Resonant power converter driving and inductive load like a discharge lamp

A resonant power converter (1) for driving an inductive load as, e.g. an inductively coupled gas- discharge lamp, is designed for operation at an operational frequency (Fop) of 13.56 MHz and comprises: a series arrangement of a first inductor (L1) and a first controllable switch (Q1) connected to a DC voltage source (DC); - a series arrangement of a second inductor (L2) and a second controllable switch (Q2) connected to said DC voltage source (DC); a first parallel capacitance (Cdsl) associated with the first controllable switch (Q1); a second parallel capacitance (Cds2) associated with the second controllable switch (Q2); a controller (30) for driving the switches (Ql, Q2); the load is coupled between said nodes (A, B); the switches alternate between a conductive state and a non-conductive state at a duty cycle of 50%; - the switching frequency (Psw) is one-third of said operational frequency (Fop)

Observer-based MPC applied to flyback converters

A digital control method combining primary-side sensing, observer and model-predictive-control techniques is proposed. A conventional isolated Flyback converter is chosen for demonstrating the method. The only measured signal is the drain-source voltage over the switch. Following a procedure of signal processing, state estimation and constraint problem formulation, the controller determines the optimal duty cycle ratio. The advantages of the proposed method include minimal overshoot and fast stabilization, converter state restriction, and measurement network simplification

High-resolution phase shift and digital implementation of a fuel cell powered UPS system

This paper presents the digital implementation of a single-phase fuel cell powered uninterruptible power supply (UPS) and distributed generation (DG) system. The power conditioning unit of the system consists of a voltage source inverter and a three-port bidirectional DC-DC converter interfacing the fuel cell and inverter with a supercapacitor. It is shown that the control of the whole system including both the DC-DC and DC-AC stages can be carried out by a single digital signal processor (DSP). In particular, in order to eliminate limit cycle oscillations in digitally controlled DC-DC converters, the generation of high-resolution phase shifts is explained in detail. The system is suitable for residential applications and can improve the power quality for the local user. Practical design issues such as the state-of-charge (SOC) management of the supercapacitor and prototype design details are discussed. Experimental results from a 3.5 kW prototype are presented to verify the effectiveness of the digitally implemented control scheme

Multiport converter for fast charging of electrical vehicle battery: focus on DC/AC converter

The availability of new electrical vehicle batteries with high current rating and capacity permits the realization of rapid charging. However, when using conventional methods, the charging process requires an expensive high-current grid interface. Therefore, a multiport converter with a stationary storage port to reduce the current required from the grid is proposed. The goal of this paper is to explore the fundamentals of the DC/AC converter used in one of the ports. Experimental results for a low-power prototype are shown to validate the theoretical study

Line-interactive UPS using a fuel cell as the primary source

This paper proposes a line-interactive fuel-cell-powered uninterruptible-power-supply system. A three-port bidirectional converter connects a fuel cell and a supercapacitor to a grid-interfacing inverter. The system can operate in both stand-alone and grid-connected modes. Moreover, an active filtering function is integrated into the system. It is shown that a supercapacitor can serve as both an active and a reactive energy storage and can buffer the periodical low-frequency ripple in the requested power. For connecting the system to the utility grid, a high-performance single-phase phase-locked loop that incorporates an orthogonal filter is presented. Resonant controllers for both the voltage and current regulations eliminate steady-state error and implement selective harmonic compensation. Simulation and experimental results are provided to show the feasibility of the proposed system and the effectiveness of the control methods

Dynamic characteristics of PEM fuel cells

Fuel cell applications have become increasingly attractive. Therefore, comprehensive models, simulation and analysis tools are required to characterize fuel cell behavior. For years, the focus has been on describing the steady state characteristics of fuel cells, which is an important application but certainly not the only one. This paper presents methods to measure steady state and transient behavior of polymer electrolyte membrane fuel cells (PEMFC). An active load that enables all required measurements is described. Furthermore, a simple large-signal dynamic PEM fuel cell model is introduced of which the parameters can be found with an interrupted current method. This method estimates the parameters of the dynamic model. However, there was doubt whether the influence of small-signal disturbances in the fuel cell operation could be analyzed with the interrupted current method. Therefore, impedance spectroscopy measurements were performed on the fuel cell stack to determine if the large-scale model was applicable to small-signal excitations. Practical measurements show that an additional small-signal model should be introduced to characterize a fuel cell stack when switching ripple is present in the output curren

Disturbance observer-based control of a dual output LLC converter for solid state lighting applications

Feedback sensor isolation is often an expensive necessity in power converters, for reasons of safety and electromagnetic compatibility. A disturbance observer-based control strategy for a dual-output resonant converter is proposed to overcome this problem. Current control of two LED loads is achieved through estimation rather than measurement. Robustness against temperature changes, which have significant impact on the behaviour of the LEDs, is achieved through estimation of offsets in the forward voltages of the LED-strings. The power converter and LEDs are modelled accurately to obtain a good estimation accuracy. The whole implementation is steered towards a low cost solution

Active power control strategies for inverter-based distributed power generation adapted to grid-fault ride-through requirements

Distributed power generation is expected to deliver power into the grid without interruption during voltage dips. To improve system ride-through capabilities, a generalized active power control strategy is proposed for grid-interfacing inverters. Specifically, a current reference generation strategy based on symmetric-sequence components of unbalanced three-phase three-wire or four-wire systems is derived. It is shown that a single adjustable parameter can smoothly change the relative amplitudes of oscillating active and reactive power. This steering possibility enables grid-side inverters to optimally meet different requirements of coming standards. Simulations and experiments are carried out to validate the proposed strategy

CCM flyback converter using an observer-based digital controller

This paper shows a concept to optimally control a nonlinear load without measuring all of the state variables. By including an observer into a digital controller module sensors can be saved. The advantages of a MP-Controller are that it takes into account the system constraints and trades-off the input effort and the settling speed. Compared to a constant input it directs the system quickly to the desired operation point; the state variables stay within pre-set margins and it reduces component stresses