Electric energy quality analysis method and system for distributed photovoltaic access rural power distribution network

Abstract

The invention discloses an electric energy quality analysis method and system for a distributed photovoltaic access rural power distribution network, and the method comprises the steps: focuses on a main loss link through building a simplified power distribution network model, and focuses on the impact mechanism of the photovoltaic access position, capacity and output fluctuation on three-phase imbalance, harmonic distortion and voltage deviation; and comprehensively evaluating a multi-factor coupling effect in a composite power quality disturbance scene, and quantitatively comparing total network loss changes before and after grid connection. According to the method, the influence path of photovoltaic access on the electric energy quality can be effectively analyzed, a basis is provided for optimization of photovoltaic layout and capacity configuration through network loss analysis, the operation reliability and the new energy consumption capability of the power distribution network are improved, and technical support is provided for upgrading and reconstruction of a rural power grid.

Description

Technical Field

[0001] The present invention belongs to the technical field of power system engineering, and more specifically, relates to a method and system for analyzing power quality of distributed photovoltaic access to a rural power distribution network. Background Art

[0002] The vigorous development of new power systems has led to a continuous increase in the penetration rate of distributed generation (DG). Faced with the access of a large number of explosive, small and medium-capacity, decentralized distributed photovoltaic systems, the safe operation of the distribution network also faces many problems, such as voltage quality issues such as voltage over-limit, voltage imbalance, and rapid voltage fluctuations. At the same time, it also faces the risk of protection system failure, and the stability of the power grid will also face severe challenges. Therefore, there is an urgent need for a power quality analysis method for high-proportion distributed photovoltaic access to rural distribution networks.

[0003] The existing technology discloses a model-based operational risk perception method, but the existing technology has poor adaptability to distribution networks containing renewable energy. In terms of simulating typical scenarios and analyzing the correlation of multiple factors, it cannot meet the requirements of refined operation of distribution networks, which brings great risks to the safe and economic operation of distribution networks. Summary of the Invention

[0004] To address the deficiencies in the prior art, the present invention provides a power quality analysis method and system for distributed photovoltaic access to rural distribution networks. By analyzing different disturbance factors, a model of how grid losses change with photovoltaic access under different disturbance factors is obtained. This method can trace the location of power quality loss and analyze its cause, meeting the requirements for refined operation of the distribution network. Furthermore, the coordinated action of multiple devices can be used to improve power quality and ensure the safety and economy of rural distribution network operation.

[0005] The present invention adopts the following technical solutions.

[0006] A first aspect of the present invention provides a method for analyzing power quality of distributed photovoltaic systems connected to a rural distribution network, comprising:

[0007] Simplify the model diagram of distributed photovoltaic access to rural distribution networks, and combine the distributed photovoltaic access location calculation to obtain the line loss change model after distributed photovoltaic access to rural distribution networks;

[0008] Based on the simplified distribution network model diagram, the three-phase imbalance and related losses are analyzed, and the distribution network three-phase unbalanced line loss change model and the transformer three-phase unbalanced line loss change model after distributed photovoltaics are connected to the rural distribution network are obtained;

[0009] The harmonic model of the distribution network is simplified, and the harmonic loss is analyzed to obtain the harmonic distortion rate model of the distributed photovoltaic access grid side. Based on the harmonic distortion rate model of the distributed photovoltaic access grid side and the simplified distribution network model diagram, the distribution network harmonic line loss change model and transformer harmonic loss change model after distributed photovoltaic access are calculated;

[0010] The voltage deviation of the transformer is analyzed to obtain the fixed loss change model of the transformer after distributed photovoltaic access;

[0011] Combined with the line loss change model after distributed photovoltaics are connected to the rural distribution network, the three-phase unbalanced line loss change model of the distribution network, the three-phase unbalanced line loss change model of the transformer, the harmonic line loss change model of the distribution network, the harmonic loss change model of the transformer and the fixed loss model of the transformer, the impact of power quality disturbances on the distribution network under the conditions of three-phase imbalance, harmonics and voltage deviation is analyzed, and the total loss change model after distributed photovoltaics are connected to the rural distribution network is obtained.

[0012] Optionally, the rural distribution network includes a transformer that connects multiple branch lines. The simplified model diagram for connecting distributed photovoltaics to the rural distribution network includes:

[0013] The loads on multiple branch lines are simplified into the line impedance on the transformer side and the line impedance on the user side, and the access locations of distributed photovoltaics are marked to obtain a model diagram of distributed photovoltaic access to the rural distribution network.

[0014] Optionally, by combining the line loss change model after distributed photovoltaics are connected to the rural distribution network, the distribution network three-phase unbalanced line loss change model, the transformer three-phase unbalanced line loss change model, the distribution network harmonic line loss change model, the transformer harmonic loss change model, and the transformer fixed loss change model, the impact of power quality disturbances on the distribution network under the conditions of three-phase imbalance, harmonics, and voltage deviation is analyzed to obtain a total loss change model after distributed photovoltaics are connected to the rural distribution network, including:

[0015] Based on the line loss change model after distributed photovoltaics are connected to the rural distribution network, combined with the distribution network three-phase unbalanced line loss change model and the distribution network harmonic line loss change model, the impact of power quality disturbances on the distribution network under the conditions of three-phase imbalance, harmonics, and voltage deviation is analyzed, and the total line loss change model after distributed photovoltaics are connected is obtained;

[0016] Combining the transformer three-phase unbalanced line loss variation model, the transformer harmonic loss variation model, and the transformer fixed loss variation model, the impact of power quality disturbances on the distribution network under the conditions of three-phase imbalance, harmonics, and voltage deviation is analyzed, and a total transformer loss variation model after distributed photovoltaic integration is obtained;

[0017] According to the total line loss change model after distributed photovoltaic access and the total transformer loss change model after distributed photovoltaic access, the total loss change model after distributed photovoltaic access to the rural distribution network is confirmed.

[0018] Optionally, based on the total line loss change model and the total transformer loss change model after distributed photovoltaic access, a total loss change model after distributed photovoltaic access is determined, including:

[0019] The total loss change model of distributed photovoltaics after access to the rural distribution network is obtained by adding the total line loss change model and the total transformer loss change model after access to the distributed photovoltaics.

[0020] Optionally, the total line loss change model after distributed photovoltaic access is expressed as follows:

[0021]

[0022] Where ΔP Lall is the change in total line loss after distributed photovoltaic access, I hAV is the three-phase average current of the hth harmonic on the load side, I DG Inject current for distributed photovoltaics, I AV is the three-phase average current on the load side, R L is the line resistance, α is the DG link position coefficient, I DG-h is the hth harmonic current generated by the distributed power supply, R L-h is the hth harmonic resistance.

[0023] Optionally, the total transformer loss change model after distributed photovoltaic access is expressed as follows:

[0024]

[0025] Where ΔP Tall is the change in total transformer loss after distributed photovoltaic access, I DG Inject current for distributed photovoltaics, I AV is the three-phase average current on the load side, R T is the transformer equivalent resistance, I DG-h is the hth harmonic current generated by the distributed power supply, I hAV is the three-phase average current of the hth harmonic on the load side, R T-h is the line resistance corresponding to the hth harmonic, ε′ is the voltage deviation of the transformer connected to distributed photovoltaics, ε is the voltage deviation of the transformer when not connected to distributed photovoltaics, ΔP 0s is the fixed loss of the transformer at rated voltage.

[0026] Optionally, the harmonic distortion rate model of distributed photovoltaic access to the grid side is expressed as follows:

[0027]

[0028] Where, THD SG is the harmonic distortion rate of the distributed photovoltaic connected to the grid side, I DG-h is the hth harmonic current generated by the distributed power supply, I L-h is the hth harmonic current generated by the load, and I1 is the effective value of the fundamental current.

[0029] A second aspect of the present invention provides a power quality analysis system for distributed photovoltaic access to a rural distribution network, characterized by comprising:

[0030] The first analysis module is used to simplify the model diagram of distributed photovoltaic access to rural distribution networks and calculate the line loss change model after distributed photovoltaic access to rural distribution networks based on the distributed photovoltaic access location;

[0031] The second analysis module is used to analyze the three-phase imbalance and related losses based on the simplified distribution network model diagram, and obtain the distribution network three-phase unbalanced line loss change model and the transformer three-phase unbalanced line loss change model after distributed photovoltaic is connected to the rural distribution network;

[0032] The third analysis module is used to simplify the harmonic model of the distribution network, analyze the harmonic loss, and obtain the harmonic distortion rate model of the distributed photovoltaic access to the grid side. Based on the harmonic distortion rate model of the distributed photovoltaic access to the grid side and the simplified distribution network model diagram, the distribution network harmonic line loss change model and transformer harmonic loss change model after the distributed photovoltaic access are calculated;

[0033] The fourth analysis module is used to analyze the voltage deviation of the transformer and obtain a fixed loss change model of the transformer after distributed photovoltaic access;

[0034] The fifth analysis module is used to combine the line loss change model after distributed photovoltaics are connected to the rural distribution network, the three-phase unbalanced line loss change model of the distribution network, the three-phase unbalanced line loss change model of the transformer, the harmonic line loss change model of the distribution network, the harmonic loss change model of the transformer and the fixed loss model of the transformer to analyze the impact of power quality disturbances on the distribution network under the conditions of three-phase imbalance, harmonics and voltage deviation, and obtain the total loss change model after distributed photovoltaics are connected to the rural distribution network.

[0035] The third aspect of the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is loaded into the processor, the method for analyzing the power quality of distributed photovoltaic access to a rural distribution network is implemented.

[0036] A fourth aspect of the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the above-mentioned power quality analysis method for distributed photovoltaic access to a rural distribution network.

[0037] Compared with the prior art, the beneficial effects of the present invention include at least:

[0038] The present invention analyzes the impact of major factors on power quality changes separately, and then analyzes in detail the complex impact of these factors on power loss under the scenario of composite power quality disturbances. The analysis obtains a model of the change of total grid loss to photovoltaic access. Based on this model, the location of power quality loss can be traced and its cause analyzed, meeting the requirements of refined operation of the distribution network. Furthermore, the coordinated action of multiple devices can be used to improve power quality and ensure the safety and economy of rural distribution network operation.

[0039] The present invention constructs a simplified distribution network model, focuses on the main loss parts, and analyzes the action mechanism of various factors more comprehensively and deeply, making the analysis of power quality problems more accurate.

[0040] Through in-depth network loss analysis, this paper clarifies the relationship between additional network losses after distributed photovoltaic integration and factors such as injected current, installation location, and average load current. It also identifies the loss reduction interval and its correlation with average current, providing a more accurate scientific basis for optimizing photovoltaic layout and capacity configuration. It can also provide technical support for upgrading and renovating rural power grids. Furthermore, by optimizing photovoltaic layout and capacity configuration, the operational reliability of the distribution network can be improved, while better accommodating new energy and promoting the sustainable development of distributed photovoltaics in rural distribution networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0042] in:

[0043] Figure 1 This is a flow chart of a method for analyzing power quality of distributed photovoltaic devices connected to a rural distribution network, provided by an embodiment of the present invention;

[0044] Figure 2 (a) is a simplified distribution network model diagram provided by an embodiment of the present invention;

[0045] Figure 2 (b) is a simplified distribution network model diagram provided by an embodiment of the present invention;

[0046] Figure 3 (a) is a diagram of the harmonic model of the distribution network without DG according to the present invention;

[0047] Figure 3 (b) is a diagram of the harmonic model of the distribution network connected to DG according to the present invention;

[0048] Figure 4 This is a transformer harmonic model diagram provided by an embodiment of the present invention;

[0049] Figure 5 This is a simulation diagram of the change of total network loss with the access of distributed photovoltaics provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0050] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0051] In the present invention, we aim to solve the following problems: 1) the traditional distribution network model has multiple branches, which is more complicated to handle, so we simplify it accordingly and then conduct a specific analysis. 2) Since the output power of distributed photovoltaics is intermittent and fluctuating, we first study the impact of distributed photovoltaics on distribution network losses. 3) The power quality is divided into several independent factors, and the impact of distributed photovoltaics on single power quality issues is explored. 4) After analyzing the disturbance of a single power quality factor on the distribution network, the impact mechanism of distributed photovoltaics on distribution network losses under complex factors is analyzed in the distribution network. 5) Under a simplified distribution network model, the impact of distributed photovoltaics on single power quality and complex power quality is theoretically analyzed. In order to verify the accuracy of the theoretical analysis, a simulation model is established based on the simplified distribution network model, and the theoretical analysis is verified with its help. By simulating multiple working conditions, the accuracy and authenticity of the results are accurately tested.

[0052] like Figure 1 As shown, embodiment 1 of the present invention provides a method for analyzing power quality of distributed photovoltaic access to a rural distribution network, which is applied to a high-proportion distributed photovoltaic access to a rural distribution network, and includes the following steps:

[0053] Step 1: Simplify the model of the rural distribution network to obtain the load power and output power expressions of distributed photovoltaics, and combine the distributed photovoltaic access location to calculate the line loss change model after distributed photovoltaics are connected to the rural distribution network.

[0054] The distribution network is an important part of the power grid system. Since the distribution network has multiple branches, it is unrealistic to calculate its individual losses. Therefore, for the subsequent specific analysis, it is necessary to simplify its model and then analyze the main loss parts.

[0055] In a preferred but non-limiting embodiment of the present invention, step 1 specifically comprises:

[0056] Distributed photovoltaics can reduce the transmission power on the distribution network feeder, thereby reducing line losses. The installation location and output power of distributed photovoltaics are important factors that determine line losses.

[0057] Step 1.1: Simplify the distribution network model diagram, where the load power and output power of distributed photovoltaics can be expressed by the following formula:

[0058]

[0059] Where α is the DG connection position coefficient, which is used to measure the impact of DG access position on distribution network loss, R SG is the line resistance near the transformer side, R GL is the line resistance near the user side, P L is the load active power, S L is the apparent power of the load, Q L is the load reactive power, S DG is the apparent power of distributed power source, P DG is the active power of distributed generation, Q DG is the reactive power of distributed generation.

[0060] Specific, combined Figure 2 (a) and Figure 2 As shown in (b), Figure 2 (a) and Figure 2 (b) shows the transformation from the original radial distribution network to the simplified model, which helps to understand the distribution network structure and subsequent analysis. Figure 2 (a) shows the radial distribution network before simplification. The figure contains the grid transformer Transformer, which is connected to multiple branch lines. Grid represents the grid side. The right side of the transformer is the complex distribution network structure, which includes multiple nodes and lines, connecting different loads, including the line impedance Z near the transformer side. SG , the line impedance Z close to the user side GL , and other line impedances Z3, Z4, PL1 +jQ L1 、P L2 +jQ L2 、P L3 +jQ L3 In actual distribution networks, this complex structure makes loss calculation difficult, so it is necessary to simplify it for analysis purposes. Figure 2 (b) is the simplified distribution network model, Z GL The right side is simplified to an aggregate load P L +jQ L , only the line impedance Z close to the transformer side is retained SG and the line impedance Z close to the user side GL , and the access location of the distributed power supply is marked.

[0061] Step 1.2: Based on the simplified distribution network model diagram and combined with the distributed photovoltaic access location, the line loss change model after distributed photovoltaic access to the rural distribution network is obtained.

[0062] In traditional distribution networks, line losses can be expressed as follows:

[0063]

[0064] Where, P LOSS is the line loss of the traditional distribution network, P L is the load active power, Q L is the load reactive power, U n is the rated voltage of the distribution network, R SG is the line resistance near the transformer side, R GL is the line resistance near the user side.

[0065] After the DG is connected, ignoring the voltage drop on the line, the line loss can be expressed by the following formula:

[0066]

[0067] Without considering the voltage drop on the line, the line loss change model after distributed photovoltaic is connected to the rural distribution network, that is, the deviation of the line loss, can be expressed by the following formula:

[0068]

[0069] Where ΔP LOSS is the deviation of line loss, R L is the line resistance, is the line resistance near the transformer side R SG and the line resistance R near the user side GLIt can be understood that (4) is the loss analysis under ideal conditions, which provides analysis ideas for subsequent steps.

[0070] Step 1.3: Analyze the power quality after distributed photovoltaics are connected to the rural distribution network based on the line loss change model after distributed photovoltaics are connected to the rural distribution network.

[0071] Equation (4) shows that additional losses (i.e., deviations in line losses) are related to the connection location and output power of the distributed photovoltaic system. When the distributed photovoltaic output is less than twice the load power, line losses decrease; conversely, when the output is greater than twice the load power, line losses increase. These effects become more pronounced the closer the distributed photovoltaic system is to the load. That is, when the distributed photovoltaic output is less than twice the load power, the loss reduction is greater; conversely, when the output is greater than twice the load power, the loss increase is greater.

[0072] Therefore, in the absence of power quality disturbances, reasonable configuration of distributed photovoltaics can reduce line losses in the active distribution network.

[0073] Step 2: Based on the simplified distribution network model diagram, combined with the distributed photovoltaic access location, the injection current of the three-phase balanced distributed photovoltaic and the three-phase load current, the three-phase imbalance and related losses after the distributed photovoltaic access to the rural distribution network are analyzed. The distribution network three-phase unbalanced line loss change model and the transformer three-phase unbalanced line loss change model after the distributed photovoltaic access to the rural distribution network are obtained.

[0074] The access location, capacity and operating characteristics of high-proportion distributed photovoltaics have a significant impact on three-phase current imbalance, especially for rural distribution networks with long lines and many branches. When the line flow changes, the imbalance effect caused by this structure and parameters may be amplified.

[0075] In a preferred but non-limiting embodiment of the present invention, step 2 specifically comprises:

[0076] Step 2.1: Based on the three-phase average current and three-phase unbalance coefficient on the load side, determine the expression for the three-phase unbalance coefficient after the distributed photovoltaic system is connected to the rural distribution network.

[0077] The three-phase average current and three-phase unbalance coefficient on the load side can be expressed by the following formula:

[0078]

[0079]

[0080] Where, I AV is the three-phase average current on the load side, I A is the load side A phase current; I Bis the load side B phase current; I C is the load side C phase current; β i is the three-phase unbalance coefficient on the load side; I i is the current value in the three-phase system, i = A, B, C.

[0081] After connecting three-phase balanced distributed photovoltaics, the average current can be expressed by the following formula:

[0082]

[0083] Where, I DG is the injection current of three-phase balanced distributed photovoltaic, I AV ′ is the three-phase average current after connecting the three-phase balanced distributed photovoltaic system, I A ′ is the phase A current in the three-phase system after DG is connected, I B ′ is the B-phase current in the three-phase system after DG is connected, I C ′ is the C-phase current in the three-phase system after DG is connected.

[0084] Through the above equation, the three-phase unbalance coefficient of distributed photovoltaic can be expressed as follows:

[0085]

[0086] Where, β i ′ is the three-phase unbalance coefficient of distributed photovoltaic, i=A, B, C.

[0087] From formula (8), it can be seen that the three-phase unbalance coefficient is related to the injection current. Under different load current imbalance conditions, the three-phase unbalance coefficient is related to the distributed photovoltaic injection current I DG It is an inversely proportional functional relationship, and its changing rules are as follows:

[0088] When I DG <I AV When , the three-phase unbalance coefficient increases with the increase of distributed photovoltaic injection current.

[0089] When I DG >I AV When , the three-phase unbalance coefficient decreases with the increase of distributed photovoltaic injection current.

[0090] Step 2.2: Based on the simplified distribution network model diagram, combined with the three-phase unbalance coefficient expression and three-phase unbalanced related line loss after distributed photovoltaics are connected to the rural distribution network, determine the three-phase unbalanced line loss change model after distributed photovoltaics are connected to the rural distribution network. Step 2.2 specifically includes:

[0091] The line loss related to three-phase imbalance in traditional distribution networks can be expressed by the following formula:

[0092] P SLOSS =(I A 2 +I B 2 +I C 2 )R L =(β A 2 +β B 2 +β C 2 +3)I AV 2 R L (9)

[0093] The three-phase unbalance coefficient of the traditional distribution network can be expressed by the following formula:

[0094] K L =β A 2 +β B 2 +β C 2 +3 (10)

[0095] Where K L is the three-phase unbalance coefficient of the traditional distribution network.

[0096] After distributed photovoltaics are connected, the active power distribution network line loss can be expressed by the following formula:

[0097]

[0098] Where R SG is the line resistance near the transformer side, R GL is the line resistance near the user side, K′ L is the three-phase unbalance coefficient after distributed photovoltaic is connected to the distribution network.

[0099] By integrating equations (1), (9)-(11), the change of the three-phase unbalanced line loss of the active distribution network with the access of distributed photovoltaic power generation, i.e., the change model of the three-phase unbalanced line loss of the distribution network, can be expressed as follows:

[0100] ΔP SLOSS =P SLOSS ′-P SLOSS =3α(I DG 2 -2I DG I AV )R L (12)

[0101] Step 2.3: Analyze the power quality after distributed photovoltaics are connected to the rural distribution network based on the three-phase unbalanced line loss change model after distributed photovoltaics are connected to the rural distribution network.

[0102] It can be seen that the change of line loss related to three-phase imbalance is related to the injected current, installation location, line impedance, and the average current of the three-phase load. Compared with the traditional distribution network, the change of line loss in distributed photovoltaic wiring is related to the injected current I under three-phase imbalance. DG It is related to the distributed photovoltaic wiring location coefficient α. The injected current is related to the average three-phase current. Its changing characteristics are as follows:

[0103] 1) When I DG <2I AV When I DG =I AV When α = 1, the loss reduction capability is the largest. When α = 0, the loss reduction capability is the smallest.

[0104] 2)I DG >2I AV When , the line loss related to three-phase imbalance increases with the increase of injected current, indicating that the line loss is increasing.

[0105] In this embodiment, the DG can be installed at a reasonable location and the injected current of the DG can be monitored to enhance and improve the power quality.

[0106] Step 2.4: Combine the distributed photovoltaic access location, the injection current of the three-phase balanced distributed photovoltaic, and the three-phase load current to calculate the transformer three-phase unbalanced line loss change model after the distributed photovoltaic is connected to the rural distribution network.

[0107] The transformer winding connection method is Dyn, where D indicates that the high-voltage winding is connected in a delta configuration, and yn indicates that the low-voltage winding is connected in a star configuration, with the neutral line leading out. The change in transformer three-phase unbalance-related losses after distributed photovoltaic integration, i.e., the change model of transformer three-phase unbalanced line losses, can be expressed by the following formula:

[0108]

[0109] Where ΔP T is the transformer three-phase unbalanced loss after distributed photovoltaic access, I DG Inject current for distributed photovoltaics, R T is the transformer equivalent resistance, I AV is the three-phase average current on the load side.

[0110] Step 3: Simplify the harmonic model of the distribution network to obtain the harmonic distortion rate model of the distributed photovoltaic access to the grid side, and calculate the distribution network harmonic line loss change model and transformer harmonic loss change model after distributed photovoltaic access based on the harmonic distortion rate model of the distributed photovoltaic access to the grid side.

[0111] Harmonic distortion rate and related loss analysis. In modern distribution network systems, since distributed photovoltaic system integrated circuits require a large number of power electronic components, a large number of harmonic components are easily generated during the switching process, affecting the stable operation of the system. Step 3 specifically includes:

[0112] Step 3.1: Simplify the harmonic model of the distribution network to obtain the harmonic distortion rate model of the distributed photovoltaic access grid side.

[0113] Combine Figure 3 (a) and Figure 3 (b), where Figure 3 (a) is the harmonic model of the traditional distribution network. Figure 3 (b) is the harmonic model of the distribution network after connecting to DG. Figure 3 (a) The harmonic impact caused by DG is introduced to show the harmonic situation of the distribution network under the combined action of DG and load harmonics. Figure 3 (a): I L-h Indicates the hth harmonic current of the load. h Indicates the harmonic resistance of the hth order line, X h Indicates the hth line harmonic reactance. Figure 3 (b) in: I L-h Indicates the hth harmonic current of the load; I DG-h represents the hth harmonic current of DG; R GLh Indicates the hth harmonic resistance of the line close to the user side; X GLh Indicates the hth harmonic reactance of the line close to the user side; R SGh Indicates the hth harmonic resistance of the line close to the transformer side; X SGh Indicates the hth harmonic reactance of the line close to the transformer side. Th Both are expressed as the equivalent impedance of the transformer under the hth harmonic.

[0114] The total harmonic distortion rate of the traditional distribution network can be expressed by the following formula:

[0115]

[0116] Where, THD is the total harmonic distortion rate of the traditional distribution network, I L-h is the hth harmonic current generated by the load, and I1 is the effective value of the fundamental current.

[0117] Since the integration of distributed photovoltaics requires a large number of power electronic devices, harmonics are easily generated near the switching frequency. The nonlinear load of the power electronic devices can be equivalent to a harmonic source, affecting the power quality of the active distribution network. The harmonic model of the active distribution network is simplified accordingly, and the harmonic distortion rate model of the distributed photovoltaic connected to the grid side is obtained, which can be expressed by the following formula:

[0118]

[0119] Where, THD SG is the harmonic distortion rate of the distributed photovoltaic connected to the grid side, I DG-h is the hth harmonic current generated by the distributed power supply.

[0120] I DG-h It can be expressed by the following formula:

[0121] I DG-h =γ h I L-h (16)

[0122] Where, γ h The ratio of the hth harmonic in distributed photovoltaics to the hth harmonic in the distribution network is called the hth-order harmonic multiplier ratio. The multiplier ratios of each order of harmonics are analyzed below.

[0123] 1) If the multiplier ratios of all harmonic orders are equal, then γ2=γ3=γ4=…=γ h =γ, grid side distortion rate THD SG It can be expressed by the following formula:

[0124]

[0125] Where γ is the harmonic multiplier ratio.

[0126] Assuming that the fundamental current and multiplier ratio of distributed photovoltaics remain unchanged, the grid-side distortion rate will increase with the increase of input current.

[0127] 2) If the multiplier ratios of each order harmonic are not equal, the grid side distortion rate THD SG It can be expressed by the following formula:

[0128]

[0129] Ignore higher harmonics, THD SG It can be expressed by the following formula:

[0130]

[0131] Where γ3 is the 3rd order harmonic multiplier ratio, γ5 is the 5th order harmonic multiplier ratio, ε is the voltage deviation of the transformer in the traditional distribution network, and IL-3 is the effective value of the third harmonic current, I L-5 It is the effective value of the 5th harmonic current.

[0132] It can be seen that the distortion rate increases with the increase of the injected current and the harmonic multiplier ratio.

[0133] In summary, the grid-connected distributed photovoltaic power generation will aggravate the harmonic pollution of the active power distribution network.

[0134] Step 3.2: Based on the harmonic distortion rate model of distributed photovoltaic access to the grid side, the harmonic line loss change model of the distribution network after distributed photovoltaic access is calculated.

[0135] The harmonic-related line loss in traditional distribution networks can be expressed by the following formula:

[0136]

[0137] Where, P L_h is the hth harmonic related line loss in the traditional distribution network, R L_h is the hth harmonic resistance.

[0138] The harmonic-related line loss of the distribution network after the distributed photovoltaic connection can be expressed by the following formula:

[0139]

[0140] Where P′ L-h is the line loss related to the hth harmonic of the distribution network after the distributed photovoltaic is connected.

[0141] From equations (20) and (21), the change of harmonic related line loss, i.e., the change model of harmonic line loss in distribution network, can be expressed by the following formula:

[0142]

[0143] Where ΔP har is the change of the harmonic-related line loss in the distribution network, and α is the DG link position coefficient.

[0144] From the above formula, we can see that the change of line loss related to each order harmonic is related to the DG connection position coefficient α, the injection current I DG , harmonic resistance R L-h and load harmonic current I L-h After the working conditions are determined, the harmonic resistance and load harmonic current are generally fixed values, and the additional harmonic related line loss is related to the injected current I DG-hThe relationship between harmonics and line losses is approximately quadratic. The greater the injected harmonic current, the greater the additional harmonic-related line losses. The magnitude of the increase in additional harmonic-related losses also depends on the location of the distributed photovoltaic system. The closer the connection is to the load, the greater the increase in additional harmonic-related line losses. The integration of distributed photovoltaic systems leads to an increase in harmonic-related line losses. Therefore, in practical applications, the main approaches are to suppress harmonic generation or to optimize the placement of DGs to reduce harmonic generation. Low-harmonic power equipment can be used to reduce harmonic pollution, and DG layout can be planned appropriately to avoid localized harmonic concentration and mitigate the harm caused by harmonics.

[0145] Step 3.2: Calculate the harmonic line loss change model of the distribution network after distributed photovoltaic access based on the transformer harmonic model.

[0146] Combine Figure 4 As shown in the figure, according to the transformer harmonic model, the change of transformer harmonic related loss, that is, the distribution network harmonic line loss change model can be expressed by the following formula:

[0147]

[0148] Where R T-h is the line resistance corresponding to the hth harmonic, ΔP T-h is the change in transformer harmonic related losses.

[0149] Since the primary side of the transformer winding adopts a triangle connection, the third harmonic current will form a circuit on the primary side, making the harmonic current three times the original current. Therefore, when h=3k, R T-h =3(N2 / N1) 2 R I-h +R II-h , otherwise it is R T-h =(N2 / N1) 2 R I-h +R II-h , where R I-h is the hth harmonic resistance component of the primary side transformer, R II-h is the hth harmonic resistance component of the secondary transformer, N1 and N2 are the turns of the primary and secondary windings respectively.

[0150] To sum up, distributed photovoltaics are equivalent to a harmonic source, which will aggravate the harmonic pollution of the system and increase the harmonic-related losses of the active distribution network.

[0151] Step 4: Based on the voltage deviation of the transformer, calculate the fixed loss change model of the transformer after distributed photovoltaic access.

[0152] Analysis of voltage deviation and related losses. After distributed photovoltaic systems are connected, their output fluctuates significantly due to natural factors such as sunlight intensity and temperature. When there is sufficient sunlight, a large amount of photovoltaic power is injected into the distribution network, causing the line voltage to increase. However, when there is insufficient sunlight or at night, the voltage may drop due to the insufficient power supply capacity of the distribution network.

[0153] The voltage deviation of the transformer in the traditional distribution network can be expressed by the following formula:

[0154]

[0155] Where, U is the operating voltage of the transformer, U n is the rated operating voltage of the distribution network, and ε is the voltage deviation of the transformer in the traditional distribution network, i.e., without access to distributed photovoltaics.

[0156] For transformers, their fixed losses are affected by the operating voltage. As distributed photovoltaics are connected, the transformer's voltage deviation decreases. The transformer's fixed losses are independent of current and are proportional to the square of the grid's operating voltage, as expressed by the following formula:

[0157]

[0158] Where ΔP0 is the fixed loss of the transformer, ΔP 0s Indicates the fixed loss of the transformer at rated voltage.

[0159] The fixed loss of the transformer connected to distributed photovoltaic can be expressed by the following formula:

[0160]

[0161] Where ε′ is the voltage deviation of the transformer connected to the distributed photovoltaic system, and U' is the operating voltage of the transformer after connecting to the distributed photovoltaic system.

[0162] It can be understood that the fixed loss variation model of the transformer is the difference between formula (26) and formula (25).

[0163] Compared to traditional distribution networks, the integration of distributed photovoltaics reduces fixed losses caused by transformer voltage deviations. The integration of distributed power sources reduces transformer voltage deviations. In practical applications, this can improve power quality by optimizing DG operation and adjusting grid operation.

[0164] Step 5: Combined with the line loss change model after distributed photovoltaics are connected to the rural distribution network, the distribution network three-phase unbalanced line loss change model, the transformer three-phase unbalanced line loss change model, the distribution network harmonic line loss change model, the transformer harmonic loss change model and the transformer fixed loss model, the impact of the composite power quality disturbance on the distribution network is analyzed, and the total loss change model after distributed photovoltaics are connected to the rural distribution network under the conditions of three-phase imbalance, harmonics and voltage deviation is obtained.

[0165] Step 5.1: Combine the distribution network three-phase unbalanced line loss change model and the distribution network harmonic line loss change model to analyze the impact of power quality disturbances on the distribution network under the conditions of three-phase imbalance, harmonics, and voltage deviation, and obtain a total line loss change model after distributed photovoltaic access.

[0166] After analyzing the single influencing factors, based on the above research, we explore their impact on the distribution network under complex conditions.

[0167] In the active power distribution network, in the case of three-phase imbalance, harmonics, and voltage deviation, the harmonic three-phase imbalance factor can be expressed by the following formula:

[0168]

[0169] Where, β hi is the harmonic three-phase unbalance factor, I hi is the current value of the hth harmonic in a certain phase (i=A, B, C), I hAV is the three-phase average current of the hth harmonic.

[0170] The three-phase harmonic unbalance coefficient can be expressed by the following formula:

[0171]

[0172] Where K Lh is the three-phase harmonic unbalance coefficient, β Ah is the harmonic three-phase unbalance factor of phase A, β Bh is the harmonic three-phase unbalance factor of phase B, β Ch is the harmonic three-phase unbalance factor of phase C.

[0173] When the three power quality disturbances exist simultaneously, the line loss of the traditional distribution network can be expressed by the following formula:

[0174]

[0175] Where, P Lall is the line loss of the traditional distribution network when the three power quality disturbances exist simultaneously, K L is the three-phase unbalance coefficient of the traditional distribution network, IAV is the three-phase average current on the load side, R L is the line resistance, K Lh is the three-phase harmonic unbalance coefficient, I hAV is the three-phase average current of the hth harmonic, R L-h is the hth harmonic resistance.

[0176] When connected to distributed photovoltaics, the line loss is:

[0177]

[0178] Where P′ Lall is the line loss after connecting distributed photovoltaics, K L and K′ L are the three-phase unbalance coefficients on the user side and the grid side, K SGh and K GLh are the harmonic three-phase unbalance coefficients on the grid side and the user side, I GLAVh is the three-phase average current of the hth harmonic on the user side after DG is connected, I SGAVh is the three-phase average current of the hth harmonic on the grid side after DG is connected, I′ AV and I AV are the three-phase average currents on the grid side and the user side, R SG is the line resistance on the transformer side, R GL is the line resistance on the user side, R SGh is the line resistance of the hth harmonic on the grid side, R GLh is the line resistance of the hth harmonic on the user side. It can be understood that when DG is not connected, the current flowing through the user side and the grid side is the same.

[0179] By combining equations (12) and (22), the line loss changes with the connection of distributed photovoltaics, that is, the total line loss change model after distributed photovoltaics are connected can be expressed by the following formula:

[0180]

[0181] Where ΔP Lall is the change in line loss after the distributed photovoltaic connection, I hAV is the three-phase average current of the hth harmonic on the load side, I DG Inject current for distributed photovoltaics, I AV is the three-phase average current on the load side, R L is the line resistance, α is the DG link position coefficient, I DG-h is the hth harmonic current generated by the distributed power supply, R L-h is the hth harmonic resistance, which characterizes the resistance characteristics of the entire line related to the hth harmonic.

[0182] Step 5.2: Combine the transformer three-phase unbalanced line loss variation model, the transformer harmonic loss variation model, and the transformer fixed loss variation model to analyze the impact of power quality disturbances on the distribution network under the conditions of three-phase imbalance, harmonics, and voltage deviation. This results in a total transformer loss variation model after distributed photovoltaic integration.

[0183] By combining equations (13), (23), (25), and (26), we can obtain the change in transformer loss, that is, the total transformer loss change model after distributed photovoltaic access, which can be expressed by the following formula:

[0184]

[0185] Where ΔP Tall is the change in transformer loss after the distributed photovoltaic connection,

[0186] Step 5.3: Based on the total line loss change model after distributed photovoltaic access and the total transformer loss change model after distributed photovoltaic access, confirm the total loss change model after distributed photovoltaic access to the rural distribution network.

[0187] Specifically, by combining equations (31) and (32), the total network loss changes with the access of distributed photovoltaics, that is, the total loss change model after distributed photovoltaics are connected to the rural distribution network can be expressed by the following formula:

[0188]

[0189] Where ΔP Lall is the change in total line loss after distributed photovoltaic access, ΔP Tall is the change in total transformer loss after distributed photovoltaic access, I DG Inject current for distributed photovoltaics, I AV is the three-phase average current on the load side, α is the DG link position coefficient, R L is the line resistance, R T is the transformer equivalent resistance, I DG-h is the hth harmonic current generated by the distributed power supply, I hAV is the three-phase average current of the hth harmonic on the load side, R L-h is the hth harmonic resistance, R T-h is the line resistance corresponding to the hth harmonic, ε′ is the voltage deviation of the transformer connected to distributed photovoltaics, ε is the voltage deviation of the transformer when not connected to distributed photovoltaics, ΔP 0s is the fixed loss of the transformer at rated voltage.

[0190] It can be obtained from formula (33) that the additional network loss after distributed photovoltaic access is mainly related to factors such as injection current, installation location, average load current, line distribution resistance parameters, and voltage deviation. After the operating state is determined, the distribution resistance of the line remains basically constant, ignoring the loss deviation caused by voltage deviation. As the distributed photovoltaic injection current increases, the overall change in network loss initially decreases and then increases. It can be understood that through formula derivation, as the DG injection current increases, the loss shows a trend of first decreasing and then increasing, that is, there is a space for loss reduction. The size of the loss reduction interval is related to the three-phase average current of the load and the three-phase average current of the harmonics of the active distribution network and the position coefficient, so the power quality can be improved by reasonably configuring these two parameters. Combined with Figure 5 As shown, there is a section (called the loss reduction interval) within the negative half-plane that effectively reduces losses. The size of the loss reduction interval is related to the three-phase average current of the active power distribution network load and the three-phase average current of the harmonics. The larger the average current, the larger the loss reduction interval. In the negative half-plane, the loss reduction effect varies with the location coefficient α, and as the location coefficient increases, the loss reduction effect gradually decreases (the loss reduction effect becomes more significant). In the positive half-plane, the loss reduction effect varies with the increase in the location coefficient α, and increases with α (indicating a more significant increase in losses).

[0191] This disclosed embodiment constructs a simplified distribution network model to focus on key loss factors. It analyzes the impact of photovoltaic access location, capacity, and output fluctuations on three-phase imbalance, harmonic distortion, and voltage deviation. It comprehensively evaluates the multi-factor coupling effect in complex power quality disturbance scenarios and quantitatively compares the changes in total network losses before and after grid connection. This method effectively analyzes the impact of photovoltaic access on power quality. Through network loss analysis, it provides a basis for optimizing photovoltaic layout and capacity configuration, improves the operational reliability of the distribution network and its ability to accommodate new energy, and provides technical support for upgrading and renovating rural power grids.

[0192] Step 6: Verification under ideal operating conditions, three-phase imbalance and loss verification, harmonic and related loss verification, and load power quality disturbance and network loss verification are carried out respectively. The correctness of the change of total network loss with the access of distributed photovoltaic is confirmed through verification.

[0193] In this embodiment, the multi-factor coupling effect is comprehensively evaluated in the scenario of complex power quality disturbance, the changes in total network losses before and after grid connection are quantitatively compared, and the proportion of three-phase imbalance and characteristic harmonic-related losses is specifically verified. This can effectively analyze the impact path of photovoltaic access on power quality, provide a basis for optimizing photovoltaic layout and capacity configuration through network loss analysis, improve the operational reliability of the distribution network and the new energy absorption capacity, and provide technical support for the upgrading and transformation of rural power grids.

[0194] It should be noted that the embodiments of this disclosure have analyzed specific influencing factors. In practical applications, power quality can be improved through the use of filters, reactive power compensation devices, and other measures. Distributed power supply connections can also be appropriately configured based on the specific load distribution to reduce their impact on line losses. Furthermore, relevant monitoring equipment and data acquisition devices can be used to fully understand the operation of the power grid and the power quality status, allowing for appropriate adjustments to optimize power quality.

[0195] Embodiment 2 of the present invention provides a method and system for analyzing power quality of distributed photovoltaic access to a rural distribution network. The method for analyzing power quality of distributed photovoltaic access to a rural distribution network as described in embodiment 1 is executed. The system includes:

[0196] The first analysis module is used to simplify the model diagram of distributed photovoltaic access to rural distribution networks and calculate the line loss change model after distributed photovoltaic access to rural distribution networks based on the distributed photovoltaic access location;

[0197] The second analysis module is used to analyze the three-phase imbalance and related losses based on the simplified distribution network model diagram, and obtain the distribution network three-phase unbalanced line loss change model and the transformer three-phase unbalanced line loss change model after distributed photovoltaic is connected to the rural distribution network;

[0198] The third analysis module is used to simplify the harmonic model of the distribution network, analyze the harmonic loss, and obtain the harmonic distortion rate model of the distributed photovoltaic access to the grid side. Based on the harmonic distortion rate model of the distributed photovoltaic access to the grid side and the simplified distribution network model diagram, the distribution network harmonic line loss change model and transformer harmonic loss change model after the distributed photovoltaic access are calculated;

[0199] The fourth analysis module is used to analyze the voltage deviation of the transformer and obtain a fixed loss change model of the transformer after distributed photovoltaic access;

[0200] The fifth analysis module is used to combine the line loss change model after distributed photovoltaics are connected to the rural distribution network, the three-phase unbalanced line loss change model of the distribution network, the three-phase unbalanced line loss change model of the transformer, the harmonic line loss change model of the distribution network, the harmonic loss change model of the transformer and the fixed loss model of the transformer to analyze the impact of power quality disturbances on the distribution network under the conditions of three-phase imbalance, harmonics and voltage deviation, and obtain the total loss change model after distributed photovoltaics are connected to the rural distribution network.

[0201] Regarding the system in the above embodiment, the specific manner in which each unit performs operations has been described in detail in the embodiment of the method, and will not be elaborated here.

[0202] Embodiment 3 of the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is loaded into the processor, the method for analyzing the power quality of distributed photovoltaic access to a rural distribution network as described in embodiment 1 is implemented.

[0203] Embodiment 4 of the present invention provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the method for analyzing power quality of distributed photovoltaic access to a rural distribution network according to embodiment 1 is implemented.

[0204] The present disclosure may be a system, method and / or computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0205] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for analyzing power quality of distributed photovoltaic access to rural distribution networks, characterized in that: include: Simplify the model diagram of distributed photovoltaic access to rural distribution networks, and combine the distributed photovoltaic access location calculation to obtain the line loss change model after distributed photovoltaic access to rural distribution networks; Based on the simplified distribution network model diagram, the three-phase imbalance and related losses are analyzed, and the distribution network three-phase unbalanced line loss change model and the transformer three-phase unbalanced line loss change model after distributed photovoltaics are connected to the rural distribution network are obtained; The harmonic model of the distribution network is simplified, and the harmonic loss is analyzed to obtain the harmonic distortion rate model of the distributed photovoltaic access grid side. Based on the harmonic distortion rate model of the distributed photovoltaic access grid side and the simplified distribution network model diagram, the distribution network harmonic line loss change model and transformer harmonic loss change model after distributed photovoltaic access are calculated; The voltage deviation of the transformer is analyzed to obtain the fixed loss change model of the transformer after distributed photovoltaic access; Combined with the line loss change model after distributed photovoltaics are connected to the rural distribution network, the three-phase unbalanced line loss change model of the distribution network, the three-phase unbalanced line loss change model of the transformer, the harmonic line loss change model of the distribution network, the harmonic loss change model of the transformer and the fixed loss model of the transformer, the impact of power quality disturbances on the distribution network under the conditions of three-phase imbalance, harmonics and voltage deviation is analyzed, and the total loss change model after distributed photovoltaics are connected to the rural distribution network is obtained.

2. The power quality analysis method for distributed photovoltaic access to rural distribution networks according to claim 1 is characterized by: The rural distribution network includes a transformer, which is connected to multiple branch lines. The simplified model diagram of distributed photovoltaic access to the rural distribution network includes: The loads on multiple branch lines are simplified into the line impedance on the transformer side and the line impedance on the user side, and the access locations of distributed photovoltaics are marked to obtain a model diagram of distributed photovoltaic access to the rural distribution network.

3. The power quality analysis method for distributed photovoltaic access to rural distribution networks according to claim 1 is characterized by: Combining the line loss change model after distributed photovoltaics are connected to the rural distribution network, the distribution network three-phase unbalanced line loss change model, the transformer three-phase unbalanced line loss change model, the distribution network harmonic line loss change model, the transformer harmonic loss change model and the transformer fixed loss change model, the impact of power quality disturbances on the distribution network under the conditions of three-phase imbalance, harmonics and voltage deviation is analyzed, and the total loss change model after distributed photovoltaics are connected to the rural distribution network is obtained, including: Based on the line loss change model after distributed photovoltaics are connected to the rural distribution network, combined with the distribution network three-phase unbalanced line loss change model and the distribution network harmonic line loss change model, the impact of power quality disturbances on the distribution network under the conditions of three-phase imbalance, harmonics, and voltage deviation is analyzed, and the total line loss change model after distributed photovoltaics are connected is obtained; Combining the transformer three-phase unbalanced line loss variation model, the transformer harmonic loss variation model, and the transformer fixed loss variation model, the impact of power quality disturbances on the distribution network under the conditions of three-phase imbalance, harmonics, and voltage deviation is analyzed, and a total transformer loss variation model after distributed photovoltaic integration is obtained; According to the total line loss change model after distributed photovoltaic access and the total transformer loss change model after distributed photovoltaic access, the total loss change model after distributed photovoltaic access to the rural distribution network is confirmed.

4. The power quality analysis method for distributed photovoltaic access to a rural distribution network according to claim 3 is characterized by: Based on the total line loss change model after distributed photovoltaic access and the total transformer loss change model after distributed photovoltaic access, the total loss change model after distributed photovoltaic access to the rural distribution network is determined, including: The total loss change model of distributed photovoltaics after access to the rural distribution network is obtained by adding the total line loss change model and the total transformer loss change model after access to the distributed photovoltaics.

5. The power quality analysis method for distributed photovoltaic access to rural distribution networks according to claim 3 is characterized by: The total line loss change model after distributed photovoltaic access is expressed as follows: Where ΔP Lall is the change in total line loss after distributed photovoltaic access, I hAV is the three-phase average current of the hth harmonic on the load side, I DG Inject current for distributed photovoltaics, I AV is the three-phase average current on the load side, R L is the line resistance, α is the DG link position coefficient, I DG-h is the hth harmonic current generated by the distributed power supply, R L-h is the hth harmonic resistance.

6. The power quality analysis method for distributed photovoltaic access to rural distribution networks according to claim 3 is characterized by: The total transformer loss change model after distributed photovoltaic access is expressed as follows: Where ΔP Tall is the change in total transformer loss after distributed photovoltaic access, I DG Inject current for distributed photovoltaics, I AV is the three-phase average current on the load side, R T is the transformer equivalent resistance, I DG-h is the hth harmonic current generated by the distributed power supply, I hAV is the three-phase average current of the hth harmonic on the load side, R T-h is the line resistance corresponding to the hth harmonic, ε′ is the voltage deviation of the transformer connected to distributed photovoltaics, ε is the voltage deviation of the transformer when not connected to distributed photovoltaics, ΔP 0s is the fixed loss of the transformer at rated voltage.

7. The power quality analysis method for distributed photovoltaic access to rural distribution networks according to claim 3 is characterized by: The harmonic distortion rate model of distributed photovoltaic access to the grid is expressed as follows: Where, THD SG is the harmonic distortion rate of the distributed photovoltaic connected to the grid side, I DG-h is the hth harmonic current generated by the distributed power supply, I L-h is the hth harmonic current generated by the load, and I1 is the effective value of the fundamental current.

8. A power quality analysis system for distributed photovoltaic access to rural distribution networks, characterized in that: include: The first analysis module is used to simplify the model diagram of distributed photovoltaic access to rural distribution networks and calculate the line loss change model after distributed photovoltaic access to rural distribution networks based on the distributed photovoltaic access location; The second analysis module is used to analyze the three-phase imbalance and related losses based on the simplified distribution network model diagram, and obtain the distribution network three-phase unbalanced line loss change model and the transformer three-phase unbalanced line loss change model after distributed photovoltaic is connected to the rural distribution network; The third analysis module is used to simplify the harmonic model of the distribution network, analyze the harmonic loss, and obtain the harmonic distortion rate model of the distributed photovoltaic access to the grid side. Based on the harmonic distortion rate model of the distributed photovoltaic access to the grid side and the simplified distribution network model diagram, the distribution network harmonic line loss change model and transformer harmonic loss change model after the distributed photovoltaic access are calculated; The fourth analysis module is used to analyze the voltage deviation of the transformer and obtain a fixed loss change model of the transformer after distributed photovoltaic access; The fifth analysis module is used to combine the line loss change model after distributed photovoltaics are connected to the rural distribution network, the three-phase unbalanced line loss change model of the distribution network, the three-phase unbalanced line loss change model of the transformer, the harmonic line loss change model of the distribution network, the harmonic loss change model of the transformer and the fixed loss model of the transformer to analyze the impact of power quality disturbances on the distribution network under the conditions of three-phase imbalance, harmonics and voltage deviation, and obtain the total loss change model after distributed photovoltaics are connected to the rural distribution network.

9. An electronic device comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

Images