Optimized Digital Controllers for Switching-Mode DC-DC Step-Down Converter

Abstract

In this paper, a nonlinear least squares optimization method is employed to optimize the performance of pole-zero-cancellation (PZC)-based digital controllers applied to a switching converter. An extensively used step-down converter operating at 1000 kHz is considered as a plant. In the PZC technique, the adverse effect of the (unwanted) poles of the buck converter power stage is diminished by the complex or real zeros of the compensator. Various combinations of the placement of the compensator zeros and poles can be considered. The compensator zeros and poles are nominally/roughly placed while attempting to cancel the converter poles. Although PZC techniques exhibit satisfactory performance to some extent, there is still room for improvement of the controller performance by readjusting its poles and zeros. The (nominal) digital controller coefficients thus obtained through PZC techniques are retuned intelligently through a nonlinear least squares (NLS) method using the Levenberg-Marquardt (LM) algorithm to ameliorate the static and dynamic performance while minimizing the sum of squares of the error in a quicker way. Effects of nonlinear components such as delay, ADC/DAC quantization error, and so forth contained in the digital control loop on performance and loop stability are also investigated. In order to validate the effectiveness of the optimized PZC techniques and show their supremacy over the traditional PZC techniques and the ones optimized by genetic algorithms (GAs), simulation results based on a MATLAB/Simulink environment are provided. For experimental validation, rapid hardware-in-the-loop (HiL) implementation of the compensated buck converter system is also performed.

A Novel Integrated Topology to Interface Electric Vehicles and Renewable Energies with the Grid

“…Finally, there is an energy management system (EMS) that dictates the proper transfer at every moment. There are several strategies to control the state variables in a switching power converter as the ones presented in Reference [52]. Nevertheless, in this work, the current through L 2 was regulated utilizing a sliding mode control (SMC) because this technique is naturally suited for the regulation of switched controlled systems such as DC-DC power converters [53] and for its robustness, as stated in References [54][55][56].…”

Real-Time Hardware in the Loop Simulation Methodology for Power Converters Using LabVIEW FPGA

“…In [17], the authors develop a new RTS method to test nonlinear control techniques and a methodology to implement the RTS is described, but it is based in a Digital Signal Processor (DSP), which is slower than an FPGA. In [18], the authors propose a methodology for the development of a fast HIL simulation based in MATLAB, but it includes just a small part of the work and is not detailed enough. In [19], the authors suggest fast HIL development based in MATLAB; however, the methodology is only for the design of PV converters.…”

Fractional-Order Approximation and Synthesis of a PID Controller for a Buck Converter

“…Different control strategies have been proposed to enhance performance of DC-DC converters, ranging from the widely used Proportional-Integral and Proportional-Integral-Derivative controllers [7][8][9], sliding mode control [10], passivity-based control [11], fuzzy logic controllers [12,13] or poles placement [14], for instance.…”

“…Step response of the closed-loop transfer function of a Buck converter by using the approximation of the fractional-order PID controller (14). One can conclude that the fractional-order PID approximation (5) regulates properly with load variations, which implies robustness of the controller.…”

“…Figure 7 shows that it took the output y(t) an approximate of t ≈ 12 µs to reach the reference, thus, the proposed approximation of fractional-order PID controller would regulate properly the output voltage. Figure 8 shows the desired output voltage and the inductor current for three different values of reference on Figure 4, i.e., a) r = 30 V, b) r = 65 V, c) r = 95 V and the corresponding control laws, produced by the fractional-order approximation of PID controller (14). As can be seen, for the three conditions of reference r, it took to the fractional-order PID controller to make the plant to reach the desired value of voltage in a very small period of time.…”