In an integrated electricity-gas system (IEGS), gas-fired units with flexibility response capabilities address the uncertainty associated with renewable energy by swiftly adapting their output, which ...may result in uncertain fluctuations in the gas withdrawal of gas-fired units, potentially posing risks to the security of IEGS. Hence, it is necessary to efficiently evaluate the dynamic security region (DSR) of natural gas systems in IEGS by considering the real-time dynamic characteristics of natural gas systems, which are not satisfactorily handled in state-of-the-art works. To bridge this gap, this paper first conceptionally verifies the necessity of the DSR and establishes its mathematical model. Then, a dimensionality reduction method is proposed for the efficient solution and visualization of the high-dimensional DSR evaluation model. A fast evaluation (FE) algorithm is developed to address the difficulties of the nonconvex dynamic constraints in the reduced DSR model. Finally, the necessity and notable advantages of the proposed DSR model and FE are verified based on small and relatively large test systems in comparison with common security region models and algorithms. To the best of our knowledge, this is the first paper that comprehensively presents models and efficient algorithms regarding the DSR of natural gas systems in IEGS.
•This paper proposes the novel dynamic security region (DSR) of the natural gas system with natural gas system dynamics.•A dimensionality reduction method for the efficient solution and visualization of the high-dimensional DSR is proposed.•A fast evaluation (FE) algorithm is developed to address the nonconvex dynamic constraints in the DSR model.•Case studies confirm the necessity and effectiveness of the DSR, dimensionality reduction method, and FE.
This paper proposes an analytical method that incorporates the time of use (TOU) strategy into the reliability evaluation of power system. The TOU electricity price strategy enables the savings of ...electricity cost, but its impact on power system reliability has not been thoroughly studied. The proposed method constructs a peak-flat-valley period partition model and develops an equal step length iteration algorithm to obtain the optimal period partition. A price-based demand response is modeled to calculate the hourly load using an apportionment method. Using the particle swarm optimization algorithm, a TOU-based optimization model with a penalty is constructed to find the optimal electricity price. Then, an analytical "electricity price-reliability" model is developed to evaluate the reliability of the power system considering TOU. The effectiveness of the proposed method is investigated through the case study on the Roy Billinton test system and reliability test system.
Low-carbon and high-efficiency mid-depth ground-source heat pumps become a promising heating option for cold regions in China towards carbon neutral. However, system-level evaluation algorithm that ...incorporates multiple influences are needed. Hence, an economic-energetic-environmental evaluation algorithm for a hybrid mid-depth geothermal heating system was established. It couples load characteristics and reflects the impact of design parameters, geological conditions, and fluctuating factors on three evaluation indicators. The economic performance increases initially as heat pump load ratio and hole depth grow but is more sensitive to the former. A recommended design parameters’ zone is given for the general case. Moreover, when the load ratio is 0.65 and the depth is 2750 m, the maximum relative NPV reaches 88.4 million CNY. The peak value of carbon reduction revenue, 54.7 CNY/tCO2, appears near the load ratio of 0.63 and the depth of 3300 m. The valley of heating cost, −15.9 CNY/GJ, occurs near the load ratio of 0.66 and the depth of 2600 m. The break-even point of geothermal gradient has a positive linear relationship with the hole completion cost, by which investing feasibility can be determined. Fluctuating factors have a significant impact on the above indicators but will not change the profit-loss status.
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•Developed an algorithm for environmental-energetic-economic evaluation.•Algorithm reflects the impact of design parameters, geological conditions, and fluctuating factors.•Recommended design parameters' zone provided, with potential max economy of 88.4 million CNY.•Investment feasibility judged by fitting curve of geothermal gradient vs hole completion cost.•Future fluctuating factors will not affect the system profit-loss status.
Interval type-2 fuzzy neural network (IT2FNN) has attracted considerable interest for modeling nonlinear dynamic systems in recent years. However, this promising technique is confronting the problem ...that constructing a suitable IT2FNN is a potential challenge ignored by most researchers. To solve this problem, a self-constructing interval type-2 fuzzy neural network (SC-IT2FNN), based on the cooperative strategies, is proposed in this paper. The main contributions of this paper are: First, a comprehensive evaluation algorithm (CEA), cooperating with the parameter optimization, is developed to design the structure of SC-IT2FNN to enhance its generalization performance. Second, a hierarchical optimization mechanism, cooperating with the nonlinear and linear parameters of SC-IT2FNN, is proposed to accelerate its learning speed. Third, the convergence of SC-IT2FNN is theoretically analyzed in detail to ensure its successful applications. Finally, several benchmark nonlinear systems and a real application are utilized to evaluate the effectiveness of SC-IT2FNN. The results demonstrate that our proposed SC-IT2FNN significantly improve the modeling performance in terms of high accuracy and compact structure.
In this paper, a bioinspired path planning approach for mobile robots is proposed. The approach is based on the sparrow search algorithm, which is an intelligent optimization algorithm inspired by ...the group wisdom, foraging, and anti-predation behaviors of sparrows. To obtain high-quality paths and fast convergence, an improved sparrow search algorithm is proposed with three new strategies. First, a linear path strategy is proposed, which can transform the polyline in the corner of the path into a smooth line, to enable the robot to reach the goal faster. Then, a new neighborhood search strategy is used to improve the fitness value of the global optimal individual, and a new position update function is used to speed up the convergence. Finally, a new multi-index comprehensive evaluation method is designed to evaluate these algorithms. Experimental results show that the proposed algorithm has a shorter path and faster convergence than other state-of-the-art studies.
An extension to triangular domains of the univariate q-Bernstein basis functions is introduced and analysed. Some recurrence relations and properties such as partition of unity and degree elevation ...are proved for them. It is also proved that they form a basis for the space of polynomials of total degree less than or equal to n on a triangle. In addition, it is presented a de Casteljau type evaluation algorithm whose steps are all linear convex combinations.
With the continuous improvement of global informatization, computer networks have basically reached complete popularization. In today's society, it has become a major application and provides ...corresponding services for various industries. Therefore, it is necessary to effectively protect various information in the network. Therefore, this article provided a detailed discussion on the problems existing in computer network information security. These issues included their own reasons, hacker intrusion, and spam. Based on this, this article explored computer network information security protection strategies such as deploying data encryption, timely patching system vulnerabilities, and installing firewalls and antivirus software. The experimental results showed that the network output values of the clustering algorithm were: 0.888 for level 1, 0.725 for level 2, 0.678 for level 3, 0.461 for level 4, and 0.211 for level 5. These were all within the scope.
