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Title: Dynamic demand for frequency response services in the Great Britain power system
Author: Cheng, Meng
ISNI:       0000 0004 5359 8544
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2014
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Dynamic Demand Technology (DDT) developed by Open Energi Ltd. adjusts the power consumption of demand to react rapidly to changes in grid frequency without undermining the inherent control of loads. In this thesis, DDT is used to regulate the power consumption of domestic refrigerators and industrial bitumen tanks for grid frequency control. The feasibility of the loads to participate in frequency response services is studied. Refrigerators are connected throughout the power system and thus have great potential to be used for frequency control. A frequency controller based on the DDT is applied to refrigerators so that their power consumption varies with frequency deviations autonomously and proportionally. The technique maintains the temperature control of refrigerators and causes little adverse impact on their cold storage of food. A thermodynamic model of refrigerators is developed and validated through field tests on a number of refrigerators at the premises of the Indesit Company. The refrigerator models equipped with frequency control are then integrated into a simplified Great Britain (GB) power system model to investigate their capability for grid frequency control. Results show that the refrigerators change their power consumption in order to reduce deviations of grid frequency. Approximately 500 MW of frequency response is provided by 40 million refrigerators when frequency dropped to below 49.5 Hz. The frequency control is faster than that provided by frequency-sensitive generation. DDT is also applied to bitumen tanks. Frequency control is developed which is similar to refrigerators. A thermodynamic model of bitumen tanks equipped with the frequency control is developed and validated through field tests. The tank models are then connected to the GB power system model to study the capability of industrial heating loads for grid frequency control. Results show that tanks provide frequency control in a manner similar to and faster than that of frequency-sensitive generation. Approximately 72 MW of frequency response is provided by 5,000 bitumen tanks. A participant in the Firm Frequency Response (FFR) service is required to deliver a minimum response of 10 MW. Loads with low power consumption need to be aggregated in order to participate. The availability of refrigerators and of tanks for ABSTRACT ii frequency response varies over a day and is measured through field tests at different times of the day. Based on the measurements of availability, the number of refrigerators and tanks to be aggregated for delivering more than 10 MW of response over a day is calculated. Simulations are carried out with an aggregation of 591 bitumen tank and 622,980 refrigerator models. Results show that more than 10 MW of response is able to be delivered. For the future GB power system, fast control of frequency is required because of the reduction in system inertia caused by the large-scale use of converter connected generation. A case study is carried out to test the impact of the fast control of loads on the frequency of the future power system. Refrigerator models representing 40 million refrigerators and 500 tank models are connected to the GB power system model with reduced system inertia of 3.1 s. Results show that with the use of DDT, the frequency drop after a sudden loss of 1.8 GW generation is halted quickly and the magnitude of the drop reduced significantly (from 1 Hz to 0.4 Hz).
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TK Electrical engineering. Electronics Nuclear engineering