Abstract
Pulse width modulation (PWM) technology is widely used in traction converters for high-speed railways. The harmonic distribution caused by PWM is quite extensive, and increases the possibility of grid–train coupling resonance in the traction power supply system (TPSS). This paper first analyzes the mechanism of resonance, when the characteristic harmonic frequency of a four-quadrant converter (4QC) current that injects into the traction grid matches the resonant frequency of the traction grid, which may result in resonance in the system. To suppress resonance, this paper adopts specific harmonic elimination–pulse width modulation (SHE-PWM) technology combined with a transient direct current control strategy to eliminate the harmonics in the resonant frequency, which may suppress the grid–train coupling resonance. Due to the fact that the SHE-PWM process with multiple switching angles contains complex transcendental equations, the initial value is difficult to provide, and is difficult to solve using ordinary iterative algorithms. In this paper, an active-set secondary optimization method is used to solve the equation. The algorithm has the benefits of low dependence on initial values, fast convergence and high solution accuracy. Finally, the feasibility of the resonant suppression algorithm is verified by means of Matlab simulation.
Highlights
Sinusoidal pulse width modulation (PWM) technology has been used in electrified railway systems for more than 20 years
The third section first gives a brief overview of the basic principles of specific harmonic elimination–pulse width modulation (SHE-PWM), and introduces in detail the specific harmonic elimination strategy based on the multiplex 4QC
In the the 4QC, 4QC,the thecurrent current harmonic distribution at primary the primary side the transformer harmonic distribution at the side of the of transformer can be can be controlled by controlling pulsebetween voltage the between the two-phase bridge using the controlled by controlling pulse voltage two-phase bridge arms usingarms the SHE-PWM
Summary
Sinusoidal pulse width modulation (PWM) technology has been used in electrified railway systems for more than 20 years. There are two main methods by which to suppress grid–train coupling resonance: changing the traction grid impedance, and improving the harmonic current that is injected into the TPSS. The second section of this paper will first introduce the transient direct current control strategy of a four-quadrant converter (4QC), derive a harmonic equation of 4QC, explain the mechanism of the grid–train coupling resonance, and propose a harmonic suppression strategy based on the specific harmonic elimination technique. The third section first gives a brief overview of the basic principles of SHE-PWM, and introduces in detail the specific harmonic elimination strategy based on the multiplex 4QC It presents the solving algorithm of a transcendental equation, and further explains the block diagram of SHE-PWM combined with transient direct current control.
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