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The squirrel-cage induction machine (IM) has been widely employed in microgrid. Accurate electrical parameters are necessary for the field-oriented control of the IM to achieve excellent performance. In this paper, a new offline identification scheme is presented based on the vector constructing method. The IM parameters are estimated using the recursive least squares (RLS) algorithm, which is applied to the continuous-time model of the IM at standstill. A single-phase ac test is used to make the machine standstill. The main feature of the proposed scheme is that the stator voltage, stator current and their derivatives, which are normally needed for the RLS algorithm, are constructed by the vector constructing method. The constructing rules are elaborated, which indicate that the phase shift and the amplitude ratio between the fundamental components of the voltage and the current have to be unchanged. This feature can avoid the analog or digital differentiators and greatly increase the noise immunity. Furthermore, the digital low-pass filter is not required for the proposed scheme, which can reduce the complexity of the identification scheme. Simulation and experimental results have been presented to demonstrate the validity and the feasibility of the proposed scheme.

There have been a number of harmonic current detecting methods for the active power filter (APF), including the filtration approach by fixed frequency filters, the composition method of the imaginary and the real power based on the instantaneous reactive power theory, etc. In this paper, firstly, according to the adaptive noise canceling technology in signal processing, an adaptive detecting approach of harmonic current based on a neuron is presented. Then, on the basis of the configuration and learning algorithm for the developed system, the realization scheme of an analog circuit of the system is discussed. Thirdly, using PSPICE software, computer simulation studies of the circuit are performed. Finally, experimental studies are carried out. The performance and feasibility of the approach are tested and verified by the simulation and experimental results.

Distributed Active Inductor is proposed dedicated to the D-FACTS application. Distributed Active Inductor is capable to generate both positive inductor and negative inductor, which makes significant sense in active power flow control. Control of Distributed Active Inductor contains AC-side Magnetic Flux control and DC-side equivalent resistor control. Distributed Active Inductor switched among three operation modes. Bypass mode can be achieved by proper control of its switching network but an additional mechanic switch. Steady-state and dynamic performance of Distributed Active Inductor are verified by simulation and experiment. The results proved that Distributed Active Inductor is capable to perform as a positive inductor and a negative inductor both in steady state and transient.

The full-bridge convertor is able to perform as the basic electrical circuit elements in its AC side with proper control. Negative inductor which is not exist in the real world is helpful to decrease the power line impedance without the possibility of resonance like the capacitor. Three different active inductor implementation methods are reviewed and compared, based on the features of the distributed FACTS. The Direct Reactance Synthesis method is chosen and analyzed in detail, especially for the negative inductor case. The impedance characteristics of virtual negative inductor is shown and discussed. The power flow controllability is verified by simulation and experiments.

Low temperature co-fired ceramic (LTCC) technology has been proved to be an effective way to realize system integration. By using this technology, passive components in a DC/DC converter could be integrated into a passive substrate. This paper presents fabrication and evaluation of LTCC capacitors and inductors and summarizes challenges of applying LTCC technology to DC/DC converters. Four capacitors are made; two of them are made with single layer high permittivity thick film paste, and maximum 1.1µF capacitance is obtained; the other two are made with multilayer low permittivity LTCC tapes, maximum 30nF capacitance is obtained. A 70nH LTCC inductor is also fabricated with ferrite tapes. It is tested in a 1.2MHz buck converter and a 30MHz class Φ 2 DC/DC converter. Finally, challenges of conductor resistance, capacitor tape permittivity, and shrinkage matching are discussed and summarized.

A mosaic structured core composed with ferrite mosaics for passive embedded substrate is described in this paper. The ferrite mosaic structured core is finished after cutting, laminating and assembling the ferrite mosaics which consist of a supporting plate and ferrite units with small size stuck on it. This structure is applied to a transformer design for 48V to 12V, 500W LLC resonant bus converter with efficiency up to 97%. Analysis is conducted to show this structure working well and finite element analysis (FEA) is executed for simulation of the power losses in the new structure core. Experiment results show that gap control is a big challenge to mosaic structured transformers.

The LLC resonant converter can easily achieve soft-switching and magnetic components integration that makes it an excellent candidate for DC Bus Converter. In low voltage high output current applications, the design of synchronous rectifier (SR) and transformer is the key issue. A SR driving scheme with less circuit complexity is adopted for switching frequency at the resonant frequency in this paper. Using Magnetic Motive Force (MMF) diagrams both in space and time, the loss model of the center-tapped planar transformer is proposed that provides insight into the mechanism of the skin and proximity losses and that also yields quantitative results. The Finite-Element analysis (FEA) is applied to demonstrate the loss model. A prototype of 1/4 brick, 48V to 12V, 500W output Bus Converter is built to verify the result. 96.6% efficiency at full load and 300W/in3 power density are achieved.

Based on the small-signal model of the half-bridge circuit, the double close loops control system of the inverter arc welding power supply was designed under the average current control mode. For the control system's voltage and current controllers, the loop gains, angular frequencies of zeros and poles were determined. The simulation model of the designed double close loops control system was established in Matlab/Simulink. The simulations of the steady-state and dynamic characteristics under the conditions of open load to short circuit, load to short circuit and short circuit to load were given out in large-signal. The parameters of the main circuit and control system were optimized according to simulation results. Finally, experiments were carried out and experimental waveforms were obtained. The experimental and simulation results were corresponded well and the rationality of the studying method was verified, a designing method to the inverter arc welding power supply was put forward.

A novel main circuit for arc welding inverter has been proposed, in which the switching frequency is no longer restricted by the electrolytic capacitor, so it enables the DSP-controlled inverter welding machine to exploit the perfect control ability on the welding procedure and to satisfy all kinds of requirements for physical properties, out-characteristics and dynamic characteristics of electric arc. The proposed main circuit can remove soft-start circuit, reduce the capacitance of the capacitors, thus the volume and the cost of the system is further reduced. The adoption of EMI filter in the proposed circuit can suppress the conducted interference. A series of comparative analysis and experiments have been carried out, and the results indicate that the proposed circuit has many other improvements in increasing the power factor and efficiency, restraining inrush current and the harmonic distortion. This study conforms to development trend of “high frequency and green welding machine”, and provides the potential for the further improvement of the dynamic performance of welding machine.

A modified speed sensorless direct torque control (DTC) scheme for surface permanent magnet synchronous machine (SPM) is investigated in this paper, which features in very low flux and torque ripple and almost fixed switching frequency. Instead of the switching table and hysteresis controllers in the basic DTC, a reference flux vector calculator (RFVC) is used to determine the reference stator flux linkage vector. The reference flux vector is produced according to the amplitude of the reference and estimated stator flux linkages, the position of the estimated stator flux linkage, the amplitude of the reference and estimated torques and the estimated rotor speed. Then the voltage vectors applied on the machine is calculated to compensate the flux and torque errors exactly, so the flux and torque are controlled in the deadbeat fashion. A speed estimation method is also introduced in this paper, in which the rotor flux linkage is calculated from the stator flux linkage and the stator current. Then the rotor speed is calculated from the rotor flux linkage. Simulation results show that the flux and torque ripples are greatly reduced when compared with those of the basic DTC. With the new scheme, the quick dynamic torque response of the basic DTC is still retained. Fixed switching frequency at different operating conditions becomes possible by means of space vector modulation.

This paper presents the analysis, control strategy and realization of a digital frequency controller of a two stage ballast for HID Lamps. First, the small signal phasor model of the LC S C P resonant inverter is established and verified. Based on this model, a dobule loop digital compensator is desigened to control the current and power of the lamp. Then the overall control strategy for the long term stability of the ballast is designed and realized on a PIC MCU controller. Finally, a electronic ballast for a 400W MH lamp is designed based on this scheme, and the experimental results are provided.

In power system, capacitors are widely used to compensate reactive power, which generally cause resonance problems in harmonic distorted network. In this paper, A method of using a parallel active power filter (PAPF) to damp the resonances is proposed. The proposed method is compound with traditional method, it shows that whether the capacitor current is included in the detecting current of PAPF or not. Also the PAPF with proposed method has strong ability in harmonic compensation. Finally, the experiment results are presented to verify the analysis. In power system, capacitors are widely used to compensate reactive power, which generally cause resonance problems in harmonic distorted network. In this paper, A method of using a parallel active power filter (PAPF) to damp the resonances is proposed. The proposed method is compound with traditional method, it shows that whether the capacitor current is included in the detecting current of PAPF or not. Also the PAPF with proposed method has strong ability in harmonic compensation. Finally, the experiment results are presented to verify the analysis.

For speed sensorless stator-flux-oriented control (SFOC), the accuracy of the estimated flux position decides the performance of the speed sensorless drive. In this paper, a novel flux estimation method is proposed in which the pure integrator is replaced by a low pass filter (LPF) to resolve the DC-drift and saturation problem and the phase error with the LPF is approximately compensated by the reference flux component to obtain the stable low-speed operation. However, the flux error due to the stator resistance deviation still remains, especially at very low speed. Therefore, a compensating method for stator resistance variation is also incorporated in the flux estimation such that the flux estimation can be independent of the stator resistance. The method is based on a current error between an estimated current obtained by the estimated flux and the real current. Comprehensive analysis was performed to investigate the relationships among flux magnitude error, flux angle error, and current estimation error in the motoring and regenerating modes. Finally, the sensorless SFOC scheme based on the proposed flux estimating method had been implemented on a 2.2kW induction motor. All experimental results show that the proposed scheme has improved low speed performance, even when there is significant stator resistance error.

This paper explores some strategies of incorporating advantages of low temperature co-fired ceramic (LTCC) technology into design and fabrication of low power high frequency DC/DC converters. High power density and high efficiency are two key factors for power modules. The development of new generation power switches with much less turn-on and turn-off time interval provides new chances for increasing switching frequency and reducing volume of passives, this makes LTCC technology which is commonly used in RF circuit applicable for fabrication and integration of high frequency DC/DC converters. Conductor paste, ceramic tapes, ferrite tapes, capacitor tapes as well as metal substrates are co-fired together to realize three-dimensional inter-connection, passive integration, thermal performance improvement and structure optimization.

In order to avoid conventional topology's drawbacks, a new topology that the diode rectifier is replaced by the thyristor rectifier and the control strategy of the active voltage quality regulator with variable dc-bus voltage are proposed in this paper. This paper analyzes the circuit topology and control strategy in detail. Then losses and efficiency of the both circuit topologies are compared in order to show the virtue of the proposed circuit and its control method. Through comparative analysis, the proposed circuit topology is verified to be better than conventional topology. At last, the validity and effectiveness of the proposed control strategy are verified by the laboratory experimental results. At the same source voltage and load condition, the efficiency increases from 89% to 96% on a 2 kVA prototype.

Multiphase motor drives have many advantages over the traditional three-phase motor drives. In this paper we firstly deduce the mathematic modeling for a dual-three-phase permanent magnet synchronous motor (PMSM) according to vector space decomposition theory. Then, a sensorless vector control based on the Model Reference Adaptive System (MRAS) is developed for a dual-three-phase PMSM and the system stability is verified by Popov super stability theory. Furthermore, a new and very simple initial rotor position estimation method is proposed by means of DC excitation without any sensors. Finally, a dual-three-phase PMSM experimental prototype is designed and fabricated in the laboratory. The simulation and experimental results are presented to demonstrate the effectiveness of the proposed scheme.

When applying parallel active power filter (PAPF) to the power transmission/distribution system that contains the reactive power compensation capacitors, the capacitors can influence the system stability and the compensation performance of PAPF. In this paper, considering the influence of capacitors, the harmonics compensation and resonance damping characteristics of PAPF with traditional load current detection methods are analyzed. The analysis results show that, when capacitor current is not included in the detected load current, PAPF has ideal performance of load harmonics compensation and parallel resonance damping, but has no effect on damping series resonance and compensating harmonic current caused by supply voltage distortion; when capacitor current is included in the detected load current, PAPF with traditional control method can't work stable. To improve the system stability and the performance of PAPF, a novel control method of PAPF is proposed. With the proposed control method, PAPF has excellent performance for harmonics compensation and resonance damping. Finally, experiment results are presented to verify the analysis.

In this paper, an extensive analysis on the influence of DC side voltage to the performance of PAPF is carried out, and a specification of the DC side voltage rated value is presented. First, through equivalent circuit analysis and Fourier Transform analytical expressions, a required lowest value of DC side voltage for full compensation (a zero source current THD) is obtained for six-pulse converter harmonic current, where PAPF is providing six-pulse converter harmonic current. For the situation, of which the DC voltage is smaller than the above-obtained lowest value, the quantitative relationship between the DC voltage and the total harmonic distortion after compensation is also elaborated in the paper by using the diagram of curve relationship. Based on these analysis, the specification of DC voltage rated value for PAPF is quite straight forward. Simulation investigation results are finally provided to verify the analysis and specification.

For higher power density of power electronics converters, the integration of passive into the printed circuit board (PCB) is a low cost and integral manufacturing approach. The passive substrate concept for power electronics is proposed in this paper. Based on it, the converter level packaging can be implemented. The commercially available ferrite materials with low high frequency loss can be embedded in the PCB. Thus, transformers and inductors can be entirely integrated in the PCB. The configuration and manufacturing processes of the embedded passive substrate are described. Accordingly, the synchronous full-bridge bus converter with 12 V/26 A output is designed and manufactured using the passive substrate. The electrical and thermal characteristics of the passive substrate are illustrated. The thin converter, better thermal performance and high power density can be achieved.

Detachable transformer is an important component of contactless power transmission system. Compared with traditional transmission modes, it has following advantages. There is no contact between supplying equipments and loads, no friction, which brings convenience to maintenance; no noise pollution et al. It can work in any formidable conditions with higher frequency and less volume. This paper offers several guidelines to realize systems by ANSYS. ANSYS relies on finite element method (FEM). Based on this theory, it may have excellent performance in AC harmonic magnetic field analysis that will be discussed in this paper by setting element types and material attributes, modeling, meshing et al. This paper sets up three-dimensional model of dissociable transformer by ANSYS. The object of 3-D analysis is to find out the optimum structure with highest transmission efficiency and smallest electromagnetic interference from all the switch- mode power supplies. Different structures suit on different application conditions and have their own features. For the sake of comparison, the analysis chooses PM-cores, and models in different structures. Detachable transformer has a loosely coupled structure. It is most important to find a way increasing efficiency as much as possible according to given conditions. This paper discusses conditions on which the highest efficiency can be acquired through emulation to eliminate bad influence to the whole system by this link. IN the end, we give some experimental results about this system.

Design of DC side voltage rated value is a very important issue for the development of static var generators (SVG), but so far is lack of discussion in a quantitative manner from previous publications. In this paper, an extensive analysis on the influence of DC side voltage to the performance of SVG is carried out, and a specification of the DC side voltage rated value is presented. First, through equivalent circuit analysis and analytical expressions, a required lowest value of DC side voltage for full compensation (a unity total power factor) is obtained for both leading compensation and lagging compensation, where SVG is providing leading reactive current and lagging reactive current respectively. For the situation of DC voltage smaller than the above-obtained lowest value, there are two basic options for the SVG PWM control. One is to keep the linear modulation of PWM but loose the compensation capability to a unity power factor, for which case the quantitative relationship between the DC voltage and the total power factor after compensation is detailed. The other is to keep the unity power factor compensation capability through over modulation of PWM control, for which case the amount of lower order harmonics generated by SVG is also elaborated in the paper. Based on these analysis, the specification of DC voltage rated value for SVG is quite straight forward. Both simulation investigations and hardware experimental results are finally provided to verify the analysis and specification.

A novel control strategy for damping power fluctuation in wind power system is proposed in this paper. This strategy is realized by an appropriate DC link voltage regulation, which takes sufficient use of DC link capacitor and tolerates DC link voltage changes within a certain range. Within the permitted voltage range of DC side, using the novel DC link voltage control to damp output power fluctuation has the advantage of no degradation of the maximum wind power tracking capability of the generator control system. Simulation results based on Saber and experimental results demonstrate the validity of the proposed control strategy.

In power system, capacitors are widely used to compensate reactive power, which generally cause resonance problems in harmonic distorted network. In this paper, parallel active power filter (PAPF) is used to damp the resonances. Firstly, the damping characteristics of PAPF with traditional load current detection methods (detecting current including or not including the capacitor current) are analyzed respectively. The analysis results show that PAPF with traditional load current detection methods is effective for parallel resonance damping, but can not damp series resonance when capacitor current is not included in the detecting current. And when capacitor current is included in the detecting current, PAPF is prone to be unstable and can not damp parallel and series resonance. Then a novel control method of PAPF is proposed. PAPF with the proposed control method has excellent performance in damping of both parallel resonance and series resonance, whether the capacitor current is included in the detecting current of PAPF or not. Also the PAPF with proposed method has strong ability in harmonic compensation. Finally, the experiment results are presented to verify the analysis.

Parallel active power filter is one of the most effective solutions to compensate the current harmonics and to enhance the power quality in industrial application. Regularly, the PAPF is controlled as a current source with the amplitude similar to the harmonics component of load current. This paper proposes a novel voltage-mode control in which the power inverter is controlled as a voltage source with a better and more general control algorithm than in regular current-mode control. Here, the APF acts as virtual transimpedance at harmonics frequency (virtual transinductor connected with resistor) to resist harmonic current flow through the source side. At low frequency, the APF act as an active impedance (virtual capacitor connected with resistor) to block the fundamental current, then all the active source current feeds to the load. Considering the algorithm with control diagram, this algorithm could be considered as two independent control loops. The fundamental loop controls the fundamental compensation current to follow zero, and the harmonic control loop restrict the harmonic source current tend to zero. If the loop gain is high enough, the harmonics of source current tends to zero, and less current flows through the shunt branch of APF. What's more, comparative study and discussion are also provided to thoroughly express the authors understanding. This shows that he proposed algorithm expands the horizon to improve the performance of PAPF with a better compensator. Simulation and experimental results are given at the end.

Active Power Filter (APF) is an effective solution to the compensation of power quality problems, especially harmonics. To achieve better performance, the control method is crucial for APF. Currently, there are many control schemes available for APF, which may be classified as two types: one needs harmonics detection from load current, while the other does not need harmonics detection but does need detecting and controlling of the DC-link voltage. This paper presents a study on the popular control schemes comparatively, and leads to the conclusion that the latter type, the control scheme without harmonics detection, is just a reduced version of the broadly used regular load current harmonics detection control, and by nature has the similar essential control principles in the system point of view. The latter type is a simple feedback control, while the regular control scheme with load harmonics detection is a composite control, with both feedback of DC-link voltage and feedforward of the fundamental load current which results in better dynamic performance. This clear disclosure of the internal relationship between the two types of the control schemes would be very helpful to choose the most appropriate control scheme effectively. The above conclusion is illustrated with signal-flow graphs and corresponding analysis, and verified by both time-domain computer simulations and experimental tests on hardware prototypes.

A 1 kW IPEM (integrated power electronic module) based PFC converter, consisting of full bridge rectifier diodes, current sensing resistor and boost converter, has been developed employing CoolMOS and SiC diodes in this paper. Some practical considerations about how to reduce the parasitic inductance of high di/dt loop by comparing three different geometric DBC layouts with Ansoft Maxwell-3D, and symmetrical design for the parallel MOSFETs are demonstrated. According to the specific application and specifications, the power loss of the module is calculated before prototype fabrication, and then the thermal performance is evaluated by simulation. That optimizes the performance and reduces the design period of IPEM. Finally, the electrical performance of the module is verified experimentally.

Power quality issues such as reactive power control and harmonics mitigation have been gaining wide attentions these years. This paper introduces a novel hybrid parallel active power filter (APF), in which the passive power filter (PPF) and the transformer-coupled APF connected in series. In the proposed hybrid APF, there is a trade-off between compensation performance and system investment. Traditionally, the parameters of the LC filter and APF are decided in an approximate and experience-dependent way. In this paper, an overall optimization design strategy is proposed aiming to reduce the system cost with the same power factor and THD requirements of the supply. Firstly, the models of PPFs and the APF are established respectively for rating evaluation. Secondly, the objective function of the whole investment in the parallel system is obtained based on assumed unit price of the resistors, reactors, capacitors and APF. These coefficients can be modified easily according to different prices for different components. Finally, the minimum value of the objective function is found out through a genetic algorithm (GA). With the parameters based on GA overall optimization strategy, the whole cost of the system decreased about 2.26 percent with less computation and better compensation behavior comparing with traditional design method. The novel hybrid APF is applied in an arc furnace.

The paper introduces a DC-DC multiple converter based on push-pull forward topology and analyzes its operation principle in detail. It has some superiority in low voltage and high current situation. Then the design procedure of the power stage and control circuit is introduced. Finally 5 kW experimental equipment is accomplished

This paper introduces a parallel hybrid active filter topology and operation principle appropriate for removing harmonics caused by single-phase nonlinear loads. Based on the characteristic of the coupling transformer of a parallel hybrid active filter, a simple method for estimating VA rating is proposed. Furthermore, by means of parameter transform, this paper presents a new design strategy for designing this kind of the transformer as a line frequency transformer. Experimental results obtained from a 1 MVA laboratory prototype verify the viability and effectiveness of these methods proposed in this paper.

This paper describes the development of high current (up to 2500 A) and low voltage (up to 12V) SMPS unit for electroplating. A special topology and structure of the inverter-transformer was developed. In such manner, the leakage inductance, skin effect and proximity effect of the transformer was greatly reduced. Based on it, a 5000 A/12 V power supply was built by two units.

The harmonic characteristics of a rectifier with a filter inductor or capacitor on the DC side are analyzed and then is classified into current or voltage-type harmonic sources. The reason why the series active power filter is suitable to compensate voltage-type harmonic sources is illustrated. A new control approach of detecting load voltage is developed. It can directly obtain the load voltage harmonic component to provide the reference voltage for the series APF and improve its compensation performance. In addition, the control method of the PWM inverter and a method to keep its DC side voltage constant are discussed. Experimental results, from a complete prototype of the series APF, are presented to show its validity for compensating voltage-type harmonic sources, and validate and compare the control approaches.

Basic characters of noncrystal and ferrite are compared, the effects to main switches and the imbalance resisting performance are discussed in detail, experiments were carried out with an 6 kW DC-DC prototype converter, and important conclusions are drawn in the end.

Using the snubber net made of diodes and capacitances, in the zero-voltage-switch full-bridge (ZVS-FB) converter, can not only decrease the parasitic resonance in the rectified voltage of the transformer secondary, but also obtain zero-current-switch (ZCS) in the lag leg. In addition, this topology can eliminate the circulating current existing in the ZVS-FB topology circuit. The diode clamp circuit introduced in the transformer primary can apparently restrain the peak voltage resonance in the rectified diodes. By applying those techniques, one 3 kW DC/DC converter has been achieved and its transformer primary current waveform and rectified voltage waveform of the transformer secondary has been illustrated in this paper.

By analyzing the causes of the flux imbalance in the utility frequency transformer of a sinusoidal wave inverter, a new approach of avoiding flux imbalance is introduced in this paper, that is to apply a DC compensation into the sinusoidal signal. Employing it into 5 kVA UPS proves the practicability of the approach.