Application of Siemens full AC variable frequency drive system on ship unloader and its speed synchronization, current balance special function

Abstract: This article describes the application of Siemens full communication system on ship unloaders and how to achieve Siemens AC drives to achieve speed synchronization and current control for grab control, optimization, and improve ship unloader operation efficiency.

Keywords: AFE/power plant unloader/crane/master/slave control/speed synchronization/current balance

1 Introduction

Since the reform and opening up, China’s economy has developed rapidly and industrial manufacturing has also developed rapidly. The country’s demand for electricity consumption is very strong. Especially in recent years, the contradiction between electricity demand supply has been very prominent. Many large-scale power plants have been launched, and the power plants generate electricity every day. To burn a large amount of coal, usually the fuel coal is transported by sea to the shore by a large transport ship, and then the coal is discharged from the cabin to the shore by a shore facility to transport the belt to the central combustion chamber. Usually we use a grab-type ship unloader to do this. In this work, the early grasping unloader control system was a DC control system. However, due to the impact of the DC system on the power grid, the maintenance cost of the DC motor is high, and with the increasingly perfect AC debugging technology, we use the Siemens AFE rectifier feedback unit and the AC drive 6SE70 full AC control system in the follow-up projects. Such as Jiangsu Nantong Power Plant 1X1500T/H unloader, Dalian Zhuanghe Power Plant 2X1250T/H unloader. After commissioning this year and putting it into use, the system has been operating stably, with simple maintenance and energy conservation. High operating efficiency and well received by users.

However, due to the poor control of the unloader grab during coal grabbing (coal moisture, particle composition is not the same, the resistance generated when the grab is closed is also very different) and the grab completely belongs to the wire rope traction, while ensuring that the wire rope force balanced The control of the entire system is relatively complex. Here we will elaborate on the entire system and the implementation of special functions separately.

2. System hardware configuration

The following figure (figure 2) is the main circuit diagram of a typical electric control system for ship unloaders. In the figure, we use Siemens' advanced AFE rectification feedback unit to rectify and use the Siemens 6SE70 series vector control speed control device to drive each mechanism's motor with current inversion.

As shown in Figure 2, we use a three-winding main transformer to provide two AFE feedback devices that actively adjust the power factor according to the load conditions to a constant value of 1, and there is no commutation gap that is not normally avoided by conventional rectifiers. The reduction of the limit can interfere with the power supply grid, and at the same time, it can effectively return the regenerated energy back to the grid to save energy. The two AFE devices in the system supply power to the common DC busbar at the same time. The common DC busbar is connected to lift, open and close. The vehicle and trolley (pitch sharing) mechanism inverters, each of which drives the corresponding mechanism motor.

In this case, to ensure that the two AFEs provide the same energy and load balance, we usually send the first AFE actual current to the second AFE current to achieve AFE current balance.

For the grab part, the whole mechanism is controlled by four wire ropes, and two hoisting wire ropes are respectively wound on the reel drum 1, 2 by the hoisting mechanism motor, and two open-closed wire ropes are respectively wrapped around the opening and closing cylinder. , 4 by the open and close mechanism motor control (as shown in Figure 3).

A closed-loop control is formed by collecting actual motor speed feedback and speed reference with a speed encoder. At this point, the grab speed is given by the speed of its own handle.

When the grab moves up and down, the speed synchronization command is enabled. Although the opening and closing lever speed is zero, the open and close driver speed input channel simultaneously accepts the hoisting speed value transmitted by the hoisting mechanism through SIMOLINK. The same as the open and close drive speed setpoints, after the closed loop through their respective speed, the actual speed remains the same, and thus to the speed synchronization.

At the same time, the current balance command is enabled and the lift driver will raise the current setpoint (at the rear of the speed regulator, front of the current regulator) through the SOMOLINK fiber to the open/close drive, which will be transmitted in the open/close drive. The lifting current value is compared with the open/closed self current, and the difference is used as a user-defined PID regulator input to perform PID adjustment and integration (regulator gain, integration parameters need to be adjusted in the field), and the regulator output value enters the open and close drive speed adjustment When the lifting current is greater than the opening and closing current, the PID regulator output is negative, and the opening and closing speed regulator input increases by a positive amount, resulting in an increase in the output of the speed regulator, and an increase of the opening and closing current, when the opening and closing current increases to When the current is the same as the lifting current, that is, the PID regulator input is zero and the output is constant. At this time, the opening and closing current is kept constant and is consistent with the lifting current. Conversely, when the lifting current is less than the opening and closing current, the PID regulator output is positive, and the opening and closing speed regulator increases a negative amount, resulting in a decrease in the output of the speed regulator, and a decrease in the opening and closing current, when the opening and closing current is reduced to When the lifting current is the same, that is, the PID regulator input is zero and the output is constant. At this time, the opening and closing current is kept constant and is consistent with the lifting current. Therefore, under the automatic adjustment of the PID regulator, lifting, the open-close current is always balanced, so as to realize the current balance function.

4 Conclusion

In most lifting equipments, due to the complexity of the grab control on the grab ship unloader, there are high requirements for the design of the electronic control system, the preparation of the PLC program and the setting of the driver parameters, and at the same time, the on-site personnel are required to be good. Debugging techniques, through the design and debugging of the unloading ship's electronic control system, enabled people to have a deeper understanding and mastery of the functions and performance of the Siemens AFE rectifier and 6SE70 frequency converter.