Direct Stator Flux Vector Control Strategy for IPMSM using a Fullorder State Observer

Qingwei Yuan,Zhiyong Zeng,Rongxiang Zhao 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.1

A direct stator flux vector control scheme in discrete-time domain is proposed in this paper for the interior permanent magnet synchronous motor (IPMSM) drive to remove the proportional-integral (PI) controller from the direct torque control (DTC) scheme applied to IPMSM and to obtain faster dynamic response and lower torque ripple output. The output of speed outer loop is used as the desired torque angle instead of the desired torque in the proposed scheme. The desired stator flux vector in dq coordinate is calculated with a given amplitude. The state-space equations in discrete-time for IPMSM are established, the actual stator flux vector is estimated in deadbeat manner by a full-order state observer, and then the closed-loop control is achieved by the pole placement. The stator flux error vector is utilized to calculate the reference stator voltage vector. Extracting the angle position and amplitude from the estimated stator flux vector and estimating the output torque are eliminated for the direct feedback control of the stator flux vector. The proposed scheme is comparatively investigated with a PI-SVM DTC scheme by experiment results. Experimental results show the feasibility and advantages of the proposed control scheme.

Investigation of Low-Frequency Characteristics of Four-Switch Three-Phase Inverter

Qingwei Yuan,Chong Cheng,Rongxiang Zhao 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.4

The low-frequency characteristics of four-switch three-phase (FSTP) inverter are investigated in this paper. Firstly, a general space vector pulse width modulation (SVPWM) directly involved the neutral point voltage of DC-link is proposed, where no sector identifications and trigonometric function calculations are needed. Subsequently, to suppress the DC offset in the neutral point voltage, the relationship between the neutral point voltage and the β-axis component of the load current is derived, and then a new neutral point voltage control scheme is proposed where no low pass filter is adopted. Finally, the relationship between the load power factor and the maximum linear modulation index of the FSTP inverter is revealed. Since the operational region for the FSTP inverter in low frequency is reduced by the enlarged amplitude of the neutral point voltage, a linear modulation range enlargement scheme is proposed. A permanent magnet synchronous motor with preset rotary speed serves as the low-frequency load of the FSTP inverter. Experimental results verify that the new neutral point voltage control scheme is effective in the deviation suppression of the neutral point voltage, and the proposed scheme is able to provide a larger linear operational region in low frequency.

Investigation of Low-Frequency Characteristics of Four-Switch Three-Phase Inverter

Yuan, Qingwei,Cheng, Chong,Zhao, Rongxiang The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.8 No.1

The low-frequency characteristics of four-switch three-phase (FSTP) inverter are investigated in this paper. Firstly, a general space vector pulse width modulation (SVPWM) directly involved the neutral point voltage of DC-link is proposed, where no sector identifications and trigonometric function calculations are needed. Subsequently, to suppress the DC offset in the neutral point voltage, the relationship between the neutral point voltage and the ${\beta}-axis$ component of the load current is derived, and then a new neutral point voltage control scheme is proposed where no low pass filter is adopted. Finally, the relationship between the load power factor and the maximum linear modulation index of the FSTP inverter is revealed. Since the operational region for the FSTP inverter in low frequency is reduced by the enlarged amplitude of the neutral point voltage, a linear modulation range enlargement scheme is proposed. A permanent magnet synchronous motor with preset rotary speed serves as the low-frequency load of the FSTP inverter. Experimental results verify that the new neutral point voltage control scheme is effective in the deviation suppression of the neutral point voltage, and the proposed scheme is able to provide a larger linear operational region in low frequency.

Performance Analysis and Comparison of Post-Fault PWM Rectifiers Using Various Space Vector Modulation Methods

Zhu, Chong,Zeng, Zhiyong,Zhao, Rongxiang The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6

In this paper, some crucial performance characteristics related to the operational reliability of the post-fault Pulse Width Modulated (PWM) rectifiers, such as line current harmonic distortion, Common Mode Voltage (CMV), and current stress on the capacitors, are fully investigated. The aforementioned performance characteristics of post-fault rectifiers are highly dependent on the utilized space vector modulation (SVM) schemes, which are also examined. Detailed analyses of the three most commonly used SVM schemes for post-fault PWM rectifiers are provided, revealing the major differences in terms of the zero vector synthesis approaches. To compare the performances of the three SVM schemes, the operating principles of a post-fault rectifier are presented with various SVM schemes. Using analytical and numerical methods in the time domain, the performances of the line current distortion, common mode voltage and capacitor current are evaluated and compared for each SVM scheme. The proposed analysis demonstrates that the zero vector synthesis approaches of the considered methods have significant impacts on the performance characteristics of rectifiers. In addition, the advantages and disadvantages of the proposed SVM schemes are discussed. The experimental results verify the effectiveness and validity of the proposed analysis.

Performance Analysis and Comparison of Post-Fault PWM Rectifiers Using Various Space Vector Modulation Methods

Chong Zhu,Zhiyong Zeng,Rongxiang Zhao 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6

In this paper, some crucial performance characteristics related to the operational reliability of the post-fault Pulse Width Modulated (PWM) rectifiers, such as line current harmonic distortion, Common Mode Voltage (CMV), and current stress on the capacitors, are fully investigated. The aforementioned performance characteristics of post-fault rectifiers are highly dependent on the utilized space vector modulation (SVM) schemes, which are also examined. Detailed analyses of the three most commonly used SVM schemes for post-fault PWM rectifiers are provided, revealing the major differences in terms of the zero vector synthesis approaches. To compare the performances of the three SVM schemes, the operating principles of a post-fault rectifier are presented with various SVM schemes. Using analytical and numerical methods in the time domain, the performances of the line current distortion, common mode voltage and capacitor current are evaluated and compared for each SVM scheme. The proposed analysis demonstrates that the zero vector synthesis approaches of the considered methods have significant impacts on the performance characteristics of rectifiers. In addition, the advantages and disadvantages of the proposed SVM schemes are discussed. The experimental results verify the effectiveness and validity of the proposed analysis.

Comparative Study on the Operating Area of M<SUP>3</SUP>C and B2B MMC for Soft Open Point Application

Mengfei Li,Huan Yang,Rongxiang Zhao,Taiying Zheng,Yi Lu,Yong Yang,Caomingzhe Si 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

Back-to-back modular multilevel converter (B2B MMC) and modular multilevel matrix converter (M<SUP>3</SUP>C) are generally considered as two promising topologies used for soft open point (SOP) in medium-voltage distribution network (DN). SOP is utilized to control the power flowing through its grid-tied point and thus its working performance is closely related to the operating area of its topology. In this paper, considering the conditions of DN and limitations of topologies themselves, the steady-state operating areas of B2B MMC and M<SUP>3</SUP>C are calculated and analyzed in detail, which provides theoretical basis for topology selection. After establishing the equivalent circuit model, operating constraints are explored. Finally, the power regulation capacities of the two topologies in different cases are presented intuitively by P-Q graphs. The results demonstrate that B2B MMC has an advantage over M3C in operating area and it is more economical than M<SUP>3</SUP>C for transformerless SOP. The causes are also explained.

Direct Stator Flux Vector Control Strategy for IPMSM using a Full-order State Observer

Yuan, Qingwei,Zeng, Zhiyong,Zhao, Rongxiang The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.1

A direct stator flux vector control scheme in discrete-time domain is proposed in this paper for the interior permanent magnet synchronous motor (IPMSM) drive to remove the proportional-integral (PI) controller from the direct torque control (DTC) scheme applied to IPMSM and to obtain faster dynamic response and lower torque ripple output. The output of speed outer loop is used as the desired torque angle instead of the desired torque in the proposed scheme. The desired stator flux vector in dq coordinate is calculated with a given amplitude. The state-space equations in discrete-time for IPMSM are established, the actual stator flux vector is estimated in deadbeat manner by a full-order state observer, and then the closed-loop control is achieved by the pole placement. The stator flux error vector is utilized to calculate the reference stator voltage vector. Extracting the angle position and amplitude from the estimated stator flux vector and estimating the output torque are eliminated for the direct feedback control of the stator flux vector. The proposed scheme is comparatively investigated with a PI-SVM DTC scheme by experiment results. Experimental results show the feasibility and advantages of the proposed control scheme.

Species resolved interaction mechanism between graphene oxide and Cu(II) in aqueous solution with implications on wastewater remediation

Chaoke Bulin,Ting Guo,Ruichao Zhao,Rongxiang Zheng,Bangwen Zhang,Fang Liu 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.1

Heavy metals discharged into water by industrial activity give rise to severe environmental pollution. Herein, graphene oxide (GO) was prepared based on an improved Hummers method and utilized as adsorbent to remove aqueous Cu(II). The “species resolved” adsorption mechanism was deeply inspected via combining multiple explorations extracted from Cu(II) species distribution, GO surface charge, adsorption experiment and fitting, hard-soft acid-base (HSAB) theory, FTIR and XPS spectra. Different adsorption mechanism resolved by Cu(II) species was proposed, corresponding to different pH range. (1) When pH<8, bare Cu2+ is the dominant Cu(II) species, ion exchange and chemical complexation are the adsorption mechanism. (2) When pH=8, Cu(OH)2 is the dominant Cu(II) species, precipitation, ion exchange and chemical complexation are the adsorption mechanism. (3) When pH>8, Cu(OH) − 3 is the dominant Cu(II) species, electrostatic attraction is the adsorption mechanism. Electron transfer and energy lowering calculated based on the HSAB theory demonstrates, OH is stronger than COOH regarding binding affinity towards Cu(II). As for adsorption efficiency, adsorption of Cu(II) onto GO equilibrated in 12 min, with adsorption percent and quantity 92.32% and 553.90 mg·g−1, respectively. Findings of this work may shed light on the interaction mechanism of graphene oxide with heavy metals. Accordingly, these as clarified mechanisms may provide guidance for developing efficient adsorbent based on graphene for heavy metal scavenging.

A Novel Approach for the Unit Commitment with Vehicle-to-grid

Jin, Lei,Yang, Huan,Zhou, Yuying,Zhao, Rongxiang Journal of International Conference on Electrical 2013 Journal of international Conference on Electrical Vol.2 No.3

The electrical vehicles (EV) with vehicle-to-grid (V2G) capability can be used as loads, energy sources and energy storage in MicroGrid integrated with renewable energy sources. The output power of generators will be reallocated in the considering of V2G. An intelligent unit commitment (UC) with V2G for cost optimization is presented in this paper. A new constraint of UC with V2G is considered to satisfy daily use of EVs. A hybrid optimiza-tion algorithm combined Binary Particle Swarm Optimization (BPSO) with Lagrange Mul-tipliers Method (LMM) is proposed. The difference between results of UC with V2G and UC without V2G is presented.

Fast, <i>In Situ</i> Demagnetization Method for Protection Current Transformers

Zheng, Taiying,Hu, Ende,Yang, Huan,Zhao, Rongxiang,Kang, Yong Cheol,Wall, Peter,Terzija, Vladimir IEEE 2016 IEEE transactions on magnetics Vol.52 No.7

<P>This paper proposes a fast, in situ demagnetization method for protection current transformers (CTs). Simulations show that the method can automatically demagnetize a CT within 300 ms in situ, i.e., while the CT is deenergized but still connected to the substation. Therefore, unlike existing methods that require the CT to be disconnected from the substation, this new method can be used to demagnetize a CT during a short interruption, e.g., the time it takes an autorecloser to operate, rather than requiring an extended outage of the substation. This will dramatically increase the number of opportunities for the demagnetization of protection CTs, which will alleviate the threat of remanent flux in the CT from causing saturation and compromising the performance of power system protection. Furthermore, by demagnetizing the CT in situ, the method avoids the risk of the improper reconnection of the CT, creating a source of hidden failure. The new method uses the existing dc voltage source in the substation to charge the CT and a parallel-connected inductor. An automatic control scheme is presented that manages the charge/discharge of the inductor, and thereby the demagnetization, by controlling three switches that reconfigure an RLC circuit. The additional hardware required by the method is the three switches, the switch controller, and the RLC circuit. The new method is tested for different hysteresis characteristics, levels of remanent flux, and errors in the assumed element parameters and measured hysteresis characteristics using EMTP-RV simulations. The results indicate that the proposed method can quickly and effectively demagnetize a protection CT in situ.</P>