Hybrid Power Quality Conditioner Research Articles

Using C‐type filter with partial compensation method for capacity reduction of hybrid power quality conditioner in co‐phase traction power system

Hybrid power quality conditioner (HPQC) has been utilised in a co-phase electrified railway system with the aim of improving power quality indices. A C-type filter is designed as an auxiliary device alongside the HPQC for high-order harmonics mitigation in this paper. Alternatively, the C-type filter compensates a selected portion of load reactive power, while the HPQC compensates for the left required power. Furthermore, the HPQC mitigates grid side unbalance and other harmonics in a co-phase supplied system simultaneously. In addition, a design procedure of LCL filters is proposed to suppress high-order harmonic contents induced by the HPQC converters to achieve lower grid-side total harmonic distortion (THD). Moreover, a flexible partial compensation (PC) method considering the C-type filter effect on the HPQC performance is adapted to maintain the grid-side power quality indices in an acceptable range. The C-type filter and PC method provide VA rating reduction of the HPQC without applying any complication to the compensation control system. Finally, simulation and experimental results are presented to validate the feasibility and functionality of the proposed configuration.

Optimal compensation control of railway co‐phase traction power supply integrated with renewable energy based on NSGA‐II

In railway traction power supply, co-phase system with hybrid power quality conditioner (HPQC) is capable of tackling the power quality issues caused by single-phase traction loads. To further reduce the overall carbon emissions in railway systems, this paper considers to integrate the renewable energy with railway power supply, which however leads to a more complicated system to model, design and control. This paper first investigates its modelling aspect. To reduce the operating capacity of HPQC while addressing the power unbalance, optimal design of the compensation scheme for co-phase system is formulated as a multi-objective optimization problem which is then solved by the nondominated sorting genetic algorithm-II (NSGA-II). To eliminate the impact of errors arising from imperfect predictions of the loads and renewable power, a hybrid optimal compensation control is proposed, yielding full and optimal compensations. Comprehensive simulation studies, considering three operation modes covering variable traction loads, renewable and regenerative braking power, are conducted. The simulation results confirm the validity of the proposed optimal compensation scheme, achieving an average of more than 20% reduction in HPQC capacity compared to the full compensation scheme. Meanwhile, the power quality requirement is satisfied, even in the presence of real-time prediction errors.

A Co-Phase Traction Power Supply System Based on Asymmetric Three-Leg Hybrid Power Quality Conditioner

Single-phase 25kV AC traction power supply system (TPSS) is widely used for electric power feeders in high-speed rail. Modern locomotives draw a large amount of unbalanced, inductive power from two phases of the grid through the traction transformer and lead to severe problems of voltage unbalance and reactive power existence. These problems are mitigated in the promising co-phase TPSS with the equipment of Railway Power Conditioner (RPC) or Hybrid Power Quality Conditioner (HPQC), in which HPQC can operate with a lower voltage and cost. However, HPQC installation involves the adoption of a bulky and expensive coupling transformer. In this paper, a co-phase TPSS employing asymmetric back-to-back modular multilevel converter (MMC) is proposed and it is named asymmetric three-leg hybrid HPQC (ATHPQC). Through the simulation verifications in this research work, the proposed design can effectively remove the additional and costly step-down coupling transformer, which is required by symmetric HPQC. For comprehensiveness of the ATHPQC design, internal circulating current modeling and analysis are investigated. Control system is implemented, including external compensating current control, internal balancing control and PWM module. ATHPQC is a promising alternative TPSS for next-generation high-speed rail.

Design and Analysis of Adaptive Impedance Structure for Cophase Railway Traction Supply Power Quality Conditioner

The electrical locomotives are treated as single-phase nonlinear loads, which can cause the low power factor, high contents of harmonic currents, and negative-sequence current. The power quality conditioners are widely used for solving the power quality issues in the railway power system. In power quality conditioners, the coupled impedance can affect the operation voltage, compensation range, and performance. Therefore, this article discusses the effect of different coupled impedances in conditioners, including fixed inductive impedance, fixed capacitive impedance, and adaptive impedance. Moreover, an adaptive impedance-coupled hybrid power quality conditioner (AI-HPQC) is proposed in comparison with inductive-coupled railway power quality compensator (RPC) and capacitive-coupled hybrid power quality conditioner (HPQC). Furthermore, a control method for the AI-HPQC is proposed for the coordination control of the adaptive impedance part and the active inverter part. The validities of the RPC, HPQC, and the proposed AI-HPQC are verified by both simulation and experimental results.

Hybrid power quality conditioner for three-phase four-wire power systems

The article considers a hybrid power quality conditioner (HQPC) for 3-phase 4-wire systems with a distributed modular structure. Some conditioner modules provide compensation for the component currents and voltages that form the negative and zero sequence systems. The open structure of the HQPC, consisting of independent modules, allows compensating for distortions of currents and voltages of the 3-phase network caused by the nonlinear nature and asymmetry of single-phase loads. The compensation characteristics of the proposed conditioner were researched using a model developed in the MatLab environment. The simulation showed that the proposed conditioner can ensure normalization of power quality in 3-phase 4-wire system at various modes of network operation.

Hybrid Power Quality Conditioner for Three-Phase Four-Wire Power Systems

In this paper hybrid power quality conditioner for three-phase four wire power systems is considered. The conditioner is composed of single modules installed at various locations of distribution power system. Individual modules ensure compensation of zero-sequence and negative- sequence voltage and current components. This open configuration of power quality conditioner composed of independent modules allows compensation voltage and current distortion caused by nonlinear and unbalanced single-phase loads. The performance of the proposed conditioner is validated through computer simulation using MatLab software. Simulation results show that the proposed conditioner achieves PQ normalization

Analysis of the Effects of Operation Voltage Range in Flexible DC Control on Railway HPQC Compensation Capability in High-Speed Co-phase Railway Power

Railway hybrid power quality conditioner (HPQC) is advantageous over conventional railway power quality conditioner (RPC) for its reduction in operation voltage and device ratings in co-phase traction power compensation. In order to further reduce the power loss during operation, flexible dc control has been proposed. However, the operation voltage range for railway HPQC has not yet been discussed. This is important since in contrast to traditional power quality compensation devices, active power compensation is involved in co-phase traction power. Compensation capability in co-phase traction power thus does refer not only to reactive power compensation but also to active power compensation ability. Satisfactory compensation performance can be provided only when railway HPQC can provide enough active and reactive compensation power output at the same time. In this paper, the effects of operation range in flexible dc voltage control on railway HPQC compensation capability is briefly discussed and analyzed. The analysis is verified via PSCAD simulations. A laboratory-scaled hardware prototype is also constructed to obtain experimental results for further verifications.

Analysis in the Effect of Co-phase Traction Railway HPQC Coupled Impedance on Its Compensation Capability and Impedance-Mapping Design Technique Based on Required Compensation Capability for Reduction in Operation Voltage

Railway hybrid power quality conditioner (HPQC) is one of the newly proposed devices for power quality compensation in co-phase high-speed traction power supply for its benefit in reduction of operation voltage over conventional railway power quality conditioner (RPC). However, initial railway HPQC design is developed based on minimum operation voltage at predefined fixed rated load. This may not be applicable in practical condition when load varies. In order to solve this problem, a railway HPQC design with increased operation voltage has been investigated to enhance the compensation capability. Nevertheless, the compensation capability is even larger than that required during load variations such that the operation voltage is higher than it actually requires. A lower operation voltage can actually be used to provide required compensation capability when the coupled impedance is different from the designed rated one. In this paper, the effect of coupled impedance on the compensation capability in co-phase railway HPQC is being analyzed. An impedance-mapping design technique based on required compensation capability is then proposed based on the analysis. The proposed method is advantageous for lower operation voltage and smaller capacitance value. The effectiveness of impedance-mapping technique is verified via simulation and experimental results.

An Innovative Research in Power Quality Conditioner for Hospitality Sector

The usage of non-linear loads in commercial sectors, hospitality and industrial sectors is increasing drastically due to its merits. The quality of power gets affected owing to the increase in the usage of non-linear loads and other harmonics creating equipment like CFL bulbs. As a result of the poor power quality, the performance of equipment such as monitors used in hospitals gets affected and the life of the equipment connected to the system also decreases. The penalty is being imposed by the utilities for high harmonic content and low power factor. Hence, a Universal Economic Hybrid Power Quality Conditioner (UEHPQC), combining active filter, passive filter and Thyristor controlled reactor is proposed and modeled through MATLAB/Simulink tool in this paper. As a case study, a famous hotel in Tamil Nadu has been identified and various power quality issues have been analyzed. The performance of the proposed power quality conditioner has been studied with the non-linear loads through MATLAB/Simulink using two controllers, i.e., Artificial Neural Network with the Generalized Radial Basis Function model and Proportional Integral. The performance of the above controllers had been compared.

A Systematic Approach to Hybrid Railway Power Conditioner Design With Harmonic Compensation for High-Speed Railway

Cophase traction power system has high potential to be power supply for high-speed railway. However, the dc operation voltage of conventional power quality compensation device within, such as railway power quality conditioner, is high and may limit its application and development. The hybrid power quality conditioner (HPQC), in which a capacitive coupled $LC$ structure is added, is thus proposed for lower operation voltage. However, there is less investigation and study on the HPQC parameter design for minimum operation voltage when harmonic compensation is concerned. In this paper, the HPQC design for minimum dc operation voltage under comprehensive fundamental and harmonic compensation is being proposed and introduced. Analysis and case study are also performed to show the advantage of the proposed HPQC design. Simulation and laboratory-scaled experimental results are presented to show effective reduction in dc operation voltage using the proposed HPQC design. Through the simulation and experimental case study and verification, there is a reduction of 15% in operation voltage using the proposed hybrid $LC$ structure design compared with the conventional design. The proposed design does not add much additional cost and can also reduce the coupling inductance value. Similar analysis procedure may be also applied to other $LC$ hybrid-structured active power compensators.

Hybrid power quality conditioner for co-phase power supply system in electrified railway

Power quality conditioners based on modern power electronics technology were proposed to solve the power quality problems of the electrified railway power supply system. Large-capacity power converters are used as the main circuits of the compensator, which is one of the main reasons for the high initial cost of the railway power conditioner. A hybrid power quality conditioner (HPQC) for co-phase power supply system in electrified railway is proposed in this study. The HPQC adopts a single-phase back-to-back converter. It connects to the feeding phase of the balance feeding transformer via an L–C branch and to the other phase via a coupling transformer. To inject the same compensating currents to the traction power supply system, the DC bus voltage of the HPQC could be much lower than that of an active power conditioner (APC). As a result, the cost of the power quality conditioner is reduced. Simulation models are built with a HPQC connected to the secondary side of a 110 kV/27.5 kV V/V transformer. Simulation results show the HPQC could compensate reactive current, unbalance current and current harmonics simultaneously. Comparisons with an APC are also given. A small-capacity experimental prototype is built in the laboratory to validate the HPQC and testing results are also provided.