scholarly journals Experimental Validation of a Reduced-Scale Rail Power Conditioner Based on Modular Multilevel Converter for AC Railway Power Grids

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 484
Author(s):  
Mohamed Tanta ◽  
Jose Cunha ◽  
Luis A. M. Barros ◽  
Vitor Monteiro ◽  
José Gabriel Oliveira Pinto ◽  
...  
Keyword(s):  
Power Quality ◽  
Reactive Power ◽  
Power Grids ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Power Circuit ◽  
Current Harmonics ◽  
Power Conditioner ◽  
Reduced Scale ◽  
Laboratory Prototype

Rail power conditioner (RPC) has the ability to improve the power quality in AC railway power grids. This power conditioner can increase the loading capacity of traction substations, balance the active power between the feeder load sections, and compensate for reactive power and current harmonics. At present, there is increasing use of multilevel converter topologies, which provide scalability and robust performance under different conditions. In this framework, modular multilevel converter (MMC) is emerging as a prominent solution for medium-voltage applications. Serving that purpose, this paper focuses on the implementation, testing, and validation of a reduced-scale laboratory prototype of a proposed RPC based on an MMC. The developed laboratory prototype, designed to be compact, reliable, and adaptable to multipurpose applications, is presented, highlighting the main control and power circuit boards of the MMC. In addition, MMC parameter design of the filter inductor and submodule capacitor is also explained. Experimental analysis and validation of a reduced-scale prototype RPC based on MMC topology, are provided to verify the power quality improvement in electrified railway power grids. Thus, two experimental case studies are presented: (1) when both of the load sections are unequally loaded; (2) when only one load section is loaded. Experimental results confirm the RPC based on MMC is effective in reducing the harmonic contents, solving the problem of three-phase current imbalance and compensating reactive power.

scholarly journals Deadbeat Predictive Current Control for Circulating Currents Reduction in a Modular Multilevel Converter Based Rail Power Conditioner

2020 ◽  
Vol 10 (5) ◽  
pp. 1849 ◽  
Author(s):  
Mohamed Tanta ◽  
J. G. Pinto ◽  
Vitor Monteiro ◽  
Antonio P. Martins ◽  
Adriano S. Carvalho ◽  
...  
Keyword(s):  
Reactive Power ◽  
Current Control ◽  
Total System ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Control Approach ◽  
Power Conditioner ◽  
Simulation Results ◽  
Control Methodology ◽  
Circulating Currents

This paper presents a deadbeat predictive current control methodology to reduce the circulating currents in a modular multilevel converter (MMC) when it operates as a rail power conditioner (RPC) in a conventional railway system-based V/V connection. For this purpose, a half-bridge MMC based on half-bridge submodules, operating as an RPC is explained, and the total system is denominated as a simplified rail power conditioner (SRPC). The SRPC in this study is used to compensate harmonics, reactive power, and the negative sequence component of currents. This paper explains the SRPC system architecture, the key control algorithms, and the deadbeat predictive current control methodology. Mathematical analysis, based on the MMC equivalent circuit, is described and the reference equations are presented. Moreover, simulation results of the deadbeat predictive current control methodology are compared with the results of the conventional proportional-integral (PI) controller. This comparison is to verify the effectiveness of the proposed control strategy. Simulation results of the SRPC show reduced circulating currents in the MMC phases when using the predictive control approach, besides accomplishing power quality improvement at the three-phase power grid side.

New PQ theory for power quality improvement using modular multilevel converter based UPFC system

2020 ◽  
pp. 1-12
Author(s):  
T.M. Thamizh Thentral ◽  
R. Jegatheesan ◽  
C. Subramani
Keyword(s):  
Power Quality ◽  
Voltage Stability ◽  
Short Circuit ◽  
Dynamic Performance ◽  
Unified Power Flow Controller ◽  
Modular Multilevel Converter ◽  
Loading Conditions ◽  
Multilevel Converter ◽  
Current Harmonics ◽  
Source Current

The source current harmonics reduction techniques were found to be unpredictable and disparity under different loading conditions. The presence of uncertainity issue in harmonics elimination is due to nonlinear loads. Filters can be used to eliminate the harmonics and power quality issues. But these filters are not cost effective to provide dynamic performance under various loading conditions. The target of this paper is to minimize source current harmonics with optimum voltage stability under different loading conditions. A new Unified Power Flow controller is developed whose series compensator is replaced by modular multilevel converter to achieve high modular level with reduced harmonics and fast current limiting during the fault short circuit and shunt compensator is replaced with four switches and one capacitor combination to achieve the twin benefit of more reliable power system and good voltage stability for different loadings. DDSRF (Decoupled Double Synchronous Reference Frame) theory is utilized in the proposed converter for generating the reference current from the AC supply. DDSRF theory generates sinusoidal harmonics with the opposite phase to the load current. The UPFC can suck or injects the responsive power in the PCC. After DDSRF theory, hysteresis controller is used to produce PWM pulse for the shunt and series compensator. The proposed DDSRF theory is compared with existing dq theory to show its effectiveness in terms of THD analysis. The PI and fuzzy logic methodology is utilized to control the capacitor DC rail voltage. The proposed approach is simulated using Matlab under various loading condition and hardware is developed using Spartan 6E FPGA Controller.

scholarly journals Voltage Ride through Control Strategy of Modular Multilevel Converter under Unbalanced Voltage Sag

2019 ◽  
Vol 9 (3) ◽  
pp. 551
Author(s):  
Seyed Hakimi ◽  
Amin Hajizadeh
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Current Control ◽  
Adaptive Robust Control ◽  
Voltage Sag ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Control Approach ◽  
Control Loops ◽  
Unbalanced Voltage

This paper develops modeling and describes a control strategy for a modular multilevel converter (MMC) for grid-connected renewable energy systems. The proposed model can be used to simulate MMC activity during normal and faulty situations. Firstly, a dynamic model of a grid-connected MMC (GC-MMC), based upon the symmetrical component of voltages and currents, was designed. Then an adaptive robust control approach was established in order to follow the reference currents of the converter and stabilize the submodule (SM) capacitor voltage. The positive and negative sequences of reference currents that were given from the demanded active and reactive power during grid voltage disturbance and a normal situation were then utilized in control loops. Finally, the numerical results for the performance of the MMC throughout voltage sag conditions and the effect of uncertainties on the filter parameters during changing power demands were evaluated. The results specified that the current control strategy is more potent under voltage sag situations and able to fulfill the stability requirements of the MMC.

Research on the Control Method of STATCOM Based on MMC

2013 ◽  
Vol 448-453 ◽  
pp. 2167-2170
Author(s):  
Kai Li ◽  
Yi Hui Zheng ◽  
Xin Wang ◽  
Li Xue Li ◽  
Gang Yao ◽  
...  
Keyword(s):  
Closed Loop ◽  
Reactive Power ◽  
Control Method ◽  
Modular Multilevel Converter ◽  
Energy Balancing ◽  
Multilevel Converter ◽  
Voltage Fluctuation ◽  
Loop Control ◽  
Voltage Balancing ◽  
High Voltage Direct Current

To realize the STATCOM based on Modular Multilevel Converter (MMC), a simplified double-closed loop structure, simplifying from the control method of High Voltage Direct Current (HVDC) based on MMC, is presented. Considering MMCs DC side using capacitors, a part-controlling method based on energy balancing is proposed, to solve the voltage balancing problem. With the part-controlling fixing the changing capacitors voltage and the simplified double-closed loop control method, voltage fluctuation could be reduced, and the loads reactive power could be compensated. The correctness and the effectiveness of the MMC-STATCOM controlling scheme is verified by Matlab/Simulink.

scholarly journals Novel Uninterruptible Phase-Separation Passing and Power Quality Compensation Scheme Based on Modular Multilevel Converter for Double-Track Electrified Railway

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 738
Author(s):  
Xu Tian ◽  
Xingcheng Li ◽  
Zibo Zhou
Keyword(s):  
Phase Separation ◽  
Power Systems ◽  
Power Quality ◽  
Control Method ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Electrified Railway ◽  
Uninterruptible Power ◽  
Negative Sequence Current ◽  
Double Track

Over-voltage and over-current problems of locomotives when passing phase separation and negative sequence current penetration seriously influence the safety of double-track electrified railway and public power systems. In order to solve these problems, this paper proposes a novel uninterruptible power supply phase separation passing and power quality compensation (UPSP-PQC) scheme for double-track electrified railway. Three working modes of UPSP-PQC are put forward, including uninterruptible phase separation passing mode, power quality compensation mode and uninterruptible phase separation passing priority, and power quality compensation optimum mode. A three-leg modular multilevel converter (MMC) topology of UPSP-PQC is proposed and the corresponding control strategy has been studied. PSCAD/EMTDC simulation is performed to verify the correctness and effectiveness of the proposed scheme and its control method.

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