milliseconds, then its duty cycle is 50%; while the high level time of signal B is 3 milliseconds and the total period is also 10 milliseconds, then its duty cycle is 30%. In this case, we can say that the duty cycle of signal A is greater than that of signal B.

[0076] The size of the duty cycle directly affects the average voltage or power of the analog signal controlled by the PWM signal. In the electronic field, by adjusting the duty cycle of the PWM signal, precise control of the output voltage, current, motor speed, LED brightness, etc. can be achieved. Therefore, when comparing the duty cycles of PWM signals, it is essentially comparing the sizes of the average voltages or powers of the analog signals they control.

[0077] Specifically, determine the target pulse width modulation signal corresponding to the minimum duty cycle, and input the target pulse width modulation signal to the control terminal of the switching device to control its conduction and cut-off. The target pulse width modulation signal is a periodic signal, and its high level time and low level time are determined according to the duty cycle. When the target pulse width modulation signal is in the high level state, the switching device conducts; when the target pulse width modulation signal is in the low level state, the switching device cuts off. In this way, precise control of the conduction time of the switching device within each cycle can be achieved.

[0078] Step 210, if the target duty cycle corresponding to the target pulse width modulation signal is greater than the preset maximum duty cycle, then based on the target pulse width modulation signal and the preset maximum duty cycle, control the on-off states of the first switching device and the second switching device simultaneously.

[0079] Specifically, a preset maximum duty cycle can also be set (for example, 95%, which is set according to the actual situation). If the target duty cycle corresponding to the target pulse width modulation signal is greater than the preset maximum duty cycle, then based on the target pulse width modulation signal and the preset maximum duty cycle (the aforementioned set 95%), the on-off states of the first switching device and the second switching device are controlled simultaneously to maintain the stability of DC conversion.

[0080] In addition, when there are multiple parallel DC converters in the photovoltaic energy storage DC flexible system, adaptive droop control can also be used to achieve current sharing among the DC converters and adaptive output of voltage, ensuring the effective output of photovoltaic power generation.

[0081] By applying the technical solution of this embodiment, through a two-way interleaved parallel BOOST DC conversion topology, its control method includes MPPT control, output voltage PI closed-loop control, and adaptive droop control. Compared with the traditional form of combining PFC and inverter, while the structure is simplified, it can also directly output direct current, and the dual inductors can reduce the volume of the DC transformer itself, making it convenient to carry and install. At the same time, the output capacitor current is reduced and it is more stable.

[0082] In one embodiment, for example Figure 4 As shown, first, the control parameters are initialized, AD sampling and data processing are performed to obtain the actual output voltage and actual output current of the photovoltaic power generation system, and the actual output power is obtained. Next, it includes a voltage PI algorithm and an MPPT control algorithm. Specifically, the aforementioned voltage PI algorithm is also affected by the droop control algorithm to maintain current sharing stability. After comparing the output results (the duty cycle corresponding to the pulse width modulation signal) of the voltage PI algorithm and the MPPT algorithm, its output is further compared with the internal limit value (preset maximum duty cycle). Finally, the actual target duty cycle is output to control Figure 2 the switching devices in the two-way interleaved parallel BOOST circuit topology in the

[0083] Based on the above methods as Figure 1 and Figure 3 shown, correspondingly, the embodiment of the present application also provides a storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements the photovoltaic DC conversion method as Figure 1 and Figure 3 shown above.

[0084] Based on such understanding, the technical solution of the present application can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (such as a CD-ROM, a USB flash drive, a portable hard drive, etc.), and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in various implementation scenarios of the present application.

[0085] Based on the above-mentioned Figure 1 and Figure 3 shown methods, in order to achieve the above object, the embodiments of the present application further provide a computer device, which can specifically be a personal computer, a server, a network device, etc. The computer device includes a storage medium and a processor; the storage medium is used for storing a computer program; the processor is used for executing the computer program to implement the photovoltaic DC conversion method as shown in the above Figure 1 and Figure 3 shown.

[0086] Optionally, the computer device may further include a user interface, a network interface, a camera, a radio frequency (RF) circuit, sensors, an audio circuit, a WI-FI module, and so on. The user interface may include a display screen (Display), an input unit such as a keyboard (Keyboard), etc. Optionally, the user interface may further include a USB interface, a card reader interface, etc. The network interface may optionally include a standard wired interface, a wireless interface (such as a Bluetooth interface, a WI-FI interface), etc.

[0087] Those skilled in the art can understand that the structure of a computer device provided in this embodiment does not constitute a limitation on the computer device, and it may include more or fewer components, or combine certain components, or have different component arrangements.

[0088] The storage medium may further include an operating system and a network communication module. The operating system is a program for managing and storing the hardware and software resources of the computer device, and supports the operation of information processing programs and other software and / or programs. The network communication module is used to implement communication between components inside the storage medium, and communication between the storage medium and other hardware and software in the entity device.

[0089] Through the description of the above embodiments, those skilled in the art can clearly understand that the present application can be implemented by means of software plus a necessary general hardware platform, or can also be implemented by hardware. By means of a voltage proportional integral algorithm, obtain the duty cycle of the first pulse width modulation signal when the actual output voltage is adjusted to the preset target output voltage; through the maximum power point tracking control algorithm and the actual output power, obtain the control output voltage when the photovoltaic power generation system operates at the maximum photovoltaic power point, and the duty cycle of the second pulse width modulation signal when it is adjusted to the preset target output voltage; based on the target pulse width modulation signal corresponding to the minimum duty cycle, simultaneously control the on-off states of the first switching device and the second switching device until a direct current with the preset target output voltage is obtained. By combining the maximum power point tracking control and the voltage proportional integral algorithm, and simultaneously controlling the first switching device and the second switching device, while simplifying the structure, it can also directly output direct current.

[0090] Those skilled in the art can understand that the drawings are only schematic diagrams of a preferred implementation scenario, and the modules or processes in the drawings are not necessarily essential for implementing the present application. Those skilled in the art can understand that the modules in the device in the implementation scenario can be distributed in the device in the implementation scenario according to the description of the implementation scenario, or can be correspondingly changed to be located in one or more devices different from the present implementation scenario. The modules in the above implementation scenario can be combined into one module, or can be further split into multiple sub-modules.

[0091] The above serial numbers of the present application are only for description and do not represent the advantages or disadvantages of the implementation scenarios. The above disclosure is only several specific implementation scenarios of the present application. However, the present application is not limited thereto, and any changes that can be thought of by those skilled in the art should fall within the protection scope of the present application.

Claims

1. A photovoltaic direct current conversion method, characterized in that: Applied to a DC converter, the DC converter is installed in a photovoltaic storage direct-flexible system, the photovoltaic storage direct-flexible system includes a photovoltaic power generation system, the electric energy generated by the photovoltaic power generation system is converted by a DC converter and output as direct current, and the DC converter includes a first switch device and a second switch device; the method includes: Acquire the actual output voltage and the actual output current of the photovoltaic power generation system in real time, and obtain the actual output power based on the actual output voltage and the actual output current; Obtaining, by means of a voltage proportional integral algorithm, a duty cycle of a first pulse width modulation signal inside the DC converter when the actual output voltage is adjusted to a preset target output voltage after being converted by the DC converter; Determine the maximum photovoltaic power point of the photovoltaic power generation system and the control output voltage when the photovoltaic power generation system always works at the maximum photovoltaic power point through the maximum power point tracking control algorithm and the actual output power, and obtain the duty cycle of the second pulse width modulation signal inside the DC converter when the control output voltage is adjusted to a preset target output voltage after being converted by the DC converter; Based on the target pulse width modulation signal corresponding to the minimum duty cycle and the target duty cycle corresponding to the target pulse width modulation signal, the on-off states of the first switching device and the second switching device are controlled simultaneously until a direct current with a preset target output voltage is obtained, wherein the conduction phase difference between the first switching device and the second switching device is 180 degrees.

2. The method according to claim 1, characterized in that The target pulse width modulation signal includes a high level state and a low level state, the target pulse width modulation signal corresponds to a signal cycle, the high level state and the low level state appear alternately in any signal cycle, the target pulse width modulation signal corresponding to the minimum duty cycle and the target duty cycle corresponding to the target pulse width modulation signal simultaneously control the on-off state of the first switching device and the second switching device, including: Determine a target pulse width modulation signal corresponding to a minimum duty cycle, and determine a target on-time and a target off-time based on a target duty cycle corresponding to the target pulse width modulation signal, wherein the target duty cycle is the time that the target pulse width modulation signal is in a high level state, as a proportion of the entire signal cycle; When the target pulse width modulation signal is in a high level state, based on the target pulse width modulation signal, the first switch device is controlled to be in an on state within a target on time, and the second switch device is controlled to be in an off state within the target on time; When the target PWM signal is in a low level state, the first switch device is controlled to be in an off state within a target off time based on the target PWM signal, and the second switch device is controlled to be in an on state within the target off time.

3. The method according to claim 2, characterized in that After determining the target pulse width modulation signal corresponding to the minimum duty cycle, the method further includes: If the target duty cycle corresponding to the target pulse width modulation signal is greater than the preset maximum duty cycle, the on-off state of the first switching device and the second switching device are controlled simultaneously based on the target pulse width modulation signal and the preset maximum duty cycle.

4. The method according to claim 1, characterized in that: Before obtaining the duty cycle of the first pulse width modulation signal inside the DC converter when the actual output voltage is adjusted to the preset target output voltage after being converted by the DC converter by using the voltage proportional integral algorithm, the method further includes: When the PV-storage-DC-flexible system contains multiple parallel DC converters, the droop control algorithm is used to balance the current of each DC converter and stabilize it.

5. The method according to claim 1, characterized in that: The step of obtaining, by means of a voltage proportional integral algorithm, a duty cycle of a first pulse width modulation signal inside a DC converter when the actual output voltage is adjusted to a preset target output voltage after being converted by the DC converter comprises: Based on the actual output voltage and the preset target output voltage, a voltage error is obtained; Obtaining a proportional part control amount that is proportional to the voltage error, integrating the voltage error, and obtaining an integral part control amount that is proportional to the integrated voltage error accumulation amount; Based on the proportional part control amount and the integral part control amount, the duty cycle of the first pulse width modulation signal inside the DC converter is obtained when the actual output voltage is adjusted to a preset target output voltage after being converted by the DC converter.

6. The method according to claim 1, characterized in that The method of determining the maximum photovoltaic power point of the photovoltaic power generation system through the maximum power point tracking control algorithm and the actual output power, and controlling the output voltage when the photovoltaic power generation system always operates at the maximum photovoltaic power point, includes: The output voltage and output current of the photovoltaic power generation system are disturbed respectively to obtain the change of the output photovoltaic power after the disturbance; Based on the change in the output photovoltaic power, the maximum photovoltaic power point of the photovoltaic power generation system and the controlled output voltage disturbed at the maximum photovoltaic power point are determined.

7. The method according to claim 1, characterized in that The obtaining of the duty cycle of the second pulse width modulation signal inside the DC converter when the controlled output voltage is adjusted to a preset target output voltage after being converted by the DC converter includes: Based on the proportional-integral control method, the duty cycle of the second pulse width modulation signal inside the DC converter is obtained when the controlled output voltage is adjusted to a preset target output voltage after being converted by the DC converter.

8. The method according to claim 1, characterized in that The DC converter internally includes a first boost topology structure circuit unit and a second boost topology structure circuit unit which are connected in parallel with each other; the first boost topology structure circuit unit includes a first inductor, a first capacitor, a second capacitor and a first switching device, and the second boost topology structure circuit unit includes a second inductor, a first capacitor, a second capacitor and a second switching device.

9. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the photovoltaic direct current conversion method described in any one of claims 1 to 8 is implemented.

10. A computer device comprising a storage medium, a processor, and a computer program stored in the storage medium and executable on the processor, characterized in that: When the processor executes the computer program, the photovoltaic direct current conversion method described in any one of claims 1 to 8 is implemented.

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