DC microgrids are getting more and more applications due to simple converters, only voltage control and higher efficiencies compared to conventional AC grids. Droop control is a well know decentralized control strategy for power sharing among converter interfaced sources and loads in a DC microgrid. This work compares the stability assessment and control of four types of droops for boost converters using the concept of passivity. EN standard 50388-2 for railway systems provides a reference to ensure system stability in perspectives of converters and system integration. Low pass filter (LPF) in the feedback of the droop control is used to ensure converter passivity. Bus impedance is derived to ensure system passivity with less conservativeness. Analytical approach for design of passive controller for all four types of droops is verified through time domain simulations of a single boost converter based microgrid feeding a Constant Power Load (CPL).

State-of-the-art microgrids are typically custom configurations of off-the-shelf equipment and custom software, but they often overlook power electronics control and system stability during design, resulting in suboptimal solutions that are not tailored to specific microgrid architecture, equipment, and physical or economic environment. This paper proposes a novel microgrid design tool that yields optimal equipment selection and guarantees system stability under different contingencies. The microgrid plant design problem has been formulated as a mixed integer linear programming type optimization problem that provides the optimal types, sizing, and placement for distributed energy resources aiming to minimize the total cost. The microgrid dynamic model is built using nonlinear differential and algebraic equations referenced to a common reference frame. The model captures the averaged dynamics of the inverter-based resources, the network, and the loads. The feasible controller space is evaluated using the IEEE 1547 standard under an islanding event. Then, the inverter controller parameters are optimally tuned based on a performance metric. The advantages of the proposed tool over the state-of-the-art microgrid design tools are shown through case studies on the Banshee Distribution Feeder.

The integration of computational capabilities with the electrical infrastructure of the grid can be envisioned as a societal scale Cyber Physical System (CPS). Middleware frameworks can act as a layer of abstraction that manages the interaction between disparate applications to facilitate intelligent control and management of energy production and consumption. This demonstration showcases Resilient Information Architecture Platform for Smart Grid (RIAPS), a distributed software platform that combines a domain specific modeling language with framework-level services such as communication, remote deployment of applications, distributed coordination, time synchronization, and fault tolerance, to develop and run distributed applications. An example of an energy demand curtailment scheme called load shedding is presented, to highlight how the RIAPS framework can be used to implement distributed algorithms to control elements of a power system, which runs as a simulation using OpenDSS.

Dynamic microgrids (MG)have shown great potential in distribution system restoration as they could be frequently and actively reconfigured as per request from system operator. MGs usually have smaller inertia compared to conventional power systems thus require more delicate controller for operation safety. In addition, most distribution systems have unbalanced configurations which requires dedicated regulations on system operation states in both positive and negative sequence. This paper proposes a distributed secondary control strategy for unbalanced dynamic MGs operation. System frequency and voltage regulation are constantly enabled, along with voltage unbalance (VU)mitigation on critical load buses. The proposed control strategy provides automatic management of DGs within the same MG and seamless system transition as reconfiguration is requested. Detailed controller designs for both positive and negative sequence regulations are presented. Small-signal stability analysis of the proposed controller is derived and its dynamic performances are validated using MATLAB/Simulink.

Inductor filter is widely used in grid-tied inverters. If an inverter with inductor filter operates in weak grid condition, voltage measurement error may exist due to the voltage sensor delay and the voltage drop on grid impedance. This can further lead to errors in the phase lock loop (PLL) and even system instability. In this paper, we analyze the voltage measurement error in weak grid condition in detail. All the essential elements in the measurement chain are considered. Analysis shows large DC offset and harmonic components may exist in the sampled voltage. To improve the PLL performance in weak grid condition, a PLL with extra DC offset and 2nd order harmonic rejection capability is presented. Further, the inverter current controller is designed considering grid impedance and grid harmonics. Experiments are performed to verify the presented method.