WIMAX Implementation of Smart Grid Wide Area Power System Load Protection Model in MATLAB/SIMULINK ()
1. Introduction
Wide Area Smart Grid Architecture defines a set of plausible scenarios spanning the entire energy enterprise utility, industrial, commercial, farm, agriculture and residential. The scenarios then enable analysis on the data and resulting communication requirement needed to construct a complete high level set of functions for the communication infrastructure. In the United States the bulk electric power system is operating ever closer to its reliability limits. The past decade has seen many efforts to achieve a smart grid that is, using digital technology to save energy, reduce cost, increase reliability, and transparency. Special efforts have been made to seek preventive and restorative methods for dealing with likely wide spread catastrophic failures, which are caused either by unanticipated disturbances, such as the North American blackout on 14th August 2003, or International attacks. It has been widely agreed [1] that there are inseparable interdependencies between reliable, robust, efficient operations of power grids, the efficient placement, and operation of related telecommunication networks, as pointed out in the work of Heydt et al. The importance of smart grid operations allows for great penetration of variable energy sources through the more flexible management of the system. This can be achieved in many ways from active demand and load side strong communication using temporary storage technologies [2,3].
Today’s network infrastructure, largely based on synchronous optical network and synchronous digital hierarchy technologies, cannot physically or economically support the ever changing demands caused by the overwhelming increase in bandwidth, transport of IP traffic, and the need for more flexible connectivity, higher resiliency, and network automation. To address this concern and main competitive, service providers have been investing heavily in building next-generation networks. Indeed, it is important to review how existing communication technologies such as IEEE 802.11 Wi-Fi, IEEE 802.15.4 ZigBee, Bluetooth, and so on respond to the bandwidth and delay requirements of Smart Grid.
In the smart grid smart meters, home gateways, and consumer devices server and respective clients communicate via wireless communication [4]. Moreover consumer can become small-scale suppliers by generating green energy at home, consume this power locally and sell the excess power to the utilities. The emerging IEEE 802.16 Broadband Wireless Access technology WIMAX [5] allows interoperability and combines the benefits that other wireless networking technologies offer individually and leads a path towards 4 G. The WIMAX spectrum uses for voice, video, and data all considered broad band Wireless Access applications. WIMAX technology enables ubiquitous delivery of wireless broadband [6] service for fixed and/or mobile users, and became a reality in 2006 when Korea Telecom started the deployment of a 2.3 GHz version of mobile WIMAX service called WIBRO in the Seoul metropolitan area to offer high performance for data and video up to 50 km.
Utility needs and problems are often formulated in very loose terms, such as “intelligent load shedding,” “protection system against major disturbances,” and “counteract cascaded line tripping.” These needs have to be broken down to physical phenomena [7], such as protection against: transient angle instability (first swing), small signal angle instability (damping), frequency instability, short-term voltage instability, long-term voltage instability, cascading outages.
The most fundamental requirement in any electrical system is proper over current protection to prevent the load from overheating and electrodynamics interactions. This article provide a detail client server bidirectional load protection system model for wide area Smart Grid network and focus on over current Power System Load Protection implementation in MATLAB/SIMULINK using WIMAX. The paper also highlights WIMAX transmitter and receiver model for desired wide area monitoring and control.
2. Related Work and Problem Formulation
The purpose of Power System Load Protection Model is to keep the power system stable by isolating only the components that are under fault, whilst leaving as much of the network as possible still in operation. Joachim Bertsch, Cedric Carnal, Daniel Karlsson, John Mcdaniel, and Khoi Vu [7] integrate the local protection center into wide solution with System Protection Scheme. These local protection centers form system Protection Scheme, while the interconnected coordinated system forms a defense plan [8,9]. Protection systems against voltage instability can use simple binary signals such as “low voltage” or more advanced indicators such as power transfer margins based on the VIP algorithm [10] or modal analysis.
Transients in substations [11] may result in current surges through the substation grounding system. Ground Potential Rise can affect the communication system located near the protective relays or communication facilities outside the substation perimeter. The Electromagnetic Interface and Ground Potential Rise problem, IEEE recently developed a new standard [12] to define an optical digital interface between relay and multiplexer. IEEE [13], ANSI and IEC Standards define transient and Surge Withstand Capabilities that should be met. Protection Model must apply a very pessimistic and pragmatic approach to clear system faults to a normal state and diminish the impact of the disturbances, the protection and control actions are required to stop power system degradation and system wide disturbances are growing issue for the power system industry [14,15].
Powerful, reliable, sensitive, and robust, Wide Area Power System systems are [16] installed in substations, where actions are to be made or measurements are to be taken. Actions are preferably local, i.e., transfer trips should be avoided in order to increase security. Relevant power system variable data is transferred through WIMAX that ties the terminals together. Different schemes should be needed to be broken down to physical phenomena, such as protection against voltage instability, frequency instability, transient angle instability, and cascaded outages.
Development of microprocessor protection [17] device based on IEC61850 on the high speed DSP hardware platform is an unavoidable trend for substation automation. A PLC-based load shedding scheme offers many advantages, such as the use of a distributed network using the power management system, as well as an automated means of load relief. However, in such applications monitoring of the power system is limited to a portion of the network with the acquisition of scattered data. This drawback [18] is further compounded by the implementation of pre-defined load priority tables at the PLC level that are executed sequentially to curtail blocks of load regardless of the dynamic changes in the system loading, generation, or operating configureuration. The system wide operating condition is often missing from the decision-making process resulting in insufficient or excessive load shedding. In addition, response time (time between the detection of the need for load shedding and action by the circuit breakers) during transient disturbances is often too long requiring even more load to be dropped.
Real-time communication IEC 61850 [19] mechanisms through Generic Substation State Event, Generic Object Oriented Substation Event per 61850-7-2, IEC 61850-9-1 Sampled analog values over serial unidirectional point-to-point link, and IEC 61850-9-2 Sampled analog values over VLAN/priority-tagged Ethernet network are very powerful but they still lack support for some of the most demanding substation applications, such as precision time synchronization (5S pts), line differential, and bus differential protection.
Strong client server communication WIMAX architecture is provided in MATLAB which enhances reliability provides intelligent control updates wide area manager (WAM) server for each and every instant which uproots the over current and under voltage faults when exceeding required thresholds. WAM provides bidirectional wireless communication channel to local area manager (LAM) for intelligent operations. Each LAM acting as a server communicates with respective area clients through WIMAX. The Model consists of compulsory loads spreading in the wide area (i.e. Residential, Commercial, Farm, Agricultural and Industrial), each type of loads as mentioned above are further expended in to its local clients. These local clients are consisting of various types of loads specially the industry and the farm loads consisting of 3-phase motors. Through bidirectional communication, internal faults are tackled by LAM and external faults are handled by WAM.
3. Wide Area Control Design
The Wide Area smart grid Architecture for power system load protection is shown in Figure 1. The architecture consists of various area loads i.e. Residential, Commercial, Farm, Agriculture, and Industrial. The residential and commercial load consists of resistive and inductive loads, the farm load, Agriculture load and Industrial load consisting of resistive, inductive and three-phase motor loads. The loads are controlled by wide area manager and further clients of each load are controlled by a local area manager (LAM). Control area Manager of each client receives signals from fault sensing system which send control signals to WAM through WIMAX sender/receiver and control each area through bidirectional communication as shown in Figure 2.
Figure 2 consists of flow chart of the whole wide area smart grid architecture in which the generating sources composed of renewable energy resources including wind power plant and solar panels. The wide area manager is the centralized portion which is the main soul of the complete wide area smart grid architecture which got its intelligent control due to its computational engine and data user defined cases. Due to these circumstances the WAM accurately control its area using WIMAX through bidirectional communication.