Rotor Flux Oriented Vector Control Research Articles

Parameter Estimation and Online Adaptation of Rotor Time Constant for Induction Motor Drive

The performance of a sensor-based rotor flux-oriented vector control induction machine drive is highly influenced by the estimated value of the rotor time constant/rotor resistance which varies continuously with temperature when it is driven with the variable loads. Therefore, to achieve accurate torque control, online tunning of the rotor time constant is necessary. This article proposes a novel and simple adaption technique to estimate the rotor time constant. In this proposed method, the reference model of the rotor flux vector is derived using the voltage model of the induction machine, which is independent of the rotor time constant. The current controller uses the model of the rotor flux vector that is derived using the current model of the induction machine. This current model is dependent on the rotor time constant. The error between the rotor flux vectors derived using the current model and the voltage model is minimized using the least-squares method. In this process, the rotor time constant is always tuned to its actual value. The article also presents a simple approach to estimate the parameters of induction machine like the stator resistance, the net leakage inductance, and the initial value of the rotor time constant in an offline mode at a standstill condition. To validate the proposed algorithm, two experimental prototypes are developed for two different power ratings of 3.7 and 67 kW. Experimental results from these prototypes confirm the effectiveness, reliability, and stability of the proposed algorithm both in the motoring and regenerative modes of operation. This method of the adaptation of the rotor time constant is simple and, therefore, useful for practicing engineers.

A Simple Flexible and Robust Control Strategy for Wind Energy Conversion Systems Connected to a Utility Grid

This paper presents a simple and robust control strategy for a variable speed wind turbine conversion system using a squirrel-cage induction generator and a three-phase voltage source (AC/DC/AC) Pulse Width Modulation (PWM) converter connected to the utility grid through an LCL filter. The control strategy integrates for the generator side an adaptive radial basis function (RBF) neurosliding mode controller associated with the rotor flux oriented vector control which is used to regulate the turbine rotation speed, rotor flux, and the DC bus voltage. For the grid side, the inverter current and voltage regulation as well as the current injected into the grid are regulated by PI controllers for two modes of operation, namely, the stand-alone mode and grid connected mode. The main contribution of this article is the introduction of a new and simple control algorithm allowing automatic mode switching method based on wind speed. The proposed scheme is very efficient and can be easily implemented in practice. Simulation results illustrate the effectiveness and feasibility of the proposed algorithm.

Design of Speed Control System for PMSM Based on Three-Level Structure

三相永磁同步电机在节约电能方面具有非常广阔的前景，它具有结构简单、体积小、效率高、易于散热和维护简单等优点。相比传统的两电平逆变器，三电平逆变器具有很多优点：单管耐压低、开关损耗降低、谐波含量小等，因此将三电平技术应用到永磁同步电机调速系统中，具有重要的理论意义和实用价值。本文主要研究了基于三电平中点箝位型(NPC)逆变器的永磁同步电机(PMSM)调速系统。电机采用转子磁场定向的矢量控制。为了达到控制目的，在三电平逆变器控制系统中引入了零序电压注入法。这种方法很好地控制了中点电压的平衡，以期降低逆变器输出电压谐波含量，改善电机定子电流波形，这将减小电机转矩脉动，改善电机控制性能。本文介绍了永磁同步电机的数学模型和矢量控制方法，阐述了中点箝位型三电平逆变器的拓扑结构和换流模式，分析了中点电位平衡算法和调制策略，最后通过实验验证了系统的可靠性和稳定性。 The three-phase PMSM has a very broad prospect in saving electrical energy. It has the characte-ristics of simple structure, small volume, high efficiency and good heat radiation. Compared with conventional two-level inverters, three-level inverter has a series of advantages such as low vol-tage-proof for single transistor, low switching loss and low harmonic content, etc. Therefore, it is of great theoretical significance and practical value to apply the three-level inverter to the speed regulating system of permanent magnet synchronous motor (PMSM). In this paper, the speed regulating system of permanent magnet synchronous motor on the basis of three level neutral point clamped (NPC) inverter is studied. Rotor flux oriented vector control method is applied on the motor. In order to implement the control process, zero sequence voltage injection method is introduced in the proposed three-level inverter control system. With this method, the balance of the neutral point voltage can be well achieved to reduce the harmonic content of the output voltage of the inverter and improve the stator current waveform, which will further minimize the motor torque ripple, and improve motor control performance. The mathematical model and vector control method of PMSM are introduced in this paper, both the topology and commutation mode of three-level inverter with neutral point clamping mode are described, and the neutral point potential balance algorithm and modulation strategy are also analyzed. Finally, the experiment verified the reliability and stability of the system.

The Optimization of Power Smoothing Control Strategy for Wind Farm Based on Flywheel Energy Storage Device

The instability and intermittency of wind makes the output power of the wind turbine randomness and volatility. Due to its fast pulse response and high charge-discharge rate, the flywheel energy storage can effectively reduce the power fluctuations caused by the wind farm. This article optimized the control strategy for the permanent magnet synchronous motor (PMSM) based flywheel energy storage system to reduce the active power fluctuations. Fuzzy inference method is used to make the desired smoothing active power value more precise. The rotor flux oriented vector control strategy with improved proportional resonant controller (PR controller) is proposed based on the mathematical model of PMSM to improve the robustness of the system in current control.

Based on Sliding Mode Variable Structure Current Controller for Induction Motor Vector Control Technology

In this paper, according to the induction motor in rotating coordinate system mathematical model, established based on rotor flux oriented vector control model and realized flux linkage and torque decoupling. In order to solve the current high coupling, designed the sliding mode variable structure control algorithm of current controller. Based on the sliding mode variable structure control algorithm achievable conditions and Lyapunov stability theorem, proved that the sliding mode of accessibility and stability, determined the sliding model parameters. The simulation results show that the sliding mode variable structure control of induction motor vector control system, can reduce the torque ripple and the speed overshoot and improve the system parameter perturbation and external disturbance signal robustness.

Study on the Vector Control of PMSM Based on a New Controller

Based on anglicizing characteristics of the proportional resonance controller (resonant, PR), against the defects of the PR controller, combined with permanent magnet synchronous motor mathematical model, a rotor flux oriented vector control strategy based on a novel improve the PR controller is introduced. Finally, MATLAB /simulink was used to simulate the model above. The system got good dynamic and static responses, verifying the correctness and feasibility of the proposed method.

Study and Implement on the Control System of Traction Locomotive Based on Torque Current Closed-Loop

In order to overcome the poor stationarity of traction locomotive during the operation mode switching, with rotor flux oriented vector control theory based on, torque model control strategy is adopted. It can overcome the DC bus pumping as Locomotive deceleration and barking. In this system, output torque can be controlled directly, experiments verify the system has good performance of stability and reliability, which can meet the traction locomotive control requirements.

A new control strategy with saturation effect compensation for an autonomous induction generator driven by wide speed range turbines

This paper presents a variable speed autonomous squirrel cage generator excited by a current-controlled voltage source inverter to be used in stand-alone micro-hydro power plants. The paper proposes a system control strategy aiming to properly excite the machine as well as to achieve the load voltage control. A feed-forward control sets the appropriate generator flux by taking into account the actual speed and the desired load voltage. A load voltage control loop is used to adjust the generated active power in order to sustain the load voltage at a reference value. The control system is based on a rotor flux oriented vector control technique which takes into account the machine saturation effect. The proposed control strategy and the adopted system models were validated both by numerical simulation and by experimental results obtained from a laboratory prototype. Results covering the prototype start-up, as well as its steady-state and dynamical behavior are presented.

A Luenberger-sliding mode observer with rotor time constant parameter estimation in induction motor drives

The performance and efficiency of an induction motor drive system can be enhanced by online estimation of critical parameters such as rotor time constant. A novel Luenberger-sliding mode observer with a parameter adaptation algorithm is proposed in this paper to compensate for the parameter variation effects. The observer is comparably simple and robust relative to the previously developed observers, and yet suitable for online implementation. Simulation studies for the proposed method were conducted in a MATLAB environment. Observer constants and the control parameters were tuned during the simulation studies and used during the experimental study stage. Experimental verification of the developed algorithm was performed with an induction motor using the rotor flux-oriented vector control. The comparative results and related overall conclusions are presented accordingly.

Comparative study of stabilising methods for adaptive speed sensorless full-order observers with stator resistance estimation

The full-order Luenberger flux (FOLO) observer combined with adaptive techniques is the most widely used method for sensorless vector-controlled drives in induction machines. These methods suffer inherently from an unstable regenerating region and the unobservable zero stator frequency operating point. Stator resistance estimation is also required in the low speed region leading to a complicated multiple-input multiple-output (MIMO) system, and a novel simplification of the MIMO system into a single-input single-output (SISO) system based on the two-time-scale approach is proposed for a simple stability analysis procedure. Four different stabilisation strategies are suggested for this comparison, based on the main stabilisation methods found in the literature. The `augmented error signal` and the `observer gains retuning' methods, based on the Routh-Hurwitz criterion, are used for the stabilisation of the motor speed estimator. The stator resistance stabilisation has been implemented using the `augmented error signal` method. This has been evaluated using two different gain tuning methods, one based on the Routh-Hurwitz criterion and the other on the averaging analysis technique. The different stabilising strategies are evaluated theoretically according to the simplified SISO system open-loop transfer function zeroes and compared by simulation and extensive experiments. The suggested observer is flexible for any vector controlled drive and results have been validated in a 7.5 kW experimental test bench for rotor flux-oriented vector control (RFOC) and indirect self-control drives. The stability and behaviour of the sensorless scheme are successfully verified for all operating conditions above 0.4 Hz stator frequency.

Vector control of autonomous induction generator taking saturation effect into account

In this paper, we present the voltage build up process and the terminal voltage control of an isolated wind powered induction generator driven by a variable speed wind turbine using rotor flux oriented vector control. A description of the studied system is provided, and a simulation study is presented. The model used for the autonomous induction generator is a diphase one obtained by application of the Park transform. This model permits, when adopting some simplifying hypotheses, taking account the saturation effect. Wind powered isolated induction generators have an input, wind, that is not controllable, but they can be set to operate within a given variation of speed. Unlike a grid connected induction generator, in an isolated case, there should be a control system that keeps the DC bus voltage at a constant value when the speed of the rotor varies. The paper presents the control system to maintain the DC bus voltage at a constant value. The obtained results are presented and discussed.

Estimation of induction machine inverse rotor time constant using torque angle tangent calculation

A new inverse rotor time constant estimation scheme for an induction machine is presented. For high performance induction machine control, indirect rotor flux oriented vector control is the most commonly applied control technique. It requires that an accurate estimate of the inverse rotor time constant is obtained to ensure correct orientation of the current vector with the rotor flux vector. An incorrect estimate will result in an incorrect flux level, reduced dynamic torque performance and reduced maximum available torque. A novel parameter estimation scheme is presented, based on the calculation of the tangent of the torque angle. The effectiveness of the technique is demonstrated through simulation and practical results.

Adaptive high bandwidth current control for induction machines

For high performance induction machine control, the technique of indirect rotor flux oriented vector control is commonly utilized. The torque performance of this technique is significantly affected by the performance of the current control loops. In this paper a new adaptive high bandwidth current controller for induction machines is presented. The technique is derived and validated through simulation and experimental results. The new architecture is shown to achieve a dead-beat response, with a rise time of one sample period and no overshoot, when the inverter voltage limit is not exceeded. When the voltage limit is exceeded the current response is achieved in a minimum time with no overshoot. It is shown that the new control technique achieves similar dynamic response to the conventional dead-beat control scheme while eliminating parameter sensitivity issues. It is demonstrated that the new algorithm offers higher bandwidth than the commonly used synchronous frame proportional plus integral control technique while maintaining good steady state performance.