Chen Jianye

Compensation for the negative-sequence currents of electric railway based on SVC

As a classic unbalanced load, the traction engines of the electric railways result in negative-sequence currents(NSC) in power systems, which cannot be ignored in most cases. SVC is considered as an effective method to reduce or even eliminate NSC, as well as some other power quality problems, such as reactive power compensation. Calculation formulae of NSC of two kinds of transformers are formed firstly in this paper. Then the mechanism of NSC compensation by SVC is discussed. Simulations by PSCAD of the system are followed. The results show that SVC is efficient to compensate NSC.

STATCOM modeling and analysis in damping power system oscillations

In this paper, we discuss the single-machine infinite-bus system with one static synchronous compensator (STATCOM) asymmetrically installed as a current source. Together with a classical two order generator model, a simple power equation is drawn to give direct and clear physical concepts on synchronizing and damping torque coefficients. On the basis of the equations, some basic issues, such as the relationship of voltage gain control and damping control, operating conditions and installation of STATCOM, are investigated by detailed theoretical analysis. Then with proportional controller for voltage and damping control, the digital simulation proves the necessity of multi-objective control of STATCOM in damping power system oscillations and supplying fast voltage support. Finally, nonlinear simulation demonstrates how STATCOM improves the power transfer ability of the system after a severe fault.

Study on the Control of Shunt Active DC Filter for HVDC Systems

A shunt active dc filter (ADF) has been applied in high-voltage dc transmission systems for harmonic suppression. Some key problems in the design of ADF control systems have not been investigated thoroughly due to high harmonic frequency and the complexity of system modeling. In this paper, a high-gain feedback control strategy is proposed, which is independent of circuit parameters. The authors draw a comparison between the harmonic suppression effects of ADF and that of a passive filter and prove that the former can increase the series impedance of the hybrid filter, while the latter can decrease the equivalent voltage. Based on circuit analyses, solutions, such as selection of the dc-side voltage, regulation of the modulation index, system stability conditions, filter design, and switching noise are presented. The consistency between theory analyses and experimental results verifies the feasibility of the proposed control strategy.

A Measuring Method of the Single-Phase AC Frequency, Phase, and Reactive Power Based on the Hilbert Filtering

This paper presents a novel measuring method based on the Hilbert filtering for the digital monitoring of the single-phase ac frequency, phase, and reactive power. According to this method, the sampled voltage signal passes a pair of the Hilbert filters. Then, the ac frequency and phase can be obtained by the phase detection and the phase-locked loop algorithm. Additionally, the sampled current signal also makes its phase shift by the other Hilbert filter. The current output is multiplied by the one of the phase-shifted voltage signals, and the reactive power is acquired from the dc component of the product. Because a type of infinite impulse response (IIR) Hilbert filters with low-order and small phase-shift error is adopted, this measuring method cannot only obtain fast and accurate digital monitoring results but also be easily realized with the DSP or other microprocessor programming codes. This method has been successfully applied in the design of a digital multifunctional power instrument

Harmonic detection method for HVDC DC-side active power filter

One of the most critical issues associated with APF control is to find an efficient algorithm that can obtain an accurate harmonic reference signal for control purpose. This paper presented two novel methods of the harmonic detection in an advanced active power filter (APF) for the compensation of instantaneous harmonic current components in high voltage direct current (HVDC) transmission system. One is based on the ameliorated adaptive noise canceling theory and the other is grounded on mean value filtering method. The two methods are implemented on TMS320C32 DSP system. Both of them can efficiently determine the instantaneous harmonic reference signal in real time. The validity of two algorithms is substantiated via simulations and experiments.

The active DC filter in HVDC resolved by the multiple PWM inverters

Because the environmental demand is becoming stricter and stricter, more and more attention should be paid to the harmonic problem in high-voltage direct current (HVDC) transmission systems. This paper details the principle of active DC filter applied in the HVDC system. It is clearly stated that the contradiction between the switching frequency of power switch and the high frequencies of harmonics in the DC side of HVDC is the main bottle-neck for the application of ADF. Multiple pulse width modulation (PWM) can increase the equivalent switching frequency, decrease the stress on switch and improve the performance of ADF in high frequency. Both results of simulations and experiments validate the proposed multiple PWM.

Research on the magnetic valve thyristor controlled reactor

The magnetic valve thyristor controlled reactor (MVTCR) is presented and its configuration and working principle are described in this paper. It is set up for the mathematical models based on equivalent electrical circuit and magnetic circuit by using an analytical method to calculate steady-state characteristics. The characteristics of the reactor are shown by numerical simulations. Some interesting features of MVTCR are revealed in the paper. As an example, model tests of a prototype of 1 kVA, 0.4 kV reactor are performed to support the theoretical results.

A Digital Controller of Hybrid Filter Based on Pseudo-Inverse Filtering Technique

A new digital controller of hybrid passive-active power filter which employs pseudo-inverse filtering control strategy is discussed in this paper. The proposed controller is composed of a bank of digital selective frequency band-pass filters, phase-shifters and amplifiers that are implemented in TMS320C32 DSP. Digital band-pass filters employs IIR algorithm to extract the corresponding harmonic components to be canceled, and then the signals are conditioned according to the magnitude and phase distortion caused by the passive filter to reconstruct the harmonic signals to be eliminated. The results of both simulations based on EMTDC/PSCAD and experiments on a 30 kVA library HVDC system validate that the digital controller can ensure the good performance of hybrid filter stably

Harmonic cancellation for HVDC using a novel control scheme

How to eliminate harmonics is one of the key technologies of high-voltage direct current (HVDC) transmission systems. In order to cancel harmonics, hybrid filters, consisting of passive filter (PF) and active power filter (APF), are employed in some recent projects. This paper proposes a novel scheme, which can take full advantage of passive filter, which is good at canceling low frequency harmonics with large power and active power filters, which is good at canceling high frequency harmonics with less power. What is more, the scheme can reduce the requirement of additional DC source in the DC part of active power filter and achieve expected effect.

Automatic inspection of the localizer slope based on improved Hough transform

In light of the present situation of inspecting slope of localizer with less accurate and low efficiency, the novel method of automatic inspection based on computer vision was proposed. This paper introduced the hardware structure for image acquisition in the automatic inspection system, and analyzed the technologies used in image processing. Otsu threshold segmentation, eliminate noise and thinning were used in image pretreatment to enhance image quality and to improve inspecting precision; an improved Hough transformation was brought forward to detect lines and calculate the slope of the localizer. The proposed approach not only has high precision, but also accelerates the compute speed. The experimental result shows that this algorithm is validate.