Venkata Ramana Kasi

Abstract: In this brief, an online relay autotuning scheme for parameter estimation of a class of time delayed systems is presented. The identification method comprises a relay and a proportional-derivative (PD) controller which helps in yielding sustained oscillation or limit cycles at the system output around the user defined setpoint. Along with the relay and controller parameters, the important limit cycle information are measured and further substituted in the derived set of mathematical expressions required for the estimation of system unknown dynamic in the form of under-damped second-order plus dead-time (SOPDT) model. Simulations of well known model dynamics from the literature are considered to illustrate the efficacy of the proposed scheme in presence of noise and static load disturbance. For the real-time validation of the proposed scheme, a pipe-line water pressure control system is identified as under-damped SOPDT transfer function model.

Abstract: In this paper, identification and control of a process whose dynamics can be described by a second-order-plus-dead-time (SOPDT) stable/unstable model is presented. Using the state-space approach and limit cycle information, analytical expressions are derived to identify the process dynamics. The wavelet decomposition is performed to recover a noise-free limit cycle output which is generally contaminated by measurement noise. The proportional–integral–derivative controller connected in the feedback loop is designed primarily to get good load disturbance rejection for the identified process. Reference tracking is achieved with the help of a set-point filter. The direct synthesis method with single tuning parameter is used to tune the controller parameters. The best value of the tuning parameter is selected using the particle swarm optimization algorithm in such a way that a good performance measure of the closed-loop system is achieved.

Abstract: The process parameters for first-order-plus-dead-time (FOPDT) and second-order-plus-dead-time (SOPDT) stable processes are obtained using relay feedback test with the help of dual input describing function (DIDF). The limit cycle data is used to identify the unknown process parameters. This paper presents identification of stable FOPDT and SOPDT process for the cases with and without load disturbance. The relay settings are unchanged during load disturbance. The bias caused due to load is incorporated in the relay approximation using DIDF. This is used to obtain the parameters for both the cases. An on-line relay feedback test using a proportional integral and derivative (PID) controller is performed to obtain the unknown parameters.

Abstract: Voltage support to the Distribution Node (DN) is necessary requirement due to fluctuations of time varying reactive load. The Photovoltaic's Arrays (PAs) and Electric Vehicles (EVs) provide active and reactive power support to DN. Voltage support can be achieved at DN node from RES and EVs. In this paper, coordination of EVs and PAs are integrated with DN to improve the voltage profile. The coordination can be achieved by providing active and reactive power support through PAs and the EVs charge/discharge (support/inject) based on the node voltage. The bulk numbers of EVs are connected to the DN through point of common coupling (PCC) which is called as Charging Station (CS). Many PAs are used to generate power for DN support; it's known as DN Supporting Point (DNSP). The main focus of this work is to predict the most accurate location of CS and DNSP. A 33kV Distribution System (DS) of Guwahati city is modeled in MATLAB Simulink environment with four types of active and reactive load profiles. Typical DS having 48 nodes, the CS and DNSP are connected in each node of the DS. To control the power flow of the CS and DNSP, fuzzy based control strategies and optimal aggregator has been implemented. Also, probability distribution function has been used to find the scheduled arrival of EVs at CS. Voltage, power and energy of the CS and DNSP are compared.

Abstract: In this paper critically damped system is identified using online relay feedback test. Relay test comprises of a PID controller connected in parallel with the relay. Limit cycle information ultimate gain and frequency are used for the identification process. The objective of the proposed method is to identify an nth order critically damped system with the same order. Simple expressions for the process parameters are derived which can be used for higher order critically damped systems. The proposed identification method is tested with different examples. Identification is also done under load disturbance using DIDF (Dual input describing function).

Abstract: Electric vehicle (EV) fleet is constantly increasing over the years and higher adoption is expected in the coming decades A key aspect to support and boost the EV uptake is the adequate availability (number, locations and sizes) of fast charging stations (FCSs) to enable inter-and intra-city travels Since these studies require modelling large regions with uncertainties, a methodology able to provide the least-cost solution is needed This study proposes a scalable methodology that integrates high-resolution traffic flow and multi-phase electrical simulations to find the number, locations and sizes of FCSs at the least societal cost considering the uncertainties in driving patterns It determines potential FCSs locations based on traffic flow and progressively explores these FCSs quantifying capital (equipment and land) and indirect (loss of productivity and reinforcements) costs to identify the least-cost solution Results from a Brazilian case study comprising of a metropolitan region with six cities and 26 primary substations show that, with high adoption of EVs, the investments in equipment represent the most significant components of societal cost Moreover, for metropolitan regions, the societal least-cost solution is found with more but smaller FCSs Finally, is found that neglecting the loss of productivity can significantly affect the results

Abstract: This brief presents a novel energy-shaping technique-based speed controller for permanent-magnet synchronous motors (PMSMs) considering machine nonlinearities and load and parameter changes. There are three features: The time-varying damping term is injected into the speed loop, which is automatically updated by the proposed self-tuner. The disturbance observers are designed for both the speed and current loops to achieve better disturbance rejection performance with removal of offset errors without the use of tracking error integral actions. Furthermore, the closed-loop analysis result is provided to demonstrate its beneficial closed-loop properties. The practical advantages are experimentally verified in several convincing scenarios with a prototype 500-W PMSM driven by a three-phase inverter.

Abstract: This brief presents an advanced proportional-derivative (PD) voltage control mechanism for DC/DC boost converters suffering from the parameter and load variations. The proposed controller eliminates the requirement for current feedback by designing the first-order observer estimating the voltage derivative without the use of converter parameters, which corresponds to the first contribution. As another contribution, a specific feedback gain structure for PD-loop and the active damping component guarantees the first-order closed-loop transfer function from the reference to the output voltage by the stable pole-zero cancellation. A prototype bi-directional 3-kW boost converter experimentally validates the closed-loop performance of the proposed technique.

Abstract: This brief presents design, development and real-time implementation of a robust decentralized PID controller based on complementary sensitivity function through a graphical tuning method for a multivariable system. ${H_{\infty }}$ criterion is adopted to find out the controller parameters of the proposed robust decentralized PI controller. To verify efficacy of the proposed controller, its performance is compared with that of other decentralized PI controllers. The proposed controller is implemented in real-time on a coupled tank liquid level system. From the simulation and experimental results obtained, it is observed that the proposed controller exhibits superior control performance over other decentralized PI controllers.

Abstract: In this article, increment count method (ICM) is proposed as a novel approach for simultaneous steady-state detection and transportation time delay estimation for industrial processes. The concept of ICM is presented, and its implementation issues are discussed. Especially, the simplicity and very low computational complexity of ICM are addressed, which support its practical implementation. Then, as a practical example, ICM is used as a part of the autotuning algorithm dedicated for reduced-order active disturbance rejection controller with Smith predictor (RADRC+SP). Jointly with dedicated optimization algorithm, it allows for identification between the first or second order of process dynamics. The results of this identification allow for effective tuning of RADRC+SP based on the novel tuning rules. The practical aspect includes programmable logic controllers (PLC) based implementation of both autotuning and RADRC+SP controller in the form of the general-purpose function blocks. The experimental validation shows the practical applicability and superiority of the proposed methods.