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| Impact Analysis of Converter Diversity on System Strength in Multi-Infeed Power System |
| Ma Fuyilong1,2, Xin Huanhai1,2, Li Zhiyi1, Huang Linbin1, Ju Ping1 |
1. College of Electrical Engineering Zhejiang University Hangzhou 310027 China;
2. Zhejiang Provincial Key Laboratory of Renewable Energy Electrical Technology and Systems Hangzhou 310027 China |
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Abstract Renewable energy and other devices are connected to the grid through the power electronic converter. The system voltage support strength (refferd to as “system strength”) characterizes the ability of power electronic converter-based multi-infeed systems (refferd to as “multi-infeed systems”) to resist voltage instability or deviation at nodes after disturbances. However, in most engineering practice and existing research, the system strength is often indirectly characterized from a single grid perspective, with limited investigation into the influence from grid impedance and network topology. In fact, the post-disturbance node voltage response represents a dynamic behavior of the entire system, and conventional methods may overlook the influence patterns of multi-converter characteristics on system strength. Also, existing studies fail to establish generalized impact mechanisms through which multi-converter characteristics influence system strength, due to the complex interactions among multiple converters. These limitations introduce challenges for planning, operation, and source-grid coordination of multi-infeed systems.
To fill this gap, this paper first introduces the concept of converter diversity to describe how differentiated features of multi-infeed converters—including operating power factors, operational states, and grid-following/grid-forming control strategies—affect system strength. Secondly, we review quantification methods for system strength of the multi-infeed system that consider closed-loop dynamic characteristics of multiple converters and the grid, establishing corresponding evaluation metrics for system strength from three analytical dimensions: voltage stability, synchronization stability, and disturbance rejection capability. Furthermore, we comparatively analyze the impacts of uniform versus diversified converter operating conditions and control strategies on system strength metrics across different dimensions. Through mathematical analysis of the evaluation metrics, we analytically demonstrate several enhancement mechanisms by which converter diversity improves system strength. Finally, simulation cases validate the effectiveness of the analytical results.
The key conclusions can be summarized as follows: (1) Implementing diversified power factor settings among grid-following multiple converters enhances system strength in the static voltage stability demension. This configuration provides superior static voltage stability margin in multi-infeed systems when compared to homogeneous power factor operation scenarios. (2) The diversified operation of grid-following multiple converters in hybrid generation-charging modes (e.g., co-deployment of renewable generation and energy storage systems) enhances system strength in the small-signal synchronization stability demension. This operational strategy achieves improved small-signal synchronization stability margins in multi-infeed systems relative to exclusive generation-mode operation paradigms (e.g., pure renewable energy integration). (3) The diversified control schemes of multiple converters in hybrid grid-following and grid-forming modes enhances system strength in the voltage disturbance rejection capability demension. Compared to homogeneous converter configurations, this heterogeneous converter architecture exhibits enhanced operational adaptability, particularly under varying grid conditions.
Future research will focus on investigating the enhancement patterns of system strength through diversity in control parameters and other factors. This will involve developing optimization strategies for practical engineering applications such as configuration of grid-forming equipment in renewable energy stations.
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Received: 02 December 2024
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2025, Vol. 40 
