scholarly journals DC-Voltage-Ratio Control Strategy for Multilevel Cascaded Converters Fed With a Single DC Source

2009 ◽  
Vol 56 (7) ◽  
pp. 2513-2521 ◽  
Author(s):  
S. Vazquez ◽  
J.I. Leon ◽  
L.G. Franquelo ◽  
J.J. Padilla ◽  
J.M. Carrasco
Keyword(s):  
Control Strategy ◽  
Dc Voltage ◽  
Voltage Ratio

scholarly journals Novel Control Strategy for Enhancing Microgrid Operation Connected to Photovoltaic Generation and Energy Storage Systems

Electronics ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1261
Author(s):  
Dina Emara ◽  
Mohamed Ezzat ◽  
Almoataz Y. Abdelaziz ◽  
Karar Mahmoud ◽  
Matti Lehtonen ◽  
...  
Keyword(s):  
Energy Storage ◽  
Control Strategy ◽  
Voltage Stability ◽  
Storage Systems ◽  
Voltage Source ◽  
Stable Operation ◽  
Energy Storage Systems ◽  
Dc Microgrid ◽  
Photovoltaic Generation ◽  
Dc Voltage

Recently, the penetration of energy storage systems and photovoltaics has been significantly expanded worldwide. In this regard, this paper presents the enhanced operation and control of DC microgrid systems, which are based on photovoltaic modules, battery storage systems, and DC load. DC–DC and DC–AC converters are coordinated and controlled to achieve DC voltage stability in the microgrid. To achieve such an ambitious target, the system is widely operated in two different modes: stand-alone and grid-connected modes. The novel control strategy enables maximum power generation from the photovoltaic system across different techniques for operating the microgrid. Six different cases are simulated and analyzed using the MATLAB/Simulink platform while varying irradiance levels and consequently varying photovoltaic generation. The proposed system achieves voltage and power stability at different load demands. It is illustrated that the grid-tied mode of operation regulated by voltage source converter control offers more stability than the islanded mode. In general, the proposed battery converter control introduces a stable operation and regulated DC voltage but with few voltage spikes. The merit of the integrated DC microgrid with batteries is to attain further flexibility and reliability through balancing power demand and generation. The simulation results also show the system can operate properly in normal or abnormal cases, thanks to the proposed control strategy, which can regulate the voltage stability of the DC bus in the microgrid with energy storage systems and photovoltaics.

Wind-Solar-Hydrogen Hybrid Energy Control Strategy Considering Delayed Power of Hydrogen Production

2021 ◽  
Vol 69 (2) ◽  
pp. 5-12
Author(s):  
Zheng Li ◽  
Yan Qin ◽  
Xin Cao ◽  
Shaodong Hou ◽  
Hexu Sun
Keyword(s):  
Energy Storage ◽  
Control Strategy ◽  
Reactive Power ◽  
Storage System ◽  
Energy Storage System ◽  
Storage Device ◽  
Solar Hydrogen ◽  
Dc Voltage ◽  
Hybrid Energy ◽  
Load Demand

In order to meet the load demand of power system, BP based on genetic algorithm is applied to the typical daily load forecasting in summer. The demand change of summer load is analysed. Simulation results show the accuracy of the algorithm. In terms of power supply, the reserves of fossil energy are drying up. According to the prediction of authoritative organizations, the world's coal can be mined for 216 years. As a renewable energy, wind power has no carbon emissions compared with traditional fossil energy. At present, it is generally believed that wind energy and solar energy are green power in the full sense, and they are inexhaustible clean power. The model of wind power solar hydrogen hybrid energy system is established. The control strategy of battery power compensation for delayed power of hydrogen production is adopted, and different operation modes are divided. The simulation results show that the system considering the control strategy can well meet the load demand. Battery energy storage system is difficult to respond to short-term peak power fluctuations. Super capacitor is used to suppress it. This paper studies the battery supercapacitor complementary energy storage system and its control strategy. When the line impedance of each generation unit in power grid is not equal, its output reactive power will be affected by the line impedance and distributed unevenly. A droop coefficient selection method of reactive power sharing is proposed. Energy storage device is needed to balance power and maintain DC voltage stability in the DC side of microgrid. Therefore, a new droop control strategy is proposed. By detecting the DC voltage, dynamically translating the droop characteristic curve, adjusting the output power, maintaining the DC voltage in a reasonable range, reducing the capacity of the DC side energy storage device. Photovoltaic grid connected inverter chooses the new droop control strategy.

Comparison of two control strategies for VSC-MTDC with wind farm

2021 ◽  
Vol 14 ◽  
Author(s):  
Congshan Li ◽  
Pu Zhong ◽  
Ping He ◽  
Yan Liu ◽  
Yan Fang ◽  
...  
Keyword(s):  
Power Control ◽  
Control Strategy ◽  
Voltage Stability ◽  
Wind Farm ◽  
Control Strategies ◽  
Wind Farms ◽  
Active Power ◽  
Stable Operation ◽  
Active Power Control ◽  
Dc Voltage

: Two VSC-MTDC control strategies with different combinations of controllers are proposed to eliminate transient fluctuations in the DC voltage stability, resulting from a power imbalance in a VSC-MTDC connected to wind farms. First, an analysis is performed of a topological model of a VSC converter station and a VSC-MTDC, as well as of a mathematical model of a wind turbine. Then, the principles and characteristics of DC voltage slope control, constant active power control, and inner loop current control used in the VSC-MTDC are introduced. Finally, the PSCAD/EMTDC platform is used to establish an electromagnetic transient model of a wind farm connected to a parallel three-terminal VSC-HVDC. An analysis is performed for three cases of single-phase grounding faults on the rectifier and inverter sides of a converter station and of the withdrawal of the converter station on the rectifier side. Next, the fault response characteristics of VSC-MTDC are compared and analyzed. The simulation results verify the effectiveness of the two control strategies, both of which enable the system to maintain DC voltage stability and active power balance in the event of a fault. Background: The use of a VSC-MTDC to connect wind power to the grid has attracted considerable attention in recent years. A suitable VSC-MTDC control method can enable the stable operation of a power grid. Objective: The study aims to eliminate transient fluctuations in the DC voltage stability resulting from a power imbalance in a VSC-MTDC connected to a wind farm. Method: First, the topological structure and a model of a three-terminal VSC-HVDC system connected to wind farms are studied. Second, an analysis is performed of the outer loop DC voltage slope control, constant active power control and inner loop current control of the converter station of a VSC-MTDC. Two different control strategies are proposed for the parallel three-terminal VSC-HVDC system: the first is DC voltage slope control for the rectifier station and constant active power control for the inverter station, and the second is DC voltage slope control for the inverter station and constant active power for the rectifier station. Finally, a parallel three-terminal VSC-HVDC model is built based on the PSCAD/EMTDC platform and used to verify the accuracy and effectiveness of the proposed control strategy. Results: The results of simulation analysis of the faults on the rectifier and inverter sides of the system show that both strategies can restore the system to the stable operation. The effectiveness of the proposed control strategy is thus verified. Conclusion: The control strategy proposed in this paper provides a technical reference for designing a VSC-MTDC system for wind farms.

scholarly journals Hybrid Modulated Model Predictive Control in a Modular Multilevel Converter for Multi-Terminal Direct Current Systems

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1861 ◽  
Author(s):  
Zhi Wu ◽  
Jiawei Chu ◽  
Wei Gu ◽  
Qiang Huang ◽  
Liang Chen ◽  
...  
Keyword(s):  
Model Predictive Control ◽  
Predictive Control ◽  
Direct Current ◽  
Control Strategy ◽  
Power Balance ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Dc Voltage ◽  
Passive Networks ◽  
Ac Systems

In this paper a hybrid modulated model predictive control (HM2PC) strategy for modular-multilevel-converter (MMC) multi-terminal direct current (MTDC) systems is proposed for supplying power to passive networks or weak AC systems, with the control objectives of maintaining the DC voltage, voltage stability and power balance of the proposed system. The proposed strategy preserves the desired characteristics of conventional model predictive control method based on finite control set (FCS-MPC) methods, but deals with high switching frequency, circulating current and steady-state error in a superior way by introducing the calculation of the optimal output voltage level in each bridge arm and the specific duty cycle in each Sub-Module (SM), both of which are well-suited for the control of the MMC system. In addition, an improved multi-point DC voltage control strategy based on active power balanced control is proposed for an MMC-MTDC system supplying power to passive networks or weak AC systems, with the control objective of coordinating the power balance between different stations. An MMC-HVDC simulation model including four stations has been established on MATLAB/Simulink (r2014b MathWorks, Natick, MA, USA). Simulations were performed to validate the feasibility of the proposed control strategy under both steady and transient states. The simulation results prove that the strategy can suppress oscillations in the MMC-MTDC system caused by AC side faults, and that the system can continue functioning if any one of the converters are tripped from the MMC-MTDC network.

The Research of SVPWM Control of Shunt Active Power Filter Based on the Inner Relationship between Current and Voltage

2014 ◽  
Vol 528 ◽  
pp. 201-209 ◽  
Author(s):  
Meng Hua Zhang ◽  
Xin Gong Cheng ◽  
Xi Ju Zong
Keyword(s):  
Control Strategy ◽  
Compensation Effect ◽  
Active Power Filter ◽  
Active Power ◽  
Voltage Reference ◽  
Shunt Active Power Filter ◽  
Harmonic Compensation ◽  
Dc Voltage ◽  
Power Filter ◽  
Low Efficiency

To achieve the goal of decreasing the harmonic level in the power grid, traditional shunt active power filter uses the methods such as triangular wave comparison and hysteresis comparator which overall exist some problems, for instance, poor ability of current tracking and low efficiency of DC voltage utilization that lead to bad compensation result. Therefore, we put forward another SVPWM based control strategy in which a relationship between the current reference instruction of active power filter and the voltage reference instruction of SVPWM is found via the topological structure of shunt active power filter. Then we can use SVPWM method to accurately track and compensate the harmonic current. Simulation and experimental results show that the control strategy can solve the above proposed problems and bring about very good harmonic compensation effect.

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