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The paper develops two computationally efficient models, namely a detailed equivalent model and an average-value model, with provisions for representation of the critical state of converter blocking, for modular multilevel converters with embedded storage. These models are indispensable in the simulation of dc faults. The developed detailed equivalent model provides accuracy that matches electromagnetic transient (EMT) simulations, with much reduced computational burden; the developed average-value model represents the averaged behavior of the converter by neglecting switching transients. Both models are extensively evaluated in the context of an HVDC system against benchmark results form a detailed switching model developed in PSCAD/EMTDC. The results confirm the validity and accuracy of the models for steady state, transient, and faulted operating conditions including when the converter is blocked in response to a dc fault. [ABSTRACT FROM AUTHOR]

This paper presents a single-objective model predictive control for a bidirectional DC-DC flying capacitor (FC) converter, which integrates a battery to the microgrid. The presence of multiple FCs facilitates the converter to interface a low-voltage battery to a high-voltage DC bus at reduced voltage stress on its power switches. However, such converter requires a controller that fulfils multiple objectives, namely DC bus and FC voltage regulations, and bidirectional power flow. The key feature of the proposed controller is that it utilizes a model predictive control with a single-objective cost function based on battery current and a redundant state selection scheme to attain these multiple objectives. Adopting such a strategy not only reduces computational burden but also eliminates the need for weighting factors and requirement of complex numerical models for its estimation. Another notable aspect is that the controller employs an improved dynamic reference model to generate appropriate battery current reference for the DC bus voltage regulation, without necessitating a secondary control loop and additional current sensors. Finally, experimental results of the proposed system for a step-response of the DC bus voltage, varying PV power, and loads are validated and compared against finite control set model predictive control. [ABSTRACT FROM AUTHOR]

A dynamic model of a battery is required for the appropriate real-time control during charging/discharging process. Present paper considers the development of nonlinear Dynamic Equivalent Electric Circuit Model (DEECM) of a Valve Regulated Lead-Acid (VRLA) battery based on the data obtained through the experimentation and the available datasheet information. Cases of charging, discharging, and the self-discharging are considered for 12V, 26Ah VRLA battery at room temperature. Accordingly, experimental ${\boldsymbol{v}} - {\boldsymbol{i}}$ characteristics of the battery are used to express the nonlinear model parameters as a function of measurable battery current and estimated open-circuit voltage as a part of parameter estimation. Further model is validated through voltage response test with maximum error of 0.4% during discharging and 0.7% during charging under different current levels. [ABSTRACT FROM AUTHOR]