Control System Of Power Unit Research Articles

The Design of Parameter Modeling Software Applicable for Turbine Control Systems of Power Units Operated at Deep Shaving States

Against the backdrop of achieving the “dual carbon” reduction goals, the proportion of renewable energy consumption in China is gradually increasing, and more and more thermal power units are gradually being operated at the deep peak shaving states, which puts forward higher requirements for stable operation of the power grid system. In view of the current situation, this paper designs a new type of Python-based parameter modeling software for turbine control systems, including the load selection module, data pre-processing module, parameter identification module, and result output module. To solve the problem that the primary frequency regulation parameters of the units operated at the deep peak shaving states change with the load, the software is designed to set key model parameters of different load segments of the units. The actual measurement results of a unit operated at the deep peak shaving state show that this developed software is convenient and friendly to operate, creates accurate parameter identification results, and has a wider range of applicability.

Modeling, Controller Design and Simulation Groundwork on Multirotor Unmanned Aerial Vehicle Hybrid Power Unit

This paper presents the results of modeling, control system design and simulation verification of a hybrid-electric drive topology suitable for power flow control within unmanned aerial vehicles (UAVs). The hybrid power system is based on the internal combustion engine (ICE) driving a brushless DC (BLDC) generator supplying the common DC bus used for power distribution within the aircraft. The overall control system features proportional-integral-derivative (PID) feedback control of the ICE rotational speed using a Luenberger estimator for engine-generator set rotational speed estimation. The BLDC generator active rectifier voltage and current are controlled by proportional-integral (PI) feedback controllers, augmented by estimator-based feed-forward load compensators. The overall control system design has been based on damping optimum criterion, which yields straightforward analytical expressions for controller and estimator parameters. The robustness to key process parameters variations is investigated by means of root-locus methodology, and the effectiveness of the proposed hybrid power unit control system is verified by means of comprehensive computer simulations.

Modeling, Control System Design and Preliminary Experimental Verification of a Hybrid Power Unit Suitable for Multirotor UAVs

A key drawback of multirotor unmanned aerial vehicles (UAVs) with energy sources based solely on electrochemical batteries is related to the available on-board energy. Flight autonomy is typically limited to 15–30 min, with a flight duration upper limit of 90 min currently being achieved by high-performance battery-powered multirotor UAVs. Therefore, propulsion systems that utilize two or more different energy sources (hybrid power systems) may be considered as an alternative in order to increase the flight duration while retaining key performance benefits of battery energy storage use. The research presented in this work considers a multirotor UAV power unit, based on the internal combustion engine (ICE) powering an electricity generator (EG) connected to the common direct current (DC) bus in parallel with the lithium-polymer (LiPo) battery, and the respective modeling and identification of individual power unit subsystem, along with the dedicated control system design. Experimental verification of the proposed hybrid power unit control system has been carried out on the custom-build power unit prototype. The results show that the proposed control system combines the two power sources in a straightforward and effective way, with subsequent analysis showing that a two-fold energy density increase can be achieved with a hybrid energy source, consequently making it possible to achieve higher flight autonomy of the prospective multirotor (hover load around 1000–1400 W) equipped with such a hybrid system.

Synthesis of Boiler Controllers of the Automatic Power Control System of Power Units

The article concerns the problem of structure-and-parametric optimization of a cascade automatic control system (CACS) by an example of a boiler power controller and a fuel controller. This CACS, which is a part of automatic control systems for power units, consists of two loops, viz. of an inner loop (which purpose is stabilization of the system) and an outer loop (designed for the adjustment) and, also, of two controller, viz. an outer controller (which is a basic one) provided for stabilization of the output value of the object (in our case, of the actual power unit capacity) and of an inner controller (which is an auxiliary one) provided to regulate fuel consumption. The internal controller builds up the control action with the aid of the boiler load controller of the power unit. As compared to single-loop automatic control systems, the cascade system provides better quality of transient control due to the higher performance of the internal loop of the system. This advantage is especially noticeable when compensating for disturbances that come through the channel of regulating impact. The article presents two methods of setting, viz. the fuel controller and the boiler power controller. The application of these methods can improve the quality of power control and reduce fuel consumption in transient modes in comparison with the setting of these controllers of a typical power unit automatic power control system. The results of computer simulation of transient processes in CACS for input step surge and internal perturbation confirm the advantages of the methods are presented in this article.

Analysis of long-term operation of the steam boiler live-steam outlet header and assessment of the feasibility of the header operation during accelerated start-ups

The energy mix in most European countries is now characterized by a growing share of renewable energy sources (RES). The random nature of RES entails the need to balance the differences between the current amount of power generated in the system and the actual power demand. For this reason, power units incorporating steam boilers are most often operated under sub-peak rather than base load regimes. This creates many challenges to boiler operators due to the advanced age of the power units in service. In Poland, for instance, 77% of power units are more than 20 years old and 45% have been working for more than 30 years, which means that most of them are approaching their design life time. Further operation of these units requires a detailed analysis of the degree of wear of critical pressure components, including a thermal and mechanical stress-state analysis. The paper aims to present a methodology of wear degree calculations incorporated in the power unit control system. The performed calculations are based on real measurement data obtained from 8 months of operation of a boiler unit with the steam output of 650·103 kg/h. Wear degree calculations and a thermal and mechanical FEM-based analysis are performed to assess the possibility of shortening start-ups to address the dynamic requirements that power units operating in the Polish power generation system will have to meet.

Parametric Optimization for Automatic Control System of Power Units of 300 MW for the Mode of Variable Pressure of Turbine Inlet Steam

The article deals with the problem of parametric optimization of automatic control systems for power units of 300 MW of Lukoml’skaya GRES in the mode of variable pressure of turbine inlet superheated steam. The modernization of automatic power control systems of all power units of Lukoml’skaya GRES was carried out in the nineties of XX century for the last time. At the moment, these systems no longer meet all the requirements of the new standard, which regulates the participation rates of thermal power units in the normalized primary frequency control and in automatic secondary control of frequency and active power flows. According to this standard, the time to achieve the half value of the required power change should be 10 seconds within the normal and emergency reserves; the time to achieve the full value of the required power change should be 30 seconds within the normal reserve and 2 minutes within the emergency one. The construction of the Belarusian NPP is also being completed; its first unit will be put into operation in 2019, and the second one–in 2020. After the launch of the NPP, the Lukoml’skaya GRES power units will be necessitated to operate in a wide range of load changes. It is for these reasons that it is necessary to improve the efficiency of power units in particular and of the entire power plant in general. This can be achieved with the help of the outlined method of parametric optimization of a typical system of automatic control of power units, which allows improving the quality of control of turbine inlet steam power and pressure. The results of computer simulation of transient processes in the system illustrate the technique described in this article and confirm its correctness and undoubted advantages over other methods of optimization of typical systems of automatic control of power units.

Parametric Optimization for Automatic Control System of 300 MW Power Units at a Constant Steam Pressure Upstream of the Turbine

The problem of parametric optimization of automatic control systems of power units (ACSPU) of 300 MW at the Lukoml’skaya GRES (Lukoml Condensing Power Plant) at a constant superheated steam pressure upstream of the turbine is under consideration. During 1974–1979, eight units of the Lukoml’skaya GRES implemented ACSPU with a leading boiler power control, which will be forced to work in a wide range of loads due to the planned commissioning of two power units of the Belarusian NPP: the first one – in 2019, and the second one – in 2020. The total capacity of the Belarusian Nuclear Power Plant will amount to 2400 MW. In addition, modern requirements for the regulation of the frequency and flows of active electric power in the power system have been tightened: the time to reach the half value of the required power alteration should be 10 seconds within the normal and emergency reserves; the time to reach the full value of the required power alteration should be 30 seconds within the range of the normal reserve and 2 minutes – within the range of the emergency reserve. With this regard, increasing the efficiency of the units operating in the variable part of the electric load schеdule by the use of modern methods of calculation of parameters of the dynamic adjustment of the regulating devices of ACSPU becomes an urgent problem. The methodology of parametric optimization of the typical ACSPU that make it possible to improve the quality of power regulation and the pressure of the superheated steam upstream of the turbine is presented. The described technique is illustrated by the results of computer simulation of transient processes in the system when the task and internal disturbances are worked out, which confirm the correctness of the proposed technique in comparison with the known methods of optimization of the typical ACSPU.

Full Power Experiment Method of Single-Phase PWM Back-to-Back Converter

Based on the single-phase H-H power unit topology in the novel co-phase power supply system, with the back-to-back grid-connected operation method, this paper aimed at solving the problem that in experiment, system capacity constraints caused the failure to achieve unit full power output and proposed the strategy of rectifier voltage, current double closed loop and full disturbance feed-forward control. Finally, based on the digital signal processor (DSP) and complex programmable logic device (CPLD), this study constructed a hardware platform of the power unit control system. Experimental results show that the system is stable, achieving two-way flow of energy.

Automated chemical monitoring in new projects of nuclear power plant units

The development of automated chemical monitoring systems in nuclear power plant units for the past 30 years is briefly described. The modern level of facilities used to support the operation of automated chemical monitoring systems in Russia and abroad is shown. Hardware solutions suggested by the All-Russia Institute for Nuclear Power Plant Operation (which is the General Designer of automated process control systems for power units used in the AES-2006 and VVER-TOI Projects) are presented, including the structure of additional equipment for monitoring water chemistry (taking the Novovoronezh 2 nuclear power plant as an example). It is shown that the solutions proposed with respect to receiving and processing of input measurement signals and subsequent construction of standard control loops are unified in nature. Simultaneous receipt of information from different sources for ensuring that water chemistry is monitored in sufficient scope and with required promptness is one of the problems that have been solved successfully. It is pointed out that improved quality of automated chemical monitoring can be supported by organizing full engineering follow-up of the automated chemical monitoring system’s equipment throughout its entire service life.

Preventing inadmissible erosion-corrosion thinning from occurring in the diffuser segments of feedwater supply control systems of power units at nuclear power stations equipped with RBMK-1000 reactors

Results obtained from investigations of erosion-corrosion processes that occur during operation of the feedwater supply control systems used in power units of nuclear power stations equipped with RBMK-1000 reactors and the sensitivity of these processes to variations in the chemical composition of metal and in the flow path geometry are presented. It is found that local erosion-corrosion thinning of the walls in the diffuser segments of feedwater supply control systems occur mainly due to intense mass transfer in the near-wall region taken in combination with a low content of chromium. Hydrodynamic simulation was carried out, and it was shown based on its results that local erosion-corrosion thinning of the walls of pipeline segments downstream of the valves controlling the supply of feedwater to power units of nuclear power stations equipped with RBMK-1000 reactors can be prevented by subjecting them to appropriate modernization. It is found that the above mentioned diffuser parts can be made more resistant to erosion-corrosion wear by keeping the content of chromium in the main metal and weld joints at a level of no less than 0.25% and concurrently reducing the hydrodynamic effect in the zones of weld connections.

Development of complex systems for automating nuclear power facilities

The basic advances made at the Dollezhal Research and Development Institute of Power Engineering in the development of the control systems and means for civilian nuclear power facilities are presented. Individual means (sensors, executing mechanisms and apparatus) and systems as a whole in the evolutionary development are reviewed in brief. The results of a comparative analysis of foreign and domestic regulatory documents, performed to substantiate the requirements for safety and control systems, are presented. The results of new developments and adoption of control systems for power units with RBMK, commercial and research reactors and new power reactor facilities in the design stage are presented. The level reached for the new systems is evaluated and the main recommendations for their further development are formulated.

Specific features and problems relating to the present stage of technology used to construct automated process control systems for thermal power stations

The main problems relating to technology for development of automated process control systems for power units at thermal power stations implemented on the basis of computerized automation suites with a network structure are analyzed. The results from studies carried out at the Ivanovo State Power Engineering University’s Department of Control Systems are generalized with the purpose of improving the technology of end-to end designing and developing the functional structure of automated process control systems for thermal power stations.

Development of technological algorithms for automated process control systems of power units

We describe the experience process engineers of the All-Russia Thermal Engineering Institute have gained with development of automated control systems for thermal and nuclear power units, including technological elaboration of equipment operating modes, statement of tasks relating to control of transients, and checking and optimization of algorithms with the use of mathematical models.

Improvement of process closed-loop control systems for power units

We describe the results of activities carried out at ZAO Interavtomatika (Interautomatika AG) on the development and putting into use of improved systems for closed-loop control of the main process values of Russian power units equipped with once-through boilers. We also consider a general approach for improving control systems and describe specific technical solutions taken for furnishing the main technological items of coal-and gas-and-oil-fired power units with closed-loop control systems.

An analysis of the effect of introducing complex laws for transforming additional signals in multiloop automatic control systems of power units

We consider the possibility of improving the control law for inertial loops in multiloop automatic control systems. A procedure for tuning such circuits is proposed. A comparison is made between a multiloop automatic control system with a model of the controlled entity and the traditional two-loop automatic control system with a differentiator.