Abstract We consider inherent robustness properties of model predictive control (MPC) for continuous-time nonlinear systems with input constraints and terminal constraints. We show that when the linear quadratic contr...
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Abstract We consider inherent robustness properties of model predictive control (MPC) for continuous-time nonlinear systems with input constraints and terminal constraints. We show that when the linear quadratic control law is chosen as the terminal control law, and the related Lyapunov matrix is chosen as the terminal penalty matrix, MPC with nominal prediction model and bounded disturbances has some degree of inherent robustness. We emphasize that the input constraint sets can be any compact set rather than convex sets, and our results do not rely on the continuity of the optimal cost functional or control law in the interior of the feasible region.
On the basis of analyzing the composition of losses in high-efficient high-voltage asynchronous motors, the approaches of increasing the efficiency of the motors is investigated in this paper. The approaches concern w...
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The paper proposes faulted feeder selector in power distribution system with neutral non-effectively grounded. At first, the paper presents basic principle of single-phase-to-ground fault feeder selection based on tra...
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In the annular power distribution system, short-circuit fault of bus-bars will do fatal harm to aircraft, and it is necessary to protect the ring-net bus-bars. Protecting bus-bars has to meet the requirements that pro...
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In order to limit short-circuit current and satisfy the need of relay setting, only part of the 220 kV power transformer is grounded, so on the neutrals of ungrounded transformers will appear the over-voltage. Current...
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In order to limit short-circuit current and satisfy the need of relay setting, only part of the 220 kV power transformer is grounded, so on the neutrals of ungrounded transformers will appear the over-voltage. Currently the value of over-voltage on transformer neutral point and the corresponding protection strategy is based on theoretical formula. This article uses the PSCAD/EMTDC software to calculate the over-voltage on the neutral point of 4 ungrounded power transformers in Chongqing 220 kV power grid. The result shows that the power frequency transient over-voltage on the neutrals may reach 178 kV. If the single-phase grounding fault occurs in ungrounded power system, the power frequency over-voltage on the neutrals will be more serious and rise to 138.6 kV. Non-full phase operation may cause serious ferro-resonance over-voltage on the neutrals of no-load transformer, which may last for seconds and may rise to 723.7 kV, causing serious threat to the transformer neutrals and line-side equipment. The article also studies the gap parameter which should be taken on the neutrals of 220 kV transformers at the end.
This paper presents a predictive control scheme of DC-link voltage for back-to-back converters based on energy balance modeling. Since the variation of DC-link voltage is affected by the energy mismatch between rectif...
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This paper presents a predictive control scheme of DC-link voltage for back-to-back converters based on energy balance modeling. Since the variation of DC-link voltage is affected by the energy mismatch between rectifier and inverter, the energy distribution in a rectifier-inverter is analyzed. Moreover, in order to calculate the input and output energy in one control period accurately, the grid current is regulated by predictive control and the instantaneous active power consumed by the induction motor is estimated. Then, an equation based on energy balance in one control period is established, and the DC-link voltage can be controlled by solving it. Finally, simulation results show that with the proposed control scheme, the back-to-back converter exhibits both good dynamic and steady-state performances.
The key parameters of SOA (safe operating area) of semiconductor devices are hard to be measured when converter is operating, which is not helpful to protect converter at any time. On the other hand, surplus estimatin...
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The key parameters of SOA (safe operating area) of semiconductor devices are hard to be measured when converter is operating, which is not helpful to protect converter at any time. On the other hand, surplus estimating method is widely used to design the main circuit. In order to guarantee the whole system works safely and improve utilization rate of devices, the concept of SSOA (systematic safe operating area) is presented. By determining the relationship of key parameters between devices and converter, the expression of SSOA is described quantitatively. Then it is implemented as a basic rule to design a back-to-back converter based on IGBT for 55kW induction motor optimally. Rated value of DC-link voltage and grid filter of the system is obtained reasonably as well.
Emergy analysis provides a feasible approach to evaluate the status and position of different energy carriers in the universal energy hierarchy. In this paper, an emergy-based method is conducted to measure the resour...
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Emergy analysis provides a feasible approach to evaluate the status and position of different energy carriers in the universal energy hierarchy. In this paper, an emergy-based method is conducted to measure the resources input of Chinese industry from 1997 to 2006. Resources inflows including fossil fuels, mineral resources, agricultural products, and other imported materials are accounted, based on which related indicators including resources intensity, industrial output, and environmental emissions are investigated. Results show a steady upward trend for the total resources input of Chinese industry during the past decade. The total resources input amounted to 1.53×1025 sej in 2006, of which non-renewable one accounted for 70.65% owing to the dominating input of fossil fuels and nonmetal minerals. Resources intensity measured by the ratio of resources input to industrial value added declined gradually during 1997–2002, but the rapid expansion of resource–intensive sub–sectors resulted in a reverse trend since 2003. The current resources use pattern of Chinese industry is characterized by increasing input of non-renewable resources, excessive expansion of resource–intensive production, and tremendous challenge from environmental pressure.
IPS has many special characteristics, such as using multi-phase, multi-frequency and hybrid AC/DC devices. As a result, existing electromagnetic transient simulators developed for powersystems on land do not apply to...
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IPS has many special characteristics, such as using multi-phase, multi-frequency and hybrid AC/DC devices. As a result, existing electromagnetic transient simulators developed for powersystems on land do not apply to IPS. This paper aims to build up a parallel based real-time electromagnetic transient simulator for IPS. A fast multi-switching process method for parallel electromagnetic transient simulations is coined to handle the tremendous switch events in IPS. To solve the difficulties brought by multi-phase machines in IPS, a multilevel hybrid parallel algorithm is forged through the combination of component level and network level parallelization. Based on the key techniques mentioned above, a parallel simulator is built up. Through sufficient testing to typical examples of IPS, the accuracy and high-efficiency of the simulator are proved.
Hard-switching technique under the high voltage and high current is one of main trends of high power inverters. Under this switching mode, the stray parameters of the commutating loops, especially the stray inductance...
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Hard-switching technique under the high voltage and high current is one of main trends of high power inverters. Under this switching mode, the stray parameters of the commutating loops, especially the stray inductance of the DC bus bar, have significant influence on the switching process, electromagnetic interference and component stress of the semiconductor switches. It becomes one of the key points for the safe operation of inverters. Based on an actual 55 kW inverter, the design, simulation and analysis for its bus bar is described in this paper. The bus bar model is built with the method of Partial Element Equivalent Circuit (PEEC), and the stray parameters are extracted from PEEC model and applied in the circuit simulation. Compared with the experimental results, the modeling validity is proved, and the simplified modeling process and design principles for complex physical bus bar are presented.
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