CN102377248B - Method for optimizing capacity of energy storage system in case of fluctuation of smooth and renewable energy sources electricity generation output - Google Patents

Abstract

The invention provides a method for optimizing the capacity of an energy storage system in case of the fluctuation of smooth and renewable energy sources electricity generation output, which comprises the steps of: selecting reasonable renewable energy output power sample data before ensuring the capacity of the energy storage system, and sequentially ensuring the power, the capacity and the initial stress optical coefficient (SOC) status of the energy storage system after ensuring the reasonable renewable energy output power sample data. Aiming at overcoming the defect that the existing method for optimizing the capacity of the energy storage system in case of the fluctuation of the smooth and renewable energy sources output can not comprehensively consider all factors and can not reach the practical applicability, the invention provides the method for optimizing the capacity of the energy storage system in case of the fluctuation of the smooth and renewable energy sources electricity generation output based on a frequency spectrum analysis result of renewable energy sources output power. The method can provide the capacity scheme of the energy storage system limited by energy storage system-compensated target power output fluctuation ratio, and the method is practical, simple, quick and easy to realize.

Description

The energy storage system capacity optimization method of level and smooth renewable energy power generation output pulsation

Technical field

The present invention is a kind of energy storage system capacity optimization method of level and smooth renewable energy power generation output pulsation, belongs to the renovation technique of the energy storage system capacity optimization method of level and smooth renewable energy power generation output pulsation.

Background technology

Existingly take regenerative resource that wind-force, photovoltaic generation is representative and there is intermittence, randomness and the feature such as uncertain.Along with regenerative resource permeability constantly increases, they have brought increasing challenge to the safe and reliable operation of electrical network.Energy-storage system relies on it can fill the operation characteristic that can put, can be effective to overcome the fluctuation of renewable energy system.

Energy-storage system is controlled different two classes that are broadly divided into of target from the matching model of renewable energy system by it: (1) coordinates the level and smooth output pulsation of regenerative resource (comprising short-term and Long-term Fluctuation); (2) batch (-type) regenerative resource is changed into and can dispatch the energy, realize peak load shifting, plan generating etc.The system of selection of existing relevant energy storage system capacity has obtained some achievements in research, as simulation method, compensation frequency range are determined method etc.1) simulation method.With " Control strategies for battery energy storage for wind farm dispatching (IEEE Trans.Energy Convers., vol.24, no.3, pp.725-732, and " New Control Method for Regulating State-of-Charge of a Battery in Hybrid Wind Power/Battery Energy Storage System (IEEE PES Power Systems Conference and Exposition Sep.2009.) ", PSCE ' 06, Oct.2006, pp.1244-1251.) " be representative, the method is by after user's process Multi simulation running, obtain satisfied capacity result.Advantage is to consider the various restrictions such as energy storage charge-discharge velocity, SOC (dump energy level), life-span, and simulation result is accurate; Shortcoming is that stored energy capacitance is often chosen rule of thumb, needs just can obtain satisfied result after Multi simulation running.And single emulation is consuming time longer, therefore total length consuming time can not guarantee to obtain optimum capacity simultaneously.2) compensation frequency range is determined method.In " the wind energy turbine set power control system design (Automation of Electric Systems of based superconductive energy-storage system, 2009, 33 (9): 86-90.) " and " Design of Hybrid Energy Storage Control System for Wind Farms Based on Flow Battery and Electric Double-Layer Capacitor (Power and Energy Engineering Conference (APPEEC), 2010Asia-Pacific, pp.1-6, 28-31March 2010) " in introduced by determining that energy-storage system compensation frequency range determines the method for energy-storage system power demand.Advantage is the computing formula that has provided energy-storage system power demand, and power determination is consuming time shorter; Shortcoming is that determining of stored energy capacitance do not elaborated, and lacks foundation when definite hybrid energy-storing reasonably compensates frequency range.Lack economic evaluation, therefore the method show that capacity result economy is unsatisfactory simultaneously.

In sum, energy-storage system is applied to the factor that the energy storage system capacity optimization method under level and smooth regenerative resource output pulsation scene considers also very not comprehensive, is far from reaching degree of being practical.

Summary of the invention

The object of the invention is to the factor considered for the energy storage system capacity optimization method under current level and smooth regenerative resource output pulsation scene not comprehensive, do not reach practical shortcoming, the present invention proposes a kind of energy storage system capacity optimization method of the level and smooth renewable energy power generation output pulsation based on regenerative resource power output result of spectrum analysis.The method can provide the lower energy storage system capacity scheme of target power output pulsation rate constraint meeting after energy-storage system compensation, practical, simple, quick and be easy to realization.The energy storage system capacity optimization method that the present invention proposes be take regenerative resource power output result of spectrum analysis as basis, can effectively provide the energy-storage system minimum capacity scheme under the target power output pulsation rate constraint meeting after energy-storage system compensation.

Technical scheme of the present invention is: the energy storage system capacity optimization method of level and smooth renewable energy power generation output pulsation of the present invention, before determining energy storage system capacity, select rational regenerative resource power output sample data, after determining rational regenerative resource power output sample data, can determine successively energy-storage system power, capacity and initial SOC state, its concrete steps are as follows:

1) power determination

For meeting the fluctuating demand of level and smooth regenerative resource power stage, and guarantee energy-storage system continuous and steady operation, should determine rational energy-storage system power stage and possess the enough large power that discharges and recharges; For given regenerative resource power stage sample data, the required maximum of energy-storage system that meets the constraint of target power output pulsation rate discharges and recharges power and can utilize simulation method to obtain; So-called simulation method, consists of following several steps:

11) to power stage sample data P _gcarry out discrete Fourier transform, obtain amplitude-frequency result S _gand f _g;

S _g＝DFT(P _g)＝[S _g[1]，...，S _g[n]，...，S _g[N _s]] ^T (1)

f _g＝[f _g[1]，...，f _g[n]，...，f _g[N _s]] ^T

In formula, P _g=[P _g[1] ..., P _g[n] ..., P _g[N _s]] ^trepresent regenerative resource power stage sample data; P _g[n] represents n sampled point power output [kW], N _srepresent sampled point number.DFT (P _g) represent sample data P _gcarry out discrete Fourier transform.S _g[n]=R _g[n]+I _g[n] i represents n frequency f in Fourier transform result _gthe amplitude that [n] is corresponding, R _g[n], I _g[n] is respectively for real part and the imaginary part of amplitude.F _gfor with S _gcorresponding column of frequencies vector;

f _g[n]＝f _s(n-1)/N _s＝(n-1)/(T _sN _s) (2)

In formula, f _s, T _sbe respectively sample data P _gsample frequency [Hz] and sampling period [s]; From the symmetry of sampling thheorem and discrete Fourier transform data, S _gwith Nyquist frequency f _n=f _s/ 2 (best result of result of spectrum analysis is distinguished frequency, for sample frequency 1/2nd) be symmetry axis, monosymmetric complex sequences is conjugation each other, mould equates; Therefore only need to consider 0～f _nthe amplitude-frequency characteristic of frequency range;

Be worth particularly pointing out the S that utilizes discrete Fourier transform directly to obtain _gbe not the actual magnitude of original signal, the frequency of the actual magnitude of original signal and correspondence thereof is respectively by column vector D _g, fN _grepresent:

(3)

In formula,

n is got in representative _s/ 2 integer part.D _g[j] represents j frequency f in spectrum analysis _gthe original signal actual magnitude size that [j] is corresponding;

Work as N _sduring for even number:

$D_g\left[j\right]=\left\{\begin{array}{cc}\sqrt{R_g^2\left[j\right]+I_g^2\left[j\right]}/N_s& j=1,N_s/2+1\\ 2\sqrt{R_g^2\left[j\right]+I_g^2\left[j\right]}/N_s& j=2,...,N_s/2\end{array}\right.---(4-1)$

Work as N _sduring for odd number:

12), based on result of spectrum analysis, determine and meet the target power output of power stage fluctuation constraint and corresponding energy-storage system compensation frequency range thereof;

Suppose f _psrepresentative is according to result of spectrum analysis D _gdefinite compensation frequency range, f _pslrepresent S _gin with Nyquist frequency f _nfor symmetry axis and f _pssymmetrical frequency range.Use S ₀=[S ₀[1] ..., S ₀[n] ..., S ₀[N _s]] ^tthe target power of representative after energy-storage system compensation exported corresponding spectrum analysis complex result; Wherein, amplitude corresponding to compensation frequency range is set to 0, represents to have eliminated after compensating the power fluctuation of corresponding band, the amplitude outside compensation frequency range is constant;

$S_0\left[n\right]=\left\{\begin{array}{cc}0+0i& f_n\∈f_{\mathrm{ps}}U{f}_{\mathrm{ps}1}\\ S_g\left[n\right]& f_n\∉f_{\mathrm{ps}}U{f}_{\mathrm{ps}1}\end{array}\right.---\left(5\right)$

To S ₀carry out discrete fourier inverse transformation and can obtain the target power Output rusults P after energy-storage system compensation ₀:

P ₀＝IDFT(S ₀)＝[P ₀[1]，...，P ₀[n]，...，P ₀[N _s]] ^T (6)

In formula, IDFT (S ₀) represent S ₀carry out discrete fourier inverse transformation; P ₀[n] represents the target output [kW] of n sampled point;

For evaluating energy-storage system compensation effect, whether meet the demands, need to introduce power stage fluctuation ratio as the index of evaluating energy-storage system compensation effect; Suppose at T _epower fluctuation rate in time period is used

represent, its computing formula is as follows:

${\mathrm{FR}}_{T_E}=\frac{P_{T_E}^{\max }-P_{T_E}^{\min }}{P_n}\×100\%---\left(7\right)$

In formula, P _nrepresent rated power [kW];

represent respectively T _emaximum and minimum output power [kW] in time period; Judge that whether target power output meets the demands, and needs to guarantee fluctuation ratio

be no more than the upper limit of setting

${\mathrm{FR}}_{T_E}\≤{\mathrm{FR}}_{T_E}^{\max }---\left(8\right)$

The object of energy storage system capacity optimization is exactly to obtain to meet the minimum compensation capacity that fluctuation ratio requires.Actual analysis result shows, the compensation capacity of energy-storage system is directly related with compensation frequency range; In general, same bin width, the required energy storage system capacity of high compensation frequency range can be less than low compensation frequency range.When definite system balance frequency range, can adopt try and error method, from high frequency, gradually frequency range is extended to low-frequency range, utilize the fluctuation ratio after analytical method check compensation above whether to meet the demands, and then determine and can meet fluctuation ratio requirement, can guarantee again the compensation frequency range that energy storage system capacity is as far as possible little, and then obtain the idealized power stage for system after the compensation of this compensation frequency range;

13) according to the ideal value of system power output, considering under the impact of the factors such as energy-storage system efficiency for charge-discharge, determine the energy-storage system power stage can guarantee energy-storage system continuous and steady operation, and then the required maximum of definite energy-storage system discharges and recharges power, that is its rated power;

At definite ideal power target output P ₀afterwards, the power stage of required energy-storage system can be by column vector P _b0=[P _b0[1] ..., P _b0[n] ..., P _b0[N _s]] ^trepresent:

P _b0[n]＝P ₀[n]-P _g[n] (9)

P _b0[n] can just can bear, and for just representing energy storage system discharges, is negative representative charging.In actual energy-storage system, in its charge and discharge process, have certain loss, the efficiency that energy-storage system discharges and recharges a circulation is called energy-storage system overall efficiency, uses η _eSrepresent.According to the power stage value of required energy-storage system, consider the overall efficiency of energy-storage system, can determine the actual power that discharges and recharges of energy-storage system, use P _b=[P _b[1] ..., P _b[n] ..., P _b[N _s]] ^trepresent:

$P_b\left[n\right]=\left\{\begin{array}{cc}{P}_{b0}\left[n\right]/{\mathrm{\&eta;}}_{\mathrm{ES},d}& P_{b0}\left[n\right]\&GreaterEqual;0\\ P_{b0}\left[n\right]g{\mathrm{\&eta;}}_{\mathrm{ES},c}& P_{b0}\left[n\right]<0\end{array}\right.---\left(10\right)$

In formula, η _{eS, c}and η _{eS, d}represent respectively energy-storage system charge efficiency and discharging efficiency, if supposition energy-storage system efficiency for charge-discharge is equal,

consider and discharge and recharge after power loss, when electric discharge, after the loss of energy-storage system actual discharge power deduction, need to meet required discharge power requirement, its value is for required discharge power is divided by discharging efficiency; When charging, the actual charge power of energy-storage system is the value after required charge power deduction charging loss, should be required charge power and is multiplied by charge efficiency;

Target power output after energy-storage system compensation not only will meet power fluctuation constraint, also will guarantee that energy-storage system can continuous and steady operation., require in whole sample cycle, in energy-storage system running, satisfied (putting) power consumption that only fills is zero, that is: for this reason

$\mathrm{\&Delta;E}=\underset{n=1}{\overset{\mathrm{Ns}}{\mathrm{\&Sigma;}}}\left(P_b\right[n\left]\right)=0---\left(11\right)$

When utilizing energy-storage system to compensate the power of given frequency range, due to what the power fluctuation of each frequency was compensated, it is complete cycle amount, if do not consider the loss that discharges and recharges of energy-storage system, the required charge capacity of energy-storage system should equal discharge electricity amount, that is to say that constraints (11) will meet naturally.Yet, energy-storage system actual efficiency η _eSbe less than 100%, now, the actual charge volume of energy-storage system should be less than discharge capacity, i.e. Δ E > 0.For guaranteeing that the output of system power target meets constraint (11) and fluctuation ratio constraint (8), can be by P ₀whole translation downwards, to do not changing power stage fluctuation ratio (by the known integral translation P of formula (7) ₀can not change power stage fluctuation ratio) prerequisite under make Δ E=0.Aims of systems power stage translational movement is designated as Δ P, can obtain by iterative computation.System power target output P after translation _a=[P _a[1] ..., P _a[n] ..., P _a[N _s]] ^trepresent:

P _a[n]＝P ₀[n]-ΔP (12)

Corresponding to the aims of systems power stage P after translation _a, the power stage of required energy-storage system is:

P _b0[n]＝P _a[n]-P _g[n] (13)

Utilize formula (10) to obtain and consider that energy-storage system discharges and recharges the actual performance number that discharges and recharges of energy-storage system after power loss;

In whole sample data in the cycle, the actual power P that discharges and recharges of energy-storage system obtaining _bthe maximum of absolute value is the maximum that energy-storage system should possess and discharges and recharges power, that is energy-storage system power-handling capability:

P _ES，0＝max{|P _b[n]|} (14)

2) capacity is determined

For meeting the demand of level and smooth regenerative resource power stage fluctuation, energy-storage system should possess enough large capacity; For definite energy-storage system power stage, the required heap(ed) capacity of energy-storage system can utilize simulation method to obtain equally.Its calculation procedure is as follows:

21) the energy-storage system real output data based on definite, add up the energy-storage system charge/discharge electricity amount of each sample point, can obtain different sampling instant energy-storage systems with respect to the energy hunting of initial condition, that is:

$E_{b,\mathrm{acu}}\left[m\right]=\underset{0}{\overset{m}{\mathrm{\&Sigma;}}}\left(P_b\right[m]g{T}_s/3600),$ m＝0，...，N _s (15)

In formula, T _s/ 3600 represent chronomere's " second " convert be chronomere " hour ".E _{b, acu}[m] represents energy-storage system energy hunting with respect to initial condition m sampling instant, that is m (from the 0th to the m) sampling period before corresponding, energy-storage system accumulative total charge-discharge energy sum [kWh];

22) for energy-storage system energy hunting in the cycle in whole sample data, calculate the poor of energy-storage system maximum, least energy, consider energy-storage system SOC restriction, obtain the capacity that energy-storage system should possess, that is energy-storage system rated capacity value:

$E_{\mathrm{ES},0}=\frac{\max \left\{E_{b,\mathrm{acu}}\right[m\left]\right\}-\min \left\{E_{b,\mathrm{acu}}\right[m\left]\right\}}{{\mathrm{SOC}}_{\max }-{\mathrm{SOC}}_{\min }}---\left(16\right)$

In formula, SOC _maxand SOC _minrepresent respectively the upper and lower limit constraint of SOC in energy-storage system actual motion.Ideally, SOC _max=1, SOC _min=0.While considering energy-storage system actual motion, for fear of overcharging, cross film playback, ring energy-storage system life-span, SOC _maxand SOC _minshould be suitably in [0,1] interior value; Max{E _{b, acu}[m] }, min{E _{b, acu}[m] } represent respectively in the whole sample data cycle that energy-storage system is with respect to minimum, the ceiling capacity of initial condition, max{E _{b, acu}[m] }-min{E _{b, acu}[m] } represented the absolute value of energy-storage system ceiling capacity fluctuation in the whole sample data cycle;

3) initial SOC determines and capacity verification

After obtaining energy storage system capacity by formula (16), can judge whether gained capacity meets constraint by verification energy-storage system SOC range of operation.SOC may be defined as energy-storage system dump energy level, and Related Computational Methods is:

$\mathrm{SOC}\left[m\right]=\mathrm{SOC}\left[0\right]-\frac{E_{b,\mathrm{acu}}\left[m\right]}{E_{\mathrm{ES},0}}---\left(17\right)$

In formula, SOC[0] represent the initial SOC value of energy-storage system;

If energy storage system capacity satisfies the demands, energy-storage system SOC range of operation must, in SOC restriction range, have

$\max \left\{\mathrm{SOC}\right[m\left]\right\}=\mathrm{SOC}\left[0\right]-\frac{\min \left\{E_{b,\mathrm{acu}}\right[m\left]\right\}}{E_{\mathrm{ES},0}}\&le;{\mathrm{SOC}}_{\max }---\left(18\right)$

$\min \left\{\mathrm{SOC}\right[m\left]\right\}=\mathrm{SOC}\left[0\right]-\frac{\max \left\{E_{b,\mathrm{acu}}\right[m\left]\right\}}{E_{\mathrm{ES},0}}\&GreaterEqual;{\mathrm{SOC}}_{\min }$

By constraint (18), can be derived

$E_{\mathrm{ES},0}\&GreaterEqual;\frac{\max \left\{E_{b,\mathrm{acu}}\right[m\left]\right\}-\min \left\{E_{b,\mathrm{acu}}\right[m\left]\right\}}{{\mathrm{SOC}}_{\max }-{\mathrm{SOC}}_{\min }}---\left(19\right)$

From formula (19), the energy storage system capacity drawing according to formula (16) is the minimum capacity that meets the constraint of SOC range of operation; If SOC is no more than restriction range while guaranteeing energy-storage system operation, SOC initial value need to meet certain requirement; According to formula (16), (18), (19), can show that SOC initial value computing formula is as follows:

$\mathrm{SOC}\left[0\right]={\mathrm{SOC}}_{\min }+\frac{\max \left\{E_{b,\mathrm{acu}}\right[m\left]\right\}}{E_{\mathrm{ES},0}}={\mathrm{SOC}}_{\max }+\frac{\min \left\{E_{b,\mathrm{acu}}\right[m\left]\right\}}{E_{\mathrm{ES},0}}---\left(20\right)$

From SOC initial value computing formula, after the energy-storage system minimum capacity that meets constraint is determined, the SOC initial value of corresponding unique satisfied constraint has also just been determined.Although some harshness of this condition, in real system, this initial condition can move a period of time at energy-storage system and naturally be met after reaching stable state.

Above-mentioned before determining energy storage system capacity, first need when long or the level and smooth application scenarios that fluctuates is in short-term selected rational regenerative resource power output sample data.

The sampling period of above-mentioned sample data, data slot length parameter are directly relevant to the particular problem of intending research, and when energy-storage system is used for the short-time rating fluctuation of level and smooth regenerative resource, smoothingtime yardstick is that second level was to tens of minutes levels.

Above-mentioned when energy-storage system is during for level and smooth regenerative resource long during power fluctuation, energy-storage system is mainly used in compensating the mismatch between regenerative resource power stage and workload demand, and its time scale is that tens of minutes levels arrive hour level.

The length of above-mentioned sample data fragment selects to meet the discharge capacity of energy-storage system in fragment and charge volume about equally, deduction discharges and recharges power loss, when meeting this necessary condition, when the primary power in the time of can guaranteeing the level and smooth sample data fragment of energy-storage system and end, energy equates substantially.

It is above-mentioned that for level and smooth output mode in short-term, its data slot length is elected 1 hour as, smooth mode when long, and data slot length is chosen as 1 day.

Above-mentioned because the regenerative resources such as photovoltaic, wind power generation have stronger seasonality, data slot can be chosen typical case's day data of Various Seasonal (summer, winter).

The present invention proposes a kind of energy storage system capacity optimization method being suitable under level and smooth regenerative resource output pulsation scene, and test.The energy storage system capacity optimization method that the present invention proposes can consider that the requirement of target power output pulsation rate, energy-storage system efficiency for charge-discharge, the SOC after energy-storage system compensation moves the constraints such as restriction, provide rational energy storage system capacity scheme, method is practical, simple, fast and be easy to realize.Aspect energy storage system capacity planning, Design and optimization, having broad application prospects and huge society, economic benefits.The present invention is that a kind of design is ingenious, function admirable, the energy storage system capacity optimization method of convenient and practical level and smooth renewable energy power generation output pulsation.

Accompanying drawing explanation

Fig. 1 is blower fan output power curve of the present invention;

Fig. 2 is blower fan power output result of spectrum analysis;

Fig. 3 is the fluctuation ratio upper limit and the energy storage system capacity that different compensation ranges are corresponding;

Fig. 4 (a) is the schematic diagram of dreamboat and the output of ESS actual power, and Fig. 4 (b) is the schematic diagram of energy-storage system energy fluctuation;

Fig. 5 is the target output that different frequency compensation policy is corresponding.

Embodiment

Embodiment:

The energy storage system capacity optimization method that the present invention proposes be take regenerative resource power output result of spectrum analysis as basis, can effectively provide the energy-storage system minimum capacity scheme under the target power output pulsation rate constraint meeting after energy-storage system compensation.

Before determining energy storage system capacity, first need to select rational regenerative resource power output sample data according to its application scenarios (fluctuating smoothly while growing or in short-term).The parameters such as the sampling period of sample data, data slot length are directly relevant to the particular problem of intending research.When energy-storage system is used for the short-time rating fluctuation of level and smooth regenerative resource, smoothingtime yardstick is generally second level to tens of minutes levels.For example, the output-power fluctuation suppressing in wind generator system 0.01～1Hz band limits (corresponding time scale is 1～100s) is the most typical, and this is because the power fluctuation of this frequency range is maximum to electric network influencing.The power fluctuation of corresponding 1Hz, according to sampling thheorem, sample frequency at least will equal 2 times of signal highest frequency just can avoid frequency aliasing, therefore sample frequency minimum should be 2Hz, the corresponding sampling period is 0.5 second.

When energy-storage system is during for level and smooth regenerative resource long during power fluctuation, energy-storage system is mainly used in compensating the mismatch between regenerative resource power stage and workload demand, and its time scale is generally that tens of minutes levels arrive hour level.If the sampling period of load monitoring system is 5 minutes, the regenerative resource power stage specimen sample cycle is also chosen as 5 minutes.Certainly, if the specimen sample cycle, to be less than this numerical value better.Without loss of generality, for the capacity under this kind of application scenarios of energy-storage system, determine, it is 1 minute that the present invention selects the sampling period.

The length of sample data fragment selects to need the discharge capacity of energy-storage system in As soon as possible Promising Policy fragment and charge volume (deduction discharges and recharges power loss) about equally.When meeting this necessary condition, when the primary power in the time of can guaranteeing the level and smooth sample data fragment of energy-storage system and end, energy equates substantially.For level and smooth output mode in short-term, its data slot length is chosen as 1 hour, smooth mode when long, and data slot length is chosen as 1 day.Because the regenerative resources such as photovoltaic, wind power generation have stronger seasonality, data slot can be chosen typical case's day data of Various Seasonal (summer, winter).

After determining rational regenerative resource power output sample data, can determine successively energy-storage system power, capacity and initial SOC state.Its concrete steps are as follows:

One, power determination

For meeting the fluctuating demand of level and smooth regenerative resource power stage, and guarantee energy-storage system continuous and steady operation, should determine rational energy-storage system power stage and possess the enough large power that discharges and recharges.For given regenerative resource power stage sample data, the required maximum of energy-storage system that meets the constraint of target power output pulsation rate discharges and recharges power and can utilize simulation method to obtain.So-called simulation method, consists of following several steps:

1, to power stage sample data P _gcarry out discrete Fourier transform, obtain amplitude-frequency result S _gand f _g.

S _g＝DFT(P _g)＝[S _g[1]，...，S _g[n]，...，S _g[N _s]] ^T

(1)

f _g＝[f _g[1]，...，f _g[n]，...，f _g[N _s]] ^T

In formula, P _g=[P _g[1] ..., P _g[n] ..., P _g[N _s]] ^trepresent regenerative resource power stage sample data.P _g[n] represents n sampled point power output [kW], N _srepresent sampled point number.DFT (P _g) represent sample data P _gcarry out discrete Fourier transform.S _g[n]=R _g[n]+I _g[n] i represents n frequency f in Fourier transform result _gthe amplitude that [n] is corresponding, R _g[n], I _g[n] is respectively for real part and the imaginary part of amplitude.F _gfor with S _gcorresponding column of frequencies vector.

f _g[n]＝f _s(n-1)/N _s＝(n-1)/(T _sN _s) (2)

In formula, f _s, T _sbe respectively sample data P _gsample frequency [Hz] and sampling period [s].From the symmetry of sampling thheorem and discrete Fourier transform data, S _gwith Nyquist frequency f _n=f _s/ 2 (best result of result of spectrum analysis is distinguished frequency, for sample frequency 1/2nd) be symmetry axis, monosymmetric complex sequences is conjugation each other, mould equates.Therefore only need to consider 0～f _nthe amplitude-frequency characteristic of frequency range.

Be worth particularly pointing out the S that utilizes discrete Fourier transform directly to obtain _gbe not the actual magnitude of original signal, the frequency of the actual magnitude of original signal and correspondence thereof is respectively by column vector D _g, f _ngrepresent:

(3)

In formula, n is got in representative _s/ 2 integer part.D _g[j] represents j frequency f in spectrum analysis _gthe original signal actual magnitude size that [j] is corresponding.

Work as N _sduring for even number:

$D_g\left[j\right]=\left\{\begin{array}{cc}\sqrt{R_g^2\left[j\right]+I_g^2\left[j\right]}/N_s& j=1,N_s/2+1\\ 2\sqrt{R_g^2\left[j\right]+I_g^2\left[j\right]}/N_s& j=2,...,N_s/2\end{array}\right.---(4-1)$

Work as N _sduring for odd number:

2,, based on result of spectrum analysis, determine and meet the target power output of power stage fluctuation constraint and corresponding energy-storage system compensation frequency range thereof.

Suppose f _psrepresentative is according to result of spectrum analysis D _gdefinite compensation frequency range, f _pslrepresent S _gin with Nyquist frequency f _nfor symmetry axis and f _pssymmetrical frequency range.Use S ₀=[S ₀[1] ..., S ₀[n] ..., S0[N _s]] ^tthe target power of representative after energy-storage system compensation exported corresponding spectrum analysis complex result.Wherein, amplitude corresponding to compensation frequency range is set to 0, represents to have eliminated after compensating the power fluctuation of corresponding band, the amplitude outside compensation frequency range is constant.

$S_0\left[n\right]=\left\{\begin{array}{cc}0+0i& f_n\&Element;f_{\mathrm{ps}}U{f}_{\mathrm{ps}1}\\ S_g\left[n\right]& f_n\&NotElement;f_{\mathrm{ps}}U{f}_{\mathrm{ps}1}\end{array}\right.---\left(5\right)$

To S ₀carry out discrete fourier inverse transformation and can obtain the target power Output rusults P after energy-storage system compensation ₀:

P ₀=IDFT (S ₀)=[P ₀[1] ..., P ₀[n] ..., P ₀[N _s]] ^t(6) in formula, IDFT (S ₀) represent S ₀carry out discrete fourier inverse transformation; P ₀[n] represents the target output [kW] of n sampled point.

For evaluating energy-storage system compensation effect, whether meet the demands, need to introduce power stage fluctuation ratio as the index of evaluating energy-storage system compensation effect.Suppose at T _epower fluctuation rate in time period is used

represent, its computing formula is as follows:

${\mathrm{FR}}_{T_E}=\frac{P_{T_E}^{\max }-P_{T_E}^{\min }}{P_n}\&times;100\%---\left(7\right)$

In formula, P _nrepresent rated power [kW];

represent respectively T _emaximum and minimum output power [kW] in time period.Judge that whether target power output meets the demands, and needs to guarantee fluctuation ratio be no more than the upper limit of setting

${\mathrm{FR}}_{T_E}\&le;{\mathrm{FR}}_{T_E}^{\max }---\left(8\right)$

The object of energy storage system capacity optimization is exactly to obtain to meet the minimum compensation capacity that fluctuation ratio requires.Actual analysis result shows, the compensation capacity of energy-storage system is directly related with compensation frequency range.In general, same bin width, the required energy storage system capacity of high compensation frequency range can be less than low compensation frequency range.When definite system balance frequency range, can adopt try and error method, from high frequency, gradually frequency range is extended to low-frequency range, utilize the fluctuation ratio after analytical method check compensation above whether to meet the demands, and then determine and can meet fluctuation ratio requirement, can guarantee again the compensation frequency range that energy storage system capacity is as far as possible little, and then obtain the idealized power stage for system after the compensation of this compensation frequency range.

3, according to the ideal value of system power output, considering under the impact of the factors such as energy-storage system efficiency for charge-discharge, determine the energy-storage system power stage can guarantee energy-storage system continuous and steady operation, and then the required maximum of definite energy-storage system discharges and recharges power, that is its rated power.

At definite ideal power target output P ₀afterwards, the power stage of required energy-storage system can be by column vector P _b0=[P _b0[1] ..., P _b0[n] ..., P _b0[N _s]] ^trepresent:

P _b0[n]＝P ₀[n]-P _g[n] (9)

P _b0[n] can just can bear, and for just representing energy storage system discharges, is negative representative charging.In actual energy-storage system, in its charge and discharge process, have certain loss, the efficiency that energy-storage system discharges and recharges a circulation is called energy-storage system overall efficiency, uses η _eSrepresent.According to the power stage value of required energy-storage system, consider the overall efficiency of energy-storage system, can determine the actual power that discharges and recharges of energy-storage system, use P _b=[P _b[1] ..., P _b[n] ..., P _b[N _s]] ^trepresent:

$P_b\left[n\right]=\left\{\begin{array}{cc}{P}_{b0}\left[n\right]/{\mathrm{\&eta;}}_{\mathrm{ES},d}& P_{b0}\left[n\right]\&GreaterEqual;0\\ P_{b0}\left[n\right]{\mathrm{g\&eta;}}_{\mathrm{ES},c}& P_{b0}\left[n\right]<0\end{array}\right.---\left(10\right)$

In formula, η _{eS, c}and η _{eS, d}represent respectively energy-storage system charge efficiency and discharging efficiency, if supposition energy-storage system efficiency for charge-discharge is equal, consider and discharge and recharge after power loss, when electric discharge, after the loss of energy-storage system actual discharge power deduction, need to meet required discharge power requirement, its value is for required discharge power is divided by discharging efficiency; When charging, the actual charge power of energy-storage system is the value after required charge power deduction charging loss, should be required charge power and is multiplied by charge efficiency.

Target power output after energy-storage system compensation not only will meet power fluctuation constraint, also will guarantee that energy-storage system can continuous and steady operation., require in whole sample cycle, in energy-storage system running, satisfied (putting) power consumption that only fills is zero, that is: for this reason

$\mathrm{\&Delta;E}=\underset{n=1}{\overset{\mathrm{Ns}}{\mathrm{\&Sigma;}}}\left(P_b\right[n\left]\right)=0---\left(11\right)$

When utilizing energy-storage system to compensate the power of given frequency range, due to what the power fluctuation of each frequency was compensated, it is complete cycle amount, if do not consider the loss that discharges and recharges of energy-storage system, the required charge capacity of energy-storage system should equal discharge electricity amount, that is to say that constraints (11) will meet naturally.Yet, energy-storage system actual efficiency η _eSbe less than 100%, now, the actual charge volume of energy-storage system should be less than discharge capacity, i.e. Δ E > 0.For guaranteeing that the output of system power target meets constraint (11) and fluctuation ratio constraint (8), can be by P ₀whole translation downwards, to do not changing power stage fluctuation ratio (by the known integral translation P of formula (7) ₀can not change power stage fluctuation ratio) prerequisite under make Δ E=0.Aims of systems power stage translational movement is designated as Δ P, can obtain by iterative computation.System power target output P after translation _a=[P _a[1] ..., P _a[n] ..., P _a[N _s]] ^trepresent:

P _a[n]＝P ₀[n]-ΔP (12)

Corresponding to the aims of systems power stage P after translation _a, the power stage of required energy-storage system is:

P _b0[n]＝P _a[n]-P _g[n] (13)

Utilize formula (10) to obtain and consider that energy-storage system discharges and recharges the actual performance number that discharges and recharges of energy-storage system after power loss.

In whole sample data in the cycle, the actual maximum that discharges and recharges power P b absolute value of energy-storage system obtaining is the maximum that energy-storage system should possess and discharges and recharges power, that is energy-storage system power-handling capability:

P _ES，0＝max{|P _b[n]|} (14)

Two, capacity is determined

For meeting the demand of level and smooth regenerative resource power stage fluctuation, energy-storage system should possess enough large capacity.For definite energy-storage system power stage, the required heap(ed) capacity of energy-storage system can utilize simulation method to obtain equally.Its calculation procedure is as follows:

1, the energy-storage system real output data based on definite, add up the energy-storage system charge/discharge electricity amount of each sample point, can obtain different sampling instant energy-storage systems with respect to the energy hunting of initial condition, that is:

$E_{b,\mathrm{acu}}\left[m\right]=\underset{0}{\overset{m}{\mathrm{\&Sigma;}}}\left(P_b\right[m]g{T}_s/3600),$ m＝0，...，N _s (15)

In formula, T _s/ 3600 represent chronomere's " second " convert be chronomere " hour ".E _{b, acu}[m] represents energy-storage system energy hunting with respect to initial condition m sampling instant, that is m (from the 0th to the m) sampling period before corresponding, energy-storage system accumulative total charge-discharge energy sum [kWh].

2, for energy-storage system energy hunting in the cycle in whole sample data, calculate the poor of energy-storage system maximum, least energy, consider energy-storage system SOC restriction, obtain the capacity that energy-storage system should possess, that is energy-storage system rated capacity value:

$E_{\mathrm{ES},0}=\frac{\max \left\{E_{b,\mathrm{acu}}\right[m\left]\right\}-\min \left\{E_{b,\mathrm{acu}}\right[m\left]\right\}}{{\mathrm{SOC}}_{\max }-{\mathrm{SOC}}_{\min }}---\left(16\right)$

In formula, SOC _maxand SOC _minrepresent respectively the upper and lower limit constraint of SOC in energy-storage system actual motion.Ideally, SOC _max=1, SOC _min=0.While considering energy-storage system actual motion, for fear of overcharging, cross film playback, ring energy-storage system life-span, SOC _maxand SOC _minshould be suitably in [0,1] interior value; Max{E _{b, acu}[m] }, min{E _{b, acu}[m] } represent respectively in the whole sample data cycle that energy-storage system is with respect to minimum, the ceiling capacity of initial condition, max{E _{b, acu}[m] }-min{E _{b, acu}[m] } represented the absolute value of energy-storage system ceiling capacity fluctuation in the whole sample data cycle.

Three, initial SOC determines and capacity verification

After obtaining energy storage system capacity by formula (16), can judge whether gained capacity meets constraint by verification energy-storage system SOC range of operation.SOC may be defined as energy-storage system dump energy level, and Related Computational Methods is:

$\mathrm{SOC}\left[m\right]=\mathrm{SOC}\left[0\right]-\frac{E_{b,\mathrm{acu}}\left[m\right]}{E_{\mathrm{ES},0}}---\left(17\right)$

In formula, SOC[0] represent the initial SOC value of energy-storage system.

If energy storage system capacity satisfies the demands, energy-storage system SOC range of operation must, in SOC restriction range, have

$\max \left\{\mathrm{SOC}\right[m\left]\right\}=\mathrm{SOC}\left[0\right]-\frac{\min \left\{E_{b,\mathrm{acu}}\right[m\left]\right\}}{E_{\mathrm{ES},0}}\&le;{\mathrm{SOC}}_{\max }---\left(18\right)$

$\min \left\{\mathrm{SOC}\right[m\left]\right\}=\mathrm{SOC}\left[0\right]-\frac{\max \left\{E_{b,\mathrm{acu}}\right[m\left]\right\}}{E_{\mathrm{ES},0}}\&GreaterEqual;{\mathrm{SOC}}_{\min }$

By constraint (18), can be derived

$E_{\mathrm{ES},0}\&GreaterEqual;\frac{\max \left\{E_{b,\mathrm{acu}}\right[m\left]\right\}-\min \left\{E_{b,\mathrm{acu}}\right[m\left]\right\}}{{\mathrm{SOC}}_{\max }-{\mathrm{SOC}}_{\min }}---\left(19\right)$

From formula (19), the energy storage system capacity drawing according to formula (16) is the minimum capacity that meets the constraint of SOC range of operation.If SOC is no more than restriction range while guaranteeing energy-storage system operation, SOC initial value need to meet certain requirement.According to formula (16), (18), (19), can show that SOC initial value computing formula is as follows:

$\mathrm{SOC}\left[0\right]={\mathrm{SOC}}_{\min }+\frac{\max \left\{E_{b,\mathrm{acu}}\right[m\left]\right\}}{E_{\mathrm{ES},0}}={\mathrm{SOC}}_{\max }+\frac{\min \left\{E_{b,\mathrm{acu}}\right[m\left]\right\}}{E_{\mathrm{ES},0}}---\left(20\right)$

From SOC initial value computing formula, after the energy-storage system minimum capacity that meets constraint is determined, the SOC initial value of corresponding unique satisfied constraint has also just been determined.Although some harshness of this condition, in real system, this initial condition can move a period of time at energy-storage system and naturally be met after reaching stable state.

Preferred forms of the present invention is as follows:

The present invention utilizes smoothly take the test example of the renewable energy system power stage that wind power generation is representative and verifies that energy storage system capacity determines method.Air speed data is Washington state whole day data on July 14th, 2010, and the sampling period is 1 minute, and blower fan rated power is 65kW.Utilize HOMER software simulation blower fan power output, as shown in Figure 1.Blower fan Maximum Power Output is 65.097kW, and minimum power is 0, and average output power is 24.869kW; 20 minutes fluctuation ratio FR ₂₀maximum is 61.7%.The comprehensive efficiency for charge-discharge η of energy-storage system _eSbe 88%, charging and discharging efficiency equates, is 93.81%; The SOC upper limit gets 1, and lower limit gets 0.3.20 minutes active power fluctuation standards of Japanese Tohoku Electric Power company wind energy turbine set access electrical network, require the 20 minutes power fluctuation rate FR of aims of systems output after energy-storage system compensation ₂₀be controlled in 10%.

First, based on discrete Fourier transform, blower fan power output is carried out to spectrum analysis, as shown in Figure 2.Accompanying drawing 2 has provided sample data in Nyquist frequency f _n=8.333 * 10 ^-3amplitude-frequency characteristic before Hz.

Based on result of spectrum analysis, can determine and meet the energy-storage system minimum compensation band limits of power fluctuation constraint and corresponding dreamboat output thereof.For explaining conveniently, band limits is described by corresponding periodic quantity.If compensation cycle scope is [T _l, T _u), T _l, T _urepresent respectively compensation cycle lower limit and the upper limit.From energy-storage system power in this paper, capacity, determine method, can start compensation from high-frequency fluctuation component.Therefore compensation cycle lower limit T _lbe made as 2 minutes (for cycle corresponding to Nyquist frequency), adopt try and error method to search and meet T corresponding to the minimum compensation range of energy-storage system that power fluctuation retrains _u=360 minutes, as shown in Figure 3.

From accompanying drawing 3, the minimum compensation range that meets fluctuation ratio constraint for [2,360) minute, the system dreamboat power stage P that this compensation range is corresponding ₀see shown in accompanying drawing 4 (a) dotted line its FR ₂₀maximum is 9.9%.

After guaranteeing that energy-storage system deduction discharges and recharges loss, sample data in the cycle actual charge/discharge electricity amount equate, by the whole translation Δ P=0.337kW downwards of P0, be met the aims of systems power stage P of fluctuation ratio constraint (8) and energy-storage system continuous and steady operation constraint (11) _a, the comprehensive efficiency for charge-discharge of consideration energy-storage system 88%, determines the actual power P that discharges and recharges of energy-storage system _b, as shown in accompanying drawing 4 (a) solid line.According to formula (15), (17), (21), can determine energy-storage system rated power, capacity and SOC initial value, as shown in table 1.

The optimum capacity scheme of table 1

Definite energy-storage system power, capacity are carried out to verification, and in its running, SOC size is as shown in accompanying drawing 4 (b) dotted line.Known SOC maximum and minimum value are respectively 100%, 30%, just equal the constraint of SOC bound; During end of run, to charge and discharge electric weight be 0 to the actual accumulative total of energy-storage system, sees accompanying drawing 4 (b) solid line, therefore definite capacity scheme can guarantee energy-storage system continuous and steady operation.

From analyzing above, energy-storage system power and the capacity according to different compensation frequency ranges, determined are also different.In table 2, provided 2 kinds of optimum capacity schemes that different compensation policies are corresponding: (1) starts compensation from low frequency component, corresponding compensation cycle is 2.38～1441 minutes; (2) from high fdrequency component, start compensation, corresponding compensation cycle is 2～360 minutes.Accompanying drawing 5 has demonstrated the compensation effect under different compensation policies.

The optimizing capacity scheme that more different compensation policies are corresponding is known, strategy (1) required energy storage system capacity very large (be equivalent to wind power generation capacity 65kW*1h 5.77 times), and economy is obviously unreasonable; Comparing method (2) is known, is meeting under the prerequisite of constraint, and the required energy-storage system power of compensation policy (2), capacity are little, are more rational compensation policy.

The contrast of table 2 different frequency compensation policy capacity scheme

When determining energy storage system capacity for real system, which frequency band to start compensating the more reasonable and actual compensation effect that will reach from closely related.For this example, the scheme that starts compensation from low frequency has mainly suppressed low frequency component, this part component has embodied the overall variation trend in blower fan power output 1 day, amplitude large (as shown in Figure 2) often, change slowly, therefore required stored energy capacitance is larger, but for suppressing 20 minutes fluctuation ratio effects not obvious of blower fan; The scheme that starts compensation from high frequency mainly suppresses high fdrequency component, and this part component is larger to blower fan influence of fluctuations in 20 minutes, because amplitude is less, and changes comparatively fast, therefore required stored energy capacitance is less.

Claims (6)

1. the energy storage system capacity optimization method of a level and smooth renewable energy power generation output pulsation, it is characterized in that before determining energy storage system capacity, select rational regenerative resource power output sample data, after determining rational regenerative resource power output sample data, can determine successively energy-storage system power, capacity and initial SOC state, its concrete steps are as follows:

1) power determination

For meeting the fluctuating demand of level and smooth regenerative resource power stage, and guarantee energy-storage system continuous and steady operation, should determine rational energy-storage system power stage and possess the enough large power that discharges and recharges; For given regenerative resource power stage sample data, the required maximum of energy-storage system that meets the constraint of target power output pulsation rate discharges and recharges power utilization simulation method and obtains; So-called simulation method, consists of following several steps:

11) to power stage sample data

carry out discrete Fourier transform, obtain amplitude-frequency result

with ;

（1）

In formula,

represent regenerative resource power stage sample data;

represent

individual sampled point power output [kW],

represent sampled point number;

representative is to sample data

carry out discrete Fourier transform;

represent in Fourier transform result

individual frequency

corresponding amplitude,

respectively for real part and the imaginary part of amplitude;

for with

corresponding column of frequencies vector;

（2）

In formula,

be respectively sample data

sample frequency [Hz] and sampling period [s]; Symmetry by sampling thheorem and discrete Fourier transform data knows,

with Nyquist frequency

for symmetry axis, monosymmetric complex sequences is conjugation each other, and mould equates; Therefore only need to consider 0 ~ the amplitude-frequency characteristic of frequency range;

Be worth particularly pointing out, utilize discrete Fourier transform directly to obtain

be not the actual magnitude of original signal, the frequency of the actual magnitude of original signal and correspondence thereof is respectively by column vector

represent:

（3）

In formula,

representative is got

integer part;

represent in spectrum analysis

individual frequency

corresponding original signal actual magnitude size;

When

during for even number:

（4-1）

When

during for odd number:

（4-2）

12), based on result of spectrum analysis, determine and meet the target power output of power stage fluctuation constraint and corresponding energy-storage system compensation frequency range thereof;

Suppose representative is according to result of spectrum analysis

definite compensation frequency range, representative

in with Nyquist frequency

for symmetry axis with

symmetrical frequency range; With

the target power of representative after energy-storage system compensation exported corresponding spectrum analysis complex result; Wherein, amplitude corresponding to compensation frequency range is set to 0, represents to have eliminated after compensating the power fluctuation of corresponding band, the amplitude outside compensation frequency range is constant;

（5）

Right

carry out discrete fourier inverse transformation and obtain the target power Output rusults after energy-storage system compensation

:

（6）

In formula, it is right to represent

carry out discrete fourier inverse transformation; represent

the target output of individual sampled point [kW];

For evaluating energy-storage system compensation effect, whether meet the demands, need to introduce power stage fluctuation ratio as the index of evaluating energy-storage system compensation effect; Suppose

power fluctuation rate in time period is used represent, its computing formula is as follows:

（7）

In formula,

represent rated power [kW];

representative respectively

maximum and minimum output power [kW] in time period; Judge that whether target power output meets the demands, and needs to guarantee fluctuation ratio

be no more than the upper limit of setting

:

（8）

The object of energy storage system capacity optimization is exactly to obtain to meet the minimum compensation capacity that fluctuation ratio requires; Actual analysis result shows, the compensation capacity of energy-storage system is directly related with compensation frequency range; In general, same bin width, the required energy storage system capacity of high compensation frequency range can be less than low compensation frequency range; When definite system balance frequency range; adopt try and error method; from high frequency; gradually frequency range is extended to low-frequency range; utilize the fluctuation ratio after analytical method check compensation above whether to meet the demands; and then determine and can meet fluctuation ratio requirement, can guarantee again the compensation frequency range that energy storage system capacity is as far as possible little, and then obtain the idealized power stage for system after the compensation of this compensation frequency range;

13) according to the ideal value of system power output; considering under the impact of energy-storage system efficiency for charge-discharge factor; determine the energy-storage system power stage can guarantee energy-storage system continuous and steady operation, and then the required maximum of definite energy-storage system discharges and recharges power, that is its rated power;

In definite ideal power target output afterwards, the power stage of required energy-storage system is by column vector

represent:

（9）

for just or for negative, for just representing energy storage system discharges, be negative representative charging; In actual energy-storage system, in its charge and discharge process, have certain loss, the efficiency that energy-storage system discharges and recharges a circulation is called energy-storage system overall efficiency, uses

represent; According to the power stage value of required energy-storage system, consider the overall efficiency of energy-storage system, determine the actual power that discharges and recharges of energy-storage system, use

represent:

（10）

In formula,

with

represent respectively energy-storage system charge efficiency and discharging efficiency, if supposition energy-storage system efficiency for charge-discharge is equal,

; Consider and discharge and recharge after power loss, when electric discharge, after the loss of energy-storage system actual discharge power deduction, need to meet required discharge power requirement, its value is for required discharge power is divided by discharging efficiency; When charging, the actual charge power of energy-storage system is the value after required charge power deduction charging loss, should be required charge power and is multiplied by charge efficiency;

Target power output after energy-storage system compensation not only will meet power fluctuation and retrain, and also will guarantee that energy-storage system can continuous and steady operation; , require in whole sample cycle for this reason, in energy-storage system running, meet and only fill or discharge electricity amount is zero, that is:

（11）

When utilizing energy-storage system to compensate the power of given frequency range, due to what the power fluctuation of each frequency was compensated, it is complete cycle amount, if do not consider the loss that discharges and recharges of energy-storage system, the required charge capacity of energy-storage system should equal discharge electricity amount, that is to say that constraints (11) will meet naturally; Yet, energy-storage system actual efficiency

be less than 100%, now, the actual charge volume of energy-storage system should be less than discharge capacity,

; For guaranteeing that the output of system power target meets constraint (11) and fluctuation ratio constraint (8), will

whole translation downwards, to make under the prerequisite that does not change power stage fluctuation ratio

; Aims of systems power stage translational movement is designated as

, by iterative computation, obtain; After translation, the output of system power target is used represent:

（12）

Corresponding to the aims of systems power stage after translation

, the power stage of required energy-storage system is:

（13）

Utilize formula (10) to obtain and consider that energy-storage system discharges and recharges the actual performance number that discharges and recharges of energy-storage system after power loss;

In whole sample data in the cycle, the actual power that discharges and recharges of energy-storage system obtaining

the maximum of absolute value is the maximum that energy-storage system should possess and discharges and recharges power, that is energy-storage system power-handling capability:

（14）

2) capacity is determined

For meeting the demand of level and smooth regenerative resource power stage fluctuation, energy-storage system should possess enough large capacity; For definite energy-storage system power stage, the required heap(ed) capacity of energy-storage system utilizes simulation method to obtain equally; Its calculation procedure is as follows:

21) the energy-storage system real output data based on definite, add up the energy-storage system charge/discharge electricity amount of each sample point, obtain different sampling instant energy-storage systems with respect to the energy hunting of initial condition, that is:

,

（15）

In formula,

/ 3600 represent chronomere's " second " convert be chronomere " hour ";

represent that energy-storage system is

individual sampling instant is with respect to the energy hunting of initial condition, that is before correspondence

the individual sampling period, energy-storage system accumulative total charge-discharge energy sum [kWh];

22) for energy-storage system energy hunting in the cycle in whole sample data, calculate the poor of energy-storage system maximum, least energy, consider energy-storage system SOC restriction, obtain the capacity that energy-storage system should possess, that is energy-storage system rated capacity value:

（16）

In formula,

with represent respectively the upper and lower limit constraint of SOC in energy-storage system actual motion; Ideally,

,

; While considering energy-storage system actual motion, for fear of overcharging, cross film playback, ring the energy-storage system life-span,

with

should be suitably in [0,1] interior value;

,

represent that respectively interior energy-storage system of whole sample data cycle is with respect to minimum, the ceiling capacity of initial condition,

represented the absolute value of energy-storage system ceiling capacity fluctuation in the whole sample data cycle;

3) initial SOC determines and capacity verification

After obtaining energy storage system capacity by formula (16), by verification energy-storage system SOC range of operation, judge whether gained capacity meets constraint; SOC is defined as energy-storage system dump energy level, and Related Computational Methods is:

（17）

In formula,

represent the initial SOC value of energy-storage system;

If energy storage system capacity satisfies the demands, energy-storage system SOC range of operation must, in SOC restriction range, have

（18）

By constraint (18), derived

（19）

By formula (19), known, the energy storage system capacity drawing according to formula (16) is the minimum capacity that meets the constraint of SOC range of operation; If SOC is no more than restriction range while guaranteeing energy-storage system operation, SOC initial value need to meet certain requirement; According to formula (16), (18), (19), show that SOC initial value computing formula is as follows:

（20）

By SOC initial value computing formula, known, after the energy-storage system minimum capacity that meets constraint is determined, although the SOC initial value of corresponding unique satisfied constraint has also just been determined some harshness of this condition, but in real system, this initial condition is naturally met after energy-storage system operation a period of time reaches stable state.

2. the energy storage system capacity optimization method of level and smooth renewable energy power generation output pulsation according to claim 1, it is characterized in that above-mentionedly before determining energy storage system capacity, first need when long or the level and smooth application scenarios that fluctuates is in short-term selected rational regenerative resource power output sample data.

3. the energy storage system capacity optimization method of level and smooth renewable energy power generation output pulsation according to claim 1, the sampling period, the data slot length parameter that it is characterized in that above-mentioned sample data are directly relevant to the particular problem of intending research, when energy-storage system is used for the short-time rating fluctuation of level and smooth regenerative resource, smoothingtime yardstick is that second level was to tens of minutes levels.

4. the energy storage system capacity optimization method of level and smooth renewable energy power generation output pulsation according to claim 1, it is characterized in that when energy-storage system is during for level and smooth regenerative resource long during power fluctuation, energy-storage system is mainly used in compensating the mismatch between regenerative resource power stage and workload demand, and its time scale is that tens of minutes levels are to hour level.

5. the energy storage system capacity optimization method of level and smooth renewable energy power generation output pulsation according to claim 1, the length that it is characterized in that above-mentioned sample data fragment selects the discharge capacity that need to meet energy-storage system in fragment to equate with charge volume, deduction discharges and recharges power loss, when meeting this necessary condition, when the primary power in the time of guaranteeing the level and smooth sample data fragment of energy-storage system and end, energy equates.

6. the energy storage system capacity optimization method of level and smooth renewable energy power generation output pulsation according to claim 1, it is characterized in that because above-mentioned regenerative resource photovoltaic, wind power generation have stronger seasonality, data slot is chosen typical case's day data of Various Seasonal.

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