Solution of Parallel Debugging Of Diesel Generator Sets

Let's take the parallel connection of two equal power units as an example to analyze the cause of circulation attack.

Current U1:1# unit terminal voltage,U2:2# unit terminal voltage,R3: load carried by parallel operation of two units,I0: current, i1:1 # unit output current,I2:2# unit output current. Haifeng diesel generator set to provide technical support. If the two units work in parallel, the circulation I0 is 0 under any load, then it is necessary that U1=U2, that is, the terminal voltage of the two units is equal under any load. The no-load parallel is equivalent to infinite load, and the no-load terminal voltage U01 and U02 should also be equal. U01=U02(1-2) We know that the average distribution of active power depends on the characteristics of the diesel engine and its speed regulating system, and the distribution of reactive power depends on the characteristics of the generator and its excitation system, that is, the voltage regulating characteristics of the generator set itself. The voltage regulating characteristic is a curve U= F (I), where U is the terminal voltage of the generator set and I is the current. To facilitate analysis, a straight line is usually used to approximate the curve. Assume that there are two parallel generating sets with voltage regulating characteristics as shown in FIG. 2 respectively, set as follows :δ1= TG β1,δ2 = TG β2, the voltage regulating characteristics of δ1:1# unit, and the voltage regulating characteristics of δ2:2# unit.

From the above analysis, it can be seen that:

(1) When two units are connected in parallel, the no-load voltage and voltage regulating characteristics of the two units should be adjusted to be exactly the same, which is the prerequisite for ensuring the complete and even distribution of reactive power of the two units and the basis for subsequent adjustment of the average power distribution of the two units. When the above two adjustments are balanced, the output voltage of the two units working in parallel is guaranteed to be equal under any load, and the average power distribution is guaranteed together, and the circulation is guaranteed to be zero (ideally). Indicate: the root cause of the circulation attack is that the no-load voltage of the two units is not completely equal or the voltage regulating characteristics are different, which constitute the output voltage is not equal and the circulation attack.

(2) The no-load voltage and voltage regulating characteristics of the two units are equal, but the output current of the two units is not equal, that is, the power distribution of the two units is not uniform, which will also constitute the imbalance of U1 and U2, resulting in the occurrence of circulation.

(3) There are many factors affecting the distribution of reactive power, such as the characteristics of automatic voltage regulator, the stability of the link using the equalizing line, etc., which will not be analyzed here.

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