John Seuss

SoC Feedback Control for Wind and ESS Hybrid Power System Frequency Regulation

With the increased penetration of wind generation, the traditional control scheme of the wind turbine (WT), which is designed for maximum wind power extraction, is no longer suitable to meet emerging grid requirements for wind farms (WFs) to participate in frequency regulation. The control scheme of the WT with respect to grid frequency regulation is proposed in many studies, such as those on pitch control. Also, energy storage technologies have drawn much attention in recent years, as the technology matures and costs decrease, and present themselves as a potential solution for the challenge brought about by the uncertainty of renewable energy generation with regard to power system stability. A power system consisting of a high penetration of wind generation and energy storage systems (ESS) is investigated in this paper for the regulation of grid frequency. A new strategy called state of charge (SOC) feedback control is proposed and the performance of the grid frequency deviation response and the SOC of the battery are presented. The model of the power system studied in this paper is established on the MATLAB/SIMULINK platform.

Improving distribution network PV hosting capacity via smart inverter reactive power support

Many utilities today have a large number of interconnection requests for new PV installations on their distribution networks. Interconnections should be approved in a timely manner but without compromising network reliability. It is thus important to know a networks PV hosting capacity, which defines the upper bound of PV sizes that pose no risk to the network. This paper investigates how implementing reactive power control on the PV inverter impacts the PV hosting capacity of a distribution network. A local Volt-Var droop control is used and simulations are performed in OpenDSS and Matlab. Multiple feeders are tested and it is found that the control greatly improves the overall hosting capacity of the feeder as well as the locational hosting capacity of most voltage constrained buses.

A Real-Time Power Allocation Algorithm and its Communication Optimization for Geographically Dispersed Energy Storage Systems

The paper presents a distributed algorithm that regulates the power outputs of multiple dispersed energy storage systems (DESS), which can be used to provide desirable services for power systems, such as renewable generation output smoothing and secondary control. The algorithm is based on the cooperative control principle of network control theory and it satisfies both the power balance requirement of power systems and the fair utilization among the DESS. The most distinct feature of the algorithm is that each DESS only requires the information from its neighbors through some local communication networks (CN), utilizing a virtual leader embedded in one or several DESS to receive a power command signal. In addition, to improve the robustness of the CN among DESS, two optimization models are formulated to design the so-called “ N-1” redundant network, while considering both economic issues and convergence rate. These features enable the DESS under the algorithm to have both self-organizing and adaptive coordination properties under some adverse conditions. Simulation on the IEEE 123-bus distribution system validates the effectiveness of the proposed algorithm.

Analysis of PV Advanced Inverter Functions and Setpoints under Time Series Simulation.

Utilities are increasingly concerned about the potential negative impacts distributed PV may have on the operational integrity of their distribution feeders. Some have proposed novel methods for controlling a PV systems grid - tie inverter to mitigate poten tial PV - induced problems. This report investigates the effectiveness of several of these PV advanced inverter controls on improving distribution feeder operational metrics. The controls are simulated on a large PV system interconnected at several locations within two realistic distribution feeder models. Due to the time - domain nature of the advanced inverter controls, quasi - static time series simulations are performed under one week of representative variable irradiance and load data for each feeder. A para metric study is performed on each control type to determine how well certain measurable network metrics improve as a function of the control parameters. This methodology is used to determine appropriate advanced inverter settings for each location on the f eeder and overall for any interconnection location on the feeder.

Advanced inverter controls to dispatch distributed PV systems

The research presented in this paper compares five real-time control strategies for the power output of a large number of distributed PV systems in a large distribution feeder circuit. Both real and reactive power controls are considered with the goal of minimizing network over-voltage violations caused by high penetrations of PV generation. The control parameters are adjusted to maximize the effectiveness of each control. The controls are then compared based on their ability to achieve multiple objectives. These objectives include minimizing the total number of voltage violations, minimizing the total amount of PV energy curtailed or reactive power generated, and maximizing the fairness of any control action among all PV systems. The controls are simulated on the OpenDSS platform using time series load and spatially-distributed irradiance data.

Multi-Objective Advanced Inverter Controls to Dispatch the Real and Reactive Power of Many Distributed PV Systems.

The research presented in this report compares several real - time control strategies for the power output of a large number of PV distributed throughout a large distribution feeder circuit. Both real and reactive power controls are considered with the goal of minimizing network over - voltage violations caused by large amounts of PV generation. Several control strategies are considered under various assumptions regarding the existence and latency of a communication network. The control parameters are adjusted to maximize the effectiveness of each control. The controls are then compared based on their ability to achieve multiple objectiv es. These objectives include minimizing the total number of voltage violations , minimizing the total amount of PV energy curtailed or reactive power generated, and maximizing the fairness of any control action among all PV systems . The controls are simulat ed on the OpenDSS platform using time series load and spatially - distributed irradiance data.

Maximum PV size limited by the impact to distribution protection

Utilities issuing new PV interconnection permits must be aware of any risks caused by PV on their distribution networks. One potential risk is the degradation of the effectiveness of the networks protection devices (PDs). This can limit the amount of PV allowed in the network, i.e. the networks PV hosting capacity. This research studies how the size and location of a PV installation can prevent network PDs from operating as intended. Simulations are carried out using data from multiple actual distribution feeders in OpenDSS. The PD TCC are modeled to find the timing of PD tripping to accurately identify when PV will cause unnecessary customer outages. The findings show that more aggressive protection settings limit the amount of PV that can be placed on a network that does not cause more customer outages or damage network equipment.

Determining reactive power levels necessary to provide optimal feeder line voltage regulation

An increasing adoption of rooftop photovoltaic (PV) generators presents a growing opportunity for the use of their grid-tie inverters to provide reactive power compensation on medium- and low-voltage distribution networks. This paper presents a generalized method based on particle swarm optimization (PSO) for determining how much reactive power is necessary to provide control over the voltage profile of the distribution line for any given operational condition and number of PV connections. The method is tested with data based on the IEEE benchmark 13-bus feeder system and simulations are run in DIgSILENT using the same system to validate the results. A future two-level distributed control architecture is described that will utilize the methods developed in this paper to provide reactive power compensation for voltage control of an entire feeder line without the need for global information sharing.

SOC feedback control for wind and ESS hybrid power system frequency regulation

With increased penetration of wind generation, the traditional control scheme of the wind turbine (WT), which is designed for maximum wind power extraction, is no longer suitable to meet emerging grid requirements for wind farms to participate in frequency regulation. The control scheme of the WT with respect to grid frequency regulation is proposed in many studies, such as those on pitch control. Also, energy storage technologies have drawn much attention in recent years because, as technology matures and costs decrease, they present themselves as a potential solution for the challenge brought about by the uncertainty of renewable energy generation with regard to power system stability. A power system consisting of a high penetration of wind generation and energy storage systems (ESS) is investigated in this paper for the regulation of grid frequency. A new strategy called state of charge (SoC) feedback control is proposed, and the performance of the grid frequency deviation response and the SoC of the battery are presented. The model of the power system studied in this paper is established on the MATLAB/SIMULINK platform.

A low-cost distributed control strategy for rooftop PV with utility benefits

Increasing adoption of rooftop photovoltaic (PV) generators presents a growing challenge to some distribution utility companies, as legacy local controls were never intended for high penetration rates. Some countries have already begun the process of updating their control standards for grid-tied PV systems. This paper presents a low-cost distributed control strategy for grid-tied, rooftop PV generators that addresses some of the concerns of high penetration PV while also adding some benefits to the utility. The control strategy does not require an advanced communications infrastructure but still allows for some aggregate control of the active and reactive power outputs of the PV units and their grid-tied inverters. The paper demonstrates that a distribution company that employs this control strategy to address the issues of high penetration PV will also be able to gain improved power factor correction and potentially new ways to gain revenue from open market interactions. Simulations of the control strategy during daily load and insolation cycles are presented based on the IEEE benchmark 13-bus feeder system.