Dale Osborn

Control of DFIG-Based Wind Generation to Improve Interarea Oscillation Damping

Power systems with high penetration of wind power usually require long-distance transmission to export wind power to the market. Interarea oscillation is an issue faced in long-distance transmission. Can wind generation based on doubly fed induction generator (DFIG) help to damp oscillations and how? In this paper, a control scheme is developed for the DFIG with rotor-side converter to damp interarea oscillations. The DFIG is modeled in MATLABreg/Simulink utilizing its vector control scheme feature, and inner current control and outer active/reactive power control loops are modeled and designed. A two-area system that suffers from poor interarea oscillation damping along with a wind farm in the area that exports power is investigated. A damping controller is designed and time-domain simulations are used to demonstrate the effectiveness of the controller. The major contributions of the paper are as follows: 1) built a wind farm interarea oscillation study system based on the classical two-area four-machine system, 2) established that in vector control scheme, active power modulation can best help to damp oscillations, 3) successfully designed a feedback controller using remote signals with good interarea oscillation observability.

Wind energy delivery issues [transmission planning and competitive electricity market operation]

Improving economics, environmental benefits, supportive state policies, and the rising costs of competing fuels are all contributing factors towards greater market regulatory interest in wind energy. However, wind energy poses several operational and planning challenges, some of which are beginning to be addressed. While the challenges are significant, they are not insurmountable.

Wind Farms With HVdc Delivery in Inertial Response and Primary Frequency Control

This paper develops a coordination control strategy for wind farms with line commutated converter-based HVdc delivery for participating in inertial response and primary frequency control. The coordination philosophy is to feedback the grid frequency and its derivative and adjust the delivery power of the HVdc link according to the feedback signals. The feedback loop employing the derivative of the grid frequency aims to improve the inertial response while the feedback loop employing the grid frequency deviation introduces a droop at the rectifier control loop. When the grid frequency is too high or too low, active power flow through the HVdc link will be ramped down or up. In turn, the wind generation will increase or decrease the blade angles to reduce or increase the captured wind power through pitch control. A case study demonstrates the effectiveness of the inertial enhancement and frequency droop in HVdc control. Simulation results in transient security assessment tool are given.

Control of DFIG based wind generation to improve inter-area oscillation damping

In this paper, control of inter-area oscillation in power systems with high wind power penetration is achieved via doubly fed induction generator (DFIG). The DFIG is modeled in Matlabreg/Simulink. A two-area system is investigated with a wind farm connected in the area that exports power. Control schemes for active power and reactive power regulation are designed firstly. The paper finds that without active power and reactive power regulation, it is impossible to design an effective inter-area oscillation damping controller through DFIG machine side inverter. An auxiliary control loop for oscillation damping that adjusts the active power command can help damp the inter-area oscillation. Time domain simulations demonstrate the effectiveness of the control.

Wind Farms With HVDC Delivery in Load Frequency Control

This letter develops a coordination control strategy for wind farms with line commutated converter (LCC) based HVDC delivery to participate in load frequency control. The coordination philosophy is to let the HVDC rectifier sense the grid frequency. If the grid frequency is too high or too low, active power flow through the HVDC link will be ramped down or up by introducing a droop at the rectifier control loop. In turn, wind generation will increase or decrease the blade angles to reduce or increase the captured wind power. This will be done by wind generation pitch controllers. A case study demonstrates the effect of the frequency droop in HVDC control. Simulation results in TSAT are given.

The view from the top

The challenge of integrating large amounts of renewable energy resources into the electric sector requires updated transmission analysis techniques. Economic planning, primarily in the form of value-based planning over interconnection-wide areas, is needed before performing the traditional single-hour, capacity-based reliability analyses. This article looks at the transmission planning processes of leading organizations from various sectors - regional transmission organizations (RTOs), investor-owned utilities, and regional organizations-within the United States to illustrate what changes to the traditional transmission planning process are required to meet the present challenges.

Impact of doubly fed wind turbine generation on inter-area oscillation damping

With the penetration of wind power being higher and higher in power systems, the impact of wind turbine generation on inter-area oscillations should be fully investigated. This paper discusses the impact of a doubly fed wind turbine induction generator on the inter-area oscillation in a two-area four-machine system. Models of an induction generator and converter/inverter control loops developed by GE are adopted in this paper, eigenvalue analysis is employed to investigate the effect of penetration, load parameter, and network topology change on the inter-area oscillation. The results show that increasing the penetration level improves damping significantly. Increasing the voltage control loop gain improves damping as well. The other control loops, such as pitch control and phase- locked loops, have negligible impact on the inter-area oscillation.

Value based transmission planning process for joint coordinated system plan

This paper describes the multi-step value based transmission planning process for Joint Coordinated System Plan with the consideration of large scale wind generation over the Eastern Interconnect footprint. As the result of the coordination of multiple RTOs, the conceptual transmission expansion plans are developed to meet both reliability and economic needs. A combined EHV AC and HVDC transmission line architecture is used for the value based planning. The initial economic analysis results are provided in this paper including LMP changes, benefit/cost ratios, interface flow energy changes.

A Novel Market Simulation Methodology on Hydro Storage

This paper presents a novel methodology to simulate the economic performance of hydro storage systems in the day-ahead (DA) and real-time (RT) markets. A detailed hydro storage system model is proposed to capture the unique characteristics of hydro storage units. A unique RT market bidding method named Tiered Bidding is proposed to represent the RT market offers of hydro storage units. In order to accurately represent the way hydro storage systems participate in the RT market, four hydro system RT bidding strategies are proposed and evaluated. The proposed methodology is applied to the Eastern Interconnection system to evaluate the economic benefits of Manitoba Hydros market participation in MISOs RT energy and ancillary services market.

Regional transmission planning for large-scale wind power

To incorporate large-scale wind generation in the Midwest ISO footprint, bulk transmission planning is necessary. In this paper, transmission planning for large-scale wind power is explained in detail. In expansion planning, the wind generation capacities are estimated from state Renewable Portfolio Standards (RPS) and the wind generator locations are chosen based on best wind source zones. From economic analysis, regional transmission enhancement or high voltage overlay projects will be developed to facilitate the transportation of low cost energy to the market. To develop additional transmission projects, two power flow cases (summer peak case and off-peak case) that represent the typical operating conditions are developed for transmission planning. In the summer peak case, wind generators are assumed to be dispatched at 15% of the capacity while in the off-peak case, the system load level is assumed at 70% of the peak load level and the wind generators are dispatched at full. The rest of the generators are dispatched based on security constrained economic dispatch. Contingency analysis of the two power flow cases will tell where are the constraints at lower voltage levels. An integrated transmission plan is therefore developed.