Revistas
Revista:
IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY
ISSN:
0018-9545
Año:
2019
Vol.:
68
N°:
4
Págs.:
3294 - 3305
Electric motorcycles use a battery storage system and a controlled inverter (motor drive) to drive the wheels. Given that the sale of electric motorcycles is expected to grow significantly over the next decade, the aim of this research is to add a supercapacitor storage system to this simple network in order to extend the autonomy of the motorcycle. This paper analyzes and demonstrates the benefits of two different structures for adding a supercapacitor bank to a lithium-ion battery pack: a passive filter and a buffer for the battery. The advantages of each structure are presented and design guidelines are provided. In addition, we propose a synthetic inductor filter typology based on the two analyzed structures in order to increase the autonomy of the motorcycle. Simulations and experimental results using real data validate the analysis. This paper then uses real data extracted from an electric motorcycle to compare the four topologies: batteries only, the passive filter, the buffer, and the synthetic inductor semi-active hybrid storage system. The comparison shows that battery capacity is extended up to 7.8% with a smoother current profile. However, due to the losses from the added converter in cascade, the net capacity of the whole system is extended only up to 3.7%. Therefore, improvements in the dc/dc converter can further increase the entire system capacity.
Revista:
INTERNATIONAL JOURNAL OF ELECTRICAL POWER AND ENERGY SYSTEMS
ISSN:
0142-0615
Año:
2018
Vol.:
95
N°:
2
Págs.:
440 - 445
This paper characterizes the bidirectional feature of the transformer-based quasi-Z-source inverter (trans-qZSI) obtained by adding a controllable power device to the input of the circuit. Different arising operation modes and states are analysed and an AC small signal model is proposed accordingly. A controller was designed using the proposed model, and an experimental validation platform was implemented. After the computational and experimental model validation, it was analysed how and when bidirectional Z topology benefits from bidirectional feature, apart from obvious inverse power conversion operation. Robustness increase and fault tolerance of the bidirectional trans-qZSI topology were characterized and validated experimentally for different current demand decrease case studies: when an open circuit is produced in one output phase or when the current demand decreases due to normal operation requirements. The paper characterizes and demonstrates, computationally and experimentally, that it is the bidirectional feature that provides the system with the robustness needed to protect against these kind of failures or operation modes. Not having the additional IGBT could cause the system to enter the discontinuous conduction mode (DCM) zone and destabilize the system¿s currents and voltages. In that case the voltage is not able to follow the control reference, which could ultimately lead to the destruction of the components.
Revista:
IET POWER ELECTRONICS
ISSN:
1755-4535
Año:
2017
Vol.:
10
N°:
10
Págs.:
1156 - 1164
This study reviews the causes of power losses in a DC/DC converter, relates those losses with efficiency profiles, and details different strategies for maximising efficiency when several converters are placed in parallel. The research is focused on electric bus applications, where several converters are usually connected in parallel in order to fulfil the power requirements of the bus models. In a bus, the low-voltage DC link (28V) resembles a microgrid that has some generators (DC/DC converters), an energy storage system (lead-acid batteries) and certain loads. To share the converters' output power, a droop control is proposed. Furthermore, traditional droop control is improved by adding a master-slave control. The proposed master-slave droop control improves efficiency by more than 3% at low power with no additional hardware. Experimental results show how two 5kW converters work in parallel using the proposed control.
Revista:
ELECTRIC POWER SYSTEMS RESEARCH
ISSN:
0378-7796
Año:
2017
Vol.:
144
Págs.:
52 - 62
This paper proposes, analyses and validates, both computationally and experimentally, an AC small signal model for a Trans quasi-Z-source inverter working in continuous conduction mode (CCM). For the implementation of the small-signal model, the dynamics of the particular Trans-gZSI network components have been considered. The presented AC small signal model is used for a detailed analysis of the performance of the Trans-gZSI topology, involving various aspects; a parametric study of the influence of the passive components on the dynamic response of the Z network, as well as the influence of their associated losses. Duty cycle and load variations are studied too, for Z topology operating point performance analysis. The AC small-signal model is then used to design a compensator for a closed -loop control scheme. Computer simulation results are presented to validate the model and the control method, comparing PSIM TransqZSI detailed simulations to the MATLAB derived results. Finally, experimental validation is achieved for the AC model in a low-medium power Trans-gZSI design, both in time and frequency domain. According to experimental results analysis, a snubber circuit is designed too, for the converter.
Revista:
ELECTRIC POWER SYSTEMS RESEARCH
ISSN:
0378-7796
Año:
2017
Vol.:
151
Págs.:
106 - 114
This paper presents a transient analysis of the trans quasi-Z-source inverter (trans-qZSI) topology operating in discontinuous conduction mode (DCM). Usually only the continuous conduction mode (CCM) is considered and high current operating points are assumed in the literature. Thus the main contributions of this article are a clear definition of the limits of the DCM and the development of a small-signal model that takes into account the dynamics introduced by the particular Z network contained in the trans-qZSI converter, which allows the behaviour of the system working in DCM to be analysed under different current demand circumstances. Moreover, the obtained small-signal model allows the expressions of the control-to-capacitor transfer function to be derived and used together with any inverter control strategy. For trans-qZSI topology performance analysis and model validation, computer simulation results are presented, including frequency domain analysis and small-signal/PSIM comparisons. Lastly, experimental validation is presented for the time and frequency domains.
Revista:
IEEE TRANSACTIONS ON POWER ELECTRONICS
ISSN:
0885-8993
Año:
2016
Vol.:
31
N°:
11
Págs.:
7953 - 7962
The introduction of fully electric vehicles (FEVs) into the mainstream has raised concerns about the reliability of their electronic components such as IGBT. The great variability in IGBT failure times caused by the very different operating conditions experienced and the stochasticity of their degradation processes suggests the adoption of condition-based maintenance approaches. Thus, the development of methods for assessing their healthy state and predicting their remaining useful life (RUL) is of key importance. In this paper, we investigate the results of performing accelerated aging tests. Our objective is to discuss the design and the results of accelerated aging tests performed on three different IGBT types within the electrical powertrain health monitoring for increased safety (HEMIS) of FEVs European Community project. During the tests, several electric signals were measured in different operating conditions. The results show that the case temperature (T-C), the collector current (I-C), and the collector-emitter voltage (V-CE) are the failure precursor parameters that can be used for the development of a prognostic and health monitoring (PHM) system for FEV IGBTs and other medium-power switching supplies.
Revista:
IET POWER ELECTRONICS
ISSN:
1755-4535
Año:
2016
Vol.:
9
N°:
4
Págs.:
710 - 718
This study presents the analysis and results of a technique that allows the conventional series resonant DC/DC converter to work as a step-up and step-down converter. The controller can choose between several novel step-up modes and the traditional step-down mode. These modes are analysed by presenting their DC characteristics. The choice of mode is governed by the converter's main controller. The converter reduces the operation frequency range and maximises efficiency by selecting the appropriate mode for the particular load and voltage conversion ratio case. Experimental results in a 6 kW prototype validate the analysis and the proposed controller. Finally, the presented converter is compared with a step-up fixed mode converter in order to appreciate the advantages.
Revista:
IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS
ISSN:
2168-6777
Año:
2016
Vol.:
4
N°:
3
Págs.:
1026 - 1035
This paper presents the analysis of a bidirectional series-resonant converter (SRC) for light loads working above or below resonance. In normal operation (heavy load), it is well known that the SRCs have a maximum voltage conversion ratio (m) equal to one. This occurs when the switching frequency (f(S)) equals the resonant frequency (f(0)) and power losses are neglected. This maximum can also be obtained for f(S) < f(0) when the switches are turned ON during a half-resonant period. Thus, zero-current switching can be achieved at both the turn-ON and turn-OFF processes. However, anomalous step-up behavior is found when the converter is attached to light loads. A comprehensive analysis of this phenomenon in the time-domain and in the state plane is presented. Based on the latter, an expression that estimates m and shows the influences of the parameters is obtained. With the aid of this expression, a solution that mitigates that effect is presented and implemented in a prototype, which is part of a bidirectional power chain for supercapacitors. This solution can be implemented for both f(S) > f(0) and f(S) < f(0).
Revista:
IEEE TRANSACTIONS ON POWER ELECTRONICS
ISSN:
0885-8993
Año:
2015
Vol.:
30
N°:
3
Págs.:
1393 - 1402
This paper presents the analysis and design of a novel technique that allows the conventional series resonant dc/dc converter (SRC) to work as a step-up and step-down converter. This is useful in bidirectional dc/dc converters where one port is attached to a fixed voltage dc line, e. g., a 360-V dc line, and the other port is attached to an energy storage device such as a bank of supercapacitors or batteries. Every converter that works in this scenario requires step-up and step-down modes to transfer energy from one port to the other. The paper presents the SRC as an alternative to the well-known dual active bridge (DAB). The dc analysis is detailed to demonstrate the step-up capability. In addition, the ac analysis is presented. Experimental results from a 6-kW prototype validate the theoretical analysis. The results indicate that this technique achieves better efficiency compared to the phase-shift DAB in a wide power range, from heavy to light loads. The main reason for this is that the converter works with smaller currents than the DAB at light loads.
Revista:
INTERNATIONAL JOURNAL OF ELECTRICAL POWER AND ENERGY SYSTEMS
ISSN:
0142-0615
Año:
2015
Vol.:
68
Págs.:
61 - 70
This paper presents an algorithm for reducing the operating cost of microgrids. The proposed algorithm determines the day-ahead microgrid scheduling and builds a fuzzy expert system to control the power output of the storage system. To perform such tasks, two genetic algorithms were employed. One of them generates the microgrid scheduling and determines the fuzzy rules of the expert system, whereas the other is used to tune the membership functions. In this way it is possible to optimize the expert system according to load demand, wind power availability and electricity prices. Simulations were carried out in a microgrid comprising a diesel generator, a microturbine, a fuel cell, a wind turbine and a battery. Both interconnected and island operation modes were considered. Simulation results verify the effectiveness of the proposed algorithm.
Revista:
IET POWER ELECTRONICS
ISSN:
1755-4535
Año:
2015
Vol.:
8
N°:
10
Págs.:
1978 - 1986
This study presents the analysis and design of a novel technique that improves the efficiency of the conventional forward DC-DC converter by reducing switching losses, along with a comprehensive analysis of the circuit and detailed information for designers. The converter uses the current control mode to trigger the switches. To use this control mode, an equalising circuit is presented in the input port to guarantee that the voltage in each half-switching period will be equal; otherwise, the current control mode cannot be applied. A 5 kW step-down (from 350-500 to 28.8 V) prototype is presented and compared with the traditional hard-switching forward converter for fully electric vehicle applications. In addition, the small-signal characteristics and the dynamic response for load variation are presented. Efficiency improvements of over 2% are obtained.
Revista:
IET POWER ELECTRONICS
ISSN:
1755-4535
Año:
2014
Vol.:
7
N°:
9
Págs.:
2374 - 2386
This study analyses the frequency response of a bidirectional series-resonant DC/DC converter (SRC) working in a discontinuous mode (DCM). The converter can reach a voltage conversion ratio higher or lower than one, depending on whether the operation mode is step-up or step-down. The analysis is based on a novel mixed technique using both the state-space average method and the Fourier method to obtain a state-space averaged model of the converter. The study presents the model for the two operation modes. It also presents the frequency response of the output voltage as a function of the input voltage and as a function of the off-time, which is the control parameter of the converter. The results of those transfer functions are compared with measurements in a 2000 W prototype. The model provides enough information to properly control the SRC in DCM.
Revista:
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS
ISSN:
0093-9994
Año:
2014
Vol.:
50
N°:
1
Págs.:
68 - 77
This paper analyzes the benefits and drawbacks of using amodified center-tab rectifier in a high-current bidirectional dc-dc converter. In order to do this, an analytical model of the rectifier is proposed, and a design procedure based on this model is presented. Simulations and experimental data from a prototype validate this model. This topology is also optimized to reduce diode/switch reverse voltage stress. The prototype is designed to be attached to a supercapacitor stack in order to generate a regulated output power supply. Because one side of the converter (the supercapacitor side) has to transfer currents of up to 100 A at a low voltage (less than 50 V), the main reason for choosing this topology is the low conduction losses that it presents.
Revista:
IET POWER ELECTRONICS
ISSN:
1755-4535
Año:
2013
Vol.:
6
N°:
5
Págs.:
1019 - 1028
This study analyses a novel technique for obtaining a voltage conversion ratio greater than one in a bidirectional series-resonant DC/DC converter (SRC). The converter works in a discontinuous mode: it transfers energy in packets, but it also accumulates some packets in order to raise the output voltage. This study presents a comprehensive theoretical analysis for the two modes: the step-down mode (common mode) and the novel step-up mode. The converter transfers energy during fixed time intervals (called states), and it is also able to accumulate energy in a novel state called the accumulation state. With this, the circuit can achieve a voltage conversion ratio of up to two. In addition, a design methodology is presented, and it is validated in the design of a high-current bidirectional DC/DC converter for battery applications. The results of the voltage conversion ratio and efficiency measurement are presented along with a comparison with an resonant LLC converter. The converter reaches an efficiency rate of 91% and the voltage conversion ratio varies from 0.8 to 1.22 at maximum power. Using this novel technique, the SRC can now be used in a bidirectional DC/DC converter applied to energy storage devices, such as batteries or supercapacitors.
Revista:
JOURNAL OF POWER ELECTRONICS
ISSN:
1598-2092
Año:
2012
Vol.:
12
N°:
2
Págs.:
233 - 241
This paper presents a design of a 30kW 250V/530V bidirectional DC-DC converter to be used in an electrical car. A detailed explanation of the design is given. The system uses two phase shifted half bridge (boost and buck) topologies to reduce the ripple current in the output capacitor. The converter has an efficiency of 95% at nominal power. It works as a constant voltage in one direction and as a constant current in the other to charge the batteries. Simulations and measurement are done at high power to test the efficiency.
Revista:
INTERNATIONAL REVIEW OF ELECTRICAL ENGINEERING-IREE
ISSN:
1827-6660
Año:
2011
Vol.:
6
N°:
3
Págs.:
1228 - 1238
This paper presents an analytical method to compute the magnetic flux distribution in spoke interior permanent-magnet (IPM) machines with non-magnetic shaft from no-load to short-circuit conditions. Despite non-magnetic shaft gets significant reduction of the PM leakage flux, this cannot be neglected to calculate correct flux distribution; thus, shaft leakage flux is analyzed and modelled. Moreover, as the demagnetization characteristic of the machine depends on the magnetic circuit, simple mathematical equations to estimate the demagnetization level of the magnets are also given. Based on this approach, protection against demagnetization due to short-circuit current and maximum field-weakening level achievable are easily estimated. The presented formulation and methods are used to optimize the rotor of an IPM machine in order to maximize the electromagnetic torque (30% higher), minimize the amount of PM material, and protect PMS against demagnetization under field-weakening and short-circuit conditions. Analytical results are compared with finite-element software, showing errors lower than 4% in the no-load magnetic circuit and lower than 12% at short-circuit conditions. Presented formulation and methods have very low computation time, so the design process time of spoke IPM machines is significantly reduced. The proposed analytical approach is also applicable to other PM machines.