Background technology
Along with petering out and day by day serious environmental pollution of conventional energy resource, within the scope of regenerative resource and distributed generation technology world in recent years, increasing attention and development have been obtained.At present, distributed power generation generally refer to generated output at the thousands of watts of miniaturizations to 50 megawatts, modularization, distributing, to be arranged near user be the small power generation system that is connected to distribution system of customer power supply.Current existing research and practice shows, by distributed power generation energy supplying system with micro power network (MicroGrid, be called for short microgrid below) form access large electrical network and be incorporated into the power networks, support each other with large electrical network, be the effective means of performance distributed power generation energy supplying system usefulness.
As one of important composition form of distributed power generation; microgrid collects by distributed power source, energy storage device, energy converter, relevant load, supervisory control system, protection system, power transmitting device etc. the small-sized electric system of being transported to forming conventionally, is one and can realizes the autonomous system that oneself controls, protects and manage.Because microgrid both can be by power distribution network and the parallel running of large-scale power net, form the combined operation system of a large-scale power grid and small grids, also can be independently for locality load provides electricity needs, its flexible operation modes has improved the power supply reliability of load side greatly; Meanwhile, microgrid accesses electrical network by single-point, can reduce the impact on traditional electrical network after a large amount of small-power distributed power sources access electrical networks.In addition, microgrid by disperse, the power supply that combines of dissimilar small power generation source (distributed power source), can make the higher utilization ratio of Miniature Power Unit acquisition.Under large electrical network normal condition, microgrid needs operation steady in a long-term; And when large electrical network is interfered, microgrid must depart from large electrical network fast, enter and be held in islet operation state, auto-parallel operation again after large electric network fault is got rid of.Above-mentioned functions is summarized as: peak load shifting, power are level and smooth, pattern switching etc.Realizing the required control mode of these functions is the difficult point of microgrid, and various countries research team is just continually developing more excellent control method and hardware forms.
Power output such as the regenerative resource of wind power generation, photovoltaic generation has very strong intermittence, randomness, and power curve fluctuation is violent, thereby causes the also fluctuation thereupon of power output of microgrid.Therefore in the system of microgrid is controlled, to regenerative resource output power curve is smoothly one of most important control object.
Fig. 1 illustrates a kind of existing microgrid topological structure.
As shown in Figure 1, microgrid comprises distributed power source 101, microgrid load 103.
Distributed power source 101, microgrid load 103 access bus BUS1.Bus BUS1 is generally low-voltage alternating-current bus, and voltage between 220V~35KV, is connected with bus BUS2 by transformer 104 conventionally.Bus BUS2 is generally high voltage AC bus, can be considered large electrical network, and voltage is conventionally between 10KV~220KV.
The power supply (for example, the regenerative resource of wind power generation, photovoltaic generation) that distributed power source 101 is violent for output power curve fluctuates.In order to eliminate the power fluctuation of distributed power source 101, conventionally adopt filter circuit to carry out the short-term Sudden Changing Rate of the power curve of filtering distributed power source 101.
Yet there are the following problems for above-mentioned microgrid output power control method: Whole Response speed slow (not reaching a second level), is not suitable for practical engineering application; Only can in direct current system, carry out direct current power and smoothly control, and can not in AC system, carry out, so be difficult to adapt to interchange micro-grid system; Poor with multiple renewable energy sources generating fiting effect.
Summary of the invention
The object of the present invention is to provide a kind of microgrid output power control method, thereby effectively reduce the fluctuation of the power output of microgrid.
One aspect of the present invention provides a kind of method of controlling the power output of microgrid, wherein, microgrid comprises the first distributed power source and the second distributed power source, and described method comprises: a plurality of output power values that (a) gather the first distributed power source in the first predetermined amount of time; (b) described a plurality of output power values are carried out to smothing filtering, acquisition and described a plurality of output power values are a plurality of meritorious desired values one to one; (c) calculate the poor of each output power value in described a plurality of output power value and corresponding meritorious desired value in described a plurality of meritorious desired values, to obtain a plurality of power control values; (d) according to the limit power of the second distributed power source, revise described a plurality of power control value, to obtain a plurality of corrected output controlling values; (e) according to the state-of-charge of the second distributed power source, determine whether the second distributed power source can be recharged and/or discharge; (f) result that whether can be recharged and/or discharge according to described a plurality of corrected output controlling values and definite the second distributed power source in the second predetermined amount of time, control the second distributed power source carries out charge or discharge.
Alternatively, at the second distributed power source, can charge, and corrected output controlling value is while being greater than zero, the second distributed power source is charged, and charge power is this corrected output controlling value.
Alternatively, at the second distributed power source, can discharge, and corrected output controlling value is while being less than zero, the second distributed power source is discharged, and discharge power is this corrected output controlling value.
Alternatively, step (d) comprising: when power control value is greater than the maximum charge performance number of the second distributed power source, power control value is modified to described maximum charge performance number; When power control value is less than the maximum discharge power value of the second distributed power source, this power control value is modified to described maximum discharge power value; In other cases, power control value is constant.
Alternatively, step (e) comprising: when the state-of-charge of the second distributed power source is greater than first threshold, determine that the second distributed power source only can discharge; When the state-of-charge of the second distributed power source is less than Second Threshold, determine that the second distributed power source only can charge; When the state-of-charge of the second distributed power source is less than or equal to first threshold and is more than or equal to Second Threshold, determine that the second distributed power source can carry out charging and discharging.
Alternatively, in step (f), when discharging or charging according to a corrected output controlling value and described output control the second distributed power source, before reaching the sequential of next corrected output controlling value, keep discharge power or charge power constant.
Alternatively, in the time of execution step (f) in the second predetermined amount of time, execution step (a).
Alternatively, the second predetermined amount of time is after the first predetermined amount of time.
Alternatively, when take scheduled duration when unit controls the power output of microgrid, the length of the first predetermined amount of time and the second predetermined amount of time is less than 1/2nd of described scheduled duration.
Alternatively, the second distributed power source is energy-storage travelling wave tube.
Alternatively, described energy-storage travelling wave tube is ultracapacitor or flywheel accumulator.
According to microgrid output power control method of the present invention, can effectively suppress the fluctuation of microgrid power output.In addition, according to microgrid output power control method of the present invention, the life-span of used energy-storage travelling wave tube can greatly be postponed.
Embodiment
Below, describe more fully with reference to the accompanying drawings exemplary embodiment of the present invention, exemplary embodiment is shown in the drawings.Yet exemplifying embodiment embodiment, and the present invention in many different forms should not be construed as limited to exemplary embodiment set forth herein.On the contrary, thereby provide these embodiment disclosure will be thoroughly and complete, and will fully the scope of exemplary embodiment be conveyed to those skilled in the art.
Fig. 2 illustrates according to microgrid topological structure of the present invention.
As shown in Figure 2, microgrid comprises the first distributed power source 101, the second distributed power source 102, microgrid load 103.Can see, compare with the microgrid topological structure shown in Fig. 1, according to microgrid of the present invention, also comprise the second distributed power source 102.
The first distributed power source 101 is the more violent power supply of output-power fluctuation (for example, the regenerative resource such as wind power generation, photovoltaic generation).The second distributed power source 102 is energy-storage travelling wave tube (for example, ultracapacitor, flywheel accumulator).
The first distributed power source 101, the second distributed power source 102, microgrid load 103 access bus BUS1.Thereby bus BUS1 is connected and accesses large electrical network with bus BUS2 by transformer 104.Large electrical network refers to the electrical network with the voltage higher than the voltage of microgrid.
Fig. 3 illustrates according to the flow chart of microgrid output power control method of the present invention.
In step 301, in predetermined amount of time T1, with preset frequency, gather a plurality of output power value P1 of the first distributed power source 101.Should be appreciated that, this preset frequency can be understood to the frequency of constant frequency or variation.
In step 302, a plurality of output power values that gather in step 301 are carried out to smothing filtering, acquisition and described a plurality of output power values are a plurality of meritorious desired value P2 one to one.
In step 303, calculate the poor of each output power value in described a plurality of output power value and corresponding meritorious desired value, to obtain a plurality of power control value P3.
In step 304, according to the limit power of the second distributed power source 102, revise described a plurality of power control value P3, obtain a plurality of corrected output controlling value P4.
Specifically, when power control value P3 is greater than maximum charge performance number (on the occasion of), this power control value is modified to described maximum charge performance number; When power control value P3 is less than maximum discharge power value (for negative value), this power control value is modified to described maximum discharge power value; In other cases, power control value P3 is constant.
When corrected output controlling value P4 be on the occasion of time, represent the second distributed power source 102 to charge, and charge power is this power control value.When corrected output controlling value P4 is negative value, represent the second distributed power source 102 to discharge, and discharge power is this power control value.When corrected output controlling value P4 is zero, the second distributed power source 102 is neither charged and also do not discharged.
In step 305, according to the state-of-charge of the second distributed power source 102 (SOC), determine the second distributed power source 102 has been opened which state in Charging state and electric discharge state.
Charging state represents to charge to the second distributed power source 102.Electric discharge state represents to discharge to the second distributed power source 102.
When the state-of-charge of the second distributed power source 102 is greater than first threshold, expression the second distributed power source 102 has only been opened electric discharge state, is merely able to discharge.
When the state-of-charge of the second distributed power source 102 is less than Second Threshold, expression the second distributed power source 102 has only been opened Charging state, is merely able to charge.
When the state-of-charge of the second distributed power source 102 is less than or equal to first threshold and is more than or equal to Second Threshold, represent that the second distributed power source 102 has been opened Charging state and the state of discharging, can carry out charging and discharging.
Should be appreciated that, first threshold is greater than Second Threshold.
In step 306, in next predetermined amount of time T2 after predetermined amount of time T1, according to the sequential of described a plurality of corrected output controlling value P4, according to described a plurality of corrected output controlling value P4 and definite state, control the second distributed power source 102 and carry out charge or discharge.
According to known to the description of power control value and state above: opened Charging state at the second distributed power source 102, and when corrected output controlling value P4 is greater than zero, control the second distributed power source 102 and charge, and the input power of control the second distributed power source 102 is described corrected output controlling value P4; At the second distributed power source 102, opened electric discharge state, and corrected output controlling value P4 is while being less than zero, controls the second distributed power source 102 and discharges, and the power output of controlling the second distributed power source 102 is described corrected output controlling value P4.
Should be appreciated that, the sequential of each corrected output controlling value P4 is the sequential of the corresponding with it output power value P1 gathering in step 301.In addition, should also be understood that when controlling the second distributed power source 102 according to a corrected output controlling value P4 and discharge or charge, before reaching the sequential of next corrected output controlling value P4, electric discharge or charge power remain unchanged.
When needs carry out output power in a plurality of predetermined amount of time, when performing step 306 in described next predetermined amount of time T2 when, can in described next predetermined amount of time T2, perform step 301, thereby next the predetermined amount of time T3 after predetermined amount of time T2 controls the second distributed power source 102, discharge and recharge simultaneously.Like this, for each predetermined amount of time repeated execution of steps 301-306, power output is controlled.
In addition, may exist and need to scheduled duration, (also can be described as assessment cycle, for example, 0.5 minute to 5 minutes) for the cycle to the power output of the first distributed power source 101 carry out level and smooth (, take described scheduled duration as unit, suppress the sudden change of the power output of the first distributed power source 101) situation, now the length of above-mentioned predetermined amount of time (also can be described as control cycle) should be less than 1/2nd of described scheduled duration.
According to Poewr control method of the present invention, although the control of power output has certain hysteresis quality, but control cycle be only a part in assessment cycle (for example, power output in two adjacent control cycles is all in the sudden change of rising), therefore still can realize on the whole the effectively level and smooth of power.
The integral multiple of the length that preferably, the length of assessment cycle is control cycle.
In the present invention, owing to initiatively opening Charging state and electric discharge state according to the state-of-charge of energy-storage travelling wave tube, can only absorbed power under Charging state, under electric discharge state, can only send power, therefore make energy-storage travelling wave tube work in the better interval of performance, and can be not frequently between discharging and recharging, do not switch, thereby extended life-span of energy-storage travelling wave tube.For example, in to the micro-grid system of the ultracapacitor that contains 200kW * 10s and 500kW solar energy power generating, in test, when control cycle is 1 second, assessment cycle is while being 60 seconds, maximum extension 30 times of ultracapacitor life-spans.
Preferably, the second distributed power source 102 according to the present invention is ultracapacitor or flywheel accumulator, compares with the energy-storage travelling wave tube of other types, and it is large that ultracapacitor and flywheel accumulator have instantaneous power, the advantage that the time that discharges and recharges is short.In the prior art, ultracapacitor, flywheel accumulator can be realized discharging and recharging of direct current or AC energy by power controller and/or inverter are set, and can control the size that charges and discharge power.
According to microgrid output power control method of the present invention, can effectively suppress the fluctuation of microgrid power output, and can postpone the life-span of used energy-storage travelling wave tube.
Although specifically shown with reference to its exemplary embodiment and described the present invention, but it should be appreciated by those skilled in the art, in the situation that do not depart from the spirit and scope of the present invention that claim limits, can carry out the various changes in form and details to it.