Abstract
The potential of variable-speed dish-Stirling (VSDS) solar-thermal generating plant in providing grid frequency support is investigated. In the proposed VSDS frequency support control scheme, the reference speed of the Stirling engine is regulated to track a deloaded power curve which is governed by the solar insolation level. The gain of a supplementary speed-frequency droop controller is then set to meet the primary frequency control requirement. Further uniqueness of the VSDS control scheme pertains to the provision of virtual inertia response by regulating the kinetic energy in the rotating mass of the engine-generator and the thermal energy in the heat absorber/receivers. Small-signal analysis shows that the frequency support scheme is inherently stable, and it will provide higher degree of damping as the penetration level of the VSDS system and/or the solar insolation level increase. The efficacy of the proposed scheme is validated by computer simulation.
Highlights
Global electricity supply systems have undergone unprecedented structural changes due to the ever-increasing penetration of renewable generation, including that of wind and solar
To the best knowledge of the authors, this would be the first reported work investigating the thermodynamic characteristics of the variable-speed dish-Stirling (VSDS) and from which, a coordinated control scheme based on the speed and temperature of the VSDS has been developed, with the aim to explore the potential of primary frequency support and virtual inertia response (VIR) offered by the VSDS system
CASE 2: VSDS SYSTEM UNDER DROOP CONTROL AT VARIOUS INSOLATION LEVEL In this case, the impact of VSDS droop control on the primary frequency support is studied at 0.3 p.u., 0.6 p.u. and 1.0 p.u. insolation levels while ks is kept at 20%
Summary
Global electricity supply systems have undergone unprecedented structural changes due to the ever-increasing penetration of renewable generation, including that of wind and solar. While the economic benefit of the increased energy harness using the VSDS system reported in [11] would be negated somewhat by the cost of the power converter which makes the variable speed operations possible, the VSDS generator permits the independent control of the real and reactive power flows at its terminals This flexibility allows for the stipulated frequency and voltage controls, a performance that is essential to ensure the successful integration of large-scale DS power generation into grid systems [15]. To the best knowledge of the authors, this would be the first reported work investigating the thermodynamic characteristics of the VSDS and from which, a coordinated control scheme based on the speed and temperature of the VSDS has been developed, with the aim to explore the potential of primary frequency support and VIR offered by the VSDS system.
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