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Design of Microgrids
Published in Sasi K. Kottayil, Smart Microgrids, 2020
Grid-support mode can be initiated during grid-connected or islanded operation of the microgrid based on a specific support service requirement. The major support services provided in the grid-connected mode by the inverters are: (i) injection of appropriate value of reactive power to regulate the grid voltage, (ii) real power curtailment or control for grid frequency regulation, (iii) low/high voltage ride-through (L/HVRT), requiring the inverter to stay connected with the microgrid for a prescribed time period following an event of voltage dip or rise, (iv) low/high frequency ride through, requiring the inverter to stay connected with the microgrid for a prescribed time period following an event of frequency dip or rise, and (v) specific power factor operation for sourcing or sinking VAR and maintaining grid voltage. The support services provided by the inverter in the islanded mode are: (i) frequency droop control for active power sharing between inverters, (ii) voltage droop control for reactive power support, and (iii) black start capability.
Resistors
Published in Kevin Robinson, Practical Audio Electronics, 2020
By definition limiting current is what a resistor does. There are a couple of commonly encountered situations where this particular aspect of its action come to the fore. Sometimes a resistor is placed between the power supply and the rest of the circuit (Figure 12.23). This has the effect of reducing the overall current drawn by the circuit and thus extending the battery life. If the circuit in question does not need the full voltage available from the power supply this is a simple way of limiting current draw and extending battery life. In fact, this technique is sometimes employed more for the effect it has on the sound than for simple power control. An audio circuit can behave in different ways as the power supply is altered. Voltage droop is a recognised effect in some circumstances.
Low-Power Testing for 2D/3D Devices and Systems
Published in Rohit Sharma, Krzysztof Iniewski, Sung Kyu Lim, Design of 3D Integrated Circuits and Systems, 2018
Lin Xijiang, Wen Xiaoqing, Xiang Dong
Figure 9.13 shows the relative relationship between voltage droop events and clocks with different frequencies. For the clock with higher frequency, the second capture clock finishes pulsing far ahead before the first voltage droop event is fully deployed. The supply voltage level seen by the capture clock pulses may be higher than the average voltage level during the functional mode. Consequently, the scan test patterns pass at the clock frequencies higher than the functional patterns. It could lead to test escape. For the clock with lower frequency, the second capture clock starts a pulse near the peak of the first voltage droop event. Although the peak voltage droop level reduces as the clock becomes slower, it is still larger than the voltage droop seen by the faster clock. Consequently, the scan test patterns fail at the clock frequencies lower than the functional patterns. It could lead to yield loss.
Effective Control of Voltage and Frequency in Microgrid Using Adjustment of PID Coefficients by Metaheuristic Algorithms
Published in IETE Journal of Research, 2022
The droop method is the basic and primary control method in the microgrid for the control of frequency and voltage in the rated values. This method is described as [29,30] where m and n are the droop gains; P and Q are active and reactive power, respectively. and are also the reference values of frequency and voltage in microgrid, respectively, while f and V show the instant frequency and voltage of the system, respectively. Using this method, if the active power is changed due to load increase or decrease, frequency drop occurs proportional to the frequency droop gain (m). The same is happened for voltage and reactive power changes, considering the voltage droop gain (n). Thus in load change, small voltage and frequency deviation is expected without undesired fluctuations because the droop control allows voltage and frequency drop and prevents the undesired fluctuations in voltage or frequency of the system by its control strategy. The droop gains can be used to balance the power sharing among distributed generators (DGs) in the microgrid and also to keep the stability of the frequency and voltage. However, returning the deviated values to the reference values is impossible using only droop control. Thus, PID controller is exploited to recover the reference values discussed in the sequel.
Design and Implementation of an Embedded Control System for the Interconnection of a DC Microgrid to the AC Main Network
Published in Electric Power Components and Systems, 2020
Juan J. Martínez-Nolasco, Sergio Cano-Andrade, José A. Padilla-Medina, Coral Martinez-Nolasco, Alejandro I. Barranco-Gutiérrez, Francisco J. Pérez-Pinal
It was observed that the DC bus suffers a voltage droop and an overshoot of 1.5%. This behavior is due to the load connection/disconnection, which is reduced by the supercapacitor bank. Figure 19a shows the effect on the DC bus (purple line) when a 300 W fluorescent lamp is connected to the DC bus, and Figure 19b shows the effect on the DC bus (purple line) when a 300 W fluorescent lamp is disconnected from DC bus. We observed that when the 300 W fluorescent lamp is connected to the DC bus, the nominal voltage is decreased by 3.15%, and when the 300 W fluorescent lamp is disconnected from the DC bus, there is an overshoot of 3.15%. The DC bus is stabilized at 6 s.
Enhancing Small Signal Stability and Reactive Power-sharing Accuracy in Autonomous Microgrids by a New Decentralized Reactive Power Controller
Published in Electric Power Components and Systems, 2012
P. Astero, S. H. Hosseinian, M. Abedi
In [14], another voltage droop method is proposed. In this method, to improve the voltage regulation, the voltage drop is a non-linear function of VSC coupling resistance (r), VSC coupling reactance (x), output active power (P), and output reactive power (Q). In other words, this method drops the VSC output voltage based on the coupling impedance of the VSC, which connects the VSC to the microgrid, and the output power of VSC. For implementation of this control method, the conventional voltage droop model in Eq. (2) should be replaced by Eqs. (4) and (5):