CN110635511A - Photovoltaic energy storage hybrid system and control method thereof - Google Patents
Photovoltaic energy storage hybrid system and control method thereof 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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
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Abstract
The invention discloses a photovoltaic energy storage hybrid system and a control method thereof, wherein the photovoltaic energy storage hybrid system comprises a photovoltaic power generation device, an energy storage device, a direct current bus, a first DC/DC converter, a first controller for controlling the output of the first DC/DC converter, a second DC/DC converter arranged between the energy storage device and a linear bus, a second controller for controlling the second DC/DC converter to stabilize the voltage of the direct current bus, a DC/AC converter arranged between the linear bus and the tail end of a power distribution network, and a third controller for controlling the DC/AC converter. The second controller can control the second DC/DC converter according to the comparison result by detecting the voltage reflected on the direct current bus and comparing the voltage with the preset reference voltage, so that the energy storage device is charged or discharged, the voltage of the direct current bus is recovered to the reference voltage, the voltage at the tail end of the power distribution network is kept stable, and the electric energy quality of a user at the tail end of the power distribution network is greatly improved.
Description
Technical Field
The invention relates to the field of electric energy quality control, in particular to a photovoltaic energy storage hybrid system and a control method thereof.
Background
In the past, power companies have focused on the management of the power quality problem of medium and high voltage systems, and have paid less attention to the power quality problem of low voltage distribution networks (mainly focusing on the short-term voltage sag and swelling (such as DVR, UPS and the like) problems of low voltage distribution networks), especially rural low voltage distribution networks. The problem of terminal voltage in low voltage distribution networks is generally divided into high voltage and low voltage. For the high voltage problem at the end of the low distribution network, the main reasons are: 1) the cable lines are largely used in the urban power grid; 2) the load power factor is too low; 3) mass access to distributed power. The high voltage at the end easily causes the temperature rise of the electric equipment and even causes the damage of the equipment, and affects the power transmission from the power grid to the load, and may cause the system breakdown. For the low voltage problem at the end of the low distribution network, the main reasons are: 1) the power load is obvious in seasonality and scattered and far away from a power supply point, and the peak-valley difference is large; 2) the line is long, the sectional area of the lead is insufficient, the power supply radius is large, and the three-phase imbalance is serious. And the low voltage at the tail end can influence the normal operation of the equipment, shorten the service life of the equipment and cause great loss for both users and power companies.
The main means adopted to solve the problem of terminal high pressure at present are as follows: on one hand, the grid-connected power factor is managed and controlled, the method does not need investment, has good effect and does not consider the reactive condition of the load; on the other hand, an inductive reactive power compensation device such as a shunt reactor is arranged, so that overvoltage can be effectively suppressed, switching and maintenance are not very convenient, and line loss can be increased under certain conditions. The treatment measures for the problem of low pressure at the tail end are as follows: 1) the power grid structure is optimized, the power quality of a large area can be improved, but certain investment is needed; 2) reactive compensation, such as a parallel passive capacitor, can realize reactive balance and improve reactive voltage level, but has no system capacity evaluation standard and difficulty in equipment switching and maintenance, and is difficult to apply to a power grid with numerous nodes and a complex structure; active power electronic devices such as SVG (scalable vector graphics) and the like are arranged, so that inductive and capacitive reactive dynamic smooth adjustment can be realized, but equipment maintenance is difficult, and reliability is not high; 3) the automatic on-load voltage regulation of distribution transformer, the two-way regulation that carries on that can be fine, the pressure regulating range is wide, and load bearing capacity is strong, and steady voltage effect is comparatively ideal, nevertheless needs real-time regulation, frequent operation, has increased the maintenance cost.
In the field of photovoltaic systems, a photovoltaic grid connection generally adopts a DC-DC-AC type topology, a front-stage DC-DC converter of the structure realizes the maximum energy tracking of a photovoltaic power generation device by adopting an MPPT controller and provides proper direct-current bus voltage, a rear-stage DC-AC converter completes grid connection power supply, and the electric energy obtained by the photovoltaic power generation device can be completely injected into a power distribution network by stabilizing a middle direct-current bus current.
Disclosure of Invention
The invention aims to provide a photovoltaic energy storage hybrid system and a control method thereof, which can realize stable and controllable output power of the photovoltaic energy storage hybrid system and match with the load power at the tail end of a power distribution network, thereby improving the electric energy quality at the tail end of the power distribution network.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
a photovoltaic energy storage hybrid system is arranged at the tail end of a power distribution network and comprises a photovoltaic power generation device, an energy storage device, a direct current bus, a first DC/DC converter arranged between the photovoltaic power generation device and the direct current bus, a first controller used for controlling the first DC/DC converter to enable the photovoltaic power generation device to generate power with the maximum power and output the power to the direct current bus, a second DC/DC converter arranged between the energy storage device and a linear bus, a second controller used for controlling the second DC/DC converter to enable the voltage of the direct current bus to be stable, a DC/AC converter arranged between the linear bus and the tail end of the power distribution network and a third controller used for controlling the DC/AC converter to enable the tail end of the power distribution network to output stably.
When the load at the tail end of the power distribution network is changed greatly, the second controller can control the second DC/DC converter according to the comparison result by detecting the voltage reflected on the DC bus and comparing the voltage with the preset reference voltage, so that the energy storage device is charged or discharged, the voltage of the DC bus is recovered to the reference voltage, and the voltage at the tail end of the power distribution network is kept stable. Therefore, the technical scheme can greatly improve the electric energy quality of the end users of the power distribution network.
Moreover, the technical scheme ensures that the direct current bus is kept stable, namely a constant voltage source is provided for the tail end of the power distribution network, so that the capacity of a network side transformer of the power distribution network can be reduced, and the transformer is prevented from being in an overload state in a load peak period.
In addition, the energy storage device of the technical scheme can enhance the controllability of the reactive component of the system pair, compensate the reactive power at the tail end of the power distribution network line and improve the power factor of the power distribution network.
Furthermore, the third controller adopts a double closed-loop control structure, the outer ring is a voltage ring, and the inner ring is a grid-connected current ring;
the voltage loop is used for comparing the actual active component of the alternating voltage at the tail end of the power distribution network with a reference value of the actual active component of the alternating voltage, and adjusting the deviation value by adopting proportional integral to be used as a reference value of the active component of the current of the grid-connected current loop;
the voltage loop is also used for comparing the actual alternating voltage reactive component at the tail end of the power distribution network with a reference value thereof, and adjusting the deviation value by adopting proportional integral to be used as a current reactive component reference value of the grid-connected current loop;
the grid-connected current loop is used for carrying out dq decoupling control according to actual alternating voltage active and reactive components at the tail end of the power distribution network, current active and reactive components and current active and reactive component reference values of the outer ring voltage loop so as to generate pulse width modulation signals;
and the pulse width modulation signal is used for controlling the active and reactive components output by the DC/AC converter.
The actual alternating voltage and current at the tail end of the power distribution network are directly collected to carry out double closed-loop control, active and reactive components of compensation power required by a user load at the tail end of the power distribution network can be reasonably distributed and tracked, the output power of the photovoltaic energy storage hybrid system is stable and controllable when the photovoltaic energy storage hybrid system is connected with the power distribution network, the output power is matched with the user load power, and the problem of high and low voltages at the tail end of the power distribution network is finally solved.
Furthermore, the second DC/DC converter adopts a boost-buck circuit, the voltage from the direct current bus to the energy storage device is reduced, and the voltage from the energy storage device to the direct current bus is increased; the second controller is used for controlling the boost/buck boost-buck circuit to charge or discharge the energy storage device by comparing the voltage of the direct current bus with a preset reference voltage, so that the voltage of the direct current bus is stabilized at the preset reference voltage.
Furthermore, the first controller adopts an MPPT control structure, and the maximum utilization of solar energy can be realized.
Further, the operational objective function of the system is:
minf＝minC＝min(Cpv+Cbat+CF+λ△P)；
in the above formula, λ is a parameter for unifying dimensions, CbatRepresenting the cost of the energy storage device, CpvRepresenting the cost of the photovoltaic power generation device, wherein Delta P is the line loss of the photovoltaic energy storage hybrid system, CFRepresents the electricity purchase cost, and has:
CF＝∑PloadK-∑(Ppv+Pbat)K；
in the above formula, K is the electric charge per unit power for each period, PpvIs the output power of the photovoltaic power generation device; pbatIs the output power of the energy storage device, negative when charging, positive when discharging; ploadIs the load consumption power at the end of the distribution network;
wherein, energy storage device satisfies the following condition:
Pbat+Ppv+Pgrid＝Pload；
Smin≤Sbat≤Smax；Ich≤Ichmax,Idch≤Idchmax；
Umin≤Ubat≤Umax；
wherein E isbatRepresenting the capacity of the energy storage device, n2Days of autonomy for the energy storage device; e1(i) Is the daily load consuming power; n is1The number of days of recovery of the energy storage device; e2(i) The average daily electric quantity surplus of the energy storage device; pgridIs the power P provided by the end of the distribution network for the current loadload；Sbat、Smin、SmaxRespectively representing the actual state of charge, the preset minimum state of charge, the preset maximum state of charge, U, of the energy storage devicebat、Umin、UmaxRespectively representing the actual terminal voltage, the preset minimum terminal voltage and the preset maximum terminal voltage of the energy storage device, Ich、IchmaxRespectively representing the actual charging current and the preset maximum charging current, I, of the energy storage devicedch、IdchmaxRespectively representing the actual discharge current and the preset maximum discharge current of the energy storage device.
When the system runs the objective function, the photovoltaic energy storage hybrid system can be expected to run in a state with the lowest total cost, so that the photovoltaic energy storage hybrid system achieves the maximum benefit aim.
The invention also provides a control method for the photovoltaic energy storage hybrid system, which comprises the following steps:
collecting actual alternating voltage and current at the tail end of the power distribution network, respectively carrying out dq decomposition, and separating the amplitude and the phase of the alternating voltage and the amplitude and the phase of the current; the amplitude and the phase of the alternating voltage are respectively an active component and a reactive infinite of the alternating voltage, and the amplitude and the phase of the current are respectively an active component and a reactive infinite of the current;
comparing the actual active component of the alternating voltage at the tail end of the power distribution network with a reference value of the actual active component of the alternating voltage, and adjusting the deviation value by adopting proportional integral to be used as a reference value of the active component of the current of the grid-connected current loop;
comparing the actual reactive component of the alternating voltage at the tail end of the power distribution network with a reference value of the reactive component, and adjusting the deviation value by adopting proportional integral to be used as a reference value of the reactive component of the current of the grid-connected current loop;
carrying out dq decoupling control according to the actual active and reactive components of the alternating voltage at the tail end of the power distribution network, the active and reactive components of the current and the reference values of the active and reactive components of the current provided by the outer ring voltage loop so as to generate pulse width modulation signals;
and controlling active and reactive components output by the DC/AC converter by using the pulse width modulation signal, and performing power compensation on the tail end of the power distribution network.
Furthermore, the second DC/DC converter adopts a boost-buck circuit, the voltage from the direct current bus to the energy storage device is reduced, and the voltage from the energy storage device to the direct current bus is increased;
the second controller judges whether the voltage of the direct-current bus is greater than a preset reference voltage, and if so, the boost/buck circuit is controlled to enable the linear bus to charge the energy storage device; if not, controlling the boost/buck boost circuit to enable the energy storage device to discharge to the direct current bus.
Further, the objective function for controlling the operation of the photovoltaic energy storage hybrid system is as follows:
minf＝minC＝min(Cpv+Cbat+CF+λ△P)；
in the above formula, λ is a parameter for unifying dimensions, CbatRepresenting the cost of the energy storage device, CpvRepresenting the cost of the photovoltaic power generation device, wherein Delta P is the line loss of the photovoltaic energy storage hybrid system, CFRepresents the electricity purchase cost, and has:
CF＝∑PloadK-∑(Ppv+Pbat)K；
in the above formula, K is the electric charge per unit power for each period, PpvIs the output power of the photovoltaic power generation device; pbatIs the output power of the energy storage device, negative when charging, positive when discharging; ploadIs the load consumption power at the end of the distribution network;
wherein, energy storage device satisfies the following condition:
Pbat+Ppv+Pgrid＝Pload；
Smin≤Sbat≤Smax；Ich≤Ichmax,Idch≤Idchmax；
Umin≤Ubat≤Umax；
wherein E isbatRepresenting the capacity of the energy storage device, n2Days of autonomy for the energy storage device; e1(i) Is the daily load consuming power; n is1The number of days of recovery of the energy storage device; e2(i) The average daily electric quantity surplus of the energy storage device; pgridIs the power P provided by the end of the distribution network for the current loadload；Sbat、Smin、SmaxRespectively representing the actual state of charge, the preset minimum state of charge, the preset maximum state of charge, U, of the energy storage devicebat、Umin、UmaxRespectively representing the actual terminal voltage, the preset minimum terminal voltage and the preset maximum terminal voltage of the energy storage device, Ich、IchmaxRespectively representing the actual charging current and the preset maximum charging current, I, of the energy storage devicedch、IdchmaxRespectively representing the actual discharge current and the preset maximum discharge current of the energy storage device.
Advantageous effects
In the invention, when the load at the tail end of the power distribution network is changed greatly, the second controller can control the second DC/DC converter according to the comparison result by detecting the voltage reflected on the DC bus and comparing the voltage with the preset reference voltage, so that the energy storage device is charged or discharged, the voltage of the DC bus is recovered to the reference voltage, and the voltage at the tail end of the power distribution network is kept stable. Therefore, the technical scheme can greatly improve the electric energy quality of the end users of the power distribution network.
Moreover, the technical scheme ensures that the direct current bus is kept stable, namely a constant voltage source is provided for the tail end of the power distribution network, so that the capacity of a network side transformer of the power distribution network can be reduced, and the transformer is prevented from being in an overload state in a load peak period.
In addition, the energy storage device of the technical scheme can enhance the controllability of the reactive component of the system pair, compensate the reactive power at the tail end of the power distribution network line and improve the power factor of the power distribution network.
Drawings
FIG. 1 is a topological structure diagram of a photovoltaic energy storage hybrid system according to the present invention;
FIG. 2 is an equivalent circuit of the photovoltaic energy storage hybrid system of the present invention;
FIG. 3 is a general diagram of the charging and discharging circuit of the energy storage device according to the present invention;
FIG. 4 is an energy storage device charging circuit of the present invention;
FIG. 5 is an energy storage device charging control according to the present invention;
FIG. 6 is an energy storage device discharge circuit of the present invention;
FIG. 7 is an energy storage device discharge control of the present invention;
FIG. 8 is a control diagram of the preceding DC/DC control in the present invention, i.e. the first controller;
FIG. 9 is a control diagram of a later stage DC/AC grid-connected control chart, i.e. a control schematic diagram of a third controller, according to the present invention;
fig. 10 is a decoupling control diagram of the grid-connected current inner loop of the third controller in the present invention.
Detailed Description
The following describes embodiments of the present invention in detail, which are developed based on the technical solutions of the present invention, and give detailed implementation manners and specific operation procedures to further explain the technical solutions of the present invention.
Aiming at the technical problems of the photovoltaic system in the prior art, namely: the photovoltaic energy storage hybrid system and the control method thereof can solve the problems that stable and reliable power supply cannot be provided for the power distribution network, the fluctuation of power transmission is aggravated on the contrary, the high-low voltage problem at the tail end of the power distribution network is more outstanding, and the later-stage DC-AC converter is in a pure functional quantity injection form and does not have the capability of carrying out reactive power regulation on the power distribution networkThe active output controllability of the photovoltaic power generation system is increased by entering an energy storage device, and a photovoltaic energy storage hybrid topological structure with controllable DC-DC/energy storage-AC output active and reactive power is formed, so that the photovoltaic energy storage hybrid topological structure can be complementary with load power, and the stability of the transmission power at the tail end of a power distribution network is improved; further, a certain output power control strategy is matched so as to regulate the line voltage drop in real time:
compared with the voltage regulation of an on-load transformer, the problem of high and low voltages at the tail end of the power distribution network is solved in the fundamental power link. The following is an explanation with reference to the examples.
The first embodiment is as follows:
the embodiment provides a photovoltaic energy storage hybrid system, which is arranged at the end of a power distribution network as shown in fig. 1, and includes a photovoltaic power generation device, an energy storage device, a direct current bus, a first DC/DC converter arranged between the photovoltaic power generation device and the direct current bus, a first controller for controlling the first DC/DC converter to enable the photovoltaic power generation device to generate power with the maximum power and output the power to the direct current bus, a second DC/DC converter arranged between the energy storage device and the linear bus, a second controller for controlling the second DC/DC converter to enable the voltage of the direct current bus to be stable, a DC/AC converter arranged between the linear bus and the end of the power distribution network, and a third controller for controlling the DC/AC converter to enable the end of the power distribution network to output stably.
The first DC/DC converter and the controller are configured to control the first DC/DC converter to enable the photovoltaic power generation device to output the maximum power to the DC bus by detecting the generated voltage of the solar panel in real time and tracking the maximum voltage and current value as shown in fig. 8.
The second DC/DC converter adopts a boost/buck boost circuit, as shown in fig. 3, the voltage from the DC bus to the energy storage device is reduced, and the voltage from the energy storage device to the DC bus is increased; the control end of a switch tube in the boost/buck boost circuit is connected with a second controller, and the second controller compares the voltage of the direct current bus with a preset reference voltage to control the switch-off or switch-on of the switch tube in the boost/buck boost circuit to enable the energy storage device to charge or discharge, so that the voltage of the direct current bus is stabilized at the preset reference voltage.
Specifically, when the voltage of the dc bus is greater than the preset reference voltage, the switching tube T2 is controlled to be turned off, the on duty ratio α of the switching tube T1 is controlled, as shown in fig. 4, so that the energy storage device is charged, and the dc bus voltage is restored to the preset reference voltage, and there are:
where T is the switching period of the switching tube T1, α is the on duty cycle of the switching tube T1, and the control signal of the on duty cycle α is obtained by the second controller shown in fig. 5.
The second controller shown in FIG. 5 utilizes the voltage U of the DC busdcAnd a predetermined reference voltage
A double closed-loop control structure of a voltage outer loop and a current inner loop is adopted to obtain a control signal for controlling the on duty ratio alpha of T1.
When the voltage of the dc bus is less than the preset reference voltage, the switching tube T1 is controlled to turn off, the turn-off duty ratio β of the switching tube T2 is controlled, as shown in fig. 6, the energy storage device is discharged, and the dc bus voltage is restored to the preset reference voltage, and the method includes:
where T is the switching period of the switching tube T2, β is the turn-off duty cycle of the switching tube T2, and the control signal of the turn-off duty cycle β is obtained by the second controller shown in fig. 7.
The second controller shown in FIG. 7 utilizes the voltage U of the DC busdcAnd a predetermined reference voltage
Using outer rings of voltage and electricityA double closed loop control structure of the inner loop of the flow to obtain a control signal for controlling the off duty ratio beta of T2.
When low voltage appears at the tail end of a conventional power distribution network, the photovoltaic energy storage hybrid system needs to provide reactive and active support for the tail end of the power distribution network so as to reduce the active and reactive power of loads absorbed from a power distribution network line, reduce the network loss voltage and improve the voltage provided by the tail end of the power distribution network for users. When the photovoltaic energy storage hybrid system is connected to realize the voltage stability of the terminal user, the second controller can control the energy storage device to charge and discharge so that the voltage of the direct current bus is kept unchanged, namely, the voltage is connected to a constant voltage source (see fig. 2), and the current flowing into the user connection point of the power distribution network is unchanged at the moment, namely, the power P provided by the power distribution network to the load is unchangedgridInvariable (P)gridGenerally, the transformer capacity at the network side is reduced, the transformer is prevented from being in an overload state in the load peak period, and when the load (the power required for driving the load to work) is greatly changed, the power difference P between the load and the transformerload-PgridProvided by a photovoltaic energy storage hybrid system, wherein PloadRepresenting the power consumed by the load. Due to the output power P of the photovoltaic power generation devicepvDependent on the current weather, so that the power P is outputpvUnstable, and generally associated with Pload-PgridIn contrast, the output power P of the photovoltaic energy storage hybrid system needs to be matched with the charging and discharging of the energy storage devicepv+PbatAnd Pload-PgridAnd (4) matching. When the battery capacity is sufficient, P ispv>Pload-PgridAt this time Pbat<0, DC bus voltage UdcGradually increasing, in order to inhibit the voltage of the direct current bus from excessively increasing, the second controller controls the energy storage device to charge, so that redundant power is input into the energy storage device to store energy, and the energy storage device is equivalent to a load at the moment; when P is presentpv<Pload-PgridAt this time Pbat>0, DC bus voltage UdcAnd gradually descending, the second controller controls the boost/buck boost circuit to discharge the energy storage device to supplement the power required by the load, and the energy storage device is equivalent to a power supply at the moment.
When high voltage appears at the tail end of the power distribution network, the photovoltaic energy storage hybrid system absorbs partial active power and reactive power provided by the power distribution network, and maintains certain active power and reactive power transmission quantity of a power distribution network line, so that the tail end voltage of the power distribution network is reduced. When the photovoltaic energy storage hybrid system is connected to realize the stable and constant voltage of a terminal user, if the load is greatly changed, the power difference P between the load and the terminal userload-PgridAbsorbed by the photovoltaic energy storage hybrid system, P in FIG. 2s、QsIs a negative number. And controlling the energy storage device to charge at the moment, so that redundant power of the power distribution network is input into the energy storage device to be stored, and the energy storage device is equivalent to a load at the moment.
Wherein the DC bus reference voltage is set to 400V.
The third controller adopts a double closed-loop control structure, as shown in fig. 9, the outer loop is a voltage loop, the inner loop is a grid-connected current loop, and the voltage stabilization of the tail end is realized by carrying out amplitude limiting control on the actual alternating voltage at the tail end of the power distribution network;
the voltage loop is used for comparing the actual active component of the alternating voltage at the tail end of the power distribution network with a reference value of the actual active component of the alternating voltage, and adjusting the deviation value by adopting proportional integral to be used as a reference value of the active component of the current of the grid-connected current loop;
the voltage loop is also used for comparing the actual alternating voltage reactive component at the tail end of the power distribution network with a reference value thereof, and adjusting the deviation value by adopting proportional integral to be used as a current reactive component reference value of the grid-connected current loop;
the grid-connected current loop, as shown in fig. 9 and 10, is configured to perform dq decoupling control according to actual AC voltage active and reactive components at the end of the power distribution network, current active and reactive components, and current active and reactive component reference values of the outer ring voltage loop, so as to generate a pulse width modulation signal, so as to control the active and reactive components output by the DC/AC converter, provide power compensation for a user load at the end of the power distribution network, and avoid a high-low voltage problem at the end of the power distribution network.
In addition, the photovoltaic energy storage hybrid system of the embodiment integrates the operation objective function of the control conditions as follows:
minf＝minC＝min(Cpv+Cbat+CF+λ△P) (3)；
in the above formula, λ is a parameter for unifying dimensions, CbatRepresenting the cost of the energy storage device, CpvRepresenting the cost of the photovoltaic power generation device, wherein Delta P is the line loss of the photovoltaic energy storage hybrid system, CFRepresents the electricity purchase cost, and has:
CF＝∑PloadK-∑(Ppv+Pbat)K (4)；
in the above formula, K is the electricity charge per unit power for each period, including the peak-valley period; ppvIs the output power of the photovoltaic power generation device; pbatIs the output power of the energy storage device, negative when charging, positive when discharging; ploadIs the load consumption power at the end of the distribution network;
wherein, the energy storage device satisfies the following constraint conditions:
1) minimum capacity constraint: when the photovoltaic power generation device generates insufficient power or no light causes no output of the photovoltaic power generation device, the photovoltaic energy storage hybrid system provides electric energy from the energy storage device, so that the capacity of the energy storage device is larger than that of the energy storage device
The continuity of power supply of the photovoltaic energy storage hybrid system can be ensured only by the formula (5);
in the formula, EbatRepresenting the capacity of the energy storage device, n1Number of days of recovery of energy storage device, E1(i) Is the daily load consuming power;
2) maximum capacity constraint: the energy storage device stores surplus energy of the photovoltaic power generation device and surplus electric energy of high voltage caused by a power distribution network, in order to avoid too many energy storage devices configured in the system, the maximum capacity of the energy storage device should not exceed surplus electric energy, and the formula (6) shows that:
in the formula, n2Days of autonomy for the energy storage device; e2(i) The average daily electric quantity surplus of the energy storage device;
3) and power balance constraint: at the intersection of the photovoltaic energy storage hybrid system, the power distribution network and the user side load, the node power balance constraints are as follows:
Pbat+Ppv+Pgrid＝Pload (7)；
in the formula, PpvIs the output power of the photovoltaic power generation device; pbatIs the output power of the energy storage device, negative when charging, positive when discharging; ploadIs the power consumed by the load; pgridThe power flowing to the node from the power grid, namely the power provided by the power distribution grid to the load;
3) and (3) charge and discharge restraint: considering the relevant characteristics of the energy storage device and reasonably using the energy storage device, the terminal voltage U of the energy storage device is used in the operation of the photovoltaic energy storage hybrid systembatCharge and discharge current (I)ch、Idch) State of charge SbatShould be within certain limits, expressed as:
Smin≤Sbat≤Smax (8)；
Ich≤Ichmax,Idch≤Idchmax (9)；
Umin≤Ubat≤Umax (10)；
in the formula, Sbat、Smin、SmaxRespectively representing the actual state of charge, the preset minimum state of charge, the preset maximum state of charge, U, of the energy storage devicebat、Umin、UmaxRespectively representing the actual terminal voltage, the preset minimum terminal voltage and the preset maximum terminal voltage of the energy storage device, Ich、IchmaxRespectively representing the actual charging current and the preset maximum charging current, I, of the energy storage devicedch、IdchmaxRespectively representing the actual discharge current and the preset maximum discharge current of the energy storage device.
The operation objective function (3) of the photovoltaic energy storage hybrid system of the embodiment is equivalent to the expectation that the photovoltaic energy storage hybrid system can operate in a state with the lowest total cost, so that the photovoltaic energy storage hybrid system achieves the maximum profit.
Example two:
the second embodiment correspondingly provides a control method for the photovoltaic energy storage hybrid system of the first embodiment, which includes the following steps:
collecting actual alternating voltage and current at the tail end of the power distribution network, respectively carrying out dq decomposition, and separating the amplitude and the phase of the alternating voltage and the amplitude and the phase of the current; the amplitude and the phase of the alternating voltage are respectively an active component and a reactive infinite of the alternating voltage, and the amplitude and the phase of the current are respectively an active component and a reactive infinite of the current;
comparing the actual active component of the alternating voltage at the tail end of the power distribution network with a reference value of the actual active component of the alternating voltage, and adjusting the deviation value by adopting proportional integral to be used as a reference value of the active component of the current of the grid-connected current loop;
comparing the actual reactive component of the alternating voltage at the tail end of the power distribution network with a reference value of the reactive component, and adjusting the deviation value by adopting proportional integral to be used as a reference value of the reactive component of the current of the grid-connected current loop;
carrying out dq decoupling control according to the actual active and reactive components of the alternating voltage at the tail end of the power distribution network, the active and reactive components of the current and the reference values of the active and reactive components of the current provided by the outer ring voltage loop so as to generate pulse width modulation signals;
and controlling active and reactive components output by the DC/AC converter by using the pulse width modulation signal, and performing power compensation on the tail end of the power distribution network.
The second DC/DC converter adopts a boost/buck boost-buck circuit, the voltage from the direct current bus to the energy storage device is reduced, and the voltage from the energy storage device to the direct current bus is increased;
the second controller judges whether the voltage of the direct-current bus is greater than a preset reference voltage, and if so, the boost/buck circuit is controlled to enable the linear bus to charge the energy storage device; if not, controlling the boost/buck boost circuit to enable the energy storage device to discharge to the direct current bus.
In addition, the objective function and the corresponding technical effect for controlling the operation of the photovoltaic energy storage hybrid system in the embodiment are the same as those in the first embodiment, and are not repeated herein.
The above embodiments are preferred embodiments of the present application, and those skilled in the art can make various changes or modifications without departing from the general concept of the present application, and such changes or modifications should fall within the scope of the claims of the present application.
Claims (8)
1. The photovoltaic energy storage hybrid system is characterized by being arranged at the tail end of a power distribution network and comprising a photovoltaic power generation device, an energy storage device, a direct current bus, a first DC/DC converter arranged between the photovoltaic power generation device and the direct current bus, a first controller used for controlling the first DC/DC converter to enable the photovoltaic power generation device to generate power with the maximum power and output the power to the direct current bus, a second DC/DC converter arranged between the energy storage device and the linear bus, a second controller used for controlling the second DC/DC converter to enable the voltage of the direct current bus to be stable, a DC/AC converter arranged between the linear bus and the tail end of the power distribution network and a third controller used for controlling the DC/AC converter to enable the tail end of the power distribution network to output stably.
2. The system of claim 1, wherein the third controller is in a dual closed loop control configuration, the outer loop is a voltage loop and the inner loop is a grid-connected current loop;
the voltage loop is used for comparing the actual active component of the alternating voltage at the tail end of the power distribution network with a reference value of the actual active component of the alternating voltage, and adjusting the deviation value by adopting proportional integral to be used as a reference value of the active component of the current of the grid-connected current loop;
the voltage loop is also used for comparing the actual alternating voltage reactive component at the tail end of the power distribution network with a reference value thereof, and adjusting the deviation value by adopting proportional integral to be used as a current reactive component reference value of the grid-connected current loop;
the grid-connected current loop is used for carrying out dq decoupling control according to actual alternating voltage active and reactive components at the tail end of the power distribution network, current active and reactive components and current active and reactive component reference values of the outer ring voltage loop so as to generate pulse width modulation signals;
and the pulse width modulation signal is used for controlling the active and reactive components output by the DC/AC converter.
3. The system of claim 1, wherein the second DC/DC converter employs a boost/buck boost circuit, with a buck from the DC bus to the energy storage device and a boost from the energy storage device to the DC bus; the second controller is used for controlling the boost/buck boost-buck circuit to charge or discharge the energy storage device by comparing the voltage of the direct current bus with a preset reference voltage, so that the voltage of the direct current bus is stabilized at the preset reference voltage.
4. The system of claim 1, wherein the first controller employs an MPPT control architecture.
5. The system of claim 1, wherein the operational objective function is:
minf＝minC＝min(Cpv+Cbat+CF+λ△P)；
in the above formula, λ is a parameter for unifying dimensions, CbatRepresenting the cost of the energy storage device, CpvRepresenting the cost of the photovoltaic power generation device, wherein Delta P is the line loss of the photovoltaic energy storage hybrid system, CFRepresents the electricity purchase cost, and has:
CF＝∑PloadK-∑(Ppv+Pbat)K；
in the above formula, K is the electric charge per unit power for each period, PpvIs the output power of the photovoltaic power generation device; pbatIs the output power of the energy storage device, negative when charging, positive when discharging; ploadIs the load consumption power at the end of the distribution network;
wherein, energy storage device satisfies the following condition:
Pbat+Ppv+Pgrid＝Pload；
Smin≤Sbat≤Smax；Ich≤Ichmax,Idch≤Idchmax；
Umin≤Ubat≤Umax；
wherein E isbatRepresenting the capacity of the energy storage device, n2Days of autonomy for the energy storage device; e1(i) Is the daily load consuming power; n is1The number of days of recovery of the energy storage device; e2(i) The average daily electric quantity surplus of the energy storage device; pgridIs the power P provided by the end of the distribution network for the current loadload；Sbat、Smin、SmaxRespectively representing the actual state of charge, the preset minimum state of charge, the preset maximum state of charge, U, of the energy storage devicebat、Umin、UmaxRespectively representing the actual terminal voltage, the preset minimum terminal voltage and the preset maximum terminal voltage of the energy storage device, Ich、IchmaxRespectively representing the actual charging current and the preset maximum charging current, I, of the energy storage devicedch、IdchmaxRespectively representing the actual discharge current and the preset maximum discharge current of the energy storage device.
6. A control method for the photovoltaic energy storage hybrid system according to claim 1, characterized by comprising the following steps:
collecting actual alternating voltage and current at the tail end of the power distribution network, respectively carrying out dq decomposition, and separating the amplitude and the phase of the alternating voltage and the amplitude and the phase of the current; the amplitude and the phase of the alternating voltage are respectively an active component and a reactive infinite of the alternating voltage, and the amplitude and the phase of the current are respectively an active component and a reactive infinite of the current;
comparing the actual active component of the alternating voltage at the tail end of the power distribution network with a reference value of the actual active component of the alternating voltage, and adjusting the deviation value by adopting proportional integral to be used as a reference value of the active component of the current of the grid-connected current loop;
comparing the actual reactive component of the alternating voltage at the tail end of the power distribution network with a reference value of the reactive component, and adjusting the deviation value by adopting proportional integral to be used as a reference value of the reactive component of the current of the grid-connected current loop;
carrying out dq decoupling control according to the actual active and reactive components of the alternating voltage at the tail end of the power distribution network, the active and reactive components of the current and the reference values of the active and reactive components of the current provided by the outer ring voltage loop so as to generate pulse width modulation signals;
and controlling active and reactive components output by the DC/AC converter by using the pulse width modulation signal, and performing power compensation on the tail end of the power distribution network.
7. The method of claim 6, wherein the second DC/DC converter employs a boost/buck boost circuit, with a buck from the DC bus to the energy storage device and a boost from the energy storage device to the DC bus;
the second controller judges whether the voltage of the direct-current bus is greater than a preset reference voltage, and if so, the boost/buck circuit is controlled to enable the linear bus to charge the energy storage device; if not, controlling the boost/buck boost circuit to enable the energy storage device to discharge to the direct current bus.
8. The method of claim 6, wherein the objective function controlling the operation of the photovoltaic energy storage hybrid system is:
minf＝minC＝min(Cpv+Cbat+CF+λ△P)；
in the above formula, λ is a parameter for unifying dimensions, CbatRepresenting the cost of the energy storage device, CpvRepresenting the cost of the photovoltaic power generation device, wherein Delta P is the line loss of the photovoltaic energy storage hybrid system, CFRepresents the electricity purchase cost, and has:
CF＝∑PloadK-∑(Ppv+Pbat)K；
in the above formula, K is the electric charge per unit power for each period, PpvIs the output power of the photovoltaic power generation device; pbatIs the output power of the energy storage device, negative when charging, positive when discharging; ploadIs the load consumption power at the end of the distribution network;
wherein, energy storage device satisfies the following condition:
Pbat+Ppv+Pgrid＝Pload；
Smin≤Sbat≤Smax；Ich≤Ichmax,Idch≤Idchmax；
Umin≤Ubat≤Umax；
wherein E isbatRepresenting the capacity of the energy storage device, n2Days of autonomy for the energy storage device; e1(i) Is the daily load consuming power; n is1The number of days of recovery of the energy storage device; e2(i) The average daily electric quantity surplus of the energy storage device; pgridIs the power P provided by the end of the distribution network for the current loadload；Sbat、Smin、SmaxRespectively representing the actual state of charge, the preset minimum state of charge, the preset maximum state of charge, U, of the energy storage devicebat、Umin、UmaxRespectively representing the actual terminal voltage, the preset minimum terminal voltage and the preset maximum terminal voltage of the energy storage device, Ich、IchmaxRespectively representing the actual charging current and the preset maximum charging current, I, of the energy storage devicedch、IdchmaxRespectively representing the actual discharge current and the preset maximum discharge current of the energy storage device.
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