N. W. A. Lidula

A Pattern Recognition Approach for Detecting Power Islands Using Transient Signals—Part I: Design and Implementation

A novel, pattern-recognition-based approach for fast detection of power islands in a distribution network is investigated. The proposed method utilizes transient signals generated during an islanding event to detect the formation of the island. A decision-tree classifier is trained to categorize the transient generating events as “islanding” or “non-islanding.” The feature vectors required for classification were extracted from the transient current and voltage signals through discrete wavelet transform. The proposed technique is tested on a medium-voltage distribution system with multiple distributed generators. The results indicate that this technique can accurately detect islanding events very fast.

A Pattern-Recognition Approach for Detecting Power Islands Using Transient Signals—Part II: Performance Evaluation

Part I of this paper describes the design and implementation of an islanding detection method based on transient signals. The proposed method utilizes discrete wavelet transform to extract features from transient current and voltage signals. A decision-tree classifier uses the energy content in the wavelet coefficients to distinguish islanding events from other transient generating events. The verification tests performed in Part I, for a two generator test system having a synchronous generator and a wind farm, showed more than 98% classification accuracy with 95% confidence and a response time of less than two cycles. In Part II, the proposed methodology is applied to an extended test system with a voltage-source converter-based dc source. The proposed relays performance is compared with the existing passive islanding detection methods under different scenarios. Furthermore, the effect of noise on the performance of the proposed method is studied. The transient-based islanding detection methodology exhibits very high reliability and fast response compared to all other passive islanding detection methods and shows that the relay can be designed with a zero nondetection zone for a particular system.

Investigation of a fast islanding detection methodology using transient signals

A novel approach for fast detection of power islands in a distribution network using the transient signals generated during the islanding event is investigated. Performance of several pattern recognition techniques in classifying the transient generating events as islanding or non-islanding was examined. Discrete wavelet transform of the transient current signals are utilized to extract feature vectors for the classifiers. Samples of the feature vectors corresponding to various islanding and non-islanding events are applied to train (i) a decision tree classifier, (ii) a probabilistic neural network classifier, and (iii) a support vector machine classifier for recognizing the transient patterns originating from the islanding events. The trained classifiers were then tested with unseen test current waveforms. The test results demonstrated that the investigated technique can potentially provide a new way for identification of islanding in distribution systems.

Fast and reliable detection of power islands using transient signals

A new technique for fast detection of power islands in a distribution network, which uses transient signals generated during the islanding event is investigated. Performance comparison of several pattern recognition techniques in classifying the transient generating events as islanding or non-islanding is presented. Features for the classifiers are extracted using the Discrete Wavelet Transform of current signal transients. Using a set of extracted features from simulated current signals, (i) a decision tree classifier, (ii) a probabilistic neural network classifier, and (iii) a support vector machine classifier were trained for recognizing the transient patterns originating from the islanding events. The trained classifiers were then tested with unseen test current waveforms. The test results demonstrated that the investigated technique can potentially provide a new way for identification of islanding in distribution systems. The approach was then extended changing the feature set and sampling frequency. Proposed method is finally compared with an existing islanding detection technique.

Hardware implementation of an islanding detection approach based on current and voltage transients

A pattern classification technique for fast detection of power islands in a distribution network is implemented and tested. It utilizes voltage and current transient signals generated during an islanding event to detect the formation of the island. A Decision Tree classifier is trained to categorize the transient generating events as ‘islanding’ or ‘non-islanding’. It involves two basic stages of signal processing to extract the required feature vectors for the classification. The first stage involves signal filtering and in the second stage signals are processed by rectifying, summing, and low-pass filtering to get the energy content in the three phases during a selected time-frame. Analog filters, rectifiers, adders and micro-controllers complete the implementation. The performance of the design was tested with signals generated using a real-time waveform playback instrument. A simple radial medium voltage distribution system with single distributed generator was simulated in PSCAD/EMTDC to obtain the transient waveforms. The experimental and simulation results give comparable results showing high accuracy in detecting islanding events very fast.

Modelling and simulation of a solar PV and battery based DC microgrid system

Energy management and control of a PV array and a battery based DC Microgrid is presented in this paper. Design and operation of PV and battery DC-DC converters are discussed in detail. Radiation input to the solar array is an actual variation which was measured in a normal sunny day. Battery is the main component responsible of keeping the DC bus voltage at a constant value by charging or discharging while serving the dynamic load. There are standard built-in models for solar PV and battery in PSCAD/EMTDC, the software which is used for the microgrid simulation. It is observable that the microgrid energy management and control works as expected.

Designing and simulation of a DC microgrid in PSCAD

DC and AC-DC hybrid microgrids are evolving technologies used in telecommunication industry concerning its reliability, safety and efficiency in supplying power. This paper presents a DC Microgrid system designed for telecommunication power supply system, and three possible modes of operations are discussed. The DC microgrid comprises of a solar PV array as the distributed energy source, a battery bank as the energy storage element and the utility grid. The solar characteristics are verified using manufacture specification. The irradiance data used for solar PV is actual data, which was measured in a typical sunny day. A proper Energy Management and Control is proposed for the reliable operation of the DC microgrid. The simulated results show that the energy management and control works as expected.

Evaluation of protection coordination violations with the integration of distributed generators

Conventional distribution system is generally passive having a unidirectional power flow from its grid substation to the loads. With the addition of Distributed Generation (DG) in to the system, power flow becomes bidirectional and fault current increases. These can influence the existing protection schemes, which are originally designed for passive networks. This paper proposes a technique, which can be used to assess the protection coordination loss quantitatively, for a DG integrated network allowing the utility to take corrective measures.