Junho Park

Interaction analysis model for transmission static compensator with EMTP

This paper describes the controller design for a static VAr compensator with mathematical analyses, and simulation model development with EMTP to analyze its dynamic interaction with the AC transmission system. The main circuit was modeled by a 12-pulse voltage source inverter with ideal gate turn-off switches, and the signal generation and control circuit was modeled using TACS in EMTP. The effects of increasing transmission capacity, damping low-frequency oscillation and improving transient stability were verified with the model developed, assuming that the static condenser is connected to the 154 kV line for a typical one-machine-infinite-bus transmission system.

Static synchronous compensator using thyristor PWM current source inverter

Summary form only given as follows. This paper describes a static synchronous compensator using a thyristor PWM current source inverter. The proposed system consists of a 3-phase thyristor bridge with a commutation circuit, a DC reactor; and AC filter capacitors. The 3-phase thyristor bridge operates os a current source PWM inverter with assistance of commutation circuit. The system operation was verified in detail through computer simulations with EMTP, and experiments with a scaled hardware model. The proposed system has two advantages of low switching loss and easy expansion of operation voltage through series connection of thyristors.

Dynamic characteristic analysis of multi-bridge PWM inverter for SSSC

This paper proposes a static synchronous series compensator (SSSC) based on multi-bridge inverters in a PWM scheme. The dynamic characteristics of the proposed SSSC was analyzed by simulation with EMTP codes, assuming that the SSSC is inserted in the transmission line of a one-machine-infinite-bus power system. The proposed SSSC has 6 H-bridge inverter modules per phase, which generates 13 pulses for each half period of power frequency. The proposed SSSC generates a quasi-sinusoidal output voltage by 90/spl deg/ phase shift to the line current. The proposed SSSC can be directly inserted in the transmission line without coupling transformers, and has flexibility in expanding the operation voltage by increasing the number of bridges in series connection.

Periodicity of the Lorenz–Stenflo equations

In this paper, we investigate periodic behaviors of the Lorenz–Stenflo equations in wide ranges of parameters. Regimes of periodic solutions and chaotic solutions are computed and distinguished by local maximum values of a dynamic variable Z. Complex behaviors of the periodic solutions are observed inside a regime of the chaotic solutions which is closed and surrounded by a regime of the periodic solutions where a feature of disconnected bifurcations is observed. It is found that not only a regime of fixed solutions but also regimes of solutions with period 1 and 2 remain for sufficiently large parameters.

Stability and periodicity of high-order Lorenz–Stenflo equations

In this paper, we derive high-order Lorenz–Stenflo equations with 6 variables and investigate periodic behaviors as well as stability of the equations. The stability of the high-order Lorenz–Stenflo equations is investigated by the linear stability analysis for various parameters. A periodicity diagram is also computed and it shows that the high-order Lorenz–Stenflo equations exhibit very different behaviors from the original Lorenz–Stenflo equations for both periodic and chaotic solutions. For example, period 3 regime for large parameters and scattered periodic regime are newly observed, and chaotic regimes exist for smaller values of r but for larger values of s than the original equations. In contrast, similarities such as the enclosure of the chaotic regime by the periodic regime or complex periodic regimes inside the chaotic regime are also observed for both the original and high-order Lorenz–Stenflo equations.

Periodic and Chaotic Dynamics of the Ehrhard–Müller System

This paper investigates nonlinear ordinary differential equations of the Ehrhard–Muller system which describes natural convection in a single-phase loop in the presence of nonsymmetric heating. Stability and dynamics of periodic and chaotic behaviors of the equations are investigated and the periodicity diagram is obtained in wide ranges of parameters. Regimes of both periodic and chaotic solutions are observed with complex behaviors such that the periodic regimes enclose the chaotic regime while they are also immersed inside the chaotic regime with various shapes. An asymptotic analysis is performed for sufficiently large parameters to understand the enclosure by the periodic regimes and asymptotic limit cycles are obtained to compare with limit cycles obtained from numerical results.

Periodicity and Chaos of High-Order Lorenz Systems

High-order Lorenz systems with five, six, eight, nine, and eleven equations are derived by choosing different numbers of Fourier modes upon truncation. For the original Lorenz system and for the five high-order Lorenz systems, solutions are numerically computed, and periodicity diagrams are plotted on (σ,r) parameter planes with σ,r ∈ [0, 1000], and b = 8/3. Dramatic shifts of patterns are observed among periodicity diagrams of different systems, including the appearance of expansive areas of period 2 in the fifth-, eighth-, ninth-, and 11th-order systems and the disappearance of the onion-like structure beyond order 5. Bifurcation diagrams along with phase portraits offer a closer look at the two phenomena.