scholarly journals An Improved Control Strategy for the Bus Interlinking Converter Based on Three-level Topology in AC-DC Hybrid Microgrid

2020 ◽  
Vol 186 ◽  
pp. 02002
Author(s):  
Yuan Ren ◽  
Jinhao Wang ◽  
Xiao Chang ◽  
Yi Du ◽  
Ying Zhang ◽  
...  
Keyword(s):  
Control Strategy ◽  
Normal Operation ◽  
Multilevel Converter ◽  
Voltage Level ◽  
Midpoint Potential ◽  
Hybrid Microgrid ◽  
Circulating Current ◽  
Converter Topology ◽  
The Cost ◽  
Hysteresis Control

Considering the increasing requirements of the AC-DC hybrid microgrid (HMG) for the transmission power capacity and voltage level, the several bus interface converters (BICs) with the two-level PWM converter topology, need to be connected between AC bus and DC bus in parallel, which could generate circulating current and cycle power. The cost of the modular multilevel converter topology based BIC is too high. Hence, this paper proposes to apply the BIC with three-level topology to the HMG, and a droop control strategy with the midpoint potential hysteresis regulation link is designed, which can effectively suppress the fluctuation of midpoint potential without affecting the normal operation of the BIC in the grid connected or off mode. In addition, the principle of neutral point fluctuation and the process of hysteresis control are introduced, and the detailed design of dual-mode control strategy based on droop curve are also given. Finally, the effectiveness of the improved control strategy is verified by simulation.

scholarly journals Circulating Current Suppression Strategy of Modular Multilevel Converter Based on Model Predictive Control

2021 ◽  
Vol 261 ◽  
pp. 01035
Author(s):  
kang Liu ◽  
Guige Gao
Keyword(s):  
Model Predictive Control ◽  
Predictive Control ◽  
Control Strategy ◽  
Control Method ◽  
Current Control ◽  
Switching Frequency ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Modulation Wave ◽  
Circulating Current

Modular Multilevel Converter (MMC) has the characteristics of high voltage level and low switching frequency. The traditional modular multilevel converter circulating current control strategy mostly adopts the PI control principle, and the parameter setting is complicated and the accuracy is not high, and the control process is more difficult. Model predictive control strategy is the optimal control method based on the model in the existing time domain. This paper proposes a Model Predictive Control (MPC) method based on carrier phase-shifted pulse width modulation (PSC-PWM) to suppress the circulating current, and output the optimal modulation wave through model prediction. Compared with the traditional control strategy, this strategy is simple to implement, does not require complex tuning calculations, and combines with the traditional capacitor voltage equalization strategy to obtain the output modulation wave. A 7-level MMC simulation control system is built in MATLAB / SIMLINK to verify the theory, comparing with existing control methods, it can be concluded that the proposed method has high calculation efficiency, good control accuracy and strong robustness.

scholarly journals Quadrature Voltage Compensation in the Isolated Multi-Modular Converter

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 529
Author(s):  
Cristian Verdugo ◽  
Jose Ignacio Candela ◽  
Pedro Rodriguez
Keyword(s):  
Control Strategy ◽  
Phase Voltage ◽  
Multilevel Converters ◽  
Photovoltaic Panels ◽  
Circulating Current ◽  
Three Phase ◽  
Voltage Compensation ◽  
Wide Range ◽  
Modular Converter ◽  
The Impact

Series connections of modules in cascaded multilevel converters are prone to power imbalances due to voltage differences on their DC side. When modules are connected to direct current (DC) sources, such as photovoltaic panels, the capability of withstanding power imbalances is crucial for generating the maximum power. In order to provide a possible solution for this requirement, this paper proposes a control strategy called Quadrature Voltage Compensation, which allows a wide range of power imbalances. The proposed control strategy regulates the power by introducing a circulating current between the arms and a phase angle in the output voltage. The impact of the circulating current and its effect on the phase voltage are studied. To highlight the features of the proposed strategy, an analytical model based on vector superposition is also described, demonstrating the strong capability of tolerating power differences. Finally, to validate the effectiveness of the Quadrature Voltage Compensation, simulation and experimental results are presented for a three-phase isolated multi-modular converter.

scholarly journals A Novel Hybrid LDC Converter Topology for the Integrated On-Board Charger of Electric Vehicles

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3603
Author(s):  
Vu-Hai Nam ◽  
Duong-Van Tinh ◽  
Woojin Choi
Keyword(s):  
Low Voltage ◽  
Operating Conditions ◽  
Maximum Efficiency ◽  
Battery Charger ◽  
Forward Converter ◽  
Vehicle To Grid ◽  
Circulating Current ◽  
In Series ◽  
Converter Topology ◽  
Output Capacitor

Recently, the integrated On-Board Charger (OBC) combining an OBC converter with a Low-Voltage DC/DC Converter (LDC) has been considered to reduce the size, weight and cost of DC-DC converters in the EV system. This paper proposes a new integrated OBC converter with V2G (Vehicle-to-Grid) and auxiliary battery charge functions. In the proposed integrated OBC converter, the OBC converter is composed of a bidirectional full-bridge converter with an active clamp circuit and a hybrid LDC converter with a Phase-Shift Full-Bridge (PSFB) converter and a forward converter. ZVS for all primary switches and nearly ZCS for the lagging switches can be achieved for all the operating conditions. In the secondary side of the proposed LDC converter, an additional circuit composed of a capacitor and two diodes is employed to clamp the oscillation voltage across rectifier diodes and to eliminate the circulating current. Since the output capacitor of the forward converter is connected in series with the output capacitor of the auxiliary battery charger, the energy from the propulsion battery can be delivered to the auxiliary battery during the freewheeling interval and it helps reduce the current ripple of the output inductor, leading to a smaller volume of the output inductor. A 1 kW prototype converter is implemented to verify the performance of the proposed topology. The maximum efficiency of the proposed converter achieved by the experiments is 96%.

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