Impedance Modeling and Stability Analysis of DFIG-Based Wind Energy Conversion System Considering Frequency Coupling

Impedance-based stability analysis is an effective method for addressing a new type of SSO accidents that have occurred in recent years, especially those caused by the control interaction between a DFIG and the power grid. However, the existing impedance modeling of DFIGs is mostly focused on a single converter, such as the GSC or RSC, and the influence between the RSC and GSC, as well as the frequency coupling effect inside the converter are usually overlooked, reducing the accuracy of DFIG stability analysis. Hence, the entire impedance is proposed in this paper for the DFIG-based WECS, taking coupling factors into account (e.g., DC bus voltage dynamics, asymmetric current regulation in the dq frame, and PLL). Numerical calculations and HIL simulations on RT-Lab were used to validate the proposed model. The results indicate that the entire impedance model with frequency coupling is more accurate, and it is capable of accurately predicting the system’s possible resonance points

Coordinated operation of coupled transportation and power distribution systems considering road solar generation

The emerging photovoltaic (PV) integration technology called solar road (SR) gives road infrastructure the possibility of not only carrying traffic loads but also generating electricity. The versatility of SR leads to the nexus between transportation network (TN) and power distribution network (PDN). Along with the increasing penetration of electric vehicles (EVs), the installation of SR can promote the reliance of transportation and electrical networks to a higher degree. In order to cope with the severe challenges brought by SR and EV to the TN-PDN coordinated operation, this paper suggests a traffic-power coordinated operation model incorporating road solar generation (TPOSR), where the impact of the traffic flow and SR on the coupled network is studied. Specifically, the user equilibrium (UE) principle is adopted to describe the traffic flow distribution in TN, while the Distflow model is employed to model the power flow in PDN. In TN, the SRs serve as links that let the vehicles through. Moreover, from the perspective of PDN, the SR output model considering traffic shading effect is proposed, based on traffic assignment problem (TAP) and traffic flow theory. In the proposed TPOSR model, we assume the independent system operator, a public organization, can imposes road tolls and dispatch generators to promote coordinated operation of the coupled network. Numerical results demonstrate the effectiveness of the proposed TPOSR for reducing social costs and improving SR performance

A joint clearing market for coupled electricity and gas system considering bilateral energy contracts

In recent years, with the progress of new energy conversion technology, especially an increasing number of gas turbine units applied to the market, the connection between the natural gas system and the electric system has become increasingly close. Initially the gas and electricity markets operated relatively independently. Therefore, it is necessary to establish the coupling architecture of natural gas market and electricity market to meet the energy demand of users. This paper attempts to propose a power and gas coupling system based on clearing market structure. Firstly, the difference between natural gas–electricity coupling market and joint settlement market is discussed. The combined market considered in this paper is somewhat different from the associated electricity market and natural gas market. The calculations are easier and the results more reliable than those of the traditional linked gas markets and electric power market. Then, a mathematical model of joint clearing market is established based on bilateral energy contracts. Then, the piecewise linearization approximation (PLA) algorithm is proposed to solve the nonlinear problem. The locational piecewise price (LMEP) and locational marginal gas price (LMGP) are identified respectively, and the bilateral contracts are processed. The solution proposed in this paper guarantees strong duality and clear meaning of dual variables, making PLA easy to apply and solve market clearing problems based on dual variables or Lagrange multiplier pricing, as well as easy to deal with bilateral contract problems. Finally, the proposed joint clearing market is verified by an improved 3-electric bus and 6-gas node system

Research on the coordinated control of large permanent magnet direct drive fan and air conditioner based on finite element method

In recent years China has committed to energy saving and emission reduction. Chinese Government has proposed a strategic policy of carbon neutrality. In the context of energy shortage, the development of sustainable cities and green buildings is a major trend. An important part of energy consumption in cities is the energy consumed by temperature regulation in buildings, and reducing this part of energy consumption can be of great help to the development of sustainable cities. In this paper, our team propose a scheme for temperature regulation with large permanent magnet direct drive fans system and air conditioners. Compare the conventional room temperature regulation scheme which only uses air conditioners with the new room temperature regulation scheme which uses the large permanent magnet direct drive fan and air conditioners by simulating the indoor temperature regulation process. The results of simulation show that the new scheme’s temperature regulation effects are more uniform than the conventional scheme. The new scheme can reach the target Comfort Index of Human Body faster than the conventional scheme, and the energy consumption can be reduced by more than 8%. The paper concludes that the new room temperature control solution is more energy efficient, reduces carbon emissions and helps to achieve the carbon neutrality target

Investigation of the wave–photovoltaic-battery​ hybrid power generation platform’s control strategy

This paper proposes a wave–photovoltaic-battery hybrid power generation platform which based on the distributed DC collection and AC inverter grid structure. To be able to simplify the control structure of the power generation system and improve the anti-interference ability of the system, a one-step delay compensation model predictive current control (MPCC) method is proposed for the wave power generation rectifier unit and the perturbation and observation (P&O) fuzzy logic maximum power point tracking (MPPT) algorithm is applied in the photovoltaic power generation unit. Meanwhile, the constant power control method is used to realize the charge and discharge control of the energy storage system to achieve the grid-connected goal of tracking the load power demand. Finally, the MATLAB/Simulink software is applied to simulate the grid-connected operation characteristics of the wave energy power generation unit in continuous power generation modes, as well as the photovoltaic power generation unit at constant temperature and variable irradiance. The results illustrate that the suggested technique for controlling the power generating unit is straightforward and feasible, DC bus voltage stability effect is effective, and the inverter output satisfies the grid-connected operating requirement, which verifies the feasibility of the proposed scheme and can provide some theoretical support for the subsequent high-capacity wave–photovoltaic-battery hybrid power generation platform

Flexibility-enhanced strategies of generations to improve the integration of renewable energy considering uncertainties

Power systems with a high proportion of renewable energy are confronted with immense challenges and a huge amount of renewable energy has been curtailed. To promote the integration of renewable energy, this paper focus on exploiting the generation flexibilities. For hydropower units, a high-resolution dynamic regulation model of reservoir volume is proposed, in which the real-time situation of inflow is considered. The reservoir’s flexibility which is hindered by the static flood water limit level (FLWL) is exploited by this method. For thermal units, a deep peak regulation of thermal is constructed to enhance the system’s flexibility. Furthermore, considering the uncertainties of renewable energy, a chance-constrained reservoir flexible model influenced by random reservoir inflow and a chance-constrained spinning reserve and power flow model influenced by the wind uncertainty are developed. Based on those models and their coordination, an optimal dispatching model considering generation flexibilities and uncertainties is proposed. Simulation results on the IEEE 30-bus system show that the proposed model with multiple flexible resources can increase wind power penetration by 10% and save half of the cost compared with the conventional dispatching methods. These results demonstrated the efficiency of the proposed method whether the integration of renewable energy or the saving of operation costs

Chromium Removal from Aqueous Solution Using Natural Clinoptilolite

This work investigates the applicability of clinoptilolite, a natural zeolite, as a low-cost adsorbent for removing chromium from aqueous solutions using fixed bed studies. To improve its removal performance for the inorganic pollutant, the adsorbent is pretreated with NaCl to prepare it in the homoionic form of Na+ before undertaking ion exchange with Cr3+ in aqueous solution. This work also evaluates if treated effluents could meet the required effluent discharge standard set by legislation for the target pollutant. To sustain its cost-effectiveness for wastewater treatment, the spent adsorbent is regenerated with NaOH. It was found that the clinoptilolite treated with NaCl has a two-times higher Cr adsorption capacity (4.5 mg/g) than the as-received clinoptilolite (2.2 mg/g). Pretreatment of the clinoptilolite with NaCl enabled it to treat more bed volume (BV) (64 BV) at a breakthrough point of 0.5 mg/L of Cr concentration and achieve a longer breakthrough time (1500 min) for the first run, as compared to as-received clinoptilolite (32 BV; 250 min). This suggests that pretreatment of clinoptilolite with NaCl rendered it in the homoionic form of Na+. Although pretreated clinoptilolite could treat the Cr wastewater at an initial concentration of 10 mg/L, its treated effluents were still unable to meet the required Cr limit of less than 0.05 mg/L set by the US Environmental Protection Agency (EPA)

Transformation of solid waste management in China: moving towards sustainability through digitalization-based circular economy

In China, environmental pollution due to municipal solid waste (MSW) over-generation is one of the country’s priority concerns. The increasing volume and complexity of the waste poses serious risks to the environment and public health. Currently, the annual growth of MSW generation is estimated to be approximately 8–10% and will increase to 323 million metric tons (Mt) by 2030. Based on the secondary data collected from a literature survey, this article critically evaluates the recent progress of MSW management (MSWM) in China and offers new insights into the waste sector in the era of Industry 4.0. This helps decision makers in China to plan a smooth transition nationwide to a circular economy (CE) in the waste sector. It is evident that digitalization is a driving force for China to move towards low-carbon development strategies within the framework of CE. Through digitalization, the waste sector has promoted prevention, reduction, reuse, and recycling (3Rs) of waste before waste disposal in landfills. A proper implementation of digitalization-based waste recycling has contributed to an efficient cooperation between the government and private sector, increased job opportunities, and promoted the conservation of resources. It is anticipated that this work not only contributes to the establishment of an integrated MSWM system in China, but also improves local MSWM through digitalization in the framework of a C