CN105633988A - Method and device for energy storage system for participating in primary frequency control of power grid - Google Patents

Abstract

The invention provides a method and a device for an energy storage system for participating in primary frequency control of a power grid. The method comprises the following steps: monitoring a grid frequency and a charged state of the energy storage system; if a grid frequency deviation does not exceed the maximum frequency deviation, monitoring the grid frequency and the charged state of the energy storage system in cycle; if the grid frequency deviation exceeds the maximum frequency deviation, determining that the energy storage system participates in the primary frequency control of the power grid according to the deviation direction of the grid frequency deviation and the charged state of the energy storage system; if primary frequency modulation starting conditions are met, starting a virtual inertial response and primary variable droop control; and adding power adjustment values of the virtual inertial response and the primary variable droop control to obtain a total active power control instruction and giving the instruction to the energy storage system, thereby achieving the primary frequency control. The method can significantly improve the frequency change amplitude and the steady speed in frequency disturbance of the power grid by quick response ability of the energy storage system, and improves the load disturbance resistance of the power grid.

Description

A kind of energy-storage system participates in method and the device of FREQUENCY CONTROL of electrical network

Technical field

The present invention relates to mains frequency and control technical field, participate in method and the device of FREQUENCY CONTROL of electrical network particularly to a kind of energy-storage system.

Background technology

Along with the growth of electricity needs, network load peak-valley difference constantly becomes big, and power system frequency modulation is had higher requirement, it is necessary to more multiple response quickly regulates power supply. The quickly increase and decrease that FREQUENCY CONTROL in tradition frequency modulation technology is by output maintains the balance of generated output and workload demand. And the low-response that electromotor has, creep speed be low etc., and characteristic is easily caused: 1) regulation goal can not be realized quickly thus quickly realizing dispatching again because climbing slow, thus it is not provided that all of area control error corrects; 2) cannot change direction rapidly because climbing slow, reverse adjustment even can be provided sometimes, thus electromotor increases area control error sometimes.

Energy-storage system has quick power response ability, and is capable of the positive and negative two-ways regulation of power. When energy-storage system participates in mains frequency control, by the conservative control to energy-storage system, it is possible to improve the frequency modulation characteristic of power system, there is better economy, but be still short of the research that energy-storage system is participated in mains frequency adjustment this respect at present.

Summary of the invention

Embodiments provide a kind of method that energy-storage system participates in FREQUENCY CONTROL of electrical network, by utilizing the capability of fast response of energy-storage system, frequency amplitude of variation and stabilized speed during mains frequency disturbance can be significantly improved, improve the ability of electrical network opposing load disturbance. The method includes:

The state-of-charge of monitor in real time mains frequency and energy-storage system, if mains frequency deviation is not less than maximum frequency deviation, then the state-of-charge of circularly monitoring mains frequency and energy-storage system; If mains frequency deviation exceedes maximum frequency deviation, then the state-of-charge according to the bias direction of mains frequency deviation and energy-storage system, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network:

If meeting primary frequency modulation entry condition, then start virtual inertia response and once variable droop control, it is determined that virtual inertia response and the once variable droop control power adjustment of energy-storage system; According to virtual inertia response and once variable droop control power adjustment, it is determined that total real power control instruction; According to total real power control instruction, meritorious the exerting oneself of energy-storage system is adjusted;

Wherein, described mains frequency deviation is the absolute value of mains frequency and the difference of the nominal frequency of power system.

In one embodiment, the state-of-charge of the described bias direction according to mains frequency deviation and energy-storage system, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network, including:

Bias direction in mains frequency deviation is f_t>50+��f_max, and SOC_BESS,t<SOC_maxTime, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network;

Or, the bias direction in mains frequency deviation is f_t<50-��f_max, and SOC_BESS,t>SOC_minTime, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network;

Wherein, f_tMains frequency for t; �� f_maxFor maximum frequency deviation; SOC_BESS,tFor the energy-storage system state-of-charge in t; SOC_maxFor the state-of-charge maximum that energy-storage system allows; SOC_minFor the state-of-charge minima that energy-storage system allows.

In one embodiment, described primary frequency modulation entry condition includes virtual inertia response entry condition and once variable droop control entry condition;

Described virtual inertia response entry condition is:

When | df_t/dt|��R_limTime, virtual inertia response starts;

Wherein, df_t/ dt is the mains frequency rate of change of t, R_limFor mains frequency rate of change dead band;

Described once variable droop control entry condition is:

When | f_t-50|>��f_maxAnd t > T_delay1Time, once variable droop control starts;

Wherein, f_tMains frequency for t; �� f_maxFor maximum frequency deviation; T_delay1For the first default time delay.

In one embodiment, the method also includes:

When meeting primary frequency modulation termination condition, terminate virtual inertia response and once variable droop control;

Described primary frequency modulation termination condition includes virtual inertia response termination condition and once variable droop control termination condition;

Described virtual inertia response termination condition is:

After mains frequency reaches peak value and postpones Preset Time, virtual inertia response terminates;

Described once variable droop control termination condition is:

Work as t > T_delay2Time, once variable droop control terminates;

Wherein, T_delay2The second time delay preset.

In one embodiment, the virtual inertia response of described energy-storage system is determined as follows:

${\mathrm{\&Delta;P}}_{Inert,t}=\left\{\begin{array}{cc}0& \left|{\mathrm{df}}_t/dt\right|<R_{\lim }\\ K_{Inert}\&times;({\mathrm{df}}_t/dt)& \left|{\mathrm{df}}_t/dt\right|\&GreaterEqual;R_{\lim }\end{array}\right.;$

Wherein, �� P_Inert,tRespond in the virtual inertia of t for energy-storage system, K_InertFor virtual inertia coefficient, K_Inert< 0, df_t/ dt is the mains frequency rate of change of t, R_limFor mains frequency rate of change dead band.

In one embodiment, the once variable droop control power adjustment of described energy-storage system is determined as follows:

${\mathrm{\&Delta;P}}_{Droop,t}=\left\{\begin{array}{cc}min\left(\frac{1}{R_{Droop,t}}\right(50-f_t),P_{BESSN})& f_t\&le;50-{\mathrm{\&Delta;f}}_{max}\\ 0& \left|f_t-50\right|<{\mathrm{\&Delta;f}}_{max}\\ max\left(\frac{1}{R_{Droop,t}}\right(50-f_t),-P_{BESSN})& f_t\&GreaterEqual;50+{\mathrm{\&Delta;f}}_{max}\end{array}\right.;$

Wherein, �� P_Droop,tFor the energy-storage system once variable droop control power adjustment in t, R_Droop,tFor the sagging coefficient of t, f_tFor the mains frequency of t, �� f_maxFor maximum frequency deviation, min is the computing that gets the small value, and max is the computing that takes large values, P_BESSNRated power for energy-storage system;

R is determined according to equation below_Droop,t:

$R_{Droop,t}=R_{\max }-(R_{\max }-R_{\min })\&lsqb;\frac{{\mathrm{SOC}}_{BESS,t}-{\mathrm{SOC}}_{\min }}{{\mathrm{SOC}}_{\max }-{\mathrm{SOC}}_{\min }}\&rsqb;;$

Wherein, R_maxFor maximum sagging coefficient, R_minFor minimum sagging coefficient, SOC_BESS,tFor the energy-storage system state-of-charge in t; SOC_maxFor the state-of-charge maximum that energy-storage system allows; SOC_minFor the state-of-charge minima that energy-storage system allows.

In one embodiment, described total real power control instruction is determined as follows:

��P_PF,t=�� P_Inert,t+��P_Droop,t;

Wherein, �� P_PF,tTotal real power control instruction for t.

The embodiment of the present invention additionally provides a kind of energy-storage system and participates in the device of FREQUENCY CONTROL of electrical network, by utilizing the capability of fast response of energy-storage system, frequency amplitude of variation and stabilized speed during mains frequency disturbance can be significantly improved, improve the ability of electrical network opposing load disturbance. This device includes:

Monitoring module, for the state-of-charge of monitor in real time mains frequency and energy-storage system, if mains frequency deviation is not less than maximum frequency deviation, then the SOC of circularly monitoring mains frequency and energy-storage system;

Frequency control module, if exceeding maximum frequency deviation for mains frequency deviation, then the SOC according to the bias direction of mains frequency deviation and energy-storage system, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network:

If meeting primary frequency modulation entry condition, then start virtual inertia response and once variable droop control, it is determined that virtual inertia response and the once variable droop control power adjustment of energy-storage system; According to virtual inertia response and once variable droop control power adjustment, it is determined that total real power control instruction; According to total real power control instruction, meritorious the exerting oneself of energy-storage system is adjusted;

Wherein, described mains frequency deviation is the absolute value of mains frequency and the difference of the nominal frequency of power system.

In one embodiment, a described frequency control module specifically for:

State-of-charge according to the bias direction of mains frequency deviation and energy-storage system as follows, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network:

Bias direction in mains frequency deviation is f_t>50+��f_max, and SOC_BESS,t<SOC_maxTime, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network;

Or, the bias direction in mains frequency deviation is f_t<50-��f_max, and SOC_BESS,t>SOC_minTime, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network;

Wherein, f_tMains frequency for t; �� f_maxFor maximum frequency deviation; SOC_BESS,tFor the energy-storage system state-of-charge in t; SOC_maxFor the state-of-charge maximum that energy-storage system allows; SOC_minFor the state-of-charge minima that energy-storage system allows.

In one embodiment, described primary frequency modulation entry condition includes virtual inertia response entry condition and once variable droop control entry condition;

Described virtual inertia response entry condition is:

When | df_t/dt|��R_limTime, virtual inertia response starts;

Wherein, df_t/ dt is the mains frequency rate of change of t, R_limFor mains frequency rate of change dead band;

Described once variable droop control entry condition is:

When | f_t-50|>��f_maxAnd t > T_delay1Time, once variable droop control starts;

Wherein, f_tMains frequency for t; �� f_maxFor maximum frequency deviation; T_delay1For the first default time delay.

In one embodiment, a described frequency control module is additionally operable to:

When meeting primary frequency modulation termination condition, terminate virtual inertia response and once variable droop control;

Described primary frequency modulation termination condition includes virtual inertia response termination condition and once variable droop control termination condition;

Described virtual inertia response termination condition is:

After mains frequency reaches peak value and postpones Preset Time, virtual inertia response terminates;

Described once variable droop control termination condition is:

Work as t > T_delay2Time, once variable droop control terminates;

Wherein, T_delay2For the second default time delay.

In one embodiment, a described frequency control module specifically for:

Determine the virtual inertia response of energy-storage system as follows:

${\mathrm{\&Delta;P}}_{Inert,t}=\left\{\begin{array}{cc}0& \left|{\mathrm{df}}_t/dt\right|<R_{\lim }\\ K_{Inert}\&times;({\mathrm{df}}_t/dt)& \left|{\mathrm{df}}_t/dt\right|\&GreaterEqual;R_{\lim }\end{array}\right.;$

Wherein, �� P_Inert,tRespond in the virtual inertia of t for energy-storage system, K_InertFor virtual inertia coefficient, K_Inert< 0, df_t/ dt is the mains frequency rate of change of t, R_limFor mains frequency rate of change dead band.

In one embodiment, a described frequency control module specifically for:

Determine the once variable droop control power adjustment of energy-storage system as follows:

${\mathrm{\&Delta;P}}_{Droop,t}=\left\{\begin{array}{cc}min\left(\frac{1}{R_{Droop,t}}\right(50-f_t),P_{BESSN})& f_t\&le;50-{\mathrm{\&Delta;f}}_{max}\\ 0& \left|f_t-50\right|<{\mathrm{\&Delta;f}}_{max}\\ max\left(\frac{1}{R_{Droop,t}}\right(50-f_t),-P_{BESSN})& f_t\&GreaterEqual;50+{\mathrm{\&Delta;f}}_{max}\end{array}\right.;$

Wherein, �� P_Droop,tFor the energy-storage system once variable droop control power adjustment in t, R_Droop,tFor the sagging coefficient of t, f_tFor the mains frequency of t, �� f_maxFor maximum frequency deviation, min is the computing that gets the small value, and max is the computing that takes large values, P_BESSNRated power for energy-storage system;

R is determined according to equation below_Droop,t:

$R_{Droop,t}=R_{\max }-(R_{\max }-R_{\min })\&lsqb;\frac{{\mathrm{SOC}}_{BESS,t}-{\mathrm{SOC}}_{\min }}{{\mathrm{SOC}}_{\max }-{\mathrm{SOC}}_{\min }}\&rsqb;;$

Wherein, R_maxFor maximum sagging coefficient, R_minFor minimum sagging coefficient, SOC_BESS,tFor the energy-storage system state-of-charge in t; SOC_maxFor the state-of-charge maximum that energy-storage system allows; SOC_minFor the state-of-charge minima that energy-storage system allows.

In one embodiment, a described frequency control module specifically for:

Determine total real power control instruction as follows:

��P_PF,t=�� P_Inert,t+��P_Droop,t;

Wherein, �� P_PF,tTotal real power control instruction for t.

In embodiments of the present invention, when energy-storage system participates in FREQUENCY CONTROL of electrical network, it is determined that virtual inertia response and the once variable droop control power adjustment of energy-storage system; Wherein, virtual inertia responds primarily responsive to frequency change rate, and once variable droop control is primarily responsive to frequency departure; Further according to virtual inertia response and once variable droop control power adjustment, it is determined that total real power control instruction; Finally according to total real power control instruction, meritorious the exerting oneself of energy-storage system is adjusted, thus controlling electrical network one secondary frequencies, so by utilizing the capability of fast response of energy-storage system, frequency amplitude of variation and stabilized speed during mains frequency disturbance can be significantly improved, improve the ability of electrical network opposing load disturbance.

Accompanying drawing explanation

Accompanying drawing described herein is used for providing a further understanding of the present invention, constitutes the part of the application, is not intended that limitation of the invention. In the accompanying drawings:

Fig. 1 is that a kind of energy-storage system that the embodiment of the present invention provides participates in control method for frequency flow chart of electrical network;

Fig. 2 is the virtual inertia response control block diagram of a kind of energy-storage system that the embodiment of the present invention provides;

Fig. 3 is a kind of dynamic sagging curve figure based on SOC value that the embodiment of the present invention provides;

Fig. 4 is the control block diagram of the once variable droop control of a kind of energy-storage system that the embodiment of the present invention provides;

Fig. 5 is a kind of NETWORK STRUCTURE PRESERVING POWER SYSTEM sketch that the embodiment of the present invention provides;

Fig. 6 be a kind of different frequency modulation control device lower frequency response ratios of providing of the embodiment of the present invention relatively;

Fig. 7 is that under a kind of different frequency modulation control devices that the embodiment of the present invention provides, the output of energy storage active power is compared;

Fig. 8 is that a kind of energy-storage system that the embodiment of the present invention provides participates in frequency control apparatus structural representation of electrical network.

Detailed description of the invention

For making the object, technical solutions and advantages of the present invention clearly understand, below in conjunction with embodiment and accompanying drawing, the present invention is described in further details. At this, the exemplary embodiment of the present invention and explanation thereof are used for explaining the present invention, but not as a limitation of the invention.

Fig. 1 is that a kind of energy-storage system that the embodiment of the present invention provides participates in control method for frequency flow chart of electrical network, as it is shown in figure 1, the method detailed step is as follows:

Step 1: energy-storage system monitors the state-of-charge (SOC of mains frequency and energy-storage system in real time, StateofCharge), when mains frequency deviation exceedes the maximum frequency deviation that electrical network allows, then entering next step to judge, otherwise circulation monitors the state-of-charge SOC of mains frequency and energy-storage system.

Wherein, mains frequency deviation is the absolute value of mains frequency and the difference of the nominal frequency of power system. The nominal frequency of power system is 50Hz or 60Hz, and China's Mainland (includes port, Australia area) and European Region adopts the many employings in 50Hz, North America and Taiwan 60Hz, and then there is 50Hz and 60Hz two kinds in Japan. Then mains frequency deviation is the absolute value of mains frequency and the difference of 50Hz, namely | and f_t-50|>��f_max, f_tFor the mains frequency of t, �� f_maxFor maximum frequency deviation, its can rule of thumb or relevant criterion set, be such as set as 0.05Hz.

Step 2: when mains frequency deviation exceedes �� f_maxTime, it is necessary to judge whether it participates in frequency and regulate according to the state-of-charge SOC of the bias direction of mains frequency deviation Yu energy-storage system.

1) f is worked as_t>50+��f_maxTime, it is necessary to energy-storage system absorbed power, if now SOC_BESS,t<SOC_max, illustrate that energy-storage system possesses the condition continuing absorbed power, then enter next step FREQUENCY CONTROL, otherwise energy-storage system is not involved in a FREQUENCY CONTROL.

2) f is worked as_t<50-��f_maxTime, it is necessary to energy-storage system sends power, if now SOC_BESS,t>SOC_min, illustrate that energy-storage system possesses the condition continuing to send power, then enter next step FREQUENCY CONTROL, otherwise energy-storage system is not involved in a FREQUENCY CONTROL.

Wherein, SOC_BESS,tFor the energy-storage system state-of-charge in t; SOC_maxFor energy-storage system allow state-of-charge maximum, be generally limited to the numerical value less than 1 for avoiding energy storage to overcharge; SOC_minFor energy-storage system allow state-of-charge minima, put for avoiding energy storage to cross and be generally limited to the numerical value more than 0.

Step 3: when satisfied startup primary frequency modulation condition, energy-storage system starts a frequency response: virtual inertia response and a droop control, determines virtual inertia response and the once variable droop control power adjustment of energy-storage system simultaneously. Wherein virtual inertia responds primarily responsive to frequency change rate, a droop control response frequency deviation.

Described primary frequency modulation entry condition includes virtual inertia response entry condition and once variable droop control entry condition;

Described virtual inertia response entry condition is:

When | df_t/dt|��R_limTime, virtual inertia response starts;

Wherein, df_t/ dt is the mains frequency rate of change of t, R_limFor mains frequency rate of change dead band;

Described once variable droop control entry condition is:

When | f_t-50|>��f_maxAnd t > T_delay1Time, once variable droop control starts;

Wherein, f_tMains frequency for t; �� f_maxFor maximum frequency deviation; T_delay1For the first default time delay.

When being embodied as, the method also includes:

When meeting primary frequency modulation termination condition, terminate virtual inertia response and once variable droop control;

Described primary frequency modulation termination condition includes virtual inertia response termination condition and once variable droop control termination condition;

Described virtual inertia response termination condition is:

After mains frequency reaches peak value and postpones Preset Time, virtual inertia response terminates;

Described once variable droop control termination condition is:

Work as t > T_delay2Time, once variable droop control terminates;

Wherein, T_delay2The second time delay preset.

Virtual inertia response and a droop control are described in detail below.

(1) virtual inertia response

The virtual inertia response of energy-storage system is when violent frequency fluctuation occurs in power system, size according to frequency change rate comes the inertia kinetic energy release of approximate simulation conventional electric generators or the process of absorption, thus the frequency change rate at relieving system fault initial stage (in 5s-10s), thus reducing the amplitude of frequency fluctuation, increase system damping simultaneously, strengthen the small-signal stability of system. The computing formula of virtual inertia response is:

${\mathrm{\&Delta;P}}_{Inert,t}=\left\{\begin{array}{cc}0& \left|{\mathrm{df}}_t/dt\right|<R_{\lim }\\ K_{Inert}\&times;({\mathrm{df}}_t/dt)& \left|{\mathrm{df}}_t/dt\right|\&GreaterEqual;R_{\lim }\end{array}\right.;$

In above formula, �� P_Inert,tRespond in the virtual inertia of t for energy-storage system, K_InertFor virtual inertia coefficient, K_Inert< 0, df_t/ dt is the mains frequency rate of change of t, R_limFor mains frequency rate of change dead band, the just startup virtual inertia response when frequency change rate is more than dead zone range.

Fig. 2 represents the basic controlling block diagram of the virtual inertia response of energy-storage system, wherein low pass filter is used for suppressing the high-frequency noise of appearance in system frequency measurement, Dead band controller can be defined according to the condition that inertial response is started by frequency change rate (dP/dt), it is to avoid frequent start-stop inertial response. Size and the rate of change of the output of inertia power need to be set according to the physical characteristic of battery, it is prevented that battery is the too fast and overshoot response of electric current in charge and discharge process.

The virtual inertia controller of energy-storage system can in frequency transient state adjustment process, it is ensured that energy-storage system injects active power rapidly to systems stay. Reach peak value (frequency reaches maximum when rising, and frequency reaches minima when declining) and time delay 0.1s when frequency after, virtual inertia response stops, and electrical network carries out frequency retrieval by the once sagging frequency modulation of self inertia response and other generating sets.

(2) once variable droop control

When frequency is through T_delay1The maximum frequency deviation �� f that later mains frequency deviation allows still above energy-storage system electrical network_max, droop control of energy storage starts. T_delay1Can be set according to the actual requirements, the present invention takes 0.1s.

Droop control of energy storage is the primary frequency modulation Margin utilizing energy-storage system, the active power output of energy-storage system is adjusted by root electrical network according to frequency departure and droop characteristic, thus ensureing that power system frequency is stable in the deviation range allowed (�� 0.2Hz), belong to the droop control of frequency. The speed governing difference formula of conventional electric generators is:

${\mathrm{\&Delta;P}}_t=\frac{1}{R_{Droop,t}}\mathrm{\&Delta;}f=\frac{1}{R_{Droop,t}}(50-f_t);$

The present invention introduces the concept of variable droop control on the basis of tradition droop control, namely sagging coefficient is dynamically adjusted according to energy storage SOC state, concrete grammar: according to system frequency modulation requirement, it is determined that maximum sagging coefficients R corresponding under the maximum of energy-storage system SOC and minima_maxWith minimum sagging coefficients R_min, then with reference to Fig. 3, actual measurement SOC value calculated the sagging coefficients R of t by equation below by linear interpolation method_Droopt:

$R_{Droop,t}=R_{\max }-(R_{\max }-R_{\min })\&lsqb;\frac{{\mathrm{SOC}}_{BESS,t}-{\mathrm{SOC}}_{\min }}{{\mathrm{SOC}}_{\max }-{\mathrm{SOC}}_{\min }}\&rsqb;;$

In above formula, R_Droop,tFor the sagging coefficient of t, R_maxFor maximum sagging coefficient, R_minFor minimum sagging coefficient, SOC_BESS,tFor the state-of-charge of energy storage t, SOC_maxFor the state-of-charge maximum that energy storage allows, SOC_minFor the state-of-charge minima that energy storage allows.

So can be obtained by the once variable droop control power adjustment of energy-storage system, formula is as follows:

${\mathrm{\&Delta;P}}_{Droop,t}=\left\{\begin{array}{cc}min\left(\frac{1}{R_{Droop,t}}\right(50-f_t),P_{BESSN})& f_t\&le;50-{\mathrm{\&Delta;f}}_{max}\\ 0& \left|f_t-50\right|<{\mathrm{\&Delta;f}}_{max}|\\ max\left(\frac{1}{R_{Droop,t}}\right(50-f_t),-P_{BESSN})& f_t\&GreaterEqual;50+{\mathrm{\&Delta;f}}_{max}\end{array}\right.;$

In above formula, �� P_Droop,tFor the energy-storage system once variable droop control power adjustment in t, P_BESSNRated power �� f for energy-storage system_maxBeing a droop control dead band or maximum frequency deviation, min is the computing that gets the small value, and (a, b) returns the smaller value in a and b to min, and max is the computing that takes large values, and (a b) returns the smaller value in a and b to max.

Fig. 4 represents the control block diagram of a droop characteristic of energy-storage system, and wherein high pass filter is for eliminating the impact on controlling system of the permanent low-frequency excitation.

State is adjusted, when primary frequency modulation response reaches T in order to avoid energy-storage system is constantly in a secondary frequencies_delay2After, the once variable droop control of energy-storage system terminates.

Step 4: virtual inertia response is added with once variable droop control power adjustment and obtains total real power control instruction, according to total real power control instruction, meritorious the exerting oneself of energy-storage system is adjusted, by total real power control instruction issuing to namely achieving a FREQUENCY CONTROL after energy-storage system.

Determine total real power control instruction as follows:

��P_PF,t=�� P_Inert,t+��P_Droop,t;

Wherein, �� P_PF,tTotal real power control instruction for t.

Citing:

A small-sized power transmission network is built by Matlab/Simulink, as shown in Figure 5, electric pressure 220kV, rated frequency 50Hz, whole system includes two 150MVA fired power generating unit models (thermoelectricity 1) and 200MVA fired power generating unit model (thermoelectricity 2) (with complete speed governing and exciter control system), energy-storage system electrical-magnetic model (the discharge and recharge rated power 20MW of one rated capacity 20MWh, rated voltage 380V), the constant power load model model (load 1) of a 322MW.

For there is under-frequency fault (during less than 50Hz) in simulation power system mesomeric state situation, suddenly the constant power load model 2 of a 24MW is increased at 15s, system active power occurs that transient state is uneven, mains frequency is instantaneous to be fallen, if energy-storage system is not involved in any system frequency modulation, only increase meritorious exerting oneself by the speed regulator of other two Synchronous generator (thermoelectricity 1 and thermoelectricity 2), can because of its electromechanical transient response speed excessively slow (second level), cause that frequency fall off rate is too fast, particularly minimum point frequency values (49.41Hz) will less than system frequency safety value 49.5Hz, UFLS protection meeting action immediately, sub-load is by cut, user and electrical network are caused certain economic loss. if energy-storage system is by virtual inertia response and a droop control, rationally quickly adjusts the meritorious of energy-storage system according to the change of system frequency and exert oneself, then system dynamics frequency characteristic will be significantly improved.

Employing virtual inertia responds, energy-storage system can simulate the inertial response of conventional electric generators, according to the inertia energy that the output of system frequency rate of change is certain, it is rapidly injected electrical network through inverter, this is equivalent to the damping inertia of equivalence enhancing system, frequency change rate can reduce and minimum frequency of pointing out can obtain certain increasing, but can not reduce the frequency departure of stable state.

Once variable droop control, compared with controlling with virtual inertia, by the output regulating energy storage power thus according to frequency difference, it is impossible to reduces the rate of change of frequency but can significantly improve the frequency size at transient state minimum point place, reduces frequency difference during systematic steady state.

Table 1 is the energy storage frequency modulation performance contrast of different primary frequency modulation strategy, and Fig. 6 is different frequency modulation control device lower frequency response comparison diagrams; Fig. 7 is energy storage active power output comparison diagram under different frequency modulation control device. By table 1, Fig. 6 and Fig. 7 it can be seen that comprehensive frequency modulation control (virtual inertia+once sagging) has possessed virtual inertia controls the advantage with variable droop control, frequency modulation best results. It is possible not only to relieving system frequency change rate, improve the size of frequency minimum point, and reduce steady frequency deviation, improve the recovery process of system frequency, after primary frequency modulation terminates, SOC may remain in higher level 41.6% simultaneously, it is ensured that has the electricity of abundance to participate in the frequency modulation frequency modulation of system.

Table 1

Based on same inventive concept, the embodiment of the present invention additionally provides a kind of energy-storage system and participates in the device of FREQUENCY CONTROL of electrical network, as described in the following examples. Owing to the principle of the device solution problem of an energy-storage system participation FREQUENCY CONTROL of electrical network is similar to the method that energy-storage system participates in FREQUENCY CONTROL of electrical network, therefore the enforcement of the device of an energy-storage system participation FREQUENCY CONTROL of electrical network may refer to the enforcement that energy-storage system participates in the method for FREQUENCY CONTROL of electrical network, repeats part and repeats no more. Used below, term " unit " or " module " can realize the software of predetermined function and/or the combination of hardware. Although the device described by following example preferably realizes with software, but hardware, or the realization of the combination of software and hardware is also likely to and is contemplated.

Fig. 8 is a kind of structured flowchart of the device of an energy-storage system participation FREQUENCY CONTROL of electrical network of the embodiment of the present invention, as shown in Figure 8, and including:

Monitoring module 801, for the state-of-charge of monitor in real time mains frequency and energy-storage system, if mains frequency deviation is not less than maximum frequency deviation, then the SOC of circularly monitoring mains frequency and energy-storage system;

Frequency control module 802, if exceeding maximum frequency deviation for mains frequency deviation, then at the SOC of the bias direction according to mains frequency deviation and energy-storage system, it is determined that when energy-storage system participates in FREQUENCY CONTROL of electrical network:

If meeting primary frequency modulation entry condition, then start virtual inertia response and once variable droop control, it is determined that virtual inertia response and the once variable droop control power adjustment of energy-storage system; According to virtual inertia response and once variable droop control power adjustment, it is determined that total real power control instruction; According to total real power control instruction, meritorious the exerting oneself of energy-storage system is adjusted;

Wherein, described mains frequency deviation is the absolute value of mains frequency and the difference of the nominal frequency of power system.

Below this structure is illustrated.

When being embodied as, a described frequency control module 802 specifically for:

State-of-charge according to the bias direction of mains frequency deviation and energy-storage system as follows, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network:

Bias direction in mains frequency deviation is f_t>50+��f_max, and SOC_BESS,t<SOC_maxTime, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network;

Or, the bias direction in mains frequency deviation is f_t<50-��f_max, and SOC_BESS,t>SOC_minTime, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network;

Wherein, f_tMains frequency for t; �� f_maxFor maximum frequency deviation; SOC_BESS,tFor the energy-storage system state-of-charge in t; SOC_maxFor the state-of-charge maximum that energy-storage system allows; SOC_minFor the state-of-charge minima that energy-storage system allows.

When being embodied as, described primary frequency modulation entry condition includes virtual inertia response entry condition and once variable droop control entry condition;

Described virtual inertia response entry condition is:

When | df_t/dt|��R_limTime, virtual inertia response starts;

Wherein, df_t/ dt is the mains frequency rate of change of t, R_limFor mains frequency rate of change dead band;

Described once variable droop control entry condition is:

When | f_t-50|>��f_maxAnd t > T_delay1Time, once variable droop control starts;

Wherein, f_tMains frequency for t; �� f_maxFor maximum frequency deviation; T_delay1For the first default time delay.

When being embodied as, a described frequency control module 802 is additionally operable to:

When meeting primary frequency modulation termination condition, terminate virtual inertia response and once variable droop control;

Described primary frequency modulation termination condition includes virtual inertia response termination condition and once variable droop control termination condition;

Described virtual inertia response termination condition is:

After mains frequency reaches peak value and postpones Preset Time, virtual inertia response terminates, now �� P_Inert,t=0;

Described once variable droop control termination condition is:

Work as t > T_delay2Time, once variable droop control terminates, now, and �� P_Droop,t=0;

Wherein, T_delay2For the second default time delay.

When being embodied as, a described frequency control module 802 specifically for:

Determine the virtual inertia response of energy-storage system as follows:

${\mathrm{\&Delta;P}}_{Inert,t}=\left\{\begin{array}{cc}0& \left|{\mathrm{df}}_t/dt\right|<R_{\lim }\\ K_{Inert}\&times;({\mathrm{df}}_t/dt)& \left|{\mathrm{df}}_t/dt\right|\&GreaterEqual;R_{\lim }\end{array}\right.;$

Wherein, �� P_Inert,tRespond in the virtual inertia of t for energy-storage system, K_InertFor virtual inertia coefficient, K_Inert< 0, df_t/ dt is the mains frequency rate of change of t, R_limFor mains frequency rate of change dead band.

When being embodied as, a described frequency control module 802 specifically for:

Determine the once variable droop control power adjustment of energy-storage system as follows:

${\mathrm{\&Delta;P}}_{Droop,t}=\left\{\begin{array}{cc}min\left(\frac{1}{R_{Droop,t}}\right(50-f_t),P_{BESSN})& f_t\&le;50-{\mathrm{\&Delta;f}}_{max}\\ 0& \left|f_t-50\right|<{\mathrm{\&Delta;f}}_{max}\\ max\left(\frac{1}{R_{Droop,t}}\right(50-f_t),-P_{BESSN})& f_t\&GreaterEqual;50+{\mathrm{\&Delta;f}}_{max}\end{array}\right.;$

Wherein, �� P_Droop,tFor the energy-storage system once variable droop control power adjustment in t, R_Droop,tFor the sagging coefficient of t, f_tFor the mains frequency of t, �� f_maxFor maximum frequency deviation, min is the computing that gets the small value, and max is the computing that takes large values, P_BESSNRated power for energy-storage system;

R is determined according to equation below_Droop,t:

$R_{Droop,t}=R_{\max }-(R_{\max }-R_{\min })\&lsqb;\frac{{\mathrm{SOC}}_{BESS,t}-{\mathrm{SOC}}_{\min }}{{\mathrm{SOC}}_{\max }-{\mathrm{SOC}}_{\min }}\&rsqb;;$

Wherein, R_maxFor maximum sagging coefficient, R_minFor minimum sagging coefficient, SOC_BESS,tFor the energy-storage system state-of-charge in t; SOC_maxFor the state-of-charge maximum that energy-storage system allows; SOC_minFor the state-of-charge minima that energy-storage system allows.

When being embodied as, a described frequency control module 802 specifically for:

Determine total real power control instruction as follows:

��P_PF,t=�� P_Inert,t+��P_Droop,t;

Wherein, �� P_PF,tTotal real power control instruction for t.

In sum, the energy-storage system that the present invention proposes participates in method and the device of FREQUENCY CONTROL of electrical network, can pass through to utilize the capability of fast response of energy storage, significantly improve frequency amplitude of variation and stabilized speed during mains frequency disturbance, improve the ability of electrical network opposing load disturbance.

Those skilled in the art are it should be appreciated that embodiments of the invention can be provided as method, system or computer program. Therefore, the present invention can adopt the form of complete hardware embodiment, complete software implementation or the embodiment in conjunction with software and hardware aspect. And, the present invention can adopt the form at one or more upper computer programs implemented of computer-usable storage medium (including but not limited to disk memory, CD-ROM, optical memory etc.) wherein including computer usable program code.

The present invention is that flow chart and/or block diagram with reference to method according to embodiments of the present invention, equipment (system) and computer program describe. It should be understood that can by the combination of the flow process in each flow process in computer program instructions flowchart and/or block diagram and/or square frame and flow chart and/or block diagram and/or square frame. These computer program instructions can be provided to produce a machine to the processor of general purpose computer, special-purpose computer, Embedded Processor or other programmable data processing device so that the instruction performed by the processor of computer or other programmable data processing device is produced for realizing the device of function specified in one flow process of flow chart or multiple flow process and/or one square frame of block diagram or multiple square frame.

These computer program instructions may be alternatively stored in and can guide in the computer-readable memory that computer or other programmable data processing device work in a specific way, the instruction making to be stored in this computer-readable memory produces to include the manufacture of command device, and this command device realizes the function specified in one flow process of flow chart or multiple flow process and/or one square frame of block diagram or multiple square frame.

These computer program instructions also can be loaded in computer or other programmable data processing device, make on computer or other programmable devices, to perform sequence of operations step to produce computer implemented process, thus the instruction performed on computer or other programmable devices provides for realizing the step of function specified in one flow process of flow chart or multiple flow process and/or one square frame of block diagram or multiple square frame.

The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, for a person skilled in the art, the embodiment of the present invention can have various modifications and variations. All within the spirit and principles in the present invention, any amendment of making, equivalent replacement, improvement etc., should be included within protection scope of the present invention.

Claims (14)

1. the method that an energy-storage system participates in FREQUENCY CONTROL of electrical network, it is characterised in that including:

The state-of-charge of monitor in real time mains frequency and energy-storage system, if mains frequency deviation is not less than maximum frequency deviation, then the state-of-charge of circularly monitoring mains frequency and energy-storage system; If mains frequency deviation exceedes maximum frequency deviation, then the state-of-charge according to the bias direction of mains frequency deviation and energy-storage system, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network:

If meeting primary frequency modulation entry condition, then start virtual inertia response and once variable droop control, it is determined that virtual inertia response and the once variable droop control power adjustment of energy-storage system; According to virtual inertia response and once variable droop control power adjustment, it is determined that total real power control instruction; According to total real power control instruction, meritorious the exerting oneself of energy-storage system is adjusted;

Wherein, described mains frequency deviation is the absolute value of mains frequency and the difference of the nominal frequency of power system.

2. the method that energy-storage system as claimed in claim 1 participates in FREQUENCY CONTROL of electrical network, it is characterised in that the state-of-charge of the described bias direction according to mains frequency deviation and energy-storage system, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network, including:

Bias direction in mains frequency deviation is f_t>50+��f_max, and SOC_BESS,t<SOC_maxTime, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network;

Or, the bias direction in mains frequency deviation is f_t<50-��f_max, and SOC_BESS,t>SOC_minTime, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network;

Wherein, f_tMains frequency for t; �� f_maxFor maximum frequency deviation; SOC_BESS,tFor the energy-storage system state-of-charge in t; SOC_maxFor the state-of-charge maximum that energy-storage system allows; SOC_minFor the state-of-charge minima that energy-storage system allows.

3. the method that energy-storage system as claimed in claim 1 participates in FREQUENCY CONTROL of electrical network, it is characterised in that described primary frequency modulation entry condition includes virtual inertia response entry condition and once variable droop control entry condition;

Described virtual inertia response entry condition is:

When | df_t/dt|��R_limTime, virtual inertia response starts;

Wherein, df_t/ dt is the mains frequency rate of change of t, R_limFor mains frequency rate of change dead band;

Described once variable droop control entry condition is:

When | f_t-50|>��f_maxAnd t > T_delay1Time, once variable droop control starts;

Wherein, f_tMains frequency for t; �� f_maxFor maximum frequency deviation; T_delay1For the first default time delay.

4. the method that energy-storage system as claimed in claim 3 participates in FREQUENCY CONTROL of electrical network, it is characterised in that also include:

When meeting primary frequency modulation termination condition, terminate virtual inertia response and once variable droop control;

Described primary frequency modulation termination condition includes virtual inertia response termination condition and once variable droop control termination condition;

Described virtual inertia response termination condition is:

After mains frequency reaches peak value and postpones Preset Time, virtual inertia response terminates;

Described once variable droop control termination condition is:

Work as t > T_delay2Time, once variable droop control terminates;

Wherein, T_delay2The second time delay preset.

5. the method that energy-storage system as claimed in claim 1 participates in FREQUENCY CONTROL of electrical network, it is characterised in that the virtual inertia response of described energy-storage system is determined as follows:

${\mathrm{\&Delta;P}}_{Inert,t}=\left\{\begin{array}{cc}0& |{\mathrm{df}}_t/dt|<R_{\lim }\\ K_{Inert}\&times;({\mathrm{df}}_t/dt)& |{\mathrm{df}}_t/dt|\&GreaterEqual;R_{\lim }\end{array}\right.;$

Wherein, �� P_Inert,tRespond in the virtual inertia of t for energy-storage system, K_InertFor virtual inertia coefficient, K_Inert< 0, df_t/ dt is the mains frequency rate of change of t, R_limFor mains frequency rate of change dead band.

6. the method that energy-storage system as claimed in claim 5 participates in FREQUENCY CONTROL of electrical network, it is characterised in that the once variable droop control power adjustment of described energy-storage system is determined as follows:

${\mathrm{\&Delta;P}}_{Droop,t}=\left\{\begin{array}{cc}\min \left(\frac{1}{R_{Droop,t}}\left(50-f_t\right),P_{BESSN}\right)& f_t\&le;50-{\mathrm{\&Delta;f}}_{\max }\\ 0& |f_t-50|<{\mathrm{\&Delta;f}}_{\max }\\ \max \left(\frac{1}{R_{Droop,t}}\left(50-f_t\right),-P_{BESSN}\right)& f_t\&GreaterEqual;50+{\mathrm{\&Delta;f}}_{\max }\end{array}\right.;$

Wherein, �� P_Droop,tFor the energy-storage system once variable droop control power adjustment in t, R_Droop,tFor the sagging coefficient of t, f_tFor the mains frequency of t, �� f_maxFor maximum frequency deviation, min is the computing that gets the small value, and max is the computing that takes large values, P_BESSNRated power for energy-storage system;

R is determined according to equation below_Droop,t:

$R_{Droop,t}=R_{max}-(R_{max}-R_{min})\&lsqb;\frac{{\mathrm{SOC}}_{BESS,t}-{\mathrm{SOC}}_{min}}{{\mathrm{SOC}}_{\max }-{\mathrm{SOC}}_{min}}\&rsqb;;$

Wherein, R_maxFor maximum sagging coefficient, R_minFor minimum sagging coefficient, SOC_BESS,tFor the energy-storage system state-of-charge in t; SOC_maxFor the state-of-charge maximum that energy-storage system allows; SOC_minFor the state-of-charge minima that energy-storage system allows.

7. the method that energy-storage system as claimed in claim 6 participates in FREQUENCY CONTROL of electrical network, it is characterised in that described total real power control instruction is determined as follows:

��P_PF,t=�� P_Inert,t+��P_Droop,t;

Wherein, �� P_PF,tTotal real power control instruction for t.

8. the device of an energy-storage system participation FREQUENCY CONTROL of electrical network, it is characterised in that including:

Monitoring module, for the state-of-charge of monitor in real time mains frequency and energy-storage system, if mains frequency deviation is not less than maximum frequency deviation, then the state-of-charge of circularly monitoring mains frequency and energy-storage system;

Frequency control module, if exceeding maximum frequency deviation for mains frequency deviation, then the state-of-charge according to the bias direction of mains frequency deviation and energy-storage system, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network:

If meeting primary frequency modulation entry condition, then start virtual inertia response and once variable droop control, it is determined that virtual inertia response and the once variable droop control power adjustment of energy-storage system; According to virtual inertia response and once variable droop control power adjustment, it is determined that total real power control instruction; According to total real power control command value, meritorious the exerting oneself of energy-storage system is adjusted;

Wherein, described mains frequency deviation is the absolute value of mains frequency and the difference of the nominal frequency of power system.

9. energy-storage system as claimed in claim 8 participates in the device of FREQUENCY CONTROL of electrical network, it is characterised in that a described frequency control module specifically for:

State-of-charge according to the bias direction of mains frequency deviation and energy-storage system as follows, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network:

Bias direction in mains frequency deviation is f_t>50+��f_max, and SOC_BESS,t<SOC_maxTime, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network;

Or, the bias direction in mains frequency deviation is f_t<50-��f_max, and SOC_BESS,t>SOC_minTime, it is determined that energy-storage system participates in FREQUENCY CONTROL of electrical network;

Wherein, f_tMains frequency for t; �� f_maxFor maximum frequency deviation; SOC_BESS,tFor the energy-storage system state-of-charge in t; SOC_maxFor the state-of-charge maximum that energy-storage system allows; SOC_minFor the state-of-charge minima that energy-storage system allows.

10. energy-storage system as claimed in claim 8 participates in the device of FREQUENCY CONTROL of electrical network, it is characterised in that described primary frequency modulation entry condition includes virtual inertia response entry condition and once variable droop control entry condition;

Described virtual inertia response entry condition is:

When | df_t/dt|��R_limTime, virtual inertia response starts;

Wherein, df_t/ dt is the mains frequency rate of change of t, R_limFor mains frequency rate of change dead band;

Described once variable droop control entry condition is:

When | f_t-50|>��f_maxAnd t > T_delay1Time, once variable droop control starts;

Wherein, f_tMains frequency for t; �� f_maxFor maximum frequency deviation; T_delay1For the first default time delay.

11. energy-storage system as claimed in claim 8 participates in the device of FREQUENCY CONTROL of electrical network, it is characterised in that a described frequency control module is additionally operable to:

When meeting primary frequency modulation termination condition, terminate virtual inertia response and once variable droop control;

Described primary frequency modulation termination condition includes virtual inertia response termination condition and once variable droop control termination condition;

Described virtual inertia response termination condition is:

After mains frequency reaches peak value and postpones Preset Time, virtual inertia response terminates;

Described once variable droop control termination condition is:

Work as t > T_delay2Time, once variable droop control terminates;

Wherein, T_delay2For the second default time delay.

12. energy-storage system as claimed in claim 8 participates in the device of FREQUENCY CONTROL of electrical network, it is characterised in that a described frequency control module specifically for:

Determine the virtual inertia response of energy-storage system as follows:

${\mathrm{\&Delta;P}}_{Inert,t}=\left\{\begin{array}{cc}0& |{\mathrm{df}}_t/dt|<R_{\lim }\\ K_{Inert}\&times;({\mathrm{df}}_t/dt)& |{\mathrm{df}}_t/dt|\&GreaterEqual;R_{\lim }\end{array}\right.;$

Wherein, �� P_Inert,tRespond in the virtual inertia of t for energy-storage system, K_InertFor virtual inertia coefficient, K_Inert< 0, df_t/ dt is the mains frequency rate of change of t, R_limFor mains frequency rate of change dead band.

13. energy-storage system as claimed in claim 12 participates in the device of FREQUENCY CONTROL of electrical network, it is characterised in that a described frequency control module specifically for:

Determine the once variable droop control power adjustment of energy-storage system as follows:

${\mathrm{\&Delta;P}}_{Droop,t}=\left\{\begin{array}{cc}\min \left(\frac{1}{R_{Droop,t}}\left(50-f_t\right),P_{BESSN}\right)& f_t\&le;50-{\mathrm{\&Delta;f}}_{\max }\\ 0& |f_t-50|<{\mathrm{\&Delta;f}}_{\max }\\ \max \left(\frac{1}{R_{Droop,t}}\left(50-f_t\right),-P_{BESSN}\right)& f_t\&GreaterEqual;50+{\mathrm{\&Delta;f}}_{\max }\end{array}\right.;$

Wherein, �� P_Droop,tFor the energy-storage system once variable droop control power adjustment in t, R_Droop,tFor the sagging coefficient of t, f_tFor the mains frequency of t, �� f_maxFor maximum frequency deviation, min is the computing that gets the small value, and max is the computing that takes large values, P_BESSNRated power for energy-storage system;

R is determined according to equation below_Droop,t:

$R_{Droop,t}=R_{max}-(R_{max}-R_{min})\&lsqb;\frac{{\mathrm{SOC}}_{BESS,t}-{\mathrm{SOC}}_{min}}{{\mathrm{SOC}}_{\max }-{\mathrm{SOC}}_{min}}\&rsqb;;$

Wherein, R_maxFor maximum sagging coefficient, R_minFor minimum sagging coefficient, SOC_BESS,tFor the energy-storage system state-of-charge in t; SOC_maxFor the state-of-charge maximum that energy-storage system allows; SOC_minFor the state-of-charge minima that energy-storage system allows.

14. energy-storage system as claimed in claim 10 participates in the device of FREQUENCY CONTROL of electrical network, it is characterised in that a described frequency control module specifically for:

Determine total real power control instruction as follows:

��P_PF,t=�� P_Inert,t+��P_Droop,t;

Wherein, �� P_PF,tTotal real power control instruction for t.