Optimal power flow in MTDC systems based on a DC-independent system operator objective

DC Independent System Operator (DC-ISO) is a single coordinate, to control and monitor the operation of the DC transmission system. It will be responsible for ensuring the reliability and security of the multi-terminal HVDC (MTDC) system in real-time and co-ordinate the supply of and demand for electricity, in a manner that avoids violations of technical and economic standards. This paper proposes a simple methodology for optimal power flow (OPF) allowing the DC-ISO objectives to be included in the solution. One of the contribution of this paper is include new operator objectives as in the OPF problem as a type linear equality constraints, it is based on nodal analysis. Proposed methodology has been thoroughly illustrated and tested with a simple 3-node MTDC system, and results show the validity of the proposed approach

Activation schemes for synthetic inertia controller on wind turbines based on full rated converter

One of the challenges in future energy systems is the massive use of high power converters that decouple new energy sources from the AC power grid, disabling natural frequency response. This situation decreases the total system inertia affecting the ability of power system to overcome system frequency's disturbances. It has been established by the wind power industry a controller to enable inertial response on wind turbines generators (WTG) enabling the frequency response: Artificial, Emulated, Simulated, or Synthetic Inertia. However, there is a clear lack of knowledge about activation scheme used for these controllers and how they work in practical manner. This paper proposes two activation schemes for synthetic inertia controller on WTG based on full rated power converters (FRC): (i) under-frequency trigger and (ii) maximum-frequency gradient trigger. Simulations considering a test system are used for evaluation of the proposed activation schemes. The main contribution of this paper is the definition of two schemes to activate the synthetic inertia controller and the simulations results that demonstrate under-frequency trigger provides the best dynamic response in term of system frequency response

Optimal power flow in VSC-HVDC networks for DC-ISO: constant current operation

DC Independent System Operator (DC-ISO) is a revolutionary concept; a single entity designed to coordinate, to control and monitor the operation of the DC transmission system. It will be responsible for ensuring the reliability and security of the VSC-HVDC meshed networks in real-time and co-ordinate the supply of and demand for electricity, in a manner that avoids violations of technical and economic standards. This paper proposes a simple methodology for optimal power flow (OPF) allowing constant current operation in a series branch of the VSC-HVDC network in order to cope with one the possible DCISO objectives. One of the contribution of this paper is a methodology that allows including new operator objectives as in the OPF problem as a type linear equality constraints, it is based on nodal analysis. Proposed methodology has been thoroughly illustrated and tested with a simple 3-node MVSCDC system, and results show the validity of the proposed approach

Impact of emulated inertia from wind power on under-frequency protection schemes of future power systems

Future power systems face several challenges. One of them is the use of high power converters that decouple new energy sources from the AC power grid. This situation decreases the total system inertia affecting its ability to overcome system frequency disturbances. The wind power industry has created several controllers to enable inertial response on wind turbines generators: artificial, emulated, simulated, or synthetic inertial. This paper deals with the issues related to the emulated inertia of wind turbines based on full-converters and their effect on the under-frequency protection schemes during the recovery period after system frequency disturbances happen. The main contribution of this paper is to demonstrate the recovery period of under-frequency transients in future power systems which integrate wind turbines with emulated inertia capability does not completely avoid the worse scenarios in terms of under-frequency load shedding. The extra power delivered from a wind turbine during frequency disturbances can substantially reduce the rate of frequency change. Thus it provides time for the active governors to respond

Activation schemes of synthetic inertia controller on full converter wind turbine (type 4)

One of the challenges in future energy systems is the massive use of high power converters that decouple new energy sources from the AC power grid, disabling natural frequency response. This situation decreases the total system inertia affecting the ability of power system to overcome system frequency's disturbances. It has been established by the wind power industry a controller to enable inertial response on wind turbines generators (WTG) enabling the frequency response: Artificial, Emulated, Simulated, or Synthetic Inertia. However, there is a clear lack of knowledge about activation scheme used for these controllers and how they work in practical manner. This paper proposes three activation schemes for synthetic inertia on WTG based on full converters: (i) Continuously Operating triggering, (ii) Under-frequency Trigger and (iii) Maximum-Frequency Gradient Trigger. Simulations over a test system are used for a preliminary evaluation of the proposed activation schemes. The main contribution of this paper is the three schemes to activate the synthetic inertia controller and the simulations results that demonstrate under-frequency trigger provides good dynamic response

Activation schemes of synthetic inertia controller on full converter wind turbine (type 4)

One of the challenges in future energy systems is the massive use of high power converters that decouple new energy sources from the AC power grid, disabling natural frequency response. This situation decreases the total system inertia affecting the ability of power system to overcome system frequency's disturbances. It has been established by the wind power industry a controller to enable inertial response on wind turbines generators (WTG) enabling the frequency response: Artificial, Emulated, Simulated, or Synthetic Inertia. However, there is a clear lack of knowledge about activation scheme used for those controllers and how they work in practical manner. This paper proposes three activation schemes for synthetic inertia on WTG based on full converters: (i) Continuously operating triggering, (ii) Under-frequency trigger and (iii) Maximum-Frequency gradient trigger. Simulations over a test system are used for a preliminary evaluation of the proposed activation schemes. The main contribution of this paper is the three schemes to activate the synthetic inertia controller and the simulations results that demonstrate under-frequency trigger provides good dynamic response

Effects of fast acting power controller of BESS in the system frequency response of a multi-machine system: probabilistic approach

This paper presents a probabilistic assessment of the effects of the fast acting power (FAP) controller of BESS in the system frequency response of a multi-machine system. Monte Carlo simulations and time-domain simulations, using DIgSILENT® PowerFactoryTM are combined in the implementation of the proposed methodology. Simulation results show the effect fast-acting power controller of BESS in the system frequency response of a multi-machine system in the form of probabilistic distribution functions (PDF) of the main system frequency response

Application of swarm mean-variance mapping optimization on location and tuning damping controllers

This paper introduces the use of the Swarm Variant of the Mean-Variance Mapping Optimization (MVMO-S) to solving the multi-scenario problem of the optimal placement and coordinated tuning of power system damping controllers (POCDCs). The proposed solution is tested using the classical IEEE 39-bus test system, New England test system. This papers includes performance comparisons with other emerging metaheuristic optimization: comprehensive learning particle swarm optimization (CLPSO), genetic algorithm with multi-parent crossover (GA-MPC), differential evolution DE algorithm with adaptive crossover operator, linearized biogeography-based optimization with re-initialization (LBBO), and covariance matrix adaptation evolution strategy (CMA-ES). Numerical results illustrates the feasibility and effectiveness of the proposed approach

Preventive security-constrained DCOPF formulation using power transmission distribution factors and line outage distribution factors

This study proposes a very effective formulation to carry out the security-constrained direct current (DC)-based optimal power flow (OPF) problem using two linear factors: (i) the power transmission distribution factors (PTDF) and (ii) the line outage distribution factors (LODF). The security-constrained (SC) DCOPF problem has been reformulated using these linear distribution factors, and mainly the pre- and post-contingency constraints have been added into the optimization problem based on the active power unit generation (decision variables). The main advantage of this formulation is the reduction of decision variables as well as equality and inequality constraints. To validate the introduced formulation, several experiments have been conducted using MatPower, DIgSILENT Power Factory and Gurobi. Simulation results demonstrate both the feasibility to carry out the SCOPF problem and the potential applicability of the proposed formulation to medium and large-scale power systems

Stochastic security-constrained generation expansion planning methodology based on a generalized line outage distribution factors

In this study, the authors proposes to develop an efficient formulation in order to figure out the stochastic security-constrained generation capacity expansion planning (SC-GCEP) problem. The main idea is related to directly compute the line outage distribution factors (LODF) which could be applied to model the N − m post-contingency analysis. In addition, the post-contingency power flows are modeled based on the LODF and the partial transmission distribution factors (PTDF). The PTDF-based generation capacity planning formulation has been reformulated in order to include the post-contingency constraint solving both pre- and post-contingency constraints simultaneously. The methodology includes in the optimization problem the load uncertainty using a two-stage multi-period model, and a K−means clustering technique is applied to reduce the load scenarios. The main advantage of this methodology is the feasibility to quickly compute the post-contingency factors especially with multiple-line outages (N − m). This idea could speed up contingency analyses and improve significantly the security-constrained analyses applied to stochastic GCEP problems. It is conducted several experiments with two electrical power systems in order to validate the performance of the proposed formulation