Variable Frequency Control System Research Articles

Simulation Research on Variable Frequency Control System of Hoist in Inland River Locks Based on Fuzzy PID

In view of the demand in the operation process of lock gate as “slow start-fast run-slow stop”, our study introduced the variable frequency control technology and established the opening and closing machine control system model. We conducted the closed-loop control simulation based on fuzzy PID to effectively suppress or eliminate the influence of error. Thus, the optimal control algorithm and strategy are obtained, and the precise control of the opening and closing process of the miter gate is realized.

The Simulation Research of Two State Markov Chain in the Double Random SVPWM of the Variable Frequency Control System

At present the Space Vector Pulse Width Modulation (SVPWM) technique has been widely used in the variable frequency control system,but the technique will make the system produce higher harmonic components at the switching frequency integer multiple times,thus the harmonic produce the high frequency noise.In the face of this problem, this paper adopts double random SVPWM technique which is added two state Markov chain to effectively reduce the high frequency noise.The technique makes the harmonic components amplitude value of the output current reduced effectively in the inverter of the variable frequency control system,so that the more output current is more relatively evenly distributed in the wide frequency range,so as to minimize the electromagnetic noise.

The Development of DSP-Based FFU Motor Digital Variable Frequency Control System

The variable frequency speed control is one of the most important issues for fan filter unit (FFU) system. A novel digital variable frequency control system for FFU motors were proposed and developed to decrease running losses, and improve the speed control effect and accuracy. The system uses high-performance digital signal processor (DSP) TMS320F2812 as the control core, which adopts a dedicated motor pulse width modulation (PWM) control module to achieve the FFU motors real-time online digital variable frequency control. The composition and working principle of control system were illustrated, the hardware and software design were illustrated in detail. Finally, the experimental results on control system prototype were given, which confirm the effectiveness and validity of the control strategy, and demonstrate that the proposed method can achieve accurate variable frequency speed control of FFU motors.

Development of Ultra Fast Cooling Variable Frequency Control System in Hot Strip Mill

With advanced high-strength steels and high value-added steels development, it is urgent to innovative run out table cooling line in hot strip mill with flexible cooling capacity to meet products metallurgical requirements of the cooling rate after rolling. The way to increase the cooling capacity is to improve the effect of heat exchange of water forced convection with hot strip. Then to raise the spraying pressure to penetrate the residual water and break the vapor inside it is the most feasible method. So, how to control the variable frequency device providing variable spraying pressure is the object of this study. Firstly, cooling after rolling process requirement under ultra fast cooling was analyzed; secondly, characteristic curves of centrifugal pump and water supply pipeline were tested; then inverter timing control, interlock control, security control and so on were studied. Since online application of the variable frequency control system, the water supply system has been running stably and reliably

Development and testing of a multi-type air conditioner without using AC inverters

This paper reports the results from the development and performance testing of a cost effective, energy efficient, multi-type air conditioner that connected five indoor units (evaporators) to one outdoor unit (condenser) with a digital scroll compressor. Instead of using inverter technology, which has a potential risk of harmonic current emissions, this study used a digital scroll compressor, which provided the variable refrigerant volumes. The measured results for this innovative design showed: (1) The relationship between the degree of opening of the electronic expansion valves (s) and the compressor output ratio (%) could be represented by regression functions, which formed the basic parameters of the system control. (2) The developed system provided true zoning capability because it could run indoor units under part load conditions, therefore wasting little energy. The power consumption of the developed system was reduced from 100% to 25% when the full load was reduced to a partial load of 17%, saving more than 75% of the work required using a conventional un-loading method. (3) The developed system has a broader range of capacity output (from 17% to 100%) than that of an AC variable frequency control system (from 48% to 104%). The developed system cost 20% less than a comparable system with an AC inverter.

Development and testing of a multi-type air conditioner without using AC inverters

This paper reports the results from the development and performance testing of a cost effective, energy efficient, multi-type air conditioner that connected five indoor units (evaporators) to one outdoor unit (condenser) with a digital scroll compressor. Instead of using inverter technology, which has a potential risk of harmonic current emissions, this study used a digital scroll compressor, which provided the variable refrigerant volumes. The measured results for this innovative design showed: (1) The relationship between the degree of opening of the electronic expansion valves (s) and the compressor output ratio (%) could be represented by regression functions, which formed the basic parameters of the system control. (2) The developed system provided true zoning capability because it could run indoor units under part load conditions, therefore wasting little energy. The power consumption of the developed system was reduced from 100% to 25% when the full load was reduced to a partial load of 17%, saving more than 75% of the work required using a conventional un-loading method. (3) The developed system has a broader range of capacity output (from 17% to 100%) than that of an AC variable frequency control system (from 48% to 104%). The developed system cost 20% less than a comparable system with an AC inverter.

A highly accurate continuously variable frequency control system

A method is described for controlling the frequency of an oscillator with crystal accuracy and at the same time permitting effectively continuous adjustment of the frequency required. A selected multiple of the oscillator period is obtained by counting the oscillator cycles with a fast binary scaler followed by a special scaler with a widely variable scaling factor. The resulting time interval is accurately compared, in a suitable circuit, with a fixed time interval, derived from a crystal oscillator. A signal is thus obtained which drives a differential motor system in the appropriate direction to correct the adjustment of the oscillator tuning condenser.