Rise in commercial buildings combined with the expectations to create more comfortable indoor environment is increasing energy demand on the already stretched supply side infrastructure. To produce reliable energy at low cost keeping sustainability into consideration has brought science and energy engineering into global focus. Power generation companies are challenged to develop new energy generation technologies to improve energy intensity by creative innovative solutions to balance demand, cost, and environmental priorities. Applying engineering simulations from product designing to development can allow economical ways to evaluate new concepts faster and more frequently. Understanding and analysing the total energy performance can become very complex with conventional computation methods and traditional prototyping and testing methods. Fortunately, there are specifically designed tools to help the designers predict and analyse the performance the energy consumption of a building with good accuracy to optimize power usage. The programs allow sensitivity analysis of various design options and decisions, from conceptual phases to detailed specification of building components and systems. The software is utilized for long-term generation and transmissions, expansion planning, short-term operational simulations.
Power system simulation is a computer-based analytical process that helps the stakeholders to evaluate energy performance and make it more efficient with necessary modifications. The software involves power system modelling and network simulation using design/offline or real-time data. The program also allows the user to observe operation through simulation without performing the operation. The electrical power system simulation has a wide range of planning and operation applications for electric power generation (Nuclear, Conventional, Renewable), commercial facilities, utility transmissions, utility distribution, railway power systems, industrial power systems etc.
In electric power generation facilities, approx. 65% of energy consumed to generate electricity is wasted in the conversion. Power simulation software uses mathematical optimization techniques like quadratic programming, linear programming, and mixed integer programming to help analyse the power system and its behaviour in hypothetical scenarios and identify opportunities for improvement.
Key Elements of Power Systems
· Load flow study
· Short circuit or fault analysis
· Protective device coordination, discrimination, or selectivity
· Transient or dynamic stability
· Harmonic or power quality analysis
· Optimal power flow
· Load Flow Study
The load flow study is a numerical analysis of the flow of electric power in an interconnected system to investigate problems in the power system operating and planning. The study focuses on various aspects of AC power parameters such as real power, voltages, voltage angles, and reactive powers. Based on an electricity generating state and transmission network structure, load flow analysis provides a balanced steady operation state of the power system without considering system transient processes.
· Short circuit or fault analysis
Short circuit failure happens when the current flow bypasses the normal load due to many different reasons such as lightening, accidents, high winds, tornadoes, earthquakes, aging equipment, etc. The objective of short circuit or fault analysis is to provide means to keep the grid safe and operating, calculating the amount of short circuit current from a system, and then comparing that data with the interrupting rate of devices that protect sections of the grid.
· Protective device coordination, discrimination, or selectivity
Discrimination, also known as selectivity, is the coordination of automatic protection devices in a wat that a fault appearing at a given point in a network is cleared by the protection device installed immediately. Protection discrimination is an essential element that must be taken into consideration at the starting of design stage to low voltage installation for ensuring highest level of availability for users.
· Transient or dynamic stability
The ability of power system to become normal or stable after being disturbed is called Stability. The transient or dynamic stability may be due to removal of load, line switching operations, fault occurrences or sudden outage of a line, etc.
· Harmonic or power quality analysis
Improper wiring, incorrect grounding and unbalanced loads can send electrical noise through the power systems and compromise its power quality. The aim of power Quality analysis is to assess the electric environment to improve modelling methods or to build up power quality reference, improve Power Factor & system efficiency, and avoid transformer overheating, capacitor burst, etc.
· Optimal power flow
The optimal power flow (OPF) model represents the best operating levels to meet the demands given throughout a transmission network with the objective of minimising operating cost. The outputs of OPF model includes voltages at different buses, lines flow in the network and system losses.
Benefits of Power System Simulators
· Avoid danger and loss of life with predictive analysis
· Allows testing a product or system before building it
· Can be utilized to find unexpected problems
· Accelerate things or slow them to see changes over long or short period of time
· Cost-effective and reduces maintenance costs
· Saves up energy and reduce carbon-footprint
Simulator technology has evolved from physical/analogue simulators to fully digital real-time simulators. Physical simulators are very large, expensive and require high skills for setting up networks and maintaining extensive inventories of complex equipment. With the introduction of microprocessor and floating-point DSP technologies, now the physical simulators have been replaced with real-time digital simulators.
Real Time Digital Simulator (RTDS)
The RTDS is a highly reliable simulation method based on electromagnetic transient simulation of complex systems. Providing a highly cost-effective alternative to analogue/hybrid transitory analysers and simulators, RTDS becomes an effective tool for modelling and simulation of power and control systems. RTDS hardware employs high-speed chips to compute simulation results with simulation step sizes as small as two microseconds. Some of the factors to consider while selecting a rea-time simulator includes the frequency of the highest transients to be simulated, size and time-step of the system to stimulate, the number of Input/Output channels required to interface the simulator with physical controllers. Real-time simulators are used in three different application categories such as Rapid Control Prototyping with Physical Plant, Software-in-Loop and Hardware-in-Loop and fully digital simulation.
Challenges associated with Real-Time Simulation of Smart Grids
With increasing complexity of modern electric systems, the demand for powerful simulation is expanding. Some of the challenges that Real-time simulation of smart grids face are as follows.
· Real-time Simulation of Large Power Systems
The ability of the simulator to replicate large power distributed systems with a considerable number of components require the computation of big matrices. Dividing the grid model into groups and assigning each group to one purpose is the only possible solution. Therefore, the challenge is to solve all the grid equations in a simulation cycle.
· Accuracy of Power Electronics’ Simulation
The accuracy of simulation depends on the simulation step size that should neither be small or large since RT processors must solve large equations in limited time cycles. For instance, EMT is simulated with a step size between 20-100 µs and power electronics need to be simulated with a step size of 1µs or below. The versatility of single simulator is constrained by the processing time, but also by the associated hardware.
The challenges can be eventually solved with increasing computing capacity. However, more research efforts towards the simulation’s validity are still needed to unleash real time simulation benefits fully.
Conclusion
The future power system will be more automated and disaggregated with enhanced communication infrastructure. Growing demand for power system simulator owing to increasing power sector worldwide is expected to drive growth of global power system simulators in the coming years. However, sluggish growth of oil & gas industry and economic slowdown might hamper the growth of power system simulator market.