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Phytic acid (PA) modified magnetic CoFe2O4 (PA/CFO) composites were successfully synthesized by a facile one-pot microwave hydrothermal method. The coating of PA onto the CFO NPs is clearly confirmed by FTIR, SEM and TEM. The characterization of the crystallinity, morphology and magnetic property reveals the effect of PA addition on the physical properties of the samples. XRD patterns indicate that,...
Due to the intermittent feature of renewable energy sources, energy storage units are needed in order to balance the electricity generation and consumption. Interface circuit is an important component of the energy storage system. This paper presents a non-isolated four-port dc-dc converter for the independent photovoltaic power generation system. The proposed four-port dc-dc convert is used to interface...
In this paper, a current control is studied based on D-Σ digital control to improve the grid-connected performance for a three-level T-type inverter. The control principle is analyzed in accordance with the single-phase equivalent circuit of the three-level T-type inverter. The influence of the neutral-point voltage on both output current error and modulation signal is discussed, and the relationship...
A novel control strategy for three-phase combined inverter is proposed in this paper, which ensures three-phase output voltage symmetry under unbalanced loads in microgrid. Based on the power, voltage and current triple-loop controller, an improved P-f and Q-U droop control strategy is designed to keep three-phase reference voltage symmetrical which is changed through adjusting each-phase droop curve...
A novel coordinate control scheme for battery and super-capacitor energy storage device used in the stand-alone photovoltaic (PV) power generation system is presented in this paper. The stand-alone PV power generation system is composed of PV arrays, battery charging and discharging circuit, super capacitor charging and discharging circuit. PV arrays provide energy for the load, excess and insufficient...
With the high penetration of distributed photovoltaic(PV) generations in low voltage (LV) distribution network, it causes overvoltage in feeder. Therefore, in this paper, impaction on voltage in radial LV grid for distributed PV generations is analyzed. Local voltage self-regulating control strategy of each PV converter to prevent overvoltage and improve the high permeability is proposed. The PV converter...
An algorithm of common mode voltage (CMV) reduction and neutral point voltage (NPV) balance was proposed for a T type three level photovoltaic grid-connected inverter. Several kinds of common mode voltage reduction methods based on space vector were analyzed. The common mode voltage size and frequency caused by the modulation method were summarized. The impact on the neutral point voltage when synthesize...
As for the off-grid distributed power generation system, basic working principle of a single-phase inverter composed of the quasi-Z source inverter and the single-phase full-bridge inverter is studied in this paper. In terms of the former Quasi-Z source inverter, direct sample and control method of DC-link peak voltage is discussed. The PWM modulation strategy of the shoot-through duty cycle with...
A neutral point voltage-balancing control algorithm is proposed for a neutral-point-clamped (NPC) three-level photovoltaic (PV) grid-connected inverter. The mathematical model of the neutral point current was deduced. The influence on the neutral point voltage for discontinuous pulse width modulation(DPWM) methods was analyzed. Comparison of the error between feedback neutral point voltages and the...
Micro grid(MG) consists of a number of parallel operating inverters. The droop control strategy is commonly used in parallel-connected inverters. The conventional PI regulator for the voltage control has little effect on restraining the voltage harmonic content under the nonlinear load conditions. So an effective and reasonable control strategy for inverters must be adopted to ensure the output power...
This article did a research about temperature fields inside the catalytic combustion. It aimed to adjust the instantaneous flow rate by changing the water temperature inside the furnace. And the temperatures from different parts were measured as well. After the experiments were performed, all the results were tabulated on my effort. From a view a environment-friendly society, only with a better understanding...
The tuned harmonic filter in series with the neutral line is an effective method for zero-sequence harmonic mitigation. However, the series tuned filter not only has the de-tuning problem but also inject fundamental impedance into the neutral line. In order to mitigate those negative effects, a continuous auto-tuning zero-sequence harmonic filter based on an active reactor was presented in this paper...
A control strategy of inverters is proposed based on the control requirements of the distributed power sources in the microgrid, which realizes the seamless transition between the grid-connected mode and islanding mode. When the microgrid is connected with the main grid, the PQ control based on the improved droop method is used so that each DG dispatch their energy according to reference energy to...
A novel digital phase-locked-loop (DPLL) method is proposed for single-phase grid-connected power generation systems in this paper. It consists of a grid voltage feed-forward network and a fictious instantaneous power feedback correction network. The fundamental signal of the grid voltage is extracted by a digital Butterworth filter to generate a unity sine reference signal for the feed-forward network,...
The unitary power factor control for distributed grid-connected power generation systems is considered in this paper, i.e., the fundamental-frequency positive-sequence components are extracted from the utility voltages under unbalanced and distorted conditions and output currents of the grid-connected power inverter are always in phase with the corresponding positive-sequence voltages. The extracted...
This paper proposes the intermittent step-varied search of maximum power point tracking (MPPT) method to solve the problem of the tracking speed and power oscillation, it is composed of three control processes including startup stage, step-varied timing search and constant duty ratio timing control. When the photovoltaic (PV) system starts up or the environment changes strongly, step-varied search...
This paper proposes an appropriate control systems aiming at the control demands of distributed generation (DG) unit in the micro-grid. When the micro-grid is connected to the main grid, PQ control with droop characteristic is adopted for the inverter; When micro-grid separates from the main grid, Vf control with droop characteristic is used. Also, the controller can make the conversion between different...
In order to solve the stability problem caused by the parameter mismatch of filter inductance for a conventional predictive current control, a predictive current control method based on on-line parameter estimation of filter inductance is proposed in this paper. The average filter inductance value is calculated in each cycle of grid voltage by means of the average inductance model and phase-locked-loop...
In general, the active frequency drift (AFD) method is used to detect the islanding phenomenon for the distributed grid-connected power system. However, when the angle of the current disturbance matches with the load angle in the range of the non-detecting zone (NDZ), AFD method cannot identify the islanding. In order to solve the above problem, an improved AFD method based on the alternate current...
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