CN104810850A - Non-critical load continuously adjustable DC (direct current) micro-grid off-grid and on-grid unified and coordinated control method - Google Patents
Non-critical load continuously adjustable DC (direct current) micro-grid off-grid and on-grid unified and coordinated control method Download PDFInfo
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Abstract
A non-critical load continuously adjustable DC micro-grid off-grid and on-grid unified and coordinated control method relates to the field of DC micro-grid control. The non-critical load continuously adjustable DC micro-grid off-grid and on-grid unified and coordinated control method solves the problem of large quantity and scattering of controllable units in a DC micro-grid system. The non-critical load continuously adjustable DC (direct current) micro-grid off-grid and on-grid unified and coordinated control method comprises establishing unified switching criteria of the operation modes of every system unit through DC bus voltages of different levels, aims at achieving rapid coordinated control of the DC micro-grid under the premise of not utilizing high-speed communication line, and meanwhile on the basis of adding non-critical load continuously adjustable control, achieves unified control of off-grid and on-grid operational modes. Even when faults occur in an AC (alternate current) grid, a system can automatically switch to an off-grid operational mode; meanwhile, when system internal energy is insufficient, through non-critical load power reduction operation, a load converter can participate in a process of stabilizing the DC bus voltage, so that the system flexibility can be enhanced, and the stable operation interval of the system can be enlarged. The non-critical load continuously adjustable DC micro-grid off-grid and on-grid unified and coordinated control method is applicable to coordinated control of the DC micro-grid.
Description
Technical field
The present invention relates to direct-current grid control field.
Background technology
Micro-capacitance sensor has low-carbon environment-friendly, controllable degree high.On the one hand, different types of distributed power generation of dispersion is formed electric power system and powers to local load by micro-capacitance sensor, can improve the utilization ratio of distributed power generation; On the other hand, the energy exchange between micro-capacitance sensor and bulk power grid is controlled, can reduce the adverse effect that a large amount of distributed power generation dispersion access electrical network produces.According to the type of micro-grid system median generatrix, micro-capacitance sensor can be divided into ac bus type, alternating current-direct current mixing bus type and DC bus type micro-capacitance sensor three class.
Relative to interchange micro-capacitance sensor, DC micro-electric web frame is simple, efficiency of energy utilization is high, and receives publicity along with the increasing of direct-flow electricity utilization apparatus.Do not exist in direct-current grid running and exchange micro-capacitance sensor medium frequency, Phase synchronization problem, control relatively easy; Do not have reactive power to flow, the quality of power supply is good; Power electronics conversion links is few, and system reliability is high.At present, the cooperation control of direct-current grid is summed up and mainly contains master & slave control and equity control two large classes.When adopting master-slave control method, generally need writing to each other between master-slave controller, whole system has very strong dependence to master unit.When adopting reciprocity control mode, do not need the high-speed traffic between each unit, each unit of system can realize " plug and play ", but the operational mode of each unit needs unified transfer criterion.
In view of the more and dispersion of the controllable in DC micro power grid system, for guaranteeing its reliable and stable operation, also further investigated is needed to the coordination control strategy of each unit under different operating mode and under grid disturbance.
Summary of the invention
The present invention is in order to solve the more and problem of dispersion of controllable in DC micro power grid system, system each unit running status transfer criterion is set up by busbar voltage information, stable operation simultaneously for raising system is interval, proposes the continuously adjustable direct-current grid of a kind of insignificant load from, grid-connected unified control method for coordinating.
The continuously adjustable direct-current grid of insignificant load that the present invention proposes is realized from, grid-connected unified control method for coordinating by following steps:
Step one, determine DC bus-bar voltage rate range, load is divided into important load and insignificant load, form low-voltage direct micro-grid system by photovoltaic generation unit DGs, energy-storage units BEs, grid-connection converter GCC and insignificant load converter NLC, load, and determine the running status of each unit and converter according to the feature of above-mentioned each unit and converter;
Step 2, in certainty annuity after the running status of each unit and converter and DC bus-bar voltage rate range, DC bus-bar voltage is divided into five different electric pressures on the basis of set point, corresponding five system running patterns respectively, and a selected unit or converter carry out stable varying DC link voltage under each electric pressure;
Corresponding respectively five system running patterns of five described different electric pressures are: pattern I, pattern II, pattern III, pattern IV and pattern V;
In described pattern I, under photovoltaic generation unit DGs is operated in the sagging pattern of constant voltage, under energy-storage units BEs is operated in current-limiting charge or shutdown mode, under grid-connection converter GCC is operated in current limliting or shutdown mode, insignificant load converter NLC works in the normal mode;
In described pattern II, under photovoltaic generation unit DGs is operated in maximal power tracing or shutdown mode, under energy-storage units BEs is operated in current-limiting charge or shutdown mode, under grid-connection converter GCC is operated in parallel network reverse pattern, insignificant load converter NLC works in the normal mode;
In described pattern III, under photovoltaic generation unit DGs is operated in maximal power tracing or shutdown mode, under energy-storage units BEs is operated in the sagging pattern of constant voltage, under grid-connection converter GCC is operated in current limliting or shutdown mode, insignificant load converter NLC works in the normal mode;
In described pattern IV, under photovoltaic generation unit DGs is operated in maximal power tracing or shutdown mode, under energy-storage units BEs is operated in current-limiting charge or shutdown mode, under grid-connection converter GCC is operated in grid-connected rectification mode, insignificant load converter NLC works in the normal mode;
In described pattern V, under photovoltaic generation unit DGs is operated in maximal power tracing or shutdown mode, under energy-storage units BEs is operated in current limliting or shutdown mode, under grid-connection converter GCC is operated in current limliting or shutdown mode, under insignificant load converter NLC is operated in and falls power mode;
Step 3, photovoltaic generation unit DGs stable DC busbar voltage is applied in system running pattern I, grid-connection converter GCC stable DC busbar voltage is applied in system running pattern II and pattern IV, energy-storage units BEs stable DC busbar voltage is arranged in system running pattern III, insignificant load converter NLC stable DC busbar voltage is applied in system running pattern V;
Step 4, certainty annuity five operational modes from and net state, in system grid connection pattern, grid-connection converter GCC carries out parallel network reverse at system running pattern I, pattern II and pattern III, carry out grid-connected rectification at system running pattern III, pattern IV and pattern V, system then comprises pattern I, pattern III and pattern V from net pattern;
The handoff relation of step 5, certainty annuity five operational modes, wherein, system running pattern I and pattern II switches mutually, and pattern III switches mutually with pattern I, pattern II, pattern IV and pattern V respectively, and pattern V and pattern IV switches mutually;
Step 6, running status according to each unit determined in step 2 and converter, control the operating state of photovoltaic generation unit DGs, energy-storage units BEs, grid-connection converter GCC and insignificant load converter NLC respectively;
Step 7, by the method in step 6, the operating state of photovoltaic generation unit DGs, energy-storage units BEs, grid-connection converter GCC and insignificant load converter NLC controlled according to the operational mode of five described in step 4 from and net state and step 5 described in the handoff relation of five operational modes be applied in DC micro power grid system.
Beneficial effect: the direct-current grid control method for coordinating that the present invention proposes sets up the unified transfer criterion of system each unit operational mode by the DC bus-bar voltage of different brackets, its objective is that the rapid coordination realizing direct-current grid under the prerequisite not adopting high speed communication line controls, and the system that realizes on the basis adding insignificant load continuously adjustable output controls from the unified of, the pattern that is incorporated into the power networks; Even if AC network breaks down, system also can automatically switch to corresponding from network operation pattern, simultaneously, falling power operation when system self-energy is not enough by insignificant load makes load converter participate in the link of stable DC busbar voltage, not only increase the flexibility of system, also improve system stable operation interval.
Accompanying drawing explanation
Fig. 1 for described in step 2 in embodiment one and step 4 DC bus-bar voltage is divided on the basis of set point the system busbar voltage of five different electric pressures and system from, be incorporated into the power networks pattern diagram;
Fig. 2 is the system running pattern handoff relation schematic diagram of five in embodiment one described in step 5;
The working state control method block diagram that Fig. 3 is the photovoltaic generation unit DGs described in embodiment two; Wherein, U
pVand I
pVbe respectively output voltage and the electric current of photovoltaic array, U
* pVfor the photovoltaic array of MPPT controller generation is with reference to given voltage, U
dCand I
dCDbe respectively DC bus-bar voltage and photovoltaic generation unit converter output current, U
* dCand I
* dCDbe respectively the given reference voltage of photovoltaic generation unit converter and given reference current, K is droop control coefficient, and CVD represents the sagging pattern of constant voltage.
The working state control method block diagram that Fig. 4 is the energy-storage units BEs described in embodiment three; Wherein, U
dCand I
dCBbe respectively DC bus-bar voltage and energy-storage units converter bus bar side input/output electric current, I
bESand I
* bESbe respectively storage battery side input/output electric current and given reference current value in energy-storage units, U
* dCfor the given reference voltage of energy-storage units converter, K is droop control coefficient.
The working state control method block diagram that Fig. 5 is the grid-connection converter GCC described in embodiment four; Wherein, U
dCfor DC bus-bar voltage, U
* dCHand U
* dCLbe respectively DC bus-bar voltage reference upper level and lower limit, Sin θ is PLL synchronous sinusoidal signal, I
* acfor the current inner loop amplitude reference signal that grid-connection converter outer voltage produces, i
* acfor the given reference signal of sinusoidal current after PLL is synchronous, i
acfor grid-connection converter alternating current current on line side, u
acfor ac grid voltage, PLL is line voltage phase-locked loop.
Fig. 6 is the working state control method block diagram of the insignificant load converter NLC described in embodiment five; Wherein, U
dCfor DC bus-bar voltage, U
oand U
* obe respectively insignificant load converter output voltage and output voltage reference set-point, I
oand I
* obe respectively insignificant load converter output current and output current reference set-point, U
* nLCfor the given reference value of insignificant load converter bus bar side input voltage.
Fig. 7-Fig. 9 is the simulation results of the continuously adjustable direct-current grid of insignificant load of the present invention from, grid-connected unified control method for coordinating; U
dCfor DC bus-bar voltage, P
dG1for the power that First photovoltaic generation unit sends, P
dG2be the power that second photovoltaic generation unit sends, P
bESthe power sending for energy-storage units or absorb, P
gCCthe power sending for grid-connection converter or absorb, P
loadfor load consuming power, wherein, the analog simulation running status of pattern I, pattern II and pattern III in Fig. 7, the analog simulation running status of pattern III, pattern IV and pattern V in Fig. 8, the analog simulation running status of pattern I, pattern III and pattern V in Fig. 9.
Embodiment
Embodiment one, composition graphs 1 and Fig. 2 illustrate this embodiment, and the continuously adjustable direct-current grid of insignificant load described in this embodiment is realized from, grid-connected unified control method for coordinating by following steps:
Step one, determine DC bus-bar voltage rate range, load is divided into important load and insignificant load, form low-voltage direct micro-grid system by photovoltaic generation unit DGs, energy-storage units BEs, grid-connection converter GCC and insignificant load converter NLC, load, and determine the running status of each unit and converter according to the feature of above-mentioned each unit and converter;
Step 2, in certainty annuity after the running status of each unit and converter and DC bus-bar voltage rate range, DC bus-bar voltage is divided into five different electric pressures on the basis of set point, corresponding five system running patterns respectively, and a selected unit or converter carry out stable varying DC link voltage under each electric pressure;
Corresponding respectively five system running patterns of five described different electric pressures are: pattern I, pattern II, pattern III, pattern IV and pattern V;
In described pattern I, under photovoltaic generation unit DGs is operated in the sagging pattern of constant voltage, under energy-storage units BEs is operated in current-limiting charge or shutdown mode, under grid-connection converter GCC is operated in current limliting or shutdown mode, insignificant load converter NLC works in the normal mode;
In described pattern II, under photovoltaic generation unit DGs is operated in maximal power tracing or shutdown mode, under energy-storage units BEs is operated in current-limiting charge or shutdown mode, under grid-connection converter GCC is operated in parallel network reverse pattern, insignificant load converter NLC works in the normal mode;
In described pattern III, under photovoltaic generation unit DGs is operated in maximal power tracing or shutdown mode, under energy-storage units BEs is operated in the sagging pattern of constant voltage, under grid-connection converter GCC is operated in current limliting or shutdown mode, insignificant load converter NLC works in the normal mode;
In described pattern IV, under photovoltaic generation unit DGs is operated in maximal power tracing or shutdown mode, under energy-storage units BEs is operated in current-limiting charge or shutdown mode, under grid-connection converter GCC is operated in grid-connected rectification mode, insignificant load converter NLC works in the normal mode;
In described pattern V, under photovoltaic generation unit DGs is operated in maximal power tracing or shutdown mode, under energy-storage units BEs is operated in current limliting or shutdown mode, under grid-connection converter GCC is operated in current limliting or shutdown mode, under insignificant load converter NLC is operated in and falls power mode;
Step 3, photovoltaic generation unit DGs stable DC busbar voltage is applied in system running pattern I, grid-connection converter GCC stable DC busbar voltage is applied in system running pattern II and pattern IV, energy-storage units BEs stable DC busbar voltage is arranged in system running pattern III, insignificant load converter NLC stable DC busbar voltage is applied in system running pattern V;
Step 4, certainty annuity five operational modes from and net state, in system grid connection pattern, grid-connection converter GCC carries out parallel network reverse at system running pattern I, pattern II and pattern III, carry out grid-connected rectification at system running pattern III, pattern IV and pattern V, system then comprises pattern I, pattern III and pattern V from net pattern;
The handoff relation of step 5, certainty annuity five operational modes, wherein, system running pattern I and pattern II switches mutually, and pattern III switches mutually with pattern I, pattern II, pattern IV and pattern V respectively, and pattern V and pattern IV switches mutually;
Step 6, running status according to each unit determined in step 2 and converter, control the operating state of photovoltaic generation unit DGs, energy-storage units BEs, grid-connection converter GCC and insignificant load converter NLC respectively;
Step 7, by the method in step 6, the operating state of photovoltaic generation unit DGs, energy-storage units BEs, grid-connection converter GCC and insignificant load converter NLC controlled according to the operational mode of five described in step 4 from and net state and step 5 described in the handoff relation of five operational modes be applied in DC micro power grid system.
Direct-current grid control method for coordinating described in present embodiment sets up the unified transfer criterion of system each unit operational mode by the DC bus-bar voltage of different brackets, its objective is that the rapid coordination realizing direct-current grid under the prerequisite not adopting high speed communication line controls, and the continuously adjustable basis of insignificant load realizes system and control from, the unified of the pattern that is incorporated into the power networks adding.
In present embodiment, in DC micro power grid system, the running status of each unit is specially: photovoltaic generation unit DGs can be operated in maximal power tracing and sagging two patterns of constant voltage, grid-connection converter GCC can be operated in parallel network reverse and grid-connected rectification and current-limit mode, energy-storage units BEs can be operated in charging, electric discharge and current-limit mode, and insignificant load converter NLC can be operated in rated power and fall power two patterns.
According to the importance of load, load is divided into important load and insignificant load, as the non-emergent power supply units such as heating, illumination can be used as insignificant load;
Because direct-current grid is connected to each generator unit and power unit by common DC bus, so, DC bus-bar voltage can be used as the unified criterion that system running pattern switches, when system cloud gray model in different modes time, inner each unit can send according to corresponding control method or absorb energy, the present invention is according to the generator unit kind in system, operational mode feature and insignificant load, propose with five kinds of busbar voltage grade distinguishing degree direct-current grid from, grid-connected unified control method for coordinating, following formula gives the energy relation between supply and demand of each unit when Different periods steady operation in system:
Wherein, P
load1(t), P
load2t () is respectively important and insignificant load consuming power, P
dGst () sends power, P for photovoltaic generation unit
bES(t), P
gCCt () is respectively energy-storage units and grid-connection converter sends or consumed power, t
0~ t
5it is running times corresponding to system five patterns corresponding to five kinds of different busbar voltage grades.
On the above basis analyzed, the system coordination control method based on five kinds of different busbar voltage grades proposed as shown in Figure 1, according to system busbar voltage five kinds of different electric pressures, system cloud gray model is divided into five kinds of patterns, in system, photovoltaic generation unit, energy-storage units, grid-connection converter and insignificant load converter can serve as the task of stable DC busbar voltage respectively in each pattern with setting voltage value.When the unit participating in voltage stabilizing enters current mode state or breaks down, generation declines or rises by busbar voltage, thus enters another electric pressure, and now busbar voltage is stablized by next unit.
As can be seen from the classification of formula 1 and Fig. 1 system running pattern, in system, the energy changing of each unit can break energy balance relations when systematic steady state runs, be mainly manifested in that load consumption energy changes, photovoltaic generation unit send energy because illumination is large or variations in temperature changes, storage battery causes charge-discharge electric power to change because of state-of-charge and grid-connection converter reaches capacity limitation or AC network breaks down.Therefore busbar voltage can rise or decline, and each unit then changes control strategy according to preset state, makes system enter next operational mode.
This embodiment describes the operating state of each unit in system five kinds of operational modes in detail, take into full account the work characteristics of different units, when breaking down in grid-connection converter side, system can steadily switch to next from net state, consider extreme ruuning situation, at electric network fault, storage battery electric energy is not enough, photovoltaic array sends energy shortage when occurring simultaneously, and insignificant load converter implements downrating, and the system of guarantee can be important load continued power.
Embodiment two, composition graphs 3 illustrate this embodiment, this embodiment is with the difference of the continuously adjustable direct-current grid of insignificant load described in embodiment one from, grid-connected unified control method for coordinating, being specially the method that the operating state of photovoltaic generation unit DGs controls described in step 6:
When photovoltaic generation unit DGs is operated in maximal power tracing pattern, maximal power tracing controller MPPT obtains the given reference voltage U of photovoltaic array after obtaining the voltage of current photovoltaic array, current value
* pV, and with its sampled value U
pVsend into voltage PI regulator after making difference and then obtain the work of corresponding pwm signal driving transducer switching tube;
When photovoltaic generation unit DGs is operated in the sagging pattern of constant voltage, now DC bus-bar voltage is by multiple photovoltaic generation unit jointly stabilizing; The given value of current signal of converter can be obtained after overcurrent amplitude limit add droop control in voltage close loop controls after.The switching of two kinds of operating states of photovoltaic generation unit DGs is determined by current DC bus-bar voltage.
Embodiment three, composition graphs 4 illustrate this embodiment, this embodiment is with the difference of the continuously adjustable direct-current grid of insignificant load described in embodiment one from, grid-connected unified control method for coordinating, being specially the method that the operating state of energy-storage units BEs controls described in step 6:
When secondary battery unit is operated in charging and discharging state, outer voltage in its control method plays a role, and be similar to the Isobarically Control of photovoltaic generation unit, add droop control equally, SOC administration module is used for preventing accumulator super-charge, crosses and put and set restrictor ring maximum with reference to the maximum charge-discharge electric power of storage battery, SOC administration module can manage discharge and recharge according to storage battery SOC state, and produce a current-order when secondary battery unit operates in current limliting charging and discharging state given as electric current loop, arrange restrictor ring is zero simultaneously, and outer voltage was lost efficacy.
Embodiment four, composition graphs 5 illustrate this embodiment, this embodiment and the continuously adjustable direct-current grid of insignificant load described in embodiment one are not from its of, grid-connected unified control method for coordinating, being specially the method that the operating state of grid-connection converter GCC controls described in step 6:
Make grid-connection converter GCC be operated in inversion and rectification two states according to DC bus-bar voltage and voltage given value, comprise outer shroud and control and inner ring control, outer shroud controls to be used for stable DC busbar voltage, in busbar voltage higher than set point U
* dCHtime, both differences are greater than 0, and grid-connection converter GCC is operated in inverter mode; In busbar voltage lower than set point U
* dCLtime, both differences are less than 0, and grid-connection converter GCC is operated in rectification mode; Inner ring is grid-connected current ring, line voltage phase-locked loop pll can real-time tracking grid phase, frequency, and wherein restrictor ring can according to the actual capacity grid-connected maximum current of restriction grid-connection converter unit of converter and current limliting operation is carried out in the current limliting instruction that can receive DC micro power grid system.
Embodiment five, composition graphs 6 illustrate this embodiment, this embodiment is with the difference of the continuously adjustable direct-current grid of insignificant load described in embodiment one from, grid-connected unified control method for coordinating, being specially the method that the operating state of insignificant load converter NLC controls described in step 6:
System cloud gray model is when pattern I to IV, and busbar voltage is higher than set point U
* nLC, the downside control loop no-output in Fig. 6, insignificant load converter NLC output voltage stabilization is at set point U
* o, insignificant load is with rated power operation; When the energy that photovoltaic generation unit DGs, energy-storage units BEs and grid-connection converter GCC send is all not enough, DC bus-bar voltage reduces, now downside control loop is had an effect, insignificant load converter NLC power output is impelled to decline, and then reach the object maintaining system capacity balance, and busbar voltage can be maintained U
* nLC, meanwhile, on minimum operating voltage point downrating working point control being allowed in insignificant load by amplitude limiter, the downrating of insignificant load, while the running space improving system, achieves the operation of level and smooth continuous print off-load.
The direct-current grid that Fig. 7 carries for the present invention from, grid-connectedly unifiedly run in coordination control strategy the simulation result that is incorporated into the power networks, wherein contain operational mode I, II, III.During beginning, two photovoltaic generation units operate in MPPT pattern, and energy-storage units operates in discharge mode, and busbar voltage is stabilized in 400V, and system is in pattern III.Afterwards, photovoltaic generation unit sends energy to be increased, energy-storage units current-limiting charge, and when busbar voltage reaches 410V, grid-connection converter stablizes busbar voltage and by excess energy feed-in electrical network, system Dietary behavior II.When load consuming power declines, when grid-connection converter enters current limliting inverter mode, busbar voltage continues to rise, and when reaching 420V, photovoltaic generation unit enters the sagging mode stable DC bus-bar voltage of constant voltage, system Dietary behavior I.
The direct-current grid that Fig. 8 carries for the present invention from, grid-connectedly unifiedly run in coordination control strategy the simulation result that is incorporated into the power networks, wherein contain operational mode III, IV, V.During beginning, energy-storage units work constant voltage hang, absorb excess energy charging, and busbar voltage is stabilized in 400V, system is in pattern III.When the energy sum that photovoltaic generation unit and energy-storage units send is not enough to supply load, busbar voltage starts to decline, and when reaching 390V, and net unit is started working, system Dietary behavior IV.Continue to reduce in photovoltaic generation unit generating, energy-storage units is shut down and net unit when reaching capacity limitation, and busbar voltage declines further, and when reaching 380V, insignificant load converter stablizes busbar voltage, accordingly, and system Dietary behavior V.
The direct-current grid that Fig. 9 carries for the present invention from, grid-connectedly unifiedly to run in coordination control strategy from network operation simulation result, wherein contain operational mode I, III, V.During beginning, busbar voltage is stablized by photovoltaic generation unit, and system is in pattern I.Afterwards important load consumed power increase, photovoltaic generation unit sends energy shortage, enters MPPT state, energy-storage units start electric discharge and stable DC busbar voltage at about 400V, system Dietary behavior III.When important load consumed energy continues to increase, energy storage sends energy and reaches the restriction of maximum discharge power when entering current limliting discharge condition, and busbar voltage declines, after reaching 380V, insignificant load enters downrating and stable DC busbar voltage, system Dietary behavior V.In this running, owing to not having the participation of grid-connection converter, system can skip mode II and IV automatically.
Claims (5)
1. the continuously adjustable direct-current grid of insignificant load is from, grid-connected unified control method for coordinating, and it is characterized in that, it is realized by following steps:
Step one, determine DC bus-bar voltage rate range, load is divided into important load and insignificant load, form low-voltage direct micro-grid system by photovoltaic generation unit (DGs), energy-storage units (BEs), grid-connection converter (GCC) and insignificant load converter (NLC), load, and determine the running status of each unit and converter according to the feature of above-mentioned each unit and converter;
Step 2, in certainty annuity after the running status of each unit and converter and DC bus-bar voltage rate range, DC bus-bar voltage is divided into five different electric pressures on the basis of set point, corresponding five system running patterns respectively, and a selected unit or converter carry out stable varying DC link voltage under each electric pressure;
Corresponding respectively five system running patterns of five described different electric pressures are: pattern I, pattern II, pattern III, pattern IV and pattern V;
In described pattern I, under photovoltaic generation unit (DGs) is operated in the sagging pattern of constant voltage, under energy-storage units (BEs) is operated in current-limiting charge or shutdown mode, under grid-connection converter (GCC) is operated in current limliting or shutdown mode, insignificant load converter (NLC) work in the normal mode;
In described pattern II, under photovoltaic generation unit (DGs) is operated in maximal power tracing or shutdown mode, under energy-storage units (BEs) is operated in current-limiting charge or shutdown mode, under grid-connection converter (GCC) is operated in parallel network reverse pattern, insignificant load converter (NLC) work in the normal mode;
In described pattern III, under photovoltaic generation unit (DGs) is operated in maximal power tracing or shutdown mode, under energy-storage units (BEs) is operated in the sagging pattern of constant voltage, under grid-connection converter (GCC) is operated in current limliting or shutdown mode, insignificant load converter (NLC) work in the normal mode;
In described pattern IV, under photovoltaic generation unit (DGs) is operated in maximal power tracing or shutdown mode, under energy-storage units (BEs) is operated in current-limiting charge or shutdown mode, under grid-connection converter (GCC) is operated in grid-connected rectification mode, insignificant load converter (NLC) work in the normal mode;
In described pattern V, under photovoltaic generation unit (DGs) is operated in maximal power tracing or shutdown mode, under energy-storage units (BEs) is operated in current limliting or shutdown mode, under grid-connection converter (GCC) is operated in current limliting or shutdown mode, under insignificant load converter (NLC) is operated in and falls power mode;
Step 3, photovoltaic generation unit (DGs) stable DC busbar voltage is applied in system running pattern I, grid-connection converter (GCC) stable DC busbar voltage is applied in system running pattern II and pattern IV, energy-storage units (BEs) stable DC busbar voltage is arranged in system running pattern III, insignificant load converter (NLC) stable DC busbar voltage is applied in system running pattern V;
Step 4, certainty annuity five operational modes from and net state, in system grid connection pattern, grid-connection converter (GCC) carries out parallel network reverse at system running pattern I, pattern II and pattern III, carry out grid-connected rectification at system running pattern III, pattern IV and pattern V, system then comprises pattern I, pattern III and pattern V from net pattern;
The handoff relation of step 5, certainty annuity five operational modes, wherein, system running pattern I and pattern II switches mutually, and pattern III switches mutually with pattern I, pattern II, pattern IV and pattern V respectively, and pattern V and pattern IV switches mutually;
Step 6, running status according to each unit determined in step 2 and converter, control the operating state of photovoltaic generation unit (DGs), energy-storage units (BEs), grid-connection converter (GCC) and insignificant load converter (NLC) respectively;
Step 7, by the method in step 6, the operating state of photovoltaic generation unit (DGs), energy-storage units (BEs), grid-connection converter (GCC) and insignificant load converter (NLC) controlled according to the operational mode of five described in step 4 from and net state and step 5 described in the handoff relation of five operational modes be applied in DC micro power grid system.
2. the continuously adjustable direct-current grid of insignificant load according to claim 1 is from, grid-connected unified control method for coordinating, it is characterized in that, the method that the operating state of photovoltaic generation unit (DGs) controls is specially described in step 6:
When photovoltaic generation unit (DGs) is operated in maximal power tracing pattern, maximal power tracing controller (MPPT) obtains the given reference voltage U of photovoltaic array after obtaining the voltage of current photovoltaic array, current value
* pV, and with its sampled value U
pVsend into voltage PI regulator after making difference and then obtain the work of corresponding pwm signal driving transducer switching tube;
When photovoltaic generation unit (DGs) is operated in the sagging pattern of constant voltage, now DC bus-bar voltage is by multiple photovoltaic generation unit jointly stabilizing; The given value of current signal of converter can be obtained after overcurrent amplitude limit add droop control in voltage close loop controls after.
3. the continuously adjustable direct-current grid of insignificant load according to claim 1 is from, grid-connected unified control method for coordinating, it is characterized in that, being specially the method that the operating state of energy-storage units (BEs) controls described in step 6:
When secondary battery unit is operated in charging and discharging state, the operating state of energy-storage units (BEs) is controlled by outer voltage, and add droop control, SOC administration module is used for preventing accumulator super-charge, crosses and put and set restrictor ring maximum with reference to the maximum charge-discharge electric power of storage battery, SOC administration module can manage discharge and recharge according to storage battery SOC state, and produce a current-order when secondary battery unit operates in current limliting charging and discharging state given as electric current loop, arrange restrictor ring is zero simultaneously, and outer voltage was lost efficacy.
4. the continuously adjustable direct-current grid of insignificant load according to claim 1 is from, grid-connected unified control method for coordinating, it is characterized in that, being specially the method that the operating state of grid-connection converter (GCC) controls described in step 6:
Make grid-connection converter (GCC) be operated in inversion and rectification two states according to DC bus-bar voltage and voltage given value, comprise outer shroud and control and inner ring control, outer shroud controls to be used for stable DC busbar voltage, in busbar voltage higher than set point U
* dCHtime, both differences are greater than 0, and grid-connection converter (GCC) is operated in inverter mode; In busbar voltage lower than set point U
* dCLtime, both differences are less than 0, and grid-connection converter (GCC) is operated in rectification mode; Inner ring is grid-connected current ring, line voltage phase-locked loop pll can real-time tracking grid phase, frequency, and wherein restrictor ring can according to the actual capacity grid-connected maximum current of restriction grid-connection converter unit of converter and current limliting operation is carried out in the current limliting instruction that can receive DC micro power grid system.
5. the continuously adjustable direct-current grid of insignificant load according to claim 1 is from, grid-connected unified control method for coordinating, it is characterized in that, the method that the operating state of insignificant load converter (NLC) controls is specially described in step 6:
System cloud gray model is when pattern I to IV, and busbar voltage is higher than set point U
* nLC, insignificant load converter (NLC) output voltage stabilization is at set point U
* o, insignificant load is with rated power operation; When the energy that photovoltaic generation unit (DGs), energy-storage units (BEs) and grid-connection converter (GCC) send is all not enough, DC bus-bar voltage reduces, now insignificant load converter (NLC) power output declines, and then reach the object maintaining system capacity balance, and busbar voltage can be maintained U
* nLC.
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