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The paper presents an overview about operation and control of the inverter-interface generation units (IGUs) when connected to a microgrid either alone or together with other generation units. The following key connection paradigms are considered: i) one IGU and a grid, ii) one IGU and one machine-interface generation unit, iii) a single IGU, and iv) two IGUs. After illustrating how the IGUs operate...
A crude oil production and shipping terminal was built and expanded over time such that the facility was powered by three isolated power systems. These separate plants have since been interconnected to permit the sharing of generation reserves. Initially, the interconnected system was supervised by a power management system (PMS) that relied on isochronous operation of one power plant for frequency...
This paper presents a method to shed off the least important loads in a microgrid operated at constant frequency under the contingency of inadequate power generation. Different from conventional frequency deviation based load shedding, this paper discusses in detail how to shed off load based on the voltage deviation. The key issue is to differentiate whether the voltage deviation is due to sudden...
With the development of microgrid technologies, more and more distributed renewable sources have been connected into microgrids to provide power for loads. The coming problem is how to manage the distributed generations (DGs) that are not within the planning of a microgrid, one feasible solution is to realize the plug-and-play function of DGs. Focusing on this problem, this paper proposes a control...
Droop control is an effective power sharing control scheme of distributed generation (DG) inverters in islanding AC microgrid, which can stabilize the grid as long as the distributed generation systems have sufficient residual power. On the contrary, many loads have equipped with power conversion circuits in front to improve the operational efficiency, e.g. air conditioners and LED lighting, which...
Massive effective integration of renewable energies into the electric grid is an issue in almost all electric power systems. These renewable energy sources (RES) are usually based on wind and solar photovoltaic generation and cannot maintain a power reference due to variations in wind and solar irradiance. Currently the integration of these renewable energy sources is possible in strong power systems...
This paper discusses the operation of the central controller for a microgrid. The central controller is responsible to maintain the voltage and frequency of the microgrid within the acceptable ranges while the distributed energy resources supply the required power demand of the loads based on the droop control. The desired ratio among the output active power of the distributed energy resources is...
This paper studies the reactive power compensation schemes using grid tie renewable energy inverters for future power grid with substantial renewable energy power generation. A traditional grid tie renewable energy inverter becomes a dynamic reactive power compensator. The objectives of the compensator are 1) to regulate the output voltage of the inverter and 2) to enhance the grid frequency stability...
This paper presents an islanded AC microgrid composed of multi-DGs and an energy storage system. The point of common coupling (PCC) frequency and voltage magnitude are controlled by the ESS while other DGs can export active power and reactive power independently. A nonlinear energy management control strategy is proposed by utilizing the PCC frequency as an agent for all constituent units, which avoids...
Due to not consider the impact of feeder impedance, conventional droop control may result in instability and errors in proportional load sharing when implemented in medium micro-grid. In this paper, inherent limitations of conventional droop control are analyzed, then an improved droop control based on complex virtual impedance is proposed to achieve accurate proportional load sharing, in which complex...
Recently the microCHP (small scale Combined Heat and Power generation unit — mCHP) systems are more common, however these systems don't have any control or protection which would meet the Smart Grid philosophy. Regular mCHP is unable to effectively manage a power outage. In this paper we investigate the base requirements of control and protection system for one (or more) mCHP if we would like to operate...
To ensure the stability of the power system, the transmission system operators (TSOs) keep a control reserve in readiness. This standby capacity is activated when the power system comes under strain and is typically provided by conventional fossil fuel-fired power plants. With the transition from fossil fuel-based energy production to sustainable renewable energy, the process of maintaining the stability...
The energy system is due to substantial changes by reason of an ongoing decentralization of power supply. A challenge will be to provide ancillary services by distributed units since they are volatile regarding their power feed-in and hard to predict. This paper presents a method that allows for the evaluation of how reliable distributed units can participate in the provision of ancillary service...
In the future, electrical systems should be able to integrate all users at the same time and guarantee power quality, stability and safety over time. The integration of renewable energy sources leads to new issues involving the intermittence of this generation typology. A high penetration of intermittent power plants will reduce the capability of the system to overcome critical events (e.g. frequency...
This paper proposes a control scheme for the reduction of the line current total harmonic distortion (THD) over wide load variation range. A new current sensing scheme is used to detect the average current under fixed or variable switching frequency condition. A repetitive controller is designed to minimize periodic errors within the current loop bandwidth. A design procedure is given for synthesizing...
Distributed energy resources (DERs) such as micro turbine, wind turbine, fuel cell, photovoltaic system and so on, which are high-efficient, high quality and high reliable electrical sources, are been able to create flexible control on power generation during the islanded mode operation of micro grid by power-electronic interface. Performances of two types of inverter controller (PQ controller and...
The growing environmental concern and various benefits of distributed generation (DG) have resulted in significant penetration of DG in many distribution systems worldwide. One of the major expected benefits of DG is the improvement in the reliability of power supply by supplying load during power outage by operating in an island mode. However, there are many challenges to overcome before islanding...
Electricity in remote communities is usually provided by diesel power plants at relatively high costs. This issue can be addressed with the addition of renewable energy sources such as wind and PV. However, due to the intermittent and fluctuating characteristics of the power produced by these sources, the dispatch of the diesel gensets for operation with variable (droop-based) frequency, high efficiency...
Photovoltaic power plants pose some challenges when integrated with the power grid. The PV plants always focus on extracting the maximum power from the arrays. This makes the PV system unavailable for helping in regulating the grid frequency as compared to conventional generators. The objective of this paper is to introduce a pseudo power point tracking which provides frequency regulation functionality...
The emergence of large amounts of distributed energy resources (DER) poses new challenges for the active participation of those units in the control of the grid. In this context, a recent development is the microgrid, which presents a coordinated approach for integrating the DER in the electrical grid. Microgrids are able to operate either connected to the distribution grid or in islanded mode. In...
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