Introduction
The electricity industry is facing numerous challenges today including environmental pollution, increased demand, and aging infrastructure. Environmental issues are the primary concern of the power generation industry and have necessitated the inclusion of renewable energy sources in the generation of electricity. Renewable portfolio standard has set forth new requirements in the industry obligating electricity generation companies to generate a certain percentage of generated electricity to come from renewable sources. However, rapid integration of new energy sources on the old transmission and distribution infrastructure will cause quality, security and reliability challenges on the electric power supply. The good thing is that the distribution grids have significant room for improvement and can benefit from being transformed into smart grids through automation of the systems, condition monitoring, and asset management.
Smart grids use some advanced digital technologies to facilitate the transport of electricity from the point of generation to the consumer. Among these technologies is advanced metering infrastructures that most state regulatory commissions have adopted as part of the automation process. The metering devices monitor the consumption of electricity and enable demand response. The demand response information increases awareness on electricity consumption, ensures reliability and efficiency of the electricity market, providing competitive pressure on the resulting in the reduction of wholesale power prices. Demand response can also be coupled up with new technologies to support the use of renewable energy.
Synchronized Measurement Technology
Monitoring and controlling smart power distribution systems are becoming challenging every day due to the increased demand for electricity. Power companies across the world are now using a real-time wide area monitoring, protection, and control (WAMPAC) system with synchronized measurement technology (SMT). The major advantage of using synchronized measurement technology is that measurement from different geographical locations can be synchronized using the global positioning system. Direct measuring of voltage phase angles is also possible using the technology. Other SMT applications include; real-time congestion management and voltage stability analysis, development of an advanced early warning systems, analyzing power failure causes, development of adaptive protection systems, and improved damping of oscillation. This improves the speed and accuracy of applications of energy management systems increases significantly.
Phasor measurement unit (PMU) is the most common SMT based device for power usage measuring. However, some issues have to be addressed before PMUs can be implemented for wide-scale use. First, a thorough analysis should be done to determine if PMUs are compatible with the current measurement system. For PMUs to be successfully deployed, the require bandwidth and communication resources have to be available. To solve this issue, manufacturers have developed software upgrades that will enable PMUs to be integrated into the existing infrastructure without any hardware changes. Second, the PMUs should be placed at an optimal location to enhance observability of the system and take into consideration strategic positions of load or generator buses. Third, the system architecture of PMUs should be flexible enough to allow for additional measurement devices and load, and also create room for any future expansion. Finally, the PMU devices should adhere to developed standard network protocols for use of the synchronized devices, measurement, storage, and utilization of acquired data. This will ensure that the devices from different manufacturers can be seamlessly integrated into the existing infrastructure and enable easy handling of data from diverse locations.
Monitoring of Power System Oscillations
Applying corrective measures to stabilize large power systems requires real-time observation and recognition of the inter-area oscillation characteristics. A wide area measurement technique based on the utilization on SMT results in more efficient damping of inter-area oscillations and identification of instabilities that might lead to power outages. Some methods to remotely monitor power system oscillations have been developed through the years. After computing inter-area oscillations using wavelet transform methods, damping and frequency elements are determined. This is done either through fast Fourier transform methods or parameter estimation methods. The prony method is the most commonly used parameter estimation method to find unknown damping and frequency of system oscillations. The method analyzes oscillations by processing vast signals provided by wide area measurements. To apply the prony method to determine unknown damping and oscillations, a fault is introduced at any of the two parallel interconnected lines. The fault breaks oscillations at all connected groups of generators, identifying the oscillations between them.
Role of Information and Automation Technologies in Smart Grid
In addition to demand response and advanced metering, implementation of smart grids will have huge impacts on many of the present utility operations and information systems including supervision control and data acquisition (SCADA). Other sectors that smart grids have an impact on include; scheduling, grid operation, billing, and asset management. With the expected future increase of plug-in vehicles and utility grade solar-generated power on the distribution grids, deviations in voltage, increased phase imbalances, and overloading of power systems will occur. To prevent these issues and maintain power system reliability, extensive monitoring and control of voltages, automated switching and relay controls. This will require central analysis and control coupled with distributed intelligent systems that are provided by smart grids.
Solar Power
Solar power generation is currently second after wind generation in the renewable energy industry. However, solar power has shown great potential in becoming the most popular renewable energy source in future. Technological advancements in manufacturing of photovoltaic cells such as using solar inks have promised to increase the amount of power produced by solar energy by thousands of megawatts every year. This will also significantly reduce the cost of solar power plants to under $1 per watt and lower the entry barrier such that any electric consumer can readily adopt it (Bebic et al.). Solar power generation can also be easily integrated into the power grid provided the grid can handle the added capacity. This is because placing photovoltaic cells is easy and can be built wherever they are needed. Also, solar electric generation is likely to be placed on the consumer’s side of the meter to offset connected loads and occasionally feeding energy into the system. Finally, solar power plants can be expanded to cater to increased power demand.
Solar Power Environmental Sustainability
Solar power is the cleanest renewable energy source and does not use any fuel in the electricity generation process. Solar energy does not emit any green house gasses or any other pollutants that might be harmful to the environment. Therefore, solar power does not promote global warming, acid rains or any other form of pollution-related effects.
Impact of High Penetration Solar Generation on Power Systems
Solar energy like any other form of renewable energy source varies at different times. Therefore, electricity generation from solar energy is directly proportional to solar radiation that is affected by various factors including time of day, the suns angle of radiation, geographical location, and weather patterns. This is the major challenge in integrating solar energy sources into power systems. As the solar energy varies so does the net load, which is the difference between load and the generated power (Bebic et al). To effectively plan for generation capacity to meet system load, the net load should be used in place of system load. The load also varies depending on electricity usage, but to ensure reliable electric service, the power systems need to be operated at a constant frequency to match the load. This can be done in two parts; first, sufficient power capacity has to be available, and second, the available power has to be brought online daily through capacity planning.
Storing of Solar Energy
Capacity planning
Capacity planning involves preparing for the daily operation of power systems through future forecasts of the net load requirements. A unit commitment schedule is then developed to meet the load forecast demands. For efficient scheduling to take place, firm commands should be issued to the power systems to avail a certain number of units to go online and produce electricity at a specific time and go offline at other times. Capacity planning can be done in long-term and short-term time frames. Long-term capacity planning involves multiyear contracts with the establishment of power plants to match the growing energy demands and compensate for retirement of old power plants. Short-term planning usually spans over one year and involves maintenance scheduling to ensure sufficient power is available to supply every day net load requirements.
Distribution of System Voltage Performance for High-Penetration Solar Photovoltaic
Current power distribution systems are designed to function based on the assumption that power also flows from the distribution point to the end user. Increased penetration of solar power usage on commercial and residential premises will offset the load and cause power to flow in the reverse direction in the distribution grid. Reverse power flow may cause loss of voltage regulation in the feeder system, wrong operation control operation that may result in wear of control equipment (Bebic et al.). The connection of solar power generation resources to a distribution feeder can also lead an increase in short circuits and protection desensitization. For solar power to be successfully integrated into the distribution system, inverters should be used to protect sensitive equipment.
Issues of voltage regulation should be considered because they are a direct impact of reverse power flow, and current interconnection requirements prevent inverters from controlling voltage. However, modern inverters can supply reactive power and are capable in participating in voltage control. The inverters can only control voltage within two quantifiable boundaries. First, if the photovoltaic cells are not producing any power, then the inverter supplies power factor. Second, when the photovoltaic cells are producing power at full capacity, the inverters reactive power capability is suppressed unless it is intentionally oversized.
Electricity Markets
The liberalization of the energy wholesale markets has led to various players the emergence of various entities performing various tasks that were once performed by integrated utilities. Some of these entities include; power generating companies, distribution companies, retailers, market operators, transmission companies among others. The unbundling of generation and transmission services in the power industry has created competition among entities offering the same service. This competition is characterized by a centralized transmission where wholesalers buy from the transmission system and sell to the retailers. The retailers then use the same distribution grid and compete for the same consumers. Currently, there are many unique markets interacting in a series of operational decision-making and planning. The open electrical market has also given rise to two types of trading. The two types of trading include bilateral trading and electricity pools.
Bilateral Trading
Bilateral trading involves only a buyer and a seller and the participants willingly enter into contracts without any third party involvement. There are different forms of bilateral trading that buyers and seller may resort to depending on time and amount of electricity to be traded. Customized long-term contracts are usually negotiated privately to meet the requirement of both buyers and sellers and usually involve huge quantities of power over long periods. Trading over the counter involves small quantities of electricity and low transaction costs. This type of bilateral trading is used by buyers and sellers to consolidate their position as delivery time approaches. Electronic trading involves anonymous direct buying and selling of energy in a computerized market place.
Electricity Pools
Electricity pools are formed by monopoly utility companies with related service areas. The pools do not rely on demand and supply to determine the market equilibrium but reach this equilibrium in a systematic way. Electricity pools operate in the following way;
Offers to supply certain amount of power are submitted by power generating companies. The offers are ranked in ascending order and a supply curve from the cumulative bid amount is created. Similarly, a demand curve is built from consumers submit bids to buy the power ranked in descending order. The point of intersection of demand and supply curve represents the market clearing price also known as system marginal price (SMP) (Kirschen and Strbac). SMP is the cost of one additional megawatt-hour of power. Power generating companies are paid this amount for every megawatt-hour produced, and consumers pay this amount for every megawatt-hour consumed regardless of submitted bids.
Conclusion
Power generating industry can significantly benefit from smart grids that provide advanced metering infrastructure and demand response for efficient power scheduling and utilization. Smart grids also allow integration of renewable energy in the distribution grids. Solar power generation has already made significant steps to becoming the renewable of the future thanks to technological advancements. The problem of uneven power generation by solar generation facilities can be solved through storing of solar energy using molten salt and capacity planning. Other challenges that might arise in integration in the solar energy can also be solved by the use of inverters. The electricity market is also a free market where buyer and sellers enter into contracts freely. Market equilibrium is determined by bids placed by power generating companies and consumers’ bids.
Works cited
Bebic, Jovan, et al. “The Sun Also Rises.” Power and Energy Magazine (2009): 53–62. Print.
Kirschen, Daniel Sadi S., and Goran Strbac. Power System Economics in a Competitive Environment. Chichester, West Sussex, England: Wiley, John & Sons, 2004. Print.
