Jiangsu Power Grid Research Articles

Research on Reactive Power Coordination Control Strategies of Multi-Infeed Line-Commutated Converter–High-Voltage Direct Current Systems

For a receiving-end power grid with multi-infeed LCC-HVDC systems, simultaneous commutation failures may seriously threaten the safe and stable operation of the system. To evaluate the impact of commutation failure and improve the voltage stability of the commutation buses in multi-infeed HVDC systems, this paper proposes a method for evaluating the voltage stability of commutation buses and a reactive power coordination control (RPCC) method for commutation failure of multiple HVDC systems. Firstly, three indicators and the entropy weight method are adopted to comprehensively evaluate the voltage stability of commutation buses. Then, an RPCC method is proposed to resist commutation failure. The proposed RPCC method uses the voltage interaction factor (VIF) to screen out DC systems that are strongly related to dynamic reactive power compensation devices and activates the devices to provide RPCC to the DC systems through an auxiliary controller. Finally, the effectiveness of the proposed method is verified through a practical example of the Jiangsu power grid.

Clustering and decision tree based analysis of typical operation modes of power systems

The increasing penetration of renewable energy resources has greatly changed the pattern of the modern power system. In this case, the operation modes of power systems are becoming much more complex and the traditional experience-based method is no longer practical in typical operation modes analysis. In this paper, a clustering and decision tree-based scheme is proposed for the analysis of the typical operation modes of power systems. Specifically, the k-means++ clustering algorithm is adopted to classify the operation data into different groups, which represent the typical operation modes. The group labels and several important operation features are used to construct a decision tree for the quantitative description of different kinds of typical operation modes. In addition, feature importance is analyzed and the decision tree is pruned with a balance between complexity and classification accuracy. Case studies are conducted based on the actual system planning data of the Jiangsu power grid to verify the effectiveness of the proposed scheme. From the results, system operators could get deep insights into system planning with a high share of renewable energy resources.

The analysis of time-varying high-order moment of wind power time series

The efficient wind power forecasting is of great significance for the safety and stability of power grid. Analysis on the high order moment of wind power time series play an important role in improving the forecasting accuracy of wind power. With the rolling subsample generalized auto-regressive conditional heteroskedasticity with skewness and kurtosis (GARCHSK) model sequence, the analysis method for conditional skewness and conditional kurtosis of wind power time series is proposed. The dynamic curves of parameter are presented by estimating the characteristic parameters in the subsample models. Moreover, the time-varying structure of high order moment of the wind power time series is analyzed. A Generalized News Impact Curve (GNIC) is proposed, and the impact of news on the conditional skewness and conditional kurtosis are measured and evaluated by the third order GNIC and the fourth order GNIC. The result of case based on the wind power data of Jiangsu power grid demonstrates that the time-varying structure of high-order moments of wind power time series is steady relatively, and the time-varying characteristics of high-order moments are further verified by GNIC.

Control Strategy and Performance Analysis of Electrochemical Energy Storage Station Participating in Power System Frequency Regulation: A Case Study of the Jiangsu Power Grid

Electrochemical energy storage stations (EESSs) have been demonstrated as a promising solution to mitigate power imbalances by participating in peak shaving, load frequency control (LFC), etc. This paper mainly analyzes the effectiveness and advantages of control strategies for eight EESSs with a total capacity of 101 MW/202 MWh in the automatic generation control (AGC) in the power system of the Jiangsu power grid. Firstly, an adaptive tracking strategy for electricity quantity that considers the state of charge (SOC) of EESSs is proposed to calculate the baseline power of the EESS participating in AGC. This strategy can simultaneously coordinate different time scale application requirements, such as peak shaving and LFC. Then, an adaptive strategy for regulation requirement allocation among AGC control groups with EESSs that considers different area regulation requirements (ARRs) is proposed to calculate the regulation power of EESS participating in AGC. This strategy can realize the balance transfer of fast and slow regulation capacity, ensure the complementary advantages of various frequency regulation resources and improve the dynamic regulation performance of the control area. Finally, the proposed strategy is validated via a test system to confirm its effectiveness and advantages, as well as via a quantitative analysis on the improvement of the control performance standard (CPS) of the Jiangsu power grid with the participation of EESSs in AGC.

Optimal Blocking Devices Placement for Geomagnetic Disturbance Mitigation Based on Sensitivity of Induced Geoelectric Fields

When geomagnetic storms occur, geomagnetically induced currents (GICs), as a kind of quasi-DC, flow through the transformer and cause the increase of reactive power loss ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GIC</sub> ). Several mitigation actions (e.g., changing grid topology or installing blocking devices) exist than can reduce the harmful GIC effects on the grids. Making such decisions can be challenging, however, because the magnitude and direction of the induced geoelectric fields (IGFs) are uncertain and non-stationary. In this paper, the sensitivity of voltage and GIC to IGF is first calculated, and the joint voltage/GIC sensitivity feature space is constructed based on principal component analysis. On this basis, scenario clustering is conducted to obtain voltage/GIC sensitivity scenarios. This scenario not only reflects the uncertainty of IGF itself, but also reflects the impact of GMD on the system operation state. Combined with the structural parameters of Jiangsu power grid, the placement of BDs is optimized. Compared with the constant IGF scenario and the IGF intensity scenario, the expected value of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GIC</sub> based on the sensitivity scenario decreases more.

Optimization of dynamic reactive power devices’ coordinate operation for minimizing HVDC’s successive commutation failure based on PSO

More and more dynamic reactive power devices (DRPDs) have been put into operation to improve voltage stability in AC/DC hybrid power system. In order to make full use of these devices, this paper presented an optimization technology for multiple DRPDs’ coordinate operation in receiving-end of AC/DC hybrid power system. DRPDs’ steady-state reactive instructions are treated as optimization variables in the proposed model, while the objective is minimizing the successive times of HVDC’s commutation failure under a number of grounding faults. Power flow constraints and electro-mechanical transient process are considered simultaneously. Based on the characteristics of the model, commutation failure of HVDC under each grounding fault could be obtained by employing time-domain simulation method. Furthermore, particle swarm optimization (PSO) is used to get DRPDs’ optimal reactive instruction in steady-state. The simulation is done by considering Jiangsu power grid in eastern china, including synchronous condenser, STATCOM and UPFC. The results show that the proposed model and algorithm are corrective and effective.

Research on the Coordinated and Sustainable Development of Jiangsu Power Grid under the “Double Carbon” Goal

Under the “double carbon” goal, renewable energy power generation will become the mainstream power generation in the future. The offshore Jiangsu Province has relatively abundant renewable resources, and it also creates favorable conditions for Jiangsu Power Grid Corporation to invest in renewable energy power generation business in the future. The new round of power system reform has had a profound impact on the determination of the investment scale of power grid companies and the optimization of the investment structure. This article first sets the future power supervision scenarios, and then measures the investment capacity and investment needs of power grid companies under different scenarios, determines the investment scale, conducts a coordinated analysis of investment capabilities and investment needs, matches investment capabilities and investment needs, and satisfies investment Under the premise of demand, improve investment efficiency, and finally realize the coordinated and sustainable development of Jiangsu Power Grid investment.

Neural-network-based Power System State Estimation with Extended Observability

This paper proposes a neural-network-based state estimation (NNSE) method that aims to achieve higher time efficiency, improved robustness against noise, and extended observability when compared with the conventional weighted least squares (WLS) state estimation method. NNSE consists of two parts, the linear state estimation neural network (LSE-net) and the unobservable state estimation neural network (USE-net). The LSE-net functions as an adaptive approximator of linear state estimation (LSE) equations to estimate the nominally observable states. The inputs of LSE-net are the vectors of synchrophasors while the outputs are the estimated states. The USE-net operates as the complementary estimator on the nominally unobservable states. The inputs are the estimated observable states from LSE-net while the outputs are the estimation of nominally unobservable states. USE-net is trained off-line to approximate the veiled relationship between observable states and unobservable states. Two test cases are conducted to validate the performance of the proposed approach. The first case, which is based on the IEEE 118-bus system, shows the comprehensive performance of convergence, accuracy, and robustness of the proposed approach. The second case study adopts realworld synchrophasor measurements, and is based on the Jiangsu power grid, which is one of the largest provincial power systems in China.

Security-Constraint Unit Commitment for AC/DC Transmission Systems with Voltage Stability Constraint

Due to the inherent characteristics of weaker voltage supporting ability, line-commutated converter based HVDC technologies have significant effects on AC/DC hybrid power grid’s voltage stability. These has led to new challenges for power grid operators in terms of ensuring power system security. To address these challenges, a unit commitment of receiving-end in AC/DC hybrid grid is presented in this paper. In the proposed model, we employ static voltage stability constraints to guarantee enough voltage supporting capacity from thermal plants at HVDC feed-in area. Based on the characteristics of the model, Benders decomposition and mixed integer programming algorithm are used to get the optimal transmission power of HVDC and schedule of thermal generators. The study is done by considering IEEE-39 and Jiangsu power grid in eastern China, containing two and three HVDC transmission projections respectively. Numerical results on two benchmark problems illustrate the effectiveness of the proposed algorithm, both in terms of convergence rate and solution quality.

Efficient uncertainty quantification in economic re-dispatch under high wind penetration considering interruptible load

Due to the high variability and intermittency of wind power generation, operators tend to have a corrective stage to adjust their predictive dispatch schedules for re-balancing the system following a contingency in the real-time market. This paper presents a new probabilistic real-time re-dispatch model integrating interruptible load (IL) programs with the aim to minimize the total operational cost. The problem is formulated in a probabilistic optimal power flow (P-OPF) framework, accounting for uncertainties on both IL response and wind power forecasts. To address this problem, we develop a probabilistic collocation method (PCM) combining techniques of sparse grids and correlation control, which enables efficient and accurate propagation of correlated uncertain variables with relatively low computational cost. The effectiveness of the proposed model and computational strategy are demonstrated on the modified IEEE RTS 24-bus test case and a simplified regional Jiangsu power grid, where the impacts of IL pricing and capacity on the re-dispatch results are further explored.

Minimum Frequency and Voltage Stability Constrained Unit Commitment for AC/DC Transmission Systems

An increased use of the high-voltage direct current (HVDC) technologies can have important effects on frequency performance and voltage stability of the receiving-end grid during normal operation as well as during blocking failure. The main reasons are the inherent characteristics of the HVDC such as its much larger capacity than thermal plants and lack of voltage supporting ability to the alternating current (AC) grid. These has led to new challenges for AC/direct current (DC) power grid operators in terms of ensuring power system security. To address these challenges, a unit commitment (UC) of the receiving-end in the AC/DC hybrid grid is presented in this paper. In the proposed model, primary frequency modulation constraints are added to provide sufficient capacity for HVDC blocking. Besides, grid security constraint after secondary frequency regulation is also considered because HVDC blocking failure would cause large range power transfer and transmission lines overload. Meanwhile, voltage stability constraints are employed to guarantee enough voltage supporting capacity from thermal plants at the HVDC feed-in area. Based on the characteristics of the model, Benders decomposition and mixed integer programming algorithm are used to get the optimal transmission power of the HVDC and schedule of thermal units. The study is done by considering the IEEE-39 and Jiangsu power grid in eastern China, containing two HVDC transmission projections respectively. The results are also validated by simulation of different HVDC blocking failure scenarios.

Study on waveform parameters of impulse test voltage and on-site docking method for EHV/UHV GIS

GIS (gas-insulated metal-enclosed switchgear) is one of the important components in modern electrical power systems. Compared with traditional open switching devices, GIS has many advantages such as compact structure, smaller occupied area, little influence from environment as well as safe and reliable operation [1–3]. Statistical data show that equipment failure rate of GIS is only 20%–40% of traditional open switching devices. However, as GIS is designed as a fully enclosed structure, once something goes wrong, the diagnosis process is much more complex and the time necessary for fault repair becomes much longer [4–5]. For instance, a severe short circuit fault occurred in Jiangsu Power Grid, China in 2014 due to the development of cracks on a disc insulator. In the same year, abnormal discharges occurred in GIS substations because of a disconnector fault that led to large economic loss and undesired social impacts. Much work had, therefore, been done on analyzing transient events in gas insulated installations in China and internationally [6–9].

Engineering practice of large‐scale millisecond accurate load control system of large power grid

Under the background of large-scale development and utilization of clean energy, there are serious security and stability risks and load balance problems in power grids with high penetration of clean energy and high portion of external power supply. Therefore, Jiangsu Electric Power Company has started the construction of the millisecond accurate load control system (MALCS). In this article, the theoretical basis of the MALCS is introduced from several aspects: the interruptible load, steady state, and transient state control technique of large-scale load. On this basis, the authors put forward the overall architecture, transmission channel structure, and control strategy of the MALCS. Subsequently, this article introduces the first-phase and the second-phase projects of MALCS construction in Jiangsu power grid, and the actual load-shedding test of Jiangsu MALCS. The results of the actual test show that the overall motion time of the Jiangsu MALCS meets the design requirements, and the MALCS can offer an effective frequency support to Jiangsu and East China Power Grid in case of severe failures. Finally, this article summarises the experience of MALCS construction, introduces the expansion plan of MALCS, and forecasts the future development direction and application of the system.

Correlation analysis and prediction of power network loss based on mutual information and artificial neural network

The research and analysis of network loss is a hot spot in power system research in recent years. This paper firstly uses the principle of mutual information to reveal the influencing factors closely related to network loss, and ranks these related factors according to the degree of influence of network loss. Secondly, according to the analysis results of mutual information, the input of neural network training is optimized, and BP neural network is used to establish corresponding prediction models for 6 different types of network losses. Finally, the actual statistical data of a certain area of Jiangsu Power Grid is used for simulation analysis. The results show that the model established by the combination of mutual information method and BP neural network has better prediction effect on network loss and less error.

Impact of Low Data Quality on Disturbance Triangulation Application Using High-Density PMU Measurements

High-density PMUs can be implemented to estimate the location of a large power system disturbances based on the theory of Time Difference of Arrival (TDOA). Unfortunately, real-world measurements suffer from low data quality issues frequently caused by various uncontrollable and unpredictable factors. In this paper, four types of practical low data quality issues from onsite PMUs are first identified from the industry perspective. Then, the impacts of each low-quality data issue on disturbance triangulation are explored using real-time measurement cases from Jiangsu power grid with a high-density PMU network. This paper provides valuable guidance for utility operators and academic researchers to use actual PMU data for power grid applications.

Brief analysis of Jiangsu grid security and stability based on multi-infeed DC index in power system

The impact of Multi-infeed HVDC has gradually increased to security and stability operating in Jiangsu power grid. In this paper, an appraisal method of Multi-infeed HVDC power grid security and stability is raised with Multi-Infeed Effective Short Circuit Ratio, Multi-Infeed Interaction Factor and Commutation Failure Immunity Index. These indices are adopted in security and stability simulating calculation of Jiangsu Multi-infeed HVDC system. The simulation results indicate that Jiangsu power grid is operating with a strong DC system. It has high level of power grid security and stability, and meet the safety running requirements. Jinpin-Suzhou DC system is located in the receiving end with huge capacity, which is easily leading to commutation failure of the transmission line. In order to resolve this problem, dynamic reactive power compensation can be applied in power grid near Jinpin-Suzhou DC system. Simulation result shows this method is feasible to commutation failure.

Statistical Analysis of Meteorological Disasters in the Jiangsu Power Grid and Prevention Methods

With the obvious global climate change and the rapid development of an industrial economy in Jiangsu, the number of failures in power equipment caused by meteorological disasters has been increasing every year, especially contamination flashover faults and wind deflection faults. Based on extensive investigation and analysis, this paper conducts a statistical analysis of the temporal and spatial distribution of the typical meteorological conditions in the Jiangsu area. This paper also analyses the effects of the main meteorological disasters and defensive measures that have been taken to prevent them in recent years, and the paper summarizes the characteristics of the faults in a typical case. Finally, the paper gives some overall advice for preventative measures from the perspective of design planning, applications of new technology, disaster warnings and so on. These recommendations may provide an important reference for the design, maintenance and accident prevention for power grids that experience similar meteorological disasters.