Adnan Tan

Analysis and comparison of passive damping methods for shunt active power filter with output LCL filter

Recently, LCL filter which is commonly preferred in grid connected inverters has found its common usage in shunt active power filters. LCL filter can suppress the switching harmonic ripples effectively. However, it has resonance problem which results unstable system. The resonance problem can be solved with damping the resonance using passive damping methods. The design of LCL filter with using PD is a challenging issue because APF generates currents in a wide harmonic spectrum range to compensate harmonics. The aim of this paper is to present the design procedure of LCL filters with different passive damping methods for SAPF and analyze them in terms of damping performances and power losses. The performance and analysis of LCL filters designed for SAPF is performed with simulation model developed in MATLAB/Simulink.

Survey of inverter topologies implemented in dynamic voltage restorers

Voltage disturbances which affect the stability of electrical networks are the most important power quality problems. The most known voltage disturbances are voltage sag and swell in distribution systems. Dynamic Voltage Restorer (DVR) is the most effective device to compensate these voltage disturbances among the custom power devices. The basic structure of a conventional DVR consists of an inverter, dc link capacitor, injection transformer and filter. The major component in DVR is inverter that generates controlled voltage to compensate voltage sag/swell and other problems such as flicker, interruption and harmonics. Each inverter implemented in DVR has individual properties such as voltage level, unbalanced compensation capability and/or dc link capacitor requirement. This paper aims a comprehensive review on different inverter topologies according to the number of phases, size, voltage level and structure of DVR. In addition, individual properties of inverters are presented in this study.

A notch filter based active damping of llcl filter in shunt active power filter

Shunt Active Power Filter (APF) is a custom power device applied in electric grid system in order to compensate harmonic currents generated by nonlinear loads. Shunt APF operates by firing power electronic devices of voltage source inverter (VSI) to produce the compensation currents. The VSI also generates high frequency switching ripple harmonics that distorts the source current. High order filters, such as LCL and LLCL, have been recently used with shunt APF to decrease the ripple harmonics and to couple shunt APF with the grid. Compared with LCL filter, LLCL filter has more effective attenuation performance at switching frequency because of demonstrating nearly zero impedance. As other high order filters, LLCL filter has resonance problem that leads the system to unstable condition. Passive damping or active damping method is exploited to mitigate the resonance impact and make the system stable. AD methods have more widespread applications and research due to no damping power losses. AD is fulfilled through making improvment in the control system. The objective of this paper is to point out notch filter based AD for shunt APF with output LLCL filter. The proposed system is constructed in Matlab/Simulink and the performance of the proposed system is investigated through simulation cases.

Design and implementation of full bridge bidirectional isolated DC-DC converter for high power applications

This paper proposes the design and implementation of a high power full bridge bidirectional isolated DC-DC converter (BIDC) which comprises of two symmetrical voltage source converters and a high frequency transformer. In the proposed BIDC, a well-known PI controller based single phase-shift (SPS) modulation technique is used in order to achieve high power transfer. Besides, different phase shift methods such as extended phase-shift (EPS) and double phase-shift (DPS) are compared with SPS. Both simulation and experimental results are caried out to verify PI controller based simple phase-shift controlled BIDC prototype that is designed for 300-V 2.4-kW and operating at 20 kHz.

Interline hybrid unified power quality conditioner

This paper proposes a new interline hybrid unified power quality conditioner (IHUPQC) structure to improve the power quality of distribution feeders and to decrease the power ratings/voltages and switching losses of voltage source converters (VSCs). The IHUPQC consists of dynamic voltage restorer (DVR), an isolated dc-dc converter and a shunt hybrid active power filter (SHAPF) with a common dc bus. The inverse park phase locked loop (IP-PLL) technique is used to detect the distortions of signals in both feeders. Sinusoidal pulse width modulation (SPWM) based voltage control and current control are used for DVR and SHAPF respectively. The isolated dc-dc converter has PI controller based simple phase shift (SPS) technique. The proposed structure is designed for 34.5 kV voltage level and simulated by using PSCAD/EMTDC to verify system.

A novel low cost sag/swell generator

This study presents a new Sag Swell Generator (SSG) topology to generate several power quality problems such as sag, swell and interruption. In this paper, bridge type bidirectional switch based SSG is presented to generate different fault conditions. The main contribution of proposed topology is to provide low-cost and simple solution compared to conventional transformer based SSG topologies. The experimental results show that the proposed SSG is a novel topology for low-cost laboratory applications.

Performance investigation of shunt hybrid active power filter with a synchronous reference frame based controller

This paper presents a novel synchronous reference frame based (SRF) control strategy for shunt hybrid active power filter (SHAPF). The control strategy includes a direct current control (DCC) and an indirect current control (ICC) strategy. SHAPF can achieve harmonic compensation and dynamic reactive power compensation with the proposed controller. In this proposed method, as distinct from studies in literature, dynamic reactive power compensation and dc link voltage control is realized with ICC and harmonic current compensation is realized with DCC. Also, the proposed controller provides a variable SHAPF dc link voltage which is adjusted according to the reactive power compensation requirements in order to decrease the switching losses of converter and achieve power savings. The performance of proposed controller is verified with experimental results.

Performance evaluation of a new hybrid unified power quality conditioner (HUPQC)

In this paper, a new hybrid unified power quality conditioner (HUPQC) is proposed to improve current and voltage imperfections in distribution systems. The proposed HUPQC is comprised of the shunt hybrid active power filter (SHAPF), the dynamic voltage restorer (DVR) and the isolated bi-directional DC-DC converter. The main contribution of the study is a new HUPQC topology that enables the reduction in the voltage rating of the DC link capacitor by the help of the SHAPF. The cost and size of the DC link are reduced and switching losses of the voltage source inverter (VSI) is reduced with the low voltage DC link advantage of SHAPF. The DC-DC converter provides isolation and bi-directional power flow between the DVR and the SHAPF during voltage sag and swell. The performance of the proposed HUPQC is evaluated through extensive simulations for mitigating unbalanced voltage sag/swell and compensating current harmonics by using PSCAD/EMTDC simulation tool.