Rolling planning model for high proportion renewable energy generation power system considering frequency security constraints

To optimize the dispatch and operation control of high proportion renewable energy power system, it is necessary to accurately quantify and evaluate the operational risk of system. For the high proportion renewable energy power system with uncertain wind and light sources, this paper presents a operational risk assessment method of wind and water systems based on probability assessment. By analyzing the distribution of uncertainty probability of system, the state probability is expressed as wind power output probability, solar output probability, transmission line probability and real-time state probability of system components. Use the analytic hierarchy process to assign weight to each type of risk indicators to solve the importance matching problem of different types of risk. On this basis, a operational risk assessment model is built by using Monte Carlo method which is used to select the real-time system states. Finally, an example is analyzed based on the actual power grid in a certain area, and calculation results show that the proposed quantitative calculation method for operational risk assessment of wind, solar and water multi-energy power systems can effectively evaluate the actual operation risk of system and meet the risk assessment requirements of high proportion renewable energy power system.

This study constructs a novel virtual synchronous generator system based on a transfer function, and optimizes the parameters of the model by using the improved whale algorithm to improve the frequency control ability of virtual synchronous generator. Virtual synchronous generator technology helps to solve the problem that the integration of large-scale renewable energy generation into the power system leads to the deterioration of system frequency stability. It can maintain the symmetry of grid-connected scale and system stability. The virtual synchronous generator technology makes the inverter to have the inertia and damping characteristics of a synchronous generator. The inverter has the inertia characteristics and damps to reduce the frequency instability of high penetration renewable energy power system. The improved whale algorithm is efficient to find the best combination of control parameters and the effectiveness of the algorithm is verified by microgrid and power system. The results show that the proposed frequency coordination control scheme suppresses the frequency deviation of power system and keep the system frequency in a reasonable range.

The UHVDC sending-end power grid with high proportion of renewable energy has serious transient voltage stability problems. Firstly, the structure of renewable power systems and the overvoltage protection logic of the convertor-based renewable generators are introduced. Then, the transient overvoltage characteristic of the high renewable power-penetrated UHVDC sending-end power grid under the DC blocking fault and the commutation failure is analyzed. And the mechanism of renewable generator cascading overvoltage tripping is analyzed in the meantime. On this basis, the transient voltage security index system based on the multiple-two-element table, consisting of the local index for a single node and the global index for the whole system, is established under the single fault and the multiple-fault set respectively. Finally, the effectiveness of the proposed indexes is shown by some case studies of Qinghai Power Grid in China.

In recent years, blackouts caused by extreme weather show a trend of frequent occurrence. This paper analyses the external causes of blackouts, summarizes the evolution process of blackouts, discusses the internal causes of blackouts in power system, analyses the challenges faced by power system under the superposition of extreme weather and renewable energy, and finally puts forward some suggestions for the planning of high proportion renewable energy power system.

Based on IGDT (Information Gap Decision Theory), this paper studies the economic dispatch problem of water, light and wind power systems based on the comprehensive consideration of the respective constraints and joint operation constraints of the four energy characteristics. Based on the actual operation situation, a joint scheduling model is built. By selecting typical daily load curves and different optimization strategies in different seasons, the participation factor is adjusted to change the cost that decision makers can bear, and the relationship between system scheduling cost and risk tolerance is verified.

In the context of the “dual carbon” goal, a high proportion of renewable energy connected to the grid to replace traditional high-carbon units has become a general trend. Taking the high proportion of renewable energy power system as the research object, the medium and long term planning of the installed capacity of source, grid, load and storage of power system is carried out considering the two dimensions of investment and operation maintenance, and the optimization model of source, grid, load and storage of power system is established. A low-carbon dispatching model considering carbon emission and demand response of distribution network is also proposed. Firstly, considering the characteristics of distribution network receiving power from the main network, the carbon emission model of distribution network based on carbon emission flow theory is constructed, and the low-carbon index of distribution network is proposed. Secondly, the improved dynamic carbon emission factor of distribution network is proposed, which is used as a guide signal to provide reference for low-carbon electricity consumption of distribution network users. According to the characteristics of users in the distribution network, the industrial demand response model aiming at low dispatch cost and low carbon and the residential demand response model aiming at electricity consumption satisfaction and low carbon satisfaction are constructed respectively.

Low inertia of distributed energy resources (DERs), high penetration levels of renewable energy sources (RESs), and load demand variations put the islanded microgrids' (MGs) security at the risk of instability. This paper proposes a two-stage stochastic model for coordination of DERs and responsive loads in islanded MGs with regard to voltage and frequency security constraints. Based on the proposed model, scheduling of the controllable units in both supply and demand sides is done in a way not only to maximize the expected profit of the MG operator (MGO) but also to minimize the energy payments of customers under the premise of security and stability of MG. An AC optimal power flow procedure is also used to study the operating condition of the system under uncertainties and to guarantee acceptable nodal voltages and system frequency under different scenarios. The proposed stochastic optimization model is then applied to a typical autonomous MG, and its effectiveness is demonstrated through different scenarios under uncertainties in load consumption and renewable energy resource (RES) productions. Simulation results demonstrate that customers' participation in DR programs has a significant effect on the system's performance in terms of voltage and frequency stability. Moreover, optimal coordination of DERs and responsive loads can increase the expected profit of MGO significantly. The effectiveness of the proposed scheduling approach is verified on an islanded MG test system over a 24-h period.

As the renewable energy generation continues to grow rapidly, the traditional power system is transitioning to a new power system with a high proportion of renewable energy. Consequently, the static voltage stability problem is becoming increasingly prominent. To address this issue, voltage support by the renewable energy generation is necessary. In this paper, we first analyze static voltage stability based on single source infinite system model. Then, we establish a simplified method to calculate the reactive power demand based on the short-circuit ratio. The method is further extended to multi-infeed renewable energy power systems using impedance matrix theory. Finally, we validate the effectiveness of the proposed method by simulating the IEEE 39 node system and a multi-infeed renewable energy power system.

In considering of high proportion of renewable energy supply in 2050, the accelerating of energy consumption gross, source and environment can affect the energy system restrict affection are stronger. Add wind and solar to electricity energy with large amount of energy source exploitation. The energy source amount per person is lower. Considering the renewable energy amount and supply, primary energy storage and structure problem is standing out. Before the wide spread of renewable energy, Using the high-carbon energy in China can pollute seriously. Chinese energy supply and demand problem is research key point. This paper researches Chinese energy supply and demand pattern system and evaluation methodology, gives out the inner and outer influencing elements. And evaluate Chinese energy supply and demand pattern from energy gross, structure, distribution and transportation. Use energy supply synthesize radar comparison chart in certain time period. From energy security, economy, clean and efficiency, analyze the benefit comparisons of Chinese energy supply and demand pattern. This energy supply and demand pattern model will give one certain theoretical analysis and practice reference to the further high proportion of renewable energy.

With the interconnection of regional grids and the increasing penetration of renewable energy, the order of the power system model is getting higher and higher, which brings great challenges to the accuracy and real‐time performance of electromagnetic transient (EMT) simulation. The simulation of power systems with a high proportion of renewable energy requires a sharp increase in the performance of the hardware platform and the parallelism of the simulation algorithm. To solve this problem, the paper proposes a fine‐grained parallel modelling method for power systems with a high proportion of renewable energy, which is inspired by the latency insertion method used in the design of large‐scale integrated circuits. And this method is implemented on GPU to achieve the component‐level and device‐level parallelized simulation of power systems with a high proportion of renewable energy. Finally, the correctness of the proposed algorithm and the CPU‐GPU cooperative architecture is verified based on an improved 118‐bus case. The cascade system of the improved 9‐bus case is used as an example to verify the superiority of the proposed algorithm in terms of simulation efficiency.

Primary frequency regulation scheme applicable to LCC – VSC series hybrid HVDC considering AC voltage stability at receiving end

Renewable power systems dynamic security using a new coordination of frequency control strategy based on virtual synchronous generator and digital frequency protection

Inertia plays a key role in power system resistance to active power disturbance. Under the background of large-scale renewable energy participating in power systems, the problem of weak inertia support brings challenges to power system security and stability operation. Based on the analysis of system equivalent inertia time constant, the inertia time constant of renewable energy access to the system in different scenarios are solved in this paper. According to the effects of inertia time constant change on the dynamic characteristics of system frequency, the assessment indexes of equivalent inertia time constant and the rate of change of frequency (RoCoF) is proposed. Then the inertia of high proportional renewable energy system and frequency stability is evaluated, combined with the assessment index of frequency deviation. Finally, the maximum renewable energy penetration of the system is analyzed with the proposed indexes. IEEE 30-bus system is used to verify the effectiveness of the proposed method by analyzing the RoCoF and equivalent inertia time constant assessment indexes.

This chapter presents a comparison of the performance of integral (I) and proportional-integral-derivative (PID) controllers in frequency stabilization or load frequency control (LFC) of two-area interconnected power system considering generation rate constraints (GRCs) with Doubly fed induction generator (DFIG)-based wind energy. Two mathematically models are identified for investigations. Power system model 1 is two-area interconnected power system which contains two identical non-reheat thermal plants without DFIG participation. Whereas, power system model 2 contains two identical non-reheat thermal plants with dynamic participation of DFIG at both areas. Moreover, Harris Hawks Optimizer (HHO), Salp Swarm Algorithm (SSA), and Sine Cosine Algorithm (SCA) are applied to find the optimal values of the controller settings mentioned above. The effectiveness of the proposed controllers, which are optimally designed by several optimization techniques (i.e., HHO, SSA, and SCA) is tested and verified through an interconnected power system comprises two identical non-reheat thermal power plants with/without DFIG participation. Time-domain simulation results of the studied power system with all mentioned optimization techniques are carried out using Matlab/Simulink® software to validate the robustness of the proposed controllers.

There will be much deep coupling among the large-scale renewable generators, multi-HVDC, and AC system after the system disturbance, in the power system with high proportion renewable energy and multi-send HVDC. As a consequence of that, the risk of cascading failures is greatly increased. Further research on the control strategy of the cascading failure is therefore required. Firstly, time domain simulation is used to search cascading chains with high risk, which is based on action evaluation index of security control devices. So that the actual evolution process of cascading failures can be better expressed in fault chain model. Secondly, a new emergency control method based on searched cascading chains is proposed, to set up emergency control measures for those events that may evolve into cascading failures. This new control method could further strengthen and perfect the ability to block the fault chain of cascading failure of current emergency control system. In order get the lowest risk cost of the control strategy, the preventive control and emergency control is coordinated and optimized. Finally, simulation results and analysis based on real-sized power grid in Northwest China prove the rationality and effectiveness of the proposed control method and strategy.