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The DC current rejection of a single phase half-bridge grid-connected inverter with a line-frequency isolation transformer is researched in this paper. The impact of the magnetic dc bias of the transformer is given out from the mathematic model of the transformer in current-mode control. For the half-bridge current-mode inverter, the dc current rejection method is presented based on the relationship...
Firstly, it introduces the different operating modes and control mechanism of the high-voltage DC transmission (HVDC) system and analyzes the fuzzy control theory. On this basis, using MATLAB, a typical 12-pulse HVDC transmission system model of the bridge has been simulated under the control of traditional PI and fuzzy intelligent respectively. Compared with the traditional control methods, the real-time...
The design of the voltage loop and current loop of three-phase high power factor PWM rectifier was introduced, the strategy of dual-mode control that combine fuzzy control to PI regulator is proposed, which use fuzzy controller to obtain quick dynamic response when deviation is in small range and adopt PI regulator to realize no static error when deviation is in long range, improving the control accuracy...
In this paper is presented the structure and working principle of the cascaded H-bridge multilevel converter with PWM rectifier and phase-shift transformer. Using the leak inductance as the filter reactor of the PWM rectifier can reducing the volume and cost of the converter; the phase-shift secondary side of the transformer can eliminate the current harmonics caused by the single power unit, restraining...
A tension adaptive variable-structure control system was designed for constant tension of electric cable plastic wrapping automatic production process. This system contains two inner loops for current and velocity control using PI regulators; its outer loop is for tension control using model reference adaptive controller. Simulation results indicate that the adaptive variable-structure controller...
To obtain the maximum efficiency from a photovoltaic panel it has to work close to the maximum power point of power-voltage P(V) characteristic. The paper presents a method to determine this point using external current-voltage characteristic, I(V), instead of P(V) characteristic. With the purpose to avoid the solving of a transcendent algebraically system, a non-linear dynamical system of second...
Lightweight power supply systems using soft-switched high frequency dc-dc converter for rolling stock is proposed in this paper. The system consists of hard switched boost chopper, soft switched high frequency inverter, high frequency transformer and rectifier. This system features a boost chopper to control the input current and to set up a controlled DC link. And A soft switched full bridge inverter...
This paper presents and compares the performance of two controllers namely Fuzzy Logic and Proportional Integral applied to a voltage source inverter/converter operating as an active power filter. The active power filter is operated to compensate harmonics and reactive power generated by the non-linear load and power factor correction simultaneously. This work is performed in order to make an accurate...
There are many consumers and equipments in distributed generation (DG) systems and distributed networks which have rapid changes in the reactive power consumption. These changes can result in large variations in the load-side voltage that may affect the operation of other power consumers which are fed from Point of Common Coupling (PCC). In this paper a current control strategy for inverters, based...
This paper proposes an improved current control scheme for the rotor-side converter of a doubly-fed induction generator (DFIG) wind power generation system. The control scheme consists of a proportional (P) controller and a harmonic resonant (R) regulator tuned at the grid frequency. Thus, the positive and negative sequence components of rotor current are fully regulated by the PR controller without...
In this paper, two control strategies for three-phase series-parallel uninterruptible power supplies are compared. A series-parallel UPS consists of a parallel and a series converter. In this topology, most power required by load is supplied directly from AC line during standby mode. Therefore the overall efficiency is higher than that of a conventional UPS. Traditionally, the control strategy of...
The current state feedback decoupled control strategy in the synchronous reference frame is generally used for the three-phase voltage-source PWM rectifier, which lies in the precise inductance measurement value. In this paper, the effect of the systempsilas performance with the varying of the inductance measurement error and the synchronous frequency is investigated, and the current error feed-forward...
In this paper a predictive control scheme is proposed for the VSC-HVDC system to achieve decoupled control of active and reactive power. The proposed control scheme, which is of simple structure, offers high tracking accuracy, fast dynamic response and good robustness. A case of two-terminal three-level VSC-HVDC system is developed in MATLAB/SIMULINK to verify the validity of the proposed control...
A simplified predictive current controller for the three-phase bidirectional voltage source PWM rectifier is proposed. Firstly, the mathematic model in synchronous d-q coordinate is founded in the discrete-time domain. Then the simplified predictive current controller with state feedback decoupling is designed and analyzed. To overcome the drawbacks of the conventional predictive current controller...
The active and reactive components of the power winding current were controlled by the control winding current, which could make power winding current only providing active current component, and the power winding supplying the dynamic torque. The exciting field for the power winding was completely provided by the control winding. On the basis of dq-rotating reference frame of brushless doubly-fed...
The single current regulator algorithm has been proven robust for flux weakening control of surface-mount PM (SPM) machines with active control of d-axis current and a fixed value of q-axis voltage applied. This paper proposes a new method to optimize the q-axis voltage adaptive to variable speeds and torque based on the single current regulator algorithm for the deep flux weakening control of a 50...
This paper proposes a four-multiple pulse width modulation (PWM) converter for grid interface, which is apply to the variable-speed constant-frequency direct-drive wind turbine systems. The paper introduces the principle of PWM converter, in order to improve DC voltage utilization, space vector pulse width modulation (SVPWM) technology is adopted. Then the advantages of the multiple based on carrier...
This paper proposes an input-paralleled output-paralleled half-bridge converter based on single half-bridge converter, which is very suitable for the low output voltage and large output current application. All modules share a common capacitor-leg, that can reduce the number of main circuitpsilas capacitors and make topology simple. The traits and rules of combination converter are introduced and...
In this paper introduced a design of the active controllable energy feedback device (ACEFD) based on dsPIC30F DSP and d-q controller. Through establishing the synchronous rotating coordinate system (dq) model, we may achieve the decoupling feed-forward control method; the advantages are discussed in the following paragraphs. We also analysis the inner current control model and calculate accurately...
Based on feedback of the stator current phase, a new control strategy of doubly-fed induction generator (DFIG) is proposed. Under the condition that stator current amplitude maintains at rated value, the required rotor control voltage is directly calculated by the stator flux, rotor rotating speed, stator current phase and its corresponding error. Constant converter switching frequency and stator...
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