Passive AC network supplying the integration of CCC-HVDC and VSC-HVDC systems

Abstract

Abstract:The integration of a capacitor-commutated converter (CCC) high-voltage direct current (HVDC) (CCC-HVDC) and voltage source converter (VSC) HVDC (VSC-HVDC) is proposed in this paper to supply entirely passive AC networks. The key point of this integration is the flat characteristic of the DC voltage of the CCC-HVDC, which provides the condition for the VSC to connect to the CCC DC link via a current regulator. The advantages of the proposed combined infeeding system are the requirement of only one DC line, and better dynamic responses. The structure of the proposed infeeding system, as well as its control system, is studied. Simulation results are provided to validate the effectiveness of the proposed system and its control strategy. Two other schemes for infeeding AC passive networks are studied to demonstrate the advantages of the proposed system.

Adaptive sliding mode with time delay control based on convolutions for power flow reference tracking using a VSC-HVDC system

“…(11), the term ∆P = P s − P r represents the DC link control and P loss is considered as a disturbance that is assumed to be unknown. Since the dynamics of the DC link is linear and relatively slow, a conventional PI controller can be used to regulate DC voltage U C2 to its rated value U C2ref and reject external disturbances P loss [6][7][8][9][10][11][12][13][14][15][16], as shown in Figure 5. …”

“…Figure 4 represents a schematic diagram of the DC subsystem (DC link), where R dc , L dc , and i dc are its resistance, inductance, and current, respectively [11][12][13][14][15][16][17][18]. P 1 and P 2 refer to real powers on both sides of the converters, as shown in Figure 4.…”

“…We intend to develop a state feedback control that forces the system to track a nonconstant reference current 2154 X ref (t) in the presence of plant uncertainties and external disturbances that unavoidably affect the state space model Eq. (5) [6][7][8][9][10][11][12][13][14][15][16].…”

“…Its various capabilities have been discussed in many papers in areas of power flow control [6][7][8], transient stability improvement, and oscillation damping control [9,10]. Furthermore, in the literature, the HVDC transmission system has been applied in a vast variety of control system investigations, including PI control [11][12][13][14], H ∞ approach method [15], linearization control [11], sliding mode control [16,17], backstepping design [18,19], flatness theory-based control [20], and passivity theory-based control [21,22]. All the aforementioned methods, including linear and nonlinear controllers, guarantee asymptotic stability of the closedloop system.…”

A novel control method for a VSC-HVDC system in a grid-connected wind farm

“…Currently, many studies on VSC-HVDC control strategies have been published, but most are based on ideal conditions with AC voltage balanced [3][4][5][6][7][8][9]. The control strategy for VSC-HVDC when AC power is unbalanced is researched less often.…”