Grid-connected Units Research Articles

Optimization technology of hydroelectric power plant unit speed control based on the constriction coefficient-based particle swarm gravitational search algorithm fusion model

In recent years, the integration of wind power into hydropower networks has become a trend. But after wind power is connected to the grid, its unstable power will have an impact on the stability of the power grid. In order to improve the impact of wind power grid connection on the stability of the power supply network, a water motor speed control fusion model considering wind power interference is proposed. Firstly, analyze the impact of wind power grid connection and construct a speed regulation model for grid connected units. Secondly, the gravity search algorithm is introduced to optimize the unit speed control parameters. Considering that the algorithm is prone to local convergence, the convergence factor particle swarm optimization algorithm is adopted to optimize the gravity search algorithm. In addition, considering the impact of wind power interference on unit regulation, the Hopf bifurcation theory is introduced to analyze the dynamic regulation parameter range of hydropower units, in order to meet the requirements of stable operation of the power grid. The research contribution is mainly reflected in suppressing wind power grid connection interference through the speed regulation of hydroelectric units. At the same time, considering the impact of multiple interferences on grid connection, an intelligent model is introduced to optimize the speed control parameters of the unit, thereby improving the stable impact of wind power grid connection on the water conservancy grid. In the simulation analysis of hydroelectric unit speed regulation, after adding 5 % disturbance signal, the proposed model under rigid water hammer disturbance could stabilize the unit's stable control within 15 s, which is superior to other models. In the simulation analysis of speed regulation under wind power disturbance, the proposed model could achieve the fastest and most stable speed regulation under rigid water hammer step wind power disturbance, with a duration of 60 s. The proposed model could respond quickly to small overshoot and overshoot in elastic water hammer slope type wind power disturbances. Therefore, the proposed speed regulation technology for hydropower units has excellent application effects in practical scenarios, which will provide effective technical references for wind power grid connection and hydropower unit regulation.

Cooperative control of time-delay wind power grid-connected unit under actuator saturation based on Hamiltonian method

In large-scale wind power generation, wide area control is often employed to overcome power oscillation, but this can result in the appearance of time-delayed voltage, which is transmitted to the wind power grid-connected system as an input signal. Additionally, ensuring the security of multi-grid parallel connection requires limiting the amplitude of the input signal. To address these challenges, this paper investigates the cooperative control problem for time-delayed wind power grid-connected unit under actuator saturation constraints. A novel control strategy that combines passive control with synchronous control is proposed. The system is transformed into a Hamiltonian structure, and a passive controller is designed using the principle of interconnection and damping assignment passivity-based (IDA-PB) to ensure stability. Based on this, an output feedback synchronous controller is proposed to account for saturation when multiple grids are connected in parallel. Stability criteria are provided to ensure the asymptotic stability of each closed-loop system and synchronous stabilization of all systems. Finally, simulation results verify the effectiveness of the proposed control strategy.

Research on Intelligent Frequency Regulation Capability Evaluation Technology for Coal-Fired Units Based on Autonomous Controllable PLC

The generation frequency of grid-connected units determines the power supply reliability of the grid and primary frequency regulation, as the first guarantee to stabilize the grid frequency is affected by the category of generating units and operation mode and lacks systematic real-time optimization and monitoring means. This paper takes a 300MW sub-critical heating unit as the research object, and researches, and analyzes three aspects of signal homologation, multi-dimensional optimization, and intelligent decision-making to establish the evaluation model of the primary frequency regulation capability of the unit. The evaluation accuracy of the assessment model reaches 83%, develops the control platform based on autonomous controllable PLC, realizes intelligent dynamic control and the replacement of traditional optimization technology means, also improves the qualification rate of primary frequency regulation by about 23.2%.

Grid-Connected Microbial Fuel Cell Modeling and Control in Distributed Generation

Water shortages and water pollution have seriously threatened the sustainable development of the community. The grid-connected microbial fuel cell is an effective way to control the cost of wastewater treatment plants. Moreover, it solves the problem of low efficiency and high energy consumption. In view of the characteristics of strong coupling, non-linearity, and internal load in the process of microbial fuel cell grid connection, it is necessary to design the grid-connected unit of power electronic device. Based on the establishment of the microbial fuel cell stack model, the stability control and the constant power control scheme were designed for the chopper and inverter, respectively. The simulation results showed that the control strategy with the combination of voltage stabilizer and constant power can make a grid-connected system of all phase voltage and frequency output. The three-phase voltage Uabc was steady at 7 h and the voltage amplitude was controlled at roughly 380 V, according to the output voltage waveform. The value was 50 Hz, which satisfies the criteria for grid connection.

Research on Dispatch Optimization of Self-owned Power Plant under High New Energy Penetration

Considering that self-owned power plant (SPP) can accommodate more new energy generation, this paper proposes a joint dispatch optimization method of SPP. First, two market patterns of SPP considering its load characteristics were established. Then, a self-optimization model of SPP was built with the goal of minimizing SPP operating costs, and a joint optimization model of both SPP and the grid was constructed with the goal of minimizing total system operating costs which comprehensively considered the constraints of SPP interests, unit generation capacity, new energy accommodation requirement and grid security in optimizing the output of SPP and grid-connected units. Next, the optimization models were solved by NSGA-II algorithm. Finally, a comparative case-study on the two models was carried out, and the results showed that SPP can help to accommodate more new energy and reduce system operating costs.

A Simple Safety Control Method for PSS Critical Gain Test

As an additional control function of the generator excitation system, power system stabilizer (PSS) plays an important role in suppressing the low frequency oscillations of the power system. In this paper, the focus of research lies in PSS field test. For the risk of oscillations that may be triggered in the PSS critical gain test, a simple safety control method is proposed. The critical gain test is performed by temporarily reducing the PSS output limit value to obtain a PSS operating gain more safely. Taking the PSS field test of a grid-connected unit of Hunan Power Grid as an example, the applicability of the method is verified.

Study on the Improved Evaluation Method of Primary Frequency Modulation for Grid-connected Units

The primary frequency modulation function of generating units is an important means to maintain the frequency stability of the power grid. The reasonable assessment criteria help to regulate the primary frequency modulation performance of generating units and enhance the enthusiasm of units to participate in frequency modulation auxiliary services. On the basis of mastering primary frequency modulation principle, the response characteristics of the electro-hydraulic governor and the turbine under frequency excursion are analysed in detail. Aiming at the shortcoming of the current primary frequency modulation evaluation standard, an integral electricity algorithm with different weights added according to the contribution of primary frequency modulation is proposed. Finally, based on the concrete example, the correctness and rationality of the improved method are verified.

Improved Boiler-Turbine Coordinated Control of CHP Units with Heat Accumulators by Introducing Heat Source Regulation

It is significant for power system stability to improve the operation flexibility of grid-connected units. Such improvement has always been a hot topic, especially for coal-fired units. In recent decades, it has become increasingly urgent and challenging as large-scale fluctuant renewable energy is connected to the power grid. Boiler-turbine coordinated control strategy (CCS), which is employed to perform unit load control according to automatic generation control (AGC), has a slow ramp rate in general on account of large delay and inertia of boiler, so to improve the unit operating flexibility, it is necessary to explore usable heat storage and optimize the control strategy. In combined heat and power (CHP) units with heat accumulators, their heat and power are decoupled. Therefore the extraction steam that goes to the heating station can be regulated flexibly even operating in “heat-led mode”. The change of extraction steam flow has a significant influence on the turbine power output, so we propose to improve the load-following capability of CHP units by regulating the heat source flow. In this paper, the influencing model is set up, and it is about heat source flow variations on the electric power output. The load control strategy is further optimized and designed through combinations of CCS and heat source regulation. Finally simulations and analysis are performed on a 330MW CHP unit, and the results reveal that the power ramp rate with our strategy is two times faster than that with traditional strategy.

Design and Implementation of a Two-Stage Grid-Connected High Efficiency Power Load Emulator

The need to reduce the time consumption in developing and implementing power converters, and to improve the effectiveness of the test equipment, continues to grow. This trend is further accelerated through the development of electricity-based technology, such as the electric or hybrid vehicle. As the price of energy continues to increase, regenerative test equipment used for validating power converters are gaining importance and attention. This paper focuses on the development of a two-stage regenerative power load emulator. This type of intelligent load requires a connection to the network interface, which, for some applications, should be bidirectional and must possess a galvanic isolation. The development of such grid-connected unit that processes ac-dc conversion is treated in this paper. A 5 kW prototype is used as a base to model, simulate, design, implement, and test such a system. The stability of the interconnection between the two conversion stages is established and tested in real-time applications. The prototype was tested at 180, 220, and 260 V RMS. The measured efficiency is higher than 90%, and the power factor is 0.99 over a wide range of operation.

Wind desalination for the Island of Mykonos in Greece: a case study

The Greek island of Mykonos belongs to a large group of islands in the Aegean Sea, which suffers from poor natural water resources. On the other hand, it is one of the windiest places in Europe. In the last decades, the exploitation of wind potential to produce potable water through desalination has been considered as a promising alternative for standalone or grid-connected units. In this paper, a methodology for the design of a wind desalination system that matches the needs of the local society are discussed. The existing, grid-connected, seawater reverse osmosis plant, producing 4,500 m3/day, is considered as the basis for the analysis. A series of common commercial wind turbines were examined to suit the site characteristics and energy demands. The target is to cover the energy needs of the desalination unit exclusively from wind energy. The work was performed under the terms of a diploma thesis, and the ultimate scope is to illustrate the benefits of the use of renewable energy sources in desalination units in the Greek islands, where electricity is covered by environmentally unfriendly, noncost effective autonomous power stations and the provision of fresh water remains an unsolved problem.

SOFC-based micro-CHP system as an example of efficient power generation unit

SOFC-based micro-CHP system as an example of efficient power generation unit Microscale combined heat and power (CHP) unit based on solid oxide fuel cells (SOFC) for distributed generation was analyzed. Operation principle is provided, and the technology development in recent years is briefly discussed. System baseline for numerical analysis under steady-state operation is given. Grid-connected unit, fuelled by biogas corresponds to potential market demand in Europe, therefore has been selected for analysis. Fuel processing method for particular application is described. Results of modeling performed in ASPEN Plus engineering software with certain assumptions are presented and discussed. Due to high system electrical efficiency exceeding 40%, and overall efficiency over 80%, technology is an example of highly competitive and sustainable energy generation unit.