A comprehensive resource optimization configuration method and system after large-scale application of high-capacity onshore power

Abstract

A comprehensive resource optimization configuration method after the large-scale application of large-capacity onshore power includes several links such as the comprehensive resource optimization of the distribution network, the parameter configuration of passive filters, the establishment of a power quality governance model, and the establishment of a calculation and solution for the optimal plan. Its system is an FC+SVG hybrid governance system structure and is configured in the central substation or the main step-down substation. Taking the best harmonic suppression effect and the minimum investment cost of the power quality governance device as the objective function, it conducts multi-objective optimization on the capacity configuration and parameter selection of the harmonic governance device for the port distribution network, considers more the influence of power quality such as harmonics, improves the filtering ability of high-order harmonics, and more effectively protects the distribution network in the case of large-scale onshore power access. Moreover, this method is simple and easy to implement.

Description

Technical Field

[0001] The present invention relates to the technical field of power quality analysis and measure governance after large-capacity shore power is applied on a large scale, and particularly relates to a comprehensive resource optimization configuration method after large-capacity shore power is applied on a large scale.

Background Art

[0002] With the increasing problems of environmental pollution and energy crisis, the country pays more and more attention to energy conservation and emission reduction and optimizing the energy consumption structure. The implementation of the "electric energy substitution" strategy has promoted the transformation of the energy development mode and played a crucial role in the high-quality development of China's future energy. Among them, the shore power system used by ships docking at ports can effectively achieve port emission reduction, improve the environmental status of the port area, and enable it to develop in harmony with the city. However, due to the large-scale application of shore power, the port distribution network is in a heavy-load working condition, and the harmonic current in the distribution network increases. Therefore, when the number of shore power access units increases, the problem of excessive harmonic distortion rate will occur.

[0003] For example, in a certain coastal port, due to the presence of high-power motor equipment with direct starting on some ships, the reactive impact current during startup causes the shore power protection to trip. In this context, the shore power supply is sensitive to the background harmonics of the distribution network. In order to reduce the harmonic current content emitted by the large-scale accessed shore power supply, the background harmonic voltage of the distribution network must be controlled within a reasonable range. At the same time, as the scale of shore power access increases, the power loss in the port distribution network also gradually increases. Therefore, the key to power quality governance of the port distribution network is harmonic filtering and reactive power compensation, to solve the power quality problem of high harmonic distortion rate caused by large-scale access and ensure the safe and stable operation of the system.

[0004] Currently, there is relatively little research on the protection of dedicated shore power systems, and it is concentrated in the improvement of ship-side protection, without essentially improving the acceptance capacity of the distribution network for ship shore power; in the only research on shore power distribution networks, it focuses on the design of the information acquisition system for shore power system protection, only designing the protection unit and the corresponding software platform. There is no comprehensive resource optimization configuration method specifically adapted to the power quality of the shore power system according to the characteristics of the shore power system. Therefore, aiming at the above power quality problems, a comprehensive resource optimization configuration method for the power quality of the shore power system is proposed to constrain or balance the power quality of the power grid and the investment in governance devices.

Summary of the Invention

[0005] The object of the present invention is to provide a comprehensive resource optimization configuration method and system after large-capacity shore power is applied on a large scale, which can overcome the deficiencies of the prior art. Aiming at the problem of high harmonic distortion rate after large-capacity shore power devices are connected on a large scale, taking power quality and safety indexes as constraint conditions, an optimization model for power quality governance of a distribution network is established. With the best harmonic suppression effect and the minimum investment cost of power quality governance devices as the objective function, multi-objective optimization is carried out on the capacity configuration and parameter selection of harmonic governance devices in a port distribution network, so as to obtain a comprehensive resource optimization configuration scheme under different load scales of the port distribution network. The system has a simple structure and the method is easy to implement.

[0006] The technical solution of the present invention: A comprehensive resource optimization configuration method after large-capacity shore power is applied on a large scale, characterized in that it includes the following contents:

[0007] (1) Comprehensive resource optimization of a distribution network after large-capacity shore power is applied on a large scale;

[0008] (1-1) Perform a fast power flow calculation according to the operation parameters of the distribution network and the harmonic source spectrum parameters after large-capacity shore power is applied on a large scale, and calculate its node voltage, power factor, active power and harmonics;

[0009] (1-2) Analyze whether the power quality emission level of ship shore power users connected to the distribution network meets the requirements of the power index standard limit; if it meets the requirements, determine the large-capacity shore power large-scale governance measures according to the shore power user access scale to improve the acceptance capacity of the distribution network for ship shore power; if it does not meet the requirements, modify the distribution network parameters and re-perform the power flow calculation and harmonic analysis.

[0010] In the step (1-2), determining the large-capacity shore power large-scale governance measures according to the shore power user access scale is obtained by calculation using MATLAB; modifying the distribution network parameters in the step (1-2) is realized by using Command statements.

[0011] (2) Configure the parameters of the passive filter;

[0012] (2-1) According to the compensation capacity of the single-tuned filter and the highest operating voltage of the access point, calculate the reactance parameter X, inductance parameter L and inductance parameter C of the single-tuned filter by formulas (1) to (5):

[0013]

[0014] In the formula, h is the filter order; h0 is the filter tuning order; q Lh0 is the quality factor at the tuning frequency of the filter reactor; Q C1，h is the fundamental wave compensation capacity of the h-th filter, Mvar; U p，maxis the highest voltage of the power supply bus during actual operation, kV; f1 is the fundamental frequency, Hz; R e is the equivalent series resistance at the tuned frequency of the filtering reactor; X L1 and X C1 are respectively the fundamental inductive reactance of the series reactor and the fundamental capacitive reactance of the capacitor in the filter;

[0015] (2-2) Calculate the reactance parameter X, inductance parameter L, and inductance parameter C of the second-order high-pass filter through formulas (6) to (8), that is:

[0016]

[0017]

[0018] In the formula, is the quality factor at the tuned frequency of the filter, generally taking values between 0.6 and 30, and should not be too small, otherwise the fundamental wave loss is large;

[0019] (3) Establish a power quality governance model for large-scale application of shore power based on the node voltage, power factor, active power, harmonics calculated in step (1-1) and the parameters of the passive filter in step (2);

[0020] (3-1) Determine the objective function:

[0021] Taking the minimum total investment of the power quality governance device and the best resonance suppression effect as two objective functions, perform multi-objective optimization on the capacity configuration and parameter selection of the harmonic governance device. Therefore, the established multi-objective optimization model is shown in formulas (9) to (11):

[0022] F = min[f cost , f THDu (9)

[0023]

[0024] In the formula, C PQC is the total investment of the harmonic governance device, C FC is the unit capacity investment cost of the passive filter device FC in the central substation; Q FC，i are respectively the installed capacities of the FC devices in the i-th central substation; N B is the number of central substations; N D is the number of nodes of the power supply bus of the port distribution network; is the state value of the total voltage harmonic distortion rate of the i-th bus; f cost is the total investment function; f THDu is the function indicating the harmonic content; F is the objective function that minimizes the comprehensive total investment and has the best resonance suppression effect.

[0025] The power quality control device in step (3-1) refers to the power quality control device installed in the port distribution network, where a passive filter is installed in the central substation of the port distribution network for harmonic filtering.

[0026] In summary, this model takes into account both the construction cost and harmonic control, and can ensure the safety after shore power access while reducing economic losses.

[0027] (3-2) Determine the constraint conditions:

[0028] The constraint conditions of the reactive power optimization control variables need to satisfy the node active and reactive power balance constraints, as shown in equations (12) and (13) respectively.

[0029]

[0030] In the formula, P Gi , P Li are the active power of the generator and the active load of node i respectively; Q Gi , Q Li , Q Ci are the reactive power of the generator, the reactive load and the reactive compensation capacity of node i respectively; U i , U j are the voltages of node i and node j respectively; G ij , B ij , θ ij - Node i and j are connected, and the conductance, susceptance and node voltage phase angle difference between them; N is the total number of nodes in the system;

[0031] The inequality constraint conditions for the large-scale application of shore power are divided into control variable constraints and state variable constraints; the capacity of the harmonic control device is selected as the control variable constraint, and the voltage deviation of each node, the total harmonic distortion rate of each node voltage, the fundamental power factor at the PCC point, and the line load rate are selected as the state variable constraints, as shown in equation (14):

[0032]

[0033] In the formula, Q h，C is the control variable of the reactive power compensation capacity of the hth filter branch; QF h is the control variable of the quality factor of the hth filter branch; Q h，Lim is the upper limit value of the reactive power compensation capacity of the hth filter branch; Q C，Lim is the upper limit value of the total reactive power compensation of all harmonic compensation branches; QF h，min , QF h，max are the minimum and maximum values of the quality factor of the hth filter branch respectively; THDU i is the state value of the total harmonic distortion rate of the voltage of the ith bus; THDU Limis the set limit value of the total harmonic distortion rate of the bus voltage; η Li is the load rate of line Li; U Li is the voltage status value of the i-th bus; U Li，min 、U Li，max and U PCC are the voltage of node i and its lower and upper limit values respectively; PF Lim and PF

[0034] (4) Establish a joint simulation platform of MATLAB and OpenDSS to calculate and solve the optimal solution

[0035] In addition to simulation, the two software platforms of MATLAB and OpenDSS also have calculation functions and can perform calculations and optimal configurations. Therefore, aiming at the problems after large-capacity shore power is scaled up and connected to the distribution network, a joint simulation calculation platform as shown in Figure 3 is built based on the Matlab and OpenDSS platforms; the entire calculation platform mainly includes three calculation modules: 1) the three-phase power flow calculation module of the distribution network, 2) the harmonic calculation module of the distribution network, and 3) the comprehensive resource optimal configuration module; among them, the three-phase power flow calculation module and the harmonic calculation module of the distribution network are built on the OpenDSS software platform and are used to perform the three-phase power flow calculation and the calculation of each harmonic of the distribution network; the comprehensive resource optimal configuration module is implemented on the MATLAB platform; data communication between the OpenDSS calculation program and the calculation and analysis module of the MATLAB platform is realized between the OpenDSS platform and the MATLAB platform based on the component object DLL (OpenDSSEngine).

[0036] A system capable of realizing the comprehensive resource optimal configuration method after the large-capacity shore power is scaled up and applied, characterized in that the power quality governance of the port distribution network adopts a hybrid governance system structure of an FC passive filter (FC passive filter) and a static var generator (Static Var Generator, SVG), and is configured in the central substation or the main step-down substation for decentralized compensation at the central substation and the main step-down substation, as shown in Figure 1 shown.

[0037] The passive filter is composed of a 5th-order monotonic filter branch, a 7th-order monotonic filter branch, and an 11th-order second-order high-pass filter branch; the 5th-order monotonic filter branch and the 7th-order monotonic filter branch mainly achieve the filtering of the 5th and 7th harmonics in the port distribution network, and the 11th-order second-order high-pass filter branch is used to achieve the filtering of the 11th and higher harmonics in the port distribution network. The filter combination method that meets the requirements is as Figure 2 shown.

[0038] The circuit structures of the 5th-order monotonic filter branch and the 7th-order monotonic filter branch are the same, and both adopt the structure of series connection of a filter capacitor, a filter inductor, and a filter reactance. Among them, the 5th-order monotonic filter branch is composed of a filter capacitor C5, a filter inductor L5, and a filter reactance X5, which are connected in series in turn. The other end of the filter reactance X5 is connected to the grounding system of the port distribution network, and the other end of the filter capacitor C5 is connected to the distribution network power supply bus in the distribution network; the 7th-order monotonic filter branch is composed of a filter capacitor C7, a filter inductor L7, and a filter reactance X7, which are connected in series in turn. The other end of the filter reactance X7 is connected to the grounding system in the port distribution network, and the other end of the filter capacitor C7 is connected to the distribution network power supply bus, as Figure 2 shown.

[0039] The 11th-order second-order high-pass filter branch is composed of a filter capacitor C 11 , a filter inductor L 11 , and a filter reactance X 11 . The filter inductor L 11 and the filter reactance X 11 are connected in parallel and then connected in series with the filter capacitor C 11 . The other end of the parallel part is connected to the grounding bus of the port distribution network, and the other end of the filter capacitor C7 is connected to the power supply bus in the distribution network, as Figure 2 shown.

[0040] The working principle of the present invention:

[0041] (1) In the selection of the large-capacity shore power large-scale governance access scheme, the power quality governance strategy of the port distribution network should preferably adopt a hybrid governance scheme of passive filters and SVG. In actual applications, since the load capacity of a single sub-substation is relatively small and the number of sub-substations is relatively large, when configuring the power quality governance device in the sub-substation, the capacity configuration of a single governance device is too small, and the economy is poor. Therefore, the power quality governance device of the port distribution network should be configured in the central substation or the main step-down substation, and decentralized compensation should be carried out in the central substation and the main step-down substation, as Figure 1 shown.

[0042] (2) Selection of passive filter configuration scheme: Considering a large number of 5th, 7th, 11th, 13th, 17th, 19th and even higher-order harmonics in the port distribution network, it is advisable to configure three branches of 5th single-tuned + 7th single-tuned + 11th second-order high-pass filter for the passive filter. Among them, the 5th and 7th single-tuned filters mainly achieve the filtering of 5th and 7th harmonics, and the 11th second-order high-pass filter achieves the filtering of 11th and higher harmonics. The filter combination mode that meets the requirements is as Figure 2 shown.

[0043] (3) Establishment of mathematical model for optimal configuration of passive filter: After a large-scale electric energy substitution load is connected to the power system, the operation level of power quality is greatly affected. According to the optimal operation of the distribution network, which is based on the economic operation of the distribution network under the constraints of power quality and safety, the power quality and safety indicators are used as constraint conditions, that is, the positive voltage deviation, negative voltage deviation, total voltage harmonic distortion rate, line load rate, and fundamental power factor at the PCC point are used as constraint conditions, and the best harmonic filtering and resonance suppression effects and the minimum investment cost of power quality control devices are used as the objective function to establish an optimal model for power quality control of onshore power supply on a large scale connected to the distribution network, and based on the particle swarm optimization algorithm for optimization and solution, the harmonic control scheme of the port distribution network under different load scales is obtained.

[0044] Superiority of the present invention:

[0045] 1. According to the power quality problems after the large-scale application of large-capacity onshore power supply, an optimal model for power quality control of onshore power supply on a large scale connected to the distribution network is established. With the best harmonic suppression effect and the minimum investment cost of power quality control devices as the objective function, multi-objective optimization is carried out on the capacity configuration and parameter selection of the harmonic control device in the port distribution network. The hybrid control scheme of FC + SVG is adopted to complete the application scheme design of large-capacity onshore power supply devices for large coastal ports. Compared with the existing onshore power supply protection technologies, the model proposed in this scheme takes more into account the influence of power quality such as harmonics, improves the filtering ability of higher-order harmonics, and more effectively protects the distribution network under the condition of large-scale onshore power supply access.

[0046] 2. From the perspective of the investment benefit of the control device and harmonic suppression, the analysis results increase the installation capacity of the second-order high-pass filter. On the one hand, it ensures the suppression of higher-order harmonics, and on the other hand, it also minimizes the installation capacity of capacitors under the same compensation ability, achieving the comprehensive optimum of the control effect and investment cost.

[0047] 3. According to the reactive power compensation capacity (3.5 Mvar) of the harmonic filters installed in two central substations, which is approximately 7% of the transformer rated capacity, the reactive power compensation requirements from light load conditions to heavy load conditions can be met, ensuring that there is no reverse reactive power transmission at each central substation under light load conditions after installing the harmonic filters at the central substations. At the same time, according to the fundamental power factor at the point of common coupling, a dynamic reactive power compensation device is installed at the main step-down substation, thereby obtaining a harmonic management scheme for the distribution network under different load scales of the port distribution network. This method is simple and easy to implement.

Description of the Drawings

[0048] Figure 1 It is a schematic diagram of the configuration of the power quality management device for the port distribution network in an integrated resource optimization configuration method for large-capacity shore power large-scale application involved in the present invention.

[0049] Figure 2 It is an operating scheme diagram of the mutual inductance type current limiter in different stages in an integrated resource optimization configuration method for large-capacity shore power large-scale application involved in the present invention.

[0050] Figure 3 It is a schematic diagram of the structure of the MATLAB and OpenDSS joint simulation platform in an integrated resource optimization configuration method for large-capacity shore power large-scale application involved in the present invention.

[0051] Figure 4 It is a flow chart of the integrated resource optimization of the distribution network for large-scale application of shore power in an integrated resource optimization configuration method for large-capacity shore power large-scale application involved in the present invention.

[0052] Figure 5 It is a node diagram of the 1# main transformer distribution network in the distribution network in an embodiment involved in the present invention.

[0053] Figure 6 is a harmonic spectrum distribution diagram of each node after the harmonic management device based on particle swarm optimization is put into operation in an embodiment involved in the present invention (where, Figure 6-a is the harmonic spectrum distribution diagram at the 110 kV bus, Figure 6-b is the harmonic spectrum distribution diagram at the 10 kV bus, Figure 6-c is the harmonic spectrum distribution diagram at the 3# substation, Figure 6-d is the harmonic spectrum distribution diagram at the 4# substation).

[0054] Figure 7 is a voltage distribution diagram of each node before and after harmonic management under light load conditions in an embodiment involved in the present invention (where, Figure 7-a is before management, Figure 7-b is after management).

[0055] Figure 8 is a voltage distribution diagram of each node before and after harmonic management under heavy load conditions in an embodiment involved in the present invention (where, Figure 8-a is before management,Figure 8-b After treatment).

[0056] Figure 9 is a comparison chart of the load rates of each line before and after harmonic treatment under heavy load conditions in an embodiment involved in the present invention (where, Figure 9-a Before treatment, Figure 9-b After treatment).

Specific implementation manner

[0057] Embodiment: A comprehensive resource optimization configuration method after large-capacity shore power is applied on a large scale, which is characterized by including the following contents:

[0058] (1) Comprehensive resource optimization of the distribution network for large-capacity shore power applied on a large scale;

[0059] (1-1) Perform fast power flow calculation according to the operation parameters of the distribution network for large-capacity shore power applied on a large scale and the harmonic source spectrum parameters, and calculate its node voltage, power factor, active power, and harmonics;

[0060] (1-2) Analyze whether the power quality emission level of ship shore power users accessing the distribution network meets the requirements of the power index standard limits; if it meets the requirements, determine the large-capacity shore power large-scale governance measures by calculation using MATLABb according to the shore power user access scale to improve the acceptance capacity of the distribution network for ship shore power; if it does not meet the requirements, modify the distribution network parameters using Command statements and re-perform power flow calculation and harmonic analysis.

[0061] (2) Configure the parameters of the passive filter;

[0062] (2-1) According to the compensation capacity of the single-tuned filter and the highest operating voltage at the access point, calculate the reactance parameter X, inductance parameter L, and inductance parameter C of the single-tuned filter using formulas (1) to (5):

[0063]

[0064] In the formula, h is the filter order; h0 is the filter tuning order; q Lh0 is the quality factor at the tuning frequency of the filter reactor; Q C1，h is the fundamental wave compensation capacity of the h-th filter, Mvar; U p，max is the highest voltage actually operating on the power supply bus, kV; f1 is the fundamental wave frequency, Hz; R e is the equivalent series resistance at the tuning frequency of the filter reactor; X L1 and X C1 are respectively the fundamental wave inductive reactance of the series reactor and the fundamental wave capacitive reactance of the capacitor in the filter;

[0065] (2-2) Calculate the reactance parameter X, inductance parameter L, and inductance parameter C of the second-order high-pass filter using formulas (6) to (8), that is:

[0066]

[0067] In the formula, is the quality factor at the filter tuning frequency, generally taking values between 0.6 and 30, and should not be too small, otherwise the fundamental wave loss is large;

[0068] (3) Establish a power quality governance model for large-scale application of onshore power based on the node voltage, power factor, active power, harmonics calculated in step (1-1) and the parameters of the passive filter in step (2);

[0069] (3-1) Determine the objective function:

[0070] Taking the minimum total investment of the power quality governance device and the best resonance suppression effect as two objective functions, multi-objective optimization is carried out on the capacity configuration and parameter selection of the harmonic governance device. Therefore, the established multi-objective optimization model is shown in formulas (9) to (11):

[0071] F = min[f cost , f THDu (9)

[0072]

[0073] In the formula, C PQC is the total investment of the harmonic governance device, C FC is the unit capacity investment cost of the passive filter device FC in the central substation; Q FC，i are the installation capacities of the FC devices in the i-th central substation respectively; N B is the number of central substations; N D is the number of nodes of the power supply bus of the port distribution network; is the state value of the total voltage harmonic distortion rate of the i-th bus; f cost is the total investment function; f THDu is the function indicating the harmonic content; F is the objective function that minimizes the comprehensive total investment and has the best resonance suppression effect.

[0074] Among them, the power quality governance device refers to the power quality governance device installed in the port distribution network, and a passive filter is installed in the central substation of the port distribution network for harmonic filtering.

[0075] In summary, this model takes into account both the construction cost and harmonic governance, and can ensure the safety after onshore power access while reducing economic losses.

[0076] (3-2) Determine the constraint conditions:

[0077] The constraint conditions of the reactive power optimization control variables need to satisfy the node active and reactive power balance constraints, as shown in formulas (12) and (13) respectively.

[0078]

[0079] Wherein, P Gi and P Li are respectively the active power and active load of the generator at node i; Q Gi and Q Li and Q Ci are respectively the reactive power of the generator, reactive load and reactive compensation capacity at node i; U i and U j are respectively the voltages of node i and node j; G ij and B ij and θ ij - Node i and j are connected, and the conductance, susceptance and node voltage phase angle difference between them; N is the total number of nodes in the system;

[0080] The inequality constraint conditions for the large-scale application of onshore power are divided into control variable constraints and state variable constraints; The capacity of the resonance control device is selected as the control variable constraint, and the voltage deviation of each node, the total harmonic distortion rate of each node voltage, the fundamental power factor at the PCC point, and the line load rate are selected as the state variable constraints, as shown in Equation (14):

[0081]

[0082] Wherein, Q h，C is the control variable of the reactive compensation capacity of the hth filter branch; QF h is the control variable of the quality factor of the hth filter branch; Q h，Lim is the upper limit value of the reactive compensation capacity of the hth filter branch; Q C，Lim is the upper limit value of the total reactive compensation amount of all harmonic compensation branches; QF h，min and QF h，max are respectively the minimum and maximum values of the quality factor of the hth filter branch; THDU i is the state value of the total harmonic distortion rate of the voltage of the ith bus; THDU Lim is the set limit value of the total harmonic distortion rate of the bus voltage; η Li is the load rate of line Li; U Li is the voltage state value of the ith bus; U Li，min and U Li，max are respectively the voltage of node i and its lower and upper limit values; PF PCC and PF Lim are respectively the state value and assessment limit value of the fundamental power factor of the total incoming line at the PCC point of the port distribution network; NC, NB, and NL are respectively the number of filters, the number of power supply buses, and the number of lines in the port distribution network.

[0083] (4) Establish a joint simulation platform of MATLAB and OpenDSS to calculate and solve the optimal solution

[0084] In addition to simulation, the two software platforms of MATLAB and OpenDSS also have calculation functions and can perform calculations and optimal configurations. Therefore, aiming at the problems after large-capacity onshore power is large-scale connected to the distribution network, a joint simulation calculation platform as shown in Figure 3 is built based on the Matlab and OpenDSS platforms; the entire calculation platform mainly includes three calculation modules: 1) a three-phase power flow calculation module for the distribution network, 2) a harmonic calculation module for the distribution network, and 3) an integrated resource optimal configuration module; among them, the three-phase power flow calculation module and the harmonic calculation module for the distribution network are built on the OpenDSS software platform and are used to perform three-phase power flow calculations and harmonic calculations of each order for the distribution network; the integrated resource optimal configuration module is implemented on the MATLAB platform; data communication between the OpenDSS platform and the MATLAB platform is realized based on the component object DLL between the OpenDSS calculation program and the calculation analysis module of the MATLAB platform.

[0085] A system capable of implementing the integrated resource optimal configuration method after the large-capacity onshore power is large-scale applied, characterized in that the power quality governance of the port distribution network adopts a hybrid governance system structure of an FC passive filter and a static var generator, and is configured in the central substation or the main step-down substation for decentralized compensation in the central substation and the main step-down substation, as shown in Figure 1 shown.

[0086] The passive filter is composed of a 5th-order monotonic filter branch, a 7th-order monotonic filter branch, and an 11th-order second-order high-pass filter branch; the 5th-order monotonic filter branch and the 7th-order monotonic filter branch mainly realize the filtering of the 5th and 7th harmonics in the port distribution network, and the 11th-order second-order high-pass filter branch is used to realize the filtering of the 11th and higher harmonics in the port distribution network. The required filter combination method is as shown in Figure 2 shown.

[0087] The circuit structures of the 5th-order monotonic filter branch and the 7th-order monotonic filter branch are the same, and both adopt the structure of series connection of a filter capacitor, a filter inductor, and a filter reactance. Among them, the 5th-order monotonic filter branch is composed of a filter capacitor C5, a filter inductor L5, and a filter reactance X5, which are connected in series in turn. The other end of the filter reactance X5 is connected to the grounding system of the port distribution network, and the other end of the filter capacitor C5 is connected to the distribution network power supply bus in the distribution network; the 7th-order monotonic filter branch is composed of a filter capacitor C7, a filter inductor L7, and a filter reactance X7, which are connected in series in turn. The other end of the filter reactance X7 is connected to the grounding system in the port distribution network, and the other end of the filter capacitor C7 is connected to the distribution network power supply bus, as shown inFigure 2 as shown

[0088] The 11th-order second-order high-pass filter branch is composed of a filtering capacitor C 11 , a filtering inductor L 11 and a filtering reactance X 11 . The filtering inductor L 11 and the filtering reactance X 11 are connected in parallel and then connected in series with the filtering capacitor C 11 . The other end of the parallel part is connected to the grounding bus of the port distribution network, and the other end of the filtering capacitor C7 is connected to the power supply bus in the distribution network, as Figure 2 shown

[0089] To enable those skilled in the art to better understand the solution of this application, the following will further elaborate on this application in conjunction with the accompanying drawings.

[0090] As Figure 1 shown, based on the established OpenDSS / MATLAB co-simulation platform, the node voltage, power loss, and harmonic components obtained through the OpenDSS power flow calculation are returned to the MATLAB optimization algorithm part via the COM interface, and the direct control of the governance device is realized in MATLAB to determine whether the constraint conditions are met, and the above process is repeatedly executed until the optimization is completed.

[0091] Specifically, it includes the following steps:

[0092] Step 1, Optimization process of comprehensive resources for large-scale application of large-capacity onshore power

[0093] OpenDSS can only be used as a basic functional module to complete the power flow calculation of the distribution network. The specific optimization calculation process is as Figure 4 shown.

[0094] 1) Build a distribution network model after large-scale access of onshore power in OpenDSS, set the network operation parameters and harmonic source spectrum parameters for fast power flow calculation, and realize data transmission between OpenDSS and MATLAB through the COM interface for node voltage, power factor, active power, and harmonic information;

[0095] 2) Considering the requirements for equipment investment cost and the improvement of system loss, build a multi-objective harmonic governance optimization model in MATLAB and use the particle swarm algorithm for solution;

[0096] 3) Analyze whether the power quality emission level of ship onshore power users accessing the distribution network meets the requirements of the power quality index standard limits;

[0097] 4) If it meets the requirements, determine the large-capacity onshore power large-scale governance measures under different access scales to improve the acceptance capacity of the distribution network for ship onshore power.

[0098] Step 2, Passive Filter Parameter Configuration

[0099] 1) Calculation Method for Parameters X, L, and C of Monotonic Tuned Filter

[0100] Given the compensation capacity of the monotonic tuned filter and the highest operating voltage at the connection point, the filter parameters can be calculated using the following formulas (1) to (5):

[0101]

[0102] In the formula, h is the filter order; h0 is the tuned order of the filter; q Lh0 is the quality factor at the tuned frequency of the filter reactor; Q C1，h is the fundamental wave compensation capacity of the h-th filter, Mvar; U p，max is the highest actual operating voltage of the power supply bus, kV; f1 is the fundamental wave frequency, Hz; R e is the equivalent series resistance at the tuned frequency of the filter reactor.

[0103] 2) Calculation Method for Parameters X, L, and C of Second-Order High-Pass Filter

[0104] The filter parameters can be calculated using the following formulas (6) to (8):

[0105]

[0106]

[0107] In the formula, is the quality factor at the tuned frequency of the filter. Generally, it should not be selected too small, otherwise the fundamental wave loss will be large.

[0108] Step 3, Power Quality Governance Model for Large-Scale Application of Shore Power

[0109] 1) Objective Function

[0110] After a large number of electric energy substitution loads are connected to the power system, the operation level of power quality is greatly affected. In this section, considering the economy and reliability of network operation, a method of installing power quality governance devices in the port distribution network is adopted to govern the power quality of the port distribution network with large-scale access of shore power. Among them, a passive filter is installed in the central substation for harmonic filtering. Considering the minimum total investment of the governance device and the best resonance suppression effect as two objective functions, the capacity configuration and parameter selection of the harmonic governance device are optimized multi-objectively, and the established multi-objective optimization model is shown in Formulas (9) to (11):

[0111] F = min[f cost , f THDu (9)

[0112]

[0113] Wherein, C PQC is the total investment of the harmonic control device, and C FC is the unit capacity investment cost of the passive filter device FC in the central substation; Q FC，i are the installed capacities of the FC devices in the i-th central substation respectively; N B is the number of central substations; N D is the number of nodes of the power supply bus of the port distribution network; is the state value of the total voltage harmonic distortion rate of the i-th bus.

[0114] (2) Constraint conditions

[0115] The constraint conditions of the reactive power optimization control variables need to satisfy the node active and reactive power balance constraints, as shown in equations (12) and (13) respectively.

[0116]

[0117] Wherein, P Gi and P Li are the generator active power and active load of node i respectively; Q Gi and Q Li and Q Ci are the generator reactive power, reactive load and reactive compensation capacity of node i respectively; U i and U j are the voltages of node i and node j respectively; G ij and B ij and θ ij - Node i and j are connected, and the conductance, susceptance and node voltage phase angle difference between them; N is the total number of nodes in the system.

[0118] The inequality constraint conditions for the large-scale application of shore power are divided into control variable constraints and state variable constraints. In this section, the capacity and parameter device of the resonance control device are selected as the control variable constraints, and the voltage deviation of each node, the total voltage harmonic distortion rate of each node, the fundamental power factor at the PCC point, and the line load rate are selected as the state variable constraints, as shown in equation (14):

[0119]

[0120] Wherein, Q h，C is the control variable of the reactive power compensation capacity of the h-th filter branch; QF h is the control variable of the quality factor of the h-th filter branch; Q h，Lim is the upper limit value of the reactive power compensation capacity of the h-th filter branch; Q C，Lim is the upper limit value of the total reactive power compensation of all harmonic compensation branches; QFh，min and QF h，max are the minimum and maximum values of the quality factor of the h-th filter branch respectively; THDU i is the total harmonic distortion rate status value of the voltage of the i-th busbar; THDU Lim is the set limit value of the total harmonic distortion rate of the busbar voltage; η Li is the load rate of line Li; U Li is the voltage status value of the i-th busbar; U Li，min and U Li，max are the voltage of node i and its lower and upper limit values respectively; PF PCC and PF Lim are the total incoming fundamental power factor status value and the assessment limit value at the PCC point of the port distribution network respectively; NC, NB, and NL are the number of filters, the number of power supply busbars, and the number of lines in the port distribution network respectively.

[0121] Step 4, case analysis

[0122] Carry out case analysis according to the distribution network of the 1# main transformer. The node diagram is as Figure 5 shown. Based on the capacity and parameter configuration results of the harmonic filtering devices of the 3# and 4# central substations based on particle swarm optimization, input the parameters of the treatment device into the port distribution network simulation model.

[0123] 1) When the simultaneous coefficient of the gantry cranes in the power supply area of the 1# main transformer is 0.5, after 4 shore power equipment are put into operation under heavy load conditions, the harmonic spectrum distribution and the total harmonic distortion rate of the voltage of each node are obtained as shown in Figure 6. After treatment, the improvement rate of the total harmonic distortion rate of the voltage of each node reaches 79%.

[0124] 2) Before and after treatment, the voltage distribution of each node under different working conditions is shown in Figures 7 and 8. After treatment, the voltage of each node is significantly improved and meets the national voltage standard requirements.

[0125] 3) Before and after power quality treatment, the load rates of each line under heavy load conditions are shown in Figure 9 respectively. After treatment, the load rate of the power supply line of the central substation is reduced from 78.6% to 72.4%, and the maximum load rate of the line is reduced by 7.9%.

[0126] It can be seen from the simulation results that from the perspectives of the investment benefit of the treatment device and harmonic suppression, the installation capacity of the second-order high-pass filter should be increased. On the one hand, it ensures the suppression of high-order harmonics, and on the other hand, it also minimizes the installation capacity of capacitors under the same compensation capacity, achieving the comprehensive optimum of the treatment effect and investment cost.

[0127] Since large-power power electronic devices such as quay cranes and shore power in the port distribution network use fully controlled power electronic devices, their reactive power demand during operation is relatively small. After installing harmonic filters in the central substation, it should be able to ensure that there is no reverse reactive power transmission in each central substation under light load conditions. According to the reactive power compensation capacity (3.5 Mvar) of the harmonic filters installed in the two central substations, which is about 7% of the transformer rated capacity, it can meet the reactive power compensation requirements from light load conditions to heavy load conditions. At the same time, it is also possible to consider installing a dynamic reactive power compensation device in the main step-down substation according to the fundamental power factor situation at the point of common coupling.

Claims

1. A comprehensive resource optimization and allocation method after large-capacity shore power is applied on a large scale, characterized in that It includes the following contents: (1) Comprehensive resource optimization of distribution network for large-capacity onshore power supply on a large scale; (1-1) Conduct rapid power flow calculation according to the operation parameters of the distribution network for large-capacity onshore power supply on a large scale and the harmonic source spectrum parameters, and calculate its node voltage, power factor, active power and harmonics; (1-2) Analyze whether the power quality emission level of ship onshore power users accessing the distribution network meets the requirements of the power index standard limits; If the requirements are met, determine the large-capacity onshore power supply governance measures on a large scale according to the access scale of onshore power users to improve the acceptance capacity of the distribution network for ship onshore power; If the requirements are not met, modify the distribution network parameters and re-conduct power flow calculation and harmonic analysis; (2) Configure the parameters of the passive filter; (2-1) Calculate the reactance parameter X, inductance parameter L and inductance parameter C of the monotonic filter according to the compensation capacity of the monotonic filter and the highest operating voltage of the access point by formulas (1) to (5): Where h is the filter order; h0 is the filter tuning order; q Lh0 is the quality factor at the tuning frequency of the filtering reactor; Q C1，h is the fundamental wave compensation capacity of the h-th filter, Mvar; U p，max is the highest voltage actually operating on the power supply bus, kV; f1 is the fundamental wave frequency, Hz; R e is the equivalent series resistance at the tuning frequency of the filtering reactor; X L1 and X C1 are respectively the fundamental wave inductive reactance of the series reactor and the fundamental wave capacitive reactance of the capacitor in the filter; (2-2) Calculate the reactance parameter X, inductance parameter L and inductance parameter C of the second-order high-pass filter by formulas (6) to (8), that is: wherein, is the quality factor at the filter tuning frequency, and the value ranges from 0.6 to 30; (3) Establish a power quality governance model for large-scale onshore power supply application based on the node voltage, power factor, active power and harmonics calculated in step (1-1) and the parameters of the passive filter in step (2); (3-1) Determine the objective function: Taking the minimum total investment of the power quality governance device and the best resonance suppression effect as two objective functions, conduct multi-objective optimization on the capacity configuration and parameter selection of the harmonic governance device. Therefore, the established multi-objective optimization model is shown in formulas (9) to (11): F = min[f cost , f THDu (9) Where, C PQC is the total investment of the harmonic control device, and C FC is the unit capacity investment cost of the passive filter device FC in the central substation; Q FC，i are the installed capacities of the FC devices in the i-th central substation respectively; N B is the number of central substations; N D is the number of nodes of the power supply bus in the port distribution network; is the state value of the total voltage harmonic distortion rate of the i-th bus; f cost is the total investment function; f THDu is the function indicating the harmonic content; F is the objective function for minimizing the comprehensive total investment and achieving the best resonance suppression effect; (3-2) Determine the constraint conditions: The constraint conditions of the reactive power optimization control variables need to meet the node active and reactive power balance constraints, as shown in formulas (12) and (13) respectively: where P Gi and P Li are the active power of the generator and the active load of node i, respectively; Q Gi , Q Li , and Q Ci are the reactive power of the generator, the reactive load, and the reactive compensation capacity of node i, respectively; U i and U j are the voltages of node i and node j, respectively; G ij , B ij , and θ ij - Node i and j are connected, and the conductance, susceptance, and phase angle difference of the node voltages between them; N is the total number of nodes in the system; The inequality constraint conditions for large-scale onshore power supply application are divided into control variable constraints and state variable constraints; select the capacity of the resonance governance device as the control variable constraint, and select the voltage deviation of each node, the total harmonic distortion rate of each node voltage, the fundamental power factor of the PCC point, and the line load rate as the state variable constraints, as shown in formula (14): Where Q h,C is the control variable of the reactive power compensation capacity of the hth filtering branch; QF h is the control variable of the quality factor of the hth filtering branch; Q h，Lim is the upper limit value of the reactive power compensation capacity of the hth filtering branch; Q C，Lim is the upper limit value of the total reactive power compensation of all harmonic compensation branches; QF h，min and QF h，max are the minimum and maximum values of the quality factor of the hth filtering branch respectively; THDU i is the state value of the total harmonic distortion rate of the voltage of the ith bus; THDU Lim is the set limit value of the total harmonic distortion rate of the bus voltage; η Li is the load rate of line Li; U Li is the voltage status value of the i-th bus; U Li,min , U Li,max are respectively the voltage of node i and its lower and upper limits; PF PCC and PF Lim are respectively the fundamental power factor status value and the assessment limit value of the total incoming line at the PCC point of the port distribution network; NC, NB, and NL are respectively the number of filters, the number of power supply buses, and the number of lines in the port distribution network; (4) Establish a MATLAB and OpenDSS joint simulation platform to calculate and solve the optimal solution A joint simulation calculation platform is built based on the Matlab and OpenDSS platforms, which is composed of a distribution network three-phase power flow calculation module, a distribution network harmonic calculation module and a comprehensive resource optimization configuration module; among them, the distribution network three-phase power flow calculation module and the distribution network harmonic calculation module are built on the OpenDSS software platform for conducting distribution network three-phase power flow calculation and each harmonic calculation; the comprehensive resource optimization configuration module is implemented on the MATLAB platform; data communication between the OpenDSS calculation program and the MATLAB platform calculation and analysis module is realized between the OpenDSS platform and the MATLAB platform based on the component object DLL.

2. The comprehensive resource optimization and allocation method after large-capacity shore power is applied on a large scale according to claim 1, characterized in that In the step (1-2), the large-capacity shore power scale management measures determined according to the access scale of shore power users are obtained by MATLAB calculation; in the step (1-2), the modification of the distribution network parameters is realized by using Command statements.

3. The comprehensive resource optimization and allocation method after large-capacity shore power is applied on a large scale according to claim 1, characterized in that The power quality management device in the step (3-1) refers to the power quality management device installed in the port distribution network, and a passive filter is installed in the central substation of the port distribution network for harmonic filtering.

4. A system for implementing the comprehensive resource optimization and allocation method after large-capacity shore power is applied on a large scale according to claim 1, characterized in that The power quality management of the port distribution network adopts a hybrid management system structure of FC passive filters and static var generators, and is configured in the central substation or the main step-down substation for decentralized compensation in the central substation and the main step-down substation.

5. The comprehensive resource optimization and allocation system after large-capacity shore power is applied on a large scale according to claim 4, characterized in thatThe passive filter is composed of a 5th-order monotonic filter branch, a 7th-order monotonic filter branch, and an 11th-order second-order high-pass filter branch; the 5th-order monotonic filter branch and the 7th-order monotonic filter branch mainly realize the filtering of the 5th and 7th harmonics in the port distribution network, and the 11th-order second-order high-pass filter branch is used to realize the filtering of the 11th and higher harmonics in the port distribution network.

6. The integrated resource optimization and allocation system after large-capacity shore power is applied on a large scale according to claim 5, wherein The circuit structures of the 5th-order monotonic filter branch and the 7th-order monotonic filter branch are the same, and both adopt a structure in which a filter capacitor, a filter inductor, and a filter reactance are connected in series. Among them, the 5th-order monotonic filter branch is composed of a filter capacitor C5, a filter inductor L5, and a filter reactance X5, which are connected in series in turn. The other end of the filter reactance X5 is connected to the grounding system of the port distribution network, and the other end of the filter capacitor C5 is connected to the distribution network power supply bus in the distribution network; the 7th-order monotonic filter branch is composed of a filter capacitor C7, a filter inductor L7, and a filter reactance X7, which are connected in series in turn. The other end of the filter reactance X7 is connected to the grounding system in the port distribution network, and the other end of the filter capacitor C7 is connected to the distribution network power supply bus.

7. The integrated resource optimization and allocation system after large-capacity shore power is applied on a large scale according to claim 5, wherein The 11th-order second-order high-pass filter branch is composed of a filter capacitor C 11 , a filter inductor L 11 , and a filter reactance X 11 . The filter inductor L 11 and the filter reactance X 11 are connected in parallel and then connected in series with the filter capacitor C 11 . The other end of the parallel part is connected to the grounding bus of the port distribution network, and the other end of the filter capacitor C7 is connected to the power supply bus in the distribution network.

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