Synchronverter Technology Research Articles

A Review on Synchronverter Technology and Its Application to Grid Connected EV Charging Station

A Review on Synchronverter Technology and Its Application to Grid Connected EV Charging Station

A Generalized Harmonic Compensation Control Strategy for Mitigating Subsynchronous Oscillation in Synchronverter Based Wind Farm Connected to Series Compensated Transmission Line

With the increasing application of synchronverter technology in renewable energy power generation, power system stability issue becomes more complicated. Due to the impedance interaction between the synchronverter based wind farm and the series compensated transmission line, the synchronverter based wind farm is prone to cause sub-synchronous oscillation (SSO). To suppress this SSO, a generalized harmonic compensation control strategy of active power filter (APF) with supercapacitor is proposed, which counteracts SSO by injecting the generalized harmonic current including reactive and oscillation current. Since the generalized harmonic current can be calculated by subtracting the sinusoidal active current from the sampling current, a first-order inertial controller of the voltage loop for APF is proposed to accurately obtain the active current. In addition, the supercapacitor of APF is used to reduce the dc-side voltage fluctuation caused by SSO. As this paper does not need to directly extract the SSO component, the proposed method does not need to know the system oscillation frequency in advance, which can be used as a defensive control method of SSO. Finally, experimental results verify the effectiveness of the proposed strategy.

Variable-Speed PICO Hydel Energy Storage With Synchronverter Control to Emulate Virtual Inertia in Autonomous Microgrids

Autonomous microgrids are potential alternative to grid connectivity for powering remote communities around the globe. A sustainable microgrid with renewables and energy storage having minimum operation and maintenance routines is the most sought option. Batteries are predominantly used to support the stochastic behavior of renewables in such microgrids. However, they are prone to frequent failure and require periodic maintenance, which demands an alternative. Thus, in this article, the renewable powered irrigation system in India was configured to form sustainable pico hydel energy storage (PHES). To enhance the inertia of the microgrid with static sources, virtual inertia capability was induced into PHES by modified synchronverter technology. First, the small-signal modeling approach was presented to derive the closed-loop transfer function of the system. Subsequently, the effect of control parameter variation on system stability and the interaction between the governor and the synchronverter was investigated using eigenvalue analysis. Next, the performance of synchronverter was compared with the established vector control through time-domain simulations in MATLAB/Simulink. The simulation results revealed that the proposed strategy improved the inertial response of PHES and outperformed vector control by reducing peak overshoot, settling time, and steady-state error.

Control strategy resilient to unbalanced faults for interlinking converters in hybrid microgrids

Hybrid microgrids (HMGs) consist of AC and DC microgrids (MGs) that are connected through bidirectional interlinking converters (ICs). In order to optimally utilize renewable generations and address their intermittency, efficient control strategies are needed for power management of ICs. The performance of available control strategies for HMGs in case of faults may be limited since the converters are usually set to trip in the event of transient stability related problems to protect converters from being damaged. Also, HMGs may face frequency instability problems due to the lower damping capability of converter-based generations compared with classical synchronous generators. In this paper, an enhanced control strategy based on the concept of 3-D droops is proposed for ICs. The proposed method makes HMGs more resilient against faults at the utility side. It also improves stability of HMGs by mitigating quasi-static active and reactive power oscillations that may be generated by renewable intermittent generations. Also, it ensures a proper transient power sharing without deteriorating the transfer capability of ICs when unbalanced faults, as the most prevalent ones, occur in HMGs. In addition, the synchronverter technology with an adaptive virtual inertia is applied to the control strategy of ICs to enhance frequency stability of HMGs in case of occurring faults or volatile renewable generations. The performance of the proposed features is evaluated by their testing on a typical HMG.

Synchronverter: A Comprehensive Review of Modifications, Stability Assessment, Applications and Future Perspectives

The increase in the penetration of renewable energy sources (RES) has reduced the effective inertia of the power system dominated by synchronous machines. The reduction in inertia has paved the way to the development of inertia emulation techniques, which complements the increased penetration of RES. The synchronverter technology is one among the virtual inertia emulation techniques which resembles close to the synchronous machine. The advancements in control and adaptations of synchronverter for various applications demand a comprehensive yet critical review. Thus, the main objective of this paper is to present a critical review of synchronverter technology which could increase the inertial response of RES. A critical analysis of modifications made to original synchronverter and the stability assessment techniques is presented. The effect of parameter variation on stability and dynamic performance is brought out as a decision matrix by analysing the movement of eigenvalues presented in various works. Towards the end, a synoptic overview is presented to depict the research trend and emphasize the domain which requires further attention. Furthermore, a brief discussion of the research gaps perceived during the phase of review is presented to leverage future research in the field.

Flexible Inertia Optimization for Single-Phase Voltage Source Inverter Based on Hold Filter

With the increasing penetration of renewable energy sources (RESs) in the power system, voltage source inverters (VSIs) are widely used as the power electronic interface of the RESs, which will decline the inertia of power system. The insufficient inertia has been becoming a big challenge for the modern power system. Synchronverter (SV) technology can operate the inverter mimic the characteristic of the synchronous generator to provide virtual inertia. However, the virtual inertia of conventional SV is associated with the frequency stability, which limits the inertia that can be provided. Taking the analysis of single-phase SV as an example, this paper proposes a flexible inertia optimization method for single-phase VSIs based on the inertial characteristic of hold filter, which gives a new degree of freedom for the optimization of single-phase VSIs inertia. In this way, the inertia of single-phase VSIs can be adjusted more freely according to system requirements without affecting the frequency stability. Furthermore, the effects of the proposed method on the system dynamic characteristics are investigated. Finally, simulation and experimental results are given to verify the feasibility and feature of the proposed inertia optimization method.

Control method for EV charging and discharging in V2G/V2H scenario based on the synchronvter technology and H ∞ repetitive control

Electric vehicles (EVs) will play a vital role in the future's transportation systems since this technology is promising for environment, energy security, and improved fuel economy. EVs have huge potential of serving as the energy storage for the power grid as well as inhabitants in vehicle-to-grid (V2G) or vehicle-to-house (V2H) scenario. In this study, a control method is proposed for EV charging and discharging by using the synchronverter technology and H ∞ repetitive controller, where synchronverter technology is used to generate the reference voltage to decide the power angle and amplitude of the AC side voltage of the charging/discharging port, so that the power flow between EV and the grid is controlled. In order to ensure the power quality of EVs provided for the grid and the load while EVs are with local loads, a H ∞ repetitive controller is designed to control the voltage between EVs and the grid to follow the reference voltage. Simulation results have shown that the proposed controller is not only able to realise bi-directional real power and reactive power control, but also keep the output voltage of EVs in V2G or V2H scenario stable and clear while they are with different kinds of local loads.

Modeling and control of a V2G charging station based on synchronverter technology

This paper proposes an idea for modeling and control of a V2G charging station (CS) for electric vehicles (EVs) by using synchronverter technology. First, the architecture of the CS is introduced. Then, a T-S fuzzy controller is designed to decide the reference real power of the synchronverter by considering the grid frequency. Due to the inner frequency- and voltage-drooping mechanisms of the synchronverter, the input and output real and reactive power of the CS will be automatically adjusted on the basis of the reference value according to the degree of deviation from the nominal value of the grid frequency and voltage. To ensure the safety of this operation, an adaptive frequency droop coefficient mechanism is designed to adapt the change of the total energy storage of a CS unit by changing the slope of the P-f control characteristic of the synchronverter. The performance of the CS with the proposed control strategy is investigated with EVs of different battery states, different users' sets and under different grid status. Simulation results demonstrate that the proposed strategy can not only effectively perform controlled charging/discharging of each single electric vehicle inside the CS, but also improve the performance of the electricity grid in terms of efficiency, stability and reliability.

Power-Electronics-Enabled Autonomous Power Systems: Architecture and Technical Routes

Power systems are going through a paradigm change from centralized generation to distributed generation and further on to smart grids. In this paper, it is shown that future power systems will be power electronics based, instead of electric machines based, with a huge number of incompatible players and that the fundamental challenge behind this paradigm change is how to make sure these players could work together and maintain system stability. Then, a lateral architecture based on the synchronization mechanism of synchronous machines (SM), which has underpinned the growth and operation of power systems for over 100 years, is proposed to unify the integration and interaction of these players with the grid by operating power electronic converters to behave like virtual synchronous machines (VSM), which are coined cyber synchronous machines (CSM) here. Thus, all the suppliers and the majority of loads can follow the same mechanism to regulate system stability. This paves the way for autonomous operation of future power systems. Moreover, two technical routes, one based on the synchronverter technology and the other based on the robust droop control technology, are proposed to implement the architecture. Real-time simulation results are presented to illustrate the operation of such a system.

Improved Control Strategy of Interlinking Converters With Synchronous Generator Characteristic in Islanded Hybrid AC/DC Microgrid

In this paper, an improved control strategy of interlinking converters for hybrid AC/DC microgrid operated in islanding mode is proposed, which applies synchronous generator model to the converters. This enhanced scheme adopts direct frequency control method to realize active power sharing and improves the transient frequency stability by using synchronverter technology. Unlike existing droop control methods of interlinking converters that mostly just focus on power sharing, this scheme can not only maintain proportional power distributed between DC and AC subgrid, but also regulate the AC subgrid voltage directly to improve its poor frequency stability during AC-side loading transitions in autonomous operation. It's noteworthy that this scheme can also keep the AC-side loads working uninterruptedly during AC subgrid faults events by using voltage-controlled method. Moreover, any additional energy storage or inverters are not required to assist interlinking converters for microgrid frequency regulation. The effectiveness of this modified control method is verified by offline time-domain simulation and real-time experiment in MATLAB/Simulink and OPAL-RT digital platform respectively.

Grid-friendly wind power systems based on the synchronverter technology

Back-to-back PWM converters are becoming a realistic alternative to conventional converters in high-power wind power applications. In this paper, a control strategy based on the synchronverter technology is proposed for back-to-back PWM converters. Both converters are run as synchronverters, which are mathematically equivalent to the conventional synchronous generators. The rotor-side converter is responsible for maintaining the DC link voltage and the grid-side converter is responsible for the maximum power point tracking (MPPT). As the two converters are operated using the synchronverter technology, the formed wind power system becomes more friendly to the grid. Extensive real-time digital simulation results are presented to verify the effectiveness of the proposed method under normal operation and grid-fault scenarios.

Synchronverter-based Control Strategy for Back-to-back Converters in Wind Power Applications

Abstract Back-to-back PWM converters are becoming a realistic alternative to the conventional converters in high-power wind-energy applications. In this paper, a control strategy based on the synchronverter technology is proposed for back-to-back PWM converters. Both converters are run as synchronverters, which are mathematically equivalent to the conventional synchronous generators. The rotor-side converter is responsible for maintaining the DC link voltage and the grid-side converter is responsible for the maximum power point tracking (MPPT). Simulation results show that the proposed method operates properly.

BP and Symyx to seek catalysts for commodities

Back-to-back PWM converters are becoming a realistic alternative to the conventional converters in high-power wind-energy applications. In this paper, a control strategy based on the synchronverter technology is proposed for back-to-back PWM converters. Both converters are run as synchronverters, which are mathematically equivalent to the conventional synchronous generators. The rotor-side converter is responsible for maintaining the DC link voltage and the grid-side converter is responsible for the maximum power point tracking (MPPT). Simulation results show that the proposed method operates properly.