This letter presents for the first time the application of multilevel dc-link inverter to overcome the problem of partial shading of individual photovoltaic (PV) sources which are connected in series. The “PV permutation algorithm,” as a new method, is developed for the control of the inverter so as to extract the maximum power form each PV source under partial shading and to deliver all that power to the load. The algorithm is based on combination of the direct pulsewidth modulation, the sequential permutation PV sources, and the output generation to control the multilevel dc-link inverter. The algorithm is applied successfully to a seven-level inverter with separate maximum power point tracking algorithm for each PV source and under nonuniform irradiance (partial shading). Digital processing unit F28335 eZdsp is used to control the PV system in the real-time mode, and MATLAB-Simulink real-time data exchange is employed to display the extracted power and to control the system parameters via a designed graphical user interface window. The implementation and experimental results are presented.

Multilevel DC-Link Inverter and Control Algorithm to Overcome the PV Partial Shading

The increasing availability of digital computers now makes the computer-aided design of powerelectronic systems an attractive and cost-effective development tool. The paper describes the detailed development of an extremely versatile PWM computer modelling package which can be used as a `stand-alone′ package for harmonic analysis, or alternatively as a `building-block′ for developing more complex systems. The capabilities of the package are demonstrated, using a number of examples of single-phase and 3-phase PWM inverters, which serve to highlight a number of important operational characteristics of PWM inverters. The validity and accuracy of the computer simulations are confirmed, using experimental results obtained from a microprocessor-controlled PWM inverter-drive system.

Computer-Aided Design of PWM Inverter Systems

There are numerous maximum power point tracking (MPPT) algorithms for improving the energy efficiency of solar photovoltaic (PV) systems. The main differences between these algorithms are digital or analog implementation, simplicity of the design, sensor requirements, convergence speed, range of effectiveness, as well as hardware costs. Therefore, choosing the right algorithm is very important to the users, because it affects the electrical efficiency of PV system and reduces the costs by decreasing the number of solar panels needed to get the desired power. This paper provides the comparison of 62 different techniques used in tracking the maximum power based on literature survey. This paper is intended to be a reference for PV systems users.

/pdf/a-review-study-of-photovoltaic-array-maximum-power-tracking-287btoyci9.pdf

A review study of photovoltaic array maximum power tracking algorithms

The model-based analysis of a switched reluctance machine, which has significant losses in the iron core, requires the machine to be represented by parameters that account for nonlinearities caused by both the magnetic saturation and the iron losses. This paper describes the methodology for determining the parameters of the equivalent electric circuit that includes the representation of iron losses. The parameters are derived from measurements performed under static conditions. The methodology is verified by comparing the dynamically measured results for the pull-out force against the results predicted by the model that is based on the equivalent circuit.

Experimental Determination of Equivalent-Circuit Parameters of a Tubular Switched Reluctance Machine With Solid-Steel Magnetic Core

Within the market evolution towards higher efficiency machines, there is a need for more precise modelling tools, taking also higher frequency power supplies into account. This paper implements the effect of cut edge degradation, due to punching, on the local magnetization curve and local losses, aiming at improved calculation of magnetization current and machine iron losses. For an induction machine, defined by Leroy Somer and a high efficiency electrical steel, selected from ArcelorMittal's range, this study combines advanced material characterization with improved modelling techniques, and is validated by selected machine testing procedures. For the sake of clear loss separation a machine with slotless rotor was characterized at two conditions regarding speed and excitation. The loss model, including already the effect of rotational losses and higher harmonics, was enhanced with the punching effect, which led to a model accuracy of 86% at synchronous speed when compared to the measured losses. This study also led to further insights in local magnetization behaviour, to be used in further design optimization.

Iron loss modelling which includes the impact of punching, applied to high-efficiency induction machines

An improved dynamic model of the switched reluctance machine for use in design has been developed. The specific requirement was for the incorporation of iron losses, but a secondary benefit has been the inclusion of the magnetic interaction between phases. The work is described in two stages: (i) modelling of iron loss and its effect on current waveform in a rudimentary one-phase static SR machine, and (ii) the development of a dynamic model, including instantaneous torque, of a three-phase machine with eddy-current, hysteresis and additional iron losses. Both stages include experimental verification. Coupling between the phases through shared portions of the magnetic circuits and also through 'leakage flux' is included. Model results are compared with measured values for a three-phase, 12/8-pole motor.

Dynamic modelling of switched reluctance machines with iron losses and phase interactions

The paper proposes an algorithm for tracking the maximum power point of a PV source which is based on the voltage-hold perturbation and observation tracking of the maximum power point during atmospheric changes The algorithm overcomes the major tracking limitations and produces improved results compared with the standard MPPT algorithms which were reviewed briefly as a background The proposed algorithm has been implemented practically by using eZdsp™ F28335 to control the DC/DC buck-converter under different irradiances

http://ieeexplore.ieee.org/iel5/6014782/6020091/06020199.pdf

Voltage-hold perturbation & observation maximum power point tracking algorithm (VH-P&O MPPT) for improved tracking over the transient atmospheric changes

The paper describes the first phase of a project to improve the prediction and modelling of iron loss for use in the design of switched-reluctance (SR) machines. Earlier models are reviewed and the development of a comprehensive model is described. Its parameters are obtained from commonly available manufacturers' data and this allows the prediction of not only average loss but also instantaneous power flow for a given flux waveform. Its validation against experimental measurements for sinusoidal and triangular fluxes up to 2 kHz, including superimposed DC bias, is demonstrated. The measurement work using toroidal specimens reveals some unexpected behaviour and a challenge to the measurement technique.

Modelling and prediction of iron loss with complex flux waveforms

In this paper the 3-level integration PWM is developed to a simplified generalized PWM algorithm which can be used to control higher level photovoltaic (PV) inverters. The proposed algorithm is implemented practically by using eZdsp™ F28335 to control the multi-level DC-link inverter and to maintain the operation of input PV sources at their maximum power point (MPP). The inverter has been tested under different loads and irradiance conditions and the obtained results are verified by comparison with the space-vector PWM (SVPWM) strategy. The introduced algorithm is simple for implementation and produces satisfactory results in the open and closed-loop systems.

Generalized integration duty cycle conversion pulse-width modulation (IPWM) algorithm for multilevel-PV DC-link inverter

http://ieeexplore.ieee.org/iel3/1147/6646/00264961.pdf

J. Corda

Papers

Dynamic modelling of switched reluctance machines with iron losses and phase interactions

Voltage-hold perturbation & observation maximum power point tracking algorithm (VH-P&O MPPT) for improved tracking over the transient atmospheric changes

Modelling and prediction of iron loss with complex flux waveforms

Generalized integration duty cycle conversion pulse-width modulation (IPWM) algorithm for multilevel-PV DC-link inverter

Analysis of losses in power electronic converter of SR drive