Stability analysis of a grid-connected VSC controlled by SPC

In the near future a large part of traditional generation based on conventional synchronous machines (SM) will be replaced by renewable generation based on voltage source converters (VSC). In this sense, power system operators have begun to demand VSC-based power plants be able to participate in the frequency and voltage regulation, and are also interested in services like inertia emulation and damping of power oscillation, functions that today are carried out by large synchronous generators. Therefore, several studies have suggested new ways to control voltage source converters, that try to emulate the behavior of synchronous generators and are known generically as Virtual Synchronous Machines. The synchronous power controller (SPC) is a flexible solution that emulates the classical swing equation of a synchronous machine and improves its response. The SPC inherits the advantages of conventional synchronous generators, while it fixes many of its drawbacks. In this work, a sensitivity analysis of a VSC connected to the grid and controlled by SPC is performed. In this sense, a non-linear mathematical model of the system is first developed. This non-linear model is then linearized, obtaining a linear model from which the eigenvalues and sensitivities of the system to some relevant parameters are calculated. Finally, time-domain simulations are performed to confirm the results of the sensitivity analysis.Postprint (author's final draft

Proportional-resonant current controller with orthogonal decoupling on the aß-reference frame

The increasing penetration of grid-connected RES systems, advanced control algorithms have been developed to operate under grid faults and fulfill strict requirements of the grid codes. In order to overcome this, the current controller performance is critical considering it as the inner control loop of any grid-connected RES system. Based on the resonant control concept, this paper presents a modified structure for this controller which results advantageous when implemented on RES systems, as it permits better performance during the dynamic state of the controller. This paper also deals with the analysis of the decoupling terms in the aß reference frame, as well as the capability to generate a decoupled control of the positive and the negative sequence. The proposed controller will be analyzed, discussed and finally validated by means of simulation analysis.Peer ReviewedPostprint (author's final draft

Synchronous power control for PV solar inverters with power reserve capability

The increasing penetration of renewable energy systems force the grid-connected power converters to use advanced active power controls, which needs to add more functionalities to their control strategies. A power reserve control is being required for grid support capabilities on Renewable Energy Sources (RES). Classical algorithms as the Maximum Power Point Tracking (MPPT) cannot withstand power reserve on its control, due to this, different control strategies have to be formulated to gain the power reserve capability. On this paper a cost-effective solution to perform the power reserve is presented, which provide a good solution for frequency regulation as well as for general grid fault conditions. Simulation test have been performed to verify the control capacity of this cost-effective solution.Peer ReviewedPostprint (author's final draft

Stability analysis of a droop-controlled grid-connected VSC

In this paper a small signal stability analysis of a reverse droop-controlled grid-connected voltage source converter has been performed. The analysis includes the getting of a state-space representation of the system and the calculation of their participation factors. Special emphasis has been given to the influence of parameters such as the short circuit ratio, the bandwidth of the phase-locked and the constants of the droop controllers on the stability of the system

Stability analysis of a droop-controlled grid-connected VSC

In this paper a small signal stability analysis of a reverse droop-controlled grid-connected voltage source converter has been performed. The analysis includes the getting of a state-space representation of the system and the calculation of their participation factors. Special emphasis has been given to the influence of parameters such as the short circuit ratio, the bandwidth of the phase-locked and the constants of the droop controllers on the stability of the system

Stability analysis of a grid-connected VSC controlled by SPC

In the near future a large part of traditional generation based on conventional synchronous machines (SM) will be replaced by renewable generation based on voltage source converters (VSC). In this sense, power system operators have begun to demand VSC-based power plants be able to participate in the frequency and voltage regulation, and are also interested in services like inertia emulation and damping of power oscillation, functions that today are carried out by large synchronous generators. Therefore, several studies have suggested new ways to control voltage source converters, that try to emulate the behavior of synchronous generators and are known generically as Virtual Synchronous Machines. The synchronous power controller (SPC) is a flexible solution that emulates the classical swing equation of a synchronous machine and improves its response. The SPC inherits the advantages of conventional synchronous generators, while it fixes many of its drawbacks. In this work, a sensitivity analysis of a VSC connected to the grid and controlled by SPC is performed. In this sense, a non-linear mathematical model of the system is first developed. This non-linear model is then linearized, obtaining a linear model from which the eigenvalues and sensitivities of the system to some relevant parameters are calculated. Finally, time-domain simulations are performed to confirm the results of the sensitivity analysis

Proportional-resonant current controller with orthogonal decoupling on the aß-reference frame

The increasing penetration of grid-connected RES systems, advanced control algorithms have been developed to operate under grid faults and fulfill strict requirements of the grid codes. In order to overcome this, the current controller performance is critical considering it as the inner control loop of any grid-connected RES system. Based on the resonant control concept, this paper presents a modified structure for this controller which results advantageous when implemented on RES systems, as it permits better performance during the dynamic state of the controller. This paper also deals with the analysis of the decoupling terms in the aß reference frame, as well as the capability to generate a decoupled control of the positive and the negative sequence. The proposed controller will be analyzed, discussed and finally validated by means of simulation analysis.Peer Reviewe

Synchronous power control for PV solar inverters with power reserve capability

The increasing penetration of renewable energy systems force the grid-connected power converters to use advanced active power controls, which needs to add more functionalities to their control strategies. A power reserve control is being required for grid support capabilities on Renewable Energy Sources (RES). Classical algorithms as the Maximum Power Point Tracking (MPPT) cannot withstand power reserve on its control, due to this, different control strategies have to be formulated to gain the power reserve capability. On this paper a cost-effective solution to perform the power reserve is presented, which provide a good solution for frequency regulation as well as for general grid fault conditions. Simulation test have been performed to verify the control capacity of this cost-effective solution.Peer Reviewe