Search Results (79)

High penetration of Inverter-Based Resources (IBRs) into the power grid could diminish the rotational inertia offered by a traditional power system and thus impact frequency stability. Several techniques are adopted to provide virtual inertial support to the grid for a short duration in the presence of IBRs. This paper uses the combined inertia support of a Dual Active Bridge (DAB) and a Voltage Source Converter (VSC)-fed Electric Vehicle Fast Charging System (EVFCS) is used to provide virtual inertia support to the grid. The Voltage Source Converter is designed to provide DC bus voltage regulation. Coordinated control of DAB converters and VSCs for mitigating frequency oscillations using cascaded droop-integrated Proportional Integral (PI) controllers is proposed. An aggregated low-frequency model of a DAB converter is considered in this work. The inertia of the DC link capacitor of the VSCs and battery is sequentially extracted to offer grid frequency support. In this work, the single droop control, dual droop control, grid-forming and Augmented Frequency Support (AFS) modes are explored to provide virtual inertia support to the grid. Full article

Wireless sensor networks (WSNs) are an advanced solution for data collection in Internet of Things (IoT) applications and remote and harsh environments. These networks rely on a collection of distributed sensors equipped with wireless communication capabilities to collect low-cost and small-scale data. WSNs face numerous challenges, including network congestion, slow speeds, high energy consumption, and a short network lifetime due to their need for a constant and stable power supply. Therefore, improving the energy efficiency of sensor nodes through solar energy harvesting (SEH) would be the best option for charging batteries to avoid excessive energy consumption and battery replacement. In this context, modern wireless communication technologies, such as Wi-Fi and Li-Fi, emerge as promising solutions. Wi-Fi provides internet connectivity via radio frequencies (RF), making it suitable for use in open environments. Li-Fi, on the other hand, relies on data transmission via light, offering higher speeds and better energy efficiency, making it ideal for indoor applications requiring fast and reliable data transmission. This paper aims to integrate Wi-Fi and Li-Fi technologies into the SEH-WSN architecture to improve performance and efficiency when used in all applications. To achieve reliable, efficient, and high-speed bidirectional communication for multiple devices, the paper utilizes a Markov model, sleep scheduling, and smart switching algorithms to reduce power consumption, increase signal-to-noise ratio (SNR) and throughput, and reduce bit error rate (BER) and latency by controlling the technology and power supply used appropriately for the mode, sleep, and active states of nodes. Full article

With the rapid development of wind turbines and rising penetration levels, grid codes now require wind farms to provide active frequency support. However, time delays in fast power response reduce the stability of system frequency modulation. This study focuses on integrated inertia control and droop control of wind turbines with explicit consideration of time delays. First, the frequency modulation process is analyzed, and the main sources of time delay are identified. A system frequency response model is then developed, incorporating the time delay link into the state-space equations. Based on this model, frequency-domain and linear matrix inequality methods are applied to analyze delay-independent stability and time delay margins of wind turbines. A PI controller for the synchronous unit is designed, and compensation parameters for wind turbine delay are calculated to enhance system stability. Simulation results show that with a wind penetration level of 50%, the system becomes unstable when the delay reaches 0.32 s. By applying the proposed strategy, stability can be maintained even with a delay of 0.5 s. These results confirm the effectiveness of the proposed strategy and highlight its potential for improving frequency regulation in high-renewable power systems. Full article

A scheme of load frequency control (LFC) is proposed based on the deep deterministic policy gradient (DDPG) and active disturbance rejection control (ADRC) for multi-region interconnected power systems considering the renewable energy sources (RESs) and energy storage (ES). The dynamic models of multi-region interconnected power systems are analyzed, which provides a basis for the subsequent RES access. Superconducting magnetic energy storage (SMES) and capacitor energy storage (CES) are adopted due to their rapid response capabilities and fast charge–discharge characteristics. To stabilize the frequency fluctuation, a first-order ADRC is designed, utilizing the anti-perturbation estimation capability of the first-order ADRC to achieve effective control. In addition, the system states are estimated using a linear expansion state observer. Based on the output of the observer, the appropriate feedback control law is selected. The DDPG-ADRC parameter optimization model is constructed to adaptively adjust the control parameters of ADRC based on the target frequency deviation and power deviation. The actor and critic networks are continuously updated according to the actual system response to ensure stable system operation. Finally, the experiment demonstrated that the proposed method outperforms traditional methods across all performance indicators, particularly excelling in reducing adjustment time (45.8% decrease) and overshoot (60% reduction). Full article

Ultra-low frequency oscillation has been regarded as a typical instability issue in power systems consisting of hydro turbine synchronous generators due to the water hammer phenomenon. However, the increasing installation of renewable power generators gradually changes the stability mechanisms within multiple frequency bands. In this digest, a new kind of ultra-low frequency oscillation caused by doubly-fed induction generators (DFIGs) equipped with a df/dt controller in a thermal power generation system is introduced. To reveal the underlying mechanism, the motion equation model of the DFIG is constructed, and the simplified analytical model is proposed. The results show that when integrating a df/dt-controlled DFIG into a normal three-machine, nine-bus system, the damping ratio decreases to more than 0.2 when the virtual inertia parameter increases from 5 to 20, leading to a conflict between fast virtual inertial response and stability requirements. Other controllers related to active power regulation are also vital to stability. The frequency domain characteristics of the system are studied to illustrate the influence of key parameters on system stability. Finally, simulation verifications are conducted in MATLAB/Simulink. Full article

Power systems are currently undergoing a transition from centralized synchronous generators to decentralized non-synchronous generators that rely on renewable energy sources. This shift poses a challenge to system operators, as the high penetration levels of renewable energy introduce variability and changes in the physics of power systems. Load-frequency control is one of the biggest challenges faced by electrical grids, especially with increased wind energy penetration in recent years. The inertial controller is one of the methods used to support system frequency in variable-speed wind turbines. In this study, a proportional resonant (PR) controller was added to an inertial controller to achieve better frequency regulation by controlling the active power of the doubly fed induction generator (DFIG). First, the impact of the PR controller parameters on the frequency deviation, overshoot, settling time, and system stability was investigated to identify the optimal values that achieved the lowest frequency deviation while maintaining system stability. Second, the performance of the proposed method was compared that of the traditional method under different load perturbations. The results prove that improperly determining the proportional gain of the PR controller negatively affects system stability and frequency deviation. In addition, the results validate the hypothesis that the proposed method would provide fast frequency support for all the studied cases. The analysis and simulation of these scenarios were performed using the MATLAB/SIMULINK program. Full article

Virtual synchronous generators (VSGs) have been developed to mitigate the increase in the rate of change of frequency (ROCOF) in power systems by replacing synchronous generators (SGs) with inverter-based resources. VSGs mimic the dynamics and control of SGs; however, the mechanical delay typical of an SG’s turbine is often excluded, limiting improvements to the VSG’s response. The fast frequency response (FFR) of VSGs can help reduce ROCOF and enhance emulated inertia. This implies that the effective inertia (EI) of VSGs can exceed the set inertia parameter, posing challenges for operators in allocating sufficient VSG capacity considering the inertia required for stable operation. In this study, we quantitatively analyzed the difference between the EI of a VSG and the set inertia parameter by separating the active power output into inertia and governor responses. The quantitative analysis revealed that when the VSG provides FFR within the inertia-time domain, the EI exceeds the set inertia parameter. Furthermore, the sensitivities of the VSG set parameters and VSG capacity ratio, which is related to synchronizing power coefficients and the initial sharing ratio, for the EI were analyzed. These factors were theoretically considered, and the simulations validated their characteristics. Full article

Hybrid energy storage systems (HESSs) are essential for adopting sustainable energy sources. HESSs combine complementary storage technologies, such as batteries and supercapacitors, to optimize efficiency, grid stability, and demand management. This work proposes a semi-active HESS formed by a battery connected to the DC bus and a supercapacitor managed by a Sepic/Zeta converter, which has the aim of avoiding high-frequency variations in the battery current on any operation condition. The converter control structure is formed by an LQG controller, an optimal state observer, and an adaptive strategy to ensure the correct controller operation in any condition: step-up, step-down, and unitary gain. This adaptive LQG controller consists of two control loops, an internal current loop and an external voltage loop, which use only two sensors. Compared with classical PI and LQG controllers, the adaptive LQG solution exhibits a better performance in all operation modes, up to 68% better than the LQG controller and up to 84% better than the PI controller. Therefore, the control strategy proposed for this HESS provides a fast-tracking of DC-bus current, driving the high-frequency component to the supercapacitor and the low-frequency component to the battery. Thus, fast changes in the battery power are avoided, reducing the degradation. Finally, the system adaptability to changes up to 67% in the operation range are experimentally tested, and the implementation of the control system using commercial hardware is verified. Full article

The flywheel energy storage system (FESS) of a mechanical bearing is utilized in electric vehicles, railways, power grid frequency modulation, due to its high instantaneous power and fast response. However, the lifetime of FESS is limited because of significant frictional losses in mechanical bearings and challenges associated with passing the critical speed. To suppress the unbalanced response of FESS at critical speed, a damping ring (DR) device is designed for a hybrid supported FESS with mechanical bearing and axial active magnetic bearing (AMB). Initially, the dynamic model of the FESS with DR is established using Lagrange’s equation. Moreover, the dynamic parameters of the DR are obtained by experimental measurements using the method of free vibration attenuation. Finally, the influence of the DR device on the critical speed and unbalanced response of FESS is analyzed. The results show that the designed DR device can effectively reduce the critical speed of FESS, and increase the first and second mode damping ratio. The critical speed is reduced from 13,860 rpm to 5280 rpm. Compared with FESS of the mechanical bearing, the unbalanced response amplitude of the FESS with DR is reduced by more than 87.8%, offering promising technical support for the design of active and passive control systems in FESS. Full article

The increasing deployment of decentralized power generation based on intermittent renewable resources to reach environmental targets creates new challenges for power systems stability. Several technologies and approaches have been proposed in recent years including the use of superconducting magnetic energy storage. This study focuses on the review of existing superconducting magnetic energy storage systems for power quality control purposes. Such systems can supply and absorb the rated power level within seconds, promoting fast power quality regulation. Systems for power quality services such as frequency regulation, power oscillation damping, power fluctuation suppression, and active power filtering are identified and described. First, the physical characterization of superconducting magnets concerning geometries, materials, associated inductances, and nominal magnetic energy storage capacities is conducted. Then, the functional description of several current conversion circuits and systems used as interfaces for superconducting magnets is performed. The existing methodologies and systems to perform the control of current converters for different power control services and applications are also identified and described. Finally, the results regarding the number of different systems identified for each power quality control service are presented, and their applicability is discussed based on the adopted control approach. Challenges concerning the development of new systems to improve the power quality on grids with high penetration of decentralized energy resources from intermittent renewables are also identified. Full article

When traditional grid-forming converters directly participate in the grid-connected operation of the power grid, due to the lack of a pre-synchronization control system, the voltage amplitude and initial phase on both sides of the grid-connected point will deviate, resulting in voltage and current distortion during grid-connected mode. An active support phase-locked loop free pre-synchronization control strategy based on the third-order model of a synchronous generator is proposed to address the grid-connected problem of the grid-forming converter mentioned above. First, a model of active support control with frequency integral feedback at small signal levels was constructed. The root locus method was employed to examine how system parameters affect the stability of the active support control system. Second, by adding phase pre-synchronization controllers and amplitude pre-synchronization controllers to the active frequency loop and excitation voltage loop of the third-order model, it was ensured that the frequency, phase, and voltage amplitude of the unit are consistent with the power grid, achieving a fast and smooth grid-connected mode of the unit. Finally, by using a DC source to simulate all types of new energy power generation equipment, the active support pre-synchronization control system based on the three-order model of synchronous generator is built in the MATLAB/Simulink simulation environment, and the accuracy and effectiveness of the control strategy in this paper is verified. Full article

The current inverter control strategies have limitations in suppressing grid resonance, especially in complex grid environments with high penetration of renewable energy sources. These strate-gies often focus on suppressing resonance at a single frequency point, but their effectiveness is constrained when dealing with multi-band resonance or dynamically changing grid conditions. The study investigates the application of parallel-operated inverters in the grid, particularly their impact on grid stability. A novel active damping strategy is developed to enhance the grid’s dynamic response and suppress grid resonance. The effectiveness of the control strategy is verified through simulation by establishing Norton equivalent circuit models for multiple in-verters. Fast Through simulation, this study comprehensively evaluates the performance and adaptability of the strategy under various conditions. Results demonstrate that implementing the active damping strategy increases the inverter output power from 9.5 kW to 10 kW, an im-provement of 5.26%. System response time is reduced from 50 ms to 30 ms, and post-stabilization fluctuations decrease to 1.5%. These data conclusively prove the effectiveness of the control strategy in enhancing grid stability and reducing resonance effects. The findings underscore the potential of active damping strategies in improving grid performance and in-verter efficiency. However, further research and optimization are necessary to assess the adapt-ability of these strategies under different grid conditions. Full article

Extended back electromotive force (EEMF)-based position sensorless field-oriented control (FOC) is widely utilized for ultra-high-speed surface-mounted permanent magnet synchronous motors (UHS-SPMSMs) driven fuel cell air compressors in medium-high speed applications. Unfortunately, the estimated position is imprecise due to too small EEMF under low speed operation. Hence, current-to-frequency (I-f) control is more suitable for startup. Conventional I-f methods rarely achieve the tradeoff between startup acceleration and load capacity, and the transition to sensorless FOC is mostly realized in the constant-speed stage, which is unacceptable for UHS-SPMSM considering the critical requirement of startup time. In this article, a new closed-loop I-f control approach is proposed to achieve fast and efficient startup. The frequency of reference current vector is corrected automatically based on the active power and the real-time motor torque, which contributes to damping effect for startup reliability. Moreover, an amplitude compensator of reference current vector is designed based on the reactive power, ensuring the maximum torque per ampere operation and higher efficiency. Furthermore, the speed PI controller is enhanced by variable bandwidth design for smoother sensorless transition. These theoretical advantages are validated through experiments with a 550 V, 35 kW UHS-SPMSM. The experimental results demonstrated the enhanced startup performance compared with conventional I-f control. Full article

This paper proposes a control strategy for grid-following inverter control and grid-forming inverter control developed for a Solar Photovoltaic (PV)–battery-integrated microgrid network. A grid-following (GFL) inverter with real and reactive power control in a solar PV-fed system is developed; it uses a Phase Lock Loop (PLL) to track the phase angle of the voltages at the PCC and adopts a vector control strategy to adjust the active and reactive currents that are injected into the power grid. The drawback of a GFL inverter is that it lacks the capability to operate independently when the utility grid is down due to outages or disturbances. The proposed grid-forming (GFM) inverter control with a virtual synchronous machine provides inertia to the grid, generates a stable grid-like voltage and frequency and enables the integration of the grid. The proposed system incorporates a battery energy storage system (BESS) which has inherent energy storage capability and is independent of geographical areas. The GFM control includes voltage and frequency control, enhanced islanding and black start capability and the maintenance of the stability of the grid-integrated system. The proposed model is validated under varying irradiance conditions, load switching, grid outages and temporary faults with fault ride-through (FRT) capability, and fast frequency response and stability are achieved. The proposed model is validated under varying irradiance conditions, load switching, grid outages and line faults incorporating fault ride-through capability in GFM-based control. The proposed controller was simulated in a 100 MW solar PV system and 60 MW BESS using the MATLAB/Simulink 2023 tool, and the experimental setup was validated in a 1 kW grid-connected system. The percentage improvement of the system frequency and voltage with FRT-capable GFM control is 69.3% and 70%, respectively, and the percentage improvement is only 3% for system frequency and 52% for grid voltage in the case of an FRT-capable GFL controller. The simulation and experimental results prove that GFM-based inverter control achieves fast frequency response, and grid stability is also ensured. Full article

With the expansion of renewable energy sources, the stable and high-quality operation of microgrids composed of new energy sources has attracted widespread attention. Among them, the power conversion system (PCS), as an important part of microgrids, plays a crucial role in their operation and management. The PCS operation modes are classified into grid-connected and off-grid modes. However, in off-grid mode, due to the access of nonlinear and unbalanced loads, the output voltage quality of a PCS is worse, and the voltage waveform distortion is serious. To solve these problems, a fast repetitive control (FRC) strategy is proposed for a power conversion system with an Active Neutral Point Clamped (ANPC) architecture of three levels. The voltage loop control strategy can be applied to the voltage/frequency ($V/f$) mode and the grid-forming mode. The control strategy can effectively realize the suppression of the harmonics of the output voltage and has a 100% capability to carry unbalanced loads. Finally, a 1725 kVA PCS prototype is developed, and the proposed control strategy is verified using the MT3200 HIL semiphysical simulator of ModelingTech in the $V/f$ mode as an example. This practically verifies the feasibility and validity of the proposed control strategy, which has a certain degree of engineering practicability and reference due to the simplicity of the design and the ease of realization. Full article