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Introducing more Distributed Generation (DG) into
power grid infrastructure drives more attention to understand
how large scale DG affects grid operation. Islanding is an important
concern in this area. Islanding refers to the condition that
DGs within a microgrid continue energizing while the microgrid
has been disconnected from the main grid. Con...
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Citations
... DR programs are recently applied to islanded microgrids also, where either voltage regulation [13,14] and/or frequency regulation are/is considered [15,16]. In addition, resilience-oriented DR programs are also available in the literature [17][18][19][20]. ...
... The state-of-charge (SOC) limits of X-side BESS in mth microgrid are given by (16). The SOC at any time interval t can be computed using the information of the amount of electricity charged/discharged at that time interval and SOC of the previous time step. ...
Microgrids have the potential to withstand the power outages due to their ability of islanding and potential to sustain the penetration of renewables. Increased penetration of renewables can be beneficial but it may result in curtailment of renewables during peak generation intervals due to the limited availability of storage capacity while shedding loads during peak load intervals. This problem can be solved by adjusting the load profiles, i.e., demand response (DR) programs. In contrast to the existing studies, where DR is triggered by market price signals, a local resource-triggered survivability-oriented demand response program is proposed in this paper. The proposed DR program is triggered by renewable and load level of the microgrid with an objective to minimize the load shedding and curtailment of renewables. The uncertainties in load and renewables are realized via a robust optimization method and the worst-case scenario is considered. The performance of the proposed method is compared with two conventional operation cases, i.e., independent operation case and interconnected operation case without DR. In addition, the impact of renewable penetration level, amount of shiftable load, and load absorption capacity on the performance of the proposed method are also analyzed. Simulation results have proved the proposed method is capable of reducing load shedding, renewable curtailment, and operation cost of the network during emergencies.
... Moreover, maximizing the reliability and security of the system is decisively desirable from a system designer viewpoint [3] and data centers can play a critical role in this regard. This is especially due to their large loads that can be a threat and opportunity for the system at same time. ...
Power consumption by data centers has become a critical issue considering their huge amount of usage. Considering the cost of this power consumption, for both the data centers' owners and also the utilities that have to meet the peak demand requirement by these data centers, from one side and its impact on global warming on the other side, it is crucially important to mitigate the negative consequences. This paper presents an optimization method for data centers power consumption cost using two paths: contracting solar systems for powering their workload processing considering the economy of scale in solar systems, and transferring their workload to other data centers in other region when it can cost for them less while they meet the maximum delay required for processing those workloads.
... DRAs can participate in the market using demand buyback program. DR is also used for frequency regulation in case of contingency [8], [9]. Finding the faults in distribution system will help reduce the amount of reserve in the form of DR and regular reserve [10], [11]. ...
With increase of renewable energy penetration, mitigating the power fluctuations in real-time demands a higher spinning reserve. Distribution System Company (DISCO) performs an optimization problem for the next day with the predicted load. In real time, due to fluctuations of renewables, DISCO uses DR to counteract the fluctuations of renewables. DR is provided by parties called demand response aggregators (DRA) which collect the DR powers from residential and commercial buildings and offer them to DISCO. The aggregators are competing to sell the amount of demand response to DISCO for next 5 or 15 minutes ahead. The competition is modeled with incomplete information Bayesian game theory. Best response of each aggregator is derived and the aggregate power of DRAs are offered to DISCO. DISCO performs an optimization to meet the load demand in real-time market with demand response contributing to remove the unbalance between load and power procurement in real time. By including the offset of demand curve, DISCO can optimize the amount of power purchased from DRAs. Day ahead as well as real-time optimizations of DISCO have been analyzed in this paper and contribution of DR as well as other factors have been presented.
... Maximizing the security of microgrid, which is desirable from a system designer viewpoint, is another important case of using these flexible loads [6]. In [7], [8], some flexible loads have been used in order to maintain continues operation of an islanded microgird until reconnection to the main grid. ...
... An example of such devices are grid interactive WHs which send the temperature and status of water heater and can be remotely controlled via utility or third part aggregator [91,92,93]. After deciding which aggregator(s) should participate for different parts of cost curve, the GENCO profit can be obtained from the following equations: ...
The increased presence of variable renewable generation drives a greater need for authorities to procure more Ancillary Services (AS) for grid balance. One of these services is Contingency Reserve (CR), which is used to regulate the grid frequency in contingencies. Many Independent System Operators (ISOs) are structuring the rules of AS markets such that DR can participate alongside traditional supply-side resources. The available capacity of the generators can be used more efficiently for power production which they were designed for and not CR; cutting costs, and reducing pollution. As the ratio of inverter-based generation compared to conventional generation increases, the mechanical inertia used to stabilize frequency decreases. When coupled with the sensitivity of inverter-based generation to transient frequencies, the provision of AS from other sources than generators becomes increasingly important. This chapter provides a method to use AS for providing CR using DR to ensure system stability for a set of credible contingencies, while also satisfying economic and market goals. In the AS market, Optimal Power Flow (OPF) is used to find the optimal offers/bids and transient behavior of frequency is considered. The proposed model separates DR into two categories—faster and slower—based on the deviation from the normal frequency of grid power. In a standard numerical example, it has been shown that the proposed model can clear energy and AS’ bids simultaneously while minimizing the total operating cost and satisfying transient frequency requirements.
... Since the islanded microgrids usually include renewable energies, they have more uncertain and stochastic behavior than power transmission systems. In some papers, demand response [3][4] and supervisory control [5] constantpower control [6] methods are applied to regulate frequency. In [7], Ziegler-Nichols method is used to tune the PID coefficients of the LFC controller. ...
... The microgrid model is as described in (1) and expanded in (2)(3)(4) where x, u, w and y are the state variables, the input control signal, unknown input signal (disturbance) and the control output signal [24]. In (3), Δf, ΔPDG, ΔXG, ΔPE1, and ΔPE2 are respectively frequency deviation, the output power of DG, increment amount of the valve position of governor, the output power of electrical vehicles. ...
Load Frequency Control (LFC) for an islanded microgrid is so critical due to intermittent behaviors of load and renewable energies. Performance of PID controllers deteriorates under uncertainties necessitating a controller that specifically considers these uncertainties. A stochastic controller can count for these uncertainties and hence a self-tuning PID controller based on Hebbian Learning method is proposed. Its varying control structure can ensure efficient control of this system under a wide range of operating conditions. For the Electric Vehicles (EV), only V2G mode of operation, where EVs give energy to grid, is considered. Comparisons of proposed controller with the PID controller demonstrate a superior operation of the proposed controller.
... In the grid-connected mode, DGs are utilized to supply power for the MG while the voltage and the frequency of the system are controlled by the grid [12][13][14]. On the other hand, in a stand-alone mode, DGs control the voltage and the frequency of the system as well as meet the balance between generation and demand [15][16][17][18]. ...
... By using Taylor Series, equations (6-10) can be written in a small signal form as in (15)(16): Fig. (2) and formulated in (17)(18)(19). (17) can be rewritten by using equation (14) as in (20): ...
... Equations of (15,16,20,24,31) can be used to find out the complete state space model for each inverter as in (32). ...
Appropriate control of high penetration renewable energies in power systems requires a complete modeling of the system. In this paper, a comprehensive state space modeling of voltage source inverters, networks and loads are studied. We have modeled a secondary voltage control that utilizes the nominal set points of the output voltage as the input for the controller design. A distributed control algorithm only requiring a sparse communication between neighboring distributed generators (DGs) is used. The proposed secondary voltage model is applied on a microgrid with three DGs and two loads to verify the results.
