Jinbang Xu

An LTCL Filter for Three-Phase Grid-Connected Converters

This paper presents a new high-order filter for three-phase grid-connected voltage source converters (VSCs) named the inductor-trap-capacitor-inductor (LTCL) filter, in which multiple LC trap filters are inserted in parallel with the branch of the capacitor in the traditional LCL filter to compose multiple series resonant circuits at the selected frequencies. Particularly, the LTCL filter can attenuate the harmonic currents around the multiples of switching frequencies and guarantee -60 dB/decade attenuation in the high-frequency band, leading to a decrease of the total inductance and volume. Furthermore, within half of the switching frequency range, an LTCL -filter-based grid-connected VSC has almost the same frequency-response characteristic as that with the traditional LCL filter. That is to say, the LTCL filter does not bring any extra control difficulties. The basic parameter selection criteria and the parameter design procedure of the LTCL filter are introduced. Moreover, the sensitivity analysis of the LTCL filter is analyzed and discussed in detail. The comparative analysis and discussion considering the LCL filter, the LLCL filter, the multituned traps filter, and the proposed LTCL filter, have been presented and evaluated through the experiments on a 65-kW three-phase grid-connected VSC prototype.

ANN Based on IncCond Algorithm for MPP Tracker

In photovoltaic (PV) generation systems, to get the maximum of the solar output power is the essential part to raise the efficiency of the whole system. A new Artificial Neural Network (ANN) based algorithm for Maximum Power Point Tracking (MPPT) has been proposed in this work. By using the duty ratio data generated from the finest results of the traditional Incremental Conductance (IncCond) method as the neural network training data, and building the DC-DC boost tracker to test it in Saber simulation software, the simulation results are shown to clarity the effectiveness of the proposed method.

Systematic Design of the Hybrid Damping Method for Three-Phase Inverters With High-Order Filters

High-order filters (HO-filters) such as LCL-LC-filters have recently drawn attention to their small size and better attenuation to switching harmonics than LCL -filters for three-phase inverter grid interfaces. Hybrid damping that combines passive damping and active damping is an effective method to suppress HO-filter resonances. However, due to the high-order characteristic of the system, the tuning procedure for the parameters of hybrid damping is complicated. Hence, an equivalent circuit analysis method is proposed in this paper to accurately simplify the model of the HO-filter. Based on this, a systematic step-by-step design method for HO-filter-type grid-connected inverters with hybrid damping has been proposed. The passive losses, effects of equivalent series resistances (ESRs) and robustness against grid impedance variation have been studied. Compared with existing design procedures, the proposed method makes the hybrid damping more reliable by locating appropriate position for closed-loop resonant poles. Experimental results verify the proposed systematic design procedure.

Initial rotor position estimation and sliding preventing for elevators with surface-mounted PMSMs

Improved methods of initial rotor position estimation and sliding prevention are presented in this paper for elevators with surface-mounted permanent magnet synchronous machines (SPMSMs). In contrast to most of the existing literature, in this paper, estimation errors caused by stator resistance and dead time are analysed in detail. The improved estimation method can reduce the errors greatly without dead-time compensations and knowledge of motor parameters. Besides, an observer-based feedforward compensation of load torque is introduced to elevator applications to prevent sliding during the starting process. Since the torque observer is widely used in other motor applications, we focus on the impact caused by the change in inertia. Finally, a series of experiments are performed on a testing system with two 13.4 kW SPMSMs and drivers to illustrate the effectiveness and improvement of the method.

An Improved Phase Disposition SPWM Strategy for Cascaded Multilevel Inverter

The Carrier Phase Shifted (CPS) strategy is conventional for cascaded multilevel inverter, because it can naturally ensure all cascaded cells to output balanced power. However, in point of spectra of the output line voltage, CPS is suboptimal to Phase Disposition (PD) strategy, because the latter can not naturally ensure power balance. This paper presents an improved PD strategy, inspiration from the disposition of CPS strategy triangle carriers. Just reconstructing the triangle carriers of PD strategy, it can not only reserve the waveform quality of the line voltage to be optimal, but also naturally ensure the output power of each cascaded cells to be balanced.

Research of a self-tuning algorithm for industrial micro-grid power conversion

With more and more attention on the grid current harmonic in recent years, many control schemes of the Pulse Width Modulation Voltage Source Converter PWM-VSC have been investigated. Conventional PI controller has limitations in sensitivity subject to load and system parameter variation. Even the stability of the system can be threatened under a large and sudden load change. In this paper, the practical situation of a VSC for industrial Micro Grid MG is considered and an Artificial Neural Network ANN based control method is employed to solve the problem. Meanwhile, an online parameter tuning algorithm is introduced for its advantage of self-tuning and system character identification. The proposed control scheme is verified through simulation and prototype experiment. The experiment is performed to demonstrate the advantages of the proposed controller under different situations.

Echo State Networks Based Method for Harmonic Extraction in Shunt Active Power Filters

With the wide use of power conversion devices, harmonic currents are being injected into the power grid. Shunt Active Power Filters (SAPF) is a power electronic device to compensate the harmonic currents caused by nonlinear loads. As the foundation of the harmonics recognition and compensation, harmonic extraction techniques are becoming more and more important. This paper proposes a new harmonic extraction method based on the Echo State Networks (ESN). ESN is a new type of Recurrent Neural Networks (RNN), which has much faster training speed than other types of RNN. To evaluate the dynamic system modeling capability of the ESN, the ESN with different dynamic reservoir size are discussed. The performance of the ESN based harmonic extraction method is compared with traditional methods and method based on multilayer perceptron networks (MLP). The ESN algorithm is trained and tested in MATLAB.

ANN-based Control Method Implemented in a Voltage Source Converter for Industrial Micro-grid

With more and more attention on the grid current harmonic in recent years, many control schemes of the Pulse Width Modulation Voltage Source Converter (PWM-VSC) have been investigated. Conventional PI controller has shown limitations such as sensitivity to load and system parameter variation. Even the stability of the system can be threatened under a large and sudden load change. In this paper, the practical situation of a VSC for industrial Micro Grid (MG) is considered and an Artificial neural network (ANN) based control method is employed to solve the problem. Meanwhile, an on-line parameter tuning algorithm is introduced for its advantage of self-tuning and system character identification. The proposed control scheme is verified through simulation based on SABER software. The simulation results have shown the advantage of the proposed method and the performance of the parameter tuning session.

Switching ripple suppressor design of the grid-connected inverters: A perspective of many-objective optimization with constraints handling

Abstract Conventional switching ripple suppressor design methods require the domain expert to tune the design parameters, which is attributed to the multiple and complicated performance requirements and real-world restrictions in switching ripple suppressor design. However, the expert tuning method is time-consuming and inefficient, and the designed switching ripple suppressors under the given topology can only achieve a barely satisfactory performance which can be far from the optima. In this study, we propose a systematic design method from the perspective of many-objective optimization with constraints handling for high-performance switching ripple suppressor design. Meanwhile, an inductor-trap-inductor-capacitor-inductor (LTLCL) switching ripple suppressor is proposed for attenuating the harmonic currents around the multiple switching frequencies and guaranteeing − 60 dB/decades attenuation in the high-frequency bands. In the proposed design method, the LTLCL switching ripple suppressor design problem is treated as a many-objective optimization problem with constraints, and an evolutionary algorithm is designed to solve this problem, furthermore, a general decision making method is used to select the final design scheme. Experimental results have verified the admirable performance of the proposed switching ripple suppressor and the effectiveness of our design method.

A Combining FPE and Additional Test Vectors Hybrid Strategy for IPMSM Sensorless Control

This paper proposes a hybrid strategy by combining fundamental pulsewidth modulation excitation (FPE) and additional test vectors, which is used in interior permanent-magnet synchronous motor (IPMSM) sensorless control. In contrast to the typical indirect flux detection by on-line reactance measurement-based methodology where the rotor position is calculated and updated in every three successive pulsewidth modulation (PWM) cycles, the proposed hybrid strategy can achieve the one-cycle acquisition of the rotor position by utilizing both response currents of FPE and additional test vectors, which makes the proposed strategy more robust and suitable in higher speed or load sudden change conditions. Meanwhile, a new PWM scheme for four-space-vector PWM (FSVPWM) is presented, which sharply simplifies the implementation process. Furthermore, for the case that the amplitude of the object fundamental voltage is so small that it cannot satisfy minimum time demand for the slopes of response currents sampling, a compensation technique is presented. In addition, the multiple-point current sampling (MPCS) technology and linear least square fitting method are used to decrease the current sampling disturbance, which improves obviously the accuracy of position estimation. Finally, the experimental results confirm that the proposed strategy can obtain the rotor position accurately and simply.