Instantaneous Output Power Research Articles

An in-depth oxidation kinetic study of CuCrxMn1-xO2 (x = 0, 0.1, 0.3) for thermochemical energy storage at medium-high temperature

In this study, we investigated the effect of Cr doping on CuMn2O4/CuMnO2 and established an oxidation (heat release) kinetic model for CuCrxMn1-xO2 (x = 0, 0.1, 0.3) as an extension of our previous research on developing medium-high temperature (500–1000 °C) redox-type thermochemical energy storage materials. Our objective is to develop a reliable model for predicting the heat release power at constant temperature conditions. The as-prepared samples were characterized using XRD Rietveld refinement, SEM-EDS, and XPS analysis to obtain a more precise crystal structure and elemental states. The oxidation kinetic model was established using an isothermal oxidation method which differs from the method (non-isothermal) used in the previous study. Additionally, the pressure term was also taken into consideration. The reaction models and kinetic parameters of CuMnO2, CuCr0.1Mn0.9O2 and CuCr0.3Mn0.7O2 were determined using master plots and Arrhenius plots. Among all sample, CuCr0.1Mn0.9O2 exhibited the smallest oxidation activation energy of 29.932 kJ/mol, which was significantly lower than the previous value obtained using the non-isothermal method. Combining the reaction rate and heat release, CuCr0.1Mn0.9O2 showed the highest instantaneous power output of 4.69 kW/kg at the oxygen partial pressure of 0.5.

Gigantic and Continuous Output Power in Ionic Thermo-Electrochemical Cells by Using Electrodes with Redox Couples.

The main obstacle of ionic thermo-electrochemical cells (TECs) in continuous power supply lies in a low heat-to-electricity energy conversion efficiency because most TECs work in thermodiffusion mode in which the ions are confined in a liquid/electrolyte media. The introduction of the redox couple onto the electrode surface may overcome the obstacle by resolving the low mass transport rate of ions caused by the redox process occurring near but not on the electrode surface. Herein, the authors demonstrate enhancement of TECs by integrating the redox couple directly onto the electrode surface to maximize the mass transport efficiency. A discontinuous interfacial modification strategy is developed by using a carbon cloth/iron (II/III) phytate as the symmetric electrodes. The gelled electrolyte consisting of a polyacrylamide matrix and phytic acid is shown to promote selective ion diffusion. A synergistic combination consisting of the thermodiffusion effect and redox reactions on the electrode is established in a pre-treated layout. Such TEC affords a high output voltage of 0.4 V, an excellent instantaneous output power density (20.26 mW m-2 K-2 ) and a record-high 2 h output energy density (2451 J m-2 ) under TH = 30 °C with TC = 15 °C, with an ultrahigh Carnot-relative efficiency of 1.12%.

Quality of moxa from Artemisia argyi and A. stolonifera in different storage years based on simultaneous thermal analysis

The quality of moxa is an important factor affecting moxibustion therapy, and traditionally, 3-year moxa is considered optimal, although scientific data are lacking. This study focused on 1-year and 3-year moxa from Artemisia stolonifera and A. argyi(leaf-to-moxa ratio of 10∶1) as research objects. Scanning electron microscopy(SEM), Van Soest method, and simultaneous thermal analysis were used to investigate the differences in the combustion heat quality of 1-year and 3-year moxa and their influencing factors. The results showed that the combustion of A. stolonifera moxa exhibited a balanced heat release pattern. The 3-year moxa released a concentrated heat of 9 998.84 mJ·mg~(-1)(accounting for 54% of the total heat release) in the temperature range of 140-302 ℃, with a heat production efficiency of 122 mW·mg~(-1). It further released 7 512.51 mJ·mg~(-1)(accounting for 41% of the total heat release) in the temperature range of 302-519 ℃. The combustion of A. argyi moxa showed a rapid heat release pattern. The 3-year moxa released a heat of 16 695.28 mJ·mg~(-1)(accounting for 70% of the total heat release) in the temperature range of 140-311 ℃, with an instantaneous power output of 218 mW·mg~(-1). It further released 5 996.95 mJ·mg~(-1)(accounting for 25% of the total heat release) in the temperature range of 311-483 ℃. Combustion parameters such as-R_p,-R_v, D_i, C, and D_b indicated that the combustion heat quality of 3-year moxa was superior to that of 1-year moxa. It exhibited greater combustion heat, heat production efficiency, flammability, mild and sustained burning, and higher instantaneous combustion efficiency. This study utilized scientific data to demonstrate that A. stolonifera could be used as excellent moxa, and the quality of 3-year moxa surpassed that of 1-year moxa. The research results provide a scientific basis for the in-depth development of A. stolonifera moxa and the improvement of moxa quality standards.

Unique Contact Point Modification Technique for Boosting the Performance of a Triboelectric Nanogenerator and Its Application in Road Safety Sensing and Detection.

A triboelectric nanogenerator (TENG) is a potential technique that can convert waste kinetic energy to electrical energy by contact separation followed by electrostatic induction. Herein, a unique contact point modification technique has been reviewed carefully via the enlargement of the effective surface area of the tribo layer by using a simple and scalable printing method. In this study, the zinc sulfide (ZnS) nanostructure morphology has been introduced directly on an aluminum electrode (Al) as a tribo positive layer by a modified hydrothermal method and different line patterns directly printed on overhead projector (OHP) transparent sheets by a monochrome laser printer as a tribo negative layer to increase the effective contact area and work-function difference between two tribo layers. This dual parameter results in ∼11 times increment in the open-circuit output voltage (∼420 V) and ∼17 times increment in the short-circuit current density (∼83.33 mA m-2) compared to the normal one. Furthermore, with the proposed surface modification technique, an ultrahigh instantaneous output power density of ∼3.9 W m-2 at a load resistance of 2 MΩ was easily achieved. The direct energy conversion efficiency reached up to 66.67% at 2 MΩ load, which is very high compared to other traditional TENGs. Further, the fabricated TENG demonstrated efficacy in novel road safety sensing applications in hilly areas to control vehicle movement. Therefore, the current idea of surface engineering using a laser printer will be helpful for energy-harvesting enthusiasts to develop more efficient nanogenerators for higher energy conversions.

Ordered mesoporous SiO2 nanoparticles as charge storage sites for enhanced triboelectric nanogenerators

Triboelectric nanogenerators (TENGs) have demonstrated great prospects in energy harvesting and self-powered sensing. However, the surface triboelectric charges are very easy to dissipate in the air atmosphere, especially after the contact electrification stops. Here, we propose ordered mesoporous SiO2 (OMS) nanoparticles with a large specific surface area (SSA) as effective body charge storage sites inside polydimethylsiloxane (OMS-PDMS) to enhance the output performance of TENGs. With the addition of 1 wt% OMS nanoparticles, the transferred charges of the TENG showed a sharp enhancement, rising from 21 nC to 60 nC. The enhancement effect of OMS nanoparticles on the output increased linearly with SSA. In addition, the OMS-PDMS also demonstrated a superior charge retention ability, with 68 % of the voltage being retained over a long time after the contact separation motion stopped, while that of the pure PDMS quickly dropped to near zero. The instantaneous output power density of the TENG with OMS-PDMS reached 5.26 W/m2, which is a 25-fold enhancement. This work proposed OMS nanoparticles with a large SSA as effective charge storage sites to enhance the output performance of TENGs.

Enhanced triboelectric nanogenerators based on 2D smectite clay nanosheets with a strong intrinsic negative surface charge

Triboelectric nanogenerators (TENGs) have demonstrated their huge potential in micro/nano energy harvesting for self-powered systems. The output performance of TENGs is largely dependent on the surface charge density of the triboelectric materials. Here, for the first time, we propose 2D smectite clay (SC) nanosheets with a strong intrinsic negative surface charge for improving the charge density of traditional triboelectric-negative materials. A single-layer 2D SC nanosheet (∼1.1 nm thick) showed a strong negative surface potential (−14.3 mV), and the SC was confirmed to have a strong triboelectric negativity close to that of polytetrafluoroethylene (PTFE). 2D SC nanosheets were blended into polyvinylidene fluoride (SC-PVDF), based on which the SC-TENG demonstrated a significantly enhanced output performance, with the transferred charge increasing from 14 nC to 35 nC at the optimal SC concentration of 5 wt%. At higher SC concentrations, the influence of decreased effective contact area because of severe aggregation of SC nanosheets began to outperform the effect of increased interior charge. The instantaneous output power density of the SC-TENG was enormously improved to 1450 mW/m2 from that of the pristine TENG (15 mW/m2). This work proposed a new 2D material, SC, with a strong intrinsic negative surface charge, which has huge prospects in enhancing the output performance of TENGs.

An Ionic Thermoelectric Generator with a Giant Output Power Density and High Energy Density Enabled by Synergy of Thermodiffusion Effect and Redox Reaction on Electrodes

AbstractIonic hydrogel thermoelectric generators (ITEGs) are becoming increasingly popular in effective recovery of low‐grade waste heat, but they suffer from relatively low output power density and energy density. In this work, by utilizing the synergetic strategy of thermodiffusion effect and redox reaction on electrodes, an ITEG is demonstrated which demonstrates impressive thermoelectric conversion properties. On the one hand, an interpenetrating network structured ionic gel with temperature‐sensitive phase transition behavior is designed as thermoelectric material to achieve a very high thermopower of 40.60 mV K−1 at a temperature gradient (ΔT) of 5 K. On the other hand, polymer redox polyaniline (PANI) is appended on the carbon weaved fabric (CWF) electrode to augment heat‐to‐electricity storage and output power performance. It is found that the PANI@CWF electrode assists to realize a larger current density output, 1 h output energy density (E1h) (570 J m−2) at a ΔT of 20 K and a maximum normalized instantaneous output power density of 11.31 mW m−2 K−2 are obtained, which is a record‐breaking result among the reported quasi‐solid‐state ITEGs. A feasible routine to design the top‐performing ITEGs is verified, which shows commercial promise for continuously powering electronic devices such as sensors and wearable electronics.

Active power control in horizontal axis wind turbine considering the fatigue structural load parameter using psuedo adaptive- model predictive control scheme

In wind turbine the optimization techniques are implemented to maximize the instantaneous power output and minimizing the structural fatigue loading. The maximum power output at an operating point is attained by increasing the lift coefficient which in-turn increase the fatigue stress on turbine components. Therefore, a regressive optimal point tracking controller has to be designed to identify the instantaneous optimal point of convergence. The typical feedback controller strives to maintains the instantaneous maximum power output without considering the fatigue loading parameters. In the same manner, the fatigue load mitigation techniques will not consider the power compromises. This work proposes a Pseudo Adaptive Model Predictive Controller (PA-MPC) which efficiently handles both the instantaneous generator power control and induced fatigue load mitigation of wind turbine. The proposed Pseudo Adaptive Model Predictive Controller framework can solve the bi-objective cost function online and ensures the optimal operation of the turbine. The objective of proposed control methodology is to improve the power output by 10% and reduce the fatigue load component by 48%. The expected response from the turbines using the proposed controller would improve the operating lifetime of the turbine by 2.5 years (12.5% of overall lifetime).

An introduction to triboelectric nanogenerators

Today, there is a continuous rise in the requirement for upgraded healthcare systems that are self-driven, dynamic and very low in maintenance. With a steep rise in the evolution of devices and their applications, such as sensors, there is an increment in the supply of sustainable energy without the replacement and recharging of the installed charge storage devices. Among the various energy scavengers, triboelectric nanogenerators (TENGs) have garnered huge attention as they have a high instantaneous output power and can be developed from a broad selection of available materials, like aluminium (Al) and copper (Cu) metal films, fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE) and green materials like cellulose-based materials. TENGs have a great ability to convert extracted mechanical energies into electrical energies very effectively due to the coupling effects of contact electrification and electrostatic induction. They have tremendous potential in a diverse range of applications, such as medical therapies that include biomedical applications, energy scavenging and active sensing. TENGs are devices made of self-energizing materials that are non-polluting, long-lasting and small sized. They can be developed through inexpensive fabrication processes and are environmentally friendly. In this paper, the mechanism by which the triboelectric nanogenerators perform their applications and how strategies are being developed to improve their performance have been discussed. We have also discussed the future research directions that are being undertaken to advance development in this field. So far, TENGs have mainly been used as mechanical and chemical stimuli to detect sensors and as an electrical source for electronic equipment and devices. Most of the studies found in the literature have reported that TENGs are primarily focused on optimization of systems and circuit designs or on the application of TENGs. A thorough review of the fundamentals of TENGs has been presented here.

Enhancing the output performance of ZnO nanosheet based piezoelectric nanogenerator by molar ratio modifications

The current work shows how the molar ratio of zinc nitrate and hexamethylenetetramine (HMTA) affects the output performance of a ZnO nanosheet-based piezoelectric nanogenerator. ZnO nanosheets were synthesized at three different molar concentrations of HMTA with fixed zinc nitrate hexahydrate concentration (1:1, 1:2, and 1:3). The shape, crystallinity, chemical composition, and photoluminescence properties of ZnO nanosheet films were further studied. The increased concentration of HMTA in solution results in larger and thinner nanosheets. In addition, three piezoelectric nanogenerators were fabricated using these ZnO nanosheet films deposited on two sides of an aluminum foil. The larger ZnO nanosheet film-based nanogenerator (PENG3) produced an enhanced output voltage than the smaller ZnO nanosheet film-based nanogenerator (PENG1) with an average output voltage of ∼423 mV and an average short-circuit current of ∼0.697 µA, respectively. The output voltage of PENG3 was enhanced by 1.55 times and short-circuit current by 1.34 times compared to the PENG1 device. PENG3 has an instantaneous output power of about 0.2277 mW/m2 at a load resistance of 250 kΩ. The photoluminescence study also confirmed that this could be used as a suitable UV light sensor. In addition, these highly porous nanosheets can also be used for photovoltaic materials in DSSC applications.

Predictive power control of induction motor drives with improved efficiency

The performance of predictive current control (PCC) of induction motor (IM) drives is sensitive to the accuracy of the rotor flux angle estimation. In addition, predictive torque control (PTC), prioritizes control objectives by weighting factor in the cost function. It is tedious work to find a suitable weighting factor. In order to overcome these issues, a predictive power control (PPC) of IM drives is proposed in this paper. It directly controls the instantaneous output power of IM and does not require weighting factor and rotor flux angle estimation. This is achieved by the use of instantaneous power theory. The decoupling control of torque and rotor flux can be realized by controlling the output active and reactive power. The proposed method is easier to implement than PCC and PTC. To improve output efficiency, an output efficiency optimization strategy is proposed based on PPC. This is realized by adding the weighted output efficiency term into the cost function directly. Moreover, in order to get a better steady-state performance, an optimization strategy is proposed according to extend the output voltage vectors. Finally, the experimental and real-time hardware-in-the-loop (HiL) results validate that the proposed strategy is easier to implement and could optimize the output efficiency of the motor.

All‐in‐One Sensing System for Online Vibration Monitoring via IR Wireless Communication as Driven by High‐Power TENG

AbstractAbnormal vibration is a direct response to the mechanical defects of electrical equipment, and requires reliable vibration sensing for health condition evaluation in the associated system. The triboelectric nanogenerator (TENG) triggered by random vibration to generate electrical energy/signal while giving feedback on the vibration state, paving a promising way towards self‐powered sensors. Here, an all‐in‐one sensing system configured with a vibration sensor demonstrates instantaneous discharge boosted TENG and IR wireless communication for vibration state online monitoring. The sandwich‐structured TENG combined with mechanical switches can release the co‐accumulated charges from dual triboelectric layers to yield giant instantaneous output power of 616 W, which is 106 times higher than that of the continuous discharge. Moreover, an IR LED as a transmitter driven by the TENG can form an all‐in‐one vibration sensor enabling wireless communication, where the sensor can be further integrated with repeaters and phones to establish a wireless vibration online monitoring system for vibration state visualization. This work presents a novel idea to implement high‐power TENG with IR communication integration for in situ vibration online monitoring. Such a strategy is potentially available for distributed sensor construction towards abnormal signal monitoring that reflects the operating state of equipment.

Limiting radial pedal forces greatly reduces maximal power output and efficiency in sprint cycling: an optimal control study.

A cyclist's performance depends critically on the generated average mechanical power output (AMPO). The instantaneous mechanical power output equals the product of crank angular velocity, crank length, and the tangential pedal force. Radial pedal forces do not contribute to mechanical power. It has been suggested that radial pedal forces arise from suboptimal pedaling technique and that limiting these would increase AMPO and efficiency. Here, we presented an optimal control musculoskeletal model of a cyclist (consisting of five segments driven by nine Hill-type muscle-tendon units) to predict maximal AMPO during sprint cycling at different levels of allowed radial pedal forces. Our findings showed that limiting radial pedal forces has a detrimental effect on maximal AMPO; it dropped from 1,115 W without a limit on radial forces to 528 W when no radial forces were allowed (both at 110 rpm). We explained that avoiding radial pedal forces causes ineffective use of muscles: muscles deliver less positive power and have a higher muscle power dissipation ratio (average mechanical power dissipated per unit of average positive power delivered). We concluded that radial pedal forces are an unavoidable by-product when optimizing for maximal AMPO and that limiting these leads to a performance decrease.NEW & NOTEWORTHY In the literature, but also in the "cycling field" [e.g., trainers, coaches, and (professional) cyclists], it is often suggested that trying to limit/avoid radial pedal forces enhances cycling technique and with that maximal average power output and efficiency. In this paper, we introduce an optimal control model of a human cyclists (consisting of five segments and driven by nine Hill-type muscle-tendon complex models). With that we not only show, but also explain why limiting radial forces is a bad idea: it will decrease maximal attainable AMPO and will decrease efficiency.

Ultrastretchable, Self-Healing Conductive Hydrogel-Based Triboelectric Nanogenerators for Human–Computer Interaction

The rapid development of wearable electronic devices and virtual reality technology has revived interest in flexible sensing and control devices. Here, we report an ionic hydrogel (PTSM) prepared from polypropylene amine (PAM), tannic acid (TA), sodium alginate (SA), and MXene. Based on the multiple weak H-bonds, this hydrogel exhibits excellent stretchability (strain >4600%), adhesion, and self-healing. The introduction of MXene nanosheets endows the hydrogel sensor with a high gauge factor (GF) of 6.6. Meanwhile, it also enables triboelectric nanogenerators (PTSM-TENGs) fabricated from silicone rubber-encapsulated hydrogels to have excellent energy harvesting efficiency, with an instantaneous output power density of 54.24 mW/m2. We build a glove-based human-computer interaction (HMI) system using PTSM-TENGs. The multidimensional signal features of PTSM-TENG are extracted and analyzed by the HMI system, and the functions of gesture visualization and robot hand control are realized. In addition, triboelectric signals can be used for object recognition with the help of machine learning techniques. The glove based on PTSM-TENG achieves the classification and recognition of five objects through contact, with an accuracy rate of 98.7%. Therefore, strain sensors and triboelectric nanogenerators based on hydrogels have broad application prospects in man-machine interface, intelligent recognition systems, auxiliary control systems, and other fields due to their excellent stretchable and high self-healing performance.

Origami Tribo-Metamaterials with Mechanoelectrical Multistability

The emerging mechanical functional metamaterials reported with promising mechanoelectrical characteristics bring increasing attention to structurally functional materials. It is essential to deploy mechanical metamaterials in energy materials for effective triggering and controllable mechanoelectrical response. This study reports origami tribo-metamaterials (OTMs) that design triboelectric materials in the origami-enabled, tubular metamaterials. The octagonal, hexagonal, and conical origami units are deployed as the metamaterial substrates to trigger the triboelectric pairs for mechanoelectrical multistability. For the octagonal OTM configuration with the triboelectric pair of fluorinated ethylene propylene-paper, the peak open-circuit voltage, short-circuit current, and transferred charge are obtained as 206.4 V, 4.66 μA, and 0.38 μC, respectively, and the maximum instantaneous output power density is 0.96 μW/cm2 with the load resistance of 20 MΩ. The OTM takes advantage of the origami metamaterials to obtain the multistable force-displacement response as effective stimuli for the triboelectric materials, which leads to tunable mechanoelectrical performance for speed and weight sensing and energy harvesting. The proposed OTM not only offers a strategy to structurally design energy materials to achieve desirable mechanoelectrical response, but also provides a guideline for the applications of mechanical functional metamaterials in practice.

Energy Harvesting from Vibrating Cantilever Structure of Different Base Materials using Piezoelectric Material: Theoretical and Experimental Approach

Energy conversion from one form to the other forms the basis for many inventions. Non utilized energy of mechanical vibration has attracted many researchers to focus on energy harvesting from vibrating structures. Piezoelectric material when attached to a vibrating structure converts mechanical energy into electrical energy. Today, harvesting energy ranges from micro level to macro level and has obtained its importance in wide range of real time application such as from low powered electronic devices to solar, wind and hydroelectric energy systems, respectively. The current work presents a detailed theoretical and experimental study on a cantilever type beam structure embedded with piezoelectric material on different base materials to understand micro level energy harvesting. Euler Bernoulli beam theory based mathematical model is excited with an impulse load at the free end for a broader frequency spectrum analysis. Finally, the proposed energy harvesters, cantilever specimens of three different base materials are ranked based on their maximum voltage and maximum instantaneous power outputs experimentally for the given impulse excitation. Out of three base materials considered steel and copper-based energy harvesters generated a maximum voltage output of 0.16mV and 0.13mV, respectively which corresponds to a maximum instantaneous power output of approximately 1.96nW and 1.69nW, respectively. Aluminum-based energy harvester performed the least among the three contributing to 0.81nW.

국내 수송환경에 적합한 마찰전기 나노발전기의 발전특성 분석

Sustainable energy supplies without the recharging and replacement of charge storage device have become increasingly important. Among various energy harvesters, the triboelectric nanogenerator (TENG) has attracted considerable attention due to its high instantaneous output power, broad selection of available materials, eco-friendly and inexpensive fabrication process, and various working modes customized for target applications. The TENG harvests electrical energy from wasted mechanical energy in the ambient environment. TENG devices are very likely to be used in next-generation renewable energy and energy harvesting. TENG devices have the advantage of being able to manufacture very simple power devices. In this experiment, various organic dielectrics and inorganic dielectrics were used to improve the open voltage of TENG, Among the various organic dielectrics, Teflon-based FEP, which has the highest electron affinity, showed the highest open voltage and Al electrode was fabricated on Teflon substrate by sputtering deposition process. And AAO (Anodized Aluminum Oxide) nanostructures were applied to maximize the specific surface area of the TENG device. The power generation of TENG within the acceleration level (0.25, 0.5, 1.0, 1.5 and 2 G) and the frequency range (5-120 Hz) of the domestic transport environment was up to 4 V.

Green-in-green biohybrids as transient biotriboelectric nanogenerators

Green self-powered devices based on biodegradable materials have attracted widespread attention. Here, we propose the construction of the transient biotriboelectric nanogenerator (TENG) using green-in-green bionanocompoites. The green-in-green nanocomposites, cellulose nanocrystal (CNC)/polyhydroxybutyrate (PHB), are prepared with a high-pressure molding method. The CNC promotes the degradation and enhances the dielectric constant of CNC/PHB. It further allows for the significant improvement of the triboelectric output of CNC/PHB-based TENG. The voltage output and current output of CNC/PHB-based TENG are 5.7 and 12.5 times higher than those of pristine PHB-based TENG, respectively. Also, the bio-TENG exhibits admirable signal stability in over 20000 cycles. Despite the high hardness of CNC/PHB, a soft but simple-structured arch sensor is successfully assembled using CNC/PHB-based TENG. It can attain the precise real-time monitoring of various human motions. This study may provide new insights into the design/fabrication of green functional materials, and initiate the next wave of innovations in eco-friendly self-powered devices.

Low Frequency Current Ripple Suppression for Two-Stage Single-Phase Inverter Based on Impedance Editing

The instantaneous output power of the two-stage single-phase inverter pulsates at double-line frequency, generating a large amount of second harmonic current (SHC) in the front-end dc-dc converter and input dc source. The SHC is harmful to the system performance. To address the issue, a control strategy based on port-impedance editing, where inductor current feedforward (ICFF) and bus voltage feedforward paths are employed, is proposed to reduce the low frequency ripple in the article. Due to only bandpass filter employed in each feedforward path, the proposed control scheme is relatively easy to be implemented. Under the control strategy, the dc-bus port-impedance of dc-dc converter is increased rapidly at double-line frequency, while staying low impedance for other frequencies. What is more, different ICFF paths are taken into insight to obtain optimized path. Meanwhile, the small signal model of front-end dc-dc converter is established and the design principle of key parameters is provided for the derived control strategy. Furthermore, the dynamic response with bandwidth limitation is also discussed in this article. Finally, a two-stage single-phase inverter prototype was fabricated and tested. The experimental results verify the performance of the proposed strategy with SHC reduction.

A novel low frequency current ripple suppression method for energy storage system in DC microgrid

• A novel control method is proposed for NF, QPR and LPF based on dual-loop control. • This method improves the suppression effect of secondary harmonic current (SHC). • This method also improves anti-load mutation ability. • SHC suppression effect and dynamic response of four control methods are analyzed. The instantaneous output power of the energy storage system pulsates at twice the output voltage frequency, generating a large amount of secondary harmonic current (SHC) in the switching tubes and batteries. The SHC is harmful to the system performance and battery life. Firstly, through the analysis of traditional dual-loop (DL) control method, it is concluded that SHC is not suppressed obviously and the dynamic characteristics of the system is inferior when load hopping. To address these two questions, a novel control method is proposed for introducing notch filter (NF), quasi-proportional resonator (QPR) and load power feedforward (LPF) based on DL control (it can be abbreviated as NQLDL). This method increases the amplitude of the inductor branch equivalent impedance (IBEI) at twice the output frequency without changing the frequency adaptability, improves the suppression effect of SHC, reduces the amplitude of the IBEI outside of twice the output frequency and also improves anti-load mutation ability. Furthermore, the SHC suppression effect and dynamic response are also discussed under four control methods. Finally, the validity of proposed control methods are demonstrated by experimental results.