Pei Bie

Probabilistic dynamic load flow algorithm considering static security risk of the power system

Nowadays, the stable and secure operation of power system has attach more and more attention. The traditional static security analysis is based on deterministic load flow, which cannot reflect the uncertainty of load and the probability of branch outage. In addition, the conventional load flow model does not consider the static power-frequency characteristic of generators and load, which is not in accordance with the real operating condition of power system. In order to provide comprehensive static security risk assessment for the power system, so that the potential dangerous and vulnerable part of power system can be recognized before serious outage happens, a Probabilistic Dynamic Load Flow considering Static Security Risk (PDLF-SSR) algorithm is proposed, in which a new state variable - system frequency is added. And the loss is no longer undertook by balancing generator only but by all generators having speed controllers. In addition, this paper also considers the contingency set of power system by calculating the probability of each contingency happening and then obtaining the PDLF of each contingency. Thus, the overall PDLF considering contingency set can be obtained by combining the full probability theory and PDLF based on cumulants. The algorithm can provide valuable information for power system planning, reliability analysis and static security risk assessment.

Economic benefits evaluating of wind power integration considering transmission congestion

In this paper, a model of evaluating the economic benefits brought by wind power integration considering transmission congestion is proposed, in which the Probabilistic Load Flow based on Cumulants Method (PLF-CM) is applied to calculate the probability distribution of section power flow. According to the case study, the transmission congestion is the main factor that limits the utilization of wind power, which also limits the economic benefits of wind power. Moreover, the different penetration of wind power and different integration places of wind farms also bring different benefits to the grid, which can provide some references of choosing appropriate wind power integrating places and deciding the best integrating wind power capacity for power grid plan-makers.

Probabilistic power flow using improved Monte Carlo simulation method with correlated wind sources

Probabilistic Power Flow (PPF) is a very useful tool for power system steady-state analysis. However, the correlation among different random injection power (like wind power) brings great difficulties to calculate PPF. Monte Carlo simulation (MCS) and analytical methods are two commonly used methods to solve PPF. MCS has high accuracy but is very time consuming. Analytical method like cumulants method (CM) has high computing efficiency but the cumulants calculating is not convenient when wind power output does not obey any typical distribution, especially when correlated wind sources are considered. In this paper, an Improved Monte Carlo simulation method (IMCS) is proposed. The joint empirical distribution is applied to model different wind power output. This method combines the advantages of both MCS and analytical method. It not only has high computing efficiency, but also can provide solutions with enough accuracy, which is very suitable for on-line analysis.

A research of D-FSC technology for improving voltage quality in distribution networks

The series capacitor can improve the transmission capacity and voltage stability effectively. The fixed series capacitor (FSC) applied to the distribution networks can improve the voltage quality and reduce the system losses. This paper presents the analysis methods of D-FSC used to regulate the distribution network voltage. For a typical radial 110kV high voltage distribution grid, we selected the compensation position and calculated the compensation capacity of single-point and multi-point compensation methods, then do the research of the relationship between the compensation capacity and compensation effects. In the scheme proposed, the D-FSC can effectively improve the voltage quality and reduce system losses.

Dynamic stability analysis of the interconnected power system with Mengxi UHVDC integration

Due to the mismatch between power supply and demand, in addition with the increasingly prominent problem of environmental pollution, UHV AC/DC power transmission over long distance obtains rapid development in our country. With the expansion of the power grid, regional low frequency oscillation has become one of the major problems that endanger safe and stable operation of power system. In this paper, taking a large-area interconnected system integrated with Mengxi UHVDC transmission line as the background, dynamic stability of the system is analyzed using small signal analysis method and time-domain simulation based on PSASP under different load and UHVDC operating conditions. The results show that when DC out of running, weak damping will appear in the interconnected power grid. PSS is the most economical and effective equipment for damping low frequency oscillation, which can perform well to both the local mode and the inter-area one. In view of the existing weak damping mode, PSS parameters are optimized which effectively improve the system damping, thus insuring the safe and stable operation of the system after the UHVDC line access.

Probabilistic Available Transfer Capability Calculation of Wind Farm Incorporated Power System

The paper mainly studies the available transfer capability of wind farm incorporated power system, and proposes an on-line calculating method considering many uncertain factors. First based on continuation power flow, an improved algorithm of the key constraint by linear prediction is proposed so as to obtain deterministic ATC with the expansion power flow equation. Then Monte Carlo simulation is used which takes many uncertain factors into considerations, such as wind speed, the random fault of generators and lines, the fluctuation of generators and load, etc. With hierarchical clustering algorithm, the samples with the same key constraint can be divided into one category without repeatedly predicting key constraint, so the probabilistic ATC in all kinds of conditions can be got rapidly and precisely. Finally a case study demonstrates the validity and superiority of method proposed in this paper. The research could be a valuable reference to power market operations and wind farm planning.