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In this article a sliding mode plus PI controller is proposed to control of the voltage and the input current of a photovoltaic system. The proposed nonlinear controller is designed to control the duty cycle of the two level interleaved boost converter due to changes in the operating conditions of the photovoltaic panel (changes in irradiance levels). Besides this, the proposed controller can operate...
In order to solve parameter testing problem in fluidized bed reactor, a system is designed based on LabVIEW in this paper, which can realize multi-channel temperature acquisition, display and preservation. And the nonlinear problem of hardware is solved by the using of inverse function in the system, which realizes the function of reactor variable power heating control and improves the test efficiency...
This paper proposes a transformer-less modular multilevel DC/DC converter. The proposed converter can be used to interconnect two HVDC systems with different dc voltage levels and realize bidirectional power flow. Based on the arm energy balance condition, the optimal design arming at minimum inner circulating current is presented. A power close-loop control method is adopted to regulate the converter...
The stability problems of power electronics interfaced distributed generators with low inertia and damping can be well solved by the virtual synchronous generator technologies. However, when the grid voltages become unbalanced, oscillations in both the real and reactive power will arise with unbalanced voltages and currents of VSG being noticed. This paper proposed a flexible power control method...
This paper presents a robust deadbeat predictive power control (DBPC) for PWM rectifiers with consideration of parameter mismatches. To achieve accurate power control with crude estimations of the grid-side impedance, the system disturbance caused by inaccurate parameter is analyzed. Then, a complex power based sliding-mode disturbance observer (SMDO) is proposed. Both DBPC and SMDO are implemented...
Direct power control (DPC) is an attractive control method for three-phase pulse-width modulation (PWM) rectifiers, due to the merits of simple structure, quick dynamic response and little tuning work. However, conventional switching table based DPC presents relatively high power ripples and current harmonics, which is especially serious when the grid voltages are unbalanced. Introducing space vector...
The control of PWM rectifiers under unbalanced network has become an important issue in recent years, especially in the applications with weak grid. Conventional methods is based on voltage oriented control (VOC), which requires several PI controllers in dual reference frame and the sequence extraction of grid/rectifier voltages and currents. To reduce the control complexity, recently direct power...
Despite distinctive advantages such as fast dynamic, simple concept and ease of implementation, model predictive direct power control (MPDPC) suffers from some major drawbacks. First, in order to provide sinusoidal currents and low-ripple powers, very high sampling rates are required for MPDPC implementation. Furthermore, this method requires accurate knowledge of system parameters and its performance...
Model predictive direct power control (MPDPC) has been widely concerned in the control of doubly fed induction generator (DFIG) systems owing to its simple concept and good multivariate control ability. The optimal voltage vector is selected based on the principle of power error minimization. Nevertheless, the conventional MPDPC still presents relatively high power ripples and the switching frequency...
Bipolar DC system provides flexible connection and decreased line-to-ground voltage level at the expense of potential voltage unbalance between positive pole and negative pole. Voltage balancer works as “Dependent Voltage Source” to eliminate the unbalance voltage. It is a critical grid-forming component for bipolar system. Considering the need of system expansion and “N+1” redundancy design, bipolar...
New sensorless virtual-flux (VF) based predictive direct power control (PDPC) (VF-PDPC) of a three-phase pulse-width modulation (PWM) rectifier is developed in this paper. The VF estimation is achieved through a simple neural filter based integrator (NF-I) in series with a multi-output adaptive linear neuron (MO-ADALINE). The NF-I leads to cancel dc offset and harmonic distortions in the estimated...
The detection of the fundamental frequency and phase angle of the positive sequence grid voltages are utmost necessary for the proper operation of controlled active power converters, which require to operate stable and robust even during the presence of diverse power quality issues. There exist various utility grid synchronization and detection methods based on Phased-Locked Loop (PLL) techniques...
This paper proposes a novel control method for voltage source converter (VSC) connected to grid under unbalanced voltage conditions. The method is based on utilizing the full control capabilities of the switching converter. The proposed method makes the voltage source inverter (VSI) supply the voltages according to the requirements of the load and/or grid. The method is tested with both the balanced...
The key to realize the low-voltage ride-through (LVRT) of the permanent-magnet synchronous generator (PMSG) is to maintain the DC-link voltage within its acceptable range. By introducing the DC-link voltage to the outer-loop power control of the machine-side converter (MSC), the PMSG may actively adjust its active power output to reduce the DC-link voltage deviation. Given the comparatively slow response...
This paper presents an optimized active power control method for two-stage photovoltaic (PV) grid-connected inverter under unbalanced grid faults. The purpose of the control method is to reduce the active power deficit of grid by injecting the maximum active power of the PV system under the premise of ensuring the safety of the inverter itself. Safe operation region (SOR), which considers the limitation...
Using the conventional look-up table-direct power control (LUT-DPC) strategy with its two-level hysteresis comparators and conventional switching table, poor regulation of active power (abnormal fluctuations appeared in reactive power waveform), non-sinusoidal input currents with a little high THD and depressed power factor are obtained. This study therefore set out to solve these problems; the conventional...
This paper presents the effectiveness of the basic Active Power Curtailment (APC), also known as Constant Power Generation (CPG) or Power Feed-in Control (PFIC), of a 6.3 kW grid-connected photovoltaic (PV) system in the voltage enhancement at the point of connection through the real-world on-site testing results. The basic APC is able to limit the range of voltage fluctuation at the point of connection...
The increasing penetration of renewable energy systems force the grid-connected power converters to use advanced active power controls, which needs to add more functionalities to their control strategies. A power reserve control is being required for grid support capabilities on Renewable Energy Sources (RES). Classical algorithms as the Maximum Power Point Tracking (MPPT) cannot withstand power reserve...
In this paper, a predictive direct power control (P-DPC) strategy for a three level NPC rectifier under ideal grid voltage is proposed, discussed and applied. With the proposed P-DPC strategy, the control targets are the active power, the reactive power and the neutral potential voltage; neither hysteresis comparators nor switching table are needed; sinusoidal input current with low total harmonic...
This paper presents a power control unit for e-class power oscillator of 6.78 MHz wireless power transfer (WPT). Generally, the E-class switching mode power amplifier is a very efficient amplifier. It is suitable for high frequency amplifier. The output power is related to a DC power supply voltage and load resistance. Thus, it is shown that the output power can be controlled by changing DC power...
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