Linear power-flow analysis method for AC-DC electric power networks

AC-DC power systems have been operating more than sixty years. Nonlinear bus-wise power balance equations provide accurate model of AC-DC power systems. However, optimization tools for planning and operation require linear version, even if approximate, for creating tractable algorithms, considering modern elements such as DERs (distributed energy resources). Hitherto, linear models of only AC power systems are available, which coincidentally are called DC power flow. To address this drawback, linear bus-wise power balance equations are developed for AC-DC power systems and presented. As a first contribution, while AC and DC lines are represented by susceptance and conductance elements, AC-DC power converters are represented by a proposed linear relationship. As a second contribution, a three-step linear AC-DC power flow method is proposed. The first step solves the whole network considering it as a linear AC network, yielding bus phase angles at all busses. The second step computes attributes of the proposed linear model of all AC-DC power converters. The third step solves the linear model of the AC-DC system including converters, yielding bus phase angles at AC busses and voltage magnitudes at DC busses. The benefit of the proposed linear power flow model of AC-DC power system, while an approximation of the nonlinear model, enables representation of bus-wise power balance of AC-DC systems in complex planning and operational optimization formulations and hence holds the promise of phenomenal progress. The proposed linear AC-DC power systems is tested on numerous IEEE test systems and demonstrated to be fast, reliable, and consistent.

Linear power-flow analysis method for AC-DC electric power networks

AC-DC power systems have been operating more than sixty years. Nonlinear bus-wise power balance equations provide accurate model of AC-DC power systems. However, optimization tools for planning and operation require linear version, even if approximate, for creating tractable algorithms, considering modern elements such as DERs (distributed energy resources). Hitherto, linear models of only AC power systems are available, which coincidentally are called DC power flow. To address this drawback, linear bus-wise power balance equations are developed for AC-DC power systems and presented. As a first contribution, while AC and DC lines are represented by susceptance and conductance elements, AC-DC power converters are represented by a proposed linear relationship. As a second contribution, a three-step linear AC-DC power flow method is proposed. The first step solves the whole network considering it as a linear AC network, yielding bus phase angles at all busses. The second step computes attributes of the proposed linear model of all AC-DC power converters. The third step solves the linear model of the AC-DC system including converters, yielding bus phase angles at AC busses and voltage magnitudes at DC busses. The benefit of the proposed linear power flow model of AC-DC power system, while an approximation of the nonlinear model, enables representation of bus-wise power balance of AC-DC systems in complex planning and operational optimization formulations and hence holds the promise of phenomenal progress. The proposed linear AC-DC power systems is tested on numerous IEEE test systems and demonstrated to be fast, reliable, and consistent.

SIMULATION MODEL AND RESEARCH OF QUASI-STEADY-STATE AND DYNAMIC OPERATION MODES OF THE AUTONOMOUS DC POWER ENERGY SYSTEM WITH PARALLEL OPERATED INVERTER EXCITED INDUCTION GENERATORS

Purpose. The development of theory and research of autonomous DC power systems based on contactless electrical machines is an important element in ensuring the improvement of the reliability and energy efficiency of autonomous power supply of remote from centralized networks facilities, ship equipment, critical to power outages consumers. Originality. The use of induction generators with squirrel-cage rotor and an electronic converter in stator circuits in the design of autonomous DC power systems is advisable due to presence of a DC power output in these generators and the possibility of stabilizing the output voltage at variable speed. One of the scientific issues needed to be solved at creating induction generators-based DC power systems with inverter-assisted self-excitation of the generators is the determination of means and as well as development and verification of algorithms for regulating the generators load. Solving this issue requires the creation of appropriate simulation models. Methodology. In this work, a simulation dynamic model of an autonomous DC power system with two parallel operated induction generators with inverterassisted self-excitation and the six-step switching control algorithm has been developed. Results. A study of quasisteady-state and dynamic operating modes of the system was carried out. The duration of the initial excitation of the generators was determined for different values of the capacitance of the filter. Practical value. The results obtained showed the compliance of the parameters of electrical energy in the system with the standards established by the relevant regulatory documents and stable operation of the system with load changing from idle to rated. Further work is planned to focus on improving control algorithms for autonomous DC power systems with parallel operating induction generators and inverter-assisted self-excitation, studying the energy performance of such systems and developing recommendations for their design.