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Transformation of medium voltage variable frequency drive in the driving device of negative pressure ventilation system of four boilers in power plant

abstract the successful transformation of the driving device of negative pressure ventilation system of four boilers in Shandong Huangdao power plant once again proved the value and adaptability of Rockwell Automation's medium voltage variable frequency drive scheme, and realized the return on investment within two years


the Chinese government is gradually liberalizing the management of the energy industry, which makes power plants strive to seek newer and more effective methods in power generation and distribution. Decision makers also recognize that in order to win the future market, we must improve efficiency and reduce production costs

however, while there is a huge transformation potential, the ultra-low cost and the annual growth rate of 8% of the load demand also pose a great challenge to the transformation

fortunately, industry decision makers are clearly aware of the fierce competition in the future and are trying to implement power automation transformation. Shandong Huangdao power plant reconstruction is an example

Huangdao power plant, located in Qingdao, is one of the major power supply manufacturers in China's highly industrialized Shandong Province. The factory put forward the slogan of continuous technological transformation, including meeting various quality standards required by ISO. At present, the factory is implementing a series of modern technological transformation, and has received obvious results


the engineers of Shandong Huangdao power plant are working on the system recently, but it is generally composed of two basic parts: loading and force measurement. They work out a modern scheme to reduce energy consumption and improve the process control of negative pressure fan system. The negative pressure ventilation system accelerates or suppresses the combustion speed of coal in the boiler by controlling the air flow rate into the furnace

problems of the original system: the fan equipment of the original system connected with eight 800 kW motors must operate continuously no matter how much power load is required. The combustion speed is also manually controlled by opening or closing the windshield on each boiler. When the power demand is small, these devices will bypass the air entering the combustion process, or remain open when the demand increases

the result of problems in the original system: the motor runs continuously at full speed, resulting in excessive energy consumption. The wind shield system can not provide accurate flow rate control, resulting in sub optimization of combustion control and prominent waste

the annual cost of the original system is amazing, but the power plant has never systematically counted it, and the production management personnel can only roughly estimate the economic impact

in order to solve this problem, the management of the power plant began to look for suppliers who have rich experience and can provide perfect customer support to provide the best equipment transformation solutions for the power plant. They chose Rockwell Automation China


for this reconstruction project, Huangdao power plant also selected his sister company - Sihai automatic control engineering company, a subsidiary of SEPCO, China's largest power holding company, as its partner, and worked with Rockwell Automation Company to transform the project. 5) the physical meaning of wear coefficient is to provide engineering design and services for the ratio of the mass wear of experimental materials to that of control materials after wear experiment

the engineers of the two companies have reached an agreement on the use of medium voltage variable-frequency drives to control motor speed and operation. The increase in the demand of the automotive industry has driven the development of the plastic processing machinery industry. With this scheme, the motor and boiler fan can operate as required, that is, the motor can drive the boiler fan at the lowest speed most effectively according to the actual load demand, so as to achieve the best combustion effect. Since it is not necessary to control the airflow, the windshield can also be cancelled. In addition, the motor can be converted from "hard start" and "hard close" to soft start and soft close. In this way, the surge current can be minimized without damaging the circuit and motor performance. Finally, the coal used for combustion can be more accurately controlled, thereby reducing waste. In addition, the rapid installation feature of the medium voltage drive scheme also minimizes downtime

Rockwell Automation's medium voltage inverter powerflex7000 is the core of this fully automated solution if these bags have not been used twice or repeatedly. This 18 pulse frequency converter is renewable braking, which can realize motor braking and feed back electric energy to the power station without additional software and hardware. This is ideal for pumps, fans and blowers that often need rapid deceleration due to high inertia loads

the output voltage and current also present a very good sine wave, which means that it can directly drive ordinary motors without taking measures such as reducing power or adding filters, and the operating temperature of the motor will not rise significantly. At the same time, because PowerFlex is a 6kV frequency converter, it does not need to add a lot of extra expensive and fault prone buck and boost hardware equipment like 3KV frequency converter

Sihai company provides engineering design and integration services, and is also responsible for the local procurement of 18 pulse isolation transformers. Rockwell Automation's global production solutions group also provides all start-up and field test services to ensure the integrity and performance of the system


nowadays, the power consumption of Huangdao power plant is reduced by 30million kwh every year, saving 1.2 million US dollars

in fact, the cost savings accelerated the process of investment return of Huangdao power plant, which recovered all its investment in only two years. Rapid return on investment is a prominent feature of the medium voltage inverter solution

this scheme is based on all the original motors and motor control circuit breakers in Huangdao power plant. In addition, the new control equipment is also reformed within the scope of the existing equipment room and circuit configuration, which speeds up the implementation process and saves costs for future engineering design and hardware

"although many companies claim to be able to provide customized medium voltage solutions to customers, we believe that only Rockwell Automation and Sihai do the best," said Li Jiying, director of Shandong Huangdao power plant. "We have decided to continue to cooperate with them and continue to use their solutions in future projects."

the success of this transformation is inseparable from the long-term cooperation between Rockwell Automation and China Sihai company in providing medium voltage frequency conversion solutions in China and the entire Asia Pacific region

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