Smart Distributed Generation System Event Classification using Recurrent Neural Network-based Long Short-term Memory

High penetration of distributed generation (DG) sources into a decentralized power system causes several disturbances, making the monitoring and operation control of the system complicated. Moreover, because of being passive, modern DG systems are unable to detect and inform about these disturbances related to power quality in an intelligent approach. This paper proposed an intelligent and novel technique, capable of making real-time decisions on the occurrence of different DG events such as islanding, capacitor switching, unsymmetrical faults, load switching, and loss of parallel feeder and distinguishing these events from the normal mode of operation. This event classification technique was designed to diagnose the distinctive pattern of the time-domain signal representing a measured electrical parameter, like the voltage, at DG point of common coupling (PCC) during such events. Then different power system events were classified into their root causes using long short-term memory (LSTM), which is a deep learning algorithm for time sequence to label classification. A total of 1100 events showcasing islanding, faults, and other DG events were generated based on the model of a smart distributed generation system using a MATLAB/Simulink environment. Classifier performance was calculated using 5-fold cross-validation. The genetic algorithm (GA) was used to determine the optimum value of classification hyper-parameters and the best combination of features. The simulation results indicated that the events were classified with high precision and specificity with ten cycles of occurrences while achieving a 99.17% validation accuracy. The performance of the proposed classification technique does not degrade with the presence of noise in test data, multiple DG sources in the model, and inclusion of motor starting event in training samples

Distributed Generation and Islanding – Study on Converter Modeling of PV Grid-Connected Systems under Islanding Phenomena

Thailand government has launched a 15-year (2008-2022) strategic plan on new and renewable energy. Possible electricity generated from solar photovoltaic has been estimated with a potential of 50,000 MW, whereas at present the cumulative installed wattage is only 32 MW. Under the Plan, numbers of measures and incentives are provided for participation of private very small power producers (VSPP) generating and selling the electricity into the utilities. Most VSPPs generate electricity from renewable sources such as mini-hydro, biogas and biomass, wind and solar. Examples of measures and incentives are the Renewable Portfolio Standard (RPS) for the generating utility and independent power producers (IPP), a feed in tariff with an extra adder, soft loans and tax reduction. The past decade in Thailand has seen shifts from PV used in the public market through government demonstration projects to the consumer market, installations of PV VSPPs and domestic roof-top grid connected PV units gain momentum. With the government incentive more households will be attracted to produce electricity from solar PV and wind energy. As domestic roof sizes are limited, PV roof-top grid-connected units will be of small capacity, less than 10 kW. It is this possible large expansion of market for thousands of small PV rooftop grid-connected units or wind systems in Thailand, and eastern Asia, that draws our attention to the study of single phase distributed generator grid-connected systems. Our focus will be on the anti-islanding protection, which is of concerns to Thai electrical utilities. In order to know the behavior and the effect of anti-islanding techniques, the converter modeling of PV grid-connected systems under islanding phenomena is studied. The approach of modeling is to model a dc-ac full bridge switching converter PV grid-connected system under islanding phenomena using two mathematical modeling techniques. One corresponds to a state-space averaging technique (no linearization) and the other a piecewise technique. The former technique applies a state-space averaging techniqu

A High-Performance Three-Phase Grid-Connected PV System Based On Multilevel Current Source Inverter

Current Source Inverter (CSI) topology is gaining acceptance as a competitive alternative for grid interface of renewable energy systems due to its unique and advantageous features. Merits of CSI over the more popular Voltage Source Inverter (VSI) topology have been elaborated on by a number of researchers. However, there is a dearth of quality work in modeling and control of CSI topology interfacing renewable energy resources to the grid. To enrich the study focussing on application of CSI for renewable energy interface, this thesis develops a multilevel structure based on CSI for three-phase grid-connected Photovoltaic (PV) application. In the first part of research, a single-stage CSI interfacing to PV array is developed. The CSI-based PV system is equipped with Maximum Power Point Tracker (MPPT), DC-link current controller, and AC-side current controller. To eliminate the nonlinearity introduced by the PV array, a feed-forward control is introduced in the DC-link current controller. The AC-side current controller is responsible for maintaining unity power factor at the Point of Common Coupling (PCC). To verify the performance of the developed CSI-based PV system, a number of simulation studies are carried out in PSCAD/EMTDC environment. To illustrate the performance of the CSI-based PV system during transients on the grid side, simulation studies are carried out for four kinds of faults. Results obtained from fault studies are highly in favor of CSI topology and provide illustrative evidence for short-circuit current protection capability of the CSI. On the other hand, the VSI-based PV system performs poorly when subjected to similar grid transients. To extend the research on CSI-based PV system further, a multilevel structure based on CSI is developed. The multilevel structure is a parallel combination of $n$ CSI units and capable of producing $2n+1$ levels of current at the terminal of the inverter. Each unit in the multilevel structure has its own MPPT, DC-link current controller. However, on the AC-side a combined current controller is proposed. The design results in a high power rating with reduced number of filters, sensors and controllers. The developed multilevel structure can operate with PV arrays exposed to equal and unequal insolation level. However, when the PV arrays are operating under unequal insolation level, low order harmonics are generated in the sinusoidal current that is injected into the grid. Elimination of these harmonics is performed by implementing a modified control strategy in stationary reference frame that corresponds to the harmonic component that needs to be minimized. The modified control strategy operates in coordination with the existing DC-side and AC-side current controllers, and MPPTs. Therefore, real-time suppression of current harmonics can be ensured. Performance of the multilevel structure is verified by different transient studies

Power Quality Improvement of Distributed Generation Integrated Network with Unified Power Quality Conditioner.

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 knowledge may not be available. Therefore, the main objective of the present research is to investigate the (i) placement (ii) integration (iii) capacity enhancement and (iv) real time control of the Unified Power Quality Conditioner (UPQC) to improve the power quality (PQ) of a distributed generation (DG) network connected to the grid or microgrid

Analisa Anti Islanding Pada Inverter 3 Fase PLTS Hybrid 5 Kw Terhadap Jaringan PLN

PLTS Hybrid adalah salah satu jenis pembangkit listrik tenaga surya yang juga menggunakan baterai sebagai penyimpanan energi listrik dan masih terhubung dengan jaringan PLN, supaya untuk menutupi kekurangan pasokan energi listrik terhadap beban (impor) maupun menyalurkan energi berlebih saat PLTS produksi berlebih dan energi beban sudah terpenuhi serta energi baterai juga terpenuhi (ekspor). Oleh karena itu pada penelitian kali ini membahas mengenai dua sumber pembangkit ketika sinkron (PLTS dan PLN) yang mana dibutuhkan system anti islanding yang baik supaya tidak terjadi islanding yang dapat mempengaruhi masalah kualitas daya, integritas sistem, serta keamanan. Penelitian dilakukan dengan membandingkan data ketika saat jaringan PLN belum tersinkron dengan PV (photovoltaick), sesudah tersinkron dengan PV, belum tersinkron dengan baterai, sesudah tersinkron dengan baterai dan pengaruh beban terhadap keandalan system. Dimana nantinya akan diketahui data-data yang membuat system islanding terjadi dan dibutuhkan metode anti islanding yang tepat.Kata kunci: PLTS Hybrid, sinkron, islanding, anti islandin

Enhancing reliability in passive anti-islanding protection schemes for distribution systems with distributed generation

This thesis introduces a new approach to enhance the reliability of conventional passive anti-islanding protection scheme in distribution systems embedding distributed generation. This approach uses an Islanding-Dedicated System (IDS) per phase which will be logically combined with the conventional scheme, either in blocking or permissive modes. Each phase IDS is designed based on data mining techniques. The use of Artificial Neural Networks (ANNs) enables to reach higher accuracy and speed among other data mining techniques. The proposed scheme is trained and tested on a practical radial distribution system with six-1.67 MW Doubly-Fed Induction Generators (DFIG-DGs) wind turbines. Various scenarios of DFIG-DG operating conditions with different types of disturbances for critical breakers are simulated. Conventional passive anti-islanding relays incorrectly detected 67.3% of non-islanding scenarios. In other words, the security is as low as 32.3%. The obtained results indicate that the proposed approach can be used to theoretically increase the security to 100%. Therefore, the overall reliability of the system is substantially increased

Islanding Detection in Micro-grids using Sum of Voltage and Current Wavelet Coefficients Energy before the Main Circuit Breaker Side

This paper presents wavelet based islanding detection in distributed generation (DG) interfaced to the microgrid. Also a new fast method is developed for islanding detection based on measuring the utility currents and voltages signals processed by discrete wavelet transform. These currents and voltages signals are measured before the main circuit breaker of microgrid network and their features extracted by discrete wavelet transform. These features are sum of wavelet coefficients energy and are used for distinguishing the islanding conditions from non-islanding ones. Because of changing in measuring point of currents and voltages signals from point of common coupling (PCC) in traditional methods to before the main circuit breaker in proposed method, this new method detects the islanding conditions faster than the other methods. The proposed method has been examined under various scenarios; including mains supply faults, various one, two, or three phases' grid faults, and changes of rate of produced energy on IEEE 1547 anti-islanding test system. The numerical studies show the feasibility and applicability of the proposed method with satisfactory results