Matching networking control method based on photovoltaic power characteristic variable

Abstract

The invention discloses a matching networking control method based on a photovoltaic power characteristic variable, and the method comprises the steps: collecting the DC side voltage and AC side output voltage and current of an inverter, and generating a vector angle and a voltage amplitude according to matching control and reactive power-voltage droop control; and network construction control of the inverter is realized through three-phase voltage synthesis and voltage and current double-loop control in sequence. Photovoltaic voltage and current output by a photovoltaic array and direct-current side voltage of an inverter are collected, output power of the photovoltaic array is adjusted by adjusting photovoltaic power characteristic variables according to changes of the direct-current side voltage, networking control of a converter is achieved, and system frequency is maintained within a reasonable range. According to the invention, when the photovoltaic output is sufficient, the converter and the inverter are independent of the power grid and can autonomously construct the AC voltage and frequency; according to the invention, automatic response and distribution of load power and adjustment of system frequency can be realized without communication between photovoltaic systems and real-time MPPT monitoring, so that investment and maintenance costs are reduced.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic power generation control technology, and specifically to a matching grid control method based on photovoltaic power characteristic variables. Background Technology

[0002] With the continuous increase in the penetration rate of photovoltaic power generation systems, constructing autonomous islanded microgrids using grid-based control technology has become an important research direction in the field of new energy. In islanded operation mode, if the photovoltaic system still adopts the traditional maximum power point tracking (MPPT) control strategy, the energy captured may far exceed the load absorption capacity, causing microgrid instability. Therefore, there is an urgent need for a photovoltaic controller capable of operating in a flexible power adjustment mode. This controller can achieve real-time source-load matching by dynamically adjusting the output power, while also undertaking the responsibility of system frequency regulation.

[0003] Furthermore, current load distribution among photovoltaic (PV) units primarily employs two approaches: one is a fixed-ratio allocation based on the rated installed capacity of each PV unit. However, due to environmental factors such as irradiance fluctuations and temperature changes, the actual maximum available power deviates significantly from the rated value, easily leading to overload or underload issues in some power sources. The other approach determines the load distribution ratio by real-time monitoring of the maximum available power of each unit. While this improves distribution accuracy, it requires deploying numerous environmental sensors or constructing complex power prediction models, significantly increasing hardware costs and causing an exponential increase in control system response delay and algorithm complexity. Therefore, developing an efficient, economical, and easy-to-implement PV control technology has become a core technological challenge for promoting the large-scale application of high-penetration PV microgrids. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a matching grid control method based on photovoltaic power characteristic variables. This invention, based on matching control and reactive power-voltage droop control, autonomously constructs AC voltage and frequency to achieve grid control, and dynamically adjusts photovoltaic power and load distribution in response to frequency changes based on photovoltaic power characteristic variables.

[0005] The objective of this invention is achieved through the following technical solution: a matching grid control method based on photovoltaic power characteristic variables, comprising the following steps: (1) Collect the DC side voltage and AC side output voltage and current of the DC / AC inverter, generate the vector angle and output voltage amplitude according to the matching control and reactive power-voltage droop control, and realize the grid control of the DC / AC inverter through three-phase voltage synthesis and voltage and current dual-loop control in sequence. (2) Collect the photovoltaic voltage and current output of the photovoltaic array and the DC side voltage of the DC / AC inverter. Based on the change of the DC side voltage, adjust the photovoltaic power characteristic variable designed according to the output characteristics of the photovoltaic array to adjust the output power of the photovoltaic array and realize the grid control of the DC / DC converter.

[0006] Furthermore, step (1) specifically includes the following sub-steps: (1.1) Collect the DC side voltage, AC side three-phase output voltage, AC side three-phase output current and bridge arm side three-phase inductor current of the DC / AC inverter; (1.2) The DC side voltage is used to obtain the inverter's angular frequency through the matching control equation, and then the inverter's vector angle is obtained through integration; (1.3) Based on the inverter's vector angle, the three-phase output voltage on the AC side, the three-phase output current on the AC side, and the three-phase inductor current on the bridge arm side are transformed by the synchronous rotating coordinate system abc / dq to obtain the dq-axis components of the output voltage, the dq-axis components of the output current, and the dq-axis components of the inductor current, respectively. The reactive power is then calculated based on the dq-axis components of the output voltage and the dq-axis components of the output current. (1.4) Based on the reactive power, the rated reactive power, the rated output voltage of the inverter, and the reactive power droop coefficient, the output voltage amplitude of the inverter is obtained through the reactive power-voltage amplitude droop equation. (1.5) Based on the inverter's vector angle and output voltage amplitude, the three-phase reference voltage is obtained through the three-phase voltage synthesis stage, and then the dq axis reference component of the output capacitor voltage is obtained after synchronous rotating coordinate system abc / dq transformation. (1.6) Based on the dq-axis components of the output voltage and the dq-axis reference components of the output capacitor voltage, the dq-axis reference components of the inductor current are obtained through the voltage control equation; (1.7) Based on the dq-axis component of the inductor current and the reference dq-axis component of the inductor current, the output voltage dq-axis control signal of the inverter is obtained through the current control equation; (1.8) Based on the inverter's output voltage dq axis control signal and vector angle, the three-phase voltage control signal is obtained through synchronous rotating coordinate system dq / abc inverse transformation. Then, the three-phase voltage control signal generates SVPWM signal to control the switching transistors of the DC / AC inverter, forming a closed-loop control and realizing the grid control of the DC / AC inverter.

[0007] Furthermore, the expression for the matching control equation is:

[0008]

[0009] In the formula, Let ω be the vector angle of the inverter, and w be the angular frequency of the inverter. This is the rated AC angular frequency value. The collected DC-side voltage, This is the rated DC voltage value.

[0010] Furthermore, the synchronous rotating coordinate system abc / dq transformation is specifically implemented through the following formula:

[0011] In the formula, d represents the d-axis component in the two-phase rotating coordinate system, q represents the q-axis component in the two-phase rotating coordinate system, k represents the transformation coefficient, and a, b, and c represent the output voltage, output current, or inductor current of phase a, phase b, and phase c on the AC side, respectively. The formula for calculating the reactive power is:

[0012] In the formula, Q represents reactive power. Let be the cutoff frequency of the second-order low-pass filter, and s be the Laplace operator. The damping ratio of the second-order low-pass filter. and These are the d-axis and q-axis components of the inverter's output voltage, respectively. and These are the d-axis and q-axis components of the inverter's output current, respectively.

[0013] Furthermore, the expression for the reactive power-voltage amplitude droop equation is as follows:

[0014] In the formula, U is the output voltage amplitude of the inverter. This refers to the rated output voltage of the inverter. is the rated reactive power, and n is the reactive power droop coefficient.

[0015] Furthermore, the three-phase voltage synthesis stage is specifically represented by the following formula:

[0016]

[0017]

[0018] In the formula, , , These are the reference voltages for phases a, b, and c, respectively.

[0019] Furthermore, the expression for the voltage control equation is:

[0020]

[0021] In the formula, and These are the d-axis and q-axis reference components of the inductor current, respectively. and These are the proportional and integral control parameters for the voltage control loop, respectively. and Output the d-axis reference component and q-axis reference component of the capacitor voltage respectively; The expression for the current control equation is:

[0022]

[0023] In the formula, and These are the d-axis and q-axis control signals for the inverter's output voltage, respectively. and These are the proportional and integral control parameters for the current control loop, respectively. and These are the d-axis and q-axis components of the inductor current, respectively.

[0024] Furthermore, step (2) specifically includes the following sub-steps: (2.1) Collect the photovoltaic voltage and photovoltaic current output by the photovoltaic array and the DC-side voltage of the DC / AC inverter; (2.2) Calculate the current photovoltaic power characteristic variables based on photovoltaic voltage and photovoltaic current; and generate reference values ​​for photovoltaic power characteristic variables based on DC side voltage and rated DC voltage value through droop control and upper limit constraint based on DC voltage change; (2.3) The error is obtained by subtracting the photovoltaic power characteristic variable from the photovoltaic power characteristic variable reference value. Then, the PWM signal is generated by the PI controller to control the switching transistors in the DC / DC converter, forming a closed-loop control and realizing the grid control of the DC / DC converter.

[0025] Furthermore, the formula for calculating the photovoltaic power characteristic variable is as follows:

[0026] In the formula, R is the characteristic variable of photovoltaic power. and These are the real-time collected photovoltaic voltage and photovoltaic current, respectively. This represents the change in photovoltaic current at the current sampling time relative to the previous sampling time. This represents the change in photovoltaic voltage at the current sampling time relative to the previous sampling time. The reference values ​​for the photovoltaic power characteristic variables are obtained using the following formula:

[0027]

[0028] In the formula, This serves as a reference value for photovoltaic power characteristic variables. Let m be the droop coefficient, and m be the intermediate variable. This is the rated DC voltage value. DC side voltage The set value for the rated photovoltaic power characteristic variable.

[0029] Furthermore, the PWM signal is specifically generated using the following formula:

[0030]

[0031] In the formula, This is a PWM signal used to control the on / off state of the switching transistors in a DC / DC converter. and Here, represents the proportional and integral control parameters of the PI controller, and s is the Laplace operator. This represents the error of the photovoltaic power characteristic variable.

[0032] Compared with the prior art, the beneficial effects of the present invention are: (1) When the photovoltaic output is sufficient, the present invention can independently construct AC voltage and frequency without relying on the grid to realize grid control. It is applicable to high-penetration distributed photovoltaic systems in isolated microgrids that need to coordinate power distribution and maintain system frequency stability.

[0033] (2) Based on the output characteristics of photovoltaics, this invention designs a photovoltaic power characteristic variable; the photovoltaic power characteristic variable can quantitatively characterize the proportion of photovoltaic output to the real-time available maximum output, so that load allocation does not require the use of sensors and complex algorithms to monitor the real-time available maximum power of photovoltaics, thereby reducing investment and maintenance costs.

[0034] (3) Based on the matching relationship between DC voltage and islanded microgrid frequency and system frequency, the present invention automatically adjusts the reference value of photovoltaic power characteristic variable according to the change of DC voltage, and automatically adjusts the photovoltaic output power through the power characteristic variable control loop to respond to frequency changes, thereby achieving real-time source-load balance and maintaining the system frequency within a reasonable range.

[0035] (4) The power characteristic variable of the present invention can quantitatively characterize the proportion of photovoltaic output to the real-time available maximum output, so that the load distribution ratio between photovoltaic units can adapt to changes in ambient irradiance and temperature, and is basically unaffected by irradiance and temperature, making the load distribution more efficient and accurate, and avoiding some power supply underload or overload.

[0036] (5) The control method of the present invention can be used to realize new photovoltaic power control, distribution and system frequency support; it enables the converter and inverter to build AC voltage and frequency independently without relying on the grid when the photovoltaic output is sufficient; it can realize automatic response and distribution of load power and system frequency adjustment without communication between photovoltaic systems or real-time MPPT monitoring, thereby reducing investment and maintenance costs. Attached Figure Description

[0037] Figure 1 This is a block diagram of the overall architecture and grid control method of the photovoltaic system in this invention; Figure 2 It is a characteristic curve of photovoltaic power-characteristic variables under different irradiance conditions; Figure 3 These are photovoltaic power-characteristic variable curves under different temperature conditions; Figure 4 This is a schematic diagram of the output three-phase AC voltage; Figure 5 This is a schematic diagram showing the change in photovoltaic output power after the load, irradiance, and temperature increase or decrease; Figure 6 This is a schematic diagram illustrating the changes in photovoltaic power characteristic variables after the load, irradiance, and temperature increase or decrease; Figure 7 It is a schematic diagram showing the change in AC frequency after the load, irradiance, and temperature increase or decrease. Detailed Implementation

[0038] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.

[0039] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “the,” and “the” used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0040] It should be understood that although the terms first, second, third, etc., may be used in this invention to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first information may also be referred to as second information without departing from the scope of this invention, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to a determination."

[0041] The present invention will now be described in detail with reference to the accompanying drawings. Unless otherwise specified, the features of the following embodiments and implementations can be combined with each other.

[0042] Figure 1 The overall topology of the photovoltaic system is shown, which mainly includes a photovoltaic array, a DC / DC converter, a DC / AC inverter, an inductor, a capacitor, and a load.

[0043] like Figure 1 As shown, the matching grid control method based on photovoltaic power characteristic variables of the present invention specifically includes the following steps: (1) Collect the DC side voltage and AC side output voltage and current of the DC / AC inverter, generate the vector angle and output voltage amplitude according to the matching control and reactive power-voltage droop control, and realize the grid control of the DC / AC inverter through three-phase voltage synthesis and voltage and current dual-loop control in sequence.

[0044] (1.1) Acquire the DC-side voltage of the DC / AC inverter AC side three-phase output voltage AC side three-phase output current and the three-phase inductor current on the bridge arm side .

[0045] (1.2) The DC side voltage collected in step (1.1) The inverter's angular frequency w is obtained through the matched control equations, and the inverter's vector angle is obtained by integrating the angular frequency w. .

[0046] Furthermore, the expression for the matching governing equation is:

[0047]

[0048] In the formula, Let ω be the vector angle of the inverter, and w be the angular frequency of the inverter. This is the rated AC angular frequency value. The DC-side voltage acquired in step (1.1) is... This is the rated DC voltage value.

[0049] (1.3) The vector angle of the inverter obtained in step (1.2) The three-phase output voltage of the AC side collected in step (1.1) AC side three-phase output current and the three-phase inductor current on the bridge arm side The dq-axis components of the output voltage are obtained by synchronously rotating coordinate system abc / dq transformation. dq-axis components of the output current and the dq-axis components of the inductor current And based on the dq axis components of the output voltage and the dq-axis components of the output current Calculate the reactive power Q.

[0050] Furthermore, the synchronous rotating coordinate system abc / dq transformation is specifically achieved through the following formula:

[0051] In the formula, d represents the d-axis component in the two-phase rotating coordinate system, q represents the q-axis component in the two-phase rotating coordinate system, and k represents the transformation coefficient. This represents a constant amplitude change. This represents constant power transformation, where the power remains unchanged before and after the transformation. The vector angle of the inverter obtained in step (1.2); a, b, and c represent the output voltage, output current, or inductor current of phase a, phase b, and phase c on the AC side, respectively.

[0052] It should be understood that the collected AC three-phase output voltage The dq-axis components of the output voltage are obtained by synchronously rotating coordinate system abc / dq transformation. At that time, Substituting a, b, and c respectively into the above synchronous rotating coordinate system abc / dq transformation formula for calculation, the obtained values ​​of d and q are the dq-axis components of the output voltage. Similarly, the dq-axis component of the output current can also be calculated using the above-described synchronous rotating coordinate system abc / dq transformation formula. and the dq-axis components of the inductor current .

[0053] Furthermore, the formula for calculating reactive power Q is:

[0054] In the formula, Q represents reactive power. Let be the cutoff frequency of the second-order low-pass filter, and s be the Laplace operator. The damping ratio of the second-order low-pass filter. and These are the d-axis and q-axis components of the inverter's output voltage, respectively. and These are the d-axis and q-axis components of the inverter's output current, respectively.

[0055] (1.4) Based on the reactive power Q and the rated reactive power obtained in step (1.3) Inverter output voltage rating The output voltage amplitude U of the inverter is obtained by using the reactive power-voltage amplitude droop equation, along with the reactive power droop coefficient n.

[0056] Furthermore, the expression for the reactive power-voltage amplitude droop equation is:

[0057] In the formula, U is the output voltage amplitude of the inverter. Let Q be the rated output voltage of the inverter, and Q be the reactive power obtained in step (1.3). is the rated reactive power, and n is the reactive power droop coefficient.

[0058] (1.5) The vector angle of the inverter obtained from step (1.2) The output voltage amplitude U of the inverter obtained in step (1.4) is used to obtain the three-phase reference voltage through a three-phase voltage synthesis stage. After undergoing a synchronous rotating coordinate system abc / dq transformation, the dq-axis reference component of the output capacitor voltage is obtained. .

[0059] Furthermore, the three-phase voltage synthesis process is specifically represented by the following formula:

[0060]

[0061]

[0062] In the formula, , , These are the reference voltages for phases a, b, and c, respectively. U is the vector angle of the inverter obtained in step (1.2), and U is the output voltage amplitude of the inverter obtained in step (1.4).

[0063] (1.6) The dq-axis components of the output voltage obtained from step (1.3) The dq-axis reference component of the output capacitor voltage obtained in step (1.5) The dq-axis reference component of the inductor current is obtained through the voltage control equation. .

[0064] Furthermore, the expression for the voltage control equation is:

[0065]

[0066] In the formula, and These are the d-axis and q-axis reference components of the inductor current, respectively. and , respectively, are the proportional and integral control parameters of the voltage control loop, and s is the Laplace operator. and These are the d-axis and q-axis reference components of the output capacitor voltage obtained in step (1.5), respectively. and These are the d-axis and q-axis components of the output voltage obtained in step (1.3), respectively.

[0067] (1.7) The dq-axis components of the inductor current obtained from step (1.3) The dq-axis reference component of the inductor current obtained in step (1.6) The output voltage dq-axis control signal of the inverter is obtained through the current control equation. .

[0068] Furthermore, the expression for the current control equation is:

[0069]

[0070] In the formula, and These are the d-axis and q-axis control signals for the inverter's output voltage, respectively. and ... and These are the d-axis and q-axis reference components of the inductor current obtained in step (1.6), respectively. and These are the d-axis and q-axis components of the inductor current obtained in step (1.3), respectively.

[0071] (1.8) Based on the inverter output voltage dq axis control signal obtained in step (1.7) and the inverter vector angle obtained in step (1.2) The three-phase voltage control signal is obtained by inverse transformation of the synchronous rotating coordinate system dq / abc. Then controlled by three-phase voltage signals The SVPWM signal is generated to control the switching transistors of the DC / AC inverter, forming a closed-loop control and realizing the grid control of the DC / AC inverter.

[0072] (2) Collect the photovoltaic voltage and current output of the photovoltaic array and the DC side voltage of the DC / AC inverter. Based on the change of the DC side voltage, adjust the photovoltaic power characteristic variable designed according to the output characteristics of the photovoltaic array to adjust the output power of the photovoltaic array and realize the grid control of the DC / DC converter.

[0073] (2.1) Acquire the photovoltaic voltage output by the photovoltaic array Photovoltaic current and the DC-side voltage of the DC / AC inverter .

[0074] (2.2) Based on the photovoltaic voltage collected in step (2.1) and photovoltaic current Calculate the current photovoltaic power characteristic variable R; and based on the DC side voltage collected in step (2.1) and rated DC voltage value Reference values ​​for photovoltaic power characteristic variables are generated through droop control and upper limit constraints based on DC voltage variations. .

[0075] Furthermore, the formula for calculating the photovoltaic power characteristic variable R is as follows:

[0076] In the formula, R is the characteristic variable of photovoltaic power. and These are the photovoltaic voltage and photovoltaic current collected in real time in step (2.1), respectively. This represents the change in photovoltaic current at the current sampling time relative to the previous sampling time. This represents the change in photovoltaic voltage at the current sampling time relative to the previous sampling time.

[0077] Figure 2and Figure 3 This diagram illustrates the photovoltaic power-characteristic variable curves under different irradiance G and temperature T conditions. The photovoltaic power here has been normalized to represent the actual photovoltaic output as a percentage of the maximum available output in real time. ,in This indicates the actual photovoltaic power output of the photovoltaic array. This represents the actual maximum usable power of the photovoltaic system. The R-value corresponding to the maximum power point of photovoltaics is always -1, unaffected by various conditions such as irradiance and temperature. Within the vast area, The characteristic curve corresponds one-to-one with R, and its variation with irradiance and temperature remains within an acceptable range. Therefore, defining R as a characteristic variable of photovoltaic power allows for the quantitative characterization of the proportion of photovoltaic output to the maximum available output in real time. .

[0078] It should be noted that the power allocation principle among photovoltaic array units is:

[0079] In the formula, This represents the real-time output power of the i-th photovoltaic array. This represents the real-time maximum available power of the i-th photovoltaic array. Therefore, by simply controlling the photovoltaic power characteristic variable R of each photovoltaic array unit to be equal, the power among photovoltaic array units under various environments can be reasonably and evenly distributed according to the real-time capacity, without the need for real-time monitoring of the maximum power.

[0080] Furthermore, reference values ​​for photovoltaic power characteristic variables Obtain it using the following formula:

[0081]

[0082] In the formula, This serves as a reference value for photovoltaic power characteristic variables. The variable m is an intermediate variable with no practical significance; it represents the droop coefficient. This is the rated DC voltage value. The DC-side voltage acquired in step (2.1) is... The set value for the rated photovoltaic power characteristic variable.

[0083] It should be noted that, due to the matching relationship established between the DC voltage and the microgrid frequency, the DC voltage can sense frequency fluctuations in real time. By introducing droop control of the DC voltage-photovoltaic power characteristic variable, the reference value of the photovoltaic power characteristic variable is adjusted according to the change of DC voltage, thereby guiding the adjustment of photovoltaic output power and maintaining the system frequency within a reasonable range.

[0084] (2.3) Combine the photovoltaic power characteristic variable R and the photovoltaic power characteristic variable reference value calculated in step (2.2). The difference is obtained by subtraction, and the error is then used by the PI controller to generate a PWM signal. It is used to control the switching transistors in the DC / DC converter to regulate the photovoltaic voltage, thereby regulating the output power of the photovoltaic array, forming a closed-loop control, and realizing the grid control of the DC / DC converter.

[0085] Furthermore, the PWM signal is specifically generated using the following formula:

[0086]

[0087] In the formula, This is a PWM signal used to control the on / off state of the switching transistors in a DC / DC converter. and Here, represents the proportional and integral control parameters of the PI controller, and s is the Laplace operator. Let R be the error of the photovoltaic power characteristic variable. These are reference values ​​for photovoltaic power characteristic variables.

[0088] For example, to demonstrate the control effect of the method described in this invention, a dynamic model of an AC microgrid consisting of two photovoltaic array units with different rated installed capacities and multiple AC loads was established using Matlab / Simulink. The two photovoltaic array units are composed of CSG PVTech CSG190S1 photovoltaic modules, and the specific parameters are shown in Table 1. The installed capacity of photovoltaic array 1 is twice that of photovoltaic array 2.

[0089] Table 1: Photovoltaic Array Parameters

[0090] In this embodiment, the initial irradiance and temperature are respectively set as follows: At 25℃, the initial load was 560kW. The load was decreased by 160kW and increased by 60kW at t=2s and t=4s respectively. At t=6s, the irradiance of photovoltaic array 2 changed by a step change of 600 ppm. The step change at t=7s is 1000. At t=7s, the irradiance of photovoltaic array 1 changes by a step change of 800. At t=8s, the irradiance changed by a step of 1000. The temperature step change was 15℃, and the temperature step change of photovoltaic array 2 was 35℃ at t=9s. During this test, according to the above load and environmental conditions, the dynamic changes of output AC voltage, photovoltaic output power, photovoltaic power characteristic variables, and AC frequency were as follows: Figure 4 , Figure 5 , Figure 6 and Figure 7 As shown. Figure 4 The diagram shows the automatic establishment of AC voltage by the photovoltaic system. Before the change in operating conditions, the system frequency was around 50.02Hz, and the photovoltaic power characteristic variables of the two photovoltaic array units were equal, with output powers of 370.6kW and 184.9kW, a ratio of 2, consistent with the ratio of rated installed capacity. From t=2 to 4s, the load decreased, and the output power of the photovoltaic array units decreased to 267.7kW and 133.6kW respectively, while the system frequency adjusted to 50.32Hz. From t=4 to 6s, the load increased, and the output power of the photovoltaic array units increased to 304.4kW and 151.9kW respectively, while the system frequency adjusted to 50.22Hz. During this period, the ratio of the output power of the photovoltaic array units remained 2, consistent with the ratio of rated installed capacity. From t=6s to 10s, due to the different irradiance and temperature settings of the two photovoltaic array units, their real-time maximum available power also changed. Figure 5 As can be seen, the two photovoltaic array units adjust the load distribution ratio according to real-time capacity changes, automatically adjusting the output power, and Figure 6 The displayed photovoltaic power characteristic variables completely overlap, indicating that the two photovoltaic array units output power exactly according to the real-time capacity ratio, and the power allocation and sharing objectives are achieved. During this stage, the system frequency changes accordingly as follows: Figure 7 As shown, but still within a reasonable range.

[0091] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A matching grid control method based on photovoltaic power characteristic variables, characterized in that, Includes the following steps: (1) Collect the DC side voltage and AC side output voltage and current of the DC / AC inverter, generate the vector angle and output voltage amplitude according to the matching control and reactive power-voltage droop control, and realize the grid control of the DC / AC inverter through three-phase voltage synthesis and voltage and current dual-loop control in sequence. (2) Collect the photovoltaic voltage and current output of the photovoltaic array and the DC side voltage of the DC / AC inverter. Based on the change of the DC side voltage, adjust the photovoltaic power characteristic variable designed according to the output characteristics of the photovoltaic array to adjust the output power of the photovoltaic array and realize the grid control of the DC / DC converter.

2. The matching grid control method based on photovoltaic power characteristic variables according to claim 1, characterized in that, Step (1) specifically includes the following sub-steps: (1.1) Collect the DC side voltage, AC side three-phase output voltage, AC side three-phase output current and bridge arm side three-phase inductor current of the DC / AC inverter; (1.2) The DC side voltage is used to obtain the inverter's angular frequency through the matching control equation, and then the inverter's vector angle is obtained through integration; (1.3) Based on the inverter's vector angle, the three-phase output voltage on the AC side, the three-phase output current on the AC side, and the three-phase inductor current on the bridge arm side are transformed by the synchronous rotating coordinate system abc / dq to obtain the dq-axis components of the output voltage, the dq-axis components of the output current, and the dq-axis components of the inductor current, respectively. The reactive power is then calculated based on the dq-axis components of the output voltage and the dq-axis components of the output current. (1.4) Based on the reactive power, the rated reactive power, the rated output voltage of the inverter, and the reactive power droop coefficient, the output voltage amplitude of the inverter is obtained through the reactive power-voltage amplitude droop equation. (1.5) Based on the inverter's vector angle and output voltage amplitude, the three-phase reference voltage is obtained through the three-phase voltage synthesis stage, and then the dq axis reference component of the output capacitor voltage is obtained after synchronous rotating coordinate system abc / dq transformation. (1.6) Based on the dq-axis components of the output voltage and the dq-axis reference components of the output capacitor voltage, the dq-axis reference components of the inductor current are obtained through the voltage control equation; (1.7) Based on the dq-axis component of the inductor current and the reference dq-axis component of the inductor current, the output voltage dq-axis control signal of the inverter is obtained through the current control equation; (1.8) Based on the inverter's output voltage dq axis control signal and vector angle, the three-phase voltage control signal is obtained through synchronous rotating coordinate system dq / abc inverse transformation. Then, the three-phase voltage control signal generates SVPWM signal to control the switching transistors of the DC / AC inverter, forming a closed-loop control and realizing the grid control of the DC / AC inverter.

3. The matching grid control method based on photovoltaic power characteristic variables according to claim 2, characterized in that, The expression for the matching control equation is: In the formula, Let ω be the vector angle of the inverter, and w be the angular frequency of the inverter. This is the rated AC angular frequency value. The collected DC-side voltage, This is the rated DC voltage value.

4. The matching grid control method based on photovoltaic power characteristic variables according to claim 2, characterized in that, The synchronous rotating coordinate system abc / dq transformation is specifically achieved through the following formula: In the formula, d represents the d-axis component in the two-phase rotating coordinate system, q represents the q-axis component in the two-phase rotating coordinate system, k represents the transformation coefficient, and a, b, and c represent the output voltage, output current, or inductor current of phase a, phase b, and phase c on the AC side, respectively. The formula for calculating the reactive power is: In the formula, Q represents reactive power. Let be the cutoff frequency of the second-order low-pass filter, and s be the Laplace operator. The damping ratio of the second-order low-pass filter. and These are the d-axis and q-axis components of the inverter's output voltage, respectively. and These are the d-axis and q-axis components of the inverter's output current, respectively.

5. The matching grid control method based on photovoltaic power characteristic variables according to claim 2, characterized in that, The expression for the reactive power-voltage amplitude droop equation is as follows: In the formula, U is the output voltage amplitude of the inverter. This refers to the rated output voltage of the inverter. is the rated reactive power, and n is the reactive power droop coefficient.

6. The matching grid control method based on photovoltaic power characteristic variables according to claim 2, characterized in that, The three-phase voltage synthesis process is specifically represented by the following formula: In the formula, , , These are the reference voltages for phases a, b, and c, respectively.

7. The matching grid control method based on photovoltaic power characteristic variables according to claim 2, characterized in that, The expression for the voltage control equation is: In the formula, and These are the d-axis and q-axis reference components of the inductor current, respectively. and These are the proportional and integral control parameters for the voltage control loop, respectively. and Output the d-axis reference component and q-axis reference component of the capacitor voltage respectively; The expression for the current control equation is: In the formula, and These are the d-axis and q-axis control signals for the inverter's output voltage, respectively. and These are the proportional and integral control parameters for the current control loop, respectively. and These are the d-axis and q-axis components of the inductor current, respectively.

8. The matching grid control method based on photovoltaic power characteristic variables according to claim 1, characterized in that, Step (2) specifically includes the following sub-steps: (2.1) Collect the photovoltaic voltage and photovoltaic current output by the photovoltaic array and the DC-side voltage of the DC / AC inverter; (2.2) Calculate the current photovoltaic power characteristic variables based on photovoltaic voltage and photovoltaic current; and generate reference values ​​for photovoltaic power characteristic variables based on DC side voltage and rated DC voltage value through droop control and upper limit constraint based on DC voltage change; (2.3) The error is obtained by subtracting the photovoltaic power characteristic variable from the photovoltaic power characteristic variable reference value. Then, the PWM signal is generated by the PI controller to control the switching transistor in the DC / DC converter, forming a closed-loop control and realizing the grid control of the DC / DC converter.

9. The matching grid control method based on photovoltaic power characteristic variables according to claim 8, characterized in that, The formula for calculating the photovoltaic power characteristic variable is as follows: In the formula, R is the characteristic variable of photovoltaic power. and These are the real-time collected photovoltaic voltage and photovoltaic current, respectively. This represents the change in photovoltaic current at the current sampling time relative to the previous sampling time. This represents the change in photovoltaic voltage at the current sampling time relative to the previous sampling time. The reference values ​​for the photovoltaic power characteristic variables are obtained using the following formula: In the formula, This serves as a reference value for photovoltaic power characteristic variables. Let m be the droop coefficient, and m be the intermediate variable. This is the rated DC voltage value. DC side voltage The set value for the rated photovoltaic power characteristic variable.

10. The matching grid control method based on photovoltaic power characteristic variables according to claim 8, characterized in that, The PWM signal is generated using the following formula: In the formula, This is a PWM signal used to control the on / off state of the switching transistors in a DC / DC converter. and Here, represents the proportional and integral control parameters of the PI controller, and s is the Laplace operator. This represents the error of the photovoltaic power characteristic variable.

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