Ponències/Comunicacions de congressos
http://hdl.handle.net/2117/3865
2018-02-25T03:55:50ZPower station for large scale photovoltaic power plants
http://hdl.handle.net/2117/113934
Power station for large scale photovoltaic power plants
Verdugo Retamal, Cristian Andrés; Candela García, José Ignacio; Luna Alloza, Álvaro; Rodríguez Cortés, Pedro
Most of the large scale photovoltaic power plants (LS-PVPP) count on power converters with a central configuration. Advantages such as robustness, low maintenance and installation cost makes this configuration the preferred specially suitable in large scale systems. However, important drawbacks like the low efficiency level make necessary to develop new solutions for future power plants. In this paper a power station for large scale PV systems is proposed, which consists of power inverters synchronized with an interleaving modulation and connected to a multi-winding transformer. The main principles that support this proposal, as well as, simulation results are presented to validate the effectiveness of the proposed configuration.
2018-02-08T09:38:07ZVerdugo Retamal, Cristian AndrésCandela García, José IgnacioLuna Alloza, ÁlvaroRodríguez Cortés, PedroMost of the large scale photovoltaic power plants (LS-PVPP) count on power converters with a central configuration. Advantages such as robustness, low maintenance and installation cost makes this configuration the preferred specially suitable in large scale systems. However, important drawbacks like the low efficiency level make necessary to develop new solutions for future power plants. In this paper a power station for large scale PV systems is proposed, which consists of power inverters synchronized with an interleaving modulation and connected to a multi-winding transformer. The main principles that support this proposal, as well as, simulation results are presented to validate the effectiveness of the proposed configuration.Grid synchronization of renewable generation systems using synchronous power controllers
http://hdl.handle.net/2117/113928
Grid synchronization of renewable generation systems using synchronous power controllers
Remón Rodríguez, Daniel; Zhang, Weiyi; Luna Alloza, Álvaro; Candela García, José Ignacio; Rodríguez Cortés, Pedro
The increasing penetration of renewable energy sources in power systems has increased the amount of generating units employing power electronics as their grid interface, instead of synchronous generators. Their different dynamics have brought new challenges for power system operators; in particular, the reduction of the total inertia of power systems, which leads to larger frequency disturbances. Different methods have been proposed to address this issue, with virtual synchronous machines as a promising solution; however, the start-up process of these controllers has not received much attention. This paper proposes a start-up strategy for the synchronous power controller, explaining its working principle in detail, and assessing its performance through time-domain simulation.
2018-02-07T17:48:44ZRemón Rodríguez, DanielZhang, WeiyiLuna Alloza, ÁlvaroCandela García, José IgnacioRodríguez Cortés, PedroThe increasing penetration of renewable energy sources in power systems has increased the amount of generating units employing power electronics as their grid interface, instead of synchronous generators. Their different dynamics have brought new challenges for power system operators; in particular, the reduction of the total inertia of power systems, which leads to larger frequency disturbances. Different methods have been proposed to address this issue, with virtual synchronous machines as a promising solution; however, the start-up process of these controllers has not received much attention. This paper proposes a start-up strategy for the synchronous power controller, explaining its working principle in detail, and assessing its performance through time-domain simulation.Grid voltage harmonic damping method for SPC based power converters with multiple virtual admittance control
http://hdl.handle.net/2117/113563
Grid voltage harmonic damping method for SPC based power converters with multiple virtual admittance control
Tarrasó, Andres; Candela García, José Ignacio; Rocabert Delgado, Joan; Rodríguez Cortés, Pedro
The appearance of harmonics in the grid voltage is an issue for the generation systems and grid connected consumers. This paper presents the basic control strategy to be implemented in Synchronous Power Control (SPC) based power converters, which contributes to reduce the harmonic content in the voltage by means of injecting different harmonic current to the grid using a separated virtual admittance algorithm. This control strategy is capable of generating such a current reference that attenuates the harmonic values at the point of connection of the converter.
2018-02-01T12:46:15ZTarrasó, AndresCandela García, José IgnacioRocabert Delgado, JoanRodríguez Cortés, PedroThe appearance of harmonics in the grid voltage is an issue for the generation systems and grid connected consumers. This paper presents the basic control strategy to be implemented in Synchronous Power Control (SPC) based power converters, which contributes to reduce the harmonic content in the voltage by means of injecting different harmonic current to the grid using a separated virtual admittance algorithm. This control strategy is capable of generating such a current reference that attenuates the harmonic values at the point of connection of the converter.Phase stability enhancement in big power networks using renewable generation units controlled by SPC
http://hdl.handle.net/2117/113537
Phase stability enhancement in big power networks using renewable generation units controlled by SPC
Abdollahi, Mostafa; Candela García, José Ignacio; Rocabert Delgado, Joan; Muñoz Aguilar, Raúl Santiago; Hermoso Costa, Juan Ramón
High penetration of Renewable Generation Units (RGU), has led to that the interaction of this newfound participators in power network with conventional units be more critical challenges for network operators. Effect on the phase stability in emplacement as well as on neighbor generation units is one of this essential challenges. In this paper, a RGU controlled by Synchronous Power Controller (SPC) which behaves as a big Static Synchronous Generation (SSG-SPC) units, are presented as solution to cope with this challenge. Small signal modelling of a power network in presence of SSG-SPC unit is used to analysis this solution. After illustrating SPC dynamic capabilities, study on IEEE-14B test system based on modal analysis, time domain investigation and real time test confirms that a SSG-SPC not only has not damaging impact on phase stability and dynamic of network, but on the contrary can improve it. Moreover, by having at least two dynamic freedom degrees in SPC, the SSG-SPC can adapt itself for keeping this improvement effect.
2018-02-01T11:05:56ZAbdollahi, MostafaCandela García, José IgnacioRocabert Delgado, JoanMuñoz Aguilar, Raúl SantiagoHermoso Costa, Juan RamónHigh penetration of Renewable Generation Units (RGU), has led to that the interaction of this newfound participators in power network with conventional units be more critical challenges for network operators. Effect on the phase stability in emplacement as well as on neighbor generation units is one of this essential challenges. In this paper, a RGU controlled by Synchronous Power Controller (SPC) which behaves as a big Static Synchronous Generation (SSG-SPC) units, are presented as solution to cope with this challenge. Small signal modelling of a power network in presence of SSG-SPC unit is used to analysis this solution. After illustrating SPC dynamic capabilities, study on IEEE-14B test system based on modal analysis, time domain investigation and real time test confirms that a SSG-SPC not only has not damaging impact on phase stability and dynamic of network, but on the contrary can improve it. Moreover, by having at least two dynamic freedom degrees in SPC, the SSG-SPC can adapt itself for keeping this improvement effect.Frequency support properties of the synchronous power control for grid-connected converters
http://hdl.handle.net/2117/103395
Frequency support properties of the synchronous power control for grid-connected converters
Zhang, Weiyi; Remón Rodríguez, Daniel; Rocabert Delgado, Joan; Luna Alloza, Álvaro; Candela García, José Ignacio; Rodríguez Cortés, Pedro
Grid-connected converters with primary frequency control and inertia emulation have emerged and are promising for future renewable generation plants because of the contribution in power system stabilization. This paper gives a synchronous active power control solution for grid-connected converters. As design considerations, the virtual angle stability and transient response are both analyzed, and the detailed implementation structure is also given without entailing any difficulty in practice. The analysis and validation of frequency support characteristics are particularly addressed. The 10 kW simulation and experimental frequency sweep tests on a regenerative source test bed present good performance of the proposed control in terms of showing inertia and droop characteristics, and the controllable transient response is also demonstrated.
2017-04-05T15:16:29ZZhang, WeiyiRemón Rodríguez, DanielRocabert Delgado, JoanLuna Alloza, ÁlvaroCandela García, José IgnacioRodríguez Cortés, PedroGrid-connected converters with primary frequency control and inertia emulation have emerged and are promising for future renewable generation plants because of the contribution in power system stabilization. This paper gives a synchronous active power control solution for grid-connected converters. As design considerations, the virtual angle stability and transient response are both analyzed, and the detailed implementation structure is also given without entailing any difficulty in practice. The analysis and validation of frequency support characteristics are particularly addressed. The 10 kW simulation and experimental frequency sweep tests on a regenerative source test bed present good performance of the proposed control in terms of showing inertia and droop characteristics, and the controllable transient response is also demonstrated.A comparative study of methods for estimating virtual flux at the point of common coupling in grid connected voltage source converters with LCL filter
http://hdl.handle.net/2117/101896
A comparative study of methods for estimating virtual flux at the point of common coupling in grid connected voltage source converters with LCL filter
Roslan, Nurul Fazlin; Suul, Jon Are; Luna Alloza, Álvaro; Rocabert Delgado, Joan; Candela García, José Ignacio; Rodríguez Cortés, Pedro
Grid connected Voltage Source Converters (VSCs) with LCL filters usually have voltage measurements at the filter capacitors, while it can be important to control the active or reactive power injection at the grid-side of the LCL filter, for instance at a Point of Common Coupling (PCC). Synchronization to the PCC voltage can be obtained by Virtual Flux (VF) estimation, which can also allow for voltage sensor-less operation of VSCs. This paper is presenting a comparative evaluation of methods for estimating the VF at the PCC, considering a VSC connected to the grid through an LCL filter with a Proportional Resonant (PR) controller as the inner current control loop. The VF estimation is achieved by using frequency adaptive dual SOGI-QSGs (DSOGI-VF). The Frequency Locked Loop (FLL) is used in order to keep the positive and negative sequence (PNS) VF estimation inherently frequency adaptive. Three different methods are considered for obtaining the capacitor current needed for estimating the VF at the grid side of the LCL filter which are based on fully estimation by using the voltage sensor-less method, by estimating the capacitor current from the measured voltage or by using additional capacitor current sensors. The results have been compared and validated by simulation studies.
2017-03-03T09:18:11ZRoslan, Nurul FazlinSuul, Jon AreLuna Alloza, ÁlvaroRocabert Delgado, JoanCandela García, José IgnacioRodríguez Cortés, PedroGrid connected Voltage Source Converters (VSCs) with LCL filters usually have voltage measurements at the filter capacitors, while it can be important to control the active or reactive power injection at the grid-side of the LCL filter, for instance at a Point of Common Coupling (PCC). Synchronization to the PCC voltage can be obtained by Virtual Flux (VF) estimation, which can also allow for voltage sensor-less operation of VSCs. This paper is presenting a comparative evaluation of methods for estimating the VF at the PCC, considering a VSC connected to the grid through an LCL filter with a Proportional Resonant (PR) controller as the inner current control loop. The VF estimation is achieved by using frequency adaptive dual SOGI-QSGs (DSOGI-VF). The Frequency Locked Loop (FLL) is used in order to keep the positive and negative sequence (PNS) VF estimation inherently frequency adaptive. Three different methods are considered for obtaining the capacitor current needed for estimating the VF at the grid side of the LCL filter which are based on fully estimation by using the voltage sensor-less method, by estimating the capacitor current from the measured voltage or by using additional capacitor current sensors. The results have been compared and validated by simulation studies.Control of VSC-HVDC with electromechanical characteristics and unified primary strategy
http://hdl.handle.net/2117/101875
Control of VSC-HVDC with electromechanical characteristics and unified primary strategy
Zhang, Weiyi; Rouzbehi, Kumars; Candela García, José Ignacio; Luna Alloza, Álvaro; Rodríguez Cortés, Pedro
High voltage dc (HVDC) systems act as the prevailed solution for transmitting offshore wind energy to onshore main grids. Control of the voltage source converters (VSC) in HVDC systems is decisive for the performance. This paper proposes the control of VSC-HVDC with electromechanical characteristics and unified primary strategy, as a reaction to the updated requirements of the ac grid transmission system operators. As two important aspects of VSC-HVDC control, converter control and primary control are both designed in detail. Electromechanical characteristics make the VSC capable of providing inertia to the ac networks as well as simplicity in island operation. Besides, unified primary control is given as a universal primary strategy for VSC stations, and especially takes into account frequency support and control mode transition. The proposed converter control is validated in scaled-down 10 kW laboratory setups, while the proposed primary control is endorsed by the simulation tests on a CIGRE multi-terminal HVDC model.
2017-03-02T16:07:35ZZhang, WeiyiRouzbehi, KumarsCandela García, José IgnacioLuna Alloza, ÁlvaroRodríguez Cortés, PedroHigh voltage dc (HVDC) systems act as the prevailed solution for transmitting offshore wind energy to onshore main grids. Control of the voltage source converters (VSC) in HVDC systems is decisive for the performance. This paper proposes the control of VSC-HVDC with electromechanical characteristics and unified primary strategy, as a reaction to the updated requirements of the ac grid transmission system operators. As two important aspects of VSC-HVDC control, converter control and primary control are both designed in detail. Electromechanical characteristics make the VSC capable of providing inertia to the ac networks as well as simplicity in island operation. Besides, unified primary control is given as a universal primary strategy for VSC stations, and especially takes into account frequency support and control mode transition. The proposed converter control is validated in scaled-down 10 kW laboratory setups, while the proposed primary control is endorsed by the simulation tests on a CIGRE multi-terminal HVDC model.Control of D-STATCOM during unbalanced grid faults based on DC voltage oscillations and peak current limitations
http://hdl.handle.net/2117/101869
Control of D-STATCOM during unbalanced grid faults based on DC voltage oscillations and peak current limitations
Khoshooei, Arash; Moghani, Javad S.; Milimonfared, Jafar; Luna Alloza, Álvaro; Candela García, José Ignacio; Rodríguez Cortés, Pedro
The safe operation of grid connected power converters during abnormal condition is a key issue in order to guarantee its operation and to avoid undesired trips. In this paper different control methods for the operation of a D-STATCOM are evaluated, where the reference currents are determined in such a way that none of the phase currents goes over the limits, as well as the DC voltage fluctuations remain in safe operation limit. Therefore, the contribution of this paper lays on the combination of the DC voltage oscillations and the current limit control. As it is shown in the following, three different control strategies are evaluated. The amplitude of the oscillations which are superimposed on the DC voltage as well as peak amplitude of the phase currents are calculated for each, considering a generic imbalance in the network. The effectiveness of the presented control strategies are verified by simulating a D-STATCOM tied to an industrial distribution network. Moreover a scaled scenario has been reproduced experimentally which shows that the results cope well with the analytical equations and the simulation results.
2017-03-02T15:47:38ZKhoshooei, ArashMoghani, Javad S.Milimonfared, JafarLuna Alloza, ÁlvaroCandela García, José IgnacioRodríguez Cortés, PedroThe safe operation of grid connected power converters during abnormal condition is a key issue in order to guarantee its operation and to avoid undesired trips. In this paper different control methods for the operation of a D-STATCOM are evaluated, where the reference currents are determined in such a way that none of the phase currents goes over the limits, as well as the DC voltage fluctuations remain in safe operation limit. Therefore, the contribution of this paper lays on the combination of the DC voltage oscillations and the current limit control. As it is shown in the following, three different control strategies are evaluated. The amplitude of the oscillations which are superimposed on the DC voltage as well as peak amplitude of the phase currents are calculated for each, considering a generic imbalance in the network. The effectiveness of the presented control strategies are verified by simulating a D-STATCOM tied to an industrial distribution network. Moreover a scaled scenario has been reproduced experimentally which shows that the results cope well with the analytical equations and the simulation results.Advanced control of a high power converter connected to a weak grid
http://hdl.handle.net/2117/101726
Advanced control of a high power converter connected to a weak grid
Shahparasti, Mahdi; Catalán, Pedro; Candela García, José Ignacio; Luna Alloza, Álvaro; Rodríguez Cortés, Pedro
This paper addresses the stability problems of a high power converter connected to a weak grid. The wide range values that grid impedance can take, challenges the stability and the performance of the controllers, which are responsible of regulating the current injection in such converters. In this work, a control strategy based on stationary reference frame controllers is selected and implemented using a proportional resonant (PR) controller, with capacitor voltage feedforward and a phase shifter. As it will be demonstrated in this paper, although the feedforward contributes to enhance the transient response of the converter, it may cause also deep unstable dynamics near to the medium frequency and decreases the phase margin in low frequency ranges. Therefore, it can be used to damp the unstable dynamics near to resonance frequency range and the LCL-filter can be adopted for the high frequency one. In order to improve the controller performance, a new phase shifter is added to the control scheme to enhance the phase margin at low frequency ranges. Simulation and experimental results considering weak grid conditions are shown to validate the proposed method.
2017-02-28T17:18:06ZShahparasti, MahdiCatalán, PedroCandela García, José IgnacioLuna Alloza, ÁlvaroRodríguez Cortés, PedroThis paper addresses the stability problems of a high power converter connected to a weak grid. The wide range values that grid impedance can take, challenges the stability and the performance of the controllers, which are responsible of regulating the current injection in such converters. In this work, a control strategy based on stationary reference frame controllers is selected and implemented using a proportional resonant (PR) controller, with capacitor voltage feedforward and a phase shifter. As it will be demonstrated in this paper, although the feedforward contributes to enhance the transient response of the converter, it may cause also deep unstable dynamics near to the medium frequency and decreases the phase margin in low frequency ranges. Therefore, it can be used to damp the unstable dynamics near to resonance frequency range and the LCL-filter can be adopted for the high frequency one. In order to improve the controller performance, a new phase shifter is added to the control scheme to enhance the phase margin at low frequency ranges. Simulation and experimental results considering weak grid conditions are shown to validate the proposed method.Enhancement of the stability of a distribution system through synchronous PV
http://hdl.handle.net/2117/100977
Enhancement of the stability of a distribution system through synchronous PV
Remón Rodríguez, Daniel; Mir Cantarellas, Antoni; Zhang, Weiyi; Candela García, José Ignacio; Rodríguez Cortés, Pedro
Distributed renewable energy sources progressively gain importance in power systems, with which new challenges, but also new opportunities, arise. Therefore, it is necessary to analyze the interaction between this type of generators and the grid, and to study adequate control methods that allow small generating units to operate harmoniously within power systems and contribute to their control, stability, and reliability. In this paper, the stability of a distribution system with several renewable energy generators is studied, focusing on its ability to maintain power supply during a transmission blackout. The response of the distribution system after a sudden disconnection from the main network is simulated and analyzed, comparing the results obtained using a conventional control for the renewable generators with those of controllers that enable a synchronous interaction between these generators and the power system.
2017-02-14T12:55:50ZRemón Rodríguez, DanielMir Cantarellas, AntoniZhang, WeiyiCandela García, José IgnacioRodríguez Cortés, PedroDistributed renewable energy sources progressively gain importance in power systems, with which new challenges, but also new opportunities, arise. Therefore, it is necessary to analyze the interaction between this type of generators and the grid, and to study adequate control methods that allow small generating units to operate harmoniously within power systems and contribute to their control, stability, and reliability. In this paper, the stability of a distribution system with several renewable energy generators is studied, focusing on its ability to maintain power supply during a transmission blackout. The response of the distribution system after a sudden disconnection from the main network is simulated and analyzed, comparing the results obtained using a conventional control for the renewable generators with those of controllers that enable a synchronous interaction between these generators and the power system.