Control method for long-term equalization of output electric energy of two independent power supply devices

Abstract

The invention discloses a long-term balance control method for output of double independent power supply equipment, which is used for controlling the double independent power supply equipment, double independent power supplies take power from a center tap of a storage battery pack, a first power supply device takes power from a first pole (such as a positive pole) and a middle point of the storage battery pack, and a second power supply device takes power from a second pole (such as a positive pole); the second power supply device takes power from the midpoint and the second pole (such as the negative pole) of the battery pack, and at least the first power supply device is controlled according to the following method. According to the equalization scheme, the output electric energy of the two direct-current power supply devices is equalized for a long time, the service life of the storage battery pack can be prolonged, and additional hardware equipment is not needed. And the device is also suitable for other application occasions requiring long-term equalization of output electric energy of the power supply device. After the two power supplies controlled by the method operate for 3 months, the voltage difference is only about 10V, the service life of the storage battery pack is prolonged, and the output electric energy of the two power supply devices is kept balanced for a long time.

Description

Technical Field

[0001] The invention relates to the field of uninterruptible power supply, and in particular to a control method for long-term balancing of output electric energy of two independent power supply devices. Background Art

[0002] The DC power grid is an important part of the ship's power system. The DC power supply device is the power supply equipment of the DC power grid, providing highly reliable and high-quality electricity to various types of loads on the ship. In order to ensure the power supply reliability of key loads, some DC power supply devices will use battery packs as input to ensure reliable power supply when the power generation system fails. However, the battery pack voltage may be quite different from the power supply voltage required by the load, that is, the input voltage and output voltage of the DC power supply device are quite different, which will make the design of the DC power supply device difficult and the stability is poor under light load. Therefore, the input voltage of the DC power supply device will be drawn from the center tap of the battery pack, such as Figure 1 As shown, the two DC power supply devices draw power from the upper and lower parts of the battery pack respectively. Since the output characteristics of the two DC power supply devices are inconsistent and the output power is unbalanced, after long-term operation, the voltage of the upper and lower parts of the battery pack will be unbalanced, which seriously affects the service life of the battery pack. Therefore, it is necessary to balance the output power of the two DC power supply devices.

[0003] The traditional method of balancing the output power is to add switches, switching control devices and energy meters to the input end of the DC power supply device. When the voltage of one half of the battery is lower than that of the other half, the input switch of the low-voltage corresponding branch power supply device is automatically disconnected, allowing the high-voltage branch power supply device to provide all the power to the load. However, this method requires the addition of additional hardware equipment and requires advance design and planning, which is difficult to implement for power systems and equipment that have been installed on ships.

[0004] In addition, the current conventional DC power supply output power balance control methods include: average current equalization method, external current equalization controller equalization method, etc., but these methods require the setting of a special monitoring module, which is suitable for multiple power modules in a power supply to equalize current. For two independent DC power supply devices, the commonly used current equalization methods are mainly droop current equalization methods. This method has a good current equalization effect when the DC power supply device is in short-term operation, but after long-term operation, such as 2-3 months of operation, the current equalization effect deteriorates, and the droop coefficient of the device needs to be adjusted again, which is not suitable for actual engineering. Summary of the invention

[0005] In view of the above problems, the present invention proposes a control method for long-term balancing of the output power of two independent power supply devices, which is applicable to two DC power supply devices that draw power from the center tap of a battery pack in a DC power grid, and can achieve long-term balancing of the output power of the two DC power supply devices, thereby extending the service life of the battery pack without adding additional hardware equipment. It can also be applied to other application occasions that require long-term balancing of the output power of the power supply device.

[0006] The technical solution of the present invention is as follows:

[0007] A long-term balanced control method for the output of a dual independent power supply device is used to control the dual independent power supply device, wherein the dual independent power supplies are powered from the center tap of a battery pack, a first power supply device is powered from a first pole and a midpoint of the battery pack, and a second power supply device is powered from a midpoint and a second pole of the battery pack, wherein at least the first power supply device is controlled according to the following method, and the method comprises the following steps:

[0008] 1) If the input voltage of the second power supply device is greater than the input voltage of the first power supply device and reaches the first threshold value ΔU in1 Above, according to the step size ΔU c Gradually reduce the output voltage command U of the first power supply unit c Each time a step is adjusted, a certain time delay is set between each step adjustment to ensure that the output voltage command U c It changes slowly, so set Flag = 4 and set the lower limit value U of the output voltage command. cl1 , limit the output voltage command, when U c cl1 When U c =U cl1 , output voltage error value err = U c -U o , feeding back the output voltage error value err to the PI control loop of the first power supply device to control the first power supply device;

[0009] 2) If the input voltage of the second power supply device is less than the input voltage of the first power supply device and reaches the first threshold value ΔU in1 Above, according to the step size ΔU c Gradually increase the output voltage command U of the first power supply unit c Each time a step is adjusted, a certain time delay is set between each step adjustment to ensure that the output voltage command U c It changes slowly, so set Flag = 3; and set the upper limit value U of the output voltage command cl2 , limit the output voltage command, when U c >U cl2 When U c =U​cl2 , output voltage error value err = U c -U o , feeding back the output voltage error value err to the PI control loop of the first power supply device to control the first power supply device;

[0010] 3) When the input voltage difference between the second power supply device and the first power supply device is within the second threshold ±ΔU in2 When the output voltage error is within err=U c -U o -U Id , where the output voltage command U c No adjustment is made, error adjustment coefficient U Id =I d / 128, and set Flag = 2, and feed the output voltage error value err back to the PI control loop of the first power supply device to control the first power supply device, where I d is the load current;

[0011] 4) When the input voltage of the second power supply device differs from the input voltage of the first power supply device by ΔU in2 ~ΔU in1 or -ΔU in2 ~-ΔU in1 When Flag=2, the output voltage error value err=U c -U o -U Id , where the output voltage command U c No adjustment is made, error adjustment coefficient U Id =I d / 128, and feeds the output voltage error value err back to the PI control loop of the first power supply device to control the first power supply device, wherein I d is the load current;

[0012] 5) When the input voltage of the second power supply device differs from the input voltage of this device by ΔU in2 ~ΔU in1 or -ΔU in2 ~-ΔU in1 When Flag is not equal to 2, the output voltage error value err = U c -U o , where the output voltage command U c Without making any adjustment, the output voltage error value err is fed back to the PI control loop of the first power supply device to control the first power supply device.

[0013] Preferably, the first threshold ΔU in1=0.1*(highest voltage of battery pack-lowest voltage of battery pack).

[0014] The second threshold ΔU in2 =0.075*(highest voltage of battery pack-lowest voltage of battery pack).

[0015] The lower limit value U of the output voltage command cl1 =0.99*rated output voltage.

[0016] The upper limit value U of the output voltage command cl2 =1.07*rated output voltage.

[0017] Adjustment step ΔU c =0.0016*rated output voltage.

[0018] Among them, the highest voltage of the battery pack refers to the voltage after the battery part that supplies power to a single power supply device is fully charged (corresponding to 600V in the embodiment); the lowest voltage of the battery pack refers to the voltage after the battery part that supplies power to a single power supply device is fully discharged (corresponding to 400V in the embodiment).

[0019] It should be noted that the scheme of the invention is carried out in combination with PI control. For one of the power supply devices, traditional voltage PI control can be adopted, while for the other power supply device, the control method of the present invention is adopted to generate an error signal to be fed back to the PI loop for feedback control.

[0020] Technical Effects

[0021] The balancing scheme of the present invention enables the output of electric energy of two DC power supply devices to be balanced for a long time, which can extend the service life of the battery pack without adding additional hardware equipment. It can also be applied to other application occasions that require the output of electric energy of the power supply device to be balanced for a long time.

[0022] The field test results show that when the traditional PI control or droop control method is used, the initial voltage of the upper half of the battery group is about DC580V, and the voltage of the lower half is about DC574V. After about 3 months of operation, the voltage of the upper half of the battery group is about DC492V, and the voltage of the lower half is about DC417V. The voltage difference is large, which seriously affects the service life of the battery group. When the method proposed by the present invention is used, the initial voltage of the upper half of the battery group is about DC585V, and the voltage of the lower half is about DC578V. After about 3 months of operation, the voltage of the upper half of the battery group is about DC453V, and the voltage of the lower half is about DC443V. The voltage difference is small, which is conducive to extending the service life of the battery group, and the output power of the two power supply devices can be kept balanced for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1A schematic diagram of power supply for two DC power supply devices of the present invention that draw power from the center tap of a battery pack;

[0024] Figure 2 The invention discloses a method for controlling the output voltage of a DC power supply device.

[0025] Figure 3 The invention provides a long-term balanced control algorithm for the output electric energy. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0027] The present invention proposes a control method for long-term balancing of the output power of two independent power supply devices. Figure 2 As shown in the control algorithm flow chart, Figure 3 shown.

[0028] The following is an example of a DC25V DC power supply device. The battery pack voltage is about DC800-1200V. The DC power supply device draws power from the center tap of the battery pack (divide the entire battery into 2 parts, such as Figure 1 As shown), the input voltage is about DC400-600V and the rated output voltage is DC25V.

[0029] Parameter Description:

[0030] U c : Output voltage command, the initial value is 25V;

[0031] err: output voltage error value;

[0032] U in1 : The input voltage of the first DC power supply device is obtained by sampling;

[0033] U in2 : The input voltage of the second DC power supply device is obtained by sampling or communication;

[0034] ΔU in1 =20V: first threshold of input voltage regulation range;

[0035] ΔU in2 =15V: second threshold of input voltage regulation range;

[0036] ΔU c =0.04V: output voltage adjustment step;

[0037] U cl1 =24.8V: output voltage regulation lower limit;

[0038] Ucl2 =26.8V: output voltage regulation upper limit;

[0039] U o : The actual output voltage of the device is obtained by sampling;

[0040] U Id =I d / 128: error adjustment coefficient;

[0041] I d : Load current, obtained by sampling;

[0042] Flag: Flag bit.

[0043] The DC power supply device generally adopts the output voltage PI control method, that is, the output voltage instruction is subtracted from the actual output voltage to obtain the output voltage error value err, and PWM modulation is performed after PI adjustment to generate a PWM wave to control the output of the hardware circuit. The method proposed in the present invention will be used to generate the output voltage error value err, thereby realizing long-term balanced control of the output electric energy. The control method only needs to be used for one of the DC power supply devices, and the other still adopts the traditional output voltage PI control method. Here, the first power supply device adopts the control method of the present invention as an example for description, and the specific method is described as follows:

[0044] 1) If the input voltage of the second power supply device is greater than the input voltage of the first power supply device by ΔU in1 =20V or more, according to the step size ΔU c =0.04V Gradually reduce the output voltage command U of the first power supply device c , each time a step is adjusted, a certain delay is set to ensure that the output voltage command U c It changes slowly to avoid instability of the power supply device, set Flag = 4. And set the lower limit value U of the output voltage command cl1 =24.8V, limit the output voltage command, when U c cl1 When U c =U cl1 =24.8V, output voltage error value err=U c -U o .

[0045] 2) If the input voltage of the second power supply device is lower than the input voltage of the first power supply device by ΔU in1 =20V or more, according to the step size ΔU c =0.04V Gradually increase the output voltage command U of the first power supply device c , each time a step is adjusted, a certain delay is set to ensure that the output voltage command U c ​It changes slowly to avoid instability of the power supply device, set Flag = 3. And set the upper limit value U of the output voltage command cl2 =26.8V, limit the output voltage command, when U c >U cl2 When U c =U cl2 =26.8V, output voltage error value err=U c -U o .

[0046] 3) When the input voltage difference between the second power supply device and the first power supply device is within ±ΔU in2 = Within ±15V, the output voltage error value err = U c -U o -U Id , where the output voltage command U c No adjustment is made (it may be the initial value, or the value adjusted according to 1) and 2) before), the error adjustment coefficient U Id =I d / 128, and set Flag=2.

[0047] 4) When the input voltage of the second power supply device differs from the input voltage of this device by ΔU in2 ~ΔU in1 or -ΔU in2 ~-ΔU in1 Between, that is, between 15V and 20V or -15V and -20V, and when Flag = 2, the output voltage error value err = U c -U o -U Id , where the output voltage command U c No adjustment is made (it can be the initial value, or the value adjusted according to 1) and 2) before), the error adjustment coefficient U Id =I d / 128.

[0048] 5) When the input voltage of the second power supply device differs from the input voltage of this device by ΔU in2 ~ΔU in1 or -ΔU in2 ~-ΔU in1 Between, that is, between 15V and 20V or -15V and -20V, and when Flag is not equal to 2, the output voltage error value err = U c -U o , where the output voltage command U c No adjustment is made (it can be the initial value, or the value adjusted according to 1) and 2) before).

[0049] In the above steps, the obtained output voltage error value err is fed back to the power supply device used in the method of the present invention, and sent into the PI control loop for PI control.

[0050] Taking the power supply of this embodiment as an example, the field test results show that when the traditional PI control or droop control method is adopted, the initial voltage of the upper half of the battery group is about DC580V, and the voltage of the lower half is about DC574V. After about 3 months of operation, the voltage of the upper half of the battery group is about DC492V, and the voltage of the lower half is about DC417V. The voltage difference is relatively large, about 70-80V, which seriously affects the service life of the battery group.

[0051] When the method proposed in the present invention is adopted, the initial voltage of the upper half of the battery group is about DC585V, and the voltage of the lower half is about DC578V. After about 3 months of operation, the voltage of the upper half of the battery group is about DC453V, and the voltage of the lower half is about DC443V. The voltage difference is small, only about 10V, which is beneficial to prolonging the service life of the battery group. The output power of the two power supply devices can remain balanced for a long time.

[0052] Therefore, by adopting the control method proposed in the present invention, the two DC power supply devices can maintain balanced output power for a long time, and the voltage of the upper and lower halves of the battery pack will be balanced, thereby extending the service life of the battery.

[0053] In summary, the present invention proposes a control method for long-term balanced output of electric energy of two independent power supply devices, which is applicable to two DC power supply devices that draw power from the center tap of a battery pack in a ship's DC power grid, and can make the output of electric energy of the two DC power supply devices long-term balanced, extend the service life of the battery pack, and do not need to add additional hardware equipment. It can also be applied to other application occasions that require long-term balanced output of electric energy of power supply devices.

[0054] Although the principles of the present invention are described in detail above in conjunction with the preferred embodiments of the present invention, those skilled in the art should understand that the above embodiments are merely explanations of the exemplary implementations of the present invention, and are not intended to limit the scope of the present invention. The details in the embodiments do not constitute limitations on the scope of the present invention, and any obvious changes such as equivalent transformations, simple replacements, etc. based on the technical solution of the present invention, without departing from the spirit and scope of the present invention, fall within the protection scope of the present invention.

Claims

1. A long-term balanced control method for the output of a dual independent power supply device, used for controlling the dual independent power supply device, wherein the dual independent power supplies are powered from the center tap of a battery pack, the first power supply device is powered from the first pole and the midpoint of the battery pack, and the second power supply device is powered from the midpoint and the second pole of the battery pack, wherein: At least the first power supply device is controlled according to the following method, characterized in that the method comprises the following steps: 1) Real-time measurement of the input voltages of the first power supply device and the second power supply device. If the input voltage of the second power supply device is greater than the input voltage of the first power supply device and reaches a first threshold value ΔU in1 , with a step size of ΔU c Gradually reduce the output voltage command U of the first power supply unit c , each time a step is adjusted, a certain delay is set to ensure that the output voltage command U c It changes slowly, so set Flag = 4 and set the lower limit value U of the output voltage command. cl1 , limit the output voltage command, when U c cl1 When U c =U cl1 , output voltage error value err = U c -U o , feeding back the output voltage error value err to the PI control loop of the first power supply device to control the first power supply device;​ 2) If the input voltage of the second power supply device is less than the input voltage of the first power supply device and reaches the first threshold value ΔU in1 , with a step size of ΔU c Gradually increase the output voltage command U of the first power supply unit c , each time a step is adjusted, a certain delay is set to ensure that the output voltage command U c It changes slowly, so set Flag = 3; and set the upper limit value U of the output voltage command cl2 , limit the output voltage command, when U c >U cl2 When U c =U cl2 , output voltage error value err = U c -U o , feeding back the output voltage error value err to the PI control loop of the first power supply device to control the first power supply device; 3) When the input voltage difference between the second power supply device and the first power supply device is within the second threshold ±ΔU in2 When the output voltage error is within err=U c -U o -U Id , where the output voltage command U c No adjustment is made, error adjustment coefficient U Id =I d / 128, and set Flag = 2, and feed the output voltage error value err back to the PI control loop of the first power supply device to control the first power supply device, where I d is the load current; 4) When the input voltage of the second power supply device differs from the input voltage of the first power supply device by ΔU in2 ~ΔU in1 or -ΔU in2 ~-ΔU in1 When Flag=2, the output voltage error value err=U c -U o -U Id , where the output voltage command U c No adjustment is made, error adjustment coefficient U Id =I d / 128, and feeds the output voltage error value err back to the PI control loop of the first power supply device to control the first power supply device, wherein I d is the load current; 5) When the input voltage of the second power supply device differs from the input voltage of the first power supply device by ΔU in2 ~ΔU in1 or -ΔU in2 ~-ΔU in1 When Flag is not equal to 2, the output voltage error value err = U c -U o , where the output voltage command U c Without making any adjustment, the output voltage error value err is fed back to the PI control loop of the first power supply device to control the first power supply device.

2. The long-term balanced control method for the output of dual independent power supply equipment according to claim 1, characterized in that: The first threshold ΔU in1 =0.1*(highest voltage of battery pack-lowest voltage of battery pack).

3. The long-term balanced control method for the output of dual independent power supply equipment according to claim 1, characterized in that: The second threshold ΔU in2 =0.075*(highest voltage of battery pack-lowest voltage of battery pack).

4. The long-term balanced control method for the output of dual independent power supply equipment according to claim 1, characterized in that: The lower limit value U of the output voltage command cl1 =0.99*rated output voltage.

5. The long-term balanced control method for the output of dual independent power supply equipment according to claim 1, characterized in that: The upper limit value U of the output voltage command cl2 =1.07*rated output voltage.

6. The long-term balanced control method for the output of dual independent power supply equipment according to claim 1, characterized in that: Adjustment step ΔU c =0.0016*rated output voltage.

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