Air abrasion has a greater effect than CO₂and Er,Cr:YSGG lasers in the treatment of zirconia ceramic surfaces to enhance the bonding strength of resin cement to zirconia. CO₂laser at 4W and Er,Cr:YSGG laser at only 3-W output power can be regarded as surface treatment options for roughening the zirconia surface to establish better bond strength with resin cements.

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The major drawback of most control methods for uninterruptible power supply (UPS) inverters is complexity. In this study, a simple voltage sensorless multi-loop control method is proposed for the single-phase UPS inverter and the parameters are designed systematically based on a frequency domain method. The suggested control scheme uses two nested simple proportional controllers instead of proportional-integral/resonant controllers to regulate the output voltage and produce active resonance damping. In addition, a feedforward compensation of the reference voltage is used to enhance the performance of the control system. The proposed controller does not need any reference frame transformation or integration/derivation of measured quantities in its structure. To reduce the cost and at the same time to improve the reliability of the converter system, the output voltage sensor is replaced by a simple estimation algorithm based on the digital Kalman filter. Experimental results with a 500 VA prototype, as well as simulation results validate the excellent performance of the suggested estimation and control scheme.

This paper addresses a novel and flexible control algorithm based on complex virtual impedance for improvement of power sharing in a multi-bus microgrid with complex impedance of lines. In the proposed method, first, the Extended Impedance-Power droop equations are derived. Using nonlinear droop equations, equivalent resistance and inductance of each DG unit are obtained by active and reactive power, separately. Then, an appropriate algorithm is employed to implement Impedance-Power droop to manage the virtual impedances adaptively. The proposed algorithm can optimally share both active and reactive power, even when the structure is changed without any knowledge of microgrid parameters and high-bandwidth communication links. The parameters of the proposed controller are designed based on the nominal power of inverters. Moreover, the stability margin of the system is analyzed. Finally, the feasibility of the proposed control scheme is confirmed via simulations and experiments.

Many studies show that collaborations between renewable energy sources especially PV arrays and plug-in electric vehicles can have a positive impact on the utilization of both emerging technologies. In fact, the intermittent nature of renewable sources and the highdemand for PEV charging will address by this partnership. This paper proposes a user-friendly algorithm for the control of PEV charging and discharging, aiming to satisfy all involved parties including user, parking owner and grid operator by considering the health of batteries and costs. First, the predicted input data are used to obtain the optimal position of PEVs through an extended linear optimization method in different scenarios. In this regard, three scenarios including uncontrolled, unidirectional and bidirectional are used and their impact on the battery health and charging cost is specified. Then, based on energy-awareness, the user selects one of those scenarios arbitrary by comparing their results. Finally, the real-time controller compensates the errors based on a traditional rule-based method. This procedure is repeated upon on arrival of each PEV, and the results are considered as input for the next step.

This study deals with the design of a load sensorless multi-loop control system for the stand-alone inverter. In the proposed strategy, only the inverter current is measured, which is practically required for both control and protection purposes, then the load voltage and current are both estimated using the linear Kalman filter algorithm, and the gradient descent adaptive control method, respectively. The estimated quantities are used as feedback signals of an inner-outer double-loop controller, which uses a proportional-resonant outer-controller to regulate the output voltage with minimum steady-state error and a simple proportional inner-controller to provide active damping and improve the transient performance. The controller parameters are designed in the frequency domain based on the required bandwidth and stability margin. Furthermore, the controllability and observability, as well as the stability of overall digital control system, including the dynamics of estimators, are analytically investigated. Simulation and experimental results, with a 600 VA prototype, confirm the theoretical achievements and illustrate the excellent performance of the proposed estimation and control scheme.

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