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The deep concern towards efficient and green energy has brought to the development of intermediate energy storage system. Electric vehicles (EVs), for example, is an application where the energy storage devices are vital. In EV, the bidirectional DC-DC converter is high in demand due to its nature EV of having two or more separate DC sources. A recent technology called the dual active bridge (DAB) converter has quickly become popular in DC-DC converter thanks to its inherent galvanic isolation via a high-frequency transformer. Furthermore, DAB topology allows for high-efficiency conversion and soft switching adaption. This paper presents the optimization of the phase shift angle controller of DAB using Particle Swarm Optimization (PSO). From the preliminary study, it was found out that the optimization performs well until there are abrupt changes in the system. The system is not able to respond to the reference voltage step change as the traditional one-time execution PSO have local optima entrapped in react to the changes. The paper proposes a reset function to allow PSO to identify that its current optimized value is not optimal anymore. This drives PSO to look for a new optimal value to improve DAB's overall dynamic performance. Simulation of the modified PSO is done on a 200 kW DAB system with 20 kHz switching frequency is developed in MATLAB/Simulink environment. Simulation has been carried out with the objective to minimize the steady-state error as well as to improve the dynamic performance of the DAB. The DAB performance with the proposed solution is evaluated in terms of steady-state error and transient response by testing the system under various reference voltage and step-change input voltage. The self-excited re-exploration PSO also have been presented as to respond to the reference voltage step change as the basic PSO have local optima entrapped in react to the changes. In order to validate the simulation results, a hardware-in-the-loop (HIL) experimental circuit is built in Typhoon HIL-402 to verify the dynamic response and the steady state performance of the system.

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This paper presents an extension work on the application of interconnection and damping assignment passivity-based controller (IDA-PBC) from the conventional H-bridge inverter to a 5-level Cascaded H-bridge Multilevel Inverter (CHMI). With the controller, the inductor current and the voltage capacitor track the desired reference of the inverter to ensure that the output voltage maintains its regulation while the Total Harmonic Distortion (THD) is kept at low levels with fast transient response. It is designed based on the Port-Control Hamiltonian theory exploiting the dissipation properties of the averaged model of inverter circuits. The results obtained have proven that the IDA-PBC previously developed for the H-bridge inverter can be easily extended and applied to the CHMI circuit. The simulation results showed that the IDA-PBC is able to maintain the output voltage regulation in both circuits in the case of no-load to full-load condition, load uncertainty, and structural uncertainty while maintaining THD of less than 5%. However, in all cases, CHMI has shown better performance in terms of THD percentage and transient response compared to the H-bridge inverter, which are 290 µs and 150 µs respectively. Keyword:CHMI H-Bridge IDA-PBC Interconnection and damping assignment Multilevel inverter Passivity based controller

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Direct Torque Control using multilevel inverter (DTC-MLI) with hysteresis controller suffers from high torque and flux ripple and variable switching frequency. In this paper, a constant frequency torque controller is proposed to enhance the DTC-MLI performance. The operational concepts of the constant switching frequency torque controller of a DTC-MLI system followed by the simulation results and analysis are presented. The proposed system significantly improves the DTC drive in terms of dynamic performance, smaller torque and flux ripple, and retains a constant switching frequency. Keyword:Constant INTRODUCTIONSince it has been introduced in early 1980s [1], Direct Torque Control (DTC) has gained its popularity in electrical drives research area. Recently, the application of high-power medium voltage in AC drives has shown rapid development. Thus, the use of multilevel inverters in DTC scheme has become an important structure for further development and improvement. Numerous technical papers have shown a superior performance of DTC scheme using multilevel inverters .By utilizing the multilevel inverter in DTC scheme, the choices of voltage vectors that can be used to control the torque and flux are increased. As a result, more precise control can be obtained. Several control method have been proposed for DTC scheme using multilevel inverter (DTC-MLI); hysteresis-based and non-hysteresis-based such as predictive control strategy [11,15,17,18,20,22,26,27,30], space vector modulation strategy [2, 4, 8-10, 14, 21, 28, 29, 33] and fuzzy logic control strategy [3,5,7,19,31,[34][35][36].The employment of hysteresis-based control strategy in discrete implementation has led to high torque ripple even with a small hysteresis band. This is due to the delay in sampling time. Besides that, it created a variable switching frequency of the switching devices which leads to an unpredictable harmonics current.As a result, some researchers preferred to use non-hysteresis-based control strategy. Significant improvements are accomplished in terms of flux and torque ripple and devices switching frequency. However it involves a complex mathematical equations and algorithm which has led to the complexity of the DTC-MLI scheme and high computational burden particularly when the multilevel inverter's level is increased.