Pumped Storage Hydro Units Research Articles

Technical investigation of the ternary pumped storage hydro units with ultra-high-water head

Abstract This paper introduces the ternary pumped storage hydro unit technology and its development status, discusses the technical characteristics of the ternary unit, and looks forward to the broad application prospect of the ternary unit technology in the ultra-high head pumped storage power station. The main technical advantage of the ternary pumped storage hydro unit by using the Pelton turbine as the turbine component is that the hydraulic short circuit operation mode of the combined operation of pump and turbine can realize the smooth adjustment of the input power of the unit pumping condition. In addition, the conversion time between working conditions is greatly shortened compared with the conventional reversible pumped storage unit, thus greatly enhancing the power grid’s ability to absorb and adjust new energy.

Optimal allocation of energy storage capacity for hydro-wind-solar multi-energy renewable energy system with nested multiple time scales

Multi-energy supplemental renewable energy system with high proportion of wind-solar power generation is an effective way of “carbon neutral”, but the randomness and volatility of wind-solar power generation seriously affects the safe and stable operation of power grid. With the development of energy storage technology, this problem can be effectively solved by configuring energy storage, but how to reasonably configure energy storage is one of the key issues due to the expensive energy storage. To this end, a multi-timescale nested energy storage capacity optimization model for multi-energy supplemental renewable energy system with pumped storage hydro plant based on a three-battery group control operation strategy is proposed. First, the electrochemical energy storage is added to the supplemental renewable energy system containing hydro-wind-solar to form a hybrid energy storage system with pumped storage hydro units, and its group control strategy and charging/discharging coordinated operation are investigated. Then, a double-layer energy storage capacity optimization model nested in multiple time scales is developed. The inner layer optimizes hydropower and pumped storage output to smooth out the more fluctuating wind power output with large time scales. The outer layer optimizes energy storage taking into account factors such as output deviation, cost, attenuation, and dynamic prediction life to smooth out the less volatile and smaller time-scale wind power. Finally, simulation demonstrates that the proposed model can make full use of the flexible regulation capability of pumped storage hydro units and the fast response capability of batteries to maximize the fluctuation of the supplemental system into the grid, and further reduce the peaking pressure of the receiving end of the grid. In addition, the superiority of the proposed three-battery grouping strategy over the traditional battery control method in terms of saving investment cost and mitigating battery life loss is also verified. The advantages of the strategy in terms of carbon reduction and cleaner production are also illustrated in quantifiable terms.

On improved active disturbance rejection controller design for a pumped storage hydro unit

The pumped storage hydro unit (PSHU) shows bad dynamic performance because of the frequent switching of working conditions and the S-shaped characteristics of pump turbine. This paper proposes an improved fixed-time active disturbance rejection controller to improve the control performances and counteract the influences of uncertainties including modeling error and friction. A disturbance observer is designed to estimate the total uncertainty by using the information of the states and outputs, compensating the adverse effects of the total uncertainty actively by feed-forward principle as a result. The outstanding benefit of the disturbance observer lies in that it can be designed separately from the original controller and can enhance the performances of the PSHU without changing the original controller. Simulation results show that comparing with the conventional active disturbance rejection controller, the improved active disturbance rejection controller has better adaptability and higher robustness towards the system load disturbance, and the dynamic performance of the system is improved.

DDPG-based load frequency control for power systems with renewable energy by DFIM pumped storage hydro unit

DDPG-based load frequency control for power systems with renewable energy by DFIM pumped storage hydro unit

Emended Harris Hawk Optimizer for Mixed Energy Generation Scheduling Problem

This paper proposes an emended Harris hawk optimizer (EHHO) to solve the mixed energy generation scheduling problem with available resources from hydrothermal, pumped storage hydro, solar, and wind units while minimizing the operating cost, utilizing the available water, and satisfying the other operational constraints. Direct heuristics are applied to solve the constraints imposed on the generation scheduling problem. An optimistic binary optimizer is utilized to commit solar and wind units so that solar and wind units share a certain percentage of power demand to meet the uncertainty of renewable power. The hunting behavior of the hawks for the desired prey inspires the Harris hawk optimizer (HHO) because of its flexibility, sturdiness, and scalability features. Despite HHO giving premature convergence as it tends to trap into the local optima while solving complex non-linear optimization problems. Hence, the local search technique (LST) is employed with the HHO to overcome it. LST also empowers the exploitation phase of HHO. Two practical electric power test systems are successfully solved using the proposed EHHO. On implementing the proposed EHHO, with the penetration of pumped storage hydro units, savings in the cost of thermal units range from 3.90 to 11.44%. Further, with the penetration of wind and solar power, the savings in operating costs of thermal units have increased from 12.15 to 20.19%. The main idea and contribution of the proposed work is the thermal fuel cost reduction using renewable energy sources by utilizing EHHO. The convergence curves and whisker box plots demonstrate the EHHO’s robustness while solving the electric power test systems.

A Coordinated Pumped Storage Dual Compensated Hydro Governor with PSS Action to Damp Electromechanical Power Oscillations

Subject to increasing penetrations of renewable sources like solar photovoltaic (SPV) and wind energy sources, power system oscillation damping is going to be a critical challenge for system operators. This work proposes a new dual compensated governor (DCG) in coordination with a power system stabilizer (PSS) of a pumped storage hydro plant for power oscillation damping subject to intermittent SPV and wind penetration for a hydro, wind, and SPV integrated power system. The phase lag provided by the hydro governor is compensated by additional phase lead contributed by the dual compensation, where speed and real power deviations brought by uncertain SPV and wind penetrations are simultaneously controlled by two lead-lag controllers before being applied to conventional Proportional-Integral-Derivative (PID) governor. Again, subject to critical oscillatory unstable conditions, the DCG is coordinated with PSS through a multiobjective function employing a new modified Differential Evolutionary-Particle swarm optimization (MDEPSO) algorithm. Different case studies with sudden and random SPV and wind penetrations being executed with the proposed controller considering a two area four machine and 39 bus multimachine system with pumped storage hydro units to observe system oscillations are considered. The proposed damping control action has been implemented to damp these oscillations, and the damped response has been analyzed with eigenvalue distributions and Bode plots with sensitivity analysis. The proposed action is found to be much more efficient in contrast to conventional PID governor and PSS damping action. Also, the usage of present hydro governors can be much improved by this coordinated controller action.

Frequency Regulation Control and Parameter Optimization of Doubly-Fed Induction Machine Pumped Storage Hydro Unit

Since doubly-fed induction machine pumped storage hydro (DFIM-PSH) unit can adjust active power flexibly through adjustable-speed operation, it has frequency regulation capability in both generating and pumping modes. In order to explore the frequency regulation capability of DFIM-PSH unit under different working conditions, this paper develops a frequency control module for DFIM-PSH unit in pumping mode, which is quite different from that in generating mode, and then optimizes the frequency control parameters aimed at minimizing the frequency deviation in multiple operating conditions. Based on the dynamic model of the DFIM-PSH unit, the system frequency response model is built to analyze the influence of parameters on frequency dynamic characteristics. An optimization method of frequency control parameters is developed based on improved particle swarm optimization algorithm to maximize its frequency regulation capability under different operating conditions while ensuring safe and stable operation. Finally, a four-machine two-zone power system model with a DFIM-PSH unit is simulated, and the simulation results show that the proposed strategy can make the DFIM-PSH unit have great frequency regulation performance in a wide range of operating conditions.

Modeling State Transition and Head-Dependent Efficiency Curve for Pumped Storage Hydro in Look-Ahead Dispatch

As one of the most widely installed utility-scale storage facilities, pumped storage hydro (PSH) plays an essential role in providing flexibility for power systems worldwide. Thus, to accurately quantify the flexibility of PSH units in operational optimization problems is important. The conventional PSH models in the literature rarely consider detailed state transitions due to their hourly-based settings. However, it becomes imperative for operational optimization on short-term intervals, especially with increasing shares of renewable energy in power systems. To this end, this paper presents a novel deterministic PSH model that considers the transition time and trajectory between three states of PSH units in look-ahead dispatch. Moreover, to better characterize the varying efficiency of PSH units with water head and flow rate, this paper proposes to model detailed head-dependent efficiency curves (hereafter called input-output curves) in look-ahead dispatch, which encounters heavy computational burdens when short time intervals are applied. In this work, a zig-zag piece-wise linear approximation method is used for input-output curve modeling. This can enable an accurate quantification for variable efficiency and head dependence in a computationally effective manner. Numerical results are presented to show performances of the proposed PSH model in both flexibility quantification and computation time.

Research on the Differential Protection of the SFC Output Transformer for Pumped Storage Hydro Unit

Pumped storage power stations play an great role in promoting new energy consumption, ensuring the safety of power grid, building clean, low-carbon, safe and efficient energy system, and has a broad development prospect. SFC is the most important start-up mode of pumped storage unit, and the output transformer is an important equipment of SFC system, which needs to be equipped with reliable and fast differential protection to ensure its safe and reliable operation. The current frequency varies from 0 to 50Hz during SFC start-up, so the conventional transformer differential protection can not adapt. In this paper, the output transformer differential protection technology is studied according to the electrical characteristics and short circuit fault characteristics of SFC start-up process, the high precision frequency algorithm and the RMS integration algorithm with compensation are proposed to realize the precise measurement of frequency and amplitude, and the ultra-low frequency CT saturation identification technology is proposed to realize the whole process protection of the output transformer from start-up to grid-connection.

A Mixed-Integer Convex Programming Algorithm for Security-Constrained Unit Commitment of Power System with 110-kV Network and Pumped-Storage Hydro Units

The secure operation of 110-kV networks should be considered in the optimal generation dispatch of regional power grids in large central cities. However, since 110-kV lines do not satisfy the premise of R << X in the direct current power flow (DCPF) model, the DCPF, which is mostly applied in the security-constrained unit commitment (SCUC) problem of high-voltage power grids, is no longer suitable for describing the active power flow of regional power grids in large central cities. Hence, the quadratic active power flow (QAPF) model considering the resistance of lines is proposed to describe the network security constraints, and an SCUC model for power system with 110-kV network and pumped-storage hydro (PSH) units is established. The analytical expressions of the spinning reserve (SR) capacity of PSH units are given considering different operational modes, and the SR capacity of PSH units is included in the constraint of the SR capacity requirement of the system. The QAPF is a set of quadratic equality constraints, making the SCUC model a mixed-integer nonlinear non-convex programming (MINNP) model. To reduce the computational complexity of solving the model when applied in actual large-scale regional networks, the QAPF model is relaxed by its convex hull, and the SCUC model is transformed into a mixed-integer convex programming (MICP) model, which can be solved to obtain the global optimal solution efficiently and reliably by the mature commercial solver GUROBI (24.3.3, GAMS Development Corporation, Guangzhou, China). Test results on the IEEE-9 bus system, the PEGASE 89 bus system and the Shenzhen city power grid including the 110-kV network demonstrate that the relaxed QAPF model has good calculation accuracy and efficiency, and it is suitable for solving the SCUC problem in large-scale regional networks.

Coordination of Wind Farm and Pumped-Storage Hydro for a Self-Healing Power Grid

The increasing penetration of wind energy poses great challenges to the operation of power systems in normal and emergency states. However, energy storage technologies can help accommodate wind power uncertainty and variability due to their flexible characteristics. This paper focuses on the restoration phase, and provides a novel coordination strategy of wind and pumped-storage hydro (PSH) units for a faster and reliable self-healing process. The wind-PSH assisted power system restoration is formulated as a two-stage adaptive robust optimization problem. The first-stage problem determines the start-up sequence of generators and the energization times of transmission paths; and the second-stage problem decides load pickup sequences, wind power dispatch levels, and PSH units’ operating modes. The column-and-constraint generation decomposition algorithm is applied to solve the two-stage adaptive robust optimization problem, which has a mixed-integer optimization in the inner-level problem. The developed coordination strategy is tested on the modified IEEE 39-bus system. Numerical results demonstrate that the coordinated wind and PSH units can increase the total energy served, enhance wind power dispatchability, and reduce wind power curtailment.

Unit commitment and dispatch with coordination of wind and pumped storage hydro units by using cuckoo search algorithm

This paper proposes a multi objective model for Advanced Unit Commitment (AUC) with wind power and Pumped Storage (PS) units using Cuckoo Search (CS) algorithm. The novelty of the proposed method is improved levy flight searching ability, random reduction and ability to adapt complex optimization problems. Here, the CS algorithm to accommodate wind output uncertainty, with the multi-objective of providing an optimal AUC schedule for the thermal generators in the day-ahead market that minimizes the total cost under the different wind power output scenario. The proposed method is more reliable for AUC because it considering the wind power uncertainty using the Artificial Neural Network (ANN) and PS units, which are significantly reduces the total cost. Then the proposed method is implemented in the MATLAB/simulink platform and tested under IEEE standard bench mark system. The proposed method performance has been verified through the comparison analysis with the existing techniques. The comparison results were proved the superiority of the proposed method.

Optimization of Guide Vane Closing Schemes of Pumped Storage Hydro Unit Using an Enhanced Multi-Objective Gravitational Search Algorithm

The optimization of guide vane closing schemes (OGVCS) of pumped storage hydro units (PSHUs) is a cooperative control and optimal operation research field in renewable energy power generation technology. This paper presents an OGVCS model of PSHUs considering the rise rate of the unit rotational speed, the specific node pressure of each hydraulic unit, as well as various complicated hydraulic and mechanical constraints. The OGVCS model is formulated as a multi-objective optimization problem to optimize conflicting objectives, i.e., unit rotational speed and water hammer pressure criteria. In order to realize an efficient solution of the OGVCS model, an enhanced multi-objective bacterial-foraging chemotaxis gravitational search algorithm (EMOBCGSA) is proposed to solve this problem, which adopts population reconstruction, adaptive selection chemotaxis operator of local searching strategy and elite archive set to efficiently solve the multi-objective problem. In particular a novel constraints-handling strategy with elimination and local search based on violation ranking is used to balance the various hydraulic and mechanical constraints. Finally, simulation cases of complex extreme operating conditions (i.e., load rejection and pump outage) of a ‘single tube-double units’ type PSHU system are conducted to verify the feasibility and effectiveness of the proposed EMOBCGSA in solving OGVCS problems. The simulation results indicate that the proposed EMOBCGSA can provide a lower rise rate of the unit rotational speed and smaller water hammer pressure than other methods established recently while considering various complex constraints in OGVCS problems.

A parameter adaptive identification method for a pumped storage hydro unit regulation system model using an improved gravitational search algorithm

With increasing wind farm, solar farm, and pump storage plant integrations, intense frequency fluctuation of the pumped storage hydro unit (PSHU) under the no-load running condition, which is caused by its operation along the S-shaped curve, has been noted and researched. So, parameter identification of the PSHU regulation system (PSHURS) is crucial in precise modeling of the PSHU and can provide support for the optimized control and stability analysis of the power system. In this paper, a parameter adaptive identification method together with an improved gravitational search algorithm (IGSA) is proposed and applied to solve the identification problem for a PSHURS under the no-load condition. The IGSA, which is based on the standard gravitational search algorithm, accelerates convergence speed with a combination of the Pbest- Gbest-guided search strategy and the adaptive elastic-ball method and improves the local optimal with the added chemotaxis operator of the bacterial foraging algorithm. Furthermore, for the parameter adaptive identification method, the parameter performance evaluator is employed to devise the moving step of the agent of the chemotaxis operator. The illustrative experiment for parameter identification of the PSHURS is used to verify the feasibility and effectiveness of the proposed method. Comparison with other methods clearly shows that the adaptive parameter identification method along with the IGSA perform best for all identification indicators.

Rescheduling of real power for congestion management with integration of pumped storage hydro unit using firefly algorithm

Post-deregulation era of power system operation produces more pressure on Independent System Operator (ISO) to ensure congestion free transmission network without destroying system security. In order to relieve transmission congestion, ISO initiates correct methods by maintaining system reliability and security. This paper considers a novel efficient technique for congestion management like generator real power rescheduling by integrating a pumped storage hydro unit (PSHU) in the system. This paper presents an optimization model for congestion management by incorporating the calculation of two factors like generator sensitivity factor (GSF) and bus sensitivity factor (BSF). Optimal location of PSHU is identified using the value of BSF’s and the numbers of participated generators for congestion management by rescheduling their outputs are determined using the value of GSF’s. The impact of PSHU has been investigated to manage transmission congestion which further reduces the congestion cost and improves security of the system. The proposed method for congestion management considering PSHU is tested on modified IEEE-39 bus New England test system and the validity is obtained by considering the same problem without the presence of PSHU. The result of proposed work with proper utilization of PSHU illustrates the impact of PSHU towards the congestion management and also exploration of firefly algorithm for minimizing the transmission congestion cost.

A virus-evolutionary differentiated-PSO approach for short-term generation scheduling with uncertainties

Summary This paper presents a virus-evolutionary differentiated-particle swarm optimization approach for short-term generation scheduling with uncertainties consideration. Different from the traditional power generation scheduling problems, the paper considers the characteristics of the change of atmospheric flow at day and night. This paper also considers the uncertainties in the load demand, available water in the reservoir, wind speed, and radiation. This paper studies on the best dispatch both economic and emission, which include two objective functions of generation cost and emission cost at different time periods. The proposed method that combines differentiated-particle swarm optimization with virus-evolutionary technique can expand the scope and increase the diversity of search. The study system comprises 10 thermal units, seven hydro units (including one pumped-storage hydro unit), one equivalent wind energy system, and one equivalent solar energy system. The results from the proposed method are compared with those from other intelligent algorithms. The test results show that the proposed method can indeed obtain a better solution. Copyright © 2016 John Wiley & Sons, Ltd.

An adaptively fast fuzzy fractional order PID control for pumped storage hydro unit using improved gravitational search algorithm

With increasing wind or solar farm and pump storage plant integrations, more and more large-scale renewable energy integration systems are taking shape gradually, which brings up challenges to optimized control these systems. Especially, due to the reversible properties of pumped storage hydro unit (PSHU), it is apt to fall into the ‘S’ characteristic area which can lead to a wide range of unit rotational speed oscillation under no-load condition at middle-low water head. In order to solve these unstable running problems effectively, an adaptively fast fuzzy fractional order PID (AFFFOPID) control method for PSHU is proposed in this paper. A combination of fuzzy logic controller and fractional order PID is adopted by the proposed control method, and error tracking element of PSHU guide vane opening is added to improve the regulation rate. Then, an accurate mathematical model of pump-turbine with complete characteristic curves is established for the PSHU regulating system (PSHURS). Meantime, a novel bacterial-foraging chemotaxis gravitational search algorithm (BCGSA) is used for optimized parameters selection of AFFFOPID method. The BCGSA which is based on the standard gravitational search algorithm accelerates convergence speed with a combination of the Pbest–Gbest-guided strategy and adaptive elastic-ball method. Chemotaxis operator of bacterial foraging algorithm is also added into the BCGSA which is devised to step out the local optimal with a certain probability. Furthermore, simulation tests under different running conditions are utilized to demonstrate the feasibility and robustness of the AFFFOPID. The results are analyzed in detail, which demonstrates the pump-turbine model and the proposed AFFFOPID method are practicable. Comparison with other methods clearly shows that AFFFOPID using BCGSA outperforms the others in most cases.

A multiple criteria utility-based approach for unit commitment with wind power and pumped storage hydro

The integration of wind power in electricity generation brings new challenges to the unit commitment problem, as a result of the random nature of the wind speed. The scheduling of thermal generation units at the day-ahead stage is usually based on wind power forecasts. Due to technical limitations of thermal units, deviations from those forecasts during intra-day operations may lead to unwanted consequences, such as load shedding and increased operating costs. Wind power forecasting uncertainty has been handled in practice by means of conservative stochastic scenario-based optimization models, or through additional operating reserve settings. However, generation companies may have different attitudes towards the risks associated to wind power variability. In this paper, operating costs and load shedding are modeled by non-linear utility functions aggregated into a single additive utility function of a multi-objective model. Computational experiments have been done to validate the approach: firstly we test our model for the wind–thermal unit commitment problem and, in a second stage, pumped storage hydro units are added, leading to a model with wind–hydro-thermal coordination. Results have shown that the proposed methodology is able to correctly reflect different risk profiles of decision makers for both models.

Impact of a price-maker pumped storage hydro unit on the integration of wind energy in power systems

The increasing integration of larger amounts of wind energy into power systems raises important operational issues, such as the balance between power generation and demand. The pumped storage hydro (PSH) units are one possible solution to mitigate this problem, once they can store the excess of energy in the periods of higher generation and lower demand. However, the behavior of a PSH unit may differ considerably from the expected in terms of wind power integration when it operates in a liberalized electricity market under a price-maker context. In this regard, this paper models and computes the optimal PSH weekly scheduling in a price-taker and price-maker scenarios, either when the PSH unit operates in standalone and integrated in a portfolio of other generation assets. Results show that the price-maker standalone PSH will integrate less wind power in comparison with the price-taker situation. Moreover, when the PSH unit is integrated in a portfolio with a base load power plant, the role of the price elasticity of demand may completely change the operational profile of the PSH unit.

Enhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systems

The ever-increasing penetration of variable wind energy in power systems affects the hourly dispatch of thermal power generation in electricity markets. The variability of wind energy, which makes the wind energy non-dispatchable and difficult to control, could bring significant challenges to power system operators. The hourly coordination of wind power generation units with pumped-storage hydro (PS) generation could relieve the variability of wind energy and increase its dispatchability. The wind-PS coordination is based on the application of stochastic security-constrained unit commitment (stochastic SCUC). In this study, the coordinated hourly bus-level scheduling of wind-PS is compared with the coordinated system-level operation strategies in the day-ahead scheduling of power systems.