CN106899030B - A primary-side integrated modular independent control battery energy storage system - Google Patents

Abstract

The invention discloses a primary-side integrated modular independent control battery energy storage system. The battery energy storage system includes battery units, which are composed of multiple groups of battery modules connected in series; a main power converter is used to control the main power of the battery units. Current, the main power converter is connected in parallel with the battery unit, and the main power converter is connected to the three-phase AC power grid; and the auxiliary power converter is connected with multiple groups of battery modules and performs closed-loop independent control of each group of battery modules for control. The difference between the charging and discharging current of each battery module and the main current. The invention realizes the independent control of the differential current part of the battery module through the main power converter and the auxiliary power converter, without independent control of the entire battery current, and the primary side adopts an integrated single-winding structure to reduce the loss of the converter and cost, and improve the energy utilization of battery modules.

Description

A primary-side integrated modular independent control battery energy storage system

technical field

The invention relates to the field of energy storage systems and the field of power electronic converters, in particular to a primary-side integrated modular independent control battery energy storage system.

Background technique

As environmental and energy issues have become a global focus, renewable energy generation has developed into an important driving force for smart grids, whose intermittency and volatility have an impact on grid voltage, frequency, etc. Among them, battery energy storage systems have attracted much attention due to their functions of mitigating power fluctuations of intermittent power sources and optimizing grid quality.

Figure 1 is a schematic diagram of a conventional battery energy storage system. As shown in Figure 1, hundreds of single cells are connected in series and connected to the grid using a centralized high-power converter. Due to the inconsistency of SOC (charge level), capacity, and internal resistance between single batteries, a large number of series applications reduce battery capacity and energy utilization, and shorten battery life.

FIG. 2 is a schematic diagram of an existing modular battery energy storage system. As shown in Figure 2, according to the concept of battery modular flexible grouping, the large-scale series-connected battery group in the traditional battery energy storage system is divided into several low-voltage battery modules. Different connection methods are connected to the power grid to form a flexible group energy storage system.

Existing modular battery energy storage systems usually use full power independently controlled energy storage systems. The full-power independent control flexible group energy storage system mainly has three structures: 1. The H-bridge cascaded flexible group energy storage system adopts a three-phase AC output structure. The DC side of each sub-module is an independent battery module. The respective H-bridge DC/AC converters generate low-voltage AC voltage, and the modules are cascaded to generate the AC voltage required for grid connection, which is connected to the three-phase AC grid. The entire power of the battery module during charging and discharging is converted and controlled by the H bridge, resulting in an increase in the cost, volume and loss of the converter with the total power, and low efficiency when applied in medium and low voltage applications. Second, the modular multilevel converter (MMC, modular-multilevel-converter) battery energy storage system can realize the full power independent control of the energy storage battery module while realizing the power transmission of the AC and DC grids. The sub-module current includes DC component, first harmonic component and second harmonic component, resulting in large current stress and large on-state loss of the switching device of the module. The cost and volume of the converter increase with the total power, so it is not suitable for low and medium voltage applications. 3. The DC-DC cascading flexible group energy storage system is formed by cascading N identical DC-DC energy storage modules, which can form a separate DC energy storage system, which can be connected to the intermediate DC bus or DC power grid. It can also be connected to the AC grid through a traditional grid-connected converter. The DC-DC converter has simple structure, simple control, high reliability, no AC component, and the current stress of the switching device is lower than that of the H-bridge cascade, and the system efficiency is high. However, the full power of the module passes through the DC-DC converter, and the switch tube flows all the current, and the absolute loss is relatively large; the cost and volume of the DC-DC converter increase with the total power, accounting for a large proportion in the system.

In the above existing full-power independent control flexible group energy storage systems, regardless of the current difference, all the charging and discharging currents of the battery modules must flow through the respective converter switching devices, resulting in large current stress and high cost of the devices. , The conduction loss is large, and with the increase of the system capacity, the problem becomes more prominent. Usually, when the battery capacity is reasonably configured, the capacity of each battery module is basically within a certain range. Even if the battery is used in a cascade, the capacity difference will not be too large, and the required charge and discharge current will not be too different. Therefore, there is no It is necessary to control all the battery currents independently, and only need to control part of the differential currents, so that the energy utilization rate of the battery module can be improved.

SUMMARY OF THE INVENTION

In view of the above problems, the purpose of the present invention is to provide a primary-side integrated modular independent control battery energy storage system, so as to solve the problem that in the existing full-power modular flexible group energy storage system, the switching device flows through all parts of the battery module. The charging and discharging current leads to the problems of large current stress, high cost and large conduction loss of the device.

In order to achieve the above object, the present invention adopts the following technical solutions:

The primary-side integrated modular independent control battery energy storage system of the present invention includes:

battery cells, including multiple battery modules connected in series;

a main power converter, connected in parallel with the battery cells, for controlling the main current of the battery cells, and the main power converter is connected to the three-phase AC power grid; and

The auxiliary power converter is connected to multiple groups of battery modules and performs closed-loop independent control of each group of battery modules, so as to control the difference between the charging and discharging current of each group of battery modules and the main current.

Preferably, the main power converter includes:

a first capacitor in parallel with the battery cell; and

From the first switch tube to the sixth switch tube, each switch tube is connected in anti-parallel with a diode, the first switch tube is connected between the first end of the first inductor and the positive electrode of the battery unit, and the second switch tube is connected to the first between the first end of the inductor and the negative electrode of the battery unit, the third switch tube is connected between the first end of the second inductor and the positive electrode of the battery unit, and the fourth switch tube is connected to the first end of the second inductor Between the negative pole of the battery unit, the fifth switch tube is connected between the first end of the third inductor and the positive pole of the battery unit, and the sixth switch tube is connected between the first end of the third inductor and the negative pole of the battery unit. During the time, the second ends of the first inductor, the second inductor and the third inductor are respectively connected to one phase of the three-phase AC power grid.

Preferably, the auxiliary power converter includes:

A primary-side integrated high-frequency isolation transformer, the primary-side integrated high-frequency isolation transformer includes an integrated primary winding and a plurality of secondary windings;

a primary converter connected to the integrated primary winding; and

A plurality of secondary side converters, each secondary side winding is correspondingly connected to each group of battery modules through each secondary side converter.

Further, preferably, the primary side converter includes:

The seventh switch tube to the tenth switch tube, each switch tube is respectively connected in anti-parallel with a diode, the seventh switch tube is connected between the first terminal of the integrated primary winding and the positive electrode of the battery unit, and the eighth switch tube is connected to the integrated original Between the first terminal of the side winding and the negative pole of the battery unit, the ninth switch tube is connected between the second terminal of the integrated primary winding and the positive pole of the battery unit, and the tenth switch tube is connected to the second terminal of the integrated primary winding between the negative terminal of the battery unit.

As another preference, the primary side converter includes:

a seventh switch tube, with a diode in anti-parallel connection, the seventh switch tube is connected between the first terminal of the integrated primary winding and the positive electrode of the battery unit;

The eighth switch tube is connected in anti-parallel with a diode, and the eighth switch tube is connected between the first terminal of the integrated primary winding and the negative electrode of the battery unit;

a second capacitor connected between the second terminal of the integrated primary winding and the positive electrode of the battery cell; and

The third capacitor is connected between the second terminal of the integrated primary winding and the negative electrode of the battery unit.

Preferably, the secondary side converter includes:

From the eleventh switch tube to the fourteenth switch tube, each switch tube is connected in anti-parallel with a diode, the first end of the eleventh switch tube is connected to the positive pole of the battery module, and the second end of the eleventh switch tube The terminal is connected to the first terminal of the secondary winding through the fourth inductor, the first terminal of the twelfth switch tube is connected to the first terminal of the secondary winding through the fourth inductor, and the twelfth switch tube is connected to the first terminal of the secondary winding through the fourth inductor. The second end is connected to the negative pole of the battery module, the thirteenth switch tube is connected between the second terminal of the secondary winding and the positive pole of the battery module, and the fourteenth switch tube is connected to the second terminal of the secondary winding and the negative terminal of the battery module; and

The fourth capacitor is connected in parallel with the battery module.

As another preference, the secondary side converter includes:

The eleventh switch tube is connected in anti-parallel with a diode, the first end of the eleventh switch tube is connected to the positive pole of the battery module, and the second end of the eleventh switch tube is connected to the secondary winding through the fourth inductor the first terminal of ;

The twelfth switch tube is connected in anti-parallel with a diode, the first end of the twelfth switch tube is connected to the first terminal of the secondary winding through the fourth inductor, and the second end of the twelfth switch tube is connected to the The negative pole of the battery module;

the fourth capacitor, connected in parallel with the battery module;

a fifth capacitor connected between the second terminal of the secondary winding and the positive electrode of the battery module; and

The sixth capacitor is connected between the second terminal of the secondary winding and the negative electrode of the battery module.

Preferably, the main power converter controls the main current through one of vector control, active power and reactive power decoupling control, wherein the vector control includes sinusoidal pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM) ) one of them.

Preferably, the auxiliary power converter controls the difference through a phase-shift control strategy, and the phase-shift control strategy includes an inter-bridge phase-shift mode, an extended phase-shift mode, an inter-bridge and intra-bridge double-phase shift and triple-shift One or more of phase, pulse width modulation (PWM) plus phase shift control, triangular wave modulation and trapezoidal wave modulation.

Preferably, the primary side converter is connected to a battery unit, or the primary side converter is connected to an external DC power supply.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

In the present invention, the main power converter bears most of the power, controls the main current of the battery unit, and improves the efficiency of the whole machine; the auxiliary power converter controls the difference between the charging and discharging current of the battery module and the main current, and can adapt to multiple groups of battery modules The inconsistency of the battery unit can improve the energy utilization rate of the battery unit, and the auxiliary power converter has low control power and low absolute loss; the main power converter and the auxiliary power converter can work at the same time or separately without affecting each other;

Compared with the traditional symmetrical bidirectional full-bridge converter structure in which each secondary side corresponds to a primary side, the present invention adopts a transformer structure in which multiple secondary sides share one primary side, and the cost, loss, volume and weight are reduced by half accordingly. ; The primary side power is the sum of all secondary side powers, and the primary side power can be ignored after the positive and negative powers of the secondary side are canceled;

The invention can be applied to the application occasions of energy storage system with medium and high power, medium voltage level, and high requirements on efficiency, cost and energy utilization rate.

Description of drawings

Figure 1 is a schematic diagram of a traditional battery energy storage system;

Figure 2 is a schematic diagram of an existing modular battery energy storage system;

3 is a main circuit diagram of a preferred embodiment of the battery energy storage system according to the present invention;

4 is a main circuit diagram of another embodiment of the battery energy storage system according to the present invention;

5 is a waveform diagram of the primary and secondary voltages of the preferred embodiment of the battery energy storage system according to the present invention;

FIG. 6 is an equivalent circuit diagram of the primary side of a transformer according to a preferred embodiment of the battery energy storage system according to the present invention.

Detailed ways

The described embodiments of the present invention will be described below with reference to the accompanying drawings. As those of ordinary skill in the art would realize, the described embodiments may be modified in various different ways or combinations thereof, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and description are illustrative in nature and are not intended to limit the scope of protection of the claims. In addition, in this specification, the same reference numerals denote the same parts.

FIG. 3 is a main circuit diagram of a preferred embodiment of the battery energy storage system according to the present invention. As shown in FIG. 3 , the battery energy storage system according to the present invention includes:

A battery unit 100, wherein the battery unit 100 includes multiple groups of battery modules 110 connected in series;

The main power converter 200 is connected in parallel with the battery unit 100, the main power converter 200 is used to control the main current of the battery unit 100, and the main power converter 200 is connected to the three-phase AC power grid, wherein the main current refers to the current of all battery modules the same part of; and

The auxiliary power converter 300 is connected to the plurality of battery modules 110, and is used for independent closed-loop control of the difference between the charging and discharging current of each battery module 110 and the main current, wherein the difference between the charging and discharging current and the main current is preferably 10%-20% of the main current to adapt to the differences between different battery modules, so that each battery module works in the best state, only a small part of the current in the battery module passes through the switching device of the power converter corresponding to each battery module , reduce the current stress and conduction loss of the device, reduce the cost, and improve the energy utilization rate of the battery module;

The main power converter 200 and the auxiliary power converter 300 respectively control the main current and the differential current, thereby realizing independent control of the charging and discharging current of the battery module 110 and improving the energy utilization rate of the battery module 110 .

Among them, the battery module 110 can use newly produced batteries of various types, and can also use returned batteries from other systems, or different modules can be mixed with different types of batteries, so as to realize the cascade utilization of returned batteries and give full play to the residual value of the batteries. It is beneficial to environmental protection and resource saving, and the battery module 110 is preferably a low-voltage battery module.

As shown in FIG. 3 , the main power converter 200 is preferably a grid-connected inverter structure, including:

a first capacitor 210, connected in parallel with the battery unit 100, preferably a high frequency filter capacitor; and

The first switch tube Q1 to the sixth switch tube Q6, and each switch tube is respectively connected in anti-parallel with a diode 220,

The first switch Q1 is connected between the first end of the first inductor 230 and the positive electrode of the battery unit 100 , specifically, the first end of the first switch Q1 is connected to the first end of the first inductor 230 , and the second end of the first switch tube Q1 is connected to the positive electrode of the battery unit 100;

The second switch Q2 is connected between the first end of the first inductor 230 and the negative electrode of the battery unit 100 , specifically, the second end of the second switch Q2 is connected to the first end of the first inductor 230 , and The first end of the second switch tube Q2 is connected to the negative electrode of the battery unit 100;

The third switch Q3 is connected between the first end of the second inductor 240 and the positive electrode of the battery unit 100 , specifically, the first end of the third switch Q3 is connected to the first end of the second inductor 240 , and The second end of the third switch tube Q3 is connected to the positive electrode of the battery unit 100;

The fourth switch Q4 is connected between the first end of the second inductor 240 and the negative electrode of the battery unit 100 , specifically, the second end of the fourth switch Q4 is connected to the first end of the second inductor 240 , and The first end of the fourth switch tube Q4 is connected to the negative electrode of the battery unit 100;

The fifth switch Q5 is connected between the first end of the third inductor 250 and the positive electrode of the battery unit 100 , specifically, the first end of the fifth switch Q5 is connected to the first end of the third inductor 250 , and The second end of the fifth switch tube Q5 is connected to the positive electrode of the battery unit 100;

The sixth switch Q6 is connected between the first end of the third inductor 250 and the negative electrode of the battery unit 100 , specifically, the second end of the sixth switch Q6 is connected to the first end of the third inductor 250 , and The first end of the sixth switch tube Q6 is connected to the negative electrode of the battery unit 100;

The second ends of the first inductor 230 , the second inductor 240 and the third inductor 250 are respectively connected to one phase u _C , u _B , and u _A of the three-phase AC power grid.

Preferably, the first switch transistor Q1 to the sixth switch transistor Q6 may be insulated gate bipolar transistors (IGBT, Insulated Gate Bipolar Transistor). In this case, the first ends of the first switch transistor Q1 to the sixth switch transistor Q6 may be The collector terminal of the IGBT, and the second terminals of the first switching transistor Q1 to the sixth switching transistor Q6 may be the emitter terminal of the IGBT.

The main power converter 200 controls the main current through one of vector control, active power and reactive power decoupling control, where one of SPWM and SVPWM can be selected for vector control.

In the battery energy storage system of the present invention, when the input side adopts a series or parallel non-isolated connection mode, since the output side is also connected in series, in order to prevent the generation of circulating current, the input and output of the auxiliary power converter need to be isolated. The auxiliary power converter 300 may adopt a converter structure in which each secondary winding corresponds to an integrated primary winding, or a converter structure in which a plurality of secondary windings share an integrated primary winding.

Preferably, the auxiliary power converter 300 of the present invention adopts a primary integrated high-frequency isolation transformer 310 in which multiple secondary windings 312 share one integrated primary winding 311, thereby reducing cost, loss, volume and weight by half. , the primary side adopts an integrated single-winding structure, which can reduce the cost and loss of the auxiliary power converter and improve the efficiency of the battery energy storage system. The auxiliary power converter 300 performs closed-loop independent control on the difference between the charging and discharging current of each battery module 110 and the main current by introducing a phase-shifting control strategy, wherein the phase-shifting control strategy includes an inter-bridge phase-shifting method, an extended phase-shifting method, One or more of double-phase-shifting and triple-phase-shifting, PWM plus phase-shifting control, triangular wave modulation and trapezoidal wave modulation between bridges and bridges.

Auxiliary power converter 300 includes:

The primary side integrated high-frequency isolation transformer 310 includes an integrated primary side winding 311 and a plurality of secondary side windings 312;

a primary side converter 320, connected to the integrated primary side winding 311; and

A plurality of secondary side converters 330, each secondary side winding 312 is correspondingly connected to each group of battery modules 110 through each secondary side converter 330, so as to realize closed-loop independence of the difference between the charging and discharging current of each group of battery modules 110 and the main current control.

Based on the main current of the battery unit 100 , the difference current between the charging and discharging current of each battery module 110 and the main current is positive or negative, so the auxiliary power converter 300 is preferably a bidirectional isolated DC-DC converter.

As shown in FIG. 3, the bidirectional isolated DC-DC converter may be a bidirectional full-bridge converter structure. The primary-side converter 320 may be a full-bridge converter structure, including a seventh switch transistor Q7 to a tenth switch transistor Q10, and each switch transistor is antiparallelly connected to a diode 220 respectively.

The seventh switch transistor Q7 is connected between the first terminal of the integrated primary winding 311 and the positive electrode of the battery unit 100 , and specifically, the first end of the seventh switch transistor Q7 is connected to the first terminal of the integrated primary winding 311 , and the second end of the seventh switch tube Q7 is connected to the positive electrode of the battery unit 100;

The eighth switch transistor Q8 is connected between the first terminal of the integrated primary winding 311 and the negative pole of the battery unit 100 , specifically, the second end of the eighth switch transistor Q8 is connected to the first terminal of the integrated primary winding 311 , and The first end of the eighth switch tube Q8 is connected to the negative electrode of the battery unit 100;

The ninth switch transistor Q9 is connected between the second terminal of the integrated primary winding 311 and the positive electrode of the battery unit 100 , specifically, the first end of the ninth switch Q9 is connected to the second terminal of the integrated primary winding 311 , and The second end of the ninth switch tube Q9 is connected to the positive electrode of the battery unit 100;

The tenth switch transistor Q10 is connected between the second terminal of the integrated primary winding 311 and the negative pole of the battery unit 100 . Specifically, the second end of the tenth switch Q10 is connected to the second terminal of the integrated primary winding 311 , and The first end of the tenth switch transistor Q10 is connected to the negative electrode of the battery unit 100 .

As shown in FIG. 3 , the secondary-side converter 330 may be a full-bridge converter structure. Secondary converter 330 includes:

a fourth capacitor 331, connected in parallel with the battery module 110; and

From the eleventh switch tube S1 to the fourteenth switch tube S4 , each of the switch tubes is connected in anti-parallel with a diode 220 respectively.

The first end of the eleventh switch S1 is connected to the positive electrode of the battery module 110, and the second end of the eleventh switch S1 is connected to the first terminal of the secondary winding 312 through the fourth inductor 334;

The second end of the twelfth switch S2 is connected to the negative electrode of the battery module 110, and the first end of the twelfth switch S2 is connected to the first terminal of the secondary winding 312 through the fourth inductor 334;

The thirteenth switch S3 is connected between the second terminal of the secondary winding 312 and the positive pole of the battery module 110 , specifically, the first end of the thirteenth switch S3 is connected to the positive pole of the battery module 110 , and the thirteenth switch S3 The second end of the switch S3 is connected to the second terminal of the secondary winding 312;

The fourteenth switch S4 is connected between the second terminal of the secondary winding 312 and the negative pole of the battery module 110 , specifically, the second end of the fourteenth switch S4 is connected to the negative pole of the battery module 110 , and the fourteenth switch S4 is connected to the negative pole of the battery module 110 . The first terminal of the switch S4 is connected to the second terminal of the secondary winding 312 .

FIG. 4 is a main circuit diagram of another embodiment of the battery energy storage system according to the present invention. As shown in FIG. 4 , the primary-side converter 320 may be a half-bridge converter structure, including:

The seventh switch transistor Q7 is connected in anti-parallel with a diode 220. The seventh switch transistor Q7 is connected between the first terminal of the integrated primary winding 311 and the positive electrode of the battery unit 100. Specifically, the first end of the seventh switch transistor Q7 is connected to to the first terminal of the integrated primary winding 311, and the second terminal of the seventh switch Q7 is connected to the positive electrode of the battery unit 100;

The eighth switch transistor Q8 is connected in anti-parallel with a diode 220. The eighth switch transistor Q8 is connected between the first terminal of the integrated primary winding 311 and the negative electrode of the battery unit 100. Specifically, the second end of the eighth switch transistor Q8 is connected to to the first terminal of the integrated primary winding 311, and the first terminal of the eighth switch tube Q8 is connected to the negative electrode of the battery unit 100;

a second capacitor 321 connected between the second terminal of the integrated primary winding 311 and the positive electrode of the battery cell 100; and

The third capacitor 322 is connected between the second terminal of the integrated primary winding 311 and the negative electrode of the battery unit 100 .

As shown in FIG. 4, the secondary-side converter 330 may be a half-bridge converter structure. Secondary converter 330 includes:

the fourth capacitor 331, connected in parallel with the battery module 110;

the fifth capacitor 332 is connected between the second terminal of the secondary winding 312 and the positive electrode of the battery module 110;

The sixth capacitor 333 is connected between the second terminal of the secondary winding 312 and the negative electrode of the battery module 110;

The eleventh switch S1 is connected to a diode 220 in anti-parallel. The first end of the eleventh switch S1 is connected to the anode of the battery module 110 , and the second end of the eleventh switch S1 is connected to the battery module 110 through the fourth inductor 334 . the first terminal of the secondary winding 312; and

The twelfth switch S2 is connected in anti-parallel with a diode 220 , the second end of the twelfth switch S2 is connected to the negative electrode of the battery module 110 , and the first end of the twelfth switch S2 is connected to the battery module 110 through the fourth inductor 334 . The first terminal of the secondary winding 312 .

Preferably, the seventh switch transistor Q7 to the tenth switch transistor Q10 may be IGBTs. In this case, the first ends of the seventh switch transistor Q7 to the tenth switch transistor Q10 may be the collector terminals of the IGBT, and the seventh switch transistor Q7 The second terminal to the tenth switch transistor Q10 may be the emitter terminal of the IGBT.

Preferably, the eleventh switch transistors S1 to the fourteenth switch transistors S4 may be metal-oxide semiconductor field effect transistors (MOSFET, Metal-Oxide-Semiconductor Field-Effect Transistor). In this case, the eleventh switch transistors S1 to The first terminal of the fourteenth switch S4 may be the drain terminal of the MOSFET, and the second terminals of the eleventh switch S1 to the fourteenth switch S4 may be the source terminal of the MOSFET.

The primary-side converter 320 and the secondary-side converter 330 can adopt the full-bridge converter structure (as shown in FIG. 3 ) at the same time, or the half-bridge converter structure (as shown in FIG. 4 ) at the same time. Alternatively, the primary-side converter 320 may use a full-bridge converter structure, the multiple secondary-side converters 330 may use a full-bridge and half-bridge hybrid structure, or the primary-side converter 320 may use a half-bridge converter structure, and multiple secondary-side converters 330 may use a half-bridge converter structure. The side converter 330 adopts a hybrid structure of full bridge and half bridge. That is, the high-frequency inverter circuit on the primary side of the transformer can be a full-bridge conversion circuit composed of four switches, or a half-bridge inverter circuit composed of two switches and two DC capacitors, and the secondary circuit of the transformer can be four The full-bridge conversion circuit composed of switch tubes can also be a half-bridge conversion circuit composed of two switch tubes and two DC capacitors.

Preferably, the DC side of the primary side converter 320 can be connected to both ends of the internal battery unit 100 of the battery energy storage system as described above, or can be connected to both ends of other external DC power sources.

Taking the phase shift control of the bidirectional DC-DC full-bridge converter as an example, the working principle of the battery energy storage system of the present invention will be described in detail below with reference to FIG. 3 , FIG. 5 and FIG. 6 .

FIG. 5 and FIG. 6 are respectively the primary and secondary side voltage waveform diagram and the transformer primary side equivalent circuit diagram of the preferred embodiment of the battery energy storage system according to the present invention.

Through the superposition theorem, the voltage at point A in Figure 6 can be obtained as:

In formula (1), v _A is the voltage at point A, v _p is the voltage of the primary side of the transformer, L _p is the leakage inductance of the primary side of the transformer, v ₁ , v ₂ , ..., v _N are the voltage of the secondary side of the transformer, v' ₁ ,v' ₂ ,...,v' _N is the equivalent voltage converted from the secondary side voltage of the transformer to the primary side, L _s1 ,L _s2 ,...,L _sN is the sum of the leakage inductance and the external inductance of each winding on the secondary side, L _s1 ', L _s2 ',..., L _sN ' are equivalent inductances converted to the primary side.

Suppose L _s1 '=L _s2 '=L _s3 '=...=L _sN '=L _s , and replace (1) with e _i (i=0,1,2,...,N) terms of fractions, then:

e ₂ =...=e _N =e ₁

So you can get:

v _A = v _p ×e ₀ +v' ₁ ×e ₁ +v' ₂ ×e ₂ +...+v' _N × _en

=v _p ×e ₀ +(v' ₂ +v' ₃ +...+v' _N )×e ₁ ,

......

In the formula, i _p is the primary current of the transformer, i _{Ls1 , i Ls2 , ..., i LsN is the} secondary current of the transformer, i ₁ ', i ₂ ', ..., i _N ' is the transformer secondary current converted to the original the equivalent current of the edge.

Through the above formula, the currents of each secondary side of the transformer can be converted to the currents i ₁ ' to i _N ' of the primary side. Obviously, the current of i ₁ ' is not only determined by v _p and v' ₁ , but also by other secondary voltages. , so there is still a coupling relationship between each secondary side. In order to achieve the purpose of independently controlling the differential current of each battery module, it is necessary to decouple multiple sets of secondary sides.

Now suppose that L _s >> L _p , that is, when the equivalent inductance of each secondary side is much larger than the leakage inductance of the primary side, then:

Therefore,

......

Each secondary side current i ₁ ', i ₂ ',..., _{i N} ' converted to the primary side is calculated by the integrated primary side voltage, the secondary side voltage converted to the primary side by the integrated primary side voltage, and the secondary side voltage converted from the respective secondary side to the primary side. Determined by the equivalent inductance of the sides, they are independent of each other, so it can be known that the differential current of each module is also independent of each other. By adding an auxiliary phase-shifting inductance to each secondary winding so that the equivalent inductance of each secondary is much larger than the primary inductance, closed-loop independent control of the differential currents of multiple battery modules can be realized. I _M1 is the DC side output current of the main power converter, I _M is the main current of all battery modules in series, I _B1 , I _B2 , ..., I _BN are the charging and discharging currents of each battery module, I _d1 , I _d2 , ... ..., I _dN is the difference current between the main current and the charge and discharge current of each battery module.

Let P _di (i=1,2,...,N) be the partial control power of the ith battery module, that is, the power corresponding to the differential current, and P _sΣ is the sum of the total differential power of the N battery modules. According to the output power formula of the bidirectional full-bridge converter, the differential power of each battery module is:

P _d2 =v _d2 I _d2 ,

......

P _dN =v _dN I _dN

in:

In the formula, v _d1 , v _d2 , ..., v _dN are the voltages of N series battery modules, I _d1 , I _d2 , ..., I _dN is the difference current between the main current and the charging and discharging current of each battery module, N _T is the turns ratio of the transformer, T is the time of half a switching cycle, f is the switching frequency of the switch tube, D ₁ is the phase-shift duty cycle, are the phase differences between the pulses of the switching tubes of the primary-side converter and the pulses of the switching tubes of the plurality of secondary-side converters, respectively.

Let v _d1 =v _d2 =...=v _dN , according to the law of power conservation, it can be known that the primary side converter power P _p is equal to the sum of the secondary side converter difference powers.

P _p =P _sΣ =P _d1 +P _d2 +...+P _dn

=v _d1 I _d1 +v _d2 I _d2 +...+v _dN I _dN

=v _d1 (I _d1 +I _d2 +...+I _dN )

v _dp is the DC side voltage of the primary side, which is equal to the sum of the voltages of all battery modules, then the DC side current I _dp of the primary side converter is:

Through reasonable optimization control, the main current _IM of the battery unit is the average current of all battery currents, then the difference currents such as I _d1 , I _d2 , ..., I _dN are positive and negative, and the difference current sum is 0 after the positive and negative offset. ,Available

Since I _dp is 0, the integrated primary side power is almost 0, and the cost and loss of the primary side converter are also reduced.

Therefore, this part of the power independent control energy storage system can greatly reduce the control power and absolute loss of the auxiliary power converter of the battery energy storage system by reasonably setting the control current value.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (8)

1. a kind of primary side integrated modular independent control battery energy storage system characterized by comprising

Battery unit, the battery unit include concatenated multiple groups battery module；

Main power inverter, the main power inverter and the battery units in parallel, for controlling the master of the battery unit Electric current, the main power inverter access three-phase AC grid, and the principal current refers to the same section of all battery module electric currents； And

Auxiliary power conversion connect with multiple groups battery module and carries out closed loop independent control to every group of battery module respectively, uses In the difference for the charging and discharging currents and the principal current for controlling every group of battery module；

Wherein, the main power inverter includes:

First capacitor device, with the battery units in parallel；And

First switch tube to the 6th switching tube, each switching tube of the first switch tube to the 6th switching tube distinguishes inverse parallel one A diode, first switch tube are connected between the first end of the first inductor and the anode of the battery unit, second switch Pipe is connected between the first end of the first inductor and the cathode of the battery unit, and third switching tube is connected to the second inductor First end and the battery unit anode between, the 4th switching tube be connected to the second inductor first end and the battery Between the cathode of unit, the 5th switching tube is connected between the first end of third inductor and the anode of the battery unit, the Six switching tubes are connected between the first end of third inductor and the cathode of the battery unit, the first inductor, the second inductance The second end of device and third inductor is respectively connected to a phase of the three-phase AC grid；

The auxiliary power conversion includes:

Primary side integrated form high-frequency isolation transformer, the primary side integrated form high-frequency isolation transformer include an integrated primary side winding With multiple vice-side windings；

Primary side converter is connect with the integrated primary side winding；And

Multiple pair sides converter, each vice-side winding are correspondingly connected with by each secondary side converter with every group of battery module.

2. primary side integrated modular independent control battery energy storage system according to claim 1, which is characterized in that described Primary side converter includes:

Each switching tube of 7th switching tube to the tenth switching tube, the 7th switching tube to the tenth switching tube distinguishes inverse parallel one A diode, the 7th switching tube are connected between the first terminal of the integrated primary side winding and the anode of the battery unit, 8th switching tube is connected between the first terminal of the integrated primary side winding and the cathode of the battery unit, the 9th switching tube It is connected between the Second terminal of the integrated primary side winding and the anode of the battery unit, the tenth switching tube is connected to described Between the Second terminal of integrated primary side winding and the cathode of the battery unit.

3. primary side integrated modular independent control battery energy storage system according to claim 1, which is characterized in that described Primary side converter includes:

7th switching tube, described 7th switching tube inverse parallel, one diode, the 7th switching tube are connected to the integrated original Between the first terminal of side winding and the anode of the battery unit；

8th switching tube, described 8th switching tube inverse parallel, one diode, the 8th switching tube are connected to the integrated original Between the first terminal of side winding and the cathode of the battery unit；

Second capacitor is connected between the Second terminal of the integrated primary side winding and the anode of the battery unit；And

Third capacitor is connected between the Second terminal of the integrated primary side winding and the cathode of the battery unit.

4. primary side integrated modular independent control battery energy storage system according to claim 1, which is characterized in that described Secondary side converter includes:

11st switching tube to the 14th switching tube, each switching tube difference of the 11st switching tube to the 14th switching tube One diode of inverse parallel, the first end of the 11st switching tube are connected to the anode of battery module, the 11st switch The second end of pipe is connected to the first terminal of the vice-side winding, the first end of the 12nd switching tube by the 4th inductor The first terminal of the vice-side winding is connected to by the 4th inductor, the second end of the 12nd switching tube is connected to battery The cathode of module, the 13rd switching tube are connected between the Second terminal of the vice-side winding and the anode of battery module, 14th switching tube is connected between the Second terminal of the vice-side winding and the cathode of battery module；And

4th capacitor, it is in parallel with the battery module.

5. primary side integrated modular independent control battery energy storage system according to claim 1, which is characterized in that described Secondary side converter includes:

The first end of 11st switching tube, described 11st switching tube inverse parallel, one diode, the 11st switching tube connects The anode in battery module is connect, the second end of the 11st switching tube is connected to the vice-side winding by the 4th inductor First terminal；

The first end of 12nd switching tube, described 12nd switching tube inverse parallel, one diode, the 12nd switching tube is logical The first terminal that the 4th inductor is connected to the vice-side winding is crossed, the second end of the 12nd switching tube is connected to battery mould The cathode of block；

4th capacitor, it is in parallel with the battery module；

5th capacitor is connected between the Second terminal of the vice-side winding and the anode of the battery module；And

6th capacitor is connected between the Second terminal of the vice-side winding and the cathode of the battery module.

6. primary side integrated modular independent control battery energy storage system according to claim 1, which is characterized in that described Main power inverter controls the principal current by one of vector controlled, active power and reactive power decoupling control, In, the vector controlled includes one of sinusoidal pulse width modulation and space vector pulse width modulation.

7. primary side integrated modular independent control battery energy storage system according to claim 1, which is characterized in that described Auxiliary power conversion controls the difference by phase shifting control strategy, and the phase shifting control strategy includes phase shift between bridge Mode, extension phase shift system, two-track phase and three phase shifts, pulsewidth modulation add phase shifting control, triangular modulation and trapezoidal in bridge between bridge One of wave modulation is a variety of.

8. primary side integrated modular independent control battery energy storage system according to claim 1, which is characterized in that described Primary side converter is connect with the battery unit or the primary side converter is connect with external dc power.