Application of sliding mode controller in DC/AC and DC-DC power converter system

Maintaining good voltage regulation at output and having fast dynamic response under sudden load fluctuation are extremely important in distributed generation (DG) as well as uninterrupted power supply (UPS) systems. This work presents a fixed frequency hysteresis current (FFHC) controller, which is implemented on the basis of sliding mode control (SMC) technique and fixed frequency current controller with a hysteresis band. The controller have the benefit of hysteretic current control having fast dynamic responses and reduces the disadvantages of the variable switching frequency. For this work elliptical sliding surface was taken.These have been verified and compared with the carrier based pulse width modulated (PWM) voltage controller under the same load fluctuation. The proposed method is then applied to islanded single phase - voltage source inverter (VSI) system. The results show that the dynamic response is quite faster than that of widely used PWM-controlled inverter systems. The DC voltage that is required for the inverter input is supposed to given from the output of PV panel with buck converter.In PV system sliding mode control is used to track the maximum power point .Here inverter and buck converter connected to PV array are taken separately

Two-leg three-phase inverter control for STATCOM and SSSC applications

Flexible ac transmission systems (FACTS) devices are attracting an increasing interest both in power system academic research and in electric utilities for their capabilities to improve steady-state performance as well as system stability. Several converter topologies for FACTS applications have been proposed in the recent literature, even if those based upon voltage source inverters (VSI) seem to be more attractive due to their intrinsic capability to rapidly respond to network changes such as perturbations subsequent to a fault and their property of being immune to resonance problem. In this paper, a new topology for inverter-based FACTS is proposed. This configuration, employing a two-leg three-phase inverter is employed for both series and parallel-connected reactive power compensators. The converter utilizes a modular topology for allowing a satisfaction of electronic components rating. A control strategy based on variable structure control technique with sliding mode is employed to track appropriate reference quantities. Design and control, as well as good tracking performances, are also verified through numerical simulations

AC voltage regulation of a bidirectional high-frequency link converter using a deadbeat controller

This paper presents a digital controller for AC voltage regulation of a bidirectional high-frequency link (BHFL) inverter using Deadbeat control. The proposed controller consists of inner current loop, outer voltage loop and a feed-forward controller, which imposes a gain scheduling effect according to the reference signal to compensate the steady-state error of the system. The main property of the proposed controller is that the current- and the voltage-loop controllers have the same structure, and use the same sampling period. This simplifies the design and implementation processes. To improve the overall performance of the system, additional disturbance decoupling networks are employed. This takes into account the model discretization effect. Therefore, accurate disturbance decoupling can be achieved, and the system robustness towards load variations is increased. To avoid transformer saturation due to low frequency voltage envelopes, an equalized pulse width modulation (PWM) technique has been introduced. The proposed controller has been realized using the DS1104 digital signal processor (DSP) from dSPACE. Its performances have been tested on a one kVA prototype inverter. Experimental results showed that the proposed controller has very fast dynamic and good steady-state responses even under highly nonlinear loads

Robust and fast sliding-mode control for a DC-DC current-source parallel-resonant converter

Modern DC-DC resonant converters are normally built around a voltage-source series-resonant converter. This study aims to facilitate the practical use of current-source parallel-resonant converters due to their outstanding properties. To this end, this study presents a sliding-mode control scheme, which provides the following features to the closed-loop system: (i) high robustness to external disturbances and parameter variations and (ii) fast transient response during large and abrupt load changes. In addition, a design procedure for determining the values of the control parameters is presented. The theoretical contributions of this study are experimentally validated by selected tests on a laboratory prototype.Peer ReviewedPreprin

Fast Adaptive Robust Differentiator Based Robust-Adaptive Control of Grid-Tied Inverters with a New L Filter Design Method

In this research, a new nonlinear and adaptive state feedback controller with a fast-adaptive robust differentiator is presented for grid-tied inverters. All parameters and external disturbances are taken as uncertain in the design of the proposed controller without the disadvantages of singularity and over-parameterization. A robust differentiator based on the second order sliding mode is also developed with a fast-adaptive structure to be able to consider the time derivative of the virtual control input. Unlike the conventional backstepping, the proposed differentiator overcomes the problem of explosion of complexity. In the closed-loop control system, the three phase source currents and direct current (DC) bus voltage are assumed to be available for feedback. Using the Lyapunov stability theory, it is proven that the overall control system has the global asymptotic stability. In addition, a new simple L filter design method based on the total harmonic distortion approach is also proposed. Simulations and experimental results show that the proposed controller assurances drive the tracking errors to zero with better performance, and it is robust against all uncertainties. Moreover, the proposed L filter design method matches the total harmonic distortion (THD) aim in the design with the experimental result

Fixed-switching frequency sliding mode control applied to power converters

The application of the sliding mode control in power converters has a well-known inconvenient from the practical point of view, which is to obtain fixed switching frequency implementations. This thesis deals with the development of a hysteresis band controller in charge of fixing the switching frequency of a sliding motion in power electronics applications. The proposed control measures the switching period of the control signal and modifies the hysteresis band of the comparator in order to regulate the switching frequency of the sliding motion. The proposed structure becomes in an additional control loop aside from main control loop implementing the sliding mode controller. In the first part of the thesis, the switching frequency control system is modelled and a design criteria for the control parameters are derived for guaranteeing closed loop stability, under different approaches and taking into account the most expectable working scenarios. In the second part of the thesis, the proposed strategies are applied to several power converters prototypes. Specifically, DC-to-DC and DC-to-AC power converters are built and the experimental results are shown. In this part, the strategies used for implementing the controllers are also deeply discussed.La aplicación del control en modo deslizante en el ámbito de la electrónica de potencia presente una problemática ampliamente conocida, obtener aplicaciones a frecuencia fija de operación. Es esta tesis se estudia el desarrollo de un comparador con histéresis variable encargado de regular el periodo de conmutación de controladores bajo regímenes deslizantes en convertidores de potencia. La estructura propuesta mide el periodo de conmutación de la señal de control y actualiza, de manera adecuada, la banda de histéresis del comparador a tal fin de regular la frecuencia de conmutación al valor deseado. La solución propuesta forma un segundo lazo de control, además del lazo de control principal que implementa el controlador en modo deslizante. En la primera parte de la tesis, éste segundo lazo es modelado, haciendo posible el estudio de las condiciones de estabilidad bajo realizaciones en tiempo continuo y en tiempo discreto. Además, se estudian las condiciones típicas de trabajo de los controladores utilizados en convertidores de potencia, como son los esquemas de regulación y de seguimiento de señales variantes en el tiempo. La segunda parte de la tesis se centra en evaluar, de manera experimental, los desarrollos teóricos de los controladores propuestos en convertidores de potencia. Concretamente, en la tesis se presentan los resultados experimentales obtenidos con diversos convertidores DC-DC y DC-AC. Adicionalmente, las metodologías y técnicas de implementación de los controladores son, de igual modo, ampliamente descritas.Postprint (published version

Linearized large signal modeling, analysis, and control design of phase-controlled series-parallel resonant converters using state feedback

This paper proposes a linearized large signal state-space model for the fixed-frequency phase-controlled series-parallel resonant converter. The proposed model utilizes state feedback of the output filter inductor current to perform linearization. The model combines multiple-frequency and average state-space modeling techniques to generate an aggregate model with dc state variables that are relatively easier to control and slower than the fast resonant tank dynamics. The main objective of the linearized model is to provide a linear representation of the converter behavior under large signal variation which is suitable for faster simulation and large signal estimation/calculation of the converter state variables. The model also provides insight into converter dynamics as well as a simplified reduced order transfer function for PI closed-loop design. Experimental and simulation results from a detailed switched converter model are compared with the proposed state-space model output to verify its accuracy and robustness

Fixed-switching frequency sliding mode control applied to power converters

The application of the sliding mode control in power converters has a well-known inconvenient from the practical point of view, which is to obtain fixed switching frequency implementations. This thesis deals with the development of a hysteresis band controller in charge of fixing the switching frequency of a sliding motion in power electronics applications. The proposed control measures the switching period of the control signal and modifies the hysteresis band of the comparator in order to regulate the switching frequency of the sliding motion. The proposed structure becomes in an additional control loop aside from main control loop implementing the sliding mode controller. In the first part of the thesis, the switching frequency control system is modelled and a design criteria for the control parameters are derived for guaranteeing closed loop stability, under different approaches and taking into account the most expectable working scenarios. In the second part of the thesis, the proposed strategies are applied to several power converters prototypes. Specifically, DC-to-DC and DC-to-AC power converters are built and the experimental results are shown. In this part, the strategies used for implementing the controllers are also deeply discussed.La aplicación del control en modo deslizante en el ámbito de la electrónica de potencia presente una problemática ampliamente conocida, obtener aplicaciones a frecuencia fija de operación. Es esta tesis se estudia el desarrollo de un comparador con histéresis variable encargado de regular el periodo de conmutación de controladores bajo regímenes deslizantes en convertidores de potencia. La estructura propuesta mide el periodo de conmutación de la señal de control y actualiza, de manera adecuada, la banda de histéresis del comparador a tal fin de regular la frecuencia de conmutación al valor deseado. La solución propuesta forma un segundo lazo de control, además del lazo de control principal que implementa el controlador en modo deslizante. En la primera parte de la tesis, éste segundo lazo es modelado, haciendo posible el estudio de las condiciones de estabilidad bajo realizaciones en tiempo continuo y en tiempo discreto. Además, se estudian las condiciones típicas de trabajo de los controladores utilizados en convertidores de potencia, como son los esquemas de regulación y de seguimiento de señales variantes en el tiempo. La segunda parte de la tesis se centra en evaluar, de manera experimental, los desarrollos teóricos de los controladores propuestos en convertidores de potencia. Concretamente, en la tesis se presentan los resultados experimentales obtenidos con diversos convertidores DC-DC y DC-AC. Adicionalmente, las metodologías y técnicas de implementación de los controladores son, de igual modo, ampliamente descritas

Dynamic modelling and control schemes for current-source resonant converters

Versió amb diverses seccions retallades, per drets de l'editorThis thesis focuses on the control methods applied to current source resonant converters, especially in two different applications of switching power supplies and wire-less power transfer systems. In fact, the existing applications are mostly working with voltage source resonant converters. For voltage-source resonant converters, many control strategies have been analyzed and investigated, turning this into a mature technology nowadays. The current-source resonant converter is an alternative solution as they offer well-known advantages such as non-pulsating input current, low stress for switches, simple driving circuitry, and short circuit protection capabilities. However, there is an obvious lack of control methods applicable to current-source resonant converters. In addition, obtaining an appropriate dynamic model to be used in control design is the other challenging issue in this field. Hence, the objectives of this thesis are used to fill these gaps. The proposed control schemes are: - Frequency modulation control scheme applied to a DC/DC current-source parallel resonant converter. - Sliding mode control scheme with amplitude modulation applied to a DC/DC current-source parallel resonant converter. - A control scheme for a multiple-output DC/DC current-source parallel resonant converter. - A communication-less control scheme for a variable air-gap wireless energy transfer system using a current-source resonant converter.Esta tesis doctoral está centrada en los métodos de control aplicados a los convertidores resonantes con fuente de corriente, especialmente en dos aplicaciones distintas como son fuentes de alimentación conmutadas y sistemas de transferencia de energía sin hilos. De hecho, las aplicaciones existentes trabajan principalmente con convertidores alimentados mediante fuentes de tensión. Para los convertidores resonantes con fuente de tensión, se han analizado muchas estrategias de control en la literatura, lo que hace hoy en día que esta sea una tecnología madura. El convertidor resonante con fuente de corriente es una solución alternativa, que ofrece ventajas conocidas como corriente de entrada no pulsante, baja tensión para interruptores, circuitos de conducción sencillos y capacidades de protección contra cortocircuitos. Sin embargo, existe una falta evidente de métodos de control aplicables a los convertidores resonantes con fuente de corriente. Además, otro desafío en este tema es la obtención de modelos dinámicos apropiados para el diseño del control. Por lo tanto, los objetivos de esta tesis se utilizan para llenar estos vacíos. Los esquemas de control propuestos son: - Esquema de control en frecuencia aplicado a un convertidor resonante paralelo con fuente de corriente para reguladores de tensión en continua - Esquema de control en modo de deslizamiento con modulación de amplitud aplicado a un convertidor resonante paralelo con fuente de corriente para reguladores de tensión en continua. - Esquema de control para un convertidor resonante paralelo con fuente de corriente para la regulación de tensión en continua de varias salidas. - Esquema de control sin comunicaciones para un sistema de transferencia de energía sin hilos con un transformador con entrehierro variable basado en un convertidor resonante con fuente de corriente.Postprint (published version