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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...
A soft-switching solution implemented to the traditional bidirectional DC/DC converter is developed. The soft-switching cell, which composed of three auxiliary switches, one resonant capacitor and one resonant inductor, is equipped in the traditional bidirectional DC/DC converter to realize circuit ZCT or ZVT operations in both energy transmission directions. Two driving methods are presented to charging...
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...
To improve the dynamic performance and the anti-disturbance capability of the photovoltaic energy storage system, a control strategy of the bidirectional DC-DC converter based on Linear Active Disturbance Rejection Control (LADRC) is proposed in this paper. Firstly, the mathematical model of the bidirectional DC-DC converter is established. And then, the double closed-loop control strategy based on...
Hybrid excited axial field flux-switching permanent magnet (AFFSPM) (HEAFFSPM) machine is a novel stator-excitation hybrid excited synchronous machine, which combines the advantages of AFFSPM machine and wound-field excitation machine. In this paper, the structure feature of HEAFFSPM machine is analyzed, and the mathematical model is established. In order to improve the power factor of drive system...
Field-oriented control (FOC) is a preferred control method for induction motors. The purpose of FOC is to guarantee perfect dynamic and steady performance of induction motors, but there is cross-coupling between dq current components, which impairs the characteristics of response. Therefore, a decoupled current control strategy using internal model based on active disturbance rejection control (ADRC)...
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 speed estimation method for induction motors based on Strong Tracking Extended Kalman Filter (STEKF) is proposed in this paper, implementing optimization of speed sensorless vector control. With this method, the fading factor is introduced into the covariance matrix of the predicted state, which forces the residual sequences orthogonal to each other and tunes the gain matrix online. The estimation...
The objective of this paper is to further improve the power transmission efficiency of a three-phase four-leg inverter by means of discontinuous three-dimensional space vector modulation (D3DSVM). Three-dimensional coordinate is established by linear transformation, and space vector sections are divided. Each switching vector is studied, and the calculation method of each time allocation is analyzed...
According to the requirement of a photovoltaic grid-connected micro-inverter, the circuit topology, operating principle, control strategy and circuit design of an active clamp fly-back micro-inverter were discussed. Platforms of for both simulation and experiment were built, which had parameters as: input voltage 31 Volts, output voltage 220 Volts and output power up to 100 Watts. Simulation and experimental...
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...
Motor parameters should be on-line estimated to realize precise control of PMSM in sensorless vector control system. In this paper, an on-line identification method for PMSM parameters based on cascade MRAS is proposed by analyzing the conventional MRAS. By means of Popov's hyper-stability theory, the model of motor parameters identification is built in synchronous d-q coordinates, and PMSM stator...
Traditional Chinese Pulse Diagnosis (TCPD), one of the four diagnostic methods of Traditional Chinese Medicine (TCM), had been proved to be clinically valid in Chinese Medicine history. But traditional pulse diagnosis is subjective and deficient in quantitative criteria of diagnosis, which affects the reliability and repeatability of pulse diagnosis. Therefore, quantitative methods are needed to classify...
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...
Based on the characteristics of PV array model, static and dynamic mathematical models of the single-stage PV power grid-connected generation system under the condition of power control are established in this paper. The voltage trajectory of PV array is studied by means of phase diagram analysis, which provides the basis for designing the maximum power point tracking algorithm. A step-power tracking...
An improved grid-connected photovoltaic (PV) power generation system is proposed to solve the problem that the total harmonic distortion (THD) of grid-connected current generally exceeds 5% under the condition of low output power of PV array in this paper. The system includes a larger capacity master inverter with an LCL filter and a smaller capacity slave inverter with an L filter. Two inverters...
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