Stabilization of a power system with a distributed generator by a virtual synchronous generator function

K. Sakimoto,Y. Miura,T. Ise 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

The power capacity of distributed generators such as photovoltaic and wind turbine is growing, many of distributed generators are connected to a grid by inverters. The inverters are controlled by a PLL (Phase Locked Loop) in order to be synchronized with power system frequency. Power system will become unstable, if the capacity of inverter-connected-type distributed generators becomes larger and larger, because inverter frequency is controlled to follow the grid frequency. The concept of “Virtual Synchronous Generator” (VSG), which is to control inverters to behave like a synchronous generator, has been proposed. VSG has virtual inertia which is realized by an energy storage device to pretend rotor’s inertia. In this paper, the control scheme of VSG is investigated which is based on the swing equation of a synchronous generator. Numerical simulation results show both ride-through capability of voltage dip and enhancement ability of grid stability.

Load Sharing Control of Grid Forming Converter Based on Virtual Synchronous Generator

Chi-Hwan Bae,Hak-Soo Kim,Eui-Cheol Nho 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-

Virtual synchronous generator (VSG) is used to provide virtual inertia to the grid for the compensation of decreasing inertia with the increase of renewable energy. The virtual inertia of VSG can reduce the grid frequency variation in case of the load variation, and the conventional VSG controller contains PLL and droop control. This paper proposes a new control strategy without PLL to simplify the controller, and the proposed controller has the ability of providing both load sharing and inertia to the grid like the conventional VSG. The usefulness of the proposed controller is verified through simulations and experimental results.

A Novel Three-Phase Four-Wire Grid-Connected Synchronverter that Mimics Synchronous Generators

Qian Tan,Zhipeng Lv,Bei Xu,Wenqian Jiang,Xin Ai,Qingchang Zhong 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6

Voltage and frequency stability issues occur in existing centralized power system due to the high penetration of renewable energy sources, which decrease grid absorptive capacity of them. The grid-connected inverter that mimics synchronous generator characteristics with inertia characteristic is beneficial to electric power system stability. This paper proposed a novel three-phase four-wire grid-connected inverter with an independent neutral line module that mimics synchronous generators. A mathematical model of the synchronous generator and operation principles of the synchronverter are introduced. The main circuit and control parameters design procedures are also provided in detail. A 10 ㎾ prototype is built and tested for further verification. The primary frequency modulation and primary voltage regulation characteristics of the synchronous generator are emulated and automatically adjusted by the proposed circuit, which helps to supports the grid.

Current and power quality multi-objective control of virtual synchronous generators under unbalanced grid conditions

Wu, Jian,Liu, Tong,Qiu, Tianyi,Xu, Dianguo The Korean Institute of Power Electronics 2020 JOURNAL OF POWER ELECTRONICS Vol.20 No.2

In recent years, with the large-scale application of distributed power sources in the power grid, the power grid is moving toward low inertia and low damping. The virtual synchronous generator (VSG) has become a hot topic for scholars since it can simulate the moment of inertia, damping and frequency modulation of synchronous generators. Due to its unbalanced load distribution and the random variation of power loads, grid voltage is asymmetrical. Under grid voltage asymmetry, a VSG experiences output current imbalance and power oscillation. The grid current imbalance further reduces the transformer's three-phase voltage, which makes it unequal, cyclic, and very easy to cause electricity accidents. Aiming at this problem, this paper proposes three modes of current balance, reactive power balance and active power balance without changing the characteristics of VSGs. The output current balance and power are constant when the grid voltage is asymmetrical. The effectiveness and feasibility of the control strategy are verified by simulation and experimental results, which provides an effective scheme for balanced and stable operation of the grid.

A Novel Three-Phase Four-Wire Grid-Connected Synchronverter that Mimics Synchronous Generators

Tan, Qian,Lv, Zhipeng,Xu, Bei,Jiang, Wenqian,Ai, Xin,Zhong, Qingchang The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6

Voltage and frequency stability issues occur in existing centralized power system due to the high penetration of renewable energy sources, which decrease grid absorptive capacity of them. The grid-connected inverter that mimics synchronous generator characteristics with inertia characteristic is beneficial to electric power system stability. This paper proposed a novel three-phase four-wire grid-connected inverter with an independent neutral line module that mimics synchronous generators. A mathematical model of the synchronous generator and operation principles of the synchronverter are introduced. The main circuit and control parameters design procedures are also provided in detail. A 10 kW prototype is built and tested for further verification. The primary frequency modulation and primary voltage regulation characteristics of the synchronous generator are emulated and automatically adjusted by the proposed circuit, which helps to supports the grid.

Performance Improvement Strategy for Parallel-operated Virtual Synchronous Generators in Microgrids

Hui Zhang,Ruixue Zhang,Kai Sun,Wei Feng 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.2

The concept of virtual synchronous generators (VSGs) is a valuable means for improving the frequency stability of microgrids (MGs). However, a great virtual inertia in a VSG’s controller may cause power oscillation, thereby deteriorating system stability. In this study, a small-signal model of an MG with two paralleled VSGs is established, and a control strategy for maintaining a constant inertial time with an increasing active-frequency droop coefficient (m) is proposed on the basis of a root locus analysis. The power oscillation is suppressed by adjusting virtual synchronous reactance, damping coefficient, and load frequency coefficient under the same inertial time constant. In addition, the dynamic load distribution is sensitive to the controller parameters, especially under the parallel operation of VSGs with different capacities. Therefore, an active power increment method is introduced to improve the precision of active power sharing in dynamic response. Simulation and experimental is used to verify the theoretical analysis findings.

Performance Improvement Strategy for Parallel-operated Virtual Synchronous Generators in Microgrids

Zhang, Hui,Zhang, Ruixue,Sun, Kai,Feng, Wei The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.2

The concept of virtual synchronous generators (VSGs) is a valuable means for improving the frequency stability of microgrids (MGs). However, a great virtual inertia in a VSG's controller may cause power oscillation, thereby deteriorating system stability. In this study, a small-signal model of an MG with two paralleled VSGs is established, and a control strategy for maintaining a constant inertial time with an increasing active-frequency droop coefficient (m) is proposed on the basis of a root locus analysis. The power oscillation is suppressed by adjusting virtual synchronous reactance, damping coefficient, and load frequency coefficient under the same inertial time constant. In addition, the dynamic load distribution is sensitive to the controller parameters, especially under the parallel operation of VSGs with different capacities. Therefore, an active power increment method is introduced to improve the precision of active power sharing in dynamic response. Simulation and experimental is used to verify the theoretical analysis findings.

A Multi Renewable Source Distribution Network with Dual Adaptive Inertia Replicating Synchronous Generator

Simhachalam Ravada,Das Goswami Agam 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.2

In this paper a dual adaptive inertia module is integrated to static renewable source in a distribution network made to operate as a synchronous generator. For this a 9-bus IEEE network is considered included with renewable modules micro-grid at one of the source buses. The renewable micro-grid is included with PV array, wind farm and BES injecting powers to the grid as per the atmosphere conditions. The wind farm considered is a stand-alone PMSG source with back-to-back converter module. The BES is support to the renewable source PV array and wind farm storing and providing power as per the grid and environmental conditions. A dual adaptive inertia module is introduced into the inverter control of the PV array replicating a synchronous generator making it a VSG. A comparative analysis is done with conventional SRF control and dual adaptive inertia control implemented in the PV array module. The characteristics of the PV array source inverter are analyzed with fault conditions created on the 9-bus IEEE network.

단상 가상 동기기의 성능 개선을 위한외란 관측기 기반 가상 임피던스 구현

허건,박용순 전력전자학회 2024 전력전자학회 논문지 Vol.29 No.2

The performance of a virtual synchronous generator(VSG) depends not only on its inherent parameters, such as inertia and droop coefficients, but also on the output impedance of the inverter. If the output impedance of the inverter is not adequate, the output power of the VSG may fluctuate. In this paper, a method for implementing the virtual impedance based on a disturbance observer(DOB) in a single-phase VSG was proposed. In the proposed method, the output impedance of the inverter can be adjusted by a simple frequency-domain DOB. An output voltage distortion due to the nonlinearity of the inverter was compensated by the DOB. After the basic principle and design method of the proposed DOB were explained, the effectiveness of the proposed method was validated with the hardware-in-the-loop simulation.

Stabilization Control Strategy for Shore Power System with Surge Loads Based on Virtual Synchronous Generator

Wu Cao,Kangli Liu,Sheng Xu,Haotian Kang,Jianfeng Zhao 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.3

The frequent starting of large capacity lifting machines and other surge ship electrical loads will result in severe impacts on a shipboard power network, such as voltage and frequency fl uctuations. Therefore, a novel stabilization control strategy for shore power systems based on virtual synchronous generator is proposed in this paper, so as to improve the power quality and enhance the stability and reliability of shipboard power networks. In this strategy, a reactive power inertia component is embedded into the virtual synchronous generator aiming at shipboard surge reactive powers. On this basis, a voltage and frequency stability control method is presented to improve the static performances of shore power systems. In addition, a d-q decoupling control scheme in synchronous reference frame for the voltage and current double closed-loop control system is designed, and moreover, the infl uence of diff erent feedback voltages on the output characteristics of shore power supplies is studied. The theoretical analysis, simulation and experiment results show that, the proposed control strategy can eff ectively attenuate the frequency and voltage fl uctuations, eliminate the frequency and voltage steady-state errors, as well as realize the power distribution evenly for modular shore power supplies.