CN105391116B - A kind of Car Battery charge-discharge machine with health monitoring function - Google Patents

Abstract

The invention relates to a vehicle-mounted battery charging and discharging machine with a health monitoring function, which includes a monitoring and control unit, a bidirectional power conversion unit and a rectifier circuit. The monitoring and control unit superimposes a square wave signal on the battery charging or discharging target value, based on the The difference between the signal and the actual current calculates the duty cycle of the IGBT in the bidirectional power conversion unit, and controls the on-off of the IGBT through the PWM drive unit, so that the charging or discharging current of the battery is consistent with the superimposed signal; the signal acquisition and processing unit transmits the acquisition signal to the FPGA , the FPGA performs fast Fourier transform on the received battery current and each battery voltage, and converts the current and voltage signals into the sum of the DC component and the AC component of different frequencies. The impedance value of each battery is compared, and the health status of each battery is judged accordingly. The invention has simple circuit and compact structure, integrates battery health monitoring and charging and discharging control, and removes the AC excitation current source required by the traditional health monitoring system.

Description

A battery on-board charging and discharging machine with health monitoring function

technical field

The invention belongs to a vehicle-mounted battery charge-discharge machine, in particular to a battery-vehicle charge-discharge machine with a health monitoring function.

Background technique

Energy shortage, environmental pollution, and climate warming are common challenges faced by the global energy sector. Since the beginning of the 21st century, with the depletion of non-renewable energy sources such as petroleum and coal, environmental pollution has become increasingly serious, and energy conservation and environmental protection have become two major issues that need to be solved urgently in countries all over the world.

According to the data from the Energy Information Administration of the U.S. Department of Energy, the global oil demand in 2012 was 89.05 million barrels per day; the UBS report at the end of 2012 stated that the world has proven oil reserves of 1.8 trillion barrels, which means that according to the existing Based on the level of oil consumption and the current proven oil reserves, the world's oil can still be exploited for 46 years. The International Energy Agency predicts[1] that by 2035, the global annual energy demand will increase from 12 billion tons of oil equivalent in 2009 to 17-18 billion tons of oil equivalent; in terms of carbon dioxide emissions, if the current emission policy is maintained, the emissions will Up from 29 billion tons in 2009 to 43 billion tons, even with the new rules, emissions would rise to 36 billion tons. Vehicle emissions account for about a quarter of total emissions.

At present, my country has become the second largest energy consumption country in the world. In 2012, 493 million tons of oil were consumed, and the dependence on foreign crude oil was 56.42%, reaching the highest value in history. It is estimated that by 2030, 80% of my country's oil will depend on imports, and the problem of energy security is becoming increasingly serious. At the United Nations Climate Change Conference in Copenhagen held on December 7, 2009, the Chinese government reaffirmed the goal of non-fossil energy accounting for about 15% of primary energy consumption by 2020, and proposed for the first time that by 2020, domestic production of A plan to reduce total carbon dioxide emissions by 40%-45% compared to 2005. However, my country is in a state of economic operation with a relatively high carbon equivalent under the background of industrialization, and there is a long way to go to achieve the goal of carbon reduction. In October 2013, an official from the Department of Energy Conservation and Comprehensive Utilization of the Ministry of Industry and Information Technology stated that my country is already the largest country in carbon dioxide emissions, accounting for more than 70% of the world's increase in carbon dioxide emissions, and the international pressure on energy conservation and carbon reduction is increasing. Therefore, the development of electric vehicles is the only way for the next generation of vehicle technology, and batteries are one of the key components of electric vehicles.

In the process of battery application, ensuring the safety of its charging and discharging process is the primary problem that needs to be solved. The on-board charging and discharging machine is essential, and the health monitoring of the battery must also be carried out. Internal resistance is one of the key parameters to measure the state of health of a battery. Therefore, in order to ensure safe, stable and efficient operation, it is necessary to monitor the internal resistance of each single battery in real time. However, since the internal resistance of the battery can be capacitive, inductive and purely resistive, the internal resistance of a single chip is at the mΩ level, and it is time-varying, so it is very difficult to monitor.

At present, the battery charging and discharging machine and the health monitor are generally two independent devices, which respectively realize the functions of charging and discharging and health monitoring. Generally, the internal resistance tester cannot work online. It needs to be equipped with an AC current excitation source with a wide frequency range to provide AC disturbance signals for the battery. It also needs complex instruments such as battery test benches, electronic loads, and frequency analyzers. This makes this type of test platform very difficult. Complex, large in size, heavy in weight, high in cost, inconvenient for vehicle operation and high in operation cost, and can only be tested in a laboratory environment. The patents WO02/27342 and WO2003/083498 of Clean Energy Corporation in Ontario, Canada, and the patent WO2003/098769 of Green Light Power Technology Company in British Columbia, Canada, test the internal resistance of the battery by controlling the electronic load. Testing requires controls, so their method cannot be tested online.

Contents of the invention

The object of the present invention is to provide a simple, reliable and vehicle-mounted battery charging and discharging machine with health monitoring function to overcome the shortcomings of existing equipment.

In order to achieve the above object, the technical solution adopted in the present invention is:

A battery on-board charging and discharging machine with a health monitoring function, comprising at least one monitoring and control unit, a bidirectional power conversion unit, and a rectifier circuit, the bidirectional power conversion unit is used to connect the battery pack under test and a DC bus, and the rectifier circuit is used For connecting the power grid and the DC bus, it is characterized in that: the monitoring and control unit includes a signal acquisition and processing unit, FPGA, DSP, PWM drive unit and CAN communication interface, and the input terminal of the signal acquisition and processing unit collects the battery pack The battery current, the voltage of each single-chip battery, and the voltage and current signals at both ends of the bidirectional power conversion unit, the output of the signal acquisition and processing unit is connected to the DSP through the FPGA, and the DSP controls the bidirectional power conversion unit through the PWM drive unit , the DSP communicates with the outside through the CAN communication interface.

Based on the above-mentioned vehicle-mounted battery charge-discharge machine with health monitoring function, the present invention also provides a control method for a battery-vehicle charge-discharge machine with health monitoring function, and the control method is:

The monitoring and control unit superimposes a square wave signal on the battery charging or discharging target value, calculates the duty ratio of the IGBT in the bidirectional power conversion unit based on the difference between the signal and the actual current, and controls the on-off of the IGBT through the PWM driving unit, Make the battery charging or discharging current consistent with the superimposed signal; FPGA performs fast Fourier transformation on the received battery current and each battery voltage, and converts the current and voltage signals into the sum of the DC component and the AC component of different frequencies; Divide the voltage component of each frequency of the battery by the current component of the same frequency to obtain the impedance of the battery at each frequency, and compare it with the impedance value at the factory to judge the health status of each battery.

A square wave signal is superimposed on the battery charging or discharging target value current, the amplitude of the square wave is not greater than 5% of the effective value of the battery target current, and the frequency of the square wave is the fundamental frequency, which is set to 1kHz.

In the bidirectional power conversion unit, the on-off of the four IGBTs has a variety of combination modes. Through different combinations, the battery pack can supply power to the DC bus, step-down power supply, and the power grid or the DC bus can boost and charge the battery pack. , IGBT 210 is normally on, IGBT 220 and IGBT230 are normally off, IGBT 240 is on and off at a certain duty ratio, the battery pack supplies power to the DC bus; IGBT 220, IGBT 230 and IGBT 240 are normally off, and IGBT 210 is When the duty ratio is turned on and off, the battery pack supplies power to the DC bus; IGBT 230 is normally on, IGBT 210 and IGBT 240 are normally off, and IGBT 220 is turned on and off at a certain duty ratio, and the grid or DC bus is boosted to the battery pack. charging; IGBT 210, IGBT 220 and IGBT 240 are normally off, and IGBT 230 is on and off at a certain duty cycle, then the power grid or DC bus will step down and charge the battery pack.

When the battery pack supplies power to the DC bus, it works in step-up or step-down, depending on the voltage of the battery pack and the DC bus. If the battery pack voltage is higher than the DC bus voltage, it should work in buck mode; if the battery pack voltage is lower than the DC bus voltage, it should work in boost mode. When charging, if the battery pack voltage is higher than the DC bus voltage, it should work in boost mode; otherwise, it should work in step-down mode.

The above-mentioned DSP calculates the duty cycle of the IGBT in the bidirectional power conversion unit based on the difference between the target current superimposed square wave signal and the actual current, and controls the on-off of the IGBT through the PWM drive unit, so that the battery charging or discharging current is consistent with the superimposed signal; the signal The acquisition and processing unit collects the battery current, the voltage of each single battery, the voltage and current at both ends of the bidirectional power conversion unit in real time, and transmits the collected values to the FPGA.

The above-mentioned FPGA performs fast Fourier transform on the received battery current and each battery voltage, and converts the current and voltage signals into the sum of DC components and AC components of different frequencies. FPGA divides the voltage component of each frequency of each battery by the current component of the same frequency to obtain the impedance of each battery at each frequency, and compares it with the impedance value at the factory to judge the health status of each battery.

The battery current is transformed into:

Among them, I ₀ is the DC component, ω is the fundamental frequency, i represents the harmonic order, α _i is the i-order harmonic phase angle, and I _i is the i-order harmonic amplitude.

The voltage of the kth battery is transformed into:

Among them, U _{k, 0} is the DC component of the k-th battery voltage, β _{k, i} is the i-order harmonic phase angle, and U _{k, i} is the i-order harmonic voltage amplitude.

Then the DC impedance of the kth battery is:

The impedance of the kth battery when the frequency is iω is:

The aforementioned on-board battery charging and discharging machine with health monitoring function sets the internal resistance threshold according to the battery factory parameters, and when the detected internal resistance threshold is greater than the set value, it is determined that the battery’s health status is abnormal. The monitoring and control unit exchanges information with the outside world through the CAN communication interface.

Compared with the prior art, the present invention combines the battery on-board charger and the health monitor into one, removes the AC current excitation source with high precision and wide frequency range, reduces the volume, weight and cost, and can be used in charging Online monitoring of the battery health status during discharge does not affect the normal operation of the battery.

Description of drawings

Fig. 1 is a structural principle block diagram of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but these embodiments should not be construed as limiting the present invention.

The invention includes a monitoring and control unit, a bidirectional power conversion unit, and a rectification circuit. The battery pack to be tested is connected to one end of the bidirectional power converter, and the other end of the bidirectional power converter is connected to the DC bus. The power grid is also connected to the DC bus after the rectification circuit. connected.

The monitoring and control unit superimposes a square wave signal on the battery charge or discharge target value:

I _in (t) = I _req (t) + f(t) (1)

Among them, I _req (t) is the charging or discharging target value of the battery pack. I _req (t)>0 is the discharge target value, and I _req (t)<0 is the charge target value. f(t) is a superimposed square wave with an amplitude of 5% of I _req (t) and a frequency of 1kHz.

The square wave is superimposed because the frequency components of the square wave are very rich, and it is equivalent to the sum of multiple frequency sinusoidal signals. Therefore, adding a square wave is equivalent to adding multiple sinusoidal signals of different frequencies to the current.

The on-off of the four IGBTs in the bidirectional power conversion unit has a variety of combination modes. Through different combinations, the battery pack can be used to supply boost and step-down power to the DC bus, and the grid or DC bus can boost and charge the battery pack. . IGBT 210 is normally on, 220 and 230 are normally off, and 240 is on and off at a certain duty cycle, so the battery pack supplies power to the DC bus; IGBT 220, 230 and 240 are normally off, and 210 is on and off at a certain duty cycle. Then the battery pack supplies voltage to the DC bus; IGBT230 is normally on, 210 and 240 are normally off, and 220 is on and off at a certain duty cycle, so the grid or DC bus is boosted and charged to the battery pack; IGBT 210, 220 and 240 are normally off , 230 is turned on and off at a certain duty ratio, and the power grid or the DC bus bar will step-down charge the battery pack.

When the battery pack supplies power to the DC bus, it works in step-up or step-down, depending on the voltage of the battery pack and the DC bus. If the battery pack voltage is higher than the DC bus voltage, it should work in buck mode; if the battery pack voltage is lower than the DC bus voltage, it should work in boost mode. When charging, if the battery pack voltage is higher than the DC bus voltage, it should work in boost mode; otherwise, it should work in step-down mode.

When working in the charging mode, it is determined by the relay 320 in the rectifier circuit 300 whether the battery pack is charged by other power sources on the DC bus or by the power grid. When the vehicle is running, the DSP controls the relay 320 to disconnect, and other power sources on the DC bus charge the battery pack; when the vehicle is parked, the DSP monitors that the input end of the rectifier circuit is connected to the power grid, and then disconnects other power sources on the DC bus , turn on the relay 320, and charge the battery pack after being rectified by the power grid.

The DSP in the monitoring and control unit calculates the duty cycle of the IGBT in the bidirectional power conversion unit based on the difference between the signal I _in (t) and the actual current after the target current is superimposed on the square wave, and controls the on-off of the IGBT through the PWM drive unit, so that the battery The charge or discharge current is consistent with the superimposed signal. The signal acquisition and processing unit collects the battery current, the voltage of each single battery, the voltage and current at both ends of the bidirectional power conversion unit in real time, and transmits the collected values to the FPGA.

The FPGA performs fast Fourier transform on the received battery current and each battery voltage, and converts the current and voltage signals into the sum of the DC component and the AC component of different frequencies. The FPGA divides the voltage component of each frequency of each battery by the current component of the same frequency to obtain the impedance of the battery at each frequency.

The battery current is transformed into:

Among them, I ₀ is the DC component, ω is the fundamental frequency, i represents the harmonic order, α _i is the i-order harmonic phase angle, and I _i is the i-order harmonic amplitude.

The voltage of the kth battery is transformed into:

Among them, U _{k, 0} is the DC component of the k-th battery voltage, β _{k, i} is the i-order harmonic phase angle, and U _{k, i} is the i-order harmonic voltage amplitude.

Then the DC impedance of the kth battery is:

The impedance of the kth battery when the frequency is iω is:

In formulas (2)-(3), take n=100, that is, the value of i is 1, 2, 3, ..., 100. Because the frequency of the square wave is 1kHz, the impedance and DC impedance of each single battery at 1kHz, 2kHz, 3kHz, ..., 100kHz can be calculated. According to the characteristics of the battery, the impedance of 100kHz and below can fully describe the battery impedance.

After calculating the impedance of each battery, set the impedance threshold according to the battery factory parameters. When the detected impedance threshold is greater than the set value, it is determined that the battery health status is abnormal.

The content not described in detail in this specification belongs to the prior art known to those skilled in the art.

Claims (6)

1. a kind of control method of the Car Battery charge-discharge machine with health monitoring function, the battery with health monitoring function Vehicle-mounted charge-discharge machine includes at least one monitoring and control unit, bi-directional power conversion unit, rectification circuit, the bidirectional power Converter unit is used to connect tested battery pack and dc bus respectively, and rectification circuit is used to connect power network and dc bus, described Monitoring includes Signal acquiring and processing unit, FPGA, DSP, PWM driver element and CAN communication interface with control unit, described Signal acquiring and processing unit input gathers battery cell electric current, each monolithic battery voltage and the bi-directional power conversion Unit both end voltage and current signal, the output end of the Signal acquiring and processing unit is connected by FPGA with DSP, described DSP controls the bi-directional power conversion unit by PWM driver elements, and the DSP is led to by CAN communication interface and outside realize News, the control method of the Car Battery charge-discharge machine with health monitoring function are：The monitoring is with control unit in battery A square-wave signal is superimposed in charge or discharge desired value, bidirectional power is calculated based on the difference of the signal after superposition and actual current IGBT dutycycle in converter unit, IGBT break-make is controlled through PWM driver elements so that battery charge or discharge electric current is with folding Plus signal is consistent；FPGA carries out Fast Fourier Transform (FFT) to the battery current received and each cell voltage, and electric current and voltage are believed Number be converted to DC component and different frequency AC compounent sum；FPGA is by the component of voltage of each each frequency of battery divided by with frequency The current component of rate, each battery impedance under each frequency is obtained, and compared with impedance value when dispatching from the factory, judge each battery according to this Health status, it is characterised in that：In the bi-directional power conversion unit, four IGBT break-make has multiple combinations pattern, It can realize that battery pack is powered to dc bus boosting power supply, decompression by various combination, power network or dc bus are to battery pack liter Pressure charging, decompression charging；The normal opens of IGBT 210, IGBT220 and the normal offs of IGBT 230, IGBT 240 are led to certain dutycycle Disconnected, then battery pack is boosted to dc bus and powered；IGBT 220, IGBT 230 and the normal offs of IGBT 240, IGBT 210 is with certain Dutycycle break-make, then battery pack to dc bus be depressured power；The normal opens of IGBT 230, IGBT 210 and the normal offs of IGBT 240, IGBT 220 is with certain dutycycle break-make, then power network or dc bus are to battery pack boost charge；IGBT 210、IGBT 220 And the normal offs of IGBT 240, with certain dutycycle break-make, then power network or dc bus are depressured to battery pack charges IGBT 230.

2. the control method of the Car Battery charge-discharge machine with health monitoring function as claimed in claim 1, it is characterised in that： A square-wave signal is superimposed on battery charge or discharge desired value electric current, square wave amplitude is not more than battery target current effective value 5%, square wave frequency is fundamental frequency, is set as 1kHz.

3. the control method of the Car Battery charge-discharge machine with health monitoring function as claimed in claim 1, it is characterised in that： DSP calculates the duty of IGBT in bi-directional power conversion unit based on the signal after target current superposition square wave and the difference of actual current Than the break-make through PWM driver elements control IGBT so that battery charge or discharge electric current is consistent with superposed signal；Signal acquisition Gather battery current, each monolithic battery voltage, bi-directional power conversion unit both end voltage and electric current in real time with processing unit, will adopt Set value is sent to FPGA.

4. the control method of the Car Battery charge-discharge machine with health monitoring function as claimed in claim 1, it is characterised in that： FPGA carries out Fast Fourier Transform (FFT) to the battery current received and each cell voltage, and electric current and voltage signal are converted into direct current Component and different frequency AC compounent sum, FPGA is by the component of voltage of each each frequency of battery divided by the electric current point of same frequency Amount, obtains each battery impedance under each frequency, and compared with impedance value when dispatching from the factory, judge the healthy shape of each battery according to this State.

5. the control method of the Car Battery charge-discharge machine with health monitoring function as claimed in claim 4, it is characterised in that：

The battery current is transformed to：

<mrow> <mi>I</mi> <mo>=</mo> <msub> <mi>I</mi> <mn>0</mn> </msub> <mo>+</mo> <msubsup> <mo>&amp;Sigma;</mo> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>n</mi> </msubsup> <msub> <mi>I</mi> <mi>i</mi> </msub> <msqrt> <mn>2</mn> </msqrt> <mi>sin</mi> <mrow> <mo>(</mo> <mi>i</mi> <mi>&amp;omega;</mi> <mi>t</mi> <mo>+</mo> <msub> <mi>&amp;alpha;</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow>

Wherein, I₀For DC component, ω is fundamental frequency, and i represents overtone order, α_iFor i subharmonic phase angles, I_iFor i subharmonic width Value；

Kth piece cell voltage is transformed to：

<mrow> <msub> <mi>U</mi> <mi>k</mi> </msub> <mo>=</mo> <msub> <mi>U</mi> <mrow> <mi>k</mi> <mo>,</mo> <mn>0</mn> </mrow> </msub> <mo>+</mo> <msubsup> <mo>&amp;Sigma;</mo> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>n</mi> </msubsup> <msub> <mi>U</mi> <mrow> <mi>k</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <msqrt> <mn>2</mn> </msqrt> <mi>sin</mi> <mrow> <mo>(</mo> <mi>i</mi> <mi>&amp;omega;</mi> <mi>t</mi> <mo>+</mo> <msub> <mi>&amp;beta;</mi> <mrow> <mi>k</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow>

Wherein, U_{K, 0}For kth piece cell voltage DC component, β_{K, i}For i subharmonic phase angles, U_{K, i}For i subharmonic voltage amplitudes；

Then the DC impedance of kth piece battery is：

<mrow> <msub> <mi>Z</mi> <mrow> <mi>k</mi> <mo>,</mo> <mn>0</mn> </mrow> </msub> <mo>=</mo> <mfrac> <msub> <mi>U</mi> <mrow> <mi>k</mi> <mo>,</mo> <mn>0</mn> </mrow> </msub> <msub> <mi>I</mi> <mn>0</mn> </msub> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow>

Impedance of the kth piece battery when frequency is i ω be：

<mrow> <msub> <mi>Z</mi> <mrow> <mi>k</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mo>=</mo> <mfrac> <msub> <mi>U</mi> <mrow> <mi>k</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <msub> <mi>I</mi> <mrow> <mi>k</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> </mfrac> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mrow> <mo>(</mo> <msub> <mi>&amp;beta;</mi> <mrow> <mi>k</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mo>-</mo> <msub> <mi>&amp;alpha;</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> </mrow> </msup> <mo>.</mo> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>4</mn> <mo>)</mo> </mrow> </mrow>

6. the control method of the Car Battery charge-discharge machine with health monitoring function as claimed in claim 1, it is characterised in that： Dispatched from the factory parameter setting impedance threshold according to battery, when the impedance threshold detected is more than setting value, judge cell health state It is abnormal.