Tracking performance and stability play a major role in observer design for speed estimation purpose in motor drives used in vehicles. It is all the more prevalent at lower speed ranges. There was a need to have a tradeoff between these parameters ensuring the speed bandwidth remains as wide as possible. This work demonstrates an improved static and dynamic performance of a sliding mode state observer used for speed sensorless 3 phase induction motor drive employed in electric vehicles (EVs). The estimated torque is treated as a model disturbance and integrated into the state observer while the error is constrained in the sliding hyperplane. Two state observers with different disturbance handling mechanisms have been designed. Depending on, how they reject disturbances, based on their structure, their performance is studied and analyzed with respect to speed bandwidth, tracking and disturbance handling capability. The proposed observer with superior disturbance handling capabilities is able to provide a wider speed range, which is a main issue in EV. Here, a new dimension of model based design strategy is employed namely the Processor-in-Loop. The concept is validated in a real-time model based design test bench powered by RT-lab. The plant and the controller are built in a Simulink environment and made compatible with real-time blocksets and the system is executed in real-time targets OP4500/OP5600 (Opal-RT). Additionally, the Processor-in-Loop hardware verification is performed by using two adapters, which are used to loop-back analog and digital input and outputs. It is done to include a real-world signal routing between the plant and the controller thereby, ensuring a real-time interaction between the plant and the controller. Results validated portray better disturbance handling, steady state and a dynamic tracking profile, higher speed bandwidth and lesser torque pulsations compared to the conventional observer.
IPT (inductive power transfer) charging is a highly flexible concept that allows for charging at any possible opportunity and is highly versatile for vehicles of all sizes. IPT wireless charging technology employs high-power inductive energy transfer between the components embedded into streets and the receiving equipment mounted below the vehicle. When the vehicle moves over the charging point, the contactless charging process is initiated between the components and the vehicle. In this work, the role of power converter topologies in IPT systems are studied for electric vehicle (EV) charging applications. Further, the predominant topologies are compared and analyzed in detail. The contingency in misalignment, loading and frequency shift are discussed for various converter topologies. The tolerance in misalignment poses serious challenges for wireless chargers in EVs. Therefore, there is currently a need to design a symmetric IPT system with multiple decoupled receiving coils. The significance of power inverter topologies for achieving resonance, as well as the generation of high-frequency supply, has been studied in detail. Experimental waveforms that are related to the explanations in this work are provided to substantiate the advantages regarding the converters.
Speed Estimation without speed sensors is a complex phenomenon and is overly dependent on the machine parameters. It is all the more significant during low speed or near zero speed operation. There are several approaches to speed estimation of an induction motor. Eventually, they can be classified into two types, namely, estimation based on the machine model and estimation based on magnetic saliency and air gap space harmonics. This paper, through a brief literature survey, attempts to give an overview of the fundamentals and the current trends in various machine model based speed estimation techniques which have occupied and continue to occupy a great amount of research space.
The purpose of smart grid architecture as compared to the conventional grid is to ensure more stability, reliability and bi-directional communication between the utility and the consumer. The deployment of the same has succeeded in improving the efficiency of the distribution systems and effective co-ordination and interoperability among the different components of the grid. Smart inverters play a major role in seamless grid integration, control and conversion of power when the renewable energy sources are present. However, they come with several security challenges as well, which are of considerable concern. Certain cyber threats include physical and cyber attacks, natural phenomena which in turn can lead to grid failure, blackouts, commercial energy losses, privacy and safety issues, etc. Therefore, there is a need for critical examination of all these issues which must be considered for designing cyber secure smart inverters at the distribution level. In this comprehensive review, keeping the technological perspective in mind, the existing gaps and the necessity for the same are highlighted. The various topologies, IEEE protocols and the control strategy are presented in detail. This will enable prospective researchers to address the design issues of smart inverters with greater focus on security and reliability aspects.
Sensors of any kind contribute to extra space and electronics when they are used in any application. Besides, the sensor noise also has the effect of altering the overall gain of the system. This is more prevalent in non-linear systems like motor control. In applications which have strict space constraints like Electric vehicles, the use of sensors must be optimized, which, in turn, gave rise to many sensorless state estimation strategies. This paper proposes a novel sensorless control technique for brushless direct current (BLDC) motor used in electric vehicle applications. The concept of sensorless control in BLDC Motor drive eliminates the hall-effect position sensor, thereby giving better performance and improves the robustness of the overall drive system. The main objective of this work is to estimate the position of the motor at standstill condition using stator saturation effect concerning the rotor, accelerate the motor from standstill so that enough back EMF is generated. This acceleration technique speeds up the motor to a stage where a self-actuating control mechanism is used to generate control signals with back EMF or line voltages. The motor can be started with a load, which is a significant constraint for electric vehicle application. The proposed method will avoid the reverse rotation of the motor. The proposed work is simulated in Matlab/Simulink software, and results obtained show that it works well under dynamic conditions of starting, acceleration and load switching. The hardware setup of the proposed work is developed using the TMS320F2812 DSP processor. Simulation and experimental results validate the effectiveness of the proposed work for electric vehicle application.
Abstract:The purpose of this work is to present an adaptive sliding mode luenberger state observer with improved disturbance rejection capability and better tracking performance under dynamic conditions. The sliding hyperplane is altered by incorporating the estimated disturbance torque with the stator currents. Also, the effects of parameter detuning on the speed convergence is observed and compared with the conventional disturbance rejection mechanism. The entire drive system is first built in simulink environment. Then, the simulink model is integrated with RT-Lab blocksets and implemented in a relatively new real-time environment using OP4500 real-time simulator. Real-time simulation and testing platforms have succeeded offline simulation and testing tools due to their reduced development time. The real-time results validate the improvement in the proposed state observer and also correspond to the performance of the actual physical model.
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