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High frequency modular power converters are increasingly becoming popular due to their small size and weight. Targeting the input-series and output-parallel (ISOP) dual active bridge (DAB) DC-DC converters, this paper proposes a control scheme based on optimal triple phase-shift (TPS) control for both power sharing control and RMS current minimization. This achieves balanced power transmission, even under mismatched leakage inductance of a DAB module of the ISOP. In order to obtain the optimal zones of operation for the converter, the RMS current was minimized using the Lagrange multiplier method to obtain the optimal duty cycles. The power balancing was added to compensate unbalanced power sharing for variations in model parameters or module shutdown. Analyses and simulation results through MATLAB/Simulink are presented to validate the proposed controller. 

Solid State Transformers (SSTs) are being considered as a replacement to the classic transformers especially for renewable energy and energy storage systems mainly due to their much smaller size and controllability and regulation over the transferred power. Multi-Port SSTs share one high frequency core for the isolation between several devices and hence are even more compact and efficient but the system is complex and the control of such a system is a challenge. This paper considers a four-port, MPSST connected to a renewable source, battery, load, and the grid and discusses various scenarios and operating points. It is shown that several factors including the ratio of the renewable power to the load, battery SOC status and role of the battery in the system change the desired power flow in the system and there are several control structure needed for each mode of operation. These modes of operation and the boundary between them are recognized and eventually a MIMO control scheme is suggested that includes several switches to changes the structure of the controller to adjust the controller structure to the operating condition. Eventually, input-output linearization technique has been adopted to the system to linearize the model and achieve a better control performance. 

Generally, the output power of the Photovoltaic (PV) panels is less than the nominal rating of the panel. On the other hand, the inverters of the PV systems are normally sized smaller than the nominal rating of the photovoltaic system. A typical PV to inverter power rating ratio is 1.2, which can be influenced by the weather condition. The main drawback is that during peak irradiance and optimal temperature situation, the peak power is generated at the PV, but the inverter is not sized for absorbing the whole power. This article develops a systematic method to calculate the optimal ratio between PV panel and inverter to absorb the maximum possible power with an optimal cost. This method uses the annual irradiance and temperature of the geographical region and extracts the power curves for a photovoltaic system in specific regions. Based on the distribution of the various weather conditions, the total possible power generation of the system is calculated. Then the possible extracted and lost power for different sizes of inverters are calculated to develop an efficiency function for the extracted power of the typical power system. This function is optimized considering the price of inverters and system. Both of conventional 1000 V PV system as well as recently developed 1500 V system for 480 VAC grid connection are studied and the effect of transformer in both case is investigated. The paper shows how 1500 V system is superior to its 1000 V counterpart.