QUASI-Z-SOURCE NETWORK-BASED HYBRID POWER SUPPLY SYSTEM FOR ALUMINUM ELECTROLYSIS INDUSTRY
Abstract
A hybrid power supply system (HPSS) based on Quasi-Z-Source Network is proposed for aluminum electrolysis, which can reduce energy consuming and carbon emission through the use of renewable energy. An AC-DC integrate controller is designed in HPSS that contains a two-layer control. The first layer control is responsible for maintaining the dc bus voltage and current, which can mitigate negative effects caused by anode effect in aluminum electrolysis. The independent maximum power tracking for PV array and the dc-bus voltage balance for each Quasi-Z-Source DC-DC converter (Q-Z-C) can be achieved by using PV-voltage controller and dc-bus voltage controller for PV-System. To maintain the voltage of dc bus within the require voltage range of aluminum electrolysis production and ensure high input power quality of AC-System, the Quasi-Z-Rectifier controller (Q-Z-R) is employed, which can reduce the harmonic injection. The power allocation is addressed in the second control layer and a power scheme algorithm (PSA) is carried out to maximize the system efficiency and economic benefit. At last, the simulation and experimental results are provided to verify the effectiveness of the designed HPSS and the proposed PSA CONCLUSION In this paper, a hybrid power supply system based on QuasiZ-source network is put forward for aluminum electrolysis. The main aim of the proposed HPSS are reducing energy consumption and carbon emission. Firstly, the structure of HPSS and the PSA are discussed in detail. Then, an ACDC integrate controller contains a two-layer control algorithm is designed in HPSS which can not only remain the local\ current and voltage invariable but also can realize power allocation dynamically between the whole ac cells. Moreover, the designed controller can solve the problem caused by anode effect during aluminum electrolysis production satisfactorily. At last, simulation and experimental tests are proposed to verify the effectiveness of the designed HPSS and AC-DC integrate controller. The results show that the designed HPSS has good dynamic response and steady-state performance, and can satisfy the power supply requirements of aluminum electrolysis production.
EXISTINFG SYSTEM:
Existing research papers have focused on many aspects of aluminum electrolysis industry. Reference proposed a generator excitation voltage control scheme for emergency frequency regulation of island power systems with voltagedependent loads. It takes an actual island power system with aluminum electrolysis loads as an example, and established a frequency and excitation voltage control model for the actual island power system. References presented a multipulse rectifier system for aluminium smelting load, as well as the open loop response of aluminum smelters to short time interval feeding and their response to the adjustment of saturable reactors and tap changers are discussed. A conceptual harmonic-filter-design procedure for the filters required for grid-connected aluminum smelting plant is presented, in which the aluminium smelting load is supplied by utility grid with a number of diode rectifiers and step-up transformers. Since the aluminum smelter loads are all supplied by ac grid with rectifier system, the issue on fossil fuel consumption is not addressed fundamentally.
PROPOSED SYSTEM:
One solution is to partly supply aluminum smelter loads with PV power. PV technology is practical and cost-efficient at the megawatt level, and its dc characteristics could increase the overall efficiency by reducing the number of power conversion stages. Thus, a HPSS consisted of AC-System and PV-System is proposed in this paper. The HPSS has three significant advantages: 1) The carbon emission is significantly reduced with integrated PV penetration levels as high as 30%; 2) Compared the photovoltaic inverter power system, PVSystem in this paper eliminate inverting and rectifying process, thus reducing the energy loss. 3) The PV resources geographically match with aluminum resources in China, so the issue of large scaled PV used locally is addressed which avoids the loss of long-distance transmission. However, power balance is the most critical technical issue in HPSS . This issue becomes even more severe if a high percentage of PV power is integrated. Stepped PV power outputs may result in significant over/under power deviations, which cannot satisfy the strict power quality requirements of aluminum electrolysis production. What’s more, the demand power of aluminum electrolysis loads increases while occur anode effect. In view of this, the power deviations caused by PV-System and anode effect should be dynamically compensated in real time, which is a challenge for ac controller. Although considerable methods have been proposed to address the fluctuation problems of PV System, these methods are unsuitable for industrial aluminum electrolytic production. In case of the proposed converters are based on boost model which have limitation in boost capability and can not satisfy the wide input voltage variation range of PV-System in this paper. Besides, the industrial operating condition of aluminum electrolytic production is harsh that the electromagnetic induction intensity in production workshop is up to Tesla level. Necessitating a power conversion system that has a wide input voltage and load regulation range, and high immunity is needed
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