Real-time on-line predicting method of alternating current miniature electric network characteristic parameters
The invention discloses a real-time on-line predicting method of alternating current miniature electric network characteristic parameters. The method comprises the following steps that 1) the disturbance current value Ik of a disturbed node of an alternating current miniature electric network system is collected in real time, the sampling time interval is Ts, and according to the collected disturbance current value Ik, a disturbance current value array [I1, I2, I3, I4, I5, I6] is built; 2) the five-order differential derivative of the current value in the disturbance current value array is calculated in real time: if the one-order differential derivative f(1) is greater than Epsilon, the condition that the alternating current miniature electric network system enters a transient process is judged, if each order derivative is smaller than the preset micro quantity Epsilon, the condition that the alternating current miniature electric network system is stable is judged, the current value at the next moment is continuously collected, and in addition, the five-order differential derivative of the current value at the next moment is continuously calculated. Compared with the prior art, the method has better real-time performance, simplicity and convenience, and can be applied to various fields of transient impact current inhibition, motor parameter on-line testing, failure on-line diagnosis, low-frequency power oscillation on-line detection and inhibition and the like. 1. A characteristic parameter of the micro grid the real-time on-line prediction method, characterized in that comprises the following steps: 1), ω real-time acquisition frequency as the A.C. micro-grid system disturbance by a perturbation current value of the node Ik, sampling time interval is Ts; the perturbation current value according to the collected Ik, structure perturbation current value array ARRAY[I1, I2, I3, I4, I5, I6], ARRAY and perturbation current value of the each element in the array to an initial value of 0, each acquisition one point, make I6 = Ik; I5 = I6; I4 = I5; I3 = I4; I2 = I3; I1 = I2; k is a positive integer; 2), perturbation of the real-time calculation of the current value of the current value in array ARRAY five-order differential derivative: if a first order difference derivative f(1) is greater than ε, it is judged that the exchange system enters the transient state, the micro grid process; if the derivative is smaller than the preset small amount ε, A.C. micro-grid system is judged stable, continue to collect the current value of the next time, and to continue to calculate the current value of the next time the five-step differential derivative, wherein in the perturbation array ARRAY current value of the current value of the five-step differential derivative are f(1), f(2), f(3), f(4), f(5): 3) when the first order differential derivative f(1) is greater than ε, the current value of the next time to continue to collect, calculate a current value of the next time to the five-step differential derivative, to calculate the middle variable a, b, c: (1) a = 0 if the result of calculation, the exchange of the transient process of the micro-grid system for a smooth non-oscillatory transient process, and only the transient process containing a main mode, the main mode of exponential law characteristic is the change in the time domain; (2) if the result of calculation a ≠ 0, calculates a transient process type of discriminant Δ=b2 -4ac: (2.1) if Δ > 0, it is judged that A.C. micro-grid system for a smooth transient process of the transient process of the non-vibrating, without oscillation and steady the transient process contains two main mode, two main mode of the time-domain characteristic of the exponential law change; (2.2) if Δ < 0, it is judged that A.C. micro-grid system oscillation changes in the transient process is a transient process, and the transient process change states the vibration containing a major oscillation modes, the oscillation modes to-cycle changes in the time-domain characteristic, the oscillation amplitude changes exponentially. 2. The exchange of the characteristic parameter of the micro grid real-time on-line prediction method according to Claim 1, characterized in that step 3) the (1) containing a main mode in the stable non-oscillating transient process for the characteristic parameter of the attenuation coefficient of index mode to σ, the computing formula is as follows: 3. The exchange of the characteristic parameter of the micro grid real-time on-line prediction method as in Claim 1 or Claim 2, characterized in that one of the main-containing stable mode of oscillation-free after the end of the transient process the current value of the stable iA: 4. The exchange of the characteristic parameter of the micro grid real-time on-line prediction method according to Claim 1, characterized in that (2.1) containing two main mode in the stable non-oscillating transient process for the characteristic parameter of the attenuation coefficient ρ, that μ, attenuation coefficient ρ, μ calculation formula is as follows: If ρ > 0 and λ > 0 exchange mini-grid system is judged converged the transient process; Otherwise, the transient process of a system for judging divergence, will eventually lead to instability of the exchange system of the micro grid. 5. The exchange of the characteristic parameter of the micro grid real-time on-line prediction method according to Claim 1, characterized in that (2.1) containing two main mode in the stable non-oscillating transient process for the transient DC component Be-ρt and Ce-σt expressed, Be-ρt and Ce-σt calculation formula is as follows: 6. The exchange of the characteristic parameter of the micro grid real-time on-line prediction method as in Claim 4 or Claim 5, characterized in that if ρ > 0 and μ > 0 exchange mini-grid system is judged converged the transient process, and after the end of the transient process for a stable current iB, iB calculation formula is as follows: 7. The exchange of the characteristic parameter of the micro grid real-time on-line prediction method according to Claim 1, characterized in that (2.2) oscillation changes in the characteristic parameters of the transient process to the oscillation cycle Λ and attenuation coefficient of the calculation formula is as follows: 8. The exchange of the characteristic parameter of the micro grid real-time on-line prediction method according to Claim 7, characterized in that when the Δ <0 time, and λ> 0, the transient process of the system for judging convergence, convergence of the transient state of the transient process the AC component iC, steady-state throughput is iD: