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Li-Ion Battery (LB) stack with bi-directional DC-DC converter is used as an energy storage module in Super Uninterrupted Power Supply (UPS). In this paper, the operating mode of the LB module with bi-directional converter is analyzed. The control scheme of the bi-directional DC-DC converter for LB Stack is introduced. A power management strategy for the LB module in super UPS is investigated. The...
In this paper, demand for Solid State DC Circuit Breaker for Super Uninterruptible Power Supply (UPS) is analyzed firstly. Design of the Solid State DC Circuit Breaker is investigated. Then the optimized structure with RCD+MOV is designed to reduce the voltage stress of the power device. Furthermore, the detection of short-circuit current is provided. Finally, a prototype is built to verify the design.
Three typical models of Liu and Jordon's isotropic (extended by Klein), Hay's anisotropic model and Reindl's anisotropic model to estimate monthly-average daily total radiation on vertical surfaces with azimuth form −90° to 90° are investigated by detail. Based on the measurement of global, beam, diffused, and ground reflected radiation on the horizontal surfaces, total radiation on south-facing,...
In this paper, high-efficiency, extremely high step-up and step-down bi-directional DC-DC converter is proposed. The proposed converter consists of a flyback and an isolated switched-capacitor cell to achieve high cost competitiveness for the extreme operation. The output of the flyback converter and that of the isolated switched-capacitor is connected in series to obtain a high voltage step-up. In...
This paper presents an on/off-grid integrated photovoltaic power generation system and its control strategy. The system consists of PV, lithium battery, public grid, converters and loads. The system can work on both on-grid condition and off-grid condition depending on the operation states of PV and lithium battery. The lithium battery works as an energy storage device coordinating with PV to realize...
In this paper, an accurate small-signal model with peak current mode (PCM) control for the Active clamp forward converter under continuous inductor current condition is proposed. To obtain this model, the “Ridely Approach” is utilized to derive the accurate Modulation gain, feedback gain and feed-forward gain in which the magnetizing inductance is fully taken into account. Clamp capacitor and magnetizing...
The Boost converter with digital current-mode control and leading edge modulation is modeled in z-domain first in this paper. The influences of time delay and zero-order holder (ZOH) on digital controlled converters are taken into consideration. Then, the corresponding circuit model is established and simulations are performed to show the effectiveness of the z-model. It's shown by simulations based...
In recent years, there have been an increasing number of photovoltaic (PV) generators integrated into the modern distribution power network. However, the introduction of a large number of PV units could have a negative impact on the distributed PV grid-connected power generation systems, such as polluting the grid, and causing grid instability, even resulting in the voltage collapse if the relevant...
This paper shows that the hybrid bridge resonant converter which is based on the traditional LLC resonant converter, use DSP to toggle between the full bridge mode and the half bridge mode. So the input voltage range is enlarged, and in the high voltage range, the working efficiency is increased by 3%. The switching process between the full bridge mode and the half bridge mode could be made a smooth...
In this paper, a universal voltage clamping circuit for the T-type neutral-point-clamped (TNPC) converter is introduced. It is shown that, for any TNPC implementation, the proposed voltage clamping circuit can well suppress all voltage spikes of power devices at the switching transients. Therefore, the devices can operate in a much safer region.
The interleaving technique is necessary for multiphase LLC resonant converters in high output current high power level applications. But the conventional frequency-controlled LLC converters will lose current sharing if all the phases are operating at the same switching frequency. In this paper, a two-phase interleaved LLC-Regulated DCX (LLC-RDCX) with parallel PWM output regulation is presented to...
This paper analyzes the active power in modular multilevel converters (MMCs), and presents a novel comprehensive control scheme of low frequency operation for the arm capacitor voltages and high frequency circulating current. The inner loop of this scheme employs the arm current direct control which can control the ac side currents, dc-link current and circulating currents simultaneously; an improved...
This paper proposes a new integrated control method for modular multilevel converter (MMC). Common mode and differential mode of MMC system are established in this work. As the effect of voltage and current at different frequencies does not produce active power exchange, it is possible to use a set of orthogonal currents to achieve the balancing control of sub-module voltages based on the above modes...
In this paper, a current-feed resonant two-switch forward DC-DC Transformer (DCX) is proposed for high-efficiency and high-density unregulated bus converter applications. With a resonant capacitor in series with the leakage inductance of the transformer, ZCS turn-on and nearly ZCS turn-off can be achieved for the primary switches and there is no body diode and reverse recovery losses in the SR. Meanwhile,...
LLC resonant converter is an attractive topology to achieve high power density with high efficiency. However, the high switching frequency and circulating current result the poor efficiency of a LLC resonant converter under light load condition. To improve efficiency further, a modified burst-mode control is implemented in the proposed controller. The switching frequency decreases gradually during...
The wind power has the characteristics of intermittent, randomness and uncertainty. In order to make better use of wind power, many scholars use historical data to study the power fluctuation characteristics of wind power generation system,but as for the preparation or built-in wind farms, there are abundant wind speed data but without power data. So how to infer the electric power fluctuations from...
Renewable energy generation is widely used to solve energy shortage and environment problem. Since the output power of the solar cell and the wind turbine will change with the sunlight irradiation and the wind flow, the power of the solar cell and the wind turbine are not stable, so there is a need of a storage equipment connected to the micro-grid system. With the characteristics of high efficient...
This paper proposed an improved carrier phase disposition modulation strategy for modular multilevel converter(MMC), namely a single-carrier modulation strategy. It uses a single triangular carrier to achieve multilevel modulation. It has advantages of both good harmonic characteristics for carrier phase disposition modulation and switch balanced distribution of carrier phase shifted modulation. In...
In order to improve output waveform quality of chain STATCOM by ladder wave modulation method, put forward to conduction Angle optimization method of total harmonic distortion rate (total harmonic distortion, THD) for direct optimization target, through the particle swarm optimization (particle swarm optimization, PSO) algorithm optimizing objective function of conduction Angle educed in this paper...
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