Distributed Virtual Inertia Based Control of Multiple Photovoltaic Systems in Autonomous Microgrid

The large inertia of a traditional power system slows down system's frequency response but also allows decent time for controlling the system.Since an autonomous renewable microgrid usually has much smaller inertia,the control system must be very fast and accurate to fight against the small inertia and uncertainties.To reduce the demanding requirements on control,this paper proposes to increase the inertia of photovoltaic(PV) system through inertia emulation.The inertia emulation is realized by controlling the charging/discharging of the direct current(DC)-link capacitor over a certain range and adjusting the PV generation when it is feasible and/or necessary.By well designing the inertia,the DC-link capacitor parameters and the control range,the negative impact of inertia emulation on energy efficiency can be reduced.The proposed algorithm can be integrated with distributed generation setting algorithms to improve dynamic performance and lower implementation requirements.Simulation studies demonstrate the effectiveness of the proposed solution.

Addressing Frequency Control Challenges in Future Low-Inertia Power Systems:A Great Britain Perspective

The ambitious global targets on decarbonization present the need for massive integration of renewable generation in power systems,resulting in a significant decrease in the system inertia.In addition to the reduction in system inertia,the transmission system in Great Britain(GB)faces some unique challenges owing to its relatively small capacity,while being decoupled from other transmission systems and with the renewable resources largely non-uniformly distributed across the system.This paper presents opinions and insights on the challenges associated with frequency control in a low-inertia system and the potential solutions from a GB perspective.In this paper,we focus on three main techniques that act over different time scales:synchronous condensers,inertia emulation,and fast frequency response.We evaluate their relative advantages and limitations with learnings from recent research and development projects in GB,along with the opinions on their roles in addressing the frequency control challenges in future low-inertia systems.

Introduction of Damping,Synchronizing and Inertial Effects Using Controlled Power Injection Devices

This paper presents a theoretical study of damping,synchronizing and inertial control laws,implemented using controllable power injection devices like HVDC,FACTS or renewable-energy/storage systems which have power-electronic grid interfaces.The approach is to use a simplified dynamical model of a power system to arrive at generalized results regarding the effect of the strategies on the electro-mechanical dynamics of the system.These results are not dependent on the size,network topology and operating condition of the power system.This paper presents a differential-algebraic formulation and generalized eigenvalue analysis to facilitate a unified study of the effects of the control laws on the electro-mechanical modes.The damping,synchronizing and inertial control laws can themselves be extended to include the possibility of mutualdamping,synchronizing and inertial effects when multiple devices are present.The control laws are not only simple and intuitive,but also are found to have a predictable and generally beneficial impact on the electro-mechanical dynamics of the grid,even when detailed models are considered.

A novel inertia emulator to reduce the rate of change of frequency for power systems with solar PV and battery energy storage

Energy access,climate change and public health issues are some major drivers for the need for renewable sources.However,most renewable sources,excluding large hydro,have zero or negligible rotational inertia,which is critical to stabilizing the power system after contingency.Therefore,this paper proposes a droop-based inertia emulator to reduce the rate of change of frequency and frequency deviations.The robustness of the controller is analysed by applying various uncertainties and disturbances of power system components that were carried out using DIgSILENT PowerFactory simulations.The obtained results are compared with existing literature and the desired performance shows an improvement in the rate of change of frequency of 34.78%for an IEEE 6-bus system,24.32%for a 12-bus system and 18%for a 39-bus system.