CN103208778B - A kind of guard method for Large Copacity energy-storage system - Google Patents

Abstract

The invention discloses a kind of guard method for Large Copacity energy-storage system.Large Copacity energy-storage system is composed in parallel by multiple power inverter, energy storage device and respective step-up transformer; and be connected with external power grid by point of common coupling; its guard method is divided into the guard method at point of common coupling place and the guard method two parts in energy-storage units exit, and includes overcurrent protection, Harmonic Voltage component detection and be with the alternating current of composite voltage startup to detect three failure diagnosis links.The present invention can accurately distinguish external area error in district, and the stored energy capacitance lost after ensureing fault is minimum, improves utilance and the economic benefit of energy-storage system.

Description

A kind of guard method for Large Copacity energy-storage system

Technical field

The present invention relates to a kind of guard method of energy-storage system.

Background technology

Intermittent energy generating relies on the feature of its environmental protection to play more and more important role in the development of electric power system, but meanwhile, the randomness of intermittent energy generating can bring challenges at a large amount of grid-connected rear safe and reliable operation of whole electric power system of giving again with intermittent.

Energy storage technology then can be controlled by active reactive fast, realizes effective power fluctuation and stabilizes, and system power is exported and keeps stable within the specific limits, and this feasibility be incorporated into the power networks to fitful power and stability serve key effect.

Large Copacity energy-storage system is generally composed in parallel by multiple energy-storage units, each energy-storage units bag power inverter and energy storage device, and is connected to point of common coupling PCC(PointofCommonCoupling by respective step-up transformer), then be connected with external power grid.Structural representation as shown in Figure 1.It should be noted that, the PCS part shown in figure comprises the Y/ △ transformer that energy accumulation current converter, Inductor and nominal transformation ratio are 1:1.

Existing research mainly concentrates on the control strategy in grid-connected situation and isolated island situation of energy-storage system, comprises meritorious Reactive Power Control, determines alternating voltage control and droop control etc.And energy-storage system line protection strategy is mainly limited to for the research of energy-storage system Preservation tactics, such as adopt current differential protection to protect energy-storage system transmission line.

Because the critical component of energy-storage units is made up of energy accumulation current converter, and Preservation tactics can not be applicable to completely for energy-storage system the protection such as the fault signature of energy accumulation current converter and conventional electric generators have larger difference, therefore traditional overcurrent protection.

Summary of the invention

The problem of the protection for energy-storage system can not be applicable to for solving conventional overcurrent protection completely, the invention provides a kind of guard method being applicable to energy-storage system.One is composed in parallel and the Large Copacity energy-storage system be connected with external power grid by point of common coupling by multiple power inverter, energy storage device and respective step-up transformer, and wherein power inverter part comprises the Y/ △ transformer that energy accumulation current converter, Inductor and nominal transformation ratio are 1:1.Its guard method is divided into the guard method at point of common coupling place and the guard method two parts in energy-storage units exit, and detects three failure diagnosis link compositions by the alternating current that overcurrent protection, Harmonic Voltage component detection and band composite voltage start.

In the present invention, the criterion of overcurrent protection link is the setting value being greater than overcurrent protection through any phase current effective value of protective device, and namely criterion 1 meets following formula:

Criterion 1:I _s>I _zd=k _ii _n

In formula, I _sfor any cross streams current effective value, I _zdfor overcurrent protective device setting value, I _nfor the rated current effective value that energy-storage units or energy-storage system are crossed, k _ifor overcurrent protective device safety factor;

When above criterion 1 is set up, be judged as energy-storage units internal fault, the protective device time delay Δ T at point of common coupling place ₁tripping operation; The protective device quick-action in energy-storage units exit, excises fault energy-storage units rapidly.Δ T ₁for protection cooperation is differential, in order to ensure that when energy-storage units internal fault the protection of point of common coupling place is failure to actuate, keeping the connection of energy-storage system and external power grid, relying on energy-storage units outlet protection excision fault, ensureing normally being incorporated into the power networks of all the other energy-storage units.

In addition, in the present invention, the effect of Harmonic Voltage component detection link is, the Harmonic Voltage component detected is greater than the voltage harmonic component value that presets as criterion, namely criterion 2 meets following formula:

Criterion 2:THD _s>THD _zd

In formula, THD _sfor Harmonic Voltage component detection value, THD _zdfor Harmonic Voltage component set point;

When above criterion 2 is set up, the protective device at energy-storage units exit and point of common coupling place all determines whether cut-off breaker according to the requirement of energy-storage system islet operation.

Finally, the positive-negative sequence component of the alternating voltage detected and alternating current is greater than the predetermined value of respective components as criterion by the alternating voltage detection started with composite voltage in the present invention, namely meets following formula:

Criterion 3: $\left\{\begin{array}{c}{U}_s^{+}<k_u^{+}{U}_N\\ U_s^{-}\&NotEqual;0\end{array}\right.;$ Criterion 4: $\left\{\begin{array}{c}{I}_s^{+}<k_i^{+}{I}_N\\ I_s^{-}\&NotEqual;0\end{array}\right.$

In formula, be respectively the positive-negative sequence component of alternating voltage and alternating current, be respectively safety factor, U _n, I _nbe respectively the alternating voltage current effective value before energy-storage units or energy-storage system fault;

When criterion 3 set up, criterion 4 be false time, be judged as voltage transformer disconnection, abnormal protective device occur and sends alarm signal; When criterion 3 is all set up with criterion 4, then illustrate and energy-storage system external fault occurs, the protective device at point of common coupling place needs time delay Δ T ₂action also sends islet operation signal, the protective device time delay Δ T in energy-storage units exit ₃action.Wherein Δ T ₂effect be point of common coupling place protective device and system side protection to carry out time coordination, and as the backup protection that system side is protected, in system side distant place fault and system side relay fail time, trip and send isolated island signal, by energy-storage system and external power grid Fault Isolation; Time delay Δ T ₃also be that protection cooperation is differential; not only ensure that non-faulting unit is not excised by mistake when energy-storage units internal fault; simultaneously when tripping appears in energy-storage system external fault or energy-storage units generation internal fault protective device; protect in support and all energy-storage units and ac bus are disconnected, the power electronic device lost of life preventing the long-time overcurrent of current transformer in energy-storage units from causing even causes damage.

Beneficial effect of the present invention:

The present invention can accurately distinguish external area error in district, and the stored energy capacitance lost after ensureing fault is minimum, improves utilance and the economic benefit of energy-storage system.

Accompanying drawing explanation

Fig. 1 is the Large Copacity energy-storage system structural representation of the present invention in order to reference.

Fig. 2 is the guard method flow chart at point of common coupling place of the present invention.

Fig. 3 is the guard method flow chart in energy-storage units exit of the present invention.

Embodiment

Below in conjunction with the drawings and specific embodiments, technical scheme of the present invention is described further.

As shown in Figure 1, Figure 2, Figure 3 shows, when fault occurs in certain energy-storage units inside, the alternating current effective value size in fault energy-storage units exit meets criterion 1, i.e. I _s>I _zd=k _ii _n, the rapid action of protective device, disconnects fault energy-storage units and ac bus, and all the other non-faulting energy-storage units and point of common coupling place still keep the state of being incorporated into the power networks, and continues to be connected with external electrical network.

If consider, when the protective device generation tripping of fault energy-storage units exit, the alternating current effective value at point of common coupling place meets criterion 1, i.e. I _s>I _zd=k _ii _n, protective device time delay Δ T ₁action; The alternating voltage electric current positive-negative sequence component in all the other non-faulting energy-storage units exits meets criterion 3, criterion 4, namely $\left\{\begin{array}{c}{U}_s^{+}<k_u^{+}{U}_N\\ U_s^{-}\&NotEqual;0\end{array}\right.,$ $\left\{\begin{array}{c}{I}_s^{+}<k_i^{+}{I}_N\\ I_s^{-}\&NotEqual;0\end{array}\right.,$ Protective device time delay Δ T ₃action, excises non-faulting energy-storage units and ac bus.

When there is energy-storage system external fault, the alternating voltage electric current positive-negative sequence component at point of common coupling place meets criterion 3, criterion 4, namely $\left\{\begin{array}{c}{U}_s^{+}<k_u^{+}{U}_N\\ U_s^{-}\&NotEqual;0\end{array}\right.,$ $\left\{\begin{array}{c}{I}_s^{+}<k_i^{+}{I}_N\\ I_s^{-}\&NotEqual;0\end{array}\right.,$ Time delay Δ T answered by protective device ₂action also sends islet operation signal, requires transformation working pattern and control strategy according to islet operation.

Need equally to consider, when now there is the situation of point of common coupling place protective device tripping, energy-storage units exit alternating voltage electric current positive-negative sequence component meets criterion 3, criterion 4, namely $\left\{\begin{array}{c}{U}_s^{+}<k_u^{+}{U}_N\\ U_s^{-}\&NotEqual;0\end{array}\right.,$

$\left\{\begin{array}{c}{I}_s^{+}<k_i^{+}{I}_N\\ I_s^{-}\&NotEqual;0\end{array}\right.,$ Protective device Δ T ₃action, excises energy-storage units and ac bus, prevents its long-time running under overcurrent condition.

When the action of energy-storage system outer protection, energy-storage system and external communication electrical network are passive disconnect time, the Harmonic Voltage component in point of common coupling place and energy-storage units exit meets criterion 2, i.e. THD _s>THD _zd, now should send islet operation signal, protective device all determines whether cut-off breaker according to the requirement of energy-storage system islet operation.

When there is voltage transformer disconnection situation, the alternating voltage electric current positive-negative sequence component that abnormal protection device place detects should meet criterion 3, but does not meet criterion 4, namely $\left\{\begin{array}{c}{U}_s^{+}<k_u^{+}{U}_N\\ U_s^{-}\&NotEqual;0\end{array}\right.,$ $\left\{\begin{array}{c}{I}_s^{+}<k_i^{+}{I}_N\\ I_s^{-}\&NotEqual;0\end{array}\right.,$ Now this protective device need send alarm signal.

Although content of the present invention has done detailed introduction by above preferred embodiment, will be appreciated that above-mentioned description should not be considered to limitation of the present invention.After those skilled in the art have read foregoing, for multiple amendment of the present invention and substitute will be all apparent.Therefore, protection scope of the present invention should be limited to the appended claims.

Claims (3)

1. the guard method for Large Copacity energy-storage system; it is characterized in that: Large Copacity energy-storage system is composed in parallel by multiple energy-storage units; each energy-storage units comprises power inverter and energy storage device; be connected to point of common coupling by respective step-up transformer to be connected with external power grid again; its guard method is divided into the guard method at point of common coupling place and the guard method two parts in energy-storage units exit, and includes overcurrent protection, Harmonic Voltage component detection and be with the alternating current of composite voltage startup to detect three failure diagnosis links.

2. method according to claim 1, is characterized in that: described overcurrent protection link is as follows:

Any phase current effective value that the criterion of overcurrent protection link is through protective device is greater than the setting value of overcurrent protection, and namely criterion 1 meets following formula:

Criterion 1:I _s>I _zd=k _ii _n

In formula, I _sfor any cross streams current effective value, I _zdfor overcurrent protective device setting value, I _nfor the rated current effective value of energy-storage units or energy-storage system, k _ifor overcurrent protective device safety factor;

When above criterion is set up, be judged as energy-storage units internal fault, the protective device time delay Δ T at point of common coupling place ₁tripping operation; The protective device quick-action in energy-storage units exit, excises fault energy-storage units rapidly.

3. method according to claim 1, is characterized in that: described Harmonic Voltage component detection is as follows: the Harmonic Voltage component detected is greater than the voltage harmonic component value that presets as criterion, namely criterion 2 meets following formula:

Criterion 2:THD _s>THD _zd

In formula, THD _sfor Harmonic Voltage component detection value, THD _zdfor Harmonic Voltage component set point;

For the guard method at energy-storage units exit and point of common coupling place, when above criterion is set up, protective device all determines whether cut-off breaker according to the requirement of energy-storage system islet operation.