The control system of a diesel generator set is akin to its heart. The adoption of intelligent control systems has significantly enhanced the operational performance of diesel generator sets, ensuring their stable operation. So, what principles and algorithms underpin the functioning of these control systems? In the control section of diesel generator sets, digital excitation controllers offer advantages over traditional analog circuit controllers. These include higher precision, faster response times, and stronger adaptability in control algorithms. They can accommodate motors with varying characteristics simply by adjusting program parameters, and can even implement more advanced adaptive intelligent control algorithms. I. Software Implementation and Algorithm Research for Digital Excitation Controllers This section primarily discusses the software and control algorithms employed in digital excitation controllers. It begins with designing the main program for the digital excitation controller, followed by researching electrical parameter acquisition algorithms and intelligent excitation control algorithms, which are then implemented on the CPU. To achieve precise digital excitation control, real-time and accurate electrical data is required. Obtaining such data necessitates AC sampling methods. This involves deriving calculation formulas for each electrical parameter under AC sampling conditions and ultimately developing the algorithm program to compute the electrical data. AC sampling involves periodically capturing instantaneous values of the measured signal and then calculating the electrical parameters using specific mathematical algorithms. Below are the discrete formulas for various algorithms measuring AC voltage, AC current, active power, reactive power, and power factor.

II. Overall Design Scheme for Digital Excitation Controller

Power Supply: To meet the operating voltage requirements of the microprocessor, a stable 5V DC power supply is needed. The signal conditioning circuit's operational circuit requires a ±12V DC power supply. Power Supply: To meet the microprocessor's operating voltage requirements, a stable 5V DC power supply is needed. The signal conditioning circuit and operational circuitry require a ±12V DC power supply. Additionally, the digital output needs to drive relays, necessitating a +24V DC power supply. Therefore, a power conversion module must be designed to provide the three DC power supplies required for normal system operation.

III. Design of the Excitation Output Main Circuit

The power output of the excitation controller is a DC output capable of controlling both current and voltage. The overall design specifies a rated voltage of 80VDC for this excitation rectifier output, with a rated excitation current of 10A, reaching 25A during forced excitation. Excitation power is sourced from an AC supply, which may originate from the generator itself or an external source. External supplies typically offer superior stability. Power from the generator, however, is subject to fluctuations and distortions during startup and operation, potentially compromising excitation output performance. Therefore, our research and design focus specifically on power extraction from the generator.
    IV. AC Sampling Phase-Locked Loop Circuit

  AC sampling typically requires synchronous sampling. Current AC sampling methods primarily include hardware synchronous sampling, software synchronous sampling, and asynchronous sampling. Hardware synchronization is achieved by a hardware synchronization circuit triggering an interrupt to the CPU. Hardware synchronization circuits come in various forms, with common examples including phase-locked loop (PLL) synchronization circuits. Hardware synchronous sampling employs dedicated hardware circuits to generate sampling pulses synchronized with the measured signal. This method overcomes shortcomings such as truncation errors inherent in software-based synchronization, delivering high measurement accuracy. The schematic diagram illustrating synchronous equi-interval sampling based on phase-locked frequency tracking is shown in Figure 2.3: An n-divider is incorporated into the phase-locked loop (PLL) composed of a phase detector (PD), low-pass filter (LP), and voltage-controlled oscillator (VCO). The input frequency of the signal under test serves as the reference frequency for the PLL, while the output frequency is the sampling frequency. After n-fold frequency division, the output is compared with the input. According to the operating principle of the PLL, when locked, /n = 1, i.e., = n. Due to the PLL's time-tracking capability, when the frequency of the measured signal changes, the circuit can automatically and rapidly track and lock, always satisfying the relationship = n. That is, the sampling frequency is an integer multiple n times the frequency of the measured signal, thereby achieving n points of equidistant sampling within one cycle. Additionally, the frequency division factor n can be programmatically controlled. This allows dynamic adjustment of n based on the measured signal's frequency and the CPU/A/D converter's speed, achieving optimal performance.

The operating principles and algorithms of diesel generator set control systems are highly complex. Each circuit design employs specific algorithms for implementation.