The intelligent control system of diesel generator set

Diesel generator set control system is an important part of diesel generator set, also is the heart of the diesel generating set, diesel generating sets as the important main power supply or standby power supply has been widely used, the application of intelligent control system in diesel generator set, will help improve the quality of diesel generator output power and diesel automation level of the unit. This paper mainly studies the control part of the diesel generator set, digital excitation controller than traditional analog excitation controller has high precision, fast response, the adaptive control algorithm, for the different features of motor only by adjusting the process parameters in order to adapt to, and even can achieve higher the adaptive intelligent control algorithm, etc.

Digital excitation controller overall design scheme

Overall design scheme of digital excitation controller, the main circuit: using MOSFET single tube PWM chopper control excitation coil, can satisfy the needs of different structure brushless synchronous generator excitation control. Microprocessor (MCU) : the microprocessor is the CPU of the digital excitation controller and is the core of the whole system. The control functions to be completed include:

(1) some low-speed programs. Including frequency measurement, protection, self-inspection, communication, alarm, etc.;

(2) high order real-time control algorithm. Including complex signal processing algorithms such as sampling, digital filtering, control algorithm operation, intelligent algorithm and parameter calculation, the data obtained can be used for high performance excitation control by CPU.

(3) responsible for the detection of various power parameters and AD conversion, as the input parameters of the control algorithm.

(4) generate PWM control signal of chopper. ADC ADC analog-digital converter: multi-point ac sampling technology is adopted. The sampling period is controlled by MCU. After the sampling conversion of ADC, data is sent to MCU for further processing.

Working power supply

Due to the work of the microprocessor power requirement, we need a stable DC 5 v power supply, signal conditioning circuit of the power supply and need a set of plus or minus operation circuit 12 v DC power supply, in addition, switch output needs to drive the relay, so I need a + 24 v DC power supply, therefore we need to design a power conversion modules are required for normal work of the system and the three sets of DC power supply.

1. Design of excitation output main circuit

Excitation controller of power output for a can control current and the voltage of the dc output, total body determine when they design the whole flow excitation magnetic pressure lose out the amount of electricity is 80 VDC, excitation current ratings for 10. A, when strong excitation of 25 a. Excitation power from the ac power source, can be the generator itself, also can be provided by the external, usually are good stability, external supply power generators to provide power because of the impact of a start, and is likely to occur in the process of running wave distortion such as unstable factors, these will affect the performance of the excitation output. Therefore, we study and design the situation of electricity drawing from the generator.

The three-phase alternating current from the ac synchronous generator is output to the field coil through a MOSFET tube after passing a three-phase bridge rectifier circuit rectifier. Diagram at the top of the magnet coil resistance, diode, capacitor of buffer circuit, to join the buffer circuit, can be part of the switch power is transferred to the buffer circuit, to guarantee the safe operation of the device.

The driving circuit of MOSFET tube, selecting IR2213 integration MOSFET and IGBT drive, IR2213 is IR company released a adapt to high pressure, high speed application occasions of MOSFET and IGBT bridge integrated drive, can provide maximum 2 a suction and 2 a current gate drive ability, SD with logical shutoff input pin, can accept low to 3. 3V logical signal input, convenient CPU control.

2. MCU circuit design

MCU as the CPU of digital excitation controller, based on its various functions and working environment requirement of the diesel generating set is more special, so when doing the CPU type selection is to focus on the anti-jamming performance of CPU temperature characteristic and so on. Considering the function of MCU and high working temperature (40 ℃ to - - - + 125 ℃), we choose the military level of ADI company has 8052 core and 12 bit high performance simulation mpu ADuC831 AD.

ADuC831 is a fully integrated 247 k sampling data acquisition system, in the same film is a combination of high performance from the calibration of the 12 ADC multipath channel, double 12 DAC channel and programmable 8-bit MCU. The core of the microprocessor is 8052, providing 62kB non-volatile flash/eraser program memory in the chip. 4kB non-volatile flash/erasure data storage, 256b RAM and 2kB extended RAM are also provided.

ADuC831 also provides additional power monitors and a high precision reference source. On chip digital peripherals including two 16-bit Σ - Δ DAC, double 16-bit PWM output, the watchdog timer, time interval counter, three timer/counter, timer 3 for serial I/O interface baud rate to produce nuclear (I2C, SPI and UART).

3. Ac sampling phase-locked loop circuit

In order to conduct ac sampling, synchronous sampling is usually required. At present, there are three main modes of ac sampling: hardware synchronous sampling, software synchronous sampling and asynchronous sampling. Hardware synchronization by the hardware synchronization circuit to the CPU interrupt to achieve synchronization. Hardware synchronous circuits come in many forms, such as phase-locked loop synchronous circuits. Hardware synchronous sampling method is a kind of sampling pulse which is produced by a special hardware circuit to synchronize the measured signal. It can overcome the shortcomings of software synchronous sampling method such as truncation error and high measurement precision. Using the principle of phase-locked frequency tracking synchronization interval sampling principle is: such as the phase comparator PD, low-pass filter, LP, voltage-controlled oscillator VCO composition of phase-locked loop join in n divider, the frequency of the input for the measured signal, as the benchmark of phase-locked loop frequency, output for the sampling frequency. Compared with the phase after n frequency division,

According to the working principle of the phase-locked loop, the locking time/n =, i.e., = n. As a result of the phase-locked loop traceability, when measured signal frequency changes, circuit can automatically track and lock quickly, always meet = n relations, namely the sampling frequency of measured signal frequency integer n times, so as to realize such as interval sampling n points within a week. In addition, still can be divider coefficient n for process control, can according to the measured signal of different frequency and the speed of the CPU, A/D converter, dynamic change value of n, in order to achieve the best effect.

Digital excitation controller software implementation and algorithm research

The software of digital excitation controller and its control algorithm are discussed. Firstly, the main program of the digital excitation controller is designed. Then, the power parameter acquisition algorithm and the intelligent excitation control algorithm are studied and implemented on the CPU.

1. Design of MCU master control program

ADuC831 MCU is the core of the digital excitation controller designed in this paper the control unit, based on the idea of software modularization, can put the MCU of the master program is divided into the following modules:

(1) excitation control subroutine;

(2) protecting subroutines;

(3) communication subroutines;

(4) face procedure in man-machine field;

(5) alarm subroutine;

(6) self-inspection subroutine.

2. Research on power parameter sampling algorithm

In order to realize the accurate digital excitation control, need to get the real-time, accurate data, and to obtain the real-time, accurate data, you will need to adopt ac sampling method, and deduces the formulas for ac sampling under various power, finally write algorithm to calculate the power data program.

Ac sampling is to sample the instantaneous value of the measured signal according to a certain rule, and then calculate the measurement method of the measured electric quantity parameters according to a certain mathematical algorithm. The discrete formulas of various algorithms for ac voltage, ac current, active power, reactive power, and power factors are given below.

Where N is the number of uniform sampling points per cycle, is the instantaneous current value of the m-th sampling point, and is the instantaneous voltage of the m-th sampling point. This algorithm is not only effective for sine wave, but also can accurately measure the ac amount of waveform distortion when the sampling points are large.