CN105356506B - A kind of control method of low-voltage AC/DC mixing distribution system connection current transformer - Google Patents
A kind of control method of low-voltage AC/DC mixing distribution system connection current transformer Download PDFInfo
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- CN105356506B CN105356506B CN201510815651.0A CN201510815651A CN105356506B CN 105356506 B CN105356506 B CN 105356506B CN 201510815651 A CN201510815651 A CN 201510815651A CN 105356506 B CN105356506 B CN 105356506B
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Classifications
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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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
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
- H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
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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
- H02J5/00—Circuit arrangements for transfer of electric power between ac networks and dc networks
-
- 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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
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- Supply And Distribution Of Alternating Current (AREA)
Abstract
The present invention provides a kind of control method of low-voltage AC/DC mixing distribution system connection current transformer, by judging that low-voltage AC/DC mixes the object run mode of distribution system；If object run mode is the mode that is incorporated into the power networks, then according to cutting-in control target, if DC bus-bar voltage changing value under judging the mode of being incorporated into the power networks simultaneously controls connection current transformer and carries out control operation object run mode as isolated operation mode, target is controlled according to isolated island, judges the low-voltage alternating-current side of isolated operation mode and the overload of low-voltage direct side and light load conditions and control to connect current transformer and carry out control operation.Method proposed by the present invention is simple, reliable and effective, on the basis of the grid-connected and isolated operation mode of detailed analysis mixing distribution system, proposes to connect converter control method accordingly respectively for two kinds of operational modes；Avoid complicated control structure switching；And running wastage is reduced, it is easy to Project Realization；And then the normal operation of current low-voltage AC/DC mixing distribution system is effectively ensured.
Description
Technical field
The present invention relates to connection current transformer control technology fields, and in particular to a kind of low-voltage AC/DC mixing distribution system use
Connect the control method of current transformer.
Background technique
As house power supply source gradually develops towards multiple types, sustainable direction, such as Photovoltaic Building Integration system.Separately
Outside, it works inside the common household electrical appliance such as energy-saving lamp, PC usually using direct current, in order to reduce power consumption, air-conditioning
The rotation such as device, washing machine class equipment is increasingly turned to transducer drive or DC brushless motor development containing DC link.To sum up may be used
Know, the DC characteristic that distributed power supply source and household electricity load are shown becomes clear day by day, and the following power distribution network will will appear directly
The pattern for flowing and exchanging shared market.
In order to improve the reliability and economy of system, simple AC or DC side is reduced in the application because of multiple AC/
Power loss caused by DC or DC/AC is converted, harmonic current and control difficulty, alternating current-direct current mixing distribution system have obtained both at home and abroad
Attention and research.In low-voltage AC/DC mixing distribution system, connection current transformer controls direct current side bus and to exchange side female
Energy flow between line serves as important support and coordination role in alternating current-direct current mixing distribution system, to whole system
Stable operation plays an important role.
Currently, there is connection converter control method in low-voltage AC/DC mixing distribution system: (1) concentrating energy hole side
Method need to rely on reliable communication system, increase system cost；(2) distributed control method.It is connection current transformer there are problem
Always it is in power transmission state, increases running wastage；The energy balance of exchange side or DC side is only considered under island mode,
It cannot be guaranteed that the stable operation of system and the coordinated allocation of power.
Summary of the invention
In view of this, a kind of controlling party of low-voltage AC/DC mixing distribution system connection current transformer provided by the invention
Method, this method is simple, reliable and effective, on the basis of the grid-connected and isolated operation mode of detailed analysis mixing distribution system, needle
Two kinds of operational modes are proposed respectively to connect converter control method accordingly；Avoid complicated control structure switching；And subtract
Small running wastage, is easy to Project Realization；And then the normal operation of current low-voltage AC/DC mixing distribution system is effectively ensured.
The purpose of the present invention is what is be achieved through the following technical solutions:
A kind of control method of low-voltage AC/DC mixing distribution system connection current transformer, the low-voltage AC/DC mixing are matched
It is equipped with connection current transformer, energy storage device and energy management unit, the connection current transformer both ends in electric system and is separately connected low pressure
Direct current side bus and low-voltage alternating-current side bus；
Described method includes following steps:
Step 1. judges the object run mode of the low-voltage AC/DC mixing distribution system；
If the object run mode is the mode that is incorporated into the power networks, 2 are entered step；
If the object run mode is isolated operation mode, 4 are entered step；
Step 2. determines the cutting-in control target of the connection current transformer；
Step 3. is according to the cutting-in control target, the DC bus-bar voltage changing value that is incorporated into the power networks under mode described in judgement
And it controls the connection current transformer and carries out control operation；Enter step 6；
Step 4. determines that the isolated island of the connection current transformer controls target；
Step 5. controls target according to the isolated island, judges the low-voltage alternating-current side and the low pressure of the isolated operation mode
The overload of DC side and light load conditions simultaneously control the connection current transformer and carry out control operation；
Step 6. maintains current state of a control, and the order of the object run mode is updated until receiving, and returns to step
Rapid 1.
Preferably, the step 2 includes:
Under the mode that is incorporated into the power networks, according to the power output of the low-voltage alternating-current side be sent into path and with it is described
The equivalent relation of low-voltage direct side determines that the cutting-in control target of the connection current transformer is the energy for maintaining the low-voltage direct side
Amount balance.
Preferably, the step 3 includes:
3-1. is according to the cutting-in control target, the DC bus-bar voltage changing value △ that is incorporated into the power networks under mode described in judgement
The upper limit value Uh and lower limit value Ul relationship of U and DC voltage change:
If | △ U | < Ul；Then enter step 3-2；
If Ul < | △ U | < Uh；Then enter step 3-3；
If Uh < | △ U |；Then enter step 3-4；
3-2. obtains the connection inverter transimission power P=0；Enter step 6；
3-3. obtains the connection inverter transimission power P < S；Wherein, S is rated capacity；
The voltage stabilization that the connection current transformer maintains the low-voltage direct side is then controlled, and the low-voltage direct side is equivalent
In the power supply or load of power variable；Enter step 6；
3-4. obtains the connection inverter transimission power P=S；Then the low-voltage direct busbar voltage is by its internal distribution
Formula power supply, energy storage and Coordinated are stablized, and the low-voltage direct side is equivalent to the fixed power supply or load of power；It enters step
6。
Preferably, the step 4 includes:
Under the isolated operation mode, determine that the isolated island control target of the connection current transformer is handed over to complete the low pressure
The overload flowed between side and the low-voltage direct side distributes.
Preferably, the step 5 includes:
Target is controlled according to the isolated island, judges the low-voltage alternating-current side and low-voltage direct side of the isolated operation mode
Load condition, control a-c cycle and DC voltage and fall directly proportional, and the energy management unit for participating in operation is set
It is identical as the connection control priority of current transformer；
5-1. controls target according to the isolated island, judges the low-voltage alternating-current side and the low pressure under the isolated operation mode
The overload of DC side and light load conditions；
If the low-voltage alternating-current side and low-voltage direct side are in light load or overload state, into 5-2；
If being in light load conditions there are side in the low-voltage alternating-current side and low-voltage direct side, the other side is overload
When state, into 5-3；
5-2. obtains the connection inverter transimission power P=0；Enter step 6；
5-3. control a-c cycle and DC voltage fall the energy management unit directly proportional, and that participation operation is arranged
It is identical as the connection control priority of current transformer.
Preferably, the 5-3 includes:
Control a-c cycle fall fall with DC voltage it is directly proportional, and to load vacancy entirely mixing distribution system in
It is allocated, the energy management unit for participating in operation is identical as the connection control priority of current transformer；Then there is distribution
Principle are as follows:
Wherein, K is the ratio between the lower limit value that DC voltage and a-c cycle allow；Vdc0For DC bus-bar voltage；ΔVdcIt is straight
Flow the variable quantity of busbar voltage；f.For a-c cycle；Δ f is the variable quantity of a-c cycle.
Preferably, two close cycles are all made of with the connection inverter under isolated operation mode under the mode that is incorporated into the power networks
Vector controlled, and the switching mode being incorporated into the power networks between mode and isolated operation mode is to change exterior ring power reference value.
It can be seen from the above technical scheme that the present invention provides a kind of mixing distribution system connections of low-voltage AC/DC
The control method of current transformer, by judging that low-voltage AC/DC mixes the object run mode of distribution system；If object run mode
Judge the DC bus-bar voltage changing value being incorporated into the power networks under mode then according to cutting-in control target for the mode of being incorporated into the power networks and control
If it is isolated operation mode that system connection current transformer, which carries out control operation object run mode, target is controlled according to isolated island, judges orphan
The low-voltage alternating-current side of island operational mode and the overload of low-voltage direct side and light load conditions simultaneously control and connect current transformer and controlled
System operation.Method proposed by the present invention is simple, reliable and effective, in the grid-connected and isolated operation of detailed analysis mixing distribution system
On the basis of mode, propose to connect converter control method accordingly respectively for two kinds of operational modes；Avoid complicated control
Structure switching；And running wastage is reduced, it is easy to Project Realization；And then current low-voltage AC/DC mixing power distribution system is effectively ensured
The normal operation of system.
Compared with the latest prior art, technical solution provided by the invention has following excellent effect:
1, in technical solution provided by the present invention, grid-connected and isolated island fortune of this method in detailed analysis mixing distribution system
On the basis of row mode, propose to connect converter control method accordingly respectively for two kinds of operational modes.It is incorporated into the power networks under mode
DC voltage is controlled using connection current transformer, meets the energy requirement of DC side, with season connection current transformer prior to energy storage
Device controls power balance of DC side, optimizes the use of energy storage device；AC and DC side power grid is comprehensively considered under isolated operation mode
It is directly proportional to guarantee that a-c cycle and DC voltage fall for droop characteristic, and be arranged participate in energy management unit (distributed generation resource,
Energy storage etc.) it is identical as the connection control priority of current transformer, so that overload obtains an equitable breakdown between AC and DC side.
2, technical solution provided by the present invention, connection current transformer are all made of two close cycles vector controlled structure, therefore two kinds
The switching of control model need to only change outer ring reference value, avoid complicated control structure switching.And under two kinds of operational modes, even
Connecing the active power that current transformer transmits under certain condition is 0, reduces running wastage.This control method clear thinking, easily
In Project Realization.
3, technical solution provided by the present invention, by judging that low-voltage AC/DC mixes the object run mould of distribution system
Formula；If object run mode is the mode that is incorporated into the power networks, according to cutting-in control target, judge that the direct current being incorporated into the power networks under mode is female
If line voltage changing value and control connection current transformer carry out control operation object run mode be isolated operation mode, according to isolated island
Target is controlled, judges the low-voltage alternating-current side of isolated operation mode and the overload of low-voltage direct side and light load conditions and the company of control
It connects current transformer and carries out control operation；This method is simple, reliable and effective；Avoid complicated control structure switching；And it reduces
Running wastage is easy to Project Realization；And then the normal operation of current low-voltage AC/DC mixing distribution system is effectively ensured.
4, technical solution provided by the invention, is widely used, and has significant Social benefit and economic benefit.
Detailed description of the invention
Fig. 1 is a kind of process of the control method of low-voltage AC/DC mixing distribution system connection current transformer of the invention
Figure；
Fig. 2 is the topology diagram for connecting current transformer；
Fig. 3 is a kind of specifically answering for the control method of low-voltage AC/DC mixing distribution system connection current transformer of the invention
Grid-connect mode control characteristic figure in use-case；
Fig. 4 is a kind of specifically answering for the control method of low-voltage AC/DC mixing distribution system connection current transformer of the invention
The vector controlled block diagram of the double circle structure of connection current transformer in use-case；
Fig. 5 is a kind of specifically answering for the control method of low-voltage AC/DC mixing distribution system connection current transformer of the invention
Island mode active power reference value in use-case generates block diagram.
Specific embodiment
Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, complete
Site preparation description, it is clear that described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.It is based on
The embodiment of the present invention, every other reality obtained by those of ordinary skill in the art without making creative efforts
Example is applied, shall fall within the protection scope of the present invention.
As shown in Figure 1, the present invention provides a kind of control method of low-voltage AC/DC mixing distribution system connection current transformer,
Low-voltage AC/DC, which mixes, is equipped with connection current transformer, energy storage device and energy management unit in distribution system, connect current transformer both ends
It is separately connected low-voltage direct side bus and low-voltage alternating-current side bus；
Method includes the following steps:
Step 1. judges the object run mode of low-voltage AC/DC mixing distribution system；
If object run mode is the mode that is incorporated into the power networks, 2 are entered step；
If object run mode is isolated operation mode, 4 are entered step；
Step 2. determines the cutting-in control target of connection current transformer；
Step 3. judges DC bus-bar voltage changing value and the company of control being incorporated into the power networks under mode according to cutting-in control target
It connects current transformer and carries out control operation；Enter step 6；
Step 4. determines that the isolated island of connection current transformer controls target；
Step 5. according to isolated island control target, judge isolated operation mode low-voltage alternating-current side and low-voltage direct side it is excessively negative
Lotus and light load conditions and control connection current transformer carry out control operation；
Step 6. maintains current state of a control, and the order of object run mode, return step 1 are updated until receiving.
Wherein, step 2 includes:
Under the mode of being incorporated into the power networks, according to the power output of low-voltage alternating-current side and be sent into path and with low-voltage direct side
Equivalent relation determines that the cutting-in control target of connection current transformer is to maintain the energy balance of low-voltage direct side.
Wherein, step 3 includes:
3-1. judges the DC bus-bar voltage changing value △ U and direct current being incorporated into the power networks under mode according to cutting-in control target
The upper limit value Uh and lower limit value Ul relationship of voltage change:
If | △ U | < Ul；Then enter step 3-2；
If Ul < | △ U | < Uh；Then enter step 3-3；
If Uh < | △ U |；Then enter step 3-4；
3-2. obtaining connection inverter transimission power P=0；Enter step 6；
3-3. obtains connection inverter transimission power P < S；Wherein, S is rated capacity；
The voltage stabilization that connection current transformer maintains low-voltage direct side is then controlled, and low-voltage direct side is equivalent to power variable
Power supply or load；Enter step 6；
3-4. obtains connection inverter transimission power P=S；Then low-voltage direct busbar voltage by its internal distributed generation resource,
Energy storage and Coordinated are stablized, and low-voltage direct side is equivalent to the fixed power supply or load of power；Enter step 6.
Wherein, step 4 includes:
Under isolated operation mode, determine that the isolated island control target of connection current transformer is to complete low-voltage alternating-current side and low-pressure direct
Flow the overload distribution between side.
Wherein, step 5 includes:
Target is controlled according to isolated island, judges the low-voltage alternating-current side of isolated operation mode and the load condition of low-voltage direct side,
Control a-c cycle and DC voltage fall control directly proportional, and that the energy management unit of participation operation is arranged and connect current transformer
Priority processed is identical；
5-1. controls target according to isolated island, judges the excessively negative of low-voltage alternating-current side under isolated operation mode and low-voltage direct side
Lotus and light load conditions；
If low-voltage alternating-current side and low-voltage direct side are in light load or overload state, into 5-2；
If being in light load conditions there are side in low-voltage alternating-current side and low-voltage direct side, the other side is overload state
When, into 5-3；
5-2. obtains connection inverter transimission power P=0；Enter step 6；
5-3. control a-c cycle and DC voltage fall energy management unit and company directly proportional, and that participation operation is arranged
The control priority for connecing current transformer is identical.
Wherein, 5-3 includes:
Control a-c cycle fall fall with DC voltage it is directly proportional, and to load vacancy entirely mixing distribution system in
It is allocated, the energy management unit for participating in operation is identical as the connection control priority of current transformer；Then there is distribution principle are as follows:
Wherein, K is the ratio between the lower limit value that DC voltage and a-c cycle allow；Vdc0For DC bus-bar voltage；ΔVdcIt is straight
Flow the variable quantity of busbar voltage；f.For a-c cycle；Δ f is the variable quantity of a-c cycle.
Wherein, it is all made of two close cycles vector controlled with the connection inverter under isolated operation mode under the mode that is incorporated into the power networks,
And the switching mode being incorporated into the power networks between mode and isolated operation mode is to change exterior ring power reference value.
The present invention provides a kind of concrete application of the control method of low-voltage AC/DC mixing distribution system connection current transformer
Example, specifically includes:
Low-voltage AC/DC mixing distribution system can be divided into low-voltage alternating-current power grid, low-voltage direct power grid and connection from structure
The AC/DC connection current transformer three parts of the two.
The topological structure of inverter is connected as shown in Fig. 2, by DC bus capacitor, IGBT anti-paralleled diode, filter inductance
And filter capacitor composition.
Two sides are separately connected exchange side bus and direct current side bus, and according to actual needs, connection inverter can work
Rectification and inverter mode, electric current can be known as " connection current transformer " with two-way flow.
Exchange side bus is electrically connected by breaker with city, and when AC circuit breaker disconnects, mixing distribution system operates in orphan
Under the operational mode of island, the mode of being incorporated into the power networks otherwise is operated in.
Wherein, the mainstream control method that exchange side and DC side respectively use: droop control method and the sagging control of layering
Method.
Exchange side it is sagging control refer in AC network participate in system frequency and voltage adjustment unit (distributed generation resource or
Energy storage) respectively using a-c cycle and alternating voltage as reference quantity, the active power and idle of automatic adjustment distributed generation resource output
Power
Given P-f and Q-U droop characteristic are as follows:
Wherein, PmaxMinimum value f is dropped in frequency to participate in the unit of system frequency and voltage adjustmentminWhen export have
Function power maximum value；PNFor rated frequency fNWhen the active power rated value that exports；
QacmaxMinimum value U is dropped to for voltageacminWhen the reactive power maximum value that exports.QacNFor specified alternating voltage
UacNWhen the reactive power rated value that exports.
Droop control method is layered in DC side in energy management and refers to that system will be controlled according to the variable quantity of DC voltage
Method is divided into different control layers, and the working method of energy storage and distributed generation resource is rationally adjusted in different control layers, make be
System in different modes can stable operation；It is as shown in table 1:
Table 1
When alternating current-direct current mixing distribution system is incorporated into the power networks, exchanges side bus voltage and frequency is supported by major network, exchange side
To major network output power when power abundance, otherwise power is absorbed from major network.
DC side can be equivalent to the power supply or load of exchange side, to exchange side output power when DC side power abundance, instead
From exchange side absorb power.
Therefore connection current transformer control target is to maintain the energy balance of DC side.
According to the size of connection current transformer transimission power, the mode of being incorporated into the power networks can be further divided into three states:
State one: when | △ U | < UlWhen, P=0；
State two: work as Ul<|△U|<UhWhen, P < S, this connection current transformer is responsible for maintaining the stabilization of DC bus-bar voltage, direct current
Side is equivalent to the power supply or load of a power variable；
State three: work as Uh< | △ U | when, P=S, DC bus-bar voltage is assisted by its internal distributed generation resource, energy storage and load
It adjusts and stablizes, DC side is equivalent to the power supply or load of constant power.
The control characteristic design that current transformer is connected under grid-connect mode is as shown in Figure 3.
It can be obtained by the control characteristic of connection current transformer, connection current transformer working range corresponds to the in DC side hierarchical control
One layer of control maintains DC bus-bar voltage to stablize prior to energy storage, and connection current transformer is made full use of to adjust voltage capability, optimization storage
The use of energy device.
Meanwhile when | △ U | < UlWhen, P=0 reduces connection current transformer running wastage.
When alternating current-direct current mixes distribution system isolated operation, AC and DC side, which should cooperate with, undertakes entire mixing distribution system
Middle load.
Connecting current transformer control target is rationally divided according to the workload demand power between the two to AC and DC side
Match, support the two each other, improve the stability of mixing distribution system, and not only only considers DC side or exchange side
Workload demand.
Isolated operation mode can be further divided into four kinds of states according to AC and DC side load condition:
State one: AC and DC side is in light load conditions, and the power of connection current transformer transmission is zero, in AC and DC side
The balance of power is by respectively individually maintaining.
State two: being in overload state when exchanging side, and DC side is in light load conditions, connection current transformer transmission
Power flows to exchange side by DC side, and exchange side is equivalent to the load of DC side.
State three: it when DC side is in overload state, and exchanges side and be in light load conditions, connection current transformer transmits
For power from exchange effluent to DC side, DC side is equivalent to the load of exchange side.
State four: when AC and DC side is in overload state, the power of connection current transformer transmission is zero, AC and DC
The balance of power is by respectively individually maintaining in side.
Due to it is grid-connected when connection current transformer maintain DC side busbar voltage to stablize prior to energy storage, therefore be incorporated into the power networks under mode
Energy storage just puts into operation when connection current transformer transimission power reaches limit value.
But under isolated operation mode, guarantee the unit priority that energy management is participated in connection current transformer and AC and DC side
It is not identical.
For state one, state four, DC side with exchange the power-balance of side respectively by respective internal distributed generation resource,
Energy storage, load coordinated control, P=0.
For state two and state three, due to DC bus-bar voltage VdcIt is reflection DC side and friendship respectively with a-c cycle f
The electrical quantity of side energy requirement is flowed,
In order to guarantee the reasonable distribution of power between AC and DC side, it is reasonable that load carries out in entirely mixing distribution system
The principle of distribution is to guarantee than falling with DC voltage than directly proportional, i.e., voltage to frequency falls
Wherein, K is the ratio between DC voltage, the lower limit value of a-c cycle permission.
Converter control method is connected under isolated operation mode on the one hand comprehensively considers the two droop characteristic, rather than it is unilateral
Ground meets direct current or exchanges the energy requirement of side, on the other hand both to connect current transformer and participate in energy management unit control
Priority processed is identical.
Both it can guarantee that the lateral heavy load side of light load provided more energy as far as possible, while having avoided light load is collateral from helping power
Own power missing is excessive afterwards, so that the distribution of power is more reasonable therebetween.
Connection current transformer is the voltage source converter based on full-controlled switch device (IGBT), generallys use double circle structure
Vector controlled
Outer ring be active power/Reactive Power Control, control flow through AC/DC connection power converter active power and its
The reactive power of generation, inner ring are the current control based on d-q decoupler shaft, so that the rapid track reference value of current actual value becomes
Change.
Controller under grid-connected and isolated operation mode is all made of two close cycles vector controlled structure, control block diagram such as Fig. 4
It is shown
Since control method above-mentioned passes through active/reactive power reference qref Pref、QrefThe variation of following state and realize.
Therefore, the switching between the mode that is incorporated into the power networks and isolated operation mode need to only change value and power reference, to avoid
Complicated control mode switch.
Next grid-connected and isolated island controller value and power reference is introduced respectively to choose:
Net-connected controller active power reference value P can be obtained according to Fig. 3refAre as follows:
Due to not having reactive power in DC side, reactive power is existed only in exchange side, provides one for exchange side bus
Fixed voltage support.
Reactive power reference qref QrefSelection should meet connection current transformer active priority principle, obtain reactive power ginseng
Examine value limit value Qref_maxAre as follows:
S indicates the capacity of connection current transformer in formula.On the basis of above formula, according to Q-UacSagging control, meets as far as possible
Exchange the reactive requirement of side.
When exchanging side frequency decline Δ f, changed power Δ PacPoint including participating in exchange side voltage and frequency adjusting
Cloth power supply generates the sum of the increase of power, the reduced value for exchanging side load absorption power, i.e.,
ΔPac=kacΔf (2)
Wherein, kac=1/R1+1/R2+...+1/Rn+Lac, R1、R2..., RnIt is adjusted for participation exchange side voltage and frequency
Each sagging coefficient of AC power source, LacTo exchange side load damping constant.
When DC voltage declines Δ VdcWhen, corresponding changed power Δ PdcEnergy storage including participating in DC voltage regulation
The increase of output power, DC load absorb the sum of the power of reduced power and connection current transformer capacitor release, but connect
Current transformer stores up releasable power proportion very little, can ignore.
Wherein, kdc=1/D1+1/D2+…+1/Dn+Ldc, D1、D2、…、DnTo participate in each energy storage that DC voltage is adjusted
Sagging coefficient, LdcDC load absorbs the reduced value of power, C when declining unit value for DC voltagedcAnd Vdc0Respectively connect
The DC bus capacitor value and DC side load voltage value of current transformer.
It can be obtained by formula (1)~(3),
ΔPac+ΔPdc=Δ P (5)
Wherein, 0≤Δ Pac, Δ Pdc≤S。
Isolated island controller active power reference value PrefSelection as shown in figure 5, the selection of reactive power reference qref with it is grid-connected
Controller is identical.
S=0 is directed to state one and state four, when detecting that AC and DC side load condition is in light load or excessively negative
When lotus state, P is enabledref=0.
S=1 is directed to state two, and the power shortage value Δ P of load in exchange side, then root is calculated by formula (1) first
According to formula (4)~(5) to the active power reference value Δ P of connection current transformerdc, as DC side support exchange side performance number
Pref。
S=2 is directed to state three, and the power shortage value Δ P of load in DC side, then root is calculated by formula (2) first
According to formula (4)~(5) to the active power reference value Δ P of connection current transformerac, as exchange the collateral performance number for helping DC side
Pref。
The above embodiments are merely illustrative of the technical scheme of the present invention and are not intended to be limiting thereof, although referring to above-described embodiment pair
The present invention is described in detail, those of ordinary skill in the art still can to a specific embodiment of the invention into
Row modifies perhaps equivalent replacement and these exist without departing from any modification of spirit and scope of the invention or equivalent replacement
Apply within pending claims of the invention.
Claims (3)
1. a kind of control method of low-voltage AC/DC mixing distribution system with connection current transformer, the low-voltage AC/DC mixing distribution
Connection current transformer, energy storage device and energy management unit are equipped in system, which is characterized in that the connection current transformer both ends difference
Connect low-voltage direct side bus and low-voltage alternating-current side bus；
Described method includes following steps:
Step 1. judges the object run mode of the low-voltage AC/DC mixing distribution system；
If the object run mode is the mode that is incorporated into the power networks, 2 are entered step；
If the object run mode is isolated operation mode, 4 are entered step；
Step 2. determines the cutting-in control target of the connection current transformer；
Step 3. according to the cutting-in control target, simultaneously control by the DC bus-bar voltage changing value that is incorporated into the power networks under mode described in judgement
It makes the connection current transformer and carries out control operation；Enter step 6；
Step 4. determines that the isolated island of the connection current transformer controls target；
Step 5. controls target according to the isolated island, judges the low-voltage alternating-current side and the low-voltage direct of the isolated operation mode
The overload of side and light load conditions simultaneously control the connection current transformer and carry out control operation；
Step 6. maintains current state of a control, and the order of the object run mode, return step 1 are updated until receiving；
The step 3 includes:
3-1. according to the cutting-in control target, the DC bus-bar voltage changing value △ U that is incorporated into the power networks under mode described in judgement with
The upper limit value Uh and lower limit value Ul relationship of DC voltage change:
If | △ U | < Ul；Then enter step 3-2；
If Ul < | △ U | < Uh；Then enter step 3-3；
If Uh < | △ U |；Then enter step 3-4；
3-2. obtains the connection current transformer transimission power P=0；Enter step 6；
3-3. obtains the connection current transformer transimission power P < S；Wherein, S is rated capacity；
The voltage stabilization that the connection current transformer maintains the low-voltage direct side is then controlled, and the low-voltage direct side is equivalent to function
Rate variable power supply or load；Enter step 6；
3-4. obtains the connection current transformer transimission power P=S；Then the low-voltage direct busbar voltage is by its internal distributed electrical
Source, energy storage and Coordinated are stablized, and the low-voltage direct side is equivalent to the fixed power supply or load of power；Enter step 6；
The step 2 includes:
Under the mode that is incorporated into the power networks, according to the power output of the low-voltage alternating-current side and be sent into path and with the low pressure
The equivalent relation of DC side determines that the cutting-in control target of the connection current transformer is to maintain the energy of the low-voltage direct side flat
Weighing apparatus；
The step 4 includes:
Under the isolated operation mode, the isolated island control target of the connection current transformer is determined to complete the low-voltage alternating-current side
Overload distribution between the low-voltage direct side；
The step 5 includes:
Target is controlled according to the isolated island, judges the low-voltage alternating-current side of the isolated operation mode and bearing for low-voltage direct side
Lotus state, controls a-c cycle and DC voltage falls the energy management unit and institute directly proportional, and that participation operation is arranged
The control priority for stating connection current transformer is identical；
5-1. controls target according to the isolated island, judges the low-voltage alternating-current side and the low-voltage direct under the isolated operation mode
The overload of side and light load conditions；
If the low-voltage alternating-current side and low-voltage direct side are in light load or overload state, into 5-2；
If being in light load conditions there are side in the low-voltage alternating-current side and low-voltage direct side, the other side is overload state
When, into 5-3；
5-2. obtains the connection current transformer transimission power P=0；Enter step 6；
5-3. control a-c cycle and DC voltage fall the energy management unit and institute directly proportional, and that participation operation is arranged
The control priority for stating connection current transformer is identical.
2. the method as described in claim 1, which is characterized in that the 5-3 includes:
Control a-c cycle fall fall with DC voltage it is directly proportional, and to load vacancy entirely mixing distribution system in carry out
Distribution, the energy management unit for participating in operation are identical as the connection control priority of current transformer；Then there is distribution principle
Are as follows:
Wherein, K is the ratio between the lower limit value that DC voltage and a-c cycle allow；Vdc0For DC bus-bar voltage；ΔVdcFor direct current mother
The variable quantity of line voltage；f.For a-c cycle；Δ f is the variable quantity of a-c cycle.
3. the method as described in claim 1, which is characterized in that under the mode that is incorporated into the power networks with the institute under isolated operation mode
It states connection current transformer and is all made of two close cycles vector controlled, and the switching side being incorporated into the power networks between mode and isolated operation mode
Formula is to change exterior ring power reference value.
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