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The three-phase software phase-locked loop is widely used in electronics converters. Because of the difference in the loop filter, the precision and the speed of the phase-locked loop(PLL) have some distinction. This paper designed PI filter for loop filter and PI together with second-order HPF for loop filter respectively. The simulation result indicated that the PI controller have good tracking...
This paper presents a stochastic Newton method to compute the switching angles in multilevel converters so as to produce the required fundamental voltage while at the same time not generate higher order harmonics. For Newton method, a good initial guess which should be very close to exact solution patterns is necessary, so using stochastic techniques gives a new way to find possible initial values,...
A model of the advanced aircraft electric power system is developed and studied under variable-speed constant-frequency (VSCF) operation. The frequency of the generator's output voltage is varied from 400-Hz to 800-Hz for different loading case-studies. Non-linear DC loads in addition to the different passive and dynamic AC loads are included in the simulation of the VSCF aircraft electric power system...
Poor power quality of single-phase electric railway systems with industrial three-phase power supply will result in extra line losses, under-voltage at the terminal of contact wire, and unbalanced current of utility grid, etc. To address all of the above problems, a co-phase power supply system is adopted and an active power compensator (APC) based on electronic power converter is proposed in this...
Cascaded H-bridge inverters are commonly controlled using linear control and Phase Shifted Pulse Width Modulation, since it allows an even power distribution among the cells, which reduces the harmonic distortion by means of isolation phase-shifted transformers. Recently, predictive control schemes for power electronic converters have been developed, featuring its simplicity, flexibility using different...
Progress and developments in technology have meant that every year an increasing number of industrial applications require more careful handling of higher levels of power in the electrical motors, without ignoring the possibility of improved power quality. These developments, together with the cost of medium voltage semiconductors, have given rise to the multilevel converters with power cells conveniently...
This paper introduces a new three-phase adaptive notch filtering approach for the extraction of harmonic and reactive current components for use in grid connected converters. The main function of this PLL-less method is to provide synchronized harmonic and reactive current components for control purposes. Moreover, this method is capable of detecting a selective order of harmonics. This feature is...
The repetitive control, which is based on a delay of fundamental period, is widely used in grid-connected voltage-source converters, such as uninterruptible power supply (UPS), photovoltaic (PV) inverter and active power filter (APF). This paper presents four repetitive controllers in rotating frame for APF system, whose repetitive period is T, T/2, T/3, and T/6 respectively. Compared with traditional...
This paper presents a novel class of multipulse converter based on high-frequency-operated multipulse transformers. Utility line currents are 12-pulse in nature with the cancellation of 5th and 7th harmonic components. The method demonstrates a considerable reduction in size and weight of the multipulse transformer, due to higher frequency operation. Furthermore, the magnetic components on the rectifier...
The repetitive control and resonant control are widely used in grid-connected voltage-source converters recently, such as uninterruptible power supplies (UPS), photovoltaic inverter (PV) and active power filter (APF). This paper introduces a new repetitive control strategy in APF system, whose repetitive period is only one half of the traditional and could eliminate all odd harmonics as a bank of...
Discontinuous current mode (DCM) boost power factor correction (PFC) converter features zero-current turn-on for the switch, no reverse recovery in diode and constant frequency operation, however, the input power factor (PF) is relatively low when the duty cycle is constant in a half line cycle. This paper derives the expressions of the input current and PF of DCM boost PFC converter, and based on...
A nonlinear average current control method using only dc-rail current for three-phase power-factor-corrected (PFC) converters was introduced recently. This paper discusses the effects of dead-time, sector synchronization, input voltage harmonic distortion and sensing delay on its control performance. A dead-time compensation scheme without additional sensing requirement that is suitable to the nonlinear...
This paper describes a novel control method for a WECS (Wind Energy Conversion System) meant to partially operate as an AF (Active Filter). The control is defined in an equivalent reference frame obtained by applying the Park Transformation to the three-phase quantities. The zero-sequence component is includd in the control system; this feature enables the compensation of zero-sequence harmonics....
This review paper focuses on the three main electrical aspects in the wind energy conversion system (WECS): 1) wind turbine generators (WTGs), 2) power electronics converters (PECs) and 3) grid-connection issues. The current state of wind turbine generators are discussed and compared in some criteria along with the trends in the current WECS market, which are `Variable Speed', `Multi-MW' and `Offshore'...
The changing nature of residential network loads means that Power Quality is becoming a significant issue in New Zealand and internationally. Many residential appliances have electronic power converters that characteristically draw a non-sinusoidal current waveform. This results in increased harmonic voltage levels in the distribution network. The total impact depends on the number of appliances,...
As a compromise between economy and good performance, this paper adopts the combined system using active power filter (APF) and static var compensator (SVC) to compensate reactive power and harmonic currents simultaneously. The SVC is constructed by fixed capacitor (FC) and thyristor controlled reactor (TCR), and the APF is constructed by a voltage source converter and its filter reactor. SVC acts...
The appropriate control strategy of grid-side converter (GSC) under unbalanced grid fault is important for wind power generator's fault-ride-through (FRT) capacity. Based on the basic principles of voltage space vector control, this paper studied the mathematical model of GSC under unbalanced grid conditions, and developed one efficient separation method of positive and negative sequence components...
The Specific Harmonic Elimination Pulse Width Modulation (SHEPWM) is used in a neutral-point-clamped converter. The SHEPWM is implemented in a DSP chip by software. Transient current between different PWM in open loop operation is small. Simulations of close loop control show that work of SHEPWM in dynamic process requires the voltage vector rotate steadily while the requirement on its length change...
The converter transformer saturation model founded in the paper is based on UMEC (Unified Magnetic Equivalent Circuit) theory, which considers core flux and leakage flux uniformly, with high simulation accuracy. Based on the model founded, detailed simulations are made about the converter transformer magnetizing current, the harmonic characteristics of the primary-side and secondary-side current of...
To connect distributed generation units to a low-voltage four-wire distribution network, a suitable three-phase converter topology needs to be chosen. To improve the power quality in the grid, the distributed generation unit can be used as an active power filter (APF). When an active power filtering function is desired, the converter should have a neutral wire to allow neutral currents to flow. Therefore,...
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