A Survey on Model-Based Distributed Control and Filtering for Industrial Cyber-Physical Systems <s> 2) Distributed Control Based on Averaging Conception: <s> This paper presents a novel approach to conceive the secondary control in droop-controlled microgrids (MGs). The conventional approach is based on restoring the frequency and amplitude deviations produced by the local droop controllers by using an MG central controller (MGCC). A distributed networked control system is used in order to implement a distributed secondary control (DSC), thus avoiding its implementation in MGCC. The proposed approach is not only able to restore frequency and voltage of the MG but also ensures reactive power sharing. The distributed secondary control does not rely on a central control, so that the failure of a single unit will not produce the fail down of the whole system. Experimental results are presented to show the feasibility of the DSC. The time latency and data drop-out limits of the communication systems are studied as well. <s> BIB001 </s> A Survey on Model-Based Distributed Control and Filtering for Industrial Cyber-Physical Systems <s> 2) Distributed Control Based on Averaging Conception: <s> In this work we present new distributed controllers for secondary frequency and voltage control in islanded microgrids. Inspired by techniques from cooperative control, the proposed controllers use localized information and nearest-neighbor communication to collectively perform secondary control actions. The frequency controller rapidly regulates the microgrid frequency to its nominal value while maintaining active power sharing among the distributed generators. Tuning of the voltage controller provides a simple and intuitive trade-off between the conflicting goals of voltage regulation and reactive power sharing. Our designs require no knowledge of the microgrid topology, impedances or loads. The distributed architecture allows for flexibility and redundancy, and eliminates the need for a central microgrid controller. We provide a voltage stability analysis and present extensive experimental results validating our designs, verifying robust performance under communication failure and during plug-and-play operation. <s> BIB002 </s> A Survey on Model-Based Distributed Control and Filtering for Industrial Cyber-Physical Systems <s> 2) Distributed Control Based on Averaging Conception: <s> Conditions are derived for ultimate boundedness of voltage stabilization and reactive power balancing in electrical microgrids with voltage (E-Q) droop control and distributed secondary control loops. This paper shows that under a bound on the load reactive power demand, an ultimate bound set and its associated region of attraction can be computed for the deviation of the microgrid voltages with respect to their nominal values. The proposed approach employs a nonlinear model of the microgrid, departing from prevailing analyses of stability in microgrids with secondary controllers, typically based on linearization around equilibrium points. The obtained ultimate bounds serve as a performance measure guaranteeing tight voltage regulation under large variations of the load reactive power demand. We illustrate the results with examples of microgrids having different complexity, including a subnetwork of the CIGRE benchmark representing a medium-voltage rural distribution network. <s> BIB003
With the help of the standard frequency/active-power (f/P ) and voltage/reactive-power (V /Q) properties, one has the following conventional controller structure with the conception of distributed averaging BIB003 , BIB002 to adjust the inverter frequency ω i and the amplitude E i of output voltage: where ω * and E * are the nominal network frequency and the nominal voltage of microsource i. A feasible distributed secondary control BIB002 is where β i , κ Different from structure (10), the diffusive averaging term j is introduced into the above controller to maintain active power sharing. This kind of controllers is also named as distributed-averaging proportional-integral ones. An early version developed in BIB001 relies on both average voltage and average frequency of DG units and therefore there exists a forced assumption on the communication among all DGs. Fortunately, such a shortcoming is overcome via the above controller. As stated in BIB002 , the designed distributed control removing the need of a central supervisory satisfies a tunable tradeoff between reactive power sharing and voltage regulation. In addition, in light of the Lyapunov stability theory, some sufficient conditions are derived to evaluate the system stability and robustness to incomplete communication links.