Nowadays, to having greater protection of the environment and due to the pollution caused by using fossil fuels and the limitation of these resources, the global orientation towards is renewable energy sources. As a sustainable form of energy, solar energy is really important, because that is almost the cheapest source of energy production in areas with high solar radiation potential; so global demanding of electricity generation can be supplied with using this technology. There is possibility of direct or indirect lightning strike on photovoltaic system equipment due to the installation of this equipment outdoors or on rooftops. In this paper, the Transient overVoltage crated by direct and indirect lightning strike to the photovoltaic frame in different parts of the photovoltaic system is investigated by an accurate modeling of the frame, pillars and ground of a photovoltaic system in EMTP-RV.

Due to space limitation along with the necessity to the increase of the substations, gas insulated substations (GISs) have been favorable option owing to their minimum required space for installation. One of the main challenge in this substation is very fast Transient overVoltage (VFTO) giving rise to the operation of disconnector. These waves travel through various components. Interestingly, along with waves, a wave is inducted on the ducts called Transient enclosure Voltage (TEV) or Transient ground potential rise (TGPR). This paper has been devoted to investigate these waves through modeling GIS and presenting some analytical approach. Subsequently, the impact of GIS design, CVT, arrester, and ground strap have been discussed through simulations in EMTP-RV. Finally, the impact of high frequency ground behavior has been discussed to show the importance of the design of grounding system in GISs from high frequency point of view.

Methods for calculating Available Transfer Capability (ATC) of the transmission systems may be grouped under Static and Dynamic methods. This paper presents a fast dynamic method for ATC calculations, which considers both Transient Stability Limits and Voltage Stability Limits as terminating criteria. A variation of Energy Function Method is used to determine the Transient stability limit and the determinant of the Jacobian matrix of the system is used as an index to determine the Voltage stability limit. A novel method is used to approximately calculate this determinant. Combining these two methods, an algorithm that calculates ATC, based on both Voltage and angle dynamic stability is presented The advantage of this algorithm, besides considering both Voltage and angle dynamic stability, is its high speed This-speed of calculation makes the algorithm a perfect candidate to be used in screening contingencies and determining those cases that need to be further analyzed. To demonstrate the validity, efficiency, and the speed of the new method, it is used to calculate ATC for numerical examples with 1, 3, 7 (CIGREE), 10,30 (IEEE) and US (Iowa State) buses.

Improving Transient Voltage stability is one of the most important issues that must be provided by doubly fed induction generator (DFIG)-based wind farms (WFs) according to the grid code requirement. This paper proposes adjusted DC-link chopper based passive Voltage compensator and modified Transient Voltage controller (MTVC) based active Voltage compensator for improving Transient Voltage stability. MTVC is a controller-based approach, in which by following a Voltage dip (VD) condition, the Voltage stability for the WF can be improved. In this approach, a Voltage dip index (VDI) is proposed to activate/deactivate the control strategy, in which, two threshold values are used. In the active mode, the active and reactive power are changed to decrease the rotor current and boost the PCC Voltage, respectively. Based on the control strategy, in a faulty grid, DFIG not only will be able to smooth DC-link Voltage fluctuations and reduces rotor overcurrents but also it will increase the Voltage of point of common coupling (PCC). Therefore, it improves Transient Voltage stability. The simulation results show the effectiveness of the proposed strategy for improving Voltage stability in the DFIG.

The analysis of Transient stability in electric power systems and the penetration coefficient of scattered productions play important roles in the regulation of protective equipment, so these parameters should be considered two main factors in the electrical protection of power networks. Overcurrent relays are used as one of the simplest and most effective solutions for power system protection. The overcurrent relay has two main variables: time setting factor (TMS) and plug setting (PS). The relay operation time is a function of TMS, PS, and the current seen by the relay. This paper analyzes the Transient stability of a distribution network including distributed generation to determine the protective regulation of overcurrent relays. First, the Transient stability of scattered products is studied for different fault locations and their different penetration coefficients. Then, the limitations of distributed generation resources are considered in the protection coordination of overcurrent relays. Therefore, a new method is proposed to calculate the modified value of the time adjustment coefficient of the overcurrent relay. In other words, not only the protection limits but also the Transient stability limits are considered in the calculation of the time adjustment factor. In fact, by applying the proposed method, not only is the coordination between overcurrent relays maintained but the instability of distributed generation sources is also prevented. The performance of the proposed protection plan is evaluated with the help of simulation in an IEEE 33-bus distribution system using ETAP software. The results show the correct performance of the proposed method for the worst error conditions. It should be noted that to carry out conservation and stability studies, the following steps are performed in order, which ultimately leads to the creation of a conservation-stability algorithm: (A) protection studies in the condition of disconnection of DG resources, (B) Transient stability studies in the conditions of connection of scattered production sources, including obtaining the minimum stability time for each of the scattered production, and (C) investigating the simultaneous establishment of CTI and CCT. In this situation, two situations are possible: the simultaneous establishment of CTI and CCT, the establishment of CTI restrictions, and the non-establishment of CCT. The value of CCT for each DG is equal to the time when the speed of the DG or the power angle of its generator becomes zero. As can be seen, in the first, second, fourth, and fifth scenarios, the CCT condition of the distributed generation source is not established, and it is necessary to modify the TDS value of the main relay.

A static synchronous compensator (STATCOM) is generally used to regulate Voltage and improve Transient stability in transmission and distribution networks. This is achieved by controlling reactive power exchange between STATCOM and the grid. Unbalanced sags are the most common type of Voltage sags in distribution networks. A static synchronous compensator (STATCOM) is generally used to maintain Voltage and improve Transient stability. This is achieved by regulating reactive power exchange between compensator device and grid. In this paper, A hybrid neuro-fuzzy current controller for STATCOM control is proposed. The controller has minimum mass of calculations. Learning process is carried out by an improved supervisory error-back propagation (SEBP) method instead of usual EBP algorithm. This results in better performance and efficiency and leads to a robust model with fast Transient capability. The model is developed in MATLAB/SIMULINK environment. STATCOM operation during scenarios of balanced and unbalanced Voltage sags is studied. Performance is compared with the operation of a conventional proportional-resonant controller. The results show faster dynamic and better capability of neuro-fuzzy controller in responding to Voltage sag occurrences.

The analysis of Transient stability in electric power systems and the penetration coefficient of scattered productions play important roles in the regulation of protective equipment, so these parameters should be considered two main factors in the electrical protection of power networks. Overcurrent relays are used as one of the simplest and most effective solutions for power system protection. The overcurrent relay has two main variables: time setting factor (TMS) and plug setting (PS). The relay operation time is a function of TMS, PS, and the current seen by the relay. This paper analyzes the Transient stability of a distribution network including distributed generation to determine the protective regulation of overcurrent relays. First, the Transient stability of scattered products is studied for different fault locations and their different penetration coefficients. Then, the limitations of distributed generation resources are considered in the protection coordination of overcurrent relays. Therefore, a new method is proposed to calculate the modified value of the time adjustment coefficient of the overcurrent relay. In other words, not only the protection limits but also the Transient stability limits are considered in the calculation of the time adjustment factor. In fact, by applying the proposed method, not only is the coordination between overcurrent relays maintained but the instability of distributed generation sources is also prevented. The performance of the proposed protection plan is evaluated with the help of simulation in an IEEE 33-bus distribution system using ETAP software. The results show the correct performance of the proposed method for the worst error conditions. It should be noted that to carry out conservation and stability studies, the following steps are performed in order, which ultimately leads to the creation of a conservation-stability algorithm: (A) protection studies in the condition of disconnection of DG resources, (B) Transient stability studies in the conditions of connection of scattered production sources, including obtaining the minimum stability time for each of the scattered production, and (C) investigating the simultaneous establishment of CTI and CCT. In this situation, two situations are possible: the simultaneous establishment of CTI and CCT, the establishment of CTI restrictions, and the non-establishment of CCT. The value of CCT for each DG is equal to the time when the speed of the DG or the power angle of its generator becomes zero. As can be seen, in the first, second, fourth, and fifth scenarios, the CCT condition of the distributed generation source is not established, and it is necessary to modify the TDS value of the main relay.

This paper presents a low dropout Voltage regulator, with the specifications suitable for hearing aid devices. The proposed LDO occupies very less area on chip and provides an excellent Transient response. A novel Voltage spike suppressor block is employed in the LDO architecture which reduces undershoot and overshoot of the output Voltage during the abrupt load transition. It introduces a secondary negative feedback loop whose delay is lesser than the main loop and also steers the quiescent current to output node when required. This not only improves overall current efficiency but also reduces the on chip capacitance. The proposed LDO is laid out in 180 nm standard CMOS technology and post layout simulations are carried out. The LDO produces 0.9 V output when a minimum supply Voltage of 1 V is applied. A maximum load of 0.5 mA can be driven by the regulator. The LDO exhibits 4.4 mV/V and 800 μV/mA line and load regulations respectively. When subjected to a step load change, an undershoot of 20.34 mV and an overshoot of 30.28 mV are recorded. For proper operation of the LDO, it requires only 4.5 pF on-chip capacitance.

With the rise in the penetration of inverter based distributed energy sources, grid codes say that converters should not be disconnected during the fault. These sources should also help the grid by reactive power injection. Power system grids are resistive inductive and the converter may be unstable during the fault. Converters use phase locked loop (PLL) to synchronize with the grid. PLL is not able to be stable during severe Voltage drop, so converters cannot ride through the fault and should be disconnected. In this paper a novel method based on virtual impedance is proposed to maintain the synchronization during severe Voltage drop. This method needs grid impedance estimation and virtually connects the converter to a point that has a stronger connection. By this novel method, during Voltage drop, the converter stays connected to the grid and injects reactive power. Simulation results in MATLAB verify the ability of proposed method in improving the Transient stability of converter.

One of the most suitable models for studing the electromagnetic Transient behavior of the high Voltage winding of the power transformers is the detailed model. This model consists of inductive and capacitive effects as well as the eddy current and dielectric losses in the form of lumped parameters. The losses have significant effects on the damping of Transient over Voltages. In this paper, the eddy current losses are expressed by a matrix which its elements satisfy the proximity effects and skin effects precisely. The matrix is calculated at low frequency by the finite element method (FEM) and then generalized to the high frequencies. simulation are presented for illustration and validation.