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Photovoltaic (PV) ageing is known to cause a linear degradation of the short-circuit and maximum power point currents, which results in the corresponding power loss. Nonetheless, besides of degradation, also a dispersion of these currents has been reported in the past. Such a dispersion induces significant mismatches in the PV system, even in the absence of partial shading, further increasing the power loss. Such a phenomenon has attracted the interest of investigators, as the fraction of power loss due to mismatch is recoverable. Nonetheless, all previous works have considered module-level ageing data, whereas the recoverable power at the submodule level may be larger. This paper investigates the effects of ageing at the submodule level, and compares the results with previously reported data. It is shown that previous works have underestimated the amount of recoverable power, and that the lifetime improvement of the energy yield may add up to 4–6% of the total.

A unified set of input-dependent coordinates is proposed for the description of parallel and series resonant converters. The description naturally leads to a hybrid feedback control strategy for self-oscillating behavior. We show through a hybrid representation that the ensuing dynamics admits a unique almost globally attractive hybrid limit cycle. A tuning parameter, the switching angle, is then numerically shown to lead to monotonic variation of the peak output current/voltage and of the self-induced switching frequency. Numerical simulations with high-accuracy software illustrate the desirable behavior of the self-oscillating scheme, and it robustness to unmodeled phenomena. Copyright (C) 2021 The Authors.

One of the main critical design issues in current high-power systems is to carry out a field test in order to analyse power system stability due to its high complexity and cost. Hence, power-hardware-in-the-loop (PHIL) technology provides a powerful tool for testing scenarios where there is a high-power interchange providing preliminary analysis of the system stability. For that purpose, it is necessary to model the impedances of the different components used in the PHIL simulation. In DC-distributed applications, three-phase voltage-source inverters (VSI) are commonly used as load converters, and hence, its input impedance model is required in order to emulate its behaviour regarding stability analysis. Since a full-order approach requires a high-expensive real-time digital simulator to use PHIL technology, this paper proposes a reduced order input impedance model of a three-phase VSI which allows to overcome expensive PHIL implementations. First we show how the region of stability limits of both models are in good agreement, using a Lyapunov-based method. Then, we demonstrate the validity of a reduced-order model with respect the full-order approach, using frequency domain criteria and time-domain simulations. Finally, the validity of a reduced-order input impedance model of a three-phase VSI with respect the full-order approach has been evaluated to overcome the expensive PHIL implementations.

This paper presents a novel framework for robust linear quadratic regulator (LQR)-based control of pulse-width modulated (PWM) converters. The converter is modeled as a linear parameter-varying (LPV) system and the uncertainties, besides their rate of change, are taken into account. The proposed control synthesis method exploits the potential of linear matrix inequalities (LMIs), assuring robust stability whilst obtaining non-conservative results. The method has been validated in a PWM DC&ndash, DC boost converter, such that it has been shown, with the aid of simulations, that improved robustness and improved performance properties can be achieved, with respect to previously proposed approaches.

A comparative analysis of the dynamic features of a step-up microinverter based on the cascade connection of two synchronized boost stages and a full-bridge is presented in this work. In the conventional approach the output of the cascaded boost converter is a 350&ndash, 400 DC voltage that supplies the full-bridge that makes the DC-AC conversion. Differently from the classical approach, in this work, the cascaded boost converter delivers a sinusoidal rectified voltage of 230 Vrms to the full-bridge converter that operates as unfolding stage. This stage changes the voltage sign of one of every two periods of the rectified sinusoidal signal providing the final output AC waveform. In contrast to a classical full-bridge inverter, the unfolding stage lacks output filter, and has zero order dynamics. Thus, the approach presented here implies a second order dynamics reduction that will be increased applying sliding motions to control the system. After introducing the inverter circuit, two sliding control alternatives, input current mode and pseudo-oscillating mode, are presented. Both alternatives are analyzed, simulated, and verified experimentally. Furthermore, detailed description of the microinverter power stage and control circuits are also given.

This paper quantifies the impact of distributed power electronics in photovoltaic (PV) systems in terms of end-of-life energy-capture performance and reliability. The analysis is based on simulations of PV installations over system lifetime at various degradation rates. It is shown how module-level or submodule-level power converters can mitigate variations in cell degradation over time, effectively increasing the system lifespan by 5–10 years compared with the nominal 25-year lifetime. An important aspect typically overlooked when characterizing such improvements is the reliability of distributed power electronics, as power converter failures may not only diminish energy yield improvements but also adversely affect the overall system operation. Failure models are developed, and power electronics reliability is taken into account in this work, in order to provide a more comprehensive view of the opportunities and limitations offered by distributed power electronics in PV systems. It is shown how a differential power-processing approach achieves the best mismatch mitigation performance and the least susceptibility to converter faults. Copyright © 2017 John Wiley & Sons, Ltd.

This paper describes a novel modeling approach for self-oscillating resonant power converters operating under a control method based on the variable structure of the system (VSS). Using a fundamental harmonic approximation, the link between control and switching frequency in steady state is found to be accurately described by an affine function that depends on the load. Besides, this link has been extended in order to characterize the control-to-switching frequency dynamics, resulting in a novel small-signal continuous-time model. The resulting control-to-switching frequency transfer function can be appended to the well-known models for frequency modulation, in order to obtain a complete control-to-output system. The new model exposes that the dynamics of the converter under the VSS-based control approach presents advantages with respect to the conventional methods as frequency modulation: 1) reduced dc gain variation for uncertain loads and 2) improved phase margin at high frequencies. The dynamic modeling is complemented with the design of a controller for regulating the output voltage of a parallel resonant converter, whose performance and robustness are compared with the standard frequency modulation. Numerical simulations and experimental results confirm and verify the analytical derivations.

Large commercial photovoltaic (PV) systems can experience regular and predictable energy loss due to both inter-row shading and reduced diffuse irradiance in tightly spaced arrays. This paper investigates the advantages of replacing bypass diodes with submodule-integrated DC–DC converters (subMICs) to mitigate these losses. Yearly simulations of commercial-scale PV systems were conducted considering a range of row-to-row pitches. In the limit case of array spacing (unity ground coverage), subMICs can confer a 7% increase in annual energy output and peak energy density (kW h/m2). Simulation results are based on efficiency assumptions experimentally confirmed by prototype submodule differential power-processing converters.

This paper presents a versatile ballast for discharge lamps, whose operation is based on the notion of a loss-free resistor (LFR). The ballast consists of two stages: (1) a boost converter operating in continuous conduction mode (CCM) and exhibiting an LFR behavior imposed by sliding-mode control, and (2) a resonant inverter supplying the discharge lamp at high frequencies. Thanks to this mode of operation, the power transferred to the lamp is regulated by the LFR input resistance, allowing successful ignition, warm-up, nominal, and dimming operation of a range of discharge lamps, with no need for complex regulation schemes based on lamp models. The versatility of the ballast has been experimentally proven for both conventional and electrodeless discharge lamps. Tests include induction electrodeless fluorescent (IEFL), high-pressure sodium (HPS) vapor, and metal-halide lamps.

This paper presents the architecture and control of a LLC bidirectional isolated DC-DC converter with unity gain for low power application. The converter features zero voltage switching (ZVS) at light loads, which results in reduced switching loss and thus improves the efficiency. Further improvement of the efficiency has been achieved by operating the converter in burst mode with a constant switching frequency. A control scheme that allows bidirectional power flow is proposed. High frequency ferrite core transformer provides the galvanic isolation between primary and secondary. In addition, resonant inductors have been integrated in the transformer, which reduces the size and cost of the converter. Experimental results show power transfer efficiencies more than 90 % for loads between 1 W to 8 W.

In the presence of partial shading and other mismatch factors, bypass diodes may not offer complete elimination of excessive power dissipation due to cell reverse biasing, commonly referred to as hot-spotting in photovoltaic (PV) systems. As a result, PV systems may experience higher failure rates and accelerated ageing. In this paper, a cell-level simulation model is used to assess occurrence of hot-spotting events in a representative residential rooftop system scenario featuring a moderate shading environment. The approach is further used to examine how well distributed power electronics converters mitigate the effects of partial shading and other sources of mismatch by preventing activation of bypass diodes and thereby reducing the chances of heavy power dissipation and hot-spotting in mismatched cells. The simulation results confirm that the occurrence of heavy power dissipation is reduced in all distributed power electronics architectures, and that submodule-level converters offer nearly 100% mitigation of hot-spotting. In addition, the paper further elaborates on the possibility of hot-spot-induced permanent damage, predicting a lifetime energy loss above 15%. This energy loss is fully recoverable with submodule-level power converters that mitigate hot-spotting and prevent the damage.

Resonant converters under zero current switching control strategy can exhibit coexistence of attractors, making it difficult the startup of the system from zero initial conditions. In this paper, the problem of multiple coexisting attractors in parallel resonant converters is addressed. Appropriate modifications of the switching decision with the aim of converting undesired attractors into virtual ones are proposed. A suitable control signal is generated from the state variables of the system and used to adjust the switching decision. Numerical simulations corroborate the proposed solutions and the simplest one was finally verified by measurements from a laboratory prototype.

Switching dc–dc converters are widely used to interface the dc output of renewable energy resources with power distribution systems in order to facilitate the use of energy at the customer side. In the case of residential photovoltaic (PV) applications, high conversion ratio is usually required, in order to adapt the low output voltages of PV modules to a dc bus voltage, while dealing with the appropriate impedance matching. In this paper, a system connected to a PV panel consisting of two cascaded dc–dc boost converters under sliding-mode control and working as loss-free resistors is studied. The modeling, simulation, and design of the system are addressed. First, an ideal reduced-order sliding-mode dynamics model is derived from the full-order switched model taking into account the sliding constraints, the nonlinear characteristic of the PV module, and the dynamics of the MPPT controller. For this model, a design-oriented averaged model is obtained and its dynamic behavior is analyzed showing that the system is asymptotically globally stable. Moreover, the proposed system can achieve a high conversion ratio with an efficiency close to 95 $\%$ for a wide range of working power. Numerical simulations and experimental results corroborate the theoretical analysis and illustrate the advantages of this architecture in PV systems.

Differential power processing (DPP) architectures employ distributed, low power processing, submodule-integrated converters to mitigate mismatches in photovoltaic (PV) power systems, while introducing no insertion losses. This paper evaluates the effects of the simple voltage-balancing DPP control approach on the submodule-level maximum power point (MPP) efficiency. It is shown that the submodule MPP efficiency of voltage-balancing DPP converters exceeds 98% in the presence of worst-case MPP voltage variations due to irradiance or temperature mismatches. Furthermore, the effects of reduced converter power rating in the isolated-port DPP architecture are investigated by long-term, high-granularity simulations of five representative PV system scenarios. For partially shaded systems, it is shown that the isolated-port DPP architecture offers about two times larger energy yield improvements compared to full power processing (FPP) module-level converters, and that it outperforms module-level FPP approaches even when the power rating of DPP converters is only 20-30% of the PV system peak power. In the cases of aging-related mismatches, more than 90% of the energy yield improvements are obtained with DPP converters rated at only 10% of the PV peak power.

Recently, a variety of differential power-processing (DPP) architectures have been shown to improve the efficiency of photovoltaic (PV) systems. This paper proposes a simple control strategy for the isolated-port DPP architecture, and provides a comprehensive stability analysis for this system. The proposed controller drives the duty-cycle of the differential submodule integrated converters (subMICs) in proportion to a voltage difference between the submodule and the isolated-port. This method requires no additional sensing, complex processing, or communication between subMICs, and is therefore well suited for low-cost integrated hardware solutions. Stability of the resulting high-order nonlinear system is analyzed both in the time and frequency domains. A decoupled model is developed that reduces the high-order system dynamics to a 1-D control loop, which allows stable, well-behaved responses using a proportional or a lag compensator. Experimental results for a 72-cell PV module with three subMICs verify static and dynamic operation, and show that overall PV module efficiency exceeds 99% with no shading, and is higher than 96% under significant (50%) shading.

This paper describes the design of a 6.78 MHz self-oscillating parallel resonant power converter for wireless power transfer applications. By sensing just the polarity of the tank inductor current to generate the switch control signals, the system is able to auto-start and self-oscillate at the desired frequency only by applying power to the input port. Different current sensing techniques, including a current sensing transformer and a series resistor followed by a high-speed differential amplifier, are compared based on bandwidth limitations and noise rejection considerations. Furthermore, delay-compensation networks are included in order to mitigate effects of the propagation delays added by signal processing components in the feedback path. It is shown that the circuit is capable of meeting the A4WP/AirFuel standard specifications for wireless power charging. Both inverter and inverter+rectifier configurations are tested and their performances are verified by simulations and experiments on a 16 W prototype using GaN power devices, showing an efficiency of 98 % and 83 %, respectively.

This paper deals with the modeling and the robust controller synthesis for nonlinear dc-dc converters. In the first part of this paper, a model for the bilinear dynamics is presented. Such nonlinear dynamics can be included in a convex polytope such that the trajectories of the converter out of the equilibrium are assured to remain inside a guaranteed region of stability despite of the bilinear term. Such a description of the dynamic response of the converter is employed, in the second part of this paper, to propose synthesis algorithms that can guarantee, a priori, the stability and performance requirements of the design. The resulting region of stability can take into account not only the bilinear terms but also the saturation of the control input, which is a topic of major importance in high-performance dc-dc converters. The aim of this paper is to contribute with a robust control framework which allows the designers to deal with the common requirements of regulated dc-dc converters. The correctness of the results has been verified both with numerical simulations and experimental measurements from dc-dc converter prototypes.

Filiació URV: SI Large commercial photovoltaic (PV) systems can experience regular and predictable energy loss due to both inter-row shading and reduced diffuse irradiance in tightly spaced arrays. This paper investigates the advantages of replacing bypass diodes with submodule-integrated DC-DC converters (subMICs) to mitigate these losses. Yearly simulations of commercial-scale PV systems were conducted considering a range of row-to-row pitches. In the limit case of array spacing (unity ground coverage), subMICs can confer a 7% increase in annual energy output and peak energy density (kW h/m2). Simulation results are based on efficiency assumptions experimentally confirmed by prototype submodule differential power-processing converters.

This paper presents a robust control synthesis framework for switched DC-DC converters. The framework is based on an LMI formulation which can be solved automatically by efficient convex optimization algorithms. The method considers parameter-dependent Lyapunov functions such that it can take into account the uncertainty of converter parameters, nonlinear dynamics (such as state-dependence), as well as transient and steady-state performances that can be imposed beforehand. The result of the proposed synthesis method is a gain-scheduled controller that guarantees stability despite the accounted nonlinear dynamics and can provide excellent performances. Two different synthesis examples are shown for a DC-DC boost converter and their performance and robustness are compared with a standard control approach as current-mode control, both in nominal and non-nominal conditions. Finally, the proposed approach is verified with experimental results.

A new digital robust control law for dc–dc converters is analyzed and implemented in this paper. The robust control QFT technique, which has been successfully used with analog implementations, has been adapted to the digital domain. Concretely, this paper considers the design of a power conditioning unit, which must take into account the uncertainty of the converter, as the conduction mode, the load, the input voltage or the storage elements while assuring that the specifications of a well-known standard are met. The robust control has been implemented by means of a digital device. The sampling frequency is a critical parameter for this kind of system which exhibits fast dynamics. The paper shows a procedure to analyze the minimum sampling frequency of the regulation loop. The procedure consists of transforming an standard analog QFT design to a digital controller by means of an accurate transformation from the s to z domain. After this transformation, we assure the robust stability of the converter by means of the Kharitonov theorem. This approach allows the designer to avoid iterations while finding an appropriate sampling frequency. The experimental prototype has been implemented by means of a FPGA device where the sampling frequency is 100 kHz for a buck power stage with a switching frequency of 200 kHz. The experimental results that are in good agreement with theoretical derivations.

This paper describes a novel modeling approach for self-oscillating resonant power converters operating under a variable structure system (VSS) control method. Using a fundamental harmonic approximation, the link between control and switching frequency in steady-state is found to be accurately described by an affine function that depends on the load. In addition, the control-to-switching frequency dynamics are shown to present advantageous phase leading characteristics at high frequencies. The resulting control-to-switching frequency dynamics can be appended to the well-known transfer functions for frequency modulation, in order to obtain a complete control-to-output model. With the new model, the advantages of the VSS controller become apparent: reduced DC gain tolerance for uncertain loads, extended bandwidth and improved phase margin at high frequencies. While results for both the series and parallel resonant converters are provided, the proposed approach has been illustrated in the case of modeling the control-to-output voltage transfer function of a parallel resonant converter. Numerical simulations and experimental results confirm and verify the analytical derivations.

This paper addresses the control problem of dc–dc converters. The control law synthesis considered here exploits the potential of LMI-based control approaches, which allow to cope with model uncertainty, disturbances and bilinearities to synthesize simple state-feedback controllers with a priori guarantee of stability in a large domain of initial and operating conditions. The aim of the paper is to contribute with a robust control framework to deal with the common requirements of regulated dc–dc converters. The correctness of the results has been verified both with numerical simulations and with experimental measurements from a laboratory prototype.

This article presents a new passivity-based control law that stabilizes the output voltage of a high-order DC-DC converter. Such nonlinear control law assures robust large-signal stability, provides zero steady-state error despite uncertainty in converter parameters and has enough degree of freedom to satisfy the usual transient specifications of DC-DC converters. This new integral control is derived in three steps. First, a static law is obtained. Second, a positive semidefinite storage function is synthesized to guarantee zero steady-state error of the output voltage. Finally, the storage functions of the first two steps are combined to derive the new control law for high-order DC-DC converters. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society

A consistent framework for robust linear quadratic regulators (LQRs) control of power converters is presented. Systems with conventional LQR controllers present good stability properties and are optimal with respect to a certain performance index. However, LQR control does not assure robust stability when the system is highly uncertain. In this paper, a convex model of converter dynamics is obtained taking into account uncertainty of parameters. In addition, the LQR control for switching converters is reviewed. In order to apply the LQR control in the uncertain converter case, we propose to optimize the performance index by using linear matrix inequalities (LMIs). As a consequence, a new robust control method for dc-dc converters is derived. This LMI-LQR control is compared with classical LQR control when designing a boost regulator. Performance of both cases is discussed for load and line perturbations, working at nominal and non nominal conditions. Finally, the correctness of the proposed approach is verified with experimental prototypes.

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.

Large commercial photovoltaic systems suffer a regular and predictable energy loss due to both inter-row shading and reduced diffuse irradiance in tightly spaced arrays. This paper investigates the advantages of replacing bypass diodes with submodule-integrated DC-DC converters (subMICs) to mitigate these losses. Yearly simulations of commercial-scale PV systems were conducted considering two subMIC granularities and a range of row-to-row pitches given either a fixed array size or a fixed land area. Results show subMIC-enhanced systems can recover 35–48% of the total energy loss. In very tightly-spaced arrays, subMICS rated at 100% of maximum substring power can confer a 7% increase in annual energy output while power-limited subMICs rated at 30% or 15% of maximum substring power still provide a 6% or 3–4% increase, respectively.

This paper describes a photovoltaic (PV) power system architecture based on standard wiring of series-connected PV modules, where each PV module includes differential power processing (DPP) submodule integrated converters (subMICs). Given the absence of additional wiring commonly used to allow DPP subMICs to exchange power among PV modules, mismatches in such conventionally wired subMIC-enhanced system may result in bypassed sections, which yields a model with discontinuous-hard-nonlinearities and complicates numerical simulations. The paper presents a simple and efficient solver for the conventionally wired subMIC-enhanced system. The approach is used to examine the mismatch mitigation performance of this architecture in selected utility-scale and residential systems. Although the mismatch mitigation performance is inferior compared to the fully wired DPP subMIC-enhanced system, it is shown that there are cases where the conventionally wired DPP systems offer some energy yield and hot-spot mitigation improvements. Energy yield improvements are more significant in partially shaded systems with multiple parallel strings of modules, and in systems affected by nonuniform aging.

10.1109/JPHOTOV.2013.2281878 Mismatch power losses in photovoltaic (PV) systems can be reduced by the use of distributed power electronics at the module or submodule level. This paper presents an experimentally validated numerical model that can be used to predict power production with distributed maximum power point tracking (DMPPT) down to the cell level. The model allows the investigations of different DMPPT architectures, as well as the impact of conversion efficiencies and power constraints. Results are presented for annual simulations of three representative partial shading scenarios and two scenarios where mismatches are due to aging over a period of 25 years. It is shown that DMPPT solutions that are based on submodule integrated converters offer 6.9-11.1% improvements in annual energy yield relative to a baseline centralized MPPT scenario.

This paper presents a cell-level simulation model of photovoltaic (PV) systems that is capable of reproducing partial-shading and other mismatch effects at high granularity. The nonlinear diode voltage-current characteristic is stored in a piecewise-linear model, and the stored values are employed to compute the Jacobian matrices very efficiently. As a result, the model can be solved with low computational effort, so that simulations at cell-level granularity and over long time spans can be carried out efficiently. The model is well suited for evaluations of energy capture, including the effects of partial shading or other mismatches, in large PV systems over long periods of time. Comparisons of simulation and experimental results are provided for three representative PV systems.

Differential power processing (DPP) isolated-port architecture with submodule integrated converters (subMICs) enables improved energy capture in photovoltaic (PV) power systems. This paper describes a control scheme for flyback subMICs operating in discontinuous conduction mode (DCM). The duty-cycle is driven in proportion to a voltage error, with no further processing, thus eliminating the need to measure or to control the current explicitly. The approach is well suited for very simple, analog PWM controller implementation, but the resulting control loops become nonlinear. The system stability is demonstrated using the Lyapunov stability theorem. Experimentally measured module-level efficiency is greater than 95% for a 72-cell PV module having 3 substrings with solar irradiation of 80%, 60% and 40%, respectively.

Differential power processing (DPP) architectures employ low power rated dc-dc converters to mitigate, without insertion losses, mismatches in series strings of photovoltaic (PV) cells. This paper presents tools for simulation of PV systems based on the isolated-port submodule integrated converter (subMIC) DPP architecture. While the ideal operation with full power rated subMICs is relatively easy to solve using a combination of numerical and analytical methods, the solution with partial power rated (current limited) subMICs is more challenging. A heuristic branch and bound algorithm is proposed as an effective method to deal with nonlinearities introduced by current limited subMICs. The approach is well suited for high-granularity simulations of large PV systems over long periods of time, as illustrated by experimental and simulations results.

This paper describes a PV module architecture with submodule integrated converters (subMICs) that improve efficiency of energy capture in the presence of partial shading or other mismatch conditions. Replacing standard bypass diodes, the subMICs are bidirectional dc-dc converters capable of injecting or subtracting currents to balance the module substring voltages. When no mismatches are present, the subMICs are simply shut down, presenting no insertion losses. A simple distributed control approach is described that allows autonomous subMIC control without the need for a central controller or any communication among the subMICs. It is shown that this control approach is close to optimal. Besides, this distributed control approach allows to isolate the secondary port of subMICs from the module output. The isolated-port architecture has additional advantages in its implementation and integration within arrays of PV modules. Simulation and experimental results demonstrating effectiveness of the proposed architectures and the control approach are shown for a typical PV module with 3 substrings.

Switching regulator implementations become unsuccessful when the duty-cycle signal propagates the current ripple. We propose a new robust LMI control strategy to avoid the ripple propagation drawbacks. This control strategy is applied to boost converters ensuring that the duty-cycle signal is almost ripple free. In addition, the proposed control takes into account usual LMI constraints on stability, pole-placement and control effort while optimizes the current-disturbance rejection. In order to illustrate our approach, we compare the proposed strategy when we take into account the ripple constraint and when we do not. We verify the proposed strategy by means of PSIM simulations concluding that the corresponding waveforms are in perfect agreement with the analytical derivations.

This paper addresses a potential instability that can take place in Boost converters with average inductor current control. When the output of a Boost converter is attached to a load having bidirectional power capabilities or to an energy source such as a photovoltaic (PV) panel, instability conditions exist which prevent the design of a wide-bandwidth inductor current control. This paper discusses such instability conditions and their physical interpretation, and proposes an alternative control approach solving the problem. Simulation and experimental analyses for a non-inverting buck-boost converter interfacing a 85 W PV module are provided to demonstrate the instability condition as well as to validate the proposed alternative control solution.

The paper analyses extremum-seeking control technique for maximum power point tracking circuits in PV systems. Specifically, the paper describes and analyses the sinusoidal extremum-seeking control considering stability issues by means a Lyapunov function. Based on this technique, a new architecture of MPPT for PV generation is proposed. In order to assess the proposed solution, the paper provides some experimental measurements in a 100 W prototype which corroborate the effectiveness of the approach.

This chapter proposes a systematic approach for the synthesis of robust controllers for dc-dc converters. The approach is based on the Linear Matrix Inequalities (LMIs) framework and the associated optimization algorithms. The aim of this approach is to allow the designer to describe the uncertainty of the converter and to deal with the requirements of the application beforehand. The aforementioned dc-dc converters (see Figure 1) are devices that deliver a dc output voltage, with different properties from those in the input voltage (Erickson & Maksimovic, 1999). They are usually employed to adapt energy sources to the load requirements (or vice versa). These devices present several challenges regarding their robust control. First, the converter must maintain a tight regulation or tracking of the output. Moreover, the controller design is focused on maximizing the bandwidth of the closed-loop response in order to reject the usual disturbances that appear in these systems. Finally, the response of the converter must satisfy desirable transient characteristics, as for example, the shortest possible output settling time or the minimum overshoot. Besides of these common requirements, the converter can be affected by uncertainty in its components or by input or output disturbances that may appear.