Under the "double carbon" goal, the electricity spot market has become an important platform for renewable energy consumption. Due to the volatility and uncertainty of new energy, high proportion of new energy will bring new challenges after entering the power market. Power to hydrogen (P2H), as a green and low-carbon flexible regulatory resource, can provide a new way for large proportion of new energy into the grid. Firstly, this paper constructs an optimization model of bidding transaction in the spot market of upper electricity energy including day-ahead and real-time levels on the basis of the participation of quotations from new energy stations in the bidding of electricity market and conventional units. Furthermore, the real-time optimization model of the lower-layer wind-hydrogen combined system is further constructed to optimize the output of the wind farm containing P2H. Finally, the improved IEEE 30-node system is taken as an example to analyze the risk of price fluctuation caused by high proportion of wind power participating in the spot market under the dual carbon target, and the economy of wind-hydrogen combined system participating in the spot market is studied. The results show that the wind farm equipped with a certain scale of P2H can effectively reduce the risk of electricity price fluctuation caused by wind power uncertainty in the spot market, improve the utilization rate of wind power, and realize the cheap production of hydrogen, which is economically feasible.
Aiming at the key issues such as energy and electricity cost dredging and unbalanced cost allocation in the bilateral power market under the double-track system in China, the dual settlement system of "day-ahead benchmark, real-time difference, and contract price difference" is used to realize the coupling settlement between the contract market and the spot market, and the construction of the responsible entity is considered. The unbalanced capital apportionment/return model and the bilateral spot market settlement mechanism considering the unbalanced capital processing is designed, and the simulation analysis is carried out with the power market of Zhejiang Province. The calculation example proves the rationality of the settlement mechanism. An effective electricity bill settlement system can improve the enthusiasm of the generators to participate in the electricity market, and provide relevant reference suggestions for the settlement of bilateral electricity markets under the double-track system.
This work is supported by National Natural Science Foundation of China (No. 72174062) and Science and Technology Project of State Grid Zhejiang Electric Power Co., Ltd. (No. JY02202114).
Aiming at utilizing a large number of distributed energy sources in rural areas such as straw and garbage biomass, rooftop photovoltaic power, and decentralized wind power, this paper designs a novel structure of a virtual power plant connected with gas-power plant carbon capture (GPPCC), power-to-gas (P2G), and waste incineration power (WI), namely, a GPW-VPP. Then, the information gap decision theory (IGDT) and fuzzy satisfaction method are applied to construct a nearly zero-carbon optimal operation model. In this model, maximizing revenue and minimizing carbon emissions are selected as the initial goals of the GPW-VPP operation, which are converted into one maximum satisfaction goal. Three uncertainty variables, namely, wind power, photovoltaic power, and user load, are described using the IGDT. Finally, the Lankao Rural Energy Revolution Pilot program in China is selected as the case study to verify the effectiveness of the proposed model. The results show that the proposed operation optimization model and benefit distribution strategy can take into account the interests of different subjects, and at the same time, promote the optimal aggregation and utilization of rural distributed energy, which is conducive to the realization of a clean and low-carbon transformation of the overall energy structure.
The energy structure of the integrated energy system is diverse, and the prices and performances of different models of the same equipment vary greatly. How to determine a reasonable energy structure, equipment model combination and installed capacity in the planning stage is the premise to achieve cost savings in the operation stage. This paper studies the optimization model of "energy structure-equipment model-installed capacity" planning considering carbon dioxide emissions. Firstly, a case-based reasoning technique based on K-nearest-neighbors (KNN) to obtain the energy structure suitable for the proposed park is constructed. Considering the carbon emission ladder cost, and taking the lowest total life cycle cost as the optimization objective, the combination of ant colony algorithm and genetic algorithm is used to solve the optimal equipment model combination and the optimal installed capacity. Finally, the effectiveness of the proposed model in reducing costs is verified by example analysis.
The AC/DC hybrid distribution network has the characteristics of high flexibility and high controllability, and will be widely used in the future distribution network. A two-level planning method for energy storage in AC/DC hybrid distribution network considering flexibility is proposed in this paper. Firstly, this paper analyzes the flexibility requirements in the AC/DC hybrid distribution network and the operating characteristics of the flexible resources considered, and then establishes a quantitative calculation index to measure the flexibility in the operation of the distribution network. Then, K-means clustering algorithm is used to establish the collection of typical operation scenarios for the output and daily load of distributed power generation in distribution network. Secondly, a two-level planning model for energy storage in AC/DC hybrid distribution network is established, which takes into account flexibility. The goal is to minimize the comprehensive operation cost of the distribution network and the optimal level of system flexibility, and the genetic algorithm is used to solve the optimal planning scheme. Finally, on the basis of the improved IEEE 33-node distribution network system, the rationality and effectiveness of the two-level planning model and the optimal configuration of energy storage are verified.
An important link in the flexible DC transmission control and protection system is the communication between the internal control and external equipment, which requires high speed and stability. The localization substitution of the control and protection system puts forward higher requirements for the stability and compatibility of its communication. The measurement required by the inner loop control is collected, processed and transmitted by the merging unit or transformer. Its communication signal has the characteristics of positive and negative Manchester code and various baud rate coding. The conventional decoding algorithm is easy to fail due to poor compatibility. On the basis of the standard of electronic current and voltage transformer, this paper studies and analyzes the encoding and decoding process of its data frame format of the communication protocol, and puts forward and implements the design method for IEC60044-8 communication interface based on positive and negative Manchester code and baud rate dynamic adaptation of domestic FPGA chip. The experimental results show that the scheme has strong real-time performance, high recognition accuracy and strong compatibility, and has a wide range of application value.
The extensive access of the large-scale renewable energy, such as wind power, to power systems will be one of the important directions for the development of the new-type power systems. The power demands of customers can be adjusted by employing the demand response mechanism to improve the flexibility of power system operation and promote the consumption of wind power. In this context, a generation and transmission expansion planning model is proposed taking the incentive-based demand response into account. Firstly, the incentive-based demand response mechanism is introduced, and a demand response model based on the segmented price incentive is proposed. Secondly, a robust generation and transmission expansion planning model based on the information gap decision theory is proposed considering incentive-based demand response, and formulated as a mixed integer linear model. Finally, the Garver 6-bus system and the improved IEEE 118-bus system are served for demonstrating the feasibility and validity of the proposed method.
On March 3, 2022, the failure of Xingda power plant managed by Taiwan Power Company resulted in a large-scale blackout in Taiwan, China, and the blackout lasted for 12 hours until load was restored. The accident affected about 5.49 million people, which had a great negative impact on the local people’s life, economic development and social stability. Firstly, this paper introduces the general situation of power grid in Taiwan, China. Then, the process of power outage is described, and the reasons of power outage are analyzed and combed in combination with the public report of Taiwan Province. Finally, by summarizing the power system problems reflected by the frequent accidents in Taiwan Province in recent years, some suggestions are proposed for the power grid development in the future.
High-voltage DC cables are important equipment for cross-sea long-distance power transmission and new energy grid integration. DC cables with high voltage levels and current capacity are still in the research and development stage.In order to promote the research and development of high-voltage DC cables and test the long-term operation performance, this paper relies on a domestic ±500 kV flexible dc grid project to establish a DC cable comprehensive test station.The DC line of the domestic ±500 kV flexible dc grid project mainly adopts the overhead transmission line scheme. The test station is located at the single-pole outlet of one of the converter stations, and the trial DC cable runs in parallel with the overhead line.The operation control and protection coordination are complex, the reliability requirements are extremely high, and there is no engineering experience to follow.In this paper, aiming at the connection mode of parallel switching operation between 500k V DC cable test section and overhead line, the DC cable monitoring and input and exit control strategy, fault protection strategy and overload operation control protection strategy in the test station are proposed for the first time, and are verified by simulation experiments, it can realize reliable operation of DC cable access to flexible DC grid.
A DC microgrid needs the energy storage system to maintain its stable operation when it is off-grid. In the case of multiple energy-storage converters in parallel, the line impedance mismatch will lead to the SOC of each energy-storage unit cannot be balanced and the output current of the converter cannot be accurately distributed. At the same time, the bus voltage deviation caused by the “virtual impedance” also needs to be compensated. Aiming at a series of problems, an improved SOC equalization control strategy is proposed to adaptively adjust the “virtual impedance” to realize SOC equalization, and a distributed secondary control strategy is proposed to construct a transfer factor containing multiple information λ, thus generating a unique voltage compensation term that can both eliminate the influence of line impedance and restore bus voltage at the same time, so that the communication pressure of the system can be alleviated. In order to obtain the global average information, a distributed dynamic average algorithm controller is designed by using low bandwidth communication to exchange information between adjacent converters according to consistency algorithm. A photovoltaic multi-energy storage system model is built. Simulation and experiments verify the effectiveness and accuracy of the control strategy.
Compared with the system-level load, consumer load has the characteristics of small base, stronger volatility and randomness, which increases the difficulty of consumer load forecasting. With the help of mutual information and deep learning theory, this paper proposes a short-term consumer load forecasting model based on max-relevance and min-redundancy (mRMR) and long short-term memory network (LSTM). Firstly, the mRMR algorithm is used to sort the characteristic variables and select a suitable set of input variables. mRMR can not only ensure the maximum mutual information value between the input variable and the target value, but also minimize the redundancy between the variables. Secondly, the LSTM forecasting model is established for the selected set of input variables. LSTM can better process and forecast time series with long delays, and there will be no gradient disappearance and gradient explosion. Finally, an example is used to verify the effectiveness of the algorithm in this paper.
Power system data may miss during acquisition, measurement, transmission and storage, which threatens the security of power grid. Since traditional missing data reconstruction methods only consider the data distribution and ignore the spatio-temporal characteristics, a power system missing data reconstruction model called ST-SSIM (spatio-temporal seq2seq imputation model) is proposed in this paper. ST-SSIM has an encoder-decoder structure. The encoder is composed of a spatio-temporal information extraction unit which is constructed by graph convolution layer and long short-term memory cell. The decoder is composed of long short-term memory cell and full connection layer. The input of the proposed model includes power system timeseries and adjacency matrix, so ST-SSIM can realize the automatic learning of complex time-space relationship of data. In experiment, compared the proposed method with the existing methods in power grids of different scales, ST-SSIM has the highest reconstruction accuracy, which proves that ST-SSIM can effectively learn the spatio-temporal characteristics of power system data. By discussing the relationship between reconstruction error and the number of missing nodes and time span, it is verified that the reconstruction effect of the proposed model is stable.
As an important network reconfiguration technology, the closed-loop load transfer (CLLT) is of great significance to improve the reliability and economic efficiency of the distribution network. The conventional CLLT has a loop closing impact and the selection of loop closing point is limited by the phase angle difference between two substations. In this paper, two solutions are proposed to solve the technical problems of CLLT with the large angle difference in the Guangzhou distribution network, which are based on series-parallel compensation and back-to-back topology, respectively. They can be applied to a variety of scenarios and provide AC and DC interfaces. The wiring modes of these schemes are given, and their structural characteristics, performance parameters, and operating principles are analyzed. To adapt to the condition of three-phase imbalance and harmonic pollution, the improvement measures of the two schemes are proposed from the structure and control perspective. Finally, the operating principle of the seamless CLLT device in several typical scenarios is verified by simulation, thus providing computational support for the actual development of seamless CLLT.
Aiming at the problems of low inertia and poor anti-interference ability of bus voltage in DC microgrid, a virtual inertia control strategy based on multiple sliding mode variable structure control is proposed in this paper. Sliding mode current control based on the index reaching law is adopted in the inner loop, which can quickly track the given value of grid-connected current and improve the response speed of the system. Virtual inertia control equation and voltage sliding mode surface structure are established in the outer loop to enhance the inertia of the DC microgrid and suppress the fluctuation of the DC bus voltage. The stability of bidirectional grid-connected converter under the proposed control strategy is proved by small-signal disturbance method and Nyquist criterion. Finally, the corresponding simulation model and StarSim HIL hardware-in-the-loop experimental platform are built. The results show that, compared with the traditional virtual inertia control strategy based on PI control and passivity-based control, the proposed control strategy has better dynamic and static characteristics, and improves the stability of the DC bus voltage.
With the increasing proportion of new energy in power system, the safety and stability of large-scale new energy has become a common concern. Taking the 1 000 kV Zhangbei—Xiong’an UHVAC transmission line from the 10 million kilowatt new energy base in Zhangbei area as an example, this paper builds a PSASP electromechanical transient simulation model, which includes new energy model and distributed condenser model with low voltage crossing function. The paper analyzes the constraints of the new energy transmission capacity. And then the influence of different configuration schemes on short-circuit ratio of new energy and the suppression effect of transient overvoltage are studied. Finally, the optimization effect of transient overvoltage problem is verified by ADPSS all electromagnetic transient simulation. The results show that transient overvoltage and steady-state low voltage are the main factors restricting the transmission capacity of UHVAC line from new energy base. The distributed small-scale condenser is installed at the generator end with low short-circuit ratio of new energy, which can effectively restrain the transient overvoltage problem and improve the overall output capacity of new energy. The results of the study are of great reference value for planning, operation and design of the same kind of new energy delivery project in China.
The large-scale wind power integration brings some problems such as the reduction of inertia and the shortage of primary frequency-regulation capability to the power system. Wind farms with deloading operation and frequency-regulation function could effectively deal with these problems. Therefore, a deloading scheme and the corresponding primary frequency regulation strategy of wind farm are proposed. Firstly, the principle of integrated inertia control and pitch-angle control is introduced, and the necessity of deloading operation of wind farm is analyzed. Then the difference of deloading capability of wind turbines with different wind speeds is studied and the deloading power distribution scheme of wind farm is formulated. Furthermore, according to the deloading power distribution scheme, the corresponding primary frequency regulation strategy is proposed to make full use of the frequency regulation capability of wind farm and avoid the secondary frequency drop. The simulation system model is built based on Matlab/Simulink, and the simulation results show that the deloading scheme and frequency regulation strategy could reasonably distribute the deloading power and improve the frequency regulation effect of wind farm.
