A kind of power regulating method of hybrid energy-storing photovoltaic plant
Technical field
When the present invention relates to a kind of mixed energy storage system that ultracapacitor and ferric phosphate lithium cell are formed and being applied to large Capacity Optical photovoltaic generating system, the control method of photovoltaic plant active power of output, belong to technical field of power generation.
Background technology
MW class photovoltaic generating system is called again photovoltaic plant, and it is different from existing low capacity photovoltaic generating system, and photovoltaic plant adopts the mode that is incorporated into the power networks conventionally.Owing to being subject to the impact of the natural cause such as intensity of illumination and temperature, in power station, meritorious the exerting oneself of photo-voltaic power supply has larger fluctuation, so direct grid-connected operation can produce a series of problem, as caused, operation of power networks is unstable, power supply quality is poor, participate in dispatching of power netwoks difficulty etc.The effective measures that address the above problem add energy storage device exactly in photovoltaic plant, if energy storage device is functional and control method is proper, can improve the power supply quality of power supply of photovoltaic plant, can make again photovoltaic plant can participate in neatly dispatching of power netwoks, strengthen operation of power networks stability.
At present, the existing mixed energy storage system by the ultracapacitor of passive parallel-connection structure and storage battery formation is used for the Research Literature of low profile photovoltaic electricity generation system.Because battery cycle life is short, frequent high-power low capacity discharges and recharges the useful life that can greatly shorten storage battery, and ultracapacitor has extended cycle life, discharges and recharges, speed is fast, power density is large, this passive parallel-connection structure utilizes ultracapacitor to the storage battery regulating and controlling of charging, can make the charging current of storage battery milder, to extend the useful life of storage battery.But under this frame mode, battery discharging process can not get effective control, can not realize the fine adjustment to ultracapacitor and storage battery power output.The mixed energy storage system of mentioning in document is considered to realize the regulation and control to the photovoltaic plant quality of power supply from structure, can not realize the task of networking photovoltaic plant participation dispatching of power netwoks.
Ferric phosphate lithium cell has larger advantage than conventional accumulators at aspect of performance, and its energy storage density is large, there is no memory effect, aspect charge and discharge cycles number of times, is also being greatly improved.Therefore, the mixed energy storage system of ferric phosphate lithium cell and ultracapacitor composition is connected on the DC bus of photovoltaic plant by delivery of electrical energy controller respectively, in addition corresponding " flexibility " energy-storage system regulating strategy, is highly suitable for power output frequent fluctuation, load change at random, participates in the extremely difficult networking photovoltaic plant of dispatching of power netwoks.The control method of this class mixed energy storage system in photovoltaic plant running is also immature at present, causes the advantage of mixed energy storage system to give full play to, and has greatly limited the promotion and application at home of photovoltaic plant technology.
Summary of the invention
The object of the invention is to overcome prior art defect, provide a kind of and can improve the photovoltaic plant power supply quality of power supply and make photovoltaic plant can participate in the power regulating method of the hybrid energy-storing photovoltaic plant of dispatching of power netwoks.
The alleged problem of the present invention realizes with following technical proposals:
A kind of power regulating method of hybrid energy-storing photovoltaic plant, described method detects in real time its DC bus-bar voltage and the bank of super capacitors being connected with DC bus by two two-way DC/DC controllers respectively and the voltage of lithium battery group in photovoltaic plant running, detecting in real time the meritorious of photo-voltaic power supply exerts oneself, calculate fast the value of exerting oneself that reaches photovoltaic plant quality of power supply goal of regulation and control or complete the required bank of super capacitors of scheduler task and lithium battery group simultaneously, and according to the running status of two two-way DC/DC controllers of result of calculation control, thereby realize the control to bank of super capacitors and lithium battery group charge and discharge process.
The power regulating method of above-mentioned hybrid energy-storing photovoltaic plant, it carries out according to following steps:
A. in photovoltaic plant running, detect in real time the voltage of bank of super capacitors, lithium battery group and DC bus, detect in real time the meritorious of photo-voltaic power supply and exert oneself, and require to determine that according to dispatching of power netwoks the operational mode of the mixed energy storage system being made up of bank of super capacitors and lithium battery group is quality of power supply regulation and control model or initiatively can scheduling method;
B. determining of the mixed energy storage system value of exerting oneself:
If 1. the operational mode of dispatching of power netwoks requirement mixed energy storage system is quality of power supply regulation and control model, be to ensure that the high-quality of DC bus powered system is stable by controlling goal-setting; First judge whether DC bus-bar voltage meets quality of power supply standard-required, if meet quality of power supply standard-required,, the original state of a control of mixed energy storage system is constant; If do not meet quality of power supply standard-required, control law is divided into two kinds: if DC bus-bar voltage, lower than standard min, lower than 95% of rated voltage, is carried out Generation Control to mixed energy storage system; If DC bus-bar voltage is higher than standard max, higher than 105% of rated voltage, to the mixed energy storage system control of charging; The generated output of mixed energy storage system and charge power flow through two-way DC/DC controller I and two-way DC/DC controller II, its size and Orientation of exerting oneself depends on the control method of power electronic device in two-way DC/DC controller I and II;
If DC bus working voltage is U
d, rated voltage is U
n, the impedance of DC bus terminal shortcircuit is X, mixed energy storage system output power ratio control is:
,
If output power ratio control be on the occasion of, expression mixed energy storage system is carried out to Generation Control; If output power ratio control is negative value, represent the mixed energy storage system control of charging;
If 2. to require the operational mode of mixed energy storage system be that active can scheduling method in dispatching of power netwoks, be to meet the photovoltaic power station power generation power planning that dispatching of power netwoks department issues by controlling goal-setting, now the high-quality of DC bus-bar voltage required to be put into back burner; In photovoltaic plant running, according to the exert oneself ruuning situation of bank of super capacitors and lithium battery group in situation, photovoltaic power station power generation plan power, mixed energy storage system of the photo-voltaic power supply detecting in real time, calculate fast mixed energy storage system control strategy, and regulate accordingly; The output power ratio control of mixed energy storage system is:
(P
C+P
B)=P
D-P
V?,
The control law of energy-storage system is: work as P
v<P
dtime, control mixed energy storage system generator operation; Work as P
v=P
dtime, control mixed energy storage system standby operation; Work as P
v>P
dtime, control mixed energy storage system charge operation;
C. under every kind of operational mode, according to the result of calculation of the mixed energy storage system value of exerting oneself, the running status that discharges and recharges of being controlled in real time bank of super capacitors and lithium battery group by two-way DC/DC controller I and two-way DC/DC controller II, realizes the regulation and control of mixed energy storage system to photovoltaic plant running status;
D. under every kind of operational mode, the control of mixed energy storage system is adopted to the mode of " ultracapacitor energy storage unit preferentially charges, preferential discharge ", to reduce the number of times that discharges and recharges of lithium battery, improve the length of service of whole energy-storage system.
The present invention utilizes two two-way DC/DC controllers to discharge and recharge control to bank of super capacitors and lithium battery group, makes mixed energy storage system can participate in neatly the photovoltaic plant adjustment of exerting oneself, realize photovoltaic plant running status fast, accurately regulation and control.Described method can be given full play to the advantage that lithium battery energy density is large and ultracapacitor cycle life is high, power density is large, the quality of power supply of powering while having solved well photovoltaic electric station grid connection operation is poor and participate in the technical barrier that scheduling is difficult, for applying of photovoltaic plant paved road.
Brief description of the drawings
Fig. 1 is system configuration schematic diagram of the present invention;
Fig. 2 is the circuit diagram of two-way DC/DC controller;
Fig. 3 be initiatively can scheduling method theory diagram.
In figure, each symbol table is shown: P
v, photo-voltaic power supply is meritorious exerts oneself, P
b, lithium battery group is meritorious exerts oneself, P
c, bank of super capacitors is meritorious exerts oneself, P
d, the plan that is handed down to photovoltaic plant of dispatching of power netwoks department exerts oneself, U
d, DC bus-bar voltage, MPPT controller, maximal power tracing controlling apparatus, L, inductance, C, electric capacity, D1, D2, diode, Q1, Q2, igbt, U1, low-pressure side voltage, U2, high side voltage.
Embodiment
Mixed energy storage system structure in photovoltaic plant of the present invention is referring to Fig. 1, and its formation comprises bank of super capacitors, lithium battery group, two-way DC/DC controller I, two-way DC/DC controller II, status monitoring and controller.Described two-way DC/DC controller I and II can be made up of the circuit parallel connection of organizing as shown in Figure 2 more, the also joint group number of two-way DC/DC controller I is decided by the capacity of bank of super capacitors and the maximum transmission power of single group translation circuit, and the also joint group number of two-way DC/DC controller II is decided with the maximum transmission power of single group translation circuit by the capacity of lithium battery group.The low-pressure side access bank of super capacitors of two-way DC/DC controller I, the low-pressure side access lithium battery group of two-way DC/DC controller II, both high-pressure side access photovoltaic plant DC buss.
Bidirectional electric energy controller I, II can run on power generation mode, and the power delivery of bank of super capacitors or the storage of lithium battery group, to DC bus, also can be run on to charge mode, and remaining photovoltaic electric energy is stored in bank of super capacitors or lithium battery group.By regulating the operating state of corresponding bidirectional electric energy transmission control circuit, can realize the energy management to energy-storage system, as the timesharing that ultracapacitor and lithium battery group discharge and recharge is independently controlled etc., bank of super capacitors just can be different from the operating voltage range of lithium battery group like this, make both in capacity configuration, series parallel structure and operational mode, have larger flexibility.Utilize the unsteady flow effect of two-way DC/DC control circuit, transmission current can be limited in confidence band, greatly improve stability and the reliability of system operation, can also suppress bank of super capacitors and lithium battery group terminal voltage simultaneously and change the impact on the photovoltaic plant power supply quality of power supply.
Status monitoring and controller mainly comprise data acquisition, analytical calculation and trigger control unit, and system runtime data collecting unit detects the voltage of bank of super capacitors, lithium battery group and DC bus in real time, the power output (P of Real-time Collection MPPT controller
v).Analytical calculation unit calculates the value of exerting oneself that reaches photovoltaic plant quality of power supply goal of regulation and control or complete the required bank of super capacitors of scheduler task and lithium battery group fast.Trigger control unit regulates the running status of two-way DC/DC controller I and two-way DC/DC controller II in real time, in the time that needs energy-storage system releases energy to electrical network, turn-offs Q2, Q1 is carried out to pulse-width modulation (PWM) and control; In the time that photo-voltaic power supply charges to energy-storage system, turn-off Q1, Q2 is carried out to PWM control.U2>U1 in control procedure, PWM controls on off operating mode and the PWM duty ratio that can adopt PI closed-loop adjustment method to adjust Q1 and Q2, realizes the charge and discharge power adjustments to ultracapacitor or lithium battery energy storage battery unit.In Fig. 1, MPPT controller is photo-voltaic power supply maximal power tracing controller, and it is responsible for the maximum generation power delivery of photo-voltaic power supply, to DC bus, automatically reducing the value of exerting oneself of photo-voltaic power supply in the time receiving " abandoning light " instruction.
The present invention assigns to the generation schedule of photovoltaic plant the optimal control of exerting oneself of bank of super capacitors and lithium battery group for the requirement of the photovoltaic plant quality of power supply and electrical network according to user or electrical network, and this control method is carried out according to following steps:
A. data acquisition unit detects the operating state of DC bus, bank of super capacitors and lithium battery group in real time, detect in real time the meritorious of photo-voltaic power supply and exert oneself, require real-time judge to go out to be applicable to the mixed energy storage system operational mode that photovoltaic plant running status is adjusted in conjunction with dispatching of power netwoks.
If b. operational mode is quality of power supply regulation and control model, analytical calculation unit in status monitoring and controller is according to the running status of the situation of change of DC bus-bar voltage and energy-storage system, calculate fast that photo-voltaic power supply is exerted oneself and electric power between imbalance power, make energy-storage system and discharge and recharge control strategy.Trigger control unit is adjusted the running status of two-way DC/DC controller I and two-way DC/DC controller II in real time, relies on discharging and recharging of mixed energy storage system to reach the object that improves DC bus-bar voltage quality.
If c. operational mode is initiatively can scheduling method, the exert oneself running status of situation and mixed energy storage system of photovoltaic power station power generation power planning, the photo-voltaic power supply that status monitoring and controller issue according to dispatching of power netwoks department, calculate photovoltaic plant and complete the required photovoltaic array of scheduler task, ultracapacitor and the lithium battery plan for adjustment of exerting oneself, and control in real time.System operation logic is referring to Fig. 3.
D. under every kind of operational mode, control according to the principle of ultracapacitor energy storage unit " preferential charging, preferential discharge ".According to the operation result of analytical calculation unit, the running status of power electronic device Q1, Q2 in circuit shown in the real-time control chart 2 of trigger control unit in status monitoring and controller, regulate power delivery direction and size in two-way DC/DC controller I and two-way DC/DC controller II, realize the flexible control of ultracapacitor energy storage unit and lithium battery energy storage battery unit operational mode.
E. in mixed energy storage system charging control process, if bank of super capacitors and the lithium battery group of configuration have all reached maximum energy storage capacity, be that ultracapacitor energy storage unit side voltage is when reaching maximum operating voltage, lithium battery energy storage battery unit state-of-charge (SOC) and reaching its maximum, if photo-voltaic power supply still has unnecessary photovoltaic electric energy, bank of super capacitors and lithium battery group will no longer absorb electric energy, status monitoring in Fig. 1 and controller send " abandoning light " instruction to MPPT controller, reduce exerting oneself of photo-voltaic power supply.
F. in discharge process, if bank of super capacitors and lithium battery group have all reached minimum energy storage capacity, be that ultracapacitor energy storage unit side voltage reaches minimum operating voltage and lithium battery energy storage battery unit state-of-charge (SOC) while reaching its minimum value, still while there is power shortage in photovoltaic plant, status monitoring in Fig. 1 and controller send the instruction of " reducing grid-connected power " to networking inversion system, force photovoltaic plant power shortage to reduce.
Because ultracapacitor power density is large, charge and discharge circulation life is long, and lithium battery energy density is large, cycle life is relatively short, discharge and recharge condition stricter, the mixed energy storage system of ultracapacitor and lithium battery composition is applied in photovoltaic plant, in the time that photo-voltaic power supply goes out fluctuation or bearing power fluctuation, by controlling in an orderly manner flexibly the charge and discharge process of the each unit of mixed energy storage system and the size of exerting oneself, in ensureing that photovoltaic plant power output meets user or the requirement of the electrical network quality of power supply or meets dispatching of power netwoks mission requirements, can optimize the charge and discharge process of lithium battery, control it and discharge and recharge the degree of depth, increase the service life, reduce photovoltaic plant integrated operation cost.
As can be seen here, no matter photo-voltaic power supply power output frequent fluctuation or the very strong situation of scheduler task randomness, the mixed energy storage system of ultracapacitor and lithium battery composition all can participate in the adjustment of the photovoltaic plant quality of power supply and the adjustment of exerting oneself in real time, effectively improves the operation characteristic of photovoltaic plant.The poor technical barrier difficult with participating in scheduling of the quality of power supply of powering when this control method can effectively solve photovoltaic electric station grid connection operation.