Hardware-based methods, such as additional filters, are commonly used to suppress common-mode voltage (CMV) at the inverter output and mitigate electromagnetic interference (EMI) in permanent magnet synchronous motor (PMSM) drive systems. In this paper, a feedforward active filter based on CMV sampling and compensation is proposed. The equivalent model and transfer function of the active filter are analyzed, and the parameter design method for each filter component is derived. However, the push-pull link in a traditional feedforward active filter suffers from inherent crossover and amplitude distortions, which introduce errors between the CMV sampling and injection links and degrade the compensation performance. To address this issue, a diode-clamped push-pull structure combined with DC bias resistors is proposed. LTspice simulation results show that the improved push-pull structure effectively eliminates crossover distortion and reduces amplitude distortion compared with the traditional structure. Experimental results on a PMSM drive platform show that the improved feedforward active filter achieves a CMV peak-to-peak reduction of approximately 30% compared with the traditional feedforward active filter. Moreover, the proposed method achieves more than 10dB attenuation improvement at the fundamental switching frequency and its harmonics, verifying its superior CMV suppression capability.

Electromagnetic interference (EMI) filters are essential for attenuating high frequency noise and ensuring compliance with electromagnetic compatibility (EMC) standards in power electronic systems. However, traditional discrete EMI filters often face significant volumetric constraints due to the separate placement of magnetic components and capacitors, which limits the suitability for the compact modern devices. To address this limitation, planar magnetic integration technology has been employed to consolidate inductors and capacitors onto multilayer substrates, thereby significantly reducing the overall physical volume. However, under high-frequency operating conditions, parasitic elements intrinsic to integrated circuit structures, such as interwinding capacitance, leakage inductance and dielectric substrate losses, significantly alter the impedance profile of filter components and compromise the noise attenuation capabilities. In this paper, a high frequency parasitic model for planar integrated T-type CM EMI filters is developed to precisely characterize the impedance behavior and quantify the effect of parasitic elements on insertion loss performance. An equivalent circuit representation of the integrated filter components is derived, then a simulation framework employing coupled impedance analysis is established to evaluate insertion loss characteristics of the planar T-type configuration, this provides a theoretical basis for the design and optimization of electromagnetic integrated common-mode filters.

To address the issue of electromagnetic interference (EMI) restricting the power density improvement of on-board chargers (OBCs), a T-type passive-active hybrid EMI filter suitable for 3.3 kW single-phase input OBCs has been designed. This filter aims to comply with CISPR 32 Class B standards and targets common-mode and differential-mode interference in the $\text{1 5 0 k H z}-\text{3 0 M H z}$ frequency band. It employs a T-type passive topology to enhance the interference attenuation rate and pairs it with a voltage detection current compensation active module to make up for the deficiency in low-frequency band suppression. Through the collaborative design of active and passive circuits and PCB layout optimization, the filter volume has been reduced to $87 ~\text{cm}^{3}$, achieving a $\text{3 0 \% - 4 0 \%}$ volume reduction and a $\text{2 0 \% - 3 0 \%}$ weight reduction compared to traditional passive solutions. Experimental tests show that the filter's insertion loss in the target frequency band is stably between $-\text{4 0 d B}$ and $-\mathbf{6 0 d B}$, with an average leakage current below 10 mA. The OBC operates at an efficiency of 94 % and a power factor of 0.9948, fully meeting the EMC requirements and compact installation needs of the on-board environment. In the future, planar magnetic integration technology will be incorporated to further optimize the miniaturization level of the filter.

The inverter is an essential power conversion device in the power generation system, but the output current by the inverter system contains a large number of harmonics, and harmonic filters need to be used for harmonic suppression to meet grid connection standards. As a third-order filter, the LCL filter has a high noise attenuation rate and is widely used. However, the LCL filter is not ideal for suppressing electromagnetic interference (EMI) noise. The symmetrical LCL filter can improve the suppression effect of EMI noise while ensuring the harmonic suppression capability. However, the symmetrical LCL filter adds two inductors compared to the LCL filter, resulting in a significant increase in the volume and weight of the inverter system. This article analyzes the structure of the symmetrical LCL filter, proposes coupling integration and decoupling integration solutions, adopts the planar magnetic integration method, and integrates the inductance of the symmetrical LCL filter into the same EI magnetic core by rationally designing the winding structure, greatly reducing the size and weight of the filter. Finally, the simulation and GaN-based experimental platform are built to verify the harmonic suppression effect and EMI suppression effect of the designed magnetically integrated symmetrical LCL filter.

A planar magnetic integration method of dual-stage electromagnetic interference (EMI) filters is proposed. Common-Mode (CM) inductors, CM and differential-mode (DM) capacitors are integrated into a single planar EIE-type magnetic core, DM inductors are provided by the leakage inductance of CM inductors. A planar magnetic integrated dual-stage EMI filter (IDSEF) is built and tested on the PLECS simulation platform to verify the feasibility of the proposed method. A GaN single-phase inverter and a test platform are developed. Compared with a discrete single-stage EMI filter (DSSEF), the discrete dual-stage EMI filter (DDSEF) achieves weight and volume reductions of 22.57% and 24.42%, respectively. Furthermore, the proposed IDSEF achieves additional reductions of 33.64% in weight and 29.16% in volume relative to the DDSEF. The proposed IDSEF delivers comparable EMI attenuation performance to the DDSEF while significantly reducing the weight and volume of the filter and enhancing the power density of the inverter system.

The LCL filter grid-connected system exhibits resonance phenomena. To suppress resonance issues, it is necessary to dampen resonance peaks. Currently, the commonly used suppression method is a control strategy based on active damping, which involves sampling the current of the filter capacitor for feedback. However, to improve the power density of inverters, fully integrated LCL filters are typically used. Sampling the capacitor current of a fully integrated filter is extremely inconvenient. This paper proposes an active damping control strategy without capacitor current sensor sampling. This strategy indirectly derives the capacitor current by sampling the inverter current and grid-side current, thereby introducing virtual damping into the control loop to effectively suppress resonance modes. This overcomes the design complexity and other issues associated with traditional active damping methods when using fully integrated filters.

To address the issues of large volume and asymmetric inductance in traditional three-phase LCL filters, this paper proposes a planar magnetic integration scheme for three-phase LCL filters based on a planar Y-type symmetric magnetic core structure. Based on the magnetic circuit theory, the equivalent reluctance model and inductance expression for the Y-type core are established. Finite element simulations are utilized to verify the inductance balance, and saturation control capabilities, with an EIE-type magnetic core set up as a control group. The simulation results indicate that the designed Y-type structure exhibits significantly better three-phase inductance symmetry than the EIE-type magnetic core, and the Y-type core demonstrates a relatively weaker saturation trend. A Litz wire-type multilayer PCB winding structure is introduced, and a design method for planar Litz PCB windings aimed at high-frequency loss suppression is proposed.

The newly developed flexible multilayer foils (FMLFs) winding design holds significant potential for advancing magnetic integration technology in power electronic systems. This article proposes the application of FMLF technology in the design of EMI filters. By utilizing a shared EE-type magnetic core and optimizing the winding configuration, all the common-mode (CM) inductors, capacitors, and differential-mode (DM) inductors and capacitors in the proposed EMI filter are integrated into a single core. Additionally, compared to the discrete filter and traditional heterogeneously integrated EMI filter, the EMI filter made with FMLF demonstrates superior performance, with significant advantages in size, weight, and efficiency, while offering noise suppression comparable to that of discrete filters. Based on modeling and theoretical analysis, an experimental prototype of the proposed EMI filter is built for a single-phase 500W SiC-MOSFET inverter. Performance comparisons are conducted through experimental measurements, which confirms the validity of the proposed model.

When connected to unbalanced load, the three-phase microgrid inverter (MGI) based on traditional droop control will produce unbalanced output voltage and the total harmonic distortion (THD) of current at the point of common coupling (PCC) will surpass the grid-connected standard, resulting in reduction in power quality. Additionally, when the MGI with traditional droop control is run in parallel, the reactive power in islanded microgrid cannot be distributed properly based on capacity due to the difference in line impedance. In this article, an improved droop control strategy for MGI is proposed, which introduces positive and negative sequence voltage-current control loops superimposed with adaptive virtual impedance to generate the reference value of output voltage, so as to reduce the voltage unbalance factor at the PCC, improve the THD of output current, compensate for voltage drop due to the difference in line impedance, and realize the reactive power distribution according to the capacity. Considering that the addition of adaptive virtual impedance and positive-negative sequence separation makes controller parameters more numerous and difficult to be tuned, a particle swarm optimization algorithm for tuning controller parameters is introduced. Finally, the experiment results are included to confirm the feasibility of proposed method.

LC-type and LCL-type filters are generally employed in the power converters of electric vehicles (EVs) for attenuating the associated switching harmonics introduced by modulation schemes. The passive filters commonly occupy prominent footprints, spaces, and weights, which goes against the high power-density demand of EVs. In order to tackle these concerns, this article investigates a shared electromagnetic integration approach with a flexible multilayer foil (FMLF) technique for both LC-type and LCL-type filters. Based on the fundamental design concept of the FMLF technique for achieving electromagnetic integration of an LC low-pass module, EIE-shape magnetic cores and two regular FMLF windings are utilized for the design. The negative influence induced by magnetic coupling between the two windings can be mitigated by reasonably regulating the air gaps designed between E-shape and I-shape cores. Additionally, through properly adjusting terminal configurations of the FMLF windings, the integrated module can switch between LC and LCL filtering modes as desired. The harmonic attenuation capability and conducted electromagnetic interference (EMI) suppression capacity of the module are discussed, following which, the design guideline of the integrated module is introduced. Finally, the feasibility and validity of the proposed approach are demonstrated by the simulations and experiments carried out with a 1-kW SiC-MOSFET voltage-source converter.

The three-phase inverter is a crucial power conversion device in renewable energy generation systems, but its output current contains numerous harmonics. These harmonics necessitate the use of harmonic filters to meet grid connection standards. Compared to L or LC filters, the LCL filter is widely used as a third-order filter due to its higher noise attenuation rate. However, the LCL filter's multiple inductors result in a larger volume and weight, which hinders the improvement of the system's power density. Magnetic integration technology effectively reduces the filter's volume and weight, but the coupling between inductors can impact the high-frequency noise attenuation ability. This article proposes a planar magnetic integration scheme that achieves decoupling of inverter side and grid side inductors, with a low coupling coefficient between both inverter side inductors and grid side inductors. Compared to traditional filters, the proposed magnetic integrated LCL filter is lighter and more compact, thereby enhancing system power density. The harmonic suppression effect of the designed magnetic integrated LCL filter is validated through simulations and experiments. Even under asymmetric load conditions, the proposed filter demonstrates good harmonic suppression performance.

In renewable energy generation systems, three-phase LCL filters are widely used for their good harmonic attenuation performance to filter out output current from the inverter, which contains a large number of harmonics, so that the harmonics can meet the grid-connected standards. However, the multiple inductors and capacitors in the discrete LCL filters occupy a large volume and weight, which seriously hinders the improvement on system power density. Therefore, this paper proposes an electromagnetic integration scheme that utilizes the flexible multilayer foil (FMLF) technique to realize the integration of inductive and capacitive elements on a single EIEE core. In addition, the technique achieves the decoupling between the inverter-side and grid-side inductors to ensure the filtering effect. Through simulation and experiment, it can be found that the electromagnetic integrated filter has the same effect as the discrete filter, and the former one is more compact.

Summary In the context of the dual active bridge (DAB) bidirectional DC‐DC converter using the traditional dual‐phase‐shift (DPS) control method, a transient DC bias occurs during power co‐direction and commutation conversion. This bias negatively impacts the converter's transient performance and can lead to harsh effects, such as hard switching problems, resulting in power loss and excessive current stress. In a closed‐loop control system, poor transient response may destroy the stability of the converter. In this paper, the transient‐optimized‐dual‐phase‐shift (TODPS) control strategy is proposed to eliminate the transient DC bias and to maintain soft switching during transient states. It reduces power loss, eliminates excessive current stress, and allows for smooth transitions between single‐phase‐shift (SPS) and DPS control strategies without introducing DC bias. A closed‐loop control system based on TODPS control is established with feed‐forward compensation to adjust the primary‐side current and modify transmission power. This adjustment enhances the transient performance of the DAB converter. The proposed strategy is versatile and applicable to various power conversion scenarios involving DAB converters. It enables quick switching of the magnitude and direction of the primary‐side current during transient states, resulting in a smooth transient effect without noticeable overshoot or oscillation. The experiment results verify the effectiveness of the proposed transient optimization strategy.

When connected to the unbalanced load, a three-phase microgrid inverter (MGI) based on traditional droop control would produce an unbalanced output voltage, which will lower the system's power quality. This paper proposes a voltage balance control strategy based on positive-negative sequence separation to solve those problems. It achieves this by introducing a positive-negative sequence voltage-current control loop on the foundation of traditional droop control to generate the reference output voltage of the Bridge arm side, thereby improving the THD of current and reducing the voltage unbalance factor (VUF) of voltage. Considering that the introduction of positive-negative sequence separation makes controller parameters more numerous and difficult to be tuned, a particle swarm optimization (PSO) algorithm for tuning the parameters of the voltage loop controller is designed. Finally, the experimental results are included to confirm the feasibility of the proposed method.

AbstractHarmonics and electromagnetic interference (EMI) pose serious threats to the safety and efficiency of grid‐tied inverters. Although the inductor‐capacitor‐inductor (LCL) filter offers commendable harmonic suppression, it does not sufficiently mitigate leakage current and EMI caused by high‐frequency pulse‐width modulation (PWM). This paper examines the use of a symmetrical LCL filter to reduce the AC side leakage current in grid‐tied inverters. The symmetrical structure bolsters the conducted EMI suppression capability of the LCL filter. A magnetic integration scheme for symmetric LCL filters is introduced, and through thoughtful structural design, it achieves filter inductance integration on the EIE magnetic core. An experimental platform, equipped with a high‐frequency SiC‐MOSFET voltage source inverter with a 600 W output, is utilized. The LCL filter, symmetric LCL filter, and magnetic integrated symmetric LCL filter are contrasted, proving the effectiveness and feasibility of the proposed scheme. Furthermore, the experimental results demonstrate that the proposed magnetic integration scheme significantly reduces the filter's volume and weight, thereby enhancing the power density of the grid‐tied inverter system.

Magnetic components such as inductors constitute a major proportion of the overall size and volume of grid-connected inverters. This paper presents an exploratory investigation into the magnetic integration of a three-phase LCL filter induction system, employing a Y-configured core that achieves equal magnetic flux pathways. Compared to using a conventional rectangular core, the proposed Y -shaped core configuration demonstrates a volumetric reduction of over 10 % for the three-phase inductors, while preserving the integrity of LCL filter functionality. The magnetic circuit analysis of the Y -shaped core is complemented by three-dimensional Finite Element Analysis (FEA) simulations to validate the theoretical calculations and reduced volumetric size. By enhancing the symmetry of magnetic flux distribution, this integrated inductor design significantly contributes to the miniaturization of three-phase grid-connected inverters without compromising their filtering performance.

The application of high-frequency switching components has made the switching frequency of the inverter develop towards higher frequency, which also brings serious electromagnetic interference (EMI) problems. The LCL filter has good low frequency filtering effect. The symmetrical LCL filter can improve the EMI suppression effect while ensuring the harmonic suppression effect. However, the common mode (CM) noise cannot be suppressed below the standard line, so further design of the CM EMI filter is required. The insertion loss of a single-stage CM EMI filter is 40dB/dec, and the insertion loss of a double-stage CM EMI filter can be increased to 80dB/dec. However, the double-stage CM EMI filter uses more CM capacitors, which will lead to an increase in leakage current. Based on this, a T-type CM EMI filter is proposed, which uses two CM inductors and two CM capacitors. The insertion loss can be increased to 60 dB/dec without increasing the number of capacitors used, and planar electromagnetic integration design is carried out for T-type CM EMI filter to reduce size and weight. By building an inverter experimental platform based on GaN, the filtering effect of the designed filter is verified.

The rapid growth of renewable standalone systems, with their inherent uncertainties and intermittency, poses a huge challenge to system stability. In this paper, an intelligent microgrid is proposed that fully utilizes the complementarity characteristics in PV and battery storage system (BESS), and is capable of maintaining an economic, reliable, and environmental equilibrium in daily generation scheduling. A black widow optimization (BWO) based controller is designed to determine the best possible solution under different scheduling scenarios. In addition, an exponential cost function based on the battery’s degree of discharge (DOD) is introduced to calculate the battery generation cost. It will include the battery lifetime cost in the overall power generation cost. Furthermore, the cost of the diesel generator includes the CO2 emission cost which is inversely proportional to the generator efficiency. The BWO algorithm optimized the generation cost based on these functions and increase the reliability of the grid using reliability index. The BWO algorithm finds the optimal global solution in less than 30 iterations and avoid the local optima problem. The effectiveness and convergence speed of BWO is far better than other algorithms and is validated by simulation results.

As an important energy conversion device in renewable energy grid integration, the inverter’s output power quality will affect the stability of the power grid and the safety of users' electricity consumption. With the wide application of wide bandgap semiconductor devices such as SiC and GaN in inverter, the switching frequency of the inverter is getting higher and higher. However, excessively high switching frequency also brings serious electromagnetic interference (EMI) problems. LCL filter is widely used for harmonic suppression in inverter systems due to its high attenuation rate in high frequency bands, but its EMI noise suppression effect is not ideal. Splitting the inductors of the LCL filter and symmetrically distributing them on the L line and N line can effectively improve the EMI suppression effect of the LCL filter, but this will increase the size and weight of the filter. This article proposes a planar magnetic integration solution that can integrate the inductors of the symmetrical LCL filter into the same magnetic core. The effectiveness of the proposed scheme is verified by building finite element simulation, and the filtering effect of the designed magnetic integrated filter is verified by building an experimental platform based on SiC.

An improved amplitude-domain (IAD-PWM) technique with minimum inductor current ripple for a three-phase quasi-Z-source inverter (qZSI) is proposed in this paper. The existing amplitude-domain technique expresses the three-phase voltage in a two-dimensional Cartesian coordinate system and divides the shoot-through time into several equal parts and inserts them in the switching sequence. However, this limits the scope and requires two large inductors to limit the inductor current ripple, resulting in a large volume and weight of the qZS inverter. The proposed IAD-PWM for the qZS inverter performs shoot-through behavior based on the geometric representation of the three-phase output voltage ranges in coordinate axes. Then, the shoot-through state time is divided into six unequal parts based on the discharging inductor current ripple, to achieve the minimum qZS inductor current ripples. The advantages of the proposed IAD-PWM lie in its extreme simplicity, as there is no shoot-through reference, and it avoids the complexity of vector and trigonometric functions calculations, while also having the capability to reduce qZS inductor current ripples or use smaller inductor in the qZSI, resulting in increasing of the whole system's power density. Moreover, the relationship among v a , v b and v c could be presented visually. The principle and the derivation of the proposed IAD-PWM are presented in detail, and the inductor current ripple under the proposed IAD-PWM and traditional ZSVM-6 are compared. Simulation and experimental results verify the outstanding features of the proposed IAD-PWM.