Converter Dynamic Response Research Articles

Design of MOSFET Based Boost Converter with PID and Genetic Algorithm Optimizer for Resistive Load

The focus of this research is the development of a DC-DC boost converter employing a polymer-based MOSFET to ensure consistent output despite variations in Resistive (R)-load. An appropriate controller for the developed converter is designed through the application of diverse optimization techniques, aiming for straightforward implementation, improved convergence quality, and enhanced computational efficiency. The optimization of Proportional-Integral-Derivative (PID) controller parameters using various algorithms is performed to enhance the converter's dynamic response in the presence of R-load. To tune the PID controller, Genetic Algorithm optimization parameters are utilized, which enhance the efficiency while including R-load. The effectiveness is measured in overshoot, rise time, settling time and peak time. The analysis also encompassed time integral domain specifications, including Integral SquareError (ISE), Integral Absolute Error (IAE), and Integral Time Absolute Value Error (ITAE). The research modeling of this technique is done in MATLAB/SIMULINK 2018 platform by considering various performance metrices.

A Nonlinear Load Current Feedforward Strategy for the Charge-Controlled LLC Converter and Its Digital Implementation to Improve the Dynamic Response

Compared with the traditional single voltage loop control strategy in LLC converters, the charge-controlled LLC converter can significantly improve its dynamic response due to its model having the first-order feature. Generally, a load current feedforward method could improve the converter's dynamic response. However, for the LLC converter, it is almost impractical due to the unclear relationship between the load current and the control variable. To build this relationship, a mathematical expression between the load current change and the control variable is derived that can precisely offset the load disturbance and achieve faster dynamic response. The derived relationship is nonlinear, related to both input and output voltages and switching frequency, and is suitable for digital implementation. To further analyze the dynamic response, the output impedances with and without the load current feedforward control are established and analyzed, which visually demonstrates the dynamic improvement in the time domain through the calculation of the output impedance and load change spectrum in the frequency domain. Finally, a 120W LLC prototype with nominal 48V input and 12V output is built to verify the nonlinear load current feedforward control and its analysis.

A Comprehensive Small-Signal Model Formulation and Analysis for the Quasi-Y Impedance-Source Inverter

This paper presents a detailed derivation of the small-signal model and components design considerations for the Quasi-Y-Source inverter. The design methodology is based on the converter steady-state operation, considering the impedance network inductor and capacitor voltage and charge balances, respectively. Moreover, the additional design criteria for component selection, considering control constraints and performance compromise, are given by parametric variation analysis based on converter dynamic response. The small-signal model and transfer functions are obtained using a state-space averaged model, including converter non-ideal characteristics given by equivalent-series resistances (ESR), which makes possible the proposition of different control strategies, using both single or multi-loop schemes. To demonstrate the usefulness of the proposed small-signal model, a DSP-based single-loop type-II PI control strategy is used in which the peak DC-link voltage is indirectly controlled through the measurement of the impedance network capacitor voltage. The controller and converter performances are verified with simulation and experimental results and successfully confirm the validity of the proposed dynamic model. Finally, the obtained results are validated with a built small-scale three-phase/three-wire inverter prototype.

Digital Predictive Current-Mode Control of Three-Level Flying Capacitor Buck Converters

This article investigates the use of digital predictive current-mode control (DPCMC) in dc-dc three-level flying capacitor (3LFC) buck converters. In particular, stability and flying capacitor (FC) balancing properties of predictive peak, average, and valley current-mode controllers are studied when operated in single- and multisampled modes. A variant of the multisampled DPCMC obtained through a fast-update of the duty cycle command is also disclosed and analyzed. Results indicate that single-sampled DPCMC is always stable, and that fast-update approaches can strongly improve the converter dynamic response. Multisampled controllers are also shown to be inherently more robust than single-sampled ones against timing mismatches in the control signals, resulting in a smaller FC voltage imbalance. The analysis is validated in simulation and experimentally on a 500 kHz, 12-1.5 V, 500 mA 3LFC buck case study.

A Capacitor Voltage Balancing Approach Based on Mapping Strategy for MMC Applications

This paper proposes a new strategy to achieve balanced capacitor voltages in modular multilevel converters. Among the possible solutions, centralized arm control approaches are often adopted. These methods require a balancing technique based on a sorted list of the sub-modules according to their capacitor voltages. In order to achieve the aforementioned sorted list, different algorithms have been proposed in literature, such as: Sorting algorithms, max/min approaches, etc. However, the sorting algorithms require a long execution time, while the max/min approaches affect the converter dynamic response during faults. To overcome these issues, a new mapping strategy providing a quasi-sorted list is proposed in this paper. The suggested method is compared in simulation with both the classical bubble sorting algorithm, and the max/min method during both normal and faulty conditions. Moreover, the three methods have been implemented in a Xilinx Zynq-7000 System-on-Chip (SoC) device, in order to analyze the corresponding execution time and the required computational effort. Hardware-in-the-loop results are presented for demonstrating the superior performance of the proposed balancing strategy.

High-Accuracy Impedance Detection to Improve Transient Stability in Microgrids

The advancements in dc microgrids and the increase in distributed generation systems have led to a new trend toward the coexistence of multiple power converters from different sources (renewable, storage, etc.) supplying a variety of loads of different natures in a weak network. The loads can behave as passive loads (resistances) or be implemented by tightly regulated power converters, leading to constant power load (CPL) behavior. The CPLs present a characteristic negative incremental resistance that can alter the response of the system, even causing instability. In this work, a novel embedded technique based on a digital lock-in amplifier is proposed that enables the real-time detection of the dynamic impedance present in a power converter. The proposed technique uses a very efficient algorithm, along with standard sensors available in the converter, to measure the magnitude and phase of the dynamic load, and uses this information to improve the performance of the converter. A sample application of the proposed technique in an adaptive control system is described. Although the total output power of the converter is independent of the nature of the load, the converter's dynamic response is not. The interaction of the CPL, passive load, and control loop will determine not only the stability but also the transient response. The proposed instrument allows the incremental load of the converter to be accurately measured while reducing the complexity and sensor requirements, and improving the performance of the controller. Simulations of the proposed technique are presented to illustrate its behavior. Experimental results for different kinds of loads are presented to validate the proposed strategy.

An FPGA-Based Gain-Scheduled Controller for Resonant Converters Applied to Induction Cooktops

Domestic induction heating appliances have become popular due to their advantages such as efficiency, fast heating, cleanliness, and safety. In order to achieve high efficiency, induction cooktops usually features resonant converters in which the inductor-vessel system is a part of the resonant tank. Thus, the inductor-vessel system impedance sets the point of operation of the power converter. Due to the variability of the load with multiple parameters such as temperature, geometry, and material, the resonant converter has to work with highly varying operating conditions. When designing a classical controller, the controller gain is selected to assure the system stability in the whole range of operation and for a large amount of vessels. This study proposes an FPGA-based gain scheduled controller which makes use of the information of the modulation parameters and an online impedance identification system. As a result, the proposed controller significantly improves the converter dynamic response, improving the performance and safety operation of the power converter. The proposed control algorithm has been experimentally verified using a domestic induction heating prototype, proving the feasibility of this proposal.

A Circuit for Improving DC-DC Converter Dynamic Response

To improve the disadvantage of DC-DC converter output voltage fluctuation when output current changes in wide range, a compensation circuit for improving DC-DC converter dynamic response was presented. The circuit was based on the theory of parallel or anti-parallel capacitor. A charged capacitor was paralleled when output current positive jumped. A charged capacitor was anti-paralleled when output current negative jumped. It worked when output current changed. So DC-DC converter dynamic response was improved and efficiency could be high in the same time. The simulation results proved that the effect of compensation circuit in improving the converter dynamic response and stabilizing the output voltage.

Analysis, Design, and Experimentation on Constant-Frequency DC-DC Resonant Converters With Magnetic Control

In this paper, a new technique for controlling dc-dc resonant converters is investigated. A variable inductance is used to control and regulate the dc output voltage maintaining constant switching frequency for the half-bridge transistors. The output voltage characteristics of the series resonant and parallel resonant converters under the proposed magnetic control are obtained and analyzed. In order to evaluate the proposed technique, a laboratory prototype for a 48 V-input 5 V/10 A-output 500 kHz parallel resonant converter is presented. A methodology for obtaining the converter dynamic response using a step response test is carried out. From the dynamic response, a compensator for operating the converter at closed loop is developed and tested in the laboratory. The results prove that the proposed technique is suitable for controling resonant inverters at constant frequency using a low-cost half-bridge inverter.

Design and Development of a Feedback Controller for Boost Converter Using Artificial Immune System

The main objective of this article is to design, implement, and test a feedback controller for a boost-type DC-DC converter employing the artificial immune system technique. When a boost-type DC-DC converter is operated in a closed-loop mode with a traditionally designed controller, the dynamic response is observed to be dissimilar at different operating points of the converter system. Hence, the feedback controller design is formulated as an optimization problem, and controller parameters are estimated through an artificial immune system based algorithm. Extensive simulation and corresponding experimental work are then carried out on the DC-DC converter with the artificial immune system based feedback controller. Comparison of the converter dynamic response with the proposed scheme to the one obtained through a conventional method as well as a genetic algorithm based approach shows that the new method gives a robust controller structure that yields very good dynamic response at all operating points. Computed and measured results are supplied.

Dynamic Response of Automotive Catalytic Converters to Variations in Air-Fuel Ratio

The automotive catalytic converters, which are employed to reduce engine exhaust emissions, operate in transient conditions under all modes of operation. The fluctuation in air-fuel ratio is a major contributor to these transients. The consideration of these transients is essential in accurate modeling of catalyst operation during actual driving conditions. In this work, a numerical investigation is carried out to comprehend the dynamic response of three-way catalytic converters subjected to changes in air-fuel ratio. The mathematical model considers the coupling effect of heat and mass transfer with the catalyst reactions as exhaust gases flow through the catalyst. The converter dynamic response is studied by considering a converter operating under steady conditions, which is suddenly subjected to air-fuel ratio variations. Two types of imposed fluctuations (sinusoidal and step changes) are considered. The catalyst response is predicted by using a detailed chemical mechanism. The paper elucidates the effect of air-fuel modulations on the catalyst HC, CO, and NO conversion efficiencies.