Distribution network DTU protection method based on access of distributed power supply

Abstract

The invention relates to the technical field of DTU protection, in particular to a power distribution network DTU protection method based on access of a distributed power supply. According to the technical scheme, the system comprises an analysis module, a protection strategy making module, an optimization scheduling module and a simulation verification module, the analysis module collects data such as output characteristics and operation parameters of a distributed power supply to carry out fault characteristic analysis so as to provide a basis for making a subsequent protection strategy; the protection strategy formulating module formulates a reasonable protection strategy in combination with characteristics of the distributed power supply and protection requirements of the power distribution network, the optimal scheduling module realizes real-time monitoring and operation control of the power distribution network through optimal scheduling, and the simulation verification module ensures feasibility of the proposed method in practical application through simulation verification. Normal operation and effective protection of the DTU are ensured, the function of the DTU in the power distribution network is fully played, and safe, stable and efficient operation of the power grid is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of DTU protection, and in particular to a DTU protection method for a distribution network based on access to a distributed power source. Background Art

[0002] Distributed power generation, referred to as DG, refers to small and medium-sized power sources distributed at the user end, mainly including solar photovoltaic power generation, wind power generation, biomass power generation, fuel cells, small hydropower and gas turbines;

[0003] The access of distributed generation has expanded the operation mode of the distribution network, and at the same time has greatly increased the complexity of the distribution network. With the access of a large number of DGs, the requirement of DGs to be immediately disconnected from the grid when a grid failure occurs in the early grid connection regulations is no longer applicable, because the sudden disconnection of large-scale DGs may bring great instability to the distribution network, and even cause the grid to paralyze;

[0004] Distributed energy technology unit (DTU) plays a vital role in the distribution network. DTU can monitor and control distributed energy, ensure that distributed energy is stably and reliably connected to the distribution network, thereby improving power supply reliability. DTU helps to integrate various distributed energy sources, such as solar energy and wind energy, and promote the consumption of clean energy. DTU protection measures can effectively prevent distributed energy equipment from being damaged in the event of a fault and extend the service life of the equipment. DTU protection can ensure that when a distributed energy fails, it is isolated from the power grid in a timely manner to prevent the fault from expanding and ensure the safety of the power grid.

[0005] DTU plays an important role in the distribution network, and its protection measures are of great significance for ensuring the safety of the power grid, improving power supply reliability, and promoting energy consumption. Therefore, strengthening the protection and operation and maintenance management of DTU is an important measure to promote my country's energy transformation and the development of the power industry.

[0006] To this end, we propose a DTU protection method for distribution network based on access to distributed power sources to solve the existing problems. Summary of the invention

[0007] The purpose of the present invention is to address the problems existing in the background technology and to propose a DTU protection method for a distribution network based on access to a distributed power source.

[0008] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a DTU protection method for a distribution network based on access to distributed power sources, including an analysis module, a protection strategy formulation module, an optimization scheduling module and a simulation verification module. The analysis module collects data such as output characteristics and operating parameters of distributed power sources to perform fault characteristic analysis to provide a basis for the formulation of subsequent protection strategies. The protection strategy formulation module formulates a reasonable protection strategy based on the characteristics of distributed power sources and the protection requirements of the distribution network. The optimization scheduling module realizes real-time monitoring and operation control of the distribution network through optimization scheduling. The simulation verification module ensures the feasibility of the proposed method in practical applications through simulation verification. In summary, the normal operation and effective protection of DTU are ensured, its role in the distribution network is fully utilized, and the safe, stable and efficient operation of the power grid is guaranteed.

[0009] Preferably, the fault characteristic analysis includes current-controlled DG and voltage-controlled DG. The fault response characteristics of the current-controlled DG are mainly affected by the control loop and have little to do with the physical circuit parameters. The control loop transfer function can be used to mathematically describe the fault response characteristics of the voltage-controlled DG. The fault response characteristics are jointly determined by the control loop and the physical circuit and are coupled with each other, making it difficult to describe mathematically. Within 5-10 power frequency cycles after the fault, the fault current is significantly greater than that of the current-controlled DG, and there is a fault impact current.

[0010] Preferably, the steps of the protection strategy formulation module include determining a protection configuration scheme and designing protection logic. The steps of determining the protection configuration scheme include selecting appropriate protection devices according to the characteristics of the distributed power source, such as overcurrent protection, distance protection, and differential protection, and setting the action parameters of the protection device, such as set values ​​and time delays, according to the output characteristics of the distributed power source and the operating parameters of the distribution network. The steps of designing the protection logic include designing algorithms to detect faults in the distribution network, such as overcurrent, voltage drop, and frequency anomaly, and determining the specific location of the fault to facilitate accurate isolation. After the fault is detected, the fault area is isolated by disconnecting the corresponding switch or circuit breaker. After the fault is isolated, it is decided whether to reclose the circuit breaker according to the actual situation of the power grid to restore power supply to non-fault areas.

[0011] Preferably, the algorithms of the protection logic include an overcurrent fault detection algorithm, a voltage drop fault detection algorithm and a frequency anomaly fault detection algorithm.

[0012] Preferably, the optimization scheduling module is designed using a distributed power supply model. The constraints of the distributed power supply model include upper and lower limits of output and climbing rate limits. Its objective function includes minimizing the total cost, including electricity purchase cost, network loss cost, and environmental protection cost. A particle swarm optimization algorithm is used for solving the problem. Through the above steps, a mathematical model of a distribution network can be established to provide a basis for optimized scheduling.

[0013] Preferably, the simulation verification module includes establishing a distribution network simulation model, simulation scenario design, simulation process refinement and simulation result analysis. The simulation scenario design includes normal working condition simulation: simulating the operation of the distribution network under normal conditions to verify the effectiveness of the dispatching strategy, fault working condition simulation: designing different fault scenarios, such as overcurrent, voltage drop, and frequency anomaly, to test the response of the dispatching strategy under fault conditions, and extreme working condition simulation: simulating the operation of the distribution network under extreme weather or load conditions to evaluate the robustness of the dispatching strategy. The simulation process refinement includes setting the simulation starting conditions, including distributed power output, energy storage system status, load level, etc., inputting actual or simulated The simulation results are analyzed by real-time data such as weather data and load forecasting results, and the optimization scheduling strategy is implemented in the simulation environment, the response of the distribution network is observed, and key performance indicators are monitored, such as system operating cost, power supply reliability, and distributed power supply utilization. The simulation result analysis includes recording key data and events in the simulation process, such as protection actions, scheduling decisions, system state changes, comparing simulation results with expected goals, evaluating the performance of the scheduling strategy and analyzing the system response when a fault occurs, and evaluating the coordination between the protection device and the scheduling strategy. Through the refinement of the above simulation verification, the effectiveness and reliability of the optimization scheduling method before actual application can be ensured, and an important reference basis can be provided for on-site implementation.

[0014] Preferably, the steps of constructing the distribution network simulation model include determining the simulation purpose and requirements, determining the scope and detail level of the distribution network to be analyzed, and then selecting appropriate simulation software such as MATLAB / Simulink, DIgSILENT PowerFactory, OpenDSS, ETAP, etc. according to the requirements, collecting the topological structure, equipment parameters, and operating data of the distribution network, and then building the distributed power supply and DTU simulation model.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The DTU protection method for a distribution network connected to a distributed power source of the present invention improves the adaptability and reliability of protection during use. The DTU protection method can adapt to the fault characteristics of the distributed power source, ensuring that the protection device can still operate effectively after the distributed power source is connected. By accurately analyzing the fault characteristics of the distributed power source, the DTU protection method can more reliably identify and isolate faults, reduce false operations and missed operations, and improve the overall protection performance of the power grid.

[0017] Optimize protection coordination: The DTU protection method can adjust the protection parameters according to the fault characteristics of the distributed power supply, maintain the coordination between various levels of protection, and avoid conflicts between protection devices;

[0018] Improve fault diagnosis and processing capabilities: The DTU protection method can quickly identify various fault types caused by distributed power sources and provide timely and accurate information for fault processing. Through the advanced data processing capabilities of the DTU, the protection method can more accurately locate the fault point and speed up fault processing;

[0019] Ensure grid stability: The DTU protection method takes into account the dynamic response of distributed power sources during faults, which helps maintain the transient stability of the system. The DTU protection method can assist distributed power sources in quickly adjusting frequency and voltage during faults to ensure stable operation of the grid.

[0020] Optimize operation strategy: The DTU protection method can assist in formulating effective island operation strategies to ensure the independent operation of distributed power sources during power grid failures. Through the DTU protection method, the fault ride-through capability of distributed power sources can be improved and the impact on the power grid can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the process of the present invention; DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Embodiment 1

[0024] like Figure 1As shown, the DTU protection method for distribution network based on access to distributed power sources proposed by the present invention includes an analysis module, a protection strategy formulation module, an optimization scheduling module and a simulation verification module. The analysis module collects output characteristics, operating parameters and other data of distributed power sources to perform fault characteristic analysis to provide a basis for the formulation of subsequent protection strategies. The purpose of the analysis needs to be clarified, such as improving energy utilization efficiency, optimizing grid stability, and reducing environmental impact. The type of distributed power sources to be analyzed is determined, such as solar photovoltaic, wind power generation, fuel cells, micro hydropower stations, etc., and then the data is collected. The output characteristic data includes power output: recording power output data in different time periods (such as days, months, and years); voltage and current: recording voltage and current changes under different loads; frequency: monitoring and recording changes in grid frequency, and operating parameter data includes environmental factors: such as temperature, humidity, wind speed, sunshine intensity, etc.; equipment status: including start-up and shutdown time, fault records, maintenance conditions, etc.; load characteristics: analyzing the load characteristics connected to the distributed power source, such as load type, power demand, change law, etc., and then cleaning, normalizing and filling the data, and the processed data is sent to the distributed power model.

[0025] The protection strategy formulation module combines the characteristics of distributed power sources and the protection requirements of the distribution network to formulate a reasonable protection strategy. The optimization scheduling module realizes real-time monitoring and operation control of the distribution network through optimization scheduling. The simulation verification module ensures the feasibility of the proposed method in practical applications through simulation verification. In summary, the normal operation and effective protection of DTU are ensured, its role in the distribution network is fully utilized, and the safe, stable and efficient operation of the power grid is guaranteed.

[0026] Fault characteristic analysis includes current-controlled DG and voltage-controlled DG. The fault response characteristics of current-controlled DG are mainly affected by the control loop and have little to do with the physical circuit parameters. They can be mathematically described by the control loop transfer function. The fault response characteristics of voltage-controlled DG are jointly determined by the control loop and the physical circuit and are mutually coupled, making them difficult to describe mathematically. Within 5-10 power frequency cycles after the fault, the fault current is significantly greater than that of the current-controlled DG, and there is a fault impact current.

[0027] Embodiment 2

[0028] like Figure 1As shown, the DTU protection method for a distribution network based on access to distributed power sources proposed by the present invention, compared with the first embodiment, this embodiment also includes: the protection strategy formulation module step includes determining a protection configuration scheme and designing a protection logic, determining the protection configuration scheme includes selecting a suitable protection device according to the characteristics of the distributed power source, such as overcurrent protection, distance protection, differential protection, and setting the action parameters of the protection device according to the output characteristics of the distributed power source and the operating parameters of the distribution network, such as a set value and a time delay, and designing the protection logic includes designing an algorithm to detect faults in the distribution network, such as overcurrent, voltage drop, and frequency anomaly, and determining the specific location of the fault so as to facilitate accurate isolation, and after detecting the fault, isolating the fault area by disconnecting the corresponding switch or circuit breaker, and after the fault is isolated, deciding whether to reclose the switch according to the actual situation of the power grid to restore power supply to the non-fault area, and the idea of ​​formulating the above protection strategy: analyzing the impact of the access of distributed power sources on the protection of the distribution network, such as power supply volatility, short-term overcurrent capability, etc., and considering the impact of the grid-connected and off-grid operations of distributed power sources on the protection system;

[0029] Analyze the protection requirements of the distribution network under different operating conditions, such as normal operation, fault conditions, extreme weather conditions, etc., to ensure that the protection strategy can adapt to the complexity and dynamic changes of the distribution network;

[0030] Ensure that the protection strategy can respond to faults quickly and avoid false operations. Considering the controllability and uncontrollability of distributed power sources, design flexible protection logic, combine modern communication technology, and realize information sharing and coordinated action between protection devices. Through the above steps and ideas, the formulation of protection strategies will ensure that the distribution network can operate safely and stably after connecting to distributed power sources, while improving the automation level and power supply reliability of the distribution network.

[0031] The algorithms of protection logic include overcurrent fault detection algorithm, voltage drop fault detection algorithm and frequency anomaly fault detection algorithm. The overcurrent fault detection algorithm uses a high-precision current transformer (CT) to monitor the current in the circuit in real time to ensure that the collected data is time synchronized. A digital filter (such as a low-pass filter) is used to remove high-frequency noise in the signal to normalize the current signal, and then extract features. According to the current characteristics under normal system operation, a reasonable threshold is set. When the detected current characteristics exceed the threshold, it is determined to be an overcurrent fault. The voltage drop fault detection algorithm uses a high-precision voltage transformer (PT) to monitor the voltage in the circuit in real time. , denoise and normalize the data, and then extract features. According to the voltage characteristics under normal system operation, set a reasonable threshold. When the detected voltage characteristics are lower than the threshold, it is determined to be a voltage drop fault. The frequency abnormality fault detection algorithm uses high-precision frequency measurement equipment to monitor the frequency of the power grid in real time, and applies digital filters (such as bandpass filters) to remove irrelevant frequency components and high-frequency noise in the signal, remove the long-term trend components in the signal, normalize the frequency signal, and then extract features. According to the frequency characteristics under normal system operation, set a reasonable threshold range. When the detected frequency exceeds the preset threshold range, it is determined to be a frequency abnormality fault.

[0032] Embodiment 3

[0033] like Figure 1 As shown, the DTU protection method for the distribution network based on access to distributed power sources proposed by the present invention, compared with the first embodiment, this embodiment also includes:

[0034] The optimization scheduling module is designed using a distributed power model. The mathematical description of the distributed power model is:

[0035] Output model: P DG，i (t) = f DG，i (W solar , W wind ,θ i , ...);

[0036] Cost Model: C DG，i (t) = g DG，i (P DG，i (t), ...);

[0037] The constraints of the distributed power model include upper and lower limits of output and ramp rate limits. Its objective function includes minimizing the total cost, including power purchase cost, network loss cost, and environmental protection cost. Its mathematical description is:

[0038]

[0039] Among them C buy Meaning: Electricity purchase cost

[0040] C loss Meaning: Network loss cost

[0041] C env Environmental protection cost

[0042] P buy，i Indicates: the amount of electricity purchased from the grid in the i-th time period

[0043] C buy，i Indicates: the electricity purchase price in the i-th time period

[0044] P loss，i Means: the network loss in the i-th time period

[0045] C loss，i Unit network loss cost

[0046] E env，i Indicates: Environmental impact in the i-th time period

[0047] C env，i Indicates: unit environmental protection cost;

[0048] The constraints are:

[0049] Output upper and lower limits:

[0050] P min，DG ≤P DG，i ≤P max，DG ;

[0051] in:

[0052] P DG，i is the output power of the distributed generation in the i-th time period

[0053] P min，DG is the minimum output power of the distributed power source

[0054] P max，DG is the maximum output power of the distributed power supply

[0055] Ramp rate limit:

[0056] -R down ≤P DG，i -P DG，i-1 ≤R up

[0057] in:

[0058] R up Is the rising ramp rate limit of the distributed power supply

[0059] R down Is the ramp rate limit of the distributed power supply

[0060] Power balance constraints:

[0061] P DG，i +P buy，i =P load，i +P loss，i

[0062] in:

[0063] P load，i is the load demand in the i-th time period,

[0064] Combining these elements, we get the following mathematical description of the distributed generation optimization problem:

[0065]

[0066] (Other constraints)

[0067] The particle swarm optimization algorithm is used to solve the problem. Through the above steps, a mathematical model of the distribution network can be established to provide a basis for optimal scheduling.

[0068] Embodiment 4

[0069] like Figure 1 As shown, the DTU protection method for distribution network based on access to distributed power sources proposed by the present invention, compared with the first embodiment, this embodiment also includes: the simulation verification module includes establishing a distribution network simulation model, simulation scenario design, simulation process refinement and simulation result analysis, and the construction steps of the distribution network simulation model include determining the simulation purpose and requirements, determining the scope and detail level of the distribution network to be analyzed, and then selecting appropriate simulation software such as MATLAB / Simulink, DIgSILENT PowerFactory, OpenDSS, ETAP, etc. according to the requirements, collecting the topological structure, equipment parameters, and operation data of the distribution network, and then building the distributed power source and DTU simulation model;

[0070] The simulation scenario design includes normal operating condition simulation: simulating the operation of the distribution network under normal conditions to verify the effectiveness of the dispatching strategy;

[0071] Fault condition simulation: Design different fault scenarios, such as overcurrent, voltage drop, and frequency anomaly, to test the response of the dispatch strategy under fault conditions;

[0072] Extreme working condition simulation: simulate the operation of distribution network under extreme weather or load conditions and evaluate the robustness of dispatching strategies;

[0073] The refinement of the simulation process includes setting the simulation starting conditions, including the output of distributed power sources, the status of the energy storage system, the load level, etc., inputting actual or simulated real-time data, such as weather data, load forecast results, implementing the optimized scheduling strategy in the simulation environment, observing the response of the distribution network, and monitoring key performance indicators, such as system operating costs, power supply reliability, and distributed power utilization. The analysis of simulation results includes recording key data and events in the simulation process, such as protection actions, scheduling decisions, system status changes, comparing simulation results with expected goals, evaluating the performance of the scheduling strategy and analyzing the system response when a fault occurs, and evaluating the coordination of protection devices and scheduling strategies. Through the refinement of the above simulation verification, the effectiveness and reliability of the optimized scheduling method before actual application can be ensured, and an important reference basis can be provided for on-site implementation.

[0074] Finally, the simulation model is used to train grid operators to improve their understanding of grid behavior and their ability to respond to emergencies. During the planning and design phase of the distribution network, the simulation model is used to evaluate the performance and cost-effectiveness of different design schemes. The simulation model is used to reproduce fault conditions, analyze the causes of faults, formulate preventive measures, and test the action logic of protection devices in a simulation environment to ensure that they can operate correctly in the actual power grid. The simulation model is used to evaluate the application effect of new technologies, such as distributed power sources and smart grid technologies.

[0075] The above-mentioned specific embodiments are only several preferred embodiments of the present invention. Based on the technical solutions of the present invention and the relevant inspirations of the above-mentioned embodiments, those skilled in the art can make various alternative improvements and combinations to the above-mentioned specific embodiments.

[0076] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A DTU protection method for a distribution network based on access to distributed power sources includes an analysis module, a protection strategy formulation module, an optimization scheduling module, and a simulation verification module, and is characterized by: The analysis module collects data such as output characteristics and operating parameters of distributed power sources to perform fault characteristic analysis to provide a basis for the formulation of subsequent protection strategies. The protection strategy formulation module formulates reasonable protection strategies based on the characteristics of distributed power sources and the protection requirements of the distribution network. The optimization scheduling module realizes real-time monitoring and operation control of the distribution network through optimization scheduling. The simulation verification module ensures the feasibility of the proposed method in practical applications through simulation verification. In summary, the normal operation and effective protection of DTU are ensured, its role in the distribution network is fully utilized, and the safe, stable and efficient operation of the power grid is guaranteed.

2. The DTU protection method for a distribution network based on access to a distributed power source according to claim 1 is characterized in that: The fault characteristic analysis includes current-controlled DG and voltage-controlled DG. The fault response characteristics of the current-controlled DG are mainly affected by the control loop and have little to do with the physical circuit parameters. They can be mathematically described by the control loop transfer function. The fault response characteristics of the voltage-controlled DG are jointly determined by the control loop and the physical circuit and are mutually coupled, making them difficult to describe mathematically. Within 5-10 power frequency cycles after the fault, the fault current is significantly greater than that of the current-controlled DG, and there is a fault impact current.

3. The DTU protection method for a distribution network based on access to a distributed power source according to claim 1 is characterized in that: The steps of the protection strategy formulation module include determining the protection configuration scheme and designing the protection logic. The determining of the protection configuration scheme includes selecting appropriate protection devices according to the characteristics of the distributed power source, such as overcurrent protection, distance protection, differential protection, and setting the action parameters of the protection device according to the output characteristics of the distributed power source and the operating parameters of the distribution network, such as the set value and time delay. The design of the protection logic includes designing an algorithm to detect faults in the distribution network, such as overcurrent, voltage drop, and frequency anomaly, and determining the specific location of the fault to facilitate accurate isolation. After the fault is detected, the fault area is isolated by disconnecting the corresponding switch or circuit breaker. After the fault is isolated, it is decided whether to reclose the switch according to the actual situation of the power grid to restore power supply to the non-fault area.

4. The DTU protection method for a distribution network based on access to a distributed power source according to claim 3 is characterized in that: The algorithms of the protection logic include an overcurrent fault detection algorithm, a voltage drop fault detection algorithm and a frequency anomaly fault detection algorithm.

5. The DTU protection method for a distribution network based on access to a distributed power source according to claim 1 is characterized in that: The optimization scheduling module is designed using a distributed power supply model. The constraints of the distributed power supply model include upper and lower limits of output and climbing rate limits. Its objective function includes minimizing the total cost, including electricity purchase cost, network loss cost, and environmental protection cost. The particle swarm optimization algorithm is used for solving. Through the above steps, a mathematical model of a distribution network can be established to provide a basis for optimization scheduling.

6. The DTU protection method for a distribution network based on access to a distributed power source according to claim 1 is characterized in that: The simulation verification module includes establishing a distribution network simulation model, simulation scenario design, simulation process refinement and simulation result analysis. The simulation scenario design includes normal working condition simulation: simulating the operation of the distribution network under normal conditions to verify the effectiveness of the dispatching strategy, fault working condition simulation: designing different fault scenarios, such as overcurrent, voltage drop, and frequency anomaly, to test the response of the dispatching strategy under fault conditions, and extreme working condition simulation: simulating the operation of the distribution network under extreme weather or load conditions to evaluate the robustness of the dispatching strategy. The simulation process refinement includes setting the simulation starting conditions, including distributed power output, energy storage system status, load level, etc., inputting actual or simulated Real-time data, such as weather data, load forecast results, implement optimized scheduling strategies in a simulation environment, observe the response of the distribution network, monitor key performance indicators, such as system operating costs, power supply reliability, and distributed power supply utilization. The simulation result analysis includes recording key data and events in the simulation process, such as protection actions, scheduling decisions, system state changes, comparing simulation results with expected goals, evaluating the performance of scheduling strategies and analyzing system responses when faults occur, and evaluating the coordination of protection devices and scheduling strategies. Through the refinement of the above simulation verification, the effectiveness and reliability of the optimized scheduling method before actual application can be ensured, and an important reference basis can be provided for on-site implementation.

7. The DTU protection method for a distribution network based on access to a distributed power source according to claim 6 is characterized in that: The steps of constructing the distribution network simulation model include determining the simulation purpose and requirements, determining the scope and detail level of the distribution network to be analyzed, and then selecting appropriate simulation software such as MATLAB / Simulink, DIgSILENTPowerFactory, OpenDSS, ETAP, etc. according to the requirements, collecting the topology, equipment parameters, and operation data of the distribution network, and then building the distributed power supply and DTU simulation model.

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