Influence of Single-Phase Voltage Loss and Load Carrying Mode on Mine Drainage Pump Motor in Vietnam

Mine drainage pump is the most important load in mining which requires high reliabilitywhen operating. Currently, the power supply of a mine drainage pump is connected to the same powerline with many nonlinear loads, and is equipped with power electronic converters, which makes thepower supply nonsinusoidal. During the working process of a mine drainage pump, the load-carryingfactor often changes, and many types of failures occur, among which single-phase voltage loss is themost common problem. In the case of a nonsinusoidal power supply, if a single-phase voltage lossoccurs in different load modes, it will greatly affect the working mode of the mine drainage pumpleading to influences on the working efficiency, the life of the pump, and sometimes it is necessary torecalculate the protection parameters. This paper studies the influence of single-phase voltage loss andload carrying mode on the working mode of mine drainage pump motor in case the of nonsinusoidalpower supply. Research results show that, in the case of nonsinusoidal power supplied with single-phasevoltage loss, copper losses in the rotor and stator circuits increase with increases in voltage totalharmonic distortion (THD) and load-carrying factor, 5th order reverse harmonic increases copper loss inasynchronous motor the most, and higher harmonic components have less effect on copper loss in themotor. At the same time, the speed ripple decreases with the increase of the motor load factor anddecreases in the presence of the 5th order negative sequence harmonic, and increases significantly in thepresence of the 7th order positive sequence harmonic. 5th order negative sequence harmonic increases,the torque ripple increases, while the 7th order positive sequence harmonic reduces the torque ripple inthe case of single-phase voltage loss. The results of the paper will help improve the operationalefficiency of the mine drainage pump in Vietnam's mines.

Optimal Individual Phase Voltage Regulation Strategies in Active Distribution Networks with High PV Penetration Using the Sparrow Search Algorithm

This study aimed to propose individual phase voltage regulation strategies using the sparrow search algorithm (SSA) in the IEEE 8500-node large-scale unbalanced distribution network with high photovoltaic (PV) penetration. The proposed approach is capable of individual phase regulation, which coordinates the on-load tap changer (OLTC), voltage regulator (VR), switched capacitor bank (SCB), and volt–var setting controlled by a smart inverter to improve voltage variation and unbalance. Consequently, the change time of VRs, the switched times of SCBs, and the individual phase voltage magnitude and unbalance ratio are considered in the fitness function for the SSA. The simulation scenarios fully consider the unbalanced load conditions and PV power output patterns, and the numerical results demonstrate that the voltage variation and unbalance are clearly improved, by 15% and 26%, respectively. The fitness values, operation times of OLTC, VR, and SCB, and the settings of the volt–var controlled smart inverter are also optimized by the SSA. The outcomes of this study are helpful for distribution system operators in formulating voltage control strategies corresponding to different system conditions.

Voltage Rise Regulation with a Grid Connected Solar Photovoltaic System

Renewable Distributed Generation (RDG), when connected to a Distribution Network (DN), suffers from power quality issues because of the distorted currents drawn from the loads connected to the network over generation of active power injection at the Point of Common Coupling (PCC). This research paper presents the voltage rise regulation strategy at the PCC to enhance power quality and continuous operation of RDG, such as Photovoltaic Arrays (PVAs) connected to a DN. If the PCC voltage is not regulated, the penetration levels of the renewable energy integration to a DN will be limited or may be ultimately disconnected in the case of a voltage rise issue. The network is maintained in both unity power factor and voltage regulation mode, depending on the condition of the voltage fluctuation occurrences at the PCC. The research investigation shows that variation in the consumer’s loads (reduction) causes an increase in the power generated from the PVA, resulting in an increase in the grid current amplitude, reduction in the voltage of the feeder impedance and an increase in the phase voltage amplitude at the PCC. When the system is undergoing unity power factor mode, PCC voltage amplitude tends to rises with the loads. Its phase voltage amplitude rises above an acceptable range with no-loads which are not in agreement, as specified in the IEEE-1547 and Southern Africa grid code prerequisite. Incremental Conduction with Integral Regulator bases (IC + PI) are employed to access and regulate PVA generation, while the unwanted grid current distortions are attenuated from the network using an in-loop second order integral filtering circuit algorithm. Hence, the voltage rise at the PCC is mitigated through the generation of positive reactive power to the grid from the Distribution Static Compensator (DSTATCOM), thereby regulating the phase voltage. The simulation study is carried out in a MATLAB/Simulink environment for PVA performance.

Intelligent Islanding Detection of Microgrids Using Long Short-Term Memory Networks

This paper presents a new intelligent islanding detection scheme (IIDS) based on empirical wavelet transform (EWT) and long short-term memory (LSTM) network to identify islanding events in microgrids. The concept of EWT is extended to extract features from three-phase signals. First, the three-phase voltage signals sampled at the terminal of targeted distributed energy resource (DER) or point of common coupling (PCC) are decomposed into empirical modes/frequency subbands using EWT. Then, instantaneous amplitudes and instantaneous frequencies of the three-phases at different frequency subbands are combined, and various statistical features are calculated. Finally, the EWT-based features along with the three-phase voltage signals are input to the LSTM network to differentiate between non-islanding and islanding events. To assess the efficacy of the proposed IIDS, extensive simulations are performed on an IEC microgrid and an IEEE 34-node system. The simulation results verify the effectiveness of the proposed IIDS in terms of non-detection zone (NDZ), computational time, detection accuracy, and robustness against noisy measurement. Furthermore, comparisons with existing intelligent methods and different LSTM architectures demonstrate that the proposed IIDS offers higher reliability by significantly reducing the NDZ and stands robust against measurements uncertainty.