The position and speed estimation performance of the sliding mode observer (SMO) for permanent magnet synchronous motor (PMSM) drives under low carrier ratio degrades, due to the inherent chattering ...and enlarged control delay. To improve estimation performance, this paper proposes a quasi-proportional-resonant (QPR) based adaptive observer to obtain back electromotive force with adaptive harmonics cancellation. In this observer, the QPR controller is employed to eliminate errors between the observed currents and the actual ones in the αβ reference frame, replacing sign function and low pass filter (LPF) of the SMO to cancel the chattering, and harmonics immune performance can also be achieved thanks to frequency selection characteristic of the QPR controller. Besides cancelling the chattering, the proposed observer can also eliminate phase shift produced by the LPF, since the QPR controller is a zero phase-shift amplifier at the resonant frequency. Comparative experiments are carried out in a 3-kW PMSM drive, and the results validate the effectiveness of the proposed adaptive position observer.
•A novel control method is proposed for NF, QPR and LPF based on dual-loop control.•This method improves the suppression effect of secondary harmonic current (SHC).•This method also improves ...anti-load mutation ability.•SHC suppression effect and dynamic response of four control methods are analyzed.
The instantaneous output power of the energy storage system pulsates at twice the output voltage frequency, generating a large amount of secondary harmonic current (SHC) in the switching tubes and batteries. The SHC is harmful to the system performance and battery life. Firstly, through the analysis of traditional dual-loop (DL) control method, it is concluded that SHC is not suppressed obviously and the dynamic characteristics of the system is inferior when load hopping. To address these two questions, a novel control method is proposed for introducing notch filter (NF), quasi-proportional resonator (QPR) and load power feedforward (LPF) based on DL control (it can be abbreviated as NQLDL). This method increases the amplitude of the inductor branch equivalent impedance (IBEI) at twice the output frequency without changing the frequency adaptability, improves the suppression effect of SHC, reduces the amplitude of the IBEI outside of twice the output frequency and also improves anti-load mutation ability. Furthermore, the SHC suppression effect and dynamic response are also discussed under four control methods. Finally, the validity of proposed control methods are demonstrated by experimental results.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A grid-connected inverter (GCI) with LCL filters is widely used in photovoltaic grid-connected systems. While introducing active damping methods can improve the quality of grid-connected current ...(GCC), the influence of grid voltage disturbances can still significantly impact the quality of GCC, leading to stability degradation, especially in weak grid conditions. This paper proposes a grid-voltage-weighted feedforward control scheme based on the quasi-proportional resonance (QPR) controller. This scheme introduces compensatory terms with different proportional coefficients in the voltage feedforward, controlled by the QPR controller. Through a series of analyses, reasonable inverter parameters are first designed. Then, the proposed system model is built in Matlab Simulink. Through simulation experiments and comparisons with various types of operating conditions, the effectiveness of the proposed system scheme is validated. It minimizes the impact of grid voltage disturbances, suppresses the influence of grid harmonics on the control system, improves current quality, and enhances the stability of the GCI system.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
When the interior permanent magnet synchronous motor drive system is affected by both dc and ac disturbances, the estimation error of ac disturbance cannot be converged to the steady-state value by ...the traditional linear extended state observer (T-LESO). At the same time, the tracking and antidisturbance ability of the traditional linear active disturbance rejection controller(T-LADRC) to dc disturbance is insufficient due to the influence of observer bandwidth frequency. To solve the above-mentioned problems, an improved LADRC combining a quasi-proportional resonance (QPR) controller and disturbance differential compensation LESO is proposed in this article. In this controller, the linear state error feedback in the T-LADRC is replaced by QPR, so that the ac disturbance to the system can be effectively suppressed. Based on T-LESO, the derivative of the disturbance is introduced, whose estimation range of LESO for dc disturbance is broadened without increasing the observer bandwidth, thereby avoiding system oscillation caused by excessive observer bandwidth. Finally, the validity and availability of the proposed method are proved through theoretical analysis and experiment.
Based on partial power conversion concept, this article proposes a hybrid silicon carbide (SiC)-silicon (Si) dc-ac topology to improve performance in high power application. First, master unit (MU) ...uses Si-IGBT working in low frequency to handle main high power because of its high rated current capacity and high switching loss, whereas the low power quality of MU is induced by the low switching frequency. And SiC-MOSFET suffers from high cost and high conduction loss at high power level. To solve these problems, the partial-power slave unit (SU) based on SiC-MOSFET is connected with MU in series through line-frequency transformer, whereas SU works in high frequency to compensate the harmonic of MU and adjusts the total output voltage. In this new topology, the corresponding hybrid modulation strategy and multiple quasi-proportional-resonance control for single-phase system are introduced in detail to ensure the reliable operation. In the end, a 4.5-kW converter prototype was implemented and tested. Simulation and experiment results are given to verify the performance of the proposed hybrid dc-ac topology.
Suicide has been labeled a public health crisis. Training students in suicide prevention has been recommended. The objectives of this study were 1) test confidence and knowledge change associated ...with student pharmacists undergoing a discussion session led by a psychiatric pharmacist followed by Question Persuade Refer (QPR) training and 2) assess student feedback on the sessions.
Second-year student pharmacists attended discussion sections led by a psychiatric pharmacist and participated in QPR training as part of a 6-week Neurology-Psychiatry Integrated Pharmacotherapy course. Anonymous pre and post surveys were used to evaluate the program for changes in confidence and knowledge using independent sample t-tests. Likelihood to intervene and likelihood to seek additional training were measured and used as dependent variables in logistic ordinal regression models. Open-ended responses were coded using a descriptive qualitative content analysis approach.
All 111 students responded to both pre and post surveys. Students showed significant improvements in their confidence (p < 0.01) and knowledge (p < 0.01) related to suicide prevention. Three-quarters of students (73.0%) reported being very or extremely likely to intervene the next time they see warning signs of suicide. Confidence was significantly associated with future likelihood to intervene (p = 0.02). Students were interested in more examples, including video examples.
This educational intervention pairing engagement with a psychiatric pharmacist and training in QPR was associated with significant increases in confidence and knowledge scores related to suicide gatekeeping. The analysis showed a positive association between confidence and likelihood to intervene with persons with suicide warning signs.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In the single-phase photovoltaic (PV) grid-connected distributed generation (DG) system located at the end of the feeder, it is necessary to provide quickly active and reactive power to the local ...loads. In this paper, an improved reactive current detection and power control method are proposed to realize active power control and reactive power compensation. To detect quickly the loads reactive current, a fast reactive current detection method using the derivative and i p -i q algorithm is presented, and it can overcome the long delay in a conventional phase-shift method. In the inner current loop, the quasi-proportional-resonant (QPR) control method with grid voltage feed-forward is presented to control accurately the grid current with zero steady error, and to reduce the current distortion due to the frequency offset and distortion of the grid voltage. The inner loop stability is analyzed, and the proper parameters are selected. In the outer loop, proportional-integrator (PI) controller is applied to stabilize the dc-link voltage, and power feed-forward is introduced to speed up system response. Simulation and experimental results verified the validity of the proposed control method.
Power factor correction (PFC) converter suffers from serious double-line-frequency output voltage ripple due to the difference between instantaneous ac input power and dc output power. To suppress ...such double-line-frequency output voltage ripple, a ripple cancellation circuit (RCC) is utilized to generate the same magnitude but 180° phase shifted double-line- frequency voltage ripple. This paper provides an insight into the relationship between control scheme and double-line-frequency ripple suppression from the perspective of audio susceptibility model. For the purpose of reducing the double line frequency ripple, the closed-loop audio susceptibility of series RCC should be designed relatively low at double line frequency. According to such requirement, a ripple controller with improved voltage feed-forward (FF) scheme and quasi-proportional-resonant (QPR) compensator is designed. As QPR compensator can increase the denominator of the closed-loop audio susceptibility, while voltage FF scheme can reduce its numerator, its magnitude at double line frequency is thus greatly reduced and double-line-frequency ripple is also significantly suppressed. Moreover, due to the flexibility of QPR compensator, the proposed ripple controller presents good ripple suppression in a different line frequency application. Finally, experimental results of a flyback PFC with buck-type RCC quasi-single-stage ac-dc converter are provided to verify the validity of the proposed ripple controller.
This paper proposes a discrete-time fuzzy fractional-order sliding-mode control (Fuzzy-FOSMC) dual loop current controller for a three-phase LCL-type grid-connected converter (GCC) with reduced ...order. Conventional sliding-mode control (SMC) has been widely used in GCC due to its robustness to disturbances. However, the chattering in SMC may reduce the tracking performance of the controller, and even lead to system instability. To solve this problem, a Fuzzy-FOSMC controller is proposed in this paper. The introduced fractional-order term can suppress the chattering, and the fractional-order of FOSMC is further adjusted by the fuzzy controller to improve the overall system performance. In addition, the inner loop is implemented by a Fuzzy-FOSMC controller to ensure the tracking of the converter-side current, making the LCL-GCC converter behave like a controllable current source converter with a capacitive-inductive filter, the grid current control problem falls from a third-order to a reduced order system, which solves some difficulties on the design of most controller types. The stability of the two-stage PV system is analyzed. Finally, the effectiveness of the proposed controller is verified by experiments.
•A FOSMC controller is proposed for converter-side current tracking control, which makes the converter to behave like a current source inverter with a CL filter. Compared with existing methods, it exhibits great advantages in current convergence speed, steady-state tracking error, robustness to filter parameter variations and dc-bus voltage changes.•To increase the system robustness, based on the fixed parameters of the FOSMC, a fuzzy controller is designed to adjust the fractional order of FOSMC, which could greatly suppress the chattering in conventional SMC.•By establishing the small signal model of the PV LCL grid connected inverter, the matrix of the overall linear state equation of the PV system including MPPT is obtained, and the stability analysis of the PV system is realized.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
