Daniel Remon

Design of the LCL+trap filter for the two-level VSC installed in a large-scale wave power plant

This paper presents a methodology for designing the link passive filter of the power converters installed in a multi-megawatt wave power plant. Such filter is based on the superposition of both LCL and trap filter configurations with the purpose of achieving enhanced grid interaction of a two-level voltage source converter. The LCL+Trap filter design is highly dependent on the electrical network characteristics; hence the distribution system of the plant is introduced in the paper to take into account its effects on the tuning parameters. The proposed LCL+trap filter topology arises as a successful alternative solution for the conventional LCL filter topology, thanks to its improved filtering capability while ensuring a reduced filter size. The validation of the proposed filter performance is evaluated in simulation by performing a comparative analysis between the LCL+trap and the LCL filters when operate in a wave farm application.

Equivalent Model of Large-Scale Synchronous Photovoltaic Power Plants

The impact that power plants employing renewable energy sources have on power systems is no longer negligible due to the ever-increasing portion of the power share that these generation systems represent. Therefore, the static and dynamic effects of these power plants on the grid must be analyzed in at least the same degree of detail as conventional generating units. For this purpose, it is necessary to develop models that are accurate and able to capture the dynamics of interest for the analysis, but also taking into account that they should be manageable and have a good computational performance. In the case of power plants based on photovoltaic (PV) or wind energy, formed by many power converters, an equivalent plant model that reduces the number of devices offers a good tradeoff between accuracy and complexity. Motivated by the analysis of an actual 100 MW PV power plant formed by 100 converters, each of them governed by a synchronous power controller, this paper presents a general method to derive a dynamic equivalent model of a group of converters that use this type of controller. The method is applied to this power plant in order to obtain several equivalent models with different degrees of detail that are compared through simulation. The results prove the accuracy of the equivalent aggregated models under different conditions and allow measuring the reduction in computation time that they achieve.

An active power self-synchronizing controller for grid-connected converters emulating inertia

Renewable energy sources are increasing their penetration in power systems, making necessary new control systems that offer services usually provided only by conventional generators. In this paper, an active power controller able to achieve synchronization with the grid and to control the DC link voltage is proposed. This controller allows identifying the converter with a virtual synchronous generator whose inertia can be modified online, considering that its virtual kinetic energy is stored in the DC link. Additionally, the resulting active power loop is a second order system whose damping factor can be defined freely.

Design of passive trap-LCL filters for two-level grid connected converters

This paper proposes a passive filter design method and validation analysis based on a Trap-LCL filter topology for implementation in grid connected two-level converters for high power applications. The proposed topology appears as an alternative to the conventional LCL filter, since reduced filter parameters can be obtained while still ensuring high filtering capability for switching frequency harmonics. Furthermore, a step-by-step filter design method will be introduced in order to provide a clear scope on the tuning procedure, as well as on the main requirements that the filter should satisfy. Finally, a comparative study between a conventional LCL and a LCL-Trap filter will be performed in simulation with the goal of finding a meaningful evaluation of the advantages and disadvantages provided from the LCL-Trap configuration.

Comparison of different power loop controllers for synchronous power controlled grid-interactive converters

The impact caused by the large scale penetration of renewable energy sources into electrical grid has been given an increasing concern in the past decade. Multiple challenges will occur in the future when the share of the traditional synchronous generators is reduced. One of the main issues is the lack of rotational inertia in the grid, which may cause stability issues. Therefore, the renewable energy generation plants have been asked for new control objectives and services. In this paper, three types of active power synchronizing controllers are analyzed and compared with each other. All the three types of controllers are able to provide inertia, damping and droop characteristics, which are the favored features for the future renewable energy generation plants. The comparisons are hence conducted in these three aspects. Theoretical and experimental comparisons are both given, with the comments and conclusions.

Equivalent model of a synchronous PV power plant

The continuous integration of renewable energy sources into power systems has led to the construction of large power plants based on power electronics, with power ratings up to hundreds of megawatts, in order to accomodate technologies like solar PV and wind energy. Due to the size of these plants, they must provide support services for the grid and it is necessary to analyze the impact they have on power systems. Opposing to conventional power plants formed by a reduced number of synchronous generators in the range of several hundreds of megawatts, large power plants based on PV and wind energy are usually composed of a high number of individual generating units with power ratings of a few megawatts. Therefore, it is of great importance to develop aggregated models of power plants formed by multiple power converters to be used in the dynamic analysis of large power systems. This paper presents the control system of a 20 MW PV plant, derives an equivalent aggregated model and studies the performance of this model through simulation.

Virtual Synchronous Power Strategy for Multiple HVDC Interconnections of Multi-Area AGC Power Systems

Automatic generation control (AGC) in multi-area interconnected power systems is experiencing several adaptions due to increasing level of power converter based components in the system. The concept of virtual synchronous power (VSP) to simulate the dynamic effects of virtual inertia emulations by HVDC links for higher level control applications is introduced and reflected in the multi-area AGC model. By using this proposed combination in the AGC model, the dynamic performance of the studied system shows a significant improvement. The proposed formulation is generalized for multi-area systems with multiple HVDC links. The active power loop control in VSP-based HVDC links has a second-order characteristic, which makes a simultaneous enabling of damping and inertia emulations into the system. Trajectory sensitivities are also used to analyze the effects of VSPs parameters on the system stability. The effectiveness of the proposed concept on dynamic improvements is tested through MATLAB simulation of a four-area system.

Aggregated model of a distributed PV plant using the synchronous power controller

Power plants employing renewable energy sources connected to large power systems continue increasing their number and size. PV and wind farms are a clear example of this trend. They employ power electronics in order to inject power in the grid and in most cases the interaction does not take into account the power system needs. However, as their size increases, these plants should support the grid with ancillary services and it is necessary to analyze their impact on the grid. Despite large conventional power plants usually comprise a small amount of synchronous generators in the range of 100 MW, large power plants using power electronics are formed by a relevant number of individual generating units in the 1 MW range, which introduces additional complexity in the analysis of power systems. Therefore, it is necessary to develop aggregated models of distributed power plants. This paper presents the control of a 20 MW PV power plant and an equivalent model, which is validated through simulation.

Adaptive power control of wave energy converters for maximum power absorption under irregular sea-state conditions

This paper proposes a novel wave energy converter (WEC) control technique based on an adaptive vector controller for maximum power absorption of the wave energy resource. The proposed controller arises as a suitable solution for a realistic wave energy converter deployment, as it serves from its own wave energy converter velocity to instantaneously determine the required power-take-off force needed for maximizing the power extraction from the waves. The adaptive characteristic of the wave energy controller is achieved thanks to the implementation of advanced signal monitoring and synchronization processes along with vector control algorithms. As a result, maximum power absorption can be instantaneously achieved regardless of the dominant characteristics of the irregular waves.

Tuning of proportional resonant controllers for three phase PV power converters with LCL+trap filter

Power generation facilities based on renewable energy sources, such as PV or wind, are frequently connected to the grid through three-phase power converters. As the power of the plant increases, the design of the grid connection filters becomes critical, as a fast dynamic performance is needed while the injection of current harmonics to the network should be prevented. LCL filters, together with trap filters tuned at the switching frequency, provide a good trade-off between both needs. However, the tuning of the controllers becomes more complex as the LCL+trap filter lead to a considerably higher order system. In this paper a tuning method for determining the parameters of proportional resonant current controllers for three-phase high power converters linked to the grid through a LCL+trap filter is proposed and analyzed. In order to validate the proposed solution, different results taken in different scenarios are shown.