Control strategy for direct voltage and frequency stabilityenhancement in HVAC/HVDC grids

Direct voltage fluctuations due to the presence of relatively large DC reactors (as an essen-tial part of HVDC breakers), lack of inertia, and unwanted frequency fluctuations in theAC side of HVDC grids, have major consequences on the stability of HVAC/HVDC grids.The use of the DC Power System Stabilizer (DC-PSS) can damp and eliminate voltageoscillations caused by the presence of the DC reactors. However, DC-PSS cannot addressthe issues of inertia and unwanted frequency fluctuations. A method to improve inertiais proposed here that can operate well with the droop controller, and DC-PSS does notinterfere with power-sharing and does not interact with any of these elements. Since thepresence of a droop controller in HVAC/HVDC grids associates with power and directvoltage, the method proposed here can improve direct voltage fluctuations by eliminatingsevere power peaks. Moreover, this method does not change the voltage level of the entiresystem, so there is no need to change the set-points of controllers. In addition, all param-eters of the controllers are tuned by an intelligent algorithm, and the Participation factor(PF) scheme is used to find the proper placement of the proposed controller

Impact of controllable superconducting series reactor in transient recovery voltage of circuit breaker

Series reactors as fault current limiters (FCLs) are extensively employed to enhance power grid protection issues. Utilizing superconducting technology is a viable solution to approach FCLs toward commercializing. The concern of transient recovery voltage (TRV) of the circuit breaker becomes more considerable due to FCL’s high stored energy in the case of fault current limiting mode. This paper firstly focuses on the analysis of TRV under the presence of an inductive-based superconducting fault current limiter (SFCL) installed in a power grid, and then it investigates the impact of a controllable superconducting series reactor (CSSR) in TRV of the circuit breaker. The obtained results show that the synchronous operation of a CSSR with a circuit breaker substantially declines TRV

Impact of controllable superconducting series reactor in transient recovery voltage of circuit breaker

Series reactors as fault current limiters (FCLs) are extensively employed to enhance power grid protection issues. Utilizing superconducting technology is a viable solution to approach FCLs toward commercializing. The concern of transient recovery voltage (TRV) of the circuit breaker becomes more considerable due to FCL’s high stored energy in the case of fault current limiting mode. This paper firstly focuses on the analysis of TRV under the presence of an inductive-based superconducting fault current limiter (SFCL) installed in a power grid, and then it investigates the impact of a controllable superconducting series reactor (CSSR) in TRV of the circuit breaker. The obtained results show that the synchronous operation of a CSSR with a circuit breaker substantially declines TRV

A modified droop control structure for simultaneous power-sharing and DC voltage oscillations damping in MT-HVDC grids

With increasing energy demand, the use of renewable energy resources is increasing. Renewable energy sources require power electronic converters to get integrated into power grids. Multi-terminal high voltage direct current (MT-HVDC) systems are a promising solution for their grid integration. Using droop-based controller strategies in power converter stations of MT-HVDC grid, in addition, to providing power-sharing, can support the frequency of the connected AC grids. However, power changes lead to direct voltage deviations, thereby disrupting the stability of the MT-HVDC system. Here, a new control structure for the droop controller of the voltage source converter (VSC) controller is proposed which is named modified droop controller (M-Droop). This method, in addition to power-sharing, uses an appropriate control action to provide the required voltage stability. Here, analytical studies of the modified control strategy are reported. Moreover, through a developed MATLAB Simulink platform, its performance is verified in the events of transients, consisting of fault, variable load, and change in power generation

A hybrid active load and ideal synchronous condenser-based model for STATCOM applied to power flow studies

This study proposes a generalised STATCOM model employing active load and ideal synchronous condenser representation and its related power flow solution. The proposed method considers the effects of DC side voltage, internal switching losses, and operation mode on the power flow problem. To such aim, the proposed model tackles with a tap changing transformer accompanied by a variable conductance at the DC side in order to model the switching losses. This model can also take into account voltage regulation, reactive power control as well as amplitude modulation ratio and practical limitations. It is worth noting that the proposed model can be easily used for power flow studies by applying ordinary changes to the prevalent Newton–Raphson-based power flow methods. The introduced model is applied to two test systems including IEEE 14-Bus system, followed by a discussion on results