Optimal Multivariable MMC Energy-Based Control for DC Voltage Regulation in HVDC Applications

Abstract

The penetration of renewable energy resources is changing the way the power system is understood and operated. With an increasing number of power electronics devices integrated into the power system, the MMC is arising as one of the key technologies for HVDC applications. While several control strategies for MMCs have been proposed in the last years, designing controls for MMCs remains a challenging and non-trivial problem due to its large number of degrees of freedom. In this paper, a general multivariable control structure is proposed that generalizes and improves upon previously reported approaches. Moreover, to fully exploit the degrees of freedom offered by this control, a model-based tuning methodology is presented that extends results from optimal H2 structured control design to MMC applications. A case study using an HVDC link is used to illustrate and analyze the performance of the MMC using the proposed approach in different scenarios.

Decentralized Frequency Regulation of Hybrid MTDC-linked Grids

“…4 shows the optimal gains of the H∞ controllers for the GSVSC-and LCC-interfaced grids (i.e., k = 1, 2, and 3) particularly with regard to the measurements from the corresponding grid and the interconnected grids: i.e., Bhk and Dhk for YTk = [Y T Ek Y T Pj] T in Fig. 2 and (18). It represents the extent to which the measurements YTk affect the controller states Xhk and the reference signals rk under disturbed grid conditions.…”

“…Moreover, Fig 5(c) shows the eigenvalue analysis for an increase in Td from 0 s to 0.6 s; for brevity, the delay is assumed to be constant and identical for all decentralized H∞ controllers. Given Td, (18) changes to:…”

“…In [17], a systematic method was provided to design the H∞ controller of a VSC for optimal and robust control of active power and ac voltage. In [18] and [19], H2 and H∞ controllers were discussed to optimally regulate the dc-link voltage and the converter internal energy of an HVDC system, respectively. However, in [16]- [19], robust control was applied to only a single converter; the coordination with synchronous generators and the power sharing between regional ac grids were not considered.…”

Optimal $\mathcal {H}_{\infty }$ Control Design for MMC-Based HVDC Links

“…Moreover, the disturbance rejection capability of the controller is only investigated for the linearization errors and no physical disturbances (such as power or voltage) are considered. Recently, H 2 optimal control has been implemented to compute a twoinput two-output controller for an MMC [33]. The main objective is to improve the dynamics of the DC voltage by exploiting the extra degree of freedom provided by the internal energy of MMC.…”

H ∞-Control of Grid-Connected Converters: Design, Objectives and Decentralized Stability Certificates

“…A fixed-structure current controller based on H ∞ synthesis was developed in [13] to guarantee robust stability and performance for power converters. In [14], an H 2 -optimal tuning method was applied to optimize the PI gains in HVDC systems. In [15], H 2 -optimal design is applied to allocate the virtual inertia of grid-forming and grid-following converters in low-inertia systems.…”