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Arc fault diagnosis is necessary for the safety and efficiency of PV stations. This study proposed an arc fault diagnosis algorithm formed by combining variational mode decomposition (VMD), improved multi-scale fuzzy entropy (IMFE), and support vector machine (SVM). This method first uses VMD to decompose the current into intrinsic mode functions (IMFs) in the time-frequency domain, then calculates the IMFE according to the IMFs associated with the arc fault. Finally, it uses SVM to detect arc faults according to IMFEs. Arc fault data gathered from a PV arc generation experiment platform are used to validate the proposed method. The results indicated the proposed method can classify arc fault data and normal data effectively.
Lina Wang; Hongcheng Qiu; Pu Yang; Longhua Mu. Arc Fault Detection Algorithm Based on Variational Mode Decomposition and Improved Multi-Scale Fuzzy Entropy. Energies 2021, 14, 4137 .
AMA StyleLina Wang, Hongcheng Qiu, Pu Yang, Longhua Mu. Arc Fault Detection Algorithm Based on Variational Mode Decomposition and Improved Multi-Scale Fuzzy Entropy. Energies. 2021; 14 (14):4137.
Chicago/Turabian StyleLina Wang; Hongcheng Qiu; Pu Yang; Longhua Mu. 2021. "Arc Fault Detection Algorithm Based on Variational Mode Decomposition and Improved Multi-Scale Fuzzy Entropy." Energies 14, no. 14: 4137.
The micro-energy network is a subset of the electricity, gas, and heat energy grid. Due to its limited capacity, the energy and spare capacity of micro-energy network should be shared through interconnection. It can not only reduce the operating cost of the micro-energy network caused by power interchange deviation but also increase the consumption rate of intermittent distributed generation (IDG). On account of this assumption, a control structure and a double-layer dispatch model of the interconnected micro-energy network system are proposed in this paper. An economic dispatch model based on adaptive robust optimization is proposed to deal with the uncertainty produced by IDG and minimize the operation cost. Then, a cooperative game model of an interconnected system is built to allocate the profits obtained. Simulation results demonstrate that the proposed scheduling method can significantly reduce the cost of a single micro-energy network and interconnected system. In addition, compared to the noninteractive model and traditional deterministic method, it is proved that the proposed method has a strong capability to deal with uncertain risks, improve the consumption rate of IDG, and realize the coordinated economic optimal operation of multiple micro-energy networks.
Ziwen Liang; Longhua Mu; Chuxuan He. Robust optimal dispatch of interconnected micro-energy network based on cooperative game. Journal of Renewable and Sustainable Energy 2021, 13, 046302 .
AMA StyleZiwen Liang, Longhua Mu, Chuxuan He. Robust optimal dispatch of interconnected micro-energy network based on cooperative game. Journal of Renewable and Sustainable Energy. 2021; 13 (4):046302.
Chicago/Turabian StyleZiwen Liang; Longhua Mu; Chuxuan He. 2021. "Robust optimal dispatch of interconnected micro-energy network based on cooperative game." Journal of Renewable and Sustainable Energy 13, no. 4: 046302.
Selective ground-fault protection is greatly valued for the safe and reliable operation of power systems. With the wide adoption of fault indicator in distribution network, the amount of available fault data increases dramatically. The in-depth investigation of fault recording data helps improve the accuracy of faulty line identification. To perform fault data analysis with higher efficiency, a single-phase-to-ground fault identification model based on the k-Nearest Neighbor (kNN) classification algorithm is proposed in the paper. In this model, the eigenvectors consist of wavelet energy ratio, wavelet coefficients variance and wavelet power obtained by the decomposition of transient components. Furthermore, through the theoretical analysis and experimental comparison of three parameter adjustment algorithms, Bayesian Optimization algorithm is selected to find the optimal parameters of fault identification model, and realize the adaptive adjustment of model parameters. Finally, the validity and feasibility of the model are verified by the experimental data, and the accuracy and efficiency of fault identification are improved by using Bayesian Optimization algorithm.
Jiran Zhu; Longhua Mu; Ding Ma; Xin Zhang. Faulty Line Identification Method Based on Bayesian Optimization for Distribution Network. IEEE Access 2021, 9, 1 -1.
AMA StyleJiran Zhu, Longhua Mu, Ding Ma, Xin Zhang. Faulty Line Identification Method Based on Bayesian Optimization for Distribution Network. IEEE Access. 2021; 9 ():1-1.
Chicago/Turabian StyleJiran Zhu; Longhua Mu; Ding Ma; Xin Zhang. 2021. "Faulty Line Identification Method Based on Bayesian Optimization for Distribution Network." IEEE Access 9, no. : 1-1.
The fault calculation of microgrid is an important method for fault characteristic analysis. The traditional fault analysis methods ignore the connection of inverter interfaced distributed generation (IIDG) and are not suitable for microgrids. A new fault analysis method suitable for the master‐slave controlled microgrid is proposed in this article, which considers the control strategy of IIDGs, low voltage ride through (LVRT) and the fault current limiting. The fault models of PQ‐controlled IIDG (PQ‐IIDG) and U/f‐controlled IIDG (U/f‐IIDG) are analyzed, then an equivalent Norton model of microgrid is established, and a new fault calculation method is presented. By analyzing the fault models, the working state of U/f‐IIDG is divided into a constant voltage state and a constant current state. In the constant voltage state, a grid‐connected microgrid fault calculation method is adopted. In the constant current state, the improved nodal voltage equation based on the current limiting is adopted. Without complicated calculation, high precision results can be obtained after simple iterative calculation. The results of the microgrid simulation model established in PSCAD/EMTDC and the fault calculation method programmed on MATLAB are compared to verify the effectiveness and accuracy of the proposed fault analysis method.
Zihao Wang; Longhua Mu; Yanchang Xu; Fan Zhang; Jiran Zhu. The fault analysis method of islanded microgrid based on the U/f and PQ control strategy. International Transactions on Electrical Energy Systems 2021, 31, e12919 .
AMA StyleZihao Wang, Longhua Mu, Yanchang Xu, Fan Zhang, Jiran Zhu. The fault analysis method of islanded microgrid based on the U/f and PQ control strategy. International Transactions on Electrical Energy Systems. 2021; 31 (7):e12919.
Chicago/Turabian StyleZihao Wang; Longhua Mu; Yanchang Xu; Fan Zhang; Jiran Zhu. 2021. "The fault analysis method of islanded microgrid based on the U/f and PQ control strategy." International Transactions on Electrical Energy Systems 31, no. 7: e12919.
The conventional power system frequency estimation methods based on the Discrete Fourier Transform (DFT) normally require iterative calculations to eliminate the errors due to spectral leakage in off-nominal frequencies. It cannot provide both fast response and good accuracy under a system disturbance. In this paper, a fast and precise frequency estimation method is presented. The theoretical analysis shows the angle difference of the positive sequence voltage is exactly linear to the frequency deviation. Based on this angle characteristic, this method is able to precisely calculate the frequency deviation from angle differences between the continuous DFT calculations without the need for any iteration. Even if there is only one single phase voltage input available, the simulated positive sequence voltages can be derived by constructing the remaining two phase-voltages utilizing an appropriate phasor shift. To effectively restrain the harmonic interferences, a two-cycle Hanning window is applied as a filter. One method to detect the phase angle jump is proposed to avoid transient frequency errors by using the 2nd order derivative of the frequency. The simulation compares the frequency estimation performance between the proposed non-iterative method and the conventional iterative method. The simulation results show the frequency response is faster and the accuracy is reliable within the range 40–70 Hz, even if there are harmonic interferences or three-phase unbalances. This proposed frequency estimation method is easy to implement, and it can be widely applied in the intelligent electronic devices within the power system.
Jinlei Xing; Longhua Mu. A fast and precise power system frequency estimation method without iterations. International Journal of Electrical Power & Energy Systems 2020, 123, 106199 .
AMA StyleJinlei Xing, Longhua Mu. A fast and precise power system frequency estimation method without iterations. International Journal of Electrical Power & Energy Systems. 2020; 123 ():106199.
Chicago/Turabian StyleJinlei Xing; Longhua Mu. 2020. "A fast and precise power system frequency estimation method without iterations." International Journal of Electrical Power & Energy Systems 123, no. : 106199.
Multi-microgrids have many new characteristics, such as bi-directional power flow, flexible operation and variable fault current consisting of the different control strategy of inverter interfaced distributed generations (IIDGs), which all present challenges in multi-microgrid protection. In this paper, the current and voltage characteristics of different feeders are analyzed considering faults at different locations of the multi-microgrid. Based on the voltage and current distribution characteristics of the line parameters, a new protection scheme for the internal faults of multi-microgrids is proposed, which takes the change of phase difference and amplitude of measured bus admittances as the criterion. This proposed scheme has high sensitivity and reliability, is based on a simple principle, and can be easily adjusted. Simulation results using PSCAD/EMTDC verify the correctness and effectiveness of the protection scheme.
Fan Zhang; Longhua Mu. New protection scheme for internal fault of multi-microgrid. Protection and Control of Modern Power Systems 2019, 4, 14 .
AMA StyleFan Zhang, Longhua Mu. New protection scheme for internal fault of multi-microgrid. Protection and Control of Modern Power Systems. 2019; 4 (1):14.
Chicago/Turabian StyleFan Zhang; Longhua Mu. 2019. "New protection scheme for internal fault of multi-microgrid." Protection and Control of Modern Power Systems 4, no. 1: 14.
The fault characteristic of islanded microgrid is closely related to the control strategy of distributed generation (DG) and it is different from that of grid-connected microgrid. Also, the analysis of fault control strategy is an essential foundation of the fault location. This paper discussed the control strategy and output fault characteristic of V/f and PQ controlled DG. To establish the fault detection criterion of islanded microgrid, the coordinating control strategy between V/f and PQ controlled DG is presented. Based on the above fault analysis, the fault point is located by using a new fault detection method, which is based on the phase differences between the pre-fault bus voltage and the positive- sequence current fault component of the feeders. Finally, examples are simulated in PSCAD/EMTDC and the results verify the accuracy and effectiveness of the proposed fault detection method.
Ziwen Liang; Longhua Mu; Fan Zhang; Han Zhou; Xin Zhang. The fault detection method of islanded microgrid with the V/f controlled distributed generation. International Journal of Electrical Power & Energy Systems 2019, 112, 28 -35.
AMA StyleZiwen Liang, Longhua Mu, Fan Zhang, Han Zhou, Xin Zhang. The fault detection method of islanded microgrid with the V/f controlled distributed generation. International Journal of Electrical Power & Energy Systems. 2019; 112 ():28-35.
Chicago/Turabian StyleZiwen Liang; Longhua Mu; Fan Zhang; Han Zhou; Xin Zhang. 2019. "The fault detection method of islanded microgrid with the V/f controlled distributed generation." International Journal of Electrical Power & Energy Systems 112, no. : 28-35.
The fault characteristics of an inverter interfaced distributed generator (IIDG) depend on its control strategy and are closely related to whether it has a low voltage ride-through (LVRT) capability, which cannot be a simple equivalent to a constant power or current source. Thus, it is necessary to consider the specific control strategy of IIDGs and perform specific research on the fault detection method of a microgrid. Based on the fault models of a grid-connected PQ controlled DG (PQ-DG) with an LVRT capacity, this paper analyzed the fault component characteristics of a microgrid under different operating conditions, such as high-impedance faults (HIFs) and low-impedance faults (LIFs). The fault point is located using a new fault detection method, which is based on the phase differences between the positive-sequence fault component of the bus voltage and the positive-sequence fault components of the currents in the feeders. Finally, PSCAD/EMTDC is used in the simulation analysis, and the simulation results verified the validity of the fault detection method.
Fan Zhang; Longhua Mu. A Fault Detection Method of Microgrids With Grid-Connected Inverter Interfaced Distributed Generators Based on the PQ Control Strategy. IEEE Transactions on Smart Grid 2018, 10, 4816 -4826.
AMA StyleFan Zhang, Longhua Mu. A Fault Detection Method of Microgrids With Grid-Connected Inverter Interfaced Distributed Generators Based on the PQ Control Strategy. IEEE Transactions on Smart Grid. 2018; 10 (5):4816-4826.
Chicago/Turabian StyleFan Zhang; Longhua Mu. 2018. "A Fault Detection Method of Microgrids With Grid-Connected Inverter Interfaced Distributed Generators Based on the PQ Control Strategy." IEEE Transactions on Smart Grid 10, no. 5: 4816-4826.
The existing passive methods for islanding detection are mainly based on the detection of voltage and frequency deviation after islanding, using protections such as voltage vector shift (VVS) and rate of change of frequency (ROCOF). Although there are reported issues with these passive methods such as inherent non-detection zones and nuisance trips, utilities prefer the passive methods due to the low cost and simplicity of deployment. In this paper, one composite passive islanding detection method is presented. It tracks the voltage phase angle, the system frequency, and ROCOF every power cycle. If three phase voltage vectors shift in the same direction and the rotated angle values are balanced, the calculation of the accumulated phase angle drift (PAD) will be initiated. This calculation continues until the ROCOF measurement is below the ROCOF setting threshold. If the accumulated phase angle drift reaches the set angle threshold, the condition for islanding is claimed. The performance of this composite method is verified under different scenarios based on Matlab Simscape multidomain physical systems and practical waveforms recorded from sites. Although there are still non-detection zones, this composite PAD solution has better sensitivity than existing VVS and ROCOF methods and is stable under external system faults.
Jinlei Xing; Longhua Mu. A New Passive Islanding Detection Solution Based on Accumulated Phase Angle Drift. Applied Sciences 2018, 8, 1340 .
AMA StyleJinlei Xing, Longhua Mu. A New Passive Islanding Detection Solution Based on Accumulated Phase Angle Drift. Applied Sciences. 2018; 8 (8):1340.
Chicago/Turabian StyleJinlei Xing; Longhua Mu. 2018. "A New Passive Islanding Detection Solution Based on Accumulated Phase Angle Drift." Applied Sciences 8, no. 8: 1340.
The black start capability is vital for microgrids, which can potentially improve the reliability of the power grid. This paper proposes a black start strategy for microgrids based on a parallel restoration strategy. Considering the characteristics of distributed generations (DGs), an evaluation model, which is used to assess the black start capability of DGs, is established by adopting the variation coefficient method. Thus, the DGs with good black start capability, which are selected by a diversity sequence method, are restored first in parallel under the constraints of DGs and network. During the selection process of recovery paths, line weight and node importance degree are proposed under the consideration of the node topological importance and the load importance as well as the backbone network restoration time. Therefore, the whole optimization of the reconstructed network is realized. Finally, the simulation results verify the feasibility and effectiveness of the strategy.
Jing Wang; Longhua Mu; Fan Zhang; Xin Zhang. A Parallel Restoration for Black Start of Microgrids Considering Characteristics of Distributed Generations. Energies 2017, 11, 1 .
AMA StyleJing Wang, Longhua Mu, Fan Zhang, Xin Zhang. A Parallel Restoration for Black Start of Microgrids Considering Characteristics of Distributed Generations. Energies. 2017; 11 (1):1.
Chicago/Turabian StyleJing Wang; Longhua Mu; Fan Zhang; Xin Zhang. 2017. "A Parallel Restoration for Black Start of Microgrids Considering Characteristics of Distributed Generations." Energies 11, no. 1: 1.
Multi-microgrid has many new characteristics, such as bi-directional power flows, flexible operation modes and variable fault currents with different control strategy of inverter interfaced distributed generations (IIDGs). All these featuring aspects pose challenges to multi-microgrid protection. In this paper, current and voltage characteristics of different feeders are analyzed when fault occurs in different positions of multi-microgrid. Based on the voltage and current distribution characteristics of the line parameters, a new protection scheme for the internal fault of multi-microgrid is proposed, which takes the change of phase difference and amplitude of measured bus admittance as the criterion. This scheme with high sensitivity and reliability, has a simple principle and is easy to be adjusted. PSCAD/EMTDC is used in simulation analysis, and simulation results have verified the correctness and effectiveness of the protection scheme.
Fan Zhang; Longhua Mu; Wenming Guo. New Protection Scheme for Internal Fault of Multi-Microgrid. 2017, 1 .
AMA StyleFan Zhang, Longhua Mu, Wenming Guo. New Protection Scheme for Internal Fault of Multi-Microgrid. . 2017; ():1.
Chicago/Turabian StyleFan Zhang; Longhua Mu; Wenming Guo. 2017. "New Protection Scheme for Internal Fault of Multi-Microgrid." , no. : 1.
Wenming Guo; Longhua Mu. Control principles of micro-source inverters used in microgrid. Protection and Control of Modern Power Systems 2016, 1, 1 .
AMA StyleWenming Guo, Longhua Mu. Control principles of micro-source inverters used in microgrid. Protection and Control of Modern Power Systems. 2016; 1 (1):1.
Chicago/Turabian StyleWenming Guo; Longhua Mu. 2016. "Control principles of micro-source inverters used in microgrid." Protection and Control of Modern Power Systems 1, no. 1: 1.
The traditional overcurrent protection is not suitable for the microgrid. One of the main reasons is that the fault response of the inverter-interfaced distributed generator (IIDG) is very different from that of the rotational generator. This paper develops fault models of IIDGs within a low-voltage microgrid, including active/reactive power (PQ)-controlled IIDGs and voltage-controlled IIDGs. Considering that the control strategy of the PQ-controlled IIDG varies, this paper introduces adjustable parameters into the model to reflect its fault characteristics as comprehensive as possible. Voltage-controlled IIDG is of great significance on maintaining a stable microgrid. The model of voltage-controlled IIDG proposed in this paper keeps its voltage-source nature while accomplishing current limiting. The performance of the proposed IIDG fault models has been tested by Matlab simulations. The achievements of this paper are expected to have a positive impact on the development of microgrid fault analysis and protection.
Wen-Ming Guo; Long-Hua Mu; Xin Zhang. Fault Models of Inverter-Interfaced Distributed Generators Within a Low-Voltage Microgrid. IEEE Transactions on Power Delivery 2016, 32, 453 -461.
AMA StyleWen-Ming Guo, Long-Hua Mu, Xin Zhang. Fault Models of Inverter-Interfaced Distributed Generators Within a Low-Voltage Microgrid. IEEE Transactions on Power Delivery. 2016; 32 (1):453-461.
Chicago/Turabian StyleWen-Ming Guo; Long-Hua Mu; Xin Zhang. 2016. "Fault Models of Inverter-Interfaced Distributed Generators Within a Low-Voltage Microgrid." IEEE Transactions on Power Delivery 32, no. 1: 453-461.
Island‐capable microgrids can potentially enhance the efficiency of distributed generations. In general, protection schemes in traditional distribution network cannot meet the requirements of microgrid internal protection. In order to solve the problem, this paper proposes the positive‐sequence fault component of current as the starting criterion. And a graph model describing the overall structure of a microgrid is established. The information about fault currents, including amplitude and direction, is acquired to locate fault branch. Furthermore, a new matrix algorithm is used to locate the fault point, so that the fault can be isolated. Finally, a microgrid model is simulated in the PSCAD/EMTDC software environment to illustrate the validity of fault location principle in microgrid protection. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Longhua Mu; Haijuan Han; Bin Jiang; Wenming Guo. Microgrid protection based on principle of fault location. IEEJ Transactions on Electrical and Electronic Engineering 2015, 11, 30 -35.
AMA StyleLonghua Mu, Haijuan Han, Bin Jiang, Wenming Guo. Microgrid protection based on principle of fault location. IEEJ Transactions on Electrical and Electronic Engineering. 2015; 11 (1):30-35.
Chicago/Turabian StyleLonghua Mu; Haijuan Han; Bin Jiang; Wenming Guo. 2015. "Microgrid protection based on principle of fault location." IEEJ Transactions on Electrical and Electronic Engineering 11, no. 1: 30-35.