Search Results (147)

With the increasing penetration of distributed generation and the diversification of electrical equipment, distribution networks face issues like three-phase unbalance and harmonic currents, while the voltage stability and inertia of the grid-connected system also decrease. A certain amount of energy storage is needed in a Distribution Static Synchronous Compensator (DSTATCOM) to manage power quality and actively support voltage and inertia in the network. This paper first addresses the limitations of traditional $dq0$ compensation algorithms in effectively filtering out negative-sequence twice-frequency components. An improved $dq0$ compensation algorithm is proposed to reduce errors in detecting positive-sequence fundamental current under unbalanced three-phase conditions. Second, considering the impedance ratio characteristics of the distribution network, while reactive power voltage regulation is common, active power regulation is more effective in high-resistance distribution networks. A grid-forming model-based active and reactive power coordinated voltage regulation method is proposed. This method uses synchronous control to establish a virtual three-phase voltage internal electromotive force, forming a comprehensive compensation strategy that combines power quality improvement and active voltage support, exploring the potential of energy storage DSTATCOM applications in distribution networks. Finally, simulation and experimental results demonstrate the effectiveness of the proposed control method. Full article

In reactive power compensators applied in drives with asynchronous motors, a control strategy focusing on the compensation of higher-order current harmonics is implemented. Control schemes of such compensators typically employ low-pass Butterworth filters with fixed cut-off frequencies to isolate the reactive power component. However, the impact of alternative filter types on compensator performance remains insufficiently explored. Furthermore, in the control systems under consideration, stator phase current signals of the asynchronous motor are used as reference inputs. This approach proves effective under the steady-state operating conditions of the drive. Under non-steady-state operating conditions—typical for traction drive systems—this approach becomes ineffective due to the increased complexity in obtaining accurate reference current signals. As a result, the performance of the filters also deteriorates. It is therefore proposed to investigate the impact of alternative filter types on the efficiency of compensator operation. To address this challenge, the following strategies are suggested: implement higher-order harmonic compensation in the system of stator phase supply voltages of the asynchronous motor; use the control signals from the Field-Oriented Control (FOC) algorithm as reference inputs; and adapt the cut-off frequencies of the filters dynamically to match the frequency of the supply voltage. The simulation results indicate that the use of an elliptic filter in compensator control systems yielded the highest effectiveness. Moreover, the results confirmed the efficiency of the proposed solutions under both steady-state and non-steady-state operating conditions of the traction drive. These approaches support the development of reactive power compensators integrated into traction drive systems for railway rolling stock. Full article

This paper presents a Space Vector Modulation (SVM) method with a novel zero vector distribution system for electrical vehicle drives with a six-phase induction motor working under the Direct Field-Oriented Control (DFOC) method. Different SVM methods are described and compared, and a new approach with long vectors only and a special zero vector distribution, that compensates for the third harmonic component is proposed. The DFOC method is described and the influence of the applied modulation method on six-phase motor currents is shown. Results of our experimental studies on the DFOC method are presented and discussed. The proposed modulation method for a six-phase Voltage Source Inverter can be applied in fault-tolerant electrical vehicles. Full article

With the increasing application of electrical network frequency (ENF) in forensic audio and video analysis, ENF signal detection has emerged as a critical technology. However, high-pass filtering operations commonly employed in modern communication scenarios, while effectively removing infrasound to enhance communication quality at reduced costs, result in a substantial loss of fundamental frequency information, thereby degrading the performance of existing detection methods. To tackle this issue, this paper introduces Multi-HCNet, an innovative deep learning model specifically tailored for ENF signal detection in high-pass filtered environments. Specifically, the model incorporates an array of high-order harmonic filters (AFB), which compensates for the loss of fundamental frequency by capturing high-order harmonic components. Additionally, a grouped multi-channel adaptive attention mechanism (GMCAA) is proposed to precisely distinguish between multiple frequency signals, demonstrating particular effectiveness in differentiating between 50 Hz and 60 Hz fundamental frequency signals. Furthermore, a sine activation function (SAF) is utilized to better align with the periodic nature of ENF signals, enhancing the model’s capacity to capture periodic oscillations. Experimental results indicate that after hyperparameter optimization, Multi-HCNet exhibits superior performance across various experimental conditions. Compared to existing approaches, this study not only significantly improves the detection accuracy of ENF signals in complex environments, achieving a peak accuracy of 98.84%, but also maintains an average detection accuracy exceeding 80% under high-pass filtering conditions. These findings demonstrate that even in scenarios where fundamental frequency information is lost, the model remains capable of effectively detecting ENF signals, offering a novel solution for ENF signal detection under extreme conditions of fundamental frequency absence. Moreover, this study successfully distinguishes between 50 Hz and 60 Hz fundamental frequency signals, providing robust support for the practical deployment and extension of ENF signal applications. Full article

Electric helicopters represent a pivotal component in the advancement of urban air mobility (UAM), with considerable potential for future development. The electric propulsion system (EPS) is the core component of these systems. However, the inherent complexities of electromechanical coupling can induce excessive torsional vibrations, potentially compromising operational comfort and even threatening flight safety. This study proposes an active torsional vibration suppression method for EPS that explicitly incorporates electromechanical coupling characteristics. A nonlinear dynamic model has been developed, accounting for time-varying meshing stiffness, meshing errors, and multi-harmonic motor excitation. The motor and transmission system models are coupled using torsional angular displacement. A harmonic current command generation algorithm is then formulated, based on the analysis of harmonic torque-to-current transmission characteristics. To achieve dynamic tracking and the real-time compensation of high-order harmonic currents under non-steady-state conditions, a high-order resonant controller with frequency-domain decoupling characteristics was designed. The efficacy of the proposed harmonic current modulation is verified through simulations, showing an effective reduction of torsional vibrations in the EPS under both steady-state and non-steady-state conditions. It decreases the peak dynamic meshing force by 4.17% and the sixth harmonic amplitude by 88.15%, while mitigating overshoot and accelerating vibration attenuation during speed regulation. The proposed harmonic current modulation method provides a practical solution for mitigating torsional vibrations in electric propulsion systems, enhancing the comfort, reliability, and safety of electric helicopters. Full article

This work provides a new solution for high-power quality traction power systems. The rapid development of electrified railways not only promotes economic development, but also seriously restricts the improvement of electric locomotive operation performance due to power quality problems, such as second harmonic distortion and negative sequence in the power supply system. In view of the shortcomings of the traditional in-phase power supply system in DC bus voltage stability control, a new in-phase power supply topology based on a back-to-back H-bridge power supply unit is proposed in this study. By establishing the iterative analysis model of the rectifier side double closed-loop control system, the internal correlation mechanism between the DC bus voltage second harmonic fluctuation and the grid side current harmonic is deeply revealed. On this basis, a rectifier-side disturbance compensation control strategy with a second harmonic suppression function is designed. Through real-time detection and compensation of second harmonic components, the active stability control of DC bus voltage is realized. The simulation model of the new cophase power supply system based on the experimental platform shows that the strategy can reduce the ripple coefficient of the DC bus voltage and the total harmonic distortion of the grid side current, which effectively verifies the superiority of the second harmonic suppression strategy in improving the power quality of the cophase power supply system. This work provides a new solution for a high-power quality traction power system. Full article

The Shunt Active Filter (SAF) is an effective solution for mitigating electrical perturbations in power networks. SAFs usually consist of a voltage source inverter (VSI) with lossy transistors and bulky inductors. In this context, this article proposes analytical models to evaluate the losses and efficiency of a SAF. The models include conduction and switching losses in the transistors and diodes and are valid for both IGBT and SiC MOSFET transistors. The methodology consists of analysing the current waveform to separate the portion flowing through the transistor or diode. IGBT and SiC MOSFET are compared in two cases: firstly, the classic SAF operation with harmonic and reactive power compensation and, secondly, in the case of power injection by a photovoltaic panel or batteries, in addition to the classic SAF operation. The results are validated with real manufacturer data. A step-by-step comparison shows a good accuracy of the model. Therefore, the developed methodology is useful for a SAF designer to select relevant components for the converter and to estimate the efficiency of the system accurately and quickly. Full article

Conventional Distributed Power Flow Controllers (DPFCs) rely on third-harmonic currents to facilitate active power exchange between the series side and the system, requiring specific Δ/YN and YN/Δ transformer configurations at branch terminals. This limitation restricts their application in distribution networks. To overcome these constraints, this paper proposes a Novel Distributed Power Flow Controller (NDPFC) topology specifically designed for distribution networks. This design eliminates the need for third-harmonic currents and specific transformer configurations, enhancing deployment flexibility. The paper first explains the NDPFC operating principles and verifies its power flow regulation capabilities through a typical distribution network system. Furthermore, we develop electromagnetic transient mathematical models for both series and shunt components of the NDPFC, proposing a triple-loop control strategy for Series-I and Series-II control methods to enhance system robustness and control precision. A systematic stability analysis confirms the proposed controller’s robustness under various operating conditions. Simulation results demonstrate that in various distribution network scenarios, the NDPFC effectively achieves comprehensive power flow regulation, compensates three-phase imbalances, and facilitates renewable energy integration, significantly improving distribution network power quality. A comparative analysis shows that the NDPFC achieves 15% faster response times and 12% lower losses compared to conventional power flow controllers. Full article

Energy storage systems (ESSs) and active power filters (APFs) are key power electronic technologies for FACTS (Flexible AC Transmission Lines). Battery energy storage has a structure similar to a shunt active power filter, i.e., a storage element and a voltage source inverter (VSI) connected to the grid using a PWM filter and/or transformer. This similarity allows for the design of an ESS with the ability to operate as a shunt APF. One of the key milestones in ESS or APF development is the DC-link design. The proper choice of the capacitance of the DC-link capacitors and their equivalent resistance ensures the proper operation of the whole power electronic system. In this article, it is proposed to estimate the required minimum DC-link capacitance using a spectral analysis of the DC-link current for different operating modes, battery charge mode and harmonic compensation mode, for a nonlinear load. It was found that the AC component of the DC-link current is shared between the DC-link capacitors and the rest of the DC stage, including the battery. This relation is described analytically. The main advantage of the proposed approach is its universality, as it only requires calculating the harmonic spectrum using the switching functions. This approach is demonstrated for DC-link capacitor estimation in two-level and three-level NPC inverter topologies. Moreover, an analysis of the AC current component distribution between the DC-link capacitors and the other elements of the DC-link stage was carried out. This part of the analysis is especially important for battery energy storage systems. The obtained results were verified using a simulation model. Full article

A grid-forming converter (GFM) controls power output by adjusting the phase angle and amplitude of its output voltage, providing voltage and frequency support to the power system and effectively enhancing system stability. However, it has limitations in current control, influencing the current only indirectly through voltage regulation, which results in weaker control over current waveform quality. In the context of a large number of renewable energy generation units being connected to the grid, harmonics in the grid voltage can lead to excessively high harmonic content in the grid current, exceeding standard limits and causing oscillations. To solve this problem, this paper proposes a control strategy of harmonic voltage feedforward compensation to suppress grid current distortion. The proposed control strategy extracts harmonic voltages from the output port of the GFM converter through a harmonic extraction module, processes them via a feedforward factor, and introduces the resulting signals into the converter’s control loop as feedforward compensation terms. This allows the converter’s output voltage to compensate for the harmonic components in the grid, achieving the improvement of grid current and reducing the total harmonic distortion (THD) value. The effectiveness of the proposed control strategy is verified by simulation results. Full article

This work contributes to both Romania’s and the European Union’s energy policies by highlighting the research results obtained within the Dunarea de Jos University of Galati, but also through the technological transfer of this knowledge to the industry. In order to improve the power quality of the nonlinear loads connected to the electrical grid, a three-phase shunt active power filter prototype based on the Harmonic Component Separation Method with a Low-Pass Filter was used. The active power filter is connected at the Point of Common Coupling to compensate for individual loads or even all of them simultaneously. Therefore, active power filters can be used to compensate for the power factor and reduce the harmonic distortion of power supplies, or for processes subsequently connected to additional nonlinear loads, thus improving the energy efficiency. The shunt active power filter prototype is composed of the power side (three-phase insulated gate bipolar transistor bridge, DC link capacitor precharge system, inductive filter) and the control side (gate drive circuits, control subsystems, signal acquisition system). The filter control strategy is based on the principle of separating harmonic components with a low-pass filter, implemented by the authors on the industrial prototype. In this paper, the main technical features of the industrial shunt active power filter prototype are specified. The authors of this paper involved three cascaded control loops: the DC link voltage control loop, the shunt active power filter current control loop and the phase-locked loop. Both simulation and experimental results for the shunt-type active power filter prototype were obtained. By analyzing the obtained waveforms of the power supply source in two cases (with and without an active power filter), a decrease in the total harmonic distortion was demonstrated, both the voltage harmonic distortion factor THDu and the current harmonic distortion factor THDi in the case of the active power filter connection. By using the Field-Programmed Gate Array processing platform, the powerful computational speed features were exploited to implement the active shunt power filter control on an experimental test bench. Conducting source current harmonics mitigation increased the efficiency of the power system by decreasing the respective harmonic Joule losses. The energy-saving feature led to the increased added value of the parallel active power filter. Through the performed laboratory tests, the authors demonstrated the feasibility of the proposed control solution for the industrial prototype. In accordance with the European Union’s Research and Technological Development Policy, the development of an innovation ecosystem was taken into consideration. The unified and efficient integration of all the specific actors (enterprises, research institutes, universities and entrepreneurs) in innovation was achieved. Full article

Variable Flux Reluctance Machines (VFRMs) face multiple interconnected challenges that limit their performance, particularly in high-performance applications such as electric vehicles (EVs), where smooth torque output and robust operation are critical. Chief among these challenges are complex inter-axis couplings, including cross-coupling in the dq-axis, differential term coupling in the d0-axis, and disturbances propagating from the 0-axis to the q-axis. Additionally, harmonic disturbances associated with torque ripple exacerbate performance issues, resulting in degraded dynamic behavior. These challenges hinder current loop controllers, preventing effective management of winding impedance voltage drops and inter-axis coupling terms without advanced decoupling strategies. To address these challenges, this paper proposes a novel integrated torque harmonic extended state observer (ITHESO) within a decoupled current control designed to ensure fast and accurate current tracking, system stability, and torque ripple reduction. The ITHESO identifies and compensates for total current disturbances, including harmonic components, through feed-forward compensation within the current loop. Furthermore, the influence of control parameters and the effects of parameter mismatches on stability, torque ripple reduction, and disturbance rejection are thoroughly analyzed. Experimental validations demonstrate that the proposed strategy significantly enhances torque dynamics and reduces torque ripple, outperforming the conventional Active Disturbance Rejection Control (ADRC), which does not explicitly address disturbances associated with torque ripple. These advancements position the VFRM with the ITHESO as a competitive option for high-performance EV propulsion systems, offering smooth operation, noise reduction, and reliable performance under varying speeds and loads. Full article

Permanent Magnet Synchronous Motors (PMSMs) are nonlinear, multi-parameter systems that exhibit structural symmetry but are susceptible to parameter variations and external disturbances. These challenges can disrupt the inherent symmetrical characteristics of PMSM dynamics during real-world operations, posing difficulties for achieving efficient control. To address this issue, this paper proposes a Model-Free Generalized Super-Twisting Algorithm Fast Terminal Sliding Mode Control (MFFTSMC-GSTA) method. First, a novel ultra-local model incorporating PMSM uncertainties is established, and the MFFTSMC-GSTA controller is designed to address the system’s complex dynamic behavior. By integrating the generalized super-twisting algorithm with the nonsingular fast terminal sliding mode algorithm, the proposed controller ensures finite-time convergence and effectively mitigates chattering. Second, an extended sliding mode disturbance observer is developed to estimate the unknown components of the ultra-local model and provide feedforward compensation, further enhancing system robustness and dynamic performance. The experimental results show that the total harmonic distortion (THD) value of the proposed control method is 1.38%, demonstrating significant improvements in response speed and robustness for motor speed control, and verifying the algorithm’s superior performance under complex operating conditions. Full article

Distributed energy storage systems (DESSs), which would become key components in a new power system, can flexibly deliver peak load shaving and demand management. With the popularization of distributed renewable energy generation in a distribution network, the grid impedance varies and DESSs thus have to face stability issues. In order to enhance the system’s stability, a compensation strategy is proposed for the inverter in a DESS. First, a stability analysis model is developed to show the main factors that affect system stability. Then, an improved compensation strategy is proposed for the phase-locked loop (PLL) in a DESS, in which control parameters are adaptively tuned on-line according to real-time conditions to improve the stability of a grid-tied DESS. Simulation and hardware-in-the-loop (HIL) experimental results are given to validate the effectiveness of the proposed strategy. Simulation and experimental results show that the proposed strategy significantly increases the system’s tolerance to grid impedance variations, maintains total harmonic distortion (THD) below 5% during normal operation, and effectively reduces low-order harmonic content caused by impedance fluctuations. Moreover, the strategy is demonstrated to enhance system stability under low state-of-charge (SOC) conditions, showcasing its robustness and adaptability across various operating scenarios. Full article

In steel mills that employ the hot strip mill process, cycloconverters with nominal power ratings in the megawatt range are commonly used to drive synchronous motors. However, these cycloconverters draw highly distorted currents from the power grid, causing significant voltage distortion at the point of common coupling (PCC) and leading to numerous power quality (PQ) issues. Multi-stage passive filters are widely used to mitigate harmonics in this context. However, this approach can lead to harmonic resonance, exacerbating distortion and overloading the passive filtering system. This study presents a novel integration of a back-to-back hybrid filter, designed specifically for hot strip mills with cycloconverters at a steel mill located in the Metropolitan Area of Vitória, ES, Brazil. The proposed method combines active and passive filtering, where the active filter works in tandem with existing passive elements to compensate for harmonic components while damping resonances across a broad frequency range. Simulations are conducted to evaluate the hybrid filter’s efficacy in harmonic compensation and resonance damping, particularly during load expansion scenarios for the hot strip mill. Results indicate that the back-to-back hybrid filter significantly improves PQ by reducing harmonic overloads on pre-existing passive filter branches, thereby enhancing the reliability of the entire power system. This improvement is achieved with active filters of relatively low-rated capacity compared to the hot strip mill load, making it a cost-effective and scalable solution. Full article