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The paper presents a three-phase power converter control under grid voltage imbalance. The proposed method adapts the current imbalance in relation to the inverter or rectifier operation. Under the inverter operation, the control target is to have the nonoscillatory $p$ component of instantaneous power and the $x_{v}$ component of instantaneous virtual torque calculated as the dot product of the grid virtual flux vector and the converter current vector. Then, the phase with lower voltage is supported by higher current. In the rectifier mode, the control target is to have the nonoscillatory $q$ component of power and the $T_{v}$ component of virtual torque calculated as the cross product of the virtual flux and the converter current. This way, the phase with the highest voltage is loaded by higher current. Unbalanced current obtained in both targets is limited in the way that allows us to limit true phase current and retain sinusoidal current waveforms. However, it does not allow maximum power transfer at the given grid voltage asymmetry, so in order to increase the power value, current progressive balancing is proposed in both operation modes. Finally, converter current balancing is applied also in the case in which a significant amount of reactive power is referenced.

The dual active bridge (DAB) converter is a popular topology with the ability of galvanic isolation and bidirectional power flow. In the practical application, there could be the significant transient current overshoot between the different operating conditions or in the start-up phase of the DAB converter. Therefore, a discrete-time model based model predictive control method is proposed in this paper to constrain the transient inductor current overshoot. An experimental prototype is also built to validate the proposed method. The experimental results are consistent with simulation waveforms and the transient current overshoot can also be effectively constrained to mitigate its stress on the switch devices.

Temperature is one of the key factors to ensure reliable and efficient performance of proton exchange membrane fuel cells. Whereas, due to the limited cooling capacity in automotive application, conventional strategies may fail to remove the excessive heat when the cooling actuator saturates. Hence, three temperature control strategies based on current constraint are developed in this study. Firstly, a dynamic thermal model based on energy conservation is presented. Then a duty ratio split control strategy is proposed to calculate the reduced current from the excess of duty ratio of radiator, yet spike behavior occurs. Hence, a current governor control strategy and a constrained model predictive control strategy are derived to trade off the power demand and cooling capacity, where the maximum load current is calculated by current governor in real time and optimized under the physical constraints of duty ratio and current change rate, respectively. The performances of all the strategies are demonstrated. The current governor control strategy is easy to implement with less computational burden. The constrained model predictive control strategy has fast response and can take into account various constraints explicitly. Both of them have satisfying control performances regardless of limited cooling capacity.

In principle, quantum-dot intermediate band solar cell (QD-IBSC) operates at a higher current density than a III-V multijunction solar cell (MJSC). Due to this inherent property, heat management becomes important when it is operated under a high concentrated illumination. In this work, we propose one way to circumvent this issue, where a wide bandgap cell is placed on top of QD-IBSC, which acts as a current constraint cell, but instead leads to a higher V OC . We demonstrate a 32.1% efficiency under 225 suns with a bonded InGaP/GaAs widegap cell // InAs-InGaAs QDSC configuration.

In the transmission expansion planning (TEP) problem, it is challenging to consider a fault current level constraint due to the time-consuming update process of the bus impedance matrix, which is required to calculate the fault currents during the search for the optimal solution. In the existing studies, either a nonlinear update equation or its linearized version is used to calculate the updated bus impedance matrix. In the former case, there is a problem in that the mathematical formulation is derived in the form of mixed-integer nonlinear programming. In the latter case, there is a problem in that an error due to the linearization may exist and the change of fault currents in other buses that are not connected to the new transmission lines cannot be detected. In this paper, we use a method to obtain the exact updated bus impedance matrix directly from the inversion of the bus admittance matrix. We propose a novel method based on the inverse matrix modification lemma (IMML) and a valid inequality is proposed to find a better solution to the TEP problem with fault current level constraint. The proposed method is applied to the IEEE two-area reliability test system with 96 buses to verify the performance and effectiveness of the proposed method and we compare the results with the existing methods. Simulation results show that the existing TEP method based on impedance matrix modification method violates the fault current level constraint in some buses, while the proposed method satisfies the constraint in all buses in a reasonable computation time.

The paper introduces an examination of finite control set model predictive current control for five-leg voltage source inverter. A Matlab/Simulink model for the of finite control set model predictive current control based on cost function reduction, with load current limitation as a new control algorithm approach. The algorithm chooses one from 32 switching states that produce least error between the desired currents and the predicted currents; the algorithm applies the selected switching control signals as a command to the inverter switches. The proposed algorithm also excludes any switching state that gives currents above the desired values. Subsequently the system response is improved with the reduction of overshoots and deviations from reference. The robustness of the model is tested by applying balanced reference currents with unbalanced load, and a step change in reference currents.

Saturated load is city's maximum affordable load, which is very important for urban development planning. As the power grid matures, the short-circuit current gradually becomes the key factor affecting the security of power grid, it is urgent to analysis the saturated load based on grid technology constraint of short-circuit current. In the paper, firstly, the regular pattern of power supply partition is put forward. Secondly, the typical partition structure model is extracted and the relationship between the model parameters and the actual power supply is deduced. Furthermore, a new method of calculating the saturated load level of power grid is proposed with the consideration of different partition structures and different power supply growth modes. Finally, the saturated load of an actual grid is calculated and the accuracy and effectiveness of the method is verified.

In this paper, the effect of three device parameters, gate electrode work function (WF), device layer/film thickness (T c ) and channel doping concentration (N d ), on DC parameters has been studied in 20 nm gate length Bulk Planar Junctionless Transistor (BPJLT) using Sentaurus TCAD simulator. Using the above device parameters (I ON /I OFF ) ratio of the BPJLT is optimized with I OFF constraint. The results are compared against the literature [1]. A gate electrode work function of 4.98 eV, film thickness of 8 nm and channel doping of 3.3×1019cm−3 gives 29% increase in ION and (I ON /I OFF ) ratio.

The Belousov-Zhabotinskii system measured by a Pt electrode is investigated under external electrode current constraint. A dynamical analysis of the electrode reaction phase has been made by means of a linearized stability criterion valid for three-variable system. It turns out that limit cycle oscillatory regime and dynamical behaviors of the electrode reaction phase have been degenerated under periodical electrode current.

This paper proposes a design method for optimizing the rotor winding shape of HTS motor. The design objective is to maximize the flux-linkage of stator winding with a given amount of superconductor volume. The increase of flux-linkage results in output-power increase, compact size and quench-reliable characteristic. The optimization algorithm is a design sensitivity analysis where the HTS critical current condition is taken into account. First, the shape of rotor winding is optimized to give a boundary shape of smooth curves. Second, with the shape the rectangular sizes of windings are approximately obtained for easy manufacture. Finally, the rectangular sizes are also optimized for fine-size tuning. The proposed design method is applied to the 100-hp HTS motor.

We perform a global analysis of the lepton-quark neutral current data on the low scale gravity model, which arises from the extra dimensions. The global data include HERA neutral current deep-inelastic scattering, Drell-yan production at the Tevatron, and fermion pair production at LEPII. The Drell-yan production, due to the large invariant mass data, provides the strongest constraint. Combining all data, the effective Planck scale must be larger than about 1.12 TeV for $n=3$ and 0.94 TeV for $n=4$ at 95%CL., Comment: Analysis is updated with the newest ZEUS NC DIS data, which appeared after the first submission. Numerical results change slightly

The use of Coulomb's gauge is sufficient for a unique solution in 3-D magnetostatic field calculations in terms of the magnetic vector potential. For the sinusoidal steady-state eddy current problem Coulomb's gauge is not sufficient. The combination of Coulomb's gauge and an eddy current constraint provides a simple way of guaranteeing uniqueness. A formulation for 3-D electromagnetic fields utilizing this constraint is proposed. Results comparing this formulation with other finite-element formulations and with experimental data are given. >