International Energy Research Centre

module efficiency 20 Inverter efficiency 21 Performance ratio 22 2 3 a b s t r a c t 24 This paper presents results obtained from monitoring a 1.72 kW p photovoltaic system installed on a flat 25 roof of a 12 m high building in Dublin, Ireland (latitude 53.4°N and longitude 6.3°E). The system was 26 monitored between November 2008 and October 2009 and all the electricity generated was fed into 27 the low voltage supply to the building. Monthly average daily and annual performance parameters of 28 the PV system evaluated include: final yield, reference yield, array yield, system losses, array capture 29 losses, cell temperature losses, PV module efficiency, system efficiency, inverter efficiency, performance 30 ratio and capacity factor. The maximum solar radiation, ambient temperature and PV module tempera-31 ture recorded were 1241 W/m 2 in March, 29.5°C and 46.9°C in June respectively. 32 The annual total energy generated was 885.1 kW h/kW p while the annual average daily final yield, ref-33 erence yield and array yield were 2.41 kW h/kW p /day, 2.85 kW h/kW p /day and 2.62 kW h/kW p /day 34 respectively. The annual average daily PV module efficiency, system efficiency and inverter efficiency 35 were 14.9%, 12.6% and 89.2% respectively while the annual average daily performance ratio and capacity 36 factor were 81.5% and 10.1% respectively. The annual average daily system losses, capture losses and cell 37 temperature losses were 0.23 h/day, 0.22 h/day and 0.00 h/day respectively. 38 Comparison of this system with other systems in different locations showed that the system had the 39 highest annual average daily PV module efficiency, system efficiency and performance ratio of 14.9%, 40

Long-term monthly average daily solar radiation values on horizontal surfaces at 20 locations in Ireland were used to model the performance of a 1.72 kW p grid-connected PV system. Global solar radiation on horizontal surfaces varied between 865.1 and 1,127.9 kWh/m 2 /yr with a mean of 947.9 kWh/m 2 /yr. Annual energy yields varied between 869 and 1,156 960 kWh/kW p with a mean of 960 kWh/kW p . The capacity factor for the PV system varied between 9.9 and 13.2% while the mean was 11.0%.

This paper presents validated real-time energy models for small-scale grid-connected PV-systems suitable for domestic application. The models were used to predict real-time AC power output from a PVsystem in Dublin, Ireland using 30-min intervals of measured performance data between April 2009 and March 2010. Statistical analysis of the predicted results and measured data highlight possible sources of errors and the limitations and/or adequacy of existing models, to describe the temperature and efficiency of PV-cells and consequently, the accuracy of power prediction models. PV-system AC output power predictions using empirical models for PV-cell temperature and efficiency prediction showed lower percentage mean absolute errors (PMAEs) of 7.9e11.7% while non-empirical models had errors of 10.0e12.4%. Cumulative errors for PV-system AC output power predictions were 1.3% for empirical models and 3.3% for non-empirical models. The proposed models are suitable for predicting PV-system AC output power at time intervals suitable for smart metering. Please cite this article in press as: Ayompe LM, et al., Validated real-time energy models for small-scale grid-connected PV-systems, Energy (2010), L.M. Ayompe et al. / Energy xxx (2010) 1e6 4 EGY2969_proof ■ 9 July 2010 ■ 4/6 Please cite this article in press as: Ayompe LM, et al., Validated real-time energy models for small-scale grid-connected PV-systems, Energy (2010), L.M. Ayompe et al. / Energy xxx (2010) 1e6 6

Kutubdia is one of the coastal islands in Bangladesh. The wind speed data at the wind monitoring station of Bangladesh Meteorological Department (BMD), Kutubdia, located in a built-up area, appears to be low, but at another location, near the seashore, Bangladesh Centre for Advanced Studies (BCAS) finds that the wind energy availability should be reasonably high. Considering the surface roughness, obstacle condition and terrain information of the island, a micro-scale prediction has been done using (100 Â 100 m 2 ) grid cells in the Wind Atlas Analysis and Application Program (WAsP) to develop monthly and annual wind atlas and also a wind resource map which shows that at 50 m height, the annual wind speed over Kutubdia coast varies from 5.1 to 5.8 m/s. Southern and Eastern sides of Kutubdia appear to be promising for wind electricity generation using large turbines where wind power density at a height of 50 m or higher is found to be above 200 W/m 2 annually over the year September 1996 to August 1997. It is found that at 30 m height, the coast side of Kutubdia should be sustainable for small turbines. r resources has been growing steadily. Countries having locations where the wind speed is higher than 5 m/s or so have been going for wind energy generation. Smaller generators are being designed to work for speeds above 2.5 m/s. Windmills for water pumping or other mechanical activities continue to be used where wind speed is 2 m/s or so.

In this paper a technical review of the integration of a Unified Power Quality Conditioner (UPQC) in a distributed generation network is presented. Although the primary task of UPQC is to minimize grid voltage and load current disturbances along with reactive and harmonic power compensation, additional functionalities such as compensation of voltage interruption and active power transfer to the load and grid have also been identified. Connection methodologies with their advantages and disadvantages are also described. Recent improvements in capacity expansion techniques and future trends for the application of UPQC in distributed modes are also identified.

Capacity enhancement and operation flexibility are two of the important limitations of the centralized Shunt Active Power Filter (APF sh ) unit. This can be overcome by multiple and parallel APF sh units (in distributed mode) with a common DC link. In that case, a circulating current (CC) can flow. In the case of a hysteresis current controller based multiple APF sh units in load sharing mode, this CC control is not yet achieved. One of the difficulties of this CC flow control or reduction is the variable switching frequency of the APF sh units. In this paper, the model for CC flow is derived by the switching dynamics study of the APF sh units. Detailed simulation and real time study show that the reduction of CC flow can be achieved at an acceptable level by proper selection of design parameters.

In this paper, an alternative control method is proposed to improve the harmonic suppression efficiency of the active power filter in a distorted and an unbalanced power system to compensate for the perturbations caused by the unbalanced nonlinear loads. The proposed method uses a self-tuning filter (STF) to process the grid voltage in order to provide a uniform reference voltage to obtain the correct angular position of the phase locked loop. Moreover, the required compensation currents are obtained by implementing another STF in the transformed set of currents in order to separate the fundamental and the harmonic currents. This allows the calculation of a precise reference current for the unbalanced, the non-linear and the variable load conditions. The proposed control method gives an adequate compensating current reference even for a nonideal voltage and unbalanced current conditions. The real-time control of the filter under the distorted and the unbalanced power system is developed in an RT-LAB real-time platform. The results obtained in the software-in-the-loop configuration are presented to verify the effectiveness of the proposed control technique.

In this study a method is proposed in order to improve the voltage compensation performance of Dynamic Voltage Restorer by using Self Tuning Filter. The proposed control method gives an adequate voltage compensating even for 50% voltage sag and distorted voltage conditions. The proposed DVR control method is modelled using MATLAB/Simulink and tested both in off-line and real-time environment. Results are then presented as a verification of the proposed method.

In this paper, the placement of Custom Power Devices (CPDs) to improve the power quality of a distributed generation (DG) integrated building energy system (BES) has been analyzed. A typical residential building energy has been modeled in a Virtual Environment (VE) simulator. The extracted energy demand is generated by input load demand and hourly operating information. Based on the electrical energy demand for a typical day, a DG integrated BES (DG-BES) is then simulated in MATLAB to extract the current/voltage disturbance information into the network. Outcome of this simulation shows the voltage/current waveform along with the disturbances at different locations in the building. Finally a CPD is placed into the network and simulation in MATLAB shows the performance of the device by improving the power quality of the DG-BES. The city of Dublin, Ireland has been chosen as a geographical location and VE-Pro software has been used to develop the virtual environment simulation for the building energy system.

With the increased penetration of small scale renewable energy sources in the electrical distribution network, maintenance or improvement of power quality has become more critical than ever where the level of voltage and current harmonics or disturbances can vary widely. For this reason, Custom Power Devices (CPDs) such as the Unified Power Quality Conditioner (UPQC) can be the most appropriate solution for enhancing the dynamic performance of the distribution network, where accurate prior

In this study, the equation for the reactive and harmonic power compensation of a shunt active power filter (APF) system has been derived by studying the power exchange mechanism and power tetrahedron phasor diagram. The switching dynamics of a voltage source inverter (VSI)-based three-phase, three-wire (three-leg /half-bridge) shunt APF system with hysteresis band current control has been studied and verified by simulation. The relation between the design parameters and their effects on the active losses has also been identified. Detailed calculation and extensive simulation have been performed for a three-phase, three-wire shunt APF implemented in a 400V L-L distribution system, as an example, to study the effects of design parameter selection and their role in active power loss calculation. Simulated and calculated results are presented for the important design parameters for different switching frequencies together with their associated losses and kVA ratings. The procedure can be followed to design the parameters for other topologies, such as three-phase, four-wire or single-phase systems.

The use of replacement metamodels (global surrogate models) has become commonplace as a cost effective alternative for performing complex high fidelity computer simulations. Due to their compact formulation and negligible evaluation time, global surrogate models are very useful tools for exploring the design space, what-if analysis, optimization, and sensitivity analysis. In addition, multiple surrogate models can be chained together to easily model large scale systems where a direct, fullwave simulation would be too cumbersome. Two crucial aspects of global surrogate modeling are data collection (sequential design) and hyperparameter optimization. Kriging models have become very popular in many domains but have seen little application in electronics and Electro-Magnetism. In this paper we study the impact of different hyperparameter optimization algorithms and sampling strategies on the accuracy of Kriging models as applied to a Low Noise Amplifier (LNA) RF circuit block.

The paper deals with the problem of identification of guaranteed passive rational models for linear distributes structures. The identification is pursued in two separate steps: in the first step the Vector Fitting algorithm is used for the identification of the poles; then the identification of residues is formulated as a convex programming problem with constraints on single terms of the pole-residue expansion. This approach, although suboptimal, is easier than constraining passivity on the whole transfer function, and at the same time more rigorous than perturbative approaches. In the paper the procedure is validated in reference cases and comparatively evaluated vs. other existing passivity enforcement schemes.

The paper introduces an enhanced version of the magnitude Vector Fitting (magVF) algorithm, a robust procedure for the identification of a transfer function from magnitude frequency domain data. The approach is based on the rational approximation of the magnitude square function with enforcement of symmetric poles and zeros, followed by the elimination of poles and zeros located in the right half plane. The obtained transfer function is stable and of minimum phase shift type. Robustness and accuracy of the basic magVF algorithm are enhanced by enforcing that the magnitude square rational function is non-negative definite and by introducing a new method to remove purely imaginary conjugate poles from the approximation. Practical application of the proposed approach is demonstrated for measured transformer responses and transmission line propagation functions.

An important aspect related to wind energy integration into the electrical power system is the fluctuation of the generated power due to the stochastic variations of the wind speed across the area where wind turbines are installed. Simulation models are useful tools to evaluate the impact of the wind power on the power system stability and on the power quality. Aggregate models reduce the simulation time required by detailed dynamic models of multiturbine systems. In this paper, a new behavioral model representing the aggregate contribution of several variable-speed-pitchcontrolled wind turbines is introduced. It is particularly suitable for the simulation of short term power fluctuations due to wind turbulence, where steady-state models are not applicable. The model relies on the output rescaling of a single turbine dynamic model. The single turbine output is divided into its steady state and dynamic components, which are then multiplied by different scaling factors. The smoothing effect due to wind incoherence at different locations inside a wind farm is taken into account by filtering the steady state power curve by means of Gaussian filter as well as applying a proper damping on the dynamic part. The model has been developed to be one of the building-blocks of a model of a large electrical system, therefore a significant reduction of simulation time has been pursued. Comparison against a full model obtained by repeating a detailed single turbine model, shows that a proper trade-off between accuracy and computational speed has been achieved.