DC Bus Line Research Articles

A novel high-efficient lithium-ion battery serial formation system scheme based on partial power conversion

The formation of the battery is a crucial step in its manufacturing process. The existing battery formation system suffers from low efficiency and high energy consumption costs due to long energy flow paths, high DC bus line losses, and additional balancing circuit applications. Therefore, a novel high-efficient battery series formation system (BSFS) that combines partial power processing architecture (PPPA) with the modular converter is proposed to address this problem in this article. The PPPA-BSFS includes two-stage isolated sub-modules consisting of Buck-Boost converter and LLC converter with input-serial and output-parallel connection. The isolated converter only processes the serial compensation power, about 1/3 of the full power. Consequently, the converter capacity can be shrunk in the PPPA-BSFS, which can reduce the system's cost and power loss. Furthermore, the paper establishes the steady-state mathematical model and energy efficiency model of PPPA-BSFS based on analyzing the power compensation principle, and the key factors affecting the operational efficiency of PPPA-BSFS are studied. Finally, we construct the simulation models with 10 cells and 120 cells to compare and analyze energy efficiency between PPPA-BSFS and existing battery formation topology under various operating conditions. Our simulation results show that the highest operating efficiency of the PPPA-BSFS proposed is 99.37 % when 120 cells are formed normally, where there is an increment of 5.95 %, 2.36 %, and 0.85 % compared with others, respectively. The high efficiency of the PPPA-BSFS is verified, and the PPPA-BSFS shows great potential for application in battery formation scenarios.

A Pilot Protection Scheme of DC Lines for MMC-HVDC Grid Using Random Matrix

The over-current capacity of half-bridge modular multi-level converter (MMC) is quite weak, which requests protections to detect faults accurately and reliably in several milliseconds after DC faults. The sensitivity and reliability of the existing schemes are vulnerable to high resistance and data errors. To improve the insufficiencies, this paper proposes a pilot protection scheme by using the random matrix for DC lines in the symmetrical bipolar MMC high-voltage direct current (HVDC) grid. Firstly, the 1-mode voltage time-domain characteristics of the line end, DC bus, and adjacent line end are analyzed by the inverse Laplace transform to find indicators of fault direction. To combine the actual model with the data-driven method, the methods to construct the data expansion matrix and to calculate additional noise are proposed. Then, the mean spectral radiuses of two random matrices are used to detect fault directions, and a novel pilot protection criterion is proposed. The protection scheme only needs to transmit logic signals, decreasing the communication burden. It performs well in high-resistance faults, abnormal data errors, measurement errors, parameters errors, and different topology conditions. Numerous simulations in PSCAD/EMTDC confirm the effectiveness and reliability of the proposed protection scheme.

Design and test of a novel 1kw Stirling engine generator

This paper describes a practical design of a novel Stirling engine generator and 1kW machine test data. This machine’s configuration is a 4 cylinder double acting Stirling engine coupled with a Halback PM generator in line. This machine operates on the Stirling thermodynamic cycle and electromagnetic cycle established in 19th century by Carnot and Faraday. This machine’s unique function is bidirectional exchanging between thermal energy and electric power, as a same rotating direction of a same shaft. And the shaft speed can be controlled by three phases voltage source PWM inverter during both function such as the motor cooler mode and the engine generator mode. So, this unit can generate an electricity by using to many kinds of external heat source. As the heat source temperature changes as the shaft speed changes for the amount of absorbed heat changing in order to keep a cylinder temperature (700 ℃) and a heater tube temperature (<770 ℃). Consequently, the unit will achieve a highest efficiency keeping as a creep rapture strength limit level of the heater tubes. This unit has achieved 1.1 kW effective electric power, and 20.1% efficiency using LPG fuel, and 23.7 % thermal energy to electrical energy. This unit can connect to a commercial AC grid line by another inverter and, also connect a high voltage battery and a solar cell on the high voltage DC bus line in the PWM inverter.

Distributed control of a user-on-demand renewable-energy power-source system using battery and hydrogen hybrid energy-storage devices

A user-on-demand power source based on renewable energy requires storage devices to balance power sources and power demands because of the fluctuation of power sources like solar cells or wind power generators. The role of the control system is defined as two different tasks: allowing a power-flow imbalance between demand and power sources; and balancing the power flow inside the system. Since this control is complicated, many control methods using precise calculation of the power balance have been proposed. An analogue-like distributed control method - named “modified DC-bus signalling” - for controlling a renewable-energy power source without the need for a central processing unit is proposed. The modified DC bus signalling method discussed in this paper is composed of a DC-bus line connected with a battery, water-splitting electrochemical cell, and a fuel cell for hydrogen-energy storage via converters. The proposed control method was demonstrated to be able to control step-like and random changes in input and output power. The battery compensated high-frequency fluctuations in power demand, and the electrochemical cell and fuel cell handled the remaining low-frequency ones, which were matched to their response speeds.

Enhanced Power Line Communication Strategy for DC Microgrids Using Switching Frequency Modulation of Power Converters

To improve the reliability of dc microgrids operation, an enhanced power line communication (PLC) strategy is proposed using switching frequency modulation (SFM) of a power converter. The proposed PLC strategy uses the voltage ripple on the dc bus voltage, which is inherently generated by converter's switching activities as an information signal. By using the SFM, all microgrid components sharing the dc bus as communication channel can obtain power flow information with fast Fourier transform analysis of dc bus line frequency. In addition, the operating performance of the dc bus voltage regulator is enhanced over a range of light load conditions. The proposed PLC strategy and design of modulated frequency range are verified through experimental results using a 3.3 kW prototype dual active bridge converter.

Modeling and control strategy for grid integrated distributed generation systems with maximum power extraction capabilty

The contribution of a renewable power source to the total power generation becomes more and more important. Wind and photovoltaic (PV) power generation are two of the most promising renewable energy technologies. This p aper presents modeling, simulation and performance analysis of wind energy and PV based DG systems for grid connected mode with MPPT algorithm. Each energy system is connected in paral lel to a common dc bus line through non-isolated dc -dc boost converter. These two dc-dc boost converters are employed for MPPT of wind energy and PV systems. Perturb and Observe (P&O) technique is used for wind energy system. For PV sy stem MPPT algorithm based on incremental conductance is used to get maximum power output. The performance of the developed model is studied for different nature of the in dividual DG sources and load conditions. Simulation results show that t he controllers can regulate the DC link voltage, in jected powers and also the dc-dc converters are very effective in tracking the maximum power of the wind and photovoltaic sources.

Use of a Series Voltage Compensator for Reduction of the DC-Link Capacitance in a Capacitor-Supported System

A technique for reduction of the dc-link capacitance in a capacitor-supported system is presented. The concept is based on connecting a voltage source in series with the dc bus line to compensate the ripple voltage on the dc-link capacitor, so as to make the output have a near zero ripple voltage. Since the voltage compensator processes small ripple voltage on the dc link and reactive power only, it can be implemented with low-voltage devices. The overall required energy storage of the dc-link, formed by a reduced value of dc-link capacitor and the voltage compensator, is reduced, allowing the replacement of popularly used electrolytic capacitors with alternatives of longer lifetime, like power film capacitors, or extending the system lifetime even if there is a significant reduction in the capacitance of electrolytic capacitors due to the aging effect. Comprehensive analysis on the static and dynamic characteristics of the system, and hold-up time requirement will be discussed. The proposed technique is exemplified on an ac-dc-dc power conversion system. Theoretical predictions are favorably verified by experimental results.

Cooperative Optimal Control Strategy for Microgrid under Grid-Connected and Islanded Modes

This paper investigates the control performance of a physical configuration of a microgrid (MG), integrated with photovoltaic (PV) arrays, battery energy storage systems (BESSs), and variable loads. The main purpose is to achieve cooperative optimal control under both grid-connected and islanded modes for the MG. For the grid-connected mode, a voltage source inverter (VSI) based on swoop control is used to control the MG connection to the grid even if PV arrays are under partially shading conditions (PSC). Then, for the islanded mode, the paper analyzes the model of the PV unit and BESS unit detailed from the small signal point of view and designs the suitable control strategy for them. Finally, the whole MG system combines the droop control and the main/slave control to stabilize the DC bus line voltage and frequency. Both simulation and experimental results confirm that the proposed method can achieve cooperative control of the MG system in both grid-connected and islanded mode.

A Motor Surge Voltage Suppression Method With Surge Energy Regeneration

A novel motor surge voltage suppression method is proposed herein. The features of the proposed method are that: 1) there is no requirement for an LC filter for suppression of the motor surge voltage on the motor terminal; 2) the energy stored in the main power cable, which causes the motor surge voltage, is regenerated to the inverter dc-bus line; and 3) the motor surge voltage suppression effect is not influenced by the power cable length. Therefore, the proposed method offers advantages in terms of volume and efficiency compared with conventional surge suppression methods. The circuit configuration of the proposed system is presented and the operation principle is explained. The method used to design the circuit parameters is also presented. The effectiveness of the surge voltage suppression of the proposed method is confirmed experimentally.

Optimal Design of a DC-DC Converter for Photovoltaic Generation

This paper presents novel circuit topology of half-bridge soft-switching PWM inverter type DC-DC high power converter for DC bus feeding power plants. The proposed DC-DC power converter is composed of a typical voltage source-fed, half-bridge high frequency PWM inverter with a high frequency planar transformer link PWM control scheme and parallel capacitive lossless snubbers. The operating principle of the new DC-DC converter treated here is described by using switching mode-equivalent circuits, together with its unique features. All the active power switches in the half-bridge arms and input DC bus lines can achieve ZCS turn-on and ZVS turn-off commutation transitions. The total turn-off switching losses of the power switches can be significantly reduced. As a result, high switching frequency IGBTs can actually be selected in the frequency range of 40[㎑] under the principle of soft-switching. The performance evaluations of the experimental setup are illustrated practically.

A Motor Surge Voltage Suppression Method with Surge Energy Regeneration

A method for motor surge voltage suppression is proposed in this paper. The proposed method has following advantages: (1) an LC filter is not required for suppressing the surge voltage at the motor terminal, (2) the energy stored in the main power cable, which cause the motor surge voltage, is regenerated to the inverter dc bus line, and (3) effective surge suppression is achieved stably regardless of the power cable length and power rating of the system. Consequently, the proposed method has advantage in volume and efficiency compared to conventional surge suppression methods. In this paper, the circuit configuration of the system is shown and the operation principle of the proposed method is explained. Effectiveness of this method is confirmed through the experimental results.

New high-frequency linked half-bridge soft-switching PWM DC–DC converter with input DC rail side active edge resonant snubbers

This study presents a new circuit topology of the active edge resonant snubber-assisted half-bridge soft-switching PWM inverter-type DC-DC high-power converter for DC bus feeding power plants. The proposed DC-DC power converter is composed of a typical voltage source-fed half-bridge high-frequency PWM inverter with a high-frequency planar transformer link in addition to input DC busline side power semi-conductor switching devices for the PWM control scheme and parallel capacitive lossless snubbers. The operating principle of the new DC-DC converter treated here is described by using switching mode equivalent circuits, together with its unique features. All the active power switches in the half-bridge arms and input DC buslines can achieve zero current switching (ZCS) turn-on and zero voltage switching (ZVS) turn-off commutation transitions. The total turn-off switching losses of the power switches can be significantly reduced. As a result, a high-switching-frequency isolated gate bipolar transistor (IGBT) can be actually selected in the frequency range of 60-kHz under the principle of soft switching. The performance evaluations of the experimental setup are illustrated practically. The effectiveness of the new converter topology is proved for low-voltage and large-current DC-DC power supplies as DC bus feeding from a practical point of view.

새로운 풀-브리지 소프트 스위칭 PWM 인버터를 이용한 용접기용 DC-DC 컨버터의 개발

본 연구에서는 일반적으로 용접기의 전원장치로 사용되어지는 풀-브리지 회로에 1개의 스위치와 1개의 무손실 스너버 부분 공진 커패시터로 구성된 간단한 액티브 보조 부분 공진 스너버를 추가한 새로운 풀-브리지 소프트 스위칭 PWM DC-DC 컨버터를 제안하였다. 제안한 풀-브리지 소프트 스위칭 DC-DC 컨버터 회로는 각 액티브 스위치에 인가된 전압이 DC 버스 라인 전압의 1/2로 되기 때문에 AC 400[V]계 상용전원 라인에 적용할 경우에도 600[V]내압의 스위칭 소자(IGBT)가 적용 가능하며, 기존 회로의 DC 버스 라인 스위치에 발생되는 도통 손실을 저감하여 고주파 변압기의 1차측의 전류가 2차측보다 작아지는 저 전압, 대전류 직류 출력을 얻어 수 있었다. 그리고 모든 영역에서 ZCS/ZVS 동작함으로써 저전압, 대전류 직류 출력의 스위칭 전원 장치에 있어 고주파, 고효율, 고출력을 실현할 수 있다. 이러한 모든 사항은 시뮬레이션과 실험 결과로부터 도출하였으며, 제안한 회로의 단점을 보완할 경우에는 차세대형 TIGㆍMIGㆍMAG 아크 용접기용 전원으로 용이할 것으로 판단된다.

A Novel Prototype of Duty Cycle Controlled Soft-Switching Half-Bridge DC-DC Converter with Input DC Rail Active Quasi Resonant Snubbers Assisted by High Frequency Planar Transformer

This paper presents a new circuit topology of active edge resonant snubbers assisted half-bridge soft switching PWM inverter type DC-DC high power converter for DC bus feeding power plants. The proposed DC-DC power converter is composed of a typical voltage source-fed half-bridge high frequency PWM inverter with a high frequency planar transformer link in addition to input DC busline side power semiconductor switching devices for PWM control scheme and parallel capacitive lossless snubbers. The operating principle of the new DC-DC converter treated here is described by using switching mode equivalent circuits, together with its unique features. All the active power switches in the half-bridge arms and input DC buslines can achieve ZCS turn-on and ZVS turn-off commutation transitions. The total turn-off switching losses of the power switches can be significantly reduced. As a result, a high switching frequency IGBTs can be actually selected in the frequency range of 60 kHz under the principle of soft switching. The performance evaluations of the experimental setup are illustrated practically. The effectiveness of this new converter topology is proved for such low voltage and large current DC-DC power supplies as DC bus feeding from a practical point of view.

A Novel type of High-Frequency Transformer Linked Soft-Switching PWM DC-DC Power Converter for Large Current Applications

This paper presents a new circuit topology of DC busline switch and snubbing capacitor-assisted full-bridge soft-switching PWM inverter type DC-DC power converter with a high frequency link for low voltage large current applications as DC feeding systems, telecommunication power plants, automotive DC bus converters, plasma generator, electro plating plants, fuel cell interfaced power conditioner and arc welding power supplies. The proposed power converter circuit is based upon a voltage source-fed H type full-bridge high frequency PWM inverter with a high frequency transformer link. The conventional type high frequency inverter circuit is modified by adding a single power semiconductor switching device in series with DC rail and snubbing lossless capacitor in parallel with the inverter bridge legs. All the active power switches in the full-bridge inverter arms and DC busline can achieve ZVS/ZVT turn-off and ZCS turn-on commutation operation. Therefore, the total switching losses at turn-off and turn-on switching transitions of these power semiconductor devices can be reduced even in the high switching frequency bands ranging from 20 kHz to 100 kHz. The switching frequency of this DC-DC power converter using IGBT power modules is selected to be 60 kHz. It is proved experimentally by the power loss analysis that the more the switching frequency increases, the more the proposed DC-DC converter can achieve high performance, lighter in weight, lower power losses and miniaturization in size as compared to the conventional hard switching one. The principle of operation, operation modes, practical and inherent effectiveness of this novel DC-DC power converter topology is proved for a low voltage and large current DC-DC power supplies of arc welder applications in industry.

Locus of flux linkage for three-phase ZVS inverter

ZVS(zero voltage switching) PWM(pulse width modulation) inverters have attracted much attention recently. The basic idea is to use ZVS circuit as the main circuit of inverter resonance at the beginning of every carrier period so that each power device can com-mutate when voltage of the main circuit’s DC bus line is zero. To ensure the resonant circuit to operate properly, sawtooth with alternate slope (positive or negative) is used as carrier. But the time of zero voltage vectors with such PWM pattern is greatly different from traditional hard-switching PWM pattern. This paper discusses the locus of flux linkage under soft-switching PWM pattern by using space voltage vector. It is pointed out that, under the hard-switching PWM pattern, speed of flux linkage is adjusted by zero space voltage vector. When soft-switching PWM pattern is used, however, effective time of space voltage vector varies considerably, sometimes even without zero space voltage vector. Therefore non-zero space voltage vector has been used to make the speed of flux linkage locus equal to that of hard-switching PWM pattern. The cause of current distortion in soft-switching PWM inverters is also discussed. Based on the flux linkage locus circle, corresponding compensation methods are proposed. Experimental results show that the described method can effectively improve output current waveform of inverter.

고조파 저감 능력을 가진 직류전철 회생인버터 시스템

본 논문에서는 전철시스템의 변전소에서 직류모선에 발생하는 잉여분의 직류전력을 교류전원 측으로 회생시킬 수 있는 직류전력 회생시스템을 제안한다. 제안된 직류 전철용 회생인버터 시스템은 인버터와 능동전력필터로 사용 할 수 있다. 회생인버터 모드에서는 전철의 감속에 의해 회생되는 에너지를 재사용 할 수 있으며, 능동전력필터 모드에서는 변전소의 정류기에 의해 발생되는 고조파 왜곡을 보상하기 위해 사용할 수 있다.<br/> 전력용량과 스위칭 손실을 고려하여 시스템은 3상 PWM 인버터를 기반으로 설계되며 병렬인버터, 출력변압기와 LCL필터로 구성된다.

Effective Improvement of DC Busline Voltage Utilization Factor in Two Switch-Auxiliary Quasi-Resonant DC Link Snubber Assisted Three Phase Voltage Source Type Soft-Switching PWM Inverter

In recent years, a resonant snubber to minimize switching power losses and EMI noises have attracted special interest for the voltage-fed soft switching sinewave PWM inverters and active rectifiers. The authors have discussed the performance evaluations on lower noise and high efficiency for two switch auxiliary resonant DC link snubber assisted three-phase voltage-fed soft switching PWM inverter. It was proved that cost effective three phase soft switching inverter treated here is able to improve both efficiency and EMI noise. However, some practical problems to be improved have recognized for the soft-switching three phase PWM inverter treated here from a practical point of view. This three phase soft-switching inverter with two switch type auxiliary resonant DC link snubber has significant disadvantages of DC busline link voltage reduction for the existence of the zero voltage mode transition period as well as the larger size and physical volume of electrolytic capacitor incorporated into the resonant DC link snubber. The additional technology to minimize the busline DC link zero voltage period in order to overcome the practical problems mentioned above is newly proposed in this paper. From experimental and simulation viewpoints, the modified version of this soft-switching inverter is discussed and evaluated for the DC busline voltage utilization factor as compared with the previously developed one.

Feasible Enhancement of Three-Phase Soft-Switching Inverter with An Auxiliary Resonant DC Link Snubber

The purpose of this paper is to improve power conversion efficiency of three-phase voltage-source type soft-switching inverter with a single auxiliary resonant DC link (ARDCL) snubber. In the first place, the operating principle of an ARDCL snubber discussed here is described. In the second place, this paper proposes an effective generation scheme of zero voltage space vector of three-phase soft-switching inverter using IGBTs that can reduce power losses in the ARDCL snubber treated here. In particular, a zero voltage holding interval in the DC busline of this soft switching inverter is to be regulated due to, the generation scheme of zero voltage space vector. In the third place, the maximum modulation depth Mmax under the condition of compensation of space voltage space vector can be improved by using a new zero voltage space vector generation scheme. Finally, the feasible experimental results to confirm the operating characteristics such as power conversion efficiency, THD and RMS value of output voltage for three-phase voltage-source type soft-switching inverter using IGBTs is concretely implemented and evaluated from a practical point of view.

Auxiliary resonant DC link snubber assisted voltage-source soft switching inverter with space zero voltage vector generation method

The aim of the work is to improve the power conversion efficiency of a voltage-source three-phase inverter with a single active auxiliary resonant DC link snubber circuit (ARDCL). The operating principle and salient features of the ARDCL snubber circuit are described. An effective space voltage vector generation method is of proposed zero voltage vector of a three-phase soft-switching inverter, which can reduce power losses in the ARDCL snubber circuit. The zero voltage holding interval in the DC bus-line of the three-phase inverter is controlled due to the generation method of the zero voltage vector. The feasible experimental results confirm the relationship between the inverter power conversion efficiency and the proposed zero voltage vector generation method is concretely implemented and evaluated from a practical point of view.