A distributed photovoltaic voltage over-limit control method with optimized active and reactive power ratio

Abstract

This invention provides a method for managing voltage exceedance in distributed photovoltaic (PV) systems by optimizing the active and reactive power ratio. When the grid connection point voltage exceeds the limit, this application abandons the maximum power point tracking (MPPT) mode and performs the following steps: calculating the reactive and active power ratios that the PV system should inject into the grid connection point after the voltage exceedance, ensuring that the active power injected into the distribution network bus is maximized when the grid connection point voltage does not exceed the limit; calculating active and reactive power commands using the calculated reactive and reactive power ratios; obtaining current reference values ​​on the dq axis in a dq coordinate system with equal amplitude coordinate transformation based on the active and reactive power commands; and adjusting the active and reactive power injected into the grid connection point based on the current reference values ​​on the dq coordinate axis to regulate the grid connection point voltage. This invention ensures maximum active power flowing to the grid connection point while maintaining the grid connection point voltage within the specified limits.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic grid-connected voltage limit control technology, and in particular to a method for managing distributed photovoltaic voltage limits by optimizing the active and reactive power ratio. Background Technology

[0002] As the penetration rate of photovoltaics (PV) power in distribution networks increases, the power flow in traditional distribution networks will change, and even reverse power flow will occur, leading to voltage rise at the end of the distribution network. In rural distribution networks with lower loads, where the total load is smaller and PV penetration is high, the voltage rise phenomenon is more severe. This voltage rise at the end of the network affects grid stability; excessive voltage rise can even damage household appliances and cause PV grid-connected inverters to shut down. This is one of the main reasons hindering the increase of the proportion of renewable energy in the power grid.

[0003] In recent years, research on the voltage exceeding the limit at the grid connection point of distributed photovoltaic (PV) power generation systems has shown that providing dynamic reactive power support to the system when voltage exceeds the limit can effectively improve the degree of voltage exceeding the limit at the grid connection point and enhance the safety and stability of the distributed PV power generation system's grid connection. Current research on the voltage exceeding the limit at the PV grid connection point mainly focuses on two aspects: reactive power regulation equipment and the remaining capacity of the PV grid-connected inverter. For reactive power regulation equipment, existing technologies classify the adjustment time scale and dynamic response performance of various reactive power regulation devices and consider reactive power substitution between reactive power regulation devices to ensure a better dynamic voltage support capability of the system. Although this method can provide strong dynamic support capability while meeting the system's reactive power demand, the use of fast reactive power compensation devices (such as static var compensators and static var generators) increases the system cost, while the voltage regulation capability of slow voltage regulation equipment (such as on-load tap changers and capacitor banks) cannot meet the system's fast reactive power demand. For the remaining capacity of the PV grid-connected inverter, existing technologies utilize the remaining capacity of the grid-connected inverter to provide a certain amount of reactive power to the system for voltage regulation. Grid-connected photovoltaic (PV) inverters possess the capability for rapid reactive power compensation, and utilizing their remaining capacity can reduce the investment cost of reactive power compensation equipment in the system. However, they suffer from insufficient reactive power capacity. To address this issue, further improvements involve utilizing the entire remaining capacity of the PV grid-connected inverter for reactive power compensation while simultaneously reducing the active power output of the PV system to suppress voltage exceedances at the grid connection point. However, this significantly increases line losses, resulting in the distribution network receiving very little active power while simultaneously receiving a substantial amount of reactive power. Summary of the Invention

[0004] To solve the above-mentioned technical problems, or at least partially solve them, the present invention provides a method, device, and storage medium for managing voltage exceedance in distributed photovoltaic systems with optimized active and reactive power ratios.

[0005] In a first aspect, the present invention provides a method for managing voltage exceedance in distributed photovoltaic systems with optimized active and reactive power ratios, comprising:

[0006] After the photovoltaic system injects active power into the grid connection point under maximum power point tracking (MPPT), it detects the grid connection point voltage. If the grid connection point voltage exceeds the limit, it abandons the MPPT operating mode and executes the following:

[0007] Based on the distribution network bus voltage, active power at the end of the line, reactive power at the end of the line, the voltage limit exceeding the grid connection point, and line parameters, the reactive and active power ratio coefficient k that the photovoltaic power generation system should inject into the grid connection point after the grid connection point voltage exceeds the limit is calculated. This reactive and active power ratio coefficient k ensures that the active power P injected into the distribution network bus by the photovoltaic power generation system when the grid connection point voltage does not exceed the limit is within acceptable limits. g maximum:

[0008]

[0009] Where R is the line resistance, X is the line reactance, and P is the line inductance. L Q represents the active power at the end of the line. L U represents the reactive power at the end of the line. lim U is the voltage exceeding the limit at the grid connection point. S This refers to the voltage of the distribution network bus.

[0010] The active power command P is calculated using the reactive and active power ratio coefficient k. PV_ref Reactive power command Q PV_ref ;

[0011] In the dq coordinate system after undergoing constant amplitude coordinate transformation, based on the active power command P PV_ref Reactive power command Q PV_ref Obtain the reference current value on the dq coordinate axis;

[0012] Adjusting the active and reactive power injected into the grid connection point based on the current reference value on the dq coordinate axis to regulate the grid connection point voltage.

[0013] Furthermore, when detecting the grid connection point voltage, a mean filter is used to stabilize the detected grid connection point voltage.

[0014] Furthermore, based on the equivalent circuit model of a distributed photovoltaic power generation system connected to the distribution network, the relationship between the grid connection point voltage and the distribution network bus voltage is established:

[0015]

[0016] Among them, P PV The active power Q to be injected into the grid connection point for a distributed photovoltaic power generation system. PVThe reactive power to be injected into the grid connection point for a distributed photovoltaic power generation system, where R is the line resistance, X is the line reactance, and U... PCC This is the voltage at the grid connection point.

[0017] Furthermore, the calculation process for the reactive and active power ratio coefficient k that the photovoltaic power generation system should inject into the grid connection point is as follows:

[0018] Based on the grid connection point voltage, active power at the end of the line, reactive power at the end of the line, grid connection point voltage exceeding limits, line parameters, active power to be injected into the grid connection point by the distributed photovoltaic power generation system, and reactive power to be injected into the grid connection point by the distributed photovoltaic power generation system, the active power P flowing to the distribution network bus is calculated. g for:

[0019]

[0020] Let the reactive and active power ratio coefficients to be injected into the grid connection point of the photovoltaic power generation system be k = Q. PV / P PV (k<0), then the active power P flowing to the distribution network bus is g for:

[0021]

[0022] when At that time, the distribution network bus can obtain the maximum active power without exceeding the voltage limit. Substituting this into... P was obtained from g The relationship regarding the proportionality coefficient k is obtained by differentiating k. Again Solving for k, we get:

[0023]

[0024] Due to monotonicity, P g exist The maximum value is obtained at that point.

[0025] Furthermore, considering the constraint that the grid connection voltage cannot exceed the limit, the active power P injected by the photovoltaic power generation system into the grid connection point should be... PV Must meet:

[0026]

[0027] right China P PV While differentiating, let 0 = dP g / dP PV We can obtain:

[0028]

[0029] According to the theory of monotonic correlation, in P g To obtain the maximum value,

[0030] Considering the constraint of grid connection point voltage exceeding the limit, and also considering much smaller Therefore, when At that time, the grid connection point obtains the maximum active power without exceeding the voltage limit.

[0031] Furthermore, the active power command P is calculated using the reactive and active power ratio coefficient k. PV_ref Reactive power command Q PV_ref The formula is as follows:

[0032]

[0033] Furthermore, based on the active power command P PV_ref Reactive power command Q PV_ref In the dq coordinate system with constant amplitude coordinate transformation, the current reference value on the dq coordinate axis is obtained:

[0034]

[0035] Among them, i d_ref i is the current reference value along the d-axis. q_ref The current reference value for the q-axis, u d Let be the d-axis voltage component in the dq coordinate system.

[0036] Furthermore, adjusting the active and reactive power injected into the grid-connected point of the photovoltaic system based on the current reference value on the dq coordinate axis to regulate the grid-connected point voltage includes: subtracting the current reference value from the actual value on the dq coordinate axis and sending the difference to a PI regulator; summing the output of the PI regulator with the voltage on the dq coordinate axis; generating a dq axis reference voltage in the dq coordinate system based on the summation result and the voltage phase information in the abc coordinate system obtained by the phase-locked loop; obtaining a modulation signal after coordinate system transformation; performing SVPWM modulation on the modulation signal; and using the modulated output signal as the control signal of the photovoltaic grid-connected inverter to adjust the active and reactive power injected into the grid-connected point of the photovoltaic system to regulate the grid-connected point voltage.

[0037] Secondly, the present invention provides a distributed photovoltaic voltage over-limit control device with optimized active and reactive power ratio, comprising: at least one processing unit, wherein the processing unit, a storage unit and a photovoltaic inverter are interconnected via a bus unit, the storage unit stores a computer program, and when the computer program is executed by the processing unit, the distributed photovoltaic voltage over-limit control method with optimized active and reactive power ratio is implemented.

[0038] Secondly, the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the distributed photovoltaic voltage over-limit management method for optimizing the active and reactive power ratio.

[0039] The technical solutions provided in the embodiments of the present invention have the following advantages compared with the prior art:

[0040] This application detects that the grid connection point voltage exceeds the limit. When the limit is exceeded, the maximum power point tracking mode is abandoned, and the following steps are performed: The reactive and active power ratios that the photovoltaic power generation system should inject into the grid connection point after the voltage exceeds the limit are calculated. These ratios maximize the active power injected into the distribution network bus by the photovoltaic power generation system when the grid connection point voltage does not exceed the limit. Active power commands and reactive power commands are calculated using the calculated ratios. Based on the active and reactive power commands, a current reference value on the dq axis is obtained in a dq coordinate system with equal amplitude coordinate transformation. The active and reactive power injected into the grid connection point by the photovoltaic system is adjusted based on the current reference value on the dq coordinate axis to regulate the grid connection point voltage. This invention plays a positive role in solving the problem of grid connection point voltage exceeding the limit for distributed photovoltaic power generation, ensuring that the active power flowing to the grid connection point is maximized while the grid connection point voltage does not exceed the limit. Attached Figure Description

[0041] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 Equivalent circuit diagram of a distributed photovoltaic power generation system before it is connected to the power distribution network;

[0044] Figure 2 A vector diagram showing the voltage drop before a distributed photovoltaic power generation system is connected to the distribution network.

[0045] Figure 3 The equivalent circuit diagram of a distributed photovoltaic power generation system after it is connected to the power distribution network;

[0046] Figure 4 This is a flowchart of an optimization method for suppressing voltage exceedance in distributed photovoltaic systems based on the ratio of active and reactive power injected into the grid, provided in an embodiment of the present invention.

[0047] Figure 5This is a control block diagram for suppressing grid connection point voltage exceeding limits provided in an embodiment of the present invention;

[0048] Figure 6 Simulation results of the voltage change at the grid connection point when active power is injected into the photovoltaic grid under maximum power point tracking;

[0049] Figure 7 The simulation results of the voltage change at the grid connection point under the proportional coefficient provided in the embodiments of the present invention;

[0050] Figure 8 The simulation results show the active power received by the distribution network bus under the proportional coefficient and other coefficients provided in the embodiments of the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0053] Example 1

[0054] See Figure 1 As shown, the present invention provides a method for managing voltage exceedance in distributed photovoltaic systems by optimizing the active and reactive power ratio, comprising:

[0055] Step 1: After the photovoltaic power is injected into the grid connection point with active power under maximum power point tracking, the grid connection point voltage is detected. The grid connection point voltage is compared with the set grid connection point voltage over-limit value to detect whether the grid connection point voltage has exceeded the limit.

[0056] When detecting the grid connection point voltage, a mean filter is used to stabilize the detected grid connection point voltage, eliminating grid connection point voltage fluctuations to obtain accurate grid connection point voltage detection results.

[0057] If the grid connection point voltage exceeds the limit, abandon the maximum power point tracking mode and execute:

[0058] Step 2: Based on the distribution network bus voltage, active power at the end of the line, reactive power at the end of the line, the voltage limit exceeding the grid connection point, and line parameters, calculate the reactive and active power ratio coefficients k that the photovoltaic power generation system should inject into the grid connection point after the voltage exceeds the grid connection point limit. The reactive and active power ratio coefficients k ensure that the active power P injected into the grid connection point by the photovoltaic power generation system is within the grid connection point voltage limit. g maximum:

[0059]

[0060] Where R is the line resistance, X is the line reactance, and P is the line inductance. L Q represents the active power at the end of the line. L U represents the reactive power at the end of the line. lim U is the voltage exceeding the limit at the grid connection point. S This refers to the voltage of the distribution network bus.

[0061] In the specific implementation process, the above steps include: establishing the connection between the grid connection point voltage and the distribution network bus voltage based on the equivalent circuit model of the distributed photovoltaic power generation system connected to the distribution network.

[0062] The equivalent circuit diagram of a distributed photovoltaic power generation system before it is connected to the distribution network is as follows: Figure 1 As shown, a voltage difference will occur between node m at the grid connection point and node n on the distribution network bus due to line losses, such as... Figure 2 As shown, vector analysis reveals a voltage difference between node m and node n due to line losses.

[0063]

[0064] The real and imaginary parts are expressed in terms of power and impedance as follows:

[0065]

[0066] From the above relationships, it can be seen that the voltage difference between nodes m and n depends on the line impedance R+jX and the local power P of the line. L +jQ L .in, This refers to the voltage vector at node n, which is also the voltage vector of the distribution network bus. This is the voltage vector at node m, i.e., the voltage vector at the grid connection point. Let be the current vector on the line. Since the phase angle difference between two nodes m and n is very small in a distribution network compared to a transmission network, the real part has a much greater impact on voltage deviation than the imaginary part. Therefore, the relationship between the voltage difference between nodes m and n can be equivalently expressed as follows:

[0067]

[0068] The equivalent circuit diagram of a distributed photovoltaic power generation system connected to the distribution network is as follows: Figure 3 As shown. When photovoltaic (PV) power sources are not connected to the grid, power flow typically flows from the beginning to the end of the line. Due to line losses, low voltage usually occurs at the end of the line. However, after PV power sources are connected, because the power generated by the PV power sources exceeds the absorption capacity of the node load, the excess power is fed back into the distribution network along the line, forming a reverse power flow, which causes the voltage at the end node to rise. The relationship between the grid connection point voltage and the distribution network bus voltage is established based on the equivalent circuit model of the distributed PV power generation system connected to the distribution network as follows:

[0069]

[0070] Among them, P PV The active power Q to be injected into the grid connection point for a distributed photovoltaic power generation system. PV The reactive power that should be injected into the grid connection point for distributed photovoltaic power generation systems.

[0071] Based on the grid connection point voltage, active power at the end of the line, reactive power at the end of the line, grid connection point voltage exceeding limits, line parameters, active power to be injected into the grid connection point by the distributed photovoltaic power generation system, and reactive power to be injected into the grid connection point by the distributed photovoltaic power generation system, the active power P flowing to the distribution network bus is calculated. g for:

[0072]

[0073] Let the reactive and active power ratio coefficients to be injected into the grid connection point of the photovoltaic power generation system be k = Q. PV / P PV (k<0), then the active power P flowing to the distribution network bus is g for:

[0074]

[0075] The reactive and active power ratio coefficient k ensures that the active power P injected into the grid connection point by the photovoltaic power generation system is within the grid connection voltage limit. g At its maximum, considering the constraint that the grid connection voltage should not exceed the limit, the active power P injected by the photovoltaic power generation system into the grid connection point should be... PV Must meet:

[0076]

[0077] right China P PV While differentiating, let 0 = dP g / dPPV We can obtain:

[0078]

[0079] According to the theory of monotonic correlation, in The maximum value is obtained at this location;

[0080] Simultaneously consider much smaller Therefore At that time, the distribution network bus can obtain the maximum active power without exceeding the voltage limit. Substituting this into... P was obtained from g The relationship regarding the proportionality coefficient k is obtained by differentiating k. Again Solving for k, we get:

[0081]

[0082] Due to monotonicity, P g exist The maximum value is obtained at that point.

[0083] Step 3: Calculate the active power command P using the reactive and active power ratio coefficient k. PV_ref Reactive power command Q PV_ref :

[0084]

[0085] Step 4, based on the active power command P PV_ref Reactive power command Q PV_ref In the dq coordinate system with constant amplitude coordinate transformation, the current reference value on the dq coordinate axis is obtained:

[0086]

[0087] Among them, i d_ref i is the current reference value along the d-axis. q_ref The current reference value for the q-axis, u d Let be the d-axis voltage component in the dq coordinate system.

[0088] Step 5: Adjust the active and reactive power injected into the photovoltaic grid-connected point based on the current reference value on the dq coordinate axis to regulate the grid-connected point voltage. The difference between the current reference value and the actual value on the dq coordinate axis is fed into a PI regulator. The PI regulator output is summed with the voltage on the dq coordinate axis. Based on the summation result and the voltage phase information in the abc coordinate system obtained by the phase-locked loop, a dq axis reference voltage is generated in the dq coordinate system. After coordinate transformation, a modulation signal is obtained. This modulation signal is then subjected to SVPWM modulation. The modulated output signal serves as the control signal for the photovoltaic grid-connected inverter to adjust the active and reactive power injected into the photovoltaic grid-connected point to regulate the grid-connected point voltage. The corresponding control block diagram is shown below. Figure 5 As shown.

[0089] The maximum allowable voltage at the grid connection point is 1.1UN, where UN is the rated voltage. Figure 6 The simulation results show the change in grid connection point voltage when active power is injected into the grid connection point under maximum power point tracking of photovoltaic power, at which point the grid connection point voltage has exceeded the limit; Figure 7 The simulation results of the grid connection point voltage change under the proportional coefficient provided in the embodiment of the present invention are shown. At this time, the grid connection point voltage has stabilized near the limit value. Figure 8 The simulation results of the active power received by the distribution network bus under the proportional coefficient and other coefficients provided in the embodiments of the present invention show that when k = -0.5156, the grid connection point receives the most active power compared to other proportional coefficients.

[0090] Example 2

[0091] This invention provides a distributed photovoltaic voltage limit mitigation device for optimizing the active and reactive power ratio, comprising: at least one processing unit, interconnected with a storage unit and a photovoltaic inverter via a bus unit, wherein the storage unit stores a computer program, and when the computer program is executed by the processing unit, it implements the distributed photovoltaic voltage limit mitigation method for optimizing the active and reactive power ratio, including:

[0092] After the photovoltaic system injects active power into the grid connection point under maximum power point tracking (MPPT), it detects the grid connection point voltage. If the grid connection point voltage exceeds the limit, it abandons the MPPT operating mode and executes the following:

[0093] Based on the distribution network bus voltage, active power at the end of the line, reactive power at the end of the line, the voltage limit exceeding the grid connection point, and line parameters, calculate the reactive and active power ratio coefficient k that the photovoltaic power generation system should inject into the grid connection point after the grid connection point voltage exceeds the limit. This reactive and active power ratio coefficient k ensures that the active power P injected into the grid connection point by the photovoltaic power generation system when the grid connection point voltage does not exceed the limit. g maximum:

[0094]

[0095] Where R is the line resistance, X is the line reactance, and P is the line inductance. L Q represents the active power at the end of the line. L U represents the reactive power at the end of the line. lim U is the voltage exceeding the limit at the grid connection point. S This refers to the voltage of the distribution network bus.

[0096] The active power command P is calculated using the reactive and active power ratio coefficient k. PV_ref Reactive power command Q PV_ref ;

[0097] In the dq coordinate system after undergoing constant amplitude coordinate transformation, based on the active power command P PV_ref Reactive power command Q PV_ref Obtain the reference current value on the dq coordinate axis;

[0098] Adjusting the active and reactive power injected into the grid connection point based on the current reference value on the dq coordinate axis to regulate the grid connection point voltage.

[0099] Of course, the computer program stored in the storage unit of the distributed photovoltaic voltage over-limit control device for optimizing the active and reactive power ratio provided in the embodiments of the present invention is not limited to the operation of the method described above, and can also execute related operations in the distributed photovoltaic voltage over-limit control method for optimizing the active and reactive power ratio provided in any embodiment of the present invention.

[0100] Example 3

[0101] This invention provides a computer-readable storage medium storing a computer program. When executed, the computer program implements the distributed photovoltaic voltage over-limit mitigation method with optimized active and reactive power ratios, comprising:

[0102] After the photovoltaic system injects active power into the grid connection point under maximum power point tracking (MPPT), it detects the grid connection point voltage. If the grid connection point voltage exceeds the limit, it abandons the MPPT operating mode and executes the following:

[0103] Based on the distribution network bus voltage, active power at the end of the line, reactive power at the end of the line, the voltage limit exceeding the grid connection point, and line parameters, calculate the reactive and active power ratio coefficient k that the photovoltaic power generation system should inject into the grid connection point after the grid connection point voltage exceeds the limit. This reactive and active power ratio coefficient k ensures that the active power P injected into the grid connection point by the photovoltaic power generation system when the grid connection point voltage does not exceed the limit. g maximum:

[0104]

[0105] Where R is the line resistance, X is the line reactance, and P is the line inductance. LQ represents the active power at the end of the line. L U represents the reactive power at the end of the line. lim U is the voltage exceeding the limit at the grid connection point. S This refers to the voltage of the distribution network bus.

[0106] The active power command P is calculated using the reactive and active power ratio coefficient k. PV_ref Reactive power command Q PV_ref ;

[0107] In the dq coordinate system after undergoing constant amplitude coordinate transformation, based on the active power command P PV_ref Reactive power command Q PV_ref Obtain the reference current value on the dq coordinate axis;

[0108] Adjusting the active and reactive power injected into the grid connection point based on the current reference value on the dq coordinate axis to regulate the grid connection point voltage.

[0109] The computer-readable storage medium provided in this embodiment of the invention stores a computer program that is not limited to the method operation described above, but can also execute related operations in the distributed photovoltaic voltage over-limit management method for optimizing the active and reactive power ratio provided in any embodiment of the invention.

[0110] In the embodiments provided by this invention, it should be understood that the disclosed structures and methods can be implemented in other ways. For example, the structural embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interfaces, structures, or units, and may be electrical, mechanical, or other forms.

[0111] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0112] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0113] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for managing voltage exceedance in distributed photovoltaic systems with optimized active and reactive power ratios, characterized in that, include: After the photovoltaic system injects active power into the grid connection point under maximum power point tracking (MPPT), it detects the grid connection point voltage. If the grid connection point voltage exceeds the limit, it abandons the MPPT operating mode and executes the following: Based on the distribution network bus voltage, active power at the end of the line, reactive power at the end of the line, and the voltage limit exceedance value at the grid connection point, the proportional coefficients of reactive and active power to be injected into the grid connection point of the photovoltaic power generation system after the voltage limit exceedance at the grid connection point are calculated. The reactive and active power ratio coefficient The active power injected into the grid connection point by the photovoltaic power generation system without exceeding the grid connection voltage limit. maximum: ， Where R is the line resistance and X is the line reactance. This refers to the active power at the end of the line. This refers to the reactive power at the end of the line. The voltage at the grid connection point exceeds the limit. This refers to the voltage of the distribution network bus. The ratio of reactive to active power used Calculate active power command Reactive power command ; In the dq coordinate system with constant amplitude coordinate transformation, based on the active power command Reactive power command Obtain the reference current value on the dq coordinate axis; Adjusting the active and reactive power injected into the grid connection point based on the current reference value on the dq coordinate axis to regulate the grid connection point voltage.

2. The distributed photovoltaic voltage over-limit mitigation method with optimized active and reactive power ratio according to claim 1, characterized in that, When detecting the grid connection point voltage, a mean filter is used to stabilize the detected grid connection point voltage.

3. The distributed photovoltaic voltage over-limit mitigation method based on active and reactive power ratio optimization according to claim 1, characterized in that, The relationship between the grid connection point voltage and the distribution network bus voltage is established based on the equivalent circuit model of the distributed photovoltaic power generation system connected to the distribution network: ， in, Active power should be injected into the grid connection point for distributed photovoltaic power generation systems. This represents the reactive power that should be injected into the grid connection point for a distributed photovoltaic power generation system, where R is the line resistance and X is the line reactance. This is the voltage at the grid connection point.

4. The distributed photovoltaic voltage over-limit mitigation method with optimized active and reactive power ratio according to claim 1, characterized in that, The reactive and active power ratios of the photovoltaic power generation system should be injected into the grid connection point. The calculation process is as follows: Based on grid connection point voltage Active power at the end of the line reactive power at the end of the line Grid connection point voltage exceeding limit Line parameters, active power to be injected into the grid connection point of the distributed photovoltaic power generation system. The reactive power that should be injected into the grid connection point of the distributed photovoltaic power generation system Calculate the active power flowing to the distribution network bus. for: ， Assume the reactive and active power ratios that the photovoltaic power generation system should inject into the grid connection point. The active power flowing to the distribution network busbar for: ， when At that time, the distribution network bus can obtain the maximum active power without exceeding the voltage limit. Substituting this into... From Regarding the proportionality coefficient The relational expression, and then... Differentiation yields , and then Solving for: ， Due to monotonicity, exist The maximum value is obtained at that point.

5. The distributed photovoltaic voltage over-limit mitigation method with optimized active and reactive power ratio according to claim 4, characterized in that, Considering the constraint that the voltage at the grid connection point cannot exceed the limit, the active power that the photovoltaic power generation system should inject into the grid connection point Must meet: ， right middle While differentiating, let We can obtain: ， According to the theory of monotonic correlation, in Place To obtain the maximum value, Simultaneously consider much smaller Therefore, when At that time, the grid connection point obtains the maximum active power under the premise that the voltage does not exceed the limit.

6. The distributed photovoltaic voltage over-limit mitigation method based on active and reactive power ratio optimization according to claim 1, characterized in that, The ratio of reactive to active power used Calculate active power command Reactive power command The formula is as follows: ， 。 7. The distributed photovoltaic voltage over-limit mitigation method based on active and reactive power ratio optimization according to claim 1, characterized in that, Based on active power command Reactive power command In the dq coordinate system with constant amplitude coordinate transformation, the current reference value on the dq coordinate axis is obtained: ， ， in, This is the current reference value for the d-axis. This is the current reference value for the q-axis. Let d be the voltage component along the d-axis in the dq coordinate system.

8. The method for managing voltage exceedance in distributed photovoltaic systems by optimizing the active and reactive power ratio according to claim 1, characterized in that, Adjusting the active and reactive power injected into the grid-connected point of photovoltaic power to regulate the grid-connected point voltage based on the current reference value on the dq coordinate axis includes: subtracting the current reference value from the actual value on the dq coordinate axis and sending the result to a PI regulator; summing the output of the PI regulator with the voltage on the dq coordinate axis; generating a dq axis reference voltage in the dq coordinate system based on the summation result and the voltage phase information in the abc coordinate system obtained by the phase-locked loop; obtaining a modulation signal after coordinate system transformation; performing SVPWM modulation on the modulation signal; and using the modulated output signal as the control signal of the photovoltaic grid-connected inverter to adjust the active and reactive power injected into the grid-connected point of photovoltaic power to regulate the grid-connected point voltage.

9. A distributed photovoltaic voltage over-limit mitigation device with optimized active and reactive power ratio, characterized in that, include: At least one processing unit interconnects the processing unit, the storage unit, and the photovoltaic inverter via a bus unit. The storage unit stores a computer program. When the computer program is executed by the processing unit, it implements the distributed photovoltaic voltage over-limit control method for optimizing the active and reactive power ratio as described in any one of claims 1-8.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the distributed photovoltaic voltage over-limit control method according to any one of claims 1-8, which optimizes the active and reactive power ratio.

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