Switched-boost action: a phenomenon for achieving time-division-multiplexed multi-port power transfer for nanogrid applications

Multi-port power converter topologies are used to interface multiple terminals (source or load) using a single converter topology. In this paper, the possibility of using switch node of a power converter stage as interface to multiple output stages has been investigated. This interfacing of multiple outputs at the same switch node occurs using time-division multiplexing of the available input power. The multiplexing of input power into different ports occurs using a phenomenon that is denoted as ‘switched-boost action’ in the work and this concept has been illustrated using the boost converter topology. The proposed approach has been used to interface the boost-derived architectures to different types of outputs—ac, dc and isolated dc. The circuit operation has been validated using experimental results. These circuits have been proposed as possible candidates for nanogrid applications.     

Mathematical Morphology-Based Artificial Technique for Renewable Power Application

This paper suggests a combined novel control strategy for DFIG based wind power systems (WPS) under both nonlinear and unbalanced load conditions. The combined control approach is designed by coordinating the machine side converter (MSC) and the load side converter (LSC) control approaches. The proposed MSC control approach is designed by using a model predictive control (MPC) approach to generate appropriate real and reactive power. The MSC controller selects an appropriate rotor voltage vector by using a minimized optimization cost function for the converter operation. It shows its superiority by eliminating the requirement of transformation, switching table, and the PWM techniques. The proposed MSC reduces the cost, complexity, and computational burden of the WPS. On the other hand, the LSC control approach is designed by using a mathematical morphological technique (MMT) for appropriate DC component extraction. Due to the appropriate DC-component extraction, the WPS can compensate the harmonics during both steady and dynamic states. Further, the LSC controller also provides active power filter operation even under the shutdown of WPS condition. To verify the applicability of coordinated control operation, the WPS-based microgrid system is tested under various test conditions. The proposed WPS is designed by using a MATLAB/Simulink software.     

Optimum power-saving method for power MOSFET width of DC/DC converters

An optimum power metal-oxide-semiconductor field effect transistor (MOSFET) width technique is proposed for enhancing the efficiency characteristics of switching DC-DC converters. By implementing a one-cycle buck DC-DC converter, it is demonstrated that the dynamic power MOSFET width controlling technique has a much improved power reduction whether the load current is light or heavy. The maximum efficiency of the buck converter is ~92% with a 3% efficiency improvement for the heavy load condition. The efficiency is further improved by ~16% for the light load condition as a result of the power reduction from the large power MOSFET transistors. Also proposed is a new error-correction loop circuit to enable a better load regulation than that of previous designs. Compared with the adaptive gate driver voltage technique, the optimum power MOSFET width can achieve a significant improvement in power saving. It is also superior to the low-voltage-swing MOSFET gate drive technique for switching DC-DC converters     

High power factor operation of resonant converters on the utility line

Operation and characteristics of resonant converters on the utility line are presented. Series-parallel (LCC-type) resonant converter operating with discontinuous current mode and continuous current mode (variable frequency control as well as fixed-frequency) are considered. Design examples are presented. SPICE simulation and experimental results obtained for the designed converters (rated at 150 W) are presented to verify the theory. It is shown that high line power factor (>0.95) and line current total harmonic distortion (THD) of <25% are obtained for the LCC-type converter for a wide load range (from full load to 10% rated load) without any active control, and the switch peak current decreases with the load current. With active line current control, low distortion and zero voltage switching for the entire cycle are realized.     

Dynamics analysis of LFR model for a single‐stage high power factor correction diagonal half‐bridge flyback ac/dc converter

Abstract

By means of a graft scheme, a buck‐boost cell and a wide range diagonal half‐bridge flyback cell are combined to create a novel single‐stage high power factor correction (HPFC) diagonal half‐bridge flyback ac/dc converter in this paper. When both of the two cells operate in discontinuous conduction mode, the proposed converter exhibits high power factor and low bulk capacitor voltage stress independent of the load variations. Based on the Loss‐Free Resistor (LFR) model, a new technique, referred to as ac‐dc balancing method, is also proposed. It is useful to determine the dc values, voltage ripples, and phase angle shifts of the bulk capacitor and output voltage of the converter. Moreover, the component values are well designed according to the operation conditions and design specifications of the converter. Finally, a prototype of the proposed converter with output voltage 48 V and power 100 W is built to test the theoretical analysis. It is successfully validated by IsSpice simulations and experimental results.     

Split power hydro-mechanical transmission with power circulation

This paper presents a novel hydrodynamic-mechanical split power transmission (US patent application No. 15695671, and PL patent application No. P.422664) with an exceptionally large torque ratio and torque ratio growth rate, and a potentially wide range of (continuous and naturally automatic) torque ratio variation. The transmission features a strong positive feedback between rotors of the impeller and turbine, and makes a systematic use of power circulation (which is present in all transmissions using a hydrodynamic torque converter). The transmission is particularly suitable for vehicles and working machines operating in a start–stop mode and those subjected to heavy, fast-changing external loads, like city buses, wheel and track loaders, dozers, farm tractors, and small earth-moving machines, and most of all for emergency, military, and sports vehicles, where good acceleration is of the highest priority.     

敏感用户高品质交-直流级联供电方案研究

工业过程中大量使用的变频器(variable frequency drive,VFD)在采用传统交流供电时易受到电压暂降影响,传统治理方式存在检测延时、控制复杂等问题。为此,该文从敏感负荷变频器在电网扰动工况下的供电需求量化出发,围绕供电拓扑设计、DC/DC变换器的控制策略及储能单元容量配置等方面,构建一种实用化工业用交-直流级联供电方案。该文利用电压暂降过程中直流供电回路与敏感负荷间的压差自感应控制,实现交-直流供电回路无扰动切换,提高电压暂降治理响应的快速性;采用两相交错并联DC/DC变换器接入集中式储能,减少储能系统纹波系数,并给出两相均流控制方法。最后,通过Matlab/Simulink中的建模仿真与样机的实验测试,验证所提方案能够在交流系统发生不同严重程度电压暂降过程中为各类敏感负荷提供稳定的连续供电,为解决工业敏感用户高品质供电问题提供可实用的新思路。     

Single-stage resonant converter with power factor correction

A novel single-stage resonant converter with power factor correction is presented. Most of the researched power factor corrected rectifiers cascade a boost-type converter with the system. It is found that the half-bridge resonant converter, when the duty cycles are greater than 50%, can simplify the front end of the boost-type converter to a novel single-stage converter. To reduce the converter size and weight and to achieve ripple-free input current, coupled inductor techniques are used in the proposed converter. The operation principle and system steady analysis of the adopted converter are discussed in detail. A prototype has been built to demonstrate the system performance     

Operation margin analysis of zone 3 impedance relay based on sensitivities to power injection

Zone 3 impedance relays (mho relays) on transmission lines have an overreaching protection region. The relays are sensitive to power flow redistribution and to power swing caused by outage or switch operation outside the protected region. Traditionally, the operation margin of mho relays is expressed with impedance. Various load flow schemes that require extensive calculation are necessary to decide the optimal location to control the operation margin. The equivalent expression of the operation margin expressed by a function of bus voltage has been established, and a preventive control model based on the sensitivities of the operation margin to power injection has been proposed. On the basis of the simulation results on the IEEE 14-bus test system, it has been found that: (1) the operation margin can be effectively controlled using the sensitivity method; (2) active and reactive power controls at the same bus may yield opposite control effects; (3) the proposed method is especially effective for stressed power systems; (4) relative control error with is very small as compared to the load flow method and (5) the calculation efficiency is much higher than that of the load flow method     

基于改进型匹配网络的宽带高效率E类功放的设计

为了解决E类功放工作带宽过窄的问题,对E类功放的输入、输出匹配网络提出了一种改进方案.该方案中输出匹配网络采用微带线结构与切比雪夫低通匹配网络相结合的方法,在较宽的工作带宽内有效地抑制了谐波;并采用阻抗变换方法设计了含闭式解的宽带带通输入匹配网络,明显增强了输入匹配网络设计的灵活性.利用该方案,同时采用多谐波双向牵引技术得到功率管的最佳源阻抗和负载阻抗,基于CGH40010F功率管设计了一款应用于L波段的宽带高效率E类功放.测试结果表明,在输入功率为28dBm,漏极偏置电压VDS=28V,栅极电压VGS=-3.3V时,在整个L波段频率范围内漏极工作效率大于65%,最高达到83%,输出功率为39~41.1dBm,增益为11~13.1dB,增益平坦度为±1dB.这一结果验证了该改进方案的有效性,使得E类功放具有宽带宽、高效率的性能.     

An active current-sensing constant-frequency HCC buck converter using phase-frequency-locked techniques

A hysteresis-current-controlled (HCC) buck converter with active current-sensing and phase-frequencylocked techniques is presented in this paper. The proposed active current-sensing technique can not only consume less power than previous techniques, but also fully sense the inductor current. Although the buck converter is HCC, the switching frequency can be constant due to the devised phase-frequency-locked technique. The proposed converter has been designed and implemented with TSMC 0.35 microm DPQM CMOS processes. It is shown in the experimental results that the HCC buck converter features the following characteristics: 1) up to 800 mA of load current, 2) wide input and output voltage range, 3) high power efficiency, and 4) constant-frequency operation.     

Intelligent controlled shunt active power filter for voltage and current harmonic compensation in microgrid system

An integrated microgrid with a novel shunt active power filter (APF) using Elman neural network (ENN) is proposed in this study. The microgrid consists of a storage system, a photovoltaic (PV) system, the shunt APF, a linear load, and a nonlinear load. Moreover, the master/slave control algorithm is adopted in the microgrid. The storage system, which is considered as the master unit, is adopted to control the active and reactive power outputs (P/Q control) in grid-connected mode and the voltage and frequency of the microgrid (V/f control) in islanded mode. Furthermore, the PV system is considered as the slave unit to implement P/Q control in both grid-connected and islanded modes. In addition, the proposed shunt APF possesses dual functions of voltage and current harmonic compensation for microgrid under voltage harmonic propagation and nonlinear load to reduce the voltage and current total harmonic distortions (THD) effectively. Additionally, an ENN controller is adopted in the proposed shunt APF to improve the transient and steady-state responses of DC-link voltage during the switching between the grid-connected mode and islanded mode. Finally, some simulation results are provided to verify the feasibility and the effectiveness of the integrated microgrid with the intelligent controlled shunt APF.     

Single-stage unity power factor based electronic ballast

This paper deals with the design, modeling, analysis and implementation of unity power factor (UPF) based electronic ballast for a fluorescent lamp (FL). The proposed electronic ballast uses a boost AC–DC converter as a power factor corrector (PFC) to improve the power quality at the input ac mains. In this single-stage UPF based electronic ballast, boost PFC converter and a half bridge series resonant inverter (HBSRI) share a common power switch. Thus one power switch is reduced as compared to the conventional two-stage approach. The design, modeling, analysis and implementation of this topology were carried out in MATLAB-Simulink environment for a T8 36 W, 220 V, 50 Hz fluorescent lamp. The switching frequency was kept more than the resonant frequency of the inverter, to ensure the zero voltage switching (ZVS) operation of both power switches. This resulted in reduction of high frequency switching losses. The power quality parameters such as displacement power factor (DPF), distortion factor (DF), power factor (PF), crest factor (CF) and total harmonic distortion of ac mains current (THD_i) were evaluated to analyze the performance of proposed electronic ballast. Test results on a developed prototype of PFC electronic ballast were included to validate the design and simulated results.     

Design and analysis of a full bridge LLC DC-DC converter for auxiliary power supplies in traction

This paper focuses on an 8 kW LLC resonant full bridge DC-DC converter topology using a high frequency transformer for auxiliary power supply systems in traction. The full bridge DC-DC converter with the LLC resonant network has been tested under hard switching and zero current switching conditions with 100 kHz switching frequency. In addition to this, an observation made for the effect of dead time variation of the power switches to improve the overall system efficiency. This paper describes the efficiency of the ZCS full bridge converter by considering different input power levels and also compared with hard switched topology. This paper presents the operating principles, simulation analysis, and experimental verification for 3 kW to 8 kW LLC resonant full bridge converter with 1200 V/40 A IGBTs, and its efficiency comparison.     

Soft-switching flyback inverter with enhanced power decoupling for photovoltaic applications

A novel single-phase flyback inverter for photovoltaic applications is proposed to achieve low-frequency ripple current reduction on the DC busbar and to draw sinusoidal current into the AC grid. Based on capacitive idling techniques, the proposed circuit topology is derived from a single-ended primary-inductance converter and two-switch flyback inverter to obtain soft-switching operation for all of the active switches. Compared with a buck-boost inverter and other flyback inverter topologies for AC photovoltaic module systems, no extra active switches are used in the proposed inverter to realise both soft-switching and enhanced power decoupling with only four active switches. Peak-current mode control method is employed in the control schemes to ensure pure sinusoidal current with unity power factor on the AC grid. Laboratory experimental results based on a 500 W prototype are provided to verify the effectiveness of the proposed inverter     

Acoustic power measurement of linear compressors

The linear compressor works as an important driver for high frequency regenerative cryocoolers. The acoustic power output of the compressor is a critical parameter in the design and the optimization of a linear compressor. To measure this parameter, several approaches based on different theories have been developed. In this paper, the RC load approach and the back chamber approach have been applied to a linear compressor to measure the acoustic power output. The results measured by the approaches indicate a good consistency with the theoretical calculation and reveal the connections between different approaches.The difference between the acoustic power at the piston surface and the exit of a linear compressor has been analyzed based on the experimental results from the RC load approach and the back chamber approach. The volume flow rate difference which accounts for the acoustic power difference is studied theoretically. Furthermore, based on the RC load approach, the optimum impedance together with the impedance cloudy map for the linear compressor to reach its highest efficiency has been obtained by analyzing the experimental and the theoretical results.     

Simulative investigation of wind turbine gearbox loads during power converter fault

Three phase short circuit power converter faults in wind turbines (WT) result in highly dynamic generator torque reversals, which lead to load reversals within the drivetrain. Dynamic load reversals in combination with changing rotational speeds are, for example, critical for smearing within roller bearings. Therefore, an investigation of the correlation between three phase short circuit converter faults and drivetrain component failures is necessary.

Due to the risk of damage and the resulting costs, it is not economically feasible to extensively investigate three phase short circuit converter faults on test benches. Valid WT drivetrain models can be used instead. A WT drivetrain model, which has been developed and validated in a national project at the CWD, is used and a three phase short circuit converter fault is implemented. In this paper, the resulting torque load on the drivetrain for a three phase short circuit converter fault in rated power production is presented. This converter fault leads to a highly dynamic reversing electromagnetic torque which exceeds the rated torque by a factor of three. As a result the load on the rotor side high speed shaft (HSS) bearing oscillates and increases by around 15 per cent compared to rated power production. Simultaneously the rotational velocity of the HSS oscillates with an amplitude of 10 rpm. Therefore an increase in the risk of smearing is expected.

     

High efficiency metal halide discharge lamp ballast with an internal igniter and low ripple lamp current

This is a proposal for a half-bridge type metal halide discharge (MHD) lamp ballast with a coupled inductor and a frequency-controlled synchronous rectifier. To avoid using an external igniter, the internal LC resonance of a buck converter is used to generate a high-voltage pulse for the ignition. A coupled inductor filter is used for steady state ripple cancellation. This filter allows the MHD lamp to avoid the acoustic resonance phenomenon. To improve the efficiency of the ballast, a synchronous buck converter is used for the DC/DC converter stage and a frequency control method is proposed. This scheme reduces the circulation current and turn-off loss of the metal-oxide semiconductor field effect transistor (MOSFET) switch in the constant power operation, which results in an increase of the efficiency of the ballast system compared to fixed frequency control. A front-end power factor correction circuit is included in the ballast. This proposal is verified with hardware experiments     

Negative sequence compensation within fundamental positive sequence reference frame for a stiff micro-grid generation in a wind power system using slip ring induction machine

An isolated wind power generation scheme using slip ring induction machine (SRIM) is proposed. The proposed scheme maintains constant load voltage and frequency irrespective of the wind speed or load variation. The power circuit consists of two back-to-back connected inverters with a common dc link, where one inverter is directly connected to the rotor side of SRIM and the other inverter is connected to the stator side of the SRIM through LC filter. Developing a negative sequence compensation method to ensure that, even under the presence of unbalanced load, the generator experiences almost balanced three-phase current and most of the unbalanced current is directed through the stator side converter is the focus here. The SRIM controller varies the speed of the generator with variation in the wind speed to extract maximum power. The difference of the generated power and the load power is either stored in or extracted from a battery bank, which is interfaced to the common dc link through a multiphase bidirectional fly-back dc-dc converter. The SRIM control scheme, maximum power point extraction algorithm and the fly-back converter topology are incorporated from available literature. The proposed scheme is both simulated and experimentally verified.     

Analysis and design of a high-efficiency zero-voltage-switching step-up DC–DC converter

A high-efficiency zero-voltage-switching (ZVS) step-up DC–DC converter is proposed. The proposed ZVS DC–DC step-up converter has fixed switching frequency, simple control, and high efficiency. All power switches can operate with ZVS. The output diodes are under zero-current-switching (ZCS) during turn-off. Due to soft-switching operation of the power switches and output diodes, the proposed ZVS DC–DC converter shows high efficiency. Steady-state analysis of the converter is presented to determine the circuit parameters. A laboratory prototype of the proposed converter is developed, and its experimental results are presented for validation.