CN104779592A - DER containing dotted network reverse power protection method based on sequence current break variable and power direction thereof - Google Patents

Abstract

The invention discloses a novel DER (Distributed Energy Resource) containing dotted network reverse power protection method based on a sequence current break variable and power direction thereof. The method comprises the following steps: considering about DER output characteristics and influence of low voltage load fluctuation on current break variable constant value to recognize reverse power and normal power reverse feeding phenomenon caused by the recognition fault, utilizing the fault location section by utilizing the positive sequence power and negative sequence power directions, and at last formulating the logic and fixed value setting principle of the novel reverse power protection method. The method can effectively improve the protection performance and the operating stability of the DER height permeation dotted network.

Description

Based on sequence jump-value of current and power direction thereof containing DER point mesh network reverse power protection method

Technical field

The present invention relates to field of relay protection in power, particularly a kind of based on sequence jump-value of current and power direction thereof containing DER point mesh network reverse power protection method.

Background technology

The requirement that socioeconomic development has a power failure especially in short-term to power supply reliability is more and more higher.Traditional radiativity network improves power supply reliability mainly through mode of handing in hand, but still needs power failure to turn for load.Point mesh network (Spot Network) is as a kind of low pressure multi-source and for system, effectively can solve and continue to have a power failure and power cut problem in short-term, be generally acknowledged the most reliably and the most flexibly supply power mode, be mainly used in the important events such as airport, hospital, large-scale data center.At present, tennessee,USA St.Jude child study hospital, gymnasium, NBA Memphis Grizzlies team home court and Pearson came International airport, Toronto etc. all have employed this supply power mode.In some mesh network, generators and loads all concentrates access by low-voltage bus bar, is conducive to access control and the energy on-site elimination of distributed power source (Distributed Energy Resource, DER).The low-pressure side of conventional point mesh network is configured with reverse power protection, and during for preventing from normally running, because each bar inlet wire is exerted oneself seriously unbalanced, emergent power send; Although some corresponding flow control method can be exerted oneself problem by efficient balance inlet wire, DER access capacity is comparatively large and randomness is exerted oneself stronger time, some electric power incoming line still there will be power and send thus cause reverse power protection action; And when primary voltage out of service meets access conditions, corresponding circuit breaker can close a floodgate automatically again.Above-mentioned two processes repeat, and can make line switching frequent " jump ", system cannot normally be run.Visible, the reverse power protection of conventional point mesh network limits DER access capacity to a certain extent.

In IEEE 1547, specify that the definite value of reverse power protection is arranged according to 0.5% of transformer capacity, definite value is generally 1kW-2kW, is difficult to adapt to DER operation characteristic and tolerance access requirement.Expert is had to propose to increase delay link in reverse power protection; according to inverse time characteristic; operate time is determined in conjunction with inverse probability size; after DER fluctuation causes power to send; this protection can postpone tripping; and can instantaneous operation during medium voltage side fault; but the method is only applicable to the low capacity access of DER and the situation of inlet wire inverse probability operation in short-term; do not consider the relevance that inverse probability size and duration and part throttle characteristics, DER to be exerted oneself etc. between factor, protection definite value and setting operate time lack effective theory support.Also have expert based on the thought of territory, station protection, by low-voltage load, the inlet wire power of Real-Time Monitoring point mesh network and DER is actual exerts oneself, comprehensive descision causes the reason of inverse probability; During information completely, the method can effectively improve containing DER point-like network operation stability, but information is once disappearance, and the method will lose efficacy.Somebody proposes when load is lighter, initiatively reduces DER and exerts oneself or directly make it exit, and cause protection misoperation, but the method is exerted oneself and dealt with, and is unfavorable for making full use of of DER to prevent inverse probability operation by limiting DER.The protection's dead-zone problem separately having expert may exist for a mesh network reverse power protection, proposes to be improved by the mode of memory voltage, does not relate to the access impact of DER.In a word, existing some mesh network reverse power protection method is difficult to solve the DER tolerance and accesses the impact brought.

Summary of the invention

In view of this; technical problem to be solved by this invention is to provide a kind of reverse power protection new method containing DER point mesh network; the method utilizes sequence jump-value of current and power power direction determination abort situation interval thereof; and give the guard method of novel reverse power realize logical AND fixed value adjusting principle; object is to consider DER power producing characteristics and the impact of low-voltage load fluctuation on jump-value of current definite value, and the difference that the inverse probability that causes of fault and normal power send.

The present invention is achieved by the following technical solutions:

This distributed power source (distributed energy resource, DER) that contains based on sequence jump-value of current and power direction thereof puts mesh network reverse power protection method, and process is as follows:

(1) when three phase short circuit fault occurs in certain electric power incoming line reverse power protection upstream, the positive-sequence power direction flowing through this protection is negative, and the positive-sequence power direction flowing through the protection of all the other electric power incoming lines and distributed power source (DER) is just all;

(2), when three phase short circuit fault occurs in certain electric power incoming line reverse power protection downstream, the positive-sequence power direction flowing through the protection of all electric power incoming lines and DER is just all;

(3), when phase fault occurs in certain electric power incoming line reverse power protection upstream, the negative-sequence power direction flowing through this electric power incoming line place is just, and the negative-sequence power direction flowing through the protection of all the other electric power incoming lines and DER is all negative;

(4), when phase fault occurs in certain electric power incoming line reverse power protection downstream, the negative-sequence power direction flowing through the protection of all electric power incoming lines and DER is all negative;

(5) although DER generally has intermittent feature of exerting oneself with randomness, Relative fault electric current, its period of change is longer, can be considered level and smooth within certain hour, can not cause obvious sequence jump-value of current when it normally runs; Utilize sequence jump-value of current as starting component, effectively can escape the impact of DER power producing characteristics, can identify that the inverse probability that fault causes and DER exert oneself comparatively large in conjunction with power direction and power that is that cause send.Consider power direction computing time, sequence jump-value of current needs after starting to keep certain hour, and this Time dependent is in Sudden Changing Rate computational methods;

(6) forward-order current Sudden Changing Rate definite value is adjusted by escaping the current value flowing through incoming relay-protection when low-voltage bus bar accesses maximum threephase load, can escape the impact of low-voltage load startup on positive sequence Sudden Changing Rate:

$I_{\mathrm{set}1}=\frac{\sqrt{2}}{N-1}{K}_{\mathrm{rel}}{K}_{\mathrm{ss}}{I}_{L.\max }=\frac{\sqrt{6}{K}_{\mathrm{rel}}{K}_{\mathrm{ss}}{P}_{\max }}{3\·(N-1)\·U_N\cos \mathrm{\φ}}---\left(1\right)$

In formula, K _rel-safety factor, desirable 1.05 ~ 1.1; K _ss-comprehensive self-starting coefficient, desirable 5 ~ 7; P _maxthe active power of the maximum threephase load of-low-voltage bus bar; A N-mesh network inlet wire number, and consider according to N-1 principle; U _n-low-voltage bus bar rated voltage; power factor during-system cloud gray model;

(7) when on low-voltage bus bar, single-phase load sharply changes, its voltage unbalance factor can change, and can produce negative-sequence current Sudden Changing Rate in electrical network.According to relevant national standard regulation, low pressure public access point voltage unbalance factor need meet U ₂/ U ₁≤ 4%.Negative-sequence current Sudden Changing Rate definite value is adjusted by escaping the negative-sequence current flowing through incoming relay-protection when low-voltage bus bar accesses maximum single-phase load:

$I_{\mathrm{set}2}=\frac{\sqrt{2}}{3(N-1)}{K}_{\mathrm{rel}}{I}_{L.\max .\mathrm{\φ}}=\frac{\sqrt{6}{K}_{\mathrm{rel}}{P}_{\max .\mathrm{\φ}}}{3\·(N-1)\·U_N\cos \mathrm{\φ}}---\left(2\right)$

In formula, the single-phase load power that the maximum degree of unbalance of-low-voltage bus bar is corresponding;

(8) when medium voltage side inlet wire head end is short-circuited, reverse power protection should have enough sensitivity, therefore the sensitivity coefficient of positive sequence Sudden Changing Rate starting component is calculated as follows,

$K_{\mathrm{sen}.\mathrm{re}.1}=\frac{I_{k.\mathrm{re}.\min .1}}{I_{\mathrm{set}.\mathrm{re}.1}}---\left(3\right)$

In formula, I _k.re.min.1during for protection upstream generation symmetrical short-circuit, flow through the minimum forward-order current Sudden Changing Rate of corresponding reverse power protection;

(9) sensitivity coefficient of negative phase-sequence Sudden Changing Rate starting component is calculated as follows,

$K_{\mathrm{sen}.\mathrm{re}.2}=\frac{I_{k.\mathrm{re}.\min .2}}{I_{\mathrm{set}.\mathrm{re}.2}}---\left(4\right)$

In formula, I _k.re.min.2during for protection upstream generation unsymmetrical short-circuit, flow through the minimum negative phase-sequence jump-value of current value of corresponding reverse power protection.

Compared with prior art the invention has the beneficial effects as follows:

Method disclosed in patent of the present invention can effectively distinguish DER exert oneself the inverse probability that causes is run and medium voltage side fault causes power send between difference, the stability containing the network operation of DER point-like can be improved to a certain extent.

Accompanying drawing explanation

Accompanying drawing 1 is 3 inlet wire point-like network topology structures containing DER.

Accompanying drawing 2 is some mesh network reverse power protection logic diagram.

Accompanying drawing 3 to be exerted oneself waveform of exerting oneself with DER for inlet wire under original protection.

Accompanying drawing 4 to be exerted oneself waveform of exerting oneself with DER for inlet wire after inlet wire 1 fault under original protection.

Accompanying drawing 5 to be exerted oneself waveform of exerting oneself with DER for improving the lower inlet wire of protection.

Accompanying drawing 6 to be exerted oneself waveform for inlet wire after improving lower inlet wire 1 fault of protection and DER.

Embodiment

The present invention propose based on sequence jump-value of current and power direction thereof containing DER point mesh network reverse power protection method, below in conjunction with drawings and Examples, the present invention is described in detail.

1, embodiment 1

(1) reverse power protection method during three phase short circuit fault

As shown in Figure 1, fault signature analysis is carried out for the DER point mesh network that contains with 3 electric power incoming lines.Wherein, for the equivalent electromotive force of each bar inlet wire; for the equivalent internal impedance of each bar incoming power; for the equivalent impedance of each bar inlet wire; P _i(i=1,2,3) are reverse power protection to be analyzed.

For inlet wire 1, at protection P1 upstream and downstream, namely there is three phase short circuit fault in f1 and f2 place.When there is three-phase shortcircuit at f1 place, the positive-sequence power direction flowing through this protection when namely three-phase shortcircuit occurs in P1 upstream is negative, and the positive-sequence power direction flowing through P2, P3 and DER is just.When there is three-phase shortcircuit at f2 place, namely when P1 downstream three-phase shortcircuit, the positive-sequence power direction flowing through P1, P2, P3 and DER is just.

By judging that positive-sequence power direction effectively can identify the position of three phase short circuit fault.

(2) reverse power protection method during phase fault

For improving the sensitivity of protection, consider when phase fault to adopt negative sequence component and power direction thereof to form criterion.When in Fig. 1, phase fault occurs respectively at f1 and f2 place, during the short circuit of f1 place, when namely protecting P1 upstream phase fault, the negative-sequence power direction flowing through P1 is just, and flows through P2, and the negative-sequence power direction of P3 and DER is negative.When there is phase fault at f2 place, namely during P1 protection downstream fault, the negative phase-sequence active power direction flowing through inlet wire P1, P2, P3 and DER is negative.

The position of phase fault can be judged by negative-sequence power direction.Because medium voltage side neutral point generally adopts non-effective earthing operational mode, when there is single phase ground fault, there is special safeguard measure, do not perform an analysis herein.

(3) relay protective scheme and setting principle

Although DER generally has intermittent feature of exerting oneself with randomness, Relative fault electric current, its period of change is longer, can be considered level and smooth within certain hour, can not cause obvious sequence jump-value of current when it normally runs; Therefore utilize sequence jump-value of current as starting component, effectively can escape the impact of DER power producing characteristics, can identify that the inverse probability that fault causes and DER exert oneself comparatively large in conjunction with power direction and power that is that cause send.The reverse power protection action logic of inlet wire 1 correspondence as shown in Figure 2, considers power direction computing time, and sequence jump-value of current needs after starting to keep certain hour t, and this Time dependent is in Sudden Changing Rate computational methods.

For escaping the impact of low-voltage load startup on positive sequence Sudden Changing Rate, its definite value is adjusted by escaping the current value flowing through incoming relay-protection when low-voltage bus bar accesses maximum threephase load:

$I_{\mathrm{set}1}=\frac{\sqrt{2}}{N-1}{K}_{\mathrm{rel}}{K}_{\mathrm{ss}}{I}_{L.\max }=\frac{\sqrt{6}{K}_{\mathrm{rel}}{K}_{\mathrm{ss}}{P}_{\max }}{3\·(N-1)\·U_N\cos \mathrm{\φ}}---\left(1\right)$

In formula, K _rel-safety factor, desirable 1.05 ~ 1.1; K _ss-comprehensive self-starting coefficient, desirable 5 ~ 7; P _maxthe active power of the maximum threephase load of-low-voltage bus bar; A N-mesh network inlet wire number, and consider according to N-1 principle; U _n-low-voltage bus bar rated voltage; power factor during-system cloud gray model.

When on low-voltage bus bar, single-phase load sharply changes, its voltage unbalance factor can change, and can produce negative-sequence current Sudden Changing Rate in electrical network.According to relevant national standard regulation, low pressure public access point voltage unbalance factor need meet U ₂/ U ₁≤ 4%.Negative-sequence current Sudden Changing Rate definite value is adjusted by escaping the negative-sequence current flowing through incoming relay-protection when low-voltage bus bar accesses maximum single-phase load:

$I_{\mathrm{set}2}=\frac{\sqrt{2}}{3(N-1)}{K}_{\mathrm{rel}}{I}_{L.\max .\mathrm{\φ}}=\frac{\sqrt{6}{K}_{\mathrm{rel}}{P}_{\max .\mathrm{\φ}}}{3\·(N-1)\·U_N\cos \mathrm{\φ}}---\left(2\right)$

In formula, the single-phase load power that the maximum degree of unbalance of-low-voltage bus bar is corresponding.

(4) sensitivity check method

When medium voltage side inlet wire head end is short-circuited, reverse power protection should have enough sensitivity, therefore the sensitivity coefficient of positive sequence Sudden Changing Rate starting component is calculated as follows,

$K_{\mathrm{sen}.\mathrm{re}.1}=\frac{I_{k.\mathrm{re}.\min .1}}{I_{\mathrm{set}.\mathrm{re}.1}}---\left(3\right)$

In formula, I _k.re.min.1during for protection upstream generation symmetrical short-circuit, flow through the minimum forward-order current Sudden Changing Rate of corresponding reverse power protection.

The sensitivity coefficient of negative phase-sequence Sudden Changing Rate starting component is calculated as follows,

$K_{\mathrm{sen}.\mathrm{re}.2}=\frac{I_{k.\mathrm{re}.\min .2}}{I_{\mathrm{set}.\mathrm{re}.2}}---\left(4\right)$

In formula, I _k.re.min.2during for protection upstream generation unsymmetrical short-circuit, flow through the minimum negative phase-sequence jump-value of current value of corresponding reverse power protection.

2, embodiment 2

Adopt relevant parameter as shown in Table 1 and Table 2, for analyzing containing DER point mesh network shown in Fig. 1.

Table 1 inlet wire model parameter

Table 2 simulation model load and DER parameter list

	Load 1	Load 2	Load 3	DER
					U N(kV)	0.4	0.4	0.4	0.4
Type	Invariable power	Invariable power (single-phase)	Invariable power	Blower fan
					Apparent power (MVA)	0.09+j0.001	1.33+j0.001	2.10+j0.001	0.25+j0.05

Assuming that the separate unit maximum power with three-phase equipment in low-voltage load be P _max=0.30MW, the separate unit maximum power with equipment single-phase in low-voltage load be P _max.a=1.33MW, substitutes into formula (2) by model parameter, can obtain negative-sequence current Sudden Changing Rate setting value I _set2=1.85kA.

When t=6S, DER is dropped into, and control its meritorious constantly increase of exerting oneself; And arrange when t=19S inlet wire 1 protect upstream occur phase fault.

Under original reverse power protection, inlet wire is exerted oneself and is exerted oneself waveform as shown in Figure 3 with DER, under the prerequisite of steady load, constantly increase along with DER exerts oneself, exerting oneself of 3 power supplys reduces gradually, and when t=8.75S, inlet wire 1 emergent power send, and P1 protection act is by inlet wire 1 tripping; When P1 protects upstream to be short-circuited, traditional reverse power protection can reliably excise this faulty line, as shown in Figure 4.

Under the reverse power protection that this patent proposes, as shown in Figure 5, cause more greatly inlet wire 1 emergent power to send although DER exerts oneself, not yet reach jump-value of current and start definite value, reverse power protection can not action; As seen from Figure 6, the reverse power protection of improvement still can reliably excise inlet wire fault.

Under the reverse power protection improved, simulation analysis is carried out on DER, maximum single-phase and threephase load access and generation when exiting impact, as shown in table 3.The power that DER can make inlet wire 1 produce 80kW after accessing low-voltage bus bar send, but not yet reaches protection startup definite value, and reverse power protection can not action.Visible, the reverse power protection setting value of improvement can avoid the positive-negative sequence Sudden Changing Rate because load and DER disturbance produce, and this protection can adapt to DER tolerance access requirement.

The lower DER access of table 3 improvement protection affects simulation result with load disturbance

Under the reverse power protection improved, when all kinds fault occurs protection upstream diverse location, its operating characteristics is as shown in table 4, can find the correctness that this patent institute extracting method is analyzed protection upstream circuit fault power direction character; Point mesh network incoming relay-protection upstream is when breaking down, and the reverse power protection of corresponding inlet wire can action message, and the protection of other inlet wires is failure to actuate, and meets protective seletion requirement; The reverse power protection improved has certain tolerance transition resistance ability, and protection sensitivity value is all greater than 1.5, can meet protection sensitivity requirements.

Table 4 improves protection act result when protecting lower inlet wire medium voltage side fault

The foregoing is only an example of the present invention, do not affect dilatancy of the present invention and practicality widely.For a person skilled in the art, the present invention can have various forms of changes and improvements.All within spirit of the present invention and principle, any change of sitting is included within protection scope of the present invention.

Claims (2)

1. based on sequence jump-value of current and power direction thereof containing a distributed power source point mesh network reverse power protection new method, it is characterized in that:

(1) when three phase short circuit fault occurs in certain electric power incoming line reverse power protection upstream, the positive-sequence power direction flowing through this protection is negative, and the positive-sequence power direction flowing through the protection of all the other electric power incoming lines and distributed power source (DER) is just all;

(2), when three phase short circuit fault occurs in certain electric power incoming line reverse power protection downstream, the positive-sequence power direction flowing through the protection of all electric power incoming lines and DER is just all;

(3), when phase fault occurs in certain electric power incoming line reverse power protection upstream, the negative-sequence power direction flowing through this electric power incoming line place is just, and the negative-sequence power direction flowing through the protection of all the other electric power incoming lines and DER is all negative;

(4), when phase fault occurs in certain electric power incoming line reverse power protection downstream, the negative-sequence power direction flowing through the protection of all electric power incoming lines and DER is all negative;

(5) utilize sequence jump-value of current as starting component, effectively can escape the impact of DER power producing characteristics, can identify that the inverse probability that fault causes and DER exert oneself comparatively large in conjunction with power direction and power that is that cause send.Consider power direction computing time, sequence jump-value of current needs after starting to keep certain hour, and this Time dependent is in Sudden Changing Rate computational methods;

(6) forward-order current Sudden Changing Rate definite value is adjusted by escaping the current value flowing through incoming relay-protection when low-voltage bus bar accesses maximum threephase load, can escape the impact of low-voltage load startup on positive sequence Sudden Changing Rate:

$I_{\mathrm{set}1}=\frac{\sqrt{2}}{N-1}{K}_{\mathrm{rel}}{K}_{\mathrm{ss}}{I}_{L.\max }=\frac{\sqrt{6}{K}_{\mathrm{rel}}{K}_{\mathrm{ss}}{P}_{\max }}{3\·(N-1)\·U_N\cos \mathrm{\φ}}---\left(1\right)$

In formula, K _rel-safety factor, desirable 1.05 ~ 1.1; K _ss-comprehensive self-starting coefficient, desirable 5 ~ 7; P _maxthe active power of the maximum threephase load of-low-voltage bus bar; A N-mesh network inlet wire number, and consider according to N-1 principle; U _n-low-voltage bus bar rated voltage; power factor during-system cloud gray model;

(7) negative-sequence current Sudden Changing Rate definite value is adjusted by escaping the negative-sequence current flowing through incoming relay-protection when low-voltage bus bar accesses maximum single-phase load:

$I_{\mathrm{set}2}=\frac{\sqrt{2}}{3(N-1)}{K}_{\mathrm{rel}}{I}_{L.\max .\mathrm{\φ}}=\frac{\sqrt{6}{K}_{\mathrm{rel}}{P}_{\max .\mathrm{\φ}}}{3\·(N-1)\·U_N\cos \mathrm{\φ}}---\left(2\right)$

In formula, the single-phase load power that the maximum degree of unbalance of-low-voltage bus bar is corresponding;

(8) sensitivity coefficient of positive sequence Sudden Changing Rate starting component is calculated as follows,

$K_{\mathrm{sen}.\mathrm{re}.1}=\frac{I_{k.\mathrm{re}.\min .1}}{I_{\mathrm{set}.\mathrm{re}.1}}---\left(3\right)$

In formula, I _k.re.min.1during for protection upstream generation symmetrical short-circuit, flow through the minimum forward-order current Sudden Changing Rate of corresponding reverse power protection;

(9) sensitivity coefficient of negative phase-sequence Sudden Changing Rate starting component is calculated as follows,

$K_{\mathrm{sen}.\mathrm{re}.2}=\frac{I_{k.\mathrm{re}.\min .2}}{I_{\mathrm{set}.\mathrm{re}.2}}---\left(4\right)$

In formula, I _k.re.min.2during for protection upstream generation unsymmetrical short-circuit, flow through the minimum negative phase-sequence jump-value of current value of corresponding reverse power protection.

2. method according to claim 1, is characterized in that: there will be positive sequence in various degree or negative phase-sequence Sudden Changing Rate when protection upstream and downstream fault, and distinguish abort situation according to its sequence power direction.