Unbalanced Input Conditions Research Articles

An indirect modulation strategy of matrix converters for unbalanced input supply with reduced commutation losses

ABSTRACT This article is focussed on developing a novel hybrid modulation technique for matrix converter. The concept of singular value decomposition (SVD) is utilised to synthesise the intermediate fictitious DC link voltage whereas generalised scalar pulse width modulation (GSPWM) is utilised to generate the target output voltage. SVD provides the required flexibility in selecting the switch states to improve the input power factor. In contrast, GSPWM helps in reducing the switching losses significantly by clamping the output voltage in synchronisation with the peak of the output currents. This proposed phenomenon reduces the switchings at high current which in turn, reduces the losses and improves the efficiency of the converter. The feedforward compensation used at the input side of the converter helps in achieving the balanced output currents for unbalanced input conditions. The simulation and experimental results with loss analysis render validation of the proposed technique.

Reduced switching state multilevel improved power factor converter for level‐3 electric vehicle applications

In this study, an off-board multi-terminal dc charger with active input current shaping for level-3 electric vehicle (EV) charging applications is proposed. The configuration is based on reduced switching state multi-point clamped, three phase improved power factor converter and supplied by the standard ac grid. The topology has the advantage of reduced device count along with reduced maximum device stress. This will increase the speed of EV charging and enables the reduction of capital and maintenance costs of the charging facilities, enhancing further expansion of the eco-friendly transport. In addition, one of the key performance indicator, i.e. the fault ride-through capability, is investigated in the proposed topology under various unbalanced input conditions. Further, steady-state and transient performance of topology during load, as well as, dc-link voltage change is presented. Minimum distorted and balanced line currents are drawn from supply by implementing negative sequence elimination control algorithm. The validation of the proposed topology is verified with simulation and a down-scaled experimental setup.

Reducing Current Distortion in Indirect Matrix Converters Operating in Boost Mode under Unbalanced Input Conditions

Reducing Current Distortion in Indirect Matrix Converters Operating in Boost Mode under Unbalanced Input Conditions

Active input current shaping with new MPC structured TP-TL-5L converter with reduced PSD count for renewable energy conversion

In this paper, a new multi-point clamped (MPC), three phase two leg, five level front end high power factor converter (TP-TL-5LHPFC) for direct connected wind energy conversion system with permanent magnet synchronous generator (PMSG) is proposed. The converter can be modeled and modulated similar to other existing MPC structured converters with omission of clamping diodes and bi directional switches. The proposed converter has an advantage of reduced power semi conductor device (PSD) count along with reduced maximum device stress. The concept can be extended to increase the converter voltage levels by adding extra half bridges at the top and bottom of the converter. A factor (normalized index) is introduced and comprehensive comparative analysis with N level existing topologies is carried out. The minimum value of normalized index makes the proposed topology is suitable option for medium voltage and high power applications. In addition, the fault ride through capability is one of the key performance indicator for large motor drive systems is investigated on proposed topology under various unbalanced input conditions i.e. voltage sag and line to ground fault. Further, steady state and transient performance of topology during load as well as dc link voltage variation is presented. Minimum distorted and balanced line currents with nearly unity power factor (UPF) are drawn from supply by implementing negative sequence elimination control algorithm. The validation of proposed topology is verified with simulation and a down scaled experimental setup.

Modified modulation scheme for three‐level diode‐clamped matrix converter under unbalanced input conditions

The three-level diode-clamped matrix converter (TLDCMC) topology has outstanding performance under ideal operating conditions. However, input disturbance can influence the waveforms at the output side of the converter due to the direct coupling between the input and output. This study proposes a modified modulation scheme for TLDCMC during operation with unbalanced input voltages and when different transformer turns ratios are used for an isolation transformer at the input. With this modulation technique, sinusoidal and balanced output voltages are guaranteed and the input current harmonics are minimised. Experimental results are presented to demonstrate the feasibility and effectiveness of the proposed modulation scheme.

Asymmetrical Duty-Cycle and Phase-Shift Control of a Novel Multiport CLL Resonant Converter

In this paper, a novel multiport CLL resonant converter with a phase shift and asymmetrical duty-cycle control is analyzed. The power flow can be maintained with the phase shift between ports, whereas the asymmetric duty cycle manages the output voltage at the load terminals. Series connected transformers at the secondary side enable to split the power in each port and reduce the voltage stresses on the switches compared with the parallel connected transformers. Even under the unbalanced input conditions, the power flow between ports can be managed by the central control without any need for communication devices. In order to investigate the power distribution in each port, two different isolated dc sources and a variable load are used. The converter operation is tested at 40, 80, or 120 V inputs, with the output of 200 V at a full power of 1 kW with a maximum efficiency of 97.4%. The experimental results show that the multiport CLL resonant converter with the proposed controller is an appropriate topology for sustainable energy platforms, which are supplied by different types of energy sources, such as photovoltaic, fuel cell, wind, and so on, at various power capacities.

A Novel Control Strategy Based on Natural Frame for Vienna-Type Rectifier Under Light Unbalanced-Grid Conditions

In order to reduce the dc-link voltage ripple and the dc component of the reactive power under unbalanced input conditions, a novel natural-frame-based control scheme for a Vienna rectifier is proposed in this paper. First, by applying an early-developed direct decoupled synchronization method, the fundamental positive/negative-sequence voltage components are derived. Then, a natural-frame-based current control loop is designed based on the mathematical modeling of the Vienna rectifier under unbalanced input conditions. Based on the natural abc frame, the proposed control scheme considerably reduces total algorithm complexity and helps reduce the dc reactive components and total loss in comparison to the traditional dual-hybrid current control schemes. In addition, the stationary operation region of the Vienna-type rectifiers is analyzed, and the scheme is claimed to work out of the stationary operation region with severe voltage unbalance. The dynamic response of unbalanced input is presented. The experimental results are given to demonstrate the effectiveness of the proposed control scheme. In addition, the performance comparison between the traditional controller and the proposed controller is given by experimental results.

Natural frame‐based strategy for Vienna‐type rectifier with light unbalanced input voltages

When the Vienna-type rectifier works at unbalanced input operation conditions, the dc-link voltage ripples and the dc component of the reactive power will be introduced. Therefore a novel control scheme based on natural frame is proposed. The fundamental positive-/negative-sequence voltage components are derived by applying an early developed direct decoupled synchronisation method. A natural abc frame-based current control loop, which considerably reduces total algorithm complexity and also helps to reduce the reactive components size and total loss in comparison with the traditional dual current control schemes, is proposed based on the mathematical modelling of Vienna rectifier under unbalanced input conditions. In addition, the static operation region of the Vienna-type rectifiers is analysed and derived. Finally, the experimental results are given to verify the effectiveness of the proposed control scheme and the conclusion. Performance comparison between the traditional controller and proposed controller is demonstrated by the experimental results.