Synchronous Reluctance Generator Research Articles

A novel intelligent control approach for wind energy conversion systems with synchronous reluctance generators

SummaryThis study addresses a significant research gap in the field of wind energy, focusing on the underutilized potential of synchronous reluctance generators (SynRG) in wind power conversion systems (WPCS). Despite notable advancements in wind energy controls, the capabilities of SynRG within these systems have not been fully explored. In response, we introduce an innovative model‐free control (MFC) approach, termed intelligent proportional (iP), specifically designed and optimized for WPCS equipped with SynRG. This research encompasses the modeling, control, and simulation of SynRG‐based WPCS, aiming to optimize system performance and enhance the quality of grid power supply. The proposed vector control (VC) method utilizes a MFC approach (VC‐iP) to address the limitations inherent in traditional VC methods with proportional‐integral (PI) controllers (VC‐PI). Although widely used for their simplicity, VC‐PI methods often lead to power fluctuations and decreased power and current quality, consequently reducing overall system efficiency. In contrast, VC‐iP markedly enhances power quality and system efficiency, especially in situations involving fluctuating power demand and variable wind speeds. The efficacy of VC‐iP is demonstrated through simulations in two distinct test scenarios that include variations in power demand and random wind speed fluctuations. The results affirm the superiority of VC‐iP in maintaining stable, high‐quality power output from WPCS. This method notably minimizes fluctuations, improves current quality, reduces harmonic distortion and steady‐state error, ensures reliable grid integration, and contributes to a more efficient and sustainable energy system.

Numerical thermal analysis of synchronous reluctance generator for wind energy application

AbstractThis paper focuses on the thermal analysis of the synchronous reluctance generator with a rating of 2.1 kW. It mainly uses explicit, and implicit finite difference methods for thermal analysis to reduce the complexity of thermal calculation for the machine's components. It compares the results with the results obtained using a finite element analysis (FEA) and includes the experimental verification of the obtained results. The explicit, and implicit finite difference thermal analysis is relatively simple and computationally fast. Once the design parameters are known, the electric losses and iron losses of the synchronous reluctance generator are evaluated. These machine parameters are utilized in developing the explicit finite difference (EFD), an implicit finite difference (IFD), and a 3D FEA model for thermal analysis. It is observed that the obtained results from the EFD, IFD, FEA, and experiments are very close to each other, and the temperature rise for the designed machine is within the desired and acceptable range.

Performance of Synchronous Reluctance Generators with Series and Shunt Stator Connections

This paper reports the performance of series- and shunt-connected self-excited reluctance generators (SERG). In addition to the two stator connections, an analysis was carried out on rotor configurations (with and without a cage) a combination resulting in four different generator topologies. The loss of load and transient characteristics of each generator configuration were studied for a combination of pure resistive and R-L loads. It is shown that for the same machine size, speed and exciting capacitor value, the generator with a cage preserves a better wave shape following a transient disturbance than the cageless machine. At unity power factor, shunt generator with cage can deliver 0.691pu output power, at 1.97% regulation; its series counterpart only delivers 0.589 pu at 2.05%. The study demonstrates that while shunt generators have better regulation and supports higher loads at different power factors, series generators show a superior performance in terms of damping out transients.

Encoderless Control of PMa-SynRG Based-Stator Current Vector for Wind Generation Systems

In this paper, a novel encoderless control of permanent magnet assisted synchronous reluctance generator (PMa-SynRG) based-stator current vector for renewable energy systems is presented. For the encoderless control, the PMa-SynRG rotor position angle along with rotor angular speed are estimated ultimately from the generator's stator currents, as the stator inductance is only requisite nevertheless the stator resistance. Indeed, this encoderless control technique employs one current control loop for regulating the magnitude of the stator current instead of employing two current control loops. For eliminating the current measurement noise and enhancing the phase angle tracking performance, a modified second-order generalized integrator frequency-locked loop (MSOGI-FLL) technique is employed and compared with the standard SOGI-FLL under different voltage/frequency conditions. The proposed technique has a simple computational implementation while accomplishing a rapid along with precise estimation performance of the PMa-SynRG rotor position angle and speed. The performance is validated using simulations and real-time hardware-in-the-loop Typhoon HIL implementation.

Performance analysis of a stand-alone synchronous reluctance generator under unbalanced conditions

<span lang="EN-US">A stand-alone self-excited wind energy conversion system (WECS) is considered commonly used in remote areas due to its simple control and low cost. This paper introduces the performance analysis of a stand-alone self-excited reluctance generator (SERG) under balanced and unbalanced operations. An asymmetrical component is proposed to obtain the positive and negative sequence components of voltages and currents in addition to the unbalanced voltage factor of SERG. The obtained results have been validated and compared with experimental results obtained from a laboratory prototype of a 5.5 kW synchronous reluctance generator driven by a dc motor as a prime-mover under unbalanced excitation capacitors and unbalanced loads. The comparison verifies the applicability of the proposed model.</span>

Calculation of a Current Vector Trajectory for Enhanced Operation of Synchronous Reluctance Generators Including Saturation

This article proposes a simple method to calculate a current vector trajectory for the enhanced operation of the electric power generation system based on a synchronous reluctance machine (SynRM). Owing to magnetic saturation and cross magnetization, the performance and the torque capability of a SynRM vary according to the position and the value of the stator current. State-of-the-art control methods usually assume parameters with constant values, especially the inductance, neglecting saturation, leading to possible uncertainty in the machine operation. Therefore, a current vector trajectory to operate this type of machine, as a generator, in an extended speed range, with enhanced performance and considering magnetic saturation is proposed. A straightforward algorithm based on the inductance characteristic of the machine is used to calculate the trajectory of the stator current vector. This trajectory is evaluated via the numerical simulation of an experimentally validated finite-element model of a SynRM. The results show that the proposed current vector trajectory can improve the torque capability to 5% concerning the estimated trajectory without considering saturation. Experimental results are also provided to demonstrate the enhanced operation of the generator.

Dynamical Model of Residual Magnetism for Synchronous Reluctance Machine Control

The present article proposes an effective model of synchronous reluctance machines. This model, called the Residual Magnetism (ReMa) model, takes into account not only residual magnetism within the rotor but also that within the stator. Electromotive forces generated by the ReMa model were composed of two frequencies and exhibited similar shapes as those measured in experiments. Resultant equations in a three-phase <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$(a,b,c)$</tex-math></inline-formula> frame and in a Park reference frame <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$(d,q)$</tex-math></inline-formula> were revealed. The comparison was made with the classical model of synchronous reluctance machine commonly used. Experimental tests were carried out to prove the effectiveness of the ReMa model which was also compared to a classical counterpart in the case where a synchronous reluctance generator was connected to a three-phase diode rectifier.

A Robust Control for Solar and SyRG Based Hydro Generation Microgrid With Grid Synchronization

The control of a microgrid is quite challenging thus this work implements a robust and fast control technique based on an enhanced second-order generalized integrator with a modified frequency locked loop (ESOGI-MFLL) for switching operation between an islanded and the grid-connected mode. For phase angle estimation, a circular limited cycle oscillator frequency locked loop with an inner loop filter (CLO-FLL-WIF) is implemented instead of a conventional phase-locked loop technique to provide better synchronization performance for polluted grid voltages. This microgrid is combing a solar photovoltaic (PV) generation, a synchronous reluctance generator for pico-hydro generation, and the battery, which works in both standalone and grid-connected modes while feeding local loads uninterruptedly. The output power conversion of a PV array is influenced by irradiation of the solar PV array; therefore, a maximum power point tracking namely an incremental conductance method is used. The implemented control techniques are used for fundamental extraction of load components of voltage and currents for assessment of reference currents with their respective phases of synchronization while maintaining the required IEEE power quality standard-519. In addition, the comparative results validate the faster response of ESOGI-MFLL control algorithm to the existing control algorithm. Simulated and test results of a microgrid for islanded, switching mode, and grid-connected mode demonstrate its performance under load unbalance and generation perturbation.

Design of an Aviation Dual-Three-Phase High-Power High-Speed Permanent Magnet Assisted Synchronous Reluctance Starter-Generator With Antishort-Circuit Ability

This article proposes a novel dual-three-phase high-power high-speed permanent magnet assisted synchronous reluctance starter generator (PMaSynR SG) for aviation application, which has the characteristics of high efficiency, high power density, high reliability, and excellent antishort-circuit ability. The proposed PMaSynR SG can obtain higher efficiency and power density by embedding permanent magnet in the rotor topology compared with the synchronous reluctance generator, and has better antishort-circuit ability compared with the permanent magnet synchronous starter-generator. Moreover, design of dual-three-phase winding is adopted, which not only reduces the phase current, but also improves the reliability. In this article, the topological structure, characteristics and principle of PMaSynR SG are systematically studied at first. Second, a simplified <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axis equivalent magnetic circuit model is established, and the expressions of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axis inductance and permanent magnet flux linkage are derived on the basis of the basic parameter selection. Then, combined with parameter sensitivity analysis, the influence law of rotor structural parameters on antishort-circuit ability and electromagnetic performance is revealed. Finally, a 40 kW 24 000 r/min PMaSynR SG is designed and manufactured. The simulation and experimental results show that the proposed PMaSynR SG has excellent electromagnetic performance with the power density of 3.1 kW/kg and the efficiency of 94%, while the short-circuit current is only 59% of its rated value.

Performance Analysis of Synchronous Reluctance Generator

Abstract: The synchronous reluctance generators are a species of self-excited generators such as the induction generators. The self-excited synchronous reluctance generator (SynRG) has become a promising and viable replacement of self-excited induction generator because of the supply frequency dependence on the prime speed and not load. The self-excited synchronous reluctance generator has high reliability, low cost and robustness and capacity of variable speed operation. The aim of this research is to carry out performance analysis of shunt connected three-phase synchronous reluctance generator feeding an R-L load. The dynamic analysis is based on the classical d-q model where equations for electrical quantities were derived and implemented using a computer simulation tool, MATLAB®. The equations for steady state analysis were derived from the dynamic equations by setting all time variables to zero. The dynamic analysis was carried out on a 4-pole, speed of 1500 rpm with connected load at a fixed excitation capacitor value of 50uF for a 2.5kVA machine. Effect of excitation-capacitance variation and loadingconditions variation on the generated output voltage and frequency are presented and discussed. The load variations were done based on energy-current perturbation at a fixed power factor of 1.0. The load variations were done at several points and result shows that with the variations in the connected loads, the output frequency of the synchronous reluctance generator remains constant, which makes it a good alternative for induction generator. On the steady state analysis, it was discovered that on increasing the excitation capacitor, the terminal voltage increases as well as the output power. The result specifically revealed that when the capacitance increases from 25uF to 45uF, the terminal voltage and the output power increases from 200volts to 300volts; and 200watt to 1700watt. Therefore, it is recommended that to ensure machine excitation, the capacitor should not be reduced below a certain value. The study is beneficial for operation of an isolated power supply. Keywords: Synchronous Reluctance Generator, Direct Current and Indirect Current

Power Quality Improvement in SyRG-PV-BES-Based Standalone Microgrid Using ESOGI-FLL-WIF Control Algorithm

In this article, a resilient enhanced second-order generalized integrator with frequency locked loop and inner loop filter (ESOGI-FLL-WIF) control algorithm is implemented to enhance the power quality and to regulate the voltage/frequency of a microgrid. This control has a simple structure, fast convergence, and excellent dynamic and steady-state response. The ESOGI-FLL-WIF control algorithm is used for assessing the fundamental constituent from harmonics and dc bias infected current. ESOGI-FLL-WIF control strategy tracks the frequency and tunes to the frequency fluctuations in transient situations. To have a fair comparison, the performance of the ESOGI-FLL-WIF control algorithm is compared with already existing controls. This three-phase four-wire islanded system consists of a solar photovoltaic array and pico-hydro turbine-driven synchronous reluctance generator (SyRG). As an alternative to the conventional generators, SyRG is used because it is economical (no permanent magnets in the rotor) and has high efficiency (no electrical losses in the rotor). The four-leg converter compensates neutral current and controls the reactive power injection under unbalance load condition, whereas for active power management, battery energy storage is incorporated in the system. A prototype of the system is developed and tested under different situations of load unbalancing and solar insolation change to confirm the effectiveness and viability of the control strategy.

ANN-Based SVC for Optimal Performance of Wind-Driven Self-Excited Synchronous Reluctance Generator

ANN-Based SVC for Optimal Performance of Wind-Driven Self-Excited Synchronous Reluctance Generator

Improved generalised integrator for optimal dispatch of SyRG‐based pico‐hydro‐PV system

The fluctuating outputs from renewable energy sources (RESs) and variable load power demand deteriorate the current quality, thus an improved generalised integrator with a frequency-locked loop (IGI-FLL) control strategy is used, which is not only easy but simple to attain a quick and precise fundamental extraction. IGI-FLL control method is utilised with all-pass filter and is capable to accomplish enhanced harmonics, noise and DC offset rejection ability while estimating fundamental component of the load current. In addition, the FLL structure is used to increase the frequency immunity against voltage variations. It provides improved steady-state and dynamic performances with flexibility in parameter tuning in comparison to SOGI-FLL algorithm. It also presents a cost-effective and robust genetic algorithm (GA)-based optimisation to provide optimum battery charging and discharging power while satisfying the state-of-charge (SOC) limits under RES uncertainty. In this islanded microgrid, a Synchronous Reluctance Generator for pico-hydro and photovoltaic array is used so that this hybrid system utilises maximum solar PV array power, matches the load, or else charges the battery energy storage while maintaining power balance in the microgrid. Comparative outcomes authenticate the efficacy of the algorithm to handle the issue of RES uncertainty and load unbalance in an islanded microgrid.

Design and modelling of self‐excited SRG and FM‐SRG for wind energy generation

The paper discusses the design and analysis of synchronous reluctance generator with a rating of 2.1 kW. These generators with low power ratings may be a suitable candidate for the rural electrification. In synchronous reluctance generator, the design of the rotor is the most challenging part of the design. Here, the thickness of the axial and tangential ribs plays a significant role in its performance. The design procedure presented in the paper includes the effect of stator resistance, as it cannot be neglected in the design of synchronous reluctance generator with low power ratings. The paper discusses the design procedure of synchronous reluctance generator and analyses the self-excited ferrite-magnet synchronous reluctance generator. Various parameters of the designed machine are analysed through an analytical model and Ansys Electronics Desktop software. Further, the paper also includes the experimental validation of the synchronous reluctance generator results obtained through finite element analysis. The paper also proposes formulae to approximate the minimum values of the excitation capacitor requirement, for a self-excitation of synchronous reluctance generator with inductive load.

Minimization of the Electromagnetic Torque Ripple of a Synchronous Reluctance Generator Using External Rotor Excitation

This paper presents an approach to minimize the electromagnetic torque ripple of a synchronous reluctance generator (SynRG) with a magnetic field created by externally excited rotor coils. The synchronous reluctance machine is widely used in low and medium power systems such as wind power generation and new electric vehicle technologies. This paper proposes a rotor topology with flux barriers and direct current excited coils that reduce the torque ripple and replace the permanent magnets used in other reluctance rotor topologies. First, the initial rotor design, without excitation coils, is optimized to obtain a new rotor structure that reduces the electromagnetic torque ripple. In this work, the optimization of the rotor geometry was achieved by using genetic algorithms and the finite element method to optimize and parameterize the main components of the machine. In the optimized rotor model, an external electronic converter is included to feed the coils positioned between the magnetic flux barriers and the segments formed by the ferromagnetic material of the rotor. Finally, the electrical and magnetic machine variables obtained from implementing the coils into the optimized rotor are compared to the initial rotor structure operating under nominal load conditions to demonstrate the advantage of this topology in minimizing the electromagnetic torque ripple.

FE Simulation and Experiment of a Self-Excited SynRel Generator Based on COMSOL Software

This paper presents the performance of a self-excited synchronous reluctance generator with flux barriers rotor (transversally laminated) in standalone operation mode. This type of generator's growing interest is due to its multiple advantages (rugged structure, reliability, and low cost), which allows it to compete with conventional generators in some applications related to renewable energies. The proposed study is carried out in several steps: (i) presentation of designed low power SynRM prototype, (ii) finite element modeling (FEM) and simulation of self-excitation process based on COMSOL Multiphysics, (iii) analytical simulations performed with MATLAB/Simulink software based on a d-q model where the dq-inductances are identified experimentally, (iv) and experimental tests performed to validate the results of the simulations.

Grid-Tied Battery Integrated Wind Energy Generation System With an Ability to Operate Under Adverse Grid Conditions

An efficient control of a grid integrated microgrid with wind energy generating system (WEGS) and a battery storage, is implemented in this work. The quality of power injected to the utility is deteriorated with the level of unbalance and/or distortions present in the grid voltages. To compensate for the abnormalities, such as unbalance and distortions in the grid voltages, positive sequence components (PSCs) of grid voltages are extracted from their filtered $ \alpha \beta$ components. This work implements hybrid generalized integrator (HGI) filters for filtering the $ \alpha \beta$ components of grid voltages and also provides its 90 $\circ$ delayed signals, which are useful in generating PSCs. Phase and frequency of the grid currents are decided by the unit active templates derived from the PSCs of the grid voltages, therefore, high-quality grid currents are injected into the grid even for abnormal grid conditions. For faster dynamics during variations in load power, HGI filters are used for quick and accurate estimation of fundamental components of load currents. Intermittent power generation from WEGS is compensated for by integrating a battery bank into the system. Along with high-quality power injection, the grid side converter operates the microgrid in off-grid mode (during grid outages) and provides smooth grid integration once the grid reappears. A 3.7 kW speed sensorless synchronous reluctance generator is used in WEGS, which is controlled by the machine side converter. The control techniques are validated in MATLAB /Simulink platform, and experimental validation is done on a prototype developed in the laboratory.

A High-Performance Microgrid With a Mechanical Sensorless SynRG Operated Wind Energy Generating System

In this article, a new control methodology is implemented for a microgrid consisting of wind-battery and the grid, which operates both under grid-connected mode and standalone mode. A synchronous reluctance generator (SynRG) with a new mechanical sensorless field-oriented control is used in the wind energy generation system (WEGS). The major issues present in the sensorless control of SynRG, due to the use of conventional integrator or low-pass filter during the flux estimation, are addressed in this article by implementing a fourth-order flux estimator. To compensate for the intermittent nature of the power generated from the WEGS, and to improve the reliability of the system pertaining to power availability, energy storage is included in the system. Controlled operation of the battery is ensured by using a bidirectional dc–dc converter, to enhance the longevity of the battery. Voltage source converters (VSCs) connected in a back-to-back configuration with a common dc-link is selected here so that a complete decoupling is achieved between the grid and WEGS. Grid-side VSC (GSC) is controlled, so that power quality at the point of common coupling is improved. The positive sequence components of grid voltages are extracted using observers to implement GSC control to avoid the adverse effects of unbalance and harmonic content in grid voltages. Design, modeling, and simulation of the system are done in MATLAB/SIMULINK platform, and a prototype developed in the laboratory is used for real-time validation.

Robust MMSOGI‐FLL control algorithm for power quality improvement of solar PV‐SyRG pico hydro‐BES based islanded microgrid with dynamic load

The islanded microgrids are vulnerable to stability problems during high penetration of dynamic loads like induction motors (IMs), which results in continuous oscillations in voltage and frequency, resulting in disturbances in the islanded microgrid. In this work, a modified multi-second-order generalised frequency locked loop (MMSOGI-FLL) control algorithm is implemented. This control provides a fast response of the power converter; thereby the microgrid voltage/frequency are stabilised rapidly. Besides, the control also provides the dynamic reactive power for the sudden start of an IM load and regulates the common coupling point voltage in the islanded system. The MMSOGI-FLL control also provides harmonics elimination, fast convergence, DC offset removal and reactive power compensation in the islanded system. The implemented islanded system is a combination of a pico-hydro-based synchronous reluctance generator (SyRG), solar photovoltaic (PV) array and a battery energy storage (BES). The BES is connected at DC link to maintain the power equilibrium under a change in the load and power generation. Moreover, the system used in this work is proficient in feeding the non-linear load and dynamic load of an IM. The performance of this standalone microgrid is validated with extensive tests on the developed prototype, which meets the power quality requirement of the 1547.4 standards.

A Reliable Microgrid Comprising Solar PV-WEGS and Battery With Seamless Power Transfer Capability

This article implements a new control method for a microgrid configuration comprising wind energy generation system, a solar PV array, a battery, local loads, and the utility grid, which provides a seamless transition of power during on-grid to off-grid operations and vice versa. This microgrid uses synchronous reluctance generator (SynRG) operated by a position (mechanical) sensor-less field-oriented control, for electric power generation from a variable speed wind turbine. The output of the solar PV array is connected to the dc-link of the microgrid through a dc–dc boost converter, whose output voltage is regulated at the desired value by the battery bank. For smooth synchronization and fast dynamic response, a fourth-order generalized integrator-based frequency-locked-loop with pre-filter (C-FGI-FLL) is implemented in this work. The use of C-FGI-FLL enhances the filtering capabilities of FGI-FLL under weak grid conditions, without affecting the computational burden. The C-FGI-FLL generates filtered input and its quadrature component, and these are used for the extraction of positive sequence components of the grid voltages. For faster dynamic response during load variations, C-FGI filters are used in each phase so that fundamental peaks of load currents are extracted accurately without any delay. The accurate and quick performance of this filter makes the system dynamics fast without deteriorating the performance. Simulation and experimental validations of this microgrid have been carried out both for dynamic and steady-state conditions.