Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Doctor of Philosophy

Program

Electrical and Computer Engineering

Supervisor

Varma, Rajiv K.

Abstract

Induction motors are globally used in several critical operations such as petrochemicals, mining, process control, etc., where their shutdown during faults causes significant financial loss. System faults can also lead to Fault Induced Delayed Voltage Recovery (FIDVR) causing service disruptions. Dynamic reactive power compensators such as SVC and STATCOM are conventionally employed to mitigate these issues, however, these are very expensive.

PV solar plants are growing at unprecedented rate globally and are likely to be installed near such critical motors. This thesis presents several novel applications of a patented technology of utilizing PV solar plants, both during night and day, as STATCOM, termed PV-STATCOM, for mitigating above issues at about 50 times lower cost than equivalent-size STATCOMs.

A reactive power modulation based PV-STATCOM control is developed to stabilize remotely located motor both during night and day in a realistic distribution feeder, even when reactive power support according to the pioneering German Grid code fails. This control was field demonstrated for first time in Canada (and perhaps in world) on the 10 kW PV solar system in the utility network of Bluewater Power, Sarnia, Ontario.

Another novel control strategy based on active and reactive power modulation of PV-STATCOM is developed. MATLAB/PSCAD simulation studies show that the proposed control can stabilize remotely located motor much faster and with reduced real power curtailment than conventional strategies.

A new real and reactive power control of PV-STATCOM is proposed to alleviate FIDVR. Electromagnetic Transients simulation studies on a realistic transmission network show that the proposed control on a 100 km remote solar farm can alleviate FIDVR and stabilize a cluster of motors for wide range of system parameters and operating conditions. PV-STATCOM can alleviate the need of local STATCOM for achieving the same objective.

Comprehensive sensitivity and stability analysis of single and two distribution level PV-STATCOMs are performed with: i) equivalent and detailed PV-STATCOM model, and ii) PV-STATCOM control implemented at plant level and inverter level. The impact of modeling details, controller location and system parameters on controller interaction, are investigated.

Summary for Lay Audience

This thesis deals with stability of induction motor (IMs), which constitute 80% of industrial and commercial motors as they are reliable, rugged and economical. Induction motors are highly sensitive to under-voltages. A large disturbance such as fault can lead to shutdown of IMs. This thesis addresses two issues associated with the shutdown of induction motors. The first issue is shutdown of critical induction motors. Induction motors are widely used in critical industries such as petrochemicals, mining, automotive, medicines, etc. Shutdown of these critical induction motors, even temporarily, can cause significant financial loss to the industries. For instance, shutdown of a critical motor for one-hour can cause $1 Million loss in a petrochemical industry in Ontario, Canada. The second problem is delayed voltage recovery after a fault due to stalling of large clusters of air-conditioning motors. This prolonged low voltage can lead to service disruption and reduced reliability of power system. Dynamic reactive power compensators, such as SVC and STATCOM, are conventionally employed to mitigate these issues but, these are very expensive. This provides motivation to find cheaper and alternative solutions.

One such alternative solution is use of new controls of PV solar plants. Due to the widespread growth of solar plants, they are quite likely to be installed near such critical motors. Application of existing voltage control strategies of PV solar plants are examined. It is observed that they are not sufficient to address above problems. Novel patented technology of utilizing PV solar plants, both during night and day, as STATCOM, termed PV-STATCOM is a promising technology to provide voltage support in a similar manner as conventional solutions. In this thesis, control strategies are developed for the application of PV-STATCOM for solving the above two issues.

The PV-STATCOM can address the above problems at a 50 times lower cost than conventional SVC/STATCOM solutions. This technology thus brings significant savings for utilities by reducing the need for expensive STATCOMs or SVCs, and opens new revenue making opportunities for solar plants for providing the above critical service.

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