Aggelos S. Bouhouras

Selective Automation Upgrade in Distribution Networks Towards a Smarter Grid

Research on smart grid technologies has been advancing over the last years, producing novel practices concerning mainly the power distribution networks. However, in many countries these networks still operate in their traditional form, without offering the real-time operational characteristics which are essential for the utilization of the aforementioned practices. On the other hand, due to the extent of urban power distribution networks, as well as the substantial cost of medium voltage equipment, the full upgrade of these networks is in most cases not a feasible option. In this work, alternative options of selective automation upgrade in power distribution networks are offered, corresponding to the desired operational status of these networks. More specifically, the essential upgrades are analyzed for the implementation of reliability improvement and loss reduction techniques on such a network.

Harmonic impact of small photovoltaic systems connected to the LV distribution network

Since the penetration of photovoltaic (PV) systems in the low voltage (LV) distribution network is increasing, the need to register and model the contribution of these systems to the harmonic distortion of current and voltage waveforms is becoming an up-to-date issue. As PV systems incorporate power conditioning units, which are harmonic generating devices, they will have an influence on quality of supply, reliable operation of system equipment as well as component life expectancy. This paper investigates the harmonic impact of a 20 kWp PV system connected to the LV distribution network in Greece. The harmonic behavior of the PV plant as a function of the solar radiation under several weather conditions is analyzed. Measurements results are compared to those obtained from the power simulator package PSIMcopy. The level of penetration of PV systems in the LV distribution network without harmonic limits been exceeded is investigated.

Load signatures improvement through the determination of a spectral distribution coefficient for load identification

In this paper a novel and simple methodology for developing distinct load signatures is proposed. The analysis relies on the exhaustive utilization of the information embedded in the harmonic behavior of a load, towards the formulation of an appropriate data form that could describe the behavior of a Low Voltage (LV) load in a unique and representative way. Based only on the current magnitude during one period of the steady state, a special coefficient is formulated under a simple procedure determining the spectral distribution of the current. A load identification algorithm is also developed and presented in order to examine the robustness and effectiveness of the resulting load signatures. The results are very promising since they indicate that uniqueness in load signatures is indeed added by the proposed technique and hence, the improvement of the effectiveness of the signatures could contribute in more efficient Nonintrusive Load Monitoring (NILM) algorithms.

PV systems penetration and allocation to an urban distribution network: A power loss reduction approach

This paper examines the impact of Distributed Generation to loss reduction in power distribution networks. In specific, the way that penetration level and allocation of PV units in a distribution Medium Voltage feeder affects power losses is investigated. Different approaches, regarding PV units placement across the feeder and their capacity, are analyzed and useful conclusions regarding the penetration level of PV units and their optimal placement across distribution feeders for loss reduction are derived.

Reliability improvement resulting from the integration of PV systems in the Interconnected Greek Transmission System

Photovoltaic Systems (PV) are becoming one of the most developing investment areas in the field of renewable energy sources (RES). Environmental pollution renders the need for covering energy demands by renewable sources more imperative than ever. The aim of the paper is to use the estimated power production of PV units in order to evaluate the potential improvement of loss of load probability (LOLP) and loss of energy probability (LOEP). This analysis is implemented for the Interconnected Greek Transmission System (IGTS). The power output of PV units in Greece is calculated and the expected reduction of the above indices is demonstrated. Furthermore, peak shaving for the IGTS by the use of PV units is also illustrated. Finally, reliability improvement is expressed in terms of profit by comparing the cost for every kWh produced by PV units to the corresponding cost for every kWh produced by expensive units, which would otherwise cover a proportion of peak load demand.

Application and evaluation of UPSO to ODGP in radial Distribution Networks

In this paper, a new effort regarding the Optimal Distributed Generation Placement (ODGP) problem is presented. Loss minimization is considered as the objective while considering the networks technical characteristics as constraints, i.e. node voltage and line thermal limits. The proposed method, called Unified Particle Swarm Optimization technique (UPSO), combines the advantages while at the same time extinguishes the disadvantages of the two basic PSO variants, the Global and Local PSO. The implemented analysis demonstrates that an enhanced performance is achieved, both in terms of a better optimal solution as well as faster convergence. The method is evaluated upon IEEE-16 and IEEE-33 bus systems and compared with other techniques.

Siting and installation of PV systems in Greece and their contribution in the reliability of the distribution network

A statement of the status quo of the PV power systems in Greece, as well as their possible contribution towards the enhancement of power distribution reliability, is the scope of the present paper. Siting and installation of PV systems is performed according to a recent Greek law and by considering environmental and geographical constraints. Meteorological data about solar radiation and temperature are computed, formulated and imported to appropriate software in order to simulate the PV units and generate their power output. The above estimated power production is compared to data concerning load shedding. Assuming that a specific proportion of the eventually unsupplied power could be provided by the accessed power generation of the PV units, the reliability of the distribution system is improved. This improvement is quantified using the distribution system reliability indices SAIDI, SAIFI and CAIDI. The resulting improvement is finally expressed in financial terms through the reduction of interruption costs.

Energy loss reduction in Distribution Networks via ODGP

In this paper the Optimal Distributed Generation Problem (ODGP) towards energy minimization is solved for a large number of scenarios regarding power loss minimization. Load variations are taken into account by the formulation of different snapshots concerning the networks operational status. These snapshots refer to various load compositions and for each one the ODGP problem is applied. Load variations are formed stochastically under a uniform distribution while the initial loading conditions are considered as the mean load profile of the network. The solution algorithm relies on a Local PSO Variant and the results indicate that for not extreme load variations some specific nodes tend to participate in the majority of the different solutions. Thus, the analysis proposes a fixed solution that could yield the highest energy reduction despite the fact that it is not the optimal for each individual operating state with different load composition.

Reducing network congestion in distribution networks with high DG penetration via network reconfiguration

In this paper the problem of network congestion due to high penetration of Distribution Generation (DG) in Distribution Networks (DNs) via network reconfiguration is examined. The problem in DNs is differentiated from the respective one in Transmission Networks (TNs), since the former is examined through a technical perspective while the latter through an economical orientated aspect. In this work, DN congestion is established as the problem of increased loading of the DN branches due to bi-directional power flow. The latter is expected to occur when the load demand of the DN is low and the power production of DG is high. Therefore, a Congestion Indicator Factor (CIF) is introduced in order to describe the tendency of DN towards congestion. Based on the CIF values, network reconfiguration is proposed as a real time solution regarding the online management of the DN in order to mitigate congestions. Results indicate that local reconfigurations could yield both congestion reduction and voltage profile improvement.

Loss reduction via network reconfigurations in Distribution Networks with Photovoltaic Units Installed

The penetration of Renewable Energy Resources in Distribution Networks (DNs) is increasing rapidly, thus traditional issues regarding the DN operation should be faced through a different perspective that concerns dynamic behavior for both the distributed load consumption and power generation points of a network. Within this context, loss minimization in DNs by network reconfigurations should be examined subject to the variations regarding the load composition of the network due to the presence of Distributed Generation (DG) units. In this paper, the influence of Photovoltaic (PV) units installed in DNs to the optimal reconfiguration for loss reduction is investigated. The problem is stated, and a three level formulation is proposed in order to describe how the problem should be faced for an exhaustive and thorough analysis. Moreover, a simplified version of this proposed methodology is adopted in this work considering a two-stage sensitivity analysis: a spatial sensitivity analysis regarding the distribution of the PV units, and a quantitative sensitivity analysis concerning the penetration of the PV units in respect to the capacity of the network. The methodology is applied to three DNs by the published literature, and the results provide useful conclusions regarding the effect of the spatial distribution level along with the installed capacity of the PV units to the optimal reconfigured solution.