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A low-capacitance static compensator (LC-StatCom) based on a cascaded H-bridge (CHB) multilevel converter can be an efficient and low-cost solution for reactive power compensation in power grids. However, the reduced capacitance, and, therefore, faster capacitor voltage dynamics, makes it challenging to control it. Classical cascade control schemes, in which the bandwidths associated with the inner current loop and the outer capacitor voltage loop need to be separated enough, are the most reported approaches. Nevertheless, for the LC-StatCom case, the voltage loop can be almost as fast as that one of the current loop. For this reason, this article proposes a control approach that does not separate voltage and current dynamics. Concretely, we propose a multi-input linear time-variant control law, based on incremental passivity theory for CHB multilevel converters. The proposed control guarantees stability despite saturation in the control signal. In addition, it provides capacitor voltage balance without the need to use a specific balancing stage. This article, first, reviews the average model of the converter and, then, analyses the steady-state dynamic behavior to determine the desired and coherent reference signals. Then, it applies an incremental passivity control approach to drive the LC-StatCom state variables to the desired references. After introducing the proposed control law, experimental results on a seven-level 1-kVA CHB LC-StatCom are shown to demonstrate its excellent performance in steady state and transients. [ABSTRACT FROM AUTHOR]

In this paper, second-order sliding-mode (SOSM) control approach is applied to synchronous buck dc–dc converters. The proposed SOSM controller can stabilize synchronous buck dc–dc converters using a simple digital state-machine structure, without requiring current sensing or an integral term in the control loop. The SOSM controller results in fast step-load and start-up transient responses, and is robust against parameter uncertainties. Fast transients and current limitation during start up can be accomplished by adjusting one controller parameter. Furthermore, a hysteresis method is introduced to control the switching frequency. The proposed approach is verified by experimental results on a 1.25-V 10-A prototype. [ABSTRACT FROM PUBLISHER]

A design method using quantitative feedback theory (QFT) for robust control of PWM DC-DC converters is developed. Parametric and nonparametric uncertainty can be described accurately with this technique. Besides, with the proposed method, the controller can consider both continuous and discontinuous conduction mode models (CCM and DCM respectively). Considering these sources of uncertainty results in a robust controller insensitive to parametric variations and also to different plant cases due to different conduction modes. A power converter satisfying a well-known industry standard is presented as a design example, in order to demonstrate that, with the proposed procedure, the performance of the regulated system can be tightly specified not only in terms of frequency requirements, but also in terms of time-domain characteristics, like overshoot and establishment time. The synthesised robust controller has been verified with experimental data from a power converter prototype, achieving satisfactory results. [ABSTRACT FROM AUTHOR]

This paper presents two different robust controllers for boost converters with two stages in a cascade. The first robust controller is monovariable; that is, the duty-cycle is the same for the two switches. The monovanable controller ensures that some prescribed constraints on pole placement and control effort are met, and optimizes the load disturbance rejection, while takes into account the uncertainty in certain parameters. The first controller is then compared with a multivariable robust controller; that is, with independent duty cycles in each switch. The multivariable controller takes into account the same uncertainty, constraints and optimization function. The comparison shows that the multivariable controller performs better at the expense of a slightly more complex implementation; that is, the multivanable controller provides a better rejection of the load disturbance. The paper also describes simulations and experimental results that are in perfect agreement with theoretical derivations. [ABSTRACT FROM AUTHOR]