CN103515952A - Discharge depth control method of flywheel energy storage system connected to micro direct-current grid - Google Patents

Abstract

The invention belongs to the technical field of intelligent grids, relates to a discharge depth control method of a flywheel energy storage system connected to a micro direct-current grid. The method includes the following steps of (1) confirming a dynamic model of the flywheel energy storage system connected to the micro direct-current grid and building an equalization state equation set of the flywheel energy storage system, (2) forming a clinical stable discriminant equation of the flywheel energy storage system according to local amount measurement of the grid and a local parameter of the flywheel energy storage system, (3) detecting voltage and current of a port of an access point of the flywheel energy storage system in real time, calculating dynamic input impedance of the system and forming an equivalent parameter of the system, (4) forming a confirmed clinical stable discriminant equation of the flywheel energy storage system according to the equivalent parameter of the instant system when the phenomenon that system voltage falls is detected so that the discharge depth of the flywheel energy storage system can be controlled. The discharge depth control method has the advantages that stability of the discharge depth of the flywheel energy storage system is controlled, and accordingly voltage oscillation of the accessed system is avoided fundamentally; the current situation that the discharge depth of the flywheel energy storage system cannot be controlled according to a rule is eliminated in a certain degree.

Description

A kind of depth of discharge control method that accesses the flywheel energy storage system of DC micro-electric net

Technical field

The invention belongs to intelligent grid technical field, relate to a kind of depth of discharge control method that accesses the flywheel energy storage system of DC micro-electric net.

Background technology

Energy storage technology mainly comprises three major types, respectively that physics energy storage (comprising: pumped storage, flywheel energy storage, compressed-air energy storage etc.), chemical energy storage (comprising: lead-acid battery, nickel is that battery, lithium are battery etc.) and Power Flow (comprising: ultracapacitor, superconducting energy storage etc.) etc. [1].Wherein, flywheel energy storage has that energy storage density is large, pollution-free, the speed that discharges and recharges is fast, cycle-index is unrestricted, operation maintenance advantage easily.Under the background developing rapidly at China's intelligent grid, flywheel energy storage, as one of main energy storage support technology, has received increasing concern.Flywheel energy storage is as important mechanical energy storage mode, and it is stored in energy or kinetic energy in the flywheel rotor of High Rotation Speed, realizes the conversion that electric energy arrives electric energy again to mechanical energy.Independent flywheel energy storage system is generally by flywheel rotor, the bearing of support rotor, at a high speed generating/electronic mutual-inverse type motor and power electronic system composition.Flywheel energy storage system access DC micro-electric net, major function is when DC micro-electric net generation voltage falls fault or has power shortage, proceeds to and releases energy running status, supports the voltage of its access point.In exoergic process, its rotating speed can constantly decline along with the minimizing of flywheel energy storage system storage power.

Existing research generally believes, flywheel energy storage system is as a kind of mechanical energy storage system, there is not the problem of depth of discharge restriction, but flywheel energy storage system is strong Mechanical & Electrical Combination System, in its running, there is the difference in obvious magnitude in the speed that the variation of electric parameters (voltage, electric current) etc. and mechanical quantity (Speed of Reaction Wheels) change, makes flywheel energy storage system become a kind of fast subsystem by comprising fast state variable (voltage, electric current etc.) and typical two time scale systems that the tardyon system that comprises slow state variable (Speed of Reaction Wheels) forms.In two time scale systems, between fast subsystem and tardyon system, there is complicated Non-linear coupling relation, the slow variation of tardyon system can cause tachyon system balancing point stability to change, when the slow variation of tardyon system causes fast subsystem that Hopf fork occurs, system-wide dynamic behavior there will be complicated unstable oscillation, that is Mechanics Phenomenon [2] is started in generation bunch.In flywheel energy storage system exoergic process, the steady operational status of system can cause complicated mechanical electric vibration because rotating speed drops to a bunch unstable domain, the unstability that causes flywheel energy storage system and access DC micro-electric net thereof, not only greatly reduce the efficiency that energy transmits, more had a strong impact on the safety of DC micro-electric net.Therefore, how to try to achieve and control the minimum that Speed of Reaction Wheels declines, that is limit flywheel energy storage system depth of discharge, become the Focal point and difficult point of flywheel energy storage system operation and control.

List of references

[1]. Wang Deming etc., power storage Status of Research and development trend. chemical process automation and instrument, 2012 (7): 837-840 page.

[2]. old Zhang Yaoyu Bi Qin victory, a bunch discovery for nonlinear circuit resembles and Bifurcation Mechanism. control theory and application, 2011 (10): 1413-1420 page.

[3]. Zhang Zhi towards etc., the Routh Criterion of Hopf fork and the application in electric power system thereof. relay, 2005 (01): 34-37+41 page.

Summary of the invention

The object of the invention is, overcome the deficiencies in the prior art, a kind of depth of discharge control method that accesses the flywheel energy storage system of DC micro-electric net is provided, for the safety and stability of flywheel energy storage system self and its connecting system provides reliable guarantee.

A kind of depth of discharge control method that accesses the flywheel energy storage system of DC micro-electric net, described flywheel energy storage system is as the emergency voltage compensation arrangement in DC micro-electric net, access is on DC bus, its motor adopts brshless DC motor, by three phase full bridge translation circuit and bidirectional DC-DC converter circuit connecting system, control mode adopts dicyclo electric current and voltage to control, and the method comprises the following steps:

1) first determine the kinetic model of the flywheel energy storage system of access DC micro-electric net, set up the equations of state of flywheel energy storage system equalization, in this equations of state, comprise fast state variable and slow state variable, wherein, fast state variable comprises inductive current variable, load voltage variable, set end voltage variable, fly-wheel motor electric current variable, ring error variance in control system outer shroud error variance and control system, form fast subsystem, slow state variable is Speed of Reaction Wheels variable; This flywheel energy storage system comprises local parameter and system equivalent parameter, described local parameter comprises fly-wheel motor parameter, Power Electronic Circuit parameter and the flywheel energy storage system of fly-wheel motor access electric power system are controlled parameter, and described system equivalent parameter comprises that DC micro power grid system is in the input impedance of flywheel energy storage system access interface;

2) parameter using slow state variable as fast subsystem, try to achieve the balance point of fast subsystem, form the first row of the Routh determinant of fast subsystem, according to Routh-Hopf criterion, formation comprises local parameter variable, system equivalent parametric variable, and the discriminant equation of the flywheel energy storage system neutrality of three kinds of variablees of Speed of Reaction Wheels variable;

3) according to the flywheel energy storage system of reality access, set local parameter, the discriminant equation abbreviation of the flywheel energy storage system neutrality that comprises three kinds of variablees is become to comprise system equivalent parametric variable, the discriminant equation of the flywheel energy storage system neutrality of two kinds of variablees of Speed of Reaction Wheels variable;

4) real-time sampling flywheel energy storage system access point port voltage v _load, port current i _load, use Dai Weinan principle of equivalence, obtain DC micro power grid system in the input impedance of flywheel energy storage system access interface;

5) according to the v of local measurement _loadreal-time sampling signal, when the v of continuous 10 times being detected _loadbe less than default voltage threshold, judge that the access point generation voltage of flywheel energy storage system falls fault;

6) as the variable quantity 5V < Δ v of the access point port voltage of flywheel energy storage system _load< 10V, judges that fault is as minor failure, depth of discharge Y _minbe set to 50%, and form depth of discharge control signal, proceed to step 8); As Δ v _load> 10V, judges that fault is as catastrophe failure, continues step 7);

7) starting flywheel energy storage system depth of discharge controls:

A), according to the system equivalent parameter of fault moment, form the discriminant equation of the flywheel energy storage system neutrality that only contains a kind of variable of Speed of Reaction Wheels variable;

B) solve above-mentioned discriminant equation, try to achieve and guarantee that the depth of discharge Y of Non-Linear Ocsillation does not occur system _min;

C) by the depth of discharge Y trying to achieve _minform depth of discharge control signal.

8) the depth of discharge control signal of formation is exported to controller, guarantee that flywheel energy storage system, not causing under the prerequisite of connecting system vibration, realizes best voltage compensation effect.

As preferred implementation, in step 1), the concrete steps of equations of state of setting up flywheel energy storage system equalization are as follows:

Set up the equations of state of flywheel energy storage system equalization:

$\left\{\begin{array}{c}\stackrel{\&CenterDot;}{X}=\mathrm{AX}+B\\ d={\mathrm{CX}}_s\end{array}\right.---\left(1\right)$

In formula, X=[X _s, Y] ^tfor state variable; X _s=[X ₁, X ₂..., X ₆] ^tfor fast state variable, wherein X ₁-X ₆represent respectively inductive current variable, load voltage variable, set end voltage variable, fly-wheel motor electric current variable, control system outer shroud error variance, in control system, ring error variance, forms fast subsystem α; Y is the slow state variable of Speed of Reaction Wheels; D is the duty cycle of switching of bidirectional DC-DC converter circuit; A (Ω ^l _j, Ω ^s _k) be the coefficient matrix of state variable; B (Ω ^l _j, Ω ^s _k) be input matrix; C (Ω ^l _j, Ω ^s _k) be duty ratio expression formula coefficient matrix; Ω ^l _jj the local parameter that represents flywheel energy storage system, comprises fly-wheel motor parameter, the Power Electronic Circuit parameter of fly-wheel motor access electric power system, and flywheel energy storage system is controlled parameter; Ω ^s _kk the system equivalent parameter that represents flywheel energy storage system, comprises that DC micro power grid system is in the input impedance of flywheel energy storage system access interface;

Step 2), the parameter using Y as fast subsystem α, tries to achieve the balance point of fast subsystem α, forms the first row of the Routh determinant of fast subsystem α:

In formula, T ₁-T ₇7 variablees that represent Routh determinant first row.When Y changes, the necessary condition of flywheel energy storage system neutrality, the discriminant equation of flywheel energy storage system neutrality is:

T ₆(Y,Ω ^L _j,Ω ^S _k)＝0 (2)。

Step 3) is set Ω according to the flywheel energy storage system of reality access ^l _j, bring the discriminant equation that formula (2) forms flywheel energy storage system neutrality into:

T ₆(Y,Ω ^S _k)＝0 (3)。

In step 5), default voltage threshold is 105V.

The Ω instantaneous according to fault in step 7) ^s _k, formation only contains the discriminant equation of the flywheel energy storage system neutrality of Y:

T ₆(Y)＝0 (4)。

Beneficial effect of the present invention is as follows:

(1) the present invention is by controlling the depth of discharge of the flywheel energy storage system of access DC micro-electric net, effectively avoided the impact that self and connecting system stability thereof are brought bringing due to energy accumulation device for fly wheel deep discharge, having ensured that energy accumulation device for fly wheel is released can the efficiency of state and the security and stability of access DC micro-electric net.

(2) control method that the present invention proposes, the depth of discharge that is applicable to the flywheel energy storage system of homogeneous structure is controlled, simultaneously, the criterion of minimum depth of discharge combines real-time DC micro power grid system state, can adjust in real time criterion according to system state change, there is good intelligent and adaptivity, workable, be suitable for the real-time control of flywheel energy storage system.

(3) the present invention has overcome the present situation of flywheel energy storage system depth of discharge without Zhang Keyi to a certain extent, for further application and the popularization of flywheel energy storage system brought practical technical support.

Accompanying drawing explanation

Fig. 1 is containing the flywheel energy storage system structural representation of brshless DC motor.

The depth of discharge control flow chart of the flywheel energy storage system of the access DC micro-electric net that Fig. 2 the present invention proposes.

Specific implementation method

Below in conjunction with drawings and Examples, the present invention will be described.

The present invention is directed to the depth of discharge control containing the flywheel energy storage system access DC micro-electric net of brshless DC motor, and require in bidirectional DC-DC converter circuit by inductance transferring energy.This system mainly comprises fly-wheel motor system, control system (comprising digital signal processor, AD sampling A/D chip etc.) and power electronics interface circuit (comprising bidirectional DC-DC converter circuit, three phase full bridge translation circuit), as shown in Figure 1.Flywheel energy storage system is when its access DC micro-electric net breaks down, utilize depth of discharge fast (be flywheel energy storage system release can state under the Speed of Reaction Wheels minimum value and the ratio of rated speed that can drop to) control guarantees its output stability, do not cause under the prerequisite of DC micro-electric net Non-Linear Ocsillation guaranteeing, realize voltage compensating function.

The present invention specifically comprises the following steps:

1. first determine the kinetic model (see figure 1) of the flywheel energy storage system of access DC micro-electric net, set up the equations of state of flywheel energy storage system equalization.

Fig. 1 is the system diagram of flywheel energy storage system access DC micro-electric net.Flywheel energy storage system is as the emergency voltage compensation arrangement in DC micro-electric net, and access is on DC bus.Fly-wheel motor has adopted brshless DC motor, and by three phase full bridge translation circuit and bidirectional DC-DC converter circuit connecting system, its control mode has adopted dicyclo electric current and voltage to control.At flywheel energy storage, release under energy state, fly-wheel motor rotating speed declines, mechanical energy is converted into electric energy, rectifier diode VT1-VT6 by three phase full bridge translation circuit is delivered to bidirectional DC-DC converter circuit, control system reaches adjusting flywheel energy storage system output voltage by controlling the on off state of the switching tube V2 of bidirectional DC-DC converter circuit, maintains the voltage stabilization at place, flywheel energy storage access DC micro-electric Wang Bing site.

Switching tube V2 is with switch periods T periodicity opening and closing.In one-period, if the time that switching tube V2 opens is dT(0 < d < 1, represent duty cycle of switching), the time that switching tube V2 closes is (1-d) T, state equation under two kinds of operating states of system in one-period T is averaged, sets up the dimensionless equations of state of flywheel energy storage system equalization:

$\left\{\begin{array}{c}\stackrel{\&CenterDot;}{x}=\mathrm{AX}+B\\ d={\mathrm{CX}}_s\end{array}\right.---\left(1\right)$

In formula, X=[X _s, Y] ^tfor state variable; X _s=[X ₁, X ₂... X ₆] ^tfor fast state variable, wherein

represent respectively inductive current i _l, load voltage variable u ₁, set end voltage variable u ₂, fly-wheel motor current i _a, control system outer shroud error variance x _1c, ring error variance x in control system _2cper unit value, form fast subsystem the per unit value that represents the slow state variable ω of Speed of Reaction Wheels; $A({{\mathrm{\&Omega;}}^L}_j,{{\mathrm{\&Omega;}}^S}_k)=\left[\begin{array}{ccccccc}0& a_1& a_2& 0& 0& 0& 0\\ a_3& a_4& 0& 0& 0& 0& 0\\ a_5& 0& 0& a_6& 0& 0& 0\\ 0& 0& a_7& a_8& a_9& 0& 0\\ a_{10}& a_{11}& 0& 0& 0& a_{12}& 0\\ 0& a_{13}& 0& 0& 0& 0& 0\\ 0& 0& 0& a_{14}& a_{15}& 0& 0\end{array}\right]$ Coefficient matrix for state variable;

B (Ω ^l _j, Ω ^s _k)=[00000b ₁b ₂] ^tfor input matrix; C (Ω ^l _j, Ω ^s _k)=[a ₁₉a ₁₈00a ₁₇a ₁₆] be duty ratio expression formula

Coefficient matrix; Ω ^l _jj the local parameter that represents flywheel energy storage system; Ω ^s _kk the system equivalent parameter that represents flywheel energy storage system.

2. the parameter using Y as fast subsystem α, try to achieve the balance point of fast subsystem α, form the first row of the Routh determinant of fast subsystem, according to Routh-Hopf criterion, formation comprises local parameter variable, system equivalent parametric variable, and the discriminant equation of the flywheel energy storage system neutrality of three kinds of variablees of Speed of Reaction Wheels variable.

(1) parameter using Y as fast subsystem α, try to achieve the balance point of fast subsystem α:

${\left[\begin{array}{cccccc}\stackrel{\&OverBar;}{X_1}& \stackrel{\&OverBar;}{X_2}& \stackrel{\&OverBar;}{X_3}& \stackrel{\&OverBar;}{X_4}& \stackrel{\&OverBar;}{X_5}& \stackrel{\&OverBar;}{X_6}\end{array}\right]}^T={\left[\begin{array}{cccccc}\frac{1}{1-D}& 1& 1-D& \frac{D}{1-D}& \frac{a_{11}}{(D-1)a_{13}}& \frac{1}{a_{16}}(D+\frac{a_{19}}{D-1}+\frac{a_{11}{a}_{17}}{(1-D)a_{13}})\end{array}\right]}^T$

Wherein, represent that respectively fast state variable is in the stationary value at balance point place, D represents that duty ratio is in the stationary value at balance point place, $D=\frac{{2a}_7+a_{9}Y-a_8+\sqrt{{(a_8-a_{9}Y-{2a}_7)}^2-{4a}_7(a_{9}Y+a_7)}}{{2a}_7}.$

(2) form the first row of the Routh determinant of fast subsystem α:

In formula, T ₁-T ₇7 variablees that represent Routh determinant first row.

(3) according to Routh-Hopf[3] criterion, when Y changes, form and comprise Ω ^l _j, Ω ^s _k, and the discriminant equation of the flywheel energy storage system neutrality of tri-kinds of variablees of Y:

$T_6(Y,{{\mathrm{\&Omega;}}^L}_j,{{\mathrm{\&Omega;}}^S}_k)=a_1{a}_4{a}_6{a}_7{a}_{10}{a}_{13}{a}_{16}(\stackrel{\&OverBar;}{X_2}+\stackrel{\&OverBar;}{X_3}-D\stackrel{\&OverBar;}{X_2}-D\stackrel{\&OverBar;}{X_3}-D\stackrel{\&OverBar;}{X_1})=0---\left(2\right)$

3. set Ω ^l _j, bring formula (2) into and form neutrality discriminant equation:

$T_6(Y,{{\mathrm{\&Omega;}}^S}_k)=a_1{a}_4{a}_6{a}_7{a}_{10}{a}_{13}{a}_{16}(\stackrel{\&OverBar;}{X_2}+\stackrel{\&OverBar;}{X_3}-D\stackrel{\&OverBar;}{X_2}-D\stackrel{\&OverBar;}{X_3}-D\stackrel{\&OverBar;}{X_1})=0---\left(3\right)$

4. the sample frequency of flywheel energy storage system is 4kHz, the variation of considering DC micro-electric net is at least a second level in time scale, and consider the storage capacity of digital storage system, therefore every 40000 sampled points, extract flywheel energy storage system access point port voltage v one time _load, port current i _load, use Dai Weinan principle of equivalence, obtain Ω ^s _k.

5. according to the real-time sampling v of local measurement _load, when the v of continuous 10 times being detected _load< 105V, judges that flywheel energy storage access point generation voltage falls fault.

6. work as the variable quantity 5V < Δ v of flywheel energy storage system access point voltage _load< 10V, judges that fault is as minor failure, depth of discharge Y _minbe set to 50%, and form depth of discharge control signal, proceed to step 8.As Δ v _load> 10V, judges that fault, as catastrophe failure, continues next step.

7. starting flywheel energy storage system depth of discharge controls.

(1) Ω instantaneous according to fault ^s _k, bring neutrality discriminant equation formula (3) into, form the discriminant equation of the flywheel energy storage system neutrality that only contains Y:

$T_6\left(Y\right)=a_1{a}_4{a}_6{a}_7{a}_{10}{a}_{13}{a}_{16}(\stackrel{\&OverBar;}{X_2}+\stackrel{\&OverBar;}{X_3}-D\stackrel{\&OverBar;}{X_2}-D\stackrel{\&OverBar;}{X_3}-D\stackrel{\&OverBar;}{X_1})=0---\left(4\right)$

(2) solve above-mentioned discriminant equation, try to achieve and guarantee that the Y of Non-Linear Ocsillation does not occur system _min.

(3) by the depth of discharge Y trying to achieve _minform depth of discharge control signal.

8. the control signal of formation is exported to controller.Guarantee that flywheel energy storage system is not causing under the prerequisite of connecting system voltage oscillation, realizes best voltage compensation effect.

Flow chart of the present invention as shown in Figure 2.

Claims (6)

1. a depth of discharge control method that accesses the flywheel energy storage system of DC micro-electric net, described flywheel energy storage system is as the emergency voltage compensation arrangement in DC micro-electric net, access is on DC bus, its motor adopts brshless DC motor, by three phase full bridge translation circuit and bidirectional DC-DC converter circuit connecting system, control mode adopts dicyclo electric current and voltage to control, and the method comprises the following steps:

1) first determine the kinetic model of the flywheel energy storage system of access DC micro-electric net, set up the equations of state of flywheel energy storage system equalization, in this equations of state, comprise fast state variable and slow state variable, wherein, fast state variable comprises inductive current variable, load voltage variable, set end voltage variable, fly-wheel motor electric current variable, ring error variance in control system outer shroud error variance and control system, form fast subsystem, slow state variable is Speed of Reaction Wheels variable; This flywheel energy storage system comprises local parameter and system equivalent parameter, described local parameter comprises fly-wheel motor parameter, Power Electronic Circuit parameter and the flywheel energy storage system of fly-wheel motor access electric power system are controlled parameter, and described system equivalent parameter comprises that DC micro power grid system is in the input impedance of flywheel energy storage system access interface;

2) parameter using slow state variable as fast subsystem, try to achieve the balance point of fast subsystem, form the first row of the Routh determinant of fast subsystem, according to Routh-Hopf criterion, formation comprises local parameter variable, system equivalent parametric variable, and the discriminant equation of the flywheel energy storage system neutrality of three kinds of variablees of Speed of Reaction Wheels variable;

3) according to the flywheel energy storage system of reality access, set local parameter, the discriminant equation abbreviation of the flywheel energy storage system neutrality that comprises three kinds of variablees is become to comprise system equivalent parametric variable, the discriminant equation of the flywheel energy storage system neutrality of two kinds of variablees of Speed of Reaction Wheels variable;

4) real-time sampling flywheel energy storage system access point port voltage v _load, port current i _load, use Dai Weinan principle of equivalence, obtain DC micro power grid system in the input impedance of flywheel energy storage system access interface;

5) according to the v of local measurement _loadreal-time sampling signal, when the v of continuous 10 times being detected _loadbe less than default voltage threshold, judge that the access point generation voltage of flywheel energy storage system falls fault;

6) as the variable quantity 5V < Δ v of the access point port voltage of flywheel energy storage system _load< 10V, judges that fault is as minor failure, depth of discharge Y _minbe set to 50%, and form depth of discharge control signal, proceed to step 8); As Δ v _load> 10V, judges that fault is as catastrophe failure, continues step 7);

7) starting flywheel energy storage system depth of discharge controls:

A), according to the system equivalent parameter of fault moment, form the discriminant equation of the flywheel energy storage system neutrality that only contains a kind of variable of Speed of Reaction Wheels variable;

B) solve above-mentioned discriminant equation, try to achieve and guarantee that the depth of discharge Y of Non-Linear Ocsillation does not occur system _min;

C) by the depth of discharge Y trying to achieve _minform depth of discharge control signal.

8) the depth of discharge control signal of formation is exported to controller, guarantee that flywheel energy storage system, not causing under the prerequisite of connecting system vibration, realizes best voltage compensation effect.

2. depth of discharge control method according to claim 1, is characterized in that, in step 1), the concrete steps of equations of state of setting up flywheel energy storage system equalization are as follows:

Set up the equations of state of flywheel energy storage system equalization:

In formula, X=[X _s, Y] ^tfor state variable; X _s=[X ₁, X ₂..., X ₆] ^tfor fast state variable, wherein X ₁-X ₆represent respectively inductive current variable, load voltage variable, set end voltage variable, fly-wheel motor electric current variable, control system outer shroud error variance, in control system, ring error variance, forms fast subsystem α; Y is the slow state variable of Speed of Reaction Wheels; D is the duty cycle of switching of bidirectional DC-DC converter; A (Ω ^l _j, Ω ^s _k) be the coefficient matrix of state variable; B (Ω ^l _j, Ω ^s _k) be input matrix; C (Ω ^l _j, Ω ^s _k) be duty ratio expression formula coefficient matrix; Ω ^l _jj the local parameter that represents flywheel energy storage system, comprises fly-wheel motor parameter, the Power Electronic Circuit parameter of fly-wheel motor access electric power system, and flywheel energy storage system is controlled parameter; Ω ^s _kk the system equivalent parameter that represents flywheel energy storage system, comprises that DC micro power grid system is in the input impedance of flywheel energy storage system access interface.

3. depth of discharge control method according to claim 2, is characterized in that step 2), the parameter using Y as fast subsystem α, tries to achieve the balance point of fast subsystem α, forms the first row of the Routh determinant of fast subsystem α:

In formula, T ₁-T ₇7 variablees that represent Routh determinant first row.When Y changes, the necessary condition of flywheel energy storage system critical stable state, the discriminant equation of flywheel energy storage system neutrality is:

T ₆(Y,Ω ^L _j,Ω ^S _k)＝0 (2)。

4. depth of discharge control method according to claim 2, is characterized in that, step 3) is set Ω according to the flywheel energy storage system of reality access ^l _j, bring the discriminant equation that formula (2) forms flywheel energy storage system neutrality into:

T ₆(Y,Ω ^S _k)＝0 (3)。

5. depth of discharge control method according to claim 2, is characterized in that, in step 5), default voltage threshold is 105V.

6. depth of discharge control method according to claim 2, is characterized in that, the Ω instantaneous according to fault in step 7) ^s _k, formation only contains the discriminant equation of the flywheel energy storage system neutrality of Y:

T ₆(Y)＝0 (4)。

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