Holomorphic embedding approach for VSC‐based AC/DC power flow

Abstract

With the rapid development of voltage source converter based high‐voltage direct current, power flow analysis becomes increasingly important for AC/DC hybrid systems. This study extends the holomorphic embedding (HE) method to the VSC‐based AC/DC power flow problem. With an appropriate embedding technique, a general embedded model is established for AC/DC power flow with VSCs, which can not only preserve the deterministic property of HE that enables it to derive the desired solution in an explicit manner but also flexibly accommodate various bus types, VSC configurations, control strategies and operating conditions. Moreover, the sparsity of the recursive matrix in power series calculations and the introduction of the iterative calculation of the inverse matrix (ICIM) to rational approximants contribute to the high computational efficiency of the model. The proposed method is shown to be feasible and efficient by illustrative cases and is further extended to multi‐terminal (VSC‐MTDC) configurations to verify its flexibility.

Future Distribution Networks: A Review

“…However, their application to DC networks needs further research. For instance, regarding the Holomorphic Embedding PF method (HE-PFM) [126,127], although the HE-PFM proposed in [128] is for hybrid AC/DC grids, it can solve DC networks as well. Moreover, HE-PFM was considered in [120] for convergence and simulation time comparison.…”

A Review on Applications of Holomorphic Embedding Methods

“…Various HEM-based power flow models introduced before mainly focusing on AC transmission networks. There are papers extending the HEM to other types of power systems such as DC systems [33] , AC/DC systems [55][56][57][58][59] , three-phase distribution networks [60][61][62][63][64] , integrated systems [35,42,65,66] and isolated systems [58,67] . It is important to note that unlike the AC power flow, in which one has to take particular attention to deal with the complex conjugation operation by considering additional independent variables , all voltages variables involved in DC systems [33] are real instead of complex, so is required and satisfied, ensuring that physical solutions are real when is real.…”

“…These converters can be in the form of back-to-back converters or voltage source converters (VSCs). Furthermore, these hybrid AC/DC systems can be operated in both grid-connected mode [55][56][57] , and islanded mode [58,59] . All those features increase complexity to design embedded systems for AC/DC systems.…”

“…In Ref. [56], a systematic HEM-based power flow model is developed for the line-commutated converter based high voltage direct current (LCC-HVDC) system, including various control modes. This study also proposes a computational strategy for efficient Padé approximants using Bauer's Eta algorithm.…”

Power Flow Calculation for AC/DC Power Systems with Line-Commutated Converter–Modular Multilevel Converter (LCC-MMC) Hybrid High-Voltage Direct Current (HVDC) Based on the Holomorphic Embedding Method

“…Reference [23] uses HE formulation for LCC-HVDC power flow calculation and obtaining reliable power flow results. Reference [35] utilizes the HE method to solve power flow problems for VSC-HVDC power systems, considering multi-terminal configurations. However, the application of the HE method in LCC-MMC hybrid HVDC systems is currently limited, highlighting the need for the development of the HE method specifically for hybrid HVDC power flow calculations.…”