CN111030152B - Energy storage converter system and control method thereof - Google Patents
Energy storage converter system and control method thereof Download PDFInfo
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- CN111030152B CN111030152B CN201911309035.2A CN201911309035A CN111030152B CN 111030152 B CN111030152 B CN 111030152B CN 201911309035 A CN201911309035 A CN 201911309035A CN 111030152 B CN111030152 B CN 111030152B
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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
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
- H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
- H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/79—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/797—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
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Abstract
The invention discloses an energy storage converter system and a control method, wherein the energy storage converter system comprises the following steps: the system comprises a grid-connected/off-grid control cabinet and a plurality of energy storage converters respectively connected with the grid-connected/off-grid control cabinet; the energy storage converters are connected in parallel; the structure of the energy storage converter comprises: three-phase branches, each phase branch includes: the system comprises a grid-connected/off-grid control cabinet, a direct-current storage battery, an isolation transformer, an alternating-current filter, an alternating-current soft start circuit, a filter circuit, a bridge inverter circuit, a direct-current bus capacitor, a direct-current filter and a direct-current soft start circuit, wherein the isolation transformer, the alternating-current filter, the alternating-current soft start circuit, the filter circuit, the bridge inverter circuit, the direct-current bus capacitor, the direct-current filter and the direct-current soft start circuit are sequentially connected in series from the grid-connected/off-grid control cabinet to a direct-current storage battery end; the positive electrodes of the output ends of the three-phase branch direct-current bus capacitors are connected through a direct-current contactor; and the negative electrodes of the output ends of the three-phase branch direct-current bus capacitors are connected through a direct-current contactor. The invention has the beneficial effects that: the direct current output end can be connected with batteries with different voltage grades; the outer ring detection and control are completed by a parallel/grid-connected/off-grid control cabinet, so that the imbalance of the sampling and outer ring calculation errors is eliminated.
Description
Technical Field
The invention relates to the technical field of energy storage converters, in particular to an energy storage converter system and a control method thereof.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
At present, the new energy industry is developing rapidly, and in order to stabilize the fluctuation of the distributed new energy, an energy storage system is often equipped. In the energy storage system, an energy storage converter (PCS) enables the output of the distributed new energy microgrid system to be controllable according to a preset management strategy, effectively inhibits the rapid fluctuation of grid-connected power, and has power grid friendliness.
Most of existing energy storage converters adopt a three-phase half-bridge structure, and under the condition that the withstand voltage of power switching tubes meets requirements, the three-phase half-bridge structure only adopts six power switching tubes, each bridge arm only has two switching tubes, and any two phases are coupled, so that when a three-phase power grid is unbalanced, the control performance of the three-phase power grid is deteriorated, and even a fault occurs. The three-phase half-bridge structure determines that the single-stage energy storage converter only has one direct current output end, cannot meet the connection work of batteries with different voltage grades on the same energy storage converter, and cannot realize the gradient utilization of the batteries.
In addition, as the capacity of the new energy microgrid is continuously increased, an energy storage converter with larger capacity needs to be configured, and a plurality of energy storage converters need to be operated in parallel in consideration of the power level of the energy storage converter. At present, energy storage converters often adopt a master-slave control strategy, a master energy storage converter sends a scheduling instruction to schedule power of slave energy storage converters, but each energy storage converter usually collects information of voltage, current and the like of respective grid-connected points respectively to perform PQ control or VF control calculation, and because small differences exist in the aspects of detection systems, detection points, operation errors and the like, processing of each energy storage converter is not balanced easily, and even parallel connection failure may be caused.
Disclosure of Invention
In order to solve the problems, the invention provides an energy storage converter system and a control method thereof, which adopt a three-phase full-bridge structure to solve the working problem when the power grid is unbalanced and can effectively eliminate the unbalance problem of sampling and outer loop calculation errors of each energy storage converter.
In some embodiments, the following technical scheme is adopted:
an energy storage converter system comprising: the system comprises a grid-connected/off-grid control cabinet and a plurality of energy storage converters respectively connected with the grid-connected/off-grid control cabinet; the energy storage converters are connected in parallel; the structure of the energy storage converter comprises:
three-phase branches, each phase branch includes: the system comprises a grid-connected/off-grid control cabinet, a direct-current storage battery, an isolation transformer, an alternating-current filter, an alternating-current soft start circuit, a filter circuit, a bridge inverter circuit, a direct-current bus capacitor, a direct-current filter and a direct-current soft start circuit, wherein the isolation transformer, the alternating-current filter, the alternating-current soft start circuit, the filter circuit, the bridge inverter circuit, the direct-current bus capacitor, the direct-current filter and the direct-current soft start circuit are sequentially connected in series from the grid-connected/off-grid control cabinet to a direct-current storage battery end; the positive electrodes of the output ends of the three-phase branch direct-current bus capacitors are connected through a direct-current contactor; and the negative electrodes of the output ends of the three-phase branch direct-current bus capacitors are connected through a direct-current contactor.
In other embodiments, the following technical solutions are adopted:
an energy storage converter system comprising: the system comprises a grid-connected/off-grid control cabinet and a plurality of energy storage converters respectively connected with the grid-connected/off-grid control cabinet; the energy storage converters are connected in parallel; the structure of the energy storage converter comprises:
three-phase branches, each phase branch includes: the grid-connected/off-grid control cabinet is connected with a direct-current storage battery end in series, and an alternating-current filter, an alternating-current soft start circuit, a filter circuit, a bridge type inverter circuit, a direct-current bus capacitor, a direct-current filter and a direct-current soft start circuit are sequentially connected in series; the positive electrodes of the output ends of the three-phase branch direct-current bus capacitors are connected through a direct-current contactor; and the negative electrodes of the output ends of the three-phase branch direct-current bus capacitors are connected through a direct-current contactor.
In other embodiments, the following technical solutions are adopted:
a method of controlling an energy storage converter system, comprising:
when the direct current ends of the three-phase branch circuits are connected with storage batteries of different models and voltage grades, the connection between the output ends of the direct current bus capacitors of the three-phase branch circuits is disconnected;
after the soft start stage is completed, respectively acquiring values of alternating current voltage, inductive current, direct current bus voltage and direct current for each phase of branch; setting a direct-current voltage given value and a current given value;
according to the collected value, obtaining a driving signal for driving the switching tube of the phase branch bridge type inverter circuit to be switched on and off after operation;
and controlling the amplitude difference and the phase angle between the alternating current sinusoidal waveform output by the bridge inverter circuit and the power grid voltage to obtain a current waveform with the same phase as the power grid voltage, so as to charge the storage battery.
In other embodiments, the following technical solutions are adopted:
a method of controlling an energy storage converter system, comprising:
when the direct current ends of the three-phase branch circuits are connected with storage batteries with the same type and voltage class, the direct current bus capacitor output ends of the three-phase branch circuits are connected; setting the direct-current voltage given value and the charging current given value of the three-phase branch to be respectively the same;
after the soft start stage is completed, respectively acquiring values of alternating current voltage, inductive current, direct current bus voltage and direct current for each phase of branch;
obtaining a driving signal for driving the switching tube of the phase branch bridge type inverter circuit to be switched on and off after operation according to the collected value and the set value;
and controlling a phase angle between an alternating current sine waveform output by the bridge inverter circuit and the power grid voltage to obtain a current waveform with the same phase as the power grid voltage, so as to charge the storage battery.
In other embodiments, the following technical solutions are adopted:
a method of controlling an energy storage converter system, comprising: under the grid-connected state, generating a current component reference value through coordinate transformation and PI operation according to collected grid-connected point voltage and current information;
respectively sending the obtained current component reference values to each energy storage converter connected in parallel;
each energy storage converter respectively collects the output current thereof to carry out coordinate transformation, so as to obtain current components;
carrying out PI operation on the current component and the current component reference value to obtain a pulse width modulation coefficient component;
and generating a driving signal according to the pulse width modulation coefficient component to drive the corresponding switch tube of the energy storage converter to be switched on and off.
In other embodiments, the following technical solutions are adopted:
a method of controlling an energy storage converter system, comprising:
under the off-grid state, according to the collected voltage and current information of the parallel point, a current amplitude reference value and a reference current frequency are obtained through current and voltage amplitude calculation, phase-locked calculation and PI operation;
respectively sending the obtained current amplitude reference value and the obtained reference current frequency to each energy storage converter connected in parallel;
each energy storage current transformer respectively collects the output current of each energy storage current transformer, and the current amplitude is calculated to obtain the feedback current amplitude;
carrying out PI operation on the feedback current amplitude and a current amplitude reference value to obtain a pulse width modulation coefficient;
and generating a driving signal according to the pulse width modulation coefficient and the reference current frequency to drive the corresponding switch tube of the energy storage converter to be switched on and off.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention can realize that the direct current output end can be connected with batteries with different voltage grades, improve the power grid applicability of the energy storage converter and realize the stable and reliable work of the energy storage converter when the power grid is unbalanced.
(2) The invention provides a bidirectional alternating current-direct current conversion control method, a three-phase discrete operation circuit topology framework is constructed, the problems of single-phase digital coordinate transformation and phase locking are solved, and the adaptability and flexibility of an energy storage system to a power grid and different battery voltages are improved;
the positive pole and the negative pole of the three-phase branch direct current bus capacitor output end are connected through the direct current contactor respectively, and the energy storage converter is connected with batteries with different voltage grades to work normally by controlling the on-off of the direct current contactor, so that the input cost of the energy storage converter for different batteries is reduced.
The conversion from a three-phase four-wire system power supply mode to a three-phase three-wire system power supply mode can be realized by simply changing the wiring mode of the energy storage converter, and the same machine can be suitable for different power grid power supply modes.
(3) The invention provides an energy storage converter grid-connected control method based on three-loop control, solves the problem of unbalance caused by measurement and operation of a converter, realizes reliable and stable access of the energy storage converter to a power grid, and improves the grid-connected load balancing precision of the energy storage converter.
(4) The invention provides an off-grid parallel control algorithm of the energy storage converter based on three-loop control, solves the problem of automatic load distribution of an off-grid parallel control system, realizes ordered parallel connection of the energy storage converters, and improves the expandability of the system.
(5) The method comprises the following steps of (1) separating inner and outer ring control of the traditional PQ or VF control, performing outer ring PI operation by a grid-connected/off-grid control cabinet, distributing current inner ring reference to each parallel energy storage converter, and performing current inner ring operation by each parallel energy storage converter; the shunting coefficient is introduced into each parallel energy storage converter, and the shunting coefficient can be independently set on a human-computer interface to change the load sharing proportion of each parallel converter; the unbalance problem of sampling and outer ring calculation errors of each energy storage converter can be effectively solved, ordered parallel connection of the energy storage converters is realized, and the expandability of the system is improved.
Drawings
FIG. 1 is a topological diagram of parallel operation of energy storage converters in an embodiment of the present invention;
FIG. 2 is a circuit topology diagram of an energy storage converter with an isolation transformer according to an embodiment of the present invention;
FIG. 3 is a circuit topology diagram of an energy storage converter without an isolation transformer according to an embodiment of the present invention;
FIG. 4 is a control diagram of grid-connected parallel operation of the energy storage converter in the embodiment of the invention;
FIG. 5 is a control diagram of the off-grid parallel operation of the energy storage converter in the embodiment of the invention;
FIG. 6 is a control block diagram of an energy storage converter in an embodiment of the present invention;
FIG. 7 is a block diagram of a phase locked loop of the energy storage converter in an embodiment of the present invention;
fig. 8 is a coordinate transformation block diagram of the energy storage converter in the embodiment of the present invention.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
Example one
In one or more embodiments, an energy storage converter system is disclosed, as shown in fig. 1, including 1 set of grid-connected/off-grid control cabinets and a plurality of sets of energy storage converters (PCS), where the number of energy storage converters is N, and N is greater than 1. The grid-connected/off-grid control cabinet is provided with N +2 ports, wherein the N ports are connected with the energy storage converter, 1 grid-connected port and 1 off-grid port (load port); and grid connection and grid disconnection can be controlled.
The grid-connected port of the grid-connected/off-grid control cabinet is connected with a power grid, and the load port is connected with a load. A bypass switch is arranged between a grid-connected port and a load port of the grid-connected/off-grid control cabinet, and a power grid can directly supply power to the load. Besides the grid-connected switch, a thyristor switch is connected in series between the grid-connected port of the grid-connected/off-grid control cabinet and the power grid so as to realize the fast switching of grid connection and off-grid.
And the energy storage converters connected in parallel are respectively provided with a shunt coefficient, and the shunt coefficients are all set to be 1 or equal when the load is required to be equally divided.
And the grid-connected/off-grid control cabinet receives a user or an energy management system instruction and selects a working mode to be a grid-connected mode or an off-grid mode.
The structure of the energy storage converter comprises: three-phase branches, each phase branch includes: the system comprises a grid-connected/off-grid control cabinet, a direct-current storage battery, an isolation transformer, an alternating-current filter, an alternating-current soft start circuit, a filter circuit, a bridge inverter circuit, a direct-current bus capacitor, a direct-current filter and a direct-current soft start circuit, wherein the isolation transformer, the alternating-current filter, the alternating-current soft start circuit, the filter circuit, the bridge inverter circuit, the direct-current bus capacitor, the direct-current filter and the direct-current soft start circuit are sequentially connected in series from the grid-connected/off-grid control cabinet to a direct-current storage battery end; the positive electrodes of the output ends of the three-phase branch direct-current bus capacitors are connected through a direct-current contactor; and the negative electrodes of the output ends of the three-phase branch direct-current bus capacitors are connected through a direct-current contactor.
Referring to fig. 2, each phase of the energy storage converter is separately connected with a transformer for isolation, alternating current is directly converted into direct current to charge a battery, and meanwhile, the battery discharge grid connection is realized, and the energy storage converter can realize the functions of regulating direct current output voltage and current. The direct current end of the energy storage converter is provided with three groups of connecting terminals, and each group of terminals can be connected with a battery.
Taking the a-phase circuit structure as an example, the transformer T1 plays a role in isolation and transformation; the alternating current filter filters alternating current EMC interference; the alternating current soft start circuit consists of a main alternating current contactor, an auxiliary alternating current contactor and a soft start resistor, so that the slow charging effect on a rear-stage direct current bus capacitor is realized during power-on, and the impact of large current generated at the moment of power-on the energy storage converter and a power grid is avoided; the LC filter circuit consists of an alternating current filter inductor and a filter capacitor, and filters high-frequency components of the SPWM wave generated by the bridge type inverter circuit to obtain a smooth alternating current waveform; the bridge type inverter circuit consists of IGBTs (insulated gate bipolar transistors), the IGBTs are connected with a direct current bus capacitor, each bridge arm of the IGBT bridge type inverter circuit is connected with an absorption capacitor, the absorption capacitors absorb high-frequency peaks generated when the IGBT bridge type inverter circuit acts and play a role in protecting the IGBTs, the direct current bus capacitor plays a role in supporting and filtering direct current voltage, and the IGBT bridge type inverter circuit inverts a direct current voltage waveform into a high-frequency SPWM (sinusoidal pulse width modulation) voltage waveform; the direct current filter filters out direct current EMC interference; the direct current soft start loop consists of a main direct current contactor, an auxiliary direct current contactor and a soft start resistor, and the impact of large current generated in the electrifying moment on the energy storage converter and the battery is avoided.
B. The circuit structure and device parameters of the phase C are identical to those of the phase A, and are not described repeatedly.
A. B, C the output ends of the three-phase DC bus capacitors are connected through the DC contactor, the positive poles and the negative poles are respectively and independently connected, the three-phase DC bus capacitors can be connected together or completely separated by controlling the on-off of the DC contactor, the positive poles of the three-phase DC bus capacitors are connected together after the DC contactor is closed, the negative poles of the DC bus capacitors are connected together, at the moment, the three-phase DC + and DC-ends can only be connected with the batteries with the same voltage class, after the DC contactor is disconnected, the three-phase DC is mutually independent, at the moment, the three-phase DC + and DC-ends can be respectively connected with the batteries with different voltage classes, and the applicability of the same energy storage converter to the batteries with different voltage classes is realized.
The primary sides of the transformers of the energy storage converter shown in FIG. 2 are connected end to end in sequence, namely, the primary sides of the transformers are connected into a triangular connection relationship, three-phase three-wire power supply can be achieved, the wiring mode of the energy storage converter is simply changed, the conversion from a three-phase four-wire system power supply mode to a three-phase three-wire system power supply mode can be achieved, and the same machine can be suitable for different power grid power supply modes.
It should be noted that the parallel converters should adopt the same wiring method, the ac side of the converters and the grid side enter the grid-connected/parallel control cabinet, and the grid-connected control cabinet adopts the same wiring method.
In other embodiments, an energy storage converter without an isolation transformer is disclosed, and referring to fig. 3, one end of each ac filter of the energy storage converter is connected to N through a grid-connected/off-grid control cabinet, and the other end of each ac filter is connected to a power grid A, B, C through the grid-connected/off-grid control cabinet, so that the energy storage converter without transformer isolation can be implemented.
The energy storage converter alternating current filters shown in the figure 3 are connected end to end in sequence, namely the filters are connected into a triangular connection relation, and then three-phase three-wire power supply can be achieved.
It should be noted that the parallel converters should adopt the same wiring method, the ac side of the converters and the grid side enter the grid-connected/parallel control cabinet, and the grid-connected control cabinet adopts the same wiring method.
Example two
In one or more embodiments, in order to realize load balancing of the parallel energy storage converters, a control method of an energy storage converter system is disclosed, a grid-connected/off-grid control cabinet acquires information such as a power grid, load voltage, current and the like, fault or abnormality judgment is carried out, and a protection mode or alarm is selected according to a determined strategy.
Firstly, the parallel control method of the energy storage converter in the grid-connected state is shown in fig. 4, and the parallel/grid control cabinet executes the following operation steps:
1) collecting three-phase voltage and three-phase current of a grid connection point;
2) phase locking is carried out on the three-phase voltage of the grid-connected point to obtain the running frequency of the power grid;
3) the dq conversion module carries out alpha beta/dq conversion on the collected three-phase voltage and three-phase current to obtain actual total feedback voltage and feedback current under a two-phase synchronous rotating coordinate system;
4) the instantaneous power conversion module determines instantaneous active power and instantaneous reactive power of a grid-connected point according to the following formula according to the obtained actual total feedback voltage and feedback current under the two-phase synchronous rotating coordinate system;
wherein P and Q respectively represent the total instantaneous active power and the instantaneous reactive power of the grid-connected pointRate, udRepresenting the total d-axis actual feedback voltage, u, of the grid-connected pointqRepresenting the total q-axis actual feedback voltage, i, of the grid-connected pointdRepresenting the total d-axis actual feedback current, i, of the grid-connected pointqRepresenting the total q-axis actual feedback current of the point of grid connection.
5) The parallel/grid-connected/off-grid control cabinet obtains the active power and reactive power reference value P of the grid-connected point according to the dispatching instruction of the slave user or the energy management systemref、QrefComparing the difference value with the instantaneous active power P and the reactive power Q to obtain difference values delta P and delta Q, and carrying out proportional integral operation on the delta P and the delta Q to obtain a d-axis component reference value idrefAnd q-axis component reference value iqref. Generally, the clipping control is performed on the reference current through the dq component clipping module.
6) D-axis component reference value i of communication module of parallel/network control cabinetdrefAnd q-axis component reference value iqrefAnd broadcasting and sending the data to each energy storage converter.
7) The x-th energy storage converter receives a reference current idref、iqrefAnd collecting self-outlet inductive current iax、ibx、iaxFeedback current i under two-phase synchronous rotating coordinate system obtained by dq conversiondx、iqxObtaining a difference value delta i after comparisondx、δiqxFor δ idx、δiqxPerforming proportional-integral operation to obtain output pulse width modulation coefficient Pmdx、Pmqx。
8) The x-th energy storage current transformer is based on the pulse width modulation coefficient Pmdx、PmqxAnd PWM algorithm generates driving signals to realize the on-off control of the switching tube.
9) The x-th energy storage current transformer is based on the pulse width modulation coefficient Pmdx、PmqxAnd PWM algorithm generates driving signals to realize the on-off control of the switching tube.
10) And the energy storage converters connected in parallel automatically share the load. When the number of parallel connections changes, the current reference i output is controlled by the power outer loopd-ref、id-refIs obtained by carrying out PI operation on instantaneous power and reference power of grid-connected point voltage and total current,therefore, the system can automatically share the load, and when the number of the energy storage converters connected in parallel is changed, the system can automatically redistribute the power.
Secondly, the parallel control method of the energy storage converter in the off-grid state is shown in fig. 5, and the parallel/grid-connected/off-grid control cabinet executes the following operation steps:
1) collecting three-phase voltage and three-phase current of a parallel point;
2) phase locking is carried out on the three-phase voltage of the grid-connected point to obtain frequency feedback f of the grid-connected point;
3) the amplitude calculation module obtains voltage and current feedback amplitudes u and i of a grid connection point according to the collected three-phase voltage and three-phase current;
4) taking the feedback frequency f, the feedback voltage u and the reference frequency f of the parallel pointref50Hz reference voltage amplitude urefComparing 220V or 380V to obtain frequency error delta f and voltage amplitude error delta u, and respectively carrying out proportional integral operation to obtain frequency coefficient f of modulated signaloAnd the amplitude of the parallel point reference current iref；
It should be noted that the parallel point mentioned in the present embodiment refers to a point where the energy storage converters are connected in parallel, and refer to the position of (r) in fig. 1.
5) Parallel point reference current amplitude irefComparing with the feedback current amplitude i of the grid-connected point to obtain the current error delta i of the grid-connected point, performing proportional integral operation on the delta i, and performing parallel-connected point current inner loop operation on the result io-refAs the current inner ring reference current of each parallel energy storage converter;
6) the communication module of the parallel/network control cabinet refers to the current amplitude value io-refAnd a frequency coefficient foBroadcasting and sending to each energy storage converter;
7) the x-th energy storage converter receives a reference current idref、iqrefAnd collecting self-outlet inductive current iax、ibx、icxAnd calculating the current amplitude to obtain a feedback current amplitude ixObtaining a difference value delta i after comparisonxFor δ ixPerforming proportional-integral operation to obtain output pulse width modulation coefficient Pmx；
8) The x-th energy storage current transformer is based on the pulse width modulation coefficient PmxAnd a frequency coefficient foThe PWM algorithm generates a driving signal to realize the on-off control of the switching tube;
9) and the energy storage converters connected in parallel automatically share the load. The current amplitude reference values of each energy storage converter connected in parallel are equal and are current reference values i obtained through PI operation of the grid-connected pointo-refDue to the reference current io-refIs composed of a total current detection value i and a total current reference value irefThe system can automatically equally divide the load, especially when the number of the parallel energy storage converters is changed, the system can automatically equally divide the load again. When the number of the energy storage converters connected in parallel is changed, the system can also automatically redistribute the power.
In the control method disclosed by the embodiment, the outer ring detection and control are completed by the parallel/grid-connected control cabinet, so that the imbalance of the respective sampling of the energy storage converter and the outer ring calculation error is eliminated, the energy storage converter is reliably and stably connected into a power grid, and the grid-connected load balancing precision of the energy storage converter is improved. The parallel/grid-connected control cabinet performs power, voltage outer ring control and total current PI control, each parallel energy storage converter performs inner ring current control, and each parallel converter can be regarded as a current source no matter whether the parallel or off-grid connection is performed, so that the current sharing precision is improved;
the shunting coefficient is introduced into each parallel energy storage converter, and the shunting coefficient can be independently set on a human-computer interface to change the load sharing proportion of each parallel converter; the problem of automatic load distribution of an off-grid parallel control system is solved, ordered parallel connection of the energy storage converters is realized, and the expandability of the system is improved.
When the off-grid parallel connection is carried out, the parallel control cabinet increases a total current PI control link, the total current and the current of each parallel energy storage converter are controlled, the current control precision is improved, and the load requirement is better met.
In other embodiments, in order to realize that the dc output terminal of each parallel energy storage converter can be connected with batteries with different voltage levels, a method for controlling an energy storage converter system is disclosed, which, with reference to fig. 6, includes:
taking the control process of the A phase of a certain converter as an example, the energy storage converter passes through the alternating current filter, the transformer T1 and the grid connection-
The parallel control cabinet is connected with a power grid, DC1+ and DC 1-on the direct current side are connected with the positive electrode and the negative electrode of the battery, and meanwhile, the types and the voltage grades of the batteries connected with DC2+ and DC2-, DC3+ and DC 3-are different from those of the batteries connected with DC1+ and DC 1-.
Because the three-phase direct current output end is connected with batteries with different models and voltage grades, when the energy storage converter is electrified, the Kdc1 and the Kdc2 are firstly ensured to be disconnected, the direct current buses are respectively independent, and the three phases independently control the charging and discharging voltage and current of the batteries;
then entering a soft start stage, closing an auxiliary alternating current contactor K2, limiting the current of a soft start resistor R1, charging a direct current bus capacitor C4 after rectifying through anti-parallel diodes of bridge inverter circuits Q1, Q2, Q3 and Q4, closing an auxiliary direct current contactor K4 of a direct current soft start loop, limiting the current of a soft start resistor R2, and charging a direct current bus capacitor C4;
according to the function and performance parameters of the energy storage converter, the battery voltage is required to be greater than the direct-current voltage obtained by three-phase uncontrolled rectification; after the auxiliary contactor is closed and charged for 5s, the soft start is completed, the alternating current main contactor K1 is closed, the direct current main contactor K3 is closed, and the alternating current auxiliary contactor K2 and the direct current auxiliary contactor K4 are opened.
The control circuit samples the A-phase alternating voltage to obtain UaFor the inductor current L1Sampling to obtain iLSampling the DC bus voltage to obtain UdcSampling direct current to obtain Idc(ii) a Sampled power grid voltage UaAfter dq coordinate transformation as shown in FIG. 8, U is obtainedd、UqInductor current i obtained by samplingLI is obtained after dq coordinate transformation as shown in FIG. 8d、Iq；UaThe grid voltage phase θ is obtained through the PLL phase-locked loop shown in fig. 7, and all coordinate transformations are performed under the grid phase θ.
Setting a given value U of DC voltage in the process of charging the batterydcrefThe value of (a) is,setting a given value of charging current IdcrefValue of (D), UdcrefAnd a DC voltage sampling value UdcPerforming negative feedback operation to obtain error value UdcErr，UdcErrSending the data to a direct current voltage loop PI controller for PI operation to obtain a PI operation result UdcPI；IdcrefAnd the DC current sampling value IdcPerforming negative feedback operation to obtain error value IdcErr，IdcErrSending the current to a direct current loop PI controller for PI operation to obtain a PI operation result IdcPI；
UdcPIAnd IdcPIObtaining d-axis current loop current set value I after minimum value operationdref，IqrefSet to zero during charging, IdrefAnd idPerforming negative feedback operation to obtain IdErr，IdErrSending the current to a d-axis current loop PI controller for PI operation to obtain IdPI；
IqrefAnd iqPerforming negative feedback operation to obtain IqErr，IqErrSending the current to a q-axis current loop PI controller to carry out PI operation to obtain IqPI，UdAnd UqSubtract I respectivelydPIAnd IqPIThen divided by the sampled values of the bus voltage UdcNormalization is carried out, the normalized value is sent to an SPWM drive waveform generation circuit, four SPWM drive signals are generated to drive the on and off of Q1, Q2, Q3 and Q4 respectively, peak voltages are generated in stray inductance of the circuit in the on and off processes of Q1, Q2, Q3 and Q4, the absorption is carried out by the absorption capacitors C2 and C3, the overvoltage damage of the IGBT is avoided, the direct current voltage of the capacitor C4 is switched on and off by the Q1, the Q2, the Q3 and the Q4, high-frequency SPWM voltage waveforms are generated at the connection end of Q1 and Q2 and the connection end of Q3 and Q4, the high-frequency SPWM voltage waveforms are filtered by a filter loop consisting of L1, L2 and C1 to obtain smooth alternating current sine waveforms, the amplitude difference and the phase angle between the sine waveforms generated by the SPWM and the voltage of a power grid are controlled, therefore, a current waveform iL with the same phase as the voltage of the power grid is obtained, and the energy storage converter absorbs energy from the power grid to charge the battery.
All the PI controllers have amplitude limiting functions, and the d-axis current loop PI controller and the q-axis current loop PI controller have the same control parameters.
Setting a given value U of bus voltage when discharging the batterydcrefIs less than the rated voltage of the battery and has a given value UdcrefAnd a feedback value UdcOutput error U is always output when balance cannot be achieveddcErrThe output value of the direct current voltage loop PI controller is always the upper limit value of amplitude limiting, and after the minimum value operation module is taken, the discharge current is set to be IdcrefDetermining; i isdcrefThe discharging function of the battery can be realized only by setting the discharge voltage to be a negative value; during discharge of the battery IqrefSet to zero; other control processes are the same as the above charging process, and are not described repeatedly here.
In the charging and discharging processes, the three-phase direct-current output ends DC1+ and DC1-, DC2+ and DC2-, DC3+ and DC 3-are respectively connected with batteries of different models and voltage grades, A, B, C three-phase direct-current voltage given value Udcref and current given value Idcref need to be set to different values according to battery parameters, other control processes of the B-phase and the C-phase are the same as the processes, and repeated description is omitted here.
In other embodiments, when three-phase direct current output terminals DC1+ and DC1-, DC2+ and DC2-, DC3+ and DC 3-are connected with batteries with the same type and voltage grade, after the energy storage converter is powered on, first, Kdc1 and Kdc2 are ensured to be closed, direct current buses are ensured to be connected with each other, and A, B, C three-phase direct current voltage given value U is ensureddcrefAnd given value of current IdcrefThe same values should be set, and other charge and discharge control processes are the same as the above control processes, and will not be described again.
Other control processes connected to the power grid are the same as those described above, and will not be described again.
FIG. 7 is a block diagram of a phase-locked loop of the single-stage energy-storage converter of the present invention, where an input signal u passes through a biquad generalized integrator to obtain u 'and qu', and corresponding transfer function formulas are as follows
The method comprises the steps that an input signal u is subjected to biquad generalized integrator operation to obtain u' in phase with u and qu of a lagging u signal by 90 degrees, the two signals are respectively sent to alpha beta/dq conversion to obtain a u _ q signal, PI operation is carried out on the u _ q signal, a feedforward signal omega f is added, an integrator is used for carrying out remainder operation on an obtained integration result to 2 PI, an angle theta is obtained after the remainder operation, meanwhile, the theta is sent to alpha beta/dq conversion to form negative feedback, when the u _ q signal obtained by the alpha beta/dq conversion is zero, the numerical value of the theta is the angle of a phase-locked signal u, wherein the alpha beta/dq conversion formula is as follows
Fig. 8 is a block diagram of coordinate transformation of a single-stage energy storage converter according to an embodiment of the present invention, where the coordinate transformation implements dq coordinate transformation of a single-phase signal, a biquad generalized integrator is used to generate two orthogonal signals, and then output of a dq axis variable is implemented according to an α β/dq transformation formula, and the implementation process is similar to that of fig. 7, and will not be described again here.
According to the method, the positive electrode and the negative electrode of the output end of the three-phase branch direct-current bus capacitor are respectively connected through the direct-current contactors, the single-stage energy storage converter is connected with the batteries with different voltage levels to work normally by controlling the on-off of the direct-current contactors, and the input cost of the energy storage converter for different batteries is reduced.
EXAMPLE III
In one or more embodiments, a terminal device is disclosed that includes a processor and a computer-readable storage medium, the processor to implement instructions; the computer readable storage medium is used for storing a plurality of instructions, and the instructions are suitable for being loaded by a processor and executing the control method of the energy storage converter system in the second embodiment.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.
Claims (13)
1. An energy storage converter system, comprising: the system comprises a grid-connected/off-grid control cabinet and a plurality of energy storage converters respectively connected with the grid-connected/off-grid control cabinet; the energy storage converters are connected in parallel; the structure of the energy storage converter comprises:
a three-phase discrete operation circuit topology framework is constructed, three-phase branches are formed, and each phase branch comprises: the system comprises a grid-connected/off-grid control cabinet, a direct-current storage battery, an isolation transformer, an alternating-current filter, an alternating-current soft start circuit, a filter circuit, a bridge inverter circuit, a direct-current bus capacitor, a direct-current filter and a direct-current soft start circuit, wherein the isolation transformer, the alternating-current filter, the alternating-current soft start circuit, the filter circuit, the bridge inverter circuit, the direct-current bus capacitor, the direct-current filter and the direct-current soft start circuit are sequentially connected in series from the grid-connected/off-grid control cabinet to a direct-current storage battery end; the positive electrodes of the output ends of the three-phase branch direct-current bus capacitors are connected through a direct-current contactor; the negative pole of three-phase branch direct current bus capacitor output end is connected through direct current contactor, after direct current contactor is closed, the battery of same voltage class is connected to the energy storage converter output end, after direct current contactor breaks off, the three-phase direct current is mutually independent, and the battery of different voltage classes or the battery of same voltage class can be connected respectively to the output of energy storage converter.
2. An energy storage converter system as claimed in claim 1, wherein the three-phase three-wire power supply is achieved by connecting the primary sides of the isolation transformers of the three-phase branch end-to-end and connecting the primary sides of the transformers in a delta connection.
3. An energy storage converter system, comprising: the system comprises a grid-connected/off-grid control cabinet and a plurality of energy storage converters respectively connected with the grid-connected/off-grid control cabinet; the energy storage converters are connected in parallel; the structure of the energy storage converter comprises:
a three-phase discrete operation circuit topology framework is constructed, three-phase branches are formed, and each phase branch comprises: the grid-connected/off-grid control cabinet is connected with a direct-current storage battery end in series, and an alternating-current filter, an alternating-current soft start circuit, a filter circuit, a bridge type inverter circuit, a direct-current bus capacitor, a direct-current filter and a direct-current soft start circuit are sequentially connected in series; the positive electrodes of the output ends of the three-phase branch direct-current bus capacitors are connected through a direct-current contactor; the negative pole of three-phase branch direct current bus capacitor output end is connected through direct current contactor, after direct current contactor is closed, the battery of same voltage class is connected to the energy storage converter output end, after direct current contactor breaks off, the three-phase direct current is mutually independent, and the battery of different voltage classes or the battery of same voltage class can be connected respectively to the output of energy storage converter.
4. An energy storage converter system as claimed in claim 3, wherein the three phase three wire power supply is achieved by connecting the ac filters of the three phase legs end to end and connecting the filters in a delta connection.
5. An energy storage converter system as claimed in claim 1 or 3, wherein the energy storage converter is controlled to operate in a grid-connected state or an off-grid state by the grid-connected/off-grid control cabinet.
6. An energy storage converter system according to claim 1 or 3, wherein said grid-tie/off-grid control cabinet, when operating in a grid-tie mode, is configured to perform the following process:
generating a current component reference value through coordinate transformation and PI operation according to the collected voltage and current information of the grid-connected point;
respectively sending the obtained current component reference values to each energy storage converter connected in parallel;
each energy storage converter respectively collects the output current thereof to carry out coordinate transformation, so as to obtain current components;
carrying out PI operation on the current component and the current component reference value to obtain a pulse width modulation coefficient component;
and generating a driving signal according to the pulse width modulation coefficient component to drive the corresponding switch tube of the energy storage converter to be switched on and off.
7. An energy storage converter system according to claim 1 or 3, wherein said grid-connected/off-grid control cabinet, when operating in an off-grid mode, is configured to perform the following process:
according to the collected voltage and current information of the parallel point, obtaining a current amplitude reference value and a reference current frequency through current and voltage amplitude calculation, phase-locked calculation and PI operation;
respectively sending the obtained current amplitude reference value and the obtained reference current frequency to each energy storage converter connected in parallel;
each energy storage current transformer respectively collects the output current of each energy storage current transformer, and the current amplitude is calculated to obtain the feedback current amplitude;
carrying out PI operation on the feedback current amplitude and a current amplitude reference value to obtain a pulse width modulation coefficient;
and generating a driving signal according to the pulse width modulation coefficient and the reference current frequency to drive the corresponding switch tube of the energy storage converter to be switched on and off.
8. A method of controlling an energy storage converter system as claimed in claim 1 or 3, comprising:
when the direct current ends of the three-phase branch circuits are connected with storage batteries of different models and voltage grades, the connection between the output ends of the direct current bus capacitors of the three-phase branch circuits is disconnected;
after the soft start stage is completed, respectively acquiring values of alternating current voltage, inductive current, direct current bus voltage and direct current for each phase of branch; setting a direct-current voltage given value and a current given value;
according to the collected value, obtaining a driving signal for driving the switching tube of the phase branch bridge type inverter circuit to be switched on and off after operation;
and controlling the amplitude difference and the phase angle between the alternating current sinusoidal waveform output by the bridge inverter circuit and the power grid voltage to obtain a current waveform with the same phase as the power grid voltage, so as to charge the storage battery.
9. A method of controlling an energy storage converter system as claimed in claim 1 or 3, comprising:
when the direct current ends of the three-phase branch circuits are connected with storage batteries with the same type and voltage class, the direct current bus capacitor output ends of the three-phase branch circuits are connected; setting the direct-current voltage given value and the charging current given value of the three-phase branch to be respectively the same;
after the soft start stage is completed, respectively acquiring values of alternating current voltage, inductive current, direct current bus voltage and direct current for each phase of branch;
obtaining a driving signal for driving the switching tube of the phase branch bridge type inverter circuit to be switched on and off after operation according to the collected value and the set value;
and controlling a phase angle between an alternating current sine waveform output by the bridge inverter circuit and the power grid voltage to obtain a current waveform with the same phase as the power grid voltage, so as to charge the storage battery.
10. A method of controlling a power converter system as claimed in claim 1 or 3,
under the grid-connected state, generating a current component reference value through coordinate transformation and PI operation according to collected grid-connected point voltage and current information;
respectively sending the obtained current component reference values to each energy storage converter connected in parallel;
each energy storage converter respectively collects the output current thereof to carry out coordinate transformation, so as to obtain current components;
carrying out PI operation on the current component and the current component reference value to obtain a pulse width modulation coefficient component;
and generating a driving signal according to the pulse width modulation coefficient component to drive the corresponding switch tube of the energy storage converter to be switched on and off.
11. The control method of the energy storage converter system according to claim 10, wherein a shunt coefficient is set for each energy storage converter connected in parallel, and the generated current component reference value is multiplied by the shunt coefficient and then subjected to PI operation with the respective current component;
further, when the current division coefficients of the energy storage converters are equal, the loads are equally divided.
12. A method of controlling a power converter system as claimed in claim 1 or 3,
under the off-grid state, according to the collected voltage and current information of the parallel point, a current amplitude reference value and a reference current frequency are obtained through current and voltage amplitude calculation, phase-locked calculation and PI operation;
respectively sending the obtained current amplitude reference value and the obtained reference current frequency to each energy storage converter connected in parallel;
each energy storage current transformer respectively collects the output current of each energy storage current transformer, and the current amplitude is calculated to obtain the feedback current amplitude;
carrying out PI operation on the feedback current amplitude and a current amplitude reference value to obtain a pulse width modulation coefficient;
and generating a driving signal according to the pulse width modulation coefficient and the reference current frequency to drive the corresponding switch tube of the energy storage converter to be switched on and off.
13. The method as claimed in claim 12, wherein the current amplitude reference values of each parallel energy storage converter are equal and are current reference values obtained by PI operation of a grid-connected point, and since the reference power is generated by PI operation of the total current detection value and the total current reference value, when the number of the parallel energy storage converters is changed, the system can automatically share the load again.
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| CN111463814A (en) * | 2020-05-26 | 2020-07-28 | 广东电网有限责任公司电力科学研究院 | Energy storage converter and three-phase split-phase control method |
| CN111786550B (en) * | 2020-07-29 | 2022-04-05 | 四川长虹电器股份有限公司 | Method for realizing soft start of bidirectional converter |
| CN112165244B (en) * | 2020-10-26 | 2022-02-25 | 合肥同智机电控制技术有限公司 | Output current-sharing control method for master-slave parallel inverter |
| CN112421659A (en) * | 2020-10-26 | 2021-02-26 | 北京精密机电控制设备研究所 | Energy storage dilatation power |
| CN113904356B (en) * | 2021-10-09 | 2023-10-24 | 国网湖南省电力有限公司 | Energy storage converter fluctuation coordination control method and device |
| CN114006391B (en) * | 2021-10-28 | 2023-07-07 | 山东泰开直流技术有限公司 | Medium-voltage direct-hanging energy storage converter system and start-stop control method thereof |
| CN114069789B (en) * | 2021-11-20 | 2023-09-22 | 傲普(上海)新能源有限公司 | Control circuit of battery cluster parallel circulation transformer |
| CN115102246A (en) * | 2022-06-10 | 2022-09-23 | 荣信汇科电气股份有限公司 | SOC balance control method for multiple battery clusters in novel energy storage unit |
| CN116819201B (en) * | 2023-06-12 | 2024-03-26 | 国网湖北省电力有限公司电力科学研究院 | Device and method for testing composite function of energy storage converter in distributed new energy |
| CN117220323B (en) * | 2023-11-08 | 2024-03-01 | 深圳海辰储能科技有限公司 | Method and device for controlling network connection and disconnection |
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| CN103219899B (en) * | 2013-04-09 | 2017-12-05 | 许继集团有限公司 | A kind of mixed type energy storage converter device and its progress control method |
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