فصلنامه مهندسی و مدیریت انرژی
سال یازدهم شماره 3 (پیاپی 41، پاییز 1400)

This paper investigates a new scheme in the design of a dynamic observer for generator torque estimation in the wind turbine. Using a dynamic sliding mode observer design that has never been used for a wind turbine, we increase the Lipschitz constant, which is equivalent to increase the operation range and increasing the observer's robustness to the nonlinear term. Design innovation is the use of dynamic gain in the design of the SMO and guarantee of asymptotic stability condition by  optimal control problem. The additional degree of freedom proposed by this dynamic formula is used to cope with the nonlinearity. Finally, using the real wind profile, the design procedure is implemented on the 100 kW wind turbine of the Sun and Air Research Institute and the results are also evaluated with the wind turbine simulator software FAST. Also, as the second contribution of this paper, by adding process noise and measurement noise to the turbine, the superiority of the proposed algorithm over others is investigated.

As the penetration of wind power into the power system has increased in recent years, the importance of transient behavior analysis of wind turbine generators is felt more than ever, especially during network faults. Among the various types of generators which are used in wind power plants, studying the behavior of Doubly fed induction generator (DFIG) as the most well-known generator in the wind power industry is so important. This Paper uses a detailed model of grid-connected DFIG appropriate for fault analysis. This model includes a  order mathematical model of the wound rotor induction machine along with a two-mass model of the mechanical drive train. In the next step, transient fault responses of DFIG based wind turbine are analyzed by using simulation results from the MATLAB/Simulink software. Further examinations are also made to verify the impact of various parameters of wind turbine-generator system on fault ride-through (FRT) capability of grid-connected DFIG.

Nowadays, smart grid implementation is a new and challenging issue. One of the important parameters in the smart grids is their fast and accurate fault locator capability. This capability reduces power outage time, which the repair teams of the power distribution companies mostly lose to find the fault location in a traditional way. The fault allocation in the distribution networks, due to their topological nature (high complexity, intermediate loads, load uncertainty, no homogeneity of lines, etc.), is a very difficult and different from transmission networks. In this research, fault indicator information is used to deal with multiple result problem introduced by fault locator in distribution networks.  In this paper, a forward-backward sweep based method is introduced to find fault location. There are some uncertain parameter in fault location because of the error on the load estimation. There is correlation between these parameters due to similarity of the environmental conditions and customer behavior. Therefore, two methods (Monte Carlo and two-point estimation) are used to model probabilistic parameters on fault location. Finally, the 11-bus test network and the actual 306-bus Sharfabad feeder network in Kerman are utilized to evaluate the proposed method.

The combined heat and power (CHP) generation is an energy-saving method in which power and heat are simultaneously generated. The important features of heat and power units are the interdependence between the amount of power and heat generated, which increases the complexity of the problem and can be solved by powerful optimization methods. In this paper, planning and optimizing the combined heat and power generation, including the supply of electrical and thermal power required by the network, are performed. This goal is achieved with two main approaches, including the valve point effect and examining this effect while modeling load peak in the presence of energy storage systems of the battery type, which is the novelty of this paper. This paper offers the hyper-spherical search (HSS) algorithm and particle swarm optimization method to optimize and solve the problem of CHPED in large units and, then, compares and validates the results. The simulation results show that the proposed methods can be used as a reliable method to solve the problem of CHPED by considering different constraints.

In this paper, a new method for detecting high impedance fault in distribution networks is presented. In the proposed method, the Stationary Wavelet Transform (SWT) is used to extract features. Disturbance detection algorithm in the network, using changes in selected features in the data windows after the fault occurrence, compared with the data windows before the fault occurrence, detects the high impedance fault. It also uses the vote-based decision-making system based on the aggregation of the output of the PNN classification and the use of three post-disturbance data windows, has been improved the reliability of the proposed method. The results of the proposed method for detecting high impedance fault on the 34-node IEEE in the EMTP-RV software indicate the accuracy, reliability, and security of the proposed method at a high level.

Under the smart environment, utilizing demand side resources (DSRs), the so-called demand response resources (DRRs), provide more suitable management for the growing energy consumption as well as considerable reduction of system expenditures. Estimation of DSRs potential due to affecting the power system scheduling ranging from short-term to long-term is contemplated as an essential issue. In this paper, a two-stage structure is proposed to determine the potential of DRRs based upon the variation of energy consumption in comparison with the temperature along one year horizon time. In the first stage, utilizing a sample estimation method, the temperature threshold for commitment of cooling and heating appliances is specified. In the next stage, the energy consumption data are clustered in two categories regarding temperature thresholds. Then, the flexible load level, DRRs potential, is determined via implementing multifarious indices to the maximum and average daily load profile. Lastly, the final potential of DSRs will be determined in warm and cold weather conditions regarding the statistical analysis of computed DRRs’ potential in different years. To evaluate the capability of the proposed structure, the energy consumption as well as ambient temperature of Boston city is utilized. The obtained results show the difference between DRRs’ potential in different climate conditions.

Nowadays, the issue of power quality is an important parameter for electricity consumers. Nonlinear elements (such as electronic power equipment, electric arc furnaces, high frequency devices, etc.) are the main reason for the problems related to power quality and the creation of harmonics in the network. In this paper, a new method to improve the power quality in a steel plant is presented. A shunt active power filter is used to eliminate current and voltage harmonics of electric arc furnaces in a steel plant in this method. To improve the performance of the shunt active power filter, a new controller based on PID controller and P-Q theory has been proposed. Also, an optimization method based on the modified gray wolf optimization (MGWO) has been used to adjust the control parameters in order to improve the proper performance of the filter and the power quality indices. A 10-bus steel plant, including 6 electric induction furnaces and a shunt active power filter is simulated by MATLAB/Simulink. The analysis of harmonic indices shows the efficiency of the proposed structure to increase the power quality of the power system.

Making policies for technology development in energy sector has been amongst the most cited issues in economic studies. The first step to make policy for technology development is to recognize barriers and bottlenecks of technology development. Regarding the growing significance of CHP technology in developed economies and also the potential competence in Iran, this paper aims at identifying the most important barriers hindering the CHP development in Iran in comparison with the national plans. The Multi-Level Perspective approach was selected to recognize these bottlenecks as it considers the social and macro contextual factors. The problems were identified and then verified using confirmatory factor analysis. The results demonstrate that the social, cultural and macro-economic factors play the more important role compared to technological factors. More precisely, connecting to a centralized and public power grid has become a routine for industries in Iran. Moreover, regulations and standards required to connect the CHP plants to these centralized grid have not been designed well. At the next level of importance, some cultural attitudes such as preferring foreign technologies were noticed to have the considerable negative effect on CHP development in Iran.

In warm seasons, different types of cooling equipment can be implemented to provide cooling comfort. In Iran, the swamp cooler is very useful due to the simplicity of the mechanism and reasonable price. While due to energy management as well as the water shortage crisis and the increase in the humidity of the supplied air, the need for other systems with the same price and efficiency is felt well. The vacancy of indirect evaporative cooling products in the cooling market indicates that the need for research and development. In this paper, an indirect evaporative cooling cooler was constructed with the crossflow heat exchanger and its cooling performance was investigated. Wet-bulb effectiveness and dew point effectiveness were calculated for different inlet air conditions. Similarly, to estimate the cooler output, a code was written using the heat transfer equations and energy balance in the heat exchanger by EES software, and the code results were compared with the experimental values. The results show that an increase in the temperature and decrease in the relative humidity of the intake air improve the performance of the cooler. Also, an increase in the intake airflow improves the cooling capacity, although it increases the outlet air temperature.

Two-stage Transcritical Carbon dioxide Compression (TCC) refrigeration system is a useful tool to provide low-temperature refrigeration, but with a low coefficient of performance (COP). In this research, in order to improve this COP, a heat exchanger, called After-Cooler (AFC), is embedded into the system configuration. The AFC cools down the temperature of the refrigerant leaving the gas-cooler to the lowest possible temperature. The cooling load of the AFC is provided by an absorption refrigeration system and the heating power required to run the absorption chiller is supplied by the waste heat, recovered from the hot refrigerant, leaving the compressors. When the recovered heat is not enough to provide the maximum cooling load, an auxiliary boiler is used in order to provide the redundant heat, required by the generator of the absorption chiller. Single-effect LiBr/H2O and Ammonia/Water absorption refrigeration systems are the two options for the AFC part. The proposed configurations are modeled in EES software and analyzed from energy and exergy viewpoints. A parametric study is also performed, in order to evaluate the performance of the two proposed systems, in different operating conditions. Finally, an economic analysis reveals the system with lower annual life-cycle cost (ALCC).

In order to simiulate the proposed combined systems, mass, energy and exergy balance equations are applied on all components. These equations are solved for each componenet, so that the energy consumption and exergy destruction of that component are calculated. The results of the simulations of the TCC and absorption systems are validated by the presented literature. Then, a parametric study is performed in order to point out the optimal operating conditions. Finally, the proposed sytems are studied for the optimal operating condition, from an economic viewpoint.

Results show that in mutual operating conditions, using an ammonia/water absorption chiller results in a higher COP for TCC system, say 22% higher. But compared to the LiBr absorption system, the ammonia absorption system reduces the Energy Utilization Factor (EUF) and the exergy efficiency of the whole system, 25% and 29%, respectively. Results of the parametric study state that the accurate design of the operating conditions of a TCC system result in the increase of system performances. So that, the COP and EUF of the system with LiBr AFC could respectively increase up to 4.7% and 59.4%, compared to the NH3-AFC counterpart. On the other hand, economic analysis illustrates that with the current energy carriers’ prices in Iran, the annual cost of the system which has combined the TCC and the LiBr-AFC is 3720$ less than that of a single TCC and 4590$ less than that of the combined TCC and the NH3-AFC.

Energy and exergy analyses show that by use of a LiBr absorption chiller as the after-cooler, COP and EUF of the TCC system can be increased up to 48.73% and 73.4%, respectively. Also, it can be concluded that a LiBr after-cooler can reduce the ALCC of the combined system up to 5%, compared to a single TCC system.