CN107565652A - A kind of balancer of energy-storage system - Google Patents

Abstract

The invention discloses an equalization device of an energy storage system, comprising an equalization controller, an AC busbar and an energy equalizer; When the preset equalization control conditions are met, the working state of the target energy balancer is determined, and an equalization control command is sent to the target energy balancer, so that the target energy balancer works in the corresponding working state ; Each energy equalizer is electrically connected to the equalization controller respectively, and each energy equalizer is electrically connected through an AC busbar; the energy equalizer is used for the inflowing AC current in the charging state, and the energy storage connected to it The device is charged; and it is used for outputting an AC voltage in a discharging state, so as to provide a voltage for an energy balancer in a charging state through an AC bus. The technical solution can effectively improve the consistency of multiple energy storage devices in the energy storage system.

Description

A balance device for an energy storage system

technical field

The invention relates to the technical field of energy storage, in particular to an equalizing device for an energy storage system.

Background technique

Energy storage systems are more and more widely used in power grids and power users. For example, high-voltage and large-capacity battery energy storage systems based on H-bridge chain structure or MMC structure have become popular due to their technical advantages such as high energy efficiency, good power quality, and strong smoothing effect. An energy storage solution with strong promotional value. Taking a large-capacity battery energy storage system as an example, tens of thousands or even hundreds of thousands of battery cells usually need to be concentrated to work together. With so many batteries concentrated in one system for long-term work, the problem of battery balancing must be solved. , to avoid the decline in the overall operating capacity of the energy storage system due to the "barrel effect".

Contents of the invention

In view of the above problems, the present invention is proposed to provide an equalizing device for an energy storage system that overcomes the above problems or at least partially solves the above problems.

According to one aspect of the present invention, an equalization device for an energy storage system is provided, which is characterized in that the device includes an equalization controller, an AC busbar, and several energy equalizers for respectively connecting with each energy storage device of the energy storage system device; the working state of the energy balancer includes a charging state and a discharging state;

The balance controller is used to collect the charge amount and voltage of each energy storage device, and judge whether the preset balance control condition is satisfied according to the collected charge amount and/or voltage of each energy storage device; when the preset balance control condition is satisfied When controlling conditions, determine the working state of the target energy balancer, and send an equalization control instruction to the target energy balancer, so that the target energy balancer works in a corresponding working state;

Each energy equalizer is electrically connected to the equalization controller respectively, and each energy equalizer is electrically connected through an AC bus;

The energy balancer is used to output an incoming AC current in the charging state, so as to charge the energy storage device connected to it; The state's energy equalizer provides voltage.

Optionally, the balance controller is configured to be connected to a management system of the energy storage device, and obtain the charge amount and/or voltage of each energy storage device from the management system.

Optionally, the balance controller is configured to calculate the degree of deviation of each energy storage device according to the collected charge amount and/or voltage of each energy storage device; the balance control condition is that the calculated degree of deviation exceeds the degree of deviation threshold.

Optionally, the balance controller is configured to determine that the energy balancer connected to the energy storage device with the highest degree of positive deviation is a target energy balancer working in a discharge state, and is connected to the energy storage device with the highest degree of negative deviation The energy balancer of is the target energy balancer working in the charging state.

Optionally, the balance controller is further configured to balance the target energy in the charging state first when it is judged that the preset balance control condition is no longer satisfied according to the collected charge amount and/or voltage of each energy storage device. The device sends a control command to stop working, and then sends a control command to stop working to the target energy balancer in the discharge state.

Optionally, the energy equalizer includes: an AC-DC conversion circuit, configured to perform energy conversion between the AC bus and the energy storage device.

Optionally, the energy equalizer further includes an isolation transformer, and the AC bus is formed by sequentially connecting the primary sides of the isolation transformers of each energy equalizer;

The secondary side of the isolation transformer is connected to the AC side of the AC-DC conversion circuit.

Optionally, the AC-DC conversion circuit is a single-phase full-bridge structure or a three-phase full-bridge structure;

When the AC-DC conversion circuit has a single-phase full-bridge structure, the isolation transformer is a single-phase transformer; when the AC-DC conversion circuit has a three-phase full-bridge structure, the isolation transformer is a three-phase transformer.

Optionally, the energy balancer further includes a current sensor, the primary side of the current sensor is connected to the primary side of the isolation transformer of the energy balancer where it is located, and the secondary side of the current sensor is connected to the balance controller;

The balance controller is configured to adjust the balance control instruction sent to the target energy balancer according to the current collected by each current sensor.

Optionally, the device also includes: a voltage sensor;

The primary side of the voltage sensor is connected to the AC bus, and the secondary side of the voltage sensor is connected to the equalization controller;

The equalization controller is configured to adjust the equalization control instruction sent to the target energy equalizer according to the voltage collected by the voltage sensor.

As can be seen from the above, in the technical solution of the present invention, an equalization controller and an energy equalizer corresponding to each energy storage device are set, and the energy equalizer is controlled to work when the equalization control condition is satisfied by collecting the voltage and/or charge amount of the energy storage device In the charging state or discharging state, the connected energy storage device completes energy release or charging, so as to achieve energy balance. This technical solution can realize a repeated cycle process without failure or control signal interruption. In this cycle process, dynamic balance among multiple energy storage devices can be realized, and the balance control process is consistent with The overall working status of the energy storage system does not matter, and it can be performed at any time, which can effectively improve the consistency of multiple energy storage devices in the energy storage system.

Description of drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiment. The drawings are only for the purpose of illustrating a preferred embodiment and are not to be considered as limiting the invention. Also throughout the drawings, the same reference numerals are used to designate the same parts. In the attached picture:

Fig. 1 shows a schematic structural diagram of an equalization device of an energy storage system according to an embodiment of the present invention;

Figure 2a shows a schematic diagram of a voltage-current relationship during balanced control;

Figure 2b shows another schematic diagram of the voltage-current relationship during balanced control;

Figure 3a shows a topology diagram of a single-phase full-bridge structure;

Figure 3b shows a topology diagram of a three-phase full-bridge structure;

Fig. 4 shows a schematic topology diagram of a balancing device of an energy storage system according to an embodiment of the present invention.

detailed description

Under one solution, when balancing the energy storage devices in the energy storage system, all the required balancing current is provided by the AC side of the energy storage system. Once the energy storage system is not in operation, such as standby or shutdown, then Equilibrium control cannot be achieved.

Therefore, the technical idea of the present invention is to adopt a new balanced way to process each energy storage device.

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided for more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

Fig. 1 shows a schematic structural diagram of an equalizing device for an energy storage system according to an embodiment of the present invention. As shown in Fig. 1, the equalizing device 100 for an energy storage system includes an equalizing controller 110, an AC bus 120 and The energy balancer 130 is respectively connected to each energy storage device of the energy storage system; the working state of the energy balancer 130 includes a charging state and a discharging state.

Wherein, the energy storage system may be a battery energy storage system, and the energy storage device may be a battery. High-voltage large-capacity battery energy storage system batteries can stratify batteries and balance them by layers. A certain number of battery modules form a battery cluster, and a certain number of battery clusters combine with the corresponding energy conversion device power unit to form a battery chain, forming four levels of monomer, module, cluster, and chain. Part of the battery balance problem at the layer and module layer, and a part of the battery balance problem at the cluster layer and chain layer is solved through the energy conversion device. In an embodiment of the present invention, each energy storage device may be a battery cluster, that is, it is effectively combined with this battery balancing method.

The balance controller 110 is used to collect the charge amount and voltage of each energy storage device, and judge whether the preset balance control condition is satisfied according to the collected charge amount and/or voltage of each energy storage device; when the preset balance control condition is met, condition, determine the working state of the target energy equalizer 130, and send an equalization control instruction to the target energy equalizer 130, so that the target energy equalizer 130 works in a corresponding working state.

Each energy equalizer 130 is electrically connected to the equalization controller 110 respectively, and each energy equalizer 130 is electrically connected through an AC bus 120 .

The energy balancer 130 is used to output an incoming AC current in the charging state, so as to charge the energy storage device connected to it; The state's energy balancer 130 provides the voltage.

It can be seen that in the method shown in Figure 1, the balance controller and the energy balancer corresponding to each energy storage device are set, and the energy balancer is controlled to work at Charge state or discharge state, so that the connected energy storage device completes energy release or charge, so as to achieve energy balance. This technical solution can realize a repeated cycle process without failure or control signal interruption. In this cycle process, dynamic balance among multiple energy storage devices can be realized, and the balance control process is consistent with The overall working status of the energy storage system does not matter, and it can be performed at any time, which can effectively improve the consistency of multiple energy storage devices in the energy storage system.

In an embodiment of the present invention, among the above-mentioned devices, the balance controller 110 is configured to connect with the management system of the energy storage device, and obtain the charge amount and/or voltage of each energy storage device from the management system.

For example, when the energy storage system is a battery energy storage system, the management system may be a battery management system (BMS), from which the charge capacity and/or voltage of each battery cluster can be directly read.

In one embodiment of the present invention, among the above-mentioned devices, the balance controller 110 is used to calculate the degree of deviation of each energy storage device according to the collected charge amount and/or voltage of each energy storage device; the balance control condition is calculated The degree of deviation exceeds the deviation degree threshold.

The amount of charge can directly reflect the energy state of the battery, while the voltage can reflect the working condition of the energy storage system. In an embodiment, the charge amount and voltage of each energy storage device may be considered at the same time, and weighted combination may be performed respectively. Taking voltage as the reference quantity of deviation degree, the judgment formula can be as follows:

Among them, Δ represents the calculated deviation, U _dc is the voltage of the energy storage device collected, and n is the number of energy storage devices. In this way, the current deviation degree of each energy storage device can be calculated, and by setting the deviation degree threshold, it can be determined which energy storage devices need to be balanced.

For example, suppose the energy storage system has 4 energy storage devices, and the deviation threshold is 1%, that is, n=4. Assuming that the voltages of the four energy storage devices collected by the balance controller 110 at a certain moment are: _Udc1 = 403V, _Udc2 = 397, _Udc3 = 402V, _Udc4 = 398V, then according to the above formula, the current The deviations of the four energy storage devices are: Δ ₁ =0.75%, Δ ₂ =0.75%, Δ ₃ =0.5% and Δ ₄ =0.5%, obviously the deviations of all energy storage devices are less than 1%, that is If the balance control condition is not met, the balance controller 110 restarts to collect the voltage and calculate the degree of deviation. Before the degree of deviation reaches the equilibrium control condition, all energy equalizers are in a standby state, that is, no energy from the energy storage device flows through the energy equalizer.

Assuming that the voltages of the four energy storage devices collected by another time equalization controller are: U _dc1 = 406V, U _dc2 = 394, U _dc3 = 402V, U _dc4 = 398V, then according to the above formula, the four variables can be calculated The deviation degrees of the flow modules are: Δ ₁ = 1.5%, Δ ₂ = 1.5%, Δ ₃ = 0.5% and Δ ₄ = 0.5%, obviously the deviation degrees of the first energy storage device and the second energy storage device have been It exceeds 1%, so the equilibrium control condition is satisfied, and the equilibrium control can be performed on it.

If the calculated deviation degree is not treated as an absolute value, then there will be positive values (reflected as integer deviation degrees) and negative values (represented as negative deviation degrees). For example, an energy storage device with a higher voltage has a higher degree of positive deviation; an energy storage device with a lower charge capacity has a higher degree of negative deviation. Therefore, in one embodiment of the present invention, among the above-mentioned devices, the balance controller 110 is used to determine that the energy balancer 130 connected to the energy storage device with the highest positive deviation degree is the target energy balancer 130 working in the discharge state , the energy balancer 130 connected to the energy storage device with the highest negative deviation is the target energy balancer 130 working in the charging state. In this way, "one charging and one discharging" is realized.

In an embodiment of the present invention, in the above-mentioned device, the balance controller 110 is also used to firstly A control command to stop working is sent to the target energy balancer 130 in the charging state, and then a control command to stop working is sent to the target energy balancer 130 in the discharging state.

That is to say, the energy equalizers only work when equalization is required, and are in a standby state in other cases, and not all energy equalizers need to work at the same time. In this way, balanced dynamic automatic control is realized.

In an embodiment of the present invention, in the above-mentioned device, the energy balancer 130 includes: an AC-DC conversion circuit 131 for performing energy conversion between the AC bus 120 and the energy storage device. Specifically, power devices can be selected to form a DC/AC converter.

In one embodiment of the present invention, in the above-mentioned device, the energy equalizer 130 also includes an isolation transformer 132, and the AC busbar 120 is formed by sequentially connecting the primary sides of the isolation transformers 132 of each energy equalizer 130; The side is connected to the AC side of the AC-DC conversion circuit 131 .

The transformation ratio of the primary side and the secondary side of the isolation transformer 132 can be n (n is the number of energy storage devices), which can provide an energy path for the AC-DC conversion circuit 131, and can also isolate the direct electrical connection between the energy storage devices.

In one embodiment, as shown in FIG. 2a, during the equalization control process, the equalization controller 110 issues a pulse width modulation (PWM) instruction to control the AC/DC conversion circuit 131 of the first target energy equalizer (con 1) to output 400Hz , 200V AC voltage, and the transformation ratio of the isolation transformer 132 is set to 2, then an AC voltage of 400 Hz and 400 V is immediately established on the AC bus 120, and for the AC-DC conversion circuit 131 of the first target energy equalizer, 400 Hz is obtained , AC voltage of 200V; as shown in Figure 2b, the first target energy equalizer constitutes a voltage source and works in a discharge state.

The balance controller 110 issues a pulse width modulation (PWM) command to control the AC-DC conversion circuit 131 of the second target energy equalizer (con 2) to output an AC current with an effective value of 5A and an inflow direction, and the AC current flows through the AC bus At 120, it becomes 2.5A. For the AC/DC conversion circuit 131 of the second target energy equalizer, the effective value of the current is 5A, and the direction is outflow. As shown in Fig. 3b, the second target energy equalizer constitutes a current source and works in a charging state.

In the above process, the transformation ratio of the isolation transformer is set to 2, the output voltage frequency of the AC-DC conversion circuit 131 of the first target energy equalizer is 400Hz, and the effective value is 200V, and the AC-DC conversion circuit 131 of the second target energy equalizer The effective value of the output current is 5A, and the direction is inflow. In practical applications, the transformation ratio, voltage frequency/effective value, and current can be changed according to the specific conditions of the energy storage system. The circuit principle of energy transfer is shown in Figure 3b , the first target energy equalizer constitutes a voltage source, which determines the voltage frequency and size of the energy transfer loop, and the second target energy equalizer constitutes a current source, which determines the current magnitude and transfer direction of the energy transfer loop.

During the equalization control process, energy will always be transferred from the first target energy equalizer to the first target energy equalizer, so the deviation degrees (absolute values) of the energy storage devices connected to the two must show an equal tendency. After equalization control for a period of time, the collected voltages of the two balanced energy storage devices are both 410V, which means that the equalization has achieved the goal, and then the equalization controller controls the second target energy equalizer to stop working first (the current source Stop first), then control the first target energy equalizer to stop working (stop after the voltage source), re-enter the next round of state judgment, if the balance control conditions are met, a new round of equalization adjustment will be performed, if not, enter the equalization cut-off , to keep all the energy equalizers in the standby state.

In one embodiment of the present invention, in the above device, the AC-DC conversion circuit 131 is a single-phase full-bridge structure or a three-phase full-bridge structure; when the AC-DC conversion circuit 131 is a single-phase full-bridge structure, the isolation transformer 132 is a single-phase phase transformer; when the AC-DC conversion circuit 131 is a three-phase full-bridge structure, the isolation transformer 132 is a three-phase transformer.

Figure 3a shows a topology diagram of a single-phase full-bridge structure, and Figure 3b shows a topology diagram of a three-phase full-bridge structure. Generally speaking, the balanced current is small, and the design of single-phase full-bridge structure and single-phase transformer can be adopted. Besides, other forms of bidirectional DC/AC converters may also be used.

In one embodiment of the present invention, in the above device, the energy equalizer 130 also includes a current sensor 133, the primary side of the current sensor 133 is connected to the primary side of the isolation transformer 132 of the energy equalizer 130 where it is located, and the secondary side of the current sensor 133 One side is connected with the balance controller 110; the balance controller 110 is used to adjust the balance control instruction sent to the target energy balancer 130 according to the current collected by each current sensor 133.

In an embodiment of the present invention, the above device further includes: a voltage sensor 140 . The primary side of the voltage sensor 140 is connected to the AC bus 120, and the secondary side of the voltage sensor 140 is connected to the equalization controller 110; the equalization controller 110 is used to adjust the equalization control sent to the target energy equalizer 130 according to the voltage collected by the voltage sensor 140 instruction.

For example, according to the current collected by each current sensor 133 and the voltage collected by the voltage sensor 140, the PWM command sent to the target energy balancer 130 can be adjusted to maintain the stability of the voltage on the AC bus 120 and the stability of the charging current.

Fig. 4 shows a schematic topology diagram of a balancing device of an energy storage system according to an embodiment of the present invention. As shown in Figure 4, the equalization device of the energy storage system includes an equalization controller 110, an AC bus 120, several energy equalizers 130 respectively connected to each battery cluster 410 of the battery energy storage system, and a voltage sensor 140. For the connection relationship, reference may be made to the foregoing embodiments, which will not be repeated here. The balance controller 110 can be connected to the battery management system 420 through an optical fiber, and connected to the energy storage system controller 430 through an optical fiber. The energy equalizer 130 includes an isolation transformer 132, an AC-DC conversion circuit 131 and a current sensor 133. The positive and negative polarity ends of the DC side of the AC-DC conversion circuit 131 are respectively connected to the positive and negative poles of the battery cluster 410. For other connection relations, refer to The aforementioned embodiments will not be repeated here.

In summary, in the technical solution of the present invention, an equalization controller and an energy equalizer corresponding to each energy storage device are set, and the energy equalizer is controlled when the equalization control condition is satisfied by collecting the voltage and/or charge of the energy storage device. Work in the charging state or discharging state, so that the connected energy storage device can complete energy release or charging, so as to achieve energy balance. This technical solution can realize a repeated cycle process without failure or control signal interruption. In this cycle process, dynamic balance among multiple energy storage devices can be realized, and the balance control process is consistent with The overall working status of the energy storage system does not matter, and it can be performed at any time, which can effectively improve the consistency of multiple energy storage devices in the energy storage system.

The above descriptions are only specific implementations of the present invention. Under the above teaching of the present invention, those skilled in the art can make other improvements or modifications on the basis of the above embodiments. Those skilled in the art should understand that the above specific description is only to better explain the object of the present invention, and the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (10)

1. An equalizing device for an energy storage system, characterized in that the device comprises an equalizing controller, an AC busbar and several energy equalizers that are respectively connected to each energy storage device of the energy storage system; the energy equalizer The working state includes charging state and discharging state; The balance controller is used to collect the charge amount and voltage of each energy storage device, and judge whether the preset balance control condition is satisfied according to the collected charge amount and/or voltage of each energy storage device; when the preset balance control condition is satisfied When controlling conditions, determine the working state of the target energy balancer, and send an equalization control instruction to the target energy balancer, so that the target energy balancer works in a corresponding working state; Each energy equalizer is electrically connected to the equalization controller respectively, and each energy equalizer is electrically connected through an AC bus; The energy balancer is used to output an incoming AC current in the charging state, so as to charge the energy storage device connected to it; The state's energy equalizer provides voltage. 2. The apparatus of claim 1, wherein The balance controller is configured to be connected to the management system of the energy storage device, and obtain the charge amount and/or voltage of each energy storage device from the management system. 3. The apparatus of claim 1, wherein The balance controller is used to calculate the degree of deviation of each energy storage device according to the collected charge amount and/or voltage of each energy storage device; the balance control condition is that the calculated degree of deviation exceeds a threshold value of the degree of deviation. 4. The apparatus of claim 3, wherein The balance controller is used to determine that the energy balancer connected to the energy storage device with the highest degree of positive deviation is the target energy balancer working in the discharge state, and the energy balancer connected with the energy storage device with the highest degree of negative deviation A target energy equalizer that works in a state of charge. 5. The apparatus of claim 1, wherein The equalization controller is further configured to first send a stop working message to the target energy equalizer in the charging state when it is judged that the preset equalization control condition is no longer satisfied according to the collected charge amount and/or voltage of each energy storage device. The control command, and then send the control command to stop working to the target energy balancer in the discharge state. 6. The apparatus of claim 1, wherein The energy equalizer includes: an AC-DC conversion circuit for performing energy conversion between the AC bus and the energy storage device. 7. The apparatus of claim 6, wherein The energy equalizer also includes an isolation transformer, and the AC bus is formed by sequentially connecting the primary sides of the isolation transformers of each energy equalizer; The secondary side of the isolation transformer is connected to the AC side of the AC-DC conversion circuit. 8. The apparatus of claim 7, wherein The AC-DC conversion circuit is a single-phase full-bridge structure or a three-phase full-bridge structure; When the AC-DC conversion circuit has a single-phase full-bridge structure, the isolation transformer is a single-phase transformer; when the AC-DC conversion circuit has a three-phase full-bridge structure, the isolation transformer is a three-phase transformer. 9. The apparatus of claim 7, wherein The energy balancer also includes a current sensor, the primary side of the current sensor is connected to the primary side of the isolation transformer of the energy balancer where it is located, and the secondary side of the current sensor is connected to the equalization controller; The balance controller is configured to adjust the balance control instruction sent to the target energy balancer according to the current collected by each current sensor. 10. The device according to claim 1, further comprising: a voltage sensor; The primary side of the voltage sensor is connected to the AC bus, and the secondary side of the voltage sensor is connected to the equalization controller; The equalization controller is configured to adjust the equalization control instruction sent to the target energy equalizer according to the voltage collected by the voltage sensor.