Short-circuit Calculation Research Articles

Assessment of the Renewable Energy Consumption Capacity of Power Systems Considering the Uncertainty of Renewables and Symmetry of Active Power

The rapid growth of renewable energy presents significant challenges for power grid operation, making the efficient integration of renewable energy crucial. This paper proposes a method to evaluate the power system’s capacity to accommodate renewable energy based on the Gaussian mixture model (GMM) from a symmetry perspective, underscoring the symmetrical interplay between load and renewable energy sources and highlighting the balance necessary for enhancing grid stability. First, a 10th-order GMM is identified as the optimal model for analyzing power system load and wind power data, balancing accuracy with computational efficiency. The Metropolis–Hastings (M-H) algorithm is used to generate sample spaces, which are integrated into power flow calculations to determine the maximum renewable energy integration capacity while ensuring system stability. Short-circuit ratio calculations and N-1 fault simulations validate system robustness under high renewable energy integration. The consistency between the results from the M-H algorithm, Gibbs sampling, and Monte Carlo simulation (MCS) confirms the approach’s accuracy.

Enhancing short-circuit current calculation in active distribution networks through Fusing superposition theorem and Data-Driven approach

In the realm of active distribution networks, the Inverter Interfaced Distributed Generator (IIDG) poses a challenge with its diverse non-linear fault outputs stemming from varied control strategies and objectives. This presents a dilemma, balancing computational precision and speed in short-circuit current calculation. To address this issue, a novel methodology is proposed, utilizing a Graph Attention Network (GAT)-based model. This model is designed for rapid and precise computation of IIDG fault outputs, thereby enhancing the efficiency of the iterative calculation process. Integration of the superposition theorem significantly boosts the efficiency of short-circuit current calculation in active distribution networks. Moreover, the proposed approach successfully overcomes common problems, such as reduced accuracy and non-convergence, often encountered due to the dynamic nature of network structures. The utility and adaptability of this method are illustrated through various examples, showcasing its ability to accommodate networks with unknown structures and increased branch circuits, while ensuring consistent and reliable computational results.

Short-Circuit Current Calculation of Flexible Direct Current Transmission Lines Considering Line Distribution Parameters

Short-Circuit Current Calculation of Flexible Direct Current Transmission Lines Considering Line Distribution Parameters

Development of a DSP based collaborative computing platform for power system

Abstract With the advancement of information technology, there has been tremendous progress in data production, processing, and storage technology, especially in data processing technology. With the rapid development of the power grid, its operation has become more intelligent and efficient. Traditional power system simulation and analysis tools have disadvantages, such as slow message transmission and the inability to share data, which cannot meet the requirements of modern power system simulation calculations. DSP was introduced and developed by the Southern Power Grid Research Institute and can perform various simulation calculations such as transient stability calculation, power flow calculation, and short circuit calculation. It is widely used in departments such as power planning and design. However, the data calculated by DSP is input through a data card, which is cumbersome and difficult to manage. In order to meet the new requirements of power system simulation analysis, a power system collaborative computing platform has been developed based on DSP, which makes DSP data maintenance and management more efficient and intuitive. It comprehensively improves the efficiency of power grid planning work. This article provides a detailed analysis of the architecture design and application problems of the power system collaborative computing platform, clarifies the requirements of large-scale interconnected power grids for simulation computing data management, and proposes solutions that can meet the needs of simulation computing data management in China’s power grid from two aspects: key data architecture issues and software architecture technology.

Calculation Method and Characteristic Analysis for Fault Current of Permanent Magnet Direct-Drive Wind Power System considering Positive and Negative Sequence Decomposition

In view of the fact that the influence of positive and negative sequence decomposition, which is widely used in positive and negative sequence decoupling control in control system, on the fault current calculation process is not deeply considered in the existing transient analysis methods of permanent magnet direct-drive wind farm short circuit current, this paper proposes a transient short circuit current calculation model that takes into account positive and negative sequence decomposition. The influence of the transient characteristics of positive and negative sequence decomposition on the control system is studied, and the mechanism of its action on the transient change of short circuit current is revealed. The positive and negative sequence decoupling processes of the circuit equation are modified, and the characteristics of the coupling equation are analyzed. The difference in the converter output voltage between the circuit equation and the control equation and the depth of its influence on the calculation process is revealed. On the basis of quantifying the difference at the converter output voltage, the circuit equation and the control equation are combined to form a short-circuit current calculation model with positive and negative sequence decomposition, which accurately characterizes the transient characteristics of fault current under different voltage drops and effectively improves the accuracy of the calculation results.

A short-circuit calculation solver for power systems with power electronics converters

Power electronics converters have been widely deployed in modern power systems in different voltage levels. The complex operation characteristics of power converters, which combine different control modes and various current saturation states, are also significantly changing the power systems’ behavior in fault conditions. The objective of this paper is to develop a steady-state short-circuit calculation solver for power systems with power electronics without the need of detailed dynamic models. In particular, the steady-state operation equations related to the converter control are included in the system formulation. An extended Newton–Raphson (NR) solver is proposed to compute the short-circuit equilibrium point that considers converters’ operation limits. Also, an iterative algorithm is presented in order to efficiently identify the current saturation states of power converters under a specific short-circuit fault scenario. Case studies have been presented with several power systems with voltage source converters (VSCs). Dynamic simulations are included to validate the accuracy of the proposed methodology.

Analysis and research on short-circuit current characteristics and grid access faults of wind farms with multi-type fans

As the grid-connected capacity of a large number of wind farms continues to increase, their short-circuit current will have a great impact on protection. Therefore, accurate short-circuit current calculation is beneficial for correct protection action evaluation. Considering the issues related to the diversity of wind turbine types in wind farms and the inability to accurately simulate the failure transient process in previous studies, this research focuses on investigating the impact of control strategies during faults on the transient process of wind turbines. In this paper, the single-machine equivalent model of doubly-fed induction generators (DFIG) and permanent magnet synchronous machine (PMSM) is established by considering the types of wind turbines, and the calculation method of short-circuit current of hybrid wind farms is further proposed by using the classification aggregation equivalent effect method. The accuracy of short-circuit current calculation proposed in this article was verified on RTDS, and a power grid fault analysis method suitable for wind farm connection was proposed based on the characteristics of equivalent circuits of DFIG and PMSM during fault steady-state.

Preliminary Design of Electric Part of Thermoelectric Unit in a Power Plant

With the rapid development of society, people’s awareness of environmental protection continues to strengthen, countries also pay more and more attention to environmental protection, whether from the national policy or from the green development of enterprises in the future, the improvement of power plant operation efficiency is imperative. Among them, improving the operation efficiency of thermal power plants is the top priority, and it is also an important link of national economic transformation. The design of electrical part is an important part of improving the operation efficiency of thermal power plants. 2x300MW thermal power plant is designed, including the power plant electrical main wiring design, plant power design, the main circuit of the power plant short-circuit calculation, and it choose the electrical stability and thermal stability of the better electrical equipment. The short circuit calculation of the main circuit of the power plant is carried out and preliminary planning of the secondary circuit scheme is made. A power plant with higher operating efficiency is designed. While improving the operation and economic efficiency of the power plant, it also ensures the reliability, stability and economy of the power plant.

Calculation method of external fault short-circuit current for variable-speed pumped storage units based on time-domain dynamic circuit

The calculation method of the external fault short-circuit current of large units with clear mechanisms and practicality is of great value in engineering practice. Due to the special AC excitation structure and control mode, the external fault short-circuit characteristics of variable-speed pumped storage units (VSPSUs) are very different from those of conventional units. Therefore, this paper proposes a calculation method for external fault short-circuit current based on a time-domain dynamic circuit. According to the excitation and control characteristics of VSPSUs under external fault, the VSPSU under external fault is divided into two cases: continuous excitation and jumper action. Based on space vector analysis, the time-domain dynamic circuit models are established, respectively. On this basis, the analytical formula of the external fault short-circuit current of VSPSUs is derived by combining the transition boundary conditions of the two cases and the dynamic characteristics of the stator flux linkage. Finally, the comparison with PSCAD/EMTDC simulation results shows that the proposed VSPSUs’ external fault short-circuit current calculation method has high accuracy and practical value, which can meet the needs of primary equipment selection and relay protection of variable-speed pumped storage power plants.

Retracted: Practical Model for Short-Circuit Current Calculation of Photovoltaic Power Station Based on Improved RLS Algorithm

Retracted: Practical Model for Short-Circuit Current Calculation of Photovoltaic Power Station Based on Improved RLS Algorithm

Power-Impact-Harmonic Characteristics Analysis and Modeling of Diversified Power Loads in Urban Power Grid

Different load models of the same load have different effects on power flow calculation, short circuit calculation, voltage stability, and frequency stability after power system accidents. In this paper, some power load components in urban power grids are modeled by analyzing and fitting the measured power curve of load components, and they are divided into the power model, impact model, and harmonic model according to their characteristics. The power model includes the power models of some household appliances, industrial motors, and arc furnaces. The impact model includes the time series fitting model and probability fitting model. According to the measured power curve of load components, the load model established in this paper can avoid some risks of power calculation caused by the absence of a detailed load model.

Fast and accurate method for short-circuit current calculation in distribution network with IIDGs

The fault behavior of Inverter Interfaced Distributed Generators (IIDGs) diverges from that of synchronous generators. When a substantial number of IIDGs are integrated into the distribution network, the conventional short-circuit current calculation technique, grounded in a mechanical framework, struggles to simultaneously satisfy the demands for both rapid computation and precision. This study introduces an alternative approach reliant on data analysis, enabling swift and precise computation of short-circuit currents across the IIDG-infused distribution grid. The investigation delves into the efficacy of multi-output regression techniques and the selection of the foundational learning algorithm. Specifically, two strategies are advanced: Multi-Target Regressor Stacking and Regressor Chains, both utilizing the Light Gradient Boosting Machine as the base learner. The influence of varying sample sizes on the multi-output computational model's performance is assessed. To ascertain the real-world viability of the multi-output regression methodology, two distinct fault characteristics pertaining to data-driven short-circuit current calculation are scrutinized using existing distribution network measurement conditions. The study reveals that, given a known distribution network structure, the proposed method can compute network-wide short-circuit currents across diverse IIDG penetration levels and fault scenarios through a singular model, maintaining a balance between computation precision and speed. If the distribution network's structure undergoes minor modifications, the model demonstrates reasonable adaptability, yet a retraining of the short-circuit current calculation model is recommended to ensure sustained accuracy in the face of significant network changes.

Explicit Linear Model of Bus Impedance With Unknown Branch Status

This letter presents an accurate and explicit linear model of bus impedance for a power network with unknown branch status. Firstly, an equivalent network of the power network is constructed, and the relationship between bus voltage and bus impedance is established. Then, the linear expression of bus impedance with unknown branch status is built. This model can be easily included as constraints in various optimization problems with network topology adjustment involving short circuit calculation.

Incorporating Modern Fault Ride-Through Standards into the Short-Circuit Calculation of Distribution Networks.

Modern fault ride-through (FRT) standards in many countries require distributed generators to remain connected for a specified period during the fault by providing reactive current, to support voltage and prevent a massive renewable outage. As a result, short-circuit current is not constant, but it varies depending on the current and disconnection order of distributed generators (DGs). This time-varying short-circuit current complicates the estimation of the time it will take for an overcurrent relay or fuse to trip. The existing short-circuit calculation algorithms usually assume that the fault current is constant throughout the whole period of fault. This assumption may result in incorrect conclusions regarding the tripping time of protective devices in networks with high renewable penetration. This paper incorporates modern FRT standards into the fault analysis by considering the influence of fault current variations on the protective devices (relays, fuses), significantly increasing the accuracy of the estimated tripping time. Simulations carried out in a 13-bus and the IEEE 8500-node network indicate that the traditional short-circuit calculation approaches may miscalculate the tripping time of protective devices, with deviations up to 80 s, when applied to networks complying with modern FRT standards.

Analisis Kinerja Sistem Proteksi Berdasarkan Peramalan Beban Pada Penyulang Galunggung

The Galunggung feeder has a total line length of 10.68 kilometers and is supplied by power transformer number 1 at the Polehan substation, with a capacity of 30 MVA. As of December 2020, the peak load on the Galunggung feeder was recorded at 231.4 A, while the lowest load was 133.9 A. Up to the current condition, the Galunggung feeder is operating within standard parameters, with a voltage drop of 0.434 kV or 2.17%. However, it is possible that with future developments and an increase in the number of customers over the years, the energy demand will also increase. Due to this additional energy demand, the protection system may require adjustments to accommodate the increased load.After conducting load forecasting using simple linear regression, a forecast for the next 10 years was obtained. In the year 2030, it is anticipated that the Galunggung feeder will experience a 24% increase in load. With this load increase and no changes to transformers or conductors, there will be no alterations to impedance and short-circuit current calculations. Therefore, no protection setting adjustments are necessary. The recommended action would be to upgrade some transformers that are approaching their capacity limits.

A New Short-Circuit Current Calculation and Fault Analysis Method Suitable for Doubly Fed Wind Farm Groups.

The transient characteristics of wind farms in groups are quite different; in addition, there is a strong coupling between the wind farms and the grid, and these factors make the fault analysis of the grid with wind farm groups complicated. In order to solve this problem, a mathematical model of the converter is established based on the input-output external characteristics of the converter, and a transient model of a doubly fed wind turbine (DFIG) is presented considering the influence of the low-voltage ride-through control (LVRT) of the converter, and the effect mechanism of the LVRT strategy on the short-circuit current is analyzed. Finally, a short-circuit current calculation model of a doubly fed wind turbine with low-voltage crossing control is established. The interaction mechanism between wind farms during the fault is analyzed, and a short-circuit current calculation method of doubly fed wind farm groups is proposed. RTDS is used to verify the accuracy of the proposed short-circuit current calculation method for doubly fed field groups. On this basis, a method of power grid fault analysis after doubly fed field group access is discussed and analyzed.

Grid Equivalent Representation of Power Systems With Penetration of Power Electronics

The Thévenin equivalent is considered as the standard grid equivalent for power system analysis. The integration on power electronics components in the power systems introduces non-linear operation characteristics that cannot be captured by Thévenin equivalent. Therefore, an alternative grid equivalent representation is required. This paper presents a steady-state equivalent representation of power systems with penetration of power electronics, which is suitable for both normal operation studies and short-circuit calculations. This equivalent grid representation is developed based on the voltage-current ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">U-I</i> ) characteristic of a power system to map the relationship between voltages and currents of a specific network node. Such grid equivalent representation has been presented for single-phase, balanced and unbalanced three-phase power systems in this paper. A methodology is presented to identify operation points when the equivalent system under study is connected to any external system. The proposed equivalent grid representation and the methodology for operation points identification have been tested on the Voltage Source Converter (VSC) based test system and are validated through dynamic simulations.

Two-stage Short Circuit Current Method Based on New Energy Source Fault Characteristic Fitting

A large number of full-power inverter type new energy sources are connected to the power grid, resulting in a large error in the traditional power grid short-circuit calculation method. By analyzing the relationship between the output current of full-power inverter type new energy sources and the voltage at the parallel point, a two-stage short circuit current method based on the fitting of new energy source fault characteristics is proposed. In the first stage, the polynomial fitting method is used. The piecewise function expression of the new energy source output current is fitted into a continuous derivative curve. In the second stage, the original output characteristic function is correspondingly replaced with the fitting function in the first stage. In each iteration process, the output short-circuit current of the new energy source is corrected according to the current new energy grid-connected node voltage until the convergence conditions are met. The feasibility of the proposed method is verified by the analysis and simulation of an IEEE 15 node example system. This method can be applied to solve the short-circuit current of the power grid with a full-power inverter type new energy source.

Optimizing TOC and IOC units of directional overcurrent relays in mutually coupled circuits using evolutionary PSO: Requirements and modeling

The efficient coordination of directional overcurrent relays is a challenging problem. Recent papers in the literature have focused on developing efficient algorithms to solve this issue. However, there is a lack of reporting practical procedures that affects the mathematical formulation to ensure accurate outputs by any optimization algorithm. In this paper, we show a comprehensive procedure that considers mutually coupled circuits via Graph Theory, the requirements of short-circuit current calculation, contingencies to be considered as well as the setting of Instantaneous Overcurrent (IOC) and Time Overcurrent (TOC) units, both for phase and ground protection. The simulation has been carried out by using a real electric network and C++ language programming. Computational simulation has shown the performance of the method, which provides high-quality solutions, with adequate coordination of the selected protective devices that increase the efficiency in setting this type of protection with safety. Evolutionary Particle Swarm Optimization (EPSO) outperformed conventional Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) as the best metaheuristic for optimally minimizing the proposed problem, achieving faster convergence times for the phase overcurrent protection scenario (16.36 s vs. 22.27 s and 17.03 s, respectively), and also for the ground overcurrent protection scenario (19.87 s vs. 20.44 s and 20.11 s, respectively).

Short-Circuit Modeling of DFIG-Based WTG in Sequence Domain Considering Various Fault- Ride-Through Requirements and Solutions

The doubly fed induction generator (DFIG) based wind turbine generator (WTG) can activate different fault ride through (FRT) control schemes and circuits to comply with various grid code or utility interconnection requirements. These FRT solutions play a key role in the resulting fault current of the DFIG-based WTG as well as the voltages and currents distributed in faulted networks. This paper accounts for their impact by proposing a new generic sequence domain model of the DFIG-based WTG for static short circuit calculations. In this paper, the FRT configurations are classified into three types. The proposed model first calculates the positive- and negative-sequence current phasors under the specified FRT control. Then based on the control, the desired currents and voltages are calculated by explicit equations to determine whether the crowbar could operate during FRT operation. By comparing with detailed electromagnetic transient (EMT) simulations using an EPRI benchmark system, the proposed model, incorporated into an iterative steady state solver, is shown to be accurate to calculate voltage and current phasors in an efficient manner. The proposed model provides a rapid tool for short circuit computations and protective relaying studies considering various grid code requirements and FRT implementations.