Revistas

Revista:
ENERGIES

ISSN 1996-1073
Vol. 15
N° 1
Año 2022
Págs.208

Renewable energy sources are becoming more relevant in recent decades in power generation, leading to investment in developing efficient systems. Specifically, in photovoltaic energy, modular converters are attracting interest since their characteristics enable them to work at high voltage and optimize the generated energy. However, the control strategies found the literature limit the scalability potential of modular converters. The main aim of this paper is to propose a scalable control strategy for a grid-tied CHB (Cascaded H-Bridge) converter for large-scale photovoltaic power plants. The control proposed is able to take full advantage of converter scalability and modularity, being based on the parameters needed for bipolar sinusoidal PWM (Pulse Width Modulation), and thus reducing the calculus required and simplifying its implementation. Power imbalances are overcome including the zero-sequence vector injection to allow power exchange between phases. Furthermore, the parameter used for power factor control has been discretized and discretization time analysis shows that the control strategy is stable and does not require a high-speed communication channel. For validation purposes, simulations are conducted on a downsized 12 H-bridge model.

Revista:
INTERNATIONAL JOURNAL OF ELECTRICAL POWER AND ENERGY SYSTEMS

ISSN 0142-0615
Vol. 137
Año 2022
Págs.107777

Due to the expected lack of fossil fuels in near future as well as climate change produced by greenhouse effect as consequence of environmental emissions, renewable energy generation, and specifically solar photovoltaic generation, has become relevant in present energy generation challenge. Photovoltaic generators have strong relationship with solar irradiation and outdoor temperature in energy generation process. These meteorological parameters are volatile and uncertain in nature so, unexpected changes on these parameters produce variations on solar photovoltaic generators' output power. While many researchers have been focused in recent years on the development of novel models for forecasting involved meteorological parameters in photovoltaic generation, they commonly do not consider an analysis step of the data before using it in the developed models. Hence, the aim of this study consists in assembling a wavelet based time-frequency analysis of the used data with deep learning neural networks to forecast solar irradiation, in next 10 min, to compute solar photovoltaic generation. Results of the validation step showed that the deviation of the proposed forecaster was lower than 4% in 90.60% of studied sample days. Final forecaster's root mean square error was 35.77 W/m(2), which was an accuracy improvement of 37.52% compared against persistence benchmark model.

Revista:
ELECTRIC POWER SYSTEMS RESEARCH

ISSN 0378-7796
Vol. 185
Año 2020
Págs.106369

This paper proposes a Field Oriented Control (FOC) for a Permanent Magnet Synchronous Machine (PMSM) which is supplied by a Parallel Multi-Inverter System. The parallelization of the Voltage Source Inverters is safely achieved using a V-f Droop Control strategy as a distributed generation system would be considered like in Smart-Grids. This novel technique is the combination of the previous mentioned both strategies, and will be key when answering to the need of modularity, scalability, redundancy and parallelization for electrical machine control systems. Theoretical and experimental analysis are provided in order to validate the new combined control strategy which fulfills the motor control requirements while current balancing is safely achieved between individual parallelized inverters.

Revista:
INTERNATIONAL JOURNAL OF ELECTRICAL POWER AND ENERGY SYSTEMS

ISSN 0142-0615
Vol. 95
N° 2
Año 2018
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:
ELECTRIC POWER SYSTEMS RESEARCH

ISSN 0378-7796
Vol. 144
Año 2017
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
Vol. 151
Año 2017
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 JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS

ISSN 2168-6777
Vol. 4
N° 3
Año 2016
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
Vol. 30
N° 3
Año 2015
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:
IET POWER ELECTRONICS

ISSN 1755-4535
Vol. 7
N° 9
Año 2014
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
Vol. 50
N° 1
Año 2014
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:
JOURNAL OF POWER ELECTRONICS

ISSN 1598-2092
Vol. 12
N° 2
Año 2012
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.