WO2013078894A1

WO2013078894A1 - Alternating current source for detecting battery internal resistance in alternate current injection method and control method thereof

Info

Publication number: WO2013078894A1
Application number: PCT/CN2012/081028
Authority: WO
Inventors: 欧海辉; 陈恒留
Original assignee: 深圳市晶福源电子技术有限公司
Priority date: 2011-12-02
Filing date: 2012-09-05
Publication date: 2013-06-06
Also published as: CN102495374B; CN102495374A

Abstract

Disclosed in the present invention is an alternating current source for detecting battery internal resistance in alternate current injection method. The alternating current source comprises an isolating step-down circuit, a rectifying circuit, an inverter circuit and an inductance capacitance (LC) resonance circuit which are connected in turn. An output end of the LC resonance circuit is reversely connected to the inverter circuit through a control circuit to form a closed loop control system. A non-direct capacitor is used in the LC resonance circuit. Also disclosed in the present invention is a corresponding control method of the alternating current source. The invention can inject current into one or more groups of high-voltage battery packs using a very low busbar voltage, thereby greatly reducing voltage stress of a power semiconductor component, significantly improving reliability of the system and simultaneously obviously improving system efficiency.

Description

AC current source for detecting internal resistance of battery by AC injection method and control method thereof

Technical field

The invention relates to the field of power sources, in particular to an alternating current source for detecting an internal resistance of a battery by an alternating current injection method and a control method thereof. BACKGROUND OF THE INVENTION As a backup power source when a power supply system is powered off, a battery has been widely used in industries such as industrial production, transportation, and communications. If the battery fails or the capacity is insufficient, it may cause a major accident, so comprehensive online monitoring of the operating parameters of the battery must be performed. One of the important signs of battery status is its internal resistance state. Whether the battery is about to fail, the capacity is insufficient, or the charge and discharge are improper, it can be reflected in its internal resistance change. Therefore, the operating state of the battery can be evaluated by measuring the internal resistance of the battery. Common battery internal resistance detection methods are: density method, open circuit voltage method, DC discharge method, AC injection method. Because of the limitations of the density method and the open circuit voltage method, it is rarely used in the on-line detection of the internal resistance of the battery; while the DC discharge method usually needs to provide a discharge current of several tens of amperes, the discharge resistance is large, the power consumption is large, and the tester is large. It can't be done small, and this high-current discharge test can't be done frequently, and the monitored internal resistance data is not strong in real time. In contrast, the AC injection method does not require the discharge of the battery, which brings great convenience. For the special load of the battery, according to its equivalent model, usually only need to design an AC current source to inject a few A into the battery (depending on the battery capacity, the current setting value is different to avoid damage to the battery), the frequency is 100~500Hz The left and right AC currents are combined with a dedicated dynamic internal resistance tester to detect the amplitude between the AC current and the ripple voltage. The phase relationship can be calculated by the software through certain filtering and solving processes, and the internal resistance (milliohms level) can be calculated.

The typical topology of a conventional AC current source is shown in Figure 1. It first produces a fairly high bus voltage (the bus voltage is often 800 VDC at a battery voltage of 600 VDC). Obviously, in the equipment room and some important applications, This approach poses a significant safety hazard. Once a power device fails or fails (studies have shown that in high voltage stress situations, the failure rate of a semiconductor power device rises significantly relative to a low voltage), it will cause a bus or battery short circuit. At the same time, there is a risk of inductance saturation, and the reliability of the system is degraded.

Therefore, although the program is theoretically feasible, it has never been practically applied.

The internal resistance tester commonly used in the prior art is a hand-held detector. Although the handheld detector can realize the injection and internal resistance detection of the single cell current, it also has the corresponding disadvantages. Due to the space limitation in the actual application environment of the battery in the large computer room, the battery is often loaded into the battery cabinet or battery. Rack, so it is necessary to monitor the battery regularly. The hand-held injection method is obviously difficult to operate, and it is easy to bring personal danger to the operator;

On the other hand, in the actual application environment of the battery of the large computer room, since the number of batteries is usually more (more than 40 knots), the detection method using the handheld battery internal resistance meter takes more time and cannot be online. Time detection, therefore not conducive to continuous monitoring of battery performance, can not automatically draw a graph;

Although the handheld battery internal resistance meter can also inject current, it is easy to be affected by strong noise in the application room due to the small injection current, so it is more suitable for static measurement of single battery. Try, there is often a problem of low accuracy when testing online. Summary of the invention

The technical problem to be solved by the present invention is to provide an alternating current source for detecting the internal resistance of a battery by an alternating current injection method, which can inject current into one or more sets of high voltage battery packs with a very low bus voltage, thereby greatly reducing The voltage stress of power semiconductor devices significantly improves system efficiency while significantly improving system reliability.

A further technical problem to be solved by the present invention is to provide a control method for an alternating current source for detecting an internal resistance of a battery by an AC injection method, which can ensure the stability of an output current of an alternating current source.

In order to solve the above technical problem, the present invention adopts the following technical solutions:

An AC current source for detecting an internal resistance of a battery by an AC injection method, comprising an isolated step-down circuit, a rectifier circuit, an inverter circuit, and an LC resonance circuit, which are sequentially connected, wherein an output end of the LC resonance circuit passes through a The control circuit is reversely connected to the inverter circuit to form a closed loop control system, and a DC blocking capacitor is used in the LC resonant circuit.

Preferably, a soft start circuit is further disposed between the inverter circuit and the LC resonance circuit, and the soft start circuit is connected to the control circuit.

Preferably, the control circuit includes a sampling circuit, a control chip, a driving circuit sequentially connected from an output end of the LC resonant circuit to an input end of the inverter circuit, and the control chip and the soft start circuit Connected.

Preferably, the inverter circuit is a full bridge inverter circuit or a half bridge inverter circuit, and the rectifier circuit is a full wave rectifier circuit.

Preferably, the control chip is further provided with a background host computer communication interface and/or internal resistance Detector communication interface.

Preferably, the control chip is a TMS320F28016 type DSP.

Correspondingly, the present invention also discloses a control method for the above alternating current source, comprising the following steps:

a fixed frequency occurs, the SPWM wave is emitted at a fixed duty ratio and a center frequency; a frequency adjustment step is performed to gradually increase the frequency of the SPWM wave, and the frequency is adjusted according to a change trend of the feedback current until the The current reaches a maximum value;

The frequency selection step fixes the frequency at which the current reaches the maximum value, and uses the frequency as the optimal operating frequency of the current inverter part.

Preferably, in the frequency adjustment step, adjusting the frequency according to a change trend of the current thereof specifically includes:

Detect the trend of the current. If the current increases, continue to increase the frequency, otherwise decrease the frequency.

Preferably, the center frequency value is 400 Hz.

Preferably, before the fixed frequency occurs, the method further includes:

After the power-on self-test, a power-on reset self-test is performed;

A sampling channel calibration step is performed to calibrate the channels of the sampling circuit.

The beneficial effects of the invention are:

The embodiment of the present invention realizes the current transmission by using a high-voltage DC blocking capacitor in the power loop of the alternating current source, and the current is transmitted by using the AC coupling effect of the capacitor, and the bus voltage is ingeniously reduced because the battery voltage is all dropped on the capacitor. This means that the voltage stress of the power tube is reduced (down to within a few tens of V), so the injection source is greatly provided. Reliability and stability; and by adding a resonant inductor, the fundamental is greatly reduced

The impedance of the LC loop suppresses the harmonic current of the high-frequency component. Since the impedance of the battery itself is small, only a small amount of bus energy is needed to generate a large current, thereby improving the system efficiency; Each time the power-on self-test is performed, the natural resonant frequency of the LC network is judged to ensure that the system is always at the optimum operating frequency, thus ensuring the stability of the system output current.

The present invention will be further described in detail below with reference to the accompanying drawings. DRAWINGS

1 is a schematic diagram of a topological structure of a prior art alternating current source.

Fig. 2 is a system control block diagram of an embodiment of an alternating current source for detecting an internal resistance of a battery by an AC injection method of the present invention.

Fig. 3 is a diagram showing the main power conversion circuit of an embodiment of the alternating current source for detecting the internal resistance of the battery by the AC injection method of the present invention.

Fig. 4 is a flow chart showing an embodiment of a control method for an alternating current source for detecting an internal resistance of a battery by an alternating current injection method of the present invention. detailed description

An embodiment of the AC current source for detecting the internal resistance of the battery by the AC injection method of the present invention will be described in detail below with reference to FIG. 2 and FIG. 3. As shown in the figure, the embodiment mainly includes: an isolated step-down circuit 1 connected in sequence The rectifier circuit 2, the inverter circuit 3, and the LC resonance circuit 4, wherein the output end of the LC resonance circuit 4 is connected to the battery to be charged, and is also connected in reverse to the inverter circuit 3 through a control circuit 5 to form a closed loop control. The system, and the LC resonant circuit 4 uses a DC blocking capacitor C5-C8, C10. Further, a soft start circuit 6 is provided between the inverter circuit 3 and the LC resonance circuit 4, and the soft start circuit 6 is connected to the control circuit 5.

In a specific implementation, the control circuit 5 includes a sampling circuit 51, a control chip 52, and a driving circuit 53 connected from the output end of the LC resonant circuit 4 to the input end of the inverter circuit 3, and the control chip 53 is connected to the soft start circuit 6. .

As an implementation manner of this embodiment, the inverter circuit 3 may adopt a full bridge inverter circuit or a half bridge inverter circuit; the rectifier circuit 2 uses a full wave rectifier circuit.

In a specific implementation, the control chip is further provided with a background host computer communication interface and/or an internal resistance detector communication interface, thereby realizing a working interval period by the background host computer to prevent frequent damage to the battery; and detecting the internal resistance of the battery Communication between instruments.

As an implementation manner of this embodiment, the control chip 52 can adopt a TMS320F28016 type DSP.

As shown in FIG. 3, the front stage of the embodiment generates a low-voltage DC bus (less than 60Vdc) by power frequency isolation, step-down, rectification, and filtering, and generates a SPWM sine wave at a midpoint of the bridge arm by using a sinusoidal pulse width modulation principle. The LC is filtered in series to obtain a controllable sinusoidal current.

Compared with the prior art, the advantages of this embodiment are:

By connecting a high-voltage DC-blocking capacitor in series with the power circuit of the AC current source, the AC coupling effect of the capacitor is used to realize the current transfer, and the battery voltage is all dropped on the capacitor, thereby subtly reducing the bus voltage, which means that the voltage is reduced. The voltage stress of the power tube (down to within a few tens of V), thus greatly providing the reliability and stability of the injection source.

And on the other hand:

A. Due to the limitation of the system volume, it is impossible to use a large-capacity high-voltage DC blocking capacitor. When the frequency is only a few hundred hertz, the AC impedance is very large, and even when the bus voltage is very low, even if the duty ratio is turned to the maximum, the current is still small, and the requirement for injecting harmonics for a plurality of batteries cannot be satisfied.

B. Since the midpoint voltage of the bridge arm is SPWM wave, it is rich in harmonic components except for the fundamental wave. Because the frequency of the harmonic component is relatively high, it is easier to generate higher harmonic currents of other frequencies through the DC blocking capacitor. The component, which reduces the detection accuracy of the battery internal resistance detector.

In order to solve the above problem, the present embodiment utilizes the LC resonance principle to greatly reduce the impedance of the fundamental LC circuit by adding a resonant inductor, and suppresses the harmonic current of the high frequency component. Since the impedance of the battery itself is small, only a small amount of bus energy is required to generate a large current, and the bus voltage is lowered to further improve the system efficiency. The device is only 1U high and uses a fixed connection to inject current into one or more groups of batteries, saving cost and space.

An embodiment of a method for controlling an AC current source for detecting an internal resistance of a battery by an AC injection method according to the present invention is described in detail below with reference to FIG. 4. As shown in the figure, the first control flow of the AC current source in this embodiment mainly includes Have:

In the fixed frequency occurrence step S1, the SPWMZ wave is emitted at a fixed duty ratio and a center frequency;

In the frequency adjustment step S2, the frequency of the SPWM wave is gradually increased, and the frequency is adjusted according to the change trend of the feedback current until the current reaches a maximum value; in the frequency selection step S3, fixed The frequency at which the current reaches a maximum value, and the frequency is used as the optimum operating frequency of the current inverter portion. In a specific implementation, in the frequency adjustment step S2, adjusting the frequency according to a change trend of the current may specifically include:

In specific implementation, the center frequency value is 400 Hz.

In addition, as an implementation manner of this embodiment, before the fixed frequency generating step S1, the method further includes:

In the power-on self-test step S01, the system performs a power-on reset self-test;

In the sampling channel calibration step (omitted in the figure), the channel of the sampling circuit is calibrated.

Due to the LC resonant network and the discrete parameters of the system parameters, the LC inherent resonant frequency often has a large deviation from the control fundamental frequency, which affects the stability of the system output current. Therefore, the present embodiment adopts the principle of disturbance, automatically determines the natural resonant frequency of the LC, and reduces the impedance of the LC resonant network by frequency modulation, thereby ensuring that the system is always operating at an optimum state.

The above is a preferred embodiment of the present invention, and it should be noted that those skilled in the art can also make several improvements and retouchings without departing from the principles of the present invention. These improvements and retouchings are also considered. It is the scope of protection of the present invention.

Claims

Claim

1. An alternating current source for detecting an internal resistance of a battery by an alternating current injection method, wherein the current source comprises an isolated step-down circuit, a rectifier circuit, an inverter circuit, and an LC resonance circuit, which are sequentially connected, wherein The output of the LC resonant circuit is also reversely connected to the inverter circuit through a control circuit to form a closed loop control system, and a DC blocking capacitor is used in the LC resonant circuit.

2. The AC current source for detecting an internal resistance of a battery by an AC injection method according to claim 1, wherein: a soft start circuit is further disposed between the inverter circuit and the LC resonance circuit, and the soft start circuit is provided. Connected to the control circuit.

3. The alternating current source for detecting an internal resistance of a battery by an alternating current injection method according to claim 2, wherein: said control circuit comprises an output from said LC resonant circuit to said inverter circuit The sampling circuit, the control chip, and the driving circuit are sequentially connected to the input end, and the control chip is connected to the soft start circuit.

The AC current source for detecting the internal resistance of the battery by the AC injection method according to any one of claims 1 to 3, wherein the inverter circuit is a full bridge inverter circuit or a half bridge inverter circuit. The rectifier circuit is a full-wave rectifier circuit.

The AC current source for detecting the internal resistance of the battery by the AC injection method according to claim 4, wherein: the control chip is further provided with a background host computer communication interface and/or an internal resistance detector communication interface.

6. The AC current source for detecting an internal resistance of a battery by an AC injection method according to claim 5, wherein: the control chip is a TMS320F28016 type DSP.

7. A method of controlling an alternating current source according to any of claims 2-6, characterized in that the method comprises the following steps:

8. The method of controlling an alternating current source according to claim 7, wherein in the frequency adjusting step, adjusting the frequency according to a trend of a change in current thereof comprises:

9. The method of controlling an alternating current source according to claim 8, wherein: said center frequency value is 400 Hz.

10. The method of controlling an alternating current source according to claim 9, further comprising: before the step of generating the fixed frequency:

After the power-on self-test, a power-on reset self-test is performed;