Showing papers presented at "International Power Electronics and Motion Control Conference in 2016"

Study and comparison on standard for interconnecting distributed resources with electric power systems

Abstract: This paper introduces the domestic and foreign standards for interconnecting distributed resources with electric power systems, and compares the contents of power quality, response to abnormal conditions, power control, voltage regulation and the ability of fault ride-through in some typical standards. Some items in wind power generation and photovoltaic power generation standards are concretely introduced. The cause of the difference between the standards is analyzed, and the development trend of the future standards for interconnecting distributed resources with electric power systems is discussed. This paper provides reference for the further improvement of the standards for grid-integration of distributed resources.

Ultra-compact Power Pulsation Buffer for single-phase DC/AC converter systems

Abstract: In single-phase power conversion systems, typically bulky electrolytic capacitors are installed in order to cope with the intrinsic double-line frequency power pulsation. However, since the voltage ripple at the dc bus is typ. limited to just a few percent of the nominal voltage, only a small fraction of the actually stored energy in the capacitors is used for the power decoupling. In this paper an auxiliary buffer converter is employed, shifting the double-line frequency power pulsation away from dc bus to a buffer capacitor. Being relieved from strict voltage ripple requirements, a larger voltage ripple is allowed across the buffer capacitor, significantly reducing the capacitance requirement. In this paper an ultra compact Power Pulsation Buffer (PPB) is designed for a 2kW PV-inverter application by means of a comprehensive Pareto optimization. Besides compensating the power pulsation, the PPB must be able to quickly stabilize the dc bus in case of abrupt load variations and maintain an average buffer capacitor voltage. In this paper, a novel cascaded control structure is presented, meeting all aforementioned control objectives. A constructed prototype of the optimized PPB is presented in the paper and experimental measurements verify the outstanding performance of the proposed control system.

Comprehensive evaluation of GaN GIT in low- and high-frequency bridge leg applications

Abstract: In power electronics applications with power ratings around several kilowatts, wide band gap semiconductors are more and more replacing state-of-the-art Si MOSFET. SiC MOSFETs with blocking voltage rating up to 1200V and low-voltage GaN devices are already commercially available on the market since a couple of years. Now also 600V GaN devices are entering the market, which are a cost-effective solution in many 400V key applications in order to increase the system performance in terms of achievable efficiencies or power density. Besides the employed semiconductor devices also the design of the appropriate gate drive circuit is important. In this paper a simple and reliable gate drive circuit for driving GaN switches is presented. In addition, the proposed gate drive is used to evaluate the switching performance of a GaN Gate Injection Transistor (GIT) under soft- and hard-switching condition, which provides a basis for further optimization of totem-pole converter systems.

Review of energy routers applied for the energy internet integrating renewable energy

Abstract: A technical review of energy routers applied in the future energy internet is carried out in this paper. The energy router (E-router) as a critical equipment of the energy internet can better solve changes of the power dispatching and management caused by a variety of distributed renewable energy sources accessing to low-voltage distribution networks. Basic design considerations and components of the E-router in terms of power conversions, energy management and communication are summarized in details. This paper classifies the E-router according to different applications and further analyzes the function structures and the implementation of different types of the E-router, which shows key components/technologies are solid state transformers, multiport-converters and time-division multiplex transmission respectively.

Comparative evaluation of isolated front end and isolated back end multi-cell SSTs

Abstract: Solid-state transformers (SSTs) are power electronic interfaces between medium voltage (MV) and low voltage (LV) systems that provide galvanic isolation by means of medium frequency (MF) transformers, making them suitable for MVAC to LVDC conversion in environments where weight and volume constraints apply. This paper discusses an isolated front end (IFE) SST concept that allows to reduce the complexity and physical size of the MV side converter assemblies compared to the well-known isolated back end (IBE) SST topologies. The IFE approach performs the entire grid current and output voltage control on the LV side using standard non-isolated |AC|-DC boost converter stages. A generic comparison of the IFE and the IBE concepts reveals that the lower complexity of the IFE, e. g., a lower total MV blocking voltage requirement (number of cascaded cells), comes along with higher device RMS currents and hence slightly higher chip area requirements. On the other hand, a case study considering a 25kW, 6.6 kV AC to 400V DC SST shows advantages of the IFE in part-load operation due to lower switching and transformer core losses. This makes the IFE approach interesting for applications where MF isolation instead of low frequency isolation is required because of space and weight constraints (e. g., traction, subsea or aircraft environments), and where low system complexity is desirable.

Development of a 10kV solid-state DC circuit breaker based on press-pack IGBT for VSC-HVDC system

Abstract: With the rapid development of power electronics technology, the voltage source converter-high voltage DC (VSC-HVDC) has been drawn more attention. DC circuit breaker, which can cut off the short current immediately while DC fault occurs, is a key equipment for DC grid of VSC-HVDC, avoiding the whole DC systems shut down. This paper presents the development and test of the prototype of a solid-sate DC circuit breaker for a bipolar VSC-HVDC system based on insulated gate bipolar transistor (IGBT) series-connected technique. The dynamic characteristics of IGBT and the principle of voltage balance circuits for series-connected IGBTs are analyzed in detail. This paper not only illustrates the breaking operation of the solid-state DC circuit breaker, but also solves the press-pack (PP) IGBT mechanical design being no available in the literature of similar application. With a Saber simulation model of series-connected IGBTs, the characteristics of unbalanced voltage-sharing caused by the gate resistor, tail current and gate charge of IGBT are simulated. The simulation results show that the static and dynamic circuits can greatly improve the performance of voltage balance. At last a ten series-connected IGBTs for solid-state DC circuit breaker and its test system are developed, which successfully turns off 5.1 kA under 10 kV DC, which shows the feasibility of the solid-state DC circuit breaker based on series-connected IGBTs. This paper provides a practical engineering application of the solid-state DC circuit breaker for the medium and high VSC-HVDC systems in future.

Evaluations and applications of GaN HEMTs for power electronics

Abstract: This paper presents an overview of the latest Gallium Nitride High Electron Mobility Transistor (GaN HEMT) technology. The latest development and challenges of 30 V to 650 V GaN HEMTs are summarized. The evaluation methodology of the GaN HEMT is presented, including static characterization and dynamic characterization. The paper also demonstrates the application of GaN HEMTs developed by Center for High Performance Power Electronics (CHPPE). Various high efficiency high power density circuit prototypes based on GaN HEMTs are presented.

A review on Microgrid architectures and control methods

Abstract: Distributed generation (DG) is playing an increasingly important role in modern power systems as the carbon emission concern and electricity demand are increasing. It facilitates the development of small scaled distributed grid networks and their technologies. Microgrid is an emerging technique and it comprises a variety of distributed generators, energy storage, loads and power electronic interfaces. Most of DGs do not provide a constant amount of power generation, thus, a proper control technique is necessity to keep a microgrid stable and reliable. This paper gives a review of literature with regard to the state-of-the-art microgrid architectures and control methods. Comparisons are made between different microgrid structures and control techniques. Pros and Cons are given as reference for further Microgird system studies.

Effects of renewable energy sources on the power system

Abstract: Recently, growing electrical energy market and increasing integration of renewable energy sources (RES) in power systems have lead to new challenges on network planning step and operation, thus it is required to investigate and analyze properly the impacts of integrated RES on the power system. In this paper, the electricity transmission network with wind farms (WF) is modeled. For the grid model, a part of Izmir region is chosen due to the amount of installed generation plants based RES especially wind energy in this region. The comparison between unexpected variations to voltage profile of the power system before and after RES integration to the power system is demonstrated. In the modeling of the electricity transmission network with RES, Digsilent/Power Factory is used as software. The different case studies in integration of different amounts of RES are implemented on the developed grid model. As a result of the conducted case studies, effects of RES on existing power system are evaluated and graphics obtained from the simulation are presented. Especially, the voltage profile of power system is examined.

Winding resistance and power loss for inductors with litz and solid-round wires

Abstract: An analytical model based on one dimensional 1-D Dowell's equation for computing ac-to-dc winding resistance ratio FR of litz wire is presented. The model takes into account proximity effect within the bundle and between bundle layers as well as the skin effect. Model describes three frequency ranges: low-, medium-, and high-frequency range. In each of ranges, the behavior of the ac-to-dc winding resistance ratio FR is different. Moreover, an analytical optimization of the litz-wire winding strand diameter is performed. The boundary frequency between the low-frequency and the medium-frequency ranges, are given for both solid-round-wire and litz-wire windings. Hence, useful frequency range of both windings can be determined and compared.

Non isolated and non-invertingCockcroft-Walton multiplier based hybrid 2Nx interleaved boost converterfor renewable energy applications

Abstract: In this paper hybrid non isolated and non-invertingCockcroft-Walton multiplier based 2Nx InterleavedBoost converter (2Nx IBC) for renewable energy applications is presented. The presented hybrid boost converter topology is derived from non-inverting Nx Multilevel Boost Converter (Nx MBC) and inverting Nx Multilevel Boost Converter (Nx MBC). In renewable energy applications, generated voltage needs to be stepped up with high conversion ratio using a DC-DC converter at voltage levels as per the application requirement. The advantages of the presentedtopology of interleaved converter are high voltage conversion ratio, reduce ripple, low voltage stress, non-inverting output voltage without utilizing the high duty cycle, coupled inductors and transformer. The main advantage of presented topology consists in increasing voltage gain by adding capacitor and diode into circuitry without disturbing the main circuit. Moreover, the presented topologyis compared with several recent non isolated high gain DC-DC converters. The proposed topology is simulated in MATLAB/SIMULATION andobtained results verify the validity of the design and operation of converter.

DC short circuit fault analysis and protection of ring type DC microgrid

Abstract: DC fault location and protection is the key problem to be solved of DC microgrid in spite of the fact that it has become the ideal networking mode of distributed generation due to its obvious advantages. In this paper, a ring-type wind turbine-based DC microgrid is taken as the object of study and the transient characteristics of VSC as well as the system under DC line fault are analyzed based on which the protection scheme of current differential protection as the main protection and under-voltage protection as the backup one is proposed. In this method, the power supply security of the DC microgrid system is guaranteed by detecting the input and output currents of the DC transmission lines through which the corresponding differential currents can be calculated to locate and isolate the fault lines. Simulations are conducted on MATLAB/Simulink and the results show that the protection system can response rapidly to the line differential current value under short circuit fault, so as to realize the DC short circuit fault protection of DC microgrid system.

Wireless power transfer system for gate power supplies of modular multilevel converters

Abstract: There has been a trend of applying IGBTs to high voltage direct current (HVDC) transmissions and static compensators (STATCOMs). Thus, modular multilevel converter (MMC) is attracting attention because it can satisfy high withstand voltage and large capacity. In MMC, gate power which is required for gate drive circuit tends to be supplied from the main circuit. This method, however, has a problem that the main circuit is unable to supply power to gate drive circuits during a power outage. This paper proposes that the system for the gate power supplies of MMC using wireless power transfer (WPT). 30 kV class MMC whose arm is composed of eight cells is assumed in this study. The proposed system consists of eight primary coils in series, eight secondary coils each cells and capacitors that compensate leakage inductance. About the proposed system, the design of the circuit and computer simulations were carried out. The comparison of compensation capacitors configuration and finite element method (FEM) analysis were conducted in the design. The simulations imitate a load failure and startup in the proposed system. As the results, it is shown that the proposed system has high efficiency which exceeds 80%. The compensation method that is a series connected in the primary side and a parallel connected in secondary side (Series-Parallel configuration) is suitable for proposed system.

An improved Q-PLL to overcome the speed reversal problems in sensorless PMSM drive

Abstract: Many existing sensorless control methods are based on flux observers, where phase-locked loops (PLLs) were used to extract the position information from the estimated rotor flux. This paper proposes an improved quadrature-component-based phase locked loop (Q-PLL) scheme for sensorless control of permanent magnet synchronous motor (PMSM) drives. To show the superiority of the proposed method in solving the problem of speed reversal, other three kinds of PLLs are also presented for the aim of comparison. This improved PLL is integrated with SMO-based sensorless control of PMSM drives. Compared to conventional Q-PLL, the main advantage of the proposed PLL is that it can work well without a gain scheduling remedial strategy or a judgment of the sign of speed in terms of speed reversal. Furthermore, it has a better performance in the transient and steady state response. Both Simulation and experimental results are presented to demonstrate the good performances of the proposed Q-PLL.

A novel secondary PWM-controlled interleaved LLC resonant converter for load current sharing

Abstract: The interleaved LLC series resonant converter (LLC-SRC) is required to fulfill the demand for high power capacity, high power density and high efficiency. However, when interleaved LLC-SRCs in each module are operated at the same switching frequency, load unbalance problem occurs due to the component tolerances of the resonant ranks. In consequence, the reliability of the converter is decreased due to increased secondary current ripple. In order to solve this problem, this paper proposes a novel load current sharing method for the resonant tank gain mismatches in each phase. The proposed load current sharing method can be implemented by controlling the turn-on timing of the secondary synchronous switches. The load current can be shared equally in each module, even if the converters in each phase are operated at the same switching frequency. In order to verify proposed method, the experiments are executed on a 500W prototype.

PV module parameters extraction with maximum power point estimation based on flower pollination algorithm

Abstract: Modeling of photovoltaic (PV) module remains as an important issue for many applications like monitoring or fault detection. Hence, many models have been proposed in literature, the most popular ones are the single and double diode models. Each model have unknown parameters to be identified. In this paper, a parameters extraction for both single and double diode models by using flower pollination algorithm is proposed. This algorithm is based on flower pollination for optimal reproduction of the plants species and can be considered as an optimization technique. Experimental validation was carried out by comparing the obtained results with real measurements data. In order to give usefulness, the extracted PV module parameters values are incorporated to estimate the maximum power point (MPP) and compared it with the MPP obtained from real data of grid connected photovoltaic system (GCPVS).

Assessment of industrial robots accuracy in relation to accuracy improvement in machining processes

Abstract: Using standard 6 DOF industrial robots for machining applications represents a significant market potential. Industrial robots have become a tool for various machining processes due to its universality — an ability to perform any type of movement in space — and low price compared to CNC milling machines. However, there are still limitations concerned with a much lower absolute accuracy, in comparison with CNC machines, caused mainly by a low static stiffness of the whole serial kinematic chain of a 6 DOF robot. Using the robots for machining is rather limited to applications with lower geometrical accuracy. To expand a possible scope of applications into milling operations, a new methodology is proposed to address the problem of lower absolute accuracy and concerned with KUKA robots. First, an experimental investigation of sources of main errors, having the impact on the product accuracy and surface quality, is presented. In this paper, we also focused on a comparison of internal robots states (actual robot positions) with measurements obtained from external systems such as Ballbar and Laser Tracker systems. Based on this investigation focused on KUKA robots, an online method for compensating the main source of errors — backlash errors resulting from the drive reversion — is proposed.

Maritime DC microgrids - a combination of microgrid technologies and maritime onboard power system for future ships

Abstract: DC power distribution system is being considered as an attractive alternative to its traditional AC counterpart in many fields of applications and, in particular, for maritime onboard power systems. The adoption of DC power architecture would bring a broad range of benefits to the onboard power system. Not only frequency-related constraints are eliminated, which allows high-speed smaller generators to be used, but also new fault-tolerant configurations involving power electronics, generation control, as well as smart systemic management. For these reasons, DC power systems become natural alternative to the conventional AC power systems in the field of future maritime applications. Moreover, the inevitable cabin structure of maritime applications naturally separate the large-scale power system into several zonal parts. Furthermore, it is expected that the zonal parts can maintain autonomous power supply for a short time, which make the system highly consist with DC microgrids. In this content, it is foreseeable that the advanced research outcomes in the field of DC microgrid are also compatible with maritime onboard power systems. In this paper, DC power architectures, control and coordination methods, and specific issues of maritime onboard power system, fuel efficiency optimization and systemic reconfiguration are outlined, referring to state-of-the-art realizations as well as to novel concept designs presently under development and investigation.

High efficiency non-isolated three port DC-DC converter for PV-battery systems

Abstract: This paper presents a nonisolated Three Port Converter (TPC) with a unidirectional port for photovoltaic (PV) panels and a bidirectional port for energy storage. With the proposed topology single power conversion is performed between each port, so high efficiencies are obtained. A theoretical analysis is carried out to analyze all operating modes and design considerations with the main equations are given. A 4kW laboratory prototype is developed and tested under all operating conditions. Results obtained feature on efficiencies higher than 97% for all operating modes and all power levels from light load to full load.

A 4000V input auxiliary power supply with series connected SiC MOSFETs for MMC-based HVDC system

Abstract: Modular multi-level converter (MMC) is composed of many sub-modules (SMs). Each SM needs an independent auxiliary power supply to drive IGBT and control the system. In HVDC system, the input of the MMC is connected directly to DC bus. So, the input voltage of the auxiliary power supply (APS) is very high. Traditional solution for the APS is the input-series output-parallel structure topology. However, this solution brings severe challenges, such as: input voltage and output current unbalance between the converters, out of synchronization when start-up, and difficulty in input voltage protection. Series connected MOSFETs is another straightforward solution for the APS. In this paper, a novel auxiliary power supply solution for MMC based HVDC system is proposed. It is able to handle extremely high input voltage from 300Vto 4000V by using five MOSFETs connected in series. The design procedure of the proposed APS as well as the voltage balance scheme, driving method is discussed in detail. The proposed auxiliary power supply is verified and demonstrated through a 60W prototype. Experimental results demonstrate that the purposed APS can work stably and reliably. It simplifies the structure and reduces the cost effectively even for thousands of voltages.

EMI prediction and filter design for MHz GaN based LLC half-bridge converter

Abstract: In this paper, EMI research and filter design with shielding method for a MHz switching frequency Gallium Nitride (GaN) based LLC half-bridge resonant DC-DC converter is explored. Firstly, a high-frequency model considering overall electromagnetic coupling effects for both common mode and differential mode is proposed. And EMI prediction during the frequency spectrum from 150 kHz to 30 MHz is illustrated. Then, improved inductor with shielding method is designed. According to the accurate EMI prediction and the designed inductor, high-frequency CM and DM EMI filters of the GaN based LLC converter are designed and implemented. To achieve that, different filter topologies are compared and CLC type is selected. It is confirmed that the proposed EMI filter is a convenient and cost-effective approach to suppress the EMI noise largely by both practical experiments and theoretical analysis. Moreover, to further improve the performance of the system, an optimized prototype with planar transformer is designed and implemented, which demonstrates that planar transformer can achieve smaller size, lower loss, higher power density and efficiency compared to traditional transformer.

Contribution to the system design of contactless energy transfer systems

Abstract: This contribution propose a design procedure applicable to many kinds of wireless or contactless energy transfer systems. The design procedure is limited to near field wireless energy transfer systems in resonant operation. Therefore it is well applicable to systems with a primary side power oscillator or systems with a control strategy that forces an equal system behavior compared to a primary side power oscillator. In resonant operation the input impedance and voltage transfer function of different natural frequencies describe the system behavior and will be calculated analytically in this contribution. Not only the knowledge of these transfer functions but also the knowledge of basic magnetic properties lead to a readily applicable design procedure.

Parallel operation of a synchronous generator and a virtual synchronous generator under unbalanced loading condition in microgrids

Abstract: Parallel operation of a synchronous generator (SG) and an inverter-interfaced distributed generator (DG) is required in some islanded microgrids. However, dynamic performance of a small SG is usually poor, i.e. the rotor speed usually deviates largely during a loading transition, due to small inertia and slow governor response. Moreover, unbalanced SG current should be prevented to protect the SG, which makes this issue more challenging. In this paper, a control method for the inverter-interfaced DG based on virtual synchronous generator (VSG) concept is proposed, to improve the overall performance of parallel operation of SG and DG. Double decoupled synchronous reference frame (DDSRF) decomposition, SG negative-sequence current compensation, modified calculation methods for power and voltage, and transient virtual stator impedance are integrated into the proposed VSG control scheme, and tuning methods of main control parameters are discussed. It is demonstrated by simulation results that the proposed DG control method alleviates the SG rotor speed deviation and DG overcurrent during a loading transition, and eliminates the negative-sequence components of the SG output current.

Robust active damping control of LCL filtered grid connected converter based active disturbance rejection control

Abstract: This paper deals with the problem of LCL filter resonance in grid connected inverter control. The system equations are reformulated to allow the application of the active disturbance rejection control (ADRC). The resonance, assumed unknown, is treated as a disturbance, then estimated and mitigated. By using this new robust control, a high level of performance is achieved with a minimum complexity in the controller design, and without any adaptive algorithm. It is demonstrated that the true quality of the control system is obtained by the proposed solution. Furthermore, it is shown that this control is robust against parameter variations and disturbances.

A modular multilevel converter-based grid-tied battery-supercapacitor hybrid energy storage system with decoupled power control

Abstract: This paper presents a modular multilevel converter (MMC)-based grid-tied batter-supercapacitor hybrid energy storage system (HESS), which can mitigate the active power fluctuation caused by intermittent renewable generation and also realize reactive power compensation as required by voltage regulation. The proposed HESS is novel in that batteries and supercapacitors are distributed into the upper arm and the low arm of the MMC, respectively, and it is therefore possible to design fully decoupled real power and reactive power control and simutanesouly optimize the performances of batteries and supercapacitors. The system modeling and operational principles of the MMC are first presented in this paper. Based on these analysis, the power decoupling control between the upper arm and the lower arm is discussed in detail. Moreover, the state-of-charge balancing control strategy for batteries and the voltage balancing control strategy for supercapacitors are presented also, which are the vital elements for implementing the proposed decoupled active and reactive power control. Finally, the proposed HESS and its control strategies have been verified by MATLAB/Simulink simulations and experimental results.

A switching ringing suppression scheme of SiC MOSFET by Active Gate Drive

Abstract: This paper proposes an Active Gate Drive (AGD) to reduce unwanted switching ringing of Silicon Carbide (SiC) MOSFET module with a rating of 120 A and 1200 V. While SiC MOSFET can be operated under high switching frequency and high temperature with very low power losses, one of the key challenges for SiC MOSFET is the electromagnetic interference (EMI) caused by steep switching transients and continuous switching ringing. Compared to Si MOSFET, the higher rate of SiC MOSFET drain current variation introduces worse EMI problems. To reduce EMI generated from the switching ringing, this paper investigates the causes of switching ringing by considering the combined impact of parasitic inductances, capacitances, and low circuit loop resistance. In addition, accurate mathematical expressions are established to explain the ringing behavior and quantitative analysis is carried out to investigate the relationship between the switching transient and gate drive voltage. Thereafter, an AGD method for mitigating SiC MOSFET switching ringing is presented. Substantially reduced switching ringing can be observed from circuit simulations. As a result, the EMI generation is mitigated.

Efficiency optimization of a two-phase interleaved boost DC-DC converter for Electric Vehicle applications

Abstract: Power losses and their consequences in the addition of storage cells have the negative effect of decreasing the power density and the efficiency in Electric Vehicles. For this reason, an efficiency optimization methodology is required to help reduce that problem. Specifically, in the power converters that interface the storage unit with the electric motors and their inverters, an efficiency optimization is essential to reduce the power losses and thereby downsize the cooling components and the storage unit. In this work, the topology under evaluation is the two-phase interleaved boost converter using different magnetic components such as coupled and non-coupled inductors, which are topologies known as effective for high power density applications. This paper presents a methodology that optimizes the efficiency of the chosen topologies through a complete power loss modeling of each component. Next generation components such as Super Junction Mosfets, GaN and SiC diodes and Mosfets are compared to obtain the most efficient and suitable material to be implemented to the topologies, especially to the converter with coupled-inductor. Moreover, a design procedure is proposed to integrate the loss model and the characteristics of the selected components as the base to obtain the objective function, which is later solved using analytical calculations. Finally, the optimization methodology is validated by experimental tests.

Lifetime evaluation of solder layer in an IGBT module under different temperature levels

Abstract: Solder layers are highly important parts of the IGBT module which establish the internal electrical connections, mechanical support and cooling channel of module. The function of the IGBT module is deeply dependent on the reliability of solder layers. A Finite Element (FE) model based on actual Insulated Gate Bipolar Transistor (IGBT) module is established to analyze how temperature levels of power cycling load influence the fatigue life of solder layer. 42 power cycling loads were designed with different temperature profiles, simulation results found that with the increase of junction temperature variation, the life parameter which has a negative correlation with solder life grows at an exponential rate. As the same time, with the increase of minimum junction temperature, the life parameter will have a near linear growth. Accordingly, life of solder layer get shorter when junction temperature variation and minimum junction temperature become higher. Finally, a life evaluation function of the solder layer has been established which made temperature profiles as the input variables and life parameter as the output variable.

A battery/supercapacitor hybrid energy storage system for DC microgrids

Abstract: This paper explores the frequency coordinating virtual impedance concept and proposes a control strategy for the co-ordination control of a hybrid energy storage system in DC microgrids. It investigates power decoupling methods to better attenuate the ripple power by filtration. Lead-acid battery and supercapacitor are used to form a hybrid energy storage system and are connected to a common DC grid through bi-directional DC-DC converters. Battery converter can absorb low frequency power variations while the high frequency power variations can be absorbed by supercapacitor converter. Battery supplies the long term power demand and supercapacitor responds to the short term power fluctuations during transient process in this proposed method. For the reduction of ripple power in the battery, this paper discusses the insertion of high order low/high pass filters for battery and supercapacitor converters instead of lower order low/high pass filters. The effectiveness of the proposed concept is shown through simulation and experimental results.