Rapid MPPT method, system and apparatus based on unipolar inverter circuit

Abstract

Disclosed in the present invention are a rapid MPPT method, system and apparatus based on a unipolar inverter circuit. The method comprises the following steps: initializing MPPT control parameters; when a sampling condition is met within each computing period, triggering a sampling operation, and recording photovoltaic-side data within the current computing period; when a power grid phase meets a computing condition, computing the magnitude relationship between a voltage within the current computing period and a voltage within the previous computing period, and on the basis of the magnitude relationship, determining a power compensation factor; on the basis of the power compensation factor and a power computing strategy, determining output power and / or a reference voltage; and on the basis of the output power, controlling the power of an inverter within the computing period. In the present invention, on the basis of the characteristics of a unipolar inverter circuit, the aims of a low computing power and a high response speed are achieved.

Description

A fast MPPT tracking method, system and device based on unipolar inverter circuit Technical Field

[0001] The present invention relates to the technical field of battery capacity composition, and in particular to a fast MPPT tracking method, system and device based on a unipolar inverter circuit. Background Art

[0002] With advances in science and technology, existing MPPT (maximum power point tracking) control methods include constant voltage, perturbation-and-observe, conductance increment, and fuzzy control. These traditional methods offer advantages such as ease of implementation, moderate accuracy, and oscillation of the operating point around the maximum power point (MPPT). However, these methods are slow and unsuitable for rapidly changing conditions. When light intensity fluctuates rapidly, they cannot track the maximum power point in real time, resulting in energy loss.

[0003] In photovoltaic inverter circuits, the MPPT tracking algorithm provides a reference voltage. Typically, this is done through an external voltage loop to regulate the photovoltaic voltage, but tracking often requires multiple cycles. Using open-loop calculations can lead to discrepancies between calculated and actual results due to circuit errors, making perfect tracking impossible.

[0004] Summary of the Invention

[0005] The purpose of the present invention is to provide a fast MPPT tracking method, system and device based on a unipolar inverter circuit, which achieves the goals of low computing power and high response speed based on the characteristics of the unipolar inverter circuit.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A fast MPPT tracking method based on a unipolar inverter circuit comprises the following steps: initializing MPPT control parameters;

[0008] When the sampling conditions are met in each calculation cycle, the sampling operation is triggered and the photovoltaic side data in the current calculation cycle is recorded;

[0009] When the grid phase meets the calculation conditions, the magnitude relationship between the voltage in the current calculation cycle and the voltage in the previous calculation cycle is calculated, and the power compensation factor is determined based on the magnitude relationship;

[0010] The output power and / or reference voltage are determined according to the power compensation factor and the power calculation strategy; and the inverter power within the calculation period is controlled according to the output power.

[0011] In the above technical solution, the output power is determined according to the power compensation factor and the power calculation strategy, including:

[0012] Let the reference voltage be the maximum power point voltage among every four sampling points, and calculate the first output power according to the output power calculation formula;

[0013] Determine whether the first output power meets the power output requirement. If so, directly output the first output power. If not, determine the second output power and / or reference voltage according to the power adjustment strategy.

[0014] In the above technical solution, the output power calculation formula is:

[0015] Among them, P out is the first output power, V now 2 is the voltage in the current calculation cycle, C is the photovoltaic side input capacitance, T is the calculation cycle, k is the power compensation factor, P now is the power value in the current calculation cycle, V ref is the reference voltage.

[0016] In the above technical solution, the power output requirement is that the first output power is greater than the maximum output power or less than 0;

[0017] Determining the second output power and / or reference voltage according to the power adjustment strategy includes:

[0018] When the first output power is greater than the maximum output power, the reference voltage is determined by a first reference voltage calculation formula, and the second output power is the maximum output power;

[0019] When the first output power is less than 0, the reference voltage is determined by a second reference voltage calculation formula, and the second output power is 0.

[0020] In the above technical solution, the first reference voltage calculation formula is:

[0021] Among them, V now 2 is the voltage in the current calculation cycle, C is the photovoltaic side input capacitance, T is the calculation cycle, k is the power compensation factor, P now is the power value in the current calculation cycle, P max is the maximum output power, V ref is the reference voltage;

[0022] The second reference voltage calculation formula is:

[0023] Among them, V now 2 is the voltage in the current calculation cycle, C is the photovoltaic side input capacitance, T is the calculation cycle, Pnow is the power value in the current calculation cycle, V ref is the reference voltage.

[0024] In the above technical solution, calculating the magnitude relationship between the voltage in the current calculation cycle and the reference voltage in the previous calculation cycle, and determining the power compensation factor based on the magnitude relationship, includes:

[0025] When the voltage in the current calculation cycle is less than the reference voltage in the previous calculation cycle, the power compensation factor is set to the first power compensation factor;

[0026] When the voltage in the current calculation cycle is greater than the reference voltage in the previous calculation cycle, the power compensation factor is set to the second power compensation factor; and the first power compensation factor is less than the second compensation power factor.

[0027] In the above technical solution, the MPPT control parameters include the photovoltaic side reference voltage and the power factor, and the photovoltaic side data include the voltage value and / or the power value.

[0028] In the above technical solution, the sampling condition includes that the grid phase is an integer multiple of 45°;

[0029] Alternatively, the calculation condition is that the grid phase is 0° and / or 180°.

[0030] In a second aspect, a fast MPPT tracking system based on a unipolar inverter circuit is provided, comprising: a unipolar inverter circuit and a controller; the controller executes any one of the above-described fast MPPT tracking methods based on a unipolar inverter circuit.

[0031] In a third aspect, a fast MPPT tracking device based on a unipolar inverter circuit is also provided, comprising:

[0032] a memory storing executable program code;

[0033] a processor coupled to the memory;

[0034] The processor calls the executable program code stored in the memory, and the processor executes the above-mentioned fast MPPT tracking method based on a unipolar inverter circuit.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. This application provides a fast MPPT tracking method, system, and device based on a unipolar inverter circuit. The MPPT tracking speed is fast, with parameters updated every 10 grid cycles. Typically, the maximum power point can be reached within 10 grid cycles, greatly improving tracking speed.

[0037] 2. The algorithm is simple and the sampling frequency is low. Each calculation cycle only requires sampling and calculating data four times, which saves memory and reduces a lot of calculations for digital power supply.

[0038] 3. Due to the disturbance of power compensation factors, after rapidly approaching the maximum power point voltage, it will fluctuate around the reference voltage and finally converge to the optimal solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG1 is a schematic diagram of a unipolar inverter circuit used in an embodiment of the present invention;

[0040] FIG2 is a schematic diagram of photovoltaic side voltage and grid side voltage provided by an embodiment of the present invention;

[0041] FIG3 is a schematic diagram of a flow chart provided by an embodiment of the present invention; DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0043] The terms "including" and "having" and any variations thereof in the embodiments of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or modules is not necessarily limited to those steps or modules explicitly listed, but may include other steps or modules not explicitly listed or inherent to these processes, methods, products or apparatus.

[0044] The present application provides a fast MPPT tracking method based on a unipolar inverter circuit. A single-stage inverter circuit means that the photovoltaic side power is directly connected to the grid. Since there is no intermediate decoupling capacitor, the ripple of the output power will be directly reflected on the capacitor on the photovoltaic side. This application takes the flyback inverter circuit in Figure 1 as an example. There are actually many circuit implementation methods, including flyback inverter circuits, high-voltage full-bridge inverter circuits, T-type three-level circuits, and other circuits in which the photovoltaic front stage does not have a substantial high-voltage bus. The relationship between the photovoltaic side voltage and the grid voltage is shown in Figure 2. By detecting the disturbance of the capacitor voltage, MPPT tracking can be achieved once within half a grid cycle.

[0045] As shown in FIG3 , the method includes the following steps:

[0046] Step S1, initialize MPPT control parameters.

[0047] The MPPT control parameters include setting a reasonable photovoltaic side reference voltage (Vref , power coefficient k, such as reference voltage V ref 2 Set to 0.85 times the photovoltaic open circuit voltage. Usually, the MPPT voltage of a photovoltaic panel is between 0.7 times and 0.85 times the open circuit voltage. In this application, the minimum value is taken for initialization.

[0048] Step S2: triggering a sampling operation when a sampling condition is met in each calculation cycle, and recording photovoltaic side data in the current calculation cycle; the photovoltaic side data includes voltage value and / or power value.

[0049] The sampling conditions include the grid phase being an integer multiple of 45°. Sampling is triggered when the grid phase is an integer multiple of 45°, and the corresponding voltage and power values ​​on the photovoltaic side are recorded. By simplifying the sampling and calculation process, only the voltage and power at the voltage phase being an integer multiple of 45° need to be sampled. As shown in Figure 2, the red dotted part is the sampling point. Taking half a grid cycle as an example, it can be obtained from the characteristics of the unipolar circuit that the points with phases of 45° and 135° are the points with the highest and lowest PV side voltages. At this time, the photovoltaic side reference voltage is determined based on the PV characteristics of the photovoltaic panel.

[0050] The sampling operation first obtains the grid phase through a phase-locked loop. When the grid phase reaches an integer multiple of 45°, the microcontroller is used to sample the photovoltaic side voltage and current at the current moment and calculate the power value.

[0051] Step S3: When the grid phase meets the calculation conditions, the magnitude relationship between the voltage in the current calculation cycle and the voltage in the previous calculation cycle is calculated, and the power compensation factor is determined according to the magnitude relationship.

[0052] The calculation condition is that the grid phase is 0° and / or 180°. In this application, a calculation is performed once when the grid phase is 0° and 180° to obtain the relationship between the voltage value of the current calculation cycle and the reference voltage value.

[0053] A larger power compensation factor value results in faster convergence and larger steady-state oscillations. A smaller power compensation factor value results in slower convergence and smaller steady-state oscillations. The power compensation factor range is related to the PV curve of the PV panel, input capacitance C, power update period T, and inverter power P.

[0054] In the PV curve, there is a maximum power point P of the photovoltaic panel. mppt Voltage V mppt , making V mppt ±ΔV power P>99.5%*P mppt , the maximum value of the oscillation voltage ΔV at the maximum power point is limited by the above conditions. And the oscillation voltage By modifying the value of the power compensation factor k, a faster convergence speed or a smaller oscillation voltage can be obtained.

[0055] Therefore, the relationship between the voltage in the current calculation cycle and the reference voltage in the previous calculation cycle is calculated, and the power compensation factor is determined based on the relationship, including:

[0056] When the voltage V now 2 Less than the reference voltage (V ref When , let the power compensation factor be the first power compensation factor;

[0057] When the voltage V now 2 Greater than the reference voltage V in the previous calculation cycle ref When , let the power compensation factor be the second power compensation factor; the first power compensation factor is less than the second compensation power factor.

[0058] Schematically, in this application, when the voltage V now 2 Less than the reference voltage V in the previous calculation cycle ref When , let the power compensation factor k be the first power compensation factor, k = k*0.99;

[0059] When the voltage V now 2 Greater than the reference voltage V in the previous calculation cycle ref When , let k be the second power compensation factor, k = k*1.01.

[0060] The power compensation factor k is adjusted by output voltage feedback to compensate for output power and the disturbance of photovoltaic side voltage. The oscillation amplitude and convergence speed of the algorithm are adjusted by adjusting the power compensation factor.

[0061] Step S4: determining the output power and / or reference voltage according to the power compensation factor and the power calculation strategy; and controlling the inverter power within the calculation period according to the output power.

[0062] The output power is determined based on the power compensation factor and power calculation strategy, including:

[0063] Step S41: Let the reference voltage be the maximum power point voltage among every four sampling points, and calculate the first output power according to the output power calculation formula;

[0064] The output power calculation formula is:

[0065] Among them, P outis the first output power, V now 2 is the voltage in the current calculation cycle, C is the photovoltaic side input capacitance, T is the calculation cycle, k is the power compensation factor, P now is the power value in the current calculation cycle, V ref is the reference voltage.

[0066] Step S42: determine whether the first output power meets the power output requirement. If so, directly output the first output power. If not, determine the second output power and / or reference voltage according to the power adjustment strategy.

[0067] Furthermore, the power output requirement is that the first output power is greater than the maximum output power or less than 0. If the first output power calculated by MPPT is greater than the maximum output power, the calculated result will not match the actual result, resulting in a deviation in the power compensation factor. Therefore, the current output power of the inverter is calculated in an open loop, and the maximum power of the inverter is used according to C*U now_pv 2 =C*U old_pv 2 -P out *T+P pv *T is used to infer the current reference voltage.

[0068] Therefore, in step S42, determining the second output power and / or reference voltage according to the power adjustment strategy includes:

[0069] Step S421: When the first output power is greater than the maximum output power, a reference voltage is determined using a first reference voltage calculation formula, and the second output power is the maximum output power;

[0070] The first reference voltage calculation formula is:

[0071] Among them, V now 2 is the voltage in the current calculation cycle, C is the photovoltaic side input capacitance, T is the calculation cycle, k is the power compensation factor, P now is the power value in the current calculation cycle, P max is the maximum output power, V ref is the reference voltage.

[0072] Step S422: When the first output power is less than 0, determine the reference voltage using a second reference voltage calculation formula, and the second output power is 0.

[0073] The second reference voltage calculation formula is:

[0074] Among them, V now 2 is the voltage in the current calculation cycle, C is the photovoltaic side input capacitance, T is the calculation cycle, P now is the power value in the current calculation cycle, (V ref is the reference voltage.

[0075] The current output power of the inverter is calculated by open loop. now_pv 2 =C*U old_pv 2 -P out *T+P pv *T is derived from the MPPT. If the power calculated by MPPT is greater than the maximum power, the maximum power of the inverter should be used to reverse-calculate the current reference voltage. Otherwise, the calculated result will not match the actual result, resulting in a deviation in the k value.

[0076] The inverter power in the calculation cycle is calculated according to the output power control, that is, the output power P out The grid current reference value is generated, and the current loop is used to control the inverter's power. Compared to traditional algorithms, the MPPT side no longer directly outputs a reference voltage, but rather outputs the output power after power factor compensation. In a single-stage circuit, closed-loop voltage control can only be adjusted at the power frequency, requiring multiple cycles to reach the specified power. Using output power for calculations eliminates this time-consuming calculation and compensates for any discrepancies between calculated errors and actual circuit values ​​within the MPPT.

[0077] Based on the same inventive concept, the present application provides a fast MPPT tracking system based on a unipolar inverter circuit, comprising a unipolar inverter circuit and a controller; the controller executes any of the above-described fast MPPT tracking methods based on a unipolar inverter circuit.

[0078] The system processing method can refer to the description of the above method and will not be repeated here.

[0079] The present application also provides a fast MPPT tracking device based on a unipolar inverter circuit, which may include: a memory storing executable program code;

[0080] a memory storing executable program code;

[0081] a processor coupled to the memory;

[0082] The processor calls the executable program code stored in the memory, and the processor executes the above-mentioned fast MPPT tracking method based on a unipolar inverter circuit.

[0083] An embodiment of the present application further provides a non-transitory machine-readable storage medium having an executable program stored thereon. When the executable program is executed by a processor, the processor executes the processing method provided in the above embodiment.

[0084] An embodiment of the present invention discloses a computer-readable storage medium storing a computer program for electronic data exchange, wherein the computer program enables a computer to execute the described fast MPPT tracking method based on a unipolar inverter circuit.

[0085] An embodiment of the present invention discloses a computer program product, which includes a non-transitory computer-readable storage medium storing a computer program, and the computer program is operable to enable a computer to execute the described fast MPPT tracking method based on a unipolar inverter circuit.

[0086] The embodiments described above are merely illustrative, wherein the modules described as separate components may or may not be physically separate, and the components shown as modules may or may not be physical modules, i.e., they may be located in one place or distributed across multiple network modules. Some or all of the modules may be selected based on actual needs to achieve the objectives of the embodiments. Persons of ordinary skill in the art will be able to understand and implement the embodiments without inventive effort.

[0087] Through the detailed description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus the necessary general hardware platform, or of course, by means of hardware. Based on this understanding, the above technical solution, in essence, or the portion that contributes to the prior art, can be embodied in the form of a software product, which can be stored in a computer-readable storage medium, including a read-only memory (ROM), a random access memory (RAM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), a one-time programmable read-only memory (OTPROM), an electronically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disk storage, magnetic disk storage, magnetic tape storage, or any other computer-readable medium capable of carrying or storing data.

[0088] Finally, it should be noted that the contents disclosed in the embodiments of the present invention are merely preferred embodiments of the present invention and are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the aforementioned embodiments, it should be understood by those skilled in the art that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features therein may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A fast MPPT tracking method based on a unipolar inverter circuit, characterized in that: This method comprises the following steps: Initialize MPPT control parameters; When the sampling conditions are met in each calculation cycle, the sampling operation is triggered and the photovoltaic side data in the current calculation cycle is recorded; When the grid phase meets the calculation conditions, the magnitude relationship between the voltage in the current calculation cycle and the voltage in the previous calculation cycle is calculated, and the power compensation factor is determined based on the magnitude relationship; Determine output power and / or reference voltage according to a power compensation factor and a power calculation strategy; controlling the inverter power within a calculation period according to the output power; The output power is determined based on the power compensation factor and power calculation strategy, including: Let the reference voltage be the maximum power point voltage among every four sampling points, and calculate the first output power according to the output power calculation formula; determining whether the first output power meets the power output requirement, and if so, directly outputting the first output power; and if not, determining a second output power and / or a reference voltage according to the power adjustment strategy; The output power calculation formula is: Among them, P out is the first output power, V now 2 is the voltage in the current calculation cycle, C is the photovoltaic side input capacitance, T is the calculation cycle, k is the power compensation factor, P now is the power value in the current calculation cycle, V ref is the reference voltage.

2. A fast MPPT tracking method based on a unipolar inverter circuit according to claim 1, characterized in that: The power output requirement is that the first output power is greater than the maximum output power or less than 0; Determining the second output power and / or reference voltage according to the power adjustment strategy includes: When the first output power is greater than the maximum output power, the reference voltage is determined by a first reference voltage calculation formula, and the second output power is the maximum output power; When the first output power is less than 0, the reference voltage is determined by a second reference voltage calculation formula, and the second output power is 0.

3. A fast MPPT tracking method based on a unipolar inverter circuit according to claim 2, characterized in that: The first reference voltage calculation formula is: Among them, V now 2 is the voltage in the current calculation cycle, C is the photovoltaic side input capacitance, T is the calculation cycle, k is the power compensation factor, P now is the power value in the current calculation cycle, P max is the maximum output power, V ref is the reference voltage; The second reference voltage calculation formula is: Among them, V now 2 is the voltage in the current calculation cycle, C is the photovoltaic side input capacitance, T is the calculation cycle, P now is the power value in the current calculation cycle, V ref is the reference voltage.

4. The fast MPPT tracking method based on a unipolar inverter circuit according to claim 1, characterized in that: Calculate the magnitude relationship between the voltage in the current calculation cycle and the reference voltage in the previous calculation cycle, and determine the power compensation factor based on the magnitude relationship, including: When the voltage in the current calculation cycle is less than the reference voltage in the previous calculation cycle, the power compensation factor is set to the first power compensation factor; When the voltage in the current calculation cycle is greater than the reference voltage in the previous calculation cycle, the power compensation factor is set to the second power compensation factor; and the first power compensation factor is less than the second compensation power factor.

5. The fast MPPT tracking method based on a unipolar inverter circuit according to claim 1, characterized in that: The MPPT control parameters include a photovoltaic side reference voltage and a power factor, and the photovoltaic side data include a voltage value and / or a power value.

6. A fast MPPT tracking method based on a unipolar inverter circuit according to claim 3, characterized in that: The sampling conditions include that the grid phase is an integer multiple of 45°; Alternatively, the calculation condition is that the grid phase is 0° and / or 180°.

7. A fast MPPT tracking system based on a unipolar inverter circuit, characterized in that: include: Unipolar inverter circuit and controller; The controller executes a fast MPPT tracking method based on a unipolar inverter circuit as described in any one of claims 1-6.

8. A fast MPPT tracking device based on a unipolar inverter circuit, characterized in that: include: a memory storing executable program code; a processor coupled to the memory; The processor calls the executable program code stored in the memory, and the processor executes the fast MPPT tracking method based on a unipolar inverter circuit as described in any one of claims 1-6.

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