Jayati Dey

Sliding-Mode Control of PWM Dual Inverter-Based Grid-Connected PV System: Modeling and Performance Analysis

This paper proposes a novel robust and adaptive sliding-mode (SM) control for a cascaded two-level inverter (CTLI)-based grid-connected photovoltaic (PV) system. The modeling and design of the control scheme for the CTLI-based grid-connected PV system is developed to supply active power and reactive power with variable solar irradiance. A vector controller is developed, keeping the maximum power delivery of the PV in consideration. Two different switching schemes have been considered to design SM controllers and studied under similar operating situations. Instead of the referred space vector pulsewidth modulation (PWM) technique, a simple PWM modulation technique is used for the operation of the proposed SM controller. The performance of the SM controller is improved by using an adaptive hysteresis band calculation. The controller performance is found to be satisfactory for both the schemes at considered load and solar irradiance level variations in simulation environment. The laboratory prototype, operated with the proposed controller, is found to be capable of implementing the control algorithm successfully in the considered situation.

Periodic Compensation of Continuous-Time Plants

This note presents a periodic compensator which achieves robust stability for single-input-single-output (SISO), linear time invariant (LTI) plants having both right-half plane (RHP) poles and zeros, a job LTI controllers fail to do. In addition, for strictly proper plants this controller achieves model matching ensuring at the same time that the periodic oscillations present in the plant output are insignificant in magnitude. The design steps are straightforward and linear algebraic in nature

Robust voltage regulation of DC-DC PWM based buck-boost converter

This paper investigates the performance of DC-DC PWM based buck-boost converter with two degree-of-freedom (2 DOF) control to meet the loop robustness goals as well as to shape the output voltage response according to requirement. The design technique of this controller is simpler than that of the robust control techniques, such as H∞, control, μ-synthesis, applied in literature for converters. Moreover, 2 DOF control is already established in literature to provide robust compensation to boost converter. The performance of the buck boost converter is examined in the presence of (i) 60% perturbation in load current, (ii) 25% perturbation in input voltage and (iii) high frequency measurement noise. The 2 DOF control scheme has been shown to achieve the output regulation and obtain fast recovery in output voltage response, through simulation.

Cascaded two level inverter based grid connected photovoltaic system: Modelling and control

In this paper, isolated source cascaded two level inverter (CTLI) has been proposed for grid connected photovoltaic system. The system is operated to supply active power with available solar irradiance and to supply reactive power in absence of it. The conventional CTLI is controlled through vector control topology to provide controlled active and reactive power in the said conditions. The photovoltaic system is modelled and tested with the controlled grid connected CTLI, for solar irradiance variation, and reference reactive power variation in simulation environment. The control scheme has been introduced for dc link voltage of the dual level inverter. The dc link voltage is found to be maintained at required level for both type of power supply.

Design and performance analysis of two degree-of-freedom (2 DOF) control of DC-DC boost converter

The application of the two degree-of-freedom (2 DOF) theory to control non-minimum phase DC-DC switching converters is investigated in this paper. The robust control techniques mostly used to attain a regulated output voltage, even under perturbed condition, for DC-DC boost converter are, H∞ (both linear and nonlinear), μ-synthesis, genetic algorithm, linear quadratic regulator (LQR) control. All of these control techniques are one degree-of-freedom (1 DOF) i.e. conventional error-driven in nature. The 1 DOF control technique suffers from the limitation that there exists a compromise between response and loop goal performances. To overcome this, in the present work, a 2 DOF linear time-invariant (LTI) controller has been designed to achieve the performance goals of DC-DC PWM based boost converter. A 2 DOF controller provides additional degree-of-freedom so as to meet the loop robustness goals as well as to shape the output response according to requirement. The design technique of this controller is simpler than that of the robust control techniques mentioned above. The 2 DOF control scheme has been shown to achieve the output regulation even in the presence of 60% perturbation in load current and obtain fast recovery in output voltage response, through simulation. The veracity of the simulation results has been established through a real-time experimental setup of the boost converter.

Real-time study of robustness aspects of periodic controller for cart-inverted pendulum system

A real-time implementation of continuous-time periodic controller is carried out for cart-inverted pendulum system. The robustness (under plant parameter variations), disturbance rejection and noise attenuation properties of the periodic controller have been investigated thoroughly in real-time. The robustness aspects of the periodic controller have been compared with that of a linear quadratic regulator (LQR), and found out to be superior to LQR.

Performance analysis of a digitally controlled wind turbine emulator

This paper presents a digital control scheme for wind turbine emulator. The wind turbine is emulated with a separately excited dc motor. The controller is considered to be in the proportional-integral (PI) form, and is designed in digital time domain. These digital PI controllers are employed here for both speed and current controls. The performance of the digital control scheme proposed is simulated in MATLAB-SIMULINK environment considering the dc motor to be a continuous-time plant. The digital controllers are shown to exhibit successful tracking of the speed reference command. The veracity of the simulation results are established through real-time implementation of the digital control scheme for the dc motor under consideration. The digital control is implemented here with a digital signal processor (DSP) control board dSPACE1104. The experimental results are found out to be in good agreement with that obtained in simulation.

Modelling, control, and performance study of cascaded inverter based grid connected PV system

This paper describes a three-phase grid-connected photovoltaic (PV) generation system, using a vector controlled cascaded two-level inverter (CTLI). The system is operated to supply different active power, with variable solar irradiance. Two different schemes have been considered here to operate the inverters with either equal or unequal dc-link voltages. The unequal voltage is chosen to reduce certain harmonics in the output. In both the cases, the solar radiation has been changed in the input of solar modules, and the proposed control scheme is shown to achieve satisfactory voltage regulation for the inverters. The effects of connecting LCL filters, to the vector controlled systems, are also studied here in the simulation environment.

Performance comparison between sliding mode control and periodic controller for cart-inverted pendulum system

The objective of this paper is to compare the robustness performance of continuous time periodic controller with conventional non-linear sliding mode controller (SMC) for a highly non-linear system cart-inverted pendulum. The goal is to determine which control strategy delivers better performance to pendulums angle and carts position. It is observed that although both the controllers are capable to control the multi output inverted pendulum system successfully; time varying periodic control delivers better robustness compared to nonlinear SMC control strategy by virtue of its loop zero-placement capability. Simulation study is done in MATLAB-SIMULINK environment and the responses are presented in time domain with detailed analysis.

Global stabilization of cart-pendulum system with sliding mode controller: Experimental results

The objective of the present work is the global stabilization of a cart-pendulum system. First, an energy shaping algorithm is developed to bring up the pendulum to the close vicinity of its upright equilibrium point. The energy control technique employed here also takes care of the practical constraint of limited cart track length. Next, a sliding mode controller (SMC) does the task of keeping the pendulum at its upright position. The real-time implementation of the control scheme is carried out for the cart-inverted pendulum system. The robustness under uncertainty caused by dry friction, plant parameter variations; disturbance rejection and noise attenuation of the SMC have been investigated thoroughly in real-time.