Variable Speed Constant Frequency Research Articles

Research on fault detection and remote monitoring system of variable speed constant frequency wind turbine based on Internet of Things

In order to study the operating characteristics of variable speed constant frequency wind turbine under different working conditions and the monitoring system of wind turbine. In this paper, the simulation model of each component system of wind turbine is established by MATLAB/Simulink module, and the influence law of different wind speed and ground fault types on the output power of wind turbine is studied. The active power of wind turbines under different short-circuit fault types is compared. At the same time, in order to realize real-time monitoring of wind turbine speed and output power, an online monitoring system for wind turbine operation based on industrial Internet of Things is proposed, and the composition and operation characteristics of this remote monitoring system are given. The practical application shows that the on-line monitoring system can accurately and remotely monitor the running status of the wind turbine and avoid the unstable running of the wind turbine. The research conclusions of this paper can provide reference for the design and construction of wind turbines and the operation of connecting to the power grid.

A novel structure of magnetic geared generator in dual-rotor wind turbine

Variable-speed constant-frequency generating systems are commonly employed in wind turbines to enhance efficiency and minimize losses. Additionally, the utilization of dual-rotor wind turbines enables the capture of a greater amount of wind energy, leading to a significant increase in efficiency. Traditionally, dual-rotor wind turbines are managed by a full-scale power converter, and the rotor current is transmitted through brushes, which substantially raises the system's cost. To address these challenges, this study introduces a novel configuration that enables power control with a smaller power converter. In contrast to conventional dual-rotor wind turbines that generate power using both rotors, the proposed structure designates one rotor as a system controller. Apart from these benefits, the proposed structure greatly enhances conversion performance by notably improving the power factor. A comparison with existing configurations described in literature is conducted to demonstrate the superiority of the proposed structure.

Design of a Wound Rotor Brushless Doubly-Fed Machine With 1/5 Pole-Pair Combination

The brushless doubly-fed machine (BDFM) can be used in the variable speed constant frequency field. For BDFM, the choice of the pole-pair combination and the design of the rotor are significant. The output factor of the BDFM with 1/5 pole-pair combination is higher than that of the 2/4 pole-pair counterpart. However, the rotor of the BDFM with 1/5 pole-pair combination is hard to design for its wide pole-pair ratio. This paper presents a 1/5 pole-pair combination BDFM used in hydro power with a three-phase symmetrical wound rotor to solve the design challenge. First, the magnetic field modulation theory of the BDFM and the optimal output power in terms of different pole-pair combinations are introduced. Then, the slot-number phase diagram and the ampere-conductor wave method are applied to design windings of a BDFM with 1/5 pole-pair combination. Finally, the finite element (FE) models of the 1/5 and the 2/4 pole-pair combination BDFMs are established for comparison. A prototype of the 1/5 pole-pair combination is manufactured based on the proposed design scheme. Simulated and experimental results verified the feasibility of the design scheme.

Sliding mode control of brushless doubly-fed machine used in wind energy conversion system

This paper presents the applications of the sliding mode control to a brushless doubly fed induction generator (BDFG) used in wind-energy conversion systems. The controller is designed based on the sliding mode control combined with a the stator power winding flux oriented vector principle, the independent control of active and reactive powers has been developed and the performance of proposed the block diagram of the variable speed constant-frequency (VSCF) wind energy generation system is validated in the Matlab/Simulink environment and the computer simulation results obtained confirm the effectiveness of this control strategy.

Retracted: Simulation Analysis and Optimization Design of the Variable-Speed Constant-Frequency Doubly Fed Wind Power Generation Control System Based on PSCAD

Retracted: Simulation Analysis and Optimization Design of the Variable-Speed Constant-Frequency Doubly Fed Wind Power Generation Control System Based on PSCAD

A Permanent Magnet Brushless Doubly Fed Electric Machine for Variable-Speed Constant-Frequency Wind Turbines

A permanent magnet brushless doubly-fed electric machine is presented in this paper. This machine is developed for variable-speed constant-frequency wind energy generation applications. Differing from conventional doubly-fed electric machines based on induction machines, a permanent magnet rotor provides the magnetic field excitations for both the control winding and the power winding in the presented machine. The operating principle of the presented machine for the variable-speed constant-frequency operation is revealed in detail. Compared to a counterpart machine, the presented machine exhibits significantly improved back- electromotive force, torque/power density, torque per magnet volume, efficiency, etc. Finally, a proof-of-concept prototype of the presented machine is fabricated, and the corresponding experimental results are provided to verify the fact that the presented machine is capable of achieving the variable-speed constant-frequency function.

Research on control system for improving the grid-connected efficiency of small hydropower

Aiming at the problem of low efficiency at low flow in small hydropower stations, a permanent magnet direct-drive hydropower generation control system based on dual PWM converters is proposed to realize wide-range variable-speed constant-frequency hydropower generation of hydraulic turbine units and improve the comprehensive power generation efficiency of small hydropower stations. In this control system, the hydraulic turbine is coaxially connected to the permanent magnet synchronous generator(PMSG) through the flywheel, and the power grid is connected by back-to-back dual PWM converters, and the bidirectional energy flow is realized by the voltage space vector pulse width modulation method. The generator-side converter controls the rotating speed of hydraulic turbine units and tracks the optimal speed point of the hydraulic turbine units in real time to realize the maximum power output of hydraulic turbine units. The grid-side converter adopts active power and reactive power decomposition control method to stabilize the DC bus voltage and provide the reactive power required by the grid. Finally, the effectiveness of the proposed control system was proved by comparative experiments in a 400V/200kW/428rpm small hydropower station.

Design of a Brushless Doubly Fed Generator With Simplified Three-Phase Wound Rotor

The brushless doubly fed generator (BDFG) shows great potential for the variable speed constant frequency ship shaft power generation applications due to its high reliability and low system costs. The rotor topology, which directly couples two stator magnetomotive forces (MMFs) with different pole pairs, is essential for the BDFG. However, existing rotor topologies cannot have both strong magnetic field coupling ability and simple structure. To address this problem, this paper proposes a simplified three-phase wound rotor that can produce two MMFs with different pole pairs simultaneously. Useless harmonics are also eliminated to achieve strong magnetic field coupling ability. The complete design method of a novel integral-slot single-layer winding acting as a basic unit of the compound wound rotor is presented. Two sets of basic winding units are merged into one according to the principle of Ampere-conductor wave, whose approaches are also thoroughly developed with the design example. The maximum number of winding layers and the coil types are reduced to simplify the winding layout. Steady-state performances of a prototype generator are analyzed by both finite element simulations and experimental tests, which verify proposed design methods and schemes.

Research on variable speed constant frequency energy generation based on deep learning for disordered ocean current energy

As one of the most promising new energy sources today, ocean current energy has become an important part of energy strategies. There are short-term disorderly fluctuations in the flow rate of ocean current energy. The uncontrolled input of kinetic energy from the ocean current can lead to poor quality of power generated by current energy generators. The existing technology of current energy generation uses mechanical rigid transmission, which is prone to fatigue damage and low reliability under variable load fluctuations. In this paper, a joint simulation platform based on AMESim and Simulink is constructed based on 50kW hydraulic transmission and control power generation equipment. This paper establishes a mathematical model of the hydraulic transmission control system and proposes a constant frequency control algorithm based on a deep learning prediction model to improve the steady-state accuracy of the hydraulic motor speed. This paper proposes a deep learning prediction model based on EWT (Empirical Wavelet Transform)-LSTM (Long Short-Term Memory)-CNN(Convolutional Neural Network), which improves the prediction accuracy by 12.26% compared to short-term memory neural network. The model improves the motor speed dynamic accuracy by 90%, the standard deviation index by 78.11%, and the maximum deviation by 86.10% compared to the feed-forward Proportional Integral Derivative (PID)control algorithm. Therefore, the model can effectively improve the quality of the system’s power generation. At the same time, the time cost of the model for a single prediction is less than the sampling time of other control algorithms. In this paper, the simulation results are verified by a 50kW hydraulic transmission control experimental bench. The constant frequency control algorithm based on the deep learning prediction model can effectively improve the constant frequency dynamic accuracy of the motor of the hydraulic transmission control power generation equipment, which in turn improves the system power generation quality.

Maximum power point tracking algorithms for wind power generation system: Review, comparison and analysis

AbstractWind energy is one of the most important clean energies and the variable speed constant frequency technology is widely used in wind energy conversion systems. Maximum power point tracking (MPPT) is essential for a variable speed constant frequency wind power generation system. Concerning the current research on the MPPT algorithm, this paper studies the principle, characteristics, and reported improvement strategies of principal algorithms. Through the comparison of simulation results for selected control algorithms, the improved optimal torque control algorithm has been found to be the best MPPT algorithm for wind power generation systems because of its simplicity and efficiency. On this basis, further corresponding simulation runs are carried out to analyze the effect of the wind speed fluctuation characteristics on the systematic dynamic performance and power generation efficiency. The results show that the average wind speed, wind fluctuation frequency, and wind fluctuation amplitude can affect the performance of system operation and the efficiency of wind energy capture in different degrees, which has a great practical significance for the research of MPPT control strategy.

Minimization of DC-Link Capacitance for a DC-Link-Based Variable Speed Constant Frequency Aircraft Power System

DC-link-based variable speed constant frequency (VSCF) ac power generating system is being considered as one of the popular power architectures in the new generation aircraft to provide backup power to the 115 V, 400 Hz aircraft loads. These systems directly convert the variable frequency output of the generator to the fixed frequency of 400 Hz using a voltage source inverter. These inverters use dc-link capacitors that are heavy and space consuming. In aircraft, the weight requirement is very critical; hence, minimizing the dc-link capacitance is one of the major research challenges to achieve high power density in the VSCF power converter. In this article, novel control strategies to minimize the dc-link capacitance of the ac–dc–ac VSCF power converter are presented. The proposed control strategies enable to achieve 95% reduction in dc-link capacitance value when compared with the conventional control strategy, while the control is robust enough to meet MIL-STD-704F transient specification at the inverter output. The proposed strategies are validated through controller hardware-in-loop testing of the VSCF system based on an 80 kVA brushless synchronous generator and a four-leg inverter. The transient and steady-state operation of the VSCF system with a 95% reduction in dc-link capacitance has been verified for rated power operation.

Simulation Analysis and Optimization Design of the Variable-Speed Constant-Frequency Doubly Fed Wind Power Generation Control System Based on PSCAD

The depletion of nonrenewable energy and climate lead to increasingly bad environment. The efficient development of new energy has become an urgent problem to be solved. As a kind of new energy, how to effectively develop and utilize wind energy has aroused widespread concern all over the world. In this paper, a three-phase static a-b-c coordinate system is used for transformation. Taking the variable-speed constant-frequency doubly fed wind power generation system as the control object, the technology of generator power decoupling control is realized. The rotor side and grid side power converters adopt vector control methods based on stator flux orientation and grid voltage orientation, respectively. In this paper, the motion equation, flux equation, voltage equation, and electromagnetic torque equation of the motor are established. Vector-oriented control technology is used to control the generator. The control model of the VSCF doubly fed wind power generation system is established by using the simulation software PSCAD, and the simulation experiment is carried out. The feasibility of the power decoupling control method based on vector control is verified. The change trend of the active power of the power generation system is consistent with that of the wind speed, which shows that the control system has good stability. Using the field-oriented vector control method, the dual PWM controller can independently control the active power and reactive power. This greatly simplifies the nondecoupling control function equation in the expression. The dual PWM controller is well adjusted to minimize the power loss of the wind power generation system.

Event-triggered mechanism based robust fault-tolerant control for networked wind energy conversion system

In this paper, a novel robust fault-tolerant control scheme based on event-triggered communication mechanism for a variable-speed wind energy conversion system (WECS) with sensor and actuator failures is proposed. The nonlinear WECS with event-triggered mechanism is modeled based on the Takagi–Sugeno (T–S) fuzzy model. By Lyapunov stability theory, the parameter expression of the proposed robust fault-tolerant controller with event-triggered mechanisms is proposed based on a feasible solution of linear matrix inequalities. Compared with the existing WECS fault-tolerant control methods, the proposed scheme significantly reduces the pressure of network packet transmission and improves the robustness and reliability of the WECS. Considering a doubly-fed variable speed constant frequency wind turbine, the event- triggered mechanism based fault-tolerant control for WECS is analyzed considering system model uncertainty. Numerical simulation results demonstrate that the proposed scheme is feasible and effective.

Active and Reactive Power Control for Dual Excited Synchronous Generator in Wind Applications

This paper presents a dual excited synchronous generator (DESG) as a novel suitable alternative generation system for wind energy conversion systems. A new control strategy was proposed for the DESG wind turbine system. With this control technique, the DESG could be operated as a constant-speed constant-frequency (CSCF) generation system with the benefit of adjusting the reactive power or as a variable-speed constant-frequency (VSCF) generation system with the benefits of simple control methods and lower copper losses. Using the space phasor model of the DESG, a direct relationship between the electromechanical torque and the armature reactive power in terms of the field current space phasor magnitude and the field voltage space phasor angle is provided. The proposed control strategy is based on controlling the field-current space phasor magnitude and the field-voltage space phasor phase angle to regulate the active and reactive powers of the DESG. Simulation results, based on MATLAB/SIMULINK, for a 1.1 kW DESG wind turbine system have been executed to verify the introduced control technique under various operating conditions. Also, experimental studies have been carried out to validate the simulation results using the proposed control algorithm.

Vienna Rectifier-Fed Squirrel Cage Induction Generator Based Stand-Alone Wind Energy Conversion System

Back-to-back voltage source converters are normally preferred for interfacing squirrel cage induction generators (SCIG) with loads in stand-alone wind power generation applications as they allow for maximum power point tracking. However, the total converter losses tend to be very high, especially near the rated wind speed. Therefore, to reduce the power converter related losses, a Vienna rectifier is utilized as the machine-side converter in this article to interface the SCIG. Owing to the limited reactive power handling capability of the Vienna rectifier, a fixed capacitor bank is also required to provide the excitation VAR for the variable speed SCIG. In this article, a new computational method is proposed to calculate the value of this fixed capacitance based on maximizing the yearly energy output from the wind energy conversion system. A voltage sensorless vector control scheme for the Vienna rectifier-fed SCIG with the reference frame oriented along the machine terminal voltage is also proposed, which adheres to the operating limits of the Vienna rectifier and gives much better dynamic performance under load and wind speed transients compared to similar Vienna rectifier based variable speed constant frequency generating systems reported earlier in the literature.

Simulation and control of DFIGs connected to the grid

Due to the development of renewable energy generations, the reasonable grid-connected control strategy for wind turbines is of great significant. Doubly-fed Induction Generator (DFIG) is one of the variable speed constant frequency (VSCF) motors, which is regarded as the object in this paper. To decouple the control of active and reactive power, the strategies for both grid-side and rotor-side converter are designed. The simulation model of DFIG is built with MATLAB/Simulink software, and the grid-connection simulation experiment is carried out.

Power decoupling control of DFIG rotor‐side PWM converter based on auto‐disturbance rejection control

AbstractIn this paper, double PWM converter AC excitation system of the variable speed constant frequency doubly fed induction generator (DFIG) for wind power generation is taken as the research object. At present, most vector control systems of rotor‐side PWM converter adopt feedforward compensation to realize the purpose of power decoupling control. The decoupling effect is greatly affected by the power changes. A power decoupling control strategy based on auto‐disturbance rejection control (ADRC) is proposed. The decoupling control between active power and reactive power is realized by observing the coupling term and the total disturbance of the d‐axis and q‐axis components of the stator current and the stator voltage with the extended state observer and compensating. Simulation analysis and experimental test show that, on the basis of vector transformation, the rotor‐side PWM converter power decoupling control based on ADRC has a small overshoot and fast dynamic response when tracking the change of wind turbine input power, which can achieve the decoupling control between active power and reactive power well. The system has strong robustness and adaptability.

Impact Analysis of Increased Penetration of Variable Speed Constant Frequency Wind Power Generation on Power System Stability

Wind energy has the characteristics of randomness and intermittency. The simulation of the dynamic process on the medium and long-term time scale caused by this is of great significance to the planning and operation of power systems containing wind power. The paper discusses the operating principle of AC-excited variable-speed constant-frequency wind power generation system, analyzes the operating characteristics and control objectives of doubly-fed asynchronous wind generators before and after grid connection, and studies the grid connection of generators based on stator flux-oriented vector control technology Control and tracking control of maximum wind energy. The simulation analysis of the fault disturbance process of the power grid system with variable speed and constant frequency wind turbines, the results verify the correctness of the modeling.

A hybrid reference current extraction technique with multi-functional capability for shunt active filter in all-electric aircraft

All-Electric Aircraft (AEA) is most commonly used as an airbus system and is more efficient than conventional civil aircraft. One of the major power quality issues in AEA is the generation of harmonics. Harmonics in the AEA are due to nonlinear operations required to meet various electrical loads. Shunt Active Filters (SAFs) were used to mitigate the harmonics in Variable Speed Constant Frequency AEA systems. Time-domain techniques, such as real and reactive (p-q) power and synchronous reference frame (SRF), are having their own pros and cons. In this research paper, inverse matrix averaging pq-SRF (IMApq-SRF) control for SAF, a novel reference current control strategy is proposed that combines the features of both p–q and SRF techniques. The proposed control strategy is adaptable for all abnormal conditions in AEA like unbalancing, dynamic, distorted supply and transient conditions and the same was validated through mathematical modelling and performing MATLAB.

О современных решениях машинно-электронных генерирующих систем для малой энергетики и подвижных объектов

It is often believed that wind energy today is not always a profitable (in business terms) electricity generating technology. There is no doubt, however, that this environmentally clean technology with an inexhaustible resource implies its widespread use not only in the near future, but also nowadays under the appropriate conditions. In the final analysis, the interests of national security play a decisive role here, and, hence, the priority in solving the problem of power supply availability and the country’s security through the development of small-scale power generation (including, above all, the development of wind and hydropower industries) remains to be decided at the state level. Higher reliability of autonomous power supply (APS) and the renewable nature of energy resources used by it are the factors determining the fundamental difference between the APS for geographically dispersed consumers that are located far away from centralized power lines. The first design-and-organizational objective, which should be addressed in a particular country, is to compile a map of the distribution of wind and hydropower resources, based on which the advisability of using this technology should be analyzed. The second objective is to use the most rational technical solutions for wind (hydro) electrical installations. The article considers the structures of alternative versions of installations that are presented only by a comprehensive electrical package in the form of a combined machine-and-electronic generating system of the «variable speed-constant frequency» type. Synchronous and asynchronous machines are considered as converters of mechanical energy into electrical energy. The second version implies the use of induction machines with a squirrel-cage rotor and with a phase rotor. The mechanical energy converters operate jointly with an electronic frequency converter, which can be embodied as two series-connected four-quadrant converters. The article presents a brief comparative analysis of five wind turbine structures operating autonomously and in parallel with the grid. The results of computer simulation of the most rational options are presented. The aim of the study is to give an idea to the developers about the modern solutions for constructing comprehensive electrical packages for wind power systems and to simplify the procedure of selecting the most rational solution.