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This paper describes a three-phase shunt active power filter (APF) with improved dynamic parameters. The objective of this solution is to reduce the value of total harmonic distortion (THD) ratio of the power supply line. A predictive control algorithm is implemented in the control circuit, allowing to react in advance to predictable load changes and to reduce dynamic distortion. For loads with unpredictable...
Conventional LC filters cannot compensate effectively harmonics due to non-linear loads in a grid-connected photovoltaic (PV) system. Thus, active power filters (APF) are introduced due to its characteristics and performances, for compensation of harmonics from non-linear loads in the grid-connected photovoltaic (PV) system. This work presents a three-phase voltage-fed shunt active power filter implementation...
This paper proposed a single-phase to three-phase converter with APF in house-service power supply of traction substation. The single phase part of converter is controlled as the rectifier, with implement of the active power filter (APF). The three phase part of converter is used as an inverter. The experiment of the step-down prototype verified the control strategy of the converter.
Compared with the traditional L and LC filter, a LCL-filter can achieve higher attenuation ability with even lower L and C values. LCL filter is more suitable for the three-phase grid-connected voltage source inverters (VSIs) in high power occasion, with its lower cost and better high-order harmonic attenuation. However, the LCL filter is a three order system, which is easy to produce resonance challenging...
This paper introduces a closed loop control WPT system with LCL-LC resonance structure. The characters and advantages of this structure is analyzed. In the unstable environment such as changing bar voltage and lateral displacement, this system ensures constant current output to battery load with an efficiency above 80%, which is verified through practical measurements in this paper.
The switched inductor is a new circuit configuration for electronically varying the effective inductance of an inductor. In conjunction with a capacitor, filters with electronically adjustable tuning frequency can be constructed. This filter has the advantage to follow specific harmonics at the output of an inverter with varying frequency. In this way selective harmonic elimination is possible.
Inverters in back to back (B2B) connection are utilized to convert the voltage and frequency of the power source to another format. Typical application of inverters is the wind power system. This study presents a B2B inverter for equal voltage and frequency format conversion in which one inverter works to get power from the grid to charge the DC capacitor and another inverter returns most of the active...
In this paper a power converter topology where an Unified Power Quality Conditioner (UPQC) is combined with the photovoltaic generators is presented. This topology is based on a dual structure of the classical three-phase two level inverters. Thus, multilevel operation is achieved with the advantages of this type of inverters. Another feature of this structure is the higher reliability of the combined...
In this paper, an improved control strategy for three-phase inverter is proposed, which ensures three-phase output voltage symmetry under unbalanced grid voltage. Firstly, the positive and negative sequence separation module is used to obtain unbalance output voltage and current during the grid faults. By calculating output power of the inverter, an improved P-ƒ, Q-U and Q-G droop control strategy...
This paper presents a unified control design approach involving four topologies of shunt active power filters (SAPF), which can be applied to three-phase four-wire distribution systems. The SAPF structures are deployed by means of the following inverter topologies: full-bridge composed of three modules, four-legs, split-capacitor and neutral point clamped. The SAPFs are compared to each other through...
The work presents conception of 1-phase shunt Active Power Filter (APF) based on the modified sigma-delta modulator (SDM). The modification depends on including in SDM the dynamic hysteresis comparator. Thank to this feature the resolution of SDM output bit stream is, theoretically, unlimited. As result it is possible to precise mapping of the APF input (power grid) current in the reference signal...
The high power density converter (HPDC) in more electric aircraft gains more and more attention. However, HPDC is one of the main harmonics and electromagnetic influence (EMI) sources in aircraft network. To improve power density of HPDC, different levels with power converter includes 2-level, 3-level, and 5-level configurations will be investigated. Besides, two 3-phase power grids such as 3-phase...
This paper proposes a controller design to compensate the current harmonics from the nonlinear load when a grid-connected inverter operates as an active power filter. When the LCL filter is installed at the output of inverter, the controller should be designed differently depending on the location of the nonlinear load. As this nonlinear load is connected to the grid before or after the grid side...
Due to rapid deployments of power electronics in renewable energy sources and new loads, high levels of harmonics causes problems in current distribution systems. This paper presents an advanced harmonic extraction technique for detecting and extracting selected harmonics in a medium-voltage high-power system. A time-transformation technique is developed which can accurately extract the desired harmonics...
This paper presents a harmonic study of different parallel photovoltaic (PV) systems connected to a low voltage distribution network to identify potential resonance between PV inverters and system impedance. LCL filters are commonly employed in PV inverters and recommended by IEEE 929–2000. These filters, however, by interacting with each other as well as with the system, may generate multiple harmonic...
Photovoltaic (PV) systems are integrated into the distribution network (DN) through the grid tied inverter. This paper proposes a flexible power control scheme (FPCS) for three-phase inverters which can compensate the load asymmetries imposed by the nearby residential loads. The development of the control scheme is based on: a dynamic estimation of the load current sequences through a Compensator...
Harmonic voltage compensation of the load connected to the point of common coupling (PCC) by using a series of active power filter (SAPF) based on a single phase cascaded multilevel inverter is proposed. The proposed multilevel inverter are presented in detail. The inverter has the ability of acting as a harmonic source when the reference is a non-sinusoidal signal. To achieve this, a simple control...
This paper present the performances of five-level (NPC) shunt active power filter based on fuzzy control approaches which can mitigate current harmonics generated by nonlinear loads. Five-level inverter is strongly used in the medium and high voltage applications; these advantages are low harmonic distortions, low switching losses, low electromagnetic interference, low voltage stress of power semiconductors...
Grid connected Distributed generation (DG) provides reliable and secured power. The research focus is to achieve adequacy and security in the grid connected photovoltaic (PV) power generation system. The islanding is the situation where DG continues to operate with the utility disconnected. Islanding detection should be done with minimum possible time when it occurs to ensure continued stable operation...
The ever increase of nonlinear loads in electric distribution networks causes many problems due to the high level of harmonic currents. This paper proposes a new technique for controlling a single phase shunt active power filter based on a selective compensation using the newly developed technique of harmonic control arrays. Simulation results confirm the appropriate selective harmonic compensation...
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