Search Results (392)

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

Today’s power grids are being modernized with the integration of new technologies, making them increasingly efficient, secure, and flexible. One of these technologies, which is beginning to make great contributions to distribution systems, is solid-state transformers (SSTs), motivating the present technical and economic study of local level 2 distribution systems in Colombia. Taking into account Resolution 015 of 2018 issued by the Energy and Gas Regulatory Commission (CREG), which establishes the economic and quality parameters for the remuneration of electricity operators, the possibility of using these new technologies in electricity networks, particularly distribution networks, was studied. The methodology for developing this study consisted of creating a reference framework describing the topologies implemented in local distribution systems (LDSs), followed by a technical and economic evaluation based on demand management and asset remuneration through special construction units, providing alternatives for the digitization and modernization of the Colombian electricity market. The research revealed the advantages of SST technologies, such as reactive power compensation, surge protection, bidirectional flow, voltage drops, harmonic mitigation, voltage regulation, size reduction, and decreased short-circuit currents. These benefits can be leveraged by distribution network operators to properly manage these types of technologies, allowing them to be better prepared for the transition to smart grids. Full article

Focusing on the common problems of phase-locked loop dependence, multiple current sensor requirements, a large number of controllers, and complex settings in traditional parallel active power filter (APF) control methods, this paper proposes a harmonic compensation control strategy based on an improved proportional resonant (PR) controller. The proposed method introduces an instantaneous power theory to construct a reference current model, which relies solely on grid voltage and current signals, does not require load-side current detection and phase-locked loop modules, and effectively simplifies the sensor configuration and system structure. At the same time, compared with the traditional solution that requires PR modules to be configured for each order of harmonics, this study only uses one set of PR controllers for fundamental current tracking, which has advantages in terms of compactness and computing resource occupation. To guide the controller parameter setting, this paper systematically discusses the influence of changes in K_p and K_r on pole distribution and dynamic performance based on discrete domain modeling and root locus analysis methods. The results were verified on the MATLAB/Simulink simulation platform and the 1 kVA experimental platform and compared with the traditional control method that requires the use of phase-locked loops (PLLs), load current sensors, and multiple PR controllers. The simulation and experimental results show that the proposed method has achieved a certain degree of optimization in terms of harmonic suppression effect, dynamic response performance, and system structure complexity. Full article

For power electronic interfaces, Direct Power Control (DPC) has emerged as a leading control technique, especially in applications such as synchronous motors, induction motors, and other electric drives; renewable energy sources (such as photovoltaic inverters and wind turbines); and converters that are grid-connected, such as Virtual Synchronous Generator (VSG) and Static Compensator (STATCOM) configurations. DPC accomplishes several significant goals by avoiding the inner current control loops and doing away with coordinating transformations. The application of STATCOM based on three- and five-level diode-clamped inverters is covered in this work. The study checks the abilities of DPC during power control adjustments during diverse grid operation scenarios while detailing how multilevel inverters affect system stability and power reliability. Proportional Integral (PI) controllers are used to control active and reactive power levels as part of the control approach. This study shows that combining DPC with Sinusoidal Pulse Width Modulation (SPWM) increases the system’s overall electromagnetic performance and control accuracy. The performance of STATCOM systems in power distribution and transient response under realistic operating conditions is assessed using simulation tools applied to three-level and five-level inverter topologies. In addition to providing improved voltage quality and accurate reactive power control, the five-level inverter structure surpasses other topologies by maintaining a total harmonic distortion (THD) below 5%, according to the main findings. The three-level inverter operates efficiently under typical grid conditions because of its straightforward design, which uses less processing power and computational complexity. 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

Stability problems are increasing in current power systems with a large number of electronic converters, such as microgrids (MGs) and microgrid clusters (MGCs). Frequency-domain methods, commonly used to analyse traditional power system stability, can also be extended to MGs. In particular, the positive-mode-damping (PMD) stability criterion is a simple and practical method to evaluate the stability of multi-terminal power electronics-based systems, making it a powerful tool for addressing stability issues in MGCs. This paper extends the application of the PMD stability criterion to assess stability in MGC-integrated transmission grids. Moreover, it presents two bandpass filter-based active and passive damping compensators and examines their effectiveness in mitigating instabilities in MGCs. A modified IEEE three-bus power system integrating an MGC is used to conduct a small-signal harmonic stability study and apply active and passive damping solutions with the PMD stability criterion. The modified IEEE three-bus power system is implemented in real-time simulations using a hardware-in-the-loop setup with OPAL-RT4512 to validate the results obtained from MATLAB/Simulink R2022a simulations. 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

Wide-speed regulation control strategies for Interior Permanent Magnet Synchronous Motors (IPMSMs) are widely applied in industrial fields. However, traditional algorithms are prone to being affected by motor parameter mismatches, sensor sampling errors, and other disturbances under complex operating conditions, leading to insufficient robustness. In order to enhance dynamic performance while simultaneously ensuring robustness, we analyzed the limitations of traditional control strategies and, based on this, proposed an improved control framework. A Multi-Axis Coordinated Extended State Observer(MCESO)-based robust control framework was developed for full-speed domain operation, which enhances disturbance rejection capability against parameter uncertainties and abrupt load changes through hierarchical disturbance estimation. Subsequently, the effectiveness and stability of the proposed method were verified through theoretical analysis and simulation studies. Compared with traditional control strategies, this method can effectively observe and compensate for a series of complex issues such as nonlinear disturbances during operation without requiring additional hardware support. Finally, extensive experimental tests were carried out on a 500 W IPMSM dual-motor drive platform. The experimental results demonstrated that, even under harsh operating conditions, the proposed scheme can effectively suppress torque ripple and significantly reduce current harmonics. Full article

The proliferation of next-generation renewable energy systems has driven widespread adoption of electronic devices and nonlinear loads, causing grid distortion that degrades waveform quality in grid-forming (GFM) converters. Additionally, unbalanced grid faults exacerbate overcurrent risks and transient stability challenges when employing conventional virtual impedance strategies. While existing studies have separately examined these challenges, few have comprehensively addressed non-ideal grid conditions. To bridge this gap, a novel control strategy is proposed that reshapes the output current waveforms and enhances transient stability in GFM converters under such conditions. First, a sliding mode controller with an improved composite reaching law to achieve rapid reference tracking while eliminating chattering is designed. Second, a multi-quasi-resonance controller incorporating phase compensation is introduced to suppress harmonic distortion in the converter output current. Third, an individual-phase fuzzy adaptive virtual impedance strategy dynamically reshapes the current amplitude during unbalanced faults and improves the system’s transient stability. Validated through PSCAD/EMTDC simulations and hardware-in-the-loop experiments, the proposed strategy demonstrates superior transient stability and fault ride-through capability compared to state-of-the-art methods, ensuring reliable GFM converter operation under severe harmonic and unbalanced grid conditions. Full article

Permanent magnet flux harmonics in Permanent Magnet Synchronous Motors (PMSMs) can cause torque ripple. Traditional torque ripple suppression methods based on analytical models are highly dependent on the accuracy of motor parameters, while existing flux harmonic identification techniques often suffer from limited precision, compromising the effectiveness of ripple suppression. This paper proposes an online flux harmonic identification method that considers the dead-time effect of inverters. A dead-time compensation algorithm is introduced to effectively mitigate current harmonics induced by inverter dead-time. The current harmonic signals are extracted using a multi-synchronous rotating coordinate system. A harmonic controller is employed to suppress current harmonics, and its output voltage is used to identify the permanent magnet flux harmonics, from which a flux harmonic lookup table is constructed. Based on the identified flux harmonics, the torque ripple suppression strategy using analytical methods is further optimized. Experimental results validate the effectiveness of the proposed method in improving flux harmonic identification accuracy and reducing torque ripple. Full article

Grid-forming converters (GFMCs) have gained significant attention for their functionality in grid voltage formation and grid-supportive services. However, managing harmonic distortions caused by nonlinear loads remains a critical challenge in weak grids. This paper presents a novel grid-forming active power filter (GFMC APF) that integrates voltage and frequency regulation with effective harmonic control. The proposed control method generates harmonic voltage commands by detecting voltage at the point of common coupling. The GFMC APF compensates harmonic voltages by creating a near short-circuit impedance path for harmonics, thereby preventing harmonic currents from propagating into the grid. In addition to improving harmonic performances, the system enhances grid stability by enhancing inertia, damping, and short-circuit capacity while suppressing wide-frequency oscillations. The proposed method avoids complex parameter tuning, ensuring simplicity and scalability. Simulation results validate the effectiveness of the GFMC APF in delivering precise harmonic control, improved power quality, and enhanced grid-forming capabilities. 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

A permanent magnet synchronous motor (PMSM) is typically run at low speed with a sensorless control system using a high-frequency signal injection method. However, current harmonic and gain errors compromise rotor position observation accuracy. In this paper, we analyze the reasons for rotor observation angle error and propose a new rotor position observer with error compensation. This new sensorless control tool obtains the compensation error angle by extracting the negative high-frequency current in order to estimate the rotor position information accurately. The experimental results show that the error compensation strategy proposed in this paper can improve the accuracy of rotor position observation and achieve operation of the PMSM in both steady-state working conditions and dynamic working conditions at low speed. Full article