Wholesale price dynamics in the evolving Texas power grid

Electric power has become an essential part of daily life: we plug our electronic devices in, switch our lights on, and expect to have power. As the availability of power is usually taken for granted in modern societies, we mostly feel annoyed at its absence and perceive the importance of power during outages which have severe effects on the public order. Blackouts have had disastrous consequences for many countries and they continue to occur frequently. Such examples demonstrate the necessity for careful analysis and planning of power grids, to ultimately increase the reliability of power grids. The power grids have evolved due to economic, environmental and human-caused factors. In addition to the contingency analysis, nowadays, the operation and planning of power grids are facing many other challenges (such as demand growth, targeted attacks, cascading failures, and renewable energy integration). Thus, many questions arise, including: which buses (nodes) to connect with a new line (link)? What are the impacts of malicious attacks on power grids? How may an initial failure result in a cascade of failures? How to prepare for the integration of renewable energy? Answering such questions requires developing new concepts and tools for analysing and planning of power grids. Power grids are one of the largest and the most complex man-made systems on earth. The complex nature of power grids and its underlying structure make it possible to analyse power grids relying on network science. The applications of network science on power grids have shown the promising potential to capture the interdependencies between components and to understand the collective emergent behaviour of complex power grids. This thesis is motivated by the increasing need of reliable power grids and the merits of network science on the investigation of power grids. In this context, relying on network science, we model and analyse the power grid and its near-future challenges in terms of line removals/additions, malicious attacks, cascading failures, and renewable integration.

Texas has experienced a rapid development of wind power over the last 20 years. Since wind power was developed mostly in desolate areas that are remote from urban centers due to its nature conditions, Texas implemented the Competitive Renewable Energy Zones (CREZ) project, the goal of which is to integrate the wind supply regions with the large demand centers. The objectives of this paper are two-fold. The first is to investigate the impact of the CREZ project on market price convergence. Specifically, this paper analyzes the extent that the transmission project affected wholesale price level, variance, and difference between the regions. The second is to measure environmental benefits obtained from displacement of fossil fuel generators by wind power. The results provide a strong evidence for price convergence across the ERCOT market following the completion of the CREZ project. As well as price convergence, wholesale price level and variance are also reduced significantly. Specifically, the results show that the price difference between Houston and West which diverged up to around $100/MWh converges to zero after the project completed. The impacts are more significant during the high demand hours. The results also document significant reductions in emissions, as NOx emissions was reduced by around 4000 pounds in Texas as a whole. Effects on SO2 and CO2 are also calculated.

Power grid partition with improved biogeography-based optimization algorithm

The DC transmission, distribution and networking have been applied to medium and low voltage power grids, and have exhibited apparent advantages and favorable application perspective. Different from traditional AC power grids, DC power grids have shown features of low inertia, weak damping and the inclination of oscillation. The intermix of fast switching transients and control dynamics makes the DC grid much more complicated. In addition, the power fluctuation of renewable energy generation and demand-response loads imposes difficulties on the stable and smooth running of the DC grid. However, no comprehensive study has been reported on dynamic and transient patterns and characteristics of the DC power grid. In this paper, through both simulation and theoretical analysis, the transient and dynamic characteristics of medium and low voltage DC power grids are systematically tested, classified and analyzed. Finally, the mechanisms and general conclusions are extracted and refined.

With the accelerating urbanization, the load demand for urban power networks is swiftly increasing. Accurate prediction of changes in the power grid is extremely important to ensure stable operation, planning, and power system construction. First, this paper analyzes the load characteristics of urban power grids, including the effects of seasonal changes, daily changes, business days, and non-working days. Second, a load forecasting model is built using time series analysis, regression analysis, and machine learning. The back-test verification of the urban power grid data demonstrates that the model has achieved high prediction accuracy. Finally, this paper predicts the future development trend of power grid load, which provides a reference for the optimal operation and investment decision-making of the power grid. Various data analyses and models are adopted to analyze the complexity of urban power grid load characteristics. Specifically, time series analysis is a traditional method to deal with such problems. It can identify the periodicity and trend of data and predict accordingly. In addition, regression analysis can reveal the correlation between load and diversified factors. With the development of artificial intelligence technologies, machine learning demonstrates the great potential of load prediction, particularly deep learning techniques, which is good for dealing with big data and nonlinear issues.

Price signals provided by the nodal price can effectively guide the behaviors of power grid constructors and consumers. Based on the long-term incremental cost method, a nodal price calculation method taking power supply reliability into account is proposed. The method takes into consideration the consumers' requirements on power supply reliability as well as the influence of load growth on regional power supply reliability. Differential pricing according to the needs of different types of consumers is proposed, and the weighted average of price according to different regional reliability levels is calculated. Then a nodal pricing system of distribution network with differential pricing and regional average price combined is developed. Finally, an analysis of results of the RBTS-BUS 6 system shows that not only does the method ensure the special needs of consumers, the price signals provided, being helpful to decision-making of power grid construction, operation and maintenance plans, are more operable.

In this study, we seek to explore the impact of a state level transmission expansion project, the Competitive Renewable Energy Zone (CREZ), whose goal is to integrate a massive amount of wind energy, on the wholesale market prices in the Electric Council of Texas (ERCOT). We find strong evidence for price convergence across ERCOT with accordance to the timing of the expansion of major sections of the CREZ. A variety of empirical analyses shows a smooth transition to a well-integrated market. For example, Structural impulse responses suggest that a price shock after the integration takes double the time to die off compared with the before-integration period. We also find that regional-specific shocks became more important in terms of driving price change in other regions. Specifically, the impacts of Houston (demand) and the West (wind supply) on each other have increased dramatically. Our study contributes to the literature by connecting the expansion of physical transmission lines with electricity market integration.

In this study, we seek to explore the impact of a state level transmission expansion project, the Competitive Renewable Energy Zones (CREZ), whose goal is to integrate a massive amount of wind energy, on the wholesale market prices in the Electric Reliability Council of Texas (ERCOT). We find strong evidence for price convergence across ERCOT with accordance to the timing of the expansion of major sections of the CREZ. A variety of empirical analyses shows a gradual transition to a well-integrated market. We also find that regional-specific shocks became more important in terms of driving price change in other regions. Specifically, the impacts of Houston (demand) and the West (wind supply) on each other and the North and South regions have increased significantly. Our study contributes to the literature by connecting the expansion of physical transmission lines with electricity market integration

With the acceleration of urbanization, the proportion of power cables in urban power grid is increasing, and the peak valley difference of urban power grid is increasing year by year. The challenges in voltage stability and voltage control are becoming more and more significant. In this paper, the evaluation index of reactive power and voltage characteristics of power grid is analyzed, and then the optimization method of limit parameters of automatic voltage control system based on multiple linear regression analysis is proposed. The multiple linear regression analysis model of state variables and control variables is established, and the multi-objective quadratic programming optimization model is constructed, The optimal control variable limit is calculated. Taking the urban power grid as an example, the bus limit of 500kV to 110kV voltage is optimized, which verifies the feasibility and practicability of this method, further improves the effect of voltage control, and meets the needs of power grid safety and economic operation.

Large-scale new power supply based on power electronics equipment will replace traditional synchronous rotating equipment and lead to changes in the operation characteristics of power grid. Under the characteristics of the new power grid, it is necessary to consider the transient reactive power response characteristics of DC converters and new energy frequency converters one after another, and further explore the occurrence mechanism of transient over-voltage from the perspective of the characteristics of power electronic equipment. In this paper, large-scale wind turbines are selected to replace the weak AC power grid of traditional rotating equipment, and the transient characteristics of the grid voltage under the support of weak rotating equipment with the participation of the PLL phase-locking process of the wind turbine are explored. Combined with the electromagnetic transient simulation model for comparison and verification, the research shows that the PLL phase locking process of the wind turbine will have an impact on the transient over-voltage of the sending-end power grid.

Reasonable and strong structure is an important foundation for the smart transmission grid. For vigorously promoting construction of the smart grid, it is of great significance to have a thorough understanding of the complex structural characteristics of the power grid. The structural characteristics of several actual large-scale power grids of China are studied in this paper based on the complex network theory. Firstly, the topology-based network model of power grid is recalled for analyzing the statistical characteristic parameters. The result demonstrated that although some statistical characteristic parameters could reflect the topological characteristics of power grid from different ways, they have certain limitation in representing the electrical characteristics of power grid. Subsequently, the network model based on the electrical distance is established considering the limitation of topology-based model, which reflects that current and voltage distribution in the power grid are subject to Ohm's Law and Kirchhoff's Law. Comparing with the topology-based model, the electrical distance-based model performs better in reflecting the natural electrical characteristic structure of power grid, especially intuitive and effective in analyzing clustering characteristics and agglomeration characteristics of power grid. These two models could complement each other.

This paper presents a method for generating power grid simulation example data based on actual power grid data statistics, which can assign parameters to the example data of the existing power grid topology. Parameters include power flow parameters and component model parameters for transient stability simulation. Through the proposed method, a power grid simulation example that conforms to the characteristics of the actual grid can be generated, which can be used for steady-state simulations such as power flow and transient simulation calculations such as electromechanical transients. This paper also proposes an evaluation method for the rationality of the simulation results of a power grid example, which is used to analyze the consistency of the characteristics of the example power grid and the actual power grid. Finally, the correctness and effectiveness of the proposed method are verified by the generation and evaluation of a typical example.

In order to research the performance characteristics of power grid with putting into operation of ±800kV UHVDC power transmission project, based on higher load in winter of 2020 of an example power grid, the impact on stability of the power grid with UHVDC accessing under typical faults in AC system is analyzed, the influence on the power grid under the UHVDC bipolar blocking and restarting after DC fault is also researched. Simulation results show that during typical faults in AC system, the power grid can operate stately; if UHVDC bipolar blocking, the frequency stability and rotor-angle stability of the power grid can still be maintained, the AC bus of the example power grid also suffers from an over-voltage problem, and the example power grid can restart smoothly after the fault of the DC line.

Due to the rapid advances of integrated circuit technology, the size of power distribution network (power grid) is becoming larger and larger. There are usually multi-million nodes on a power grid. Analyzing these huge power grids has become very expensive in terms of both time and memory. This paper presents an efficient parallel implementation of the Additive Schwarz Method (ASM) for IR-drop analysis of large-scale power grid. Based on distributed memory system, a new data storage method is proposed to overcome memory bottleneck of traditional methods. Techniques including overlapping in multiple layer and irregular power grid, via detection and grouping are utilized to accelerate the simulation. Moreover, a new communication strategy exhibiting minimum communication overhead is proposed. The proposed method is very accurate in the final solution, with the maximum error less than 0.1mv. Experimental results on industrial medium size benchmarks show that the proposed method achieves more than 110X speedup over a state-of-the-art direct LU solver. The proposed approach can easily solve very large-scale benchmarks, while LU solver fails to obtain the solution because of system memory limitation. It is the first time reported in literature that IR-drop analysis of power grid with over 190M nodes is successfully solved within 5 minutes.

With the increase in the proportion of new energy power generation and DC power generation outside the region, the inertia demand under the frequency security constraints is becoming more and more urgent. Firstly, the relationship between the frequency response characteristics of the power grid and the total inertia of the system and the relationship between the frequency distribution characteristics of the multi-machine system and the inertia distribution are analyzed. Aiming at the frequency safety constraints of the power grid, an estimation method for the minimum inertia demand of the system is proposed. Considering the frequency distribution characteristics of the power grid and the distribution of load, new energy and direct current, the distribution scheme of inertia among different regions in the synchronous power grid is proposed to guide the arrangement of the power-on and output of the synchronous units in the system. The simulation analysis based on the actual large power grid in East China power grid shows that for the power system with large amount of new energy generation and DC feed, the method can effectively reduce the maximum deviation of frequency and the difference of time-space distribution, which verifies the effectiveness of the proposed method.