Carlos Meza

Energy-Balance Control of PV Cascaded Multilevel Grid-Connected Inverters Under Level-Shifted and Phase-Shifted PWMs

This paper presents an energy-balance control strategy for a cascaded single-phase grid-connected H-bridge multilevel inverter linking n independent photovoltaic (PV) arrays to the grid. The control scheme is based on an energy-sampled data model of the PV system and enables the design of a voltage loop linear discrete controller for each array, ensuring the stability of the system for the whole range of PV array operating conditions. The control design is adapted to phase-shifted and level-shifted carrier pulsewidth modulations to share the control action among the cascade-connected bridges in order to concurrently synthesize a multilevel waveform and to keep each of the PV arrays at its maximum power operating point. Experimental results carried out on a seven-level inverter are included to validate the proposed approach.This paper presents an energy-balance control strategy for a cascaded single-phase grid-connected H-bridge multilevel inverter linking n independent PV arrays to the grid. The control scheme is based on an energy-sampled data model of the PV system and enables the design of a voltage loop linear discrete controller for each array ensuring the stability of the system for the whole range of PV arrays operating conditions. The control design is adapted to Phase-Shifted and Level-Shifted Carrier PWM to share the control action among the cascadeconnected bridges in order to concurrently synthesize a multilevel waveform and to keep each of the PV arrays at its maximum power operating point. Experimental results carried out on a 7-level inverter are included to validate the proposed approach.

Boost-buck inverter variable structure control for grid-connected photovoltaic systems

The present work describes the analysis, modeling and control of a transformerless boost-buck power inverter used as a DC-AC power conditioning stage for grid-connected photovoltaic (PV) systems. The power conditioning systems control scheme includes a variable structure controller to assure output unity power factor and a sensorless maximum power point tracking (MPPT) algorithm to optimize the PV energy extraction. To maximize the steady-state input-output energy transfer ratio a discrete linear controller is designed from a large-signal sampled data model of the system. The achievement of the DC-AC conversion at unity power factor and the efficient PVs energy extraction are validated with simulation results.

Energy-Balance Modeling and Discrete Control for Single-Phase Grid-Connected PV Central Inverters

This paper presents a two-control loop design considering the nonlinear time-varying characteristics of a single-phase grid-connected photovoltaic (PV) full-bridge central inverter. The control scheme design is based on the energy-balance modeling of the PV system and enables the design of a voltage loop linear discrete controller ensuring the stability of the system for the whole range of PV array operating conditions. A set of experimental results carried out on a laboratory prototype is provided to validate the proposed approach.

Lyapunov-Based Control Scheme for Single-Phase Grid-Connected PV Central Inverters

A Lyapunov-based control scheme for single-phase single-stage grid-connected photovoltaic central inverters is presented. Besides rendering the closed-loop system globally stable, the designed controller is able to deal with the system uncertainty that depends on the solar irradiance. A laboratory prototype has been built as a proof of concept for the proposed control technique. A nonlinear passive adaptive controller has been programmed in a field-programmable gate array.

Energy-Sampled Data Modeling of a Cascade H-Bridge Multilevel Converter for Grid-connected PV Systems

This paper presents an energy-sampled data model of a cascade H-bridge multilevel converter for single-phase multi-string grid-connected photovoltaic systems. Based on this model a control scheme for the power converter is obtained. The achievement of the DC-AC conversion with an efficient PV energy extraction, low harmonic distortion and output unity power factor is validated with simulation results

Control of a buck inverter for grid-connected PV systems: a digital and sliding mode control approach

This work describes the analysis, modeling and design of a buck-based inverter control for grid-connected photovoltaic (PV) systems. On one hand a linear digital voltage controller is designed from a large-signal linear sampled-data model of the system to maximize the steady-state input-output energy transfer ratio. On the other hand, a sliding-mode current controller is also designed to assure a unity power factor. The achievement of the DC-AC conversion and the efficient PVs energy extraction are validated with simulation results.

Inverter Configurations Comparative for Residential PV-Grid Connected Systems

In the present paper three different residential grid-connected photovoltaic inverter configurations are analyzed. A unified large-signal linear energy-sampled data model is achieved which allows the design of a control scheme that extracts the maximum energy from the PV array. The application of this control approach to central, string and multi-sting inverters lead to a comparative in terms of the design restrictions for these topologies which is evidenced by means of simulation results

Energy-balance and sliding mode control strategies of a cascade H-bridge multilevel converter for grid-connected PV systems

This work presents the design of a sliding-mode based current controller for a Cascade Full Bridge Multilevel Inverter grid connected PV system. The design also includes a modulation strategy to share the control action among the cascade-connected bridges in order to concurrently synthesize a multilevel waveform and to keep each of the PVG at its maximum operating point. Experimental results are included to validate the proposed approach.

Free open source software in control engineering education: A case study in the analysis and control design of a rotary inverted pendulum

The present paper aims to show the advantages of using Free and Open Source Software for control systems in education. Accordingly, this paper presents a control assignment for an introductory control theory course that can be done entirely with FOSS. This assignment consists of the control of a rotary inverted pendulum.

Sliding-mode control design of parallel-connected switching converters for modular transformerless DC-AC step-up conversion

This paper presents the design of a sliding-mode control of parallel-connected boost-buck inverter modules for a modular transformerless DC-AC step-up conversion. Two sets of sliding control laws are proposed. The first one is based on the master-slave strategy to control the buck stages for a DC-AC conversion, ensuring at the same time an output voltage regulation and a proper current sharing among the inverter modules. The second set is devoted to the control of the boost stages in order to perform a step-up DC-DC conversion, ensuring simultaneously the buck stages proper operation by preserving their sliding domains. Experimental results carried out on two parallel-connected boost-buck inverter modules are presented to validate the proposed design.