This paper presents a closed-loop space vector modulation (SVM)-based sliding mode controller (SMC) for a three-level grid-connected neutral point clamped (3L-NPC) inverter. The nonlinear SMC based on Gao's reaching law has been designed to control the grid current and inject desired amount of active and reactive power into the network. Due to using single dc source at the NPC inverter dc bus, neutral point voltage is controlled through redundant switching states and instantaneous dc voltage feedback integrated into SVM technique. Meanwhile, there is no external voltage controller involved, thus no associated fine tuning issues are existed. The performance of the proposed hybrid controller to inject a desired active/reactive power to the grid is investigated through external perturbations such as change in the line current amplitude/phase shift, ac voltage fluctuation, as well as dc voltage variation. Full converter state-space model was developed and simulated. Experimental results are provided to verify the fast dynamic performance, low content of line current THD%, and good voltage balancing of dc bus capacitors of the NPC inverter.

The residential energy management system is an essential factor in the smart grid environment, which allows the implementation of demand response program among the residential consumers to manage their power usage aiming to reduce the electricity expenses. In this paper, an energy management model is proposed by considering both generation and consumption parts. Mathematical models for the grid, renewable energy resources, batteries and electric vehicles are presented as well as for different type of thermal and electrical appliances such as air conditioning, water heater, vacuum cleaner and others. We have implemented an exact solution method to solve the objective constrained problem that aims to minimize the electricity cost in a smart home and find out operation modes of different loads with organizing between the considered production systems. Furthermore, a math-heuristic optimization algorithm based on mixed integer linear programming formulation is proposed to solve the problem with extended simulation time horizon. The considered mathematical model has been solved with different scenarios where results have indicated a significant reduction of the electricity cost and have illustrated the efficiency of the proposed robust optimization algorithm.

In this paper, a fixed-frequency pulsewidth modulation (PWM) based on sliding-mode current controller is designed and applied to a utility interface three-phase/wire/level neutral-point-clamped inverter. The proposed design methodology of the sliding-mode control is based on a constant switching frequency operation and on Gao's reaching law that allows chattering compensation. The aim of the controller is to inject a controlled active power from renewable energy sources into the grid while controlling the power factor and minimizing supply current harmonics. Moreover, the dc-link voltages across the split capacitors are controlled with a simple proportional-integral (PI) regulator. Experimental results show the advantages of the proposed control algorithm in terms of fast dynamic response, low voltage ripple on the dc bus, low current Total Harmonic Distortion, and robustness toward external perturbations from the dc and ac sides; moreover, a comparison with a PWM-PI current controller is presented.

In islanded microgrid, the conventional voltage and frequency droop control is commonly used to share the real and reactive power among parallel inverters in autonomous fashion without communication. However, this is done at the expense of changing the system frequency and voltage. To enhance the power sharing and to restore the frequency and voltage to their nominal values, a secondary loop is added to the droop where in certain cases a communication link is imposed between a centralized controller and each associated droop control. To avoid using complicated multiloop feedbacks, this paper proposes a new angle droop control to share power with improvement in stability and power sharing enhancement. To perfectly control the output voltage of inverters with smaller THD and high bandwidth, a one-loop flatness based control is employed. For stability analysis and droop parameters settings, a model of the power system is developed. The state-space equations are formed with respect to the common reference frame. The resulting system matrix around an operating point is used to derive the eigenvalues to analyze the small-signal stability of the system. The theoretical analysis and the effectiveness of the proposed angle droop have been validated by simulation and experiments.