CN115276048A - Hybrid energy storage system power optimization distribution control method applied to black start of diesel generator of hydropower station - Google Patents
Hybrid energy storage system power optimization distribution control method applied to black start of diesel generator of hydropower station Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- H—ELECTRICITY
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- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
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- H—ELECTRICITY
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- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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- H02J2300/10—The dispersed energy generation being of fossil origin, e.g. diesel generators
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Abstract
The hybrid energy storage system comprises a storage battery, a super capacitor, a first bidirectional DC/DC converter, a second bidirectional DC/DC converter, a bidirectional PWM converter and a diesel generator set. The control method provided by the invention collects the SOC of the storage battery and the super capacitor, adopts a power optimization distribution control strategy of a hybrid energy storage system, and can change the charge-discharge power distribution of the storage battery and the super capacitor by changing the parameters of the PI controller and the time constant tau in the LPF. According to the invention, by adding the hybrid energy storage system, the system regulation function is enhanced through a power control method from the outside, and the control performance of the voltage frequency of the system is improved.
Description
Technical Field
The invention relates to the technical field of hydropower station diesel generator set control, in particular to a hybrid energy storage system power optimal distribution control method applied to black start of a hydropower station diesel generator.
Background
At present, when a speed regulating system of a hydropower station diesel generator set is designed, the traditional PID control is still mostly adopted, and the function of quick speed regulation is realized by adjusting an amplification coefficient kp, an integral coefficient ki and a differential coefficient kd of a comparative example. However, when the traditional PID control method is adopted as the control method of the diesel engine speed regulating system, once three coefficients of kp, ki and kd are determined, the coefficients cannot be changed according to different requirements during the operation of the system, so that the regulating speed and the overshoot cannot be well controlled.
More and more experts and scholars are beginning to add the idea of fuzzy control to the speed regulation control of the diesel generating set. However, the traditional fuzzy PID control method is still only an improvement on the speed regulation performance of the diesel oil speed regulation system, when the interference is too large, effective control cannot be achieved, and particularly when the method is applied to black start of a hydropower station, the power of the service load changes at any time due to starting and stopping of oil pump motors of systems such as a speed regulator hydraulic system, a water-guided oil circulation system, a high-pressure oil system and the like, so that if the traditional fuzzy PID control mode is directly and singly adopted, under the condition of black start, the voltage and the frequency of the service electric system are liable to fluctuate greatly when the load is started and stopped.
Disclosure of Invention
In order to solve the technical problems, the invention provides a hybrid energy storage system power optimal distribution control method applied to black start of a hydropower station diesel generator, and aims to utilize the hybrid energy storage system and adopt the hybrid energy storage system power optimal distribution control method to externally strengthen the system regulation function, detect the SOC of a storage battery and a super capacitor, change the charging and discharging power of the storage battery and the super capacitor through a power optimal distribution control strategy, and reduce the regulation time and overshoot of the voltage and the rotating speed of a plant power system and improve the control performance of the system voltage frequency under the black start condition when a load is started and stopped.
The technical scheme adopted by the invention is as follows:
a hybrid energy storage system for black start of a diesel generator of a hydropower station comprises:
a storage battery, a super capacitor, a first bidirectional DC/DC converter, a second bidirectional DC/DC converter, a bidirectional PWM converter,
The two poles of the storage battery are connected with one side of the first bidirectional DC/DC converter;
two ends of the super capacitor are connected with one side of the second bidirectional DC/DC converter;
the other side of the first bidirectional DC/DC converter is connected with two ends of a capacitor C1 in parallel;
the other side of the second bidirectional DC/DC converter is connected with two ends of a capacitor C1 in parallel, and the capacitor C1 plays a role in voltage stabilization and filtering.
One side of the bidirectional PWM converter is connected with two ends of a capacitor C1 in parallel;
the other side of the bidirectional DC/AC converter is connected with one side of the transformer;
the other side of the transformer is connected with a diesel generator set.
The first bidirectional DC/DC converter and the second bidirectional DC/DC converter both adopt Buck/Boost type bidirectional DC/DC converters.
When the diesel generator system is in a stable working state, the hybrid energy storage system is shut down, and at the moment, the diesel generator system, the hybrid energy storage system and the three-phase load still meet the relation of the formula (1); but when the diesel generator system fluctuates:
ΔP＝Pdiesel+Phess-Pload (3)；
in the formula: p ishessFor mixing the stored energy power, PdieselOutputting power for the diesel generator; p isloadIs the load power, and Δ P is the system power variation.
When the load is suddenly released, i.e. PloadWhen decreasing, P is nowdiesel＞PloadDelta P > 0, can let PhessThe negative increase of less than 0 is realized, and the increment of the power of the whole system including a diesel generator system, a hybrid energy storage system and a three-phase load is absorbed, so that the rise of the three-phase alternating current voltage is reducedAn increase in frequency;
when the load suddenly increases, i.e. PloadAt the time of increase, Pdiesel＜PloadDelta P is less than 0, can make PhessThe positive direction is increased to be more than 0, and the shortage of the whole system including a diesel generator system, a hybrid energy storage system and a three-phase load power is supplemented, so that the reduction of the three-phase alternating current voltage and the reduction of the frequency are restrained.
The bidirectional DC/DC converter strategy is as follows:
setting: i isbat_refFor battery command current, IbatIs the actual current of the battery, Isc_refFor the command current of the super capacitor, IscIs the actual current of the super capacitor, DbatDuty cycle of the first bidirectional DC/DC converter for the battery branch, DscAnd the duty ratio of the second bidirectional DC/DC converter of the super capacitor branch circuit.
And after power distribution, dividing the command power by the voltage respectively to obtain corresponding command current, and obtaining the duty ratio after PI.
The comparator is used for changing the working mode, when the comparator 1 works and the comparator 2 does not work, the bidirectional DC/DC converter works in a BOOST state; when the comparator 1 does not work and the comparator 2 works, the bidirectional DC/DC converter works in a BUCK state; the storage battery instruction current controls a first bidirectional DC/DC converter after passing through a PI and a comparator; and the super capacitor command current controls the second bidirectional DC/DC converter after passing through the PI and the comparator.
When the command current is larger than 0, the hybrid energy storage system works in a BOOST state at the moment and sends out power; when the command current is less than 0, the hybrid energy storage system works in a BOOST state at the moment and absorbs power.
Meanwhile, when the diesel generator set works under the condition of no fluctuation, the fact that the actual rotating speed is 100% consistent with the reference rotating speed cannot be guaranteed, so that in order to prevent the first bidirectional DC/DC converter and the second bidirectional DC/DC converter from working frequently, when the error between the actual rotating speed and the reference rotating speed is small, namely the command current is small, the first bidirectional DC/DC converter and the second bidirectional DC/DC converter are in a stop state.
The control strategy of the bidirectional PWM converter is double-loop control of a voltage outer loop and a current inner loop, and the control method after decoupling is as follows:
setting: u shapedc_refIs a reference value of the DC bus voltage, UdcIs the actual value of the DC bus voltage, Id_refIs a command value of d-axis current, IdIs the actual value of the d-axis current, Iq_refIs a command value of q-axis current, IqIs the actual value of the q-axis current, ω L is the filter inductance equivalent impedance, Ud_refIs a command value of d-axis voltage, UdIs the actual value of the d-axis voltage, Uq_refIs a command value of q-axis voltage, UqIs the actual value of the q-axis voltage.
When the hybrid energy storage system is in a discharge mode, the voltage of the direct current bus capacitor is increased, and U isdc_ref－Udc< 0, command current Id_refIf the output voltage is less than 0, the bidirectional PWM converter is in an inversion mode and sends power to the diesel generator set;
when the hybrid energy storage system is in a charging mode, the voltage of the direct current bus capacitor is reduced, and U isdc_ref－Udc> 0, command current Id_refAnd if the voltage is more than 0, the bidirectional PWM converter is in a rectification mode and absorbs power from the diesel generating set.
When the total power of the hybrid energy storage system is constant, the parameters of the PI controller and the time constant tau in the LPF are changed by detecting the SOC of the storage battery and the super capacitor and the charging and discharging states of the system,
setting a discharge dead zone threshold of the SOC to the SOCminI.e. when SOCi(i = bat (battery) or sc (super capacitor)) < SOCminIn time, the storage battery and the super capacitor can only be charged and can not be discharged;
setting a discharge buffer threshold of the SOC to be the SOClowI.e. when SOCmin＜SOCi＜SOClowIn the process, the storage battery and the super capacitor are normally charged, and the discharge power is reduced;
setting a charging dead zone threshold of the SOC to the SOCmaxI.e. when SOCmax＜SOCiIn time, the storage battery and the super capacitor cannot be charged and only can be discharged;
setting a charging buffer threshold of the SOC to SOChighI.e. when SOChigh＜SOCi＜SOCmaxIn the process, the charging power of the storage battery and the super capacitor is reduced, and the storage battery and the super capacitor are discharged normally;
when SOC is reachedlow＜SOCi＜SOChighAnd in the process, the storage battery and the super capacitor are charged and discharged normally.
The power optimization distribution control method of the hybrid energy storage system comprises the following steps:
Phess_reffor the total command power, P, of the hybrid energy storage systembat_refFor commanding power of the accumulator, Psc_refPower is commanded for the super capacitor.
(1) When SOC is reachedbat＜SOCminAnd P ishess_refWhen the voltage is more than 0, the first bidirectional DC/DC converter switch of the storage battery is closed to be in a shutdown state, and the PI parameter is reduced to enable Psc_ref＝Phess_ref；
(2) When SOC is reachedsc＜SOCminAnd P ishess_refWhen the current is more than 0, the second bidirectional DC/DC converter switch of the super capacitor is closed to enable the super capacitor to be in a shutdown state, and meanwhile, the PI parameter is reduced to enable P to bebat_ref＝Phess_ref；
(3) When the SOC ismin＜SOCbat、SOCsc＜SOClowAnd P ishess_refWhen the parameter is more than 0, the PI parameter is reduced, and the tau is unchanged;
(4) When SOC is reachedmin＜SOCbat＜SOClow，SOCsc＞SOClowAnd P ishess_refWhen the PI parameter is more than 0, the PI parameter is unchanged, and tau is reduced;
(5) When SOC is reachedmin＜SOCsc＜SOClow，SOCbat＞SOClowAnd P ishess_refWhen the PI parameter is more than 0, the PI parameter is unchanged, and tau is increased;
(6) When SOC is reachedhigh＜SOCsc＜SOCmax，SOCbat＜SOChighAnd P ishess_refWhen the PI parameter is less than 0, the PI parameter is unchanged, and tau is increased;
(7) When SOC is reachedhigh＜SOCbat＜SOCmax，SOCsc＜SOChighAnd P ishess_refWhen the PI parameter is less than 0, the PI parameter is unchanged, and tau is reduced;
(8) When SOC is reachedhigh＜SOCbat、SOCsc＜SOCmaxAnd P ishess_refWhen the parameter is less than 0, the PI parameter is reduced, and tau is unchanged;
(9) When SOC is reachedmax＜SOCbatAnd P ishess_refWhen the current is less than 0, the bidirectional DC/DC switch of the storage battery is closed to be in a shutdown state, and meanwhile, the PI parameter is reduced to enable Psc_ref＝Phess_ref；
(10) When SOC is reachedmax＜SOCscAnd P ishess_refWhen the current is less than 0, the bidirectional DC/DC switch of the super capacitor is closed to be in a shutdown state, and meanwhile, PI parameters are reduced to enable P to be in a shutdown statebat_ref＝Phess_ref；
Of course, when there is no fluctuation in the load, the bidirectional PWM converter, and the hybrid energy storage system power distribution may be turned off, and given the command power, the following is satisfied:
Pbat_ref+Psc_ref＝0 (6)。
the power optimization distribution control method of the hybrid energy storage system comprises the following steps:
(1) the method comprises the following steps When the SOC isbat＜SOCminAnd SOCsc＞SOChighWhen it is, let Psc_ref> 0, i.e. the supercapacitor discharges, at which time Pbat_refIf less than 0, the storage battery is charged, so that the storage battery is separated from the discharge dead zone.
(2) The method comprises the following steps When SOC is reachedsc＜SOCminAnd SOCbat＞SOChighWhen it is, let PbatGreater than 0, i.e. battery discharge, at which time Psc_refIf the voltage is less than 0, the super capacitor is charged, so that the super capacitor is separated from a discharge dead zone.
(3) The method comprises the following steps When SOC is reachedbat＞SOCmaxAnd SOCsc＜SOClowWhen it is, let PbatGreater than 0, i.e. battery discharge, at which time Psc_ref< 0, superAnd (4) charging the capacitor to enable the storage battery to be separated from the charging dead zone.
(4) The method comprises the following steps When SOC is reachedsc＞SOCmaxAnd SOCbat＜SOClowWhen it is, let Psc_ref> 0, i.e. the supercapacitor discharges, at which time Pbat_refIf the charging time is less than 0, the storage battery is charged, so that the super capacitor is separated from a charging dead zone.
The invention discloses a hybrid energy storage system power optimization distribution control method applied to black start of a diesel generator of a hydropower station, which has the following technical effects:
1) The invention provides a power optimization distribution control strategy method of a hybrid energy storage system applied to a diesel generating set.
2) The method provided by the invention collects the SOC of the storage battery and the super capacitor, adopts a power optimization distribution control strategy of a hybrid energy storage system, and can change the charge-discharge power distribution of the storage battery and the super capacitor by changing the parameter of the PI controller and the time constant tau in the LPF.
3) Simulation analysis proves that when 50% of rated load is suddenly loaded and unloaded, after the hybrid energy storage system is adopted, the overshoot and the overshoot time are reduced by more than 30% compared with the overshoot and the overshoot time of the traditional diesel generator set, after the hybrid energy storage power optimal distribution control method is adopted, the charging and discharging power of the storage battery and the super capacitor can be changed according to different working conditions, and the effectiveness and the reliability of the method are proved.
Drawings
FIG. 1 is a structural diagram of a Fuzzy PID and hybrid energy storage system cooperative control system applied to black start of a diesel generator of a hydropower station.
Fig. 2 is a structural view of a diesel generator set.
FIG. 3 is a mathematical model diagram of a diesel engine and its speed control system.
Fig. 4 is a hybrid energy storage system topology.
FIG. 5 is a Buck/Boost type bidirectional DC/DC converter topology.
Fig. 6 is a hybrid energy storage system power distribution block diagram.
Fig. 7 is a block diagram of a bidirectional DC/DC converter control strategy.
Fig. 8 is a bidirectional PWM converter topology.
Fig. 9 is a bidirectional PWM converter control block diagram.
Fig. 10 is a block diagram of a charge and discharge threshold structure.
FIG. 11 is a model of a diesel generator set incorporating a hybrid energy storage system
Fig. 12 is a waveform diagram comparing diesel generator speeds.
FIG. 13 is a charge-discharge power waveform diagram for a hybrid energy storage system.
Fig. 14 is a waveform diagram comparing diesel generator speeds.
FIG. 15 is a waveform diagram of charging and discharging power of the hybrid energy storage system under the working condition 1.
FIG. 16 (a) is a waveform diagram of charging and discharging power of the hybrid energy storage system under the working condition 2;
fig. 16 (b) is a charge and discharge power waveform diagram of the hybrid energy storage system under the working condition 3.
Fig. 16 (c) is a charge-discharge power waveform diagram of the hybrid energy storage system under the working condition 4.
FIG. 16 (d) is a waveform diagram of charging and discharging power of the hybrid energy storage system under the working condition 5.
Detailed Description
The structure diagram of the Fuzzy PID and hybrid energy storage system cooperative control system applied to the black start of the hydropower station diesel generator is shown in figure 1, and the Fuzzy PID and hybrid energy storage system cooperative control system applied to the black start of the hydropower station diesel generator is composed of a diesel generator set, a hybrid energy storage system, a bus and a three-phase load.
The structure of the diesel generator set is shown in figure 2. In view of the fact that the internal structure of the diesel generator set is too complicated, for the sake of facilitating electrical characteristic simulation, the internal structure of the diesel generator set needs to be properly simplified, such as: 1) The burning time of diesel oil, the flowing time of gas and the like are replaced by a first-order lag link; 2) Neglecting the influence of temperature change during diesel combustion; 3) Ignoring delays in signal transfer between components, etc. The simplified equation of the rotating speed and the torque of each part in the diesel engine speed regulating system is deduced after the simplified processing is carried out on each part, the simplified equation is converted into a transfer function, a mathematical model in the form of the transfer function is established, the mathematical model of the diesel engine and the speed regulating system is shown in figure 3 and comprises a main controller, an amplifying unit, an actuator, a diesel engine unit, an integrating unit and a unit delay (unit), and the models are explained respectively.
The main controller and the amplifying unit form a speed regulation controller of the diesel engine and the speed regulation system thereof, which is the core part of the whole speed regulation system, and the transfer function G1(s) based on the traditional PID control method is as follows:
in the formula, e(s) is the input of a speed regulation controller, namely a rotating speed error; u(s) is the output of the speed regulation controller, namely an accelerator control signal; k is a radical ofpThe proportional amplification factor of the speed regulation controller; k is a radical ofiIs the integral coefficient of the speed regulation controller; k is a radical ofdIs the differential coefficient of the speed controller.
Although the transfer function of the speed regulation controller is the same as that of the equation (1) when the Fuzzy PID and hybrid energy storage system based cooperative control is adopted, the significant difference is that: proportionality coefficient k of traditional PID controlpIntegral coefficient kiDifferential coefficient kdIs fixed, and when the Fuzzy PID and the hybrid energy storage system are adopted for cooperative control, the proportionality coefficient kpIntegral coefficient kiDifferential coefficient kdIt is automatically adjusted and its working principle is analyzed in detail later.
The actuator of the diesel generator speed regulating system adopts a direct current servo motor, and the direct current servo motor has the function of changing the displacement of a gear rod of an oil injection pump through an electromagnet of the direct current servo motor according to an input throttle control signal so as to ensure that the oil injection quantity of a diesel engine is changed in real time. The motion increment equation of the actuator is as follows:
in the formula, y is the displacement of the gear rod of the fuel injection pump; m is the mass of the sliding rod of the actuator; d is the resistance coefficient of the system; k is a radical ofsIs the stiffness of the actuator spring; delta FmIs the change of the electromagnetic force of the actuator.
The equation of motion of the electromagnetic mechanism is:
ΔFm＝KuΔu-KxΔx (3)
in the formula, kuIs the amplification factor of the actuator; k is a radical ofxIs the sum of the displacement gain and the spring stiffness of the actuator; delta u is the change of the throttle control signal; and delta x is the displacement variation of the gear rod of the fuel injection pump.
Combining formulas (2) and (3) and performing a Ralsberg transform to obtain:
ms2Δx+DSΔx+KxΔx＝KuΔu-KxΔx (4)
the transfer function G of the actuator can be obtained by simplifying the step (4)2(s) is:
in the formula, U(s) is input of an actuator, namely an accelerator control signal; the delta X(s) is the output of the actuator, namely the displacement change of the gear rod of the fuel injection pump; xiηIs the undamped natural oscillation angular frequency of the actuator; omegaηIs the damping factor of the actuator.
The parameters adopted by the simulation are set as follows: k is a radical ofu＝1、ξη＝1.414、ωη＝35.355。
The equation of motion for a diesel engine, which can be derived from the darenberg principle, is:
in the formula, J is the rotational inertia of the diesel engine set; omega is the crankshaft angular velocity of the diesel engine set; mdTorque generated for the diesel engine set; mcThe resistance moment of the diesel engine set.
Equation (6) can be expressed in incremental form as:
simplifying formula (7) and neglecting the influence of load moment, the equation of rotating speed and displacement of the gear rod of the fuel injection pump can be obtained and is equivalent to a first-order proportional inertia link, therefore, the transfer function G of the equation of motion of the diesel engine set3(s) is:
in the formula, kηThe amplification factor of the diesel engine; t isaIs the acceleration time constant of the diesel engine; t isgIs the self-stability coefficient of the diesel engine.
The parameters adopted by the simulation are set as follows: k is a radical ofη＝1、Ta＝0.0384、kη＝1。
The output part of the diesel engine and the speed regulating system thereof consists of an integral unit, a unit delay unit and a product unit which are shown in figure 3. The function of the synchronous generator is to convert the rotating speed output by the diesel engine set into mechanical power which is used as the input quantity of the synchronous generator.
The parameters adopted by the simulation are set as follows: delay time T of unitd＝0.024。
As can be taken from fig. 3, when the diesel generator system is in a stable operating state, the expression is satisfied:
Pdiesel＝Pload (1)
in the formula PdieselOutputting power for the diesel generator; ploadIs the load power.
When the load fluctuates:
ΔP＝Pdiesel-Pload (2)
in the formula: Δ P is the system power variation.
When the load is suddenly released, i.e. PloadWhen decreasing, P is nowdiesel＞Pload，△P＞0，The excessive power can increase the voltage of the three-phase alternating current and the frequency; when the load suddenly increases, i.e. PloadAt the time of increase, Pdiesel＜PloadAnd the delta P is less than 0, and the power is insufficient, so that the voltage of the three-phase alternating current is reduced, and the frequency is reduced.
Because the existing excitation system is developed more mature, the effective value of the voltage is regulated relatively quickly, and the rotating speed of the diesel engine speed regulating system is regulated slowly, the power is controlled by adding the hybrid energy storage system, so that the rotating speed regulating capability of the diesel generating set is improved.
As can be seen from fig. 3, when the three-phase ac fluctuates, a large difference in rotational speed is generated, and the entire system is adjusted by the speed controller. However, the governor can only adjust the speed difference caused by the fluctuation, and does not control the speed difference from the point of view of the fluctuation, i.e., the power change.
For this purpose, hybrid energy storage systems are added, the speed regulation capability of diesel generator systems is improved in terms of reducing power variations, and strategies for power-optimized distribution control thereof are studied.
Considering that the hybrid energy storage system operates in a dc environment and the diesel generator set supplies three-phase ac power to the main grid, the present invention was developed according to the hybrid energy storage system shown in fig. 4. In fig. 4, two bidirectional DC/DC converters are used for charging and discharging management of the storage battery and the super capacitor, respectively, and the bidirectional PWM converter performs power conversion between a direct current working environment of the storage battery and the super capacitor and an alternating current working environment of the diesel generator set.
When the diesel generator system is in a stable working state, the hybrid energy storage system is shut down, and the system still satisfies the relation of the formula (1); but when the system fluctuates:
ΔP＝Pdiesel+Phess-Pload (3)
in the formula: phessIs a hybrid energy storage power.
When the load is suddenly released, i.e. PloadWhen decreasing, P is nowdiesel＞PloadDelta P > 0, can let PhessLess than 0, absorbing system powerIncreasing the quantity, thereby reducing the rising of the three-phase alternating current voltage and the increasing of the frequency; when the load suddenly increases, i.e. PloadAt the time of increase, Pdiesel＜PloadDelta P is less than 0, can make PhessAnd if the voltage is more than 0, the shortage of the system power is supplemented, so that the reduction of the voltage and the reduction of the frequency of the three-phase alternating current are restrained.
Buck/Boost type bidirectional DC/DC converter, as shown in FIG. 5.
A hybrid energy storage system power distribution block diagram is shown in fig. 6. In FIG. 6,. Omega.refIs a reference rotating speed of the diesel generating set, omega is an actual rotating speed of the diesel generating set, Phess_refFor the total command power, P, of the hybrid energy storage systembat_refFor commanding power of the accumulator, Psc_refPower is commanded for the super capacitor.
From FIG. 6 and the previous analysis, it can be seen that when ω > ωrefWhen, explain Pdiesel＞PloadAnd DeltaP > 0. Let PhessIf the power is less than 0, absorbing the increment of the system power; when omega is less than omegarefWhen, explain Pdiesel＜PloadAnd DeltaP is less than 0. Can order PhessAnd > 0, supplement the shortage of system power.
And meanwhile, according to the characteristics of the storage battery and the super capacitor, the total command power passes through an LPF (Low-pass filter) to be used as the storage battery command power, and the rest is used as the super capacitor command power.
The power relationship of the hybrid energy storage system is then:
Psc＝Phess-Pbat (5)；
in the formula: τ is the time constant of the low pass filter.
The bidirectional DC/DC converter control strategy is shown in fig. 7. In FIG. 7, Ibat_refFor commanding the current of the accumulator, IbatIs the actual current of the battery, Isc_refThe current is commanded for the super-capacitor,Iscis the actual current of the super capacitor, DbatFor bi-directional DC/DC duty cycle of the battery branch, DscThe bidirectional DC/DC duty ratio of the super capacitor branch is adopted. After power distribution, the command power is divided by the voltage to obtain corresponding command current, and the duty ratio is obtained after the command current passes through PI.
In fig. 7, the comparator functions to change the operation mode. When the comparator 1 works and the comparator 2 does not work, the bidirectional DC/DC works in a BOOST state; when the comparator 1 does not work and the comparator 2 works, the bidirectional DC/DC works in a BUCK state.
When the command current is larger than 0, the hybrid energy storage system works in a BOOST state at the moment and sends out power; when the command current is less than 0, the hybrid energy storage system works in a BOOST state at the moment and absorbs power.
Meanwhile, when the diesel generating set works under the condition of no fluctuation, the fact that the actual rotating speed is 100% consistent with the reference rotating speed cannot be guaranteed, so that in order to prevent the bidirectional DC/DC from working frequently, when the error between the actual rotating speed and the reference rotating speed is small, namely the command current is small, the bidirectional DC/DC is in a stop state.
The topology of the bidirectional PWM converter is shown in FIG. 8, C _ dc is DC bus capacitance, D1To D6Is IGBT, L is filter inductance, and C is filter capacitance.
The control strategy of the bidirectional PWM converter is a double-loop control of a voltage outer loop and a current inner loop, and a decoupled control block diagram thereof is shown in fig. 9. In FIG. 9, Udc_refIs a reference value of the DC bus voltage, UdcIs the actual value of the DC bus voltage, Id_refIs a command value of d-axis current, IdIs the actual value of the d-axis current, Iq_refIs a command value of q-axis current, IqIs the actual value of the q-axis current, ω L is the filter inductance equivalent impedance, Ud_refIs a command value of d-axis voltage, UdIs the actual value of the d-axis voltage, Uq_refIs a command value of q-axis voltage, UqIs the actual value of the q-axis voltage.
When the hybrid energy storage system is in a discharge mode, the voltage of the direct current bus capacitor is increased, and U isdc_ref－Udc< 0, meansLet current Id_refIf the output voltage is less than 0, the bidirectional PWM converter is in an inversion mode and sends power to the diesel generator set; when the hybrid energy storage system is in a charging mode, the voltage of the direct current bus capacitor is reduced, and U isdc_ref－Udc> 0, command current Id_refAnd if the voltage is more than 0, the bidirectional PWM converter is in a rectification mode and absorbs power from the diesel generating set.
In the structure of the traditional hybrid energy storage system, the parameters of the PI controller are constant, the method does not need to be modified after the parameters are set, is quick and convenient, but has the prominent defects that the method is used when the SOC of the storage battery is finishedbatAnd SOC of super capacitorscAt lower, it cannot emit enough power; when SOC is reachedbatAnd SOCscAt higher levels, a large amount of power cannot be absorbed. If not altered, it can cause a disorder of the system.
Meanwhile, the analytical expressions (4) and (5) can obtain that when the total power of the hybrid energy storage is constant, the power of the storage battery and the super capacitor can be distributed by changing the time constant tau in the LPF. Therefore, the invention adopts optimized distribution to improve the problems, namely, the parameters of the PI controller and the time constant tau in the LPF are changed by detecting the SOC of the storage battery and the super capacitor and the charging and discharging states of the system.
Setting a discharge dead zone threshold of the SOC to the SOCminI.e. when SOCi(i = bat (battery) or sc (super capacitor)) < SOCminIn time, the storage battery and the super capacitor can only be charged and can not be discharged; setting a discharge buffer threshold of the SOC to be the SOClowI.e. when SOCmin＜SOCi＜SOClowIn the process, the storage battery and the super capacitor are normally charged, and the discharge power is reduced; setting a charging dead zone threshold of the SOC to the SOCmaxI.e. when SOCmax＜SOCiIn the process, the storage battery and the super capacitor cannot be charged and only can be discharged; setting a threshold of a charging alleviation area of the SOC to the SOChighI.e. when SOChigh＜SOCi＜SOCmaxIn the process, the charging power of the storage battery and the super capacitor is reduced, and the storage battery and the super capacitor are normally discharged; when SOC is reachedlow＜SOCi＜SOChighTime, accumulator and super capacitorCharging and discharging are carried out frequently. The threshold structure is shown in fig. 10.
The power optimization distribution control method of the hybrid energy storage system comprises the following steps:
(1) When SOC is reachedbat＜SOCminAnd P ishess_refWhen the voltage is more than 0, the bidirectional DC/DC switch of the storage battery is closed to be in a shutdown state, and the PI parameter is reduced to enable Psc_ref＝Phess_ref；
(2) When SOC is reachedsc＜SOCminAnd P ishess_refWhen the current is more than 0, the bidirectional DC/DC switch of the super capacitor is closed to be in a shutdown state, and meanwhile, the PI parameter is reduced to enable P to be in a shutdown statebat_ref＝Phess_ref；
(3) When SOC is reachedmin＜SOCbat、SOCsc＜SOClowAnd P ishess_refWhen the parameter is more than 0, the PI parameter is reduced, and the tau is unchanged;
(4) When SOC is reachedmin＜SOCbat＜SOClow，SOCsc＞SOClowAnd P ishess_refWhen the PI parameter is more than 0, the PI parameter is unchanged, and tau is reduced;
(5) When SOC is reachedmin＜SOCsc＜SOClow，SOCbat＞SOClowAnd P ishess_refWhen the PI parameter is more than 0, the PI parameter is unchanged, and tau is increased;
(6) When SOC is reachedhigh＜SOCsc＜SOCmax，SOCbat＜SOChighAnd P ishess_refWhen the PI parameter is less than 0, the PI parameter is unchanged, and tau is increased;
(7) When SOC is reachedhigh＜SOCbat＜SOCmax，SOCsc＜SOChighAnd P ishess_refWhen the PI parameter is less than 0, the PI parameter is unchanged, and tau is reduced;
(8) When SOC is reachedhigh＜SOCbat、SOCsc＜SOCmaxAnd P ishess_refWhen the parameter is less than 0, the PI parameter is reduced, and the tau is unchanged;
(9) When SOC is reachedmax＜SOCbatAnd P ishess_refWhen < 0, the power storage is turned offThe bidirectional DC/DC switch of the pool makes it in a shutdown state, and simultaneously reduces the PI parameter to make Psc_ref＝Phess_ref；
(10) When SOC is reachedmax＜SOCscAnd P ishess_refWhen the current value is less than 0, the bidirectional DC/DC switch of the super capacitor is closed to enable the super capacitor to be in a shutdown state, and meanwhile, PI parameters are reduced to enable P to be in a state ofbat_ref＝Phess_ref；
Of course, when the load does not fluctuate, the bidirectional PWM switch and the power distribution of the hybrid energy storage system may be turned off, and given the command power, the following are satisfied:
Pbat_ref+Psc_ref＝0 (6)
therefore, charging and discharging between the storage battery and the super capacitor can be carried out, and the power distribution control method is briefly described as follows:
(1) When SOC is reachedbat＜SOCminAnd SOC issc＞SOChighWhen it is, let Psc_ref> 0, i.e. the supercapacitor discharges, at which time Pbat_refIf less than 0, the storage battery is charged, so that the storage battery is separated from the discharge dead zone.
(2) When SOC is reachedsc＜SOCminAnd SOCbat＞SOChighWhen it is, let PbatGreater than 0, i.e. battery discharge, at which time Psc_refAnd (5) if the current is less than 0, charging the super capacitor to separate the super capacitor from a discharge dead zone.
(3) When SOC is reachedbat＞SOCmaxAnd SOCsc＜SOClowWhen it is, let PbatGreater than 0, i.e. battery discharge, at which time Psc_refIf the voltage is less than 0, the super capacitor is charged, so that the storage battery is separated from a charging dead zone.
(4) When SOC is reachedsc＞SOCmaxAnd SOCbat＜SOClowWhen it is, let Psc_ref> 0, i.e. the supercapacitor discharges, at which time Pbat_refIf the charging time is less than 0, the storage battery is charged, so that the super capacitor is separated from the charging dead zone.
In order to verify the power optimization distribution control strategy of the hybrid energy storage system applied to the diesel generating set, matlab/simulink simulation software is adopted to build a simulation model of the diesel generating set added with the hybrid energy storage system, and as shown in fig. 11, the simulation model consists of a diesel engine and a speed regulating system thereof, an excitation system, a synchronous generator, the hybrid energy storage system, hybrid energy storage control and a three-phase load. . For convenience of explanation, the key simulation parameters are summarized in table 1.
TABLE 1 Critical simulation parameter List
Tab.1 key simulation parameter table
The simulation setup will now be explained as follows: when the rated load is suddenly unloaded by 50% at 15s and the rated load is suddenly added by 50% at 20s, compared with the change of the rotating speed of the traditional diesel generator set and the diesel generator set after the hybrid energy storage is added, the method is shown in figure 12. In fig. 12, the red curve is the change in the rotational speed of the conventional diesel generator set; blue is the change of the rotating speed of the diesel generating set added into the hybrid energy storage system.
The charging and discharging power of the hybrid energy storage system at this time is shown in fig. 13. In fig. 13, the red curve is the power waveform of the battery; blue is the power waveform of the super capacitor.
Comparing fig. 12 and 13, it can be seen that: when 50% of rated load is suddenly loaded and unloaded, the overshoot of the traditional diesel generator set is more than 0.037, and the adjusting time is more than 3.5s. After the mixed energy storage is added, the overshoot of the rotating speed of the diesel generator is reduced to be below 0.02 through charging and discharging of the mixed energy storage, and meanwhile, the adjusting time is reduced to be below 1.5 s.
As can be known from analysis of the power optimization distribution control strategy of hybrid energy storage, the conditions of PI parameter adjustment are more, and the defined working condition 1 is: when SOC is reachedhigh＜SOCbat、SOCsc＜SOCmaxAnd P ishess_refWhen the PI parameter is less than 0, the analysis is carried out by using the working condition 1, because the PI parameter is reduced at the moment, but tau is unchanged, the analysis of the influence of the PI parameter on the system is facilitated. Correspond toThe operating condition is that 50% of rated load is suddenly unloaded when the system is in 15s, and the comparison graph of the rotating speed is shown in figure 14. In fig. 14, the red curve is the rotation speed waveform of the diesel generator set added to the hybrid energy storage system under normal conditions; and when the blue color is the working condition 1, adding the rotating speed waveform of the diesel generating set of the hybrid energy storage system. The charging and discharging power of the hybrid energy storage system at this time is shown in fig. 15. In fig. 15, the red curve is the power waveform of the battery; blue is the power waveform of the super capacitor.
Comparative analysis of FIGS. 12-15 yields: when the PI parameter is reduced, the total power of the hybrid energy storage system is reduced, so that the rotating speed adjusting capacity is reduced, the overshoot is increased to 0.028, and the adjusting time is prolonged to 2s.
As can be seen from the analysis of the power-optimized distribution control strategy for hybrid energy storage, the τ parameter is adjusted more frequently, and is analyzed under two working conditions 2 and 3:
(1) Working condition 2: when the SOC ishigh＜SOCbat＜SOCmax，SOCsc＜SOChighAnd P ishess_refWhen the parameter is less than 0, the PI parameter is unchanged, but tau is reduced;
(2) Working condition 3: when SOC is reachedhigh＜SOCsc＜SOCmax，SOCbat＜SOChighAnd P ishess_refIf < 0, the PI parameter is unchanged and τ is increased.
Because the PI parameters are unchanged under the two working conditions, the influence of the tau parameters on the system is convenient to analyze. Both operating conditions were at a sudden unloading of 50% of the rated load for 15s of the system.
Since the PI parameter is not changed at this time, the rotational speed change curves are the same, and the charge/discharge power of the hybrid energy storage system is as shown in fig. 16 (a) and 16 (b). In fig. 16 (a) and 16 (b), the red curve is a power waveform of the battery; blue is the power waveform of the super capacitor.
Comparing and analyzing fig. 13 with fig. 16 (a) and fig. 16 (b), it can be seen that when τ is decreased, the charging and discharging power of the storage battery is decreased, and the charging and discharging power of the super capacitor is increased when the total command power of the hybrid energy storage is not changed; when tau is increased, the charge and discharge power of the storage battery is increased, and the charge and discharge power of the super capacitor is reduced.
The analysis of the power optimization distribution control strategy of the hybrid energy storage shows that the system can close the bidirectional PWM switch and the power distribution of the hybrid energy storage system, give instruction power, and enable the charge and discharge management between the storage battery and the super capacitor to be carried out, and the analysis is carried out according to two working conditions 4 and 5:
(1) Working condition 4: when SOC is reachedbat＞SOCmaxAnd SOCsc＜SOClowWhen it is, let PbatGreater than 0, i.e. battery discharge, at which time Psc_refAnd (5) charging the super capacitor < 0.
(2) Working condition 5: when SOC is reachedsc＞SOCmaxAnd SOCbat＜SOClowWhen it is, let Psc_ref> 0, i.e. the supercapacitor discharges, at which time Pbat_refAnd (5) charging the storage battery when the voltage is less than 0.
At this time, the charge/discharge power of the hybrid energy storage system is as shown in fig. 16 (c) and 16 (d), and in fig. 16 (c) and 16 (d), the red curve is the power waveform of the battery; blue is the power waveform of the super capacitor. As can be seen from analyzing fig. 16 (c) and 16 (d), the hybrid energy storage system can perform internal power conversion when given the command power.
By analyzing the graphs from 12 to 15 and from 16 (a) to 16 (d), the purpose of reducing the rotating speed overshoot and the adjusting time of the diesel generating set can be achieved by charging and discharging the hybrid energy storage system after the hybrid energy storage system is added. Meanwhile, after a power optimization distribution control strategy of hybrid energy storage is adopted, the purpose of adjusting the charge and discharge power of the storage battery and the super capacitor according to different working conditions is achieved.
Claims (7)
1. The utility model provides a be applied to power station diesel generator black start's hybrid energy storage system which characterized in that includes:
the storage battery, the super capacitor, the first bidirectional DC/DC converter, the second bidirectional DC/DC converter, the bidirectional PWM converter and the two poles of the storage battery are connected with one side of the first bidirectional DC/DC converter;
two ends of the super capacitor are connected with one side of the second bidirectional DC/DC converter;
the other side of the first bidirectional DC/DC converter is connected with two ends of a capacitor C1 in parallel;
the other side of the second bidirectional DC/DC converter is connected with two ends of a capacitor C1 in parallel, and the capacitor C1 plays a role in voltage stabilization and filtering;
one side of the bidirectional PWM converter is connected with two ends of a capacitor C1 in parallel;
the other side of the bidirectional DC/AC converter is connected with one side of the transformer;
the other side of the transformer is connected with a diesel generator set.
2. The hybrid energy storage system applied to black start of the diesel generator of the hydropower station according to claim 1, characterized in that: the first bidirectional DC/DC converter and the second bidirectional DC/DC converter both adopt Buck/Boost type bidirectional DC/DC converters.
3. The hybrid energy storage system according to claim 1 or 2, characterized in that:
when the diesel generator system is in a stable working state, the hybrid energy storage system is shut down, and at the moment, the diesel generator system, the hybrid energy storage system and the three-phase load still meet the relation of the formula (1); but when the diesel generator system fluctuates:
ΔP＝Pdiesel+Phess-Pload (3)；
in the formula: phessFor mixing the stored energy power, PdieselOutputting power for the diesel generator; ploadIs the load power, and Δ P is the system power variation;
when the load is suddenly released, i.e. PloadWhen decreasing, P is nowdiesel＞PloadΔ P > 0, can let PhessThe negative increase of less than 0 absorbs the increment of the power of the whole system including a diesel generator system, a hybrid energy storage system and a three-phase load, thereby reducing the rise of the voltage of the three-phase alternating current and the increase of the frequency;
when the load suddenly increases, i.e. PloadAt the time of increase, Pdiesel＜PloadDelta P is less than 0, can make PhessThe positive direction is increased to be more than 0, and the shortage of the whole system including a diesel generator system, a hybrid energy storage system and a three-phase load power is supplemented, so that the three-phase alternating current voltage is restrainedDecrease, decrease in frequency.
4. The hybrid energy storage system according to claim 1 or 2, characterized in that:
the bidirectional DC/DC converter strategy is as follows:
setting: i isbat_refFor commanding the current of the accumulator, IbatIs the actual current of the battery, Isc_refFor the command current of the super capacitor, IscIs the actual current of the super capacitor, DbatDuty cycle of the first bidirectional DC/DC converter for the battery branch, DscA second bidirectional DC/DC converter duty cycle for the supercapacitor leg;
after power distribution, dividing the command power by voltage respectively to obtain corresponding command current, and obtaining a duty ratio after PI;
the comparator is used for changing the working mode, when the comparator 1 works and the comparator 2 does not work, the bidirectional DC/DC converter works in a BOOST state; when the comparator 1 does not work and the comparator 2 works, the bidirectional DC/DC converter works in a BUCK state; the storage battery instruction current controls the first bidirectional DC/DC converter after passing through the PI and the comparator; the super capacitor instruction current controls a second bidirectional DC/DC converter after passing through a PI and a comparator;
when the command current is larger than 0, the hybrid energy storage system works in a BOOST state at the moment and sends out power; when the command current is less than 0, the hybrid energy storage system works in a BOOST state at the moment and absorbs power;
in order to prevent the first bidirectional DC/DC converter and the second bidirectional DC/DC converter from working frequently, when the error between the actual rotating speed and the reference rotating speed is small, namely the command current is small, the first bidirectional DC/DC converter and the second bidirectional DC/DC converter are in a stop state.
5. The hybrid energy storage system according to claim 1 or 2, characterized in that:
the control strategy of the bidirectional PWM converter is double-loop control of a voltage outer loop and a current inner loop, and the control method after decoupling is as follows:
setting: u shapedc_refIs a reference value of the DC bus voltage, UdcFor dc bus voltageValue of, Id_refIs a command value of d-axis current, IdIs the actual value of the d-axis current, Iq_refIs a command value of q-axis current, IqIs the actual value of the q-axis current, ω L is the filter inductance equivalent impedance, Ud_refCommand value of d-axis voltage, UdIs the actual value of the d-axis voltage, Uq_refIs a command value of q-axis voltage, UqIs the actual value of the q-axis voltage;
when the hybrid energy storage system is in a discharge mode, the voltage of the direct current bus capacitor is increased, and U isdc_ref－Udc< 0, command current Id_refIf the output voltage is less than 0, the bidirectional PWM converter is in an inversion mode and sends power to the diesel generator set;
when the hybrid energy storage system is in a charging mode, the voltage of the direct current bus capacitor is reduced, and U isdc_ref－Udc> 0, command current Id_refIf the voltage is more than 0, the bidirectional PWM converter is in a rectification mode and absorbs power from the diesel generator set;
when the total power of the hybrid energy storage system is constant, the parameters of the PI controller and the time constant tau in the LPF are changed by detecting the SOC of the storage battery and the super capacitor and the charging and discharging states of the system,
setting a discharge dead zone threshold of the SOC to the SOCminI.e. when SOCi(i = bat (battery) or sc (super capacitor)) < SOCminIn time, the storage battery and the super capacitor can only be charged and can not be discharged;
setting a discharge buffer threshold of the SOC to be the SOClowI.e. when SOCmin＜SOCi＜SOClowIn the process, the storage battery and the super capacitor are normally charged, and the discharge power is reduced;
setting a charging dead zone threshold of the SOC to the SOCmaxI.e. when SOCmax＜SOCiIn time, the storage battery and the super capacitor cannot be charged and only can be discharged;
setting a threshold of a charging alleviation area of the SOC to the SOChighI.e. when SOChigh＜SOCi＜SOCmaxIn the process, the charging power of the storage battery and the super capacitor is reduced, and the storage battery and the super capacitor are discharged normally;
when SOC is reachedlow＜SOCi＜SOChighAnd in the process, the storage battery and the super capacitor are charged and discharged normally.
6. The power-optimized distribution control method of the hybrid energy storage system according to claim 1 or 2, characterized in that:
Phess_reffor the total command power, P, of the hybrid energy storage systembat_refFor commanding power of the accumulator, Psc_refCommanding power for the super capacitor;
(1) When SOC is reachedbat＜SOCminAnd P ishess_refWhen the voltage is more than 0, the first bidirectional DC/DC converter switch of the storage battery is closed to be in a shutdown state, and the PI parameter is reduced to enable Psc_ref＝Phess_ref；
(2) When SOC is reachedsc＜SOCminAnd P ishess_refWhen the current is more than 0, the second bidirectional DC/DC converter switch of the super capacitor is closed to enable the super capacitor to be in a shutdown state, and meanwhile, the PI parameter is reduced to enable P to bebat_ref＝Phess_ref；
(3) When SOC is reachedmin＜SOCbat、SOCsc＜SOClowAnd P ishess_refWhen the parameter is more than 0, the PI parameter is reduced, and the tau is unchanged;
(4) When the SOC ismin＜SOCbat＜SOClow，SOCsc＞SOClowAnd P ishess_refWhen the PI parameter is more than 0, the PI parameter is unchanged, and tau is reduced;
(5) When SOC is reachedmin＜SOCsc＜SOClow，SOCbat＞SOClowAnd P ishess_refWhen the PI parameter is more than 0, the PI parameter is unchanged, and tau is increased;
(6) When SOC is reachedhigh＜SOCsc＜SOCmax，SOCbat＜SOChighAnd P ishess_refWhen the PI parameter is less than 0, the PI parameter is unchanged, and tau is increased;
(7) When SOC is reachedhigh＜SOCbat＜SOCmax，SOCsc＜SOChighAnd P ishess_refWhen the PI parameter is less than 0, the PI parameter is unchanged, and tau is reduced;
(8) When SOC is reachedhigh＜SOCbat、SOCsc＜SOCmaxAnd P ishess_refWhen the parameter is less than 0, the PI parameter is reduced, and the tau is unchanged;
(9) When SOC is reachedmax＜SOCbatAnd P ishess_refWhen the current is less than 0, the bidirectional DC/DC switch of the storage battery is closed to be in a shutdown state, and meanwhile, the PI parameter is reduced to enable Psc_ref＝Phess_ref；
(10) When SOC is reachedmax＜SOCscAnd P ishess_refWhen the current is less than 0, the bidirectional DC/DC switch of the super capacitor is closed to be in a shutdown state, and meanwhile, PI parameters are reduced to enable P to be in a shutdown statebat_ref＝Phess_ref；
Of course, when there is no fluctuation in the load, the bidirectional PWM converter, and the hybrid energy storage system power distribution may be turned off, and given the command power, the following is satisfied:
Pbat_ref+Psc_ref＝0 (6)。
7. the power-optimized distribution control method of the hybrid energy storage system according to claim 1 or 2, characterized in that:
(1) the method comprises the following steps When SOC is reachedbat＜SOCminAnd SOCsc＞SOChighWhen it is, let Psc_ref> 0, i.e. the supercapacitor discharges, at which time Pbat_refIf less than 0, the storage battery is charged, so that the storage battery is separated from a discharge dead zone;
(2) the method comprises the following steps When the SOC issc＜SOCminAnd SOCbat＞SOChighWhen it is, let PbatGreater than 0, i.e. battery discharge, at which time Psc_refIf the voltage is less than 0, the super capacitor is charged, so that the super capacitor is separated from a discharge dead zone;
(3) the method comprises the following steps When SOC is reachedbat＞SOCmaxAnd SOCsc＜SOClowWhen it is, let PbatGreater than 0, i.e. battery discharge, at which time Psc_refIf the voltage is less than 0, the super capacitor is charged, so that the storage battery is separated from a charging dead zone;
(4) the method comprises the following steps When SOC is reachedsc＞SOCmaxAnd SOCbat＜SOClowWhen it is, let Psc_ref> 0, i.e. the supercapacitor discharges, at which time Pbat_refLess than 0, the storage battery is charged to separate the super capacitorA charging dead zone.
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| CN117175646A (en) * | 2023-11-02 | 2023-12-05 | 国网江西省电力有限公司电力科学研究院 | Energy storage participation primary frequency modulation control method and system for hybrid energy storage system |
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